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minocycline or an inhibitor of IL-1β receptor signaling prevented the deficits in cerebellar function in Cb1–/– and THC-withdrawn mice.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 7

Cerebellar neuroinflammation secondary to cannabinoid downregulation modulates ARC/ARG3.1 expression.

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Cerebellar neuroinflammation secondary to cannabinoid downregulation mod...
(A) Immunofluorescence detection of ARC/ARG3.1 and calbindin in Purkinje neurons in the cerebellar cortex. Scale bar: 50 μm. (B) Immunoblot detection and quantification of ARC/ARG3.1 in cerebellar homogenates obtained at the end of subchronic exposure to MIN or SAL under subchronic THC (5 and 20 mg/kg) and subchronic VEH treatment conditions (n = 5–6 mice per group). *P < 0.05, **P < 0.01 versus subchronic VEH plus SAL (5 days); #P < 0.05, ##P < 0.01 versus subchronic THC-5 plus SAL (5 days) or subchronic THC-20 plus SAL (5 days). (C) Immunoblot detection and quantification of ARC/ARG3.1 in cerebellar homogenates from Cb1–/– and WT mice at the end of subchronic exposure to MIN or SAL (n = 5–6 mice per group). *P < 0.05 versus subchronic WT plus SAL; #P < 0.05 versus WT plus SAL. (D) ARC/ARG3.1 immunostained images from mice that were subchronically treated with THC-5, THC-20, or VEH and that received MIN or SAL for 5 days. ARC/ARG3.1 intensity was measured along a 300-μm line stretched along the 3 cerebellar layers. Plot represents ARC/ARG3.1 intensity alongside the layers quantified with ImageJ software. Scale bar: 100 μm. (E) ARC/ARG3.1 immunostained images from Cb1–/– and WT mice at the end of subchronic exposure to MIN or SAL. ARC/ARG3.1 intensity was measured along a 300-μm line stretched along the 3 cerebellar layers. Plot represents ARC/ARG3.1 intensity alongside the layers quantified with ImageJ software. Scale bar: 100 μm.