Aspirin (ASA) and dexamethasone (DEX) are widely used anti-inflammatory agents yet their mechanism(s) for blocking polymorphonuclear neutrophil (PMN) accumulation at sites of inflammation remains unclear. Here, we report that inhibition of PMN infiltration by ASA and DEX is a property shared by aspirin-triggered lipoxins (ATL) and the glucocorticoid-induced annexin 1 (ANXA1)-derived peptides that are both generated in vivo and act at the lipoxin A(4) receptor (ALXR/FPRL1) to halt PMN diapedesis. These structurally diverse ligands specifically interact directly with recombinant human ALXR demonstrated by specific radioligand binding and function as well as immunoprecipitation of PMN receptors. In addition, the combination of both ATL and ANXA1-derived peptides limited PMN infiltration and reduced production of inflammatory mediators (that is, prostaglandins and chemokines) in vivo. Together, these results indicate functional redundancies in endogenous lipid and peptide anti-inflammatory circuits that are spatially and temporally separate, where both ATL and specific ANXA1-derived peptides act in concert at ALXR to downregulate PMN recruitment to inflammatory loci.

Myocardial reperfusion injury is associated with the infiltration of blood-borne polymorphonuclear leukocytes. We have previous described the protection afforded by annexin 1 (ANXA1) in an experimental model of rat myocardial ischemia-reperfusion (IR) injury. We examined the 1) amino acid region of ANXA1 that retained the protective effect in a model of rat heart IR; 2) changes in endogenous ANXA1 in relation to the IR induced damage and after pharmacological modulation; and 3) potential involvement of the formyl peptide receptor (FPR) in the protective action displayed by ANXA1 peptides. Administration of peptide Ac2-26 at 0, 30, and 60 min postreperfusion produced a significant protection against IR injury, and this was associated with reduced myeloperoxidase activity and IL-1beta levels in the infarcted heart. Western blotting and electron microscopy analyses showed that IR heart had increased ANXA1 expression in the injured tissue, associated mainly with the infiltrated leukocytes. Finally, an antagonist to the FPR receptor selectively inhibited the protective action of peptide ANXA1 and its derived peptides against IR injury. Altogether, these data provide further insight into the protective effect of ANXA1 and its mimetics and a rationale for a clinical use for drugs developed from this line of research.

We assessed here the effect of the glucocorticoid-regulated protein lipocortin 1 (LC1) in a model of rat myocardial ischemia reperfusion. Treatment of animals with human recombinant LC1 at the end of a 25-min ischemic period significantly reduced the extent of infarct size in the area at risk as measured 2 h later, with approximately 50% inhibition at the highest dose tested of 50 microg per rat (equivalent to 5.4 nmol/kg). The protective effect of LC1 was abolished by protein denaturation and not mimicked by the structurally related protein annexin V. A combination of electron and light microscopy techniques demonstrated the occurrence of the myocardial damage at the end of the reperfusion period, with loss of fiber organization. LC1 provided a partial and visible protection. The dose-dependent protection afforded by LC1 was paralleled by lower values of myeloperoxidase activity, tumor necrosis factor a, and macrophage inflammatory protein-1a. The functional link between migrated leukocytes and the myocardial damage was confirmed by electron and light microscopy, and a significantly lower number of extravasated leukocytes was counted in the group of rats treated with LC1 (50 microg). In conclusion, we demonstrate for the first time that LC1 reduces the leukocyte-dependent myocardial damage associated with an ischemia-reperfusion procedure.

Neutrophil elastase (NE) remains a controversial player in the process of leukocyte transmigration and much of this controversy stems from conflicting reports on the effects of NE inhibitors. The availability of NE-deficient mice (NE−/−) provides a clean and elegant tool for the study of leukocyte migration in vivo. In this study, NE−/− mice were used to investigate the role of NE in leukocyte migration through cremasteric venules, as observed by intravital microscopy, induced by locally administered cytokines IL-1β and TNF-α and the particulate stimulus, zymosan. Although no defects in leukocyte responses induced by the cytokines were observed, zymosan-induced leukocyte firm adhesion and transmigration was suppressed in NE−/− mice. These responses were also inhibited in wild-type mice when zymosan was coinjected with a specific NE inhibitor. Quantification of inflammatory mediator levels in homogenates of zymosan-stimulated tissues indicated reductions in levels of IL-1β, KC, and macrophage inflammatory protein-1α in NE−/− mice. Furthermore, phagocytosis of fluorescent zymosan particles, as observed by intravital microscopy, was diminished in NE-deficient animals. Collectively, the findings of this study indicate a nonredundant role for NE in zymosan-induced leukocyte firm adhesion and transmigration, and that this defect is associated with impaired generation of proinflammatory mediators as well as phagocytosis of zymosan particles in vivo.