Background Our previous research suggested that dexmedetomidine (Dex) promotes autophagy in cardiomyocytes, thus safeguarding them against apoptosis during sepsis. However, the underlying mechanisms of Dex-regulated autophagy have remained elusive. This study aimed to explore the role of exosomes and how they participate in Dex-induced cardioprotection in sepsis. The underlying microRNA (miRNA) mechanisms and possible therapeutic targets for septic myocardial injury were identified. Methods We first collected plasma exosomes from rats with sepsis induced by caecal ligation and puncture (CLP) with or without Dex treatment, and then incubated them with H9c2 cells to observe the effect on cardiomyocytes. Subsequently, the differential expression of miRNAs in plasma exosomes from each group of rats was identified through miRNA sequencing. miR-29b-3p expression in circulating exosomes of septic or non-septic patients, as well as in lipopolysaccharide-induced macrophages after Dex treatment, was analysed by quantitative real-time polymerase chain reaction (qRT–PCR). The autophagy level of cardiomyocytes after macrophage-derived exosome treatment was assessed by an exosome tracing assay, western blotting, and an autophagic flux assay. Specific miRNA mimics and inhibitors or small interfering RNAs were used to predict and evaluate the function of candidate miRNA and its target genes by qRT-PCR, annexin V/propyl iodide staining, autophagy flux analysis, and western blotting. Results We found that plasma-derived exosomes from Dex-treated rats promoted cardiomyocyte autophagy and exerted antiapoptotic effects. Additionally, they exhibited a high expression of miRNA, including miR-29b-3p. Conversely, a significant decrease in miR-29b-3p was observed in circulating exosomes from CLP rats, as well as in plasma exosomes from sepsis patients. Furthermore, Dex upregulated the lipopolysaccharide-induced decrease in miR-29b-3p expression in macrophage-derived exosomes. Exosomal miR-29b-3p from macrophages is thought to be transferred to cardiomyocytes, thus leading to the promotion of autophagy in cardiomyocytes. Database predictions, luciferase reporter assays, and small interfering RNA intervention confirmed that glycogen synthase kinase 3β (GSK-3β) is a target of miR-29b-3p. miR-29b-3p promotes cardiomyocyte autophagy by inhibiting GSK-3β expression and activation. Conclusions These findings demonstrate that Dex attenuates sepsis-associated myocardial injury by modulating exosome-mediated macrophage–cardiomyocyte crosstalk and that the miR-29b-3p/GSK-3β signaling pathway represents a hopeful target for the treatment of septic myocardial injury.

中文翻译：

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右美托咪定通过靶向糖原合成酶激酶 3β 促进心肌细胞自噬，调节巨噬细胞的外泌体 miR-29b-3p，减轻脓毒性心肌损伤


背景我们之前的研究表明，右美托咪定 （Dex） 促进心肌细胞自噬，从而保护它们在脓毒症期间免受细胞凋亡。然而，Dex 调节的自噬的潜在机制仍然难以捉摸。本研究旨在探讨外泌体的作用以及它们如何参与 Dex 诱导的脓毒症心脏保护。确定了感染性心肌损伤的潜在 microRNA （miRNA） 机制和可能的治疗靶点。方法 首先收集盲肠结扎穿刺 （CLP） 诱导的脓毒症大鼠血浆外泌体，无论是否进行 Dex 处理，然后与 H9c2 细胞一起孵育，观察对心肌细胞的影响。随后，通过 miRNA 测序鉴定每组大鼠血浆外泌体中 miRNAs 的差异表达。通过定量实时聚合酶链反应 （qRT-PCR） 分析脓毒症或非脓毒症患者循环外泌体中以及 Dex 后脂多糖诱导的巨噬细胞中 miR-29b-3p 的表达。通过外泌体示踪试验、western blotting 和自噬通量测定评估巨噬细胞衍生的外泌体处理后心肌细胞的自噬水平。采用特异性 miRNA 模拟物和抑制剂或小干扰 RNAs 通过 qRT-PCR、膜联蛋白 V/碘丙酯染色、自噬通量分析和 western blotting 预测和评价候选 miRNA 及其靶基因的功能。结果 我们发现来自 Dex 处理大鼠的血浆衍生外泌体促进心肌细胞自噬并发挥抗凋亡作用。此外，它们表现出 miRNA 的高表达，包括 miR-29b-3p。 相反，在 CLP 大鼠的循环外泌体以及脓毒症患者的血浆外泌体中观察到 miR-29b-3p 的显着降低。此外，Dex 上调了脂多糖诱导的巨噬细胞来源的外泌体中 miR-29b-3p 表达的降低。来自巨噬细胞的外泌体 miR-29b-3p 被认为被转移到心肌细胞中，从而导致心肌细胞自噬的促进。数据库预测、荧光素酶报告基因测定和小干扰 RNA 干预证实糖原合成酶激酶 3β （GSK-3β） 是 miR-29b-3p 的靶点。miR-29b-3p 通过抑制 GSK-3β 表达和激活促进心肌细胞自噬。结论这些发现表明，Dex 通过调节外泌体介导的巨噬细胞-心肌细胞串扰来减轻脓毒症相关心肌损伤，并且 miR-29b-3p/GSK-3β 信号通路代表了治疗脓毒症心肌损伤的有希望的靶点。