Protective effect of small molecule analogues of the Acanthocheilonema viteae secreted product ES-62 on oxazolone-induced ear inflammation

Abstract

ES-62 is the major secreted protein of the rodent filarial nematode Acanthocheilonema viteae. The molecule contains covalently attached phosphorylcholine (PC) residues, which confer anti-inflammatory properties on ES-62, underpinning the idea that drugs based on this active moiety may have therapeutic potential in human diseases associated with aberrant inflammation. Here we demonstrate that two synthetic small molecule analogues (SMAs) of ES-62 termed SMA 11a and SMA 12b are protective in the oxazolone-induced acute allergic contact dermatitis mouse model of skin inflammation, as measured by a significant reduction in ear inflammation following their administration before oxazolone sensitisation and before oxazolone challenge. Furthermore, it was found that when tested, 12b was effective at reducing ear swelling even when first administered before challenge. Histological analysis of the ears showed elevated cellular infiltration and collagen deposition in oxazolone-treated mice both of which were reduced by treatment with the two SMAs. Likewise, the oxazolone-induced increase in IFNγ mRNA in the ears was reduced but no effect on other cytokines investigated was observed. Finally, no influence on the mast cell populations in the ear was observed.

Keywords: ES-62; Immunomodulation; Oxazolone; Parasitic worm; Skin inflammation.

Graphical abstract

Fig. 1

The effect of treatment with 1 µg of SMAs 12b and 11a on days −1, 4 and 5 on ear thickness was assessed following sensitisation and challenge with oxazolone. A non-sensitised control group was also included. The data are obtained from a single experiment, which is representative of two (11a) and three (12b) independent experiments. **p < 0.01, ***p < 0.001. ** and *** represent a significant difference between 12b − (Oxa + 12b) or 11a − (Oxa + 11a) treated and PBS-treated mice sensitised and challenged with oxazolone (Oxazolone). Results are expressed as ear thickness in micrometres.

Fig. 2

The effect of treatment with 1 µg of SMAs 11a and 12b on days −1, 4 and 5 on mRNA levels of IFNγ (a), IL-4 (b), IL-17A (c) and TNFα (d) from day 6 ears, 1 h after challenge, as assessed by qRT-PCR where the levels of the gene of interest were normalised to the level of GAPDH. Data are presented as the means ± SEM of the mean of replicate values pooled from 3 individual experiments. **p < 0.01. **Significant difference between 12b- (Oxa + 12b) or 11a- (Oxa + 11a) treated and PBS-treated mice sensitised and challenged with oxazolone (Oxa). The non-sensitised group is represented by “non”.

Fig. 3

Ear sections from non-sensitised, oxazolone and oxazolone/SMA-treated (days −1, 4 and 5) mice were stained with haematoxylin and eosin (H&E) to show cellular infiltration and tissue structure, Gomori trichrome to show collagen deposition, and toluidine blue to stain mast cells in the tissue.