Adenosine A2A Receptor Contributes to Bidirectional Remodeling of Microglial Inflammatory Responses During Methamphetamine Exposure

Methamphetamine (MA) abuse is associated with severe neurotoxicity, with microglia-mediated neuroinflammation playing a key role in central nervous system damage. While previous research has linked drug exposure to microglial activation, the upstream regulatory mechanisms driving this process remain poorly understood. This study investigates the role of the adenosine A2A receptor (A2AR) in regulating MA-induced microglial inflammation and explores whether this pathway serves as a potential therapeutic target.

The researchers employed a multi-system approach, examining postmortem human striatal tissue from MA users, a C57BL/6 mouse model of MA exposure, and the human microglial cell line HMC3. Using Western blotting, immunofluorescence, and pharmacological intervention with the selective A2AR antagonist SCH58261, the team analyzed the expression of A2AR, downstream PKA/PKC signaling molecules, and a panel of inflammatory mediators (pro-inflammatory iNOS, IL-1β, IL-18; anti-inflammatory Arg-1, IL-10).

MA exposure consistently led to the upregulation of A2AR expression in all three experimental models, accompanied by significant alterations in downstream PKA and PKC signaling. Unexpectedly, MA did not drive a simple, unidirectional polarization of microglia; rather, it induced a mixed phenotypic state where pro-inflammatory mediators (iNOS, IL-1β) were elevated alongside repair-associated factors (Arg-1, IL-10). The researchers propose this represents a complex, maladaptive remodeling of the inflammatory program rather than a shift toward a classic M1 or M2 state.

Pharmacological inhibition of A2AR using SCH58261 effectively mitigated this mixed inflammatory response. Inhibiting the receptor reduced the MA-induced increases in both pro-inflammatory and anti-inflammatory markers and attenuated the aberrant signaling in the PKA/PKC pathways. These results suggest that A2AR acts as a central mediator in maintaining this pathological inflammatory state, providing a promising target for managing MA-related neurotoxicity.