Importance of mitochondrial calcium uniporter in high glucose-induced cardiac myocyte apoptosis

AIM: To investigate the role of mitochondrial calcium uniporter (MCU) in high glucose(HG)-induced apoptosis of cardiac myocytes. METHODS: Cardiac myocytes were exposed to normal glucose (5.5 mmol/L glucose+ 19.5 mmol/L mannitol), HG (25 mmol/L glucose), or HG combined with 5 μmol/L spermine for 72 h. Mitochondrial free Ca²⁺ concentration ([Ca²⁺]_m), MCU at mRNA and protein levels, pyruvate dehydrogenase (PDH) activity, mitochondrial membrane potential (Δψ_m), the levels of ATP and reactive oxygen species (ROS), and apoptosis were determined. RESULTS: The [Ca²⁺]_m, the mRNA and protein levels of MCU, PDH activity, ATP levels, and Δψ_m were reduced (P<0.05), while ROS content and the protein levels of caspase-9 and caspase-3 were increased in HG group (P<0.05). Adding 5 μmol/L spermine returned these parameters toward control levels (P<0.05). Moreover, apoptosis was reduced by adding spermine and HG treatment (P<0.05). CONCLUSION: HG-induced cardiac myocyte apoptosis may be associated with the decreased MCU expression and activity, abnormal mitochondrial Ca²⁺ handling, deviant mitochon-drial respiratory chain, and mitochondrial dysfunction.     

Genipin inhibits oxidative stress and apoptotic damage in high glucose-induced H9c2 cardiomyocytes

AIM:To explore the effects of genipin (GEN) on high glucose (HG)-induced oxidative stress injury and apoptosis in H9c2 cardiomyocytes.METHODS:H9c2 cells were cultured in vitro and HG-induced injury model was established. H9c2 cells were divided into 4 groups:normal control (NC) group (glucose at 5.6 mmol/L), HG group (glucose at 50 mmol/L), NG+GEN group and HG+GEN group. The concentration of genipin was used at 10 μmol/L. The viability of the H9c2 cells was measured by CCK-8 assay. The intracellular malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were determined by enzyme labeling and WST-1 methods, respectively. The activity of lactate dehydrogenase (LDH) in the cell culture supernatant was detected by microplate method. Fluorescent probe DCF was used to detect intracellular levels of reactive oxygen species (ROS). Nucleosome fragments was measured to evaluate cell apoptosis by ELISA. The intracellular mitochondrial membrane potential was detected by JC-1 method. The protein levels of Mn-SOD, cytochrome C (Cyt C), Bax and cleaved caspase-3 were determined by Western blot. RESULTS:Compared with HG group, the cell viability in HG+GEN group was increased significantly (P<0.05), the levels of MDA and LDH were decreased (P<0.05), SOD activity was increased (P<0.05), the levels of ROS and nucleosome fragments in HG+GEN group were decreased (P<0.05), and the mitochondrial membranes potential was notably increased (P<0.05). Compared with NG group, the activation of Mn-SOD was decreased, but the protein levels of Cyt C, Bax and cleaved caspase-3 were increased in HG group (P<0.05). Compared with HG group, the activation of Mn-SOD was increased, and the protein levels of Cyt C, Bax and cleaved caspase-3 were decreased in HG+GEN group (P<0.05).CONCLUSION:Genipin protects HG-induced H9c2 cardiomyocytes against oxidative stress injury and apoptosis.     

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.     

Effects of L-carnosine on NIT-1 islet cells

AIM: To investigate the protective effect of L-carnosine on insulin secretion, proliferation and apoptosis of β-cells impaired by high glucose. METHODS: NIT-1 cells were pre-treated with glucose at concentrations of 11.1 mmol/L (control level) and 33.3 mmol/L (high level) for 72 h, and then the cells were stimulated with various concentrations of glucose (0, 5 and 25 mmol/L) and/or L-carnosine (0, 1 and 20 mmol/L). The level of insulin in the medium was measured by radioimmunoassay. To detect the effect of L-carnosine on proliferation and apoptosis, NIT-1 cells were divided into 4 groups according to different culture conditions for 72 h: group C (with 11.1 mmol/L glucose), group H (with 33.3 mmol/L glucose), group H+A (with 33.3 mmol/L glucose+ 1 mmol/L L-carnosine) and group H+B (with 33.3 mmol/L glucose +20 mmol/L L-carnosine). Proliferous or apoptotic cells were identified by BrdU labeling and flow cytometry (labeling with annexin V-FITC/PI),respectively. Total RNA was extracted and the mRNA expression of caspase-3 and bcl-2 was measured by RT-PCR. The caspase-3 activity was also checked by fluorometric assay kit. RESULTS: The insulin in high-level glucose group was lower than that in control-level glucose group. L-carnosine at concentration of 20 mmol/L notably increased the insulin secretion of the cells pre-treated with glucose at control level or high level. The proliferation and apoptosis were both increased in group H compared with group C, but the total cell counts declined because the apoptotic rate was higher than the proliferation rate. L-carnosine at concentration of 1 mmol/L significantly increased the proliferation rate and decreased the apoptotic rate. The mRNA level of caspase-3 was decreased and the mRNA level of bcl-2 was increased after the cells were treated with L-carnosine at concentration of 1 mmol/L. L-carnosine at concentrations of both 1 mmol/L and 20 mmol/L significantly decreased the caspase-3 activity. CONCLUSION: L-carnosine at high level directly stimulates insulin secretion in NIT-1 cells, and L-carnosine at normal level promotes the cell proliferation and inhibits apoptosis induced by high concentration of glucose. Caspsase-3 and Bcl-2 may be partly involved in this process.     

Effects of edaravone on high glucose-induced apoptosis in SH-SY5Y cells via regulating microRNA-25

AIM: To observe the effects of edaravone on high glucose-induced apoptosis of SH-SY5Y cells and its potential mechanism. METHODS: The SH-SY5Y cells were cultured in the DMEM medium with 100 mmol/L glucose and 100 μmol/L edaravone for 24 h. The viability of the SH-SY5Y cells was detected by MTT assay. The levels of ROS in the cells were determined by DCFH-DA fluorescent probing. The apoptotic rates of the cells were analyzed by flow cytometry. The protein expression of Bax and Bcl-2 in the cells were detected by Western blot. The expression levels of micro-RNA-25 (miR-25) were determined by real-time PCR. To further clarify the target sites of edaravone on inhibiting apoptosis induced by high glucose, miR-25 inhibitor was applied to the SH-SY5Y cells and the activity of caspase-3 was measured.RESULTS: Compared with control group, the cell viability was decreased significantly in model group, and the ROS level was increased significantly. The protein expression of Bax was up-regulated significantly, while the expression levels of Bcl-2 and miR-25 were significantly down-regulated. Compared with model group, the cell viability was increased significantly in edaravone group. The ROS level was decreased significantly. Meanwhile, the expression of Bax was down-regulated, while the expression of Bcl-2 and miR-25 was up-regulated with statistical significance. The caspase-3 activity of the cells incubated with 100 mmol/L glucose and miR-25 inhibitor was increased. However, no alteration of caspase-3 activity with edaravone added simultaneously was observed. CONCLUSION: Edaravone inhibits the apoptosis of SH-SY5Y cells induced by high glucose with the potential target site of miR-25.     

Celastrol induces apoptosis of multiple myeloma H929 cells

AIM: To investigate the effect of celastrol on the apoptosis of human multiple myeloma H929 cells and its molecular mechanism. METHODS: The H929 cells were cultured in vitro and treated with celastrol at different concentrations (0.5, 1, 5 and 10 mg/L). The viability of H929 cells was analyzed by CCK8 assay. Annexin V-PE/7-AAD staining was used to analyzed the effect of celastrol on apoptosis of H929 cells, and mitochondrial membrane potential was observed by flow cytometry. The effect of celastrol on DNA damage was detected by comet assay. The protein levels of apoptosis-related molecules P53, XIAP, cleaved PARP-1 and cleaved caspase-3, and the release of mitochondrial cytochrome C in the H929 cells treated with celastrol were determined by Western blot. RESULTS: The viability of H929 cells was significantly inhibited by different concentrations of celastrol in a concentration-dependent and time-dependent manner. Apoptosis and decreased mitochondrial membrane potential of H929 cells in a concentration-dependent manner were observed after treatment with celastrol (P<0.05). The results of comet assay showed that celastrol induced DNA damage in the H929 cells. The protein levels of apoptotic molecules P53, cleaved PARP-1 and cleaved caspase-3 were significantly increased and the expression level of anti-apoptotic protein XIAP was significantly decreased in the H929 cells treated with celastrol (P<0.05). Celastrol promoted the release of cytochrome C in mitochondria, and activated caspase-3 in dependence on caspase-9. CONCLUSION: Celastrol has an apoptosis-inducing effect on multiple myeloma H929 cells. Its mechamism may be related to activation of mitochondrial apoptosis pathway by inducing DNA damage.     

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.     

Tanshinone IIA prevents high glucose-induced human umbilical vein endothelial cell apoptosis

AIM: To investigate the effect of tanshinone IIA on the apoptosis of human umbilical vein endothelial cells(HUVECs) after high glucose treatment.METHODS: The cell viability was determined by MTT assay. The cell apoptotic rate was examined by flow cytometry with Annexin V-FITC/PI double staining. The expression of Bcl-2 and Bax, and the release of mitochondrial cytochrome C(Cyt C) were analyzed by Western blotting.RESULTS: Tanshinone IIA significantly inhibited high glucose-induced decrease in cell viability and increased the cell apoptosis. Additionally, after tanshinone IIA treatment, Bax expression and the release of mitochondrial Cyt C were significantly inhibited, while Bcl-2 expression was increased.CONCLUSION: Tanshinone IIA prevents high glucose-induced endothelial cell apoptosis via mitochondria-dependent pathway.     

Effect of high glucose toxicity on JNK pathway,cell viability and apoptosis in pancreatic β-cell line INS-1

AIM: To investigate the effect of high glucose toxicity on JNK pathway and cell function of INS-1 cells.METHODS: Cultured INS-1 cells with or without IGF-1 exposure, were treated with glucose at 3 concentrations (5.6 mmol/L, 11.2 mmol/L and 33.3mmol/L), respectively. MTT was used to measure the cell viability. Apoptosis was determined by immuno-fluorescence and flow-cytometry analysis. The serine 270 phosphorylation of IRS and phosphorylation of JNK in INS-1 cells were detected in the presence or absence of SP600125 treatment.RESULTS: The cell viability decreased and apoptosis increased with elevated glucose concentrations. The percentage of apoptosis cells was 11.3% in 5.6 G group, 12.7% in 11.2 G group and 28.2% in 33.3 G group. There was remarkable increase in apoptosis in 33.3 G group with a 2.49-fold increase to the cells in the basal 5.6 mmol/L glucose. High glucose activated the serine 270 phosphorylation of IRS correlates with JNK phosphorylation in INS-1 cells. Using Western blotting analysis, the levels of JNK phosphorylation were 3.33 fold increased and serine 270 phosphorylation of IRS was 1.17 fold increased in 33.3 G group compared to 11.2 G group (P<0.01). IGF-1 treatment inhibited phosphorylation of JNK and IRS. SP600125 treatment completely blocked JNK phosphorylation in 11.2 G group and reduced JNK phosphorylation by 90% in 33.3 G group. In addition, SP600125 treatment partly reduced serine 270 phosphorylation of IRS by 88.3% in 11.2 G group and 80% in 33.3 G group, the viability of INS-1 cells increased and the apoptosis decreased.CONCLUSION: The toxicity of chronic high glucose, which inhibits the cells viability and induces the cell apoptosis, might be related to suppress IRS signal by activating the JNK pathway. Blocking the JNK pathway might relieve the effect of glucose toxicity to the β cell function by improving the IRS signal pathway.     

Effects of soybean isflavones on mitochondrial damage and neuronal apoptosis induced by cerebral ischemia/reperfusion

AIM: To study the effects of soybean isoflavones on mitochondrial ultrastructure, neuronal apoptosis and expression of cytochrome C, caspase-9 and caspase-3 in the rats with cerebral ischemia/reperfusion.METHODS: Adult healthy SD rats (n=60) were randomly divided into 3 groups: sham group, ischemia/reperfusion injury (I/R) group and soybean isoflavone (SI) pretreatment group. Soybean isoflavones (120 mg·kg-1·d-1) were fed by gastric lavage for 21 d. The global ischemia/reperfusion model of the rats was established by blocking 3 vessels, and then reperfused for 1 h after 1 h of ischemia. The morphological change of the cerebral cortex cells was observed under light microscope. The mitochondrial ultrastructure of the cerebral cortex cells was determined by transmission electron microscope. The apoptotic rate of the cerebral cortex cells was detected by flow cytometry. The expression of cytochrome C, caspase-9 and caspase-3 in the cerebral cortex cells was determined by semi-quantitative RT-PCR and immunohistochemical techniques.RESULTS: Disintegration of mitochondria membrane and disappearance of the mitochondrial cristae were seen in I/R group. Compared with I/R group, the change of ultrastructure of mitochondria was significantly improved by soybean isoflavone pretreatment, and the neuronal apoptotic rate was also significantly decreased (P<0.01). The mRNA expression and protein content of cytochrome C, caspase-9 and caspase-3 in I/R group were obviously higher than those in sham group (P<0.01). Compared with I/R group, the mRNA expression and protein content of cytochrome C, caspase-9 and caspase-3 in SI group were significantly decreased (P<0.01).CONCLUSION: Soybean isoflavones attenuate cerebral ischemia/reperfusion injury by stabilizing the structure of mitochondria, preventing cytochrome C release to the cytoplasm, inhibiting the activation of caspase-9 and caspase-3 and decreasing cell apoptosis．     

Allicin attenuates macrophage-derived foam cell apoptosis by inhibiting caspase-12

AIM: To investigate the inhibitory effect of allicin on apoptosis and caspase-12 activation of macrophage-derived foam cells, and to elucidate the underlying molecular mechanisms. METHODS: RAW264.7 macrophages were pretreated with allicin (12.5, 25 and 50 mg/L) or 4-phenylbutyric acid (PBA, 4 mmol/L) for 1 h and then treated with oxidized low-density lipoprotein (ox-LDL, 100 mg/L) or tunicamycin (TM, 4 mg/L) for 24 h. The cell viability and apoptosis were examined by MTT assay and flow cytometry with Annexin V-FITC/PI staining, respectively. The activities of caspase-3 in the cells and lactic dehydrogenase (LDH) in the medium were measured. The protein levels of caspase-12 were determined by Western blot. The intracellular lipid accumulation was measured with oil red O staining and the content of intracellular total cholesterol was determined by enzymatic colorimetry. RESULTS: Similar to the endoplasmic reticulum stress (ERS) inhibitor PBA, allicin inhibited ox-LDL-induced injury of RAW264.7 macrophages in a concentration-dependent manner, as determined by the increased cell viability and the decreased LDH leakage, apoptosis and caspase-3 activity. The decrease in cell viability and increases in LDH leakage and apoptosis induced by TM (an ERS inducer) were also suppressed by allicin. Moreover, similar to PBA, allicin remarkably inhibited ox-LDL- or TM-induced activation of caspase-12. Furthermore, allicin remarkably attenuated ox-LDL-induced lipid accumulation in the RAW264.7 cells and foam cells formation in a concentration-dependent manner. CONCLUSION: Allicin may inhibit macrophage-derived foam cell apoptosis induced by ox-LDL, and the mechanism is partially related to suppressing the activation of caspase-12.     

Ubiquitin-dependent degradation of SnoN/Ski protein in glomerular mesangial cells induced by high glucose

AIM: To observe the protein expression of SnoN/Ski and ubiqutin ligase Arkadia in rat glomerular mesangial cells (GMCs) exposed to the high glucose. METHODS: Cultured rat glomerular mesangial HBZY-1 cells were divided into control group, 20 mmol/L glucose group, 30 mmol/L glucose group, 30 mmol/L glucose+MG132 group (culture medium containing 30 mmol/L glucose and 0.5 μmol/L specific proteasome inhibitor MG132), and mannitol group. The expression levels of SnoN, Ski and Arkadia were measured by Western blotting analysis, immunofluorescence and laser scanning confocal microscopy. RESULTS: In control GMCs, the expression of SnoN/Ski was rich and Arkadia was weak. After stimulated with high glucose, the expression of SnoN/Ski was decreased and Arkadia was gradually increased (P<0.05). Compared with high glucose group, the levels of SnoN/Ski and Arkadia were mostly reverted by adding the proteasome inhibitor MG132 at concentration of 0.5 μmol/L (P<0.01). The expression levels of SnoN/Ski and Arkadia were not significantly changed in mannitol group in comparison with control group (P>0.05). CONCLUSION: High glucose decreases the expression of SnoN/Ski through ubiquitin-dependent degradation of SnoN/Ski. The degradation of SnoN/Ski mediated by Arkadia may play an important role in the pathogenesis of diabetic nephropathy.     

Effect of high fat/cholesterol diet on lipid metabolism and intimal lesion of aorta in treble genes mutant mice

AIM: To clarify the effects of high fat/cholesterol diet on lipid metabolism and atherogenesis in treble genes mutant mice. METHODS: ApoE-/-/LDLR-/-/Leprdb/db mice were generated by cross apolipoprotein E, lower density lipoprotein receptor gene knockout mice with leptin receptor gene spontaneous point mutants. The mice were fed with high fat/cholesterol diet from 22-day-old. The total plasma cholesterol (TC), triglyceride (TG) and glucose levels were measured and pathological changes of aorta intima and liver were analyzed. RESULTS: A significant elevated TC, TG and glucose levels in plasma with progress of time in young treble gene mutant mice were observed, which were higher than that in ApoE-/-/LDLR-/- and Leprdb/db mutants. At time of only 2 weeks after fed with high fat/cholesterol diet, TC and TG levels reached (106.75±3.40) mmol/L, (9.12±1.35) mmol/L, respectively in treble gene mutant mice, 4.33- and 2.36-fold higher than those in treble genes mutants fed with normal chow diet. The levels were continuously increased until final experimental point. Intima of the aorta appeared with various injuries such as edema, desquamation of the endothelial cells, foam cell formation, rupture of IEL in local regions of root and arch areas of aorta at 2 weeks after fed with high fat/cholesterol diet. Microscopic pathological complex of significant local intima incrassation and fatty change of the liver were observed in the mutants that fed with high fat/cholesterol diet for 8 weeks. Injuries of aorta were severe than normal dietetic control group. CONCLUSION: High fat/cholesterol diet as a key dietary factor is significant aggravated lipid metabolism abnormity, promotes early damage of aorta and process of atherogenesis in the treble genes mutants.     

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.     

Oxidative stress induces apoptosis in HepG2 cells

AIM: Direct exposure of cells to reactive oxygen species can induce apoptosis. In this study we investigate how oxidative stress induces cell death in HepG2 cells and characterize the molecular events involved.METHODS: Oxidative stress was created by exposing HepG2 cells to 2 mmol/L H2O2. Apoptosis was determined by analysis of DNA fragmentation by agarose gel electorphoresis. The mitochondrial membrane potential was analyzed using DePsipher fluorescent staining and the expression of cytochrome c in the cytosolic fraction was measured by Western blotting analysis. The caspase activity was detected using fluorometric assay kit by a fluorescence microplate reader.RESULTS: When HepG2 cells were treated with 2 mmol/L H2O2, the cells displayed DNA fragmentation, a typical feature of apoptosis, after 12 h. The mitochondrial membrane potential appeared different in two group of cells. H2O2-treated cells appeared green fluorescence as early as 4 h, which represents de-energized mitochondria, the untreated cells appeared red fluorescence, a feature of mitochondria with intact membrane potential. In treated cells, the expression of cytochrome c increased and accumulated in cytosolic fraction with treatment time, caspase-3 activity increased by 6.7-fold (P<0.01) at 8 h and caspase-9 activity increased by 3.6-fold (P<0.01) at 12 h, respectively, however, the activity of caspase-8 remained unchanged.CONCLUSION: These findings suggest that oxidative stress can induce apoptotic cell death in HepG2 cells, and the mechanism is related to mitochondrial pathway, which activates caspase-9 and-3, but not caspase-8.     

Silencing of FoxM1 induces apoptosis of oral squamous-cell carcinoma cells by promoting mitochondrial release of cytochrome C

AIM: To study the effect of forkhead box protein M1 (FoxM1) silencing on apoptosis of oral squamous-cell carcinoma. METHODS: Oral squamous-cell carcinoma SCC9 cells were infected with FoxM1-shRNA lentivirus or negative control lentivirus. The silencing effect was measured by RT-qPCR and Western blot. The changes of cell viability effect was measured by MTT saay. The cell colony formation ability was measured by plate experiment. Flow cytometry was used to analyze the changes of apoptotic rate. Western blot was used to measure the protein levels of cleaved caspase-3 and cleaved caspase-9 in the cells. The changes of mitochondrial membrane potential were measured by JC-1 method. Western blot was used to measure the protein level of cytochrome C in the mitochondria and cytoplasm. RESULTS: Infection with FoxM1-shRNA lentivirus successfully reduced the expression of FoxM1 in oral squamous-cell carcinoma cells (P<0.05). Negative control lentivirus had no effect on the expression level of FoxM1 in the cells. The cell viability was reduced by FoxM1 silencing, and the ability of cell colony formation was also decreased. The apoptotic rate and the protein levels of cleaved caspase-3 and cleaved caspase-9 were all increased (P<0.05), and the mitochondrial membrane potential was decreased. The protein level of cytochrome C in the cytoplasm was increased, while the protein level of cytochrome C in the mitochondria was decreased (P<0.05). CONCLUSION: Silencing of FoxM1 induces the apoptosis of oral squamous-cell carcinoma cells by decreasing the mitochondrial membrane potential and promoting the release of cytochrome C from mitochondria.     

Tert-butyl hydroperoxide damages mitochrondria and induces apoptosis in cortical neurons

AIM: To explore the possible mechanism of tert-butyl hydroperoxide (t-BHP)-induced apoptosis in rat cortical neurons. METHODS: Primary cultured rat cortical neurons were performed in vitro and cell viability was measured by MTT assay. DNA fragmentation was used to evaluate cell apoptosis and mitochondrial transmembrane potential (ΔΨm) was determined by flow cytometric assay. Cellular glutathione (GSH) content was measured by spectrophotometer. Bcl-2 and Bax protein, cytosolic cytochrome c, cleaved caspase-3 and poly (ADP-ribose) polymerase (PARP) were detected by Western blotting. RESULTS: After exposure of cortical neurons to tBHP (25-400 μmol/L), the cell viability was reduced. ΔΨm and cellular GSH content were also decreased significantly. The level of Bcl-2 protein was reduced and Bax was elevated. Meanwhile, tBHP exposure resulted in cytochrome c release, caspase-3 and PARP proteolysis, DNA fragmentation and eventually neuron apoptosis. CONCLUSION: Mitochondrial damage may mediate tBHP- induced apoptosis in cortical neurons.     

Effect of metformin combined with paclitaxel on apoptosis and AMPK signaling in human breast cancer cells

AIM:To investigate the effect of metformin combined with paclitaxel on the viability and apoptosis of breast cancer cell line MCF-7 and its possible mechanism. METHODS:MCF-7 cells were treated with metformin at different concentrations (2, 5, 10, 20, 40 and 80 mmol/L) and in vitro cultured. The viability of MCF-7 cells was measured by MTT assay. Metformin at 2 mmol/L or paclitaxel at 2.4 mg/L alone or in combination was used to treat the cells, and compound C, an inhibitor of adenosine monophosphate-activated protein kinase (AMPK) signaling transduction pathway, was also used. The cells were divided into control group, metformin group, paclitaxel group, combination group, and combination +compound C group. The apoptosis of the cells was analyzed by flow cytometry. The expression of Bax, Bcl-2 and caspase-3 at mRNA and protein levels was determined by RT-qPCR and Western blot. The protein levels of AMPK and P21 were examined by Western blot. RESULTS:Metformin at different concentrations (2, 5, 10, 20, 40 and 80 mmol/L) significantly inhibited the cell viability in a concentration-dependent manner (P<0.05). Compared with control group, treatment with metformin at 2 mmol/L or paclitaxel at 2.4 mg/L alone or in combination significantly inhibited the cell viability, induced apoptosis (P<0.05), decreased the level of Bcl-2 (P<0.05), increased the levels of Bax and caspase-3 (P<0.05), and promoted the protein expression of AMPK and P21 (P<0.05). The effects of metformin and paclitaxel in combination were better than those of single drug treatment, while AMPK inhibitor weaken these effects. CONCLUSION:Metformin combined with paclitaxel inhibits the viability and induces the apoptosis of breast cancer MCF-7 cells by activating AMPK signaling pathway and regulating apoptosis signaling pathway.     

Protective effects of Zhouluotong extract Z-6 on Schwann cells damaged by high-glucose and PI3K/Akt/nNOS pathway

AIM:To explore the role of PI3K/Akt/nNOS in Zhouluotong extract resisting diabetic peripheral neuropathy. METHODS:The Schwann cells were divided into normal group (D-glucose 25 mmol/L), model group (D-glucose 100 mmol/L), Zhouluotong extract Z-6 + high glucose group, Zhouluotong + high glucose group, mecobalamine + high glucose group. The viability, nitric oxide content and the Ca2+-ATPase activity in Schwann cells were determined by Cell Counting Kit-8 , nitric oxide assay kit and Ca2+-ATPase assay kit, respectively. The apoptosis of Schwann cells were analyzed by flow cytometry. The expression of Bcl-2, Bcl-xL, Bax, Bak and caspase-3, and the phosphorylation levels of nNOS and Akt were determined by Western blotting. The signal pathway of PI3K/Akt was explored by dominant negative PI3K and Akt (δp85 and DN-Akt) transient transfection assay. RESULTS:Under high-glucose culture, the cell viability, nitric oxide content in culture supernatant, the expression of Bcl-2 and Bcl-xL, and the phosphorylation levels of Akt and nNOS in the Schwann cells were significantly increased. The cell apoptosis, the expression of Bax, Bak and caspase 3 in the Schwann cells were significantly decreased by Zhouluotong extract Z-6, compared with model group. Increased nitric oxide content and the up-regulation of nNOS were observed. However, the effects of blocking PI3K/Akt, the upstream pathway of nNOS , by transfection with DN-δp85 on Akt phosphorylation in the Schwann cells was still unclear. CONCLUSION: Zhouluotong extract Z-6 changes the phosphorylation of nNOS, and the expression of anti-apoptotic factors, caspase-3 and pro-apoptotic factors in Schwann cells under high-glucose culture, thus reducing apoptosis and elevating viability. The relationship to PI3K/Akt/nNOS pathway needs further investigation.     

Effect of lentinan on apoptosis and PI3K/AKT signaling pathway in leukemic HL-60 cells in vitro

AIM:To study of the regulatory effect of lentinan on human leukemic HL-60 cell apoptosis and its effect on PI3K/AKT signaling pathway in HL-60 cells in vitro.METHODS:Lentinan at concentrations of 0 mg/L, 15 mg/L, 30 mg/L and 45 mg/L was applied to HL-60 cells cultured to the logarithmic phase in vitro, and the inhibitory effect of lentinan on the viability of HL-60 cells was measured by MTT assay after 24 h, 48 h and 72 h. The apoptosis induced by lentinan was analyzed by flow cytometry. The protein levels of cleaved PARP, cleaved caspase-9, cleaved caspase-3, cleaved caspase-8, cytochrome C, PI3K, AKT and p-AKT were determined by Western blot. After treatment with PI3K inhibitor LY294002 at 5 mg/L for 72 h, the apoptosis of HL-60 cells was analyzed by flow cytometry. RESULTS:The viability of HL-60 cells was inhibited after treatment with lentinan at concentrations of 15 mg/L, 30 mg/L and 45 mg/L for 24 h, 48 h and 72 h in concentration-dependent and time-dependent manners (P<0.05). The apoptosis of HL-60 cells was promoted after treatment with lentinan (15 mg/L, 30 mg/L and 45 mg/L) for 72 h in a concentration-dependent manner (P<0.05). The protein levels of cleaved PARP, cleaved caspase-9, cleaved caspase-3 and cytoplasmic cytochrome C in the HL-60 cells induced by 30 mg/L lentinan were increased significantly with the increase in the treatment time (P<0.05), but caspase-8 did not show any change. The protein levels of PI3K, AKT and p-AKT were decreased obviously with the increase in the lentinan concentration (P<0.05). Treatment of HL-60 cells with LY294002, a PI3K pathway inhibitor, produced apoptosis-inducing effect similar to lentinan (P<0.05). CONCLUSION:Lentinan induces HL-60 cell apoptosis by inhibiting PI3K/AKT signaling pathway.