Effects of Mycobacterium bovis BCG infection on regulation of L-arginine uptake and synthesis of reactive nitrogen intermediates in J774.1 murine macrophages

The generation of nitric oxide (NO) by activated macrophages is believed to control mycobacterial infection in the murine system. In this study we exa mined the effect of Mycobacterium bovis BCG infection on the L-arginine-dep endent NO pathway in J774.1 murine macrophages. We have confirmed previous results by demonstrating that stimulation of J774.1 with lipopolysaccharide (LPS) and gamma interferon (IFN-gamma) results in an increase in the uptak e of H-3-labeled L-arginine and a concomitant increase in the production of NO. We have also shown that BCG can mimic LPS treatment, leading to enhanc ed L-[H-3]arginine uptake by IFN-gamma -stimulated macrophages. Lipoarabino mannan, a component of the BCG cell wall that is structurally similar to LP S, is not responsible for the uptake stimulation in IFN-gamma stimulated ma crophages. Although we demonstrated that there was a 2.5-fold increase in N O production by macrophages 4 h after LPS-IFN-gamma stimulation, BCG infect ion (with or without IFN-gamma stimulation) did not lead to the production of NO by the macrophages by 4 h postinfection. At 24 h postinfection, the i nfected macrophages that were stimulated with IFN-gamma produced amounts of NO similar to those of macrophages stimulated with LPS-IFN-gamma. This sug gests that there are multiple regulatory pathways involved in the productio n of NO. Finally, our data suggest that increased expression of the arginin e permease, MCAT2B, after 4 h of LPS-IFN-gamma treatment or BCG infection-I FN-gamma treatment is not sufficient to account for the increases in L-[3H] arginine uptake detected. This suggests that the activity of the L-arginine transporter(s) is also altered in response to macrophage activation.