Pressor effect of ethanol in the isolated perfused human placental lobule

Placental Proteomics Reveal Insights into Fetal Alcohol Spectrum Disorders

BACKGROUND

Fetal alcohol spectrum disorders (FASD) describe many of the well-known neurodevelopmental deficits afflicting children exposed to alcohol in utero. The effects of alcohol on the maternal-fetal interface, especially the placenta, have been less explored. We herein hypothesized that chronic binge alcohol exposure during pregnancy significantly alters the placental protein profile in a rat FASD model.

METHODS

Pregnant rats were orogastrically treated daily with alcohol (4.5 g/kg, gestational day [GD] 5 to 10; 6.0 g/kg, GD 11 to 19) or 50% maltose dextrin (isocalorically matched pair-fed controls). On GD 20, placentae were collected, flash-frozen, and stored until tissues were homogenized. Protein lysates were denatured, reduced, captured on a 10-kDa spin filter, and digested. Peptides were eluted, reconstituted, and analyzed by a Q Exactive™ Hybrid Quadrupole-Orbitrap™ mass spectrometer.

RESULTS

Mass spectrometry (MS) analysis identified 2,285 placental proteins based on normalized spectral counts and 2,000 proteins by intensity-based absolute quantification. Forty-five placental proteins were significantly (p < 0.05) altered by gestational alcohol exposure by both quantification approaches. These included proteins directly related to alcohol metabolism; specific isoforms of alcohol dehydrogenase and aldehyde dehydrogenase were up-regulated in the alcohol group. Ingenuity analysis identified ethanol degradation as the most significantly altered canonical pathway in placenta, and fetal/organ development as most altered function, with increased risk for metabolic, neurological, and cardiovascular diseases. Physiological roles of the significantly altered proteins were related to early pregnancy adaptations, implantation, gestational diseases, fetal organ development, neurodevelopment, and immune functions.

CONCLUSIONS

We conclude that the placenta is a valuable organ not only to understand FASD etiology but it may also serve as a diagnostic tool to identify novel biomarkers for detecting the outcome of fetal alcohol exposure. Placental MS analysis can offer sophisticated insights into identifying alcohol metabolism-related enzymes and regulators of fetal development.

First trimester alcohol exposure alters placental perfusion and fetal oxygen availability affecting fetal growth and development in a non-human primate model

BACKGROUND

Prenatal alcohol exposure leads to impaired fetal growth, brain development, and stillbirth. Placental impairment likely contributes to these adverse outcomes, but the mechanisms and specific vasoactive effects of alcohol that links altered placental function to impaired fetal development remain areas of active research.

OBJECTIVE

Recently, we developed magnetic resonance imaging techniques in nonhuman primates to characterize placental blood oxygenation through measurements of T2* and perfusion using dynamic contrast-enhanced magnetic resonance imaging. The objective of this study was to evaluate the effects of first-trimester alcohol exposure on macaque placental function and to characterize fetal brain development in vivo.

STUDY DESIGN

Timed-pregnant Rhesus macaques (n=12) were divided into 2 groups: control (n=6) and ethanol exposed (n=6). Animals were trained to self-administer orally either 1.5 g/kg/d of a 4% ethanol solution (equivalent to 6 drinks/d) or an isocaloric control fluid from preconception until gestational day 60 (term is G168). All animals underwent Doppler ultrasound scanning followed by magnetic resonance imaging that consisted of T2* and dynamic contrast-enhanced measurements. Doppler ultrasound scanning was used to measure uterine artery and umbilical vein velocimetry and diameter to calculate uterine artery volume blood flow and placental volume blood flow. After noninvasive imaging, animals underwent cesarean delivery for placenta collection and fetal necropsy at gestational day 110 (n=6) or 135 (n=6).

RESULTS

Fetal weight and biparietal diameter were significantly smaller in ethanol-exposed animals compared with control animals at gestational day 110. By Doppler ultrasound scanning, placental volume blood flow was significantly lower (P=.04) at gestational day 110 in ethanol-exposed vs control animals. A significant reduction in placental blood flow was evident by dynamic contrast-enhanced magnetic resonance imaging. As we demonstrated recently, T2* values vary throughout the placenta and reveal gradients in blood deoxyhemoglobin concentration that range from highly oxygenated blood (long T2*) proximal to spiral arteries to highly deoxygenated blood (short T2*). Distributions of T2*throughout the placenta show significant global reduction in T2* (and hence high blood deoxyhemoglobin concentration) in ethanol-exposed vs control animals at gestational day 110 (P=.02). Fetal brain measurements indicated impaired growth and development at gestational day 110, but less so at gestational day 135 in ethanol-exposed vs control animals.

CONCLUSION

Chronic first-trimester ethanol exposure significantly reduces placental perfusion and oxygen supply to the fetal vasculature later in pregnancy. These perturbations of placental function are associated with fetal growth impairments. However, differences between ethanol-exposed and control animals in placental function and fetal developmental outcomes were smaller at gestational day 135 than at gestational day 110. These findings are consistent with placental adaptation to early perturbations that allow for compensated placental function and maintenance of fetal growth.

The effect of maternal smoking and ethanol on fatty acid transport by the human placenta

The role of the placenta in controlling the supply of fatty acids to the fetus was investigated in term placentas from non-smokers (n5), smokers (>ten cigarettes/d;n5) and after addition of ethanol at 2 mg/ml (n4). The maternal side was of the placenta was perfusedex vivofor 90 min with a physiological mixture of fatty acids and fatty acid:human albumin ratio. There was no effect of smoking on the transfer of linoleic (LA, 18 : 2n-6), α-linolenic (αLN, 18 : 3n-3), arachidonic (AA, 20 : 4n-6) or docosahexaenoic acid (DHA, 22 : 6n-3), expressed per perfused area (calculated from H218O exchange). However, the presence of ethanol in the perfusate at a concentration of 2 mg/ml significantly reduced (P<0·01) the absolute rate of transfer of the twon-3 polyunsaturated fatty acids, αLN and DHA. This specific effect of ethanol on αLN and DHA also resulted in an altered selectivity for transfer of individual fatty acids. In the non-smoking control group the placenta selectively transferred polyunsaturated fatty acids to the fetus in the order DHA>AA>αLN>LA. The order of selectivity was unaltered in placentas from smokers, but the addition of ethanol to the perfusion medium altered the order of selectivity to AA>αLN>LA>DHA. The presence of ethanol in the perfusate was also associated with a significant reduction (P<0·05) in the clearance of H218O. These results suggest that the presence of ethanol at a concentration of 2 mg/ml may reduce the availability of polyunsaturated fatty acids to the developing fetus.

Human placenta: a human organ for developmental toxicology research and biomonitoring

Pregnant mothers are exposed to a wide variety of foreign chemicals. This exposure is most commonly due to maternal medication, lifestyle factors, such as smoking, drug abuse, and alcohol consumption, or occupational and environmental sources. Foreign compounds may interfere with placental functions at many levels e.g. signaling, production and release of hormones and enzymes, transport of nutrients and waste products, implantation, cellular growth and maturation, and finally, at the terminal phase of placental life, i.e. delivery. Placental responses may also be due to pharmaco-/toxicodynamic responses to foreign chemicals, e.g. hypoxia. On the other hand, placental xenobiotic-metabolizing enzymes can detoxify or activate foreign chemicals, and transporters either enhance or prevent cellular accumulation and transfer across the placenta. The understanding of what xenobiotics do to the placenta and what the placenta does to the xenobiotics should provide the basis for the use of placenta as a tool to investigate and predict some aspects of developmental toxicity. This review aims to give an update of the fate and behavior of xenobiotics in the placenta from the viewpoint of xenobiotic-metabolizing enzymes and transporters. Their response levels will be described according to gestational status and methods used. The effects of foreign chemicals on placental metabolizing enzymes will be discussed. Also, interactions in the transporter protein level will be covered. The role of the placenta in contributing to developmental effects and fetotoxicity will be examined. The toxicological effects of maternal medications, smoking, and environmental exposures (dioxins, pesticides) as well as some possibilities for biomonitoring will be highlighted.

Effect of ethanol on human placental transport and metabolism of adenosine

It has been suggested that adenosine is involved in the acute effects of ethanol in a number of tissues. The present study was undertaken to evaluate the role of adenosine on the vascular responses of perfused isolated human placental cotyledons after the acute administration of ethanol. The possibility that ethanol may effect the uptake and metabolism adenosine was also investigated. Uptake of adenosine was studied using the single-circulation paired-tracer dilution technique. Both adenosine and ethanol caused a dose-related increase in perfusion pressure of placental lobules. Pharmacologically relevant concentrations of ethanol (10-65 mM) significantly inhibited the uptake of [3H]adenosine between 25 and 50 per cent. Thin-layer chromatographic analysis of the perfusate after the administration of ethanol showed in a 17.9 +/- 0.6 per cent reduction of [3H]adenosine metabolism. These findings support the working hypothesis that placental adenosine, at least partially, mediates the placental disturbance elicited by the administration of acute ethanol, which may contribute to the pathogenesis of fetal alcohol syndrome.

Increase in vasoactive prostaglandin E production after perfusion in human placental cotyledons

Studies from our laboratory indicate that prostaglandins may be mediators of at least some of the teratogenic actions of ethanol in both mouse and human tissue model systems. The present studies were designed to evaluate the relationship between ethanol and prostaglandin E (PGE) production in isolated human placental cotyledons. Placentas were obtained immediately after cesarean section delivery. A fetal artery supplying a single cotyledon was identified and cannulated, and the isolated cotyledon was placed in a perfusion chamber where maternal circulation was established and dual circulation continued throughout the perfusion procedure. Antipyrine clearance, oxygen consumption, and placental production of human chorionic gonadotropin were measured to verify tissue viability. PGE levels of the perfusate were measured by radioimmunoassay. Study 1 evaluates the effect of perfusion with 25 and 100 mM ethanol on placental PGE production. It was found that PGE production increased after perfusion with 25 mM ethanol, but not during the perfusion period per se. The paradigm for study 2 was identical to that of study 1, with the addition of a buffer washout period after 100-mM ethanol perfusion. Again, results indicate that perfusate PGE levels were increased in the buffer washout periods after the 25-mM and the 100-mM ethanol perfusions. The effect was not concentration dependent. An increase in circulating PGE associated with ethanol administration may be teratogenic actions and represent a potential mechanism underlying at least some aspects of fetal alcohol syndrome.