Effects of the sstr4 agonist J-2156 on neuropeptide release and inflammation

Erika Pintér1, Zsuzsanna Helyes1, József Németh1, Katalin Sándor1, Krisztián Elekes1, Árpád Szabó1, Gábor Pozsgai1, Dániel Keszthelyi1, Mia Engström2, Siegfried Würster2 and János Szolcsányi1. 1Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Pécs. 2Juvantia Pharma Ltd., Turku, Finland

Neuropeptides released from capsaicin-sensitive sensory nerve terminals induce neurogenic inflammation.Tachykinins like substance P (SP) evoke plasma protein extravasation and calcitonin gene-related peptide (CGRP) produce vasodilatation. On the other hand, somatostatin exerts anti-inflammatory and analgesic actions presumably via sst 4 and/or sst 1 receptor subtypes. Since native somatostatin cannot be a potential candidate for therapy due to its short plasma life time and broad range of effects, the aim of the present study was to investigate a high affinity, sstr 4 selective synthetic agonist, J-2156 (Engström et al., 2005) on sensory neuropeptide release in vitro and acute inflammatory processes in vivo in rats and mice.

Experiments were performed on male Wistar rats (250-300g), and m ale Balb/c mice (20-25g). Rats were anaesthesized with sodium-pentobarbitone (Nembutal, 50 mg/kg i.p.). Ketamine (100 mg/kg, i.p.) and xylazine (10 mg/kg, i.m.) anaesthesia was used for mice. Release of SP, CGRP and somatostatin from isolated rat tracheae was evoked by electrical field stimulation and measured with radioimmunoassay. J-2156 was added to the medium at the beginning of each experiment. Mustard oil-induced neurogenic inflammation in the skin of the acutely denervated rat hindpaw was determined by the Evans blue leakage technique and in the mouse ear with a micrometer. In chronically denervated hindpaw dextran-evoked non-neurogenic oedema was measured with plethysmometry and bradykinin-induced plasma extravasation by the Evans blue method. Granulocyte accumulation evoked by IL-1β, carrageenan or zymosan in the murine back skin was determined with a myeloperoxidase (MPO) assay.

J-2156 was injected i.p. 20 min and for examining its duration of action 2h or 6h before the induction of inflammation. In separate groups it was administered orally 30 min before mustard oil. J-2156 (100-2000 nM) concentration-dependently diminished electrically-evoked release of all the three measured neuropeptides, but did not influence their basal outflow. The EC50 values for the inhibition of the release of substance P, CGRP and somatostatin were 650.6 nM, 1.4 m M and 11.0 μM, respectively. J-2156 significantly, but not dose-dependently inhibited both neurogenic and non-neurogenic acute inflammatory processes in the dose range of 1-100 μg/kg. However, it had not significant influence on granulocyte accumulation.

These results suggest that J-2156 acting on sstr4 effectively inhibits both neurogenic and non-neurogenic components of inflammatory processes, therefore it might provide a novel therapeutical target for the treatment of several inflammatory diseases.

Engström, M. et al. (2005) J. Pharm. Exp. Ther. 312, 332-338.

This work supported by Hungarian Research Grants, OTKA T-043467, T-037523, F-046635.