Search

Objective: Tuberous sclerosis complex (TSC) is a genetic disorder, characterized by tumor formation in the brain and other organs, and severe neurological symptoms, such as epilepsy. Abnormal vascular endothelial growth factor (VEGF) expression may promote angiogenesis in kidney and lung tumors in TSC and has been identified in brain specimens from TSC patients, but the role of VEGF and vascular abnormalities in neurological manifestations of TSC is poorly defined. In this study, we investigated abnormalities in brain VEGF expression, cerebral blood vessel anatomy, and blood-brain barrier (BBB) structure and function in a mouse model of TSC., Methods: Tsc1 GFAP CKO mice were used to investigate VEGF expression and vascular abnormalities in the brain by Western blotting and immunohistochemical analysis of vascular and BBB markers. In vivo two-photon imaging was used to assess BBB permeability to normally impenetrable fluorescently labeled compounds. The effect of mechanistic target of rapamycin (mTOR) pathway inhibitors, VEGF receptor antagonists (apatinib), or BBB stabilizers (RepSox) was assessed in some of these assays, as well as on seizures by video-electroencephalography., Results: VEGF expression was elevated in cortex of Tsc1 GFAP CKO mice, which was reversed by the mTOR inhibitor rapamycin. Tsc1 GFAP CKO mice exhibited increased cerebral angiogenesis and vascular complexity in cortex and hippocampus, which were reversed by the VEGF receptor antagonist apatinib. BBB permeability was abnormally increased and BBB-related tight junction proteins occludin and claudin-5 were decreased in Tsc1 GFAP CKO mice, also in an apatinib- and RepSox-dependent manner. The BBB stabilizer (RepSox), but not the VEGF receptor antagonist (apatinib), decreased seizures and improved survival in Tsc1 GFAP CKO mice., Significance: Increased brain VEGF expression is dependent on mTOR pathway activation and promotes cerebral vascular abnormalities and increased BBB permeability in a mouse model of TSC. BBB modulation may affect epileptogenesis and represent a rational treatment for epilepsy in TSC., (© 2023 International League Against Epilepsy.)

Objective: Neurostimulation is an emerging treatment for patients with drug-resistant epilepsy, which is used to suppress, prevent, and terminate seizure activity. Unfortunately, after implantation and despite best clinical practice, most patients continue to have persistent seizures even after years of empirical optimization. The objective of this study is to determine optimal spatial and amplitude properties of neurostimulation in inhibiting epileptiform activity in an acute hippocampal seizure model., Methods: We performed high-throughput testing of high-frequency focal brain stimulation in the acute intrahippocampal kainic acid mouse model of status epilepticus. We evaluated combinations of six anatomic targets and three stimulus amplitudes., Results: We found that the spike-suppressive effects of high-frequency neurostimulation are highly dependent on the stimulation amplitude and location, with higher amplitude stimulation being significantly more effective. Epileptiform spiking activity was significantly reduced with ipsilateral 250 μA stimulation of the CA1 and CA3 hippocampal regions with 21.5% and 22.2% reductions, respectively. In contrast, we found that spiking frequency and amplitude significantly increased with stimulation of the ventral hippocampal commissure. We further found spatial differences with broader effects from CA1 versus CA3 stimulation., Significance: These findings demonstrate that the effects of therapeutic neurostimulation in an acute hippocampal seizure model are highly dependent on the location of stimulation and stimulus amplitude. We provide a platform to optimize the anti-seizure effects of neurostimulation, and demonstrate that an exploration of the large electrical parameter and location space can improve current modalities for treating epilepsy., Plain Language Summary: In this study, we tested how electrical pulses in the brain can help control seizures in mice. We found that the electrode's placement and the stimulation amplitude had a large effect on outcomes. Some brain regions, notably nearby CA1 and CA3, responded positively with reduced seizure-like activities, while others showed increased activity. These findings emphasize that choosing the right spot for the electrode and adjusting the strength of electrical pulses are both crucial when considering neurostimulation treatments for epilepsy., (© 2023 The Authors. Epilepsia Open published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.)

Objective: Tuberous sclerosis complex (TSC) is a genetic disorder, characterized by tumor formation in multiple organs and severe neurologic manifestations, including epilepsy, intellectual disability, and autism. Abnormalities of both neurons and astrocytes have been implicated in contributing to the neurologic phenotype of TSC, but the role of microglia in TSC has not been investigated. The objectives of this study were to characterize microglial activation in a mouse model of TSC, involving conditional inactivation of the Tsc1 gene predominantly in glial cells (Tsc1(GFAP) CKO mice), and to test the hypothesis that microglial activation contributes to epileptogenesis in this mouse model., Methods: Microglial and astrocyte activation was examined in Tsc1(GFAP) CKO mice by ionized calcium binding adaptor molecule 1 and glial fibrillary acidic protein immunohistochemistry. Cytokine and chemokine expression was evaluated with quantitative polymerase chain reaction. Seizures were monitored by video-electroencephalography (EEG). The effect of minocycline in inhibiting microglial and astrocyte activation, cytokine expression, and seizures was tested., Results: Microglial cell number and size were increased in cortex and hippocampus of 3- to 4-week-old Tsc1(GFAP) CKO mice, which correlated with the onset of seizures. Minocycline treatment prevented the increase in number and cell size of microglia in 4-week-old Tsc1(GFAP) CKO mice. However, minocycline treatment had no effect on astrocyte proliferation and cytokine/chemokine expression and the progression of seizures in Tsc1(GFAP) CKO mice., Significance: Microglia cell number and size are abnormal in Tsc1(GFAP) CKO mice, and minocycline treatment inhibits this microglia activation, but does not suppress seizures. Microglia may play a role in the neurologic manifestations of TSC, but additional studies are needed in other models and human studies to determine whether microglia are critical for epileptogenesis in TSC., (Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.)

Summary: Objective: Microglial abnormalities have been reported in pathologic specimens from patients with tuberous sclerosis complex (TSC), a genetic disorder characterized by epilepsy, intellectual disability, and autism. However, the pathogenic role of microglia in epilepsy in TSC is poorly understood, particularly whether microglia defects may be a primary contributor to epileptogenesis or are secondary to seizures or simply epiphenomena. In this study, we tested the hypothesis that Tsc1 gene inactivation in microglia is sufficient to cause epilepsy in mouse models of TSC. Methods: Using a chemokine receptor, Cx3cr1, to target microglia, conventional Tsc1Cx3cr1‐CreCKO (conditional knockout) mice and postnatal‐inducible Tsc1Cx3cr1‐CreERCKO mice were generated and assessed for molecular and histopathologic evidence of microglial abnormalities, mechanistic target of rapamycin 1 (mTORC1) pathway activation, and epilepsy. Results: Tsc1Cx3cr1‐CreCKO mice exhibited a high efficiency of microglia Tsc1 inactivation, mTORC1 activation, increased microglial size and number, and robust epilepsy, which were rapamycin‐dependent. However, Cre reporter studies demonstrated that constitutive Cx3cr1 expression affected not only microglia, but also a large percentage of cortical neurons, confounding the role of microglia in epileptogenesis in Tsc1 Cx3cr1‐CreCKO mice. In contrast, postnatal inactivation of Tsc1 utilizing a tamoxifen‐inducible Cx3cr1‐CreER resulted in a more‐selective microglia Tsc1 inactivation with high efficiency, mTORC1 activation, and increased microglial size and number, but no documented epilepsy. Significance: Microglia abnormalities may contribute to epileptogenesis in the context of neuronal involvement in TSC mouse models, but selective Tsc1 gene inactivation in microglia alone may not be sufficient to cause epilepsy, suggesting that microglia have more supportive roles in the pathogenesis of seizures in TSC. [ABSTRACT FROM AUTHOR]

Objective Inhibitors of the mechanistic target of rapamycin (m TOR) pathway have antiepileptogenic effects in preventing epilepsy and pathologic and molecular mechanisms of epileptogenesis in mouse models of tuberous sclerosis complex ( TSC). However, long-term treatment with m TOR inhibitors may be required to maintain efficacy and potentially has chronic side effects, such as immunosuppression. Attempts to minimize drug exposure will facilitate translational efforts to develop m TOR inhibitors as antiepileptogenic agents for patients with TSC. In this study, we tested intermittent dosing paradigms of m TOR inhibitors for antiepileptogenic properties in a TSC mouse model. Methods Western blot analysis of phosphorylation of S6 protein was used to assess the dose- and time-dependence of m TOR inhibition by rapamycin in control mice and conditional knockout mice with inactivation of the Tsc1 gene in glial fibrillary acidic protein ( GFAP)-expressing cells ( Tsc1 GFAPCKO mice). Based on the Western blot studies, different dosing paradigms of rapamycin starting at postnatal day 21 were tested for their ability to prevent epilepsy or pathologic abnormalities in Tsc1 GFAPCKO mice: 4 days of rapamycin only (4-∞), 4 days on-24 days off (4-24), and 4 days on-10 days off (4-10). Results m TOR activity was inhibited by rapamycin in a dose-dependent fashion and recovered to baseline by about 10 days after the last rapamycin dose. The 4-10 and 4-24 dosing paradigms almost completely prevented epilepsy and the 4-10 paradigm inhibited glial proliferation and megalencephaly in Tsc1 GFAPCKO mice. Significance Intermittent dosing of rapamycin, with drug holidays of more than 3 weeks, maintains significant antiepileptogenic properties in mouse models of TSC. These findings have important translational applications in developing m TOR inhibitors as antiepileptogenic agents in TSC patients by minimizing drug exposure and potential side effects. [ABSTRACT FROM AUTHOR]