Roles of Voltage- and cation-independent TRPC channels in cardiac hypertrophy

我们已报道血管紧张素II或内皮素-1的刺激通过瞬时受体电位规范通道3(TRPC3)和TRPC6介导的钙内流诱导新生大鼠心肌细胞肥大反应。TRPC3/TRPC6是一种电压不依赖、阳离子非选择性的离子通道，可被GQ刺激磷脂酶C激活产生的二酰甘油激活。然而，这些结果是从体外细胞系统中获得的，使用的是新生大鼠心肌细胞的受体刺激。说明TRPC3/TRPC6在体内肥大模型中的重要性是非常必要的。因此，我们研究了TRPC3/TRPC6是否参与了压力超负荷诱导的心肌肥厚。压力超负荷被认为是一种慢性人类高血压的小鼠模型，并导致心肌肥厚。由于有选择性抑制TRPC3的化合物Pyr3的存在，我们获得了它，并将其应用于压力超负荷的小鼠。压力过载由…施加更多的横向主动脉缩窄程序(TAC)，PYR3使用渗透压微泵。与野生型小鼠相比，PYR3治疗组小鼠的压力超负荷诱导的肥大受到抑制，这是通过增加心肌细胞的大小和ANP表达的增加来评估的。此外，通过使用PYR3治疗可以改善心脏功能，如缩短率。接下来，我们还研究了TRPC6在压力超负荷诱导的心肌肥厚中的作用。由于TRPC6的功能被TRPC6的磷酸化抑制，我们使用了cGMP选择性磷酸二酯酶(磷酸二酯酶5：PDE5)抑制剂西地那非来增加心脏cGMP的含量。西地那非可抑制压力超负荷所致的心肌肥厚。西地那非可抑制多种肥大标志物基因表达的增加。在西地那非治疗的小鼠中，抗磷酸化的TRPC6抗体显示TRPC6在特定的位置被磷酸化，这是TRPC6介导的钙离子内流所必需的。这些结果表明，TRPC3/TRPC6介导的钙内流在体内和体外心肌肥厚中都起着重要的作用。较少

We have reported that angiotensin II or endothelin-1 stimulation induce hypertrophic responses through transient receptor potential canonical channel 3 (TRPC3) and TRPC6-mediated Ca2+ influx using rat neonatal cardiomyocytes. TRPC3/TRPC6 are voltage-independent and cation-non-selective ion channels, and activated by diacylglycerol generated by Gq-stimulated phospholipase C activation. However, these results were obtained from in vitro cell system using receptor stimulation of cardiomyocytes isolated from newborn rats. It is essential to demonstrate the importance of TRPC3/TRPC6 in in vivo hypertrophy model. Therefore, we have examined whether TRPC3/TRPC6 are involved in pressure overload-induced cardiac hypertrophy. Pressure overload is considered as a mouse model of chronic human hypertension, and induces cardiac hypertrophy. As the compound Pyr3 that selectively inhibits TRPC3 was available, we obtained it and administered to pressure overloaded mice. Pressure overload is applied by … More transverse aortic constriction procedure (TAC), and Pyr3 is administered by osmotic mini-pump. Pressure overload-induced hypertrophy was inhibited in Pyr3-treated mice as compare to wild type mice, which was as assessed by increased size of cardiomyocytes and increased expression of ANP. Furthermore, cardiac function such as fractional shortening is improved by the treatment with Pyr3. Next, we also examined the involvement of TRPC6 in pressure overload-induced cardiac hypertrophy. As the function of TRPC6 is inhibited by phosphorylation of TRPC6, we used a cGMP-selective phosphodiesterase (phosphodiesterase type 5:PDE5) inhibitor, sildenafil, for the increase in cardiac cGMP content. The treatment with sildenafil inhibited cardiac hypertrophy by pressure overload. The increased expression of various marker genes of hypertrophy was inhibited by the treatment with sildenafil. In sidenafil-treated mice, anti-phospho-TRPC6 antibody revealed that TRPC6 was phosphorylated at a specific site that is essential for TRPC6-mediated Ca^<2+> influx. These results suggest that TRPC3/TRPC6-mediated Ca^<2+> influx plays an important role in cardiac hypertrophy in vivo as well as in vitro. Less