Mesenchymal Stem Cell-Derived Exosomal miR-150-3p Affects Intracerebral Hemorrhage By Regulating TRAF6/NF-κB Axis, Gut Microbiota and Metabolism

Intracerebral hemorrhage (ICH) is a severe subtype of stroke for which there is no effective treatment. Stem cell and exosome (Exo) therapies have great potential as new approaches for neuroprotection and neurorestoration in treating ICH. We aimed to investigate whether Exo affects ICH by regulating the ecology of gut microbiota and metabolism and the mechanisms involved. First, differential miRNAs in ICH were screened by bioinformatics and verified by qRT-PCR. Then, Exo was extracted from mouse bone marrow mesenchymal stem cells (MSCs) and identified. Dual-luciferase reporter gene assay was utilized to verify the binding relationship between miR-150-3p and TRAF6. A mouse ICH model was constructed and treated with Exo. Next, we knocked down miR-150-3p and performed fecal microbiota transplantation (FMT). Then changes in gut microbiota and differential metabolites were detected by 16S rRNA sequencing and metabolomics analysis. We found that miR-150-3p expression was lowest in the brain tissue of the ICH group compared to the Sham group. Besides, low miR-150-3p level in ICH was encapsulated by MSC-derived Exo. Moreover, miR-150-3p bound to TRAF6 and was negatively correlated. With the addition of Exo^{miR-150-3p inhibitor}, we found that MSC-derived exosomal miR-150-3p may affect ICH injury via TRAF6/NLRP3 axis. MSC-derived exosomal miR-150-3p caused changes in gut microbiota, including Proteobacteria, Muribaculaceae, Lachnospiraceae_NK4A136_group, and Acinetobacter. Moreover, MSC-derived exosomal miR-150-3p caused changes in metabolism. After further FMT, gut microbiota-mediated MSC-derived Exo affected ICH with reduced apoptosis and reduced levels of inflammatory factors. In conclusion, MSC-derived exosomal miR-150-3p affected ICH by regulating TRAF6/NF-κB axis, gut microbiota and metabolism.

m6A methyltransferase METTL3 participated in sympathetic neural remodeling post-MI via the TRAF6/NF-κB pathway and ROS production

OBJECTIVE

Sudden cardiac death caused by ventricular arrhythmias (VAs) is the main cause of high mortality in patients with myocardial infarction (MI). Sympathetic neural remodeling caused by inflammation after MI is closely associated with the occurrence of VAs. METTL3, the earliest identified m⁶A methyltransferase, is critical in mediating inflammatory responses. Our aim was to investigate whether the m⁶A methyltransferase METTL3 was involved in sympathetic remodeling post-MI and its specific mechanism.

METHODS AND RESULTS

A rat MI model was established via left coronary artery ligation. The expression of METTL3, TRAF6, NOX2, and NF-κB increased at 3 days and remained elevated at 7 days after MI, as determined via Western blotting. METTL3 was primarily present in macrophages, as determined via immunofluorescence. Intramyocardial injection of lentivirus carrying METTL3-shRNA inhibited METTL3 expression in vivo. Methylated immunoprecipitation-qPCR determined the METTL3 knockdown inhibited the m⁶A level of TRAF6 mRNA 3'-UTR. The co-immunoprecipitation experiment proved that METTL3 combines with TRAF6. Western blotting showed that silencing METTL3 inhibited TRAF6 level, NF-κB activation, and ROS production; decreased cytokine release (TNF-α and IL-1β); and downregulated nerve growth factor expression. Finally, METTL3 knockdown reduced sympathetic remodeling after MI, as determined via immunofluorescence assays of tyrosine hydroxylase and growth-associated protein 43. Programmed electrical stimulation, renal sympathetic nerve activity recording, and haemodynamic measurements showed that METTL3 inhibition decreased sympathetic activity and improved cardiac function.

CONCLUSIONS

Downregulation of METTL3 expression attenuated the excessive sympathetic neural remodeling induced by MI, further reducing the incidence of VAs and improving cardiac function. This was partly associated with the inhibition of the TRAF6/NF-κB pathway and ROS production.

Depression of lncRNA MINCR antagonizes LPS-evoked acute injury and inflammatory response via miR-146b-5p and the TRAF6-NFkB signaling

BACKGROUND

Inflammation plays an important role in the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The long non-coding RNA (lncRNA) MINCR is closely related to inflammation injury. This study was performed to explore the protective effects and mechanisms of MINCR in lipopolysaccharide (LPS)-induced lung injury and inflammation.

METHODS

The expression levels of MINCR and miR-146b-5p in lung tissue status were detected by using quantitative real-time polymerase chain reaction (qRT-PCR), hematoxylin and eosin staining, immunohistochemical staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Enzyme-linked immunosorbent assay and Western blotting analysis were used to detect the expression of inflammatory factors such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 in lung tissue. The relationship between MINCR, miR-146b-5p, and TRAF6 was explored using bioinformatics analysis and luciferase assay.

RESULTS

The expression levels of MINCR were increased in a mouse model of LPS-induced ALI and small airway epithelial cells (SAECs). shMINCR resulted in increased cell viability and decreased apoptosis, which protected against LPS-induced cell damage. shMINCR can inhibit the formation of neutrophil extracellular traps, neutrophil numbers, myeloperoxidase activity, and the production of inflammatory cytokines IL-6, IL-1β, and TNF-α induced by LPS. The silencing of miR-146b-5p reversed the effects of MINCR on LPS-induced lung damage. Sh-MINCR decreased the expression levels of TRAF6 and p-P65 in LPS-induced SAECs and lung tissues. Co-transfection of sh-MINCR with miR-146b-5p inhibitor reversed the effect of sh-MINCR on the expression of TRAF6 and p-P65.

CONCLUSIONS

MINCR may induce alveolar epithelial cell injury and inflammation and aggravate the progression of ALI/ARDS through miR-146b-5p and TRAF6/NF-κB pathways, which would provide a promising target for the treatment of ALI/ARDS.