Article

Molecular and Cellular Biochemistry

, Volume 210, Issue 1, pp 153-158

First online:

Flufenamic acid as an inducer of mitochondrial permeability transition

  • Maria C. JordaniAffiliated withDepartment of Physics and Chemistry, School of Pharmaceutical Sciences, University of São Paulo
  • , Antonio C. SantosAffiliated withDepartment of Clinical, Toxicological and Bromatological Analysis, School of Pharmaceutical Sciences, University of São Paulo
  • , Ieda M.R. PradoAffiliated withDepartment of Physics and Chemistry, School of Pharmaceutical Sciences, University of São Paulo
  • , Sérgio A. UyemuraAffiliated withDepartment of Clinical, Toxicological and Bromatological Analysis, School of Pharmaceutical Sciences, University of São Paulo
  • , Carlos CurtiAffiliated withDepartment of Physics and Chemistry, School of Pharmaceutical Sciences, University of São Paulo

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Abstract

To assess the mechanism by which mitochondrial permeability transition (MPT) is induced by the nonpolar carboxylic acids, we investigated the effects of flufenamic acid (3′-trifluoromethyl diphenylamine-2-carboxylic acid, FA) on mitochondrial respiration, electrical transmembrane potential difference (ΔΨ), osmotic swelling, Ca2+ efflux, NAD(P)H oxidation and reactive oxygen species (ROS) generation. Succinate-energized isolated rat liver mitochondria incubated in the absence or presence of 10 μM Ca2+, 5 μM ruthenium red (RR) or 1 μM cyclosporin A (CsA) were used. The dose response-curves for both respiration release and ΔΨ dissipation were nearly linear, presenting an IC50 of approximately 10 μM and reaching saturation within 25-50 μM, indicating that FA causes mitochondrial uncoupling by a protonophoric mechanism. Within this same concentration range FA showed the ability to induce MPT in energized mitochondria incubated with 10 μM Ca2+, followed by ΔΨ dissipation and Ca2+ efflux, and even in deenergized mitochondria incubated with 0.5 mM Ca2+. ADP, Mg2+, trifluoperazine (TFP) and N-ethylmaleimide (NEM) reduced the extent of FA-promoted swelling in energized mitochondria by approximately one half, whereas dithiothreitol (DTT) slightly enhanced it. NAD(P)H oxidation and ROS generation (H2O2 production) by mitochondria were markedly stimulated by FA; these responses were partly prevented by CsA, suggesting that they may be implicated as both a cause and effect of FA-induced MPT. FA incubated with mitochondria under swelling assay conditions caused a decrease of approximately 40% in the content of protein thiol groups reacting with 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB). The present results are consistent with a ROS-intermediated sensitization of MPT by a direct or indirect FA interaction with inner mitochondrial membrane at a site which is in equilibrium with the NAD(P)H pool, namely thiol groups of integral membrane proteins.

nonsteroidal antiinflammatory drugs nonpolar carboxylic acids flufenamic acid liver mitochondria mitochondrial uncoupling mitochondrial permeability transition mitochondrial Ca2+ efflux NAD(P)H oxidation reactive oxygen species