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Persistent proteinuria has been indicated to be a major risk factor for the development of tubulointerstitial damage through a process of proinflammatory molecule expression. Monocyte chemoattractant protein-1 (MCP-1) was shown to contribute to recruitment of immune cells into the renal interstitium in acute and chronic renal diseases. However, the molecular mechanisms by which proteinuria causes MCP-1 expression in proximal tubular cells have not been fully clarified. In this study, we examined whether albumin overload-induced MCP-1 expression was regulated by mitogen-activated protein kinase (MAPK) in mouse proximal tubular (mProx) cells. Exposure of mProx cells to delipidated bovine serum albumin (BSA) induced mRNA and protein expression of MCP-1 in a time- and dose-dependent manner. BSA activated extracellular signal-regulated kinase (ERK1/2) and p38 MAPK. The MEK inhibitor U-0126 partially suppressed BSA-induced MCP-1 expression and MCP-1 promoter/luciferase reporter activity. U-0126 also inhibited an increase in nuclear factor-kappaB and activator protein-1 DNA-binding activity of MCP-1 promoter by protein overload in mProx cells. In addition, we found that U-0126 inhibited BSA-induced nuclear factor-kappaB reporter activity and inhibitory protein degradation in mProx cells. In conclusion, these findings indicate that ERK signaling is involved in BSA-induced MCP-1 expression in mProx cells.
Takaya et al. (Thu,) studied this question.