Targeted disruption of the endothelin-B-receptor gene attenuates inflammatory nociception and cutaneous inflammation in mice.

Endothelin-1 (ET-1) has been suggested to have a potential function as an inflammatory mediator. The study reported here assessed the putative inflammatory/nociceptive actions of the ET isopeptides using endothelin-B (ET B )-receptor knockout (KO) mice and ET A . (SB 234551) and ET B - (A192621) selective antagonists. Phenylbenzoquinone (PBQ)-induced algesia was evident in the wild-type (WT) ET B (+/+) mice, attenuated by 80% in the heterozygous ET B (+/-) mice, and absent in the ET B (-/-) homozygotes. This was reproduced pharmacologically in WT ET B (+/+) mice where the algesic effect of PBQ was inhibited 74% by A192621, but unaffected by SB 234551 (both at 25 mg/kg p.o.). Similar observations were made in a model of cutaneous inflammation: ET B (+/+) mice had a marked inflammatory response to topical arachidonic acid, ET B (+/-) and ET B (-/-) mice had significantly reduced edema responses (37% and 65% inhibition). Neutrophil infiltration was reduced in the ET B (+/-) and ET B (-/-) mice (51% and 65% reduction, respectively). Topical administration of A192621 (500 μg/ear) inhibited arachidonic acid-induced swelling (39%) in WT ET B (+/+) mice. Collectively, these results support a role for the ET B -receptor in the mediation of inflammatory pain and cutaneous inflammatory responses. As such, the development of ET B -receptor-selective antagonists may be of therapeutic utility in the treatment of inflammatory disorders.