Heme oxygenase expression in human placental villous tissue in response to exposure to in vitro ischemia-reperfusion injury.

Heme oxygenases (HO-1 and HO-2) are responsible for the production of carbon monoxide, a vasodilator. The products of heme oxygenase are also anti-oxidants. HO is expressed within the placenta and is important in controlling placental blood flow. HO can be sensitive to oxygen, with responses differing depending on the cell type. Recent studies have suggested that in preeclampsia, the placenta would be subjected to fluctuations in oxygen tension analogous to an ischemia-reperfusion injury. Thus the present study tested the hypothesis that HO-1 and or HO-2 expression in placental villous explants would be altered by an ischemic-reperfusion insult. Human term placental explants were exposed to hypoxia then re-oxygenation in 5% or 20% O(2) or repeated cycles of hypoxia-re-oxygenation. HO protein concentrations were assessed by Western blotting. No changes in HO-1 or HO-2 were found with any treatment protocol. Chemical induction of HO-1 was possible in explants showing that HO-1 induction in explants is possible. The results suggest that cells in term placental villous tissue do not respond to hypoxia-re-oxygenation by altering the amount of HO-1 or HO-2 protein.