Analysis of free hemoglobin level and hemoglobin peptides from human puerperal uterine secretions

Hemocidins are a novel class of antibacterial peptides generated proteolytically from hemoglobin. These peptides play a particularly important role in maintaining vaginal homeostasis during menstrual bleeding. To investigate the hemoglobin fragmentation process during the last stages of pregnancy, we examined uterine secretion (lochia) samples from a group of 22 healthy women who underwent cesarean delivery at term.

Patients were divided into three groups: (1) the elective cesarean deliveries without symptoms of spontaneous labor, (2) the nonelective cesarean deliveries with spontaneous beginning of labor, and (3) the nonelective cesarean deliveries during advanced labor. The samples were subjected to chromatographic estimation of free hemoglobin and peptides. In three representative patients the identification of all lochial peptides was performed.

All samples contained a significant amount of free hemoglobin and its level increased with labor progression. The presence of peptide fractions was also detected in most lochia samples. They were confirmed to be human hemoglobin fragments, almost identical to the recently described bactericidal hemocidins from menstrual discharge. The level of peptides also increased during labor. The subgroup with advanced labor demonstrated the highest amount of hemocidins.

The presented results prove that proteolysis of free hemoglobin in the female upper reproductive tract begins together with the clinical symptoms of normal labor. We speculate that cesarean delivery affects molecular mechanisms involved in antibacterial hemocidins generation and, in effect, might be responsible for the increased risk of gynecologic infections in cesarean deliveries.