Differential effects of ginsenosides on Ca2+ regulation in rotenone-treated neuronal and microglial cells

Parkinson's disease is one of the most common neurodegenerative disorders, and the pesticide rotenone is widely used to model Parkinson's disease in experimental studies. Rotenone-induced mitochondrial dysfunction is associated with oxidative stress and intracellular Ca2+ ([Ca2+]ᵢ) dysregulation in neuronal systems. L-type Ca2+ channels (LTCCs) contribute to Ca² ⁺ influx under oxidative stress conditions, but pharmacological inhibition of LTCCs is limited by cardiovascular side effects. Phospholipase D (PLD) has also been implicated in cellular stress-associated signaling pathways. Ginsenosides are known to influence Ca² ⁺ -related signaling; however, differences among ginsenosides in neuronal and microglial Ca² ⁺ regulation have not been fully characterized. Therefore, this study aimed to investigate the effects of ginsenosides on intracellular Ca² ⁺ homeostasis and oxidative stress of rotenone-exposed SH-SY5Y neuronal cells and BV2 microglial cells. Cell viability, superoxide dismutase (SOD) activity, interleukin-6 (IL-6) levels, intracellular Ca² ⁺ influx, and malondialdehyde (MDA) levels were evaluated. Intracellular Ca² ⁺ was measured using Fura-2 AM ratiometric fluorescence analysis. The effects of ginsenosides Rg1, Rg2, and Rd were examined using pharmacological inhibitors targeting PLD, LTCCs, and protein kinase A (PKA). Rotenone reduced cell viability and SOD activity, while increasing IL-6 levels, [Ca2+]ᵢ influx, and MDA levels in both cell types. Treatment with ginsenosides immediately before rotenone exposure attenuated rotenone-induced increases in [Ca2+]ᵢ and MDA levels. Ca² ⁺ responses in both SH-SY5Y and BV2 cells were sensitive to PLD inhibition. In SH-SY5Y cells, responses were additionally sensitive to LTCC inhibition, whereas BV2 cells showed weaker LTCC-associated pharmacological responses. Rd showed broader pharmacological sensitivity involving PLD-, LTCC-, and PKA-associated components, whereas Rg1 and Rg2 showed predominantly PLD-associated response patterns. These findings suggest that ginsenosides differentially modulate rotenone-associated Ca² ⁺ dysregulation through PLD-associated pharmacological pathways in a cell type-dependent manner. Overall, the present findings demonstrate distinct pharmacological response profiles among structurally different ginsenosides under rotenone-induced oxidative stress conditions.