Anti-IL-31 receptor antibody is shown to be a potential therapeutic option for treating itch and dermatitis in mice

Abstract

Background and purpose: IL-31, which is described as a pruritogenic cytokine, is linked to the itching that is associated with allergic and non-allergic eczema, but the precise pruritogenic mechanism of IL-31 and its potential as a therapeutic target for atopic dermatitis (AD) have not been determined.

Experimental approach: We investigated the effects of existing drugs on the scratching behaviour induced by an i.v. injection of IL-31 to clarify whether IL-31 induced pruritus indirectly. In addition, we studied the effects of an anti-IL-31 receptor α subunit (anti-IL-31 receptor α) neutralizing antibody on chronic pruritus-inducing dermatitis in an AD-like model to determine whether IL-31 not only induces scratching behaviour, but is also the causative factor in an AD phenotype.

Key results: The scratching behaviour induced by an i.v. injection of IL-31 was inhibited by pretreatment with an anti-IL-31 receptor α-neutralizing antibody. In contrast, it was not inhibited significantly by a non-sedative antihistamine (terfenadine), immunosuppressants (dexamethasone and tacrolimus), or a μ-opioid receptor antagonist (naloxone). The anti-IL-31 receptor α-neutralizing antibody reduced the ear swelling and dermatitis score in a chronic pruritus-inducing AD-like model. Moreover, treatment with the anti-IL-31 receptor α-neutralizing antibody showed therapeutic effects on the dermatitis even if it was injected after the disease had developed.

Conclusions and implications: Anti-IL-31 receptor α is a potential novel therapeutic approach for escaping from the itch-scratch cycle and also a treatment for dermatitis in AD.

Figure 1

Inhibition of IL-31 response by anti-IL-31 receptor α Ab. The neutralizing activity of purified anti-IL-31 receptor α Ab (BM095) was evaluated using Ba/F3 cells transfected with mouse IL-31 receptor α and mouse OSMR genes. Using cell growth as the indicator, % inhibition of responses to 2 ng·mL⁻¹ IL-31 by BM095 was evaluated (mean ± SD).

Figure 2

Scratching behaviour induced in BALB/c mice by IL-31. (A) Mice were i.v. injected with 10 μg IL-31 or vehicle after treatment with 300 mg·kg⁻¹ control Ab or BM095. Scratching behaviour was recorded and analysed for 12 h after the injection, and the number of scratching bouts in each hour was counted. Each point represents the mean ± SEM of seven to eight mice. *P < 0.05, **P < 0.01 versus the vehicle group at the corresponding time point. (B) Scratching bouts were counted for 12 h in mice injected with IL-31 (black column) or vehicle (open column) after treatment with control Ab or BM095 (grey column). Each column represents the mean ± SEM of seven to eight mice. *P < 0.05, **P < 0.01 versus the non-agent group (control Ab/IL-31).

Figure 3

Effects of antihistamine, dexamethasone (DEX), tacrolimus (TAC) and naloxone (NAL) on the scratching behaviour induced by IL-31. Terfenadine (TER) at 30 mg·kg⁻¹, DEX at 3 mg·kg⁻¹ and TAC at 0.1 mg·kg⁻¹ were injected i.p., and NAL at 10 mg·kg⁻¹ s.c. Vehicle or agent was administered 1 h before the IL-31 injection, or a vehicle injection only was given. The total number of scratching bouts was counted for 12 h. Each column represents the mean ± SEM of seven to eight mice. **P < 0.01, ***P < 0.001 versus the untreated group (vehicle/IL-31). NS, not significant.

Figure 4

Effect of an anti-IL-31 receptor α Ab on the CS reaction produced by hapten-sensitization and challenge. The degree of ear swelling was determined by ear thickness of the sensitized ear compared with that of the vehicle-treated ear at 24 or 48 h after the challenge. Each column represents the mean ± SEM of five or six mice. **P < 0.01, ***P < 0.001 at the corresponding time point. NS, not significant.

Figure 5

Exacerbation of dermatitis symptoms was inhibited by anti-IL-31 receptor α Ab in the chronic AD-like model. Ear thickness (A) and dermatitis score (B) measured for six weeks show the preventive effect of BM095 injected i.p. at 10 mg·kg⁻¹ weekly from day −9 and the therapeutic effect of BM095 injected weekly from day 20. In the disease control, vehicle was injected weekly from day −9. Each symbol with a vertical bar represents the mean ± SEM of 12 or 13 mice. (C) The severity of the scab on day 42 was scored (−: none observed, +: mild, ++: moderate, +++: severe). Photographs show the appearance of the ear skin for each grade. *P < 0.05, **P < 0.01 versus the disease control group at the corresponding time point. (D) Histological appearance of the treated ear, 4 h after PiCl application on day 44. Images show inflammatory cell infiltration in the dermis of representative ear tissues from the disease control (a), BM095 therapeutic (b) and BM095 preventive group (c). The tissues were stained with haematoxylin and eosin. Bar = 50 μm.