Genetic variation in cyclooxygenase 1: Effects on response to aspirin

Background: A critical clinical application of the Human Genome Project is to identify functional variation in genes related to disease or responses to xenobiotics. This study moved toward that goal by combining polymorphism detection with functional assays for the therapeutic target gene cyclooxygenase 1 (COX-1). Cyclooxygenase 1 (prostaglandin endoperoxide G/H synthase [PTGS1]) catalyzes the metabolism of arachidonic acid to prostaglandin H₂, which is subsequently metabolized to thromboxane A₂. Methods: Thirty-eight healthy participants were enrolled in this study to correlate functional and genetic variation of cyclooxygenase 1. Arachidonic acid, with and without aspirin (acetylsalicylic acid) and ethanol pretreatment, was used to stimulate the formation of prostaglandin H₂, measured as prostaglandin F_2α (PGF_2α), in human platelets. The cyclooxygenase 1 complementary deoxyribonucleic acid coding sequence and genomic deoxyribonucleic acid upstream from the cyclooxygenase 1 transcription start site (2.9 kilo-bases) were sequenced in 38 individuals, with 9 single-nucleotide polymorphisms identified. Results: Two single-nucleotide polymorphisms, A-842G and C50T, were in complete linkage disequilibrium. Participants who were heterozygous for the A-842G/C50T haplotype showed significantly (P = .01) greater inhibition of prostaglandin H₂ formation by acetylsalicylic acid (30 μmol/L) compared with common allele homozygotes. Conclusions: The discovery of a functional single-nucleotide polymorphism in the cyclooxygenase 1 locus may ultimately improve the safe and effective use of acetylsalicylic acid by better tailoring of dosage with an individual's genetic variation.