TCH-165 attenuates cardiac ischaemia/reperfusion injury by balancing mitochondrial dynamics via increasing proteasome activity

Abstract

The proteasome is the main complex responsible for maintaining intracellular protein homeostasis, impairment of which is associated with cardiac ischaemia/reperfusion (I/R) injury. The small molecule TCH-165 has been found to activate the 20S proteasome to remove disordered proteins in multiple myeloma and glioblastoma. However, the preventive effect of TCH-165 against I/R-mediated cardiac impairment in mice remains largely unknown. Here, a cardiac I/R model was established in mice. Heart function was assessed with echocardiography. Cardiac infarction, myocyte death, and superoxide level were evaluated by 2,3,5-triphenyltetrazolium chloride (TTC)-Evans blue staining, terminal deoxynucleotidyl transferase-mediated dUTP nick and labelling (TUNEL) assay and immunostaining, respectively. Our results showed that TCH-165 treatment markedly ameliorated I/R-mediated cardiac dysfunction and decreased the infarct size, apoptosis, and superoxide levels. Mechanistically, TCH-165 increased immunoproteasome subunit expression/activity, increasing pro-fission protein dynamin-1-like protein (DNM1L, also known as DRP1) degradation and the expression of the pro-fusion proteins mitofusin 1/2 (Mfn1/2) and thereby leading to mitochondrial fission/fusion balance. In vitro experiments confirmed that inhibition of proteasome activity by epoxomicin abolished the protective effect of TCH-165 against hypoxia/reoxygenation (H/R)-induced increases in cardiomyocyte apoptosis, superoxide production and mitochondrial fission. In summary, TCH-165 is a newly discovered inducer of immunoproteasome activity that exerts a preventive effect against cardiac I/R damage by targeting Drp1 degradation, indicating that it may be as a potential therapeutic candidate for ischaemic heart disease.