Nicotine modulates proinflammatory monocyte proportions and phenotype in the bone marrow in vivo.

<p>WT, α7 KO and α9 KO mice were treated with nicotine for 4 days and then injected with a single dose of LPS. Bone marrow was collected 24 hours later, and monocytes were analyzed by flow cytometry. <b>A</b>, Monocyte proportions were reduced by LPS treatment in the bone marrow, and effect that was prevented by nicotine in WT mice. <b>B</b>, The proportions of monocytes that expressed CCR2 was reduced in the bone marrow of nicotine-treated WT mice, an effect that was not observed in α7 KO and α9 KO mice. <b>C</b>, The proportions of Ly6C^highCCR2⁺ cells were lower in the bone marrow of nicotine-treated WT mice and α9 KO mice, but not α7 KO mice. <b>D</b>, MHC-II^high monocyte proportions were also lower in the bone marrow of nicotine-treated WT and α9 KO mice, while nicotine’s effect was not present in α7KO mice. <b>E</b>, Nicotine reduced the proportions of monocytes that expressed high levels of CD80 in WT mice, but not in α9 KO or α7 KO mice. <b>F</b>, There were fewer CD86^high monocytes in nicotine-treated WT and α9 KO mice, but not in α7 KO mice. Overall, these data demonstrate that nicotine inhibits the presence of pro-inflammatory monocytes in the bone marrow of mice. Data shown are means ± SEM (n = 4 per group), while * denotes P < 0.05 between indicated groups (two-way ANOVA, Tukey’s post-hoc test).