DIFFERENTIAL MODULATION OF L-TYPE CA²⁺ CHANNEL- AND PLD-DEPENDENT CALCIUM SIGNALING BY GINSENOSIDE RD IN ROTENONE-STRESSED NEURONAL AND MICROGLIAL CELLS

Dysregulation of intracellular Ca²⁺ homeostasis is a central mechanism underlying dopaminergic neurodegeneration and neuroinflammation in Parkinson’s disease (PD). Rotenone-induced cellular stress recapitulates key PD-related pathological features in both neuronal and microglial cells and serves as a useful model for investigating Ca²⁺-dependent neurotoxicity. Although ginsenosides are known to influence Ca²⁺-related signaling, their pathway-specific actions across different neural cell types remain incompletely characterized. Human neuroblastoma SH-SY5Y cells and murine microglial BV2 cells were exposed to rotenone to induce intracellular Ca²⁺ imbalance. Ca²⁺ influx was quantified using Fura-2 fluorescence imaging, and cytotoxic and inflammatory responses were assessed by measuring cell viability, confluency, and interleukin-6 (IL-6) production. The modulatory effects of ginsenosides Rd, Rg1, and Rg2 were evaluated. Pharmacological inhibitors targeting L-type Ca²⁺ channels (nifedipine), phospholipase D (PLD; FIPI), and protein kinase A (PKA; H-89) were used to delineate Ca²⁺ influx–associated signaling pathways. Rotenone significantly increased intracellular Ca²⁺ levels, reduced cell viability, and enhanced inflammatory responses in both neuronal and microglial cells. All tested ginsenosides attenuated Ca²⁺ influx; however, distinct pathway sensitivities were observed. Ginsenoside Rd showed sensitivity to both L-type Ca²⁺ channel- and PLD-associated signaling in neurons and microglia, with additional modulation via PKA-dependent pathways. In contrast, Rg1 and Rg2 primarily acted through PLD-associated pathways, with L-type Ca²⁺ channel involvement mainly observed in neuronal cells. These findings support ginsenoside Rd as a potential modulator of Ca²⁺-driven neurotoxicity and neuroinflammation in PD-relevant cellular contexts. This work was supported by NRF (RS-2024-00353184) and NST (CRC22021-300). ^*Corresponding author: ghseol@korea.ac.kr