Molecular Biology and Genetics / Moleküler Biyoloji ve Genetik
Permanent URI for this collectionhttps://hdl.handle.net/11147/9
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Master Thesis Investigation of the Pathology of Brain Derived Endothelial Cells in In-Vitro Hypoxia Models(01. Izmir Institute of Technology, 2021) Erdemli, Kısmet Tuğçe; Tosun, ÇiğdemThe blood brain barrier (BBB) is a vital structure that protects brain homeostasis. Endothelial cells (EC) have a significant role in regulating the BBB structure and function. Several studies have revealed the association of SUR1-TRPM4 channels that regulate this secondary damage of CNS injuries. After the activation of the channel, Na+ influx causes depolarization, cell swelling (edema) and ultimately oncotic cell death. Hypoxia inducing factor (HIF) transcription factor that has been reported to activate more than 100 genes to adapt to a hypoxic condition. Once Hif1-⍺ is translocated into the nucleus, it can dimerize with HIF1-ß to produce HIF that is critical in hypoxic conditions and regulate cell cycle arrest or cell death pathways. Hypoxia can occur in an O2 dependent and independent manner. In this study, CoCl2 and hypoxia chamber which was cost-effective and reliable were optimized. Cellular death was calculated with Trypan blue staining in this novel hypoxia chamber model and compared with CoCl2 models. In addition, morphological changes were observed in microscopic analysis. Hif1-⍺, caspase-3 and NF-κB translocation to the nucleus localization were quantified. Cell viability was different between the CoCl2 model and novel hypoxia chamber model at 24 hours. The cellular death increased with CoCl2 exposure, where no change was noted in the hypoxia chamber model. Time dependent Hif1-⍺ upregulation was also demonstrated that peaked at 12-hours. Finally, NF-κB translocation into the nucleus was significantly increased at 24 hours of hypoxia exposure. The results reveal that the inflatable hypoxia chamber model could be reliably used to mimic hypoxia in an in-vitro setting. Hif1-⍺ activated in a time dependent manner, along with NF-κB. The upregulation of these transcription factors can ultimately affect the cellular death mechanisms differentlyArticle Citation - WoS: 24Citation - Scopus: 23Polyethers Isolated From the Marine Actinobacterium Streptomyces Cacaoi Inhibit Autophagy and Induce Apoptosis in Cancer Cells(Elsevier, 2019) Khan, Nasar; Yılmaz, Sinem; Aksoy, Semiha; Uzel, Ataç; Tosun, Çiğdem; Ballar Kırmızıbayrak, Petek; Bedir, ErdalPolyether compounds, a large group of biologically active metabolites produced by Streptomyces species have been reported to show a variety of bioactivity such as antibacterial, antifungal, antiparasitic, antiviral, and tumour cell cytotoxicity. Since some of these compounds target cancer stem cells and multi-drug resistant cancer cells, this family of compounds have become of high interest. In this study, three polyether-type metabolites (1-3), one of which was a new natural product (3), were isolated from the marine derived Streptomyces cacaoi via antimicrobial activity-guided fractionation studies. As several polyether compounds with structural similarity such as monensin have been linked with autophagy and cell death, we first assessed the cytotoxicity of these three compounds. Compounds 2 and 3, but not 1, were found to be cytotoxic in several cell lines with a higher potency towards cancer cells. Furthermore, 2 and 3 caused accumulation of both autophagy flux markers LC3-II and p62 along with cleavage of caspase-3, caspase-9 and poly (ADP-ribose) polymerase 1 (PARP-1). Interestingly, prolonged treatment of the compounds caused a dramatic downregulation of the proteins related to autophagasome formation in a dose dependent manner. Our findings provide insights on the molecular mechanisms of the polyether-type polyketides, and signify their potency as chemotherapeutic agents through inhibiting autophagy and inducing apoptosis.Article Citation - WoS: 88Citation - Scopus: 92Sur1-Trpm4 Cation Channel Expression in Human Cerebral Infarcts(Oxford University Press, 2015) Mehta, Rupal I.; Tosun, Çiğdem; Ivanova, Svetlana; Tsymbalyuk, Natalia; Famakin, Bolanle M.; Kwon, Min Seong; Castellani, Rudy J.; Gerzanich, Volodymyr; Simard, J. MarcThe nonselective monovalent cation channel transient receptor potential melastatin 4 (Trpm4) is transcriptionally upregulated in neural and vascular cells in animal models of brain infarction. It associates with sulfonylurea receptor 1 (Sur1) to form Sur1-Trpm4 channels, which have critical roles in cytotoxic edema, cell death, blood-brain barrier breakdown, and vasogenic edema. We examined Trpm4 expression in postmortem brain specimens from 15 patients who died within the first 31 days of the onset of focal cerebral ischemia. We found increased Trpm4 protein expression in all cases using immunohistochemistry; transcriptional upregulation was confirmed using in situ hybridization of Trpm4 messenger RNA. Transient receptor potential melastatin 4 colocalized and coassociated with Sur1 within ischemic endothelial cells and neurons. Coexpression of Sur1 and Trpm4 in necrotic endothelial cells was also associated with vasogenic edema indicated by upregulated perivascular tumor necrosis factor, extravasation of serum immunoglobulin G, and associated inflammation. Upregulated Trpm4 protein was present up to 1 month after the onset of cerebral ischemia. In a rat model of middle cerebral artery occlusion stroke, pharmacologic channel blockade by glibenclamide, a selective inhibitor of sulfonylurea receptor, mitigated perivascular tumor necrosis factor labeling. Thus, upregulated Sur1-Trpm4 channels and associated blood-brain barrier disruption and cerebral edema suggest that pharmacologic targeting of this channel may represent a promising therapeutic strategy for the clinical management of patients with cerebral ischemia.