Preeclampsia is thought to arise from inadequate cytotrophoblast migration and invasion of the maternal spiral arteries, resulting in placental ischemia and hypertension. Evidence suggests that altered expression of epithelial Na(+) channel (ENaC) proteins may be a contributing mechanism for impaired cytotrophoblast migration. ENaC activity is required for normal cytotrophoblast migration. Moreover, β-ENaC, the most robustly expressed placental ENaC message, is reduced in placentas from preeclamptic women. We recently demonstrated that heme oxygenase-1 (HO-1) protects against hypertension in a rat model of placental ischemia; however, whether HO-1 regulation of β-ENaC contributes to the beneficial effects of HO-1 is unknown. The purpose of this study was to determine whether β-ENaC mediates cytotrophoblast migration and whether HO-1 enhances ENaC-mediated migration. We showed that placental ischemia, induced by reducing uterine perfusion suppressed, and HO-1 induction restored, β-ENaC expression in ischemic placentas. Using an in vitro model, we found that HO-1 induction, using cobalt protoporphyrin, stimulates cytotrophoblast β-ENaC expression by 1.5- and 1.8-fold (10 and 50 μM). We then showed that silencing of β-ENaC in cultured cytotrophoblasts (BeWo cells), by expression of dominant-negative constructs, reduced migration to 56 ± 13% (P < 0.05) of control. Importantly, HO-1 induction enhanced migration (43 ± 5% of control, P < 0.05), but the enhanced migratory response was entirely blocked by ENaC inhibition with amiloride (10 μM). Taken together, our results suggest that β-ENaC mediates cytotrophoblast migration and increasing β-ENaC expression by HO-1 induction enhances migration. HO-1 regulation of cytotrophoblast β-ENaC expression and migration may be a potential therapeutic target in preeclamptic patients.
Keywords: cytotrophoblast; heme oxygenase-1; placenta; preeclampsia; β-ENaC.