Figure 3.

Long-term exposure to PM_2.5 impairs leptin sensitivity, alters the expression of hypothalamic neuropeptides and increases inflammatory mediators. Mice were exposed to particulate matter less than 2.5 micrometers in diameter (PM_2.5) or filtered air (FA) for 12 weeks. (A) Npy (neuropeptide Y), Agrp (Agouti-related protein) and Pomc (Pro-opiomelanocortin) gene expression in the hypothalamus after 24 h of fasting n = 5 for each group. (B) Intraperitoneal (IP) leptin sensitivity test, the results of food intake during the 3 days of leptin injection was compared to the basal FI for each mouse and were expressed as a percent of the basal (saline) food intake for each mouse n = 4 for each group. (C) STAT3 phosphorylation (Arbitrary Units) in response to IP leptin or saline injection was measured in the hypothalamus of overnight fasted mice; n = 2 for FA (saline, leptin) and PM_2.5 (saline) groups and n = 3 for PM_2.5 (leptin) group (full-length gels are presented in Supplementary Fig. 1A). (D) Iba-1-ir density expression in hypothalamic nuclei and (E) hypothalamic gene expression of mice exposed to FA or PM_2.5 for 12 weeks n = 4–6. Abbreviations: Ikbke - inhibitor of nuclear factor kappa-B kinase subunit epsilon; Nos2 - inducible nitric oxide synthase 2; Tnf - Tumor necrosis factor alpha; Tlr4 - Toll-like receptor 4; Eifak2 - Eukaryotic translation initiation factor-α kinase 2; Il6 - Interleukin 6. All of the mice studied were 6–8 weeks of age. Data were presented as the mean ± SD. One-way ANOVA (Panels A and C) and two-way ANOVA (Panel B) followed by a Tukey post hoc test were used for the statistical analysis *P < 0.05 vs FA; #P < 0.05 vs. FA leptin; ^&P < 0.05 vs. PM_2.5 leptin; **P < 0.05 vs PM_2.5 leptin; ^##P < 0.05 vs FA (same gene).