Elucidation of a tripartite mechanism underlying the improvement in cardiac tolerance to ischemia by coenzyme Q10 pretreatment

Coenzyme Q10 Reduces Infarct Size in Animal Models of Myocardial Ischemia-Reperfusion Injury: A Meta-Analysis and Summary of Underlying Mechanisms

Objective

Effective interventions that might limit myocardial ischemia-reperfusion (I/R) injury are still lacking. Coenzyme Q₁₀ (CoQ₁₀) may exert cardioprotective actions that reduce myocardial I/R injury. We conducted this meta-analysis to assess the potential cardioprotective effect of CoQ₁₀ in animal models of myocardial I/R injury.

Methods

We searched PubMed and Embase databases from inception to February 2022 to identify animal studies that compared the effect of CoQ₁₀ with vehicle treatment or no treatment on myocardial infarct size in models of myocardial I/R injury. Means and standard deviations of the infarct size measurements were pooled as the weighted mean difference with 95% confidence interval (CI) using the random-effects model. Subgroup analyses were also conducted according to animals' species, models' type, and reperfusion time.

Results

Six animal studies (4 in vivo and 2 ex vivo) with 116 animals were included. Pooled analysis suggested that CoQ₁₀ significantly reduced myocardial infarct size by −11.36% (95% CI: −16.82, −5.90, p < 0.0001, I² = 94%) compared with the control group. The significance of the pooled effect estimate was maintained in rats, Hartley guinea pigs, and Yorkshire pigs. However, it became insignificant in the subgroup of rabbits −5.29% (95% CI: −27.83, 17.26; I² = 87%). Furthermore, CoQ₁₀ significantly reduced the myocardial infarct size regardless of model type (either in vivo or ex vivo) and reperfusion time (either ≤ 4 h or >4 h).

Conclusion

Coenzyme Q₁₀ significantly decreased myocardial infarct size by 11.36% compared with the control group in animal models of myocardial I/R injury. This beneficial action was retained regardless of model type and reperfusion time.

Myocardial Metabolism and Improved OutcomesAfter High Risk Heart Surgery

The healthy heart relies primarily upon the oxidation of fatty acids for energy, with the remaining coming from the oxidation of glucose and lactate. Changes in energy requirements are met by altering the balance of fuels depending upon the hormonal milieu as well as upon the availability of oxygen and substrates. The use of carbohydrates for fuel is metabolically more efficient and may improve the coupling between glycolysis and pyruvate oxidation. Therefore, promoting a shift in metabolic fuel substrate use during times of reduced oxygen availability may represent a cardioprotective strategy. Subsequently, there has been interest in pharmacologic strategies such insulin or drugs like ranolazine and dichloroacetate that stimulate carbohydrate oxidation either by enhancing oxidation at the pyruvate dehydrogenase complex or by limiting fatty acid oxidation. There is evidence that nutrients may also be able to stimulate carbohydrate oxidation. Previous studies by our group suggest that a combination of nutrients (carnitine, coenzyme Q10, and taurine) may work together, resulting in pleiotropic cardioprotective effects. Our current studies are investigating the potential of nutrients as both a preventative and adjunctive treatment before and after an ischemic event. These investigations will determine the role of nutritional supplementation in the care of patients with ischemic injury.

Effect of lead toxicity on coenzyme Q levels in rat tissues

Lead is a persistent and common environmental contaminant, which chiefly plays a significant role in modern industry. Coenzyme Q acts as electron and proton carrier in mitochondria and functions as an antioxidant in its reduced form (ubiquinol). To investigate the hazardous effects of lead on the coenzyme Q level, rats were injected i.p. with lead acetate (5 mg/kg b.wt. daily for 6 weeks). Our results showed that the levels of both oxidized (ubiquinone) and reduced (ubiquinol) forms of coenzyme Q(9) and Q(10) in serum, brain, liver and kidney of lead-treated rats are quite different depending on the organ tissue type.

Protective effect of coenzyme Q10-loaded liposomes on the myocardium in rabbits with an acute experimental myocardial infarction

PURPOSE

We assessed whether the infusion of Coenzyme Q10-loaded liposomes (CoQ10-L) in rabbits with an experimental myocardial infarction can result in increased intracellular delivery of CoQ10 and thus limit the fraction of the irreversibly damaged myocardium.

METHODS

CoQ10-L, empty liposomes (EL), or Krebs-Henseleit (KH) buffer were administered by intracoronary infusion, followed by 30 min of occlusion and 3 h of reperfusion. Unisperse Blue dye was used to demarcate the net size of the occlusion-induced ischemic zone ("area at risk") while nitroblue tetrazolium staining was used to detect the final fraction of the irreversibly damaged myocardium within the total area at risk.

RESULTS

The total size of the area at risk in all experimental animals was approx. 20% wt. of the left ventricle (LV). The final irreversible damage in CoQ10-L-treated animals was only ca. 30% of the total area at risk as compared with ca. 60% in the group treated with EL (p < 0.006) and ca. 70% in the KH buffer-treated group (p < 0.001).

CONCLUSIONS

CoQ10-L effectively protected the ischemic heart muscle by enhancing the intracellular delivery of CoQ10 in hypoxic cardiocytes in rabbits with an experimental myocardial infarction as evidenced by a significantly decreased fraction of the irreversibly damaged heart within the total area at risk. CoQ10-L may provide an effective exogenous source of the CoQ10 in vivo to protect ischemic cells.

Coenzyme Q10 in cardiovascular disease

In this review we summarise the current state of knowledge of the therapeutic efficacy and mechanisms of action of CoQ(10) in cardiovascular disease. Our conclusions are: 1. There is promising evidence of a beneficial effect of CoQ(10) when given alone or in addition to standard therapies in hypertension and in heart failure, but less extensive evidence in ischemic heart disease. 2. Large scale multi-centre prospective randomised trials are indicated in all these areas but there are difficulties in funding such trials. 3. Presently, due to the notable absence of clinically significant side effects and likely therapeutic benefit, CoQ(10) can be considered a safe adjunct to standard therapies in cardiovascular disease.

Chronic administration of coenzyme Q10 limits postinfarct myocardial remodeling in rats

The effect of chronic coronary artery occlusion on the content of rat myocardial coenzymes Q (CoQ) and evaluation of the applicability of CoQ(10) for limiting postinfarct remodeling have been investigated. Left ventricle myocardium hypertrophy was characterized by the decrease in CoQ(9) (-45%, p < 0.0001), CoQ(10) (-43%, p < 0.001), and alpha-tocopherol (-35%, p < 0.05). There were no differences between the parameters of postinfarction and sham-operated rats in plasma. Administration of CoQ(10) (10 mg/kg) via a gastric probe for 3 weeks before and 3 weeks after occlusion maintained higher levels of CoQ in the postinfarction myocardium: the decrease in CoQ(9) and CoQ(10) was 25% (p < 0.05) and 23% (p < 0.05), respectively (versus sham-operated animals). Plasma concentrations of CoQ(10) were more than 2 times higher (p < 0.05). In CoQ treated rats there was significant correlation between plasma levels of CoQ and the infarct size: r = -0.723 (p < 0.05) and r = -0.839 (p < 0.01) for CoQ(9) and CoQ(10). These animals were also characterized by earlier and more intensive scar tissue formation in the postinfarction myocardium and also by more pronounced cell regeneration processes. This resulted in the decrease in both the infarct size (16.2 +/- 8.1 vs. 27.8 +/- 12.1%) and also mass index of left ventricle (2.18 +/- 0.24 vs. 2.38 +/- 0.27 g/kg) versus untreated rats (p < 0.05). Thus, long-term treatment with ubiquinone increases plasma and myocardial CoQ content and this can improve the survival of myocardial cells during ischemia and limit postinfarct myocardial remodeling.

Quinones in long-lived clk-1 mutants of Caenorhabditis elegans

Ubiquinone (UQ) (coenzyme Q) is a lipophilic redox-active molecule that functions as an electron carrier in the mitochondrial electron transport chain. Electron transfer via UQ involves the formation of semiubiquinone radicals, which causes the generation of superoxide radicals upon reaction with oxygen. In the reduced form, UQ functions as a lipid-soluble antioxidant, and protects cells from lipid peroxidation. Thus, UQ is also important as a lipophilic regulator of oxidative stress. Recently, a study on long-lived clk-1 mutants of Caenorhabditis elegans demonstrated that biosynthesis of UQ is dramatically altered in mutant mitochondria. Demethoxy ubiquinone (DMQ), that accumulates in clk-1 mutants in place of UQ, may contribute to the extension of life span. Here we elucidate the possible mechanisms of life span extension in clk-1 mutants, with particular emphasis on the electrochemical property of DMQ. Recent findings on the biochemical function of CLK-1 are also discussed.

Effect of coenzyme Q10 supplementation on mitochondrial function after myocardial ischemia reperfusion

BACKGROUND

Coenzyme Q10 (CoQ10) protects myocardium from ischemia-reperfusion (IR) injury as evidenced by improved recovery of mechanical function, ATP, and phosphocreatine during reperfusion. This protection may result from CoQ10's bioenergetic effects on the mitochondria, from its antioxidant properties, or both. The purpose of this study was to elucidate the effects of CoQ10 supplementation on mitochondrial function during myocardial ischemia-reperfusion using an isolated mitochondrial preparation.

METHODS

Isolated hearts (n = 6/group) from rats pretreated with liposomal CoQ10 (10 mg/kg iv, CoQ10), vehicle (liposomal only, Vehicle), or saline (Saline) 30 min before the experiments were subjected to 15 min of equilibration (EQ), 25 min of ischemia (I), and 40 min of reperfusion (RP). Left ventricular-developed pressure (DP) was measured. Mitochondria were isolated at end-equilibration (end-EQ), at end-ischemia (end-I), and at end-reperfusion (end-RP). Mitochondrial respiratory function (State 2, 3, and 4, respiratory control index (RCI, ratio of State 3 to 4), and ADP:O ratio) was measured by polarography using NADH (alpha-ketoglutarate, alpha-KG)- or FADH (succinate, SA)-dependent substrates.

RESULTS

CoQ10 improved recovery of DP at end-RP (67 +/- 11% in CoQ10 vs 47 +/- 5% in Vehicle and 50 +/- 11% in Saline, P < 0.05 vs Vehicle and Saline). CoQ10 did not change preischemic mitochondrial function. IR decreased State 3 and RCI in all groups using either substrate. CoQ10 had no effect in the mitochondrial oxidation of alpha-KG at end-I. CoQ10 improved State 3 at end-I when SA was used (167 +/- 21 in CoQ10 vs 120 +/- 10 in Saline and 111 +/- 10 ng-atoms O/min/mg protein in Vehicle, P < 0.05). Using alpha-KG as a substrate, CoQ10 improved RCI at end-RP (4.2 +/- 0.2 in CoQ10 vs 3.2 +/- 0.2 in Saline and 3.0 +/- 0.3 in Vehicle, P < 0.05). Using SA, CoQ10 improved State 3 (181 +/- 10 in CoQ10 vs 142 +/- 9 in Saline and 140 +/- 12 ng-atoms O/min/mg protein in Vehicle, P < 0.05) and RCI (2.21 +/- 0.06 in CoQ10 vs 1.85 +/- 0.11 in Saline and 1.72 +/- 0.08 in Vehicle, P < 0.05) at end-RP.

CONCLUSIONS

The cardioprotective effects of CoQ10 can be attributed to the preservation of mitochondrial function during reperfusion as evidenced by improved FADH-dependent oxidation.

Mitochondria as target for antiischemic drugs

The cessation of blood flow followed by a reperfusion period results in severe damages to cell structures. This induces a complex cascade of events involving, more particularly, a loss of energy, an alteration of ionic homeostasis promoting H(+) and Ca(2+) build up and the generation of free radicals. In this context, mitochondria are highly vulnerable and play a predominant role in the cell signaling leading from life to death. This is why, recently, efforts to find an effective therapy for ischemia-reperfusion injury have focused on mitochondria. This review summarizes the pharmacological strategies which are currently developed and the potential mitochondrial targets which could be involved in the protection of cells.

Three classes of ubiquinone analogs regulate the mitochondrial permeability transition pore through a common site

To identify the structural features required for regulation of the mitochondrial permeability transition pore (PTP) by ubiquinone analogs (Fontaine, E., Ichas, F., and Bernardi, P. (1998) J. Biol. Chem. 40, 25734-25740), we have carried out an analysis with quinone structural variants. We show that three functional classes can be defined: (i) PTP inhibitors (ubiquinone 0, decylubiquinone, ubiquinone 10, 2,3-dimethyl-6-decyl-1,4-benzoquinone, and 2,3,5-trimethyl-6-geranyl-1,4-benzoquinone); (ii) PTP inducers (2,3-dimethoxy-5-methyl-6-(10-hydroxydecyl)-1,4-benzoquinone and 2,5-dihydroxy-6-undecyl-1,4-benzoquinone); and (iii) PTP-inactive quinones that counteract the effects of both inhibitors and inducers (ubiquinone 5 and 2,3,5-trimethyl-6-(3-hydroxyisoamyl)-1,4-benzoquinone) . The structure-function correlation indicates that minor modifications in the isoprenoid side chain can turn an inhibitor into an activator, and that the methoxy groups are not essential for the effects of quinones on the PTP. Since the ubiquinone analogs used in this study have a similar midpoint potential and decrease mitochondrial production of reactive oxygen species to the same extent, these results support the hypothesis that quinones modulate the PTP through a common binding site rather than through oxidation-reduction reactions. Occupancy of this site can modulate the PTP open-closed transitions, possibly through secondary changes of the PTP Ca(2+) binding affinity.

Coenzyme Q versus hypertension: does CoQ decrease endothelial superoxide generation?

Reports from several research groups--including two small double-blind clinical studies--indicate that supplemental coenzyme Q10 (CoQ) is moderately effective as a treatment for hypertension, in humans and in animals. Its efficacy is associated with a decrease in total peripheral resistance, and appears to reflect a direct impact of CoQ on the vascular wall. A reasonable interpretation of these findings is that CoQ is acting as an antagonist of vascular superoxide--either scavenging it, or suppressing its synthesis. By improving the efficiency of shuttle mechanisms that transfer high-energy electrons from the cytoplasm to the mitochondrial respiratory chain, CoQ may decrease cytoplasmic NADH levels and thereby diminish the reductive power that drives superoxide synthesis in endothelium and vascular smooth muscle. If CoQ therapy does indeed lower vascular superoxide levels, it can be expected to decrease the atherothrombotic risk associated with hypertension, and may have broader utility in the management of disorders characterized by endotheliopathy.

Effects of coenzyme Q10 on changes in the membrane potential and rate of generation of reactive oxygen species in hydrazine- and chloramphenicol-treated rat liver mitochondria

Effects of CoQ10 and cycloheximide (CHX) on hydrazine- and chloramphenicol (CP)-induced morphological and some functional changes of mitochondria using cultured rat hepatocytes and effects on the process of recovery from CP intoxication using mouse liver were examined. Results obtained are summarized as follows: (1) The formation of megamitochondria induced in the hepatocytes cultured for 22 h in the presence of 2 mM hydrazine or CP (300 microgram/ml) was suppressed by pretreatment of hepatocytes with CoQ10 (1 microM) or CHX (0.5 microgram/ml). This was proved by electron microscopic analysis of mitochondria. (2) Treatment of hepatocytes with hydrazine for 48 h or longer caused decreases in the membrane potential of mitochondria, which were suppressed by CoQ10. (3) Treatment of hepatocytes with hydrazine for 22 h or longer caused remarkable increases in intracellular levels of reactive oxygen species in hepatocytes, which were suppressed by CoQ10. (4) The process of recovery from the CP-induced changes of mitochondria in mouse liver was accelerated by CoQ10 and CHX.

Coenzyme Q10 supplementation and recovery from ischemia in senescent rat myocardium

Many studies have suggested that parenteral administration of coenzyme Q10 (Q10) protects the myocardium of young experimental animals from post-ischemic reperfusion injury. Although parenteral administration, in contrast to per os supplementation, seems to elevate coenzyme Q concentrations in heart tissue, it is not suitable for prophylactic use. In addition, the incidence of ischemic events is greatest in older age. We studied the effect of Q10 supplementation on myocardial postischemic recovery in 18-month-old Wistar rats. The treated group (n=9) received 10 mg/kg/day of Q10 for 8 weeks in their chow while the normal chow of the control group (n=9) contained less than 0.5 mg/kg/day of Q10. The treatment clearly elevated plasma Q10 concentration (286 +/- 25 micromol/l and 48 +/- 30 micromol/l, treated and controls, respectively, p<0.0001) but neither Q9 nor Q10 concentrations in heart tissue were affected by the supplementation. The isolated perfused hearts were subjected to 20 minutes of ischemia and 30 minutes of reperfusion. The preischemic values of developed pressure (DP) but not contractility (+DP/delta t) and relaxation (-DP/delta t) were improved by Q10 supplementation (p=0.034, p=0.057 and p=0.13, respectively) while in postischemic recovery no differences were observed between the groups (p>0.05 at all time points). Also, in myocardial flow, myocardial oxygen consumption (MVO2) and myocardial aerobic efficiency (DP/MVO2) the groups did not differ at any time points. Although dietary Q10 supplementation clearly elevated plasma Q10 concentrations in senescent rats, the coenzyme Q contents in heart tissue and myocardial recovery from ischemia were not affected. However, it is possible that the site of action for the reported beneficial effects of Q10 is in the coronary endothelium rather than myocardium itself.

Overview of the use of CoQ10 in cardiovascular disease

The clinical experience in cardiology with CoQ10 includes studies on congestive heart failure, ischemic heart disease, hypertensive heart disease, diastolic dysfunction of the left ventricle, and reperfusion injury as it relates to coronary artery bypass graft surgery. The CoQ10-lowering effect of HMG-CoA reductase inhibitors and the potential adverse consequences are of growing concern. Supplemental CoQ10 alters the natural history of cardiovascular illnesses and has the potential for prevention of cardiovascular disease through the inhibition of LDL cholesterol oxidation and by the maintenance of optimal cellular and mitochondrial function throughout the ravages of time and internal and external stresses. The attainment of higher blood levels of CoQ10 (> 3.5 micrograms/ml) with the use of higher doses of CoQ10 appears to enhance both the magnitude and rate of clinical improvement. In this communication, 34 controlled trials and several open-label and long-term studies on the clinical effects of CoQ10 in cardiovascular diseases are reviewed.

Bioenergetic effect of liposomal coenzyme Q10 on myocardial ischemia reperfusion injury

The antioxidant and bioenergetic effects of CoQ10 are well known but its clinical utility is limited by the requirement for enteral administration. A newly developed liposomal CoQ10 (CoQ) is water soluble and capable of intravenous administration. The purpose of this study is to determine the mechanism by which acute administration CoQ protects myocardium from reperfusion (Rp) injury. Rats were pretreated with CoQ 10 mg/kg i.v. 30 min prior to the experiment. Control rats were pretreated with liposome only. Hearts were excised and subjected to equilibration, 25 min of normothermic ischemia and 40 min of Rp on a Langendorff apparatus. At end Rp, CoQ hearts recovered 74 +/- 5% of their DP vs. 50 +/- 9% in control (p < 0.05). Aerobic efficiency was maintained (0.66 +/- 0.02 vs. control, 0.5 +/- 0.04, p < 0.003) and CoQ hearts lost less CK activity vs. control (p < 0.02). PCr and ATP were higher than control (p < 0.05, 0.02, respectively). Results show that i.v. CoQ improves recovery of function, aerobic efficiency, CK activity, and recovery of PCr and ATP after Rp. This suggests that acute administration of liposomal CoQ improves myocardial tolerance to I/R via its role as an antioxidant as well as improving oxygen utilization and high energy phosphate production.

Acute administration of liposomal coenzyme Q10 increases myocardial tissue levels and improves tolerance to ischemia reperfusion injury

The antioxidant and bioenergetic effects of CoQ10 (CoQ) suggest it might be ideal therapy for acute myocardial ischemia. Its utility is limited by the requirement for enteral administration. This study related the administration of a new liposomal suspension of CoQ given intravenously to (1) serum and myocardial [CoQ] and (2) recovery of function, myocardial efficiency, and oxidant injury after cardiac ischemia and reperfusion (I/R). Rats (n = 8/group) were given liposomal CoQ 10 mg/kg iv or placebo (Control), 15 min (C-15), 30 min (C-30), and 60 min (C-60) before (1) measurement of serum and myocardial CoQ or (2) Langendorff perfusion of hearts subjected to 15 min equilibration, 25 min ischemia (37 degrees C), and 40 min reperfusion (RP). Developed pressure (DP) was measured via an intraventricular balloon and coronary flow was measured by a digital flow meter. Myocardial efficiency was defined as DP/MVO2 where MVO2 = microl O2 consumed/min/gram LV. At end RP hearts were assayed for CK, an oxidant sensitive enzyme. Maximum preischemic CoQ levels in serum and myocardium occurred 15 and 30 min after administration, respectively. At end reperfusion, C-30 hearts improved the most, recovering 75 +/- 4% of their preischemic DP while Control recovered only 52 +/- 6% (P < 0.03) as well as maintaining better myocardial efficiency (0.69 +/- 0.02 vs Control, 0.43 +/- 0.05) (P < 0.001). C-15, C-30, and C-60 groups all lost less CK activity after RP vs Control (P < 0.04).

CONCLUSION

(1) Serum and myocardial levels of CoQ can be raised acutely by iv liposomal CoQ. (2) Myocardial CoQ levels correlate best with I/R protection. (3) Acute iv CoQ improves function and efficiency and decreases oxidant injury after I/R. Intravenous CoQ may be effective clinically for acute cardiac ischemic syndromes.

Coenzyme Q10 administration increases brain mitochondrial concentrations and exerts neuroprotective effects

Coenzyme Q10 is an essential cofactor of the electron transport chain as well as a potent free radical scavenger in lipid and mitochondrial membranes. Feeding with coenzyme Q10 increased cerebral cortex concentrations in 12- and 24-month-old rats. In 12-month-old rats administration of coenzyme Q10 resulted in significant increases in cerebral cortex mitochondrial concentrations of coenzyme Q10. Oral administration of coenzyme Q10 markedly attenuated striatal lesions produced by systemic administration of 3-nitropropionic acid and significantly increased life span in a transgenic mouse model of familial amyotrophic lateral sclerosis. These results show that oral administration of coenzyme Q10 increases both brain and brain mitochondrial concentrations. They provide further evidence that coenzyme Q10 can exert neuroprotective effects that might be useful in the treatment of neurodegenerative diseases.

Coenzyme Q10 in the central nervous system and its potential usefulness in the treatment of neurodegenerative diseases

Coenzyme Q10 is an essential cofactor of the electron transport chain and is an antioxidant. We examined the effects of oral feeding with coenzyme Q10 in young animals on brain concentrations. Feeding with coenzyme Q10 at a dose of 200 mg/kg for 1-2 months in young rats resulted in significant increases in liver concentrations, however, there was no significant increase in brain concentrations of either reduced- or total coenzyme Q10 levels. Nevertheless there was a reduction in malonate-induced increases in 2,5 dihydroxybenzoic acid to salicylate, consistent with an antioxidant effect. In other studies we found that oral administration of coenzyme Q10 significantly reduced increased concentrations of lactate in the occipital cortex of Huntington's disease patients. These findings suggest that coenzyme Q10 might be useful in treating neurodegenerative diseases.

The mechanisms of coenzyme Q10 as therapy for myocardial ischemia reperfusion injury

It has been hypothesized that CoQ10 (CoQ) pretreatment protects myocardium from ischemia reperfusion (I/R) injury by its ability to increase aerobic energy production as well as its activity as an antioxidant. Isolated hearts from rats pretreated with either CoQ 20 mg/kg i.m. and 10 mg/kg i.p. or vehicle 24 and 2 h prior to the experiment, were subjected to 15 min of equilibration (EQ), 25 min of ischemia, and 40 min of reperfusion (RP). Developed pressure, +/-dp/dt, myocardial oxygen consumption, and myocardial aerobic efficiency (DP/MVO2) were measured. 31P NMR spectroscopy was used to determine ATP and PCr concentrations. Lucigenin-enhanced chemiluminescence of the coronary sinus effluent was utilized to determine oxidative stress through the protocol. CoQ pretreatment improved myocardial function after ischemia reperfusion. CoQ pretreatment improved tolerance to myocardial ischemia reperfusion injury by its ability to increase aerobic energy production, and by preserving myocardial aerobic efficiency during reperfusion. Furthermore, the oxidative burst during RP was diminished with CoQ. Similarly it was hypothesized that CoQ protected coronary vascular reactivity after I/R via an antioxidant mechanism. Utilizing a newly developed lyposomal CoQ preparation given i.v. 15 min prior to ischemia, ischemia reperfusion was carried out on Langendorff apparatus as previously described. Just prior to ischemia and after RP, hearts were challenged with bradykinin (BK) and sodium nitroprusside (SNP) and change in coronary flow was measured. CoQ pretreatment protected endothelial-dependent and endothelial-independent vasodilation after I/R. We conclude that CoQ pretreatment protects coronary vascular reactivity after I/R via OH radical scavenger action.

Coenzyme Q10 protects coronary endothelial function from ischemia reperfusion injury via an antioxidant effect

BACKGROUND

Cardiac ischemia reperfusion (I/R) injury causes coronary vascular dysfunction. Coenzyme Q10 (CoQ), which preserves cardiac mechanical function after I/R, recently has been recognized as a free radical scavenger. We hypothesized that CoQ protects coronary vascular reactivity after I/R via an antioxidant mechanism.

METHODS

Rats were pretreated with either CoQ (20 mg/kg intramuscular and 10 mg/kg intraperitoneal [CoQ group]) or a vehicle (Control) before the experiment. Isolated perfused rat hearts were subjected to 25 minutes of global normothermic ischemia and 40 minutes of reperfusion. The reperfusion-induced oxidative burst was directly assessed by lucigenin enhanced chemiluminescence. Coronary flow was measured at equilibration and after reperfusion with or without bradykinin, an endothelium-dependent vasodilator, and sodium nitroprusside (SNP), an endothelium-independent vasodilator. The effect of intracoronary infusion of hydrogen peroxide (H2O2 0.1 mumol/gm body weight given over 5 minutes), simulating the free radical burst after I/R, also was evaluated.

RESULTS

I/R decreased the bradykinin-induced change in coronary flow (-5% +/- 4% versus 26% +/- 3% at equilibration; p < 0.05) and the SNP-induced change (+20% +/- 6% versus +56% +/- 5% at equilibration; p < 0.05). The coronary vasculature after H2O2 infusion revealed a similar loss in vasodilatory responsiveness (+4% +/- 4% in response to bradykinin, +35% +/- 8% in response to SNP; p < 0.05 versus equilibration). Pretreatment with CoQ improved BK-induced vasorelaxation after I/R (+12% +/- 2%; p < 0.05 versus control I/R) or H2O2 infusion (18% +/- 4%; p < 0.05 versus control I/R) but failed to improve SNP-induced vasorelaxation. The CoQ pretreatment decreased the I/R-induced maximal free radical burst (9.3 +/- 0.8 x 10(3) cpm versus 11.5 +/- 1.1 x 10(3) cpm; p < 0.05) during the early period of reperfusion.

CONCLUSIONS

Endothelium-dependent vasorelaxation is more sensitive than endothelium-independent relaxation to I/R injury. Via a direct antioxidant effect, CoQ preserved endothelium-dependent vasorelaxation by improving tolerance to I/R injury.