Evidence for the existence of [³H]‐trimetazidine binding sites involved in the regulation of the mitochondrial permeability transition pore

Abstract

Trimetazidine is an anti‐ischaemic drug effective in different experimental models but its mechanism of action is not fully understood. Data indicate that mitochondria could be the main target of this drug. The aim of this work was to investigate the binding of [3H]‐trimetazidine on a purified preparation of rat liver mitochondria. [3H]‐trimetazidine binds to two populations of mitochondrial binding sites with Kd values of 0.96 and 84 μm. The total concentration of binding sites is 113 pmol mg−1 protein. Trimetazidine binding sites are differently distributed. The high‐affinity ones are located on the outer membranes and represent only a small part (4%) of total binding sites, whereas the low‐affinity ones are located on the inner membranes and are more abundant (96%) with a Bmax=108 pmol mg−1 protein. Drug displacement studies with pharmacological markers for different mitochondrial targets showed that [3H]‐trimetazidine binding sites are different from previously described mitochondrial sites. The possible involvement of [3H]‐trimetazidine binding sites in the regulation of the mitochondrial permeability transition pore (MTP), a voltage‐dependent channel sensitive to cyclosporin A, was investigated with mitochondrial swelling experiments. Trimetazidine inhibited the mitochondrial swelling induced by Ca2+ plus tert‐butylhydroperoxide (t‐BH). This effect was concentration‐dependent with an IC50 value of 200 μm. Assuming that trimetazidine effectiveness may be related to its structure as an amphiphilic cation, we compared it with other compounds exhibiting the same chemical characteristic both for their ability to inhibit MTP opening and to displace [3H]‐trimetazidine bound to mitochondria. Selected compounds were drugs known to interact with various biological membranes. A strong correlation between swelling inhibition potency and low‐affinity [3H]‐trimetazidine binding sites was observed: r=0.907 (n=24; P<0.001). These data suggest that mitochondrial sites labelled with [3H]‐trimetazidine may be involved in the MTP inhibiton. British Journal of Pharmacology (1998) 123, 1385–1394; doi:

Trimetazidine Reduces Basal Cytosolic Ca2+ Concentration During Hypoxia in Single Xenopus Skeletal Myocytes

“…Increased mitochondrial Ca 2+ uptake has been attributed to the development of the mitochondrial permeability transition (MPT) pore, which may affect cell function and cause necrosis through abolition of the mitochondrial membrane potential (Lemasters et al 1997). Although it has previously been demonstrated that TMZ increases mitochondrial Ca 2+ uptake during conditions of high extracellular PJ in isolated mitochondria (Guarnieri et al 1997), it has more recently been demonstrated that it reduces the opening of the MPT pore by competing with increases in cytosolic Ca 2+ concentration (Morin et al 1998(Morin et al , 2000, as occurs during hypoxia. This suggests that mitochondrial uptake of Ca 2+ during hypoxia was unlikely and that increased Ca 2+ uptake into the SR may be a possible mechanism responsible for the decrease in basal [Ca 2+ ] c .…”

Effects of trimetazidine on the Akt/eNOS signaling pathway and oxidative stress in anin vivorat model of renal ischemia-reperfusion

“…7,8 Trimetazidine or (1-2(2,3,4-trimeoxibenzyl)-piperazine) (TMZ), is used as an anti-anginal agent, selectively inhibits long-chain 3-ketoacyl coenzyme A thiolase (the last enzyme involved in b-oxidation) activity. 9 Its anti-ischemic effects on the kidney have been experimentally assessed in various models including cell culture 10 isolated and perfused kidneys 11 and in vivo. 12,13 TMZ has different pharmacological properties that could be relevant for the prevention of organ damage from I/R by reduction of intracellular acidosis, 14 preservation of ATP production, limitation of inflammatory reaction, and thus of ROS generation.…”

Trimetazidine reduces early and long-term effects of experimental renal warm ischemia: A dose effect study

“…27 Recent studies has confirmed that the low-affinity TMZ sites on mitochondria are involved in the inhibition of mitochondrial swelling and this behavior was associated to an inhibition of mitochondrial transition pore opening. 28 In the present study, TMZ effect could be correlated to the down regulation of Bcl-xL during the early stage of reperfusion after WI.…”