Modulation of the 5-Lipoxygenase Pathway by Chalcogen-Containing Inhibitors of Leukotriene A Hydrolase.

The 5-lipoxygenase (5-LOX) pathway gives rise to bioactive inflammatory lipid mediators, such as leukotrienes (LTs). 5-LOX carries out the oxygenation of arachidonic acid to the 5-hydroperoxy derivative and then to the leukotriene A epoxide which is converted to a chemotactic leukotriene B (LTB) by leukotriene A hydrolase (LTAH). In addition, LTAH possesses aminopeptidase activity to cleave the N-terminal proline of a pro-inflammatory tripeptide, prolyl-glycyl-proline (PGP).

The IRE1α Inhibitor KIRA6 Blocks Leukotriene Biosynthesis in Human Phagocytes.

The ER stress and Unfolded Protein Response (UPR) component inositol-requiring enzyme 1α (IRE1α) has been linked to inflammation and lipid mediator production. Here we report that the potent IRE1α inhibitor, KIRA6, blocks leukotriene biosynthesis in human phagocytes activated with lipopolysaccharide (LPS) plus N-formyl-methionyl-leucyl-phenylalanine (fMLP) or thapsigargin (Tg). The inhibition affects both leukotriene B (LTB) and cysteinyl leukotriene (cys-LTs) production at submicromolar concentration.

Human leukocytes selectively convert 4,5-epoxy-resolvin to resolvin D3, resolvin D4, and a cys-resolvin isomer.

Human phagocytes have key functions in the resolution of inflammation. Here, we assessed the role of the proposed 4,5-epoxy-resolvin intermediate in the biosynthesis of both resolvin D3 and resolvin D4. We found that human neutrophils converted this synthetic intermediate to resolvin D3 and resolvin D4.

Modulation of microRNA processing by 5-lipoxygenase.

The miRNA biogenesis is tightly regulated to avoid dysfunction and consequent disease development. Here, we describe modulation of miRNA processing as a novel noncanonical function of the 5-lipoxygenase (5-LO) enzyme in monocytic cells. In differentiated Mono Mac 6 (MM6) cells, we found an in situ interaction of 5-LO with Dicer, a key enzyme in miRNA biogenesis.