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Prolonged Abeta treatment leads to impairment in the ability of primary cortical neurons to maintain K+ and Ca2+ homeostasis.

Shabala L, Howells C, West AK, Chung RS - Mol Neurodegener (2010)

Bottom Line: This decrease in survival correlated with increased K+ efflux from the cells.Ca2+ uptake was significantly higher only after prolonged Abeta treatment with 2.5-fold increase in total Ca2+ uptake over 20 min post glutamate application after six days of Abeta treatment or longer (P < 0.05).Our data suggest that long term exposure to Abeta is detrimental because it reduces the ability of cortical neurons to maintain K+ and Ca2+ homeostasis in response to glutamate challenge, a response that might underlie the early symptoms of AD.

View Article: PubMed Central - HTML - PubMed

Affiliation: NeuroRepair Group, Menzies Research Institute, University of Tasmania, Private Bag 23, Hobart, Tasmania, 7001, Australia. L.Shabala@utas.edu.au.

ABSTRACT

Background: Alzheimer's disease (AD) is a progressive neurodegenerative disease, characterised by the formation of insoluble amyloidogenic plaques and neurofibrillary tangles. Beta amyloid (Abeta) peptide is one of the main constituents in Abeta plaques, and is thought to be a primary causative agent in AD. Neurons are likely to be exposed to chronic, sublethal doses of Abeta over an extended time during the pathogenesis of AD, however most studies published to date using in vitro models have focussed on acute studies. To experimentally model the progressive pathogenesis of AD, we exposed primary cortical neurons daily to 1 muM of Abeta1-40 over 7 days and compared their survival with age-similar untreated cells. We also investigated whether chronic Abeta exposure affects neuronal susceptibility to the subsequent acute excitotoxicity induced by 10 muM glutamate and assessed how Ca2+ and K+ homeostasis were affected by either treatment.

Results: We show that continuous exposure to 1 muM Abeta1-40 for seven days decreased survival of cultured cortical neurons by 20%. This decrease in survival correlated with increased K+ efflux from the cells. One day treatment with 1 muM Abeta followed by glutamate led to a substantially higher K+ efflux than in the age-similar untreated control. This difference further increased with the duration of the treatment. K+ efflux also remained higher in Abeta treated cells 20 min after glutamate application leading to 2.8-fold higher total K+ effluxed from the cells compared to controls. Ca2+ uptake was significantly higher only after prolonged Abeta treatment with 2.5-fold increase in total Ca2+ uptake over 20 min post glutamate application after six days of Abeta treatment or longer (P < 0.05).

Conclusions: Our data suggest that long term exposure to Abeta is detrimental because it reduces the ability of cortical neurons to maintain K+ and Ca2+ homeostasis in response to glutamate challenge, a response that might underlie the early symptoms of AD. The observed inability to maintain K+ homeostasis might furthermore be useful in future studies as an early indicator of pathological changes in response to Abeta.

No MeSH data available.


Related in: MedlinePlus

Viability of cortical neurons in response to daily treatments of Aβ1-40. 6DIV cortical neurons were treated daily with 1 μM Aβ1-40 for seven days. Neuronal viability was recorded at Day 2, 3, 4, 6 and 7 of treatment and expressed as the percentage of surviving Aβ-treated neurons compared to age-matched, untreated controls. At Day 7, neuronal viability was significantly lower than the vehicle-treated controls. *P < 0.05 between Aβ1-40 treated and age-similar control on the same day of measurement. All data are means ± standard error of the mean (SEM), n = 4.
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Figure 1: Viability of cortical neurons in response to daily treatments of Aβ1-40. 6DIV cortical neurons were treated daily with 1 μM Aβ1-40 for seven days. Neuronal viability was recorded at Day 2, 3, 4, 6 and 7 of treatment and expressed as the percentage of surviving Aβ-treated neurons compared to age-matched, untreated controls. At Day 7, neuronal viability was significantly lower than the vehicle-treated controls. *P < 0.05 between Aβ1-40 treated and age-similar control on the same day of measurement. All data are means ± standard error of the mean (SEM), n = 4.

Mentions: We first examined whether chronic exposure of mature neurons to low levels of Aβ caused cell death. Cortical neurons were maintained for 6 DIV, by which time they had formed a dense meshwork of neuritic processes. They were then treated with soluble monomeric Aβ1-40 (1 μM) daily for up to a further seven days. Daily determination of neuronal viability by an Alamar Blue assay revealed that Aβ1-40 treatment did not reduce cell viability for cells treated for up to six days (Figure 1). However, by seventh day of the treatment neuronal viability decreased by 20% (P < 0.05).


Prolonged Abeta treatment leads to impairment in the ability of primary cortical neurons to maintain K+ and Ca2+ homeostasis.

Shabala L, Howells C, West AK, Chung RS - Mol Neurodegener (2010)

Viability of cortical neurons in response to daily treatments of Aβ1-40. 6DIV cortical neurons were treated daily with 1 μM Aβ1-40 for seven days. Neuronal viability was recorded at Day 2, 3, 4, 6 and 7 of treatment and expressed as the percentage of surviving Aβ-treated neurons compared to age-matched, untreated controls. At Day 7, neuronal viability was significantly lower than the vehicle-treated controls. *P < 0.05 between Aβ1-40 treated and age-similar control on the same day of measurement. All data are means ± standard error of the mean (SEM), n = 4.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2927593&req=5

Figure 1: Viability of cortical neurons in response to daily treatments of Aβ1-40. 6DIV cortical neurons were treated daily with 1 μM Aβ1-40 for seven days. Neuronal viability was recorded at Day 2, 3, 4, 6 and 7 of treatment and expressed as the percentage of surviving Aβ-treated neurons compared to age-matched, untreated controls. At Day 7, neuronal viability was significantly lower than the vehicle-treated controls. *P < 0.05 between Aβ1-40 treated and age-similar control on the same day of measurement. All data are means ± standard error of the mean (SEM), n = 4.
Mentions: We first examined whether chronic exposure of mature neurons to low levels of Aβ caused cell death. Cortical neurons were maintained for 6 DIV, by which time they had formed a dense meshwork of neuritic processes. They were then treated with soluble monomeric Aβ1-40 (1 μM) daily for up to a further seven days. Daily determination of neuronal viability by an Alamar Blue assay revealed that Aβ1-40 treatment did not reduce cell viability for cells treated for up to six days (Figure 1). However, by seventh day of the treatment neuronal viability decreased by 20% (P < 0.05).

Bottom Line: This decrease in survival correlated with increased K+ efflux from the cells.Ca2+ uptake was significantly higher only after prolonged Abeta treatment with 2.5-fold increase in total Ca2+ uptake over 20 min post glutamate application after six days of Abeta treatment or longer (P < 0.05).Our data suggest that long term exposure to Abeta is detrimental because it reduces the ability of cortical neurons to maintain K+ and Ca2+ homeostasis in response to glutamate challenge, a response that might underlie the early symptoms of AD.

View Article: PubMed Central - HTML - PubMed

Affiliation: NeuroRepair Group, Menzies Research Institute, University of Tasmania, Private Bag 23, Hobart, Tasmania, 7001, Australia. L.Shabala@utas.edu.au.

ABSTRACT

Background: Alzheimer's disease (AD) is a progressive neurodegenerative disease, characterised by the formation of insoluble amyloidogenic plaques and neurofibrillary tangles. Beta amyloid (Abeta) peptide is one of the main constituents in Abeta plaques, and is thought to be a primary causative agent in AD. Neurons are likely to be exposed to chronic, sublethal doses of Abeta over an extended time during the pathogenesis of AD, however most studies published to date using in vitro models have focussed on acute studies. To experimentally model the progressive pathogenesis of AD, we exposed primary cortical neurons daily to 1 muM of Abeta1-40 over 7 days and compared their survival with age-similar untreated cells. We also investigated whether chronic Abeta exposure affects neuronal susceptibility to the subsequent acute excitotoxicity induced by 10 muM glutamate and assessed how Ca2+ and K+ homeostasis were affected by either treatment.

Results: We show that continuous exposure to 1 muM Abeta1-40 for seven days decreased survival of cultured cortical neurons by 20%. This decrease in survival correlated with increased K+ efflux from the cells. One day treatment with 1 muM Abeta followed by glutamate led to a substantially higher K+ efflux than in the age-similar untreated control. This difference further increased with the duration of the treatment. K+ efflux also remained higher in Abeta treated cells 20 min after glutamate application leading to 2.8-fold higher total K+ effluxed from the cells compared to controls. Ca2+ uptake was significantly higher only after prolonged Abeta treatment with 2.5-fold increase in total Ca2+ uptake over 20 min post glutamate application after six days of Abeta treatment or longer (P < 0.05).

Conclusions: Our data suggest that long term exposure to Abeta is detrimental because it reduces the ability of cortical neurons to maintain K+ and Ca2+ homeostasis in response to glutamate challenge, a response that might underlie the early symptoms of AD. The observed inability to maintain K+ homeostasis might furthermore be useful in future studies as an early indicator of pathological changes in response to Abeta.

No MeSH data available.


Related in: MedlinePlus