15-Deoxy-Δ<sup>12,14</sup>-Prostaglandin J<sub>2</sub> Modulates Lipopolysaccharide-Induced Chemokine Expression by Blocking Nuclear Factor-κB Activation via Peroxisome Proliferator Activated Receptor-γ-Independent Mechanism in Renal Tubular Epithelial Cells

<b><i>Background/Aims:</i></b> Inflammation is an unavoidable milieu for renal tubular cells during the development of renal tubulointerstitial fibrosis. It has been demonstrated that chemokines including monocyte chemoattractant protein-1 (MCP-1) and IL-8 are related to tubulointerstitial lesions. 15d-PGJ₂ may modulate renal tubulointerstitial fibrosis progression via anti-inflammatory effects. However, no information is known about the effects of 15d-PGJ₂ on chemokine expression in human proximal renal tubular cells (HPTECs) under inflammation. <b><i>Methods:</i></b> In the present study, HPTECs (HK-2 cells) were stimulated with lipopolysaccharide (LPS) only, or preincubated with 15d-PGJ₂. IL-8 and MCP-1 expressions were determined by real-time PCR and ELISA. Nuclear factor-&#947;B (NF-&#947;B) location was detected by immunofluorescence analysis. The p-IKK, p-I&#947;Ba and p65/p50 were analyzed by immunoblotting. To investigate the mechanism of inhibitory effects of 15d-PGJ₂, the PPAR-&#947; gene was effectively silenced in HK-2 cells using specific siRNA. <b><i>Results:</i></b> The results showed that application of LPS significantly increased IL-8 and MCP-1 production. Phosphorylation of I&#947;Ba, IKK and nucleus translocation of NF-&#947;B significantly increased in LPS-stimulated HK-2 cells. 15d-PGJ₂ downregulated LPS-induced IL-8 and MCP-1 production. Interestingly, in PPAR-&#947;-deficient HK-2 cells, 15d-PGJ₂ was still capable of inhibiting chemokines expression and attenuating phosphorylation of I&#947;Ba and nucleus translocation of NF-&#947;B. <b><i>Conclusion:</i></b> Collectively, these results suggest that 15d-PGJ₂ exerts anti-inflammatory actions on HK-2 cells by attenuating chemokines expression. 15d-PGJ₂ inhibits chemokines expression via a PPAR-&#947;-independent way, which is related to block NF-&#947;B pathway. Since NF-&#947;B is an important regulator of the response of HPTECs to injury, PPAR-&#947; agonists may represent a key pharmacological target for ameliorating inflammation-associated tubulointerstitial fibrosis.