Cyclosporine A attenuates mitochondrial permeability transition and improves mitochondrial respiratory function in cardiomyocytes isolated from dogs with heart failure

100

Morphine has been shown to protect the myocardium against ischemia-reperfusion injury through inhibition of glycogen synthase kinase-3␤ (GSK-3␤). Given that GSK-3␤ is known to modulate the mitochondrial permeability transition pore (mPTP), we investigated the role of mPTP in the cardioprotective effect of morphine and the GSK-3␤ inhibitor SB216763 [SB; 3-(2,4-dichlorophenyl)-4(1-methyl-1H-indol-3-yl)-1H-pyrrole-2,5-dione] during ischemia-reperfusion. Both morphine (0.3 mg/kg) and SB (0.6 mg/kg) reduced infarct size in a model of regional myocardial ischemia-reperfusion in rats (13 Ϯ 1 and 14 Ϯ 3% of the area at risk versus 33 Ϯ 4% in controls; p Ͻ 0.05). Morphine and SB protected the ischemic myocardium against Ca 2ϩ -induced mPTP opening as demonstrated by the increased capacity of mitochondria to retain Ca 2ϩ when they were isolated from the ischemic zone 10 min after the onset of reperfusion (59 Ϯ 8 and 66 Ϯ 3 versus 29.5 Ϯ 6 nmol Ca 2ϩ /mg ⅐ protein, respectively; p Ͻ 0.05). This was associated with a restoration of mitochondrial oxidative phosphorylation parameters. In isolated adult rat cardiomyocytes subjected to anoxiareoxygenation, morphine (2 M), SB (3 M), and the direct mPTP inhibitor cyclosporine A (3 M) delayed mPTP opening as assessed by the calcein loading Co 2ϩ -quenching technique. This was accompanied by an increase in cell survival as measured by nuclear staining with propidium iodide. These in vitro effects of morphine on inhibition of mPTP opening during anoxia-reoxygenation were suppressed by the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor wortmannin (0.1 M). These data indicate that the infarct-limiting effect of morphine and SB is linked by a cause-effect relationship, which leads to an increased mitochondrial resistance and inhibition of mPTP opening through the PI3-kinase pathway and subsequent inactivation of GSK-3␤.There are many investigations that suggest that the opening of mitochondrial permeability transition pore (mPTP) is involved in myocardial ischemia-reperfusion injury (Di Lisa and Bernardi, 2006;Halestrap, 2006;Javadov and Karmazyn, 2007) and that raising the threshold for mPTP opening is a relevant strategy to provide cardioprotection (Tissier et al., 2008).

Section: Discussionsupporting

confidence: 86%

Cardioprotective Effect of Morphine and a Blocker of Glycogen Synthase Kinase 3β, SB216763 [3-(2,4-Dichlorophenyl)-4(1-methyl-1H-indol-3-yl)-1H-pyrrole-2,5-dione], via Inhibition of the Mitochondrial Permeability Transition Pore

Obame¹,

Plin-Mercier²,

Assaly³

et al. 2008

100

“…Two types of fluorescent signal kinetics were observed: either a gradual decrease or a complete and rapid drop in calcein fluorescence. These phenomena probably correspond to the transient (reversible) and long-lasting (irreversible) opening of the mPTP as described previously (Sharov et al, 2007). TRO40303 greatly increased the percentage of cardiomyocytes that displayed gradual mPTP openings compared with that in control cells (Table 1).…”

Section: Tro40303 a Newsupporting

confidence: 78%

TRO40303, a New Cardioprotective Compound, Inhibits Mitochondrial Permeability Transition

Schaller¹,

Paradis²,

Ngoh³

et al. 2010

103

104

3,5-Seco-4-nor-cholestan-5-one oxime-3-ol (TRO40303) is a new cardioprotective compound coming from a chemical series identified initially for neuroprotective properties. TRO40303 binds specifically to the mitochondrial translocator protein 18 kDa (TSPO) at the cholesterol site. After intravenous administration, TRO40303 tissue distribution was comparable to that of TSPO, and, in particular, the drug accumulated rapidly in the heart. In a model of 35 min of myocardial ischemia/24 h of reperfusion in rats, TRO40303 (2.5 mg/kg) reduced infarct size by 38% (p Ͻ 0.01 versus control), when administered 10 min before reperfusion, which was correlated with reduced release of apoptosis-inducing factor from mitochondria to the cytoplasm in the ischemic area at risk. Although TRO40303 had no effect on the calcium retention capacity of isolated mitochondria, unlike cyclosporine A, the drug delayed mitochondrial permeability transition pore (mPTP) opening and cell death in isolated adult rat cardiomyocytes subjected to 2 h of hypoxia followed by 2 h of reoxygenation and inhibited mPTP opening in neonatal rat cardiomyocytes treated with hydrogen peroxide. The effects of TRO40303 on mPTP in cell models of oxidative stress are correlated with a significant reduction in reactive oxygen species production and subsequent calcium overload. TRO40303 is a new mitochondrial-targeted drug and inhibits mPTP triggered by oxidative stress. Its mode of action differs from that of other mPTP inhibitors such as cyclosporine A, thus providing a new pharmacological approach to study mPTP regulation. Its efficacy in an animal model of myocardial infarctions makes TRO40303 a promising new drug for the reduction of cardiac ischemia-reperfusion injury.

“…Indeed, MPTP opening has been demonstrated in HF induced by myocardial infarction in rats (Javadov et al, 2005) and intracoronary microembolizations in dogs (Sharov et al, 2007), as well as in Ca 2ϩ -induced cardiomyopathy (Nakayama et al, 2007) and diabetic cardiomyopathy (Oliveira et al, 2003). Notably, our studies have demonstrated that the extent of MPTP opening in failing hearts 12 and 18 weeks after coronary artery ligation (Javadov et al, 2005) is lower than that found following acute IR (Griffiths and Halestrap, 1995;Kerr et al, 1999;Javadov et al, 2003).…”

Section: Heart Failurementioning

confidence: 50%

Mitochondrial Permeability Transition Pore Opening as a Promising Therapeutic Target in Cardiac Diseases

Javadov¹,

Karmazyn²,

Escobales³

2009

217

166

In addition to their central role in ATP synthesis, mitochondria play a critical role in cell death. Oxidative stress accompanied by calcium overload, ATP depletion, and elevated phosphate levels induces mitochondrial permeability transition (MPT) with formation of nonspecific MPT pores (MPTP) in the inner mitochondrial membrane. Pore opening results in mitochondrial dysfunction with uncoupled oxidative phosphorylation and ATP hydrolysis, ultimately leading to cell death. For the past 20 years, three proteins have been accepted as key structural components of the MPTP: adenine nucleotide translocase (ANT) in the inner membrane, cyclophilin D (CyP-D) in the matrix, and the voltage-dependent anion channel (VDAC) in the outer membrane. However, most recent studies have questioned the molecular identity of the pores. Genetic studies have eliminated the VDAC as an essential component of MPTP and attributed a regulatory (rather than structural) role to ANT. Currently, the phosphate carrier appears to play a crucial role in MPTP formation. MPTP opening has been examined extensively in cardiac pathological conditions, including ischemia/ reperfusion as well as heart failure. Accordingly, MPTP is accepted as a therapeutic target for both pharmacological and conditional strategies to block pore formation by direct interaction with MPTP components or indirectly by decreasing MPTP inducers. Inhibition of MPTP opening by reduction of CyP-D activity by nonimmunosuppressive analogs of cyclosporine A or sanglifehrin A, as well as attenuation of reactive oxygen species accumulation through mitochondria-targeted antioxidants, is the most promising. This review outlines our current knowledge of the structure and function of the MPTP and describes possible approaches for cardioprotection.Mitochondria play an important role as ATP producers and as regulators of cell death, which make them essential for cell survival. In the heart, mitochondria occupy approximately 30% of cardiomyocyte volume and provide more than 90% ATP necessary for cardiac function. One of the key factors regulating mitochondrial function and ATP synthesis is the mitochondrial Ca 2ϩ concentration. Cardiomyocyte Ca 2ϩ homeostasis is altered under pathological conditions, such as ischemia and heart failure (HF), due to decreased ATP levels resulting from inadequate oxygen consumption. Furthermore, dysfunction of the electron transport chain, particularly during reperfusion, results in increased generation of ROS. Calcium overload and oxidative stress combine with other factors, including high phosphate and low adenine nucleotide concentrations to induce the formation of nonspecific mitochondrial permeability transition pores (MPTP) in the inner mitochondrial membrane (Bernardi et al., 1992;Crompton, 1999;Halestrap et al., 2004). Opening of MPTP causes uncoupling of the mitochondria and swelling of the matrix leading to rupture of the outer mitochondrial membrane and ultimately cell death. In recent years, MPTP openThis work was supported by the Canadian Ins...