RNA binding protein HuR contributes to HIV protease inhibitor‐induced TNF‐a and IL‐6 expression in macrophages

HIV protease inhibitors (PIs) have been associated with serious metabolic syndrome, which is the major risk factor of atherosclerotic cardiovascular disease. Atherosclerosis is widely considered to be a chronic inflammatory disease. Macrophages are the most prominent cell type present in atherosclerotic lesions and play essential roles in both early lesion development and late lesion complications. We previously reported that all HIV PIs, except amprenavir, induced accumulation of intracellular free cholesterol and lipids, activated the unfolded protein response (UPR), significantly increased the expression of pro‐inflammatory cytokines (TNF‐a and IL‐6) in macrophages. The present study further examines whether RNA binding protein HuR is involved in the HIV PI‐induced TNF‐a and IL‐6 expression in macrophages. Methods: Mouse macrophages were treated with individual HIV PI and mRNA and protein levels of TNF‐a and IL‐6 were measured by real‐time RT‐PCR and ELISA, respectively. HuR binding to 3′‐untranslated region (UTR) of TNF‐a and IL‐6 mRNA was identified by RNA pull‐down and HuR‐immunoprecipitation assays. Functions of HuR in HIV PI‐induced TNF‐a and IL‐6 expression were investigated by using lentiviral siRNA that specifically targets HuR. Results: Atazanavir increased the cytoplasmic levels of HuR and enhanced the binding of HuR to 3′UTR of TNF‐a and IL‐6. However, amprenavir had no effect on HuR expression and binding to 3′UTR of TNF‐a and IL‐6. Down regulation of HuR expression by siRNA prevented atazanavir‐induced increase of TNF‐a and IL‐6. Conclusions: These results demonstrate that HIV PI‐induced cytoplasmic translocation of HuR contributes to the increased TNF‐a and IL‐6 expression in macrophages.