Berberine up‐regulates miR‐340‐5p to protect myocardial ischaemia/reperfusion from HMGB1‐mediated inflammatory injury

AIMS: Myocardial ischaemia/reperfusion injury (MIRI) is a major cause of heart failure after myocardial infarction. Berberine (BBR) presents anti‐inflammatory and immunosuppressive properties in many diseases. Our research looked into the therapeutic effects and mechanism of BBR in MIRI. METHODS AND RESULTS: MIRI animal and cell models were established. The mRNA and protein expressions were assessed using reverse transcription and quantitative real‐time polymerase chain reaction and western blot. The haemodynamic parameters (left ventricular ejection fraction and left ventricular ejection fraction) were detected by echocardiography. The myocardial infarct size and myocardium lesion were assessed by triphenyltetrazolium chloride and haematoxylin–eosin staining. The levels of injury factors were determined by ELISA. Terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labelling staining was performed to analyse cell apoptosis. Dual luciferase reporter gene and RNA immunoprecipitation assays were carried out to verify the interaction between miR‐340‐5p and HMGB1. BBR administration could improve the haemodynamic parameters and infarct size in MIRI rats (all P < 0.05). In MIRI rat model, BBR reduced cardiomyocyte apoptosis and inflammation (all P < 0.05). BBR could promote miR‐340‐5p expression (0.64 ± 0.21, P < 0.05), which is lowly expressed in MIRI group (0.24 ± 0.10, P < 0.01) in compare with the sham group (0.99 ± 0.01). MiR‐340‐5p knockdown abolished the protective effects of BBR on H/R‐treated cardiomyocytes (all P < 0.05). BBR suppressed the HMGB1/TLR4/NF‐κB pathway activation in MIRI. HMGB1 functioned as the target of miR‐340‐5p, and its silencing reversed the effect of miR‐340‐5p inhibitor on BBR‐treated MIRI. CONCLUSIONS: In MIRI, BBR repressed HMGB1‐mediated TLR4/NF‐κB signalling pathway through miR‐340‐5p to suppress cardiomyocyte apoptosis and inflammation.