Interleukin 1β regulates the expression of peroxisome proliferator-activated receptor γ and its coregulators in renal tubular cells / 中华肾脏病杂志

ABSTRACT

Objective To investigate the changes of expression of peroxisome proliferator-activated receptor γ (PPARγ) and its coregulators and monocyte chemotactic factor (MCP-1) treated with intedeukin-1β (IL-1β), and to analyze the mechanism of interaction of these factors. Methods Renal tubular cells (HK-2 cells) were cultured in vitro. Total cellular RNA was isolated for real-lime quantitative polymerase chain reaction (real-time PCR), nuclear extracts were prepared for Western blot analysis and EMSA. The supernatant was collected for ELISA after the treatment of IL-1β at different concentrations and time points. Results Under stimulus of different concentrations of IL-1β (0～20 μg/L) for 24 hours, the mRNA expression of PPARγ, SRC-1, SRC-2 and PGC-1 decreased significantly (P<0.05), meanwhile NCoR increased obviously (P<0.05). In further time-dependent experiment, the mRNA levels of SRC-2 and PGC-1 decreased by 57% and 48%, respectively, at 1 hour after treatment with 10 μg/L IL-1β (P<0.05). The expression of SRC-1 decreased by 43%only after 2 hours (P<0.05). The expression of NCoR was not obviously changed until stimulated by IL-1β for 8 hours (2.17 folds, P<0.05), then it decreased slowly. In the same time-dependent experiment, Western blot analysis showed that IL-1β (10 μg/L) significantly decreased the protein level of PPARγ at 4 hours (P<0.05). ELISA analysis revealed that the secretion of MCP-1 kept on rising and reached the peak (160.56±2.80) ng/L at 8 hours (P<0.01), then decreased to (50.82±1.25) ng/L at 24 hours (P<0.01). IL-1β could down-regulate the DNA binding activity of PPARγ, and the activity of NF-κB was up-regulated. Conclusions PPARγ and its eoregulators are closely related to MCP-1 and NF-κB during inflammation response in kidney. The activation of NF-κB by IL-1β leads to the decrease of PPARγ, and its coactivators expression levels, however the expression of MCP-1 and NCoR in renal tubular epithelial cells is up-regulated. PPARγ together with its coregulators participate in the inflammation response in kidney.