ARAP3 protects from excessive formylated peptide-induced microvascular leakage by acting on endothelial cells and neutrophils

Vascular permeability is temporarily heightened during inflammation, but excessive
inflammation-associated microvascular leakage can be detrimental, as evidenced in the inflamed
lung. Formylated peptides regulate vascular leakage indirectly via formylated peptide receptor-1
(FPR1) mediated recruitment and activation of neutrophils. Here we identify how the GTPase
activating protein ARAP3 protects against formylated peptide-induced microvascular
permeability via endothelial cells and neutrophils. In vitro, Arap3-/- endothelial monolayers were
characterised by enhanced formylated peptide-induced permeability due to upregulated
endothelial FPR1 and enhanced VE-cadherin internalisation. In vivo, enhanced inflammationassociated microvascular leakage was observed in Arap3-/- mice. Leakage of plasma protein into
the lungs of Arap3-/- mice increased within hours of formylated peptide administration.
Adoptive transfer experiments indicated this was dependent upon ARAP3 deficiency in both
immune and non-immune cells. Bronchoalveolar lavages of formylated peptide-challenged
Arap3-/- mice contained neutrophil extracellular traps (NETs). Pharmacological inhibition of
NET formation abrogated excessive microvascular leakage, indicating a critical function of
NETs in this context. The observation that Arap3-/- mice developed more severe influenza
suggests these findings are pertinent to pathological situations characterised by abundant
formylated peptides.