Transcriptome-wide identification of altered RNA m6A profiles in cardiac tissue of rats with LPS-induced myocardial injury.

Purpose: Myocardial injury is a common complication in patients with endotoxaemia/sepsis, especially in children. Moreover, it develops through an unclear pathophysiological mechanism, and effective therapies are lacking. Recently, RNA modification, particularly N 6-methyladenosine (m6A) modification, has been found to be involved in various physiological processes and to play important roles in many diseases. However, the role of m6A modification in endotoxaemia/sepsis-induced myocardial injury is still in its infancy. Therefore, we attempted to construct the m6A modification map of myocardial injury in a rat model treated by lipopolysaccharide (LPS) and explore the role of m6A modification in LPS-induced myocardial injury. Method: Myocardial injury adolescent rat model was constructed by intraperitoneal injection of LPS. m6A RNA Methylation Quantification Kit was used to detect overall level of m6A modification in rat cardiac tissue. m6A-specific methylated RNA immunoprecipitation followed by high-throughput sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were conducted to identify the altered m6A-modified genes and differentially expressed genes in cardiac tissue of rats treated by LPS and control rats (6 versus. 6). Bioinformatics was used to analyze the functions of differentially m6A modified genes, differentially expressed genes, and genes with both differential m6A modification and differential expression. qPCR was used to detect expression of m6A modification related enzymes. Result: We found that the overall level of m6A modification in cardiac tissue of the LPS group was up-regulated compared with that of the control group. MeRIP-seq and RNA-seq results showed that genes with differential m6A modification, genes with differential expression and genes with both differential m6A modification and differential expression were closely associated with inflammatory responses and apoptosis. In addition, we found that m6A-related enzymes (Mettl16, Rbm15, Fto, Ythdc2 and Hnrnpg) were differentially expressed in the LPS group versus. the control group. Conclusion: m6A modification is involved in the pathogenesis process of LPS-induced myocardial injury, possibly through the regulation of inflammatory response and apoptosis-related pathways. These results provide valuable information regarding the potential pathogenic mechanisms underlying LPS-induced myocardial injury.

The Trend of ß3-Adrenergic Receptor in the Development of Septic Myocardial Depression: A Lipopolysaccharide-Induced Rat Septic Shock Model.

Septic shock with low cardiac output is very common in children. However, the mechanism underlying myocardial depression is unclear. The role of ß3-AR in the development of myocardial depression in sepsis is unknown. In the present study, we generated an adolescent rat model of hypodynamic septic shock induced by lipopolysaccharide (LPS). Neonatal cardiomyocytes were also treated with LPS to mimic myocardial depression in sepsis, which was confirmed via an in vivo left ventricular hemodynamic study, and measurements of contractility and the Ca2+ transient in isolated adolescent and neonatal cardiomyocytes. After 16 h of LPS treatment, cultured neonatal cardiomyocytes showed a diminished Ca2+ transient amplitude associated with an increase in the ß3-AR level. With the addition of a ß3-AR agonist, the Ca2+ transient in LPS-treated neonatal rat cardiomyocytes gradually decreased over time; such a change was absent in cells treated with nitric oxide synthase (NOS) inhibitors prior to treatment with a ß3-AR agonist. In adolescent rats with septic myocardial depression, cardiac function declined as indicated by decreased MAP, dP/dtmax, and dP/dtmix for 6 h after LPS injection; however, the ß3-AR level first increased 2 h after LPS treatment and then decreased 6 h after LPS treatment in the absence of exogenous catecholamines. The results indicate that, in vitro, at the cellular level ß3-AR may be involved in the development of myocardial depression (Ca2+ transient depression) in sepsis through NOS signaling pathways; however, in vivo, a complicated mechanism for modulating ß3-AR may exist.