CCAAT/enhancer-binding protein-d is induced in mesangial area during the early stages of anti-Thy1.1 glomerulonephritis and regulates cell proliferation and inflammatory gene expression in cultured rat mesangial cells

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Abstract

Background.

Interleukin (IL)-6, cyclooxygenase (COX)-2, and monocyte chemoattractant protein (MCP)-1 contribute to renal injury. The promoter regions of these genes contain CCAAT/enhancer-binding protein (C/EBP)-binding sites. In this study, we investigated the role of C/EBP-δ in mesangial cells (MCs).

Methods.

In an in vivo study, anti-Thy 1.1 glomerulonephritis rats were generated and C/EBP-δ, IL-6, COX-2, and MCP-1 expressions were assessed by immunohistochemistry. In an in vitro study, cultured MCs were transfected with non-silencing (NS) short interfering RNA (siRNA) or C/EBP-δ siRNA. Subsequently, after stimulation with IL-1β, C/EBP-δ, IL-6, COX-2, and MCP-1 mRNA expression levels were evaluated using real-time polymerase chain reaction (PCR). IL-6 concentration in the culture medium was determined by enzyme-linked immunosorbent assay. In addition, cell proliferative activity against IL-1β or platelet-derived growth factor-BB was assessed by bromodeoxyuridine incorporation.

Results.

In the in vivo study, C/EBP-δ, IL-6, COX-2, and MCP-1 were expressed in the mesangial region of anti-Thy 1.1 glomerulonephritis rats on day 1. In the in vitro study, IL-1β increased C/EBP-δ mRNA levels in NS siRNA-transfected MCs (7.3-fold), but no increase was evident in C/EBP-δ siRNA-transfected MCs. IL-6, COX-2, and MCP-1 mRNA levels in C/EBP-δ siRNA-transfected MCs were all lower than those in NS siRNA-transfected MCs (decreases of 57.7%, 85.7%, and 69.3%, respectively). The IL-6 concentration in the culture medium from C/EBP-δ siRNA transfected MCs (7.37 ± 4.3 pg/ml) was also lower than that in the culture medium from NS siRNA-transfected MCs (25.2 ± 3.4 pg/ml). Cell proliferative activity in C/EBP-δ siRNA-transfected MCs was lower than that in NS siRNA transfected MCs.

Conclusions.

C/EBP-δ was induced in the mesangial region during the early stages of anti-Thy1.1 glomerulonephritis. C/EBP-δ contributes to inflammatory gene expression and MC proliferation.

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