Papers by Barbara Sahagan
Current opinion in investigational drugs (London, England : 2000), 2009
This review discusses current knowledge of the complex interactions between amyloid-beta (A beta)... more This review discusses current knowledge of the complex interactions between amyloid-beta (A beta) peptide, the receptor for advanced glycation endproducts (RAGE), and inflammatory mediators, focusing on the roles of such interactions in the pathogenesis of Alzheimer's disease. As a ubiquitous cell-surface receptor, RAGE demonstrates enhanced expression in an A beta-rich environment; the effects of RAGE on microglia, the blood-brain barrier and neurons are mediated through various signaling pathways. Relevant preclinical models illustrate that the A beta-RAGE interaction amplifies neuronal stress and the accumulation of A beta, impairs memory and learning, and exaggerates neuroinflammation. These findings suggest that RAGE may mediate a common proinflammatory pathway in neurodegenerative disorders.
The Biochemical journal, 1993
Activation of human platelets by the arachidonic acid metabolite thromboxane A2 and the thromboxa... more Activation of human platelets by the arachidonic acid metabolite thromboxane A2 and the thromboxane A2 mimic U46619 is mediated through phosphoinositide-specific phospholipase C-catalysed hydrolysis of phosphoinositides. We have established conditions to reconstitute U46619-stimulated phosphoinositide breakdown by addition of guanine nucleotides and soluble platelet phospholipase C activities to isolated 32P-labelled membranes. Receptor-activated phosphoinositide hydrolysis was observed in the presence of guanosine 5'-[gamma-thio]triphosphate (GTP[S]) or GTP plus U46619. Phosphoinositide hydrolysis was dependent on both GTP and U46619, with half-maximal stimulation observed at 5 microM and 500 nM respectively. Phospholipase C isoenzymes beta, gamma 1, gamma 2 and delta were purified from platelet cytosol and their ability to reconstitute GTP[S]-dependent and GTP/U46619-dependent phosphoinositide hydrolysis determined. Phospholipase C-beta and -delta, but not phospholipase C-gamm...
Journal of immunology (Baltimore, Md. : 1950), 1990
Chimeric immunoglobulin genes were constructed by fusing murine variable region exons to human co... more Chimeric immunoglobulin genes were constructed by fusing murine variable region exons to human constant region exons. The ultimate goal was to produce an antibody capable of escaping surveillance by the human immune system while retaining the tumor specificity of a murine monoclonal. The murine variable regions were isolated from the functionally expressed kappa and gamma 1 immunoglobulin genes of the murine hybridoma cell line B6.2, the secreted monoclonal antibody of which reacts with a surface antigen from human breast, lung, and colon carcinomas. The kappa and gamma 1 chain fusion genes were co-introduced into non-antibody producing murine myeloma cells by electroporation. Transfectants that produced murine/human chimeric antibody were obtained at high frequency as indicated by immunoblots probed with an antisera specific for human immunoglobulin. Enzyme-linked immunoabsorbent assay analysis demonstrated that this chimeric antibody was secreted from the myeloma cells and retained the ability to bind selectively to membrane prepared from human tumor cells. The chimeric immunoglobulin was also shown by indirect fluorescence microscopy to bind to intact human carcinoma cells with specificity expected of B6.2. The ability of chimeric antibody to recognize human tumor-associated antigen makes feasible a novel approach to cancer immunotherapy.
Haematology and blood transfusion, 1979
G 3 2~-~ RNA en in Pedersen and Haseltine, 1978 and diagrammed in ) involve specific cleavage of ... more G 3 2~-~ RNA en in Pedersen and Haseltine, 1978 and diagrammed in ) involve specific cleavage of a small amount of non-radioactive RNA after guanosine residues by ribonuclease Tl followed by 5'-32P-labelling of the Tl resistant oligonucleotides. The mixture of 5'-32P-labelled oligonucleotides is then fractionated by two-dimensional gel electrophoresis. By autoradiography of the gel these oligonucleotides will show a Pattern (termed a RNase Tl fingerprint) which is characteristic for each RNA sample. For further analysis the unique oligonucleotides can be eluted and their nucleotide sequence determined using recently developed methods for RNA sequencing that depend upon partial digestion of 5' end-labelled RNA with ribonucleases that cleave the RNA at specific nucleotides .
International Journal of Alzheimer's Disease, 2011
Background. Alzheimer's disease (AD) is a devastating neurological disorder and the main cause of... more Background. Alzheimer's disease (AD) is a devastating neurological disorder and the main cause of dementia in the elderly population worldwide. Adult neurogenesis appears to be upregulated very early in AD pathogenesis in response to some specific aggregates of beta-amyloid (Aβ) peptides, exhausting the neuronal stem cell pools in the brain. Previously, we characterized a conserved nonprotein-coding antisense transcript for β-secretase-1 (BACE1), a critical enzyme in AD pathophysiology. We showed that the BACE1-antisense transcript (BACE1-AS) is markedly upregulated in brain samples from AD patients and promotes the stability of the (sense) BACE1 transcript. In the current paper, we examine the relationship between BACE1, BACE1-AS, adult neurogenesis markers, and amyloid plaque formation in amyloid precursor protein (APP) transgenic mice (Tg-19959) of various ages. Results. Consistent with previous publications in other APP overexpressing mouse models, we found adult neurogenesis markers to be noticeably upregulated in Tg-19959 mice very early in the development of the disease. Knockdown of either one of BACE1 or BACE1-AS transcripts by continuous infusion of locked nucleic acid-(LNA-) modified siRNAs into the third ventricle over the period of two weeks caused concordant downregulation of both transcripts in Tg-19959 mice. Downregulation of BACE1 mRNA was followed by reduction of BACE1 protein and insoluble Aβ. Modulation of BACE1 and BACE1-AS transcripts also altered oligomeric Aβ aggregation pattern, which was in turn associated with an increase in neurogenesis markers at the RNA and protein level. Conclusion. We found alterations in the RNA and protein concentrations of several adult neurogenesis markers, as well as non-protein-coding BACE1-AS transcripts, in parallel with the course of β-amyloid synthesis and aggregation in the brain of Tg15999 mice. In addition, by knocking down BACE1 or BACE1-AS (thereby reducing Aβ production and plaque deposition), we were able to modulate expression of these neurogenesis markers. Our findings suggest a distortion of adult neurogenesis that is associated with Aβ production very early in amyloid pathogenesis. We believe that these alterations, at the molecular level, could prove useful as novel therapeutic targets and/or as early biomarkers of AD.
ChemInform, 2008
3. ChemInform Abstract ChemInform is a weekly Abstracting Service, delivering concise information... more 3. ChemInform Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full ...
Neurobiology of Aging, 2003
We have engineered transgenic Caenorhabditis elegans animals to inducibly express the human beta ... more We have engineered transgenic Caenorhabditis elegans animals to inducibly express the human beta amyloid peptide (A). Gene expression changes resulting from A induction have been monitored by cDNA hybridization to glass slide microarrays containing probes for almost all known or predicted C. elegans genes. Using statistical criteria, we have identified 67 up-regulated and 240 down-regulated genes. Subsets of these regulated genes have been tested and confirmed by quantitative RT-PCR. To investigate whether genes identified in this model system also show gene expression changes in Alzheimer's disease (AD) brain, we have also used quantitative RT-PCR to examine in post-mortem AD brain tissue transcript levels of ␣B-crystallin (CRYAB) and tumor necrosis factor-induced protein 1 (TNFAIP1), human homologs of genes found to be robustly induced in the transgenic C. elegans model. Both CRYAB and TNFAIP1 show increased transcript levels in AD brains, supporting the validity of this approach.
Nature Medicine, 2008
Recent transcriptomics efforts have revealed that numerous protein-coding messenger RNAs have nat... more Recent transcriptomics efforts have revealed that numerous protein-coding messenger RNAs have natural antisense transcript partners, most of which seem to be noncoding RNAs. Here we identify a conserved noncoding antisense transcript for β-secretase-1 (BACE1), a crucial enzyme in Alzheimer's disease pathophysiology. The BACE1-antisense transcript (BACE1-AS) regulates BACE1 mRNA and subsequently BACE1 protein expression in vitro and in vivo. It seems that the argument for concordant regulation can only be made in the experiments with the siRNA against BACE1-AS. This convention has been followed throughout the manuscript. Please check carefully.]. Upon exposure to various cell stressors including amyloid-β 1-42 (Aβ 1-42), expression of BACE1-AS becomes elevated, increasing BACE1 mRNA stability and generating additional Aβ 1-42 through a post-transcriptional feed-forward mechanism. BACE1-AS concentrations were elevated in subjects with Alzheimer's disease as well as in amyloid precursor protein transgenic mice. These data show that BACE1 mRNA expression is under the control of a regulatory noncoding RNA that may drive Alzheimer's disease-associated pathophysiology. In summary, we report that a long noncoding RNA is directly implicated in the increased abundance of Aβ 1-42 in Alzheimer's disease.
Mayo Clinic Proceedings, 2002
Cognitive vitality is essential to quality of life and survival in old age. With normal aging, co... more Cognitive vitality is essential to quality of life and survival in old age. With normal aging, cognitive changes such as slowed speed of processing are common, but there is substantial interindividual variability, and cognitive decline is clearly not inevitable. In this review, we focus on recent research investigating the association of various lifestyle factors and medical comorbidities with cognitive aging. Most of these factors are potentially modifiable or manageable, and some are protective. For example, animal and human studies suggest that lifelong learning, mental and physical exercise, continuing social engagement, stress reduction, and proper nutrition may be important factors in promoting cognitive vitality in aging. Manageable medical comorbidities, such as diabetes, hypertension, and hyperlipidemia, also contribute to cognitive decline in older persons. Other comorbidities such as smoking and excess alcohol intake may contribute to cognitive decline, and avoiding these activities may promote cognitive vitality in aging. Various therapeutics, including cognitive T he "longevity revolution" has increased the focus on many aspects of health in aging. The older population is growing rapidly, and individuals are typically living AAMI = age-associated memory impairment; AD = Alzheimer disease; apoE4 = apolipoprotein E4; BDNF = brain-derived neurotrophic factor; CREB = cyclic adenosine monophosphate response element binding protein; FDA = Food and Drug Administration; MCI = mild cognitive impairment; MMSE = Mini-Mental State Examination; MRI = magnetic resonance imaging; NGF = nerve growth factor; NSAID = nonsteroidal anti-inflammatory drug; PET = positron emission tomography; SPECT = single-photon emission computed tomography enhancers and protective agents such as antioxidants and anti-inflammatories, may eventually prove useful as adjuncts for the prevention and treatment of cognitive decline with aging. The data presented in this review should interest physicians who provide preventive care management to middle-aged and older individuals who seek to maintain cognitive vitality with aging.
Journal of Molecular Biology, 1979
Journal of Experimental Medicine, 1998
Chemokines are essential mediators of normal leukocyte trafficking as well as of leukocyte recrui... more Chemokines are essential mediators of normal leukocyte trafficking as well as of leukocyte recruitment during inflammation. We describe here a novel non-ELR CXC chemokine identified through sequence analysis of cDNAs derived from cytokine-activated primary human astrocytes. This novel chemokine, referred to as I-TAC (interferon-inducible T cell alpha chemoattractant), is regulated by interferon (IFN) and has potent chemoattractant activity for interleukin (IL)-2-activated T cells, but not for freshly isolated unstimulated T cells, neutrophils, or monocytes. I-TAC interacts selectively with CXCR3, which is the receptor for two other IFN-inducible chemokines, the IFN-␥ -inducible 10-kD protein (IP-10) and IFN-␥induced human monokine (HuMig), but with a significantly higher affinity. In addition, higher potency and efficacy of I-TAC over IP-10 and HuMig is demonstrated by transient mobilization of intracellular calcium as well as chemotactic migration in both activated T cells and transfected cell lines expressing CXCR3. Stimulation of astrocytes with IFN-␥ and IL-1 together results in an ف 400,000-fold increase in I-TAC mRNA expression, whereas stimulating monocytes with either of the cytokines alone or in combination results in only a 100-fold increase in the level of I-TAC transcript. Moderate expression is also observed in pancreas, lung, thymus, and spleen. The high level of expression in IFN-and IL-1-stimulated astrocytes suggests that I-TAC could be a major chemoattractant for effector T cells involved in the pathophysiology of neuroinflammatory disorders, although I-TAC may also play a role in the migration of activated T cells during IFN-dominated immune responses.
Bioorganic & Medicinal Chemistry Letters, 2011
Bioorganic & Medicinal Chemistry Letters, 2011
The synthesis and structure-activity relationship (SAR) of a novel series of di-substituted imida... more The synthesis and structure-activity relationship (SAR) of a novel series of di-substituted imidazoles, derived from modification of DAPT, are described. Subsequent optimization led to identification of a highly potent series of inhibitors that contain a b-amine in the imidazole side-chain resulting in a robust in vivo reduction of plasma and brain Ab in guinea pigs. The therapeutic index between Ab reductions and changes in B-cell populations were studied for compound 10h.
Bioorganic & Medicinal Chemistry Letters, 2007
The thiazole-diamide series (1) has been identified as highly potent c-secretase inhibitors. Seve... more The thiazole-diamide series (1) has been identified as highly potent c-secretase inhibitors. Several representative compounds showed IC 50 values of <0.3 nM. The synthesis and SAR, as well as a radiolabeled synthesis of [ 3 H]-2a, are described.
Alzheimer's & Dementia, 2008
Background: Aggregates of alpha-synuclein (a-syn) are present as Lewy bodies and Lewy neurites in... more Background: Aggregates of alpha-synuclein (a-syn) are present as Lewy bodies and Lewy neurites in the brains of patients suffering from dementia with Lewy bodies (DLB) and ParkinsonЈs disease (PD). Accumulating evidence suggests that oligomers, intermediately sized soluble species of the a-syn aggregation process, are primarily responsible for the neurotoxicity in these disorders. Our aim is to develop oligomer specific monoclonal antibodies as tools for studies on cell cultures and transgenic mice with a-syn pathology. Such antibodies might be useful for diagnostic purposes and for immunotherapy of DLB and PD. Methods: Mice were repeatedly immunized subcutaneously with preparations of oligomeric recombinant a-syn. Next, spleen cells were fused with mouse myeloma cells to generate antibody producing hybridomas. Finally, the generated clones were screened, using ELISA, for a-syn antibodies specifically binding to the oligomeric state. Results: A total of five mice (Balb/c) were immunized with oligomeric a-syn preparations. All mice responded to the immunization and antibodies against monomeric, oligomeric and fibrillar a-syn forms were detected in plasma. After generation of hybridomas, some of the clones showed specificity to a-syn oligomers whereas others were more selective for a-syn monomers and fibrils. Ongoing subcloning aims at further isolating IgG-positive clones with a high degree of a-syn oligomer specificity. Conclusions: Preliminary results indicate that we have generated antibodies specific to a-syn oligomers. Further screening and characterization of these antibodies are ongoing.
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Papers by Barbara Sahagan