Regional Patterns of Alcohol‐Induced Neuronal Loss Depend on Genetics: Implications for Fetal Alcohol Spectrum Disorder

• Published in: Alcoholism, clinical and experimental research Vol. 42; no. 9; pp. 1627 - 1639
• Main Authors: Todd, Dylan, Bonthius, Daniel J., Sabalo, Lia Marie, Roghair, Jasmine, Karacay, Bahri, Bousquet, Samantha Larimer
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.09.2018
• Subjects: Alcohol Drinking - adverse effects; Alcohol Drinking - genetics; Alcohol Drinking - metabolism; Alcohol Drinking - pathology; Alcohol use; Alcohols; Animals; Animals, Newborn; Brain; Brain stem; Cell death; Children; Ethanol - toxicity; Facial Nucleus; Female; Fetal Alcohol Spectrum Disorder; Fetal Alcohol Spectrum Disorders - genetics; Fetal Alcohol Spectrum Disorders - pathology; Fetal alcohol syndrome; Genetics; Genotypes; Granular materials; Granule cells; Immunohistochemistry; Male; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Mutation; Neuronal Nitric Oxide Synthase; Neurons; Neurons - drug effects; Neurons - metabolism; Neurons - pathology; Neuropathology; Neuroprotection; Nitric oxide; Nitric Oxide Synthase Type I - deficiency; Nitric Oxide Synthase Type I - genetics; Nitric-oxide synthase; Nuclei (cytology); Olfactory Bulb; Olfactory Bulb - drug effects; Olfactory Bulb - metabolism; Olfactory Bulb - pathology; Pregnancy; Random Allocation; Smell; Teratogenicity; Neuroprotection; Facial Nucleus; Olfactory Bulb; Neuronal Nitric Oxide Synthase; Fetal Alcohol Spectrum Disorder
• DOI: 10.1111/acer.13824
• ISSN: 0145-6008

Background Alcohol exposure during pregnancy can kill developing neurons and lead to fetal alcohol spectrum disorder (FASD). However, affected individuals differ in their regional patterns of alcohol‐induced neuropathology. Because neuroprotective genes are expressed in spatially selective ways, their mutation could increase the vulnerability of some brain regions, but not others, to alcohol teratogenicity. The objective of this study was to determine whether a null mutation of neuronal nitric oxide synthase (nNOS) can increase the vulnerability of some brain regions, but not others, to alcohol‐induced neuronal losses. Methods Immunohistochemistry identified brain regions in which nNOS is present or absent throughout postnatal development. Mice genetically deficient for nNOS (nNOS−/−) and wild‐type controls received alcohol (0.0, 2.2, or 4.4 mg/g/d) over postnatal days (PD) 4 to 9. Mice were sacrificed in adulthood (~PD 115), and surviving neurons in the olfactory bulb granular layer and brain stem facial nucleus were quantified stereologically. Results nNOS was expressed throughout postnatal development in olfactory bulb granule cells but was never expressed in the facial nucleus. In wild‐type mice, alcohol reduced neuronal survival to similar degrees in both cell populations. However, null mutation of nNOS more than doubled alcohol‐induced cell death in the olfactory bulb granule cells, while the mutation had no effect on the facial nucleus neurons. As a result, in nNOS−/− mice, alcohol caused substantially more cell loss in the olfactory bulb than in the facial nucleus. Conclusions Mutation of the nNOS gene substantially increases vulnerability to alcohol‐induced cell loss in a brain region where the gene is expressed (olfactory bulb), but not in a separate brain region, where the gene is not expressed (facial nucleus). Thus, differences in genotype may explain why some individuals are vulnerable to FASD, while others are not, and may determine the specific patterns of neuropathology in children with FASD.