Browsing by Subject "Oxidative stress"
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Item Open Access Acquired tolerance of hepatocellular carcinoma cells to selenium deficiency: a selective survival mechanism?(American Association for Cancer Research, 2003) Irmak, M. B.; Ince, G.; Ozturk, M.; Cetin Atalay, R.Selenium is essential to human health, and its deficiency is associated with different diseases including liver necrosis. Selenium is protective against viral hepatitis and hepatocellular carcinoma (HCC). The underlying molecular mechanisms of selenium effects are not well known. In this study, in vitro response of HCC-derived cell lines to selenium deficiency is examined alone or in conjunction with Vitamin E and copper/zinc. Here, we show that itt vitro selenium deficiency in a subset of HCC-derived cell lines causes oxidative stress and cytochrome c release with subsequent cell death by apoptosis. The oxidative stress and consequent cell death induced by selenium deficiency on these cells are reverted by the antioxidant effect of Vitamin E. However, most HCC cell lines (10 of 13) tolerate selenium deficiency. Consequently, they escape apoptosis. Moreover, nine of these tolerant cell lines have integrated hepatitis B Virus (HBV) DNA in their genomes, and some display p53-249 mutation, indicating past exposure to HBV or aflatoxins, established factors for oxidative stress and cancer risk in liver. An HBV-transfected clone (2.2.15) of the sensitive HepG2 cell line has gained tolerance to selenium deficiency. Our findings indicate that selenium deficiency induces apoptosis in some "hepatocyte-like" cells. However, most HCC cells, particularly HBV-related ones, tolerate selenium deficiency and escape its deadly consequences. Thus, as demonstrated by the gain of survival capacity of apoptosis-sensitive cell lines with Vitamin E, such malignant cells have acquired a selective survival advantage that is prominent under selenium-deficient and oxidative-stress conditions.Item Open Access Antioxidant response of Chlamydomonas reinhardtii grown under different element regimes(Blackwell Publishing, 2015) Çakmak, Z. E.; Ölmez, T. T.; Çakmak, T.; Menemen, Y.; Tekinay, T.Nutrient stress is one of the most favorable ways of increasing neutral lipid and high value-added output production by microalgae. However, little is known about the level of the oxidative damage caused by nutrient stress for obtaining an optimal stress level for maximum production of specific molecules. In this study, the antioxidant response of Chlamydomonas reinhardtii grown under element deprivation (nitrogen, sulfur, phosphorus and magnesium) and supplementation (nitrogen and zinc) was investigated. All element regimes caused a decrease in growth, which was most pronounced under N deprivation. Element deprivation and Zn supplementation caused significant increases in H2O2 and lipid peroxidation levels of C.reinhardtii. Decrease in total chlorophyll level was followed by an increase of total carotenoid levels in C.reinhardtii under N and S deprivation while both increased under N supplementation. Confocal imaging of live cells revealed dramatic changes of cell shape and production of neutral lipid bodies accompanied by a decrease of chlorophyll clusters. Antioxidant capacity of cells decreased under N, S and P deprivation while it increased under N and Zn supplementation. Fluctuation of antioxidant enzyme activities in C.reinhardtii grown under different element regimes refers to different metabolic sources of reactive oxygen species production triggered by a specific element absence or overabundance. © 2015 Japanese Society of Phycology.Item Open Access Effect of high intensity interval training on elite athletes' antioxidant status(Elsevier Masson, 2013) Ugras, A. F.Objective: The effects of high intensity interval exercises on antioxidant defense system are not clear. Since there is an evident lack of studies focused on oxidative stress experienced following combat sports and high intensity interval training, we investigated oxidative stress markers (malondialdehyde [MDA], catalase [CAT], glutathione peroxidase [GPX], superoxide dismutase [SOD]) by completing high intensity interval training program (HIITP) and following International Muay Thai Championship (IMTC). Methods: The study was carried out on 21 elite players (15 males and six females) who had regular exercising and training habits. The participants were subjected to a daily 3-hour HIITP during brief training camp (10-day) before IMTC. They were instructed to maintain their normal dietary practices throughout the camp and during the study to take no antioxidant containing vitamin tablets. Results: There was a significant increase in MDA levels and significant decrease in CAT activities of players (P<. 0.05). The differences in SOD and GPX activities were not significant. Conclusion: These results suggested that high intensity interval training and competition could affect the oxidative status of Muay Thai (MT) athletes. © 2012 Elsevier Masson SAS.Item Open Access ER-mitochondrial communication gets stressful(American Association for the Advancement of Science, 2014) Erbay, EbruItem Open Access Evaluation of cytotoxicity and oxidative DNA damaging effects of di(2-ethylhexyl)-phthalate (DEHP) and mono(2-ethylhexyl)-phthalate (MEHP) on MA-10 Leydig cells and protection by selenium(Elsevier, 2010) Erkekoglu, P.; Rachidi, W.; Yuzugullu, O. G.; Giray, B.; Favier, A.; Ozturk, M.; Hincal, F.Di(2-ethylhexyl)-phthalate (DEHP) is the most abundantly used phthalate derivative, inevitable environmental exposure of which is suspected to contribute to the increasing incidence of testicular dysgenesis syndrome in humans. Oxidative stress and mitochondrial dysfunction in germ cells are suggested to contribute to phthalate-induced disruption of spermatogenesis in rodents, and Leydig cells are one of the main targets of phthalates' testicular toxicity. Selenium is known to be involved in the modulation of intracellular redox equilibrium, and plays a critical role in testis, sperm, and reproduction. This study was aimed to investigate the oxidative stress potential of DEHP and its consequences in testicular cells, and examine the possible protective effects of selenium using the MA-10 mouse Leydig tumor cell line as a model. In the presence and absence of selenium compounds [30. nM sodium selenite (SS), and 10 μM selenomethionine (SM)], the effects of exposure to DEHP and its main metabolite mono(2-ethylhexyl)-phthalate (MEHP) on the cell viability, enzymatic and non-enzymatic antioxidant status, ROS production, p53 expression, and DNA damage by alkaline Comet assay were investigated. The overall results of this study demonstrated the cytotoxicity and genotoxicity potential of DEHP, where MEHP was found to be more potent than the parent compound. SS and SM produced almost the same level of protection against antioxidant status modifying effects, ROS and p53 inducing potentials, and DNA damaging effects of the two phthalate derivatives. It was thus shown that DEHP produced oxidative stress in MA-10 cells, and selenium supplementation appeared to be an effective redox regulator in the experimental conditions used in this study, emphasizing the critical importance of the appropriate selenium status. © 2010 Elsevier Inc.Item Open Access Impact of the inflammatory process in the aging brain: evidence from in Vitro and Ex Vivo models(Bilkent University, 2023-08) Aktürk, Serena SevdiyeAging is a complex and dynamic process that is characterized by a gradual decline over time in the physiological integrity of organisms. Several cellular mechanisms contribute to aging, including telomere shortening, damage accumulation in DNA, disabled macroautophagy, mitochondrial dysfunction, and cellular senescence. These processes, consecutively, lead to impaired cellular function, declined tissue repair, and stem cell exhaustion and are seen in the development of neurodegenerative disorders and healthy aging. One of the hallmarks of brain aging is the altered chronic inflammatory status of the brain. The over-activation and polarization of microglia, increased secretion of pro-inflammatory cytokines and reactive oxygen species, inflammasome activation, and the upregulation of the NF- κB signaling pathway are among the markers of neuroinflammation. This mechanism's anticipated effects include dysregulated nutrition sensing via the mTOR (mammalian target of rapamycin) pathway, decreased neurogenesis, and synaptic integrity over time. Another element that contributes to vulnerability to inflammation is genetic predisposition. Hence, additional research endeavors are required to investigate the influence of dietary interventions and therapeutic modalities targeting inflammation on genetic pathways. Thus, this study aimed to understand how inflammation can be triggered on different models, investigate potential inflammation-related biomarkers with meta-analysis and observe the effect of inflammation for both zebrafish primary brain cells and murine microglial cells. We conducted short-term copper sulfate treatments on both models for this objective. Moreover, to examine the effects of intermittent fasting, an mTOR downregulator, and high-fat diet, an inflammation inducer, on the brain of zebrafish at the molecular level by primary cell culture method. Finally, we applied rapamycin+DMSO treatment to primary cells to assess the possibility of reversing the progression of inflammation. The results showed that copper sulfate is an efficient oxidative stress-induced inflammatory reagent for zebrafish; however, it did not cause a direct inflammatory response in murine microglial cells. For zebrafish, in the copper sulfate+DMSO treated group, age affected Nrf2a mRNA, altering oxidative stress in old animals. Regardless of diet and treatment group, inflammation markers were higher in old animals, which underscores the association between aging and chronic inflammation. Elevated Lc3b levels in young and old animals captured that high copper concentrations can trigger autophagy. Results for neurogenesis markers revealed that overfeeding or acute inflammation could contribute to compromised neurogenesis in advanced stages of life. On the contrary, the enhanced neurogenesis potential of intermittent fasting in old animals was revealed. In conclusion, this study has demonstrated that the modulation of neuroinflammatory responses, as well as oxidative stress, neurogenesis, and autophagy, occurs in an age-related manner. Moreover, dietary or pharmaceutical interventions could yield comprehensive outcomes in perceiving the brain's neuroinflammatory profile during aging.Item Open Access Liver cancer cells are sensitive to Lanatoside C induced cell death independent of their PTEN status(Elsevier, 2016) Durmaz, I.; Guven, E. B.; Ersahin, T.; Ozturk, M.; Calis, I.; Cetin Atalay, R.Background Hepatocellular carcinoma is the second deadliest cancer with limited treatment options. Loss of PTEN causes the P13K/Akt pathway to be hyperactive which contributes to cell survival and resistance to therapeutics in various cancers, including the liver cancer. Hence molecules targeting this pathway present good therapeutic strategies for liver cancer. Hypothesis It was previously reported that Cardiac glycosides possessed antitumor activity by inducing apoptosis of multiple cancer cells through oxidative stress. However, whether Cardiac glycoside Lanatoside C can induce oxidative stress in liver cancer cells and induce cell death both in vitro and in vivo remains unknown. Methods Cell viability was measured by SRB assay. Cell death analysis was investigated by propidium iodide staining with flow cytometry and PARP cleavage. DCFH-DA staining and cytometry were used for intracellular ROS measurement. Protein levels were analyzed by western blot analysis. Antitumor activity was investigated on mice xenografts in vivo. Results In this study, we found that Cardiac glycosides, particularly Lanatoside C from Digitalis ferruginea could significantly inhibit PTEN protein adequate Huh7 and PTEN deficient Mahlavu human liver cancer cell proliferation by the induction of apoptosis and G2/M arrest in the cells. Lanatoside C was further shown to induce oxidative stress and alter ERK and Akt pathways. Consequently, JNK1 activation resulted in extrinsic apoptotic pathway stimulation in both cells while JNK2 activation involved in the inhibition of cell survival only in PTEN deficient cells. Furthermore, nude mice xenografts followed by MRI showed that Lanatoside C caused a significant decrease in the tumor size. In this study apoptosis induction by Lanatoside C was characterized through ROS altered ERK and Akt pathways in both PTEN adequate epithelial and deficient mesenchymal liver cancer cells. Conclusion The results indicated that Lanatoside C could be contemplated in liver cancer therapeutics, particularly in PTEN deficient tumors. This is due to Lanatoside C's stress inducing action on ERK and Akt pathways through differential activation of JNK1 and JNK2 by GSK3β. © 2015 Elsevier GmbH. © 2016 Elsevier GmbH. All rights reserved.Item Open Access Novel triazolothiadiazines act as potent anticancer agents in liver cancer cells through Akt and ASK-1 proteins(Elsevier, 2016) Aytaç, P. S.; Durmaz, I.; Houston, D. R.; Çetin-Atalay R.; Tozkoparan, B.Newly designed triazolothiadiazines incorporating with structural motifs of nonsteroidal analgesic anti-inflammatory drugs were synthesized and screened for their bioactivity against epithelial cancer cells. Compounds with bioactivities less then ∼5 μM (IC50) were further analyzed and showed to induce apoptotic cell death and SubG1cell cycle arrest in liver cancer cells. Among this group, two compounds (1g and 1h) were then studied to identify the mechanism of action. These molecules triggered oxidative stress induced apoptosis through ASK-1 protein activation and Akt protein inhibition as demonstrated by downstream targets such as GSK3β, β-catenin and cyclin D1. QSAR and molecular docking models provide insight into the mechanism of inhibition and indicate the optimal direction of future synthetic efforts. Furthermore, molecular docking results were confirmed with in vitro COX bioactivity studies. This study demonstrates that the novel triazolothiadiazine derivatives are promising drug candidates for epithelial cancers, especially liver cancer. © 2016 Published by Elsevier Ltd.Item Open Access Transcriptome profiles associated with selenium-deficiency-dependent oxidative stress identify potential diagnostic and therapeutic targets in liver cancer cells(Scientific and Technical Research Council of Turkey - TUBITAK,Turkiye Bilimsel ve Teknik Arastirma Kurumu, 2021-04-20) Gözen, D.; Kahraman, D. C.; Narcı, K.; Shehwana, H.; Konu, Özlen; Çetin-Atalay, RengülHepatocellular carcinoma (HCC) is one of the most common cancer types with high mortality rates and displays increased resistance to various stress conditions such as oxidative stress. Conventional therapies have low efficacies due to resistance and off-target effects in HCC. Here we aimed to analyze oxidative stress-related gene expression profiles of HCC cells and identify genes that could be crucial for novel diagnostic and therapeutic strategies. To identify important genes that cause resistance to reactive oxygen species (ROS), a model of oxidative stress upon selenium (Se) deficiency was utilized. The results of transcriptome-wide gene expression data were analyzed in which the differentially expressed genes (DEGs) were identified between HCC cell lines that are either resistant or sensitive to Se-deficiency-dependent oxidative stress. These DEGs were further investigated for their importance in oxidative stress resistance by network analysis methods, and 27 genes were defined to have key roles; 16 of which were previously shown to have impact on liver cancer patient survival. These genes might have Se-deficiency-dependent roles in hepatocarcinogenesis and could be further exploited for their potentials as novel targets for diagnostic and therapeutic approaches.