A defect in HIV-1 transgenic murine macrophages results in deficient nitric oxide production

HIV transgenic mice bearing multiple copies of a noninfectious (Delta gag/p ol) proviral DNA were tested for the systemic production of nitric oxide (N O). Serum levels of NO metabolites were reduced about 50% in HIV transgenic mice compared with nontransgenic sibling mice. This difference persisted w hen NO production was induced with peritoneal injections of bacterial endot oxin (LPS). Peritoneal inflammatory macrophages, but not resident peritonea l macrophages, derived from HIV-1 transgenic mice and activated in vitro wi th LPS and IFN-T (or tumor necrosis factor a and IFN-gamma) also produced a bout 50% less NO than did macrophages harvested from nontransgenic litter-m ates. Isogenic, transgenic mice bearing mutated nef or vpr genes had normal serum levels of NO metabolites and their macrophages produced normal level s of NO when stimulated. An explanation for the reduced NO response of HIV[ Vpr+Nef+] macrophages was not apparent from measured levels of iNOS express ion, viral gene expression, or arginase activity in activated macrophages. Inhibition of nitric oxide synthase (NOS) isoforms with L-NAME or aminoguan idine blocked time-dependent increases in HIV gene expression in activated macrophages cultured ex vivo. Inhibition with L-NAME occurred despite high levels of NO generated by iNOS, and exogenously supplied NO induced HIV gen e expression only weakly, suggesting that cNOS had the greater influence on proviral gene induction. This system is presented as a model of HIV-1 prov iral gene expression and dysfunction in macrophages.