Acid-sensitive channel inhibition prevents fetal alcohol spectrum disorders cerebellar Purkinje cell loss

Abstract

Ethanol is now considered the most common human teratogen. Educational campaigns have not reduced the incidence of ethanol-mediated teratogenesis, leading to a growing interest in the development of therapeutic prevention or mitigation strategies. On the basis of the observation that maternal ethanol consumption reduces maternal and fetal pH, we hypothesized that a pH-sensitive pathway involving the TWIK-related acid-sensitive potassium channels (TASKs) is implicated in ethanol-induced injury to the fetal cerebellum, one of the most sensitive targets of prenatal ethanol exposure. Pregnant ewes were intravenously infused with ethanol (258+/-10 mg/dl peak blood ethanol concentration) or saline in a "3 days/wk binge" pattern throughout the third trimester. Quantitative stereological analysis demonstrated that ethanol resulted in a 45% reduction in the total number of fetal cerebellar Purkinje cells, the cell type most sensitive to developmental ethanol exposure. Extracellular pH manipulation to create the same degree and pattern of pH fall caused by ethanol (manipulations large enough to inhibit TASK 1 channels), resulted in a 24% decrease in Purkinje cell number. We determined immunohistochemically that TASK 1 channels are expressed in Purkinje cells and that the TASK 3 isoform is expressed in granule cells of the ovine fetal cerebellum. Pharmacological blockade of both TASK 1 and TASK 3 channels simultaneous with ethanol effectively prevented any reduction in fetal cerebellar Purkinje cell number. These results demonstrate for the first time functional significance of fetal cerebellar two-pore domain pH-sensitive channels and establishes them as a potential therapeutic target for prevention of ethanol teratogenesis.

Alcohol and Maternal Uterine Vascular Adaptations During Pregnancy-Part I: Effects of Chronic In Vitro Binge-Like Alcohol on Uterine Endothelial Nitric Oxide System and Function

“…To mimic maternal binge drinking patterns, uterine artery endothelial cells were cultured to 70% confluence in the absence (0 mg/dl; Control, Ctrl) or presence of two doses of alcohol. To achieve a magnitude that is similar to the peak blood alcohol concentrations (BACs) obtained in previously published Fetal Alcohol Spectrum Disorders (FASD) studies performed using the sheep model system (Cudd et al, 2001; Ramadoss et al, 2008; West et al, 2001), we utilized a lower dose (LD, 300 mg/dl) group. In addition, to mimic clinically relevant abusive patterns of drinking in women of child-bearing age and those who are admitted to emergency wards (Church and Gerkin, 1988; Hammond et al, 1973; Urso et al, 1981; Wells and Barnhill, 1996), we utilized a higher dose (HD, 600 mg/dl) group.…”

Fetal stress. Focus on “Effects of acute acidemia on the fetal cardiovascular defense to acute hypoxemia” by Thakor and Giussani

“…Thakor and Giussani demonstrate that acute acidemia augments the cardiovascular and endocrine reflex response to hypoxia, essentially increasing the sensitivity of the fetus to hypoxia. The augmentation in reflex responsiveness to hypoxia could result from synergism between acidemia and hypoxia at the peripheral chemoreceptor or, as perhaps suggested by Ramadoss et al (16), by a direct action of H ϩ within the fetal central nervous system.…”

“…Acidemia resulting from metabolic disturbance in the fetus can have more lasting effects, raising the question of where the pH changes are sensed. It has been recently reported by Ramadoss et al (16) that neuronal damage in the fetal central nervous system after repeated exposure to alcohol (perhaps one of the sequelae of fetal alcohol syndrome) is actually secondary to acidemia that results from maternal "binge" exposure to alcohol. In that model of fetal acidemia, neuronal damage could be prevented by blockade of TWIK-related acid-sensitive potassium channels (TASK channels), strongly suggesting that H ϩ in blood acts directly in the fetal brain, bypassing the fetal blood-brain barrier.…”

The Role of Acidemia in Maternal Binge Alcohol-Induced Alterations in Fetal Bone Functional Properties

“…The experiment was conducted on three consecutive days per week, followed by 4 days without treatment, beginning on GD 109 until GD 132 to mimic a weekend binge drinking pattern common in women who abuse alcohol during pregnancy (Maier and West, 2001; Ramadoss et al, 2008a). In all treatment groups, the infusion solutions were delivered intravenously over one hour by peristaltic pump (Masterflex, model 7014-20 Cole Parmer, Niles, IL) and pumps were calibrated before each infusion.…”