THE EXPRESSION OF 15-LIPOXYGENASE GENE AND THE PRESENCE OF FUNCTIONAL ENZYME IN CYTOPLASM AND NUCLEI OF PREGNANCY HUMAN MYOMETRIA

The expression of the 15-lipoxygenase (15-LO) gene in pregnancy human myometria, from messenger RNA (mRNA) to the product of the enzyme reaction, was investigated. In situ hybridization with antisense riboprobe synthesized from human reticulocyte 15-LO complementary DNA has revealed the presence of mRNA in myometrial smooth muscle as well as in myometrial blood vessels. Immunoblot analysis with a polyclonal antibody to recombinant human 15-LO enzyme showed a single 110-kilodalton immunoreactive protein in myometria. Light microscope immunocytochemistry using polyclonal antibodies has demonstrated the presence of immunoreactive 15-LO protein and 15-hydroxyeicosatetraenoic acid (15-HETE), the primary product of the 15-LO pathway. While myometrial blood vessels did not show any obvious change, myometrial smooth muscle showed lower 15-LO mRNA, 15-LO immunoreactive protein, and 15-HETE at term pregnancy and during labor. Immunogold electron microscopy showed the presence of immunoreactive 15-LO in rough endoplasmic reticulum and 15-HETE in myofilaments. Quite unexpectedly, both are also present in nuclear chromatin. In summary, the present study demonstrates for the first time the expression of 15-LO gene in pregnancy human myometria and the mRNA and catalytically active enzyme are lower at term pregnancy and during labor. Quite unexpectedly, catalytically active 15-LO is also present in nuclear chromatin. These findings suggest that 15-LO/15-HETE may have genomic as well as nongenomic actions, both of which may either initiate and/or facilitate the progression of labor in women.