Yoshifumi Ueda

Different role of IL‐4 in the onset of hapten‐induced contact hypersensitivity in BALB/c and C57BL/6 mice

To study the role of interleukin (IL)‐4 in the onset of contact hypersensitivity (CH) in mice, the effect of IL‐4 gene‐depletion and anti‐IL‐4 monoclonal antibody treatment on dinitrofluorobenzene (DNFB)‐induced CH was examined. Simultaneously, to clarify the effect of background gene, DNFB‐induced CH in BALB/c and C57BL/6 mice was compared. Five repeated topical applications of DNFB to the ears of mice resulted in CH of the ears in terms of increases in ear thickness and histopathological changes. The magnitude of ear thickness increase in BALB/c mice was almost three times greater than that in C57BL/6 mice. The CH in BALB/c mice was significantly suppressed by IL‐4 gene‐depletion and anti‐IL‐4 monoclonal antibody treatment. In contrast, the symptoms of dermatitis in C57BL/6 mice were slightly affected by the same treatment. These changes corresponded well to the production of specific IgE antibody. Total IgE antibody production and the expression of productive Cε mRNA were dramatically suppressed by IL‐4 gene‐depletion and anti‐IL‐4 treatment in BALB/c and C57BL/6 mice. Neither total IgG nor IgM levels in either strain of mice was altered by depletion of IL‐4. The expression of IFN‐γ in the skin lesion was dramatically suppressed by IL‐4 gene‐depletion in BALB/c mice, but not in C57BL/6 mice. These findings indicate that IL‐4 plays an important role in the onset of DNFB‐induced CH in BALB/c mice, but not in C57BL/6 mice.

Involvement of the Endogenous Cannabinoid 2 Ligand 2-Arachidonyl Glycerol in Allergic Inflammation

Background: Cannabinoid (CB) 2 is expressed on immune and inflammatory cells. Identification of 2-arachidonyl glycerol (2-AG) and anandamide as endogenous CB2 ligands has allowed investigations of the roles of CB2 and its endogenous ligand system in inflammatory cells. However, the roles of this receptor-ligand system in inflammatory and allergic immune responses in vivo have not been fully elucidated. Methods: Two mouse allergy models, namely ear dermatitis induced by 2,4-dinitrofluorobenzene and allergic bronchitis induced by ovalbumin, were analyzed for 2-AG amounts in allergic tissues, with reference to allergic and inflammatory symptoms. To investigate the gene expression via CB2 in inflammatory cells, human promyelocytic HL-60 cells were stimulated by the CB2 ligand 2-AG ether and analyzed using a DNA microarray. Results: In the ear dermatitis model, the 2-AG amount increased upon serial 2,4-dinitrofluorobenzene challenges and was correlated with ear weight gain. The increased ear thickness in this allergy model was clearly suppressed in CB2 knockout mice, suggesting that the generated endogenous CB2 ligands induce ear thickness through aberrant inflammatory responses and remodeling mediated via CB2. In the allergic bronchitis model, the 2-AG level in bronchoalveolar lavage was increased and sustained during the elevation of inflammatory cell infiltration. The DNA microarray analysis of human HL-60 cells revealed that 2-AG ether induced expressions of not only inflammatory chemokines/cytokines but also of cell growth factors. Conclusion: Our data strongly suggest that endogenous CB2 ligands upregulated upon disease progression in allergic models are involved in aberrant alterations of both inflammatory responses and tissue cell growth.

Possible Role of Nitric Oxide in IgE-Mediated Allergic Cutaneous Reaction in Mice

The role of nitric oxide (NO) in the development of allergic cutaneous reactions in mice was investigated. A biphasic cutaneous reaction composed of an immediate-phase edema and a late-phase edema was evoked by epicutaneous application of 2,4-dinitrofluorobenzene on the ear of mice passively sensitized with mouse anti-dinitrophenol monoclonal IgE. Two NO synthase inhibitors, L-NG-nitroarginine methyl ester (L-NAME) and NG-monomethyl-L-arginine, significantly inhibited both phases of the IgE-mediated biphasic cutaneous reaction. Simultaneous treatment with L-arginine attenuated the inhibitory effect of L-NAME. An NO donor, 3-morpholinosydononimine-N-ethylcarbamide, caused a potent edematous reaction in the mouse ear. Furthermore, L-NAME inhibited the cutaneous reactions caused by both interleukin-1β and tumor necrosis factor-α, putative mediators of the late-phase edema in the biphasic cutaneous reaction. These results indicate that a gaseous mediator, NO, participates, at least in part, in the development of ear edema in the IgE-mediated biphasic cutaneous reaction in mice.

The cannabinoid receptor-2 is involved in allergic inflammation

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.