NEOPTERIN AND 7,8-DIHYDRONEOPTERIN INDUCE APOPTOSIS IN THE RAT ALVEOLAR EPITHELIAL-CELL LINE L2

The neopterin derivatives, neopterin and 7,8-dihydroneopterin, modulat e the cellular oxidant-antioxidant balance as well as the expression o f the inducible nitric oxide synthase (iNOS) gene, Since apoptosis can be induced by reactive oxygen intermediates and nitric oxide (NO) we investigated whether these neopterin derivatives induce apoptotic cell death, As model we selected the rat alveolar epithelial cell. line L2 , 24 h incubation of neopterin (1-1000 mu M) as well as 7,8-dihydroneo pterin (1-1000 mu M) resulted in a significant increase of percent apo ptotic cells (measured by FACS analysis). Coincubation of both pteridi nes with the cytomix (interferon-gamma plus tumor necrosis factor-alph a) led to a significantly higher apoptosis than the cytomix alone, In contrast to the cytomix, no iNOS gene expression and no NO release cou ld be detected after incubation with neopterin or 7,8-dihydroneopterin . We conclude that neopterin and 7,8-dihydroneopterin are per se induc ers of apoptosis which is not mediated by nitric oxide. This may be of importance in inflammatory pulmonary diseases associated with an acti vation of the cellular immune system.