Center for Cardiovascular Research, John A. Burns School of Medicine, University of Hawaii , Honolulu, Hawaii.
Am J Physiol Heart Circ Physiol. 2019 Mar 1;316(3):H554-H565. doi: 10.1152/ajpheart.00617.2018. Epub 2018 Dec 21.
The principal regulator of cellular response to low oxygen is hypoxia-inducible factor (HIF)-1, which is stabilized in several forms of heart failure. Our laboratory developed a mouse strain in which a stable form of HIF-1 can be inducibly expressed in cardiomyocytes. Strikingly, these mice show a rapid decrease in cardiac contractility and a rapid loss of SERCA2 protein, which is also seen in heart failure. Interestingly, while the SERCA2 transcript decreased, it did not fully account for the observed decrease in protein. We therefore investigated whether HIF-1-regulated microRNA could impair SERCA translation. Multiple screening analyses identified the microRNA miR-29c to be substantially upregulated upon HIF-1 induction and to have complementarity to SERCA, and therefore be a potential regulator of SERCA2 expression in hypoxia. Subsequent evaluation confirmed that miR-29c reduced SERCA2 expression and Ca reuptake. Additionally, administration of an antagonist sequence (antimir) improved cardiac contractility and SERCA2 expression in HIF transgenic mice. To extend the significance of these findings, we examined miR-29c expression in physiological hypoxia. Surprisingly, miR-29c decreased in these settings. We also treated mice with antimir before infarction to see if further suppression of miR-29c could improve cardiac function. While no improvement in contractility or SERCA2 was observed, reduction of heart size after infarction indicated that the antimir could modulate cardiac physiology. These results demonstrate that while a HIF-1-regulated microRNA, miR-29c, can reduce SERCA2 expression and contractility, additional factors in the ischemic milieu may limit these effects. Efforts to develop miRNA-based therapies will need to explore and account for these additional countervailing effects. NEW & NOTEWORTHY Our study demonstrated hypoxia-inducible factor-1-dependent upregulation of miR-29c, which, in turn, inhibited SERCA2 expression and reduced cardiac contractility in a transgenic overexpression system. Interestingly, these results were not recapitulated in a murine myocardial infarction model. These results underscore the complexity of the pathological environment and highlight the need for therapeutic target validation in physiologically relevant models.
细胞对低氧反应的主要调节剂是缺氧诱导因子（HIF）-1，它在几种心力衰竭形式中稳定存在。我们的实验室开发了一种小鼠品系，其中 HIF-1 的稳定形式可以在心肌细胞中诱导表达。引人注目的是，这些小鼠表现出心肌收缩力的快速下降和 SERCA2 蛋白的快速丢失，这在心力衰竭中也有发现。有趣的是，虽然 SERCA2 转录物减少，但它并没有完全解释观察到的蛋白质减少。因此，我们研究了 HIF-1 调节的 microRNA 是否会损害 SERCA 的翻译。多项筛选分析表明，HIF-1 诱导后 miR-29c 大量上调，并与 SERCA 互补，因此可能是低氧条件下 SERCA2 表达的潜在调节剂。随后的评估证实，miR-29c 降低了 SERCA2 的表达和 Ca2+摄取。此外，给予拮抗剂序列（antimir）可改善 HIF 转基因小鼠的心脏收缩力和 SERCA2 表达。为了扩展这些发现的意义，我们在生理低氧条件下检查了 miR-29c 的表达。令人惊讶的是，miR-29c 在这些环境中减少。我们还在梗塞前用 antimir 治疗小鼠，以观察进一步抑制 miR-29c 是否可以改善心脏功能。虽然没有观察到收缩力或 SERCA2 的改善，但梗塞后的心脏缩小表明 antimir 可以调节心脏生理学。这些结果表明，虽然 HIF-1 调节的 microRNA，miR-29c 可以降低 SERCA2 的表达和收缩力，但缺血环境中的其他因素可能会限制这些影响。基于 miRNA 的治疗方法的开发将需要探索和解释这些额外的抵消作用。新的和值得注意的是，我们的研究表明，缺氧诱导因子-1 依赖性 miR-29c 的上调，反过来又抑制了转基因过表达系统中 SERCA2 的表达并降低了心脏收缩力。有趣的是，这些结果在小鼠心肌梗塞模型中没有重现。这些结果强调了病理环境的复杂性，并突出了在生理相关模型中验证治疗靶点的必要性。
