| Acute myocardial infarction (AMI), which is characterized by regional myocardialischemia and hypoxia caused by reduction of blood perfusion that originates from urgentocclusion of the coronary artery, leads to energy metabolic disorder. AMI could lead toacute myocardium injury and even sudden death due to delayed and inappropriatetreatment. Percutaneous coronary intervention (PCI) and thrombolytic therapy arecommonly used in clinic, which is aimed to reopen the occlusive coronary artery and tosave the residual cardiomyocytes. However, ischemia/reperfusion (I/R) injury andno-reflow (NR) phenomenon are still problematic. Therefore, a better way to reduce theI/R and NR injuries seems to be necessary and important for clinical experience.More and more attentions have been paid to a promising treatment about magneticfield therapy. Studies have shown that magnetic field could improve the morphology andfunction of cells, tissues and organs through different mechanisms such as anti-inflammatory, antioxidant, anti-thrombus, generation of nitric oxide (NO),angiogenesis in ischemic myocardium.restrains the formation of plaque in the aorta anddamage caused by I/R, and consequently improves function of heart. However, thespecific mechanism under these protective effects is still unclear.Therefore, we try to partially elucidate the connection magnetic field, NO, oxidativestress and myocardial ischemia. This study was designed to observe the effects of lowfrequency pulsed magnetic fields (LF-PMFs) on H/R neonatal rat cardiomyocytes andNO/ONOO~-as well as its signaling pathway in LF-PMFs-induced cardiomyocytes survival.Objective1. To investigate the effects of LF-PMFs with different parameters on theproliferation and apoptosis of neonatal rat cardiomyocytes under hypoxia/reoxygenation(H/R) treatment, and decide the optimal magnetic field.2. To observe the effects of LF-PMFs on NO/ONOO~-and its pathways under H/R,and t discuss the protective mechanism of LF-PMFs in H/R cardiomyocytes.MethodsNeonatal SD rat cardiomyotes were isolated by enzyme digestion and the purified bydifferential adhesion method. Immunohistochemistry stanning of cardiac troponin I (cTnI)is applied to identify cardiomyocytes and growth curve was determined by MTT. NeonatalSD rat cardiomyocytes went hypoxia for3hours and reoxgenated for another3hours. Theselected magnetic field parameters are frequency (15Hz and20Hz), intensity (1.5mT,3.0mT,4.5mT,6.0mT) and duration (1h,3h,5h).Neonatal rat cardiomyocytes were randomly divided into3groups: Control, H/Rtreatment and H/R with LF-PMFs treatment (1.5mT,3.0mT,4.5mT,6.0mT). Afterintervention of H/R and LF-PMFs, the viability and apoptosis of cardiomyocytes wereassessed by MTT assay and TUNEL, respectively. The optimal parameter of LF-PMFswas selected by the result. Superoxide anion and NO/ONOO~-levels were tested bySuperoxide Assay Kit and Griess Assay. Superoxide anion was detected bydihydroethidium and WST-1. NADPH oxidase activity was measured bychemiluminescence method, and eNOS phosphorylation level was determined by Western-Blot.Results1. LF-PMFs promote proliferation of the neonatal rat cardiomyocytes as well asinhibit its apoptosis under H/R condition. LF-PMFs significantly reduces the levels of O2-and ONOO~-, and upregulates NO expression in vitro. Additonally, LF-PMFs with15Hz,4.5mT have the most beneficial effect compared with other parameters.2. LF-PMFs reduce the activity of NADPH oxidase and O2-release as well asincrease the eNOS phosphorylation and NO production. Thereby LF-PMFs seems to keepthe balance between NO and ONOO~-in neonatal rat cardiomyocytes under H/R condition.ConclusionsLF-PMFs exert protective effects on cardiomyocytes from H/R injury by promotingits proliferation and attenuating its apoptosis. The protective mechanism of LF-PMFs maybe caused by affecting the balance of NO/ONOO~-through two pathways: enhance theprotective NO output by the phosphorylation of eNOS in cardiomyocyte and inhibit thehighly cytotoxic ONOO~-production by suppressing NADPH oxidase and O2-activity. |
PDF Full Text Request