The cannabinoid receptor-2 is involved in allergic inflammation.

Abstract

AIM: To investigate the role of cannabinoid receptor-2 (CB2) in allergic inflammation in CB2 knockout (CB2-KO) mice. MAIN METHODS: The swelling reaction of the pinna to various stimuli was compared between CB2-KO and wild-type (WT) mice in terms of edema and acanthosis. KEY FINDINGS: Ear swelling induced by repeated application of 2,4-dinitrofluorobenzene in CB2-KO mice was significantly decreased compared with that in WT mice. In an ovalbumin model, pinna edema was significantly suppressed in CB2-KO mice in comparison with that in WT mice. The contribution of CB2 to edema was investigated in a more extreme dermatitis model using oxazolone. Delayed-type hypersensitivity reactions in this model were also suppressed in CB2-KO mice. In each of these three different allergic dermatitis models, there was a significant decrease in edema and acanthosis in CB2-KO mice compared with WT mice. SIGNIFICANCE: These results clearly demonstrate that CB2 and its endogenous ligands participate not only in the acute, edematous phase of allergic dermatitis, but also in the chronic irreversible acanthosis reaction.