β2-adrenoreceptor stimulation dampens the LPS-induced M1 polarization in pig macrophages.

The cross-talk between sympatho-adreno-medullar axis and innate immunity players was mainly studied in rodents. In intensive husbandry, pigs are exposed to multiple stressors inducing repeated releases of catecholamines that bind to adrenoreceptors (AR) on target cells. Among adrenoreceptors, the β2-AR is largely expressed by immune cells including macrophages. We report herein on the effects of catecholamines, through β2-AR stimulation, on pig macrophage functions activated by LPS. β2-AR stimulation of porcine macrophages prevented the LPS-induced increase in TNFα and IL-8 secretion while increasing IL-10 secretion. In contrast, treatment with a β2-agonist had no effect on anti-microbial functions. Lastly, β2-AR stimulation of macrophages reduced the expression of genes up-regulated by LPS. Altogether, we demonstrated that β2-AR stimulation of porcine macrophages prevented polarization towards a pro-inflammatory phenotype. Since porcine macrophages are a suitable model for human macrophages, our results might be relevant to appreciate catecholamine effects on human macrophages.