Leptin protects rat cardiomyocytes from H2O2-induced apoptosis

AIM: To investigate the effect of leptin on H₂O₂-induced apoptosis in rat cardiomyocytes (H9c2 cells) and the underlying mechanisms.METHODS: Terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) was used to determine H₂O₂-induced apoptosis in H9c2 cells in the absence or presence of leptin. The activities of caspase-3 and extracellular signal-regulated kinase (ERK) were examined by Western blotting.RESULTS: (1)Leptin significantly inhibited H₂O₂-induced apoptosis in H9c2 cells (P<0.01). This effect of leptin was opposed by MEK inhibitor PD98059. (2)H₂O₂ inhibited basal ERK activity. Leptin activated ERK and partially inhibited H₂O₂-induced caspase-3 activation.CONCLUSION: Leptin protects H9c2 cells from H₂O₂-induced apoptosis possibly by activating ERK.     

Adiponectin activates AKT and protects rat cardiomyocytes against H2O2-induced apoptosis

AIM: To study the effect of adiponectin on H₂O₂-induced apoptosis in rat cardiomyocytes (H9c2 cells). METHODS: Terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) was used to determine H₂O₂-induced apoptosis of H9c2 cells in the absence or presence of adiponectin. The content of caspase-3 and Akt (protein kinase B, PKB) was examined by Western blotting. RESULTS: Adiponectin significantly inhibited H₂O₂-induced apoptosis in H9c2 cells (P<0.01). Adiponectin increased basal and H₂O₂-induced Akt activity and significantly inhibited H₂O₂-induced activation of caspase-3 (P<0.01). Pretreatment with LY294002, a specific inhibitor of Akt upstream kinase PI3K (phosphatidylinositol 3-kinase), not only increased H₂O₂-induced H9c2 cell apoptosis, but also abrogated the anti-apoptotic effect of adiponectin. CONCLUSION: Adiponectin protects H9c2 cells against H₂O₂-induced apoptosis by activating PI3K/Akt signaling pathway.     

Effects of luteolin on endothelial cell injury induced by H2O2

AIM: To study the effect of luteolin on endothelial cell injuries induced by H₂O₂. METHODS: Endothelial cells were cultured in vitro and divided into seven groups: control; solvent; H₂O₂; quercetin+H₂O₂; luteolin-L+H₂O₂; luteolin-M+H₂O₂; luteolin-H+H₂O₂ group, respectively. Endothelial cells were incubated with 750 μmol/L H₂O₂ for 18 h or 14 h in the absence or presence of various concentrations of luteolin and quercetin. The expression of caspase-3, the pro-apoptotic factors, was detected by immunohistochemical technique, and the apoptotic index was detected by flow cytometry. Meanwhile, the amount of malondialdehyde (MDA), nitric oxide (NO), lacate dehydrogenase (LDH) in serum, and cell viability were measured. RESULTS: Incubation of endothelial cells with H₂O₂ for 18 h elicited the increase in the extent of immunostaining for caspase-3, the rate of apoptosis, the release of LDH, and the number of dead cells accompanied by the decrease in the content of NO in the medium, which were inhibited by pretreatment of luteolin at concentrations of 0.5-50 μmol/L in a concentration-dependent manner (P<0.01). CONCLUSION: Luteolin possesses a protective effect against endothelial cell injuries induced by H₂O₂, which may be related with anti-oxidation, increasing the concentration of NO and inhibiting the activation of caspase-3.     

Role of ERK1/2-STAT3 pathway in adaptive cytoprotection induced by H2O2 preconditioning

AIM:To explore the role of extracellular signal-regulated kinases ERK1/2-STAT3 pathway in adaptive cytoprotection induced by H₂O₂ preconditioning in PC12 cells. METHODS:In PC12 cells, the experimental model of cytoprotection by H₂O₂ preconditioning against oxidative stress-induced injury was set up. The morphological changes in the apoptotic cells were observed by using of chromatin dye Hoechst 33258. The percent of apoptotic cells was determined by flow cytometry (FCM) with propidium iodide staining. The levels of p-ERK1/2 and p-STAT3 expression were detected by Western blotting assay. RESULTS:Preconditioning with H₂O₂ at concentration of 100 μmol/L for 90 min obviously inhibited apoptosis induced by 300 μmol/L H₂O₂, and both ERK1/2 and STAT3 were activated. UO126 (10 μmol/L, an inhibitor of ERK1/2) or AG-490 (10μmol/L, an inhibitor of JAK2) significantly blocked the cytoprotection effect of H₂O₂ preconditioning. Moreover, UO126 (10 μmol/L) also markedly inhibited the up-regulation of p-STAT3 expression by H₂O₂ preconditioning. CONCLUSION:H₂O₂ preconditioning activates ERK1/2-STAT3 signal pathway, which may be one of the mechanisms underlying H₂O₂ preconditioning-induced cytoprotection.     

Effect of diazoxide on change of H2O2 in rat pulmonary artery smooth muscle cells and proliferation of hypoxic rat pulmonary artery smooth muscle cells

AIM: To investigate the contribution of diazoxide,an opener of mitochondrial ATP-sensitive K+ channel (MitoK_ATP),and mitochondrial membrane potential (ΔΨm) to change of H₂O₂ in rat pulmonary artery smooth muscle cells (PASMCs) and to unbalance between cell proliferation and apoptosis of PASMCs induced by hypoxia.METHODS: The rat PASMCs were isolated from fresh normal lung tissues and cultured,which were divided into 6 groups,as follows: ① control group;② diazoxide group;③ 5-HD group;④chronic hypoxia group;⑤ chronic hypoxia+diazoxide group;⑥ chronic hypoxia +5-HD group.The relative change in mitochondrial potential was detected with rhodamine fluorescence (R-123) technique.The level of H₂O₂ in rat PASMCs was detected with chemiluminescence method.The proliferation of rat PASMCs was examined by cell cycle analysis and MTT colorimetric assay.RESULTS: After exposed to diazoxide for 24 h,the intensity of R-123 fluorescence,the level of H₂O₂ and the A value in normoxic rat PASMCs were significantly increased,and the apoptosis of rat PASMCs was significantly decreased as compared with control group (P<0.05).However,there were no significant changes in these tests after the rat PASMCs had been exposed to 5-HD for 24 h.Chronic hypoxia or chronic hypoxia+diazoxide markedly increased the intensity of R-123 fluorescence,the level of H₂O₂ and the A value in rat PASMCs,and also markedly decreased the apoptosis of rat PASMCs as compared with control group (P<0.05),and these changes were more significant in chronic hypoxia +diazoxide group than those in chronic hypoxia group (P<0.05).5-HD partly weakened the effect of hypoxia on the intensity of R-123 fluorescence,the level of H₂O₂,the A value and the apoptosis of rat PASMCs (P<0.05).Significant and positive correlations were found between the intracellular H₂O₂ and the R-123 fluorescence or the A value.Significant and negative correlation was found between the intracellular H₂O₂ and the apoptosis of rat PASMCs.CONCLUSION: The results suggest that the opening of MitoK_ATP followed by a depolarization of ΔΨm can contribute to the increase in the level of H₂O₂ in rat PASMCs and to the proliferation of rat PASMCs induced by hypoxia.This might be a mechanism of the development of hypoxic pulmonary hypertension.     

Effect of NPPB and niflumic acid on expression of GCL and CLIC4 in H2O2 injured C6 glioma cells

AIM: To observe the effect of 5-nitro-2- (3-phenylpropylamino) benzoate acid (NPPB), niflumic acid (NFA) (chloride channel blockers) on malignant glioma C6 cells injured by hydrogen peroxide (H₂O₂). METHODS: The viability of C6 cells treated with NPPB, NFA and H₂O₂ was measured by MTT assay. LDH release rate and GSH contents were detected by ultraviolet spectrophotometry. mRNA levels of GCLC, GCLM and CLIC4 were determined by RT-PCR. CLIC4 protein level was detected by Western blotting. RESULTS: Compared to the control group, H₂O₂ treatment induced the decrease in cell viability and GSH contents, the increase in LDH release rate, the decrease in the expression of GCLC, GCLM and CLIC4 mRNA and the increase in CLIC4 protein level (P<0.05 ), respectively. Compared with the H₂O₂ group, H₂O₂ combined with NPPB or NFA treatment did not change the cell viability, the GSH contents and the GCLC, GCLM mRNA expression. However, the LDH release rate and CLIC4 protein level decreased (P<0.05). CONCLUSION: The chloride channel blockers NPPB or NFA lessen the oxidative injury of C6 cells through modulating the function of membrane and down-regulating the protein expression of CLIC4.     

JAK-STAT pathway modulates NF-кB-mediated cytoprotection of H2O2 preconditioning

AIM: To investigate the role of nuclear factor-kappa B (NF-кB) in the adaptive cytoprotection of H₂O₂ preconditioning and modulation of NF-кB expression by JAK-STAT pathway. METHODS: In PC 12 cells, the experimental model of cytoprotection of H₂O₂ preconditioning against oxidative stress-induced injury was set up. The apoptotic cells were measured by propidium iodide staining and flow cytometry (FCM). The levels of NF-кB and STAT3 expression were detected by Western blotting. RESULTS: Preconditioning with 100 μmol/L H₂O₂ for 90 min significantly inhibited apoptosis induced by 300 μmol/L H₂O₂, and up-regulated expression of NF-кB and STAT3. Both MG-132 (10 μmol/L, an inhibitor of NF-кB) and AG-490 (an inhibitor of JAK2) obviously blocked the expression of NF-кB and cytoprotection induced by H₂O₂ preconditioning. CONCLUSION: JAK-STAT pathway modulates the cytoprotection of H₂O₂ preconditioning that is mediated by NF-кB.     

Effects of crocetin on the apoptosis and the changes of its related regulating proteins caspase-3 and Bcl-2 induced by H2O2 in myocardial cells

AIM: To observe the effect of crocetin on the apoptosis and the changes of its related regulating proteins caspase-3 and Bcl-2 expression induced by hydrogen peroxide (H₂O₂) in cultured cardiomyocytes. METHODS: Changes of cellular morphology were detected under microscope. Apoptosis rates of the cells were analyzed by PI staining with flow cytometry. Expressions of caspase-3 and Bcl-2 proteins in the cells were determined by immunofluorescence with flow cytometry. RESULTS: In the concentrations used, more severe morphological changes with higher apoptosis rate of the cultured myocardial cells were seen in each H₂O₂ group than that in control group. When treated with 1×10-4 mol·L^－1 H₂O₂, the caspase-3 was increased and Bcl-2 protein decreased remarkably in the cells. But each dosage of crocetin, especially the highest one (5×10^－5 mol·L^－1, P<005 compared with 5×10^－7 mol·L^－1 group), seemed efficient in maintaining the cell morphology, reducing the cell apoptosis rate and improving the changes in caspase-3 and Bcl-2 protein expression in the cells exposed to 1×10^－4 mol·L^－1 H₂O₂. CONCLUSION: Crocetin obviously inhibits the apoptosis induced by H₂O₂ in the cultured myocardial cells. The mechanisms may involve the balance of the functions of the apoptosis-related regulating proteins, caspase-3 and Bcl-2 protein.     

Role of preconditioning to oxidative stress in HepG2 cells

AIM:To induce preconditioning and oxidativ e stress by H₂O₂ in HepG2 cells.METHODS:The different doses of H₂O₂ were used to induce apo ptosis in HepG2 cells,which was estimated by AO/EB staining,MTT assay and flow cytometry.RESULTS:The different group of HepG2 cells stained with AO/EB s howed different staining state.The high dose of H₂O₂ resulted in the increa se in apoptosis rate of HepG2 cells and made MTT activity decreased.However,af ter pretreated with low dose of H₂O₂,the apoptosis rate was decreased and M TT activity was increased.CONCLUSION:The high dose H₂O₂ induced apoptosis in HepG2 ce lls and the low dose H₂O₂ protected HepG2 cells against the oxidative stress .     

Inhibitory effects of Co-SZ eye drops on apoptosis of lens epithelial cells and their signal transduction mechanisms

AIM: To investigate the inhibitory effect of Co-SZ eye drops on apoptosis of lens epithelial cells (LEC) induced by H₂O₂ and to study the cellular and molecular mechanisms.METHODS: (1) All lenses of Sprague-Dawley rats were incubated with H₂O₂ and Co-SZ eye drops.The apoptosis rates of LEC were determined by TUNEL method.The changes of LEC ultrastructure and the formation of apoptotic body were observed by electron microscopy.(2) Bovine LEC were incubated with H₂O₂ and Co-SZ eye drops.The inhibitory of LEC apoptosis was detected by MTT after incubation.The changes of fractional DNA content in LEC were detected by flow cytometry (FCM).［Ca2+］i , cAMP and cGMP of LEC were determined by spectrofluoremeter and radioimmunoassay, respectively.RESULTS: The LEC apoptosis rates in Co-SZ eye drops group were decreased significantly compared with H₂O₂ group by TUNEL.The ultrastructure changes in LEC of Co-SZ eye drops group were lighter than that in H₂O₂ group.The LEC apoptosis rates of Co-SZ eye drops group were dose-dependently decreased significantly compared with H₂O₂ groups via MTT assay.LEC apoptosis induced by H₂O₂ was inhibited by Co-SZ eye drops, and showing dose-dependent.The DNA contents in LEC of Co-SZ group were increased.The ［Ca2+］i and cAMP in Co-SZ group were decreased obviously.The cGMP was increased.CONCLUSION: The LEC apoptosis induced by H₂O₂ was inhibited by Co-SZ eye drops.The mechanism of apoptosis inhibition by Co-SZ eye drops maybe contribute to the increase in DNA content.The signal transduction mechanisms are related to the decrease in ［Ca2+］i and cAMP and the increase in cGMP.     

VEGF induces HUVECs to produce extracellular H2O2 and its proliferation role

AIM:To study the effect of VEGF on extracellular H₂O₂ production in HUVECs and the role of H₂O₂ in the VEGF-induced proliferation. METHODS:HUVECs was stimulated with 500 μg/L VEGF. Products of extracellular H₂O₂ was detected by H₂DCFDA staining. MTT method was used to value the influences of 3×10⁶ U/L catalase and 5-20 mmol/L H₂O₂ to VEGF function. RESULTS:After treatment for 15 min with VEGF, HUVECs appeared fluorescence, and continued to become stronger, peaked at 45 min then decreased. HUVECs, which was treated simultaneity with VEGF and 3×10⁶ U/L catalase, only appeared very faint fluorescence. The proliferation of HUVECs by VEGF was restrained when treated with 3×10⁶ U/L catalase. The extrinsic H₂O₂ at concentration of 5-10 mmol/L promoted the proliferation of HUVECs but inhibited the proliferation effect of VEGF on HUVECs (P<0.01). CONCLUSION:These findings indicate that VEGF induces HUVECs to produce extracellular H₂O₂ and plays role in proliferation, but extrinsic H₂O₂ restrains VEGF function.     

Role of mtCLIC/CLIC4 in injured C6 glioma cells induced by hydrogen peroxide

AIM: To explore the changes and the possible function of mtCLIC/CLIC4 (mitochondrial chloride intracellular channel 4) proteins in malignant C6 glioma cells treated with hydrogen peroxide (H₂O₂). METHODS: The viability of C6 cells was measured by MTT assay, LDH release rate was detected by ultraviolet spectrophotometry, CLIC4 mRNA level was determined by RT-PCR and CLIC4 protein level was measured by Western blotting. RESULTS: Compared with the control group, the cell viability was constant, the LDH release rate increased obviously, and the CLIC4 protein level also increased significantly in 500 μmol/L H2O2 treated group (P<0.05, respectively). However, the cell viability decreased, LDH release rate increased significantly (P<0.01, respectively), and the CLIC4 protein level increased obviously in 1 000 μmol/L H₂O₂ treated group (P<0.05). CONCLUSION: The CLIC4 protein may be involved in the process of C6 injuries induced by H₂O₂.     

Calreticulin is involved in the protection of hypoxic preconditioning against cardiomyoblast H9c2 cell oxidative injury

AIM: To investigate whether hypoxic preconditioning (HPC) protects cardiomyoblast H9c2 cells against oxidative injury, and to discuss whether calreticulin (CRT) contribute to this protection through p38 MAPK signaling pathway. METHODS: Cardiomyoblast H9c2 cells were randomly divided into eight groups as follows: hydrogen peroxide stress (H₂O₂); brief hypoxic exposure of 20 min to simulate hypoxic preconditioning (HPC); 20 min of hypoxic exposure followed by 24 h of normoxic reoxygenation before hydrogen peroxide stress (HPC+H₂O₂), SB203580 (the specific inhibitors of p38 MAPK)+HPC+H₂O₂, antisense oligonucleotides transfection of calreticulin (AS), AS+H₂O₂, AS+HPC+H₂O₂ and control. Morphological studies, estimation of lactate dehydrogenase (LDH) leakage and flow cytometry were employed to assess the cell apoptosis and necrosis. RT-PCR and Western blotting analysis was used to detect calreticulin expression and phosphorylation of p38 MAPK. RESULTS: The results obtained are as follows: (1) HPC relieved cell injury caused by H₂O₂. Compared with those in H₂O₂ group, apoptosis rate and LDH leakage in culture medium in HPC + H₂O₂ group decreased 13.4% and 44.0%, respectively (P<0.05), and cell survive rate increased 12.7% (P<0.05). SB203580, a selective p38 MAPK inhibitor presented before HPC, eliminated the cytoprotection of HPC. Compared with HPC+H₂O₂ group, apoptosis rate and LDH leakage increased 5.4% and 45.0%, respectively (P<0.05), and cell survive rate decreased 5.0%(P<0.05). (2) Brief hypoxia intimating HPC resulted in mild CRT up-regulation (1.4-fold increased vs control group, P<0.05), but this up-regulation was lower than that of 3.6-fold increase induced by oxidative stress. HPC relieved the over-expression of CRT induced by H₂O₂ (26% decreased vs H₂O₂ group, P<0.05). (3) Transfection of antisense oligonucleotides of CRT before HPC reduced cytoprotection against oxidative stress. Correlative analysis indicated that mild up-regulation of CRT induced by HPC was positively correlated with survive rate (r=0.8573, P<0.05). (4) SB203580 suppressed CRT up-regulation (the expression of CRT decreased 38% or 23%, vs HPC+H₂O₂ group or HPC group, respectively). CONCLUSION: These results suggest that hypoxic preconditioning up-regulates calreticulin expression through p38 MAPK signaling pathway and protects cardiomyoblast H9c2 cells against oxidative injury.     

Effects of bilirubin on oxygen free radicals and caspase-3 in acute lung injury rats

AIM:To investigate the mechanisms by which bilirubin inhibits acute lung injury (ALI). METHODS:30 female Wistar rats were divided into normal group, ALI group and bilirubin treatment group. ALI was induced by intravenous injection of LPS. The contents of OH^-, H₂O₂ and O₂^· in the lung as well as the expression of caspase-3 in the lungs were investigated. RESULTS:(1) The contents of OH^-, H₂O₂ and O₂^· in the lung homogenate and the expression of caspase-3 in the lungs in ALI group increased compared with those in normal group (P<0.05). (2) The contents of OH^-, H₂O₂ and O₂^· in the lung homogenate and the expression of caspase-3 in the lungs in bilirubin treatment group increased compared with those in normal group, but decreased compared with those in ALI models (P<0.05). CONCLUSION:(1) Bilirubin was shown to be able to ameliorate apoptosis in ALI rats. (2) The increase in the contents of OH^-, H₂O₂, O₂^· in ALI group indicated the development of oxidative lung injury, which was ameliorated by bilirubin. (3) Expression of caspase-3 confirmed that the model made by LPS was associated with apoptosis, which was reduced by bilirubin.     

Change of mitochondria during apoptosis in Jurkat cells induced by arsenic trioxide

AIM: To study the changes of mitochondria during apoptosis in Jurkat cells induced by arsenic oxide (As₂O₃). METHODS: By treated with 4×10^-6 mol/L As₂O₃, apoptosis and necrosis of Jurkat cells were assessed by annexin V-FITC/PI double staining flowcytometry. Mitochondrial mass and its membrane potential (△ψm) was measured by NAO/PI and DiOC₆ (3)/PI staining, respectively. Free radical formation was detected by DCFDA staining. RESULTS: After 48 h of As₂O₃ treatment, the rates of early apoptotic Jurkat cells in As₂O₃ and control groups were (18.98±1.40)% and (5.17±0.80)%, respectively (P<0.01). The necrotic rate in As₂O₃ group was significantly higher than that in control group (P<0.01), they were (8.56±0.70)% and (1.53±0.55)%, respectively. △ψm decreased Jurkat cells in As₂O₃ groups and control groups were (23.07±3.62)% and (6.63±1.46)%. The percentages of low mitochondrial mass cells in As₂O₃ and control groups were (25.90±1.80)% and (6.37±1.04)% (P<0.01). Intracellular free radicals in As₂O₃ group was increased, compared with control group, their DCFDA-fluorescence mean intensities were (24.41±0.75) and (17.06±0.48) (P<0.01). CONCLUSION: During apoptotsis process in As₂O₃-induced Jurkat cells, mitochondrial membrane potential and mitochondrial mass loses significantly, with increase in free radicals.     

Effect of H2O2 on voltage-gated potassium channels in rat pulmonary artery smooth muscle cells

AIM:To determine the effect of hydrogen peroxide (H₂O₂) on voltage-gated potassium channel currents (IKv) in pulmonary vascular smooth muscle cells (PASMCs). METHODS:Using whole cell patch-clamp technique, IKv was recorded in freshly isolated rat PASMCs with acute enzymatic digestion method. The effect of hydrogen peroxide on IKv in PASMCs was investigated in normoxia. RESULTS:IKv in PASMCs was increased significantly by H₂O₂ and the increase depended on the concentration in normoxia. Current-voltage relationship curve shifted to the left. CONCLUSION:Hydrogen peroxide is an important K+ channel opener.     

Upregulatory effect of isopsoralen on expression of estrogen receptor in human lens epithelial cells

AIM: To investigate the effect of isopsoralen(ISR) on the expression of estrogen receptor (ER) in human lens epithelial cells (HLECs). METHODS: HLECs were cultured and sub-cultured in vitro. The cultured HLECs pretreated with E₂ or ISR were exposed to H₂O₂ at the concentration of 300 μmol/L. The expression of ERα and ERβ in HLECs was analyzed by flow cytometry. RESULTS: The expression of ERα and ERβ in H₂O₂ group was obviously decreased as compared to control group (P<0.01). The expression of ERα and ERβ in the cells treated with E₂ and with ISR at the concentration of 10^-5 mol/L, 10^-6 mol/L or 10^-7 mol/L plus H₂O₂ was obviously increased as compared to the cells treated with H₂O₂ only (P<0.01). A concentration-dependent effect of ISR was observed. CONCLUSION: H₂O₂ decreases the expression of ERα and ERβ in HLECs.E₂ and ISR increase the expression of ERα and ERβ in HLECs treated with H₂O₂ in a concentration-dependent manner, which may account for their antioxidative effect.     

Acetyl-L-carnitine attenuates H2O2-induced oxidative damage of PC12 cells

AIM: To investigate the effect of acetyl-L-carnitine (ALC) on H₂O₂-induced oxidative damage in PC12 cells and its possible mechanism. METHODS: A moderate oxidative damage PC12 cell model was induced by exposure of the PC12 cells to H₂O₂. ALC at different concentrations (100, 200 and 400 μmol/L) was applied to the PC12 cells cultured in vitro, and CCK8 assay was used to detect the cell viability. The cells were divided into control group, H₂O₂ group, and low-ALC, medium-ALC and high-ALC groups. The apoptosis of the cells was analyzed by flow cytometry. The protein levels of Nrf2 and cleaved caspase-3 were determined by Western blot. The nuclear translocation of Nrf2 was observed by immunofluorescence staining. RESULTS: ALC at different concentrations (100, 200 and 400 μmol/L) significantly inhibited H₂O₂-induced PC12 cell apoptosis, and the medium concentration group had the best effect. Compared with H₂O₂ group, low, medium and high concentrations of ALC significantly increased the viability of the PC12 cells induced by H₂O₂, inhibit cell apoptosis (P<0.05), significantly down-regulated the protein level of cleaved caspase-3 (P<0.05), up-regulated the protein level of Nrf2 (P<0.05), and promoted the translocation of Nrf2 from the cytoplasm to the nucleus. CONCLUSION: Acetyl-L-carnitine attenuates H₂O₂-induced oxidative damage of PC12 cells, inhibits the apoptosis and increases the viability, which is related to the activation of Nrf2 signaling pathway.     

Protective effect of procyanidins on PC12 cells exposed to Aβ25-35

AIM: To investigate the protective effect of procyanidins on the PC12 cells exposed to Aβ_25-35 and the mechanisms.METHODS: Aβ_25-35 at 25 μmol/L was used to treat the PC12 cells for 48 h, and the PC12 cells were pretreated with procyanidins at 25, 50 and 100 mg/L for 24 h. The cell vitality was measured by MTT assay. The content of reactive oxygen species (ROS) was detected by DCFH-DA staining. The change of mitochondrial membrane potential was examined by JC-10 staining. The apoptosis was analyzed by flow cytometry with Annexin V/PI double staining. The protein levels of activated caspase-3 was determined by Western blot.RESULTS: Under the exposure of the PC12 cells to Aβ_25-35, procyanidins increased the cell viability, reduced intracellular ROS level, prevented mitochondrial membrane potential decline, attenuated the caspase-3 activation and inhibited the apoptosis of PC12 cells (P<0.05 or P<0.01).CONCLUSION: Procyanidins have a significant protective effect on the PC12 cells exposed to Aβ_25-35. Its mechanism may be related to removing intracellular ROS induced by Aβ_25-35, relieving the damage to the mitochondrial membrane, and thereby inhibiting cell apoptosis.