Thiophene-Benzimidazole Conjugates Attenuate IL-33-induced Inflammation in Human Mast Cell Line and in ex vivo Human Skin Organ Cultures

Introduction: Aberrant Interleukin-33 (IL-33) activation is associated with numerous dermatological inflammatory and autoimmune diseases, such as atopic dermatitis, lupus, vitiligo and psoriasis. Thus, the inhibition of this pathway may provide therapeutic options in multiple pathologies. We hypothesized that targeting the IL-33 critical site of interactions with its membranal receptor, Suppression of Tumorigenicity 2 (ST2), will generate highly selective inhibitors capable of alleviating the detrimental effects of IL-33 activation. Methods: In silico-based methods for the identification of possible inhibitors of IL-33/ST2 interaction were used. Employing two structure-based pharmacophore models designed by LigandScout, a virtual screening of commercially available compounds and in house library revealed 13 compounds that may reduce level of IL-33/ST2 interaction. To verify their capacity to attenuate IL-33-induced inflammation, the compounds were tested in HMC-1.1 mast cell line and human skin slices. Results: Two lead compounds, both thiophene-benzimidazole conjugates methyl-1-(pentan-3-yl)-2-(thiophen-2-ylmethyl)-1H-benzo[d]imidazole-5-carboxylate (LT-105) and methyl (S)-5-methyl-3-{(1-(pentan-3-yl)-2-(thiophen-2-ylmethyl)-1H-benzo[d]imidazole-5-carboxamido)}hexanoate (LT-108), were able to attenuate IL-33-induced IL-6 and IL 8 hypersecretion in pharmacological relevant concentrations. This effect correlated with reduced IL-6 and IL-8 mRNA levels, determined by RT-PCR. In addition, LT-105 and LT-108 reduced the phosphorylation of IL-33 downstream effectors; p-IRAK1 and p-P38. Further docking studies revealed possible molecular interactions of the compounds with key sites of IL-33 that are responsible for the binding with ST2. To validate the findings, the compounds were also tested in the ex vivo human skin organ culture. Both compounds LT-105 and LT-108 reduced inflammation when applied topically to the human skin samples stimulated by IL-33 in pharmacological concentrations. Conclusions: Our results indicate that thiophene-benzimidazole conjugates LT-105 and LT-108 can reduce IL-33 mediated inflammation both in vitro and ex vivo. Nevertheless, additional in vivo and clinical studies are required to further evaluate the ability of these compounds to treat autoimmune/inflammatory cutaneous disorders mediated by IL-33.