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Impaired ILK Function Is Associated with Deficits in Hippocampal Based Memory and Synaptic Plasticity in a FASD Rat Model.

Bhattacharya D, Dunaway EP, Bhattacharya S, Bloemer J, Buabeid M, Escobar M, Suppiramaniam V, Dhanasekaran M - PLoS ONE (2015)

Bottom Line: This reduced memory performance was consistent with decrease in LTP as compared to controls.Furthermore, immunoprecipitation of ILK revealed a decreased interaction with GluR2.These impairments appear to be mediated by reduced GSK3β regulation and increased synaptic stabilization of the calcium-impermeable GluR2 AMPA receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Drug, Discovery and Development, Auburn University, Auburn, Alabama, United States of America.

ABSTRACT
Fetal Alcohol Spectrum Disorder (FASD) is an umbrella term that encompasses a wide range of anatomical and behavioral problems in children who are exposed to alcohol during the prenatal period. There is no effective treatment for FASD, because of lack of complete characterization of the cellular and molecular mechanisms underlying this condition. Alcohol has been previously characterized to affect integrins and growth factor signaling receptors. Integrin Linked Kinase (ILK) is an effector of integrin and growth-factor signaling which regulates various signaling processes. In FASD, a downstream effector of ILK, Glycogen Synthase Kinase 3β (GSK3β) remains highly active (reduced Ser9 phosphorylation). GSK3β has been known to modulate glutamate receptor trafficking and channel properties. Therefore, we hypothesize that the cognitive deficits accompanying FASD are associated with impairments in the ILK signaling pathway. Pregnant Sprague Dawley rats consumed a "moderate" amount of alcohol throughout gestation, or a calorie-equivalent sucrose solution. Contextual fear conditioning was used to evaluate memory performance in 32-33-day-old pups. Synaptic plasticity was assessed in the Schaffer Collateral pathway, and hippocampal protein lysates were used to evaluate ILK signaling. Alcohol exposed pups showed impaired contextual fear conditioning, as compared to control pups. This reduced memory performance was consistent with decrease in LTP as compared to controls. Hippocampal ILK activity and GSK3β Ser21/9 phosphorylation were significantly lower in alcohol-exposed pups than controls. Increased synaptic expression of GluR2 AMPA receptors was observed with immunoprecipitation of post-synaptic density protein 95 (PSD95). Furthermore, immunoprecipitation of ILK revealed a decreased interaction with GluR2. The ILK pathway appears to play a significant role in memory and synaptic plasticity impairments in FASD rats. These impairments appear to be mediated by reduced GSK3β regulation and increased synaptic stabilization of the calcium-impermeable GluR2 AMPA receptors.

No MeSH data available.


Related in: MedlinePlus

Prenatal alcohol impairs synaptic plasticity.(a) Input-output curves showing hippocampal basal synaptic transmission did not change in rats prenatally exposed to alcohol compared to controls. The graph shows f-EPSP amplitudes (mean ± SEM) as a function of stimulus intensity in the CA1 stratum radiatum. (b) TBS-induced LTP was recorded in hippocampal brain slices from prenatal alcohol exposed and nonexposed control rats (n = 5). The figure presents the time-course of percentage change in field EPSP slopes (mv/ms) with representative traces. The arrow indicates the time at which TBS protocol was delivered and 5 minute baseline is shown for clarity. Inset, representative fEPSP traces taken before the TBS (1,3) and after stabilization of LTP expression (2,4) for control and alcohol groups accordingly. (c) LTP was reduced in animals exposed to prenatal alcohol as compared to the nonexposed controls; [average for exposed animals was 162.2 ± 19.0%, and for nonexposed animals was 129.6 ± 20%, F = 6.217; p < 0.05].
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pone.0135700.g002: Prenatal alcohol impairs synaptic plasticity.(a) Input-output curves showing hippocampal basal synaptic transmission did not change in rats prenatally exposed to alcohol compared to controls. The graph shows f-EPSP amplitudes (mean ± SEM) as a function of stimulus intensity in the CA1 stratum radiatum. (b) TBS-induced LTP was recorded in hippocampal brain slices from prenatal alcohol exposed and nonexposed control rats (n = 5). The figure presents the time-course of percentage change in field EPSP slopes (mv/ms) with representative traces. The arrow indicates the time at which TBS protocol was delivered and 5 minute baseline is shown for clarity. Inset, representative fEPSP traces taken before the TBS (1,3) and after stabilization of LTP expression (2,4) for control and alcohol groups accordingly. (c) LTP was reduced in animals exposed to prenatal alcohol as compared to the nonexposed controls; [average for exposed animals was 162.2 ± 19.0%, and for nonexposed animals was 129.6 ± 20%, F = 6.217; p < 0.05].

Mentions: Deficits in hippocampus-dependent associative learning and memory have been supported with long-term potentiation (LTP) in the Schaffer collateral pathway. We measured the changes in field potential in one-month old rat brains. In animals exposed to alcohol during the prenatal period, both moderate and binge drinking have been shown to result in deficits in cognitive function and neurogenesis [28, 29]. However, some studies questioned the amount of alcohol intake that can influence the deficits in memory impairment [30–32]. The differences in the pattern of administration of alcohol could also be a reason for the differences seen in behavioral studies. In this study, we looked into moderate continuous drinking, in which the animal has access to an alcohol solution as their only source of fluid. Following this administration regime, we initially determined the overall CA3-CA1 synaptic neurotransmission in the brain of animals prenatally exposed to alcohol, as well as in control rats. We monitored input-output (I/O) curves as a measure of overall basal synaptic transmission. Prenatal exposure to alcohol had no impact on I/O (p = .96; Fig 2A; also see [33]), which appears to be affected in acute or binge alcohol consumption models [34]. LTP was recorded from the Schaffer collateral pyramidal cell region at CA1 using theta burst stimulation (TBS) applied at CA3. Moderate prenatal alcohol decreased LTP measured as percentage change of fEPSP from baseline as compared to the unexposed controls (Fig 2B and 2C; 121.453 ± 8.2% vs 167.188± 16.5%, p < 0.05). LTP induction was lowered in exposed animals, which suggests a possible modulation of glutamate receptors at the synapse.


Impaired ILK Function Is Associated with Deficits in Hippocampal Based Memory and Synaptic Plasticity in a FASD Rat Model.

Bhattacharya D, Dunaway EP, Bhattacharya S, Bloemer J, Buabeid M, Escobar M, Suppiramaniam V, Dhanasekaran M - PLoS ONE (2015)

Prenatal alcohol impairs synaptic plasticity.(a) Input-output curves showing hippocampal basal synaptic transmission did not change in rats prenatally exposed to alcohol compared to controls. The graph shows f-EPSP amplitudes (mean ± SEM) as a function of stimulus intensity in the CA1 stratum radiatum. (b) TBS-induced LTP was recorded in hippocampal brain slices from prenatal alcohol exposed and nonexposed control rats (n = 5). The figure presents the time-course of percentage change in field EPSP slopes (mv/ms) with representative traces. The arrow indicates the time at which TBS protocol was delivered and 5 minute baseline is shown for clarity. Inset, representative fEPSP traces taken before the TBS (1,3) and after stabilization of LTP expression (2,4) for control and alcohol groups accordingly. (c) LTP was reduced in animals exposed to prenatal alcohol as compared to the nonexposed controls; [average for exposed animals was 162.2 ± 19.0%, and for nonexposed animals was 129.6 ± 20%, F = 6.217; p < 0.05].
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4549293&req=5

pone.0135700.g002: Prenatal alcohol impairs synaptic plasticity.(a) Input-output curves showing hippocampal basal synaptic transmission did not change in rats prenatally exposed to alcohol compared to controls. The graph shows f-EPSP amplitudes (mean ± SEM) as a function of stimulus intensity in the CA1 stratum radiatum. (b) TBS-induced LTP was recorded in hippocampal brain slices from prenatal alcohol exposed and nonexposed control rats (n = 5). The figure presents the time-course of percentage change in field EPSP slopes (mv/ms) with representative traces. The arrow indicates the time at which TBS protocol was delivered and 5 minute baseline is shown for clarity. Inset, representative fEPSP traces taken before the TBS (1,3) and after stabilization of LTP expression (2,4) for control and alcohol groups accordingly. (c) LTP was reduced in animals exposed to prenatal alcohol as compared to the nonexposed controls; [average for exposed animals was 162.2 ± 19.0%, and for nonexposed animals was 129.6 ± 20%, F = 6.217; p < 0.05].
Mentions: Deficits in hippocampus-dependent associative learning and memory have been supported with long-term potentiation (LTP) in the Schaffer collateral pathway. We measured the changes in field potential in one-month old rat brains. In animals exposed to alcohol during the prenatal period, both moderate and binge drinking have been shown to result in deficits in cognitive function and neurogenesis [28, 29]. However, some studies questioned the amount of alcohol intake that can influence the deficits in memory impairment [30–32]. The differences in the pattern of administration of alcohol could also be a reason for the differences seen in behavioral studies. In this study, we looked into moderate continuous drinking, in which the animal has access to an alcohol solution as their only source of fluid. Following this administration regime, we initially determined the overall CA3-CA1 synaptic neurotransmission in the brain of animals prenatally exposed to alcohol, as well as in control rats. We monitored input-output (I/O) curves as a measure of overall basal synaptic transmission. Prenatal exposure to alcohol had no impact on I/O (p = .96; Fig 2A; also see [33]), which appears to be affected in acute or binge alcohol consumption models [34]. LTP was recorded from the Schaffer collateral pyramidal cell region at CA1 using theta burst stimulation (TBS) applied at CA3. Moderate prenatal alcohol decreased LTP measured as percentage change of fEPSP from baseline as compared to the unexposed controls (Fig 2B and 2C; 121.453 ± 8.2% vs 167.188± 16.5%, p < 0.05). LTP induction was lowered in exposed animals, which suggests a possible modulation of glutamate receptors at the synapse.

Bottom Line: This reduced memory performance was consistent with decrease in LTP as compared to controls.Furthermore, immunoprecipitation of ILK revealed a decreased interaction with GluR2.These impairments appear to be mediated by reduced GSK3β regulation and increased synaptic stabilization of the calcium-impermeable GluR2 AMPA receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Drug, Discovery and Development, Auburn University, Auburn, Alabama, United States of America.

ABSTRACT
Fetal Alcohol Spectrum Disorder (FASD) is an umbrella term that encompasses a wide range of anatomical and behavioral problems in children who are exposed to alcohol during the prenatal period. There is no effective treatment for FASD, because of lack of complete characterization of the cellular and molecular mechanisms underlying this condition. Alcohol has been previously characterized to affect integrins and growth factor signaling receptors. Integrin Linked Kinase (ILK) is an effector of integrin and growth-factor signaling which regulates various signaling processes. In FASD, a downstream effector of ILK, Glycogen Synthase Kinase 3β (GSK3β) remains highly active (reduced Ser9 phosphorylation). GSK3β has been known to modulate glutamate receptor trafficking and channel properties. Therefore, we hypothesize that the cognitive deficits accompanying FASD are associated with impairments in the ILK signaling pathway. Pregnant Sprague Dawley rats consumed a "moderate" amount of alcohol throughout gestation, or a calorie-equivalent sucrose solution. Contextual fear conditioning was used to evaluate memory performance in 32-33-day-old pups. Synaptic plasticity was assessed in the Schaffer Collateral pathway, and hippocampal protein lysates were used to evaluate ILK signaling. Alcohol exposed pups showed impaired contextual fear conditioning, as compared to control pups. This reduced memory performance was consistent with decrease in LTP as compared to controls. Hippocampal ILK activity and GSK3β Ser21/9 phosphorylation were significantly lower in alcohol-exposed pups than controls. Increased synaptic expression of GluR2 AMPA receptors was observed with immunoprecipitation of post-synaptic density protein 95 (PSD95). Furthermore, immunoprecipitation of ILK revealed a decreased interaction with GluR2. The ILK pathway appears to play a significant role in memory and synaptic plasticity impairments in FASD rats. These impairments appear to be mediated by reduced GSK3β regulation and increased synaptic stabilization of the calcium-impermeable GluR2 AMPA receptors.

No MeSH data available.


Related in: MedlinePlus