Journal
BRITISH JOURNAL OF PHARMACOLOGY
Volume 167, Issue 8, Pages 1665-1678Publisher
WILEY
DOI: 10.1111/j.1476-5381.2012.02120.x
Keywords
PAR2; joint pain; inflammation; leukocyte accumulation
Categories
Funding
- Canadian Institutes for Health Research
- Canadian Foundation for Innovation (CFI)
- Alberta Science and Research Authority
- Alberta Heritage Foundation for Medical Research (AHFMR)
- Arthritis Society of Canada
- AHFMR
- Canadian Arthritis Network
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Background and Purpose The PAR2 receptors are involved in chronic arthritis by mechanisms that are as yet unclear. Here, we examined PAR2 activation in the rat knee joint. Experimental Approach PAR2 in rat knee joint dorsal root ganglia (DRG) cells at L3-L5, retrogradely labelled with Fluoro-gold (FG) were demonstrated immunohistochemically. Electrophysiological recordings from knee joint nerve fibres in urethane anaesthetized Wistar rats assessed the effects of stimulating joint PAR2 with its activating peptide, 2-furoyl-LIGRLO-NH2 (1100?nmol center dot 100?mu L-1, via close intra-arterial injection). Fibre firing rate was recorded during joint rotations before and 15?min after administration of PAR2 activating peptide or control peptide. Leukocyte kinetics in the synovial vasculature upon PAR2 activation were followed by intravital microscopy for 60?min after perfusion of 2-furoyl-LIGRLO-NH2 or control peptide. Roles for transient receptor potential vanilloid-1 (TRPV1) or neurokinin-1 (NK1) receptors in the PAR2 responses were assessed using the selective antagonists, SB366791 and RP67580 respectively. Key Results PAR2 were expressed in 59 +/- 5% of FG-positive DRG cells; 100?nmol 2-furoyl-LIGRLO-NH2 increased joint fibre firing rate during normal and noxious rotation, maximal at 3?min (normal; 110 +/- 43%, noxious; 90 +/- 31%). 2-Furoyl-LIGRLO-NH2 also significantly increased leukocyte rolling and adhesion over 60?min. All these effects were blocked by pre-treatment with SB366791 and RP67580 (P < 0.05 compared with 2-furoyl-LIGRLO-NH2 alone). Conclusions and Implications PAR2 receptors play an acute inflammatory role in the knee joint via TRPV1- and NK1-dependent mechanisms involving both PAR2-mediated neuronal sensitization and leukocyte trafficking.
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