The Effects And Mechanisms Of Advanced Glycation End Products On Mitophagy And Aging In Cardiomyocytes

Background:Aging,which is a process driven by randomly occurring damage and its accumulation,is an inevitable physiological phenomenon.Age associated degenerative diseases such as cardiovascular diseases play a central role as the dominant cause of death due to the continuously increasing number of aged people.Advanced glycation end products(AGEs)are a heterogeneous group of compounds that are formed by the non-enzymatic glycation of proteins,lipids and nucleic acids.The accumulation of AGEs is one of the major mechanisms of aging and plays an important role in age-related diseases.Cardiac aging is an independent risk factor for cardiovascular diseases.In the myocardium,the AGEs-dependent modification of protein structure and related inhibition of function induce collagen cross-linking in the extracellular matrix and,subsequently,fibrotic cardiac remodeling,which leads to ventricular stiffness and diseases.In addition,soluble AGEs can bind to specific cell surface receptors(RAGE being the best known)to activate several intracellular signaling pathways.The aging process is coupled with another cell process,mitochondrial autophagy,which selectively targets and removes damaged or old mitochondria.Several studies have shown that changes in the mitophagy system are implicated in a plethora of age related diseases,such as cardiovascular diseases,diabetes,Alzheimer's,Parkinson's and Huntington's diseases.The PINK1/Parkin pathway is a canonical mechanism that is involved in the regulation of mitophagy in mammal cells,and it was reported to be a mechanism in neurodegenerative disorders.Recent observations have suggested that senescence and mitophagy share a number of common characteristics and are regulated by overlapping signaling pathways.However,the potential roles of mitophagy during senescence remain unclear.Further,accumulating evidence has indicated that AGEs can trigger mitophagy in a variety of cell types but that suppressing one of its receptors,RAGE,markedly reduces the formation of autolysosomes.However,the effect of AGEs-activated mitophagy on AGEs induced aging and the manner in which the mitophagic pathway changes are rarely reported in cardiomyocytes.For these reasons,we investigated the role of PINK1/Parkin-mediated mitophagy in AGEs induced senescence in cardiomyocytes.Objective:To study the mechanism of mitophagy induced by advanced glycation end productcs(AGEs)and what role mitophagy play in cardiomyocytes senescence process.Methods:Neonatal rat cardiomyocytes were incubated with AGEs,and cellular senescence was evaluated by senescence-associated beta-galactosidase(SA-?-gal)activity and aging-associated p16 expression.In addition,mitophagic activity was evaluated by measuring the expression of the PINK1,Parkin,LC3 and p62 proteins.The mitophagy inhibitor cyclosporine A(CsA)or PINK1 siRNAs was then administered to cardiomyocytes to study the role of mitophagy in AGE-induced aging.Results:A significantly increased number of SA-(3-gal positive cells and increased p16 protein levels were observed in cardiomyocytes treated with AGEs.Moreover,AGEs significantly increased the protein levels of PINK1 and Parkin as well as the LC3-II/LC3-I ratio,which occurred in a dose-dependent manner.However,the expression of p62 decreased significantly in the AGE group compared to the control.Surprisingly,both CsA and the knockdown of PTNK1 by small-interfering RNA(siRNA)significantly decreased the LC3-?/LC3-? ratio and the PINK1 and Parkin protein levels in AGE-treated cardiomyocytes.Moreover,CsA treatment or knockdown of PINK1 expression attenuated the increased number of SA-?-gal positive cells and the upregulated p16 level in cardiomyocytes induced by AGEs.Conclusion:PINK1/Parkin-mediated mitophagy is involved in the process of cardiomyocyte senescence induced by AGEs,and a reduction in mitophagic activity might be a promising approach to block the senescent state in cardiomyocytes.