Effect of anti-leprosy drugs on superoxide anion production by rat peritoneal macrophage with special reference to light exposed clofazimine

The present study describes the in vitro effect of anti-leprosy drugs on superoxide anion (O 2 −) production by rat resident peritoneal macrophages. Of the three drugs tested i.e. clofazimine, rifampicin and dapsone, the first was most effective in increasing O 2 − production in a dose dependent manner, while rifampicin had some stimulatory effect and dapsone exhibited minimal action. Furthermore, when clofazimine and dapsone were added together it was observed that the increase of O 2 − production by macrophages due to clofazimine was not significantly altered by the addition of dapsone. Moreover, it was found that killed Mycobacterium leprae could induce a lesser amount of O 2 − production in comparison to that of Staphylococcus aureus and the enhancement of O 2 − release due to clofazimine was stimulus dependent. This increase of O 2 − release after addition of clofazimine was inhibited by the addition of p-bromophenacyl bromide. Another interesting finding was that the enhancement of O 2 − production by clofazimine gradually decreased as clofazimine was exposed to light for days. On further investigation it was found that ultraviolet, NMR, infrared and mass spectra of the light unexposed and exposed drug were similar, but the diffusion current of the polarogram of light exposed drug was remarkably more than that observed in light unexposed drug, indicating, thereby, a possible increase in the electron accepting capacity of the light reacted molecule. As far as we know this is the first report describing the effect of light exposed clofazimine on the respiratory burst activity of macrophages.