Inherited human cPLA2α deficiency is associated with impaired eicosanoid biosynthesis, small intestinal ulceration, and platelet dysfunction
David H. Adler, Joy D. Cogan, John A. Phillips III, Nathalie Schnetz-Boutaud, Ginger L. Milne, Tina Iverson, Jeffrey A. Stein, David A. Brenner, Jason D. Morrow, Olivier Boutaud, John A. Oates
David H. Adler, Joy D. Cogan, John A. Phillips III, Nathalie Schnetz-Boutaud, Ginger L. Milne, Tina Iverson, Jeffrey A. Stein, David A. Brenner, Jason D. Morrow, Olivier Boutaud, John A. Oates
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Research Article Genetics

Inherited human cPLA2α deficiency is associated with impaired eicosanoid biosynthesis, small intestinal ulceration, and platelet dysfunction

Abstract

Cytosolic phospholipase A2α (cPLA2α) hydrolyzes arachidonic acid from cellular membrane phospholipids, thereby providing enzymatic substrates for the synthesis of eicosanoids, such as prostaglandins and leukotrienes. Considerable understanding of cPLA2α function has been derived from investigations of the enzyme and from cPLA2α-null mice, but knowledge of discrete roles for this enzyme in humans is limited. We investigated a patient hypothesized to have an inherited prostanoid biosynthesis deficiency due to his multiple, complicated small intestinal ulcers despite no use of cyclooxygenase inhibitors. Levels of thromboxane B2 and 12-hydroxyeicosatetraenoic acid produced by platelets and leukotriene B4 released from calcium ionophore–activated blood were markedly reduced, indicating defective enzymatic release of the arachidonic acid substrate for the corresponding cyclooxygenase and lipoxygenases. Platelet aggregation and degranulation induced by adenosine diphosphate or collagen were diminished but were normal in response to arachidonic acid. Two heterozygous single base pair mutations and a known SNP were found in the coding regions of the patient’s cPLA2α genes (p.[Ser111Pro]+[Arg485His; Lys651Arg]). The total PLA2 activity in sonicated platelets was diminished, and the urinary metabolites of prostacyclin, prostaglandin E2, prostaglandin D2, and thromboxane A2 were also reduced. These findings characterize what we believe is a novel inherited deficiency of cPLA2.

Authors

David H. Adler, Joy D. Cogan, John A. Phillips III, Nathalie Schnetz-Boutaud, Ginger L. Milne, Tina Iverson, Jeffrey A. Stein, David A. Brenner, Jason D. Morrow, Olivier Boutaud, John A. Oates

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Figure 6

Platelet PLA2 quantity and activity.

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Platelet PLA2 quantity and activity. (A) Western blot of platelet ly...
(A) Western blot of platelet lysate from the patient demonstrates cPLA2α protein of expected molecular weight but in diminished quantity compared with controls. Band intensity was quantified using Quantity One image analysis software (n = 3). Error bars represent ± SD. (B) PLA2 activity in platelet lysate measured by hydrolysis of a radiolabeled substrate, l-3-phosphatidylcholine, 1-stearoyl-2-[1-14C] arachidonyl (14C-SAPC). Points represent mean values for each time point (n = 4; 2 separate experiments performed in duplicate: 2 control volunteers and 2 different collection days for patient). Error bars represent ± SD.