With economic development, changes in people's living habits and accelerated pace of life, the incidence of diabetes is increasing. 1,2 Diabetic nephropathy is the most common microvascular complication of diabetes and the most common cause of end-stage renal disease, which seriously threatens human health. 3,4 Diabetes mellitus accelerates the loss of kidney function in people with chronic kidney disease and profoundly increases the risks of major cardiovascular events, end-stage kidney disease, and mortality for this population. 5,6 However, the current clinical treatment methods have great limitations and cannot effectively slow down disease progression.Numerous blood-pressure lowering agents are used to prevent or slow the progression of diabetic nephropathy. [6][7][8] Commonly used antihypertensive drugs are diuretics, angiotensin-converting enzyme inhibitors (ACEIs), angiotensin II receptor antagonists (ARBs), and calcium channel blockers (CCBs). ACEI and ARB drugs can not only lower blood pressure, but also increase glomerular function and inhibit renal fibrosis. The use of ACEI drugs can not only reduce the levels of circulating angiotensin II and aldosterone, but also increase circulating bradykinin and ultimately lower blood pressure. In addition, it can also reduce renal fibrosis and inflammation. 9 However, because of the negative feedback regulation of the renin-angiotensin system, the use of ACEI or ARB drugs leads to the compensatory increase of renin and angiotensin in the body, which limits the further protective effects of ACEI and ARB drugs. Renin inhibitors, such as Aliskiren, can reduce the level of angiotensin, angiotensin
Objectives
To study the effect of hepatocyte growth factor (HGF) on glycogen synthase kinase-3β (GSK-3β) and AMP-activated protein kinase (AMPK) activity in cardiomyocytes under diabetic conditions.
Methods
We used high concentration glucose and HGF to stimulate the cultured rats cardiomyocytes. To investigate the direct effect of GSK-3β on cardiomyocytes, we changed its activity by transient transfection with three kinds of GSK-3β mutant plasmids, nonphosphorylatable constitutively active mutant of GSK-3β(S9A-GSK-3β), catalytically inactive GSK-3β (KM-GSK-3β) and adenoviral vectors encoding wild-type (WT- GSK-3β). The protein expression of GSK-3β, pGSK-3β, AMPK, pAMPK was determined by Western blot. The levels of monocyte chemoattractant protein-1(MCP-1) and intercellular adhesion molecule-1 (ICAM-1) in the supernatants were determined by enzyme-linked immunosorbant assay (ELISA).
Results
HGF increased the expression of pGSK-3β and pAMPK protein in cardiomyocytes induced by high glucose. C-Met inhibitor completely inhibited the phosphorylation of GSK-3β protein, PI3K, PKC and p38MAPK inhibitors could partially inhibit the phosphorylation of GSK-3β protein, while JAK2 and ERK1/2 inhibitors had no effect. In contrast, ectopic expression of S9A- GSK-3β abolished the HGF regulatory action on MCP-1 and ICAM-1 protein expression. Activation of MAPK by HGF leads to the rapid and transient phosphorylation of cAMP response element-binding protein (CREB).
Conclusions
These results support the conclusion that regulation of cardiomyocytes metabolism by HGF is mediated by activation of the AMPK/GSK-3β pathway. HGF-induced downregulation of MCP-1 and ICAM-1 protein involves activation of the C-Met, PI3K, PKC and p38MAPK pathway and requires the activity of early GSK-3β. These findings suggest that inhibitory phosphorylation of GSK-3β at Ser-9 is required for HGF inhibition of STAT3 in cardiomyocytes induced by high glucose.
Acknowledgements
This work was supported by the National Nature Science Foundation of China (NSFC) Grant 81000576 to Fei Cai, Foundation of Department of education of Hubei Province of China Q20112804, Q20112801 to Fei Cai and Cai-rong Li.
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