Mitigating neuroinflammation in Parkinson's disease: Exploring the role of proinflammatory cytokines and the potential of phytochemicals as natural therapeutics

Narirutin reduces microglia-mediated neuroinflammation by inhibiting the JAK2/STAT3 pathway in MPP+/MPTP-induced Parkinson's disease models

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, characterized by the loss of dopaminergic neurons in the substantia nigra compacta (SNc). Although the detailed molecular mechanisms of PD remain unknown, microglia-mediated neuroinflammation undoubtedly plays a key role in disease progression. Narirutin (Nar), a major flavonoid naturally occurring in citrus fruits, has garnered considerable research attention due to its various therapeutic applications and low toxicity. However, its effects on PD remain unclear. In this study, we explored the protective effects of Nar in 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP)-induced PD mouse model as well as in 1-methyl-4-phenyl-pyridinium (MPP+)-induced BV2 cells. Treatment with Nar (2.0, 10.0, and 50.0 mg/kg) reduced dopaminergic neuronal loss in a dose-dependent manner and ameliorated motor impairment in PD mice. Moreover, Nar administration inhibited microglia-mediated inflammation, evidenced by decreased microglial activation in SNc and BV2 cells, and lowered levels of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in the serum and cells. In addition, we found that Nar exerted anti-inflammatory effects by inhibiting the JAK2/STAT3 pathway. Importantly, using molecular docking and cellular thermal shift assay, we confirmed that JAK2 was a potential binding target of Nar. Overall, Nar attenuated MPTP/MPP+-induced neuroinflammation by inhibiting the JAK2/STAT3 pathway in activated microglia, thereby preventing dopaminergic neuron loss and improving motor disorders in PD mice. Our results provide new evidence supporting that Nar is promising for PD treatment and should be considered for further clinical development.

Regulation of chronic neuroinflammation through dietary herbal products

Chronic neuroinflammation is a consequence of disease pathogenesis underlying neurological disorders at large. While the immune response that triggers inflammatory signaling cascades is unresolved, its progression could cause functional damage to neurons and glial cells, including astrocytes, microglia, and oligodendrocytes. Controlling neuroinflammatory signaling at the early stage of disease pathogenesis is critical to prevent irreversible tissue necrosis. While the application of anti-inflammatory drugs is standard practice, their protracted use is known to cause gastrointestinal injuries, further enhancing the risk of cardiovascular, renal, liver, and lung diseases. Several medicinal herbs and herbal products with anti-inflammatory potential could be effective substitutes. This review aims to identify the preclinical data from important dietary herbal products that have demonstrated anti-neuroinflammatory efficacy in several animal models. The reviewed dietary herbal products are sourced from Bacopa monnieri, Centella asiatica, Emblica officinalis, Piper nigrum, Zingiber officinale, Punica granatum, Mucuna pruriens, Clitoria ternatea, Moringa oleifera, Phoenix dactylifera and Curcuma longa. This review is based on emphatic data from these products demonstrating the significant anti-neuro-inflammatory potential that could probably reduce neuroinflammatory signaling in a neurological disorder and promote brain health and well-being. Abundant scientific evidence shows that critical proinflammatory cytokines in the brain, such as tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-six (IL-6), could be controlled through regular consumption of such dietary herbal products without debilitating side effects for their disease-modifying impacts.

Exploring Therapeutic Potential of Phytoconstituents as a Gut Microbiota Modulator in the Management of Neurological and Psychological Disorders

The functioning of the brain and its impact on behavior, emotions, and cognition can be affected by both neurological and psychiatric disorders that impose a significant burden on global health. Phytochemicals are helpful in the treatment of several neurological and psychological disorders, including anxiety, depression, Huntington's disease (HD), Parkinson's disease (PD), Alzheimer's disease (AD), and autism spectrum disorder (ASD), because they have symptomatic benefits with few adverse reactions. Changes in gut microbiota have been associated with many neurological and psychiatric conditions. This review focuses on the potential efficacy of phytochemicals such as flavonoids, terpenoids, and polyphenols in regulating gut flora and providing symptomatic relief for a range of neurological and psychological conditions. Evidence-based research has shown the medicinal potentials of these phytochemicals, but additional study is required to determine whether altering gut microbiota might slow the advancement of neurological and psychological problems.

Valeric acid reduction by chitosan oligosaccharide induces autophagy in a Parkinson's disease mouse model

Parkinson's disease (PD) is a central nervous system disease with the highest disability and mortality rate worldwide, and it is caused by a variety of factors. The most common medications for PD have side effects with limited therapeutic outcomes. Many studies have reported that chitosan oligosaccharide (COS) crossed blood-brain barrier to achieve a neuroprotective effect in PD. However, the role of COS in PD remains unclear. The present study demonstrated that COS increased dopaminergic neurons in the substantia nigra (SN) and ameliorated dyskinesia in a PD mouse model. Moreover, COS reduced gut microbial diversity and faecal short-chain fatty acids. Valeric acid supplementation enhanced the inflammatory response in the colon and SN, and it reversed COS - suppressed dopamine neurons damage. Autophagy was involved in COS modulating inflammation through valeric acid. These results suggest that COS reduces bacterial metabolites - valeric acid, which diminishes inflammation via activating autophagy, ultimately alleviating PD.