In-situ hybridization studies of protein kinase C α and β I isoforms in human diabetic nephropathy

Background. Hyperglycemia is the most important contributor to the development of diabetic nephropathy (DN). The activation of protein kinase C (PKC) caused by hyperglycemia is implicated in the pathogenesis of DN. PKC, which comprises a family of enzymes, plays a role in many signal transduction pathways and is involved in the regulation of cell growth and differentiation. However, the precise role of PKC in the progression of human DN is not fully understood. Methods. To evaluate the pathological role of PKC in DN, we examined the mRNA expression levels of PKC α and PKC β I isoforms in normal renal tissues and in renal tissues affected by DN. Tissues from open renal biopsies were obtained from 20 type 2 diabetic patients with DN. The expression levels of PKC α and PKC β I mRNA in kidneys with DN and in normal human kidney (NHK) were evaluated by in-situ hybridization, using digoxigenin-labeled oligonucleotide probes. Results. Cells positive for PKC α and β I mRNA were mainly observed in glomeruli, and some mRNA was also detected in the tubulointerstitium. The percentages of glomerular cells positive for PKC α and β I mRNA were higher in kidneys with DN than in NHK. In the glomeruli of kidneys with DN, the percentage of cells positive for PKC β I mRNA, but not the percentage of cells positive for PKC α mRNA, tended to be decreased with the degree of mesangial expansion. Conclusions. Our results suggest that the expression of mRNA for PKC α and/or β I may be associated with the progression of DN.