Inhibition of Neutrophil Extracellular Trap Formation after Stem Cell Transplant by Prostaglandin E₂

Abstract

ORCID IDs: 0000-0003-4387-7673 (S.M.); 0000-0003-3051-745X (B.B.M.). AbstractRationale: Autologous and allogeneic hematopoietic stem cell transplant (HSCT) patients are susceptible to pulmonary infections, including bacterial pathogens, even after hematopoietic reconstitution. We previously reported that murine bone marrow transplant (BMT) neutrophils overexpress cyclooxygenase-2, overproduce prostaglandin E 2 (PGE 2 ), and exhibit defective intracellular bacterial killing. Neutrophil extracellular traps (NETs) are DNA structures that capture and kill extracellular bacteria and other pathogens.Objectives: To determine whether NETosis was defective after transplant and if so, whether this was regulated by PGE 2 signaling.Methods: Neutrophils isolated from mice and humans (both control and HSCT subjects) were analyzed for NETosis in response to various stimuli in the presence or absence of PGE 2 signaling modifiers.Measurements and Main Results: NETs were visualized by immunofluorescence or quantified by Sytox Green fluorescence. Treatment of BMT or HSCT neutrophils with phorbol 12-myristate 13-acetate or rapamycin resulted in reduced NET formation relative to control cells. NET formation after BMT was rescued both in vitro and in vivo with cyclooxygenase inhibitors. Additionally, the EP2 receptor antagonist (PF-04418948) or the EP4 antagonist (AE3-208) restored NET formation in neutrophils isolated from BMT mice or HSCT patients. Exogenous PGE 2 treatment limited NETosis of neutrophils collected from normal human volunteers and naive mice in an exchange protein activated by cAMP-and protein kinase A-dependent manner.Conclusions: Our results suggest blockade of the PGE 2 -EP2 or EP4 signaling pathway restores NETosis after transplantation. Furthermore, these data provide the first description of a physiologic inhibitor of NETosis.

Antibiotic pretreatment alleviates liver transplant damage in mice and humans

“…In parallel, the EP4 antagonist restored CHOP and p-S6K, decreased LC3B, and recreated IRI in otherwise stress-resistant, Abx-pretreated OLT recipients. Meanwhile, the influence of PGE2 on mTORC1 and cellular autophagy seems to be tissue specific (53)(54)(55)(56), whereas the mechanism by which the PGE2/EP4 axis regulates hepatocyte ER stress and mTORC1 activation remains unknown. Consistent with a previous study (57), we found that treatment with PGE2 caused phosphorylation of AMPK in hepatocytes (our unpublished data), while AMPK is known to suppress mTORC1 activation as well as decrease the ER stress response (58,59).…”

Prostaglandin‐cytokine crosstalk in chronic inflammation

“…NET formation also occurs during various chronic inflammatory diseases (Kolaczkowska and Kubes, 2013). PGE 2 inhibited NET formation in isolated neutrophils induced by PMA or rapamycin through EP 2 /EP 4 -cAMP receptor signalling (Domingo-Gonzalez et al, 2016;Shishikura et al, 2016), although the extent to which this mechanism operates in vivo remains unknown.…”

A pathologic two‐way street: how innate immunity impacts lung fibrosis and fibrosis impacts lung immunity

“…Taken together, these data suggest that PMNs may contribute to fibrosis via release of NE and NETs and one hypothesised reason that IPF patients may be at risk of increased NETosis to drive fibrogenesis is because they have a deficit of prostaglandin E 2 (PGE 2 ) in the lung . PGE 2 is a molecule we have previously shown to be an endogenous inhibitor of NETosis …”

“…42,43 PGE 2 is a molecule we have previously shown to be an endogenous inhibitor of NETosis. 44 Silicosis is a fibrotic lung disease caused by toxicity due to inhalation of silica glass particles. PMNs are important for clearance of particulate matter from the lung, and PMNs are capable of phagocytising many different particle types, including silica.…”