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.

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.

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.

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.

Sepsis-induced myocardial injury (SIMI) is recognized as a severe complication of sepsis which characterized by a high mortality rate. Notably, the pathophysiology of SIMI involves complex mechanisms, including dysregulation of autophagy. Exosomes contribute to crucial biological processes during sepsis, modulating autophagy processes and facilitating communication between cells. PIWI-interacting RNAs (piRNAs) are highly expressed in myocardial tissue and exert cardiovascular regulation properties. Therefore, we investigated the role of macrophage-derived exosome piRNAs, specifically piR-50971, in SIMI and their impact on autophagy through N6-Methyladenosine (m⁶A) modification of mTOR.

A cecal ligation and puncture model was established to mimic the pathophysiological features of SIMI. Plasma exosomes were isolated and sequenced to characterize the expression of sepsis-related piRNAs. Bioinformatics analysis was employed to predict the potential regulatory mechanisms involving piR-50971. To investigate the direct interaction between piR-50971 and mTOR, a dual-luciferase reporter assay was conducted. Moreover, a methylated RNA immunoprecipitation assay was conducted to verify the involvement of piR-50971 in the m⁶A methylation modification of mTOR transcripts. Additionally, the m⁶A methylation level was assessed using dot blotting. Left ventricular ejection fraction and left ventricular fractional shortening of rats were detected by animal echocardiography. Transmission electron microscopy was used to detect autophagy flux in the myocardial tissue of rats in vivo. Cardiac enzymes were detected using a biochemical analyzer.

piR-50971 was identified as a key piRNA upregulated in plasma exosomes during SIMI, which was correlated with the inhibition of autophagy. Increased macrophage infiltration was observed in the myocardium of rats with SIMI. Additionally, cardiomyocytes treated with macrophage-derived exosomes exhibited impaired autophagy. RNA binding protein immunoprecipitation assay demonstrated an interaction between Wilms’ tumor 1-associated protein (WTAP) protein and mTOR mRNA. piR-50971 interacted with mTOR, leading to increased m⁶A modification through the regulation of WTAP and subsequent suppression of autophagy. Notably, this regulation upregulated mTOR translation, thereby inhibiting autophagy and exacerbating myocardial injury under septic conditions. In vivo experiments demonstrated that piR-50971 inhibition ameliorated myocardial injury and improved autophagy in rats with SIMI.

Our findings reveal a novel mechanism by which macrophage-derived exosome piR-50971 contributes to SIMI by suppressing autophagy via m⁶A modification of mTOR. Overall, our results implicate piR-50971 as a potential target for therapeutic intervention in sepsis-related myocardial dysfunction.