Methamphetamine Activates Toll-Like Receptor 4 toInduce Central Immune Signaling within the Ventral Tegmental Areaand Contributes to Extracellular Dopamine Increase in the NucleusAccumbens Shell

Methamphetamine (METH) is a globally abused, highly addictive stimulant. While investigations of the rewarding and motivational effects of METH have focused on neuronal actions, increasing evidence suggests that METH can also target microglia, the innate immune cells of the central nervous system, causing release of proinflammatory mediators and therefore amplifying the reward changes in the neuronal activity induced by METH. However, how METH induces neuroinflammatory responses within the central nervous system (CNS) is unknown. Herein, we provide direct evidence that METH creates neuroinflammation, at least in part, via the activation of the innate immune Toll-like receptor 4 (TLR4). Biophysical studies revealed that METH bound to MD-2, the key coreceptor of TLR4. Molecular dynamics simulations showed METH binding stabilized the active heterotetramer (TLR4/MD-2)2 conformation. Classic TLR4 antagonists LPS-RS and TAK-242 attenuated METH induced NF-κB activation of microglia, whereas added MD-2 protein bo...