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Background Cooking oil fumes are closely related to immune response, and adipose tissue also plays an important role in immune regulation. At present, the biological effect and mechanism of inflammation of adipose tissue induced by oil fume exposure are not clear yet. Objective To investigate the inflammatory effect of different exposure duration of cooking fumes on adipose tissue in mice and explore the role of Nod-like receptor pyrin domain 3 (NLRP3)/cysteinyl aspartate specific proteinase 1 (Caspase 1)/interleukin (IL)-1β signaling pathway. Methods Forty 8-week-old female C57BL/6J mice were randomly divided into 3-day control group (CON3 group), 7-day control group (CON7 group), 3-day oil fume exposure group (COF3 group), and 7-day oil fume exposure group (COF7 group), with 10 mice in each group. The mice were exposed to oil fumes in a cooking oil fume formation and exposure equipment (COFFEE) for 20 min, followed by a 10-min pause, 1 h a day for consecutive 3 d or 7 d. General condition of mice was observed and body weight was measured every day. After exposure, blood was sampled from the eyeball. Serum levels of IL-6, IL-27, and IL-1β were detected by enzyme-linked immunosorbent assay (ELISA). The adipose tissue of mice was collected and observed after hematoxylin-eosin (HE) staining. The percentages of CD4+ and CD8+T cells in adipose tissue were detected by flow cytometry. Real-time quantitative PCR (RT-qPCR) was used to detect the expression levels of nuclear factor-κB (NF-κB), NLRP3, Caspase 1, and IL-1β in adipose tissue. Western blot was used to detect the expression levels of NLRP3, Caspase 1, and IL-1β in adipose. Results Compared with the corresponding control group, serum IL-6, IL-27, and IL-1β contents in the COF3 group and the COF7 group were significantly increased (P<0.05) except IL-6 in the COF3 group, and the levels in the COF7 group were significantly higher than those in the COF3 group (P<0.05). Vacuolar lipid droplets in adipocytes decreased, cytoplasm shrank, and inflammatory cells infiltrated in the COF7 group after HE staining. The flow cytometry results showed that the proportions of CD4+ and CD8+T cells in adipocytes of the COF3 group and the COF7 group were increased compared to the corresponding control group, with a significant increase in the COF7 group (P<0.05), and the CD4+/CD8+T ratio also significantly increased progressively in the two groups (P<0.05). The results of RT-qPCR showed that compared with the corresponding control group, the mRNA expression levels of NF-κB, NLRP3, Caspase 1, and IL-1β in adipose tissue of mice in the COF3 group and the COF7 group were significantly increased (P<0.05, P<0.01). The mRNA expression levels of mice in each exposure group gradually increased over time. The Western blot results showed that compared with the corresponding control group, the protein expressions of NLRP3 and Caspase 1 in the COF3 group were significantly increased (P<0.01), and the expression of IL-1β protein also increased but without statistical significance. The protein expressions of NLRP3, Caspase 1, and IL-1β in the COF7 group were significantly higher than those in the CON7 group (P<0.05, P<0.01). Conclusion Acute exposure to cooking oil fumes can induce significant inflammatory response in adipose tissue, and the effect gradually increases with the extension of exposure time. The mechanism of action may be related to the activation of NLRP3 inflammasome signaling pathway.
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Background It is unclear if there is any combined effect of air pollutants and non-optimal temperature on metabolic syndrome, or any molecular mechanisms of related signaling pathways in the process, which requires urgent systematic research. Objective To observe the effects of combined exposure to PM2.5 and non-optimal temperature on metabolic damage at gene and protein levels in mice, and elucidate the role of related signaling pathway in crucial organs. Methods A total of 60 six-week-old male C57BL/6J mice were randomly divided into six groups: a normal temperature-filter air group (TN-FA), a normal temperature-concentrated PM2.5 group (TN-PM), a heat-filter air group (TH-FA), a heat-concentrated PM2.5 group (TH-PM), a cold-filter air group (TC-FA), and a cold-concentrated PM2.5 group (TC-PM). The Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) was used to provide combined exposure settings of air types [concentrated PM2.5 and filter air (FA)] and temperatures [normal (22°C), cold (4°C), and heat (30°C)] for 4 weeks. Skeletal muscle and white adipose tissue (WAT) of the mice were sampled at the end of exposure, and transcriptomics and Western blot (WB) assay were adopted to observe selected gene and protein expression levels in the samples respectively. Results The transcriptomics results indicated that the PM2.5 exposure enhanced the number of differentially expressed genes. Specifically, 4820 genes were differentially expressed in the TN-PM mice compared to the TN-FA mice at normal temperature, and 1143 genes were differentially expressed in the Tc-PM mice compared to the Tc-FA mice in the cold environment. The phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway and the endoplasmic reticulum protein processing pathway were identified as the most significant pathways in metabolic injury resulting from combined exposure to PM2.5 and non-optimal temperature exposure. The WB results showed that exposure to PM2.5 in the normal temperature and the cold environments led to a significant increase in the expression of p-AKT in WAT (P<0.01, P<0.05) and a significant decrease in the expression of GLUT4 (P<0.05, P<0.01). In skeletal muscle, exposure to PM2.5 led to a significant decrease in GLUT4 (P<0.05) in all environments, with a consistent trend of change as observed in WAT. Conclusion Cold/heat exposure might promote PM2.5-induced metabolic disorder through suppression of the AKT/GLUT4 pathway, aggravating metabolic damage.