Ascorbate Protects Neurons against Oxidative Stress: A Raman Microspectroscopic Study

Abstract

Oxidative stress due to excessive accumulation of reactive oxygen or nitrogen species in the brain as seen in certain neurodegenerative diseases can have deleterious effects on neurons. Hydrogen peroxide, endogenously generated in neurons under normal physiological conditions, can produce an excess of hydroxyl radical via a Fenton mediated mechanism. This may induce acute oxidative injury if not scavenged or removed effectively by antioxidants. There are several biochemical assay methods to estimate oxidative injury in cells; however, they do not provide information on the biochemical changes as the cells get damaged progressively under oxidative stress. Raman microspectroscopy offers the possibility of real time monitoring of the chemical composition of live cells undergoing oxidative stress under physiological conditions. In the present study, a hippocampal neuron coculture was used to observe the acute impact of hydroxyl radicals generated by hydrogen peroxide in the presence of Fe(2+) (Fenton reaction). Raman peaks related to nucleic acids (725, 782, 1092, 1320, 1340, 1420, and 1576 cm(-1)) showed time-dependent changes over the experimental period (60 min), indicating the breakdown of the phosphodiester backbone as well as nuclear bases. Interestingly, ascorbic acid (a potent antioxidant) when cotreated with Fenton reactants showed protection of cells as inferred from the Raman spectra, presumably by scavenging hydroxyl radicals. Little or no change in the Raman spectra was observed for untreated control cells and for cells exposed to Fe(2+) only, H2O2 only, and ascorbate only. A live-dead assay study also supported the current observations. Hence, Raman microspectroscopy has the potential to be an excellent noninvasive tool for early detection of oxidative stress that is seen in neurodegenerative diseases.

Challenges in application of Raman spectroscopy to biology and materials

“…47 Further improvements in the instrumentation have enabled studying of various problems concerning the structure and interaction in nucleic acids, nucleic acid hydration, interaction with metal ions, DNA melting, DNA damage etc. [48][49][50][51] Raman spectra of nucleic acids contain a large number of bands originating from various moieties like sugar, phosphate, bases etc. which provide very useful information about backbone conformation, base pairing etc.…”

Ascorbyl‐6‐O‐oleate: A Bioconjugate Antioxidant Lipid

“…In order to check the efficacy of ascorbyl‐oleate against radical‐induced oxidative degradation, we carried out some experiments to assess the protective activity performed by Asc‐OL. In fact Vitamin C can inhibit radical‐initiated lipid peroxidation, a process probably implicated in a variety of chronic health problems such as neurodegenerative, cancer and cardiovascular diseases . However, due to its scarce solubility in lipophilic media Vitamin C is active only in aqueous environments .…”

“…The efficiency of Asc‐OL in inhibiting lipid peroxidation in a lipophilic environment can be assessed by the ability to prevent or inhibit the oxidative degradation of ethyl linoleate in hexane induced by a lipophilic radical initiator, AIBN . As shown in Figure , the absorbance at 234 nm increases, due to the formation of a conjugated diene in the linoleic chain because of the radical attack.…”

A novel class of thiosemicarbazones show multi-functional activity for the treatment of Alzheimer's disease

“…In these studies, ascorbate was used as a substrate because of its abundance in neurons and its strong anti-oxidant potential to protect these cells from oxidative stress [70][71][72]. For comparison, the well-known, redox-active Fe(III) complexes of EDTA and Dp44mT were included as positive controls [54,56,73].…”