TGF-ß1/SMAD3 Regulates Programmed Cell Death 5 That Suppresses Cardiac Fibrosis Post-Myocardial Infarction by Inhibiting HDAC3.

BACKGROUND: Progressive cardiac fibrosis leads to ventricular wall stiffness, cardiac dysfunction, and eventually heart failure, but the underlying mechanism remains unexplored. PDCD5 (programmed cell death 5) ubiquitously expresses in tissues, including the heart; however, the role of PDCD5 in cardiac fibrosis is largely unknown. Therefore, this study aims at exploring the possible role and underlying mechanisms of PDCD5 in the pathogenesis of cardiac fibrosis. METHODS AND RESULTS: PDCD5 levels were found to be elevated in the serum obtained from patients with cardiac fibrosis, in fibrotic mice heart tissues after myocardial infarction, and in cardiac fibroblasts stimulated by Ang II (angiotensin II)- or TGF-ß1 (transforming growth factor-ß1). Overexpression of PDCD5 in cardiac fibroblasts or treatment with PDCD5 protein reduced the expression of profibrogenic proteins in response to TGF-ß1 stimulation, while knockdown of PDCD5 increased fibrotic responses. It has been demonstrated that SMAD3, a protein that is also known as mothers against decapentaplegic homolog 3, directly upregulated PDCD5 during cardiac fibrosis. Subsequently, the increased PDCD5 promoted HDAC3 (histone deacetylase 3) ubiquitination, thus, inhibiting HDAC3 to reduce fibrotic responses. Fibroblast-specific knock-in of PDCD5 in mice ameliorated cardiac fibrosis after myocardial infarction and enhanced cardiac function, and these protective effects were eliminated by AAV9-mediated HDAC3 overexpression. CONCLUSIONS: The findings of this study demonstrated that PDCD5 is upregulated by SMAD3 during cardiac fibrosis, which subsequently ameliorated progressive fibrosis and cardiac dysfunction through HDAC3 inhibition. Thus, this study suggests that PDCD5 functions as a negative feedback factor on fibrotic signaling pathways and might serve as a potential therapeutic target to suppress the progression of fibrotic responses.

CMTM3 deficiency induces cardiac hypertrophy by regulating MAPK/ERK signaling.

OBJECTIVES: Cardiac hypertrophy is the heart's compensatory response stimulated by various pathophysiological factors. However, prolonged cardiac hypertrophy poses a significant risk of progression to heart failure, lethal arrhythmias, and even sudden cardiac death. For this reason, it is crucial to effectively prevent the occurrence and development of cardiac hypertrophy. CMTM is a superfamily of human chemotaxis, which is involved in immune response and tumorigenesis. CMTM3 expressed widely in tissues, including the heart, but its cardiac function remains unclear. This research aims to explore the effect and mechanism of CMTM3 in the development of cardiac hypertrophy. METHODS AND RESULTS: We generated a Cmtm3 knockout mouse model (Cmtm3-/-) as the loss-of-function approach. CMTM3 deficiency induced cardiac hypertrophy and further exacerbated hypertrophy and cardiac dysfunction stimulated by Angiotensin Ⅱ infusion. In Ang Ⅱ-infusion stimulated hypertrophic hearts and phenylephrine-induced hypertrophic neonatal cardiomyocytes, CMTM3 expression significantly increased. However, adenovirus-mediated overexpression of CMTM3 inhibited the hypertrophy of rat neonatal cardiomyocytes induced by PE stimulation. In terms of mechanism, RNA-seq data revealed that Cmtm3 knockout-induced cardiac hypertrophy was related to MAPK/ERK activation. In vitro, CMTM3 overexpression significantly inhibited the increased phosphorylation of p38 and ERK induced by PE stimulation. CONCLUSIONS: CMTM3 deficiency induces cardiac hypertrophy and aggravates hypertrophy and impaired cardiac function stimulated by angiotensin Ⅱ infusion. The expression of CMTM3 increases during cardiac hypertrophy, and the increased CMTM3 can inhibit further hypertrophy of cardiomyocytes by inhibiting MAPK signaling. Thus, CMTM3 plays a negative regulatory effect in the occurrence and development of cardiac hypertrophy.