112 Exogenous Dihydrosphingosine 1 Phosphate Mediates Collagen Synthesis in Cardiac Fibroblasts Through PI3K/Akt- mTOR Signalling

Abstract

Cardiac fibrosis is one of the hallmarks of cardiac remodelling in cardiomyopathies such as heart Failure (HF). Dyslipidemia plays a role in the progression of HF. The sphingolipid, dihydrosphingosine 1 phosphate (dhS1P) has been shown to bind to high density lipids in plasma. Unlike its analog, spingosine 1 phosphate (S1P), the role of dhS1P in cardiac fibrosis is not known. The aim of this study is to determine the role dhS1P plays in cardiac fibrosis through the PI3K/Akt- mTOR pathway. Neonatal rat cardiac fibroblasts (NCF) were isolated from 1-2 day old pups with enzymic digestion. After pre-treating with the PI3K inhibitor, Wortmannin (W, 0.1 – 10.0μM), cells were stimulated with dhS1P for 48 hours. NCF collagen synthesis was determined by 3H-proline incorporation. NCF were also treated for protein and gene expression analysis. Exogenous addition of 3 μM dhS1P stimulated significant increase in collagen synthesis (p<0.005) which was dose dependently inhibited by W (p<0.0001, Fig. 1A). Western blot analysis showed that W reduced Akt, mTOR, and S6 activation in the presence of dhS1P. dhS1P also increased protein levels of TGFβ, Coll 1 and TIMP1. W reduced dhS1P elevated TIMP1, and SK1, but not TGFβ1 gene expression (Fig. 1B). Our study demonstrates for the first time that dhS1P can cause cardiac cellular fibrosis via PI3K/Akt- mTOR pathway. Its inhibition may represent a novel therapeutic strategy for cardiac fibrosis.