Impact of endoplasmic reticulum aminopeptidases 1 (ERAP1) and 2 (ERAP2) on neutrophil cellular functions

Introduction: Endoplasmic reticulum aminopeptidases 1 (ERAP1) and 2 (ERAP2) modulate a plethora of physiological processes for the maintenance of homeostasis in different cellular subsets at both intra and extracellular level.

Materials and methods: In this frame, the extracellular supplementation of recombinant human (rh) ERAP1 and ERAP2 (300 ng/ml) was used to mimic the effect of stressor-induced secretion of ERAPs on neutrophils isolated from 5 healthy subjects. In these cells following 3 h or 24 h rhERAP stimulation by Western Blot, RT-qPCR, Elisa, Confocal microscopy, transwell migration assay, Oxygraphy and Flow Cytometry we assessed: i) rhERAP internalization; ii) activation; iii) migration; iv) oxygen consumption rate; v) reactive oxygen species (ROS) accumulation; granule release; vi) phagocytosis; and vii) autophagy.

Results: We observed that following stimulation rhERAPs: i) were internalized by neutrophils; ii) triggered their activation as witnessed by increased percentage of MAC-1⁺CD66b⁺ expressing neutrophils, cytokine expression/release (IL-1β, IL-8, CCL2, TNFα, IFNγ, MIP-1β) and granule enzyme secretion (myeloperoxidase, Elastase); iii) increased neutrophil migration capacity; iv) increased autophagy and phagocytosis activity; v) reduced ROS accumulation and did not influence oxygen consumption rate.

Conclusion: Our study provides novel insights into the biological role of ERAPs, and indicates that extracellular ERAPs, contribute to shaping neutrophil homeostasis by promoting survival and tolerance in response to stress-related inflammation. This information could contribute to a better understanding of the biological bases governing immune responses, and to designing ERAP-based therapeutic protocols to control neutrophil-associated human diseases.