Acute hyperglycemia regulates transcription and posttranscriptional stability of PKCβII mRNA in vascular smooth muscle cells

Acute hyperglycemia may contribute to the progression of atherosclerosis by regulating protein kinase C (PKC) isozymes and by accelerating vascular smooth muscle cell (VSMC) proliferation. We investigated acute glucose regulation of PKC beta gene expression in A10 cells, a rat aortic smooth muscle cell line. Western blot analysis showed that PKC beta II protein levels decreased with high glucose (25 mM) compared to normal glucose (5.5 mM), whereas PKC beta I levels were unaltered. PKC beta mRNA levels were depleted by 60-75% in hyperglycemic conditions. To elucidate whether high glucose regulated PKC beta expression via the common promoter for PKCPI and PKC beta II, deletion constructs of the PKC beta promoter ligated to CAT as reporter gene were transfected into A10 cells, Construct D (-411 to +179CAT) showed quenching in high glucose (25 mM) and suggested the involvement of a carbohydrate response element in the 5' promoter region of the PKC beta gene. In actinomycin D-treated A10 cells, a 60% decrease in PKC beta mRNA with high glucose treatment indicated that posttranscriptional destabilization by glucose was also occurring, We have demonstrated that glucose-induced posttranscriptional destabilization of PKC beta II message is mediated via a nuclease activity present in the cytosol, The specificity of glucose to posttranscriptionally destabilize PKC beta II mRNA, but not the PKC beta I mRNA, was confirmed in both A10 cells and primary cultures from human aorta.