INTRODUCTION: Astrocytes and microglia are the primary resident glial cells involved in the initiation, propagation, and resolution of neuroinflammation. Cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) play pivotal roles in the pathophysiology of neurodegenerative disorders, including Alzheimer’s disease and neuropathic pain. GPR55, a G-protein-coupled receptor, modulates inflammatory responses and is a putative cannabinoid receptor, suggesting its involvement in regulating neuroinflammation.

AIM(S): This study aimed to investigate the effects of GPR55 ligands: CBD, ML-193, and O-1602 on cortical astrocytes and microglia in primary mixed glial cultures, with and without IL-1β+TNF-α cotreatment.

METHOD(S): Immunocytochemistry was used to verify GPR55 expression in microglia and astrocytes, and to assess the compounds’ effects on markers including SOX2, Iba-1, CD11b, BDNF, GFAP, Nestin, and Ki-67. Morphological analyses of Iba-1-positive cells were performed (area and perimeter). IL-6 concentrations in culture media were quantified using ELISA.

RESULTS: GPR55 expression was confirmed in both astrocytes and microglia. ML-193 cotreatment with IL-1β + TNF-α significantly increased IL-6 levels in a dose-dependent manner. No significant IL-6 changes were observed following CBD or O-1602 treatment. ML-193 treatment also reduced microglial cell numbers and induced morphological alterations under both basal and inflammatory conditions.

CONCLUSIONS: ML-193 exhibits pro-inflammatory effects in mixed glial cultures, promoting IL-6 release and microglial cell loss. These findings support a modulatory role of GPR55 in neuroinflammation and suggest ML-193 as a potential pro-inflammatory agent in glial contexts.

FINANCIAL SUPPORT: This research was funded in whole by National Science Centre, Poland 2021/43/B/NZ7/01162.