Choline Glycerophospholipid-Derived Prostaglandins Attenuate TNFα Gene Expression in Macrophages via a cPLA2α/COX-1 Pathway

Abstract

Macrophages are professional antigen presenting cells with intense phagocytic activity, strategically distributed in tissues and cavities. These cells are capable of responding to a wide variety of innate inflammatory stimuli, many of which are signaled by lipid mediators. The distribution of arachidonic acid (AA) among glycerophospholipids and its subsequent release and conversion into eicosanoids in response to inflammatory stimuli such as zymosan, constitutes one of the most studied models. In this work, we used liquid and/or gas chromatography coupled to mass spectrometry to study the changes in the levels of membrane glycerophospholipids of mouse peritoneal macrophages and the implication of group IVA cytosolic phospholipase A2 (cPLA2α) in the process. In the experimental model used, we observed that the acute response of macrophages to zymosan stimulation involves solely the cyclooxygenase-1 (COX-1), which mediates the rapid synthesis of prostaglandins E2 and I2. Using pharmacological inhibition and antisense inhibition approaches, we established that cPLA2α is the enzyme responsible for AA mobilization. Zymosan stimulation strongly induced the hydrolysis of AA-containing choline glycerophospholipids (PC) and a unique phosphatidylinositol (PI) species, while the ethanolamine-containing glycerophospholipids remained constant or slightly increased. Double-labeling experiments with 3H- and 14C-labeled arachidonate unambiguously demonstrated that PC is the major, if not the exclusive source, of AA for prostaglandin E2 production, while both PC and PI appeared to contribute to prostaglandin I2 synthesis. Importantly, in this work we also show that the COX-1-derived prostaglandins produced during the early steps of macrophage activation restrict tumor necrosis factor-α production. Collectively, these findings suggest new approaches and targets to the selective inhibition of lipid mediator production in response to fungal infection.

BASHY Dyes Are Highly Efficient Lipid Droplet-Targeting Photosensitizers that Induce Ferroptosis through Lipid Peroxidation

“…Additionally, we evaluated whether LDs could be involved in this process. The cytosolic phospholipase A2 alpha (cPLA2α) is a key enzyme in the process of LD formation. , We used pyrrolidine-2, a known inhibitor of this enzyme, , to further examine whether reducing the formation of LDs could have an impact on the phototoxicity of 3 and 4 (Figure ). The treatment with pyrrolidine-2 resulted in a significant increase in cell viability, which is consistent with our initial assumption that the accumulation of these dyes in LDs could enhance LPO and ferroptosis upon photosensitization.…”

BASHY Dyes Are Highly Efficient Lipid Droplet-targeting Photosensitizers That Induce Ferroptosis Through Lipid Peroxidation

“…The cytosolic phospholipase A2 alpha (cPLA2α) is a key enzyme in the of lipid droplet formation. 31,32 We used pyrrolidine-2, a known inhibitor of this enzyme, 33,34 to further examine whether reducing the formation of lipid droplets could have an impact on the phototoxicity of 3 and 4 (Figure 5). The treatment with pyrrolidine-2 resulted in a significant increase in cell viability, which is consistent with our initial assumption that the accumulation of these dyes in LDs could enhance LPO and ferroptosis upon photosensitization.…”

Lipid Droplets, Phospholipase A2, Arachidonic Acid, and Atherosclerosis

“…A myriad of stimuli, acting on surface receptors, are able to trigger the translocation activation of cPLA 2 α from the cytosol to a number of intracellular membranes, including the LD monolayer [ 19 , 20 ]. This allows positioning of the enzyme in the vicinity of cyclooxygenases and lipoxygenases for efficient supply of the free fatty acid for eicosanoid formation [ 126 , 127 ].…”