AB0095 Investigating The Role of Transient Receptor Potential Canonical 5 (TRPC5) in Complete Freund's Adjuvant (CFA)-Induced Arthritis
Authors: K. Alawi, F.A. Russell, A.A. Aubdool, Y. Riffo-Vasquez, L. Baldissera, P. Thakore, E.S. Fernandes, S.D. Brain
Journal: Annals of the Rheumatic Diseases (2016)

<h3>Background</h3> Rheumatoid arthritis (RA) is a chronic autoimmune disease characterised by inflammation of diarthrodial joints. Sensory neurons expressing transient receptor potential (TRP) channels, a wide family of non-selective cation channels, have been shown to play a role in the pathogenesis of RA<sup>1</sup>. Transient receptor potential 5 (TRPC5) is a member of the canonical family of TRPC channels and is abundantly expressed in the central nervous system and periphery<sup>2</sup>, including CD55<sup>+</sup> fibroblast-like synoviocytes<sup>3</sup>, but the role of TRPC5 in arthritis is unknown. <h3>Objectives</h3> To evaluate the for the first time, the contribution of TRPC5 in an <i>in vivo</i> model of arthritis and investigate the role of TRPC5 in the modulation of hyperalgesia and joint inflammation. <h3>Methods</h3> All experiments were conducted under the guidelines of the United Kingdom Home Office Animals (Scientific Procedures) Act 1986. Age-matched, male 129S1/SvImJ wildtype (WT) and TRPC5 knockout (KO) mice littermates bred from heterozygotic mice provided by Prof. D.E. Clapham, USA<sup>2</sup>. Induction of arthritis using CFA was performed as previously described<sup>1</sup>; inflammation was allowed to progress to 14 days. Nociceptive tests were carried out weekly. Synovial blood flow was assessed in anaesthetised WT and TRPC5 KO mice using a full-field laser perfusion imager (FLPI)<sup>4</sup> on day 14. <i>Ex vivo</i> analysis included assessment of cellular infiltration in the knee joint, and determination of cytokine concentrations. In separate studies, WT and TRPC5 KO mice received the TRPC4/5 antagonist, ML204<sup>5</sup>(2mg/kg, <i>i.p</i>., n=6) or vehicle (2% DMSO in saline, n=4) daily following <i>i.art</i>. injection of CFA. Results are presented as mean ± s.e.m. and analysed by 2-way ANOVA and Bonferonni <i>post hoc</i> test. <h3>Results</h3> WT mice developed primary hyperalgesia with a significant reduction in withdrawal threshold compared to baseline responses (334.7±25.7 vs 452.2±8.2 gram force (gf); p&lt;0.01]). Primary hyperalgesia was exacerbated in TRPC5 KO mice compared to WT mice on day 14 (267.4±34.2 vs 334.7±25.4gf; p&lt;0.05]). This was associated with similar deficits in weight-bearing on the ipsilateral hind-limb which was significantly reduced compared to WT mice. Ipsilateral synovial blood flow was significantly increased in TRPC5 KO mice compared to the contralateral synovium (291.3±50.2 vs 198.2±21.4 flux units (AU); p&lt;0.01), and WT ipsilateral synovium (p&lt;0.001). Pharmacological antagonism of TRPC5 in WT mice corroborated the results observed in TRPC5 KO mice, where hyperalgesia and joint inflammation was significantly exacerbated compared to vehicle treated WT mice. <h3>Conclusions</h3> Our results reveal a protective ability of TRPC5 in inflammatory joint conditions <i>in vivo</i>. Genetic deletion or pharmacological antagonism of TRPC5 resulted in an exacerbated inflammatory response highlighted by heightened nociceptive responses, increased cellular infiltration and cytokine concentrations in the knee joint. <h3>References</h3> Fernandes, E.S., et al. 2011. Arthritis Rheum 63, 819–829. Riccio, A., et al. 2009. Cell 137, 761–772. Xu, S.Z., et al. 2008. Nature 451, 69–72 Fernandes, E.S., et al. 2016. Arthritis Res Ther 18(1), 7 Miller, M., et al. 2011. J Biol Chem 286, 33436–46. <h3>Acknowledgement</h3> Supported by Arthritis Research UK. <h3>Disclosure of Interest</h3> None declared