The Mechanism Of TRB3 Aggravated Pressure Overload-induced Cardiac Remodeling

Hypertension-induced chronic cardiac ventricular pressure overload leads to changes in myocardial structure and function that are referred to as myocardial remodeling, consisting of cardiomyocyte hypertrophy and cardiac fibrosis. Pathological cardiac hypertrophy is a key risk factor for chronic heart failure (CHF). Cardiac hypertrophy represents an increase in cardiac muscle mass in response to a chronic increase in cardiac workload. It is associated with enhanced contractile function of the heart, increased interstitial fibrosis, cell death and cardiac dysfunction. Tribbles homologue 3 (TRB3) is a pseudokinase that modifies the activation of various intracellular signalling pathways to control fundamental processes extending from mitosis and cell activation to apoptosis and modulation of gene expression. Recent studies found that TRB3 activity participated with the tissue fibrosis, tumor carcinogenesis and cardio-cerebrovascular diseases. Accumulating evidence demonstrated TRB3 gene silencing alleviates diabetic cardiomyopathy in a type 2 diabetic rat model. In this study, enhanced expression of TRB3 was observed both in hypertrophic cardiac cells and infiltrated cells. Therefore, it is important to study the role of TRB3 in cardiac hypertrophy and the signalling components are promising target candidates for drug development. We established an aotric arches constriction(AAC) induced cardiac hypertrophy mouse model to study how TRB3 influence cardiac hypertrophy. The major research results are shown as following:1. TRB3 aggravates pressure overload-induced cardiac remodeling.Here we show that TRB3 levels are increased in AAC-induced hypertrophic mice hearts, whereas mice lacking TRB3 specifically in the heart are resistant to pressure overload induced cardiac hypertrophy. Mice overexpressing TRB3 specifically in the heart can increase the level of cytosolic p53. Consistently, silencing TRB3 expression increase the expression of p53. We also found that TRB3 directly interacts with P53. To map the p53 interaction region, we made a series of deletion mutants of HA-tagged TRB3 that were subjected to immunoprecipitation with P53-DDK. We found that the AN and KDdomains could interact with P53. It is well known that cytosolic p53 impairs autophagic degradation of damaged mitochondria and facilitates mitochondrial dysfunction. However, whether TRB3 can influence mitophagy is unknown. Here we show colocalization between fragmented mitochondria and LC3-labelled autophagosomes is decreased in TRB3 expressing cardiomyocytes. We also found TRB3 inhibits Nix-mediated mitophagy and promotes mitochondrial dysfunction in the mouse heart.2. Treatment of animals with peptides corresponding to a-helix peptide of p62 binding to TRB3 attenuated cardiac hypertrophy.Our previous research indicated TRB3 physically interacted with p62 to interfere with binding of p62 to LC3 and ubiquitinated proteins, resulting in an inhibition of autophagy-dependent ubiquitination degradation. Our lab has established the peptides Pep2-A2, which can disturbe TRB3-p62 conjunction significantly and decrease the expression levels of TRB3 and P62. In this study, we show that the level of IL-6 and IL-17 are increased in AAC induced cardiac hypertrophy, and our study also found that the expression level of TRB3 and P62 are also increased in the infiltrated cells. Treatment with Pep2-A2 exhibits attenuated cardiac hypertrophy and decrease the P62 load in infiltrated cells, which can increase the survival of mice and attenuates cardiac fibrosis in response to chronic pressure overload. Targeting the TRB3/p62 interaction is a therapeutic strategy against cardiac hypertrophy.