Mechanisms of N-acetylcysteine-driven enhancement of MK886-induced apoptosis.
N-Acetylcysteine (NAC), besides being a precursor of glutathione, has an array of other effects including an ability to scavenge free radicals, modulate gene expression and signal transduction pathways, and regulate cell survival and apoptosis. At concentrations lower than 20 mmol/L, NAC is nontoxic to cultured cells and can protect against apoptosis induced by a number of agents. A few recent reports, however, have indicated that NAC can also increase apoptosis. MK886, a 5-lipoxygenase activating protein (FLAP) inhibitor, induces apoptosis in many cell lines by an unknown mechanism that is independent of FLAP and lipoxygenase activity but is possibly related to effects on kinases such as Akt. In Jurkat T lymphocytes, NAC pretreatment (10 mmol/L) enhanced MK886-induced apoptosis by 2.4-fold. Following NAC-MK886 treatment, there was a significant increase in caspase-3 activity, and a decrease in mitochondrial transmembrane potential compared to MK886 alone. However, the extent of cytochrome c release was comparable between MK886 alone and MK886-NAC treatments. The enhancement of MK886-induced apoptosis by 10 mmol/L NAC appears to be partly related to a decrease in pH caused by this concentration of NAC, because an acidic environment favors activation of effector caspases and triggering of mitochondrial apoptosis. However, because neutralized NAC also enhanced apoptosis (1.6-fold), a direct role for NAC in augmenting the apoptotic pathways initiated by MK886 is suggested.
Deshpande
V S
VS
Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, USA. vaidehee@hotmail.com
Kehrer
James P
JP
D058927:5-Lipoxygenase-Activating Proteins; D000111:Acetylcysteine / Q000494:pharmacology*; D017304:Annexin A5 / Q000494:pharmacology; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D016650:Fluorescein-5-isothiocyanate / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000494:pharmacology*; D019169:Jurkat Cells; D008565:Membrane Proteins / Q000378:metabolism; D011419:Propidium / Q000494:pharmacology; D002722:Chlorobenzenes
D058927:5-Lipoxygenase-Activating Proteins; D000111:Acetylcysteine; D017304:Annexin A5; D002352:Carrier Proteins; D053148:Caspase 3; D045304:Cytochromes c; D016650:Fluorescein-5-isothiocyanate; D016166:Free Radical Scavengers; D007211:Indoles; D008565:Membrane Proteins; D011419:Propidium; C548592:ALOX5AP protein, human; C060893:MK-886; D002722:Chlorobenzenes