Anti-IL5 decreases the number of eosinophils but not the severity of dermatitis in Sharpin-deficient mice

Abstract

Sharpin-deficient (Sharpin(cpdm)) mutant mice develop a chronic eosinophilic dermatitis. To determine the efficacy of eosinophil-depletion in chronic inflammation, Sharpin(cpdm) mice were treated with anti-IL5 antibodies. Mice treated with anti-IL5 had a 90% reduction of circulating eosinophils and a 50% decrease in cutaneous eosinophils after 10 days compared with sham-treated littermates. Reducing the number of eosinophils resulted in increased severity of alopecia and erythema and a significant increase in epidermal thickness. Skin homogenates from mice treated with anti-IL5 had decreased mRNA expression of arylsulfatase B (Arsb), diamine oxidase (amiloride-binding protein 1, also called histaminase; Abp1) and Il10, which are mediators that eosinophils may release to quench inflammation. Skin homogenates from mice treated with anti-IL5 also had decreased mRNA expression of Il4, Il5, Ccl11, kit ligand (Kitl) and Tgfa; and increased mRNA expression of Tgfb1, Mmp12 and tenascin C (Tnc). In order to further decrease the accumulation of eosinophils, Sharpin(cpdm) mice were crossed with IL5 null mice. Il5(-/-), Sharpin(cpdm)/Sharpin(cpdm) mice had a 98% reduction of circulating eosinophils and a 95% decrease in cutaneous eosinophils compared with IL5-sufficient Sharpin(cpdm) mice. The severity of the lesions was similar between IL5-sufficient and IL5-deficient mice. Double mutant mice had a significant decrease in Abp1, and a significant increase in Tgfb1, Mmp12 and Tnc mRNA compared with controls. These data indicate that eosinophils are not essential for the development of dermatitis in Sharpin(cpdm) mice and suggest that eosinophils have both pro-inflammatory and anti-inflammatory roles in the skin of these mice.

Figure 1

The number of eosinophils in the blood (A) and skin (B) of Sharpin^cpdm mice treated with anti-IL-5 was significantly decreased compared to Sharpin^cpdm mice treated with a nonspecific rat IgG. Similar results were seen in the blood (C) and skin (D) of Il5^−/−Sharpin^cpdm mice compared to Il5^+/− Sharpin^cpdm mice. Data expressed as mean ± SEM for 5 mouse pairs. *P < 0.05; **P < 0.005

Figure 2

The epidermis was increased in thickness in Sharpin^cpdm mice treated with anti-IL-5 compared to Sharpin^cpdm littermates given non-specific IgG. Data expressed as mean ± SEM for 5 mouse pairs. *P < 0.05

Figure 3

Fold change in mRNA expression of Mmp9, Mmp12, Mmp13, and Tnc in the skin of Sharpin^cpdm mice (n=8) compared to control littermates (n=7). The bars represent the mean ± SD. * P < 0.05; ** P < 0.001.

Figure 4

Fold change in mRNA expression for Sharpin^cpdm mice treated with anti-IL5 compared to Sharpin^cpdm mice treated with non-specific rat IgG for mediators of inflammation (A) and remodeling (B). Data expressed as mean ± standard deviation for 5 mouse pairs. Data expressed as mean ± SD for 5 mouse pairs. * P < 0.05; **P < 0.005. (Abbreviations: Arsb=arylsufataseB, Apb1=histaminase,Ccl11=eotaxin, Kitl=kit ligand, Tgfa=transforming growth factor alpha, Tgfb1=transforming growth factor beta1, Mmp12=matrix metalloproteinase 12, Tnc=tenascin C).