The cannabinoid receptor-2 is involved in allergic inflammation

To investigate the role of cannabinoid receptor-2 (CB2) in allergic inflammation in CB2 knockout (CB2-KO) mice.

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.

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.

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.