TGF‑β/Smad3 pathway enhances the cardio‑protection of S1R/SIPR1 in in�vitro ischemia‑reperfusion myocardial cell model

Abstract

Ischemia-reperfusion (IR) injury is usually associated with a high risk of cardiomyocyte death in patients with acute myocardial infarction. Sphingosine 1‑phosphate (S1P) and transforming growth factor (TGF)‑β are thought to be involved in the protection of cardiomyocyte and heart function following IR‑induced injury. However, the possible association of S1P and S1P receptor 1 (S1PR1) with the TGF‑β/Smad3 pathway as the potential protective mechanism has remained to be investigated. In the present study, an in vitro ischemia/reperfusion injury model was established and evaluated by analysis of apoptosis, lactate dehydrogenase (LDH) release and caspase3 activity. The mRNA and protein levels of S1PR1, TGF‑β and Smad3 after treatment with 1 µM S1P alone or combined with 0.4 µM W146 (a specific S1PR1 antagonist) were assessed. The mRNA expression of five S1PRs (S1PR1‑5) and the protein levels of S1PR1 were also assayed following treatment with 1 ng/ml TGF‑β for 0, 4 or 24 h. The mRNA expression of S1PR1 and the levels of S1P were further assessed following exposure to 10 µM SB4 (TGFβR1 inhibitor) plus 1 ng/ml TGF‑β and 2 µM SIS3 (Smad3 inhibitor) plus 1 ng/ml TGF‑β. The results indicated that apoptosis, LDH release and caspase3 activity were all increased in the established IR model. Exogenous S1P increased the mRNA and protein levels of S1PR1, TGF‑β and Smad3, which was abolished by addition of W146. Extraneous TGF‑β resulted in the stimulation of several S1PRs, most prominently of S1PR1, while supplementation with SB4 and SIS3 offset the stimulation by TGF‑β. These results suggested that the TGF‑β/Smad3 pathway was closely associated with S1P/S1PR1 in the protection of myocardial cells from IR injury.