Angiotensin II-induced calcium overload affects mitochondrial functions in cardiac hypertrophy by targeting the USP2/MFN2 axis

USP2 Mitigates Reactive Oxygen Species-Induced Mitochondrial Damage via UCP2 Expression in Myoblasts

Ubiquitin-specific protease 2 (USP2) maintains mitochondrial integrity in culture myoblasts. In this study, we investigated the molecular mechanisms underlying the protective role of USP2 in mitochondria. The knockout (KO) of the Usp2 gene or the chemical inhibition of USP2 induced a robust accumulation of mitochondrial reactive oxygen species (ROS), accompanied by defects in mitochondrial membrane potential, in C2C12 myoblasts. ROS removal by N-acetyl-L-cysteine restored the mitochondrial dysfunction induced by USP2 deficiency. Comprehensive RT-qPCR screening and following protein analysis indicated that both the genetic and chemical inhibition of USP2 elicited a decrease in uncoupling protein 2 (UCP2) at mRNA and protein levels. Accordingly, the introduction of a Ucp2-expressing construct effectively recovered the mitochondrial membrane potential, entailing an increment in the intracellular ATP level in Usp2KO C2C12 cells. In contrast, USP2 deficiency also decreased peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) protein in C2C12 cells, while it upregulated Ppargc1a mRNA. Overexpression studies indicated that USP2 potentially stabilizes PGC1α in an isopeptidase-dependent manner. Given that PGC1α is an inducer of UCP2 in C2C12 cells, USP2 might ameliorate mitochondrial ROS by maintaining the PGC1α-UCP2 axis in myoblasts.

Qiangxinyin formula protects against isoproterenol-induced cardiac hypertrophy

Heart failure is a life-threatening cardiovascular disease and characterized by cardiac hypertrophy, inflammation and fibrosis. The traditional Chinese medicine formula Qiangxinyin (QXY) is effective for the treatment of heart failure while the underlying mechanism is not clear. This study aims to identify the active ingredients of QXY and explore its mechanisms protecting against cardiac hypertrophy. We found that QXY significantly protected against isoproterenol (ISO)-induced cardiac hypertrophy and dysfunction in zebrafish. Eight compounds, including benzoylmesaconine (BMA), atractylenolide I (ATL I), icariin (ICA), quercitrin (QUE), psoralen (PRN), kaempferol (KMP), ferulic acid (FA) and protocatechuic acid (PCA) were identified from QXY. PRN, KMP and icaritin (ICT), an active pharmaceutical ingredient of ICA, prevented ISO-induced cardiac hypertrophy and dysfunction in zebrafish. In H9c2 cardiomyocyte treated with ISO, QXY significantly blocked the calcium influx, reduced intracellular lipid peroxidative product MDA, stimulated ATP production and increased mitochondrial membrane potential. QXY also inhibited ISO-induced cardiomyocyte hypertrophy and cytoskeleton reorganization. Mechanistically, QXY enhanced the phosphorylation of Smad family member 2 (SMAD2) and myosin phosphatase target subunit-1 (MYPT1), and suppressed the phosphorylation of myosin light chain (MLC). In conclusion, PRN, KMP and ICA are the main active ingredients of QXY that protect against ISO-induced cardiac hypertrophy and dysfunction largely via the blockage of calcium influx and inhibition of mitochondrial dysfunction as well as cytoskeleton reorganization.

Mycn ameliorates cardiac hypertrophy-induced heart failure in mice by mediating the USP2/JUP/Akt/β-catenin cascade

BACKGROUND

Pathological cardiac hypertrophy is associated with cardiac dysfunction and is a key risk factor for heart failure and even sudden death. This study investigates the function of Mycn in cardiac hypertrophy and explores the interacting molecules.

METHODS

A mouse model of cardiac hypertrophy was induced by isoproterenol (ISO). The cardiac dysfunction was assessed by the heart weight-to-body weight ratio (HW/BW), echocardiography assessment, pathological staining, biomarker detection, and cell apoptosis. Transcriptome alteration in cardiac hypertrophy was analyzed by bioinformatics analysis. Gain- or loss-of-function studies of MYCN proto-oncogene (Mycn), ubiquitin specific peptidase 2 (USP2), and junction plakoglobin (JUP) were performed. The biological functions of Mycn were further examined in ISO-treated cardiomyocytes. The molecular interactions were verified by luciferase assay or immunoprecipitation assays.

RESULTS

Mycn was poorly expressed in ISO-treated mice, and its upregulation reduced HW/BW, cell surface area, oxidative stress, and inflammation while improving cardiac function of mice. It also reduced apoptosis of cardiomyocytes in mice and those in vitro induced by ISO. Mycn bound to the USP2 promoter to activate its transcription. USP2 overexpression exerted similar myocardial protective functions. It stabilized JUP protein by deubiquitination modification, which blocked the Akt/β-catenin pathway. Knockdown of JUP restored phosphorylation of Akt and β-catenin protein level, which negated the protective effects of USP2.

CONCLUSION

This study demonstrates that Mycn activates USP2 transcription, which mediates ubiquitination and protein stabilization of JUP, thus inactivating the Akt/β-catenin axis and alleviating cardiac hypertrophy-induced heart failure.