Bisphenol A (BPA) and its replacement analog, bisphenol S (BPS), have been proposed as environmental obesogen to disrupt the lipid metabolism through regulating peroxisome proliferator-activated receptor gamma (PPARγ) receptor. However, there is a dearth of information on whether this biological effect can occur in human macrophage, a cell type which closely interacts with adipocytes and hepatocytes to control lipid metabolism. Here, we for the first time investigate the activity of BPA and BPS on PPARγ pathway in human macrophages. The results demonstrated that BPA and BPS served as activators of PPARγ in human macrophage cell line, and significantly induced the expression of lipid metabolism-related genes, including fatty acid binding protein 4 (FABP4), cluster of differentiation 36 (CD36) and nuclear receptor subfamily 1 group H member 3 (NR₁H₃). In PPARγ knockout cells, expression of these genes was down-regulated, suggesting that these genes are dependent on PPARγ. The underlying mechanisms were further investigated using an in vivo mouse model, and the results confirmed the induction of PPARγ and its respective target genes in mice following exposure to BPA or BPS. Moreover, the observed alteration of PPARγ expression highly correlated with the disturbance of metabolism profiles in liver tissues as detected by ¹H Nuclear Magnetic Resonance (NMR)-based metabonomics. Overall, this study provided the first evidence that BPA and BPS activated PPARγ and its target genes in human macrophages, and provided comprehensive information to confirm that BPA and BPS disturb the metabolism through targeting PPARγ via both in vitro assays and in vivo animal models.

Endoplasmic reticulum (ER) stress contributes to the development and progression of many chronic inflammatory diseases, including type 2 diabetes, obesity, atherosclerosis, neurodegenerative diseases, and cancer. ER stress has been reported to induce inflammasome activation and release of mature IL-1β, which contributes to many inflammatory diseases. The molecular mechanisms that activate the inflammasome during ER stress are still poorly understood. Here we report that the kinase receptor-interacting protein 1 (RIP1) plays an important role in ER stress-induced activation of inflammasome. Inhibition of RIP1 kinase activity by Necrostatin-1 or siRNA-mediated RIP1 knockdown significantly reduced ER stress-induced caspase-1 cleavage and IL-1β secretion in both bone marrow-derived macrophages (BMDMs) and J774A.1 macrophages. We speculate that the mitochondria fission factor dynamin-related protein 1 (DRP1) and reactive oxygen species (ROS) might function as the effectors downstream of RIP1 to mediate inflammasome activation. Our study reveals a critical role for RIP1 in regulating ER stress-induced inflammation responses, and proposes RIP1 as a potential pharmaceutical target to treat diseases resulting from unresolved ER stress-related inflammation.