Abstract
Familial hypertrophic cardiomyopathy (FHCM), an autosomal dominant disease, is caused by mutations in genes encoding cardiac sarcomeric proteins. E22K, a mutation in the myosin regulatory light chain sarcomere gene, is associated with the development of FHCM. However, the molecular mechanisms by which E22K mutation promotes septal hypertrophy are still elusive. The hypertrophic markers, including beta-myosin heavy chain, atrial natriuretic peptide and B-type natriuretic peptide, were upregulated, as detected by fluorescence quantitative PCR. The gene expression profiles were greatly altered in the left ventricle of E22K mutant mice. Among these genes, nuclear factor of activated T cells (NFAT) and protein kinase C-alpha (PKC-α) were upregulated, and their protein expression levels were also verified to be elevated. The fibrosis markers, such as phosphorylated Smad and transforming growth factor beta receptor, were also elevated in transgenic E22K mice. After receiving 6 weeks of procedural exercise training, the expression levels of PKC-α and NFAT were reversed in E22K mouse hearts. In addition, the expression levels of several fibrosis-related genes such as transforming growth factor beta receptor 1, Smad4, and alpha smooth muscle actin in E22K mouse hearts were also reversed. Genes that associated with cardiac remodeling such as myocyte enhancer factor 2C, extracellular matrix protein 2 and fibroblast growth factor 12 were reduced after exercising. Taken together, our results indicate that exercise can improve hypertrophy and fibrosis-related indices in transgenic E22K mice via PKC-α/NFAT pathway, which provide new insight into the prevention and treatment of familial hypertrophic cardiomyopathy.
Highlights
Familial hypertrophic cardiomyopathy (FHCM) is an autosomal dominant genetic disease featured by myofibrillar disarray and left ventricle or septal hypertrophy [1, 2]
Our study showed that E22K mutation resulted in the upregulated gene expression of hypertrophy and fibrosis markers, and the gene and protein levels of Protein kinase C-alpha (PKC-α) and nuclear factor of activated T cells (NFAT) were significantly elevated in E22K mouse myocardium
We elucidated that the elevated expression of PKCα and NFAT in E22K mouse myocardium may be a potential mechanism of E22K-induced hypertrophy
Summary
Familial hypertrophic cardiomyopathy (FHCM) is an autosomal dominant genetic disease featured by myofibrillar disarray and left ventricle or septal hypertrophy [1, 2]. It originates from gene mutations encoding major proteins of myocardial filaments (e.g., myosin) and other related proteins. E22K (glutamic acid to lysine substitution at position 22), a genetic mutation in myosin regulatory light chain (RLC) sarcomeric protein, is located near the Ca2+ binding site and RLC phosphorylation site (Ser15) [3]. The E22K mutation in RLC gene may cause hypertrophic cardiomyopathy with septal hypertrophy and midventricular obstruction [3], and is closely associated with the eventual formation of FHCM. Previous research has shown that E22K mutation prevents RLC phosphorylation and decreases its affinity for Ca2+ binding [3]. Other physiological studies indicated that the Ca2+ activated force and myofibrillar ATPase activity in E22K mice were increased compared to those in wild-type mice [2]
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