Icariin improves cardiac function and remodeling via the TGF-β1/Smad signaling pathway in rats following myocardial infarction

Abstract

Background: Postinfarction cardiac remodeling presents a compensatory mechanism aimed at mitigating congestive heart failure. It is distinguished by progressive dilatation and hypertrophy of the ventricular chambers, fibrotic alterations, and prolonged apoptosis of cardiomyocytes. The primary objective of this study was to assess the effects of icariin on myocardial fibrosis and ventricular remodeling in rats subjected to myocardial infarction (MI).

Methods: Male Sprague‒Dawley (SD) rats were subjected to randomization and subsequently divided into distinct groups: the control group, the sham group (undergoing sham operation), the MI group (experiencing ligation of the left anterior descending artery), and the icariin group. Within the icariin group, rats were further categorized into three different dose groups based on the administered icariin dosage: the MI30 group (30 mg/kg/day), the MI60 group (60 mg/kg/day), and the MI120 group (120 mg/kg/day). Cardiac function evaluation was carried out using echocardiography. Histological examinations, including hematoxylin and eosin (HE) staining, Masson staining, and immunohistochemistry studies, were conducted 90 days after the occurrence of MI. Additionally, Western blotting was employed to assess TGF-β1, p-Smad2, and p-Smad3 levels.

Results: The administration of icariin revealed a noteworthy enhancement in cardiac function among rats afflicted with left anterior descending coronary artery (LAD) ligation. In comparison to the icariin groups, the MI group exhibited reduced EF and FS, along with elevated LVEDD and LVESD. Furthermore, the cardiac fibrosis levels in the MI group rats exhibited a considerable increase compared to those in the icariin group. Notably, the levels of Collagen I, Collagen III, MMP2, and MMP9 were significantly higher in the MI group than in the icariin group, with evident distinctions. Moreover, the expression levels of TGF-β, IL-13, p-Smad2, and p-Smad3 were notably upregulated in the MI group compared to the icariin group.

Conclusions: In an experimental rat model of MI, the administration of icariin resulted in the amelioration of both cardiac function and remodeling processes, operating through the intricate TGF-β1/Smad signaling pathway.

Keywords: Icariin; Myocardial fibrosis; Myocardial infarction; TGF-β1/Smad signaling pathway; Ventricular remodeling.

Fig. 1

The echocardiogram results showed a significant improvement in cardiac function in rats after icariin treatment. A M-mode echocardiography was used to capture representative images of SD rats before and after myocardial infarction (MI) in the icariin treatment group, MI group, sham group, and control group. B The left ventricular ejection fraction (EF), left ventricular fractional shortening (FS), left ventricular end-diastolic diameter (LVEDD), and left ventricular end-systolic diameter (LVESD) were subjected to comparative analysis among different MI groups receiving various dosages of icariin at 0, 15, 30, 60, and 90 days after MI. *P < 0.05, **P < 0.01

Fig. 2

Oral administration of icariin attenuated myocardial ischemic injury and diminished the histological lesions. Representative photos of heart sections stained with H&E. A The control group, B The sham group, C The MI group, D The MI 30 group, E The MI 60 group, F The MI 120 group. (magnification, × 40; scale bar, 250 μm, with black arrows pointing to infiltrating immune cells)

Fig. 3

Icariin inhibited myocardial fibrosis. Masson trichrome staining revealed that the icariin group had less fibrous connective tissue than the MI group. A The control group, B The sham group, C The MI group, D The MI 30 group, E The MI 60 group, F The MI 120 group. (magnification, × 40; scale bar, 250 μm. The regions indicated by the black arrows correspond to collagen stained in blue)

Fig. 4

The bar graph depicts the quantitative analysis of TGF-β and IL-13, presented as the means ± SDs. Statistical analysis was performed using one-way analysis of variance (ANOVA) followed by Tukey's multiple comparison test, ****P < 0.0001

Fig. 5

Icariin reduced the levels of collagen I, collagen III, MMP2 and MMP9. Immunohistochemical staining of collagen I (A), collagen III (B), MMP2 (C) and MMP9 (D) in heart sections. (magnification, × 40; scale bar, 250 μm)

Fig. 6

Western blot analysis of TGF‐β, p-Smad2, and p-Smad3. The bar graph shows quantitative analysis of the TGF‐β, p-Smad2, p-Smad3 and β-actin proteins, and the results were normalized to the RAW246.7 group (A–C). TGF‐β, p-Smad2, p-Smad3 and β-actin protein expression in different groups was detected by Western blot (D). The data are shown as the means ± SDs, one-way ANOVA followed by Tukey's multiple comparison test, ****P < 0.0001