On the mechanisms of phenothiazine-induced mitochondrial permeability transition: Thiol oxidation, strict Ca2+ dependence, and cyt c release

Abstract

Phenothiazines (PTZ) are drugs widely used in the treatment of schizophrenia. Trifluoperazine, a piperazinic PTZ derivative, has been described as inhibitor of the mitochondrial permeability transition (MPT). We reported previously the antioxidant activity of thioridazine at relatively low concentrations associated to the inhibition of the MPT (Brit. J. Pharmacol., 2002;136:136-142). In this study, it was investigated the induction of MPT by PTZ derivatives at concentrations higher than 10 microM focusing on the molecular mechanism involved. PTZ promoted a dose-response mitochondrial swelling accompanied by mitochondrial transmembrane potential dissipation and calcium release, being thioridazine the most potent derivative. PTZ-induced MPT was partially inhibited by CsA or Mg(2+) and completely abolished by the abstraction of calcium. The oxidation of reduced thiol group of mitochondrial membrane proteins by PTZ was upstream the PTP opening and it was not sufficient to promote the opening of PTP that only occurred when calcium was present in the mitochondrial matrix. EPR experiments using DMPO as spin trapping excluded the participation of reactive oxygen species on the PTZ-induced MPT. Since PTZ give rise to cation radicals chemically by the action of peroxidases and cyanide inhibited the PTZ-induced swelling, we propose that PTZ bury in the inner mitochondrial membrane and the chemically generated PTZ cation radicals modify specific thiol groups that in the presence of Ca(2+) result in MPT associated to cytochrome c release. These findings contribute for the understanding of mechanisms of MPT induction and may have implications for the cell death induced by PTZ.

Perphenazine and trifluoperazine induce mitochondria-mediated cell death in SH-SY5Y cells

“…In contrast, it has been recently shown that a higher concentration of trifluoperazine can induce MPT in isolated mitochondria and apoptosis of melanoma cells (Gil-Ad et al 2006;Cruz et al 2010). In the report by Cruz et al (2010), it has been shown that phenothiazine derivatives such as trifluoperazine and thioridazine induced swelling of isolated mitochondria and cytochrome c release. Concordantly, we observed neurotoxicity at a similar concentration range and we could detect cytochrome c release following perphenazine or trifluoperazine treatment in the cultured cells.…”

“…Therefore, trifluoperazine at this concentration range has been shown to partially protect cells from oxidative damage (Liu et al 2011). In contrast, it has been recently shown that a higher concentration of trifluoperazine can induce MPT in isolated mitochondria and apoptosis of melanoma cells (Gil-Ad et al 2006;Cruz et al 2010). In the report by Cruz et al (2010), it has been shown that phenothiazine derivatives such as trifluoperazine and thioridazine induced swelling of isolated mitochondria and cytochrome c release.…”

“…However, perphenazine and trifluoperazine at higher concentration have been shown to induce cell death in neuronal cell lines and primary cultured neurons (Gil-Ad et al 2001. Trifluoperazine has been shown to induce mitochondrial permeability transition (MPT) and cytochrome c release from the isolated mitochondria (Cruz et al 2010). In patients, antipsychotics have been reported to exert direct toxicities on many organs or cells, including liver and blood cells, in addition to the indirect systemic side effects such as endocrine disturbances, hypotension and seizures (Lader 1999;Flanagan and Dunk 2008).…”

Toxic effects of xylazine on endothelial cells in combination with cocaine and 6-monoacetylmorphine

“…Phenothiazines are commonly used in combination with other drugs in antipsychotic treatment, showing also various biological activities involving antibacterial, antiplasmid, antitumor and antihelmintic properties [49, 50]. These compounds have been shown to possess cytostatic and cytotoxic effects in a variety of non-CNS cells [51]. …”

Redox proteomics and drug development

“…Some drugs which are routinely used in the treatment for schizophrenia, psychosis and anxiety, such as phenothiazines (PTZ), are known to act through stimulation of mitochondrial permeability, thus enhancing OS in target cells, although at the expenses of increased hepatotoxicity [154]. Conversely, trifluoperazine, a piperazinic PTZ derivative, has been reported to show antioxidant activity at relatively low concentrations, which has been associated with its inhibition of mitochondrial permeability [155].…”