Cigarette smoke-induced NF-kappaB activation in human lymphocytes: the effect of low and high exposure to gas phase of cigarette smoke.

Cigarette smoking is linked to various human disorders. Active and passive smokers suffer from inflammatory diseases of lungs and airways. Smoking-dependent airway inflammation is related to the cytotoxic effects of cigarette smoke (CS) and chronic recruitment of neutrophils and macrophages. NF-kappaB is a key inflammatory, redox-sensitive transcription factor. Its role in CS-induced airway inflammation is unclear. This study investigated CS-induced NF-kappaB activation in human lymphocytes and the possible involvement of oxidative insult in this activation. A method for accurate and reproducible exposure of lymphocytes to CS was developed. The intensity of CS exposure was linearly correlated with nitrite concentration originating from reactive oxygen species in CS. Mild, but not high exposure to CS, induced NF-kappaB in lymphocytes through the increase in oxidative stress and the reduction in the intracellular glutathione levels. These findings may have implications to active as well as to passive smokers, suffering from inflammatory diseases of lungs and airways.

Mechanisms underlying cigarette smoke-induced NF-kappaB activation in human lymphocytes: the role of reactive nitrogen species.

Cigarette smoke (CS) is an important source of reactive nitrogen species (RNS). It has been demonstrated that CS constitutes the highest source of exogenous nitric oxide and peroxynitrite to which humans are exposed. NF-kappaB is a key inflammatory, redox-sensitive transcription factor, which role in CS-induced airway inflammation is unclear. Moreover, the role of RNS in the activation of NF-kappaB and in inflammation has remained vague. This study investigated CS-induced NF-kappaB activation in human lymphocytes and assessed the involvement of CS-derived RNS in NF-kappaB activation and their possible biological effects. Mild, but not high, exposure to CS induced NF-kappaB in lymphocytes through IKK activation, I-kappaBalpha degradation, and the reduction in the intracellular glutathione levels. Peroxynitrite, but not NO, mimicked the effects of CS on NF-kappaB. Reduction of intracellular peroxynitrite formation by the inhibition of the mitochondrial respiratory chain resulted in decreased activation of NF-kappaB by CS. NF-kappaB-induced iNOS levels were increased in response to CS. Low levels of CS exposure induced classical NF-kappaB activation pathway in lymphocytes via intracellular formation of peroxynitrite, through a reaction between smoke-derived NO and endogenously produced superoxide. This NF-kappaB activation resulted in inflammatory gene expression, which may contribute to CS-related airway inflammation.

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.