The role of arachidonic acid 12-lipoxygenase (ALOX12) in pulmonary fibrosis

Abstract

Background: 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) is a product of arachidonic acid metabolism produce by arachidonic acid 12-lipoxygenase (ALOX12) in human platelets or leukocytes. It was well known that ALOX12 plays an important role in inflammation and oxidation and is involved in development of various human diseases. However, the role of 12(S)-HETE and ALOX12 in the pathogenesis of idiopathic pulmonary fibrosis (IPF) remains unexplored. Therefore, we investigated the role of ALOX12 in IPF in this study.

Methods: The level of 12(S)-HETE was measured in human plasma (healthy control = 40, IPF = 76) by liquid chromatography-mass spectrometry (LC-MS/MS). The function of 12(S)-HETE and ALOX12 were evaluated in transforming growth factor beta-1 (TGF-β1)-stimulated human lung fibroblasts (MRC-5 cell and primary lung fibroblast) using ALOX12 inhibitor or RNA interference (RNAi). The anti-fibrotic effect of ALOX12 inhibitor was assessed through cell migration assay and evaluated in pulmonary fibrosis mice model induced by bleomycin.

Results: The levels of 12(S)-HETE were significantly increased in plasma of IPF patients compared with that of controls. Exposure of human lung fibroblast to 12(S)-HETE increased the expression of collagen Ⅰ and fibronectin in human lung fibroblast. In addition, the levels of ALOX12 were increased in lung tissues of patients with IPF and human lung fibroblasts stimulated by TGF-β1 compared with those of controls. ALOX12 inhibitor and ALOX12 specific siRNA downregulated protein expression of collagenⅠand fibronectin increased by TGF-β1 in human lung fibroblasts. ALOX12 inhibitor also suppressed migration and TGF-β1 induced phosphorylation of Smad2/3 in MRC-5 cells. In bleomycin treated mice, administration of ALOX12 inhibitor decreased levels of hydroxyproline in the lung compared of control mice.

Conclusions: These results suggest that inhibition of ALOX12 may have anti-fibrotic effects on pulmonary fibrosis, suggesting that ALOX12 is implicated as a potential therapeutic target in IPF.