Excessive inflammatory responses can cause collateral tissue damage or autoimmune inflammation, sometimes with severe morbidity or mortality. During host defense responses, numerous negative feedback mechanisms are established to prevent excessive unchecked inflammation. However, this restraint can sometimes come at the cost of suboptimal infection control, and we do not fully understand how this balance is maintained during different infection settings. The endoribonuclease Regnase-1 (Reg1, Zc3h12a, MCPIP1) is an RNA binding protein (RBP) that binds and degrades many target mRNA transcripts. Reg1 is a potent feedback regulator of IL-17 and LPS signal transduction, among other stimuli. Consequently, Reg1 deficiency exacerbates autoimmune inflammation in multiple mouse models, but on the other hand, reduced Reg1 improves immunity to fungal infection. To date, the role of Reg1 in bacterial immunity is poorly defined. Here, we show that mice deficient in Reg1 are more resistant to pulmonary Klebsiella pneumoniae (KP) infection. Unexpectedly, effects of Reg1 deficiency were not due to accelerated eradication of bacteria or increased pro-inflammatory cytokine expression. Rather, alveolar macrophages from Reg1-deficient mice showed enrichment of Type I IFN-related genes upon KP infection, accompanied by increased Ifnb1 expression. Surprisingly, the stability of Ifnb1 mRNA was not altered by Reg1-deficiency; rather, mRNA encoding its upstream regulator IRF7 appeared to be a more prominent target. Thus, impaired Reg1 induces Type I IFN and enhances resistance to KP, raising the possibility that Reg1 could be a potential clinical target in acute bacterial infections.
Contribution of increased ISG15, ISGylation and deregulated type I IFN signaling in Usp18 mutant mice during the course of bacterial infections