ABSTRACT
Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases worldwide, which includes a spectrum of histological liver changes. Non-alcoholic steatohepatitis (NASH) is considered to be the progressive subtype of NAFLD, which is characterized by lobular inflammation and cellular ballooning on the basis of steatosis. There is a critical need to develop novel and effective therapeutic approaches for NAFLD/NASH. The activation of toll-like receptor 2 (TLR2) signaling pathway plays a key role in high-fat-related inflammation, triggering the occurrence and development of NASH. Herein, the anti-TLR2 monoclonal antibody (TLR2 mAb) was prepared and investigated for its ability to ameliorate the inflammatory response in vivo and in vitro. The anti-inflammatory role of TLR2 mAb in vitro was examined in NR8383 macrophage cells and THP-1 derived macrophage cells. For confirmation in vivo, three groups of SD rats were treated for 20 weeks: rats in the control were fed with a standard diet; rates in the IgG and TLR2 mAb groups were fed with a high-fat diet and with IgG or TLR2 mAb, respectively. Liver tissue and serum were collected for further analysis. Results showed that after 4-week treatment with TLR2 mAb, metabolic parameters in rats were improved markedly (body weight, fasting blood glucose level, liver steatosis, inflammatory response and fibrosis). Moreover, western blotting demonstrated that the TLR2 mAb blocked MAPKs and NF-κB activation, and inhibited the expression of inflammatory factors in rat liver tissue. These effects suggested that TLR2 mAb could improve HFD-induced hepatic injury, inflammation, fibrosis and steatosis by suppressing inflammatory response and regulating the hepatic MAPKs and NF-κB signaling pathways. This suggests that TLR2 may be a novel therapeutic target for metabolic diseases especially NASH.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the regulatory effect of ATP?binding cassette transporter A1 (ABCA1) knockdown on inflammatory response induced by Pam3CSK4 in mouse mononuclear macrophage RAW264.7 cell line.</p><p><b>METHODS</b>A mouse mononuclear macrophage RAW264.7 cell line with stable ABCA1 knockdown was constructed and stimulated with Toll?like receptor 2 (TLR2) ligand Pam3CSK4, and the changes in the transcriptional levels of the proinflammatory and anti-inflammatory cytokines were analyzed in this cell model.</p><p><b>RESULTS</b>In RAW264.7 cells, ABCA1 knockdown significantly up-regulated Pam3CSK4 stimulation?induced expressions of IL?1β, TNF?α and IL?6 and also enhanced the expression of transcription factor cAMP?dependent transcription factor 3 (ATF3) without obviously affecting the expressions of the transcription factors ATF1, ATF2, ATF4 or ATF5.</p><p><b>CONCLUSION</b>ABCA1 knockdown in macrophages may have both proinflammatory and anti?inflammatory effects. ABCA1 knockdown up?regulates the transcription of ATF3 possibly through a mechanism that is different from that for the other members of the ATF protein family.</p>
