Roflupram Reduces 6-OHDA-Induced Cellular Damage in SH-SY5Y Cells by Inhibiting PDE4

Background: The main symptoms of Parkinson’s disease (PD) include olfactory impairment and tremor. Current treatment methods for PD generally have limitations such as short duration and severe side effects. The novel phosphodiesterase 4 (PDE4) inhibitor Roflupram (Roflu) mitigates inflammatory responses and enhances cognitive functions in individuals with neurological conditions. However, it remains unknown whether Roflu provides neuroprotection in a PD model induced by 6-hydroxydopamine (6-OHDA). Methods: Cell viability was assessed using a 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. The expression level of tyrosine hydroxylase (TH) was evaluated by immunoblotting or immunofluorescence. Lactate dehydrogenase (LDH) release was measured to assess cytotoxicity. Intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential (MMP) were determined using fluorescent probes. Results: Roflu significantly increased cell viability in 6-OHDA-treated cells, as demonstrated by both MTT assay (17.18%, p < 0.001) and flow cytometry (12.20%, p < 0.001). It also upregulated the expression level of TH by 28.53% (p < 0.05). Furthermore, Roflu reduced LDH release by 23.54% (p < 0.001), indicating decreased cellular damage. Roflu markedly suppressed 6-OHDA-induced ROS accumulation by 57.82% (p < 0.001) and enhanced mitochondrial membrane potential (MMP) by 21.07% (p < 0.01). In addition, Roflu downregulated PDE4B expression in 6-OHDA-treated cells by 88.40% (p < 0.001). Knockdown of PDE4B mimicked the protective effects of Roflu, increasing cell survival by 18.43% (p < 0.001) and reducing LDH release by 21.54% (p < 0.001). Conversely, overexpression of PDE4B completely abolished the protective effects of Roflu, reversing both the increase in cell survival and the reduction in LDH release induced by Roflu in 6-OHDA-treated cells. Conclusion: Roflu has demonstrated a clear protective effect against cell damage caused by 6-OHDA, which is closely related to the inhibition of PDE4B. These findings indicate that Roflu has substantial preclinical potential as a therapeutic candidate for PD and other neurodegenerative disorders involving oxidative damage.