1. Academic Validation
  2. RIPK3-MLKL-Mediated Neutrophil Death Requires Concurrent Activation of Fibroblast Activation Protein-α

RIPK3-MLKL-Mediated Neutrophil Death Requires Concurrent Activation of Fibroblast Activation Protein-α

  • J Immunol. 2020 Sep 15;205(6):1653-1663. doi: 10.4049/jimmunol.2000113.
Xiaoliang Wang 1 Francois Gessier 2 Remo Perozzo 3 Darko Stojkov 1 Aref Hosseini 1 Keyvan Amirshahrokhi 1 4 Stefan Kuchen 5 Shida Yousefi 1 Pius Lötscher 2 Hans-Uwe Simon 6 7
Affiliations

Affiliations

  • 1 Institute of Pharmacology, University of Bern, CH-3010 Bern, Switzerland.
  • 2 Novartis Institutes for BioMedical Research, CH-4056 Basel, Switzerland.
  • 3 School of Pharmaceutical Sciences, School of Pharmacy Geneva-Lausanne, University of Geneva, 1211 Geneva, Switzerland.
  • 4 Department of Pharmacology, School of Pharmacy, Ardabil University of Medical Sciences, 561893141 Ardabil, Iran.
  • 5 Department of Rheumatology, Clinical Immunology and Allergology, Inselspital, Bern University Hospital, University of Bern, CH-3012 Bern, Switzerland; and.
  • 6 Institute of Pharmacology, University of Bern, CH-3010 Bern, Switzerland; hus@pki.unibe.ch.
  • 7 Department of Clinical Immunology and Allergology, Sechenov University, 119991 Moscow, Russia.
Abstract

Cytokine-primed neutrophils can undergo a nonapoptotic type of cell death using components of the necroptotic pathway, including receptor-interacting protein kinase-3 (RIPK3), mixed lineage kinase-like (MLKL) and NADPH Oxidase. In this report, we provide evidence for a potential role of serine proteases in CD44-mediated necroptotic death of GM-CSF-primed human neutrophils. Specifically, we observed that several inhibitors known to block the enzymatic function of fibroblast activation protein-α (FAP-α) were able to block CD44-mediated Reactive Oxygen Species production and cell death, but not FAS receptor-mediated Apoptosis. To understand how FAP-α is involved in this nonapoptotic death pathway, we performed immunoblotting experiments in the presence and absence of inhibitors of RIPK3, MLKL, p38 MAPK, PI3K, and FAP-α. The results of these experiments suggested that FAP-α is active in parallel with RIPK3, MLKL, and p38 MAPK activation but proximal to PI3K and NADPH Oxidase activation. Interestingly, neutrophils isolated from the joints of patients suffering from rheumatoid arthritis underwent a GM-CSF-independent Necroptosis following CD44 ligation; this effect was also blocked by both FAP-α and MLKL inhibitors. Taken together, our evidence shows that the RIPK3-MLKL pathway activates NADPH Oxidase but requires, in addition to p38 MAPK and PI3K, a serine Protease activity, whereby FAP-α is the most likely candidate. Thus, FAP-α could be a potential drug target in neutrophilic inflammatory responses to avoid exaggerated nonapoptotic neutrophil death, leading to tissue damage.

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