Resolvin D1 limits 5-lipoxygenase nuclear localization and leukotriene B ₄ synthesis by inhibiting a calcium-activated kinase pathway

Abstract

Imbalances between proinflammatory and proresolving mediators can lead to chronic inflammatory diseases. The balance of arachidonic acid-derived mediators in leukocytes is thought to be achieved through intracellular localization of 5-lipoxygenase (5-LOX): nuclear 5-LOX favors the biosynthesis of proinflammatory leukotriene B 4 (LTB 4 ), whereas, in theory, cytoplasmic 5-LOX could favor the biosynthesis of proresolving lipoxin A 4 (LXA 4 ). This balance is shifted in favor of LXA 4 by resolvin D1 (RvD1), a specialized proresolving mediator derived from docosahexaenoic acid, but the mechanism is not known. Here we report a new pathway through which RvD1 promotes nuclear exclusion of 5-LOX and thereby suppresses LTB 4 and enhances LXA 4 in macrophages. RvD1, by activating its receptor formyl peptide receptor2/lipoxin A 4 receptor, suppresses cytosolic calcium and decreases activation of the calcium-sensitive kinase calcium-calmodulin-dependent protein kinase II (CaMKII). CaMKII inhibition suppresses activation P38 and mitogen-activated protein kinase-activated protein kinase 2 kinases, which reduces Ser271 phosphorylation of 5-LOX and shifts 5-LOX from the nucleus to the cytoplasm. As such, RvD1's ability to decrease nuclear 5-LOX and the LTB 4 :LXA 4 ratio in vitro and in vivo was mimicked by macrophages lacking CaMKII or expressing S271A-5-LOX. These findings provide mechanistic insight into how a specialized proresolving mediator from the docosahexaenoic acid pathway shifts the balance toward resolution in the arachidonic acid pathway. Knowledge of this mechanism may provide new strategies for promoting inflammation resolution in chronic inflammatory diseases.P ersistent inflammation and its failed resolution underlie the pathophysiology of prevalent human diseases, including cancer, diabetes, and atherosclerosis (1). Hence, uncovering mechanisms to suppress inflammation and enhance resolution is of immense interest (2-5). Resolution is orchestrated in part by specialized proresolving mediators (SPMs), including lipoxins, resolvins, protectins, and maresins (2), and by protein and peptide mediators (6). A common protective function of SPMs is their ability to limit excessive proinflammatory leukotriene formation without being immunosuppressive (2, 7). Specifically, resolvin D1 (RvD1) is protective in several disease models (8) and limits excessive leukotriene B 4 (LTB 4 ) production without compromising host defense (7, 9). However, the mechanism underlying these actions of RvD1 is not well understood.Arachidonic acid (AA) is first converted into 5-hydroperoxyeicosatetraenoicacid (5-HPETE) and then into leukotriene A 4 (LTA 4 ) by 5-lipoxygenase (5-LOX) (10, 11). Subsequent hydrolysis of LTA 4 by LTA 4 hydrolase yields LTB 4 (10, 11). During inflammation, 5-LOX is phosphorylated and translocates to the nuclear membrane, which favors the biosynthesis of LTB 4 (12-17). However, major gaps remain in our understanding of the relevance of this pathway to primary cells and animal models and how they are regulated by...

MerTK cleavage limits proresolving mediator biosynthesis and exacerbates tissue inflammation

“…5D). To examine causation, we transfected macrophages lacking 5-LOX (Alox5 −/− ) with either WT Alox5 or S271D-mutant Alox5, which mimics p-5-LOX and promotes its nuclear retention (11). In contrast to the case with WT 5-LOX macrophages, MerTK activation was unable to increase the cytoplasmic:nuclear 5-LOX ratio or LX-i in S271D 5-LOX macrophages (Fig.…”

“…Examples include arachidonic acid (AA)-derived lipoxins, like LXA 4 , and docosahexaenoic acid (DHA)-derived resolvins, such as RvD1 (1,9,10). Interestingly, SPMs can promote their own synthesis; for example, RvD1 promotes the biosynthesis of LXA 4 via nuclear exclusion of 5-lipoxygenase (5-LOX) (11,12). Despite these advances, a major gap is the identification of upstream regulators of SPM production.…”

CAMKIIγ suppresses an efferocytosis pathway in macrophages and promotes atherosclerotic plaque necrosis

“…In this context, it is possible that the loss of macrophage CaMKIIγ improves resolution in plaques. If so, one mechanism could be related to our recent finding that CaMKII activation in macrophages preferentially channels the common precursor lipid mediator arachidonic acid into proinflammatory leukotriene B 4 rather than proresolving lipoxin A 4 (17). If the resolution process is improved in M-CaMKII-KO lesions, as we predict, this might explain the improvement in protective fibrous cap formation (45).…”

“…Based on previous studies with cultured macrophages (16,17), we hypothesized that CaMKII would be activated in macrophages in advanced atherosclerotic lesions and that this process would further promote the development of advanced atherosclerotic plaque characteristics. To begin to explore this hypothesis, we sought evidence of CaMKII activation in macrophages of human advanced atherosclerotic lesions.…”

N-3 PUFAs and neuroinflammatory processes in cognitive disorders

“…Some of the biological activities of resolvins are mediated by specific G-protein coupled receptors. Indeed, RvD1 activates lipoxin A4 receptor/formyl peptide receptor 2 (ALX/FPR2) and orphan receptor G protein coupling receptor 32 (GPR32) to limit leukocyte infiltration in tissues and attenuate the production of proinflammatory cytokines (Fredman et al, 2014;Wang et al, 2014). Interestingly, RvD1 promotes the synthesis of pro-resolvin miRNAs and elicits macrophage polarization toward an M2-like phenotype (Pierdomenico et al, 2015).…”