Pyrrolidine Inhibitors of Human Cytosolic Phospholipase A₂

Abstract

Introduction. Phospholipase A 2 (PLA 2 ) is a group of lipolytic enzymes that catalyze the hydrolysis of fatty acid ester bonds at the sn-2 position of phospholipids. This enzyme is thought to play an important role in the biosynthesis of eicosanoids via the release of arachidonic acid from biomembranes. Another product from biomembranes, a lysophospholipid, is converted to plateletactivating factor (PAF) known as an inflammatory mediator. PLA 2 s have been generally classified into secretory PLA 2 (sPLA 2 ), cytosolic PLA 2 (cPLA 2 ), and Ca 2+ -independent PLA 2 (iPLA 2 ) by their molecular weights, amino acid sequences, and calcium requirements. 1 cPLA 2 comprises three distinct types of enzymes: R, β, and γ. 2 cPLA 2 R, an 85-kDa protein, contains a calcium-dependent lipid binding domain and a catalytic domain, requires micromolar levels of Ca 2+ for membrane translocation, and has a specificity for arachidonic acid bound to the sn-2 position of phospholipids 3 in contrast with sPLA 2 and iPLA 2 which have broad substrate specificities, suggesting that cPLA 2 R is involved in the production of eicosanoids.

Arachidonic Acid Release from Mammalian Cells Transfected with Human Groups IIA and X Secreted Phospholipase A2 Occurs Predominantly during the Secretory Process and with the Involvement of Cytosolic Phospholipase A2-α

“…In our studies with CHO-K1 and HEK293 cells, it is clear that essentially all of the released [ 3 H]arachidonate is accounted for by that which accumulates in the culture medium. Also the fact that the cPLA 2 -␣ inhibitors reduce accumulation of [ 3 H]arachidonate in the medium in the present as well as in previous studies (2,26,28,42) The data presented in this paper provide a particularly clear example of cross-talk between hGIIA or hGX and cPLA 2 -␣. A second clear example of this cross-talk comes from the recent study of Han et al (15).…”

Pharmacological inhibition of lipid droplet formation enhances the effectiveness of curcumin in glioblastoma

“…Our research group has previously reported the incorporation of curcumin into A2B star polymer micelles and effectiveness of this preparation in glioblastoma [63,64]. A retention of curcumin's biological activity in nanocarriers, an enhanced permeability and retention (EPR) effect and diffusion of curcumin into the neighboring glioblastoma cells could provide an improved therapeutic intervention in vivo [65] Pyrrolidine-2 is an inhibitor of cPLA2a, a key rate limiting enzyme in the synthesis of eicosanoids and a necessary player in the formation of lipid droplets [66,67]. In normal brain tissues, particularly in astrocytes and microglia, excessive PLA2 activation in response to stressors (e.g.…”

Polychlorinated biphenyls induce arachidonic acid release in human platelets in a tamoxifen sensitive manner via activation of group IVA cytosolic phospholipase A2-α

“…Tamoxifen, (E)-1-(4-(2-(N,Ndimethylamino)ethoxy)phenyl)-1,2-diphenylbut-1-ene, and nafoxidin, 1-(2-(P-(3,4-dihydro-6-methoxy-2-phenyl-1-naphtyl)phenoxy)-ethyl)pyrrolidine hydrochloride were obtained from Sigma. Pyrrolidine-1 was synthesized as previously described [48,49]. 1-palmitoyl-2-[1-14 C]arachidonyl phosphatidylcholine (PtdCho) (57 mCi/mmol) and 1-palmitoyl-2-[1-14 C]arachidonyl phosphatidylethanolamine (PtdEtn) (57 mCi/mmol) were from New England Nuclear.…”

“…To discriminate between secretory PLA 2 (sPLA 2 ) and intracellular PLA 2 -mediated arachidonic acid release, we employed the PLA2 inhibitors pyrrolidine-1, AACOCF 3 and BEL. Pyrrolidine-1 is a potent and selective inhibitor of cPLA 2 -α [48,49]. BEL is an inhibitor of iPLA 2 [56,57] whereas AACOCF 3 inhibits both cPLA 2 -α and iPLA 2 [56,58].…”