Sphingosine 1-Phosphate Receptor Modulator Fingolimod (FTY720) Attenuates Myocardial Fibrosis in Post-heterotopic Heart Transplantation

Abstract

Background and Objective: Sphingosine 1-phosphate (S1P), and S1P receptor modulator fingolimod have been suggested to play important cardioprotective role in animal models of myocardial ischemia/reperfusion injuries. To understand the cardioprotective function of S1P and its mechanism in vivo, we analyzed apoptotic, inflammatory biomarkers, and myocardial fibrosis in an in vivo heterotopic rat heart transplantation model.Methods: Heterotopic heart transplantation is performed in 60 Sprague–Dawley (SD) rats (350–400 g). The heart transplant recipients (n = 60) are categorized into Group A (control) and Group B (fingolimod treated 1 mg/kg intravenous). At baseline with 24 h after heart transplantation, blood and myocardial tissue are collected for analysis of myocardial biomarkers, apoptosis, inflammatory markers, oxidative stress, and phosphorylation of Akt/Erk/STAT-3 signaling pathways. Myocardial fibrosis was investigated using Masson’s trichrome staining and L-hydroxyline.Results: Fingolimod treatment activates both Reperfusion Injury Salvage Kinase (RISK) and Survivor Activating Factor Enhancement (SAFE) pathways as evident from activation of anti-apoptotic and anti-inflammatory pathways. Fingolimod treatment caused a reduction in myocardial oxidative stress and hence cardiomyocyte apoptosis resulting in a decrease in myocardial reperfusion injury. Moreover, a significant (p < 0.001) reduction in collagen staining and hydroxyproline content was observed in fingolimod treated animals 30 days after transplantation demonstrating a reduction in cardiac fibrosis.Conclusion: S1P receptor activation with fingolimod activates anti-apoptotic and anti-inflammatory pathways, leading to improved myocardial salvage causing a reduction in cardiac fibrosis.

Cardioprotective mechanism of FTY720 in ischemia reperfusion injury

“…The anti-remodeling effect is also confirmed at the histological level, as demonstrated by reduced collagen deposition in the myocardial interstitium and smaller cardiomyocytes in the fingolimod-treated group [98]. The attenuation of anatomical remodeling is also supported by lower neurohormonal activation, indicated by reduced levels of aldosterone and blood metanephrines.…”

“…S1P on cardiomyocytes binds to the G-protein coupled receptors S1PR1 and S1PR3, leading to the activation of numerous intracellular signal transduction pathways involved in cardioprotective action. S1PR1, in particular, is the main receptor of S1P in cardiomyocytes and typically activates the RISK (reperfusion injury salvage kinase) and SAFE (surviving activating factor enhancement) signal transduction pathways [76], [94], [98]. These pathways mediate the cardioprotective effects of fingolimod.…”

“…To further investigate the drug's role in reducing IRI, a study was carried out by Santos-Gallego et al in a model of myocardial ischemia-reperfusion in pigs, including a short-term protocol (fingolimod administration 15 min before reperfusion in the study group vs saline in controls) and a long-term protocol (fingolimod 15 min before reperfusion vs saline in controls; the same treatment repeated once a day for 3 days) [116]. The fingolimod group showed a significant reduction of cardiomyocyte apoptosis [98] in the periphery of ischemic myocardium, resulting in decreased infarct size as compared to controls. It was quantified by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL).…”

Fingolimod Plays Role in Attenuation of Myocardial Injury Related to Experimental Model of Cardiac Arrest and Extracorporeal Life Support Resuscitation

“…Heart tissue sections of 3 um thickness were placed on slides and heated to 60 • C for 1 h, and then rehydrated using graded concentration ethanol. Antigen retrieval was carried out using appropriate buffer and the procedure explained previously [12]. Endogenous peroxidase activity was blocked by incubation of tissue section, carried out at 4 • C overnight.…”

“…Sphingosine 1-phosphate (S1P) is known to play a role in cellular changes such as differentiation, proliferation, migration, contraction, and survival [6][7][8][9][10][11]. Sphingosine 1-phosphate sphingolipid derivatives are known to have anti-inflammatory, anti-apoptotic, and anti-oxidant activities, and have significant roles in the cardiovascular system [12,13]. Sphingosine 1-phosphate increases the survival of cardiomyocytes during episodes of hypoxia [14].…”