Zhao Huanhuan, Liu Dan, Yan Qiumei, Bian Xiyun, Yu Jing, Wang Jingjing, Cheng Xinxin, Xu Zhelong
Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China.
Central Laboratory, Tianjin, China.
Front Physiol. 2022 Jan 5;12:736920. doi: 10.3389/fphys.2021.736920. eCollection 2021.
Zinc homeostasis has been known to play a role in myocardial ischemia/reperfusion (I/R) injury, but the precise molecular mechanisms regulating the expression of ZIP transporters during reperfusion are still unclear. The aim of this study was to determine whether ER Stress/CaMKII/STAT3 pathway plays a role in the regulation of cellular zinc homeostasis. Zinc deficiency increased mRNA and protein expressions of the ER stress relevant markers Chop and Bip, and STAT3 phosphorylation in H9c2 or HL-1 cells, an effect that was abolished by ZnCl. ER calcium concentration [(Ca)] was decreased and cytosolic calcium concentration [(Ca)] was increased at the condition of normoxia or ischemia/reperfusion, indicating that zinc deficiency triggers ER stress and Ca leak. Further studies showed that upregulation of STAT3 phosphorylation was reversed by Ca chelator, indicating that intracellular Ca is important for zinc deficiency-induced STAT3 activation. In support, zinc deficiency enhanced ryanodine receptors (RyR), a channel in the ER that mediate Ca release, and Ca-calmodulin-dependent protein kinase (CaMKII) phosphorylation, implying that zinc deficiency provoked Ca leak from ER via RyR and p-CaMKII is involved in STAT3 activation. Moreover, inhibition of STAT3 activation blocked zinc deficiency induced ZIP9 expression, and resulted in increased Zn loss in cardiomyocytes, further confirming that STAT3 activation during reperfusion promotes the expression of ZIP9 zinc transporter to correct the imbalance in zinc homeostasis. In addition, suppressed STAT3 activation aggravated reperfusion injury. These data suggest that the ER Stress/CaMKII/STAT3 axis may be an endogenous protective mechanism, which increases the resistance of the heart to I/R.
锌稳态在心肌缺血/再灌注（I/R）损伤中发挥作用，这一点已为人所知，但再灌注期间调节ZIP转运体表达的精确分子机制仍不清楚。本研究的目的是确定内质网应激/钙调蛋白依赖性蛋白激酶/信号转导和转录激活因子3（ER Stress/CaMKII/STAT3）通路是否在细胞锌稳态调节中发挥作用。锌缺乏增加了H9c2或HL-1细胞中内质网应激相关标志物CHOP和Bip的mRNA和蛋白表达以及STAT3磷酸化，而ZnCl可消除这种作用。在常氧或缺血/再灌注条件下，内质网钙浓度[(Ca)]降低，胞质钙浓度[(Ca)]升高，表明锌缺乏引发内质网应激和钙泄漏。进一步研究表明，钙螯合剂可逆转STAT3磷酸化的上调，表明细胞内钙对锌缺乏诱导的STAT3激活很重要。此外，锌缺乏增强了兰尼碱受体（RyR）（一种在内质网中介导钙释放的通道）和钙调蛋白依赖性蛋白激酶（CaMKII）的磷酸化，这意味着锌缺乏通过RyR引发内质网钙泄漏，且p-CaMKII参与STAT3激活。此外，抑制STAT3激活可阻断锌缺乏诱导的ZIP9表达，并导致心肌细胞锌流失增加，进一步证实再灌注期间STAT3激活促进ZIP9锌转运体的表达以纠正锌稳态失衡。此外，抑制STAT3激活会加重再灌注损伤。这些数据表明，ER Stress/CaMKII/STAT3轴可能是一种内源性保护机制，可增加心脏对I/R的抵抗力。
