Studies of the antioxidant and chelating properties of phytic acid and its effects on α-synuclein aggregation

Abstract

[eng] If a given compound could regulate, destroy and prevent the formation of reactive oxygen species (ROS) but also chelate metals, it is highly likely that it would have many beneficial properties, such as anticancerogenic, crystallization inhibitor, sugar blood regulator, etc… This compound not only exists, but it comes naturally from legume diets, and it has already been tested on humans. This compound is phytate, an hexa-phosphated form of myo-inositol. The therapeutic and medicinal use of phytate has come a long way over the past few years. In less than a decade, phytate has overcome its reputation as antinutrient, and it has made its way into a few treatments against several calcification pathologies. The abovementioned molecular properties let us to hypothesize that phytate could also hold power properties as a drug to treat neurodegenerative diseases, which are stimulated by the formation of ROS and the uncontrolled release of metal cations. Many neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington disease, Amyotrophic Lateral Sclerosis, etc… have common pathological pathways and mechanisms. They involve the breakage of the metal homeostasis in the brain, and the increase of the oxidative stress, which comes from unregulated amounts of ROS, protein aggregation, and neuronal cells apoptosis, among others. All these pathways are also related one to another in many levels of complexity. Preventing one of them may extensively slow down the ongoing of the other detrimental pathways. Nevertheless, a multifactorial disease, requires a treatment using a multifunctional drug. Therefore, this study was focused on the possibility of phytate of being a candidate to treat or aid patients suffering from these neurodegenerative diseases. To study this we used human αsynuclein, a small protein strictly related to the development of Parkinson’s Disease. Accounting the vastly present amount of ascorbic acid (AA) in the brain, and the neurotoxicity of ROS, which may be generated from an unregulated AA metabolism and from its improper metal-catalyzed degradation, we first used phytate, ascorbic acid and metal cations to perform a series of experiments. The AA degradation was followed by UV-visible spectroscopy, measuring the decrease in the absorption of AA. In addition, the ROS formed from the degradation of AA were also monitored using fluorescence spectroscopy. More specifically, we also followed the formation of hydroxyl radicals (OH·). These studies proved that phytate could prevent the degradation of AA when it was alone but also in the presence of metal cations which are able to catalyze this process. The amount of OH· radicals formed was significantly reduced in the presence of phytate, thus proving the protective effect and its antioxidant capacity. Since DA is the main neurotransmitter allowing the crosstalk between neurons, we also carried out similar experiments using dopamine (DA). UV-visible spectroscopy was used to monitor the formation of a quinolone product, which allowed to indirectly monitor the degradation of DA. Once again, the presence of phytate allowed to inhibit the metal-catalyzed degradation of DA. Furthermore, to unmistakably account the non-observable presence of hydroxyl radicals on the previous studies to the antioxidant properties of phytate and not to the metal chelation properties (and thus preventing the formation of ROS), the scavenging of OH· was observed with the CUPRAC method. With the proven results, it is clear that a small concentration of phytate may neutralize large amounts of pre-formed hydroxyl radicals. Finally, the formation of amyloid fibrils of α-synuclein on various experimental conditions was monitored in the presence and absence of phytate. With these experiments, we obtained different aggregation profiles over time when phytate was added. The results implicated that the number of amyloid fibrils formed would not increase. However, the pathway of aggregation would seem to undergo on a different mechanism unknown. In closure, the hereby reported results on this minute study indicate that the extrapolation of the already clinically used phytate, may be possible and suggest the inclusion of further studies and more implication on the matter at hand to attend and resolve this possible inquiry. Hopefully, the use of phytate against neurodegenerative diseases may be another chapter on the over time increasing reputation of well-doings and beneficial properties and uses of phytate.