Myeloperoxidase (MPO)-derived hypochlorous (HOCl) reacts with membrane
plasmalogens to yield α-chlorofatty
aldehydes such as 2-chlorofatty
aldehyde (2-ClFALD) and its metabolite 2-chlorofatty
acid (2-ClFA). Recent studies showed that 2-ClFALD and 2-ClFA serve as mediators of the inflammatory responses to
sepsis by as yet unknown mechanisms. Since no scavenger for chlorinated
lipids is available and on the basis of the well-established role of the MPO/HOCl/chlorinated
lipid axis in inflammatory responses, we hypothesized that treatment with MPO inhibitors (
N-acetyl lysyltyrosylcysteine amide or
4-aminobenzoic acid hydrazide) would inhibit
inflammation and proinflammatory mediator expression induced by cecal
ligation and
puncture (CLP). We used intravital microscopy to quantify in vivo inflammatory responses in
Sham and CLP rats with or without MPO inhibition. Small intestines, mesenteries, and lungs were collected to assess changes in MPO-positive staining and
lung injury, respectively, as well as free 2-ClFA and proinflammatory mediators levels. CLP caused neutrophil infiltration, 2-ClFA generation,
acute lung injury, leukocyte-/platelet-endothelium interactions, mast cell activation (MCA),
plasminogen activator inhibitor-1 (PAI-1) production, and the expression of several
cytokines,
chemokines, and
vascular endothelial growth factor, changes that were reduced by MPO inhibition. Pretreatment with a
PAI-1 inhibitor or MC stabilizer prevented CLP-induced leukocyte-endothelium interactions and MCA, and abrogated exogenous 2-ClFALD-induced inflammatory responses. Thus, we provide evidence that MPO instigates these inflammatory changes in CLP and that chlorinated
lipids may serve as a mechanistic link between the enzymatic activity of MPO and PAI-1- and mast cell-dependent adhesive interactions, providing a rationale for new therapeutic interventions in
sepsis.NEW & NOTEWORTHY Using two distinct
myeloperoxidase (MPO) inhibitors, we show for the first time that MPO plays an important role in producing increases in free 2-chlorofatty
aldehyde (2-ClFALD)-a powerful proinflammatory chlorinated
lipid in plasma and intestine-a number of
cytokines and other inflammatory mediators, leukocyte and platelet rolling and adhesion in postcapillary venules, and
lung injury in a cecal
ligation and
puncture model of
sepsis. In addition, the use of a
plasminogen activator inhibitor-1 (PAI-1) inhibitor or a
mast cell stabilizer prevented inflammatory responses in CLP-induced
sepsis.
PAI-1 inhibition also prevented the proinflammatory responses to exogenous 2-ClFALD superfusion. Thus, our study provides some of the first evidence that MPO-derived free 2-ClFA plays an important role in CLP-induced
sepsis by a PAI-1- and mast cell-dependent mechanism.