Biosynthesis Of Proresolving Mediators Research Articles

Therapeutic potential of the FPR2/ALX agonist AT-01-KG in the resolution of articular inflammation

The resolution of inflammation is a dynamic process, characterized by the biosynthesis of pro-resolving mediators, including the lipid Lipoxin A4 (LXA4). LXA4 acts on the N-formyl peptide receptor 2 (FPR2/ALX) to mediate anti-inflammatory and pro-resolving effects. In order to exploit the therapeutic potential of endogenous LXA4 in the context of inflammation we have recently developed synthetic LXA4 mimetics (sLXms) including a dimethyl-imidazole-containing FPR2/ALX agonist designated AT-01-KG. Here, we have investigated the effect of treatment with AT-01-KG in established models of articular inflammation. In a model of gout, mice were injected with MSU crystals and treated with AT-01-KG at the peak of inflammatory response. The treatment decreased the number of neutrophils in the knee exudate, an effect which was accompanied by low levels of myeloperoxidase, CXCL1 and IL-1β in periarticular tissue. AT-01-KG treatment led to reduced tissue damage and hypernociception. The effects of AT-01-KG on neutrophil accumulation were not observed in MSU treated FPR2/3−/−mice. Importantly, AT-01-KG induced resolution of articular inflammation by increasing neutrophil apoptosis and subsequent efficient efferocytosis. In a model of antigen-induced arthritis, AT-01-KG treatment also attenuated inflammatory responses. These data suggest that AT-01-KG may be a potential new therapy for neutrophilic inflammation of the joints.

Functional Characterization of Knock-In Mice Expressing a 12/15-Lipoxygenating Alox5 Mutant Instead of the 5-Lipoxygenating Wild-Type Enzyme.

Aims: Most mammalian genomes involve several genes encoding for functionally distinct arachidonate lipoxygenase (ALOX isoforms). Proinflammatory leukotrienes are formed via the ALOX5 pathway, but 12/15-lipoxygenating ALOX isoforms have been implicated in the biosynthesis of pro-resolving mediators. In vitro mutagenesis of the triad determinants abolished the leukotriene synthesizing activity of ALOX5, but the biological consequences of these alterations have not been studied. To fill this gap, we created Alox5 knock-in mice, which express the 12/15-lipoxygenating Phe359Trp + Ala424Ile + Asn425Met Alox5 triple mutant and characterized its phenotypic alterations. Results: The mouse Alox5 triple mutant functions as arachidonic acid 15-lipoxygenating enzyme, which also forms 12S-hydroxy and 8S-hydroxy arachidonic acid. In contrast to the wild-type enzyme, the triple mutant effectively oxygenates linoleic acid to 13S-hydroxy linoleic acid (13S-HODE), which functions as activating ligand of the type-2 nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ). Knock-in mice expressing the mutant enzyme are viable, fertile, and develop normally. The mice cannot synthesize proinflammatory leukotrienes but show significantly attenuated plasma levels of lipolytic endocannabinoids. When aging, the animals gained significantly more body weight, which may be related to the fivefold higher levels of 13-HODE in the adipose tissue. Innovation: These data indicate for the first time that in vivo mutagenesis of the triad determinants of mouse Alox5 abolished the biosynthetic capacity of the enzyme for proinflammatory leukotrienes and altered the catalytic properties of the protein favoring the formation of 13-HODE. Conclusion:In vivo triple mutation of the mouse Alox5 gene impacts the body weight homeostasis of aging mice via augmented formation of the activating PPARγ ligand 13-HODE.