"Methods in Biological Oxidative Stress: K. Hensley and R.A. Floyd (Eds), 2003. Humana Press, New Jersey." Free Radical Research, 37(10), p. 1145
4‐Hydroxy‐2,3‐ trans ‐nonenal (HNE) is a neurotoxic unsaturated aldehyde end‐product of lipid peroxidation. The addition of HNE to NT‐2 and SK‐N‐MC cell lines induces apoptosis and we now investigated the time‐course of events occurring prior to apoptosis. Treatment of both NT‐2 and SK‐N‐MC cell lines with HNE led to HNE association with the proteasome, increased levels of protein carbonyls and ubiquitinated proteins, and decreased proteasomal function. There was also decreased metabolic activity, cytochrome c release and activation of caspase 3, followed by apoptotic changes including chromatin condensation, cell shrinkage and DNA fragmentation and laddering. Overexpression of mutant superoxide dismutase 1 proteins associated with amyotrophic lateral sclerosis decreased proteasomal activities in the absence of HNE and accelerated the apoptosis induced by HNE. By contrast, overexpression of wild‐type superoxide dismutase 1 did not affect basal levels of proteasomal activity. The data suggest that accumulation of ubiquitinated proteins and impairment of proteasomal function are important events in HNE toxicity. We propose that the proteasomal system is a significant target of HNE neurotoxicity in a wide range of neurodegenerative diseases, especially if abnormal proteins are being expressed.
1. The conditions under which peroxisomal preparations from leaves of spinach beet and spinach catalyse the release of 14CO2 from [1-14C]glycollate and [1-14C]glyoxylate were investigated. 2. At pH8, 14CO2 production from [1-14C]glyoxylate was accompanied by equivalent quantities of formate. The accumulation of oxalate and the effects of various reagents, especially catalase inhibitors, show that glyoxylate is non-enzymically oxidized by H2O2, which is generated by the oxidation of glyoxylate to oxalate by the action of glycollate oxidase. 3. 14CO2 is shown to be generated from [1-14C]glycollate at pH8 by a similar reaction, but the H2O2 is generated mainly by the oxidation of glycollate to glyoxylate. 4. The physiological significance of these reactions is discussed, with special reference to their role in photorespiration.
No abstract is provided for this article.
Dramatic increases in human lifespan and declining population growth are monumental achievements but these same achievements have also led to many societies today ageing at a faster rate than ever before. Extending healthy lifespan (healthspan) is a key translational challenge in this context. Disease-centric approaches to manage population ageing risk are adding years to life without adding health to these years. The growing consensus that ageing is driven by a limited number of interconnected processes suggests an alternative approach. Instead of viewing each age-dependent disease as the result of an independent chain of events, this approach recognizes that most age-dependent diseases depend on and are driven by a limited set of ageing processes. While the relative importance of each of these processes and the best intervention strategies targeting them are subjects of debate, there is increasing interest in providing preventative intervention options to healthy individuals even before overt age-dependent diseases manifest. Elevated oxidative damage is involved in the pathophysiology of most age-dependent diseases and markers of oxidative damage often increase with age in many organisms. However, correlation is not causation and, sadly, many intervention trials of supposed antioxidants have failed to extend healthspan and to prevent diseases. This does not, however, mean that reactive species (RS) and redox signalling are unimportant. Ultimately, the most effective antioxidants may not turn out to be the best geroprotective drugs, but effective geroprotective interventions might well turn out to also have excellent, if probably indirect, antioxidant efficacy.
Many papers in the literature have described complex effects of flavonoids and other polyphenols on cells in culture. In this paper we show that hydroxytyrosol, delphinidin chloride and rosmarinic acid are unstable in three commonly-used cell culture media (Dulbecco’s modified Eagle’s medium (DMEM), RPMI 1640 (RPMI) and Minimal Essential Medium Eagle (MEM)) and undergo rapid oxidation to generate H2O2. This may have confounded some previous studies on the cellular effects of these compounds. By contrast, apigenin, curcumin, hesperetin, naringenin, resveratrol and tyrosol did not generate significant H2O2 levels in these media. Nevertheless, curcumin and, to a lesser extent, resveratrol (but not tyrosol) were also unstable in DMEM, so the absence of detectable H2O2 production by a compound in cell culture media should not be equated to stability of that compound. Compound instability and generation of H2O2 must be taken into account in interpreting effects of phenolic compounds on cells in culture.
Nitric oxide, a gaseous free radical, is poorly reactive with most biomolecules but highly reactive with other free radicals. Its ability to scavenge peroxyl and other damaging radicals may make it an important antioxidant in vivo, particular in the cardiovascular system, although this ability has been somewhat eclipsed in the literature by a focus on the toxicity of peroxynitrite, generated by reaction of O·-2 with NO· (or of NO- with O2). On balance, experimental and theoretical data support the view that ONOO- can lead to hydroxyl radical (OH·) generation at pH 7.4, but it seems unlikely that OH· contributes much to the cytotoxicity of ONOO-. The cytotoxicity of ONOO- may have been over-emphasized: its formation and rapid reaction with antioxidants may provide a mechanism of using NO· to dispose of excess O·-2, or even of using O·-2 to dispose of excess NO·, in order to maintain the correct balance between these radicals in vivo. Injection or instillation of "bolus" ONOO- into animals has produced tissue injury, however, although more experiments generating ONOO- at steady rates in vivo are required. The presence of 3-nitrotyrosine in tissues is still frequently taken as evidence of ONOO- generation in vivo, but abundant evidence now exists to support the view that it is a biomarker of several "reactive nitrogen species". Another under-addressed problem is the reliability of assays used to detect and measure 3-nitrotyrosine in tissues and body fluids: immunostaining results vary between laboratories and simple HPLC methods are susceptible to artefacts. Exposure of biological material to low pH (e.g. during acidic hydrolysis to liberate nitrotyrosine from proteins) or to H2O2 might cause artefactual generation of nitrotyrosine from NO-2 in the samples. This may be the origin of some of the very large values for tissue nitrotyrosine levels quoted in the literature. Nitrous acid causes not only tyrosine nitration but also DNA base deamination at low pH: these events are relevant to the human stomach since saliva and many foods are rich in nitrite. Several plant phenolics inhibit nitration and deamination in vitro, an effect that could conceivably contribute to their protective effects against gastric cancer development.Keywords: Nitric oxideperoxynitritedeamination3-nitrotyrosinexanthinehypoxanthinereactive nitrogenspeciesgastric cancerlipid peroxidationsuperoxidehydroxyl radicalnitrous acidnitritecatechins
1. (a) Phagocytic cells produce oxygen radicals when exposed to opsonised bacteria or “foreign cells” generally. 2. (b) These oxygen radicals are an important part of the mechanism by which foreign particles are destroyed. 3. (c) Release of oxygen radicals and enzymes into the surrounding environment by phagocytic cells causes damage. I propose that chronic inflammatory disease, as illustrated by the autoimmune diseases, results when this damage gets out of hand. 4. (d) I further propose that excessive oxygen radical production due to environmental factors can initiate the autoimmune diseases.
