N-acetyl-seryl-aspartyl-lysyl-proline prevents cardiac remodeling and dysfunction induced by galectin-3, a mammalian adhesion/growth-regulatory lectin

Abstract

Galectin-3 (Gal-3) is secreted by activated macrophages. In hypertension, Gal-3 is a marker for hypertrophic hearts prone to develop heart failure. Gal-3 infused in pericardial sac leads to cardiac inflammation, remodeling, and dysfunction. N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), a naturally occurring tetrapeptide, prevents and reverses inflammation and collagen deposition in the heart in hypertension and heart failure postmyocardial infarction. In the present study, we hypothesize that Ac-SDKP prevents Gal-3-induced cardiac inflammation, remodeling, and dysfunction, and these effects are mediated by the transforming growth factor (TGF)-beta/Smad3 signaling pathway. Adult male rats were divided into four groups and received the following intrapericardial infusion for 4 wk: 1) vehicle (saline, n = 8); 2) Ac-SDKP (800 microg x kg(-1) x day(-1), n = 8); 3) Gal-3 (12 microg/day, n = 7); and 4) Ac-SDKP + Gal-3 (n = 7). Left ventricular ejection fraction, cardiac output, and transmitral velocity were measured by echocardiography; inflammatory cell infiltration, cardiomyocyte hypertrophy, and collagen deposition in the heart by histological and immunohistochemical staining; and TGF-beta expression and Smad3 phosphorylation by Western blot. We found that, in the left ventricle, Gal-3 1) enhanced macrophage and mast cell infiltration, increased cardiac interstitial and perivascular fibrosis, and causes cardiac hypertrophy; 2) increased TGF-beta expression and Smad3 phosphorylation; and 3) decreased negative change in pressure over time response to isoproterenol challenge, ratio of early left ventricular filling phase to atrial contraction phase, and left ventricular ejection fraction. Ac-SDKP partially or completely prevented these effects. We conclude that Ac-SDKP prevents Gal-3-induced cardiac inflammation, fibrosis, hypertrophy, and dysfunction, possibly via inhibition of the TGF-beta/Smad3 signaling pathway.

Fig. 1.

Effect of N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) on myocardial macrophage and mast cell infiltration induced by intrapericardial infusion of galectin-3 (Gal-3). Top left: four panels are representative images showing macrophages (brown color with immunohistochemical staining, ×400; black bar = 100 μm). Bottom left: four panels are representative images showing mast cell infiltration (dark blue with toluidine blue staining, ×400; black bar = 100 μm) in the myocardium 4 wk after treatment with vehicle, Ac-SDKP, Gal-3, or Gal-3 + Ac-SDKP. Right: quantitative results of myocardial macrophage (top) and mast cell density (bottom) in 4 treatment groups. *P < 0.05. **P < 0.01.

Fig. 2.

Effect of Ac-SDKP on myocardial interstitial collagen fraction (ICF) and perivascular fibrosis (PVF) induced by intrapericardial infusion of Gal-3. Left: representative images of ICF and PVF following vehicle, Ac-SDKP, Gal-3, or Gal-3 + Ac-SDKP infusion (Picrosirius red staining, ×400, black bar = 100 μm). Right: quantitative results of ICF and PVF in the 4 groups. **P < 0.01. ***P < 0.001.

Fig. 3.

Effect of Ac-SDKP on cardiomyocyte hypertrophy induced by intrapericardial infusion of Gal-3. Solid bars represent myocyte cross-sectional area of epicardial myocardium (Epi); open bars represent myocyte cross-sectional area of endocardial myocardium (Endo). *P < 0.05. ***P < 0.001.

Fig. 4.

Effect of Ac-SDKP on myocardial transforming growth factor (TGF)-β expression and Smad3 phosphorylation (p-Smad3) induced by intrapericardial infusion of Gal-3. TGF-β expression (left) and p-Smad3 (right) in the left ventricle were detected by Western blot, showing bands of the typical homodimer (TGF-β: 25 kDa; Smad3: 52 kDa) (top) and quantitative analysis (bottom). *P < 0.05. **P < 0.01. ⁺P = 0.052.

Fig. 5.

Effect of Ac-SDKP on Gal-3 induced reduction of minimum rate of left ventricular change in pressure over time (dP/dt min) (−dP/dt) response to isoproterenol (impairment of left ventricular relaxation). *P < 0.05.

Fig. 6.

Effect of Ac-SDKP on Gal-3-induced diastolic dysfunction measured by transmitral Doppler velocity ratio of early left ventricular filling phase to atrial contraction phase (E/A ratio). Right: representative images showing mitral Doppler velocity E/A ratio following vehicle, Ac-SDKP, Gal-3, or Gal-3 + Ac-SDKP treatment. Left: quantitative results of E/A ratio in each group. **P < 0.01. ***P < 0.001.

Fig. 7.

Effect of Ac-SDKP on left ventricular ejection fraction (LVEF; left) and cardiac output (CO; right) in Gal-3-induced cardiac dysfunction. *P < 0.05. **P < 0.01. ***P < 0.001.