PGC1α Promotes Cisplatin Resistance in Ovarian Cancer by Regulating the HSP70/HK2/VDAC1 Signaling Pathway.

Mitochondrial apoptosis is one of the main mechanisms for cancer cells to overcome chemoresistance. Hexokinase 2 (HK2) can resist cancer cell apoptosis by expressing on mitochondria and binding to voltage-dependent anion channel 1 (VDAC1). We previously reported that peroxisome proliferator-activated receptor coactivator 1 α (PGC1α) is highly expressed in ovarian cancer cisplatin-resistant cells. However, the underlying mechanism remains unclear. Therefore, we evaluated the interaction between PGC1α and HK2 in ovarian cancer cisplatin-resistant cells. We found that the knockdown of PGC1α promotes the apoptosis of ovarian cancer cisplatin-resistant cells and increases their sensitivity to cisplatin. In addition, we found that the knockdown of PGC1α affects the mitochondrial membrane potential and the binding of HK2 and VDAC1. As the heat shock protein 70 (HSP70) family can help protein transport, we detected it and found that PGC1α can promote HSP70 gene transcription. Furthermore, HSP70 can promote an increase of HK2 expression on mitochondria and an increase of binding to VDAC1. Based on these results, PGC1α may reduce apoptosis through the HSP70/HK2/VDAC1 signaling pathway, thus promoting cisplatin resistance of ovarian cancer. These findings provide strong theoretical support for PGC1α as a potential therapeutic target of cisplatin resistance in ovarian cancer.

Major contribution of the 3/6/7 class of TRPC channels to myocardial ischemia/reperfusion and cellular hypoxia/reoxygenation injuries.

The injury phase after myocardial infarcts occurs during reperfusion and is a consequence of calcium release from internal stores combined with calcium entry, leading to cell death by apoptopic and necrotic processes. The mechanism(s) by which calcium enters cells has(ve) not been identified. Here, we identify canonical transient receptor potential channels (TRPC) 3 and 6 as the cation channels through which most of the damaging calcium enters cells to trigger their death, and we describe mechanisms activated during the injury phase. Working in vitro with H9c2 cardiomyoblasts subjected to 9-h hypoxia followed by 6-h reoxygenation (H/R), and analyzing changes occurring in areas-at-risk (AARs) of murine hearts subjected to a 30-min ischemia followed by 24-h reperfusion (I/R) protocol, we found: (i) that blocking TRPC with SKF96365 significantly ameliorated damage induced by H/R, including development of the mitochondrial permeability transition and proapoptotic changes in Bcl2/BAX ratios; and (ii) that AAR tissues had increased TUNEL+ cells, augmented Bcl2/BAX ratios, and increased p(S240)NFATc3, p(S473)AKT, p(S9)GSK3ß, and TRPC3 and -6 proteins, consistent with activation of a positive-feedback loop in which calcium entering through TRPCs activates calcineurin-mediated NFATc3-directed transcription of TRPC genes, leading to more Ca2+ entry. All these changes were markedly reduced in mice lacking TRPC3, -6, and -7. The changes caused by I/R in AAR tissues were matched by those seen after H/R in cardiomyoblasts in all aspects except for p-AKT and p-GSK3ß, which were decreased after H/R in cardiomyoblasts instead of increased. TRPC should be promising targets for pharmacologic intervention after cardiac infarcts.

An integrated transcriptomic and computational analysis for biomarker identification in gastric cancer.

This report describes an integrated study on identification of potential markers for gastric cancer in patients' cancer tissues and sera based on: (i) genome-scale transcriptomic analyses of 80 paired gastric cancer/reference tissues and (ii) computational prediction of blood-secretory proteins supported by experimental validation. Our findings show that: (i) 715 and 150 genes exhibit significantly differential expressions in all cancers and early-stage cancers versus reference tissues, respectively; and a substantial percentage of the alteration is found to be influenced by age and/or by gender; (ii) 21 co-expressed gene clusters have been identified, some of which are specific to certain subtypes or stages of the cancer; (iii) the top-ranked gene signatures give better than 94% classification accuracy between cancer and the reference tissues, some of which are gender-specific; and (iv) 136 of the differentially expressed genes were predicted to have their proteins secreted into blood, 81 of which were detected experimentally in the sera of 13 validation samples and 29 found to have differential abundances in the sera of cancer patients versus controls. Overall, the novel information obtained in this study has led to identification of promising diagnostic markers for gastric cancer and can benefit further analyses of the key (early) abnormalities during its development.

Regulation of endoplasmic reticulum stress in rat cortex by p62/ZIP through the Keap1-Nrf2-ARE signalling pathway after transient focal cerebral ischaemia.

PRIMARY OBJECTIVE: p62/ZIP as the autophagy receptor can transport the misfolded proteins to a macroautophagy-lysosome system for degradation and also create a positive feedback loop between p62/ZIP and Nrf2. However, the role of p62/ZIP on cerebral ischaemia is unclear. The aim of this study was to evaluate the role of p62/ZIP in the regulation of endoplasmic reticulum(ER) stress induced by cerebral ischaemia/reperfusion. RESEARCH DESIGN: Different ischemic periods were designed by transient middle cerebral artery occlusion (tMCAO) using the suture method. METHODS AND PROCEDURES: At 24 hours after reperfusion, the ischaemic brain tissue was studied histologically and biochemically for autophagic, ER stress and Keap1-Nrf2-ARE signalling pathway markers. MAIN OUTCOMES AND RESULTS: Prolongation of ischaemia significantly increased the cortical injury observed in rats and was associated with a gradual increase in the protein expression of ubiquitin-aggregates, Grp78, GADD153/CHOP and p62/ZIP. Autophagy marker Atg12-Atg5 and LC3-PE increased and then decreased. Moreover, p62/ZIP mRNA expression increased and then decreased and was consistent with Nrf2 activation. CONCLUSIONS: p62/ZIP not only plays a key role in scavenging protein aggregates during autophagy, but it may also be involved in preventing oxidative injury and alleviating ER stress through the Keap1-Nrf2-ARE signalling pathway during cerebral ischaemia/reperfusion injury.

Chronological changes of viral shedding in adult inpatients with Omicron infection in Shanghai, China.

Background: Coronavirus disease 2019 (COVID-19) caused by the Omicron variant occurred in Shanghai, China, but its clinical characteristics and virology have not been comprehensively described. Methods: This retrospective cohort study included adult inpatients (≥18 years) diagnosed with COVID-19 at Changhai Hospital. Laboratory and clinical data were obtained from electronic medical records to investigate the clinical characteristics of COVID-19 and the variations in the patients' laboratory indexes were examined. Results: The symptoms of COVID-19 caused by the Omicron variant were relatively mild. Upper respiratory tract specimens yielded higher positive detection rates than lower respiratory tract and intestinal specimens. Peak COVID-19 viral load was reached at the time of admission; quantification cycle (Cq) values increased to approximately 35 after 8.54 days. In vivo viral shedding duration correlated with age and disease severity (p<0.05). The older the patient and the more severe the disease, the longer the duration of viral shedding was. Portion parameters of blood routine, coagulative function, clinical chemistry, and inflammatory factor showed a certain correlation with the SARS-CoV-2 viral load. Conclusions: Virus replication and shedding are rapid in Omicron-positive patients; COVID-19 in these patients is characterized by acute onset, mild symptoms, and fast recovery. Older patients and those with more severe disease demonstrate prolonged virus shedding. Routine hematological indexes can reveal disease severity and help clinically evaluate the patient's condition.

[Significance and expression of FKHR and AKT after subarachnoid hemorrhage in rat brain cortex].

OBJECTIVE: To study the significance and expression of FKHR and AKT after subarachnoid hemorrhage (SAH) in rat brain cortex. METHODS: Twenty-four rats were randomly divided into three groups: sham, SAH and SAH plus nimodipine (n=8 each). A reliable SAH model was established by double injections of blood into cistern magna in Wistar rats. The neurological scores were measured by Loeffler and the expressions of FKHR, P-FKHR, AKT and P-FKHR detected by Western blot. RESULTS: Compared with sham group, the neurological score of SAH group obviously decreased (P < 0.05), the expression of FKHR became elevated in rat cortex (P < 0.01), the expression of AKT had no change and the expressions of P-AKT and P-FKHR obviously decreased (all P < 0.01). But the neurological score markedly increased (P < 0.01) and the expressions of P-AKT and P-FKHR became elevated (all P < 0.01) after administration of nimodipine. CONCLUSION: Both P-AKT and P-FKHR are involved in the process of brain cortex damage induced by SAH. The protective effects of nimodipine on brain injury induced by SAH may be related to the elevated expressions of P-AKT and P-FKHR in brain cortex.

Mitochondrial serine protease Omi/HtrA2 accentuates brain ischemia/reperfusion injury in rats and oxidative stress injury in vitro by modulating mitochondrial stress proteins CHOP and ClpP and physically interacting with mitochondrial fusion protein OPA1.

Serine protease Omi/HtrA2, a member of the HtrA family, is closely related to the maintenance of mitochondrial integrity and participates in apoptosis but its role in cerebral ischemia/reperfusion (I/R) injury and cellular oxidative stress response remains unclear. In this study, we found that I/R injury resulted in a time-dependent increase in Omi/HtrA2 expression in rat brain tissue. Inhibition of Omi/HtrA2 significantly inhibited XIAP cleavage in H2O2-induced PC12 cells. In addition, inhibition of Omi/HtrA2 significantly inhibited the up-regulation of mitochondrial stress proteins CHOP and ClpP, significantly reduced mitochondrial aggregation, and attenuated the decline of mitochondrial ΔΨm in PC12 cells. Studies show that there is a physical interaction between Omi/HtrA2 and OPA1. We found that Omi/HtrA2 and OPA1 are closely related to the oxidative stress mitochondrial response in PC12 cells. The current study has demonstrated that Omi/HtrA2 is upregulated in brain I/R injury in vivo and is implicated in mitochondrial response to oxidative stress in vitro by regulating mitochondrial stress proteins CHOP and CLpP and by interacting with mitochondrial cristae remodeling protein OPA1. These findings suggest that Omi/HtrA2 could be a candidate molecular target in diseases that involve oxidative stress such as in I/R injury. Abbreviation: ATP: Adenosine tripHospHate; Bax: BCL2-Associated X; Bcl-2: B-cell lympHoma-2; BSA: Albumin from bovine serum; DMEM: Dulbecco's Minimum Essential Medium; DMSO: Dimethyl sulfoxide; HSP60: Heat shock protein60, 70; L-OPA1: Long forms of OPA1; Omi/HtrA2: high-temperature-regulated A2; MCAO: Middle cerebral artery occlusion; OPA1: Optic AtropHy; PBS: PHospHate buffered saline; PMSF: pHenylmethyl sulfonylfluoride; ROS: reactive oxygen species; SDS: Sodium dodecyl sulfate; S-OPA1: Short forms of OPA1; TTC: TripHenyltetrazalium chloride; XIAP: X-linked inhibitor apoptosis protein.

Genipin protects against cerebral ischemia-reperfusion injury by regulating the UCP2-SIRT3 signaling pathway.

Cerebral ischemia-reperfusion injury is a thorny issue in the treatment of stroke. Energy depletion and oxidative stress are the core mechanisms underlying cerebral ischemia-reperfusion injury. Mitochondrial function is involved in energy production and oxidative stress. It has been reported that mitochondrial uncoupling protein 2 (UCP2) may be involved in the regulation of cerebral ischemia-reperfusion injury. We hypothesized that UCP2 can regulate cerebral ischemia-reperfusion injury by regulating energy supply and oxidative stress. To test this hypothesis, we used a middle cerebral artery occlusion model in male C57BL/6 mice with/without genipin--an UCP2-specific inhibitor. We measured the expression and/or activity of UCP2, SIRT3, the level of ATP, and antioxidant-related molecules in the cerebral cortex and the LDH in serum after ischemia-reperfusion, the level of apoptosis was reflected by the level of cleaved-caspase3 and tunel staining. The results showed an increase in the expression of UCP2, coinciding with an increase in the level of apoptosis, NAD+/NADH ratio, SIRT3 activity, LDH release and a decrease in the level of ATP and antioxidant-related molecules after 1 h of ischemia and 24 h of reperfusion. These findings suggest that UCP2 may regulate energy supply and oxidative stress in ischemia-reperfusion injury. Interestinly, above changes can be reserved by administration of genipin with the brain damage level going down. In conclusion, the UCP2-SIRT3 signaling pathway is involved in the regulation of cerebral ischemia-reperfusion injury as a bridge between energy metabolism and oxidative stress. Genipin protects against cerebral ischemia-reperfusion injury by inhibiting UCP2.

Role of the PI3K/AKT signalling pathway in apoptotic cell death in the cerebral cortex of streptozotocin-induced diabetic rats.

Diabetes mellitus is associated with cognitive dysfunction. Numerous previous studies have shown that type 1 diabetes-induced hyperglycaemia causes structural brain damage, such as a decrease in whole-brain grey matter. The impact of diabetes mellitus on the cerebral cortex is poorly understood and requires further clarification. In the present study, diabetes was induced via an intraperitoneal injection of streptozotocin (50 mg/kg). Hematoxylin and eosin (H&E) staining was performed to detect the morphological changes in the cerebral cortex, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) staining was used to detect neuronal apoptosis and western blotting was performed to determine protein expression levels. Nine weeks after the induction of diabetes, the body weight was significantly lower and the blood glucose levels were significantly higher in the diabetic rats than in the control rats (P<0.05). H&E staining revealed nuclear chromatin condensation and cytoplasmic shrinkage in the cerebral cortex of the diabetic rats and TUNEL staining further indicated apoptotic changes in the cerebral cortex of the diabetic rats. The ratio of B-cell lymphoma 2 (Bcl-2) -associated X protein/Bcl-2 and the expression of cytochrome c and activated caspase-3 (cleaved caspase-3) were significantly increased, whereas the ratio of phosphorylated AKT/AKT was significantly decreased in the diabetic rats compared with that in the control rats (P<0.05). Taken together, these results suggested that diabetes mellitus may induce neuronal apoptosis in the cerebral cortex by downregulating AKT phosphorylation.

Novel and Practical Scoring Systems for the Diagnosis of Thyroid Nodules.

OBJECTIVE: The clinical management of patients with thyroid nodules that are biopsied by fine-needle aspiration cytology and yield indeterminate results remains unsettled. The BRAF V600E mutation has dubious diagnostic value due to its low sensitivity. Novel strategies are urgently needed to distinguish thyroid malignancies from thyroid nodules. DESIGN: This prospective study included 504 thyroid nodules diagnosed by ultrasonography from 468 patients, and fine-needle aspiration cytology was performed under ultrasound guidance. Cytology and molecular analysis, including BRAF V600E, RET/PTC1 and RET/PTC3, were conducted simultaneously. The cytology, ultrasonography results, and mutational status were gathered and analyzed together. Predictive scoring systems were designed using a combination of diagnostic parameters for ultrasonography, cytology and genetic analysis. The utility of the scoring systems was analyzed and compared to detection using the individual methods alone or combined. RESULT: The sensitivity of scoring systema (ultrasonography, cytology, BRAF V600E, RET/PTC) was nearly identical to that of scoring systemb (ultrasonography, cytology, BRAF V600E); these were 91.0% and 90.2%, respectively. These sensitivities were significantly higher than those obtained using FNAC, genetic analysis and US alone or combined; their sensitivities were 63.9%, 70.7% and 87.2%, respectively. Scoring systemc (ultrasonography, cytology) was slightly inferior to the former two scoring systems but still had relatively high sensitivity and specificity (80.5% and 95.1%, respectively), which were significantly superior to those of single cytology, ultrasonography or genetic analysis. In nodules with uncertainty cytology, scoring systema, scoring systemb and scoring systemc could elevate the malignancy detection rates to 69.7%, 69.7% and 63.6%, respectively. CONCLUSION: These three scoring systems were quick for clinicians to master and could provide quantified information to predict the probability of malignant nodules. Scoring systemb is recommended for improving the detection rate among nodules of uncertain cytology.

SIRT3 participates in glucose metabolism interruption and apoptosis induced by BH3 mimetic S1 in ovarian cancer cells.

The Bcl-2 antiapoptotic proteins are important cancer therapy targets; however, their role in cancer cell metabolism remains unclear. We found that the BH3-only protein mimetic S1, a novel pan Bcl-2 inhibitor, simultaneously interrupted glucose metabolism and induced apoptosis in human SKOV3 ovarian cancer cells, which was related to the activation of SIRT3, a stress-responsive deacetylase. S1 interrupted the cellular glucose metabolism mainly through causing damage to mitochondrial respiration and inhibiting glycolysis. Moreover, S1 upregulated the gene and protein expression of SIRT3, and induced the translocation of SIRT3 from the nucleus to mitochondria. SIRT3 silencing reversed the effects of S1 on glucose metabolism and apoptosis through increasing the level of HK-II localized to the mitochondria, while a combination of the glycolysis inhibitor 2-DG and S1 intensified the cytotoxicity through further upregulation of SIRT3 expression. This study underscores an essential role of SIRT3 in the antitumor effect of Bcl-2 inhibitors in human ovarian cancer through regulating both metabolism and apoptosis. The manipulation of Bcl-2 inhibitors combined with the use of classic glycolysis inhibitors may be rational strategies to improve ovarian cancer therapy.

Non-secreting multiple myeloma switches to IgD of lamda type: a case report and review of literature.

We report a case of a woman, who initially presented with an non-secreting multiple myeloma, 11 months later, she was diagnosed as an IgD-secreting myeloma. In December, 2010, the patient's serum protein quantification and immunofixation electrophoresis (IFE) revealed polyclonal immunoglobulin with no evidence of monoclonal immunoglobulin. However, her bone marrow smears revealed an abnormal proliferation of atypical plasma cells (46.5%), so she was diagnosed as non-secreting multiple myeloma. After three cycles of administration of Velcade plus Dexamethasone (VD), she achieved a complete remission (CR). Unfortunately, on October 31, 2011, our patient was found to have a separate peak of monoclonal component on the γ-region of cellulose-acetate electrophoresis, and the serum immunofixation electrophoresis revealed the monoclonal component was IgD. Several months later, she presented with a large swelling of the left side of her neck. Microscopic examination of a biopsy specimen from the cervical mass showed a neoplastic plasma cell tumor and she died on January 28, 2013 from acute respiratory failure resulting from neoplastic plasma cells infiltration and infection. Here we report this rare case and review the literature for similar cases.

p62 participates in the inhibition of NF-κB signaling and apoptosis induced by sulfasalazine in human glioma U251 cells.

Nuclear factor-κB (NF-κB) is constitutively activated in most malignant gliomas and is involved in cancer progression and drug resistance to chemotherapy. Sulfasalazine (SAS) is a classic inhibitor of NF-κB. Apoptosis and autophagy were induced by SAS accompanied by inhibition of NF-κB signaling in U251 cells. Inhibition of autophagy by 3-MA suppressed the effects of SAS on NF-κB signaling and apoptosis in U251 cells. Multifunctional scaffold protein p62 is well known as an autophagy marker protein and provides crosstalk for important signaling pathways, including NF-κB signaling. SAS-induced decrease in the p62 protein levels may be the result of degradation through autophagy. SAS induced the inhibition of NF-κB signaling and apoptosis at least partly via a p62-dependent effect in U251 cells. Collectively, our data shed light on the link between p62 and the NF-κB signaling pathway, particularly in glioma cells. The results may facilitate the design of more effective targeted therapies for the treatment of tumors in which NF-κB signaling is altered.

Autophagic flux promotes cisplatin resistance in human ovarian carcinoma cells through ATP-mediated lysosomal function.

Lysosomes are involved in promoting resistance of cancer cells to chemotherapeutic agents. However, the mechanisms underlying lysosomal influence of cisplatin resistance in ovarian cancer remain incompletely understood. We report that, compared with cisplatin-sensitive SKOV3 cells, autophagy increases in cisplatin-resistant SKOV3/DDP cells treated with cisplatin. Inhibition of early-stage autophagy enhanced cisplatin-mediated cytotoxicity in SKOV3/DDP cells, but autophagy inhibition at a later stage by disturbing autophagosome-lysosome fusion is more effective. Notably, SKOV3/DDP cells contained more lysosomes than cisplatin-sensitive SKOV3 cells. Abundant lysosomes and lysosomal cathepsin D activity were required for continued autolysosomal degradation and maintenance of autophagic flux in SKOV3/DDP cells. Furthermore, SKOV3/DDP cells contain abundant lysosomal ATP required for lysosomal function, and inhibition of lysosomal ATP accumulation impaired lysosomal function and blocked autophagic flux. Therefore, our findings suggest that lysosomes at least partially contribute to cisplatin resistance in ovarian cancer cells through their role in cisplatin-induced autophagic processes, and provide insight into the mechanism of cisplatin resistance in tumors.

Effects of ghrelin on the proliferation and secretion of splenic T lymphocytes in mice.

Ghrelin, a novel gut--brain peptide predominantly produced by the stomach, displays strong growth hormone (GH)-releasing activity mediated by the hypothalamus-pituitary GH secretagogue receptor (GHS-R). Recently, the ghrelin receptor has also been detected in peripheral systems including immune tissues, suggesting that ghrelin may play an important role in the regulation of immune function. In this paper, we assessed the presence and function of the ghrelin receptor in murine splenic T cells. The enriched T cells express the mRNA of ghrelin and ghrelin receptor mRNA, and there is a significantly positive correlation between them. Moreover, we showed that ghrelin dose-dependently inhibits proliferation of splenic T cells when they are costimulated by anti-CD3. In addition, ghrelin suppressed Th(1) (IL-2 and IFN-gamma) and Th(2) (IL-4 and IL-10) cytokines mRNA expression. These results demonstrate the presence of the ghrelin receptor in murine spleen T lymphocytes and a functional role of ghrelin as a modulator of lymphocyte function. This function of ghrelin may have some relevance to the pathophysiology of immunologic alterations related to metabolism.

p62/SQSTM1 is involved in cisplatin resistance in human ovarian cancer cells via the Keap1-Nrf2-ARE system.

The mechanisms underlying cisplatin resistance in tumors are not fully understood. Previous studies have reported that cellular resistance to oxidative stress is accompanied by resistance to cisplatin. However, the relationship between the resistance to oxidative stress and cisplatin drug resistance in human ovarian cancer cells (HOCCs) is not clear. Here, we reveal a critical role for the multifunctional protein p62/SQSTM1 in cisplatin resistance in human ovarian cancer cells (HOCCs). p62/SQSTM1 (sequestosome 1) plays important roles in cell differentiation, proliferation and as an antiapoptotic molecule. We found that cisplatin-resistant SKOV3/DDP cells express much higher levels of p62 than do cisplatin-sensitive SKOV3 cells. The protein p62 can activate the Keap1-Nrf2-ARE signaling pathway and induce the expression of antioxidant genes in SKOV3/DDP cells. Knockdown of p62 resensitizes SKOV3/DDP cells to cisplatin. Collectively, our data indicate that cisplatin resistance in HOCCs is partially attributable to their high expression of p62, which plays an important role in preventing ROS stress-induced apoptosis by regulating the Keap1-Nrf2-ARE signaling pathway.

Hyperbaric oxygen enlarges the area of brain damage in MCAO rats by blocking autophagy via ERK1/2 activation.

Hyperbaric oxygen (HBO) is emerging as a therapy for brain ischemia, although its benefits are still debated. The present study aimed to investigate the effect of HBO on brain damage in a rat model of transient focal cerebral ischemia and its underlying mechanism of action. Male Wistar rats, which had suffered 1.5h of transient middle cerebral artery occlusion (tMCAO) and had a Longa's neuron score of 3, were given pure oxygen at 3.0 atm absolute, for 60 min after the third hour of reperfusion. After 24h of reperfusion, rat brains were removed and studied. 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin and eosin staining revealed that the infarct ratio in the HBO group increased remarkably when compared with the MCAO group. Up-regulation of extracellular signal-regulated kinase 1/2 (ERK1/2) activation was detected in the HBO group because of reactive oxygen species (ROS) generation. Autophagy appeared to be obstructed in the HBO group. Administration of the ERK1/2 inhibitor U0126 decreased the infarct ratio and improved protein clearance by autophagy in the HBO group. Collectively, these results suggest that HBO enlarges the area of brain damage via reactive oxygen species-induced activation of ERK1/2, which interrupts autophagy flux.

Suppression of CLIC4/mtCLIC enhances hydrogen peroxide-induced apoptosis in C6 glioma cells.

CLIC4/mtCLIC (referred to here as CLIC4) is one of the seven-member family of chloride intracellular channels (CLIC). CLIC4 localizes to the mitochondria, nucleus, cytoplasm and other organellular compartments and participates in the apoptotic response to stress. However, the role of CLIC4 in oxidative stress and apoptosis is not well understood. In this study, we showed the important role of CLIC4 in apoptosis of C6 glioma cells induced by hydrogen peroxide (H2O2). Our results showed that CLIC4 protein expression was upregulated following H2O2-induced C6 cell apoptosis. The upregulation of CLIC4 protein expression was paralleled with an increased Bax/Bcl-2 ratio, cytochrome c and cleaved caspase-3 protein expression upon H2O2-induced C6 cell apoptosis. Suppression of CLIC4 expression by RNA interference enhanced cell apoptosis, but the ratio of Bax/Bcl-2 was not involved in this process. Dissipation of mitochondrial membrane potential and nuclear translocation of CLIC4 were involved in the activation of apoptosis induced by H2O2. Our data indicate that CLIC4 protein may be a key element in the apoptotic response to oxidative stress.

Suppression of chloride channel 3 expression facilitates sensitivity of human glioma U251 cells to cisplatin through concomitant inhibition of Akt and autophagy.

Cisplatin resistance is a difficult problem in clinical chemotherapy, and the mechanisms involved in cisplatin resistance require further study. In this study, we investigated the role of chloride channel-3 (ClC-3) in cisplatin resistance. Autophagy was demonstrated by accumulation of LC3-II, beclin 1 and Atg12-Atg5. The ultrastructure changes were observed under electron microscope. Chemical staining with acridine orange or MDC was used to detect acidic vesicular organelles. Quantification of apoptosis was detected by PI and Annexin V staining. The mechanisms involved in the Akt pathway and autophagy were studied by western blot analysis. Our results showed that Akt phosphorylation and autophagy were induced by cisplatin in human glioma U251 cells. Specific inhibition of ClC-3 by ClC-3 siRNA sensitized the apoptosis-resistant U251 cells to cisplatin-mediated cell death and downregulated phosphorylated Akt. Interestingly, ClC-3 suppression also inhibited induction of autophagy by cisplatin although the Akt/mTOR pathway was deregulated. Counteracting the autophagic process by 3-methylademine enhanced cytotoxicity of cisplatin, revealing that autophagy plays a key role in chemoresistance. Suppressing the Akt/mTOR pathway by the NADPH oxidase inhibitor diphenyl iodonium (DPI) indicated that cisplatin-induced activation of Akt/mTOR pathway requires generation of reactive oxygen species (ROS) through NADPH oxidase. Collectively, our results suggest that ClC-3 suppression causes the inhibition of Akt and autophagy, which can enhance the therapeutic benefit of cisplatin in U251 cells.

Lysosome dysfunction enhances oxidative stress-induced apoptosis through ubiquitinated protein accumulation in Hela cells.

The role of lysosomal system in oxidative stress-induced apoptosis in cancer cells is not fully understood. Menadione is frequently used as oxidative stress model. It is indicated that menadione could induce autophagy in Hela cells. In the present study, we examined whether the lysosomal inhibitor, ammonium chloride (NH(4)Cl) could prevent the autophagy flux by inhibiting the fusion of autophagosomes with lysosomes and enhance apoptosis induced by menadione via mitochondrial pathway. The results demonstrated generation and accumulation of reactive oxygen species and increased levels of ubiquitinated proteins and GRP78 in cells treated with both menadione and NH(4)Cl. Our data indicates that lysosomal system through autophagy plays an important role in preventing menadione-induced apoptosis in Hela cells by clearing misfolded proteins, which alleviates endoplasmic reticulum stress.