components of cigarette smoke previously suggested to have negative effects on both the placenta and fetus, on miRNA expression in placental cells. Downregulation of miR-146a in one placental cell line, TCL-1 cells, treated with nicotine and benzo(a)pyrene suggested that miR-146a may be especially sensitive to agents of cellular stress, such as prenatal smoke exposure. Moreover, this result suggests that two specific components of cigarette smoke which affect the expression of miR-146a in term placentas may be nicotine and benzo(a)pyrene (Maccani, et al., 2010).
