Abstract
With an increase in life expectancy, there has been tremendous growth in the proportion of the population older than 65 years. Age-related neurodegenerative disorders have become a serious public health concern for this group as they are incurable and traumatic. They are characterized by progressive degeneration or death of neurons resulting in the loss of movement, speech, and mental functions. Alzheimer's disease (AD) is one of the most common and dreaded pathological neurodegenerative disorders with a range of unknown causes and mechanisms. Several hypotheses have been proposed as potential causes for AD, including the dysfunction of cholinergic signaling, oxidative stress, neuronal inflammation, misfolded amyloid precursor protein, and tau protein. A variety of biomarkers including gene expression analysis are extensively studied to detect the onset or risk of AD and other pathological disorders. Once diagnosed, it is crucial to deliver safe, reliable, and effective therapies to patients. Only 0.1% of drug candidates eventually reach the market with an estimated cost of $985 million and over 10 years of development time for each successful drug. Such a low success rate for drug development led to the path of nutraceuticals. Bioactive compounds, naturally occurring in plants, possess an ability to participate in various biological processes in living organisms and hence have gained the attention of the research industry. Blueberry is rich in phytonutrients and therefore has been largely studied for the development of potential therapeutic drugs for several disorders. Ribonucleic acid (RNA) sequencing coupled with phytonutrients research is a powerful tool for identifying impacts on important signaling pathways involved in biological processes by phytochemicals. The potential mechanism by which blueberries impart health benefits remains to be defined. This study examined the effect of various solvents for the estimation of total phenolic, flavonoids, and anthocyanin content along with a detailed comparison of anti-acetylcholinesterase, anti-tyrosinase, and anti-inflammatory activities of blueberry extracts obtained from commercially available fresh fruit and lyophilized blueberry powder from United States High Bush Blueberry Council (USHBC). The profiling of polyphenols in the extracts using Liquid chromatography – Mass Spectrometry (LC-MS) showed the presence of sixteen phenolic compounds with high levels of total phenolic, flavonoid, and anthocyanin content from established colorimetric assays. The two sources of blueberries indicated identical profiles, comparable contents of polyphenols, and inhibition on acetylcholinesterase (involving dysfunction of cholinergic signaling) and cyclooxygenase-2 (involving neuronal inflammation) (p<0.005), while the extract from USHBC showed higher inhibition activity on tyrosinase (involving oxidation stress). Further, RNA sequencing was employed to study the response of blueberries on the human neuronal (M17) cell model and make advancements in understanding the pathways involved in various biological processes. The comparison between the treated blueberry and untreated M17 cells in RNA sequencing identified 3357 differentially expressed genes, of which 2053 genes were upregulated, and 1304 genes were downregulated (p<0.05). These genes were categorized as neurological and biological annotation groups including nervous system development, apoptosis, cell-cell adhesion, signal transduction, extracellular matrix organization, inflammatory response, etc. It was noted from this study that the up-regulated group contained regulation of voltage-gated calcium channel activity, nervous system development, G-protein coupled receptor signaling pathway, and metabolic processes. In contrast, the down-regulated groups contained cell cycle processes including cell surface receptor signaling pathway, regulation of osteoblast differentiation, negative regulation of dendrite development, etc. This study concludes that blueberries can improve the imbalance of the genetic alterations and offers a molecular basis for imparting neuroprotective effects.