N-acetylcysteine prevents beta-amyloid toxicity by a stimulatory effect on p35/cyclin-dependent kinase 5 activity in cultured cortical neurons.
Although previous studies have indicated that the neuroprotective effect of N-acetylcysteine (NAC) required activation of the Ras-extracellular-signal-regulated kinase (ERK) pathway, the detailed mechanisms and signal cascades leading to activation ERK are not clear. In the present study, we investigated the effect of NAC on A beta(25-35)-induced neuronal death. Pretreatment of neurons with NAC 1 hr before application of A beta prevented A beta-mediated cell death. NAC increased cyclin-dependent kinase 5 (Cdk5) phosphorylation, an effect that was blocked by Cdk5 inhibitor. The neuroprotective effect of NAC was significantly attenuated by Cdk5 inhibitors or in neurons transfected with Cdk5 or p35 small interfering RNA (siRNA). Conversely, pretreatment of neurons with the calpain inhibitors calpeptin or MDL28170 enhanced the neuroprotective effect of NAC. A beta(25-35) caused a significant decrease in the level of p35, with a concomitant increase in p25, which was completely prevented by NAC. This effect of NAC was blocked by the Cdk5 inhibitors roscovitine and butyrolactone. In addition, NAC increased Cdk5/p35 kinase activity but reduced Cdk5 kinase activity. A beta(25-35) treatment decreased phosphorylated levels of ERK, which could be reversed by NAC. The effect of NAC was completely blocked by Cdk5 inhibitors. NAC reversed the A beta(25-35)-induced decrease in the expression of Bcl-2, which could be blocked by the MAPK kinase (MEK) inhibitor or Cdk5 inhibitors. These results suggest that NAC-mediated neuroprotection against A beta toxicity is likely mediated by the p35/Cdk5-ERKs-Bcl-2 signal pathway.
Department of Pharmacology, Center for Gene Regulation and Signal Transduction Research, National Cheng-Kung University, Tainan, Taiwan.
Ya-Hsin
YH
Hsiao
Po-See
PS
Chen
Shiu-Hwa
SH
Yeh
Chia-Ho
CH
Lin
Po-Wu
PW
Gean
D000111:Acetylcysteine / Q000494:pharmacology*; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000633:toxicity*; D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D016229:Amyloid beta-Peptides; C492235:Cdk5r1 protein, rat; D010770:Phosphotransferases; D051360:Cyclin-Dependent Kinase 5; D000111:Acetylcysteine