Oxidative damage in alveolar macrophages exposed to cigarette smoke extract and participation of nitric oxide in redox balance.

Nitric oxide (NO) acts in both pathological and biological processes. We investigated the role of NO in the regulation of cigarette smoke-induced oxidative stress in rat alveolar macrophages (RAM). RAM collected from Wistar rats were cultured in 5% concentration cigarette smoke extract (CSE) for 1h. RAM exposed to CSE were then co-incubated with L-NAME (LN), L-arginine (LA), N-acetylcysteine (NAC) and both LN and NAC. RAM cultured only with medium was considered as control group. Biochemical analysis were performed to measure cellular metabolism (MTT), nitrite levels, superoxide dismutase (SOD) and glutathione peroxidase activities, reduced glutathione (GSH) and oxidized (GSSG), malondialdehyde and myeloperoxidase activity. During exposure to CSE, increased NO levels were not only associated with an increase of cell activation, but also affected MTT levels in RAM. CSE exposure resulted in significant redox imbalance in RAM. NAC administration affected SOD antioxidant profile regardless NO levels; however nitrite values were associated with GSH/GSSG ratio. In addition, lipid peroxidation appeared to be nitric-oxide dependent. Furthermore, the use of NAC significantly reduced the expression of NFkB normally observed in RAM exposed to CSE. The present results show that NO appeared to be involved in RAM activation, oxidative status maintenance and lipid peroxidation process during exposure to CSE.