Abstract
IntroductionArticular tissues are capable of producing a range of eicosanoid mediators, each of which has individual biological effects and may be affected by anti-inflammatory treatment. We set out to develop and evaluate a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) approach for the simultaneous analysis of multiple eicosanoid lipid mediators in equine synovial fluid (SF), and to illustrate its use for investigation of the in vivo effects of non-steroidal anti-inflammatory drug (NSAID) treatment.MethodsSynovial fluid samples were obtained from normal joints of 6 adult horses at baseline (0 hr) and at 8, 24 and 168 hours after experimental induction of transient acute synovitis, with horses treated once daily with oral NSAID (meloxicam, 0.6 mg/kg) or placebo. Following solid-phase extraction, SF lipid mediator quantitation was based on liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis, and results were compared between disease states using linear discriminant analysis (LDA) and analysis of variance (ANOVA) with multiple comparisons corrections.ResultsOf a total of 23 mediators targeted, 14 could be reliably identified and quantified in SF samples based on detection of characteristic fragment ions at retention times similar to those of commercial standards. LDA analysis of baseline, 8, 24 and 168 hour synovial fluid samples revealed a separation of these groups into discrete clusters, reflecting dynamic changes in eicosanoid release over the course of synovitis. Prostaglandin (PG) E2 was significantly lower in NSAID vs. placebo treated samples at all time points; PGE1, 11-hydroxyeicosatetraenoic acid (11-HETE) and 13,14-dihydro-15keto PGF2α were reduced at 8 and 24 hours by NSAID treatment; while 15-HETE, 6-keto PGF1α, PGF2α, 13,14-dihydro-15keto PGE2 and thromboxane B2 (TXB2) were reduced at the 8 hour time point only. An interesting pattern was seen for Leukotriene B4 (LTB4), NSAID treatment causing an initial increase at 8 hours, but a significant reduction by 168 hours.ConclusionsThe described method allows a comprehensive analysis of synovial fluid eicosanoid profiles. Eicosanoid release in inflamed joints as well as differences between NSAID treated and placebo treated individuals are not limited to PGE2 or to the early inflammatory phase.
Highlights
Articular tissues are capable of producing a range of eicosanoid mediators, each of which has individual biological effects and may be affected by anti-inflammatory treatment
We describe the application of recently developed high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) mediator lipidomics techniques to the study of eicosanoid release in equine synovial joints
We report the application of a sensitive HPLC-MS/MS technique for the simultaneous detection of more than 20 eicosanoids in synovial fluid (SF)
Summary
Articular tissues are capable of producing a range of eicosanoid mediators, each of which has individual biological effects and may be affected by anti-inflammatory treatment. Lipid mediators of inflammation play an important role in the local inflammatory response associated with inflammatory arthritides as well as orthopedic arthropathies [1]. Of these mediators, the E-series prostaglandins (most notably PGE2) are most noted in arthritis research for their pro-inflammatory and pro-nociceptive actions in synovial joints [2,3]. COX and LOX enzyme activity within the arachidonic acid cascade generates a range of eicosanoid mediators that have widely varying biological actions, including anti-inflammatory and pro-resolving effects [4,5]. In an early study, NSAID (naproxen) treatment tended to reduce PGE2 and TXB2 and 6-keto PGF1a concentration in the SF of human patients with rheumatoid arthritis [8]
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