Molecular biological studies on cyclooxygenases and lipoxygenases dynamics

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This project is a molecular biological approach to cyclooxygenases and lipoxygenases which are responsible for the syntheses of bioactive arachidonate metabolites.(1) Cyclooxygenases : A murine osteoblastic cell line MC3T3-E1 produces prostaglandin E2, and its cyclooxygenase enzyme was shown to be induced by various hormones, growth factors and prostaglandins. Further studies demonstrated the involvement of two cyclooxygenase isozymes in the prostaglandin E2 production. Cyclooxygenase-1 was induced gradually only by 2-3 fold, whereas cyclooxygenase-2 appeared rapidly within 1-2 h and increased by 15-60 fold.(2) Lipoxygenases : The leukocyte-type and platelet-type of 12-lipoxygenase were distinguishied in terms of substrate specificity and immunogenicity. Their cDNAs and genomic DNAs were cloned, and their structures were elucidated. The leukocyte-type enzyme was found not only in leukocytes but also in porcine pituitary, bovine trachea, canine brain and rat pineal gland. The platelet-type 12-lipoxygenase, which had been found only in platelets, was recently found in human epidermal cells. A method for PCR-amplification of 12-lipoxygenase mRNA was established, and a low level of 12-lipoxygenase together with a decreased enzyme activity and protein was demonstrated in the platelets of three patients with myeloproliferative diseases.