Topical Application of the PI3Kβ-Selective Small Molecule Inhibitor TGX-221 Is an Effective Treatment Option for Experimental Epidermolysis Bullosa Acquisita.

Hannah Zillikens,Gestur Vidarsson,Tamás Laskay,Natalie Gross,Colin Osterloh,Anika Kasprick,Martina Behnen-Härer,Frank Petersen,Ralf J Ludwig,Xinhua Yu,Nancy Ernst,Veronika Hartmann,Katja Bieber,Cindy Hass,Michael Radziewitz,Remco Visser,Katharina Boch

doi:10.3389/fmed.2021.713312

Abstract

Class I phosphoinositide 3-kinases (PI3K) have been implemented in pathogenesis of experimental epidermolysis bullosa acquisita (EBA), an autoimmune skin disease caused by type VII collagen (COL7) autoantibodies. Mechanistically, inhibition of specific PI3K isoforms, namely PI3Kβ or PI3Kδ, impaired immune complex (IC)-induced neutrophil activation, a key prerequisite for EBA pathogenesis. Data unrelated to EBA showed that neutrophil activation is also modulated by PI3Kα and γ, but their impact on the EBA has, so far, remained elusive. To address this and to identify potential therapeutic targets, we evaluated the impact of a panel of PI3K isoform-selective inhibitors (PI3Ki) on neutrophil function in vitro, and in pre-clinical EBA mouse models. We document that distinctive, and EBA pathogenesis-related activation-induced neutrophil in vitro functions depend on distinctive PI3K isoforms. When mice were treated with the different PI3Ki, selective blockade of PI3Kα (alpelisib), PI3Kγ (AS-604850), or PI3Kβ (TGX-221) impaired clinical disease manifestation. When applied topically, only TGX-221 impaired induction of experimental EBA. Ultimately, multiplex kinase activity profiling in the presence of disease-modifying PI3Ki identified unique signatures of different PI3K isoform-selective inhibitors on the kinome of IC-activated human neutrophils. Collectively, we here identify topical PI3Kβ inhibition as a potential therapeutic target for the treatment of EBA.

Highlights

Class I phosphoinositide 3-kinases (PI3Ks) are heterodimers consisting of one regulatory and one homologous p110 catalytic subunit
Based on the current understanding of autoantibody-induced tissue pathology in the inflammatory variant of epidermolysis bullosa acquisita (EBA) [12, 21], where neutrophils migrate form the blood into the skin, form an immunological synapse by binding to the immune complexes located at the dermal-epidermal junction, and release reactive oxygen species (ROS), we evaluated the impact of the PI3K isoform-selective inhibitors (PI3Ki) on (i) IL-8-induced neutrophil migration, (ii) IC-induced neutrophil spreading, and (iii) IC-induced ROS release form neutrophils
PI3K inhibitors mainly selective for PI3Kδ(AMG319 and IC87114) as well as PI3Kγ-selective (AS604850 and AMG319) and PI3Kβ-selective inhibitors (TGX-221) inhibited chemotaxis at concentrations within the described IC50 values (Figure 1)

Summary

Introduction

Class I phosphoinositide 3-kinases (PI3Ks) are heterodimers consisting of one regulatory and one homologous p110 catalytic subunit. The p110γ subunit is highly expressed in the immune system and in other tissues, including heart and central nervous system [8, 9]. Downstream kinases, including PI3K, are activated [13,14,15]. PI3Kβ [16] and PI3Kδ [18] were shown to be crucial for IC-induced neutrophil activation, the release of reactive oxygen species (ROS). PI3Kδ inhibition leads to selective impairment of neutrophil functions, including IC-, C5a-, and fMLP-induced ROS release, while no impact on PMA-induced ROS release is observed. IL-8- or fMLP-induced migration are impaired by PI3Kδ inhibition, while C5a-induced migration remains unaffected [18]. TNF- and LPS-induced cytokine release from neutrophils [19, 20] and extravasation [7] are controlled by PI3Kδ

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Conclusion