The enteropathy of prostaglandin deficiency

Background. Small intestinal ulcers are frequent complications of therapy with nonsteroidal antiinflammatory drugs (NSAIDs). We present here a genetic deficiency of eicosanoid biosynthesis that illuminates the mechanism of NSAID-induced ulcers of the small intestine. Methods. Eicosanoids and metabolites were measured by isotope dilution with mass spectrometry. cDNA was obtained by reverse transcription and sequenced following amplification with RT-PCR. Results. We investigated the cause of chronic recurrent small intestinal ulcers, small bowel perforations, and gastrointestinal blood loss in a 45-year-old man who was not taking any cyclooxygenase inhibitor. Prostaglandin metabolites in urine were significantly depressed. Serum thromboxane B 2 (TxB(2)) production was 4.6% of normal controls (P < 0.006), and serum 12-HETE was 1.3% of controls (P < 0.005). Optical platelet aggregation with simultaneous monitoring of ATP release demonstrated absent granule secretion in response to ADP and a blunted aggregation response to ADP and collagen, but normal response to arachidonic acid (AA). LTB(4) biosynthesis by ionophore-activated leukocytes was only 3% of controls, and urinary LTE(4) was undetectable. These findings suggested deficient AA release from membrane phospholipids by cytosolic phospholipase A2-alpha (cPLA(2)-alpha), which regulates cyclooxygenase- and lipoxygenase-mediated eicosanoid production by catalyzing the release of their substrate, AA. Sequencing of cPLA(2)-alpha cDNA demonstrated two heterozygous nonsynonymous single-base-pair mutations: Ser111Pro (S111P) and Arg485His (R485H), as well as a known single nucleotide polymorphism (SNP), Lys651Arg (K651R). Conclusions. Characterization of this cPLA2-alpha deficiency provides support for the importance of prostaglandins in protecting small intestinal integrity and indicates that loss of prostaglandin biosynthesis is sufficient to produce small intestinal ulcers.