Oxidative stress, an imbalance between reactive oxygen species (ROS) and endogenous antioxidants, plays an important role in the development of neurodegenerative diseases, including Parkinson’s. The human brain is vulnerable to oxidative stress because of the high rate of oxygen that it needs and the high levels of polyunsaturated fatty acids, which are substrates of lipid peroxidation. Natural antioxidants inhibit oxidation and reduce oxidative stress, preventing cancer, inflammation, and neurodegenerative disorders. Furthermore, in the literature, it is reported that antioxidants, due to their possible neuroprotective activity, may offer an interesting option for better symptom management, even Parkinson’s disease (PD). Natural antioxidants are usually found in several foods, such as fruits, vegetables, meat, fish, and oil, and in food wastes, such as seeds, peels, leaves, and skin. They can help the system of endogenous antioxidants, protect or repair cellular components from oxidative stress, and even halt lipid, protein, and DNA damage to neurons. This review will examine the extent of knowledge from the last ten years, about the neuroprotective potential effect of natural antioxidants present in food and food by-products, in in vivo and in vitro PD models. Additionally, this study will demonstrate that the pool of dietary antioxidants may be an important tool in the prevention of PD and an opportunity for cost savings in the public health area.

Hyperglycemia, which arises in type 1 or 2 diabetes, leads to different complications, such as macrovascular disease, nephropathy, retinopathy, and neuropathy. In addition, different cognitive variations are associated with type 1 diabetes. Long-term changes in glucose metabolism might induce effects on the central nervous system (CNS) such as reduced mental performance and loss of consciousness, which could be implicated in neurotoxicity. The direct impact of hyperglycemia and elevated glucose concentrations on neuronal cells remains to be fully elucidated, primarily due to the multifaceted mechanisms underlying glucose neurotoxicity, including apoptosis, oxidative stress, and alterations in signaling cascades. The multifaceted mechanisms further complicate the study of the relationship between diabetes and neurodegeneration. Research in this field is continually advancing, with the aim of investigating these eventual connections and developing more effective preventive and therapeutic strategies. The present study aims to assess the damage induced by different glucose concentrations (from 25 to 150 mM) in a neuronal model, such as PC12 cells, rat pheochromocytoma cells. In glucose-exposed PC12 cells, we have tested oxidative stress, apoptosis, and cell migration by (a) viability screening, (b) intracellular levels of anion superoxide (O₂⁻), (c) extracellular levels of MDA and nitrites, (d) apoptosis, and (e) the wound healing assay. By the cell viability assay, it has emerged that glucose (25–150 mM) showed a stronger effect at the highest concentrations (100 and 150 mM). The increase in MDA and O₂⁻ levels was determined in PC12 cells treated with high glucose concentrations (6.5–8.8 fold for MDA). High concentrations (100 and 150 mM) significantly reduced the expression of full-length caspase-3 (2.8-fold and 4.2-fold decrease at 24 and 72 h) and caspase-9 (3.4-fold and 2.8-fold decrease at 24 h and 5-fold decrease at 72 h) compared with control conditions. Finally, the wound healing assay showed different scenarios during the several time points. Indeed, the wound closure rate was reduced in a dose-dependent manner (24 h: control 18%, G 50 mM 9%, 100 and 150 mM 8%; 48 h: control 26%, G 50 mM 20%, G 100 mM 13%, 150 mM 11%), following the treatment with three concentrations considered (50, 100, 150 mM). The results obtained in these experimental conditions highlight that glucose, at high concentrations, induced cell damage and corroborate the hypothesis that it could be involved in neurodegenerative diseases.

Efflux pumps are essential components of cellular detoxification mechanisms, regulating the intracellular accumulation of xenobiotics and endogenous compounds. Among them, P-glycoprotein (P-gp) plays a role in protecting the brain from potentially toxic molecules, and alterations in its function have been associated with neurodegenerative disorders, including Parkinson’s disease (PD). Although P-gp inhibitors have been extensively investigated in the context of multidrug resistance, their effects on neuronal cells remain poorly characterized. In the present study, we investigated the biological effects of the pyridoquinoxaline-based efflux pump inhibitor 2,2′-(pyrido[2,3-g]quinoxaline-2,3-diylbis(methylene))bis(oxy)bis(N-phenylbenzamide) (10d) in PC12 cells, a widely used dopaminergic neuronal model. The effects of 10d were evaluated by an MTT-based cell viability assay, while intracellular and extracellular dopamine (DA) levels and DA metabolites were quantified by high-performance liquid chromatography (HPLC). In addition, the ability of 10d to modulate MPTP-induced neurotoxicity was assessed, alone and in combination with amantadine (AMA), a known antiparkinsonian drug. Exposure to 10d (5 and 10 μM) reduced PC12 cell viability and markedly enhanced MPTP-induced cytotoxicity. Furthermore, 10d altered dopaminergic homeostasis by decreasing intracellular DA levels and modifying DA metabolite profiles, with more pronounced effects following co-treatment with MPTP. The combined administration of 10d, MPTP and AMA produced a stronger disruption of DA metabolism compared with individual treatments or 10d/MPTP co-exposure.