Phoenix dactylifera L. Pollen and Fluvoxamine Maleate Protect PC12 Cells Against H2O2-Induced Oxidative Stress by Involvement of Nrf2 and SIGMAR1 Gene Expression

 The association between oxidative stress and the pathogenesis of neurodegenerative diseases has been documented. Besides, there is evidence that antidepressant agents, such as fluvoxamine maleate (Flv), can ameliorate neurotoxicity. The date palm (Phoenix dactylifera L.) pollen (DPP) contains various compounds with antioxidant capacity; however, its underlying mechanism of function has not been fully understood.

 The present study aimed to compare the neuroprotective effects of DPP and Flv on H2O2-induced oxidative damage and their effects on Nrf2, SIGMAR1, and Bcl2 gene expression in PC12 cells.

 First, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay examined the toxicities of DPP, Flv, and H2O2 at various concentrations on the PC12 cells. Real-time polymerase chain reaction (PCR) measured the expression of Nrf2, SIGMAR1, and Bcl2 in PC12 cells in the presence or absence of DPP or Flv after 4 h of treatment with 100 μM H2O2.

 Based on the MTT results, DPP at concentrations of 200 - 1000 µg/mL had no toxic effect on PC12 cells. The IC50 was evaluated at 57.26 μM and 109.5 μM under treatment with Flv and H2O2. Real-time PCR analysis showed a decrease in the expression of Nrf2 and SIGMAR1 in PC12 cells treated with 100 μM H2O2, an indicator of oxidative stress recruitment in PC12 cells. Pretreatment with DPP and Flv (500 µg/mL and 10 µM, respectively) for 24 h resulted in the upregulation of Nrf2 relative to the vehicle control. In addition, pretreatment with DPP increased the level of SIGMAR1 in PC12 cells compared with H2O2-exposed cells. Considering the role of SIGMAR1 in endoplasmic reticulum oxidative stress, the SIGMAR1 level should be evaluated at the translational level. Compared to the untreated cells, the expression of Bcl2 decreased in all the experimental cases, and the difference in Bcl2 expression was not significant between the co-treatment experimental cases.

 Taken together, DPP and Flv have neuroprotective effects against oxidative damage in PC12 cells. Exposure of PC12 cells to 500 μg/mL DPP and 10 μM Flv for 24 h protected the morphology and function of PC12 cells under H2O-induced oxidative stress via regulating oxidative stress-involved genes.