Person: YILMAZ, BETÜL
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YILMAZ
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BETÜL
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Publication Metadata only Hypercholesterolemia Mediated Endoplasmic Reticulum Stress Response Might Be Related to Autophagic Death of Cardiomyocytes in Heart Failure(ELSEVIER SCIENCE INC, 2016) YILMAZ, BETÜL; Ozer, Nesrin Kartal; Sozen, A. Erdi; Yazgan, Burak; Karademir, BetulPublication Metadata only ER stress related lipid accumulation and apoptotic cell death in nonalcoholic fatty liver diesease(ELSEVIER SCIENCE INC, 2017) ŞAHİN, ALİ; Demirel, Tugce; Sozen, Erdi; Sahin, Ali; Karademir, Betul; Ozer, Nesrin KartalPublication Open Access Potential role of proteasome on c-jun related signaling in hypercholesterolemia induced atherosclerosis(ELSEVIER SCIENCE BV, 2014) SÖZEN, AHMET ERDİ; Sozen, Erdi; Karademir, Betul; Yazgan, Burak; Bozaykut, Perinur; Ozer, Nesrin KartalAtherosclerosis and its complications are major causes of death all over the world. One of the major risks of atherosclerosis is hypercholesterolemia. During atherosclerosis, oxidized low density lipoprotein (oxLDL) regulates CD36-mediated activation of c-jun amino terminal kinase-1 (JNK1) and modulates matrix metalloproteinase (MMP) induction which stimulates inflammation with an invasion of monocytes. Additionally, inhibition of proteasome leads to an accumulation of c-jun and phosphorylated c-jun and activation of activator protein-1 (AP-1) related increase of MMP expression. We have previously reported a significant increase in cluster of differentiation 36 (CD36) mRNA levels in hypercholesterolemic rabbits and shown that vitamin E treatment prevented the cholesterol induced increase in CD36 mRNA expression. In the present study, our aim is to identify the signaling molecules/transcription factors involved in the progression of atherosclerosis following CD36 activation in an in vivo model of hypercholesterolemic (induced by 2% cholesterol containing diet) rabbits. In this direction, proteasomal activities by fluorometry and c-jun, phospo c-jun, JNK1, MMP-9 expressions by quantitative RT-PCR and immunoblotting were tested in aortic tissues. The effects of vitamin E on these changes were also investigated in this model. As a result, c-jun was phosphorylated following decreased proteasomal degradation in hypercholesterolemic group. MMP-9 expression was also increased in cholesterol group rabbits contributing to the development of atherosclerosis. In addition, vitamin E showed its effect by decreasing MMP-9 levels and phosphorylation of c-jun. (C) 2014 The Authors. Published by Elsevier B.V.Publication Metadata only Heat shock proteins and proteasomal degradation in normal and tumor cells(ELSEVIER SCIENCE INC, 2014) YILMAZ, BETÜL; Betul, Karademir; Perinur, Bozaykut; Nesrin, Kartal OzerPublication Metadata only Cellular Protection and Therapeutic Potential of Tocotrienols(BENTHAM SCIENCE PUBL LTD, 2011) YILMAZ, BETÜL; Catalgol, Betul; Batirel, Saime; Ozer, Nesrin KartalTocotrienols, components belonging to vitamin E members, are used as potent therapeutics in the treatment of several diseases. Recent studies suggested tocotrienol to have better activity in many situations compared to tocopherols. Tocotrienols have been shown to lower the atherogenic apolipoprotein B and lipoprotein plasma levels. Additionally, tocotrienols with their anti-tumor effect together with anti-angiogenic and anti-thrombotic effects may serve as effective agents in cancer therapy. Besides these effects, some properties such as water insolubility and low stability limit the usage of tocotrienols in the clinic. However recent studies tried to increase the bioavailability with esterification and combination use. These efforts for the clinical usage of tocotrienols which may help them to take a wide place in the clinic and additional studies are needed to identify their therapeutical mechanisms.Publication Metadata only Chromatin repair after oxidative stress: Role of PARP-mediated proteasome activation(ELSEVIER SCIENCE INC, 2010) YILMAZ, BETÜL; Catalgol, Betul; Wendt, Brigitte; Grimm, Stephanie; Breusing, Nicolle; Ozer, Nesrin Kartal; Grune, TilmanOxidative stress is an inevitable process in the nucleus, especially in antitumor chemotherapy, and adaptation by defense mechanisms seems to be one element in the development of long-term resistance to many chemotherapeutic drugs. In this study, a potential chromatin repair mechanism during oxidative stress was investigated in HT22 cells. The 20S proteasome has been shown to be largely responsible for the degradation of oxidatively modified histone proteins in the nucleus. Poly(ADP-ribosyl)ation reactions also play an important role in DNA repair as a consequence of oxidative damage and single-strand breaks. Such a reaction may occur also with the 20S proteasome-with a known increase in enzymatic activity-and also with histones-reducing their proteolytic susceptibility as shown for the first time here. After hydrogen peroxide treatment of HT22 cells, degradation of the model peptide substrate suc-LLVY-MCA and degradation of oxidized histones by nuclear proteasome increased. During the removal of protein carbonyls, single-strand breaks and 8-hydroxy-2'-deoxyguanosine, proteasome, and poly(ADP-ribose) polymerase-1 enzymes were shown to play tightly interacting roles. Our results following the repair of oxidative damage show the proteolytic activation of proteasome concerning poly(ADP-ribosyl)ation together with a decline in poly(ADP-ribosyl)ation of oxidized histones, leading to a selective recognition of oxidatively modified histones. (C) 2009 Elsevier Inc. All rights reserved.Publication Metadata only Age-related loss of stress-induced nuclear proteasome activation is due to low PARP-1 activity(ELSEVIER SCIENCE INC, 2011) YILMAZ, BETÜL; Bakondi, Edina; Catalgol, Betul; Bak, Istvan; Jung, Tobias; Bozaykut, Perinur; Bayramicli, Mehmet; Ozer, Nesrin Kartal; Grune, TilmanChanges in protein turnover are among the dominant metabolic changes during aging. Of special importance is the maintenance of nuclear protein homeostasis to ensure a coordinated cellular metabolism. Therefore, in the nucleus a special PARP-1-mediated mechanism of proteasomal activation exists to ensure a rapid degradation of oxidized nuclear proteins. It was already demonstrated earlier that the cytosolic proteasomal system declines dramatically with aging, whereas the nuclear proteasome remains less affected. We demonstrate here that the stress-mediated proteasomal activation in the nucleus declines during replicative senescence of human fibroblasts. Furthermore, we clearly show that this decline in the PARP-1-mediated proteasomal activation is due to a decline in the expression and activity of PARP-1 in senescent fibroblasts. In a final study we show that this process also happens in vivo, because the protein expression level of PARP-1 is significantly lower in the skin of aged donors compared to that of young ones. Therefore, we conclude that the rate-limiting factor in poly(ADP-ribose)-mediated proteasomal activation in oxidative stress is PARP-1 and not the nuclear proteasome itself. (C) 2010 Elsevier Inc. All rights reserved.Publication Open Access Resveratrol: French paradox revisited(FRONTIERS MEDIA SA, 2012) YILMAZ, BETÜL; Catalgol, Betul; Batirel, Saime; Taga, Yavuz; Ozer, Nesrin KartalResveratrol is a polyphenol that plays a potentially important role in many disorders and has been studied in different diseases. The research on this chemical started through the French paradox, which describes improved cardiovascular outcomes despite a high-fat diet in French people. Since then, resveratrol has been broadly studied and shown to have antioxidant, anti-inflammatory, anti-proliferative, and anti-angiogenic effects, with those on oxidative stress possibly being most important and underlying some of the others, but many signaling pathways are among the molecular targets of resveratrol. In concert they may be beneficial in many disorders, particularly in diseases where oxidative stress plays an important role. The main focus of this review will be the pathways affected by resveratrol. Based on these mechanistic considerations, the involvement of resveratrol especially in cardiovascular diseases, cancer, neurodegenerative diseases, and possibly in longevity will be is addressed.Publication Metadata only CD36 expression in peripheral blood mononuclear cells reflects the onset of atherosclerosis(WILEY, 2018) SÖZEN, AHMET ERDİ; Yazgan, Burak; Sozen, Erdi; Karademir, Betul; Ustunsoy, Seyfettin; Ince, Umit; Zarkovic, Neven; Ozer, Nesrin KartalTogether with complex genetic and environmental factors, increased serum cholesterol and ox-LDL levels are considered as major triggering factors of atherosclerosis. Mononuclear cell infiltration to the arterial wall and uptake of ox-LDL, which is facilitated by CD36 receptor through an uncontrolled manner, play a key role in foam cell formation followed by atherogenesis development. The aim of this study was to analyze if CD36 expression in peripheral blood mononuclear cells reflect its aortic tissue level in hypercholesterolemia. In this study, CD36 protein expression was evaluated in aortic specimens of cholesterol or cholesterol plus Vitamin E treated animals in relation to the immunohistochemical analyses for the HNE-protein adducts, as well as for smooth muscle actin and vimentin. The CD36 mRNA expression was determined by RT-PCR in PBMC of hypercholesterolemic rabbits and hypercholesterolemic versus normocholesterolemic individuals. Immunohistochemistry findings revealed that smooth muscle actin, smooth muscle vimentin, HNE-protein conjugates, and CD36 protein expressions were significantly increased in aorta of hypercholesterolemic group where foam cells were present. High cholesterol diet significantly induced CD36 mRNA expression in both rabbit aorta and PBMCs, while positive correlation between aortic and PBMC CD36 expression has been found. In addition, consistent with the rabbit model, CD36 mRNA expression levels in human PBMCs were significantly higher in hypercholesterolemic patients than in normocholesterolemic individuals. Taken together, these results demonstrate that the CD36 mRNA levels of PBMCs could reflect the CD36 mRNA levels in aorta and could be used as a biomarker for diagnosis of atherosclerotic burden. (c) 2018 BioFactors, 44(6):588-596, 2018Publication Metadata only Proteasome inhibitors in cancer therapy: Treatment regimen and peripheral neuropathy as a side effect(ELSEVIER SCIENCE INC, 2017) YILMAZ, BETÜL; Kaplan, Gulce Sari; Torcun, Ceyda Corek; Grune, Tilman; Ozer, Nesrin Kartal; Karademir, BetulProteasomal system plays an important role in protein turnover, which is essential for homeostasis of cells. Besides degradation of oxidized proteins, it is involved in the regulation of many different signaling pathways. These pathways include mainly cell differentiation, proliferation, apoptosis, transcriptional activation and angiogenesis. Thus, proteasomal system is a crucial target for treatment of several diseases including neurodegenerative diseases, cystic fibrosis, atherosclerosis, autoimmune diseases, diabetes and cancer. Over the last fifteen years, proteasome inhibitors have been tested to highlight their mechanisms of action and used in the clinic to treat different types of cancer. Proteasome inhibitors are mainly used in combinational therapy along with classical chemo-radiotherapy. Several studies have proved their significant effects but serious side effects such as peripheral neuropathy, limits their use in required effective doses. Recent studies focus on peripheral neuropathy as the primary side effect of proteasome inhibitors. Therefore, it is important to delineate the underlying mechanisms of peripheral neuropathy and develop new inhibitors according to obtained data. This review will detail the role of proteasome inhibition in cancer therapy and development of peripheral neuropathy as a side effect. Additionally, new approaches to prevent treatment limiting side effects will be discussed in order to help researchers in developing effective strategies to overcome side effects of proteasome inhibitors.
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