The fact that smoking pregnant women have a lesser chance to develop pre-eclampsia was well known before. What was not known is the mechanism behind this peculiar finding. The research carried by a team at the Queen’s University, Kingston, Ontario, Canada and published in the latest American Journal of Pathology might answer the question and possibly pave the way for a clinical therapy:
Interestingly, mothers who smoke cigarettes during pregnancy have a 33% decreased risk of developing pre-eclampsia compared to nonsmokers. New research questions whether the carbon monoxide found in cigarette smoke, and subsequently carried in a smoking mother’s blood, may be the cause. Carbon monoxide, which is produced naturally by the body at low levels, possesses vessel-relaxing and cytoprotective activities that may prevent syncytiotrophoblast cell death and the resulting injury to fetus and mother.
Dr. Graeme Smith and colleagues examined this hypothesis using tissue from term human placentas obtained following elective caesarian section from nonsmoking, low-risk women. When cultured tissues were exposed to oxidative stress (hypoxia and re-oxygenation), syncytiotrophoblast cell death occurred. However, when tissues were treated with carbon monoxide, at levels similar to those found in blood of smoking mothers, cell death was significantly reduced. Further, carbon-monoxide-treated tissues did not demonstrate the hallmarks of syncytiotrphoblast cell injury and death, such as condensation of DNA, clumping of nuclei, and separation of cells from the rest of the tissue.
These studies have delineated possible mechanisms behind smoking’s protective effects on pre-eclampsia and identified carbon monoxide as a possible treatment modality. The use of carbon monoxide in preventing hypoxia/re-oxygenation injury in organ transplantation underscores its potential usefulness here. Future studies will determine whether carbon monoxide can prevent syncytiotrophoblast death in animal models and whether other approaches similar to carbon monoxide may provide feasible protection.