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Transient activation of microglia following acute alcohol exposure in developing mouse neocortex is primarily driven by BAX-dependent neurodegeneration
Journal article   Peer reviewed

Transient activation of microglia following acute alcohol exposure in developing mouse neocortex is primarily driven by BAX-dependent neurodegeneration

Katelin E Ahlers, Bahri Karaçay, Leah Fuller, Daniel J Bonthius and Michael E Dailey
Glia, Vol.63(10), pp.1694-1713
10/2015
DOI: 10.1002/glia.22835
PMCID: PMC4534325
PMID: 25856413
url
http://doi.org/10.1002/glia.22835View
Open Access

Abstract

Fetal alcohol exposure is the most common known cause of preventable mental retardation, yet we know little about how microglia respond to, or are affected by, alcohol in the developing brain in vivo. Using an acute (single day) model of moderate (3 g/kg) to severe (5 g/kg) alcohol exposure in postnatal day (P) 7 or P8 mice, we found that alcohol-induced neuroapoptosis in the neocortex is closely correlated in space and time with the appearance of activated microglia near dead cells. The timing and molecular pattern of microglial activation varied with the level of cell death. Although microglia rapidly mobilized to contact and engulf late-stage apoptotic neurons, apoptotic bodies temporarily accumulated in neocortex, suggesting that in severe cases of alcohol toxicity the neurodegeneration rate exceeds the clearance capacity of endogenous microglia. Nevertheless, most dead cells were cleared and microglia began to deactivate within 1-2 days of the initial insult. Coincident with microglial activation and deactivation, there was a transient increase in expression of pro-inflammatory factors, TNFα and IL-1β, after severe (5 g/kg) but not moderate (3 g/kg) EtOH levels. Alcohol-induced microglial activation and pro-inflammatory factor expression were largely abolished in BAX null mice lacking neuroapoptosis, indicating that microglial activation is primarily triggered by apoptosis rather than the alcohol. Therefore, acute alcohol exposure in the developing neocortex causes transient microglial activation and mobilization, promoting clearance of dead cells and tissue recovery. Moreover, cortical microglia show a remarkable capacity to rapidly deactivate following even severe neurodegenerative insults in the developing brain.
 Apoptosis - drug effects Cell Count Caspase 3 - metabolism Gene Expression Regulation, Developmental - genetics Apoptosis - genetics Nerve Degeneration - chemically induced Nerve Degeneration - metabolism Central Nervous System Depressants - pharmacology Neocortex - metabolism Neocortex - drug effects Peptides - metabolism Time Factors Receptors, Chemokine - genetics Receptors, Purinergic P2Y12 - metabolism bcl-2-Associated X Protein - genetics Animals, Newborn Cytokines - metabolism Microglia - drug effects Mice, Inbred C57BL Receptors, Chemokine - metabolism Gene Expression Regulation, Developmental - drug effects bcl-2-Associated X Protein - metabolism Neocortex - growth & development Mice, Transgenic Nerve Degeneration - pathology CD18 Antigens - metabolism Ethanol - pharmacology Animals Mice CX3C Chemokine Receptor 1

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