The role of Gch1 and Nos2 in the macrophage response to BCG infection

Inducible nitric oxide synthase (iNOS) plays a crucial role in controlling growth of mycobacteria, presumed to be via nitric oxide (NO) mediated killing. However, NOS enzymes can also signal through NO-independent pathways, and production of NO by NOS requires the cofactor tetrahydrobiopterin (BH4). We compared Nos2-/- mice to mice with macrophage BH4 deficiency (Gch1fl/flTie2cre), due to a leukocyte-specific deletion of Gch1, to uncover the specific contribution of NO-independent NOS functions to anti-mycobacterial immunity. We used microarrays to detail the global programme of gene expression in uninfected and BCG infected macrophages that were either deficient in iNOS (Nos2-/- vs C57bl6/J) or BH4/Gch1 (GCHfl/flTie2cre vs GCHfl/fl) Bone Marrow Derived Macrophages (BMDM) were cultured form C57bl6/J (Nos2+/+), Nos2-/-, GCHfl/fl and GCHfl/flTie2cre bone marrow. Differentiated macrophages from 4 animals per genotype were infected with BCG (Pasteur) in the presence of interferon gamma or left uninfected for 24 hours as control samples.