Research Institute of Bioengineering, Regenerative Medicine and Neurophysiology
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Browsing Research Institute of Bioengineering, Regenerative Medicine and Neurophysiology by Author "Askarova, Sholpan"
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Item Open Access Amyloid-b peptide on sialyl-LewisX-selectin-mediated membrane tether mechanics at the cerebral endothelial cell surface(PLOS ONE:Open Access journal, 2013-04-12) Askarova, Sholpan; Sun, Zhe; Sun, Grace Y.; Meininger, Gerald A.; Lee, James C-M.Increased deposition of amyloid-b peptide (Ab) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer’s disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewisx (sLex) were employed to investigate Ab-altered mechanics of membrane tethers formed by bonding between sLex and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Ab to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Ab to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Ab lowered the overall force of membrane tether formation (Fmtf), and produced a bimodal population of Fmtf, suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Ab and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf. In addition, these cerebral endothelial alterations induced by Ab were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Ab to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB.Item Open Access Effects of amyloid beta peptide on neurovascular cells(Central Asian Journal of Global Health, 2012) Askarova, Sholpan; Tsoy, Andrey; Shalakhmetova, Tamara; Lee, James C-M.Alzheimer’s disease (AD) is a chronic neurodegenerative disorder, which is characterized by the accumulation of amyloid plaques and neurofibrillary tangles in specific regions of the brain, accompanied by impairment of the neurons, and progressive deterioration of cognition and memory of affected individuals. Although the cause and progression of AD are still not well understood, the amyloid hypothesis is dominant and widely accepted. According to this hypothesis, an increased deposition of amyloid-β peptide (Aβ) in the brain is the main cause of the AD’s onset and progression. There is increasing body of evidence that blood-brain barrier (BBB) dysfunction plays an important role in the development of AD, and may even precede neuron degeneration in AD brain. In the early stage of AD, microvasculature deficiencies, inflammatory reactions, surrounding the cerebral vasculature and endothelial dysfunctions are commonly observed. Continuous neurovascular degeneration and accumulation of Aβ on blood vessels resulting in cerebral amyloid angiopathy is associated with further progression of the disease and cognitive decline. However, little is known about molecular mechanisms that underlie Aβ induced damage of neurovascular cells. In this regards, this review is aimed to address how Aβ impacts the cerebral endothelium. Understanding the cellular pathways triggered by Aβ leading to alterations in cerebral endothelial cells structure and functions would provide insights into the mechanism of BBB dysfunction and inflammatory processes in Alzheimer’s, and may offer new approaches for prevention and treatment strategies for AD.Item Metadata only Engineering of cell membranes with a bisphosphonate-containing polymer using ATRP synthesis for bone targeting(2014-11-01) D'Souza, Sonia; Murata, Hironobu; Jose, Moncy V.; Askarova, Sholpan; Yantsen, Yuliya; Andersen, Jill D.; Edington, Collin D.J.; Clafshenkel, William P.; Koepsel, Richard R.; Russell, Alan J.; Sonia, D'SouzaAbstract The field of polymer-based membrane engineering has expanded since we first demonstrated the reaction of N-hydroxysuccinimide ester-terminated polymers with cells and tissues almost two decades ago. One remaining obstacle, especially for conjugation of polymers to cells, has been that exquisite control over polymer structure and functionality has not been used to influence the behavior of cells. Herein, we describe a multifunctional atom transfer radical polymerization initiator and its use to synthesize water-soluble polymers that are modified with bisphosphonate side chains and then covalently bound to the surface of live cells. The polymers contained between 1.7 and 3.1 bisphosphonates per chain and were shown to bind to hydroxyapatite crystals with kinetics similar to free bisphosphonate binding. We engineered the membranes of both HL-60 cells and mesenchymal stem cells in order to impart polymer-guided bone adhesion properties on the cells. Covalent coupling of the polymer to the non-adherent HL-60 cell line or mesenchymal stem cells was non-toxic by proliferation assays and enhanced the binding of these cells to bone.Item Open Access Impacts of membrane biophysics in Alzheimer’s disease: from amyloid precursor protein processing to Aβ peptide-induced membrane changes(SAGE-Hindawi Access to Research International Journal of Alzheimer’s Disease, 2011-01-21) Askarova, Sholpan; Yang, Xiaoguang; Lee, James C-M.An increasing amount of evidence supports the notion that cytotoxic effects of amyloid-β peptide (Aβ), the main constituent of senile plaques in Alzheimer’s disease (AD), are strongly associated with its ability to interact with membranes of neurons and other cerebral cells. Aβ is derived from amyloidogenic cleavage of amyloid precursor protein (AβPP) by β- and γ-secretase. In the nonamyloidogenic pathway, AβPP is cleaved by α-secretases. These two pathways compete with each other, and enhancing the non-amyloidogenic pathway has been suggested as a potential pharmacological approach for the treatment of AD. Since AβPP, α-, β-, and γ-secretases are membrane-associated proteins, AβPP processing and Aβ production can be affected by the membrane composition and properties. There is evidence that membrane composition and properties, in turn, play a critical role in Aβ cytotoxicity associated with its conformational changes and aggregation into oligomers and fibrils. Understanding themechanisms leading to changes in a membrane’s biophysical properties and how they affect AβPP processing and Aβ toxicity should prove to provide new therapeutic strategies for prevention and treatment of AD.Item Open Access Low energy laser light (632.8 nm) suppresses amyloid-β peptide-induced oxidative and inflammatory responses in astrocytes(US National Library of Medicine National Institutes of Health, 2010-09-25) Yang, Xiaoguang; Askarova, Sholpan; Sheng, Wenwen; Chen, JK; Sun, Albert Y.; Sun, Grace Y.; Yao, Gang; Leea, James C-M.Oxidative stress and inflammation are important processes in the progression of Alzheimer's disease (AD). Recent studies have implicated the role of amyloid β-peptides (Aβ) in mediating these processes. In astrocytes, oligomeric Aβ induces the assembly of NADPH oxidase complexes resulting in its activation to produce anionic superoxide. Aβ also promotes production of pro-inflammatory factors in astrocytes. Since low energy laser has previously been reported to attenuate oxidative stress and inflammation in biological systems, the objective of this study was to examine whether this type of laser light was able to abrogate the oxidative and inflammatory responses induced by Aβ. Primary rat astrocytes were exposed to Helium-Neon laser (λ=632.8 nm), followed by the treatment with oligomeric Aβ. Primary rat astrocytes were used to measure Aβ-induced production of superoxide anions using fluorescence microscopy of dihydroethidium (DHE), assembly of NADPH oxidase subunits by the colocalization between the cytosolic p47phox subunit and the membrane gp91phox subunit using fluorescent confocal microscopy, phosphorylation of cytosolic phospholipase A2 (cPLA2), and expressions of pro-inflammatory factors including interleukin-1β (IL-1β) and inducible nitric-oxide synthase (iNOS) using Western blot Analysis. Our data showed that laser light at 632.8 nm suppressed Aβ-induced superoxide production, colocalization between NADPH oxidase gp91phox and p47phox subunits, phosphorylation of cPLA2, and the expressions of IL-1β and iNOS in primary astrocytes. We demonstrated for the first time that 632.8 nm laser was capable of suppressing cellular pathways of oxidative stress and inflammatory responses critical in the pathogenesis in AD. This study should prove to provide the groundwork for further investigations for the potential use of laser therapy as a treatment for AD.Item Open Access Membrane biophysics and mechanics in Alzheimer's disease(Mol Neurobiol, 2010-05-01) Yang, Xiaoguang; Askarova, Sholpan; Lee, James C-M.Alzheimer's disease is a chronic neurodegenerative disorder characterized by neuronal loss, cerebrovascular inflammation, and accumulation of senile plaques in the brain parenchyma and cerebral blood vessels. Amyloid-β peptide (Aβ), a major component of senile plaques, has been shown to exert multiple toxic effects to neurons, astrocytes, glial cells, and brain endothelium. Oligomeric Aβ can disturb the structure and function of cell membranes and alter membrane mechanical properties, such as membrane fluidity and molecular order. Much of these effects are attributed to their capability to trigger oxidative stress and inflammation. In this review, we discuss the effects of Aβ on neuronal cells, astrocytes, and cerebral endothelial cells with special emphasis on cell membrane properties and cell functions.Item Open Access Role of Aβ-RAGE interaction in oxidative stress and cPLA2 activation in astrocytes and cerebral endothelial cells(Neuroscience. Author manuscript; available in PMC, 2012-12-29) Askarova, Sholpan; Yang, Xiaoguang; Sheng, Wenwen; Sun, Grace Y.; Lee, James C-M.Blood–brain barrier (BBB) dysfunctions have been implicated in the progression of Alzheimer's disease. Cerebral endothelial cells (CECs) and astrocytes are the main cell components of the BBB. Although amyloid-β oligomers (Aβ42) have been reported to mediate oxidative damage to the CECs and astrocytes and trigger the downstream mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway, the cell surface binding site for Aβ42 and exact sequence of these events have yet to be elucidated. In this study, the receptor for advanced glycation endproducts (RAGE) was postulated to function as a signal transducing cell surface receptor for Aβ42 to induce reactive oxygen species (ROS) generation from NADPH oxidase and trigger downstream pathways for the phosphorylation of extracellular signal-regulated kinases (ERK1/2) and cytosolic phospholipase A2 (cPLA2). We found that Aβ42 competed with the anti-RAGE antibody (AbRAGE) to bind to RAGE on the surfaces of CECs and primary astrocytes. In addition, AbRAGE abrogate Aβ42-induced ROS production and the colocalization between the cytosolic (p47-phox) and membrane (gp91-phox) subunits of NADPH oxidase in both cell types. AbRAGE as well as NADPH oxidase inhibitor and ROS scavenger suppressed Aβ42-induced ERK1/2 and cPLA2 phosphorylation in CECs. At the same time, only AbRAGE, but neither NADPH oxidase inhibitor nor ROS scavenger, inhibited the ERK1/2 pathway and cPLA2 phosphorylation in primary astrocytes. Therefore, this study demonstrates that NADPH oxidase complex assembly and ROS production are not required for Aβ42 binding to RAGE at astrocytic surface leading to sequential phosphorylation of ERK1/2 and cPLA2, and suggests the presence of two different RAGE-dependent downstream pathways in the CECs and astrocytes.Item Open Access Role of membrane biophysics in Alzheimer’s–related cell pathways(Frontiers inNeuroscience, 2015-05-27) Zhu, Donghui; Bungart, BrittaniL; Yang, Xiaoguang; Zhumadilov, Zhaxybay; Lee, James C-M.; Askarova, SholpanP-selectin and actin cytoskeleton reorganization play an important role in vascular inflammation. In turn, there is increasing evidence that cerebrovascular factors contribute significantly to the development and progression of Alzhemer’s disease. In this study we have evaluated the effects of Aβ42 oligomers on P-selectin expression and actin polymerization in mouse endothelial cells (bEnd3). Our results indicated that Aβ42 induced plasma membrane accumulation of P-selectin and promoted actin polymerization, and these events were correlated with increased reactive oxygen species (ROS) generation. The rapid, posttranslational cell signaling response mediated by ROS may well represent an important physiological trigger of the microvascular inflammation in Alzheimer disease.