NEUROPROTECTIVE EFFECTS OF PLANT EXTRACTS
Dr. A. Justin Thenmozhi is an Assistant Professor in the Department of Biochemistry and Biotechnology of the Faculty of Science at Annamalai University, Tamil Nadu, India. She is working in the field of neuroscience, and has published a good number of peer review articles and edited a book. Dr. Thenmozhi gave a talk entitled “Polyphenols from edible items and their action on Alzheimer’s disease” at the 4th International Workshop on Food and Brain Health, organized by the Department of Food Science & Nutrition of the College of Agricultural & Marine Sciences at SQU.
- Neurodegenerative disorders will become a major challenge for medicine and public health in future years because of demographic changes worldwide. Can you elaborate?
Dr. Thenmozhi: According to the World Health Organization, the three main causes of death in developed countries are cardiovascular disease, cancer and neurodegenerative diseases (NDDs). It predicts that NDDs will have overtaken cancer to become the world’s second-leading cause of death, after cardiovascular disease by 2040. Alzheimer’s disease (AD) is the most common neurodegenerative disease, characterized by notable memory loss, cognitive impairment and personality disorders accompanied by diffuse structural abnormalities in the brain of aged population. It affects millions of people and has become a major medical and social burden globally. Acetylcholine (ACh), a neurotransmitter essential for processing memory and learning, is decreased in both concentration and function in brain of AD patients. The gradual death of cholinergic brain cells results in a progressive and significant loss of cognitive and behavioral function.
- What does Alzheimer’s do to the Brain?
Dr. Thenmozhi: During the course of the disease, the senile plaques of amyloid β (Aβ) peptide, found outside the brain cells and the neurofibrillary tangles of the tau protein, found inside brain cells, are considered as the key pathological hallmarks of AD. These plaques impair synapses; so signals cannot pass between neurons. Tangles kill neurons by preventing the normal transport of food and energy around the brain cell. Therapeutic approaches targeting plaques or tangles have not yet resulted in satisfactory improvements in AD treatment. Unfortunately, to date no pharmacological interventions that effectively prevent or stall AD have been developed.
- What causes Alzheimer’s disease?
Dr. Thenmozhi: In addition to Aβ with tau deregulation, genes, chronic inflammation, mitochondrial, metabolic dysfunctions, impaired insulin signaling, oxidative stress, aberrant cell cycle reentry, cholesterol dysmetabolism as well as metal ion dyshomeostasis synergistically work to promote AD pathological manifestation. Numerous natural compounds have been shown to offer neuroprotection against AD, e.g., by preventing the accumulation of Aβ and hyperphosphorylation of tau protein, inhibiting the activity of acetylcholinesterase (AChE), reducing the damage caused by reactive oxygen, suppressing the inflammatory reaction and neuronal apoptosis, etc. A numerous lines of evidences implicated that Aluminium (Al), an environmental toxin, acts as a causative factor for AD. Its exposure to humans is a massive possibility due to its presence in food, water, dust, air and medicines.
- Can you explain your research that explores the capability of natural products to combat Alzheimer’s disease?
Dr. Themozhi: Our aim is to slow, block or reverses the process of neurodegeneration in AD through the administration of plant products. In our laboratory, we are working in the plant extracts and phytochemicals, which are a part of our diet against AlCl3 induced AD models. We analyzed the neuroprotective effect of hesperidin, tannoid principles of Emblica officinalis, black tea extract and fenugreek seed powder against AlCl3 induced rat model of AD. Hesperidin, a pharmacologically active citrus bioflavonoid, attenuated aluminium chloride induced learning and memory impairments, aluminium loading, cholinergic deficit, Aβ anabolism, oxidative stress and apoptosis in the hippocampus, cortex and cerebellum of the rat. Emblica officinalis is mentioned in many Ayurvedic texts and promotes intelligence, memory, longevity and strength of the senses. We found that the memory-enhancing effect of the tannoid principles of E. officinalis (EoT) through modifying biochemical, anatomical, behavioral and molecular indices against AlCl3 induced AD in rats. Black tea extract treatment attenuated AlCl3 induced AD associated pathologies including AChE activity, Aβ burden, oxidative stress and apoptosis. Our results demonstrated that fenugreek seed powder suppressed the AlCl3 induced memory and learning impairments, Al overload, AChE hyperactivity, Aβ burden and apoptosis via activating Akt/GSK3β signaling pathway. Our data sustain our contention that plant extracts and phytochemicals offered neuroprotection against experimental AD through various pharmaceutical properties and may be used as therapeutic agents against AD in future.