Targeting sphingosine kinase 1 attenuates bleomycin‐induced pulmonary fibrosis

Abstract

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease, wherein transforming growth factor β (TGF-β) and sphingosine-1-phosphate (S1P) contribute to the pathogenesis of fibrosis. However, the in vivo contribution of sphingosine kinase (SphK) in fibrotic processes has not been documented. Microarray analysis of blood mononuclear cells from patients with IPF and SphK1- or SphK2-knockdown mice and SphK inhibitor were used to assess the role of SphKs in fibrogenesis. The expression of SphK1/2 negatively correlated with lung function and survival in patients with IPF. Also, the expression of SphK1 was increased in lung tissues from patients with IPF and bleomycin-challenged mice. Knockdown of SphK1, but not SphK2, increased survival and resistance to pulmonary fibrosis in bleomycin-challenged mice. Administration of SphK inhibitor reduced bleomycin-induced mortality and pulmonary fibrosis in mice. Knockdown of SphK1 or treatment with SphK inhibitor attenuated S1P generation and TGF-β secretion in a bleomycin-induced lung fibrosis mouse model that was accompanied by reduced phosphorylation of Smad2 and MAPKs in lung tissue. In vitro, bleomycin-induced expression of SphK1 in lung fibroblast was found to be TGF-β dependent. Taken together, these data indicate that SphK1 plays a critical role in the pathology of lung fibrosis and is a novel therapeutic target.

Lysophosphatidic Acid Receptor–2 Deficiency Confers Protection against Bleomycin-Induced Lung Injury and Fibrosis in Mice

“…S1P levels are elevated in the BAL fluid of patients with IPF and bleomycin-challenged mice (43). S1P levels are regulated by a synthetic pathway mediated by two isoforms of sphingosine kinases (SphKs), SphK1/2, that phosphorylate sphingosine and generate S1P, and by the catabolic pathways that break down S1P because of the actions of S1P lyase and other lipid phosphatases (28). Our recent study revealed that the expression of SphK1 was increased in lung-tissue samples from patients with IPF and bleomycin-challenged mice (28).…”

“…S1P levels are regulated by a synthetic pathway mediated by two isoforms of sphingosine kinases (SphKs), SphK1/2, that phosphorylate sphingosine and generate S1P, and by the catabolic pathways that break down S1P because of the actions of S1P lyase and other lipid phosphatases (28). Our recent study revealed that the expression of SphK1 was increased in lung-tissue samples from patients with IPF and bleomycin-challenged mice (28). SphK1 is a known effector of the TGF-b-mediated signal transduction and expression of profibrogenic molecules in bleomycin-challenged lung tissue and in human lung fibroblasts (44).…”

“…SphK1 is a known effector of the TGF-b-mediated signal transduction and expression of profibrogenic molecules in bleomycin-challenged lung tissue and in human lung fibroblasts (44). In vivo, SphK1 deficiency or the inhibition of SphK activity protects mice from bleomycin-induced pulmonary fibrosis, and in these mice, S1P levels in lung tissue were reduced and TGF-b signaling was inhibited (28). Previous studies also indicated that the SphK1/ S1P 3 signaling axis plays a role in the TGF-b-induced transdifferentiation of myoblasts to myofibroblasts.…”

“…Hematoxylin and eosin staining, trichrome staining, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assays were performed by the Pathology Core Facility at the University of Illinois at Chicago. Other related assays were described previously (28,29), and detailed methods are described in the online supplement. The experiments reported here were approved by the Animal Care Use Committee of the University of Illinois at Chicago, and conform to the principles outlined by the Animal Welfare Act and the National Institutes of Health guidelines for the care and use of animals in biomedical research.…”

Microbes Are Associated with Host Innate Immune Response in Idiopathic Pulmonary Fibrosis

“…Integrin alpha(v)beta3, commonly expressed in platelets, is involved in Rho GTPases mediated activation of sphingosine-1-phosphate (S1P) endothelial cell chemotaxis (35) and also acts as a receptor for another gene in the set, Von Willebrand Factor. S1P activity has been shown to be involved in the onset of pulmonary fibrosis (36,37). Interestingly, integrin alpha(v)beta6, also linked to pulmonary fibrosis via Rho-mediated signaling (38)(39)(40) is not included in the magenta module.…”