A Review article on Mechanistic Insight into Neuroprotection by Natural Antioxidants in Parkinson’s Disease

Parkinson’s disease (PD) is a progressive neurological disorder resulting from the death of dopamine-producing cells and decreased dopamine production within the brain. PD causes various motor symptoms like tremors, rigidity, slow movements, and postural imbalance, along with non-motor manifestations including mood disorders, sleep disorders, fatigue, and cognitive decline. Various factors like oxidative stress, mitochondrial defects, neuroinflammation, alpha-synuclein protein accumulation, and apoptosis contribute significantly to the progression of Parkinson’s disease. Existing treatment methods like Levodopa can only provide temporary relief and are incapable of preventing nerve cell death. Therefore, natural antioxidants found in food sources and plants have been extensively researched to assess their neuroprotective, antioxidant, anti-inflammatory, and mitochondrial-preserving activities in managing PD. Various natural antioxidants like curcumin, resveratrol, quercetin, EGCG, vitamin C, and vitamin E have exhibited considerable neuroprotective properties in experimental research studies. They aid in mitigating oxidative stress, enhancing mitochondrial functionality, controlling inflammation, and safeguarding nerve cells from damage. Natural antioxidants have emerged as potent therapeutic support agents in the management of Parkinson’s disease.

2. PATHOPHYSIOLOGY OF PARKINSON’S DISEASE

•  The pathophysiology of Parkinson’s disease is complex and involves multiple interrelated processes that result in neuronal degeneration
•  Oxidative Stress: Too much production of reactive oxygen species (ROS) leads to damage of lipids, proteins, DNA and mitochondria. Dopamine metabolism produces free radicals, and dopaminergic neurons are highly vulnerable.
•  Mitochondrial Dysfunction: Mitochondria dysfunction leads to reduced ATP synthesis and increased ROS formation, thus causing neuronal injury and cell death.
• Neuroinflammation: Inflammatory cytokines are released by activated microglia, including TNF-α, IL-1β, and IL-6, which can promote inflammation and accelerate the degeneration of neurons. All of these activities work together to support the development of Parkinson's  disease.

Figure 1. pathophysiology of Parkison’s disease

Figure 2. mechanism of neuroprotection in brain

5. EXPERIMENTAL AND CLINICAL EVIDENCE

a.? ?Experimental Evidence

Experimental studies show that natural antioxidants such as resveratrol, quercetin, and EGCG protect neurons by reducing oxidative stress, inhibiting α-synuclein aggregation, and improving motor function in animal models. Their action includes free radical scavenging, Nrf2 activation, and anti-inflammatory effects..

b.? ?Clinical Evidence

Clinical evidence is limited, but it suggests that Vitamin E, green tea (EGCG), and resveratrol may help lower disease risk and slow progression.

6. CONCLUSION

Natural antioxidants have shown significant potential in neuroprotection in Parkinson’s disease via targeting multiple pathological mechanisms such as oxidative stress, mitochondrial dysfunction, and neuroinflammation. They include compounds such as resveratrol, quercetin, EGCG, and vitamin E, which help in reducing neuronal damage and improving cellular defense systems. There is overwhelming experimental evidence in support of their effectiveness, and although the clinical evidence is limited, it is positive. These antioxidants act through pathways like free radical scavenging and induction of endogenous antioxidant systems. Poor bioavailability, and lack of large-scale clinical trials, among other factors, are still issues despite the encouraging results. Therefore, further researches are required to validate their therapeutic potential. Besides, enhanced drug delivery systems and formulation mechanisms may improve on the potency of these natural compounds. This approach of natural antioxidants, in combination with conventional therapies, could act synergistically to slow down the disease progression. Also, future studies should focus on personalized treatment approaches based on biomarkers. Overall, natural antioxidants may work well as adjuncts in the management of Parkinson’s disease.

REFERENCES

1. Dauer W, Przedborski S. Parkinson’s disease: mechanisms and models. Neuron. 2003;39(6):889–909.
2. ?Schapira AHV, Jenner P. Etiology and pathogenesis of Parkinson’s disease. Movement Disorders. 2011;26(6):1049–1055.
3. ?Dias V, Junn E, Mouradian MM. The role of oxidative stress in Parkinson’s disease. Journal of Parkinson’s Disease. 2013;3(4):461–491.
4. ?Dexter DT, Jenner P. Parkinson disease: from pathology to molecular disease mechanisms. Free Radical Biology and Medicine. 2013;62:132–144.
5. ?Anandhan A, Jacome MS, Lei S, et al. Metabolic dysfunction in Parkinson’s disease: bioenergetics, redox homeostasis and central carbon metabolism. Brain Research Bulletin. 2017;133:12–30.
6. ?Reale M, Iarlori C, Thomas A, et al. Peripheral cytokines profile in Parkinson’s disease. Brain, Behavior, and Immunity. 2009;23(1):55–63.
7. ?Mandel S, Weinreb O, Amit T, Youdim MBH. Cell signaling pathways in the neuroprotective actions of the green tea polyphenol EGCG. Journal of Neurochemistry. 2004;88(6):1555–1569.
8. ?Mythri RB, Bharath MMS. Curcumin: a potential neuroprotective agent in Parkinson’s disease. Current Pharmaceutical Design. 2012;18(1):91–99.
9. ?Bournival J, Quessy P, Martinoli MG. Protective effects of resveratrol and quercetin against MPP+-induced oxidative stress act by modulating markers of apoptosis in dopaminergic neurons. Cellular and Molecular Neurobiology. 2009;29(8):1169–1180.
10. ?Levy OA, Malagelada C, Greene LA. Cell death pathways in Parkinson’s disease: proximal triggers, distal effectors, and final steps. Apoptosis. 2009;14(4):478–500.