Expression of inducible nitric oxide synthase and nitrotyrosine in borderline leprosy lesions

Background In the response to T-helper cell. (Th1)-type cytokines and inter actions with pathogens, high levels of nitric oxide (NO) are produced by ac tivated macrophages. expressing the inducible NO synthase (iNOS). The role and importance of reactive nitrogen intermediates (RNIs) such as NO and per oxynitrite in the host response to diseases caused by intracellular pathoge ns such as Mycobacterium leprae and M. tuberculosis is unclear. Objectives The aim of this study was to investigate the presence of local p roduction of NO and peroxynitrite in borderline leprosy by using antibodies against iNOS and the product of peroxynitrite, nitrotyrosine (NT). Methods We detected the presence of iNOS and NT in skin biopsies from borde rline leprosy patients, with and without reversal reaction (RR), by immunoh istochemistry (n=26). Results In general, the granulomas from borderline leprosy lesions with and without RR showed high and specific expression of iNOS and NT. Moreover, s trong immunoreactivity to iNOS and NT was observed in granulomas surroundin g and infiltrating dermal nerves. The expression of iNOS and NT was also st rong in keratinocytes, fibroblasts and endothelial cells in close relation to the granulomatous reaction. In contrast, normal human skin showed no exp ression of iNOS. and NT in these cells. Conclusions We conclude that iNOS and NT are expressed in granulomas from b orderline leprosy patients with and without RR and propose that RNIs might be involved in the nerve damage following RR in leprosy.