Mitochondrial Bionergetics

The permeability transition pores (PTPs) are a large channel of the mitochondrial inner membrane, the opening of which is the central event in many types of stress-induced cell death. PTP opening is induced by elevated concentrations of mitochondrial calcium. It has been demonstrated that spermine and other polyamines can delay calcium-induced swelling of isolated mitochondria, suggesting their role as inhibitors of the mitochondrial PTP. Here we further investigated the mechanism by which spermine inhibits the calcium-induced, cyclosporine A (CSA) — sensitive PTP by using three indicators: 1) calcium release from the mitochondria detected with calcium green, 2) mitochondrial membrane depolarization using TMRM, and 3) mitochondrial swelling by measuring light absorbance. We found that despite calcium release and membrane depolarization, indicative of PTP activation, mitochondria underwent only partial swelling in the presence of spermine. This was in striking contrast to the high-amplitude swelling detected in control mitochondria and in mitochondria treated with the PTP inhibitor CSA. We conclude that spermine selectively prevents opening of the high-conductance state, while allowing activation of the lower conductance state of the PTP. We propose that the existence of lower conductance, stress-induced PTP might play an important physiological role, as it is expected to allow the release of toxic levels of calcium, while keeping important molecules (e.g., NAD) within the mitochondrial matrix. http://www.sciencedirect.com/science/article/pii/S0005272814006318

Brain hexokinase is associated with the outer membrane of mitochondria, and its activity has been implicated in the regulation of ATP synthesis and apoptosis. Reactive oxygen species (ROS) are by-products of the electron transport chain in mitochondria. Here we show that the ADP produced by hexokinase activity in rat brain mitochondria (mt-hexokinase) controls both membrane potential (m) and ROS generation. Exposing control mitochondria to glucose increased the rate of oxygen consumption and reduced the rate of hydrogen peroxide generation. Mitochondrial associated hexoki-nase activity also regulated m , because glucose stabilized low m values in state 3. Interestingly, the addition of glucose 6-phosphate significantly reduced the time of state 3 persistence, leading to an increase in the m and in H 2 O 2 generation. The glucose analogue 2-de-oxyglucose completely impaired H 2 O 2 formation in state 3-state 4 transition. In sharp contrast, the mt-hexoki-nase-depleted mitochondria were, in all the above mentioned experiments, insensitive to glucose addition, indicating that the mt-hexokinase activity is pivotal in the homeostasis of the physiological functions of mitochon-dria. When mt-hexokinase-depleted mitochondria were incubated with exogenous yeast hexokinase, which is not able to bind to mitochondria, the rate of H 2 O 2 generation reached levels similar to those exhibited by control mitochondria only when an excess of 10-fold more enzyme activity was supplemented. Hyperglycemia induced in embryonic rat brain cortical neurons increased ROS production due to a rise in the intracellu-lar glucose 6-phosphate levels, which were decreased by the inclusion of 2-deoxyglucose, N-acetyl cysteine, or carbonyl cyanide p-trifluoromethoxyphenylhydrazone. Taken together, the results presented here indicate for the first time that mt-hexokinase activity performed a key role as a preventive antioxidant against oxidative stress, reducing mitochondrial ROS generation through an ADP-recycling mechanism.

High Altitude Pulmonary Edema (HAPE) is a threatening disorder caused due to acute exposure to high
altitude above 3000m. Apart from multiple factors involved, the genetic factors also play an important
function in the pathogenesis of HAPE. This study aims to evaluate the role of mtDNA polymorphism
and their association with haplogroup in understanding the etiology of HAPE. In this study, all the
HAPE susceptible and acclimatized control subjects could be classifed into nine haplogroups pertaining
mostly to Macrohaplogroup M and U. The frequency of haplogroup M was signifcantly higher in HAPE
susceptibles whereas the haplogroup M33a2′3 was found only in HAPE susceptibles. The variant
G4491A and A4944G of MT-ND2, A14002G of MT-ND5, and C8562T of MT-ATP8, were defnition site of
haplogroup M33a2′3. The frequency of A10398G of MT-ND3, A8701G of MT-ATP6 and C14766T of MTCYB
genes were signifcantly higher in HAPE susceptibles. mtDNA copy number also plays a signifcant
synergistic role in HAPE susceptibility. Our fndings suggests that variants in MT-ND2 and MT-ND5 were
predicted to confer decreased protein stability in HAPE susceptibles and in particular, highly conserved
variants G4491A, A4944G and A14002G associated with haplogroup M33a2′3 may be the primary cause
of susceptibility to HAPE in Indian male lowlanders.

Insulin resistance is defined as a reduced ability of insulin to stimulate glucose utilization. C57BL/6 mice fed with a high-fat diet (HFD) are a model of insulin resistance. In skeletal muscle, hydrogen peroxide (H 2 O 2 ) produced by NADPH oxidase 2 (NOX2) is involved in signaling pathways triggered by insulin. We evaluated oxidative status in skeletal muscle fibers from insulin-resistant and control mice by determining H 2 O 2 generation (HyPer probe), reduced-to-oxidized glutathione ratio and NOX2 expression. After eight weeks of HFD, insulin-dependent glucose uptake was impaired in skeletal muscle fibers when compared with control muscle fibers. Insulin-resistant mice showed increased insulin-stimulated H 2 O 2 release and decreased reduced-to-oxidized glutathione ratio (GSH/GSSG). In addition, p47 phox and gp91 phox (NOX2 subunits) mRNA levels were OPEN ACCESS

Recent evidence highlights that the cancer cell energy requirements vary greatly from normal cells and that cancer cells exhibit different metabolic phenotypes with variable participation of both glycolysis and oxidative phosphorylation. NADH–ubiquinone oxidoreductase (Complex I) is the largest complex of the mitochondrial electron transport chain and contributes about 40% of the proton motive force required for mitochon-drial ATP synthesis. In addition, Complex I plays an essential role in biosynthesis and redox control during proliferation, resistance to cell death, and metastasis of cancer cells. Although knowledge about the structure and assembly of Complex I is increasing, information about the role of Complex I subunits in tumorigenesis is scarce and contradictory. Several small molecule inhibitors of Complex I have been described as selective anticancer agents; however, pharmacologic and genetic interventions on Complex I have also shown pro-tumorigenic actions, involving different cellular signaling. Here, we discuss the role of Complex I in tumorigenesis, focusing on the specific participation of Complex I subunits in proliferation and metastasis of cancer cells.

Lactate, the conjugate base of lactic acid occurring in aqueous biological fluids, has been derided as a “dead-end” waste product of anaerobic metabolism. Catalyzed by the near-equilibrium enzyme lactate dehydrogenase (LDH), the reduction of pyruvate to lactate is thought to serve to regenerate the NAD+ necessary for continued glycolytic flux. Reaction kinetics for LDH imply that lactate oxidation is rarely favored in the tissues of its own production. However, a substantial body of research directly contradicts any notion that LDH invariably operates unidirectionally in vivo. In the current Perspective, a model is forwarded in which the continuous formation and oxidation of lactate serves as a mitochondrial electron shuttle, whereby lactate generated in the cytosol of the cell is oxidized at the mitochondria of the same cell. From this perspective, an intracellular lactate shuttle operates much like the malate-aspartate shuttle (MAS); it is also proposed that the two shuttles are necessarily interconnected in a lactate-MAS. Among the requisite features of such a model, significant compartmentalization of LDH, much like the creatine kinase of the phosphocreatine shuttle, would facilitate net cellular lactate oxidation in a variety of cell types. http://journal.frontiersin.org/Journal/10.3389/fnins.2014.00366/abstract

Mitochondria provide cellular energy through oxidative phosphorylation, but as an integral part of this process, superoxides and other reactive
oxygen species (ROS) are also produced. When the balance between the production of free radicals and antioxidant capacity of the cardiac cells
altered, oxidative stress is induced. Oxidative stress has been linked to the development of ischemic heart disease, atherosclerosis, congestive heart
failure, ischemic-reperfusion injury, and vascular endothelial dysfunction. Although several clinical trials over the past decades employed different
strategies of antioxidants supplementation, the results were generally negative in the setting of chronic preventative therapy. Less attention has
been paid to the modulation of ROS production, despite the fact that prevention, rather than cure, would appear to be the logic approach to attenuate
the oxidative damage. There is increasing evidence that endogenous myocardial uncoupling proteins (UCPs) can play a vital role in regulating ROS
generation to protect against various pathogenic stresses. Their expression, which can be induced, may well be a potential therapeutic target for
various drugs to alleviate the harmful effects of pathogenic processes and hence modify the progression of cardiovascular diseases (CVDs).
Myocardial function depends on the energy that it is able to synthesize and transfer in the form of energy-rich energy for phosphate bonds to
fuel excitation-contraction coupling. More than 90% of cardiac cells energy is produced in the mitochondria from oxidative phosphorylation activity
[1]. Oxidative phosphorylation is the process by which energy from fuel oxidation is converted to the high-energy phosphate bonds of adenosine
triphosphate (ATP). The chemiosmotic hypothesis suggests that the ATP synthesis is provided by the electrochemical gradient across the inner
mitochondrial membrane. This electrochemical gradient is maintained by constituents of the electron transport chain (ETC), which acts to pump
protons from the mitochondrial matrix to the intermembrane space of the mitochondria as they accept and donate electrons in a prescribed manner
Figure. This process of electron transport and oxidative metabolism in cardiac cells are accompanied by the reduction of oxygen to superoxide and
other ROS which considered as a by-product of mitochondrial respiration.

High Altitude pulmonary edema (HApe) is a threatening disorder caused due to acute exposure to high altitude above 3000 m. Apart from multiple factors involved, the genetic factors also play an important function in the pathogenesis of HApe. this study aims to evaluate the role of mtDnA polymorphism and their association with haplogroup in understanding the etiology of HAPE. In this study, all the HAPE susceptible and acclimatized control subjects could be classified into nine haplogroups pertaining mostly to Macrohaplogroup M and U. The frequency of haplogroup M was significantly higher in HAPE susceptibles whereas the haplogroup M33a2′3 was found only in HAPE susceptibles. The variant G4491A and A4944G of MT-ND2, A14002G of MT-ND5, and C8562T of MT-ATP8, were definition site of haplogroup M33a2′3. The frequency of A10398G of MT-ND3, A8701G of MT-ATP6 and C14766T of MT-CYB genes were significantly higher in HAPE susceptibles. mtDNA copy number also plays a significant synergistic role in HAPE susceptibility. Our findings suggests that variants in MT-ND2 and MT-ND5 were predicted to confer decreased protein stability in HApe susceptibles and in particular, highly conserved variants G4491A, A4944G and A14002G associated with haplogroup M33a2′3 may be the primary cause of susceptibility to HAPE in Indian male lowlanders. Mitochondria are semiautonomous cytoplasmic organelles of the eukaryotic system that imparts essential functions in energy metabolism, free radical production, calcium homeostasis and apoptosis 1-3. In humans, mitochondrial DNA (mtDNA) is the extranuclear circular molecule that spans 16,569 bp and encodes genes of 13 proteins, 2 rRNAs and 22 tRNAs, as well as 121 bp regulatory region (the D-Loop), all of which are components of the electron transport chain (ETC), and are essential for oxidative phosphorylation (OXPHOS) 4. The OXPHOS system has a mixed genetic origin, nuclear and mitochondrial. It consists of approximately 90 different structural protein subunits of which thirteen are encoded by the mtDNA in humans 5. The mitochondrial genome encode seven subunits of complex I, one subunit of complex III, three subunits of complex IV and two subunits of complex V 6. High altitude Pulmonary Edema (HAPE) is a life threatening, multifactorial complex disease condition which occurs due to rapid ascent to high altitude ̴ 3000 m above sea level, where the oxygen content in air is only 60% of that at sea level 7. Genetic predisposition to the disease is largely unknown, but it would be a function of gene environment interaction 8. The role of genetics in determining the individual's susceptibility to HAPE is unclear. Variants of some genes CYP11B2, ACE, EDN1(nuclear genes) were previously investigated for their association with HAPE 9. The pathophysiology of HAPE is attributed to several etiological factors like pulmonary

Although mitochondrial Ca 2þ overload and ROS production play a critical role in mitochondria-mediated cell death, a cause-effect relationship between them remains elusive. This study elucidated the crosstalk between mitochondrial swelling, ROS production, and electron transfer chain (ETC) supercomplexes in rat heart mitochondria in response to Ca 2þ and tert-butyl hydroperoxide (TBH), a lipid-soluble organic peroxide. Results showed that ROS production induced by TBH was significantly increased in the presence of Ca 2þ in a dose-dependent manner. TBH markedly inhibited the state 3 respiration rate with no effect on the mitochondrial swelling. Ca 2þ exerted a slight effect on mitochondrial respiration that was greatly aggravated by TBH. Analysis of supercomplexes revealed a minor difference in the presence of TBH and/or Ca 2þ. However, incubation of mitochondria in the presence of high Ca 2þ (1 mM) or inhibitors of ETC complexes (rotenone and antimycin A) induced disintegration of the main supercomplex, respi-rasome. Thus, PTP-dependent swelling of mitochondria solely depends on Ca 2þ but not ROS. TBH has no effect on the respirasome while Ca 2þ induces disintegration of the supercomplex only at a high concentration. Intactness of individual ETC complexes I and III is important for maintenance of the structural integrity of the respirasome.

A ligand stabilizes a mammalian mitochondrial cholesterol transporter, allowing highresolution structural analysis. SURESH KUMAR.S TSPO is organized into five transmembrane helices, which further associates into a homodimer.TSPO is found in mitochondrial membranes and mediates the import of cholesterol and porphyrins into mitochondria. Transport of porphyrins into mitochondria is energy-dependent, as expected for the movement of anions into a negatively charged environment.Heme , an endogenous porphyrin derivative, is an essential molecule in living aerobic organisms and plays a role in a variety of physiological processes such as oxygen transport, respiration, and signal transduction. For the biosynthesis of heme or the mitochondrial heme proteins, heme or its biosynthetic precursor porphyrin must be transported into mitochondria from cytosol.TSPO nano helical biostructures are possibly facilitating this by local confinement of phonon vibrational modes for enhanced dynamics and conformational kinetics.The homodimers with their non-covalent bonds are ideal candidates for polarisation state coupling in bioenergetic staes,in the presence of calcium ionic migration into mitochondria in active states of the respiratory chain.Calcium ionic coupling to endogenous elctromagnetic fields based on ionic molecules and chemical structures would imply non-linear excitonic media for phonon photon interactions.The optical range phonon modes would be able to couple to higher frequency photon fields even in the low and ultra low power presence in mitochondria linked to active states of respiratory chain and associated electronically excited molecular states.The energy field exchange enable long range signal communication for dynamical order in biosystems and optimised functionality based on nanoresonant nonlinear media,facilitated by protein electrostatics and endogenous emf in nanoconfined cavities.The porphyrins are ideal structures for photoeffects similar to quantum dots facilitating optical transitions and switching behaviour based on critical thresholds,which are important in optimal energy coupling.The charged patches exposed to the solvent might be important for interaction with proteins carrying endogenous TSPO ligands ,thus providing scope for non-molecular signalling based on ultra low and low power optical photons.There is a transduction principle in biosystems where external bulk signals are microscopically translated as calcium,which signals photonically,based on molecular optical signal interactions,in the presence of non-linear nanoresonant media,as is true.

High Altitude pulmonary edema (HApe) is a threatening disorder caused due to acute exposure to high altitude above 3000 m. Apart from multiple factors involved, the genetic factors also play an important function in the pathogenesis of HApe. this study aims to evaluate the role of mtDnA polymorphism and their association with haplogroup in understanding the etiology of HAPE. In this study, all the HAPE susceptible and acclimatized control subjects could be classified into nine haplogroups pertaining mostly to Macrohaplogroup M and U. The frequency of haplogroup M was significantly higher in HAPE susceptibles whereas the haplogroup M33a2′3 was found only in HAPE susceptibles. The variant G4491A and A4944G of MT-ND2, A14002G of MT-ND5, and C8562T of MT-ATP8, were definition site of haplogroup M33a2′3. The frequency of A10398G of MT-ND3, A8701G of MT-ATP6 and C14766T of MT-CYB genes were significantly higher in HAPE susceptibles. mtDNA copy number also plays a significant synergistic role in HAPE susceptibility. Our findings suggests that variants in MT-ND2 and MT-ND5 were predicted to confer decreased protein stability in HApe susceptibles and in particular, highly conserved variants G4491A, A4944G and A14002G associated with haplogroup M33a2′3 may be the primary cause of susceptibility to HAPE in Indian male lowlanders. Mitochondria are semiautonomous cytoplasmic organelles of the eukaryotic system that imparts essential functions in energy metabolism, free radical production, calcium homeostasis and apoptosis 1-3. In humans, mitochondrial DNA (mtDNA) is the extranuclear circular molecule that spans 16,569 bp and encodes genes of 13 proteins, 2 rRNAs and 22 tRNAs, as well as 121 bp regulatory region (the D-Loop), all of which are components of the electron transport chain (ETC), and are essential for oxidative phosphorylation (OXPHOS) 4. The OXPHOS system has a mixed genetic origin, nuclear and mitochondrial. It consists of approximately 90 different structural protein subunits of which thirteen are encoded by the mtDNA in humans 5. The mitochondrial genome encode seven subunits of complex I, one subunit of complex III, three subunits of complex IV and two subunits of complex V 6. High altitude Pulmonary Edema (HAPE) is a life threatening, multifactorial complex disease condition which occurs due to rapid ascent to high altitude ̴ 3000 m above sea level, where the oxygen content in air is only 60% of that at sea level 7. Genetic predisposition to the disease is largely unknown, but it would be a function of gene environment interaction 8. The role of genetics in determining the individual's susceptibility to HAPE is unclear. Variants of some genes CYP11B2, ACE, EDN1(nuclear genes) were previously investigated for their association with HAPE 9. The pathophysiology of HAPE is attributed to several etiological factors like pulmonary