Neuro-Developmental Disorders & Substance Abuse: Alana Conti, PhD
Fetal Alcohol Syndrome
Alcohol consumption during pregnancy can result in intrauterine fetal neurotoxicity, i.e., fetal alcohol syndrome/effects (FAS/E). FAS/E infants develop severe impairments in cognitive functions that are largely attributed to volume reductions in the striatum, a brain region which is consistently and dramatically reduced in volume in children exposed to alcohol in utero. Defining the molecular mechanisms and targets that determine sensitivity or resistance to ethanol neurotoxicity in the striatum and other brain regions is critical to the design of therapies for intervention in the pathological sequelae associated with FAS/E.
Ethanol exposure during brain development (synaptogenesis) results in massive apoptotic neuronal death in the rodent brain, with rapid and synchronous apoptosis occurring in the striatum. Ethanol acts to potentiate GABAA receptor activity and the antagonize NMDA receptor function. Antagonism of NMDA receptor-mediated calcium entry results in impairment of intracellular signaling pathways, such as those involving the calcium-stimulated adenylyl cyclases, AC1 and AC8. AC immunoreactivity is highly represented in the pre- and postsynaptic compartments (adjacent to NMDA receptors) making the ACs likely to be key targets for alterations of cellular responses.
Mice with single deficiency of AC1 (AC1KO) or AC8 (AC8KO), and mice with combined AC1 and AC8 deficiency (DKO) have increased vulnerability to neuronal apoptosis in the striatum following treatment with ethanol, as well as to NMDA receptor antagonists and GABAA agonists in the brain during the synaptogenesis period compared to wild type (WT) controls. However, the mechanisms by which AC1 and AC8 confer resistance to ethanol-induced apoptosis are yet unknown.
Recent evidence from our lab has demonstrated that the enhanced neuroapoptotic response observed in the striatum of DKO mice is accompanied by significant reductions in phosphorylation of known pro-survival proteins, insulin receptor substrate-1 (IRS-1), Akt and extracellular signal-regulated kinases (ERKs). These data suggest that AC1/AC8 are crucial activators of cell survival signaling pathways acutely following ethanol exposure and represent molecular factors that may directly modulate the severity of symptoms associated with Fetal Alcohol Syndrome.
DKO mice demonstrate increased apoptosis following acute ethanol treatment. Representative sagittal sections depicting ethanol-induced apoptosis in the striatum 4 h after 2.5 g/kg or 5.0 g/kg in neonatal WT and DKO mice. DKO mice demonstrated 2.5 fold increases in activated caspase-3 expression compared to WT mice at both doses. (Conti, et al., Neurobiol. Dis. (2008) 33(1):111-8)
Neuronal Reactivation after Ethanol Exposure
Ethanol is a widely used central nervous system depressant that results in sedation. In the rodent model, the duration of sedation is affected by neuroadaptation to acute ethanol doses; however, the neuroadaptive mechanisms resulting from ethanol exposure remain unclear. The cAMP signaling pathway has emerged as an important modulator of ethanol sensitivity. Reductions in cAMP signaling increase behavioral sensitivity to ethanol in the mouse. We have previously demonstrated that in DKO mice, which are lacking the calcium-stimulated adenylyl cyclases 1 and 8 (AC1 and AC8) ethanol-induced sedation is increased compared to wild type (WT) controls.
We have demonstrated previously that the increased sensitivity of DKO mice to ethanol-induced sedation was accompanied by impaired protein kinase A (PKA) phosphorylation of target proteins of unknown identity. We hypothesize that ethanol-mediated induction of PKA phosphorylation is part of a compensatory homeostatic mechanism initiated by AC1 and/or AC8. Our recent use of phosphoproteomic techniques has allowed for identification of several PKA target proteins involved with presynaptic function, including synapsin, vacuolar H+-ATPase, and dynein, that are phosphorylated following acute ethanol exposure in WT mice. Identification of additional proteins phosphorylated after ethanol treatment include dynamin and eukaryotic elongation factor-2 (eEF-2). Of these, we have demonstrated that phosphorylation of synapsin I, II, eEF-2 and dynamin is impaired in the brains of DKO, and in some cases, AC1KO mice following acute ethanol exposure.
Together these data suggest that calcium-stimulated ACs, largely involving AC1, contribute to the presynaptic homeostatic response to ethanol-induced inhibition of neuronal function by facilitating PKA activation of proteins involved in presynaptic vesicle release. Further identification of PKA targets uniquely regulated by AC1 and AC8 will provide additional insight into the mechanisms of the neuronal response to the inhibitory effects of ethanol.
Immunohistochemical detection of phospho-synapsin protein following ethanol treatment in WT and ACKO mice. Representative coronal sections demonstrate robust induction of phospho-synapsin in the cortex and hippocampus of ethanol- treated WT mice compared to saline controls. DKO mice demonstrate no induction of phospho-synapsin in either brain region following ethanol treatment compared to saline controls. Representative coronal sections demonstrate robust induction of phospho-synapsin in the hippocampus of ethanol-treated WT and AC8KO mice. In contrast, AC1KO mice impaired induction of phospho-synapsin in following ethanol treatment compared to WT and AC8KO mice. (Conti, et al., (2009) PLoS ONE 4(5):e5697)
Find Dr. Conti's lab webpage here.
Education and Training
BSE, Bioengineering, University of Pennsylvania
Ph.D., Neuroscience, University of Pennsylvania (Advisor: Julie A. Blendy, PhD)
Postdoctoral Fellow, Pediatrics, Washington University in St. Louis School of Medicine (Advisor: Louis J. Muglia)
Research Instructor, Washington University in St. Louis School of Medicine (Psychiatry)
Active Research Funding
K01- AA017683 NIH/NIAAA; Effects of Adenylyl Cyclases 1 and 8 on Neuronal Sensitivity to Ethanol; AC Conti, PI; DM Kuhn, Mentor (2008-2013)
Alana C. Conti, Ph.D. (Principal Investigator)
Director of Research, Pediatric Neurosurgery
Assistant Professor, Department of Neurological Surgery
Wayne State University School of Medicine
4646 John R. St. (11R)
Detroit, MI 48201