BioProject

Nitric oxide (NO) produced by macrophages (MØs) is toxic to both host tissues and invading pathogens and its regulation is therefore essential to suppress host cytotoxicity. More...

Nitric oxide (NO) produced by macrophages (MØs) is toxic to both host tissues and invading pathogens and its regulation is therefore essential to suppress host cytotoxicity. MØ arginase 1 (Arg1) inhibits NO production by competing with NO synthases for arginine, the common substrate of NO synthases and arginases. Two signal transduction pathways control Arg1 expression in MØs. First, a MyD88-dependent pathway induces Arg1 in intracellular infections, while a second Stat6-dependent pathway is required for Arg1 expression in alternativelyactivated MØs. We found that mycobacteria-infected MØs produce soluble factors that induce Arg1 in an autocrine-paracrine manner via Stat3. We identify these factors as IL-6, IL-10 and GCSF. We further establish that Arg1 expression is controlled by the MyD88-dependent production of IL-6, IL-10 and G-CSF rather than cell intrinsic MyD88 signaling to Arg1. Our data reveal the MyD88-dependent pathway of Arg1induction following BCG infection requires Stat3 activation and may result in the development of an immunosuppressive niche in granulomas due to the induced Arg1 production in surrounding uninfected MØs Overall design: We used microarrays to perform genome wide expression analysis in mycobacteria-infected macrophages from C57Bl/6 WT and MyD88-knockout mice. Less...