In utero ethanol exposure induces mitochondrial DNA damage and inhibits mtDNA repair in developing brain

Abstract

IntroductionMitochondrial dysfunction is postulated to be a central event in fetal alcohol spectrum disorders (FASD). People with the most severe form of FASD, fetal alcohol syndrome (FAS) are estimated to live only 34 years (95% confidence interval, 31 to 37 years), and adults who were born with any form of FASD often develop early aging. Mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage, hallmarks of aging, are postulated central events in FASD. Ethanol (EtOH) can cause mtDNA damage, consequent increased oxidative stress, and changes in the mtDNA repair protein 8-oxoguanine DNA glycosylase-1 (OGG1). Studies of molecular mechanisms are limited by the absence of suitable human models and non-invasive tools.MethodsWe compared human and rat EtOH-exposed fetal brain tissues and neuronal cultures, and fetal brain-derived exosomes (FB-Es) from maternal blood. Rat FASD was induced by administering a 6.7% alcohol liquid diet to pregnant dams. Human fetal (11–21 weeks) brain tissue was collected and characterized by maternal self-reported EtOH use. mtDNA was amplified by qPCR. OGG1 and Insulin-like growth factor 1 (IGF-1) mRNAs were assayed by qRT-PCR. Exosomal OGG1 was measured by ddPCR.ResultsMaternal EtOH exposure increased mtDNA damage in fetal brain tissue and FB-Es. The damaged mtDNA in FB-Es correlated highly with small eye diameter, an anatomical hallmark of FASD. OGG1-mediated mtDNA repair was inhibited in EtOH-exposed fetal brain tissues. IGF-1 rescued neurons from EtOH-mediated mtDNA damage and OGG1 inhibition.ConclusionThe correlation between mtDNA damage and small eye size suggests that the amount of damaged mtDNA in FB-E may serve as a marker to predict which at risk fetuses will be born with FASD. Moreover, IGF-1 might reduce EtOH-caused mtDNA damage and neuronal apoptosis.

Effects of In Utero EtOH Exposure on 18S Ribosomal RNA Processing: Contribution to Fetal Alcohol Spectrum Disorder

“…We previously organized a human tissue bank of alcohol-exposed fetuses and maternal blood throughout a pregnancy to study the effects of prenatal alcohol (EtOH) exposure on the fetal brain and eye development in humans [ 31 , 32 , 33 , 34 ], and to confirm our preliminary data from the in vivo animal model of prenatal alcohol exposure [ 34 ]. To study in utero effects of alcohol on 18S rRNA, we used brain tissues and maternal blood from 11–21 weeks gestational age (GA).…”

“…One such anatomical hallmark that is easy to measure in the fetus, even after pregnancy termination, is eye size (because eyes are so small, they are almost always intact). We previously demonstrated a negative correlation between EtOH use by pregnant mothers and several parameters of fetal development, including smaller eye sizes compared to controls [ 32 , 34 ]. We now demonstrate a high correlation between EtOH-induced reduction in FB-E srRNA content and a reduction in fetal eye size.…”

“…We used 20 EtOH-exposed human fetuses and 20 unexposed controls matched by gestation age, selected from among a total of 153 EtOH-exposed and 71 unexposed control elective pregnancy terminations, in which none of the pregnant women used drugs or medications [ 31 , 32 , 33 , 34 ]. The selection of cases and controls was made by the availability of matching maternal blood samples and intact fetal eye and brain tissues, and the availability of data for matching of sex, ethnicity/race, and gestational age (GA).…”

“…Assessment of Alcohol Exposure in Pregnancy: Maternal EtOH exposure was determined with a face-to-face questionnaire that also included questions regarding many types of drugs/medications used, as well as tobacco exposure [ 31 , 32 , 33 , 34 , 55 , 56 , 57 , 61 ]. EtOH exposure was defined as current daily use, and samples were matched based on the last incidence of alcohol consumption, as indicated by the survey.…”

“…The total cumulative alcohol dose for EtOH-consuming mothers ranged from 57–168 drinks (or 12–30 drinks/month) in the first trimester, and from 54.4 to 1827.5 drinks (or 6–320 drinks/month) for the second trimester. A drink was estimated as the equivalent of one shot (1.5 oz of brandy or 5 oz of wine [ 32 , 34 ]. Women with a known urinary tract infection or a urinalysis with white blood cells or nitrates were not enrolled.…”