Engebretsen Kristin V T, Skårdal Kristine, Bjørnstad Sigrid, Marstein Henriette S, Skrbic Biljana, Sjaastad Ivar, Christensen Geir, Bjørnstad Johannes L, Tønnessen Theis
Department of Cardiothoracic Surgery, Oslo University Hospital Ullevål, Oslo, Norway; Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
J Mol Cell Cardiol. 2014 Nov;76:148-57. doi: 10.1016/j.yjmcc.2014.08.008. Epub 2014 Aug 26.
Pressure overload-induced TGF-β signaling activates cardiac fibroblasts (CFB) and leads to increased extracellular matrix (ECM) protein synthesis including fibrosis. Excessive ECM accumulation may in turn affect cardiac function contributing to development of heart failure. The aim of this study was to examine the effects of SM16, an orally active small molecular inhibitor of ALK5, on pressure overload-induced cardiac fibrosis. One week after aortic banding (AB), C57Bl/6J mice were randomized to standard chow or chow with SM16. Sham operated animals served as controls. Following 4 weeks AB, mice were characterized by echocardiography and cardiovascular magnetic resonance before sacrifice. SM16 abolished phosphorylation of SMAD2 induced by AB in vivo and by TGF-β in CFB in vitro. Interestingly, Masson Trichrome and Picrosirius Red stained myocardial left ventricular tissue revealed reduced development of fibrosis and collagen cross-linking following AB in the SM16 treated group, which was confirmed by reduced hydroxyproline incorporation. Furthermore, treatment with SM16 attenuated mRNA expression following induction of AB in vivo and stimulation with TGF-β in CFB in vitro of Col1a2, the cross-linking enzyme LOX, and the pro-fibrotic glycoproteins SPARC and osteopontin. Reduced ECM synthesis by CFB and a reduction in myocardial stiffness due to attenuated development of fibrosis and collagen cross-linking might have contributed to the improved diastolic function and cardiac output seen in vivo, in combination with reduced lung weight and ANP expression by treatment with SM16. Despite these beneficial effects on cardiac function and development of heart failure, mice treated with SM16 exhibited increased mortality, increased LV dilatation and inflammatory heart valve lesions that may limit the use of SM16 and possibly also other small molecular inhibitors of ALK5, as future therapeutic drugs.
压力超负荷诱导的转化生长因子-β（TGF-β）信号激活心脏成纤维细胞（CFB），并导致包括纤维化在内的细胞外基质（ECM）蛋白合成增加。过多的ECM积累反过来可能影响心脏功能，促进心力衰竭的发展。本研究的目的是研究ALK5的口服活性小分子抑制剂SM16对压力超负荷诱导的心脏纤维化的影响。在主动脉缩窄（AB）一周后，将C57Bl/6J小鼠随机分为标准饲料组或含SM16的饲料组。假手术动物作为对照。AB术后4周，在处死小鼠前通过超声心动图和心血管磁共振对其进行表征。SM16在体内消除了AB诱导的SMAD2磷酸化，并在体外消除了CFB中TGF-β诱导的SMAD2磷酸化。有趣的是，Masson三色染色和天狼星红染色的心肌左心室组织显示，在SM16治疗组中，AB后纤维化的发展和胶原交联减少，这通过羟脯氨酸掺入减少得到证实。此外，SM16治疗在体内诱导AB后以及在体外CFB中用TGF-β刺激后，减弱了Col1a2、交联酶LOX以及促纤维化糖蛋白SPARC和骨桥蛋白的mRNA表达。CFB减少的ECM合成以及由于纤维化和胶原交联发展减弱导致的心肌僵硬度降低，可能与体内观察到的舒张功能改善和心输出量增加有关，同时SM16治疗还降低了肺重量和心钠素表达。尽管对心脏功能和心力衰竭发展有这些有益作用，但用SM16治疗的小鼠死亡率增加、左心室扩张增加以及出现炎症性心脏瓣膜病变，这可能会限制SM16以及可能其他ALK5小分子抑制剂作为未来治疗药物的使用。
