Topical acetone treatment induces neurogenic oedema on the sensitized mouse ear: an in vivo study using transient receptor potential vanilloid 1 (TRPV1) receptor knockout mice.

OBJECTIVE: The participation of sensory neurons and transient receptor potential vanilloid 1 (TRPV1) receptors in phorbol 12-myristate 13-acetate (PMA)-induced nerve-sensitizing effect was examined. MATERIALS AND METHODS: PMA dissolved in acetone and acetone were applied to the ears of TRPV1 receptor knockout and wild-type mice. Different groups of animals received ibuprofen, anti-interleukin-1 beta (IL-1beta) antibody, resiniferatoxin (RTX) or capsaicin pretreatment. Ear thickness, myeloperoxidase activity and IL-1beta content of the ears were determined. Histological evaluation was performed. RESULTS: PMA exerted potentiating action on contralateral acetone-induced ear oedema, which was inhibited by ibuprofen, topical capsaicin desensitization of the acetone-treated ear as well as by systemic RTX pretreatment. Neither the lack of TRPV1 receptors nor anti-IL-1beta antibody prevented sensitizing effect. CONCLUSIONS: The TRPV1 receptor-independent potentiating action of PMA on contralateral acetone-induced ear oedema is mediated via capsaicin-sensitive afferents and prostanoids are involved. IL-1beta is not essential in this process.

Effects of the somatostatin receptor subtype 4 selective agonist J-2156 on sensory neuropeptide release and inflammatory reactions in rodents.

BACKGROUND AND PURPOSE: Substance P (SP) and calcitonin gene-related peptide (CGRP) released from capsaicin-sensitive sensory nerves induce local neurogenic inflammation; somatostatin exerts systemic anti-inflammatory actions presumably via sst4/sst1 receptors. This study investigates the effects of a high affinity, sst4-selective, synthetic agonist, J-2156, on sensory neuropeptide release in vitro and inflammatory processes in vivo. EXPERIMENTAL APPROACH: Electrically-induced SP, CGRP and somatostatin release from isolated rat tracheae was measured with radioimmunoassay. Mustard oil-induced neurogenic inflammation in rat hindpaw skin was determined by Evans blue leakage and in the mouse ear with micrometry. Dextran-, carrageenan- or bradykinin-induced non-neurogenic inflammation was examined with plethysmometry or Evans blue, respectively. Adjuvant-induced chronic arthritis was assessed by plethysmometry and histological scoring. Granulocyte accumulation was determined with myeloperoxidase assay and IL-1beta with ELISA. KEY RESULTS: J-2156 (10-2000 nM) diminished electrically-evoked neuropeptide release in a concentration-dependent manner. EC50 for the inhibition of substance P, CGRP and somatostatin release were 11.6 nM, 14.3 nM and 110.7 nM, respectively. J-2156 (1-100 microg kg(-1) i.p.) significantly, but not dose-dependently, inhibited neurogenic and non-neurogenic acute inflammatory processes and adjuvant-induced chronic oedema and arthritic changes. Endotoxin-evoked myeloperoxidase activity and IL-1beta production in the lung, but not IL-1beta- or zymosan-induced leukocyte accumulation in the skin were significantly diminished by J-2156. CONCLUSIONS AND IMPLICATIONS: J-2156 acting on sst4 receptors inhibits neuropeptide release, vascular components of acute inflammatory processes, endotoxin-induced granulocyte accumulation and IL-1beta synthesis in the lung and synovial and inflammatory cells in chronic arthritis. Therefore it might be a promising lead for the development of novel anti-inflammatory drugs.