The Effect of Exogenously added and Endogenously Produced Cytokines on the Regulation of Inflammatory Mediators and SOCS Proteins in Mouse Macrophages Exposed to Chlamydia muridarum Major Outer Membrane Protein

Abstract

Abstract The major outer membrane protein (MOMP) of Chlamydia is a candidate for vaccine developmental efforts due to its high immunogenic potential. We previously reported that IL-10 can regulate Chlamydia inflammation by inhibiting its associated-induced inflammatory mediators possibly via induction of the Suppressor of Cytokine Signaling (SOCS) proteins. In this study, we determined the effect of exogenously added and endogenously produced cytokines on the regulation of inflammatory mediators and SOCS proteins as induced in mouse J774 macrophages exposed to C. muridarum (Cm) recombinant MOMP. Macrophages were stimulated with rMOMP (10 ug/mL) in the presence and absence of exogenous IL-10, TNF and IL-6 (each at 10 ng/mL). Cytokine and chemokine specific ELISAs revealed that exogenously added IL-6 and TNF did not alter the levels of inflammatory mediators (CCL5, CXCL10, IL-12) induced by rMOMP; whereas IL-10 downregulated all mediators. Neutralization of endogenously produced IL-6 and TNF, respectively by anti-IL-6 or anti-TNF antibodies (each at 25 μg/mL) did not significantly perturb the expression of rMOMP-induced inflammatory mediators. On the contrary, neutralization of IL-10 by an anti-IL-10 antibody increased the production of all mediators, thus confirming that IL-10 regulates Cm-induced inflammation. Removal of endogenously produced IL-10 increased SOCS1 expression, which suggest an important role of IL-10 in the regulation of SOCS1 expression to potentially control Cm-induced inflammatory responses. Collectively, our data sheds more light on the potential roles of these cytokines implicated during chlamydial infections, but more importantly, how IL-10 regulates Chlamydia inflammation via SOCS proteins.