Hydrogen peroxide modifies both activity and isoforms of acetylcholinesterase in human neuroblastoma SH-SY5Y cells

The involvement of cholinergic system and the reactive oxygen species (ROS) in the pathogenesis of some degenerative diseases has been widely reported; however, the specific impact of hydrogen peroxide (H₂O₂) on the acetylcholinesterase (AChE) activity as well as AChE isoform levels has not been clearly established. Hence, the purpose of present study is to clarify whether H₂O₂ alters these parameters. Human neuroblastoma SH-SY5Y cells were treated with H₂O₂ (1-1000µM) for 24h and AChE activity and AChE and cytochrome c levels were evaluated. AChE activity was strongly increased from 1µM to 1000µM of H₂O_2. The results of the kinetic study showed that H₂O₂ affected Vmax but not Km; and also that H₂O₂ changed the sigmoid kinetic observed in control samples to hyperbolic kinetic. Thus, results suggest that H₂O₂ acts as an allosteric activators. In addition, H₂O₂, (100-1000µM) reduced the total AChE content and modified its isoform profile (mainly 50-, 70-, and 132-kDa)·H₂O₂ from 100µM to 1000µM induced cytochrome c release confirming cell death by apoptosis. All these results together suggest: a) the involvement of oxidative stress in the imbalance of AChE; and b) treatment with antioxidant agents may be a suitable strategy to protect cholinergic system alterations promoted by oxidative stress.