Protective Effect of Coenzyme Q10 on Ischemic Reperfused Myocardium

 The most effective way to reduce mortality in patients with acute coronary occlusion is to reperfuse the myocardium as rapidly as possible, and reperfusion-induced injury significantly reduces the benefits of coronary revascularization. Reducing reperfusion injury and protecting ischemic reperfused myocardium are important to further increase the benefits of coronary revascularization. The aim of this study was to investigate the protective effect of coenzyme Q10 (COQ10) on ischemia-reperfused myocardium.

 

1 Materials and Methods

1 . 1 Animal grouping 19 Japanese big-eared white rabbits (18 survivors), male and female, average weight 2.5 kg (2.5 kg), 2.5 kg (2.5 kg), 2.5 kg (2.5 kg). The average weight was 2.55 kg (2.1 ~ 2.5 kg). The average weight was 2.55 kg (2.1 ~ 2.8 kg). The animals were randomly divided into Group A: control group (n = 6); Group B: ischemia-reperfusion group (n = 6); and Group C: COQ10 treatment group (n = 6).

 

1 . 2 Experimental modeling  

The myocardial ischemia-reperfusion model was modified from the Simp- SOn method, with 3% pentobarbital sodium 30-50 mg-kg -1 via auricular vein anesthesia, endotracheal intubation to keep the airway open, and isolation of the left common carotid artery for insertion of a homemade cardiac catheter into the left ventricle to monitor left ventricular function.Group A was only threaded but not ligated after opening the chest, and in group B, the beginning segment of the left anterior descending branch of coronary artery (LAD) was ligated for 20 min and then reperfused. （Group A was ligated at the beginning of the left anterior descending branch of the coronary artery (LAD) for 20 min and then reperfused, while group C was ligated in the same way for 20 min and then reperfused, and was given COQ10 10 mg kg-1 + 40 ml of saline intravenously, which was started at the time of opening of the chest and was completed before reperfusion, and equal amounts of saline were given to groups A and B in the same way. All animals were executed 360 min after reperfusion. The signs of successful ligation are ST-segment elevation in the I and aVL leads, ST-segment elevation in the epicardial ECG of the ischemic area, T-wave elevation or ST-segment depression, and deep inversion of the T-wave.

 

1 . 3 Observations of indicators

1 .3 . 1 Indicators of heart rate and left ventricular function

Heart rate (HR), left ventricular peak systolic pressure (LVSP), the maximum rate of increase of LVSP (+ dP/dTmax), and the maximum rate of decrease of LVSP (- dP/dTmax) were synchronously monitored with a Nippon Kohden RM-600 eight-channel physiological recorder in each group.

 

1 . 3 . 2 Biochemical indicators  

The endocardial myocardium in the central part of the ischemic zone of the animals in each experimental group (the corresponding part of the myocardium was taken in Group A) was homogenized in an ice bath, and the supernatant and right atrial blood were used to determine the contents of malondialdehyde (MDA) and superoxide dismutase (SOD) by colorimetric method.

 

1 .3 . 3 Adenosine triphosphate (ATP)

The endocardial myocardium in the center of the ischemic zone of the animals in each experimental group was homogenized in an ice bath and centrifuged at low temperature, and then the ATP content was measured by worm luciferase-bioluminescence assay.

 

1 . 3 . 4 Morphological indicators  

The endocardial myocardium in the central part of the ischemic zone of the animals in each experimental group (the corresponding part of the myocardium was taken in Group A) was fixed, sectioned ultrathinly, and then examined by transmission electron microscopy.

 

1 .4 Statistical Methods  

All data were expressed as x- ± s, analyzed by ANOVA and q-test for two-by-two comparisons, with P < 0.05 as a statistically significant difference. P < 0.05 was taken as the statistical difference.

 

2 Results

2 . 1 The effect of COQ10 on HR (see Table 1) There was no significant difference between the basal HR values of the control group, the ischemia-reperfusion group, and the COQ10-treated group (P > 0.05). There was no significant difference between the basal HR values of the control, ischemia-reperfusion and COQ10 treatment groups (P > 0.05). There was no significant difference between the baseline HRs of the control, ischemia-reperfusion, and COQ10 treatment groups (P > 0.05), whereas the HRs of the ligation and reperfusion time points were significantly different (P < 0.05 or P < 0.05). 05 or P < 0 . In contrast, there was a significant difference in HR at all points of ligation and reperfusion (P < 0.05 or P < 0.01), with the COQ10-treated group > control group > ischemia-reperfusion group.

Table 1 HR (x- ± s, times-min— 1  ) at each time point in the groups with 360 min of absconding or reperfusion

 

	underlying asset	Ligation 20 min	recharge
			30 min	60 min	120 min	240 min	360 min
A	292 . 0 ± 19 . 4	267 . 2 ± 10 . 6●	263 . 8 ± 8 . 7O	55 . 5 ± 11 . 4O	240 . 5 ± 18 . 3O	211 . 3 ± 22 . 8O	198 . 8 ± 10 . 6●
B	303 . 7 ± 15 . 0	234 . 1 ± 12 . 8▲	213 . 7 ± 28 . 1▲	214 . 4 ± 23 . 0▲	188 . 3 ± 16 . 8▲	173 . 0 ± 19 . 4△	160 . 8 ± 21 . 7▲
C	306 . 0 ± 31 . 0	290 . 8 ± 13 . 2★	276 . 8 ± 18 . 8★	70 . 0 ± 19 . 1★	251 . 0 ± 10 . 3★	238 . 0 ± 20 . 5★	228 . 0 ± 20 . 3★

● P < 0 . 01,O  P < 0 . 05: C VS A;★  P < 0 . 01: C VS B;▲  P < 0 . 01,△  P < 0 . 05: B VS A

Table 2 Indicators of left ventricular function at each time point in the groups left out or reperfused for 360 min (x- ± s)

 

	underlying asset		Ligation value 20 min	recharge
				30 min	60 min	120 min	240 min	360 min
LVSP (mmHg)	A	110 . 0 ± 13 . 0	99 . 2 ± 18 . 0	100 . 0 ± 18 . 2	109 . 2 ± 13 . 2	97 . 0 ± 10 . 4	95 . 6 ± 10 . 2	88 . 2 ± 10 . 4
	B	110 . 0 ± 9 . 5	85 . 0 ± 15 . 6Δ	78 . 1 ± 15 . 4△	82 . 7 ± 18 . 7▲	82 . 0 ± 18 . 7Δ	72 . 7 ± 22 . 1▲	63 . 1 ± 18 . 1▲
	C	107 . 4 ± 11 . 2	88 . 6 ± 13 . 1☆	96 . 8 ± 22 . 6★	102 . 0 ± 16 . 0★	103 . 0 ± 21 . 7★	105 . 0 ± 17 . 6★	97 . 6 ± 17 . 0★
+ dP/dTmax (mmHg-S— 1 )	A	3 991 ± 102	3 461 ± 367	3 493 ± 402	3 685 ± 265	3 568 ± 414	3 390 ± 416	3 233 ± 345
	B	3 975 ± 143	2 776 ± 449Δ	2,639 ± 492Δ	2 387 ± 526▲	2 870 ± 436△	2 370 ± 741Δ	1621 ± 766▲
	C	4 002 ± 140	3 302 ± 278☆	3,532 ± 303☆	3 692 ± 24★	3 558 ± 342☆	3 606 ± 230☆	3 516 ± 185★
- dP/dTmax (mmHg-S— 1 )	A	3 888 ± 132	2 983 ± 570	2 981 ± 581	3 325 ± 729	3 220 ± 540	3 098 ± 392	2 758 ± 628
	B	3 976 ± 143	2 037 ± 503Δ	1 996 ± 616Δ	1 956 ± 616▲	2 190 ± 529Δ	1,838 ± 692Δ	1 400 ± 517▲
	C	3 958 ± 135	2 975 ± 354☆	3 006 ± 439☆	3 490 ± 388★	3 248 ± 548☆	3 214 ± 483☆	3 218 ± 521★

 

2 .2 Effect of COQ10 on left ventricular function (see Table 2)

There were no significant differences in the basal values of LVSp, + dp/dTmax, and - dp/ dTmax in the control, ischemia-reperfusion, and COQ10 treatment groups (p > 0 . 05）。 Compared with the ischemia-reperfusion group, LVSp, + dp/dTmax, and - dp/dTmax at each time point of ligation and reperfusion were significantly better in the control and COQ10 treatment groups than in the ischemia-reperfusion group (P < 0.05 or P < 0.05). 05 or P < 0 . (P < 0.05 or P < 0.01). There was no significant difference in LVSp, + dp/dTmax, and - dp/dTmaxx between the control group and the COQ10-treated group at all time points.

 

2 . 3 Effect of COQ10 on biochemical indicators (see Table 3)

Compared with the ischemia-reperfusion group, myocardial SOD content was significantly higher and MDA content was significantly lower in the control group and COQ10-treated group, with significant differences (P < 0.01). There was a significant difference (P < 0.01). The differences in myocardial MDA and SOD levels between the control and COQ10 treatment groups were not significant (P > 0.05). (P > 0.05).

 

2 .4 Effect of COQ10 on ATP (see Table 3)

Compared with the ischemia-reperfusion group, the myocardial ATp content in the control group and the COQ10-treated group increased significantly, with significant differences (P < 0.01). Myocardial ATp levels in the COQ10-treated group were significantly higher than those in the control group, with a significant difference (P < 0.01). There was a significant difference (P < 0.01).

Table 3 Biochemical indexes (x- ± s) of each group after 360 min of absconding or reperfusion

 

	MDA (μmOl-L— 1  )		SOD (μmOl-L— 1  )		ATp (μmOl-g— 1  )
	plasma	myocardium	plasma	myocardium
A	2 . 33 ± 0 . 37	3 . 79 ± 0 . 50	420 . 02 ± 27 . 93	166 . 32 ± 12 . 01	0 . 409 ± 0 . 100●
B	3 . 68 ± 0 . 59▲	5 . 17 ± 0 . 76▲	314 . 76 ± 28 . 0▲	98 . 51 ± 18 . 36▲	0 . 116 ± 0 . 094▲
C	1 . 85 ± 0 . 54★	3 . 85 ± 0 . 47★	441 . 27 ± 25 . 46★	179 . 60 ± 44 . 41★	0 . 713 ± 0 . 115★

● P < 0 . 01: C VS A;★  P < 0 . 01: C VS B;▲  P < 0 . 01: B VS A

 

2 . 5 Effect of COQ10 on ultrastructure (Figures 1 ~ 3) Control group

In the ischemia-reperfusion group, myocardial myofibrils were neatly arranged, with clear myonodes; mitochondrial membrane was intact, and vacuoles and cristae were partially visible (see Figure 1). In the ischemia-reperfusion group, myocardial myofibrillar fibers were neatly arranged, with broken myonodes; mitochondrial membranes were incomplete, and cristae could be seen to be broken and disappeared (see Figure 2). in the COQ10-treated group, myocardial myofibrillar fibers were neatly arranged, with clearly defined myonodes; mitochondrial membranes were intact, no vacuole formation, and cristae could be seen to be fuzzy in some cases (see Figure 3).

 

3 Discussion

COQ10 is a lipid vitamin-like substance found in large quantities in mitochondria, especially in cardiomyocytes, where it is an important component of the respiratory chain and is involved in phosphorylation and energy biosynthesis. The results of the present study showed that the administration of COQ10 to ischemia-reperfused myocardium of rabbits in vivo could significantly promote the recovery of cardiac function, as evidenced by the fact that the HR, LVSp, + dp/dTmax, - dp/dTmax at all time points increased significantly compared with that in the ischemia-reperfusion group and reached the level of the control group, which suggests that COQ10 can prevent or alleviate myocardial reperfusion injury.

 

Numerous studies have shown that oxygen free radicals are one of the main pathological bases of myocardial ischemia/reperfusion injury [1], and their main sources are xanthine oxidation and neutrophils. Oxygen free radicals attack unsaturated fatty acids on the cell membrane, increasing membrane permeability and causing large amounts of Ca2+ to flow inward. Ca2+ activates the enzyme phospholipase, which breaks down phospholipids into arachidonic acid and forms leukotrienes, which activate leukocytes to release large amounts of oxygen free radicals. The above pathologic processes are mutually causal and vicious circle, which ultimately leads to the generation of oxygen radicals in the reperfusion phase.

 

Large amounts of oxygen free radicals can cause structural damage to biological membranes, massive release of intracellular enzymes, myocardial edema, and mitochondrial dysfunction. MDA is an intermediate metabolite of lipid peroxides produced by oxygen free radicals, which is often used as an indicator of the generation of oxygen free radicals and membrane damage; SOD is an enzyme necessary for myocardial scavenging of oxygen free radicals, and its activity reflects the degree of antioxidant effect in ischemia/reperfusion myocardium. In this experiment, the content of MDA and SOD in the CoQ10-treated group decreased significantly compared with that in the ischemia-reperfusion group, suggesting that exogenous CoQ10 can enter into the cells as an oxygen radical scavenger and combine with various parts of the cells nonspecifically to reduce the generation of oxygen radicals, accelerate the scavenging of oxygen radicals, protect the myocardium after ischemia-reperfusion, and promote the recovery of cardiac function.

 

The relationship between ischemia/reperfusion injury and myocardial energy metabolism has received increasing attention. The degree of myocardial injury during ischemia and the recovery of cardiac function (systolic and diastolic function) after reperfusion are closely related to myocardial energy metabolism and ATP reserve [2]. When myocardial cells are reperfused after severe ischemia, a series of changes in energy metabolism occur due to abnormal blood flow, which are mainly manifested in the uncoupling of glucose fermentation and oxidation during ischemia, the imbalance between glucose oxidation and fatty acid oxidation during reperfusion, and the serious lack of ATP production. During myocardial ischemia, the concentration of CoQ10 in cardiomyocytes is significantly reduced [3].

 

In this experiment, the myocardial ATP content of the CoQ10 treatment group increased significantly, suggesting that supplementation of exogenous CoQ10 can increase the level of mitochondrial CoQ10 in cardiomyocytes, reduce the ratio of acetyl CoA/CoA, enhance the activity of succinate-cytochrome reductase, increase the utilization rate of oxygen in the anaerobic state of the myocardium, promote glucose oxidation, and improve the obstacles in energy metabolism of myocardium, and increase the production of ATP, which is a direct energy-supporting substance in cardiomyocytes. ATP production is increased, which has a protective effect on cardiac function during ischemia and after reperfusion.

 

The results of the present study also showed that myofilaments of cardiomyocytes in the CoQ10-treated group were intact, nodes were clear, and mitochondrial membranes and cristae were intact, while myocytes in the ischemia-reperfusion group had broken nodes, incomplete mitochondrial membranes and cristae, and the cristae gap widened significantly, and could be seen to be fractured and disappeared. This indicates that CoQ10 can enhance the ability of cardiomyocytes to resist ischemia, and has a direct protective effect on the cell membrane, avoiding the damage of membrane integrity and permeability, thus providing a good structural basis for the recovery of myocardial function.

 

Reference:

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[3] Folkers K, vadhanavikit S, Mortensen SA .  Biochemical rationale and myocardial tissue data on the effective therapy of cardiomy- opathy with coenZyme Q10 .  Pro Natl Aead Sci USA, 1985, 82: 901

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