Objective: Ginsenoside Rb1, a major saponin component of Panax ginseng, exhibits anti-inflammatory and neuroprotective effects, but its receptor-associated mechanism in microglia remains incompletely defined. This study investigated whether Rb1 suppresses microglial neuroinflammation through an adenosine A2A receptor (A2AR)-associated, Gαs-sensitive mechanism.
Materials and Methods: Rb1 concentration in brain tissue after repeated systemic administration was quantified by ultra-high-performance liquid chromatography-high-resolution mass spectrometry. Anti-inflammatory effects were evaluated in a lipopolysaccharide (LPS)-induced mouse neuroinflammation model and in LPS-stimulated BV2 microglial cells. Pharmacological blockade with the Gαs inhibitor NF449 and the A2AR antagonist ZM241385 was used to examine pathway sensitivity. Molecular docking was performed to explore the possible spatial relationship between Rb1 and adenosine-bound A2AR.
Results: Intraperitoneally administered Rb1 reached measurable brain concentrations of 30.88 ± 0.94 ng/mg protein 24 hr after injection. Rb1 reduced LPS-induced brain levels of tumor necrosis factor-α, interleukin-1β, interleukin-6, and interleukin-10. In BV2 cells, Rb1 attenuated LPS-induced cytokine production at non-cytotoxic concentrations, while Rb1 alone did not alter basal cytokine release. The anti-inflammatory effects of Rb1 were reduced by NF449 and ZM241385. Docking suggested that Rb1 may localize within the extracellular vestibule of adenosine-bound A2AR without overlapping with the orthosteric adenosine-binding site.
Conclusion: These findings support an A2AR-associated, Gαs-sensitive anti-inflammatory mechanism for Rb1 in microglia and provide a receptor-level basis for further mechanistic studies.