Abstract
Cardiac hypertrophy is caused by cardiac volume or pressure overload conditions and ultimately leads to contractile dysfunction and heart failure. Oxytocin (OT), an endocrine nonapeptide, has been identified as a cardiovascular homeostatic hormone with anti-hypertrophic effects. However, the underlying mechanism remains elusive. In this study, we aimed to investigate the role and mechanism of OT in cardiac hypertrophy. The rats with cardiac hypertrophy induced by isoproterenol (ISO) were treated with or without oxytocin. Cardiac functional parameters were analyzed by echocardiography. The changes in cell surface area were observed using wheat germ agglutinin (WGA) or immunofluorescence staining. The expressions of cardiac hypertrophy markers (B-Natriuretic Peptide, BNP and β-myosin heavy chain, β-MHC), long non-coding RNA Growth (LcRNA) Arrest-Specific transcript 5 (lncRNA GAS5), miR-375-3p, and Kruppel-like factor 4 (Klf4) were detected by qRT-PCR. KLF4 protein and PI3K/AKT pathway related proteins were detected by Western blot. The interactions among lncRNA GAS5, miR-375-3p, and Klf4 were verified by dual-luciferase reporter assays. The findings showed that OT significantly attenuated cardiac hypertrophy, increased expressions of lncRNA GAS5 and KLF4, and decreased miR-375-3p expression. In vitro studies demonstrated that either knock-down of lncRNA GAS5 or Klf4, or over-expression of miR-375-3p blunted the anti-hypertrophic effects of OT. Moreover, down-regulation of lncRNA GAS5 promoted the expression of miR-375-3p and inhibited KLF4 expression. Similarly, over-expression of miR-375-3p decreased the expression of KLF4. Dual-luciferase reporter assays validated that lncRNA GAS5 could sponge miR-375-3p and Klf4 was a direct target gene of miR-375-3p. In addition, OT could inactivate PI3K/AKT pathway. The functional rescue experiments further identified OT regulated PI3K/AKT pathway through lncRNA GAS5/miR-375-3p/KLF4 axis. In summary, our study demonstrates that OT ameliorates cardiac hypertrophy by inhibiting PI3K/AKT pathway via lncRNA GAS5/miR-375-3p/KLF4 axis.
Highlights
The prevalence of heart failure (HF) is increasing at an alarming rate worldwide (Benjamin et al, 2019)
Cardiomyocyte hypertrophy was evaluated by cell surface area and expressions of B-Natriuretic Peptide (BNP) and β-myosin heavy chain (β-MHC), which have been wellestablished as cardiac hypertrophy markers
We observed the expressions of long non-coding RNA (lncRNA) Growth ArrestSpecific transcript 5 (GAS5) (Figure 2E), Klf4 mRNA (Figure 2G) and Kruppel-like factor 4 (KLF4) protein (Figures 2H,K) were down-regulated in ISO group when compared with control group, while up-regulated significantly after OT treatment
Summary
The prevalence of heart failure (HF) is increasing at an alarming rate worldwide (Benjamin et al, 2019). Pathological cardiac hypertrophy is an independent predictor of HF, commonly induced by hypertension, myocardial injury, valvular heart diseases or excessive neurohumoral stimulation. It is characterized by myocardial fibrosis, apoptosis and necrosis, leading to cardiac dysfunction and to heart failure (Azevedo et al, 2016). Dozens of researches have delineated the cardioprotective effects of this endogenous hormone, including alleviation of ischemiareperfusion (I/R) injury (Alizadeh et al, 2010; Gonzalez-Reyes et al, 2015; Polshekan et al, 2019), cardiomyocyte hypertrophy (Menaouar et al, 2014), myocardial infarction (Kobayashi et al, 2009), and diabetic cardiomyopathy (Plante et al, 2015), as well as mitigation of development of atherosclerosis (Wang et al, 2019). The cardioprotective properties of oxytocin make this endogenous hormone of special potential to be a “natural medicine” against cardiovascular diseases. Due to lack of deep knowledge of its molecular mechanism, therapeutic potential of OT in treating cardiovascular disease is largely unexplored
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