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Front. Immunol. | doi: 10.3389/fimmu.2019.02320

Effect of Adhesion and Substrate Elasticity on Neutrophil Extracellular Trap Formation

 Luise Erpenbeck1*,  Antonia L. Gruhn1, 2, Galina kudryasheva3,  Gökhan Günay1, 4, Daniel Meyer4, 5, Julia Busse1, Elsa Neubert1, 4,  Michael P. Schön1, 6,  Florian Rehfeldt3 and  Sebastian Kruss4*
  • 1Department of Dermatology, Venereology and Allergology, University Medical Center, University of Göttingen, Germany
  • 2Klinik für Dermatologie, Venerologie und Allergologie, Universitätsmedizin Göttingen, Germany
  • 3Third Institute of Physics - Biophysics, University of Göttingen, Germany
  • 4Institute of Physical Chemistry, University of Göttingen, Germany
  • 5University of Göttingen, Germany
  • 6Lower Saxony Institute of Occupational Dermatology, University Medical Center Göttingen, Germany

Neutrophils are the most abundant type of white blood cells. Upon stimulation, they are able to decondense and release their chromatin as neutrophil extracellular traps (NETs). This process (NETosis) is part of immune defense mechanisms but also plays an important role in many chronic and inflammatory diseases such as atherosclerosis, rheumatoid arthritis, diabetes and cancer. For this reason, much effort has been invested into understanding biochemical signaling pathways in NETosis. However, the impact of the mechanical micro-environment and adhesion on NETosis is not well understood.
Here, we studied how adhesion and especially substrate elasticity affect NETosis. We employed polyacrylamide (PAA) gels with distinctly defined elasticities (Young’s modulus E) within the physiologically relevant range from 1 kPa to 128 kPa and coated the gels with integrin ligands (collagen I, fibrinogen). Neutrophils were cultured on these substrates and stimulated with potent inducers of NETosis: phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS). Interestingly, PMA-induced NETosis was neither affected by substrate elasticity nor by different integrin ligands. In contrast, for LPS stimulation, NETosis rates increased with increasing substrate elasticity (E > 20 kPa). LPS-induced NETosis increased with increasing cell contact area, while PMA-induced NETosis did not require adhesion at all. Furthermore, inhibition of phosphatidylinositide 3 kinase (PI3K), which is involved in adhesion signaling, completely abolished LPS-induced NETosis but only slightly decreased PMA-induced NETosis.
In summary, we show that LPS-induced NETosis depends on adhesion and substrate elasticity while PMA-induced NETosis is completely independent of adhesion.

Keywords: Neutrophil extracellular traps (NET), substrate elasticity, Stiffness & its variations, Inflammation, Immunomodulation, Adhesion, innate immunity, Neutrophil (PMN)

Received: 20 May 2019; Accepted: 13 Sep 2019.

Copyright: © 2019 Erpenbeck, Gruhn, kudryasheva, Günay, Meyer, Busse, Neubert, Schön, Rehfeldt and Kruss. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Dr. Luise Erpenbeck, University of Göttingen, Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany, luise.erpenbeck@med.uni-goettingen.de
Dr. Sebastian Kruss, Institute of Physical Chemistry, University of Göttingen, Göttingen, D-37077, Lower Saxony, Germany, skruss@gwdg.de