Trypanocidal drug benznidazole impairs lipopolysaccharide induction of macrophage nitric oxide synthase gene transcription through inhibition of NF-kappa B activation

In murine macrophages, inducible NO synthase II (NOSII) gene expression is promoted at a transcriptional level by LPS and/or IFN-gamma with benznidazo le (BZL), a trypanocidal drug, acting to down-regulate NOSII gene induction and hence inhibiting NO production. By performing transient transfection e xperiments, we now report that BZL also inhibited the expression of NOSII g ene promoter or multimerized NF-kappaB binding site controlled reporter gen es. By contrast, no effect was observed on the expression of a reporter gen e under the control of the NOSII promoter-derived IFN regulatory factor ele ment. EMSAs demonstrated that BZL inhibited the nuclear availability of NF- kappaB in stimulated macrophages. NF-kappaB is activated in macrophages by phosphorylation, ubiquitination, and subsequent proteolysis of I kappaB. Wi thin this setting, Western blot was also performed to show that BZL blocked I kappaB alpha degradation. Collectively, these results demonstrate that B ZL is able to specifically inhibit macrophage NF-kappaB activation after LP S plus IFN-gamma stimulation.