Study On Trimetazidine As A Protective Agent In Radiation-induced Heart Injury

Objective: The aims of this study are to stage Radiation-Induced heart damage(RIHD)model in mice and observe RIHD myocardial histopathological changes,and to investigate the protective effect and potential molecular mechanisms of trimetzidine against RIHD in mice.Methods: Sixty male C57BL/6 mice were randomly divided into six groups: Control group(Con)?Irradiation Group(Mod)?and four experimental groups receiving low dose(10 mg/kg/day)or high dose(20 mg/kg/day)trimetazidine before or after radiation treatment(LDT1,HDT1,LDT2,HDT2),with 10 mice in each group.1 Radiation: All the mice expect Group Con were exposed to one-time local heart irradiation with a single fraction of 20 Gy from a precise type medical high-energy linear accelerator producing 6 MV X-ray in the second week of the experiment.2 Trimetazidine treatment: Trimetazidine at doses of 10 mg/kg were used to treat animals in group LDT1 by intragastric administration from one week before radiation to the end of the experiment.Group HDT1 were treated by trimetazidine at doses of 20 mg/kg from one week before radiation to the end of the experiment.Group LDT2 were treated by trimetazidine at doses of 10 mg/kg from one week after radiation to the end of the experiment.Group HDT2 were treated by trimetazidine at doses of 20 mg/kg from one week after radiation to the end of the experiment.3 Morphological observation: the mice were sacrificed at 8 weeks after irradiation,and the morphological changes of the hearts of the mice were observed by hematoxylin-eosin(HE)staining.Masson staining was used to observe the myocardial fibrosis in mice,and software quantitative analysis was used to evaluate the degree of myocardial fibrosis.4 Biochemical assays in mice cardiac tissues: The expression levels of CTGF protein and TGF-?1 protein were analyzed by Immunohistochemical.The m RNA expression levels of CTGF and TGF-?1 were determined by Quantitative Real-time PCR(rt PCR).Results: 1 Morphological results(1)HE staining: The myocardial tissue of mice in each irradiation group presented different degrees of pathological changes,mainly inflammatory reaction and fibrosis.The nuclei of the myocardium were slightly constricted,the staining of the nuclei was deeper than that of the Con group,and a large number of inflammatory cells infiltrated into the interstitium of the myocardium.Among them,the degree of myocardial injury in each trimetazidine group was significantly reduced compared with that in the Mod group.(2)Masson staining results: Compared with Con group,the myocardial collagen fibers of each irradiated group were stained blue and were more widely distributed in the myocardial interstroma.The quantitative analysis of myocardial collagen volume fraction(CVF)in mice found that the treatment group was significantly lower than the Mod group(P < 0.05),the high-dose groups were significantly lower than the low-doses group(P < 0.05),and all groups were significantly higher than the Con group(P < 0.05).There was no significant change in CVF between the pre-irradiation group and the post-irradiation group(P > 0.05).2 Immunohistochemical and rt PCR analysis: The expression of CTGF and TGF-b1 protein and m RNA levels in each group were significantly different(P < 0.05).Both the proteins and m RNA expressions of CTGF and TGF-b1 in each groups were significantly higher than that in group Mod,group LDT1 were higher than group HDT1,group LDT2 were higher than group HDT2,and group Con were significantly lower than other groups(P < 0.05).There was no significant difference between group LDT1 and group LDT2,group HDT1 and group HDT2(P>0.05).Conclusion: Radiation exposure on the precardiac area of mice can cause myocardial cell inflammation and fibrosis and increase in the expression of CTGF and TGF-?1 at protein and gene levels in myocardial tissue associated with fibrosis.Trimetazidine attenuates radiation-induced heart injury loss by decrease the expression of CTGF and TGF-?1 in hearts exposed to radiation.The influence of it was positively correlated with the dose of the drug,but not with the initiation of the drug before radiation.