Simvastatin Prevents Neuroinflammation by Inhibiting N-methyl-D-aspartic Acid Receptor 1 in 6-hydroxydopamine-treated PC12 Cells

This study investigates the impact of simvastatin on neuroinflammation in experimental parkinsonian cell models. 6-Hydroxydopamine (6-OHDA)-treated pheochromocytoma-12 (PC12) cells were used to investigate the neuroprotective nature of simvastatin. After incubation with 6-OHDA, simvastatin, and/or N-methyl-D-aspartic acid receptor 1 (NMDAR1) siRNA for 24 hr, test kits were used to detect the levels of lactate dehydrogenase (LDH) and glutamate released from PC12 cells exposed to different culture media. The mRNA levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 were determined by RT-PCR, and the protein levels were analyzed by Western blot. NMDAR1 were also determined by RT-PCR and the protein levels were analyzed by Western blot. LDH and glutamate levels in 6-OHDA-incubated PC12 cells increased compared with those in the controls, and incubation with simvastatin inhibited this elevation. Silencing of NMDAR1 with siRNA inhibited the expression of LDH and glutamate to a degree similar to simvastatin. The expression levels of NMDAR1, TNF-α, IL-1β, and IL-6 were significantly upregulated after treatment with 6-OHDA. The 6-OHDA-stimulated mRNA and protein levels of the proinflammatory cytokines NMDAR1, TNF-α, IL-1β, and IL-6 were reduced by simvastatin. Silencing of NMDAR1 with siRNA decreased the NMDAR1, TNF-α, IL-1β, and IL-6 mRNA and protein expression levels in 6-OHDA-stimulated PC12 cells. Simvastatin could also inhibit the expression of NMDAR1 and cytokines to a degree similar to silencing of NMDAR1 with siRNA. Our results suggest that NMDAR1 modulation could explain the anti-inflammatory mechanisms of simvastatin in experimental parkinsonian cell models.