The role of reactive nitrogen species and cigarette smoke in activation of transcription factor NF-kappaB and implication to inflammatory processes.

Using the electromobility shift assay (EMSA) in the rat myoblast system, the activation of transcription factor NF-kappaB by reactive nitrogen species was evaluated. Two distinct patterns of activation were demonstrated. Whereas NO donor, SNAP, activated NF-kappaB in the classical pathway, which led to a transient response, NF-kappaB activation by peroxynitrite donor, SIN-1, was mediated by an alternative pathway, which has been demonstrated in previous works to involve tyrosine nitration of the NF-kappaB inhibitory protein I-kappaB alpha. This led to a constitutive non-transient activation of NF-kappaB and a prolonged inflammatory reaction. Lymphocytes exposed to mild intensity of cigarette smoke for 8 h, which activated NF-kappaB, exhibited a decrease in the fraction of apoptotic cells from 27% to 19% compared with lymphocytes exposed to atmospheric air, using the FACS Annexin V assay. This also has been shown in previous works to be mediated by peroxynitrite. Thus, mild exposure to cigarette smoke induces NF-kappaB activation, which can attenuate apoptosis in human lymphocytes and lead to prolonged inflammatory response. A possible proposed mechanism for induction of chronic inflammatory response may involve peroxynitrite-induced activation of NF-kappaB.