探討運動訓練介入對合併化療與放射照射誘發之心肌功能異常之成效

Abstract

研究背景與目的：同步化學合併放射治療（concurrent chemoradiotherapy, CCRT）是常用的癌症綜合治療方案，且已知具心臟毒性。心肌受傷後的重塑過程，對於心臟功能是否會持續惡化是重要關鍵。心肌受傷後會產生病理性慢性代償肥大，最後導致心臟衰竭。急性心肌梗塞的動物模型研究顯示梗塞後介入運動訓練，可以降低心肌受傷後的病理性心肌肥大和纖維化。但運動訓練對心肌在CCRT後受傷的復原與重塑，是否具相似效益，則尚不清楚。因此，本研究的目的是探討心肌在放射合併化學治療模式傷害後，介入運動訓練，對心肌功能及重塑改善之影響及相關機制之探討。方法：本研究將18隻7週大之雄性Wistar大鼠，以每組6隻隨機分配到控制組（Ctrl）、同步化學合併放射照射組（CCRT）、及同步化學合併放射照射後運動訓練組（CCRTEx）。CCRT及CCRTEx組大鼠，接受單次，劑量8mg/kg的cisplatin注射，並在接受注射24小時後開始放射照射，照射劑量為每次5 Gy、一天1次，共5天總量為25 Gy。在完成CCRT後，CCRTEx組進行6週，每週5天，每次60分鐘之運動訓練。CCRT及CCRTEx大鼠在接受CCRT後第四週（T1）及第七週（T2）及Ctrl組在相對應周齡，皆以心臟超音波進行非侵入性心臟功能測試。所有大鼠在完成所有介入後一週，以導電心導管進行活體心臟功能測試（壓力-容積分析）。待分析結束後犧牲大鼠，取出其左心室組織進行心臟氧化壓力、抗氧化能力及纖維化分析。心臟所受之氧化壓力以活性氧含量；抗氧化能力以CuZnSOD及MnSOD mRNA表現量分析；纖維化及心肌重塑指標以MMP-2/-9、type I III collagen蛋白質表現量及以Masson's trichrome染色計算膠原容積分數（collagen volume fraction; CVF）觀察纖維化變化。結果：相較於控制組，CCRT組左心室心肌纖維斷裂及白血球浸潤現象較為明顯，活性氧含量顯著較高（p< 0.05），以超音波測得之心臟收縮（fraction shortening (FS)；p= 0.002）及舒張功能（isovolumic relaxation time (IVRT)；p= 0.004）在T2顯著較差，MMP-2蛋白質表現量（p= 0.04）顯著較低，type III collagen蛋白質表現量（p= 0.02）及CVF（p= 0.01）皆顯著較高。相較於無運動訓練之對照組，CCRTEx組之大鼠，以壓力-容積分析測得之心臟收縮（ejection fraction (EF)；p= 0.017）及舒張功能（Tau Weiss；p= 0.014）顯著較佳，左心室氧化壓力顯著較低（p< 0.05）。相較於未訓練的對照組，運動訓練組的抗氧化MnSOD mRNA表現量（p= 0.02）較高，MMP-2蛋白質表現量（p= 0.02）顯著較高，纖維化分析則可見CVF（p= 0.03) 在運動訓練組顯著較低。結論：本研究結果顯示6週之運動訓練可改善心臟之收縮及舒張功能，並藉由調控其抗氧化能力及心肌重塑之基質金屬蛋白酶表現量來降低同步化學合併放射照射引起之心肌功能異常。

Background and purpose: Concurrent chemoradiotherapy (CCRT) is a common treatment option for patients with cancers and is known to induce cardiotoxicity. Adverse cardiac remodeling leads to pathological cardiomyocyte hypertrophy and progressively deteriorating cardiac function to the point of failure. Compelling animal evidence has shown that post myocardial infarction exercise protects heart against pathological cardiac hypertrophy and fibrosis. Whether exercise training after CCRT provides similar beneficial effects remains to be determined. Therefore, this study aimed to investigate post-CCRT exercise training on cardiac remodeling and function, and the potential mechanisms were also explored in the rodent model. Methods: A total of 18 adult male Wistar rats aged 7-week-old were randomly assigned into control (Ctrl), CCRT, or exercise training after CCRT (CCRTEx) group (n= 6 per group). The CCRT and CCRTEx received a single cisplatin injection with a dose of 8 mg/kg. The radiation started 24 hours after cisplatin injection, with a dose of 5 Gy/fraction/day for 5 days (total dose of 25 Gy). 1 week after received CCRT, The CCRTEx underwent exercise training on a motor-driven treadmill for 60 minutes/day, 5 days/week, for a total of 6 weeks. The myocardial function was examined using non-invasive echocardiography at 4-week (T1) and 7-week post-CCRT (T2) and invasive pressure-volume (P-V) analysis after T2. Rats were sacrificed after myocardial function analysis, and the hearts were removed en bloc. The left ventricular tissue was used for oxidative stress, antioxidant capacity, and fibrosis analysis. Oxidative stress was determined by analyzing reactive oxygen species (ROS) level and antioxidant capacity was determined by analyzing CuZnSOD and MnSOD mRNA expression. Myocardial fibrosis and remodeling were examined using protein expression of MMP-2/-9, type I and III collagen, and myocardial interstitial collagen volume fraction (CVF) measured by Masson’s trichrome staining. Results: Compared to Ctrl group, sporadic fragmentation of myocardial fibers and leukocyte infiltration were more obvious in the LV myocardium in CCRT group. In CCRT group, the level of ROS (p< 0.05) was significantly higher, the cardiac systolic (fraction shortening (FS); p= 0.002) and diastolic function (isovolumic relaxation time (IVRT); p= 0.004) measured by echocardiography at T2 were significantly worse compared to those of Ctrl group. Compared to Ctrl group, protein expression level of MMP-2 (p= 0.04) was significantly lower, and type III collagen protein expression level (p= 0.02) and the CVF (p= 0.01) were significantly higher in CCRT group. Compared to CCRT group with no exercise training, rats in CCRTEx group demonstrated better cardiac systolic (ejection fraction (EF); p= 0.017) and diastolic function (Tau Weiss; p= 0.014) in PV analysis. In CCRTEx group, ROS level was significantly lower (p< 0.05), and MnSOD mRNA (p= 0.02) was higher than those of CCRT group. In CCRTEx group, protein expression level of MMP-2 (p= 0.02) was significantly higher, and CVF was significantly lower than those of CCRT group (p= 0.03). Conclusions: This study showed that aerobic exercise training after CCRT could enhance cardiac antioxidant defense system and reduce myocardial contractile dysfunction due to remodeling.