Autotaxin Production of Lysophosphatidic Acid Mediates Allergic Asthmatic Inflammation

Abstract

Rationale: Bioactive lipid mediators, derived from membrane lipid precursors, are released into the airway and airspace where they bind high-affinity cognate receptors and may mediate asthma pathogenesis. Lysophosphatidic acid (LPA), a bioactive lipid mediator generated by the enzymatic activity of extracellular autotaxin (ATX), binds LPA receptors, resulting in an array of biological actions on cell proliferation, migration, survival, differentiation, and motility, and therefore could mediate asthma pathogenesis.Objectives: To define a role for the ATX-LPA pathway in human asthma pathogenesis and a murine model of allergic lung inflammation. Methods: We investigated the profiles of LPA molecular species and the level of ATX exoenzyme in bronchoalveolar lavage fluids of human patients with asthma subjected to subsegmental bronchoprovocation with allergen. We interrogated the role of the ATX-LPA pathway in allergic lung inflammation using a murine allergic asthma model in ATX-LPA pathway-specific genetically modified mice. Measurements and Main Results: Subsegmental bronchoprovocation with allergen in patients with mild asthma resulted in a remarkable increase in bronchoalveolar lavage fluid levels of LPA enriched in polyunsaturated 22:5 and 22:6 fatty acids in association with increased concentrations of ATX protein. Using a triple-allergen mouse asthma model, we showed that ATX-overexpressing transgenic mice had a more severe asthmatic phenotype, whereas blocking ATX activity and knockdown of the LPA 2 receptor in mice produced a marked attenuation of Th2 cytokines and allergic lung inflammation. Conclusions: The ATX-LPA pathway plays a critical role in the pathogenesis of asthma. These preclinical data indicate that targeting the ATX-LPA pathway could be an effective antiasthma treatment strategy.Keywords: asthma; lysophosphatidic acid; autotaxin; allergic airway inflammation supplied the ATX inhibitor, GWJ-23. V.A., E.K., and I.N. were involved in discussions related to animal dosage. A.J.M. and S.S.S. provided breeding pairs of ATX-Tg and ATX 1/2 mice. S.J.A. managed the inflammatory cell purification core lab for the SBP-AG protocol, designed experiments, interpreted data, coordinated regular scientific research meetings for the project, and edited the manuscript. V.N. conceptualized the study, designed mouse experiments, interpreted data, provided genetically modified mice, and wrote part of and edited the manuscript. J.W.C. obtained the SBP-AG IRB and IND approval, supervised mouse experiments and performance of the human SBP-AG protocol, designed experiments, interpreted and analyzed data, and edited the manuscript. All authors contributed to data discussion and review of the manuscript.Correspondence and requests for reprints should be addressed to John W. What This Study Adds to the FieldThe enzyme autotaxin (ATX) and two of its LPA products, LPA 22:5 and LPA 22:6, are markedly and selectively increased in the bronchoalveolar lavage fluid of human patients with asthma in response to airway allergen ch...

Challenges in accurate quantitation of lysophosphatidic acids in human biofluids

“…between laboratories. BALF LPA levels reported to date have been measured by LC/MS and range from approximately 0.5 to <1000 nM in human BALF (following allergen challenge) and approximately 5-20 nM in human BALF from healthy or IPF patients ( 3,18,19 ).…”

“…Chemical conversion of lysophospholipid such as LPC to LPA can also occur in the presence of strong acid ( 26 ). The most commonly reported sample preparation method for LPA extraction from biological fl uids involves LLE with acidification ( 3,12,14,15,18,19,(27)(28)(29). Scherer et al showed that under strong acidic conditions, LPC degrades to LPA in the presence of plasma, and the total LPA concentration in human plasma was almost 10-fold higher in plasma extracted under acidic conditions versus plasma extracted polypropylene microcentrifuge tube) was spiked with 10 µl of internal standard (IS) (C17:0-LPA) working solution (in methanol) followed by 200 ul of extraction buffer (30 mM citrate/40 mM sodium phosphate in water) and 600 µl of butanol.…”

Autotaxin signaling, purinergic receptors and lung damage

“…embryogenesis and basic cell functions including growth, migration, DNA repair etc. Several studies indicate a role for the ATX-LPA axis in inflammatory conditions of the lung such as asthma [2] and idiopathic lung fibrosis [3] , but also in wound healing [4] , rheumatoid arthritis [5,6] and in linking inflammation and carcinogenesis in e.g. mammary cancer [7] .…”

“…Of these eight chemicals, TDI is so far the only one that we have studied in some detail, but the potency of TDI to induce ATX is now a stimulus for further investigations. In particular lung toxicants should be of interest as ATX might be a sensitive target in bronchial cells, and as mentioned above, ATX also has a role in allergic asthma and in idiopathic lung fibrosis [2,3] . In earlier studies ATX has been implicated in lung fibrosis induced by bleomycin, a cancer drug with serious fibrotic side effects in the lung [22] .…”

Update in Asthma 2013

“…In comprehensive studies in murine and human cells, Li and colleagues identified cyclooxygenase-2-induced prostaglandin D 2 and prostaglandin E 2 as negative regulators of Th9 development and identified potential negative effects of cyclooxygenase-2 inhibitors in allergic diseases (45). Lysophosphatidic acid (LPA), a biologically active lipid, and autotaxin, the enzyme that generates it, were both elevated in the airways of allergen-challenged subjects with asthma (46). Deficiency of LPA and autotaxin attenuated the development of allergic airway inflammation, and thus these studies show proinflammatory functions of LPA and autotaxin in allergic asthma.…”