Immune and Glial Cell Alterations in the Rat Brain after Repeated Exposure to the Synthetic Cannabinoid JWH-018.

The use of synthetic cannabinoid receptor agonists (SCRAs) poses major psychiatric risks. We previously showed that repeated exposure to the prototypical SCRA JWH-018 induces alterations in dopamine (DA) transmission, abnormalities in the emotional state, and glial cell activation in the mesocorticolimbic DA circuits of rats. Despite growing evidence suggesting the relationship between substance use disorders (SUD) and neuroinflammation, little is known about the impact of SCRAs on the neuroimmune system. Here, we investigated whether repeated JWH-018 exposure altered neuroimmune signaling, which could be linked with previously reported central effects. Adult male Sprague-Dawley (SD) rats were exposed to JWH-018 (0.25 mg/kg, i.p.) for fourteen consecutive days, and the expression of cytokines, chemokines, and growth factors was measured seven days after treatment discontinuation in the striatum, cortex, and hippocampus. Moreover, microglial (ionized calcium-binding adaptor molecule 1, IBA-1) and astrocyte (glial fibrillary acidic protein, GFAP) activation markers were evaluated in the caudate-putamen (CPu). Repeated JWH-018 exposure induces a perturbation of neuroimmune signaling specifically in the striatum, as shown by increased levels of cytokines [interleukins (IL) -2, -4, -12p70, -13, interferon (IFN) γ], chemokines [macrophage inflammatory protein (MIP) -1α, -3α], and growth factors [macrophage colony-stimulating factor (M-CSF), vascular endothelial growth factor (VEGF)], together with increased IBA-1 and GFAP expression in the CPu. JWH-018 exposure induces persistant brain region-specific immune alterations up to seven days after drug discontinuation, which may contribute to the behavioral and neurochemical dysregulations in striatal areas that play a role in the reward-related processes that are frequently impaired in SUD.