基于心肌摄取型转运体选择性抑制减轻阿霉素心脏毒性研究

阿霉素对血液系统恶性肿瘤和乳腺癌等有很好疗效，但具心脏毒性。阿霉素亲心肌/线粒体的特性是其毒性的基础。因阿霉素被动透过差，其跨膜转运需转运体介导。我们前期发现：阿霉素为人OCTN2（人心脏中高表达）、OCTN1、PMAT底物；心肌线粒体表达OCTN1；OCTN2/1抑制剂降低阿霉素在心肌细胞/小鼠心脏积聚，减轻心脏毒性。由于肿瘤组织中OCTN2表达被抑制，而PMAT和OCT6（阿霉素为其底物）则高表达。推测，OCTN2/1和PMAT/OCT6可能分别为心肌/线粒体和肿瘤组织摄取阿霉素的关键转运体；选择性抑制OCTN2/1可能降低阿霉素心脏毒性，而不影响其抗肿瘤药效。本项目拟应用多种细胞模型、临床肿瘤样本、整体动物，阐明心肌/线粒体对阿霉素的摄取机制；明确介导心肌/线粒体和肿瘤组织摄取阿霉素的关键转运体差异；探究选择性抑制心肌/线粒体摄取阿霉素，以降低其心脏毒性而不减弱抗肿瘤药效的可能性。

Doxorubicin (DOX) is one of the most effective anthracycline antitumor agents to treat various forms of cancers; however, its therapeutic utility is severely limited by its associated cardiotoxicity. Despite the enormous amount of research conducted in this area, the exact molecular mechanisms underlying DOX toxic effects on the heart are still unknown. The high affinity of doxorubicin to heart/myocardial mitochondria is the key factor of its cardiotoxicity. Due to the poor passive permeability of doxorubicin, transporters contribute to membrane transfer of doxorubicin through cardiomyocytes/myocardial mitochondria. Our previous studied shows that doxorubicin is the substrate of human carnitine/organic cation transporter 2 (OCTN2, highly expressed in human cardiomyocytes), human carnitine/organic cation transporter 1(OCTN1) and human plasma membrane monoamine transporter (PMAT). Our study also confirmed that OCTN1 protein is expressed in myocardial mitochondria. Our further in vitro and in vivo studies demonstrated that the inhibitor of OCTN2/OCTN1 reduced the concentration of doxorubicin in primary cardiomyocytes (in vitro study) and mouse hearts (in vivo study), and subsequently attenuated the cell toxicity/cardiotoxicity. Due to OCTN2 expression is down-regulated whereas PMAT and organic cation transporter 6 (OCT6) are high expressed in tumors, we deduced that OCTN2/OCTN1 and PMAT/OCT6 probably are the key transporters mediated cardiomyocytes/myocardial mitochondria or tumor tissue uptake of doxorubicin, respectively, therefore, selective inhibition of the key uptake transporters for doxorubicin will probably reduce the accumulation of doxorubicin in heart but not in tumor, thus the selective inhibitor can attenuate doxorubicin-induced cardiotoxicity but not impair its anti-tumor effect. The present study will apply multiple transfected cell models with stable expression of human transporters and primary cardiomyocytes and human resource cardiomyocytes, clinical tumor samples, to clarify the uptake mechanism of doxorubicin by cardiomyocytes/myocardial mitochondria; to elucidate the difference of mechanism for doxorubicin uptake by heart and by tumor, and to elucidate whether the selective inhibitor can attenuate the cardiotoxicity of doxorubicin but not impair its anti-tumor efficient. The study will provide the useful information for good therapeutic strategy of doxorubicin in clinical application.