Protective effect of nicotine through nicotinic acetylcholine receptor alpha 7 on hypoxia-induced membrane disintegration and DNA fragmentation of cultured PC12 cells.
Anahtar kelimeler
Öz
To investigate the effect of nicotine on hypoxic neuronal damage, cultured PC12 cells were exposed to hypoxia for 9 h and then reoxygenated for 72 h. The cells were stained by propidium iodide (PI), a marker of cell membrane disintegration and the TUNEL method, which indicates DNA fragmentation. In control cultures, the ratio of PI-positive cells to total cells progressively increased during and after exposure to hypoxia, constituting 39% of total cells at 72 h posthypoxia. This increase in PI-positive cells was completely inhibited by nicotine until 12 h posthypoxia, and was partially and dose-dependently inhibited thereafter. The ratio of TUNEL-positive cells to total cells started to increase at 24 h posthypoxia and reached 36% at 72 h in control cultures. This ratio was also dose-dependently inhibited by nicotine. These inhibitory effects of nicotine on the increase in PI-positive and TUNEL-positive cells were abolished by the addition to the medium of alpha-bungarotoxin, an antagonistic ligand for nicotinic acetylcholine receptor (AChR) alpha7. These findings suggest that nicotine inhibits, through AChR alpha7, hypoxia-induced cell membrane disintegration and DNA fragmentation of cultured PC12 cells exposed to hypoxia.