RENAL CCAAT ENHANCER BINDING-PROTEINS IN EXPERIMENTAL DIABETES-MELLITUS/

There is evidence that mediators of inflammation including components of the cytokine system are present in human and experimental diabetic kidney disease. CCAAT/enhancer-binding proteins (C/EBPs) represent a f amily of cytokine-inducible transcription factors. C/EBPs themselves r egulate cytokine expression and also the expression of acute-phase rea ctants and connective tissue proteins. At least three C/EBP isoforms ( alpha, beta, delta) are known. Upon stimulation with cytokines or bact erial lipopolysaccharide, the expression of the a isoform typically de creases, and the expression of the beta and/or delta isoforms increase s. In view of the fact that components of the inflammatory response ar e present in diabetic kidney disease, there is a potential that the ex pression and activity of renal C/EBPs are altered in the diabetic stat e. In this study we sought to examine the status of C/EBP proteins in kidneys of rats with streptozotocin-induced diabetes mellitus. Diabete s was induced in 5 male Sprague-Dawley rats. Eight weight-matched non- diabetic rats were used as controls. Animals were sacrificed after 4 w eeks, and the whole kidney nuclear protein was extracted. An electroph oretic mobility shift assay showed that DNA-binding activity was prese nt in all five kidney nuclear extracts of the diabetic animals, but in only 2 out of 8 control samples (p < 0.05). A supershift assay showed that the DNA-bound protein complex consisted mainly of the C/EBP beta isoform. Western analysis showed an increase of the C/EBP beta protei n in renal nuclear extracts of the diabetic animals compared to contro ls (p < 0.05). There was a decrease of the C/EBP alpha protein in the kidney nuclear extracts of the diabetic animals compared to controls ( p < 0.05). We conclude that renal C/EBP dynamics are altered in experi mental diabetes mellitus and that the patterns of C/EBP changes resemb le those observed after cytokine or lipopolysaccharide stimulation.