Up-Regulation of IL-10R1 Expression Is Required to Render Human Neutrophils Fully Responsive to IL-10

Abstract

We have recently shown that IL-10 fails to trigger Stat3 and Stat1 tyrosine phosphorylation in freshly isolated human neutrophils. In this study, we report that IL-10 can nonetheless induce Stat3 tyrosine phosphorylation and the binding of Stat1 and Stat3 to the IFN-γ response region or the high-affinity synthetic derivative of the c-sis-inducible element in neutrophils that have been cultured for at least 3 h with LPS. Similarly, the ability of IL-10 to up-regulate suppressor of cytokine signaling (SOCS)-3 mRNA was dramatically enhanced in cultured neutrophils and, as a result, translated into the SOCS-3 protein. Since neutrophils’ acquisition of responsiveness to IL-10 required de novo protein synthesis, we assessed whether expression of IL-10R1 or IL-10R2 was modulated in cultured neutrophils. We detected constitutive IL-10R1 mRNA and protein expression in circulating neutrophils, at levels which were much lower than those observed in autologous monocytes or lymphocytes. In contrast, IL-10R2 expression was comparable in both cell types. However, IL-10R1 (but not IL-10R2) mRNA and protein expression was substantially increased in neutrophils stimulated by LPS. The ability of IL-10 to activate Stat3 tyrosine phosphorylation and SOCS-3 synthesis and to regulate IL-1 receptor antagonist and macrophage-inflammatory protein 1β release in LPS-treated neutrophils correlated with this increased IL-10R1 expression, and was abolished by neutralizing anti-IL-10R1 and anti-IL-10R2 Abs. Our results demonstrate that the capacity of neutrophils to respond to IL-10, as assessed by Stat3 tyrosine phosphorylation, SOCS-3 expression, and modulation of cytokine production, is very dependent on the level of expression of IL-10R1.

Molecular mechanisms underlying the synergistic induction of CXCL10 by LPS and IFN‐γ in human neutrophils

“…Finally, our data do not exclude that the induction of CXCL10 mRNA expression by IFN-c and LPS in neutrophils might also be favored because it is not counter regulated by attenuators of cytokine-induced responses, such as the SOCS proteins [29]. Indeed, our previous observations have shown that in contrast to monocytes, neither SOCS-1 nor SOCS-3 protein expression is induced by LPS in neutrophils [11,30].…”

“…Finally, our data do not exclude that the induction of CXCL10 mRNA expression by IFN-c and LPS in neutrophils might also be favored because it is not counter regulated by attenuators of cytokine-induced responses, such as the SOCS proteins [29]. Indeed, our previous observations have shown that in contrast to monocytes, neither SOCS-1 nor SOCS-3 protein expression is induced by LPS in neutrophils [11,30].Conversely, it appears that monocyte responses are attenuated by LPS-activated SOCS-1/SOCS-3, since the induction of CXCL10 mRNA expression by IFN-c plus LPS is much lower than that exerted by IFN-c alone [6]. Interestingly, the reason why SOCS-1 is not inducible by LPS in neutrophils derives from the lack of mobilization of the MyD88-independent pathway, which controls SOCS-1 gene via endogenous .…”

“…Interestingly, the reason why SOCS-1 is not inducible by LPS in neutrophils derives from the lack of mobilization of the MyD88-independent pathway, which controls SOCS-1 gene via endogenous IFN-b [11]. By comparison, SOCS-3 mRNA is induced in LPS-treated neutrophils, but not the related protein [30]. It is also interesting to mention that, in preliminary experiments, neutrophils preincubated with LPS for up to 6 h prior to the addition of IFN-c for further 18 h, or vice versa, produced less CXCL10 than neutrophils costimulated with IFN-c plus LPS for the same overall time.…”

Prostaglandin E2 Augments IL-10 Signaling and Function

“…Crepaldi et al (32) demonstrated that IL-10 induced STAT3 phosphorylation not seen in freshly isolated human neutrophils, but is found in LPS-treated neutrophils, thus demonstrating that IL-10R1 mRNA and protein expression are substantially increased in LPS-stimulated neutrophils. Another report demonstrated that PGE 2 stimulates soluble IL-6R release, gp130 dimerization, and STAT3 phosphorylation (11).…”

“…In contrast, its augmentation is poorly understood. In this study we have examined several possible mechanisms for augmented cytokine-induced STAT signaling, such as increased cell surface expression of cytokine receptors (11,32), induction of cytokine to activate STAT phosphorylation (11,33), and increased STAT protein expression (34).…”