Oxidative stress and P53 involve in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells

AIM: To explore the mechanism of fluctuant high blood glucose-induced apoptosis of renal tubular epithelial cells. METHODS: Cultured human renal tubular epithelial cells (HK-2) were treated with stable high glucose or fluctuant high glucose. Antioxidant and specific inhibitor of P53 were applied for identifying the role of oxidative stress and P53 in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells. Additionally, SD rats were randomly divided into normal control group (A), stable high blood glucose group (B) and fluctuant high blood glucose group (C). Diabetic rats were induced by intraperitoneal injection of streptozocin(STZ,65 mg/kg), and the fluctuant high blood glucose animal model was induced by intraperitoneal injection of ordinary insulin and glucose at different time points every day. The activity of superoxide dismutase (SOD) and the content of malonaldehyde (MDA) were detected by the method of colorimetry. The protein expression of NADPH oxidase 4(Nox4) and P53 were examined by immunohistochemistry and Western blotting. Apoptosis was assessed by flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). RESULTS: The cultured HK-2 cells treated with fluctuant high glucose had significantly higher apoptotic rate and expression level of P53 protein than those in the cells treated with stable high glucose. Compared with the culture solution of the cels treated with stable high glucose, the SOD activity was decreased and the concentration of MDA was increased in the culture solution of the cells treated with fluctuant high glucose. The antioxidant and specific inhibitor of P53 significantly inhibited the p-P53 expression and decreased the apoptotic rate. After 12 experimental weeks, the cell apoptotic index and protein expression of Nox4 and p-P53 in the kidney tubular epithelial cells isolated from the diabetic rats were significantly increased in C group as compared with B group. CONCLUSION: Oxidative stress and P53 are involved in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells.     

Carnosine protects against high glucose-induced injury in H9c2 cells

AIM： To explore the protective effect of carnosine (Car) on cardiomyocytes with high glucose (HG)-induced injury. METHODS：Rat H9c2 cardiomyocytes were cultured in vitro and divided into three groups: normal control (NC) group, HG group and Car pretreatment (Car+HG) group. The survival rate of H9c2 cells was measured by MTT assay. Intracellular level of reactive oxygen species (ROS) was detected by fluorescent probe DCFH-DA. The protein expression of caspase-8, caspase-9 and caspase-3 was determined by Western blotting. RESULTS：The survival rate of H9c2 cells decreased with the increases in glucose concentration and time, while pretreatment with 20 mmol/L Car could increase the survival rate significantly (P<0.05). The intracellular level of ROS in HG group was significantly increased compared with NC group (P<0.05), while that in Car+HG group was significantly decreased compared with HG group (P<0.05). The expression of caspase-8, caspase-9 and caspase-3 proteins in HG group was significantly increased compared with NC group (P<0.05). Compared with HG group, the expression of caspase-9 and caspase-3 was significantly decreased in Car+HG group (P<0.05), but the expression of caspase-8 did not obviously change (P>0.05). CONCLUSION：Carnosine can protect H9c2 cells against the injury of oxidative stress and apoptosis induced by high glucose.     

Trx-1 over-expression attenuates oxidative stress injury in MPP+ -induced PC12 cells by regulating NF-κB signaling pathway

AIM:To investigate the inhibitory effect of thioredoxin 1 (Trx-1) over-expression on oxidative stress injury in 1-methyl-4-phenylpyridinium (MPP⁺)-induced rat pheochromocytoma PC12 cells by regulating NF-κB signaling pathway.METHODS:The PC12 cells were damaged by treatment with MPP⁺ at 1, 3 and 5 mmol/L, and the optimal concentration of 3 mmol/L was selected. The cell viability was measured by MTT assay. The oxidative stress indexes lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in the cell culture supernatant were detected, and the protein expression of Trx-1 was determined by Western blot. Lentiviral infection with Ad-Trx-1-GFP sequence was used to establish a model of MPP⁺-treated PC12 cells with Trx-1 over-expression. The effects of Trx-1 over-expression on the cell viability, oxidative stress responses and NF-κB signaling pathway were determined by MTT assay, commercial kits and Western blot. The effects of phorbol 12-myristate 13-acetate (PMA), an activator of NF-κB signaling pathway, on the viability and oxidative stress of PC12 cells were observed. The NF-κB signaling pathway inhibitor pyrrolidine dithiocarbamate (PDTC) was used in MPP⁺-treated PC12 cells with Trx-1 over-expression, and the cell viability and oxidative stress responses were measured. RESULTS:The viability of PC12 cells, SOD activity in the supernatant and protein expression of Trx-1 were decreased, while LDH activity and MDA content in the supernatant were increased significantly by treatment with MPP⁺ at 1, 3 and 5 mmol/L. The effect of MPP⁺ at 3 mmol/L and 5 mmol/L was significantly greater than that at 1 mmol/L (P<0.05), and no significant difference between 3 mmol/L and 5 mmol/L was observed (P>0.05). The inhibitory effect of MPP⁺ on the viability of PC12 cells, and the oxidative stress injury and activation of NF-κB signaling pathway induced by MPP⁺ were significantly attenuated by over-expression of Trx-1. The inhibitory effect of MPP⁺ on the viability of PC12 cells and the oxidative stress injury induced by MPP⁺ were promoted by the activation of NF-κB signaling pathway, while the protective effects of Trx-1 over-expression on the MPP⁺-treated PC12 cells were enhanced by the inhibition of NF-κB signaling pathway. CONCLUSION:Over-expression of Trx-1 protects MPP⁺-treated PC12 cells from oxidative stress injury by regulating NF-κB signaling pathway.     

Effect of hydrogen molecule on apoptosis-related proteins and Nrf2 signaling pathway in glomerular mesangial cells cultured with high glucose

AIM: To investigate the role of hydrogen molecule on apoptosis-related proteins in glomerular mesangial cells cultured with high glucose and to explore its possible mechanism. METHODS: Mouse glomerular mesangial cells cultured in vitro were divided into 4 groups:normal control group (C group, 5.5 mmol/L glucose), mannitol group (G group, 5.5 mmol/L glucose+19.5 mmol/L mannitol), high glucose group (H group, 25 mmol/L glucose), high glucose+hydrogen-rich water group (HH group, 25 mmol/L glucose+hydrogen-rich water), and cultured for 48 h. The protein levels of Bax, Bcl-2, cleaved caspase-3, nuclear factor E2-related factor-2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase-1 (NQO-1) were determined by Western blot, and the mRNA expression of HO-1 and NQO-1 was determined by RT-PCR. The level of intracellular reactive oxygen species (ROS) was detected by dihydroethidium method, and the activity of superoxide dismutase (SOD) was measured by WST-8 assay. RESULTS: Compared with C group, the protein levels of Bax and cleaved caspase-3 were up-regulated, and Bcl-2 was down-regulated in H group (P <0.05). No significantly difference of the protein levels mentioned above between C and HH group was observed. Compared with H group, the protein levels of Bax and cleaved caspase-3 were down-regulated, and Bcl-2 was up-regulated in HH group (P <0.05). The level of intracellular ROS was higher and the activity of SOD was lower in H group than those in C group (P<0.05). However, there was no difference of the SOD activity between C group and HH group. The level of intracellular ROS decreased and the activity of SOD increased in HH group as compared with H group (P<0.05). Compared with C group, clearly reduced protein expression of Nrf2, HO-1 and NQO-1, and decreased mRNA expression of HO-1 and NQO-1 in H group were observed (P<0.05). Compared with H group, the protein levels of Nrf2, HO-1 and NQO-1 as well as the mRNA levels of HO-1 and NQO-1 were obviously increased in HH group (P<0.05).CONCLUSION: Hydrogen molecule inhibits the expression of pro-apoptotic proteins and induces the expression of anti-apoptotic proteins in glomerular mesangial cells cultured with high glucose. The mechanism may be related to activation of Nrf2 signaling pathway.     

Effect of shikonin on high glucose-induced apoptosis and oxidative stress in vascular endothelial cells

AIM:To investigate the effect of shikonin on the apoptosis and oxidative stress induced by high concentration of glucose in vascular endothelial cells. METHODS:Rat thoracic aortic endothelial cells were randomly divided into 5 groups:normal control group (with glucose at concentration of 5.5 mmol/L in cell culture medium), high glucose group (with glucose at concentration of 33 mmol/L in cell culture medium), high glucose+low shikonin group (with glucose at concentration of 33 mmol/L and shikonin at concentration of 0.1 μmol/L in cell culture medium), high glucose+medium shikonin group (with glucose at concentration of 33 mmol/L and shikonin at concentration of 1 μmol/L in cell culture medium), and high glucose+high shikonin group (with glucose at concentration of 33 mmol/L and shikonin at concentration of 10 μmol/L in cell culture medium). After treatments, the cell viability was measured by CCK-8 assay and cell apoptotic rate was analyzed by flow cytometry. In addition, the status of oxidative stress was evaluated by determining the levels of malondialdehyde (MDA), reactive oxygen species (ROS), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). The activation of Nrf2/HO-1 signaling pathway was determined by Western blot. RESULTS:Compared with high glucose group, shikonin reversed high glucose-induced decrease in cell viability and increase in apoptosis in a concentration-dependent manner. High concentration of glucose induced high levels of MDA and ROS, while decreased the levels of SOD and GSH-Px. However, after treatment with shikonin, the contents of MDA and ROS were decreased, while the activities of SOD and GSH-Px were increased as compared with high glucose group. Furthermore, the high concentration of glucose up-regulated the protein levels of cleaved caspase-3, HO-1 and Nrf2 (nuclear). Compared with high glucose group, the protein levels of cleaved caspase-3, HO-1 and Nrf2 (nuclear) were partly decreased after treatment with shikonin. CONCLUSION:Shikonin alleviates high glucose-induced vascular endothelial cell apoptosis. Its mechanism may be related to activation of Nrf2/HO-1 signaling pathway and down-regulation of oxidative stress in vascular endothelial cells.     

ROCK promotes high glucose-induced cardiomyocyte apoptosis by inhi-biting PI3K/Akt signaling pathway

AIMTo investigate whether Rho-associated coiled-coil kinase (ROCK) is involved in high glucose-induced apoptosis of primary cardiomyocytes by regulating PI3K/Akt signaling pathway. METHODSPrimary Wistar rat cardiomyocytes were cultured and identified by α-sarcomeric actin (α-SCA) immunohistochemistry. Cardiomyocytes were treated with 5.5, 33 and 40 mmol/L glucose for 48 h. The cell viability was measured by MTT assay, and the mRNA expression of ROCK1 and ROCK2 in the cardiomyocytes was detected by RT-qPCR. Flow cytometry was used to analyze the apoptosis of the cardiomyocytes. The protein levels of ROCK1, ROCK2, cleaved caspase-3, Bcl-2, PI3K, Akt and p-Akt were determined by Western blot. In order to confirm the regulatory effect of ROCKs on PI3K/Akt signaling pathway, the cells were divided into control group (5.5 mmol/L glucose), high glucose group (33 mmol/L glucose) and high glucose+Y27632 (ROCK inhibitor) group. Western blot was used to detect the protein levels of ROCK1, ROCK2, PI3K, Akt and p-Akt. RESULTSAfter 48 h of high glucose exposure, the values of relative cell viability in 33 and 40 mmol/L glucose groups were (79.71±2.43)% and (68.41±7.49)%, respectively, both of which were significantly decreased compared with normal control group (P<0.05). After 48 h of high glucose exposure, the relative mRNA levels of ROCK1 and ROCK2 in 33 and 40 mmol/L glucose groups were significantly increased compared with normal control group (P<0.05). Compared with normal control group, the apoptotic rate in 33 and 40 mmol/L glucose groups was increased significantly (P<0.05). Compared with normal control group, the protein expression of ROCK1, ROCK2 and cleaved caspase-3 in 33 and 40 mmol/L glucose groups was increased (P<0.05), while the protein expression of Bcl-2 was decreased (P<0.05). No significant difference in the protein levels of PI3K and Akt among the 3 groups was observed, while the protein level of p-Akt in 33 and 40 mmol/L glucose groups was decreased compared with normal control group (P<0.05). Compared with high glucose group, the expression of ROCK1 and ROCK2 was decreased in high glucose+Y27632 group. No significant difference in the protein levels of PI3K and Akt among the 3 groups was observed. Compared with normal control group, the protein level of p-Akt in high glucose group was decreased, and the protein level of p-Akt in high glucose+Y27632 group was increased significantly compared with high glucose group. CONCLUSION Under high glucose environment, ROCK may reduce the level of p-Akt by inhibiting the PI3K/Akt signaling pathway, thus promoting the apoptosis of cardiomyocytes.     

Wnt signaling pathway is involved in catalpol-induced proliferation of rat bone marrow mesenchymal stem cells

AIM：To investigate the changes of Wnt signaling pathway in catalpol-induced proliferation of rat bone marrow mesenchymal stem cells (BMSCs). METHODS：The BMSCs were isolated from SD rats, purified by differential time adherent method and divided into control group and catalpol (1.0 mg/L) group. Flow cytometry was used to detect the proliferation index of BMSCs. The mRNA levels of Wnt3a, Wnt5a, Wnt11 and β-catenin was evaluated by real-time PCR. In addition, the protein expression level of β-catenin was determined by Western blotting. RESULTS：Prolife-ration index was increased from 8.90%±0.46% to 17.93%±1.68% after treatment with catalpol (P<0.01). Compared with control group, the mRNA expression of Wnt5a, Wnt11 and β-catenin was all increased with catalpol treatment. No difference of Wnt3a mRNA expression between control group and catalpol group was observed. Meanwhile, the protein expression of β-catenin was increased in catalpol group compared with control group. CONCLUSION：Catalpol promotes BMSCs going into the cell cycle. Classical and non-classical Wnt signaling pathways are activated in this process.     

Glucagon-like peptide-1 protects against cardiac microvascular injury in diabetic rats via Keap1-Nrf2 signaling pathway

AIM: To investigate the protective effects of glucagan-like peptide-1 (GLP-1) on cardiac microvascular injury in diabetic rats and the underlying mechanism. METHODS: Diabetic rats were induced by intraperitoneal injection of streptozocin, and then randomized to 3 months of vehicle or exenatide (a GLP-1 analogue) treatment. Before and after the treatment, body weight, blood glucose and blood pressure were measured. Cardiac microvascular permeability was detected by transmission electron microscopy. Cardiac microvascular endothelial cells (CMECs) were isolated and cultured in normal glucose (5.5 mmol/L), high glucose (25 mmol/L), and high glucose plus GLP-1 (10^-8 mol/L). The production of reactive oxygen species (ROS) was examined by superoxide assay kit and dihydroethidium staining. The protein expression of GLP-1 receptor (GLP-1R), Kelch-like epichlorohydrin-associated protein 1 (Keap1), nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) was determined by Western blot. RESULTS: Exenatide treatment for 3 months improved the cardiac microvascular permeability in the diabetic rats. The GLP-1R was expressed in CMECs. GLP-1 inhibited high glucose-induced ROS production (P<0.05). Compared with high glucose group, the protein expression of Keap1 was decreased, and Nrf2 and HO-1 were increased significantly (P<0.05). CONCLUSION: GLP-1 inhibits oxidative stress in high glucose-induced CMECs, and improves the cardiac microvascular permeability in diabetic rats. The protective effects of GLP-1 may be related to Keap1-Nrf2 signaling pathway.     

Effect of HMGA2 gene on high glucose-induced apoptosis of renal tubular epithelial cells by regulating Notch signaling pathway

AIM:To investigate the effect of HMGA2 down-regulation on apoptosis and Notch signaling pathway in renal tubular epithelial cells exposed to high glucose (HG). METHODS:D-glucose at 5, 10, 20 and 30 mmol/L was used to stimulate human renal tubular epithelial HK-2 cells for 2 h, and D-glucose at 30 mmol/L was used to stimulate the HK-2 cells for 10 min, 60 min and 120 min. The protein expression of HMGA2 was determined by Western blot. The HK-2 cells were divided into normal glucose (NG) group, HG group, HG+si-HMGA2 group and HG+NC group, in which siRNA was transfected by Lipofectamine^TM 2000 for 48 h. Flow cytometry was used to analyze the apoptotic rate, reactive oxygen species (ROS) assay kit was used to detect ROS content, and Western blot was used to detect the protein levels of Notch1, Hes1 and Bcl-2. The HK-2 cells were treated with the Notch signaling pathway inhibitor DAPT, and then the cells were divided into HG group, HG+DAPT group and HG+si-HMGA2+DAPT group. The apoptotic rate was analyzed by flow cytometry. RESULTS:Exposure of the HK-2 cells to D-glucose at different concentrations for different time significantly increased the expression of HMGA2 (P<0.05). Compared with NG group, the protein expression of HMGA2, Notch1 and Hes1 in HG group was increased, the expression of Bcl-2/Bax was decreased, the apoptotic rate was increased, and the content of ROS was increased obviously (P<0.05). Compared with HG group, the protein expression of HMGA2, Notch1 and Hes1 of HG+si-HMGA2 group was decreased, the expression of Bcl-2/Bax was increased, the apoptotic rate was decreased, and the content of ROS was decreased significantly (P<0.05). The apoptotic rate in HG+DAPT group was significantly lower than that in HG group, while the apoptotic rate in HG+si-HMGA2+DAPT group was significantly lower than that in HG+DAPT group (P<0.05). CONCLUSION:Down-regulation of HMGA2 expression inhibits the apoptosis of renal tubular epithelial cells by regulating Notch signaling pathway and decreasing ROS production.     

Liraglutide attenuates hyperhomocysteinemia-induced oxidative stress and inflammatory response in rat hippocampus via p38 MAPK signaling pathway

AIM: To investigate the protective effect of liraglutide (Lir), an analog of glucgon-like peptide-1 (GLP-1), on hyperhomocysteinemia (Hhcy)-induced hippocampal pathological injury and the underlying molecular mechanisms in rats. METHODS: Sprague-Dawley rats (n=40) were randomly divided into 5 groups:control (Ctrl) group, model (Hhcy) group, low-dose Lir treatment (Lir-L) group, medium-dose Lir treatment (Lir-M) group and high-dose Lir treatment (Lir-H) group. The protein levels of p-p38, p-ERK1/2, p-JNK, immunoglobulin heavy chain binding protein (BIP) and C/EBP homology protein (CHOP) were determined by Western blot and immunohistochemical staining. The activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH), and the content of malondialdehyde (MDA) were measured. The expression levels of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) were examined by ELISA. RESULTS: Hhcy increased the levels of p-p38, BIP, CHOP, MDA, IL-1β, IL-6 and TNF-α,and reduced the activity of SOD and GSH, while simultaneous administration of Lir dose-dependently attenuated the Hhcy-induced oxidative stress and inflammatory responses, accompanied with the inhibition of p38 MAPK signaling pathway. CONCLUSION: Lir ameliorates Hhcy-induced oxidative stress and inflammatory injury in rat hippocampi with the mechanisms involving suppression of p38 MAPK pathway.     

PPARs signaling pathway is involved in diabetic hepatopathy in mice

AIM: To investigate the role of peroxisome proliferator-activated receptors (PPARs)-inflammation signaling pathways in diabetic hepatopathy. METHODS: Diabetic mouse model was established by feeding the mice with a high-energy diet for 4 weeks combined with intraperitoneal injection of streptozotocin (STZ; 40 mg·kg^-1·d^-1 for 5 d). The hepatopathy model was confirmed by histopathological observation and the indexes of liver function, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP), after another 4 weeks. Moreover, fasting blood glucose (FBG), and serum levels of total cholesterol (TC), triglyceride (TG) and insulin were measured, and the HOMA insulin resistance index (HOMA-IR) was calculated. The mRNA and protein expression levels of PPARs and inflammation-related factors were measured by qPCR and Western blot, respectively. RESULTS: After treatment with STZ for 7 d, the FBG of mice exceeded 11.1 mmol/L, suggesting that the diabetic model was established. After 4 weeks, the structural deformation of the hepatocytes (including hepatocytes containing abundant fat vacuoles, and inflammatory cell infiltration), and the increases in the serum levels of insulin, HOMA-IR, TC, TG, ALT, AST and ALP were observed (P<0.01), indicating the occurrence and progression of hepatopathy in diabetic mice. Meanwhile, compared with the control group, the mRNA and protein expression of PPARα, PPARβ and PPARγ decreased, but the expression of nuclear factor-κB (NF-κB), cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) significantly increased in the diabetic hepatopathy mice (P<0.01). CONCLUSION: Down-regulation of PPARα, PPARβ and PPARγ and activation of NF-κB-COX-2/iNOS signaling pathways may be involved in the diabetic hepatopathy in mice induced by long-term high-energy diet feeding combined with intraperitoneal injection of STZ.     

CHIP participates in high glucose-induced vascular endothelial cell injury

AIM To investigate the effects of carboxy terminus of heat shock protein 70-interacting protein (CHIP) on high glucose (HG)-induced vascular endothelial cell injury. METHODS Human umbilical vein endothelial cells (HUVECs) were cultured in vitro and treated with 5.5 mmol/L glucose (normal glucose, NG) or 25.5 mmol/L glucose (HG) for 24 h. Down-regulation of CHIP expression by RNA interference was conducted. Before the experiment, mannitol was used to eliminate the interference of osmotic pressure. Subsequently, the cells was divided into 4 groups: NG+siRNA NC group, NG+siRNA CHIP group, HG+siRNA NC group, and HG+siRNA CHIP group. Additionally, MTT assay and TUNEL staining were used to detect the viability and apoptosis. The level of endothelin-1 (ET-1) was measured by ELISA, and the level of reactive oxygen species (ROS) was detected by fluorescence probe dihydroethidium. The level of nitric oxide (NO), and the activity of superoxide dismutase (SOD) and inducible nitric oxide synthase (iNOS) in the cells were detected by their respective kits. The mRNA expression of interleukin-8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) was detected by RT-qPCR. The protein levels of CHIP, NADPH oxidase (NOX) 2, NOX4, p38, p65, p-p38, p-p65, Bax and Bcl-2 were determined by Western blot. RESULTS Compared with NG+siRNA NC group, the cell viability was decreased, the apoptosis rate, the mRNA expression of IL-8 and MCP-1, and the level of ROS were increased (P<0.05), the activity of SOD was decreased (P<0.05), while the levels of ET-1, NO and iNOS and the protein levels of p-p38, p-p65 and Bax were increased in HG+siRNA NC group (P<0.05). Compared with HG+siRNA NC group, the inflammatory response, the oxidative stress, the apoptosis rate, and the protein levels of p-p38, p-p65 and Bax were significantly increased in HG+siRNA CHIP group (P<0.05). CONCLUSION Down-regulation of CHIP expression aggravates HG-induced vascular endothelial cell injury.     

Atorvastatin inhibits high glucose-induced oxidative stress by depressing PKC activity in human umbilical vein endothelial cells

AIM:To explore the effect of atorvastatin on high glucose-induced oxidative stress and underlying mechanisms in human endothelial cells. METHODS:Human umbilical vein endothelial cells(HUVECs) were cultured in medium 199 containing normal concentration of glucose(5.5 mmol/L). For high glucose treatment, glucose solution was added to the final concentration of 25 mmol/L. Reactive oxygen species(ROS) were detected by flow cytometry and confocal microscopy. The activity of nicotinamide adenine dinucleotide phosphate(NADPH) oxidase was measured by lucigenin assay. Phosphorylated protein kinase C(PKC) and the expression levels of NADPH oxidase subunits Nox4 and Nox2/gp91^phox were determined by quantitative real-time PCR and immunoblotting. RESULTS:High glucose increased ROS production, NADPH oxidase activity and the expression of Nox4 and Nox2/gp91^phox subunits. Treatment of endothelial cells with atorvastatin resulted in significant inhibition(in a concentration-dependent manner) of high glucose-induced ROS production, NADPH oxidase activation and the expression of Nox4 and Nox2/gp91^phox subunits. PKC inhibitor showed a similar effect to that of atorvastatin on high glucose-induced oxidative stress. Furthermore, atorvastatin rapidly inhibited high glucose-induced activation of protein kinase C, an upstream activator of NADPH oxidase. CONCLUSION:PKC is involved in high glucose-induced oxidative stress in HUVECs. Atorvastatin inhibits high glucose-induced oxidative stress by depressing PKC activity in human endothelial cells.     

Screen of novel candidate regulators involved in oxidative stress-reprogrammed LPS signaling pathway by comparative phosphoprotein-affinity profiling

AIM: To determine the differences in phosphoproteome between LPS stimulated THP-1 cells with and without previous oxidative stress for screening of more potential regulators.METHODS: Differentiation of THP-1 cells into macrophages was induced by treatment with 100 μg/L PMA for 36 h. Differentiated cells were rested for additional 36 h without PMA treatment, then treated with 100 μmol/L H₂O₂ or medium for 1 h followed by LPS or medium treatment for 30 min. After desalted, phosphoproteins were enriched by phosphoprotein metal affinity column, and were run on 2-D electrophoresis, then the spots were analyzed to show the difference between LPS group (cells treated with LPS alone) and H₂O₂+LPS group (LPS stimulated cells also pretreated with H₂O₂). Finally, some of these spots were identified by MS and subsequent bioinformatic analysis was also conducted. RESULTS: Compared to LPS group, 29 reproducibly changed spots on the 2-D map in H₂O₂+LPS group were visualized and selected for MS analysis. Among these, 12 down-regulated spots (include those disappeared), 17 up-regulated spots (include those newly emerged) were selected. Up to now, 5 of these were identified, which were shown to be involved in various cellular processes such as proteolysis, signal transduction and protein folding. Among these, proteasome beta-4 subunit, which was dramatically down-regulated in H₂O₂+LPS group, was a major component of the proteasome complex and might participate in LPS signalling through various ways.CONCLUSION: With comparative phosphoprotein-affinity profiling, the interference brought by highly abundant house-keeping proteins is minimized, rendering us to detect less abundant signalling molecules. Aforementioned 5 proteins, especially proteasome beta-4 subunit, might be involved in LPS pathway reprogrammed by oxidative stress.     

Role of PERK pathway in morphine-induced myocardial protection of H9c2 cells

AIM: To explore whether morphine protects oxidative stress-damaged myocardial cells by inhibiting the PERK pathway to reduce endoplasmic reticulum stress and prevent mitochondrial permeability transition pore (mPTP) opening. METHODS: Rat myocardial H9c2 cells were cultured to establish an oxidative stress model, and then randomly divided into control group, H₂O₂ group, H₂O₂+morphine group, H₂O₂+morphine+PERK pathway inhibitor GSK2656157 group, morphine group and GSK2656157 group. Immunohistochemical method was used to detect the effects of morphine on expression of glucose-regulated protein (GRP) 78 and GRP94 induced by oxidative stress. The protein levels of PERK signaling pathway-related molecules were determined by Western blot. Confocal microscopy was used to observe the effects of morphine on mPTP opening and endoplasmic reticulum induced by oxidative stress. Cellular toxicity was detected by lactate dehydrogenase (LDH) kit and cell viability was measured by MTT assay. RESULTS: Compared with control group, GRP78 and GRP94 proteins in H₂O₂ group were strongly expressed, and the brown-yellow particles were significantly increased, but morphine significantly inhibited this process. Compared with control group, the phosphorylation of PERK was significantly reduced with GSK2656157 treatment at different concentrations, among which 2 μmol/L had the most significant effect (P < 0.05). Oxidative stress significantly increased the protein levels of GRP78, GRP94, p-PERK and CHOP, but significantly decreased p-GSK-3β level. These changes were inhibited by morphine, and the effects of morphine were further enhanced by GSK2656157 (P < 0.05). Compared with control group, oxidative stress significantly reduced the fluorescence intensity of mitochondrial TMRE and ER-Tracker Red. Morphine significantly inhibited this effect even when mitochondrial membrane potential was reduced, mPTP was open, and endoplasmic reticulum was damaged, while GSK2656157 further enhanced the effect of morphine (P < 0.05). Compared with control group, H₂O₂ significantly increased cellular toxicity and decreased the cell viability. Morphine inhibited this effect and GSK2656157 significantly enhanced the effect of morphine (P < 0.05). CONCLUSION: Morphine protects cardiac H9c2 cells under oxidative condition by inhibiting endoplasmic reticulum stress through PERK pathway and preventing the mPTP opening via GSK-3β inactivation.     

Role of ghrelin in cell protection by up-regulating HSP70 through ERK1/2 signaling pathway in PC12 cells

AIM:To study the role of ghrelin in cell protection by up-regulating heat shock protein 70 (HSP70) and inhibiting apoptosis induced by oxidative stress through extracellular regulated protein kinases 1/2 (ERK1/2) signaling pathway in the PC12 cells. METHODS:Sodium nitoprusside (SNP) was used to induce oxidative stress injury in the PC12 cells. The cultured PC12 cells were divided into SNP-injured group (incubated with SNP at 0.5 mmol/L for 6, 12, 18 and 24 h), ghrelin pretreatment group (ghrelin at 100 nmol/L was given 30 min before adding SNP); HSP70 inhibitor group (quercetin at 10 μmol/L was added 60 min before ghrelin treatment), ERK inhibitor group (ERK 1/2 inhibitor PD98059 was added 60 min before ghrelin treatment) and control group (added same amount of culture medium only). The apoptotic rate was detected by flow cytometry. The protein expression was determined by Western blot and immunocytochemistry. RESULTS:Compared with control group, the apoptotic rate of PC12 cells in SNP-injured group was significantly increased (P<0.05). Compared with SNP-injured group, ghrelin (100 nmol/L) pretreatment significantly inhibited SNP-induced apoptosis of PC12 cells (P<0.05), and significantly up-regulated the protein expression of HSP70 (P<0.05). Time-effect analysis showed that ghrelin had the most significant effect at 18 h after SNP injury. Quercetin, an inhibitor of HSP 70, significantly reduced the anti-apoptotic effect of ghrelin (P<0.05). Ghrelin pretreatment promoted the phosphorylation of ERK1/2. ERK1/2 inhibitor PD98059 significantly inhibited the effects of ghrelin on up-regulation of HSP70 expression (P<0.05). CONCLUSION:Ghrelin upregulates the expression of HSP70 and inhibits the apoptosis in the PC12 cells induced by oxidative stress by promoting the phosphorylation of ERK1/2.