Abstract
This study aimed to investigate the effects of myocardial injury in a minimally-invasive miniature swine model with different levels of coronary artery stenosis (CAS) and exposed to maximal tolerated +Gz. Proximal left anterior descending branch was ligated in 20 swine. Five swine underwent a sham operation. A trapezoid acceleration curve was used for +Gz stress. Pathological changes of myocardial tissue were detected by H&E staining. Apoptotic cardiomyocytes were detected by TUNEL. GRP78 and CHOP were investigated by immunohistochemistry and western blot. CAS models were successful in 18 animals.Compared with the sham-operated group (+8.00±0.71 Gz), the maximal tolerated +Gz values of the moderate stenosis (+6.00±0.89 Gz, P<0.05) and severe stenosis groups (+5.20±0.84 Gz, P<0.05) were decreased.Compared with sham animals (12.16±1.25%), after exposure to maximum +Gz, apoptotic cells of the moderate (43.53±8.42%, P<0.05) and severe stenosis group (60.50±9.35%, P<0.05) were increased, MDA content was increased (1.89 and 4.91 folds, respectively, P<0.05), and SOD activity was reduced (-13.66% and -21.71%, respectively). After exposure to maximum +Gz, GRP78 protein expression was low in the sham-operated (0.29±0.05) and mild stenosis groups (0.35±0.04), while expression was high in the moderate (0.72±0.04, P<0.05) and severe stenosis groups (0.65±0.07, P<0.05). CHOP protein expression was not observed in the sham-operated group, while expression was high in the moderate and severe stenosis groups. These results indicated that Under maximum exposure to +Gz stress, different levels of CAS led to different levels of myocardial injury. Endoplasmic reticulum response is involved in the apoptosis of cardiomyocytes after +Gz stress.
Highlights
In the search to gain advantages in planes combat, higher performance aircrafts are being developed, imposing ever greater acceleration forces on pilots [1]
Twenty miniature swine underwent left anterior descending (LAD) artery ligation and the degree of coronary artery stenosis (CAS) was quantified by quantitative computerized angiography (QCA)
Seven swine were in the mild stenosis group (36.8±7.4% stenosis; Fig 1B), six were in the moderate stenosis group (61.5±6.2% stenosis; Fig 1C), and seven were in the severe stenosis group (81.9±8.6% stenosis; Fig 1D)
Summary
In the search to gain advantages in planes combat, higher performance aircrafts are being developed, imposing ever greater acceleration forces on pilots [1]. Pilots suffer from detrimental environmental conditions, such as acceleration-associated stress (+Gz stress), noise, radiations, heat, hypoxia and vibration, all of which can induce cardiac structural damages [2,3,4], and increasing the risk of coronary heart diseases (CHDs) [5]. Repeated exposured to high +Gz induce significant physiological adaptation reactions associated with blood pressure regulation (blood volume reduction, cardiac output decreases)[8,9,10,11]. Due to mechanical force and severe hemodynamic changes, cardiomyocytes and muscle fibers will suffer from some damages. Some authors have confirmed the effects of high +Gz were similar to hemodynamic changes observed in ischemia reperfusion (I/R) [12]
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