Mitochondria N‐formyl peptides in plasma of polytrauma patients cause vascular endothelial barrier dysfunction through formyl peptide receptor‐1 activation

Mitochondrial damage‐associated molecular patterns (DAMPs), such as N‐formyl peptides (F‐MITs), are endogenous molecules that share similarities with bacteria. F‐MITs activate the innate immune system through formyl peptide receptors (FPR). Traumatic tissue injury causes the release of F‐MIT, which is associated with vascular collapse during systemic inflammatory response syndrome (SIRS). However, exactly how F‐MITs lead to vascular injury and leakage is unknown. We hypothesized that F‐MITs via FPR‐1 activation, lead to increased vascular permeability via actin cytoskeletal rearrangement and dysfunction of tight junctions, resulting in the anasarca. Methods Plasma from four polytrauma injured adult patients with SIRS in the ICU was collected. Human primary aortic endothelial cells (HAEC) were cultured and treated under the following conditions: 1) Control (HAEC), 2) HAEC + plasma, 3) HAEC + plasma + 10 μM Cyclosporin H (CsH, FPR‐1 antagonist), 4) HAEC + plasma + 1 μM WRW4 (FPR‐2 antagonist), 5) HAEC + plasma + 4 mM Deformylase (enzyme that degrades F‐MITs). CsH and WRW4 were administered as pre‐treatment to HAEC 45‐min prior to 2‐hr plasma incubation and Deformylase plasma pre‐treatment followed the same timeframe. Western blot was performed to analyze occludin, a tight‐junction protein, pERK, p38 and b‐actin. In a separate experiment, cells were cultured on slides for confocal imaging and the above‐mentioned conditions were replicated. In a separate experiment, F‐G actin ratio was performed to delineate the effect on actin polymerization Results Plasma from SIRS patients leads to increased occludin expression (p=0.02). CsH (p=0.03) and Deformylase (p=0.04) abolished these increases, suggesting FMIT's role in this phenomenon. WRW4 did not abolish plasma's effect on occludin expression, suggesting FPR‐2 is not involved in cytoskeletal integrity. This was independent of MAPK activation, pERK (p>0.05) or p38 (p>0.05), and likely due to actin polymerization and RhoA activation (p<0.05). b‐actin expression was altered by FPR‐1 antagonist treatment (p=0.03, 61.1% reduction compared to control), but not FPR‐2 antagonism, suggesting that FPR‐1 function is necessary for endothelium cytoskeleton integrity. FMITs also increased the F:G actin ratio (1.8 fold vs control p<0.05) and FPR antagonists abolished this result. The confocal imaging revealed that plasma incubation caused HAEC detachment and this was prevented with deformylase treatment. Conclusion FPR‐1 activation causes increased endothelial cell permeability which contributes to loss of vascular tone and anasarca seen in SIRS after polytraumatic injury. FPR‐1 activation leads to increased endothelial permeability through actin cytoskeleton rearrangement as demonstrated by F‐G actin ratio and b‐actin expression alteration. This alteration in cytoskeleton and tight junction protein contributes to the loss of vascular tone and anasarca seen in SIRS after polytraumatic injury. These data reveal deformylase may be a novel treatment for traumatic‐injury induced SIRS. Support or Funding Information NIH 1K99GM118885‐01 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .