Immunohistochemical determination of thioredoxin and glutaredoxin distribution in the human cervix, and possible relation to cervical ripening.

Thioredoxin (Trx) and glutaredoxin (Grx) are dithiol redox enzymes, catalyzing general thiol-disulfide oxidoreductions apart from being hydrogen donors for ribonucleotide reductase, an enzyme essential for DNA synthesis. In mammals, isoenzymes of Trx and Grx are found in the cytoplasm (Trx1 and Grx1) or in mitochondria (Trx2 and Grx2). Trx and Grx play a role in cellular defence against oxidative stress and in redox regulation of cellular function. The localization and levels of human Trx1 and human Grx1 have been determined in the human cervix by immunohistochemistry and image analysis. Cervical biopsies were obtained from five non-pregnant, five term pregnant and five postpartum women. The levels of both Trx1 and Grx1 were increased in the nuclei (after translocation from the cytoplasm) of stromal cells in cervices from the term pregnant group as compared to the non-pregnant group, but the levels in the postpartum group did not differ significantly from those of the other two groups. These results are in agreement with our previous data on the mRNA expression of these two redox enzymes. The increased levels of the redox enzymes in term pregnancy suggest that they can be regulating factors involved in the process of cervical ripening, e.g. transcription factors and enzymes. Secreted Trx may participate in removing inhibitors of collagen-degrading metalloproteinases.