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Boron improves cardiac contractility and fibrotic remodeling following myocardial infarction injury

ABSTRACT: Myocardial fibrosis is a major determinant of clinical outcomes in heart failure (HF) patients. It is characterized by the emergence of myofibroblasts and early activation of pro-fibrotic signaling pathways before adverse ventricular remodeling and progression of HF. Boron has been reported in recent years to augment the innate immune system and cell proliferation, which play an important role in the repair and regeneration of the injured tissue. Currently, the effect of boron on cardiac contractility and remodeling is unknown. In this study, we investigated, for the first time, the effect of boron supplementation on cardiac function, myocardial fibrosis, apoptosis and regeneration in a rat model myocardial infarction (MI)-induced HF. MI was induced in animals and borax, a sodium salt of boron, was administered for 7 days, p.o., 21 days post-injury at a dose level of 4 mg/kg body weight. Transthoracic echocardiographic analysis showed a significant improvement in systolic and diastolic functions with boron treatment compared to saline control. In addition, boron administration showed a marked reduction in myocardial fibrosis and apoptosis in the injured hearts, highlighting a protective effect of boron in the ischemic heart. Interestingly, we observed a tenfold increase of nuclei in thin myocardial sections stained positive for the cell cycle marker Ki67 in the MI boron-treated rats compared to saline, indicative of increased cardiomyocyte cell cycle activity in MI hearts, highlighting its potential role in regeneration post-injury. We similarly observed increased Ki67 and BrdU staining in cultured fresh neonatal rat ventricular cardiomyocytes. Collectively, the results show that boron positively impacted MI-induced HF and attenuated cardiac fibrosis and apoptosis, two prominent features of HF. Importantly, boron has the potential to induce cardiomyocyte cell cycle entry and potentially cardiac tissue regeneration after injury. Boron might be beneficial as a supplement in MI and may be a good candidate substance for anti-fibrosis approach.

SUBMITTER: Bouchareb R

PROVIDER: S-EPMC7553911 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Project description:Rationale: The transformation of fibroblasts into activated myofibroblasts is a critical step that results in cardiac fibrosis upon myocardial infarction (MI). Leucine-rich repeat-containing protein-8A (LRRC8A) is a multi-functional protein involved in cell survival, growth, and proliferation, whereas its role in regulating myofibroblast phenotypes and myocardial fibrosis remains unknown. Methods: Conditional myofibroblast-specific Lrrc8a knockout mouse models were established by crossing the Lrrc8a flox/flox mice with the tamoxifen-inducible periostin-Cre transgenic mice. The involvement of LRRC8A in regulating cardiac fibrosis post-MI and myofibroblast phenotypes induced by transforming growth factor-β1 (TGF-β1) was comprehensively evaluated. The mechanisms underlying LRRC8A regulation of myofibroblast phenotypes were determined by RNA sequencing-driven analysis followed by cause-effect experiments. Results: LRRC8A expression was significantly elevated in the fibrotic tissues and the fibroblasts isolated from the post-MI hearts. Compared with the wild-type (WT) littermates, the specific knockout of LRRC8A in myofibroblasts greatly attenuated myofibroblast transformation, fibrotic remodeling, and ventricular dysfunction after MI. Silencing of LRRC8A expression suppressed, whereas overexpression of LRRC8A enhanced, the pro-fibrotic myofibroblast phenotypes in isolated cardiac fibroblasts upon stimulation with TGF-β1. LRRC8A participated in TGF-β1-induced myofibroblast transformation via activating JAK2-STAT3 signaling. Furthermore, LRRC8A activated the JAK2-STAT3 pathway via its C-terminal leucine-rich repeat-domain (LRRD), directly interacting with growth factor receptor-bound protein 2 (GRB2), an adaptor protein associated with and necessary for tyrosine-phosphorylated JAK2. Conclusions: LRRC8A regulates myofibroblast transformation and cardiac fibrosis following MI. LRRC8A inhibition might be a promising strategy for cardiac fibrosis and heart failure.

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Boron improves cardiac contractility and fibrotic remodeling following myocardial infarction injury

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