Ginsenoside Compound K Differentially Regulates Neuronal and Astrocytic Ca²⁺ Homeostasis Under Trimethyltin-Induced...

Background: Intracellular Ca²⁺ dysregulation and neurovascular dysfunction are increasingly recognized as important mechanisms underlying neurodegenerative disorders, including Alzheimer's disease (AD). Restoration of pathological Ca²⁺ imbalance has therefore emerged as a potential therapeutic strategy. Although ginsenoside compound K (CK) has demonstrated neuroprotective and anti-inflammatory properties, its role in Ca²⁺ homeostasis remains unclear. Methods: SH-SY5Y neuronal cells, U373 astrocytes, BV2 microglia, bEND brain endothelial cells, and MOVAS vascular smooth muscle cells were exposed to trimethyltin chloride (TMT, 5 μM, 24 h). Cell viability, real-time cell confluence, intracellular Ca²⁺ influx, and endoplasmic reticulum (ER) Ca²⁺ store release were evaluated. Ca²⁺ dynamics were analyzed using Fura-2 fluorescence, and signaling associated with CK-mediated Ca²⁺ regulation was investigated using pharmacological inhibitors. Orai1 protein expression was evaluated by Western blot analysis in SH-SY5Y and U373 cells. Results: TMT increased store-operated Ca²⁺ entry (SOCE)-mediated Ca²⁺ influx in SH-SY5Y neuronal cells without significant cytotoxicity. In contrast, TMT reduced both Ca²⁺ influx and cell viability in U373 astrocytes, BV2 microglia, and MOVAS cells, whereas bEND cells showed minimal changes. CK restored abnormal Ca²⁺ responses in a cell type-specific manner, reducing elevated Ca²⁺ influx in neuronal cells while restoring suppressed Ca²⁺ signaling in astrocytes. Consistent with these functional findings, Orai1 protein expression was increased by TMT in SH-SY5Y cells and attenuated by CK, whereas TMT reduced Orai1 expression in U373 cells, which was restored by CK. Pharmacological analyses suggested involvement of PKA- and LTCC-associated signaling in neuronal cells and PLC- and PLD-associated signaling in astrocytes. In both cell types, CK-associated Ca²⁺ responses were sensitive to NAC and the SOCE inhibitor BTP2, supporting ROS- and SOCE-associated mechanisms. Additional controls showed no significant inhibitor effects under control or CK-only conditions, strengthening the pharmacological interpretation of responses under TMT-containing conditions. Conclusions: TMT-induced Ca²⁺ dysregulation differed markedly by cell type. CK restored disrupted Ca²⁺ homeostasis in association with distinct pharmacological signaling profiles in neuronal and astrocytic cells. These findings suggest that CK may function as a cell type-specific Ca²⁺ homeostatic regulator under neurotoxic stress conditions and highlight the importance of differential Ca²⁺ regulation in neurodegenerative disease models.