Proteasome Inhibitors Improve Cardiomyocyte Hypertrophy By Promoting Autophagy

Objective:To investigate whether proteasome inhibitors can improve myocardial hypertrophy by promoting myocardial autophagy.Materials and methods:(1)Establishment of hypertrophic cardiomyocyte model:AC16 cardiomyocytes were cultured and divided into ISO group and control group;The ISO group was treated with 20umol/L Isoproterenol(ISO)for 48h.The expression levels of ANP and BNP genes in AC 16 cardiomyocytes were detected by quantitative PCR.Image analysis software was used to calculate the size of AC 16 cardiomyocytes after cellular immunofluorescence immunoassay.(2)Experimental groups:① control group,no intervention drugs;② The ISO group was given 20umol/L ISO intervention for 48h;③ The ISO+MG132 group was treated with 20umol/L ISO for 6h,and then 20nm/L proteasome inhibitor(MG 132)was added for 42 h.④ISO+proteasome inhibitor(MG 132)and autophagy inhibitor(Dorsomorphin 2HCl)groups:After 6h 20umol/L ISO intervention,20nm/L proteasome inhibitor(MG132)and 5umol/L autophagy inhibitor(Dorsomorphin 2HC1)were added for 42 h.(3)The expression levels of ANP and BNP genes in AC 16 cardiomyocytes of each group were detected by quantitative PCR.Image analysis software was used to calculate the size of AC 16 cardiomyocytes in each group after cell immunofluorescence immunoassay.The expressions of β-actin and LC3 in AC 16 cardiomyocytes of each group were detected by Western blotting.(4)SPSS software was used for analysis,and single sample t test or two independent samples t test were used.Results:The mRNA expression levels of ANP and BNP in AC 16 cardiomyocytes of ISO group were significantly increased compared with control group(P<0.05).AC 16 myocardial cell area in ISO group was significantly increased compared with control group(P<0.05).The mRNA expression levels of ANP and BNP in AC 16 cardiomyocytes in ISO+MG132 group were significantly lower than those in ISO group(P<0.05).The AC 16 cardiomyocyte area in ISO+MG132 group was significantly decreased compared with that in ISO group(P<0.05).The mRNA expression level of ANP in AC 16 cardiomyocytes of ISO+MG132+Dorsomorphin 2HCl group was significantly decreased compared with that of ISO group(P<0.05),but the decrease rate was not as high as that of ISO+MG132 group.The mRNA expression of BNP in AC 16 cardiomyocytes of ISO+MG132+Dorsomorphin 2HCl group was not significantly different from that of ISO group.The area of ISO+ISO+MG132+Dorsomorphin 2HCl was reduced compared with that of ISO group(P<0.05),but the reduction was less than that of ISO+MG132 group.Western boltting strips showed that the expression level of LC3II in the ISO group was higher than that in the control group(P<0.05).The expression level of LC3II in ISO+MG132 group was higher than that in ISO group(P<0.05),but there was no statistical difference in LC3II expression between ISO+MG132 group and ISO+MG132+Dorsomorphin 2HCl groups.Conclusion:Proteasome inhibitors can improve the hypertrophy of AC 16 cardiomyocytes induced by ISO intervention,AMPK and its downstream pathway played a minor role in the process of proteasome promoting autophagy and improving myocardial hypertrophy.The results of this study provide certain clues for finding new targets and methods for the treatment of myocardial hypertrophy.