Endothelins induce ETB receptor-mediated mechanical hypernociception in rat hindpaw: roles of cAMP and protein kinase C.

The present study assesses the capacity of endothelins to induce mechanical hypernociception, and characterises the receptors involved and the contribution of cAMP and protein kinases A (PKA) and C (PKC) to this effect. Intraplantar administration of endothelin-1, endothelin-2 or endothelin-3 (3-30 pmol) induced dose- and time-dependent mechanical hypernociception, which was inhibited by BQ-788 (N-cys-2,6-dimethylpiperidinocarbonyl-l-gamma-methylleucyl-d-1-methoxycarboyl-d-norleucine; endothelin ET(B) receptor antagonist), but not BQ-123 (cyclo[d-Trp-d-Asp-Pro-d-Val-Leu]; endothelin ET(A) receptor antagonist; each at 30 pmol). The selective endothelin ET(B) receptor agonist BQ-3020 (N-Ac-Ala(11,15)-endothelin-1 (6-21)) fully mimicked the hypernociceptive effects of the natural endothelins. Treatments with indomethacin, atenolol or dexamethasone did not inhibit endothelin-1-evoked mechanical hypernociception. However, endothelin-1-induced mechanical hypernociception was potentiated by the cAMP phosphodiesterase inhibitor rolipram (4-[3-(cyclopentyloxy)-4-methoxyphenyl]-2-pyrrolidinone) and inhibited by the PKC inhibitors staurosporine and calphostin C, but was unaffected by the PKA inhibitor H89 (N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide). Thus, endothelins, acting through endothelin ET(B) receptors, induce mechanical hypernociception in the rat hindpaw via cAMP formation and activation of the PKC-dependent phosphorylation cascade.

Pharmacological analysis of the neutrophil migration induced by D. rostrata lectin: involvement of cytokines and nitric oxide.

In the present study, we investigated the involvement of resident cell and inflammatory mediators in the neutrophil migration induced by chemotactic activity of a glucose/mannose-specific lectin isolated from Dioclea rostrata seeds (DrosL). Rats were injected i.p. with DrosL (125-1000 microg/cavity), and at 2-96 h thereafter the leukocyte counts in peritoneal fluid were determined. DrosL-induced a dose-dependent neutrophil migration accumulation, which reached maximal response at 24 h after injection and declines thereafter. The carbohydrate ligand nearly abolished the neutrophil influx. Pre-treatment of peritoneal cavities with thioglycolate which increases peritoneal macrophage numbers, enhanced neutrophil migration induced by DrosL by 303%. However, the reduction of peritoneal mast cell numbers by treatment of the cavities with compound 48/80 did not modify DrosL-induced neutrophil migration. The injection into peritoneal cavities of supernatants from macrophage cultures stimulated with DrosL (125, 250 and 500 microg/ml) induced neutrophil migration. In addition, DrosL treatment induced cytokines (TNF-alpha, IL-1beta and CINC-1) and NO release into the peritoneal cavity of rats. Finally, neutrophil chemotaxis assay in vitro showed that the lectin (15 and 31 microg/ml) induced neutrophil chemotaxis by even 180%. In conclusion, neutrophil migration induced by D. rostrata lectin occurs by way of the release of NO and cytokines such as IL-1beta, TNF-alpha and CINC-1.