Adolescent Δ 9 -Tetrahydrocannabinol Exposure and Astrocyte-Specific Genetic Vulnerability Converge on Nuclear Factor-κB-Cyclooxygenase-2 Signaling to Impair Memory in Adulthood.

BACKGROUND: Although several studies have linked adolescent cannabis use to long-term cognitive dysfunction, there are negative reports as well. The fact that not all users develop cognitive impairment suggests a genetic vulnerability to adverse effects of cannabis, which are attributed to action of Δ9-tetrahydrocannabinol (Δ9 -THC), a cannabis constituent and partial agonist of brain cannabinoid receptor 1. As both neurons and glial cells express cannabinoid receptor 1, genetic vulnerability could influence Δ9 -THC-induced signaling in a cell type-specific manner.

METHODS: Here we use an animal model of inducible expression of dominant-negative disrupted in schizophrenia 1 (DN-DISC1) selectively in astrocytes to evaluate the molecular mechanisms, whereby an astrocyte genetic vulnerability could interact with adolescent Δ9 -THC exposure to impair recognition memory in adulthood.

RESULTS: Selective expression of DN-DISC1 in astrocytes and adolescent treatment with Δ9 -THC synergistically affected recognition memory in adult mice. Similar deficits in recognition memory were observed following knockdown of endogenous Disc1 in hippocampal astrocytes in mice treated with Δ9 -THC during adolescence. At the molecular level, DN-DISC1 and Δ9 -THC synergistically activated the nuclear factor-κB-cyclooxygenase-2 pathway in astrocytes and decreased immunoreactivity of parvalbumin-positive presynaptic inhibitory boutons around pyramidal neurons of the hippocampal CA3 area. The cognitive abnormalities were prevented in DN-DISC1 mice exposed to Δ9 -THC by simultaneous adolescent treatment with the cyclooxygenase-2 inhibitor, NS398.

CONCLUSIONS: Our data demonstrate that individual vulnerability to cannabis can be exclusively mediated by astrocytes. Results of this work suggest that genetic predisposition within astrocytes can exaggerate Δ9 -THC-produced cognitive impairments via convergent inflammatory signaling, suggesting possible targets for preventing adverse effects of cannabis within susceptible individuals.