Attenuation of Myocardial Fibrosis Using Molecular Hydrogen by Inhibiting the TGF-β Signaling Pathway in Spontaneous Hypertensive Rats

Abstract

Background: Previous studies have shown that hydrogen can antagonize the fibrosis of various organs. We investigated whether hydrogen-rich saline (HRS) can attenuate myocardial fibrosis in spontaneously hypertensive rats (SHRs) and clarified the mechanisms involved.

Methods: We examined the effect of HRS and pirfenidone (PFD) on myocardial fibrosis in SHR. Systolic blood pressure, left ventricular mass index (LVMI), and heart weight index (HWI) were measured, Masson trichrome staining was performed. We assessed the role of superoxide dismutase (SOD), malondialdehyde (MDA), Alpha-smooth muscle actin (α-SMA), collagen I, collagen III, and tissue inhibitors of metalloproteinases (TIMPs) in myocardium. We detected the concentrations of procollagen type-I C-terminal propeptide (PICP), procollagen type-III N-terminal propeptide (PIIINP), and angiotensin II (Ang II) in rat serum. Furthermore, the relative protein levels of the transforming growth factor beta (TGF-β)/Smad pathway were tested.

Results: We discovered that HRS decreases LVMI (P < 0.05) and HWI (P < 0.05) in vivo. Compared with model group, HRS decreases the level of collagen volume fraction (P < 0.0001), collagen I (P < 0.001), and collagen III (P < 0.001) in myocardium, and Ang II (P < 0.05), PICP (P < 0.001), and PIIINP (P < 0.05) in serum. In addition, HRS downregulates the expression of MDA (P < 0.01), α-SMA (P < 0.05), and TIMPs (P < 0.05), and increased SOD (P < 0.05). Furthermore, HRS downregulated the expression levels of TGF-β1 (P < 0.0001), Smad3 (P < 0.0001), and Smad2/3 (P < 0.001), but had no effect on Smad7 expression (P > 0.05). PFD had similar effect compared with HRS and control group.

Conclusions: HRS reduced oxidative stress and improved myocardial collagen content, which may be related to inhibition of the TGF-β signaling pathway. This suggests that HRS is an effective therapeutic strategy for myocardial fibrosis.

Keywords: blood pressure; hydrogen; hypertension; myocardial fibrosis; oxidative stress; pirfenidone.