A HIGH GLUCOSE-CONCENTRATION STIMULATES THE EXPRESSION OF MONOCYTE CHEMOTACTIC PEPTIDE-1 IN HUMAN MESANGIAL CELLS

The mechanism of glomerular infiltration of monocytes remains unknown in diabetic nephropathy. We examined the effect of a high glucose conc entration on monocyte chemotactic peptide 1 (MCP-1) expression in huma n mesangial cells (MCs) by using enzyme-linked immunosorbent assay and reverse transcription coupled with polymerase chain reaction (PCR). M ore than a 50% increase in the MCP-1 protein production was observed i n MCs cultured in high-glucose medium (450 mg/dl) as compared to norma l glucose (100 mg/dl; 1,496 +/- 75 vs. 966 +/- 15 pg/ml after 24 h, 1, 910 +/- 93 vs. 1,250 +/- 55 pg/ml after 48 h). Semiquantitative PCR sh owed that phorbol. myristate acetate (100 nM) increased the ratio of P CR products for MCP-1 to housekeeping gene glyceraldehyde-3-phosphate dehydrogenase on densitometric results at 24 h by 2.7-fold, which was prevented by calphostin C (200 nM) pretreatment. High glucose increase d the ratio by 3-fold as compared to normal glucose at 24 h (0.72 +/- 0.11 vs. 0.24 +/- 0.01). This was also suppressed by calphostin C pret reatment. These findings demonstrate that high glucose can directly in crease MCP-1 expression in MCs, which may contribute to monocyte infil tration in diabetic nephropathy, and this is regulated by protein kina se C.