Differential expression of solute carrier family 11a member 1 and inducible nitric oxide synthase 2 in skin biopsies from leprosy patients

Leprosy is a chronic granulomatous infection caused by Mycobacterium leprae, an intracellular parasite that resides within macrophages and cannot be eliminated effectively. Solute carrier family 11a member 1 (Slc11a1) and inducible nitric oxide synthase (iNOS), both expressed in macrophages, play major roles in host defense against several intracellular pathogens. However, the roles of these molecules in natural infection with M. leprae remain unknown. We aimed to investigate the expression of Slc11a1 and iNOS in macrophages (CD68+ cells) infiltrating skin lesions in leprosy. Skin biopsies from 48 Mexican patients of leprosy [(33 lepromatous (LL), 15 tuberculoid (TT)] and from 10 healthy controls, were subjected to immunohistochemistry to determine expression of CD68, Slc11a1 and iNOS. We found a high expression of Slc11a1 and iNOS in most lepromatous leprosy samples. In tuberculoid leprosy samples, Slc11a1 expression was moderate or low, and that of iNOS was almost always low. In addition, Slc11a1 and iNOS expression levels were positively associated with bacillary loads in lepromatous leprosy lesions (P=0.05). These observations suggest that M. leprae infection promotes the expression of Slc11a1 and iNOS in macrophages and that lepromatous leprosy can occur despite this response.