Impact of Seipin in cholesterol mediated lipid droplet maturation; status of endoplasmic reticulum stress and lipophagy.

The global prevalence of nonalcoholic fatty liver disease (NAFLD) defined by the increased number of lipid droplets (LDs) in hepatocytes, have risen continuously in parallel with the obesity. LDs and related proteins are known to affect cellular metabolism and signaling. Seipin, one of the most important LD-related proteins, plays a critical role in LD biogenesis. Although the role of adipose tissue-specific Seipin silencing is known, hepatocyte-specific silencing upon cholesterol-mediated lipid accumulation has not been investigated. In our study, we investigated the effect of Seipin on endoplasmic reticulum (ER) stress and lipophagy in cholesterol accumulated mouse hepatocyte cells. In this direction, cholesterol accumulation was induced by cholesterol-containing liposome, while Seipin mRNA and protein levels were reduced by siRNA. Our findings show that cholesterol containing liposome administration in hepatocytes increases both Seipin protein and number of large LDs. However Seipin silencing reduced the increase of cholesterol mediated large LDs and Glucose-regulated protein 78 (GRP78) mRNA. Additionally, lysosome-LD colocalization increased only in cells treated with cholesterol containing liposome, while the siRNA against Seipin did not lead any significant difference. According to our findings, we hypothesize that Seipin silencing in hepatocytes reduced cholesterol mediated LD maturation as well as GRP78 levels, but not lipophagy.

Vitamin E discussion forum position paper on the revision of the nomenclature of vitamin E.

This position paper opens a discussion forum of this Journal dedicated to a scientific debate on Vitamin E nomenclature. With this article we provide the scientific and medical communities with what we consider relevant information in favor of revising the nomenclature of vitamin E. To our knowledge, only RRR-α-tocopherol has been medically used to protect against a deficiency disease in humans, and therefore, it would be appropriate to restrict the term vitamin to this molecule. The direct demonstration of a vitamin function to other tocochromanols (including other tocopherols, tocotrienols and eventually tocomonoenols), has not yet been scientifically shown. In fact, the medical prescription of a molecule against the deficiency disease only because it has been included in the "Vitamin E family", but not tested as vitamin E, could lead to ineffective therapy and potentially dangerous consequences for patients. The idea of this revision launched during the recent 3rd Satellite Symposium on Vitamin E of the 2022 SFRR-Europe meeting, offers a open platform of discussion for the scientists involved in vitamin E research and scientific societies interested to this subject.

Protective effects of an electrophilic metabolite of docosahexaenoic acid on UVB-induced oxidative cell death, dermatitis, and carcinogenesis.

Docosahexaenoic acid (DHA), a representative omega-3 (ω-3) polyunsaturated fatty acids, undergoes metabolism to produce biologically active electrophilic species. 17-Oxo-DHA is one such reactive metabolite generated from DHA by cyclooxygenase-2 and dehydrogenase in activated macrophages. The present study was aimed to investigate the effects of 17-oxo-DHA on ultraviolet B (UVB)-induced oxidative stress, inflammation, and carcinogenesis in mouse skin. UVB-induced epidermal cell death was ameliorated by topically applied 17-oxo-DHA. Topical application of 17-oxo-DHA onto hairless mouse skin inhibited UVB-induced phosphorylation of the proinflammatory transcription factor, STAT3 on tyrosine 705 (Tyr705). The 17-oxo-DHA treatment also reduced the levels of oxidative stress markers, 4-hydroxynonenal-modified protein, malondialdehyde, and 8-oxo-2'-deoxyguanosine. The protective effects of 17-oxo-DHA against oxidative damage in UVB-irradiated mouse skin were associated with activation of Nrf2. 17-Oxo-DHA enhanced the engulfment of apoptotic JB6 cells by macrophages, which was related to the increased expression of the scavenger receptor CD36. The 17-oxo-DHA-mediated potentiation of efferocytic activity of macrophages was attenuated by the pharmacologic inhibition or knockout of Nrf2. The pretreatment with 17-oxo-DHA reduced the UVB-induced skin carcinogenesis and tumor angiogenesis. It was also confirmed that 17-oxo-DHA treatment significantly inhibited the phosphorylation of the Tyr705 residue of STAT3 and decreased the expression of its target proteins in cutaneous papilloma. In conclusion, 17-oxo-DHA protects against UVB-induced oxidative cell death, dermatitis, and carcinogenesis. These effects were associated with inhibition of STAT3-mediated proinflammatory signaling and also activation of Nrf2 with subsequent upregulation of antioxidant and anti-inflammatory gene expression.

Cholesterol accumulation in hepatocytes mediates IRE1/p38 branch of endoplasmic reticulum stress to promote nonalcoholic steatohepatitis.

Non-alcoholic fatty liver disease (NAFLD), based on the elevating obesity incidence, is one of the major health issue worldwide. Transition from NAFLD to non-alcoholic steatohepatitis (NASH) is driven by increased apoptosis and is relevant to higher morbidity rates. In regard to limited understanding on cholesterol mediated hepatocyte alterations in NALFD/NASH transition, we investigated endoplasmic reticulum (ER) stress and related apoptosis. Our findings suggest that cholesterol upregulates ER stress and enhances C/EBP homologous protein (CHOP) either in hypercholesterolemic rabbits or in hepatocytes treated with liposome-cholesterol complex. Mechanistically, cholesterol accumulation in hepatocytes activates IRE1/p38 branch of ER stress, stimulating CHOP levels. In liver tissues of cholesterol fed rabbits, α-tocopherol supplementation decreased IRE1/p38/CHOP activation and prevented NASH development. Thus, our study provides a critical role of hepatocyte cholesterol in inducing IRE1/p38/CHOP pathway and suggests novel candidates for therapeutic targets against NASH.

High cholesterol diet activates ER stress mediated apoptosis in testes tissue: Role of α-tocopherol.

The seminiferous tubules where spermatogenesis occurs are enveloped and protected by the Sertoli cells to support germ cells undergoing meiosis to produce haploid gametes. Clearly, induction of apoptosis in seminiferous tubules leads to abnormalities in spermatogenesis and male infertility. Studies demonstrated that increased hyperlipidemia impairs male infertility and spermatogenesis by enhancing seminiferous tubules apoptosis. However, molecular mechanisms underlying high-cholesterol-mediated testicular damage remain poorly elucidated. In this scope, we established a rabbit model and investigated the role of endoplasmic reticulum (ER) stress on high cholesterol diet induced seminiferous tubule apoptosis. Histopatological examinations revealed increased seminifer tubule apoptosis in testes of rabbits fed high cholesterol diet. In addition, phosphorylated forms of IRE1 and PERK, two well-identified markers of ER stress, were significantly induced in accordance with high cholesterol diet. High cholesterol diet also exhibited CHOP induction in testes, indicating increased ER stress related apoptosis. Supplementation of α-tocopherol significantly attenuated cholesterol mediated ER stress, and restored seminiferous tubules apoptosis. Taken together, our findings suggest that α-tocopherol might be capable to reduce testicular damage via ameliorating histopatological features and inhibiting seminiferous tubules apoptosis in hypercholesterolemic rabbits.

Deficiency of SREBP1c modulates autophagy mediated lipid droplet catabolism during oleic acid induced steatosis.

OBJECTIVE: Increased fatty acid and triglyceride synthesis in liver, majorly modulated by Sterol Regulator Elementing Binding Protein 1c (SREBP1c), is one of the main features of non-alcoholic fatty liver disease (NAFLD). In the present study, we aimed to identify the relation between SREBP1c and autophagy mediated lipid droplet (LD) catabolism in oleic acid (OA) induced lipid accumulation. METHODS: Increased LD formation and SREBP1c induction were identified in hepatocytes (AML12 cells) following the OA administration. SREBP1c level was reduced through siRNA against SREBP1c. The amount and the size of LDs were determined by BODIPY, while protein and mRNA expressions were identified by immunoblotting and qRT-PCR, respectively. LD-lysosome colocalization was determined with immunofluorescence. RESULTS: Increased LD formation and SREBP1c levels were determined at 0.06 mM OA concentration. SREBP1c silencing reduced the number of LDs, while increasing mRNA levels of PPARα. On the other hand, SREBP1c silencing in non-OA and OA treated cells enhanced autophagy mediated LD catabolism. CONCLUSION: Our results implicate the effect of SREBP1c deficiency in modulating PPARα signaling and autophagy mediated LD catabolism against OA induced lipid accumulation.

alpha-Tocopherol supplementation reduces inflammation and apoptosis in high cholesterol mediated nonalcoholic steatohepatitis.

Inflammation and apoptosis signaling are crucial steps in the progression from nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis (NASH). Alpha-tocopherol, the most active form of vitamin E, is an important modulator of signaling mechanisms, but its involvement to cholesterol-induced NASH pathogenesis remains poorly defined. Herein we have reported a novel effect of α-tocopherol in the transition from hepatic steatosis to NASH. High cholesterol diet alone (without α-tocopherol) in rabbits elevated NASH development as indicated by increased inflammatory response, apoptotic activity and liver fibrosis. Such elevation results from induction of signaling mechanisms since the expressions of IL1ß, phospho c-Jun/c-Jun ratio, JNK, caspase 9, CHOP and Bax were increased, and recruitment of macrophage, α-smooth muscle actin (α-SMA) and COL1A1 into the liver tissue were induced. Alpha-tocopherol supplementation inhibited inflammatory response, apoptosis and fibrosis development without affecting lipid accumulation in high cholesterol-induced NASH. Specifically, α-tocopherol lowered the inflammatory level as observed by reduced macrophage infiltration and JNK/c-Jun signaling. Lower inflammatory status co-occurred with the reduction of CHOP and Bax expressions as well as fibrosis-related COL1A1 and α-SMA levels. Taken together, α-tocopherol supplementation inhibits cholesterol-induced NASH development by lowering JNK/c-Jun/inflammation axis in addition to JNK/CHOP/apoptosis signaling, which might contribute to resistance against NAFLD/NASH transition.

Endoplasmic Reticulum Stress and miRNA Impairment in Aging and Age-Related Diseases.

Aging is a physiological process defined by decreased cellular and tissue functions. Reduced capacity of protein degradation is one of the important hallmarks of aging that may lead to misfolded protein accumulation and progressive loss of function in organ systems. Recognition of unfolded/misfolded protein aggregates via endoplasmic reticulum (ER) stress sensors activates an adaptive mechanism, the unfolded protein response (UPR). The initial step of UPR is defined by chaperone enhancement, ribosomal translation suppression, and misfolded protein degradation, while prolonged ER stress triggers apoptosis. MicroRNAs (miRNAs) are non-coding RNAs affecting various signaling pathways through degradation or translational inhibition of targeted mRNAs. Therefore, UPR and miRNA impairment in aging and age-related diseases is implicated in various studies. This review will highlight the recent insights in ER stress-miRNAs alterations during aging and age-related diseases, including metabolic, cardiovascular, and neurodegenerative diseases and several cancers.

High-throughput profiling reveals perturbation of endoplasmic reticulum stress-related genes in atherosclerosis induced by high-cholesterol diet and the protective role of vitamin E.

Formation of atherosclerotic plaques, called atherogenesis, is a complex process affected by genetic and environmental factors. It was proposed that endoplasmic reticulum (ER) stress is an important factor in the pathogenesis of atherosclerosis and that vitamin E affects atherosclerotic plaque formation via its antioxidant properties. Here, we investigated ER stress-related molecular mechanisms in high-cholesterol diet (HCD, 2%)-induced atherosclerosis model and the role of vitamin E supplementation in it, beyond its antioxidant properties. The consequences of HCD and vitamin E supplementation were examined by determining protein levels of ER stress markers in aortic tissues. As vitamin E supplementation acts on several unfolded protein response (UPR) factors, it decreased ER stress induced by HCD. To elucidate the associated pathways, gene expression profiling was performed, revealing differentially expressed genes enriched in ER stress-related pathways such as the proteasome and the apoptosis pathways. We further assessed the proteasomal activity impaired by HCD in the aorta and showed that vitamin E reversed it to that of control animals. Overall, the study characterized the effects of HCD and vitamin E on ER stress-related gene expression, revealing the role of proteolytic systems during atherogenesis.

Cholesterol induced autophagy via IRE1/JNK pathway promotes autophagic cell death in heart tissue.

BACKGROUND: Cardiovascular diseases (CVDs), with highest mortality and morbidity rates, are the major cause of death in the world. Due to the limited information on heart tissue changes, mediated by hypercholesterolemia, we planned to investigate molecular mechanisms of endoplasmic reticulum (ER) stress and related cell death in high cholesterol fed rabbit model and possible beneficial effects of α-tocopherol. METHODS: Molecular changes in rabbit heart tissue and cultured cardiomyocytes (H9c2 cells) were measured by western blotting, qRT-PCR, immunflouresence and flow cytometry experiments. Histological modifications were assessed by light and electron microscopes, while degradation of mitochondria was quantified through confocal microscope. RESULTS: Feeding rabbits 2% cholesterol diet for 8 weeks and treatment of cultured cardiomyocytes with 10 µg/mL cholesterol for 3 h induced excessive autophagic activity via IRE1/JNK pathway. While no change in ER-associated degradation (ERAD) and apoptotic cell death were determined, electron and confocal microscopy analyses in cholesterol supplemented rabbits revealed significant parameters of autophagic cell death, including cytoplasmic autophagosomes, autolysosomes and organelle loss in juxtanuclear area as well as mitochondria engulfment by autophagosome. Either inhibition of ER stress or JNK in cultured cardiomyocytes or α-tocopherol supplementation in rabbits could counteract the effects of cholesterol. CONCLUSION: Our findings underline the essential role of hypercholesterolemia in stimulating IRE1/JNK branch of ER stress response which then leads to autophagic cell death in heart tissue. Results also showed α-tocopherol as a promising regulator of autophagic cell death in cardiomyocytes.

Vitamin E: Regulatory role in the cardiovascular system.

Cardiovascular disease (CVD) is one of the major causes of morbidity and mortality, all around the world. Vitamin E is an important nutrient influencing key cellular and molecular mechanisms as well as gene expression regulation centrally involved in the prevention of CVD. Cell culture and animal studies have focused on the identification of vitamin E regulated signaling pathways and involvement on inflammation, lipid homeostasis, and atherosclerotic plaque stability. While some of these vitamin E functions were verified in clinical trials, some of the positive effects were not translated into beneficial outcomes in epidemiological studies. In recent years, the physiological metabolites of vitamin E, including the liver derived (long- and short-chain) metabolites and phosphorylated (α-, γ-tocopheryl phosphate) forms, have also provided novel mechanistic insight into CVD regulation that expands beyond the vitamin E precursor. It is certain that this emerging insight into the molecular and cellular action of vitamin E will help to design further studies, either in animal models or clinical trials, on the reduction of risk for CVDs. This review focuses on vitamin E-mediated preventive cardiovascular effects and discusses novel insights into the biology and mechanism of action of vitamin E metabolites in CVD. © 2019 IUBMB Life, 71(4):507-515, 2019.

High Cholesterol Diet-Induced Changes in Oxysterol and Scavenger Receptor Levels in Heart Tissue.

Involvement of high cholesterol and oxidative stress in cardiovascular diseases is well studied, as it can be hypothesized that various products originated from lipid peroxidation, such as oxysterols, or affected protein expression might lead to cardiomyocyte damage followed by the pathological modifications. Although oxidation of excessive cholesterol to oxysterols in elevated stress conditions is identified by a number of studies, the role of a high cholesterol diet in regulating fatty acid and oxysterol accumulation, together with scavenger receptor mRNA levels, in the heart remains little investigated. Our study provides a detailed analysis of the changes in fatty acid, oxysterol, and scavenger receptor profiles and its relation with histological alterations in the heart tissue. We evaluated alterations of fatty acid composition, by the GC-MS method, while 4ß-, 25-, and 27-hydroxycholesterol and 7-ketocholesterol levels by means of LC-MS/MS in high cholesterol diet-fed rabbits. Additionally, a number of proteins related to lipid metabolism and scavenger receptor mRNA expressions were evaluated by Western blotting and RT-PCR. According to our in vivo results, a high cholesterol diet enhances a number of unsaturated fatty acids, oxysterols, and LXRα, in addition to CD36, CD68, CD204, and SR-F1 expressions while α-tocopherol supplementation decreases LXRα and SR expressions together with an increase in 27-hydroxycholesterol and ABCA1 levels. Our results indicated that the high cholesterol diet modulates proteins related to lipid metabolism, which might result in the malfunction of the heart and α-tocopherol shows its beneficial effects. We believe that this work will lead the generation of different theories in the development of heart diseases.

CD36 expression in peripheral blood mononuclear cells reflects the onset of atherosclerosis.

Together 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. © 2018 BioFactors, 44(6):588-596, 2018.

Impact of high cholesterol and endoplasmic reticulum stress on metabolic diseases: An updated mini-review.

Endoplasmic reticulum (ER) is the major site of protein folding and calcium storage. Beside the role of ER in protein homeostasis, it controls the cholesterol production and lipid-membrane biosynthesis as well as surviving and cell death signaling mechanisms in the cell. It is well-documented that elevated plasma cholesterol induces adverse effects in cardiovascular diseases (CVDs), liver disorders, such as non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatosis hepatitis (NASH), and metabolic diseases which are associated with oxidative and ER stress. Recent animal model and human studies have showed high cholesterol and ER stress as an emerging factors involved in the development of many metabolic diseases. In this review, we will summarize the crucial effects of hypercholesterolemia and ER stress response in the pathogenesis of CVDs, NAFLD/NASH, diabetes and obesity which are major health problems in western countries.

Vitamin E: Emerging aspects and new directions.

The discovery of vitamin E will have its 100th anniversary in 2022, but we still have more questions than answers regarding the biological functions and the essentiality of vitamin E for human health. Discovered as a factor essential for rat fertility and soon after characterized for its properties of fat-soluble antioxidant, vitamin E was identified to have signaling and gene regulation effects in the 1980s. In the same years the cytochrome P-450 dependent metabolism of vitamin E was characterized and a first series of studies on short-chain carboxyethyl metabolites in the 1990s paved the way to the hypothesis of a biological role for this metabolism alternative to vitamin E catabolism. In the last decade other physiological metabolites of vitamin E have been identified, such as α-tocopheryl phosphate and the long-chain metabolites formed by the ω-hydroxylase activity of cytochrome P-450. Recent findings are consistent with gene regulation and homeostatic roles of these metabolites in different experimental models, such as inflammatory, neuronal and hepatic cells, and in vivo in animal models of acute inflammation. Molecular mechanisms underlying these responses are under investigation in several laboratories and side-glances to research on other fat soluble vitamins may help to move faster in this direction. Other emerging aspects presented in this review paper include novel insights on the mechanisms of reduction of the cardiovascular risk, immunomodulation and antiallergic effects, neuroprotection properties in models of glutamate excitotoxicity and spino-cerebellar damage, hepatoprotection and prevention of liver toxicity by different causes and even therapeutic applications in non-alcoholic steatohepatitis. We here discuss these topics with the aim of stimulating the interest of the scientific community and further research activities that may help to celebrate this anniversary of vitamin E with an in-depth knowledge of its action as vitamin.

Proteasome inhibitors in cancer therapy: Treatment regimen and peripheral neuropathy as a side effect.

Proteasomal 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.

Endoplasmic reticulum stress related molecular mechanisms in nonalcoholic steatohepatitis.

Nonalcoholic steatohepatitis (NASH) is considered to be a common health problem since the incidence of nonalcoholic fatty liver disease (NAFLD) has increased in recent years. Disturbed hepatic cholesterol homeostasis and free cholesterol accumulation in liver results in increased oxidative stress leading to the endoplasmic reticulum (ER) stress. Activated ER stress maintains protein homeostasis however, delayed or inadequate ER stress responses may induce fat accumulation, insulin resistance, inflammation, apoptosis, and autophagy, all of which increase with age and play crucial roles in the pathogenesis of NASH. In aging research, there is a growing interest for the role of ER stress in the progression of NASH since aging seems to favor NAFLD according to its pathogenesis. On the other hand, specific microRNAs (miRNAs) expression profiles are strongly related with ER stress as well as NASH progresses. This review highlights molecular mechanisms related to ER stress in the pathogenesis of NASH and miRNAs for the progression and treatment of the disease.

Effect of a hypercholesterolemia as a starting factor on spinal degeneration in rabbits and role of Vitamin E (α-tocopherol).

BACKGROUND: To identify the role of the hypercholesterolemia as a starting factor in discovertebral degeneration that ultimately causes lower back pain, and investigate the role of Vitamin E in this process. METHODS: The rabbits (n = 32) were divided into two broad experimental groups: A control group, and a hypercholesterolemia group, namely cholesterol, and cholesterol plus Vitamin E groups and they were fed sequentially for 4 or 8 weeks. Serum cholesterol and Vitamin E (α-tocopherol) levels were determined; vascular tissue was prepared for histopathological analyses and vertebra was decalcified for the study. RESULTS: Cholesterol diet group resulted approximately 44-fold of increase plasma cholesterol levels over the 4-week control values. Additional supplementation with Vitamin E group induced a plasma cholesterol level increase of only 37-fold as compared to the control group. In the cholesterol groups, light microscope examination revealed atherosclerotic plaque in major arteries. However, in the cholesterol plus Vitamin E treatment groups, no lipid accumulation or foam cell formation was visible in the abdominal aorta and vertebral segmental artery. In histopathological examination, we found degenerative changes in the discovertebral unit in cholesterol treated groups. CONCLUSION: Hypercholesterolemia causes fat accumulation in the disc endplate and vertebral body that causes blood supply disturbances which might be a starting factor of discovertebral degeneration. This event was not reversed by the elimination of cholesterol from the diet. Vitamin E supplementation was not effective in reducing fat accumulation in vertebral bone marrow. As a result, we conclude that degeneration of the discovertebral unit is not related to atherosclerotic changes in the major blood vessels.

Nrf2 silencing to inhibit proteolytic defense induced by hyperthermia in HT22 cells.

Nrf2 pathway has been known to be protective against cancer progression however recent studies have revealed that the antioxidant activity of Nrf2 contributes to chemotherapy resistance. For many years, hyperthermia has been used as an additional therapy to increase the efficiency of chemotherapy and radiotherapy. Besides the positive effects of hyperthermia during treatment procedure, thermotolerance has been found to develop against heat treatment. Although the involved molecular mechanisms have not been fully clarified, heat shock proteins (HSP) and proteasome activity are known to be involved in the acquisition of thermotolerance. The aim of this study was to investigate the potential beneficial effects of combining hyperthermia with Nrf2 silencing to inhibit molecular mechanisms leading to induction of defense mechanisms in transcription level. Following heat treatment of HT22 cells, HSP70 and the proteasome levels and as well as proteasome activity were found to be elevated in the nucleus. Our results demonstrated that Nrf2 silencing reduced defense mechanisms against heat treatment both in antioxidant and proteolytic manner and Nrf2 may be a potential target for therapeutic approach in order to improve the beneficial effects of hyperthermia in cancer therapy.

Endoplasmic reticulum stress and proteasomal system in amyotrophic lateral sclerosis.

Protein processing including folding, unfolding and degradation is involved in the mechanisms of many diseases. Unfolded protein response and/or endoplasmic reticulum stress are accepted to be the first steps which should be completed via protein degradation. In this direction, proteasomal system and autophagy play important role as the degradation pathways and controlled via complex mechanisms. Amyotrophic lateral sclerosis is a multifactorial neurodegenerative disease which is also known as the most catastrophic one. Mutation of many different genes are involved in the pathogenesis such as superoxide dismutase 1, chromosome 9 open reading frame 72 and ubiquilin 2. These genes are mainly related to the antioxidant defense systems, endoplasmic reticulum stress related proteins and also protein aggregation, degradation pathways and therefore mutation of these genes cause related disorders.This review focused on the role of protein processing via endoplasmic reticulum and proteasomal system in amyotrophic lateral sclerosis which are the main players in the pathology. In this direction, dysfunction of endoplasmic reticulum associated degradation and related cell death mechanisms that are autophagy/apoptosis have been detailed.