Abstract 353: High Density Lipoprotein Regulates Tumor Necrosis Factor Alpha and Jun Kinase Signaling Pathway in Adipocytes

Background: High-density lipoproteins (HDL) is presumed to exhibit cardiovascular protection, since HDL mediate the reverse transport of cholesterol and exhibit strong anti-inflammatory potential. Previous studies have found that HDL can reduce the level of IL-8 secreted by the inflammatory adipocytes, as well as affect the expression of adiponectin and tumor necrosis factor-alpha (TNF-α) under the inflammatory condition in adipocytes. These studies indicate that HDL is closely related to the inflammatory response of adipose tissue, yet its mechanism has not been fully understood. Secretory leucocyte protease inhibitor (SLPI), a nonglycosylated single-chain polypeptide protein, may play an important role in diet-induced obesity and adipocyte inflammation. Purpose: To study the role of SLPI in HDL anti-inflammatory action in the adipocytes, and explore the mechanism of the action. Methods: 3T3-L1 Adipocytes were induced to differentiation and maturation by culturing. Acute inflammation in adipocytes was induced by LPS (100 ng/ml, 6h), and then the adipocytes were pretreated with HDL and/or SLPI-siRNA. The protein and mRNA levels of SLPI, TNF-α and JNK were examined by Western blotting and qRT-PCR assay, respectively. In addition, the levels of inflammatory factors were measured by ELISA. Results: HDL up-regulated SLPI expression, down-regulated TNF-α expression, and inhibited the secretion of inflammatory factors such as IL-1, IL-6, IL-8 and MCP-1 in 3T3-L1 Adipocytes pre-treated by LPS. Silencing of SLPI by its siRNA effectively abolished the anti-inflammatory effect of HDL. JNK inhibitor (SP600125) partially restored the anti-inflammatory effects of HDL decreased by SLPI knockdown and decreased the secretion of inflammatory factors. Conclusions: These data suggest that HDL up-regulate the expression of SLPI and inhibit the inflammation in 3T3-L1 Adipocytes pre-treated by LPS. The anti-inflammatory effect of HDL, including inhibition of the secretion of inflammatory factors via TNF-α/JNK signaling pathway, probably viat up-regulating the SLPI expression. Key words: high-density lipoprotein, Inflammation, Adipocytes