Induction of apoptosis by vanilloid compounds does not require de novo gene transcription and activator protein 1 activity.

Abstract

The vanilloid compounds, capsaicin and resiniferatoxin, are quinone analogues that inhibit the NADH-plasma membrane electron transport system and induce apoptosis in transformed cells. Because disruption of the mitochondrial transmembrane potential (deltapsi(m)) is a common metabolic alteration in all apoptotic processes, we have evaluated the role of mitochondrial permeability transition in apoptosis induced by vanilloids in Jurkat cells. Using a cytofluorimetric approach, we have determined that DNA nuclear loss induced by vanilloids is preceded by an increase of the production of reactive oxygen species (ROS) and by a subsequent deltapsi(m) dissipation in T-cell lines. Overexpression of Bcl-2 and pretreatment with either the immunosuppressant cyclosporin A or the glutathione precursor N-acetyl-L-cysteine blocked deltapsi(m) disruption and apoptosis, but not the generation of ROS induced by these compounds. Capsaicin and resiniferatoxin were found to activate both isoforms of c-jun-NH2-kinase (JNK), with a maximal activity after 30 min of treatment. Despite the activation of JNK, there was no induction of activator protein 1 (AP-1) activity as determined by gel shift assay or of induction of an AP-1-responsive reporter. On the other hand, vanilloids did not signal for c-Raf kinase and extracellular signal-regulated kinases 1 and 2. We suggest that ROS generation by inhibition of the NADH-dependent plasma membrane electron transport system resulted in the oxidation of mitochondrial megachannel pores that allows for the disruption of deltapsi(m) and apoptosis, and that AP-1 activation is not required for vanilloid-induced apoptosis.