PP007. Nicotinic acetylcholine receptor subunits in the pre-eclamptic and cigarette smoke exposed human placenta.

INTRODUCTION: Cigarette smoking during pregnancy is associated with low birth weight, prematurity and neonatal morbidity and mortality. Nicotine, a major constituent of cigarette smoke, binds to nicotinic acetylcholine receptors (nAChRs). To date, 16 mammalian nAChR subunits have been identified. The effect of smoking on these subunits in human placenta has not yet been determined. Smoking is also associated with reduced pre-eclampsia (PE) risk and its protective effects may occur via changes in nAChRs.

OBJECTIVES: This study aimed to determine which nAChR subunits are present in the normal human placenta, and whether any changes are occur from smoking or PE.

METHODS: Using RT-qPCR, all 16 nAChR subunits were investigated in normal, healthy human placentas, and mRNA expression compared between controls (n=8), smokers (n=8) and PE (n=7). Results All 16 nAChR subunits were expressed in healthy placentas. Smoke exposure significantly increased α2 (p=0.006) and α9 (p=0.038), and decreased δ (p=0.013), subunit mRNA expression. In PE placentas, β1 (p=0.048) and β2 (p=0.031) subunit mRNA expression was increased.

CONCLUSION: Nicotine exposure in pregnancy increases nAChR subunit mRNAs that play a role in vasoconstriction and amino acid uptake, possibly contributing to abnormalities in placentas from smoking mothers. Different subunits were affected in PE placentas, thus the hypoxic environment may induce changes in endogenous ACh levels, yielding compensatory increases in β1 and β2 subunits.