Glycosphingolipids modulate TGF-β fibrotic signaling in human lung fibroblasts

Background: In Idiopathic pulmonary fibrosis (IPF), fibroblasts are recruited to the wounded area and exhibit a fibroproliferative phenotype. Tumor growth factor-beta-1 (TGF-beta) could play a role in mediating this process. TGFbeta1 receptors may cooperate with integrins and lipid rafts from cellular membrane micro-domains. We have investigated the role of PDMP (D-threo-1-Phenyl-2-decanoylamino-3- morpholino-1-propanol-HCl.), a glycosphingo-lipid inhibitor, as a potential modulator of TGF-beta signaling in human lung fibroblasts. Methods: MRC-5 cultures (human lung fibroblast cell line) were stimulated with TGF-beta1 (5ng/ml) in the presence or absence of PDMP. Generation of fibronectin and collagen I was measured by real time PCR. We also studied the role of PDMP in abrogating the conversion from epithelial cell to mesenchymal cells in TGF-beta-stimulated rat lung epithelial cells (RLE) measuring alpha smooth muscle actin by rt-PCR. Results: Our results indicate that PDMP treated cells exhibit decreased collagen and fibronectin formation in a human lung fibroblast cell line. We also found that PDMP reduced the expression of alpha smooth muscle in RLE cells as indicative of reduced myofibroblast transformation. Conclusions: We have identified glycosphingolipids as important immuno-mediators in TGF-beta signaling. Disruption of glycosphingolipids with PDMP results in the decrease of extracellular matrix proteins and epithelial mesenchymal transformation, both important processes in IPF.