Fig. 6.

Regulation of CCL22 and cytokine mRNAs via histamine receptors in macrophages

Fig. A shows real-time (q) PCR of CCL22 (A-ⅰ), interleukin (IL)-6 (A-ⅱ), inducible nitric oxide synthase iNOS (A-ⅲ), and TNF-α (A-ⅳ) mRNAs in peritoneal macrophages from WT; n = 10), histamine receptor 1 knockout (H1R-KO; n = 10) and histamine receptor 2 knockout (H2R-KO; n = 10) mice. CCL22 was regulated by H2R. In comparison, IL-6, iNOS, and TNF-α were regulated by H1R. Furthermore, we examined the relationship between macrophage phenotypes and histamine receptors. Fig. B and C relate to human and mouse monocytes and macrophages, respectively. Human (PromoCell) monocytes (B-ⅰ) expressed predominantly H2R. In contrast, human M1-like macrophages (B-ⅱ) expressed predominantly H1R. Human M2-like macrophages (B-ⅲ) exhibited intermediate expression of H1R and H2R relative to monocytes and M1-like macrophages, without a significant difference in the expression of H1R and H2R being apparent. Mouse monocytes and macrophages displayed the same trends as for human monocytes and macrophages (C-ⅰ, -ⅱ, and -ⅲ). Values represent the mean ± SD of triplicate measurements from three independent experiments.

(*P < 0.05, **P < 0.01, ***P < 0.001; N.S., not significant).