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Kurki SN, Srinivasan R, Laine J, Virtanen MA, Ala-Kurikka T, Voipio J, Kaila K. Acute neuroinflammation leads to disruption of neuronal chloride regulation and consequent hyperexcitability in the dentate gyrus. Cell Rep 2023; 42:113379. [PMID: 37922309 DOI: 10.1016/j.celrep.2023.113379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 09/15/2023] [Accepted: 10/19/2023] [Indexed: 11/05/2023] Open
Abstract
Neuroinflammation is a salient part of diverse neurological and psychiatric pathologies that associate with neuronal hyperexcitability, but the underlying molecular and cellular mechanisms remain to be identified. Here, we show that peripheral injection of lipopolysaccharide (LPS) renders the dentate gyrus (DG) hyperexcitable to perforant pathway stimulation in vivo and increases the internal spiking propensity of dentate granule cells (DGCs) in vitro 24 h post-injection (hpi). In parallel, LPS leads to a prominent downregulation of chloride extrusion via KCC2 and to the emergence of NKCC1-mediated chloride uptake in DGCs under experimental conditions optimized to detect specific changes in transporter efficacy. These data show that acute neuroinflammation leads to disruption of neuronal chloride regulation, which unequivocally results in a loss of GABAergic inhibition in the DGCs, collapsing the gating function of the DG. The present work provides a mechanistic explanation for neuroinflammation-driven hyperexcitability and consequent cognitive disturbance.
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Affiliation(s)
- Samu N Kurki
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Neuroscience Center (HiLIFE), University of Helsinki, Helsinki, Finland.
| | - Rakenduvadhana Srinivasan
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Neuroscience Center (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Jens Laine
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Neuroscience Center (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Mari A Virtanen
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Neuroscience Center (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Tommi Ala-Kurikka
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Neuroscience Center (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Juha Voipio
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland
| | - Kai Kaila
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland; Neuroscience Center (HiLIFE), University of Helsinki, Helsinki, Finland.
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Madar AD, Pfammatter JA, Bordenave J, Plumley EI, Ravi S, Cowie M, Wallace EP, Hermann BP, Maganti RK, Jones MV. Deficits in Behavioral and Neuronal Pattern Separation in Temporal Lobe Epilepsy. J Neurosci 2021; 41:9669-86. [PMID: 34620720 DOI: 10.1523/JNEUROSCI.2439-20.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 09/09/2021] [Accepted: 09/21/2021] [Indexed: 11/21/2022] Open
Abstract
In temporal lobe epilepsy, the ability of the dentate gyrus to limit excitatory cortical input to the hippocampus breaks down, leading to seizures. The dentate gyrus is also thought to help discriminate between similar memories by performing pattern separation, but whether epilepsy leads to a breakdown in this neural computation, and thus to mnemonic discrimination impairments, remains unknown. Here we show that temporal lobe epilepsy is characterized by behavioral deficits in mnemonic discrimination tasks, in both humans (females and males) and mice (C57Bl6 males, systemic low-dose kainate model). Using a recently developed assay in brain slices of the same epileptic mice, we reveal a decreased ability of the dentate gyrus to perform certain forms of pattern separation. This is because of a subset of granule cells with abnormal bursting that can develop independently of early EEG abnormalities. Overall, our results linking physiology, computation, and cognition in the same mice advance our understanding of episodic memory mechanisms and their dysfunction in epilepsy.SIGNIFICANCE STATEMENT People with temporal lobe epilepsy (TLE) often have learning and memory impairments, sometimes occurring earlier than the first seizure, but those symptoms and their biological underpinnings are poorly understood. We focused on the dentate gyrus, a brain region that is critical to avoid confusion between similar memories and is anatomically disorganized in TLE. We show that both humans and mice with TLE experience confusion between similar situations. This impairment coincides with a failure of the dentate gyrus to disambiguate similar input signals because of pathologic bursting in a subset of neurons. Our work bridges seizure-oriented and memory-oriented views of the dentate gyrus function, suggests a mechanism for cognitive symptoms in TLE, and supports a long-standing hypothesis of episodic memory theories.
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Pun RY, Rolle IJ, LaSarge CL, Hosford BE, Rosen JM, Uhl JD, Schmeltzer SN, Faulkner C, Bronson SL, Murphy BL, Richards DA, Holland KD, Danzer SC. Excessive activation of mTOR in postnatally generated granule cells is sufficient to cause epilepsy. Neuron 2012; 75:1022-34. [PMID: 22998871 PMCID: PMC3474536 DOI: 10.1016/j.neuron.2012.08.002] [Citation(s) in RCA: 200] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/02/2012] [Indexed: 12/30/2022]
Abstract
The dentate gyrus is hypothesized to function as a "gate," limiting the flow of excitation through the hippocampus. During epileptogenesis, adult-generated granule cells (DGCs) form aberrant neuronal connections with neighboring DGCs, disrupting the dentate gate. Hyperactivation of the mTOR signaling pathway is implicated in driving this aberrant circuit formation. While the presence of abnormal DGCs in epilepsy has been known for decades, direct evidence linking abnormal DGCs to seizures has been lacking. Here, we isolate the effects of abnormal DGCs using a transgenic mouse model to selectively delete PTEN from postnatally generated DGCs. PTEN deletion led to hyperactivation of the mTOR pathway, producing abnormal DGCs morphologically similar to those in epilepsy. Strikingly, animals in which PTEN was deleted from ≥ 9% of the DGC population developed spontaneous seizures in about 4 weeks, confirming that abnormal DGCs, which are present in both animals and humans with epilepsy, are capable of causing the disease.
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Affiliation(s)
- Raymund Y.K. Pun
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Centre, Cincinnati, OH, 45229
| | - Isaiah J. Rolle
- Program in Neuroscience, University of Cincinnati, Cincinnati, OH, 45267
| | - Candi L. LaSarge
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Centre, Cincinnati, OH, 45229
| | - Bethany E. Hosford
- Program in Neuroscience, University of Cincinnati, Cincinnati, OH, 45267
| | - Jules M. Rosen
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Centre, Cincinnati, OH, 45229
| | - Juli D. Uhl
- Division of Molecular and Developmental Biology, Cincinnati Children’s Hospital Medical Centre Research Foundation, Cincinnati, OH, 45229
| | | | - Christian Faulkner
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Centre, Cincinnati, OH, 45229
| | | | - Brian L. Murphy
- Program in Neuroscience, University of Cincinnati, Cincinnati, OH, 45267
| | - David A. Richards
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Centre, Cincinnati, OH, 45229
- Departments of Anesthesia and Pediatrics, University of Cincinnati, Cincinnati, OH, 45267
- Program in Neuroscience, University of Cincinnati, Cincinnati, OH, 45267
| | - Katherine D. Holland
- Department of Neurology, Cincinnati Children’s Hospital Medical Centre, Cincinnati, OH, 45229
| | - Steve C. Danzer
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Centre, Cincinnati, OH, 45229
- Departments of Anesthesia and Pediatrics, University of Cincinnati, Cincinnati, OH, 45267
- Program in Neuroscience, University of Cincinnati, Cincinnati, OH, 45267
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