Iron nitrosyl complexes are formed from nitrite in the human placenta

Area of Science:

• Obstetrics and Gynecology
• Physiology
• Biochemistry

Background:

• Nitric oxide (NO) is vital for placental circulation.
• Elevated NO metabolites are observed in pregnancy complications like preeclampsia.
• The placenta's response to increased NO or its metabolites is not fully understood.

Purpose of the Study:

• To investigate NO metabolite levels in preeclampsia placental tissue.
• To explore the conversion of nitrite to iron nitrosyl complexes (FeNOs) in the placenta.
• To assess the significance of FeNOs in placental physiology and pathology.

Main Methods:

• Measurement of NO metabolites in human placental tissue from preeclampsia patients and controls.
• Ozone-based chemiluminescence and electron paramagnetic resonance spectroscopy to detect FeNOs.
• Investigation of endogenous FeNOs in placental tissue from animal models (sheep, rats).

Main Results:

• NO metabolites are significantly increased in placentas from preeclampsia patients compared to healthy controls.
• Nitrite is efficiently converted into protein-bound heme-FeNOs within the human placenta.
• Endogenous FeNOs were detected in placental tissues of sheep and rats, indicating conserved mechanisms.

Conclusions:

• The human placenta efficiently forms FeNOs from nitrite, highlighting their potential physiological or pathological importance.
• FeNOs are relatively short-lived and primarily exist as heme-FeNOs.
• Iron nitrosylation by FeNOs affects iron-containing proteins, suggesting FeNOs warrant further investigation in pregnancy complications.