The Neuroprotective and Therapeutic Effects of Anthocyanins and Their Metabolites In Vitro and in a Mouse Model of Amyotrophic Lateral Sclerosis

Anthocyanins, a unique class of flavonoid compounds, have recently come to the forefront of investigative research aimed at evaluating the potential applications of natural products to human health. Evidence demonstrating the beneficial effects of anthocyanin consumption has been reported for a myriad of conditions including cancer, cardiovascular disease, and lately, neurodegenerative disease. Neurodegenerative diseases such as Alzheimer\u27s disease, Parkinson\u27s disease, and amyotrophic lateral sclerosis (ALS) are characterized by the death of specific neuronal populations within the brain and spinal cord, leading to cognitive and/or motor impairment. While the etiology of many of these diseases is largely unknown, several factors have emerged as contributors to the neurodegenerative process. These include conditions such as oxidative and nitrosative stress, glutamate excitotoxicity, endoplasmic reticulum stress, protein aggregation, and neuroinflammation, which ultimately culminate in the death of susceptible neuronal populations. Since anthocyanins have been shown to modulate these phenomena in numerous ways, interest in evaluating their use as therapeutic agents for neurodegenerative diseases has grown. Additionally, the observation that the bioavailability of anthocyanins is very low following consumption relative to that of their metabolites suggests that anthocyanin metabolites may also play a significant role of mediating the beneficial effects of anthocyanin-rich diets. Therefore, we examined the neuroprotective and therapeutic effects of both anthocyanins and phenolic acid metabolites derived from anthocyanins in vitro and in a mouse model of ALS. The results of our work reveal that different anthocyanin species possess differential neuroprotective effects in vitro against toxicity induced by nitric oxide and define a novel neuroprotective mechanism for cyanidin-O-3-glucoside under these conditions. Furthermore, we demonstrate that presymptomatic supplementation with an anthocyanin-enriched extract from strawberries significantly delays disease onset and extends survival in the transgenic G93A mutant Cu, Zn-superoxide dismutase (hSOD1G93A) mouse model of ALS. These observations correlate with significant preservation of hind limb grip strength and function in mice treated with anthocyanins. Anthocyanin supplementation is also shown to improve histopathological indices of disease, reducing reactive astrogliosis in lumbar spinal cord tissue, and preserving neuromuscular junctions in gastrocnemius muscle tissue. We next illustrate that phenolic acid metabolites derived from anthocyanins display distinct and complimentary neuroprotective effects in vitro against a diverse array of stressors in cerebellar granule neurons. Lastly, our work shows that treatment with protocatechuic acid, a metabolite of cyanidin-O-3-glucoside, beginning at disease onset provides significant therapeutic benefit to hSOD1G93A mice, extending survival and preserving hind limb grip strength in animals supplemented with this compound. The results of this dissertation are the first to evaluate the therapeutic efficacy of anthocyanins and their metabolites for the treatment of ALS. Collectively, these data demonstrate that both anthocyanins and their metabolites may be of significant clinical benefit for treating this insidious disease, and suggest that further preclinical and clinical examination of these compounds is warranted