The novel anti-IL17A monoclonal antibody Secukinumab in the treatment of psoriasis: biological effects on angiogenesis and extracellular vesicles

Psoriasis is a chronic inflammatory skin disease. The role of Interleukin-17A (IL-17A) is emerging in the pathogenesis of psoriasis and considered the main driver of inflammation and dysregulated angiogenesis promoting in psoriatic keratinocytes the release of soluble mediators including the vascular endothelial factor-A (VEGF-A). The early growth response-1 (Egr-1) transcription factor, recently demonstrated upregulated in the skin of patients with psoriasis, has been suggested to influence angiogenesis by regulating VEGF-A expression. It is reported that IL-17A increases Egr-1 expression in human keratinocytes, however little is known about the biological function of Egr-1 in psoriasis. Notably, the successful employment of the novel therapeutic monoclonal antibody anti-IL-17A Secukinumab (Cosentyx, Novartis) is ascribable to the indirect inhibition of angiogenesis. Beside cell-to-cell contacts and release of cytokines, hormones and second messangers, cells communicate each other through the release of extracellular vesicles (EVs) containing DNA, RNA, microRNAs and proteins. It has been reported the alteration of EVs trafficking in several diseases, but there is scare evidence of the involvement of EVs trafficking in the pathogenesis of psoriasis. Accordingly, we investigated the molecular mechanism by which Egr-1 could affect psoriasis angiogenesis in response to IL-17A signaling and if Secukinumab reduces angiogenesis in psoriatic keratinocytes by an Egr-1-dependent mechanism. We also aimed to characterize the release, the cargo content and the capacity to transfer bioactive molecules of EVs produced by keratinocytes following IL-17A treatment compared to untreated keratinocytes. Results indicate that Secukinumab downregulates VEGFA mRNA and its soluble levels in human keratinocytes (HaCaT) treated with IL-17A. Conditioned medium from keratinocytes previously exposed to Secukinumab significantly decreases cell proliferation and migration of endothelial cells and inhibits capillary tube formation in vitro. The use of Egr-1 siRNA downregulates IL-17A-mediated VEGF-A expression. Overall, these data suggest that Secukinumab indirectly inhibits keratinocytes angiogenic property by interfering with IL-17A/Egr-1/VEGF-A axis. As what concern the study of keratinocyte-derived EVs, results indicate that the treatment with IL-17A significantly modifies the EVs cargo and release. Vesicles from IL-17A-treated cells display a specific pattern of mRNA which is abrogated by Secukinumab. Further, EVs are taken up by acceptor cells irrespective of their content but only those derived from IL-17A-treated cells enable recipient cells to express psoriasis-associated mRNA. These results imply a role of EVs in amplifying the pro-inflammatory cascade induced in keratinocytes by pro-psoriatic cytokines.