AMPK Mediated Downregulation Of Connexin43and Premature Senescence Of Mesangial Cells In High Glucose Conditions

Backgroud and objective: Cell premature senescence elicited by extracellular pressures such as high glucose and oxidative stress is involvedin many pathogenesis of human disease including diabetic nephropathy.Our previously study proved that glomerular mesangial cell (GMC) appeared senescence-related phenotypes under high glucose conditions, whichwere correlated with downregulation of connexin43and dysfunction of ga-p junctional intercellular communication. Because of the close link between Cx43expression and the high glucose condition, we examined how a-denosine monophosphate-activated serine/threonine protein kinase (AMPK),a sensor of cellular energy status, may affect Cx43in cultured GMC.Methods: We collected human diabetic nephropathy renal biopsy spe-cimen and nephrectomized samples used as controls. Cx43, p-AMPK andp21staining on kidney frozen sections were studied by immunofluorescence. Furthermore, GMC were incubated in high glucose medium and trea-ted with AMPK agonist (metformin) or mTOR antagonist (rapamycin), fo-r determination of the effects of AMPK and mTOR in mediation of Cx4-3expression in high-glucose condition. Gene transfer techniques were used to inhibit AMPK expression to determine the contribution of AMPK to-maintain the expression of Cx43. Senescence-associated β-galactosidase s-taining, p21cip1and p27kip1, cell cycle and cell proliferation rate as well a-s the aging-related phenotypes to testify GMC senescence induced by hig-h glucose.Results: The expression of Cx43and p-AMPK inhibited, but p21overexpression in glomerular sections of diabetic nephropathy than normal c- ontrols analysed by the mean fluorescent intensity. GMC exposed to highconcentration of glucose presented decreased Cx43, inhibited activity ofAMPK and activated downstream mTOR, led to cell cycle arrest, declinein proliferation rate and occurrence of senescence. Activing AMPK or inhibiting mTOR could prevent downregulation of Cx43, resulted in amelioration of cell cycle arrest and proliferation ability, and reversed GMC senescence. Furthermore, dominant-negative AMPK expression reduced both Cx43expression and cell proliferation, induced GMC present aging-related phenotypes.Conclusions: These results suggest that high glucose inhibit Cx43via AMPK dependent signaling pathway. Inhibition of Cx43by high glucose was one mechanism by which high glucose modulates GMC senescence. AMPK plays an important role in regulation of Cx43provided new insights into the regulation mechanism of Cx43expression and demonstrated the complex coordination of molecular events that accompany GMC senescence, which may be involved in the pathogenesis of diabetic nephropathy.