Treatment of human immunodeficiency virus (HIV)-infected patients with HIV protease inhibitors (PIs) has been associated with serious lipid disturbances. However, the incidence and degree of impaired lipid metabolism observed in the clinic vary considerably between individual HIV PIs. Our previous studies demonstrated that HIV PIs differ in their ability to increase the levels of transcriptionally active sterol regulatory element-binding proteins (SREBPs), activate the unfolded protein response (UPR), induce apoptosis, and promote foam cell formation in macrophages. In the present study, we examined the effects of three HIV PIs, including amprenavir, atazanavir, and ritonavir, on the UPR activation and the expression of key genes involved in lipid metabolism in primary rodent hepatocytes. Both atazanavir and ritonavir activated the UPR, induced apoptosis, and increased nuclear SREBP levels, but amprenavir had no significant effect at the same concentrations. In rat primary hepatocytes, cholesterol 7alpha-hydroxylase (CYP7A1) mRNA levels were significantly decreased by atazanavir (38%) and ritonavir (56%) but increased by amprenavir (90%); 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase mRNA levels were increased by amprenavir (23%) but not by ritonavir and atazanavir; low-density lipoprotein receptor mRNA was increased by atazanavir (20%) but not by amprenavir and ritonavir. Similar results were obtained in mouse primary hepatocytes. Atazanavir and ritonavir also decreased CYP7A1 protein levels and bile acid biosynthesis, while amprenavir had no significant effect. The current results may help provide a better understanding of the cellular mechanisms of HIV PI-induced dyslipidemia and also provide useful information to help predict clinical adverse effects in the development of new HIV PIs.

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HIV Protease inhibitor (PI)-associated cardiovascular risk, especially atherosclerosis, has become a major concern in the clinic. Macrophages are key players in the inflammatory response and atherosclerosis formation. We have previously shown that HIV PIs induce endoplasmic reticulum (ER) stress, activate the unfolded protein response (UPR), and increase the synthesis of the inflammatory cytokines, TNF-α and IL-6, by regulating the intracellular translocation of RNA binding protein HuR in macrophages. However, the underlying signaling mechanisms remain unclear. We show here that the HIV PI lopinavir significantly activated the extracellular-signal regulated protein kinase (ERK), but not c-Jun N-terminal kinase (JNK) and p38 MAPK. Lopinavirinduced cytosolic translocation of HuR and TNF-α and IL-6 synthesis were attenuated by specific chemical inhibitor of MEK (PD98058) or over-expression of dominant negative mutant of MEK1. In addition, we demonstrated that lopinavir-induced ERK activation and TNF-a and IL-6 expression were completely inhibited in macrophages from CHOP null mice. Taken together, these results indicate activation of the UPR plays an essential role in HIV PI-induced inflammatory cytokine synthesis and release by activating ERK, which increases the cytosolic translocation of HuR and subsequent binding to the 3′UTR of TNF-α and IL-6 mRNAs in macrophages.

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Macrophages are the key players in the inflammatory response. Our previous studies have shown that HIV protease inhibitors (PIs) induce ER stress and increase TNF‐¦Á and IL‐6 expression in macrophages. However, the underlying signaling mechanisms remain unclear. The aim of present study was to determine if MAPKs are involved in HIV‐PI‐induced inflammatory response in macrophages. J774A.1 cells and primary mouse peritoneal macrophages isolated from wild type and CHOP knock out mice were used in this study. Cells were treated with individual HIV PI. The mRNA and protein levels of TNF‐¦Á and IL‐6 were measured by real‐time RT‐PCR and ELISA, respectively. Activation of MAPKs was detected by Western blot using phospho‐specific antibodies. Results: HIV PIs, atazanavir and lopinavir, activated ERK1/2 and JNK, but not p38. HIV PI‐induced TNF‐¦Áand IL‐6 expression was attenuated by PD98059 and JNKII, but not SB203580. Furthermore, HIV PI‐induced ERK1/2 activation was completely inhibited by CHOP knock down using siRNA or in CHOP knock out macrophages. However, HIV PI‐induced CHOP expression was only inhibited by JNKII but not PD98059 and SB203580. Conclusions: Both ERK1/2 and JNK signaling pathways are involved in HIV PIs‐induced increase of TNF‐¦Á and IL‐6 expression in macrophages. CHOP plays an essential role in HIV PI‐induced inflammatory cytokine release by activating ERK1/2 and JNK signaling pathways in macrophages.