Exosomal TNF-α mediates voltage-gated Na+ channel 1.6 overexpression and contributes to brain tumor–induced neuronal hyperexcitability
Cesar Adolfo Sanchez Trivino, … , Fabrizia Cesca, Vincent Torre
Cesar Adolfo Sanchez Trivino, … , Fabrizia Cesca, Vincent Torre
Published August 1, 2024
Citation Information: J Clin Invest. 2024;134(18):e166271. https://doi.org/10.1172/JCI166271.
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Research Article Neuroscience Oncology

Exosomal TNF-α mediates voltage-gated Na+ channel 1.6 overexpression and contributes to brain tumor–induced neuronal hyperexcitability

Abstract

Patients affected by glioma frequently experience epileptic discharges; however, the causes of brain tumor–related epilepsy (BTRE) are still not completely understood. We investigated the mechanisms underlying BTRE by analyzing the effects of exosomes released by U87 glioma cells and by patient-derived glioma cells. Rat hippocampal neurons incubated for 24 hours with these exosomes exhibited increased spontaneous firing, while their resting membrane potential shifted positively by 10–15 mV. Voltage clamp recordings demonstrated that the activation of the Na+ current shifted toward more hyperpolarized voltages by 10–15 mV. To understand the factors inducing hyperexcitability, we focused on exosomal cytokines. Western blot and ELISAs showed that TNF-α was present inside glioma-derived exosomes. Remarkably, incubation with TNF-α fully mimicked the phenotype induced by exosomes, with neurons firing continuously, while their resting membrane potential shifted positively. Real-time PCR revealed that both exosomes and TNF-α induced overexpression of the voltage-gated Na+ channel Nav1.6, a low-threshold Na+ channel responsible for hyperexcitability. When neurons were preincubated with infliximab, a specific TNF-α inhibitor, the hyperexcitability induced by exosomes and TNF-α was drastically reduced. We propose that infliximab, an FDA-approved drug to treat rheumatoid arthritis, could ameliorate the conditions of glioma patients with BTRE.

Authors

Cesar Adolfo Sanchez Trivino, Renza Spelat, Federica Spada, Camilla D’Angelo, Ivana Manini, Irene Giulia Rolle, Tamara Ius, Pietro Parisse, Anna Menini, Daniela Cesselli, Miran Skrap, Fabrizia Cesca, Vincent Torre

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Figure 7

TNF-α depolarizes RMP and increases firing frequency similarly to exosomes, an effect that is antagonized by infliximab.

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TNF-α depolarizes RMP and increases firing frequency similarly to exosom...
(A–C) Representative current clamp traces under control conditions (black) and in a neuron treated for 24 hours with low (blue/green) and high (blue) TNF-α concentration. (D and E) Quantification of spontaneous firing frequency, RMP, and AP threshold for control neurons and those treated with low and high TNF-α concentration. Solid lines for RMP, dashed lines for threshold values. (F) Raster plots of the firing in the 3 experimental conditions. (G and H) Representative current clamp traces of a neuron treated with patient-derived exosomes (red, n = 6) and neurons pretreated with 1.5 ng/mL infliximab (yellow, n = 3–5), both showing high spiking frequency. (I and J) As in G and H but for control neurons (black, n = 10) and neurons pretreated with 2.5 ng/mL infliximab before exosome application (purple, n = 8). Dashed lines indicate AP threshold for the 4 experimental conditions. (K) AP frequency for the groups in G–J. (L) AP threshold (open circles) and RMP (filled circles) for the treatments in G–J. Infliximab 2.5 ng decreased AP frequency and increased the difference between the RMP and AP threshold. (M) Raster plots of the firing in the 4 experimental conditions. Control values: RMP = –58.7 ± 2 mV; threshold = –37.4 ± 1 mV. *P < 0.05, **P < 0.01, ***P < 0.001, Kruskal-Wallis followed by Bonferroni-corrected Dunn’s test.