Glucose-induced changes in Na+/H+ antiport activity and gene expression in cultured vascular smooth muscle cells. Role of protein kinase C.
Increased Na+/H+ antiport activity has been implicated in the pathogenesis of hypertension and vascular disease in diabetes mellitus. The independent effect of elevated extracellular glucose concentrations on Na+/H+ antiport activity in cultured rat vascular smooth muscle cells (VSMC) was thus examined. Amiloride-sensitive 22Na+ uptake by VSMC significantly increased twofold after 3 and 24 h of exposure to high glucose medium (20 mM) vs. control medium (5 mM). Direct glucose-induced Na+/H+ antiport activation was confirmed by measuring Na(+)-dependent intracellular pH recovery from intracellular acidosis. High glucose significantly increased protein kinase C (PKC) activity in VSMC and inhibition of PKC activation with H-7, staurosporine, or prior PKC downregulation prevented glucose-induced increases in Na+/H+ antiport activity in VSMC. Northern analysis of VSMC poly A+ RNA revealed that high glucose induced a threefold increase in Na+/H+ antiport (NHE-1) mRNA at 24 h. Inhibiting this increase in NHE-1 mRNA with actinomycin D prevented the sustained glucose-induced increase in Na+/H+ antiport activity. In conclusion, elevated glucose concentrations significantly influence vascular Na+/H+ antiport activity via glucose-induced PKC dependent mechanisms, thereby providing a biochemical basis for increased Na+/H+ antiport activity in the vascular tissues of patients with hypertension and diabetes mellitus.
Williams
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B
Department of Medicine, University of Leicester School of Medicine, United Kingdom.
Howard
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RL
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005786:Gene Expression Regulation; D005947:Glucose / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007546:Isoquinolines / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000502:physiology*
D007546:Isoquinolines; D010879:Piperazines; D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D003609:Dactinomycin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D003513:Cycloheximide; D011493:Protein Kinase C; D005947:Glucose