The inhibition of human T cell proliferation by the caspase inhibitor z-VAD-FMK is mediated through oxidative stress.
The caspase inhibitor benzyloxycarbony (Cbz)-l-Val-Ala-Asp (OMe)-fluoromethylketone (z-VAD-FMK) has recently been shown to inhibit T cell proliferation without blocking caspase-8 and caspase-3 activation in primary T cells. We showed in this study that z-VAD-FMK treatment leads to a decrease in intracellular glutathione (GSH) with a concomitant increase in reactive oxygen species (ROS) levels in activated T cells. The inhibition of anti-CD3-mediated T cell proliferation induced by z-VAD-FMK was abolished by the presence of low molecular weight thiols such as GSH, N-acetylcysteine (NAC) and l-cysteine, whereas d-cysteine which cannot be metabolised to GSH has no effect. These results suggest that the depletion of intracellular GSH is the underlying cause of z-VAD-FMK-mediated inhibition of T cell activation and proliferation. The presence of exogenous GSH also attenuated the inhibition of anti-CD3-induced CD25 and CD69 expression mediated by z-VAD-FMK. However, none of the low molecular weight thiols were able to restore the caspase-inhibitory properties of z-VAD-FMK in activated T cells where caspase-8 and caspase-3 remain activated and processed into their respective subunits in the presence of the caspase inhibitor. This suggests that the inhibition of T cell proliferation can be uncoupled from the caspase-inhibitory properties of z-VAD-FMK. Taken together, the immunosuppressive effects in primary T cells mediated by z-VAD-FMK are due to oxidative stress via the depletion of GSH.
School of Science, Monash University Sunway Campus, Jalan Lagoon Selatan, Bandar Sunway, 46150 Selangor Darul Ehsan, Malaysia.
T
T
Rajah
School of Science, Monash University Sunway Campus, Jalan Lagoon Selatan, Bandar Sunway, 46150 Selangor Darul Ehsan, Malaysia. Electronic address: chow.sek.chuen@monash.edu.
S C
SC
Chow
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology*; D061945:Caspase Inhibitors / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D005978:Glutathione / Q000378:metabolism; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects* / Q000276:immunology; D017382:Reactive Oxygen Species / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D006131:Growth Inhibitors; D017382:Reactive Oxygen Species; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D005978:Glutathione
Caspases; Oxidative stress; T cell activation; T lymphocytes; Thiols; z-VAD-FMK