Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/20/2006
Publication Date: 9/15/2006
Citation: Weber, T.E., Kerr, B.J. 2006. Butyrate differentially regulates cytokines and proliferation in porcine peripheral blood mononuclear cells. Veterinary Immunology and Immunopathology. p. 139-147. Interpretive Summary: The volatile fatty acid butyrate has been shown to alter immune system function in some species. However, the role of butyrate as a regulator of immune function in the pig has not been studied. Therefore, in this series of experiments we determined whether treating porcine lymphocytes with butyrate could alter lymphocyte proliferation and cytokine production by lymphocytes. We also sought to determine whether certain signaling pathways were involved in butyrate-induced alterations in immune response. Lymphocytes were isolated from the blood of healthy donor pigs, and the cells were activated with the polyclonal mitogen, concanavalin A and cultured in the presence of sodium butyrate at different concentrations. It was found that treating activated lymphocytes with butyrate at a high dose increased the mRNA expression of interleukion-2, but decreased cell proliferation. In addition, the higher dose of butyrate increased interferon-gamma production and decreased the production of interleukin-10 by activated lymphocytes. In contrast, treating the lymphocytes with a lower dose of butyrate increased the gene expression and secretion of the anti-inflammatory cytokine interleukin-10. Blocking the cyclic AMP mediated pathway with 2, 5-dideoxy adenosine modified the cytokine alterations induced by butyrate. These findings indicate that butyrate regulates immune function in swine and that feeding practices that alter butyrate concentrations could potentially alter the immune system. The research results described in this report provide nutritionists at universities, feed companies, allied industries, and swine production facilities data showing that feeding practices that alter endogenous butyrate production may have an impact on immune system function in growing pigs.
Technical Abstract: Although butyrate modulates proliferation and cytokine production by PBMC in some species, the role of butyrate as a regulator of immunocyte function in the pig has not been studied. Therefore, the primary objective of this study was to determine whether butyrate influences peripheral blood mononuclear cell (PBMC) proliferation, cytokine secretion and mRNA expression in the pig in vitro. We also sought to determine whether alterations in cytokine production attributable to butyrate were associated with changes in the expression of suppressor of cytokine signaling-3 (SOCS3). Porcine PBMC were isolated from venous blood and stimulated with concanavalin A (ConA) in the presence or absence of sodium butyrate at 0.2 or 2.0 mM. Butyrate at 2.0 mM suppressed ConA-induced PBMC proliferation and led to a paradoxical increase in IL-2 mRNA expression. The secretion and mRNA expression of interferon- gamma (IFN-gamma) by ConA-activated PBMC was increased by butyrate at 2.0 mM. Exposing activated PBMC to butyrate at 2.0 mM decreased the secretion of interleukin-10 (IL-10). In contrast, butyrate at 0.2 mM increased both IL-10 secretion and mRNA expression. Activation of porcine PBMC with ConA increased the expression of SOCS3 mRNA, and butyrate treatment further augmented SOCS3 mRNA expression in a dose-dependent manner. Mechanistically, pretreatment with the adenyl cyclase inhibitor 2,5-dideoxyadenosine abolished the inhibitory effect of 2.0 mM butyrate on IL-10 secretion, and partially reversed the increase in IFN-gamma secretion induced by 2.0 mM butyrate. These data indicate that the effect of butyrate on cytokine production by porcine PBMC is dose-dependent, and that butyrate increases the expression of SOCS3 in activated PBMC. In addition, we provide evidence that the effects of butyrate on IFN-gamma and IL-10 production are mediated in part via a cAMP-dependent mechanism.