Lipoprotem phospholipid composition and LCAT activity in nephrotic and analbuminemic rats. Albumi... more Lipoprotem phospholipid composition and LCAT activity in nephrotic and analbuminemic rats. Albumin is an acceptor of lysophosphatidylcholine (LPC), product of the lecithin:cholesterol acyl transferase (LCAT) reaction, and it has been suggested that low LCAT activity and reduced cholesterol esterification rate in patients with the nephrotic syndrome may be linked to depletion of albumin. Effects of low plasma albumin levels on LCAT activity, cholesterol esterification rates and LPC-binding were therefore studied in hyperlipidemic nephrotic (NS) and analbuminemic (NAR) rats. LPC-binding was also measured in normoalbuminemic rats with dietary hypercholesterolemia. Remarkably, LCAT activity, measured with excess exogenous substrate, was not decreased but increased in both NAR and NS rats. Molar esterification rates with endogenous substrate were increased in NAR but normal in NS rats. In normoalbuminemic rats, with or without hypercholesterolemia, LPC was primarily found in the lipoprotein-deficient plasma and the HDL3 fraction. In NAR and NS rats LPC levels were increased in lipoproteins (notably in LDL and HDL2), but, in marked contrast to normoalbuminemic rats, decreased in lipoprotein-deficient plasma. Phosphatidylcholine, quantitatively the major phospholipid, was distributed proportionally over the lipoproteins in NS, NAR and control rats. Therefore, in hypoalbuminemia and analbuminemia LPC is mainly bound to lipoproteins, which is in contrast to the paucity of LPC in these particles in normoalbuminemic rats. Cholesterol esterification in nephrotic plasma is thus not impaired by lack of an acceptor for LPC-binding. The absence of an increase in molar cholesterol esterification in conjunction with increased LCAT activity points to a possible defect of the substrate for this reaction in nephrotic plasma. Increased LPC levels in LDL, a characteristic of oxidized LDL, may be a hitherto unrecognized atherosclerotic risk factor in the nephrotic syndrome.
Proteinuria, lipoproteins and renal apolipoprotein deposits in uninephrectomized female analbumin... more Proteinuria, lipoproteins and renal apolipoprotein deposits in uninephrectomized female analbuminemic rats. To elucidate the pathogenetic role of hyperlipidemia per se in the development of glomeruloscierosis, severely hyperlipidemic female analbuminemic rats (NAR) and mildly hyperlipidemic male NAR were studied for a period of 37 weeks after uninephrectomy (UNX). Plasma cholesterol increased from 6.3 0.4 (week 4) to 11.9 0.6 mmol/liter (week 37) in the 9 NAR, and from 4.3 0.1 to 6.4 0.5 mmol/liter in the 3 NAR in the same period. Plasma protein concentration was also consistently higher in 9 NAR (60 1 g/liter) as compared to 3 NAR (52 1 g/liter). Plasma viscosity was higher in 9 NAR than in 3 NAR, but there were no differences in blood viscosity. Proteinuria increased progressively in the UNX 9 NAR from 25 weeks after surgery, reaching a final value of 141 37 mg/day. No proteinuria occurred in the UNX 6 NAR (final value 15 2 mg/day). Glomerular capillary pressure, measured prior to the onset of proteinuria, was not significantly different in UNX 9 NAR and UNX 6 NAR. At the end of the study glomerulosclerosis and lipid deposition was only found in the UNX 9 NAR. Throughout the study hyperfiltration and hyperperfusion, relative to the one-kidney clearances of the sham-operated (2K) animals, were not different in UNX 6 and 9 NAR. No differences were observed in blood pressure. Hypertrophy, evaluated by glomerular diameters, was less pronounced in UNX 9 NAR (174 3 jim) than in UNX 6 NAR (190 7 jim). Glomerular diameters in 2K 9 and 6 NAR were similar (respectively 158 2 and 157 4 jim). Plasma apo B levels were similar (2K 9 NAR: 204 8 U; 2K 6 NAR 204 13 U), but cholesterol and triglyceride content of apo B-containing lipoproteins, namely VLDL, IDL and LDL, was increased twofold in the 9 NAR as compared to the 6 NAR, implying a larger particle size in the 9 NAR. Deposition of apo B and apo E was observed in the glomerular mesangium of UNX 9 NAR, particularly in sclerotic lesions. Glomerular apo A-I deposits were localized primarily in visceral epithelial cells and were not associated with sclerotic lesions. The development of proteinuria and glomerulosclerosis after UNX in 9 NAR but not in 6 NAR may depend upon differences in plasma lipoprotein composition, but is apparently not related to differences in whole kidney hyperfiltration and hyperperfusion, glomerular capillary pressure, or blood viscosity.
Connective tissue growth factor (CTGF; CCN2) plays a role in the development of diabetic nephropa... more Connective tissue growth factor (CTGF; CCN2) plays a role in the development of diabetic nephropathy (DN). Urinary CTGF (uCTGF) is elevated in DN patients and has been proposed as a biomarker for disease progression, but it is unknown which pathophysiological factors contribute to elevated uCTGF. We studied renal handling of CTGF by infusion of recombinant CTGF in diabetic mice. In addition, uCTGF was measured in type 1 DN patients and compared with glomerular and tubular dysfunction and damage markers. In diabetic mice, uCTGF was increased and fractional excretion (FE) of recombinant CTGF was substantially elevated indicating reduced tubular reabsorption. FE of recombinant CTGF correlated with excretion of endogenous CTGF. CTGF mRNA was mainly localized in glomeruli and medullary tubules. Comparison of FE of endogenous and recombinant CTGF indicated that 60% of uCTGF had a direct renal source, while 40% originated from plasma CTGF. In DN patients, uCTGF was independently associated with markers of proximal and distal tubular dysfunction and damage. In conclusion, uCTGF in DN is elevated as a result of both increased local production and reduced reabsorption due to tubular dysfunction. We submit that uCTGF is a biomarker reflecting both glomerular and tubulointerstitial hallmarks of diabetic kidney disease.
Males are at greater risk for renal injury than females. This may relate to NOavailability becaus... more Males are at greater risk for renal injury than females. This may relate to NOavailability because female rats have higher renal endothelial NO synthase (NOS) levels. Previously, we found susceptibility to proteinuria induced by NOS inhibition in male as compared to female rats. Dyslipidemia and hypercholesterolemia dosedependently decreased renal NOS activity and caused renal injury in female rats. We hypothesized that exposure of male rats to hypercholesterolemia would lead to more renal injury in male than in female rats, due to an a priori lower renal NO-system. Female and male rats were fed no, low-dose, or high-dose cholesterol for 24 weeks.
In fawn-hooded hypertensive (FHH) rats, a model of hypertension, impaired preglomerular resistanc... more In fawn-hooded hypertensive (FHH) rats, a model of hypertension, impaired preglomerular resistance, hyperfiltration, and progressive renal injury, we recently observed that supporting perinatal nitric oxide (NO) availability with the NO donor molsidomine persistently reduced blood pressure (BP) and ameliorated renal injury in male and female offspring. However, beneficial effects of perinatal molsidomine treatment were more pronounced in female than in male FHH rats. To evaluate whether such protective effects could also be achieved with micronutrients, and whether the gender-dependent differences could be confirmed, we tested perinatal exposure to the micronutrients L-arginine, taurine, vitamin C, and vitamin E (ATCE) in FHH rats. Perinatal micronutrients increased urinary NO metabolite, sodium and potassium excretion only at 4 weeks of age, i.e., at the end of treatment. From 12 weeks onwards, control males had a significantly higher systolic BP (SBP) than females (P < 0.01); however after perinatal micronutrients, this difference was no longer present, indicating a pronounced antihypertensive effect of perinatal micronutrients in males (interaction P < 0.001). Development of proteinuria was attenuated by perinatal micronutrients in males and females. However, only females showed reduced glomerular filtration rate, filtration fraction, and glomerulosclerosis (GS) after perinatal micronutrients. In sum, perinatal micronutrients that enhance NO availability ameliorated development of hypertension and proteinuria in FHH rats. Antihypertensive effects were more pronounced in male FHH offspring, whereas renal protective effects were more pronounced in female FHH offspring. Mechanisms underlying gender-specific consequences of perinatal micronutrients require further study.
Limiting enteric sodium absorption is an attractive option when renal sodium excretion is disturb... more Limiting enteric sodium absorption is an attractive option when renal sodium excretion is disturbed. An effective approach in the gut appears to be inhibition of the electroneutral Na(+)/H(+) exchangers (NHE), in particular NHE3. Recently, fluid retention, blood pressure and target organ injury were limited in rats with cardiorenal syndrome when treated with the NHE3 inhibitor tenapanor. The downside was that the osmotic fecal load leads to watery feces. Tenapanor also induced marked reductions in enteric phosphorus absorption in rats with cardiorenal syndrome on a high phosphorus intake and resulted in marked reductions in renal injury and practically prevented vascular calcification. We have yet to discover the clinical relevance in volume terms and vascular calcifications in patients in relation to the tolerated dose. However, even if the tenapanor-induced reduction in sodium adsorption is limited in humins, combination of tenapanor therapy with diuretics may be an interesting op...
Journal of the American Society of Nephrology : JASN, 2001
Chronic nitric oxide (NO) synthase inhibition in rats causes hypertension, renal vascular injury,... more Chronic nitric oxide (NO) synthase inhibition in rats causes hypertension, renal vascular injury, and proteinuria. NO deficiency increases superoxide (O(2)(-)) activity, but the effects of antioxidant treatment on renal injury have not been studied in this model. Exposure of rats to N omega-nitro-L-arginine (L-NNA) for 4 d markedly decreased NO-dependent relaxation in aortic rings and increased glomerular and renal interstitial monocyte influx, but renal O(2)(-) activity was not increased. After 7 d, BP and proteinuria were significantly increased. After 21 d of L-NNA treatment, rats displayed severe hypertension, decreased GFR, marked proteinuria, glomerular ischemia, renal vascular and tubulointerstitial injury, and complete loss of NO-dependent relaxation. Renal O(2)(-) activity was markedly increased [lucigenin-enhanced chemiluminescence (LEC), 279 +/- 71 versus 50 +/- 7 counts/10 mg, P < 0.01; electron paramagnetic resonance spectroscopy, 0.57 +/- 0.05 versus 0.34 +/- 0.04 U...
Journal of the American Society of Nephrology : JASN, 2001
Recovery from ischemia/reperfusion and immune-mediated injury in the renal transplant is associat... more Recovery from ischemia/reperfusion and immune-mediated injury in the renal transplant is associated with reduced renal hemodynamics and increased leukocyte infiltration. In diverse models of renal failure, L-arginine supplementation improved hemodynamics and reduced inflammation. However in a proinflammatory environment, L-arginine can worsen renal injury. This study investigated the therapeutic potential of L-arginine supplementation in allogeneic renal transplantation: Brown Norway rat kidneys were transplanted into Lewis rat recipients, with one native kidney remaining. Recipients received low-dose cyclosporin A (2.5 mg/kg per d subcutaneously) to obtain moderate vascular and interstitial rejection, with or without 1% L-arginine in drinking water for 7 d posttransplantation. Transplantation increased renal vasoconstriction (from 16.9 +/- 1.33 to 35.1 +/- 8.6 units; P: < 0.01), thereby reducing GFR (from 0.96 +/- 0.09 to 0.48 +/- 0.10 ml/min; P: < 0.05). Treatment with L-arg...
Journal of the American Society of Nephrology : JASN, 2000
Hyperlipidemia in conjunction with uninephrectomy leads to renal injury in rats. It is unknown wh... more Hyperlipidemia in conjunction with uninephrectomy leads to renal injury in rats. It is unknown whether this is due to mesangial cell or podocyte injury and whether the injuries induced by hypercholesterolemia and hypertriglyceridemia share a similar pathogenesis. Therefore, renal effects of hypercholesterolemia were studied in male rats with dietary hypercholesterolemia compared with rats on a regular diet. Renal effects of hypertriglyceridemia were studied in female Nagase analbuminemic rats (NAR). Hypertriglyceridemia was reduced in NAR by ovariectomy. Both models were studied after uninephrectomy or sham operation. Dietary hypercholesterolemia had little effect on plasma triglycerides, whereas ovariectomy in the NAR had no effect on plasma cholesterol. However, an increase in intermediate density lipoprotein cholesterol was common to both models. Dietary hypercholesterolemia and uninephrectomy separately induced a similar increase in proteinuria after 13 wk, which was additive wh...
Journal of the American Society of Nephrology : JASN, 1998
Unopposed actions of vasoconstrictors, such as angiotensin, play an important role in the effects... more Unopposed actions of vasoconstrictors, such as angiotensin, play an important role in the effects of chronic nitric oxide synthase (NOS) inhibition. In this study, it is hypothesized that endothelin (ET), another important vasoconstrictor, may also play a role in the development of hypertension and renal lesions during chronic NOS inhibition. The ET(A) receptor was blocked with A-127722 during chronic NOS inhibition with Nomega-nitro-L-arginine (L-NNA), a potent NOS inhibitor without antimuscarinic action. Male Sprague Dawley rats were treated for 3 wk with L-NNA (40 mg/kg per d), L-NNA (40 mg/kg per d) + A-127722 (30 mg/kg per d), or remained untreated (control). In preliminary experiments, L-NNA (40 mg/kg per d) had been found to cause the maximum increase of systolic BP and a 35% decrease in renal NOS activity. Three weeks of L-NNA treatment resulted in a marked rise in systolic BP (240+/-4 versus control 151+/-7 mmHg; P < 0.01), proteinuria (209+/-46 versus control 27+/-3 mg/...
Journal of the American Society of Nephrology : JASN, 1997
Estrogen replacement therapy is considered antiatherosclerotic because it reduces LDL cholesterol... more Estrogen replacement therapy is considered antiatherosclerotic because it reduces LDL cholesterol and fibrinogen and increases HDL cholesterol concentrations. However, exogenous estrogen is also known to increase hepatic triglyceride production. Hyperlipidemia in the nephrotic syndrome is probably due to increased lipoprotein secretion into plasma and decreased clearance of lipoprotein cholesterol and triglycerides. Previously, lipid-lowering effects of ovariectomy in analbuminemic rats were observed, suggesting that in the presence of hypoalbuminemia, estrogen replacement may have adverse effects on the lipid profile. To test this hypothesis, ovariectomized control rats and rats with Adriamycin-induced nephrotic syndrome were treated with estradiol. In ovariectomized controls, estradiol reduced plasma LDL cholesterol, apolipoprotein B, and fibrinogen and increased apolipoprotein A-I and triglycerides. Nephrotic rats were characterized by a marked decrease in plasma colloid osmotic ...
Best practice & research. Clinical endocrinology & metabolism, 2012
According to the Developmental Origins of Health and Disease hypothesis intrauterine or postnatal... more According to the Developmental Origins of Health and Disease hypothesis intrauterine or postnatal adaptations to the environment causes morphologic, physiologic or metabolic changes that influence health later in life. These adaptations seem to be carried out through structural, functional and epigenetic modifications. Multiple animal models of cardiovascular programming have been developed, and a brief overview of well-known models and mechanisms is presented. However, developmental programming also offers a novel approach to prevent cardiovascular and related diseases through so-called Reprogramming: administration of appropriate or inhibition of deleterious perinatal factors in induced or genetic models ameliorated undesirable development that otherwise would inevitably have lead to more severe hypertension, cardiovascular and renal disease. A comprehensive overview of these studies suggests that, in analogy to what has been previously recognised in programming, many quite differ...
Combined cardiac and renal dysfunction has gained considerable attention. Hypotheses about its pa... more Combined cardiac and renal dysfunction has gained considerable attention. Hypotheses about its pathogenesis have been formulated, albeit based on a relatively small body of experimental studies, and a clinical classification system has been proposed. Cardiorenal syndrome, as presently defined, comprises a heterogeneous group of acute and chronic clinical conditions, in which the failure of one organ (heart or kidney) initiates or aggravates failure of the other. This conceptual framework, however, has two major drawbacks: the first is that, despite worldwide interest, universally accepted definitions of cardiorenal syndrome are lacking and characterization of heart and kidney failure is not uniform. This lack of consistency hampers experimental studies on mechanisms of the disease. The second is that, although progress has been made in developing hypotheses for the pathogenesis of cardiorenal syndrome, these initiatives are at an impasse. No hierarchy has been identified in the myriad of haemodynamic and non-haemodynamic factors mediating cardiorenal syndrome. This Review discusses current understanding of cardiorenal syndrome and provides a roadmap for further studies in this field. Ultimately, discussion of the definition and characterization issues and of the lack of organization among pathogenetic factors is hoped to contribute to further advancement of this complex field.
Hypoxia is an acknowledged pathway to renal injury and ischemia-reperfusion (I/R) and is known to... more Hypoxia is an acknowledged pathway to renal injury and ischemia-reperfusion (I/R) and is known to reduce renal oxygen tension (Po2). We hypothesized that renal I/R increases oxidative damage and induces mitochondrial uncoupling, resulting in increased oxygen consumption and hence kidney hypoxia. Lewis rats underwent syngenic renal transplantation (TX) and contralateral nephrectomy. Controls were uninephrectomized (1K-CON) or left untreated (2K-CON). After 7 days, urinary excretion of protein and thiobarbituric acid-reactive substances were measured, and after 14 days glomerular filtration rate (GFR), renal blood flow, whole kidney Qo2, cortical Po2, kidney cortex mitochondrial uncoupling, renal oxidative damage, and tubulointerstitial injury were assessed. TX, compared with 1K-CON, resulted in mitochondrial uncoupling mediated via uncoupling protein-2 (16 ± 3.3 vs. 0.9 ± 0.4 pmol O2 · s(-1)· mg protein(-1), P &amp;amp;lt; 0.05) and increased whole kidney Qo2 (55 ± 16 vs. 33 ± 10 μmol O2/min, P &amp;amp;lt; 0.05). Corticomedullary Po2 was lower in TX compared with 1K-CON (30 ± 13 vs. 47 ± 4 μM, P &amp;amp;lt; 0.05) whereas no significant difference was observed between 2K-CON and 1K-CON rats. Proteinuria, oxidative damage, and the tubulointerstitial injury score were not significantly different in 1K-CON and TX. Treatment of donors for 5 days with mito-TEMPO reduced mitochondrial uncoupling but did not affect renal hemodynamics, Qo2, Po2, or injury. Collectively, our results demonstrate increased mitochondrial uncoupling as an early event after experimental renal transplantation associated with increased oxygen consumption and kidney hypoxia in the absence of increases in markers of damage.
Mycophenolate mofetil (MMF) is now part of standard immunosuppression in the first phase after re... more Mycophenolate mofetil (MMF) is now part of standard immunosuppression in the first phase after renal transplantation. A relevant question is if it can replace drugs such as cyclosporine (CsA) in the maintenance treatment, improving cardiovascular risk profile. In 17 patients with a stable renal function (at least 6 months) posttransplantation, we studied the effect of CsA replacement by MMF. After starting MMF (1 g b.i.d.), CsA dosage was reduced from regular to low (median trough level 130 microg/L, respectively, 45 microg/L), followed by complete withdrawal, while prednisone (7.5 mg daily) was continued. We measured ambulatory blood pressure, glomerular filtration rate, renal plasma flow, renal vascular resistance, and metabolic factors at start and after 8 weeks on regular, low-dose CsA, respectively, no CsA with MMF and prednisone. Two patients dropped out after the switch to low-dose CsA/MMF, due to diarrhea in one and a steroid responsive rejection in the other. The complete switch from CsA to MMF was successful in all 15 patients and accompanied by a decrease in 24 hr systolic blood pressure (from 152+/-13 to 145+/-13 mmHg; P&lt;0.01), diastolic blood pressure (93+/-9 to 89+/-12 mmHg; P&lt;0.05), RVR (0.29+/-0.06 to 0.25+/-0.09 mmHg.ml/min; P&lt;0.05), and an increase in glomerular filtration rate (46.6+/-8.8 to 58.0+/-10.5 ml/min; P&lt;0.01) and renal plasma flow. Intermediate low density lipoprotein-cholesterol decreased (0.79+/-0.37 to 0.41+/-0.16 mmol/L; P&lt;0.01). High density lipoprotein-cholesterol decreased, but remained in the safe range. After 1 year two patients stopped the MMF; one because of Kaposi&#39;s sarcoma and one because of recurrent infections The stepwise switch from CsA to MMF was safe and mostly successful, and had beneficial effects on blood pressure, glomerular hemodynamics, and lipid profile. Beneficial trends were already present after partial withdrawal of CsA.
Oxidative stress contributes to the development of early transplant failure. As nitric oxide synt... more Oxidative stress contributes to the development of early transplant failure. As nitric oxide synthases (NOS) can act as sources of superoxide, we investigated the effect of the NOS cofactor tetrahydrobiopterin (BH 4 ) on oxyradical production and early rejection in a rat kidney transplantation model. Allograft transplantation (Brown Norway to Lewis) showed more renal superoxide production and monocyte infiltration when compared with isografts (Lewis to Lewis). Administration of the stable BH 4 precursor sepiapterin had no effect on superoxide production in the isografts (51±10 vs. 69±17 cps/10 mg protein), but led to a marked decrease in superoxide production in the allografts (116±11 vs. 60±6 cps/10 mg protein; P<0.05) and was accompanied by a reduction in periarterial macrophage infiltration (3.3±0.7 vs. 1.3±0.3 cells/vessel; P<0.05) and an increase in NO production (78±22 vs. 173±12 AU/g kidney) (P<0.01). In vitro experiments confirm that iNOS can produce superoxide mainly from the heme domain, whereas BH 4 administration can reverse this superoxide production in the presence of adequate anti-oxidant defense. Our findings support the hypothesis that BH 4 can be used to modulate the function of the inflammatory iNOS isoform and suggest a potential therapeutic role for sepiapterin in early allograft rejection.
ResultsSHRSP invariably developed cerebral edema in 30 days (range, 8 to 54 days). At this point... more ResultsSHRSP invariably developed cerebral edema in 30 days (range, 8 to 54 days). At this point neurological signs were absent in 16 of 23 rats. SBP rose until 1 week before detection of cerebral edema, and then stabilized at approximately 265 mm Hg. Proteinuria ...
Stroke-prone spontaneously hypertensive rats (SHRSP), subjected to high NaCl intake, show severe ... more Stroke-prone spontaneously hypertensive rats (SHRSP), subjected to high NaCl intake, show severe hypertension, organ damage, and early death. Preventive treatment with an angiotensin-converting enzyme (ACE) inhibitor is known to reduce mortality. Previously we found that proteinuria always precedes cerebral edema in SHRSP. Hence, in this study ACE inhibition was started later, ie, directly after manifestation of either proteinuria or cerebral edema. SHRSP were subjected to 1% NaCl intake. Group 1 served as a control. In group 2 early-onset treatment with the ACE inhibitor enalapril was initiated after proteinuria was &gt;40 mg/d. In group 3 late-onset ACE inhibition was started after the first observation of cerebral edema with T2-weighted MRI. Cerebral edema was expressed as the percentage of pixels with an intensity above a defined threshold. In controls median survival was 54 days (range, 32 to 80 days) after start of salt loading. The terminal level of cerebral edema was 19.0+/-3.0%. Under early-onset enalapril, median survival increased to 320 days (range, 134 to 368 days; P&lt;0.01 versus group 1). Cerebral edema was prevented in all but 1 rat. Systolic blood pressure was slightly and transiently reduced at day 14. Proteinuria was markedly reduced (52+/-7 versus 190+/-46 mg/d in group 1 at day 7; P&lt;0.05). Under late-onset enalapril, median survival was 264 days (range, 154 to 319 days; P&lt;0.01 versus group 1). Cerebral edema decreased to baseline levels (9.6+/-2.9 at day 0 to 3.4+/-0.5% at day 3; (P&lt;0.05). Ultimately cerebral edema reoccurred in 6 of the 8 rats. SBP decreased slightly at day 7 only. Proteinuria decreased from 283+/-27 at day 0 to 116+/-22 mg/d at day 7 (P&lt;0.05). Complete remission of the original locus of cerebral edema was confirmed histologically. In SHRSP with proteinuria, treatment with an ACE inhibitor both prevented the development of cerebral edema and reduced manifest cerebral edema and proteinuria. Survival was markedly prolonged. These findings support the use of ACE inhibition for treatment in hypertensive encephalopathy.
Lipoprotem phospholipid composition and LCAT activity in nephrotic and analbuminemic rats. Albumi... more Lipoprotem phospholipid composition and LCAT activity in nephrotic and analbuminemic rats. Albumin is an acceptor of lysophosphatidylcholine (LPC), product of the lecithin:cholesterol acyl transferase (LCAT) reaction, and it has been suggested that low LCAT activity and reduced cholesterol esterification rate in patients with the nephrotic syndrome may be linked to depletion of albumin. Effects of low plasma albumin levels on LCAT activity, cholesterol esterification rates and LPC-binding were therefore studied in hyperlipidemic nephrotic (NS) and analbuminemic (NAR) rats. LPC-binding was also measured in normoalbuminemic rats with dietary hypercholesterolemia. Remarkably, LCAT activity, measured with excess exogenous substrate, was not decreased but increased in both NAR and NS rats. Molar esterification rates with endogenous substrate were increased in NAR but normal in NS rats. In normoalbuminemic rats, with or without hypercholesterolemia, LPC was primarily found in the lipoprotein-deficient plasma and the HDL3 fraction. In NAR and NS rats LPC levels were increased in lipoproteins (notably in LDL and HDL2), but, in marked contrast to normoalbuminemic rats, decreased in lipoprotein-deficient plasma. Phosphatidylcholine, quantitatively the major phospholipid, was distributed proportionally over the lipoproteins in NS, NAR and control rats. Therefore, in hypoalbuminemia and analbuminemia LPC is mainly bound to lipoproteins, which is in contrast to the paucity of LPC in these particles in normoalbuminemic rats. Cholesterol esterification in nephrotic plasma is thus not impaired by lack of an acceptor for LPC-binding. The absence of an increase in molar cholesterol esterification in conjunction with increased LCAT activity points to a possible defect of the substrate for this reaction in nephrotic plasma. Increased LPC levels in LDL, a characteristic of oxidized LDL, may be a hitherto unrecognized atherosclerotic risk factor in the nephrotic syndrome.
Proteinuria, lipoproteins and renal apolipoprotein deposits in uninephrectomized female analbumin... more Proteinuria, lipoproteins and renal apolipoprotein deposits in uninephrectomized female analbuminemic rats. To elucidate the pathogenetic role of hyperlipidemia per se in the development of glomeruloscierosis, severely hyperlipidemic female analbuminemic rats (NAR) and mildly hyperlipidemic male NAR were studied for a period of 37 weeks after uninephrectomy (UNX). Plasma cholesterol increased from 6.3 0.4 (week 4) to 11.9 0.6 mmol/liter (week 37) in the 9 NAR, and from 4.3 0.1 to 6.4 0.5 mmol/liter in the 3 NAR in the same period. Plasma protein concentration was also consistently higher in 9 NAR (60 1 g/liter) as compared to 3 NAR (52 1 g/liter). Plasma viscosity was higher in 9 NAR than in 3 NAR, but there were no differences in blood viscosity. Proteinuria increased progressively in the UNX 9 NAR from 25 weeks after surgery, reaching a final value of 141 37 mg/day. No proteinuria occurred in the UNX 6 NAR (final value 15 2 mg/day). Glomerular capillary pressure, measured prior to the onset of proteinuria, was not significantly different in UNX 9 NAR and UNX 6 NAR. At the end of the study glomerulosclerosis and lipid deposition was only found in the UNX 9 NAR. Throughout the study hyperfiltration and hyperperfusion, relative to the one-kidney clearances of the sham-operated (2K) animals, were not different in UNX 6 and 9 NAR. No differences were observed in blood pressure. Hypertrophy, evaluated by glomerular diameters, was less pronounced in UNX 9 NAR (174 3 jim) than in UNX 6 NAR (190 7 jim). Glomerular diameters in 2K 9 and 6 NAR were similar (respectively 158 2 and 157 4 jim). Plasma apo B levels were similar (2K 9 NAR: 204 8 U; 2K 6 NAR 204 13 U), but cholesterol and triglyceride content of apo B-containing lipoproteins, namely VLDL, IDL and LDL, was increased twofold in the 9 NAR as compared to the 6 NAR, implying a larger particle size in the 9 NAR. Deposition of apo B and apo E was observed in the glomerular mesangium of UNX 9 NAR, particularly in sclerotic lesions. Glomerular apo A-I deposits were localized primarily in visceral epithelial cells and were not associated with sclerotic lesions. The development of proteinuria and glomerulosclerosis after UNX in 9 NAR but not in 6 NAR may depend upon differences in plasma lipoprotein composition, but is apparently not related to differences in whole kidney hyperfiltration and hyperperfusion, glomerular capillary pressure, or blood viscosity.
Connective tissue growth factor (CTGF; CCN2) plays a role in the development of diabetic nephropa... more Connective tissue growth factor (CTGF; CCN2) plays a role in the development of diabetic nephropathy (DN). Urinary CTGF (uCTGF) is elevated in DN patients and has been proposed as a biomarker for disease progression, but it is unknown which pathophysiological factors contribute to elevated uCTGF. We studied renal handling of CTGF by infusion of recombinant CTGF in diabetic mice. In addition, uCTGF was measured in type 1 DN patients and compared with glomerular and tubular dysfunction and damage markers. In diabetic mice, uCTGF was increased and fractional excretion (FE) of recombinant CTGF was substantially elevated indicating reduced tubular reabsorption. FE of recombinant CTGF correlated with excretion of endogenous CTGF. CTGF mRNA was mainly localized in glomeruli and medullary tubules. Comparison of FE of endogenous and recombinant CTGF indicated that 60% of uCTGF had a direct renal source, while 40% originated from plasma CTGF. In DN patients, uCTGF was independently associated with markers of proximal and distal tubular dysfunction and damage. In conclusion, uCTGF in DN is elevated as a result of both increased local production and reduced reabsorption due to tubular dysfunction. We submit that uCTGF is a biomarker reflecting both glomerular and tubulointerstitial hallmarks of diabetic kidney disease.
Males are at greater risk for renal injury than females. This may relate to NOavailability becaus... more Males are at greater risk for renal injury than females. This may relate to NOavailability because female rats have higher renal endothelial NO synthase (NOS) levels. Previously, we found susceptibility to proteinuria induced by NOS inhibition in male as compared to female rats. Dyslipidemia and hypercholesterolemia dosedependently decreased renal NOS activity and caused renal injury in female rats. We hypothesized that exposure of male rats to hypercholesterolemia would lead to more renal injury in male than in female rats, due to an a priori lower renal NO-system. Female and male rats were fed no, low-dose, or high-dose cholesterol for 24 weeks.
In fawn-hooded hypertensive (FHH) rats, a model of hypertension, impaired preglomerular resistanc... more In fawn-hooded hypertensive (FHH) rats, a model of hypertension, impaired preglomerular resistance, hyperfiltration, and progressive renal injury, we recently observed that supporting perinatal nitric oxide (NO) availability with the NO donor molsidomine persistently reduced blood pressure (BP) and ameliorated renal injury in male and female offspring. However, beneficial effects of perinatal molsidomine treatment were more pronounced in female than in male FHH rats. To evaluate whether such protective effects could also be achieved with micronutrients, and whether the gender-dependent differences could be confirmed, we tested perinatal exposure to the micronutrients L-arginine, taurine, vitamin C, and vitamin E (ATCE) in FHH rats. Perinatal micronutrients increased urinary NO metabolite, sodium and potassium excretion only at 4 weeks of age, i.e., at the end of treatment. From 12 weeks onwards, control males had a significantly higher systolic BP (SBP) than females (P &amp;amp;lt; 0.01); however after perinatal micronutrients, this difference was no longer present, indicating a pronounced antihypertensive effect of perinatal micronutrients in males (interaction P &amp;amp;lt; 0.001). Development of proteinuria was attenuated by perinatal micronutrients in males and females. However, only females showed reduced glomerular filtration rate, filtration fraction, and glomerulosclerosis (GS) after perinatal micronutrients. In sum, perinatal micronutrients that enhance NO availability ameliorated development of hypertension and proteinuria in FHH rats. Antihypertensive effects were more pronounced in male FHH offspring, whereas renal protective effects were more pronounced in female FHH offspring. Mechanisms underlying gender-specific consequences of perinatal micronutrients require further study.
Limiting enteric sodium absorption is an attractive option when renal sodium excretion is disturb... more Limiting enteric sodium absorption is an attractive option when renal sodium excretion is disturbed. An effective approach in the gut appears to be inhibition of the electroneutral Na(+)/H(+) exchangers (NHE), in particular NHE3. Recently, fluid retention, blood pressure and target organ injury were limited in rats with cardiorenal syndrome when treated with the NHE3 inhibitor tenapanor. The downside was that the osmotic fecal load leads to watery feces. Tenapanor also induced marked reductions in enteric phosphorus absorption in rats with cardiorenal syndrome on a high phosphorus intake and resulted in marked reductions in renal injury and practically prevented vascular calcification. We have yet to discover the clinical relevance in volume terms and vascular calcifications in patients in relation to the tolerated dose. However, even if the tenapanor-induced reduction in sodium adsorption is limited in humins, combination of tenapanor therapy with diuretics may be an interesting op...
Journal of the American Society of Nephrology : JASN, 2001
Chronic nitric oxide (NO) synthase inhibition in rats causes hypertension, renal vascular injury,... more Chronic nitric oxide (NO) synthase inhibition in rats causes hypertension, renal vascular injury, and proteinuria. NO deficiency increases superoxide (O(2)(-)) activity, but the effects of antioxidant treatment on renal injury have not been studied in this model. Exposure of rats to N omega-nitro-L-arginine (L-NNA) for 4 d markedly decreased NO-dependent relaxation in aortic rings and increased glomerular and renal interstitial monocyte influx, but renal O(2)(-) activity was not increased. After 7 d, BP and proteinuria were significantly increased. After 21 d of L-NNA treatment, rats displayed severe hypertension, decreased GFR, marked proteinuria, glomerular ischemia, renal vascular and tubulointerstitial injury, and complete loss of NO-dependent relaxation. Renal O(2)(-) activity was markedly increased [lucigenin-enhanced chemiluminescence (LEC), 279 +/- 71 versus 50 +/- 7 counts/10 mg, P < 0.01; electron paramagnetic resonance spectroscopy, 0.57 +/- 0.05 versus 0.34 +/- 0.04 U...
Journal of the American Society of Nephrology : JASN, 2001
Recovery from ischemia/reperfusion and immune-mediated injury in the renal transplant is associat... more Recovery from ischemia/reperfusion and immune-mediated injury in the renal transplant is associated with reduced renal hemodynamics and increased leukocyte infiltration. In diverse models of renal failure, L-arginine supplementation improved hemodynamics and reduced inflammation. However in a proinflammatory environment, L-arginine can worsen renal injury. This study investigated the therapeutic potential of L-arginine supplementation in allogeneic renal transplantation: Brown Norway rat kidneys were transplanted into Lewis rat recipients, with one native kidney remaining. Recipients received low-dose cyclosporin A (2.5 mg/kg per d subcutaneously) to obtain moderate vascular and interstitial rejection, with or without 1% L-arginine in drinking water for 7 d posttransplantation. Transplantation increased renal vasoconstriction (from 16.9 +/- 1.33 to 35.1 +/- 8.6 units; P: < 0.01), thereby reducing GFR (from 0.96 +/- 0.09 to 0.48 +/- 0.10 ml/min; P: < 0.05). Treatment with L-arg...
Journal of the American Society of Nephrology : JASN, 2000
Hyperlipidemia in conjunction with uninephrectomy leads to renal injury in rats. It is unknown wh... more Hyperlipidemia in conjunction with uninephrectomy leads to renal injury in rats. It is unknown whether this is due to mesangial cell or podocyte injury and whether the injuries induced by hypercholesterolemia and hypertriglyceridemia share a similar pathogenesis. Therefore, renal effects of hypercholesterolemia were studied in male rats with dietary hypercholesterolemia compared with rats on a regular diet. Renal effects of hypertriglyceridemia were studied in female Nagase analbuminemic rats (NAR). Hypertriglyceridemia was reduced in NAR by ovariectomy. Both models were studied after uninephrectomy or sham operation. Dietary hypercholesterolemia had little effect on plasma triglycerides, whereas ovariectomy in the NAR had no effect on plasma cholesterol. However, an increase in intermediate density lipoprotein cholesterol was common to both models. Dietary hypercholesterolemia and uninephrectomy separately induced a similar increase in proteinuria after 13 wk, which was additive wh...
Journal of the American Society of Nephrology : JASN, 1998
Unopposed actions of vasoconstrictors, such as angiotensin, play an important role in the effects... more Unopposed actions of vasoconstrictors, such as angiotensin, play an important role in the effects of chronic nitric oxide synthase (NOS) inhibition. In this study, it is hypothesized that endothelin (ET), another important vasoconstrictor, may also play a role in the development of hypertension and renal lesions during chronic NOS inhibition. The ET(A) receptor was blocked with A-127722 during chronic NOS inhibition with Nomega-nitro-L-arginine (L-NNA), a potent NOS inhibitor without antimuscarinic action. Male Sprague Dawley rats were treated for 3 wk with L-NNA (40 mg/kg per d), L-NNA (40 mg/kg per d) + A-127722 (30 mg/kg per d), or remained untreated (control). In preliminary experiments, L-NNA (40 mg/kg per d) had been found to cause the maximum increase of systolic BP and a 35% decrease in renal NOS activity. Three weeks of L-NNA treatment resulted in a marked rise in systolic BP (240+/-4 versus control 151+/-7 mmHg; P < 0.01), proteinuria (209+/-46 versus control 27+/-3 mg/...
Journal of the American Society of Nephrology : JASN, 1997
Estrogen replacement therapy is considered antiatherosclerotic because it reduces LDL cholesterol... more Estrogen replacement therapy is considered antiatherosclerotic because it reduces LDL cholesterol and fibrinogen and increases HDL cholesterol concentrations. However, exogenous estrogen is also known to increase hepatic triglyceride production. Hyperlipidemia in the nephrotic syndrome is probably due to increased lipoprotein secretion into plasma and decreased clearance of lipoprotein cholesterol and triglycerides. Previously, lipid-lowering effects of ovariectomy in analbuminemic rats were observed, suggesting that in the presence of hypoalbuminemia, estrogen replacement may have adverse effects on the lipid profile. To test this hypothesis, ovariectomized control rats and rats with Adriamycin-induced nephrotic syndrome were treated with estradiol. In ovariectomized controls, estradiol reduced plasma LDL cholesterol, apolipoprotein B, and fibrinogen and increased apolipoprotein A-I and triglycerides. Nephrotic rats were characterized by a marked decrease in plasma colloid osmotic ...
Best practice & research. Clinical endocrinology & metabolism, 2012
According to the Developmental Origins of Health and Disease hypothesis intrauterine or postnatal... more According to the Developmental Origins of Health and Disease hypothesis intrauterine or postnatal adaptations to the environment causes morphologic, physiologic or metabolic changes that influence health later in life. These adaptations seem to be carried out through structural, functional and epigenetic modifications. Multiple animal models of cardiovascular programming have been developed, and a brief overview of well-known models and mechanisms is presented. However, developmental programming also offers a novel approach to prevent cardiovascular and related diseases through so-called Reprogramming: administration of appropriate or inhibition of deleterious perinatal factors in induced or genetic models ameliorated undesirable development that otherwise would inevitably have lead to more severe hypertension, cardiovascular and renal disease. A comprehensive overview of these studies suggests that, in analogy to what has been previously recognised in programming, many quite differ...
Combined cardiac and renal dysfunction has gained considerable attention. Hypotheses about its pa... more Combined cardiac and renal dysfunction has gained considerable attention. Hypotheses about its pathogenesis have been formulated, albeit based on a relatively small body of experimental studies, and a clinical classification system has been proposed. Cardiorenal syndrome, as presently defined, comprises a heterogeneous group of acute and chronic clinical conditions, in which the failure of one organ (heart or kidney) initiates or aggravates failure of the other. This conceptual framework, however, has two major drawbacks: the first is that, despite worldwide interest, universally accepted definitions of cardiorenal syndrome are lacking and characterization of heart and kidney failure is not uniform. This lack of consistency hampers experimental studies on mechanisms of the disease. The second is that, although progress has been made in developing hypotheses for the pathogenesis of cardiorenal syndrome, these initiatives are at an impasse. No hierarchy has been identified in the myriad of haemodynamic and non-haemodynamic factors mediating cardiorenal syndrome. This Review discusses current understanding of cardiorenal syndrome and provides a roadmap for further studies in this field. Ultimately, discussion of the definition and characterization issues and of the lack of organization among pathogenetic factors is hoped to contribute to further advancement of this complex field.
Hypoxia is an acknowledged pathway to renal injury and ischemia-reperfusion (I/R) and is known to... more Hypoxia is an acknowledged pathway to renal injury and ischemia-reperfusion (I/R) and is known to reduce renal oxygen tension (Po2). We hypothesized that renal I/R increases oxidative damage and induces mitochondrial uncoupling, resulting in increased oxygen consumption and hence kidney hypoxia. Lewis rats underwent syngenic renal transplantation (TX) and contralateral nephrectomy. Controls were uninephrectomized (1K-CON) or left untreated (2K-CON). After 7 days, urinary excretion of protein and thiobarbituric acid-reactive substances were measured, and after 14 days glomerular filtration rate (GFR), renal blood flow, whole kidney Qo2, cortical Po2, kidney cortex mitochondrial uncoupling, renal oxidative damage, and tubulointerstitial injury were assessed. TX, compared with 1K-CON, resulted in mitochondrial uncoupling mediated via uncoupling protein-2 (16 ± 3.3 vs. 0.9 ± 0.4 pmol O2 · s(-1)· mg protein(-1), P &amp;amp;lt; 0.05) and increased whole kidney Qo2 (55 ± 16 vs. 33 ± 10 μmol O2/min, P &amp;amp;lt; 0.05). Corticomedullary Po2 was lower in TX compared with 1K-CON (30 ± 13 vs. 47 ± 4 μM, P &amp;amp;lt; 0.05) whereas no significant difference was observed between 2K-CON and 1K-CON rats. Proteinuria, oxidative damage, and the tubulointerstitial injury score were not significantly different in 1K-CON and TX. Treatment of donors for 5 days with mito-TEMPO reduced mitochondrial uncoupling but did not affect renal hemodynamics, Qo2, Po2, or injury. Collectively, our results demonstrate increased mitochondrial uncoupling as an early event after experimental renal transplantation associated with increased oxygen consumption and kidney hypoxia in the absence of increases in markers of damage.
Mycophenolate mofetil (MMF) is now part of standard immunosuppression in the first phase after re... more Mycophenolate mofetil (MMF) is now part of standard immunosuppression in the first phase after renal transplantation. A relevant question is if it can replace drugs such as cyclosporine (CsA) in the maintenance treatment, improving cardiovascular risk profile. In 17 patients with a stable renal function (at least 6 months) posttransplantation, we studied the effect of CsA replacement by MMF. After starting MMF (1 g b.i.d.), CsA dosage was reduced from regular to low (median trough level 130 microg/L, respectively, 45 microg/L), followed by complete withdrawal, while prednisone (7.5 mg daily) was continued. We measured ambulatory blood pressure, glomerular filtration rate, renal plasma flow, renal vascular resistance, and metabolic factors at start and after 8 weeks on regular, low-dose CsA, respectively, no CsA with MMF and prednisone. Two patients dropped out after the switch to low-dose CsA/MMF, due to diarrhea in one and a steroid responsive rejection in the other. The complete switch from CsA to MMF was successful in all 15 patients and accompanied by a decrease in 24 hr systolic blood pressure (from 152+/-13 to 145+/-13 mmHg; P&lt;0.01), diastolic blood pressure (93+/-9 to 89+/-12 mmHg; P&lt;0.05), RVR (0.29+/-0.06 to 0.25+/-0.09 mmHg.ml/min; P&lt;0.05), and an increase in glomerular filtration rate (46.6+/-8.8 to 58.0+/-10.5 ml/min; P&lt;0.01) and renal plasma flow. Intermediate low density lipoprotein-cholesterol decreased (0.79+/-0.37 to 0.41+/-0.16 mmol/L; P&lt;0.01). High density lipoprotein-cholesterol decreased, but remained in the safe range. After 1 year two patients stopped the MMF; one because of Kaposi&#39;s sarcoma and one because of recurrent infections The stepwise switch from CsA to MMF was safe and mostly successful, and had beneficial effects on blood pressure, glomerular hemodynamics, and lipid profile. Beneficial trends were already present after partial withdrawal of CsA.
Oxidative stress contributes to the development of early transplant failure. As nitric oxide synt... more Oxidative stress contributes to the development of early transplant failure. As nitric oxide synthases (NOS) can act as sources of superoxide, we investigated the effect of the NOS cofactor tetrahydrobiopterin (BH 4 ) on oxyradical production and early rejection in a rat kidney transplantation model. Allograft transplantation (Brown Norway to Lewis) showed more renal superoxide production and monocyte infiltration when compared with isografts (Lewis to Lewis). Administration of the stable BH 4 precursor sepiapterin had no effect on superoxide production in the isografts (51±10 vs. 69±17 cps/10 mg protein), but led to a marked decrease in superoxide production in the allografts (116±11 vs. 60±6 cps/10 mg protein; P<0.05) and was accompanied by a reduction in periarterial macrophage infiltration (3.3±0.7 vs. 1.3±0.3 cells/vessel; P<0.05) and an increase in NO production (78±22 vs. 173±12 AU/g kidney) (P<0.01). In vitro experiments confirm that iNOS can produce superoxide mainly from the heme domain, whereas BH 4 administration can reverse this superoxide production in the presence of adequate anti-oxidant defense. Our findings support the hypothesis that BH 4 can be used to modulate the function of the inflammatory iNOS isoform and suggest a potential therapeutic role for sepiapterin in early allograft rejection.
ResultsSHRSP invariably developed cerebral edema in 30 days (range, 8 to 54 days). At this point... more ResultsSHRSP invariably developed cerebral edema in 30 days (range, 8 to 54 days). At this point neurological signs were absent in 16 of 23 rats. SBP rose until 1 week before detection of cerebral edema, and then stabilized at approximately 265 mm Hg. Proteinuria ...
Stroke-prone spontaneously hypertensive rats (SHRSP), subjected to high NaCl intake, show severe ... more Stroke-prone spontaneously hypertensive rats (SHRSP), subjected to high NaCl intake, show severe hypertension, organ damage, and early death. Preventive treatment with an angiotensin-converting enzyme (ACE) inhibitor is known to reduce mortality. Previously we found that proteinuria always precedes cerebral edema in SHRSP. Hence, in this study ACE inhibition was started later, ie, directly after manifestation of either proteinuria or cerebral edema. SHRSP were subjected to 1% NaCl intake. Group 1 served as a control. In group 2 early-onset treatment with the ACE inhibitor enalapril was initiated after proteinuria was &gt;40 mg/d. In group 3 late-onset ACE inhibition was started after the first observation of cerebral edema with T2-weighted MRI. Cerebral edema was expressed as the percentage of pixels with an intensity above a defined threshold. In controls median survival was 54 days (range, 32 to 80 days) after start of salt loading. The terminal level of cerebral edema was 19.0+/-3.0%. Under early-onset enalapril, median survival increased to 320 days (range, 134 to 368 days; P&lt;0.01 versus group 1). Cerebral edema was prevented in all but 1 rat. Systolic blood pressure was slightly and transiently reduced at day 14. Proteinuria was markedly reduced (52+/-7 versus 190+/-46 mg/d in group 1 at day 7; P&lt;0.05). Under late-onset enalapril, median survival was 264 days (range, 154 to 319 days; P&lt;0.01 versus group 1). Cerebral edema decreased to baseline levels (9.6+/-2.9 at day 0 to 3.4+/-0.5% at day 3; (P&lt;0.05). Ultimately cerebral edema reoccurred in 6 of the 8 rats. SBP decreased slightly at day 7 only. Proteinuria decreased from 283+/-27 at day 0 to 116+/-22 mg/d at day 7 (P&lt;0.05). Complete remission of the original locus of cerebral edema was confirmed histologically. In SHRSP with proteinuria, treatment with an ACE inhibitor both prevented the development of cerebral edema and reduced manifest cerebral edema and proteinuria. Survival was markedly prolonged. These findings support the use of ACE inhibition for treatment in hypertensive encephalopathy.
Uploads
Papers by Jaap A. Joles