Nicotine causes depolarization, decreased intracellular calcium concentration ([Ca2+]i) and reduced nitric oxide (NO) production in human umbilical artery endothelial cells (HUAECs)

Abstract

Maternal environmental tobacco smoke (ETS) exposure has been associated with intrauterine growth retardation (IUGR) and low birth weight, both of which increase infant morbidity and mortality. Nicotine, an active component in ETS, is known to decrease birth weight and postnatal weight gain, yet the mechanism remains unclear. We hypothesized that nicotine alters membrane potential (Em)‐dependent regulation of [Ca2+]i and nitric oxide (NO) production in endothelial cells, which could cause umbilical vessel contraction, impairment of blood flow and IUGR. Fluorescent microscopy was used in HUAECs treated with nicotine (10–100ng/ml; 15m–24hr). Fura‐2 was used to measure [Ca2+]i and DiBAC4(3) was used to measure changes in Em. We found that HUAECs treated with 100ng/ml of nicotine showed depolarization and an immediate dramatic decrease in [Ca2+]i. Prolonged nicotine treatment (10 and 100ng/ml; 1–24 hr) also decreased [Ca2+]i . In addition, total nitrite levels in the cell media were measured via Griess reaction following total nitrate reduction. Treatment with nicotine (10ng/ml; 1–4hrs) reduced total nitrite levels in the media in comparison to untreated HUAECs. From these results, we conclude that nicotine, at concentrations comparable to plasma levels in non‐smokers exposed to ETS, caused decreased NO production in HUAECs, perhaps secondary to depolarization and decreased [Ca2+]i. Funded by: HL73859