Microglial activation underlies cerebellar deficits produced by repeated cannabis exposure
Laura Cutando, Arnau Busquets-Garcia, Emma Puighermanal, Maria Gomis-González, José María Delgado-García, Agnès Gruart, Rafael Maldonado, Andrés Ozaita
Laura Cutando, Arnau Busquets-Garcia, Emma Puighermanal, Maria Gomis-González, José María Delgado-García, Agnès Gruart, Rafael Maldonado, Andrés Ozaita
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Research Article

Microglial activation underlies cerebellar deficits produced by repeated cannabis exposure

Abstract

Chronic cannabis exposure can lead to cerebellar dysfunction in humans, but the neurobiological mechanisms involved remain incompletely understood. Here, we found that in mice, subchronic administration of the psychoactive component of cannabis, delta9-tetrahydrocannabinol (THC), activated cerebellar microglia and increased the expression of neuroinflammatory markers, including IL-1β. This neuroinflammatory phenotype correlated with deficits in cerebellar conditioned learning and fine motor coordination. The neuroinflammatory phenotype was readily detectable in the cerebellum of mice with global loss of the CB1 cannabinoid receptor (CB1R, Cb1–/– mice) and in mice lacking CB1R in the cerebellar parallel fibers, suggesting that CB1R downregulation in the cerebellar molecular layer plays a key role in THC-induced cerebellar deficits. Expression of CB2 cannabinoid receptor (CB2R) and Il1b mRNA was increased under neuroinflammatory conditions in activated CD11b-positive microglial cells. Furthermore, administration of the immunosuppressant minocycline or an inhibitor of IL-1β receptor signaling prevented the deficits in cerebellar function in Cb1–/– and THC-withdrawn mice. Our results suggest that cerebellar microglial activation plays a crucial role in the cerebellar deficits induced by repeated cannabis exposure.

Authors

Laura Cutando, Arnau Busquets-Garcia, Emma Puighermanal, Maria Gomis-González, José María Delgado-García, Agnès Gruart, Rafael Maldonado, Andrés Ozaita

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Figure 8

CB1R downregulation in the parallel fibers is sufficient to trigger cerebellar neuroinflammation and IL1-RA–sensitive motor coordination impairment.

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CB1R downregulation in the parallel fibers is sufficient to trigger cere...
(A) Morphological analysis of IBA1+ cells in the cerebellar cortex of Cb1a6– and control mice (n = 4–5 per group, 6 cells per mouse). Scale bar: 25 μm. *P < 0.05, ***P < 0.001 versus control. (B) Analysis of Cb2r mRNA expression by qRT-PCR and inflammation-related genes in the cerebellum of Cb1a6– and control mice (n = 5 per group). *P < 0.05 versus control. (C) Flow cytometric analysis of CD11b expression and qRT-PCR analysis of Cb1r, Cb2r, and Il1b of acutely dissociated cerebellar cells from Cb1a6– and control mice (n = 3–4 per group). *P < 0.05 versus control. (D) Immunoblot detection and quantification of ARC/ARG3.1 in cerebellar homogenates from Cb1a6– and control mice (n = 5–6 mice per group). *P < 0.05 versus control. (E) ARC/ARG3.1 immunostaining in Cb1a6– and control mice. Plot represents ARC/ARG3.1 intensity along the cerebellar layers. Scale bar: 100 μm. (F) Motor coordination analysis of Cb1a6– and control mice (n = 11–15 per group). (G) Motor coordination analysis with the coat-hanger test in Cb1a6– and control mice (n = 8–10 per group). Four hours before the test, the mice received an injection of IL-1RA (100 mg/kg, i.p.) or its VEH (DMSO). *P < 0.05, **P < 0.01, ***P < 0.001 versus control. #P < 0.05 versus Cb1a6– plus DMSO.