Maternal smoking and pulmonary neuroendocrine cells in sudden infant death syndrome

Background. Maternal smoking is a well-recognized risk factor for sudden infant death syndrome (SIDS), but the precise mechanism is unknown. We tested a hypothesis that maternal smoking affects pulmonary neuroendocrine cells (PNECs) and neuroepithelial bodies (NEBs), which are innervated PNEC clusters and presumed airway chemoreceptors. Methods. Lung sections from infants who died of SIDS and whose mothers smoked during pregnancy (n = 22), infants who died of SIDS and whose mothers were nonsmokers (n = 17), ahd age-matched control infants (n = 15) who died of other causes were immunostained for bombesin (a PNEC and NEB marker) and assessed morphometrically. Results. The frequency of PNEC (the percentage of airway epithelium immunoreactive for bombesin) was increased up to twofold in the lungs of infants who died of SIDS (7.7 +/- 0.4%) compared with controls (4.9 +/- 0.4%), as was the frequency (40 +/- 3.5 vs 23 +/- 3.7/cm(2)) and size (748 +/- 46.5 vs 491 +/- 25.8 mu m(2)) of NEBs. In infants who died of SIDS and who were born to smoking mothers, PNEC frequency was increased significantly compared with that in those born to nonsmoking mothers, but the frequency and size of NEBs were not significantly different between the two groups. Conclusion. Our findings suggest that maternal smoking potentiates hyperplasia of the PNEC system in the lungs of infants who die of SIDS and that a dysfunction of these cells may contribute to the pathophysiology of SIDS.