Nalmefene alleviates the neuroimmune response to repeated binge-like ethanol exposure: A TSPO PET imaging study in adolescent rats.

A large body of preclinical research has shown that neuroimmunity plays a key role in the deleterious effects of alcohol (ethanol) to the brain. Translational imaging techniques are needed to monitor the efficacy of strategies to prevent or mitigate neuroinflammation and alleviate ethanol-induced neurotoxicity. Opioid receptor antagonists such as nalmefene are antagonists of the toll-like receptor 4, which may block the proinflammatory signaling cascade induced by ethanol at this specific target. Male adolescent rats received a validated protocol of ethanol injection (i.p, 3 g/kg daily for two consecutive days followed by two resting days) during 14 days. Positron emission tomography (PET) imaging with the translocator protein 18 kDa (TSPO) radioligand [18 F]DPA-714 was performed at day-15. Toxicity induced by repeated binge-like ethanol exposure (71% mortality) was drastically reduced by nalmefene pretreatment (0.4 mg/kg, 14% mortality). No mortality was observed in animals that received vehicle (control) or nalmefene alone. Compared with control animals (n = 10), a significant 2.8-fold to 4.6-fold increase in the volume of distribution (VT ) of [18 F]DPA-714 was observed among brain regions in animals exposed to ethanol only (n = 9). Pretreatment with nalmefene significantly alleviated the neuroimmune response to ethanol exposure in all brain regions (1.2-fold to 2.5-fold increase in VT ; n = 5). Nalmefene alone (n = 6) did not impact [18 F]DPA-714 VT compared with the control group. Nalmefene may protect against the neuroinflammatory response and overall toxicity associated with binge drinking. [18 F]DPA-714 PET imaging can be used to noninvasively address the neuroimmune impact of ethanol exposure and its modulation by pharmacological strategies in vivo, with translational perspectives.