Secreted and intracellular phospholipases A2 inhibition by 1-decyl 2-octyl-glycerophosphocholine in rat peritoneal macrophages

Compounds able to inhibit phospholipases A, can be considered as potential anti-inflammatory drugs. In this respect, the inhibitory effect of the phospholipid analogue 1-decyl 2-octyl-rac-glycero-3-phosphocholine (decyloctyl-GPC) added to the culture medium of rat peritoneal macrophages stimulated with ionophore A23187 was determined. (a) The substrate of phospholipase A, 1-octadecanoyl 2-[ 14 C]eicosatetraenoyl -sn-glycero-3-phosphocholine ([ 14 C]20:4-GPC) was added to the culture medium. In macrophages + extracellular fluids, its hydrolysis at the 2-position, produced [ 14 C]non-phosphorous lipids which reached 12% of the dose at 0.14 μM, 73% at 0.9 and > 90% at 1.6 μM; in experiments where macrophages and extracellular fluids were analyzed separately, decyloctyl-GPC initially added at 4 μM, significantly inhibited the release of [ 14 C]fatty acids and the eicosanoid synthesis, demonstrating its ability to inhibit secreted and/or intracellular phospholipases A 2 . (b) Extracellular fluids were separated from the macrophages and incubated with [ 14 C]20:4-GPC: 48% of the dose was hydrolyzed by extracellular fluid-associated secreted phospholipase A 2 and decyloctyl-GPC at 3 μM, reduced this hydrolysis by 50%. (c) [ 3 H]arachidonic acid ([ 3 H]20:4) was added to the culture medium and was esterified in the macrophage membrane phospholipids. Activation of intracellular phospholipase A 2 induced the release of [ 3 H] fatty acids and eicosanoid synthesis. These releases were inhibited by 50% with decyloctyl-GPC added at 4 μM. (d) [ 3 H]20:4 and [ 14 C]20:4-GPC were added to the culture medium of the macrophages. [ 3 H] and [ 14 C] fatty acids and eicosanoids were released in macrophages or extracellular fluids. They were significantly reduced by the phospholipid analogue added at 4 μM. It is concluded that secreted and intracellular phospholipases A 2 were both inhibited by decyloctyl-GPC which extensively reduced the 20:4 release from exogenous and membrane phospholipids and therefore eicosanoid synthesis.