Ferroptosis: An Iron-Dependent Form of Nonapoptotic Cell Death

There is an increasing amount of experimental evidence that oxidative stress is a causal, or at least an ancillary, factor in the neuropathology of several adult neurodegenerative disorders, as well as in stroke, trauma, and seizures. At the same time, excessive or persistent activation of glutamate-gated ion channels may cause neuronal degeneration in these same conditions. Glutamate and related acidic amino acids are thought to be the major excitatory neurotransmitters in brain and may be utilized by 40 percent of the synapses. Thus, two broad mechanisms--oxidative stress and excessive activation of glutamate receptors--are converging and represent sequential as well as interacting processes that provide a final common pathway for cell vulnerability in the brain. The broad distribution in brain of the processes regulating oxidative stress and mediating glutamatergic neurotransmission may explain the wide range of disorders in which both have been implicated. Yet differential expression of components of the processes in particular neuronal systems may account for selective neurodegeneration in certain disorders.

https://science.sciencemag.org/content/sci/262/5134/689.full.pdf

Oxidative stress, glutamate, and neurodegenerative disorders

https://minerva-access.unimelb.edu.au/bitstream/handle/11343/194901/Stockwell_Cell_review+2017.pdf

Ferroptosis: A Regulated Cell Death Nexus Linking Metabolism, Redox Biology, and Disease

This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell dea...

Ischemic Cell Death in Brain Neurons

The use of dichlorofluorescin (DCFH) as a measure of reactive oxygen species was studied in aqueous media. Hydrogen peroxide oxidized DCFH to fluorescent dichlorofluorescein (DCF), and the oxidation was amplified by the addition of ferrous iron. Hydrogen peroxide-induced DCF formation in the presence of ferrous iron was completely inhibited by deferoxamine and partially inhibited by ethylenediaminetetraacetic acid, but was augmented by diethylenetriaminepentaacetic acid. Iron-peroxide-induced oxidation of DCFH was partially inhibited by catalase but not by horseradish peroxidase. Nonchelated iron-peroxide oxidation of DCFH was partially inhibited by several hydroxyl radical scavengers, but was independent of the scavenger concentration, and this suggests that free hydroxyl radical is not involved in the oxidation of DCFH in this system. Superoxide anion did not directly oxidize DCFH. Data suggest that H2O2-Fe(2+)-derived oxidant is mainly responsible for the nonenzymatic oxidation of DCFH. In addition, peroxidase alone and oxidants formed during the reduction of H2O2 by peroxidase oxidize DCFH. Since DCFH oxidation may be derived from several reactive intermediates, interpretation of specific reactive oxygen species involved in biological systems should be approached with caution. However, DCFH remains an attractive probe as an overall index of oxidative stress in toxicological phenomena.

/pdf/evaluation-of-the-probe-2-7-dichlorofluorescin-as-an-12xsy2rql9.pdf

Evaluation of the probe 2',7'-dichlorofluorescin as an indicator of reactive oxygen species formation and oxidative stress.

Glutamate toxicity in a neuronal cell line involves inhibition of cystine transport leading to oxidative stress

The effects of reducing agents and antioxidants on L-Glutamate (Glu)-induced cytotoxicity were examined in the N18-RE-105 neuronal cell line. The cytotoxicity by Glu (1 and 10mM) was potentiated by exposure to growth medium containing a low concentration of cystine (5-100 microM), instead of the normal medium containing 200 microM cystine. In contrast, the toxicity was suppressed by increasing the cystine concentration to 500 to 1000 microM. Reducing agents, cysteine (30-1000 microM), dithiothreitol (10-250 microM) and glutathione (GSH, 10-1000 microM) also protected the cells against the cytotoxicity of 10 mM Glu in a concentration-dependent manner. The antioxidants vitamin E (10-100 microM), idebenone (0.1-3 microM) and vinpocetine (10-100 microM) also provided marked protection against the cytotoxicity of Glu (10 mM) or quisqualate (1 mM). Antioxidants also prevented the delayed cell death caused by lowering the concentration of cystine in the medium to 5 microM. Incubation of the cells with 10 mM Glu caused a marked decrease in cellular GSH levels. Although cysteine and dithiothreitol prevented the GSH reduction caused by Glu, antioxidants did not. The cellular levels of oxidants were assessed using 2,7-dichlorofluorescin, a probe that accumulates within cells and is converted to a fluorescent product by oxidation. Glu (10 mM) caused a marked increase in such fluorescence, whereas vitamin E and idebenone reduced markedly the number of fluorescent cells to control levels even added with 10 mM Glu. These results indicate that oxidative stress due to loss of cellular levels of GSH is one mechanism whereby Glu/quisqualate exert cytotoxicity and suggest that centrally active antioxidants may reduce neuronal damage in pathologic conditions associated with excessive Glu release.

Masaomi Miyamoto

Papers

Glutamate toxicity in a neuronal cell line involves inhibition of cystine transport leading to oxidative stress

Antioxidants protect against glutamate-induced cytotoxicity in a neuronal cell line.

Idebenone attenuates neuronal degeneration induced by intrastriatal injection of excitotoxins