n-3 Polyunsaturated Fatty Acids Suppress the Localization and Activation of Signaling Proteins at the Immunological Synapse in Murine CD4+ T Cells by Affecting Lipid Raft Formation

Abstract

The molecular properties of immunosuppressive n-3 polyunsaturated fatty acids (PUFA) have not been fully elucidated. Using CD4+ T cells from wild-type control and fat-1 transgenic mice (enriched in n-3 PUFA), we show that membrane raft accumulation assessed by Laurdan (6-dodecanoyl-2-dimethyl aminonaphthalene) labeling was enhanced in fat-1 cells following immunological synapse (IS) formation by CD3-specific Ab expressing hybridoma cells. However, the localization of protein kinase Cθ, phospholipase Cγ-1, and F-actin into the IS was suppressed. In addition, both the phosphorylation status of phospholipase Cγ-1 at the IS and cell proliferation as assessed by CFSE labeling and [3H]thymidine incorporation were suppressed in fat-1 cells. These data imply that lipid rafts may be targets for the development of dietary agents for the treatment of autoimmune and chronic inflammatory diseases.

n-3 PUFA improves fatty acid composition, prevents palmitate-induced apoptosis, and differentially modifies B cell cytokine secretion in vitro and ex vivo

“…The rapid improvement in the n-6/n-3 ratio points to the possibility that n-3 PUFAs could be used as nutraceuticals to modify composition and organization to selectively initiate a change in cellular function with a high dose of PUFAs for a short time period. Based on data presented here and elsewhere, the most plausible splenic targets that respond to a change in membrane composition to suppress cellular function are CD4 + T cells and possibly DCs ( 13,15,37,38 ). The data from this study allow us to propose that n-3 PUFA inhibition of lymphocyte activation is not universal.…”

“…From a mechanistic perspective, the inhibition in activation of CD4 + T cells, and possibly DCs, has been linked, in part, to an improvement in the membrane n-6/n-3 ratio. In the case of CD4 + T cells, n-3 PUFAs suppressed cellular activation, in part by modifying the organization of sphingolipid-cholesterol-rich lipid rafts by accumulating n-3 PUFAs into lipid rafts ( 13,17 ). This disrupted protein lateral organization and inhibited subsequent signaling necessary for lymphocyte activation.…”

Fish oil increases raft size and membrane order of B cells accompanied by differential effects on function

“…There was a tendency for EPA treatment to lower DRM cholesterol relative to BSA when analyzed as a t -test ( P < 0.05). The ratio of cholesterol in DRM to DSM also had a tendency to be accompanied by suppressive effects on downstream innate and adaptive B-cell function, as reported for T cells, macrophages, and splenocytes ( 6,11,12 ). Two different B-cell functional studies were conducted.…”

“…Based on studies with CD4 + T cells, macrophages, and splenocytes, disruption of rafts with n-3 PUFAs generally suppresses cellular function ( 6,11,12 ). Far less is known about the relationship between disruption of lipid rafts with n-3 PUFAs and downstream function in other cell types.…”

“…This directly addressed two opposing models in which n-3 PUFAs in response to stimulation increase membrane order ex vivo versus a decrease in membrane order in vitro ( 6,25 ). To measure molecular order, we used di-4-ANEPPDHQ, an environmental sensing fl uorescent dye that can shift its emission spectra 30 nm depending on the degree of packing in the surrounding lipid chains ( Fig.…”