Background: Sphingolipids have recently emerged as a biomarker of recurrence and mortality after myocardial infarction (MI). The increased ceramide levels in mammalian heart tissues during acute MI, as demonstrated by several groups, is associated with higher cell death rates in the left ventricle (LV) and deteriorated cardiac function. Ceramidase, the only enzyme known to hydrolyze pro-apoptotic ceramide, generates sphingosine, which is then phosphorylated by sphingosine kinase (Sphk) to produce the pro-survival molecule sphingosine-1-phosphate (S1P). We hypothesized that Acid Ceramidase (AC) overexpression would counteract the negative effects of elevated ceramide and promote cell survival, thereby providing cardioprotection after MI. Methods: We performed transcriptomic, sphingolipid and protein analyses to evaluate sphingolipid metabolism and signaling post MI. We investigated the effect of altering ceramide metabolism through a loss (chemical inhibitors) or gain (modified mRNA (modRNA)) of AC function post hypoxia or MI. Results: We found that several genes involved in de novo ceramide synthesis were upregulated and that ceramide (C16, C20, C20:1 and C24) levels had significantly increased 24 hours after MI. AC inhibition post hypoxia or MI resulted in reduced AC activity and increased cell death; by contrast, enhancing AC activity via AC modRNA treatment increased cell survival post hypoxia or MI. AC modRNA-treated mice had significantly better heart function, longer survival and smaller scar size than control mice 28 days post MI. We attributed the improvement in heart function post MI following AC modRNA delivery to decreased ceramide levels, lower cell death rates and changes in the composition of the immune cell population in the LV manifested by lowered abundance of pro-inflammatory detrimental neutrophils. Conclusions: Our findings suggest that transiently altering sphingolipid metabolism through AC overexpression is sufficient and necessary to induce cardioprotection post MI, thereby highlighting the therapeutic potential of AC modRNA in ischemic heart disease.

中文翻译：

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改变鞘脂代谢可减轻心肌梗死后的细胞死亡和炎症反应。

背景：鞘脂最近已成为心肌梗死（MI）后复发和死亡的生物标志物。几组研究表明，急性心梗期间哺乳动物心脏组织中神经酰胺水平的升高与左心室（LV）的较高细胞死亡率和心脏功能恶化有关。陶瓷酰胺酶是已知的唯一水解促凋亡神经酰胺的酶，可生成鞘氨醇，然后被鞘氨醇激酶（Sphk）磷酸化，生成促存活分子鞘氨醇-1-磷酸（S1P）。我们假设酸性神经酰胺酶（AC）的过表达将抵消神经酰胺升高的负面影响并促进细胞存活，从而在MI后提供心脏保护作用。方法：我们进行了转录组学，鞘脂和蛋白质分析以评估MI后鞘脂的代谢和信号传导。我们研究了通过缺氧或MI后AC功能丧失（化学抑制剂）或获得（修饰的mRNA（modRNA（modRNA）））改变神经酰胺代谢的影响。结果：我们发现与新生神经酰胺合成有关的几个基因被上调，MI后24小时神经酰胺（C16，C20，C20：1和C24）的水平显着增加。缺氧或心肌梗死后AC抑制导致AC活性降低和细胞死亡增加；相反，通过AC modRNA处理增强AC活性可提高缺氧或MI后的细胞存活率。MI后28天，AC modRNA处理的小鼠比对照组小鼠具有明显更好的心脏功能，更长的生存期和更小的疤痕大小。我们将AC modRNA传递后MI后心脏功能的改善归因于神经酰胺水平降低，细胞死亡率降低以及左室免疫细胞群组成的变化，这由促炎性有害嗜中性粒细胞的减少所表现。结论：我们的研究结果表明，通过AC过表达瞬时改变鞘脂代谢足以诱导MI后的心脏保护，因此突出了AC modRNA在缺血性心脏病中的治疗潜力。