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Selective induction of astrocytic gliosis generates deficits in neuronal inhibition.

ABSTRACT: Reactive astrocytosis develops in many neurologic diseases, including epilepsy. Astrocytotic contributions to pathophysiology are poorly understood. Studies examining this are confounded by comorbidities accompanying reactive astrocytosis. We found that high-titer transduction of astrocytes with enhanced green fluorescent protein (eGFP) via adeno-associated virus induced reactive astrocytosis without altering the intrinsic properties or anatomy of neighboring neurons. We examined the consequences of selective astrocytosis induction on synaptic transmission in mouse CA1 pyramidal neurons. Neurons near eGFP-labeled reactive astrocytes had reduced inhibitory, but not excitatory, synaptic currents. This inhibitory postsynaptic current (IPSC) erosion resulted from a failure of the astrocytic glutamate-glutamine cycle. Reactive astrocytes downregulated expression of glutamine synthetase. Blockade of this enzyme normally induces rapid synaptic GABA depletion. In astrocytotic regions, residual inhibition lost sensitivity to glutamine synthetase blockade, whereas exogenous glutamine administration enhanced IPSCs. Astrocytosis-mediated deficits in inhibition triggered glutamine-reversible hyperexcitability in hippocampal circuits. Thus, reactive astrocytosis could generate local synaptic perturbations, leading to broader functional deficits associated with neurologic disease.

SUBMITTER: Ortinski PI

PROVIDER: S-EPMC3225960 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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Selective induction of astrocytic gliosis generates deficits in neuronal inhibition.

Ortinski Pavel I PI Dong Jinghui J Mungenast Alison A Yue Cuiyong C Takano Hajime H Watson Deborah J DJ Haydon Philip G PG Coulter Douglas A DA

Nature neuroscience 20100425 5

Reactive astrocytosis develops in many neurologic diseases, including epilepsy. Astrocytotic contributions to pathophysiology are poorly understood. Studies examining this are confounded by comorbidities accompanying reactive astrocytosis. We found that high-titer transduction of astrocytes with enhanced green fluorescent protein (eGFP) via adeno-associated virus induced reactive astrocytosis without altering the intrinsic properties or anatomy of neighboring neurons. We examined the consequence ...[more]

PMID: 20418874

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Project description:BACKGROUND:Knock-in (KI) mouse models of Alzheimer's disease (AD) that endogenously overproduce A? without non-physiological overexpression of amyloid precursor protein (APP) provide important insights into the pathogenic mechanisms of AD. Previously, we reported that AppNL-G-F mice, which harbor three familial AD mutations (Swedish, Beyreuther/Iberian, and Arctic) exhibited emotional alterations before the onset of definitive cognitive deficits. To determine whether these mice exhibit deficits in learning and memory at more advanced ages, we compared the Morris water maze performance of AppNL-G-F and AppNL mice, which harbor only the Swedish mutation, with that of wild-type (WT) C57BL/6J mice at the age of 24 months. To correlate cognitive deficits and neuroinflammation, we also examined A? plaque formation and reactive gliosis in these mice. RESULTS:In the Morris water maze, a spatial task, 24-month-old AppNL-G-F/NL-G-F mice exhibited significantly poorer spatial learning than WT mice during the hidden training sessions, but similarly to WT mice during the visible training sessions. Not surprisingly, AppNL-G-F/NL-G-F mice also exhibited spatial memory deficits both 1 and 7 days after the last training session. By contrast, 24-month-old AppNL/NL mice had intact spatial learning and memory relative to WT mice. Immunohistochemical analyses revealed that 24-month-old AppNL-G-F/NL-G-F mice developed massive A? plaques and reactive gliosis (microgliosis and astrocytosis) throughout the brain, including the cortex and hippocampus. By contrast, we observed no detectable brain pathology in AppNL/NL mice despite overproduction of human A?40 and A?42 in their brains. CONCLUSIONS:A? plaque formation, followed by sustained neuroinflammation, is necessary for the induction of definitive cognitive deficits in App-KI mouse models of AD. Our data also indicate that introduction of the Swedish mutation alone in endogenous APP is not sufficient to produce either AD-related brain pathology or cognitive deficits in mice.

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Selective induction of astrocytic gliosis generates deficits in neuronal inhibition.

Publications

Selective induction of astrocytic gliosis generates deficits in neuronal inhibition.

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