Inhibition of Leukotriene A4 Hydrolase Suppressed Cartilage Degradation and Synovial Inflammation in a Mouse Model of Experimental Osteoarthritis

Abstract Chronic inflammation plays an important role in the osteoarthritis (OA) pathology but how this influence OA disease progression is unclear. Leukotrienes (LT) are biologically active lipids that are implicated in various pathological process. Leukotriene B4 (LTB4) is a potent proinflammatory lipid mediator generated from arachidonic acid through the sequential activities of 5-lipoxygenase, 5-lipoxygenase–activating protein, Leukotriene A4 hydrolase (LTA4H) and its downstream product leukotriene B4 (LTB4 or BLT1). The aim of this study is to investigate the involvement of the LTB4 pathway in OA disease progression. Both clinical human samples and mice experimental OA models were used to determine whether LTA4H could serve as a potential therapeutic target for OA. We also determined whether the LTA4H pathway was associated with cartilage degeneration and synovitis inflammation in OA mice models and human articular chondrocytes. We found that both LTA4H and LTB4 receptor BLT1 were highly expressed in human and mice OA cartilage. Inhibition of LTA4H suppressed cartilage degeneration and synovitis in OA mice model. Furthermore, inhibition of LTA4H promoted cartilage regeneration by upregulating chondrogenic genes expression such as aggrecan (ACAN), collagen 2A1 (COL2A1) and SRY-Box transcription factor 9 (SOX9). Our results indicate that the LTA4H pathway is a crucial regulator of OA pathogenesis and suggest that LTA4H could be a therapeutic target in combat OA.