Oxidant modulation of apoptotic cell death
Sten Orrenius
Institute of Environmental Medicine, Karolinska Institutet, Box 210, S-171 77 Stockholm, Sweden
Apoptosis is a special form of cell death, which is now widely recognized as being a distinct process of importance both in normal physiology and pathology. In the current paradigm for apoptotic cell death, the activity of a family of caspases (cysteine proteases with a stringent requirement for Asp in the P1 position of the substrate) orchestrates the multiple downstream events (such as cell shrinkage, membrane blebbing, glutathione efflux and chromatin degradation) that comprise apoptosis. The proteolytic cascade may involve other proteases in addition to caspases, e.g. calpain, and the relative contribution of the different proteases to the apoptotic process may vary between different cell types and triggers of apoptosis.
In TNF- and Fas/APO-1/CD95-mediated apoptosis the proteolytic cascade is believed to be triggered directly by caspase (caspase-8) binding to the activated plasma membrane receptor complex. In other forms of apoptosis, the mechanisms of activation of the proteolytic cascade are less well established but may involve imported proteases, i.e., granzyme B or factors released from the mitochondria and, possibly, other organelles. Recently, the possibility that cytochrome c released from the mitochondria may serve to activate dormant caspases in the cytosol, and thereby to amplify the apoptotic process, has attracted considerable attention.
One of the most reproducible inducers of apoptosis is mild oxidative stress, although it is yet unclear how an oxidative stimulus can activate the caspase cascade. Similarly, a variety of antioxidants are known to inhibit the death process. Oxidative modification of proteins and lipids have also been observed in cells undergoing apoptosis in response to non-oxidative stimuli, suggesting that intracellular oxidation may be a general feature of the effector phase of apoptosis. Our recent work suggests that the proteolytic activation of a glutathione (GSH) efflux mechanism contributes to this shift in the intracellular redox state during apoptosis. The possible significance of these redox changes for the initiation and termination of the apoptotic proteolytic cascade will be discussed.
Fasmediated apoptosis: cellular events and lipoate regulation
Chandan K. Sen, Sashwati Roy, and Lester Packer
Department of Molecular and Cell Biology, University of California at Berkeley
Fas-ligand mediated killing of tumor cells is a novel strategy that is being explored for cancer therapy. In contrast to healthy peripheral blood lymphocytes, apo-Fas receptors are highly expressed in leukemic cells such as Jurkat. We explored the possibility to modulate Fas mediated killing of tumor cells by redox active compounds. The effect of a-lipoate was tested. Pretreatment of Jurkat T cells with 100 µM lipoate for 72 h markedly potentiated Fas-mediated apoptotic death of Jurkat cells but not peripheral blood lymphocytes. The potentiating effect of lipoate on Fas-mediated apoptosis of Jurkat cells was consistently manifested as increased loss of cell viability, faster DNA laddering kinetics, enhanced TUNEL staining and increased flip-out of membrane phosphatidylserine.
In Jurkat, Fas ligand activation was followed by rapid loss of cell thiols, increased [Ca2+]i and increased PKC activity. These cellular responses were potentiated in lipoate pretreated cells. PKCd played an important role in mediating the effect of lipoate on Fas-mediated cell death. TIA-1 recognizes a 15 kD protein usually expressed in lymphocytes with cytolytic potential such as during programmed cell death. Anti-Fas challenge of lipoate pretreated cells resulted in increased TIA-1 expression. In mammalian cells the cysteine protease caspase 3 is known to play a central role in apoptosis signal transduction. Lipoate pretreatment did not alter basal caspase 3 expression. However, activation of caspase 3 following Fas-activation was markedly stronger in lipoate treated cells compared to corresponding controls suggesting that Fas-induced caspase 3 activation is a lipoate sensitive step. Because human caspase 3 is known to have a putative cysteine active site, the observed effect of lipoate on caspase 3 response is likely to be mediated by a redox dependent mechanism. Lipoate pretreatment of Jurkat T cells markedly influenced several key signaling mechanisms and sensitized leukemic cells to Fas-medi-ated cell death.
Dissecting the signal transduction pathway for the activation of NF-kB by hydrogen peroxide
Kirsty McPherson and Christine Winterbourn
Free Radical Research Group, Department of Pathology, Christchurch School of Medicine, PO Box 4345, Christchurch, New Zealand
Exogenous H2O2 has been shown to activate the transcription factor NF-kB in a number of cell types including B and T lymphocytes, monocytes, fibroblasts, myoblasts and epithelial cells. In contrast to the rapid induction by cytokines such as TNF-a, activation of NF-kB by hydrogen peroxide is very slow, taking two hours to achieve maximal DNA-binding activity. We have taken advantage of this time-lag to add inhibitors at various stages after the addition of H2O2 in order to dissect the signal transduction pathway in the Jurkat T lymphoma subclone Wurzburg. Our studies have shown inhibition by BAPTA-AM added shortly after the peroxide, indicating an early requirement for elevated intracellular Ca2+ levels, and subsequent mitochondrial involvement. Interestingly, mitochondrial inhibitors were effective if added well after the cells had consumed all the exogenous H2O2. Furthermore, TNF-a-mediated activation was unaffected by the mitochondrial inhibitors or the Ca2+-chelator .
A number of established cytochrome P450 inhibitors also block the H2O2 -mediated activation of NF-kB, although the specificity of these inhibitors (econazole, a-naphthoflavone, piperonyl butoxide, meytrapone, and methoxsalen) has yet to be evaluated. Others have suggested heme proteins such as prostaglandin H synthase and lipoxygenase to be involved in the activation of NF-kB but we have ruled these out based on their lack of expression in Wurzburg cells and careful inhibitor studies.
Redox regulation of NF-kB and novel therapeutic application
Takashi Okamoto
Department of Molecular Genetics, Nagoya City University, Nagoya, Japan
The concept of redox regulation as a modality in cellular signal transduction has been widely accepted. Based on this notion, we have been investigating a mechanism which regulates one of a multipoten tial transcription factor, nuclear factor kappa B (NF-kB). In this symposium, I will be describing the nature of redox regulation of NF-kB by thioredoxin especially in rheumatoid arthritis (RA). For pathogenesis of RA, thioredoxin is considered to be involved at least in two fold: (1) Trx works as a redox effector to activate the DNA-binding of NF-kB, and (2) Trx appears to lower the threshold of the TNFa induced NF-kB activation as a co-factor when apresent extracellularly (the details will be presented by S. Yoshida in this meeting as a separate paper).
Since RA and AIDS shares common property that both pathologies are initiated and maintained by actions of NF-kB, it is conceivable that some effective anti-RA drugs, which have been safely used in human for decades, if they have anti-NF-kB property, should also be effective in blocking HIV-replication. Based on this idea, we found that one such anti-RA compounds, aurothioglucose, was effective in blocking the TNFa-induced induction of HIV replication from the latently-infecetd cells.
These observations confirm that a concept of redox regulation has a wide variety of application in understanding as well as treating various diseases sharing the same redox background.
Yvonne M.W. Janssen, Brooke T. Mossman, and Balaraman Kalyanaraman
Department of Pathology, University of Vermont, Burlington VT 05405 and the Biophysics Research Institute, Medical College of Wisconsin, Milwaukee WI 53226
Reactive oxygen and nitrogen species (ROS and RNS) induce multiple signaling cascades that mediate diverse phenotypic endpoints in lung epithelium. Cell proliferation and apoptosis are outcomes of exposure to ROS/RNS and may be critical in the pathogenesis of many lung diseases. Activation of mitogen activated protein kinase (MAPK) cascades occurs in RLE cells exposed to ROS/RNS and may regulate these phenotypic outcomes. For instance, phosphorylated extracellular signal regulated kinase (ERK) protein, representing the activated form is found in apoptotic cells whereas phospho-c-Jun-N terminal kinase (JNK) occurs in cells in G2/M, indicating a differential role of these MAPK. We recently demonstrated that depletion of NO. from cells using the specific NO. trap, PTIO causes increases in the oxidation of dichlorofluorescin (DCF) and leads to an activation of the cell cycle as well as apoptosis. Addition of 8-Br-cGMP ameliorated these responses whereas the inhibitor of guanylate cyclase, ODQ mimicked the effects of NO. depletion. These findings illustrate that a guanylate cyclase-dependent signaling pathway mediates cell cycle progression and apoptosis.
Our results demonstrate that critical levels of ROS and RNS are important in normal cell cycle regulation and survival. Disturbances of these balances causes aberrant activation of signaling pathways and cell death.
A role of NF-kB/p53 interactions in cellular response to oxidative stress
Ken-ichi Yamamoto
Department of Molecular Pathology, Cancer Research Institute, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa 920, Japan
Both of NF-kB and p53 transcription factors are activated in response to various noxious stimuli and play important roles in cellular response to noxious stimuli. However, it remains to be established how NF-kB and p53 are activated, how their activities are regulated, and what roles these factors play in cellular response to noxious stimuli including oxidative stress. We previously showed that oxidative stress such as hydrogen peroxide effectively activates both p53 and NF-kB. We now found that NF-kB overexpression inhibits p53-dependent as well as p53-independent promoter activation of the p21-CDK inhibitor gene in p53-null Saos-2 cells. In a similar experiment, the overex pression of a dominant negative form of IkBa enhanced both of p53-dependent and p53-independent p21 promoter activation. Since both of p65 and p53 have been recently shown to interact with p300 and CBP transcriptional coactivators, it is possible that this functional interference between p53 and p65 is mediated through their interactions with p300 and CBP. However, while p65-mediated inhibition of p53-idependent p21 promoter activation was reversed by CBP overexpression, CBP overexpression did not aborogate p65-mediated inhibition of p53-dependent p21 promoter activation. These results suggest a direct interaction between NF-kB, p65 and p53. We further discuss a possible physiological significance of this interaction in cellular response to oxidative stress.
Glenn F. Vile*, Lincoln A. Rothwell and Anthony J. Kettle
Free Radical Research Group, Department of Pathology Christchurch School of Medicine, P.O. Box 4345 Christchurch New Zealand
Neutrophils have been implicated in the carcinogenicity associated with chronic inflammatory diseases. In inflamed tissue, neutrophils are stimulated to produce hydrogen peroxide which is converted to hypochlorous acid by co-released myeloperoxidase. We report here that levels of the tumour suppressor protein p53 were increased in cultured human skin fibroblasts that had been incubated with stimulated neutrophils. The increase in p53 required the myeloperoxidase- dependent generation of hypochlorous acid, and could be mimicked by treating cells with purified myeloperoxidase and a hydrogen peroxide generating system. Our results implicate hypochlorous acid in the neutrophil-dependent initiation of a signal transduction pathway which could minimise the carcinogenicity of chronic inflammation.
Redox events in the cytokine-induced expression of adhesion molecules in endothelial cells
Regina Brigelius-Flohé, Bärbel Friedrichs, Frank Tewes, and Gaby-Fleur Böl
German Institute of Human Nutrition, Potsdam-Rehbrücke, Germany
Interleukin-1 (IL-1) exerts its various signals via binding to the IL-1 receptor type I (IL-1RI). One of the earliest signals in T cells has been shown to be the activation of a serine/threonine kinase, which coprecipitates with the IL-1RI (1). An IL-1RI-associated kinase has later been cloned and named IRAK (2). It is, however, not yet clear whether this kinase is identical with the one described previously. IL-1 signaling is accompanied by oxidative processes and the cascade contains multiple putative targets for redoxregulation. Recently, we have demonstrated that the activation of the IL-1RI-associated kinase can be inhibited by thiol modifying compounds in the T cell line EL 4 (3). In endothelial cells, IL-1 is one of the most potent inducers of cellular adhesion molecules (CAM), like E-selectin, ICAM or VCAM. We therefore tested whether the expression of CAMs depended on the activation of the kinase and whether this kinase could be a target for the regulation by redox active compounds in the human umbilical endothelial cell line, ECV 304. We found that the IL-1RI-associated kinase was activated upon IL-1 treatment and that also the IL-1-induced activation of the endothelial kinase was inhibited by pretreating the cells with thiol modifying agents like diamide, menadione or phenylarsine oxide. All compounds described prevented the IL-1 mediated induction of E-selectin also in primary human endothelial cells (HUVEC). This shows that the IL-1-induced CAM expression depends on the activation of the IL-1RI-associated kinase. Further, the transduction of IL-1-mediated signals appears to generally depend on the availability of free, probably vicinal thiols in some of the proteins involved. Similarly, TNFa-induced E-selectin expression in HUVEC proved to be identically inhibited by diamide, menadione and phenylarsine oxide suggesting the involvement of related redox sensitive transducers in the TNF signaling pathway.
(1) Martin, M., Böl, G.-F. Eriksson, A., Resch, K. and Brigelius-Flohé, R.(1994) Eur. J. Immunol. 24, 1566-1571
(2) Cao, Z., Henzel, W.J. and Gao, X. (1996) Science 271, 1128-1131
(3) Tewes, F., Böl, G.-F. and Brigelius-Flohé, R. (1997) Eur. J. Immunol. 27, 3015-3021
Redox control of Thioredoxin (TRX) on the cytotoxic/death signal
Junji Yodoi1, Shugo Ueda1,2, Masaya Ueno1,2, Tetsuro Sasada1, and Hiroshi Masutani1
1Department of Biological responses, Institute for Virus Research and 2Department of Gastroenterological Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
There are accumulating evidences indicating the importantce of host defence mechansims against a variety of oxidative stress. It has been recently recognized that thioredoxin (TRX), as well as glutathione (GSH), is a key molecule in the control of redox states of the cells. TRX is a ubiquitous redox-active protein with multiple functions. We have previously shown that TRX is induced by a variety of oxidative stresses including UV, X-ray, ROI (reactive oxygen intermediates) and heavy metals, humoral transmittors such as hormones and cytokines, and viral infections. TRX is thought to involve in many aspects of fundamental cellular functions including signal transduction, gene regulation, and DNA repair.
Especially, TRX has been shown to modulate the signaling processes of cell death (apoptosis). We have previously demonstrated a protective activity of TRX and other thiol compounds against cytotoxicity and apoptosis induced by various oxidative stresses. For example, Fas and TNFa-dependent cell death was protected by intracellular as well as extracellular TRX. Thus, we have recently examined whether the activaty of ICE (interleukin 1b-converting enzyme) family proteases(caspases) with cysteine residue in their active site, are regulated by redox mechanism. The activity of caspase-3(CPP32), an important member of caspases, in Jurkat T cell lysate was markedly inhibited by diamide, a reversible thiol-oxidizing agent, and this inhibition was counteracted by DTT or TRX. In contrast, when Jurkat cells were excposed to diamide or hydogen peroxide, a marked increase of CPP32 protease activity in cells was observed after 4 hours of culture. These results suggest that intracellular redox state profoundly modulates the signaling processes of apoptosis by regulating the activity of caspases. Many transcription factors and DNA-binding proteins seem to require redox regulation by TRX. We have shown that the DNA binding activities of transcription factors, such as NF-kB, AP-1, and PEBP2/AML-1, are redox regulated. In addition, we have recently found that the activity of p53, a tumor suppressor gene product, is also modulated by the reducing activity of TRX. Further studies to clarify the function of TRX and its target molecules will elucidate the intracellular signaling pathways leading to cell death (apoptosis).
Differential regulation of oxidative and hyperosmotic stress-induced Syk activation in B cells
Suofu Qin and Hirohei Yamamura
Department of Biochemistry, Kobe University School of Medicine, Kobe 650, Japan
To address the distinctive roles of Syk in oxidative and osmotic stress signaling, we first investigated the effect of Syk structure on its activation, by expressing various Syk mutants in Syk-negative DT40 cells. Phosphorylation of Y518Y519 within the activation loop was required for both oxidative and hyperosmotic stress-induced Syk activation that was a combination result of both Syk activity and the addtional tyrosine kinase activity. Syk activity was responsible for the majority of oxidative stress-induced Syk tyrosine phosphorylation, while hyperosmotic stress-induced Syk tyrosine phosphorylation was mainly accounted for by additional tyrosine kinase(s), rather than Syk. Moreover, the SH2 domains of Syk differentially regulated Syk activation. Both mSH2(N) Syk and mSH2(C) Syk, in which the phospho-tyrosine-dependent binding motif within the SH2 domains contained point-mutations, showed a significantly higher activity than that observed in wild-type Syk, following hyperosmotic stress treatment. In contrast, only mSH2(N) Syk demonstrated a stronger activation than wild-type Syk after oxidative stress treatment.
We next examined the involvement of membrane receptor aggregation and intracellular free oxygen radicals on Syk activation. Treatment of cells with suramin, an inhibitor of growth factor receptor aggregation, could block hyperosmotic, but not oxidative stress-induced Syk activation, indicating the requirement of growth factor receptor aggregation for hyperosmotic stress-induced Syk activation. Following pre-incubation with antioxidants, N-acetyl-cysteine and reduced glutathione, both oxidative and hyperosmotic stress-induced Syk activation was reduced significantly. When cells were stimulated by both sodium chloride and hydrogen peroxide, a synergistic effect for Syk activation was observed. These results suggested that raising intracellular oxygen radicals might be a common prerequisite and integrating step for mediating oxidative and hyperosmotic stress induced Syk activation. Intriguingly, raising intracellular antioxidant potential could also activate Syk in Raji and DT40 cells. Taken together, these observations may give an insight into the distinctive functions of Syk in oxidative and osmotic stress signaling.
Ascorbic acid and atherosclerosis
Takao Fujinami
Department of Internal Medicine, Nagoya City University Medical School, Nagoya, Japan
Ascorbic acid deficiency, scurvy causes endothelial injury not only capillary but also of the aorta in guinea pig. Scurvy also induced increase in serum lipoproteins in guinea pig. Recently, scurvy proneoseto-dystrophic rat (ODS-rat) with lack of L-gulonolactone alpha-oxidase was separated. In the serum of the LDS-rat, we could not find apparent changes in serum lipid compositions, but found significant increase in oxidized lipid. Further, low serum tocopherol level in the scorbutic rat was found even alpha-tocopherol was supplemented in the diet. Electron-microscopic observations revealed flattened endothelial cells in the aorta and coronary artery, and caused increasing adhesiveness toward monocytes which migrate across the endothelial layer to the subendothelial space of the intima, and differentiate into resident macrophage. Macrophage scavenges oxidized LDL and transform to lipid-laden foam cells. From this view, we made guinea pig to marginal vitamin C deficient state. In the aorta of the latent vitamin C deficient guinea pig, we found accumulation of foam cell as fatty streak without cholesterol feeding. These findings support response to injury hypothesis as a pathogenesis of atherosclerosis. Ascorbic acid can protect peroxidation of LDL in the medium existing copper ion. In the patient with coronary heart disease, concentrations of malondialdehide and vitamin C showed significant negative correlations. Administration of 500 mg/day of vitamin C or 50 mg/day of alpha-tocopherol for 4 weeks to the patients caused reduction in serum malondialdehide. Coronary heart disease is predicted by established risk factors such as hypercholesterolemia, hypertension, diabetes, obesity and smoking only about 50-60%. Complementary direct risk factors are aggressive free radical species. Their scavengers, antioxidants are defense factor of atherosclerosis. Antioxidants state is a key for protection or prevent progression of atherosclerosis. In other words, lack of antioxidants in the tissue might be one of risk factors for atherosclerosis.
M. Maiorino, A. Roveri, L. Flohé* and F. Ursini
Department of Biological Chemistry, University of Padova, Padova, Italy and *Deptartment of Physiological Chemistry, Technical University of Braunschweig, Braunschweig, Germany
Selenium deficiency is known to affect the structure of mitochondria in epididimal sperm, which is the result of a damage to the mitochondrial sheaths occurring during the maturation of germ cells (1).
The 20kD selenoperoxidase PHGPx, specifically reducing PCOOH, is present, in testis mitochondria from adult mammals, and the specific activity is much higher than in any sub-cellular fraction of somatic cells. In testis mitochondria PHGPx is imported from the cytosol as a 23 KD precursor, containing a leader sequence which is eventually cleaved off (2,3). Also the 84 KD tetrameric selenoperoxi dase (cGPx) is present in testis, although the specific activity is markedly lower than in other tissues.
The changes of specific activity of selenium dependent peroxi dases following puberty or hormone withdrawal, suggest that PHGPx but not cGPx is proportional to the tissue content of maturating germ cells. In situ-hybridization studies confirmed this view, showing that PHGPx is preferentially expressed in late round spermatids while just a weak diffuse stain due to cGPx mRNA was observed. This argues for a dual role of selenium and suggests an involvement of PHGPx in the process of spermatogenesis.
In epididimal rat spermatozoa, a substatial amount of PHGPx can be detected by immunological procedures, although no peroxidase activity can be measured. This suggests that the physiological function of PHGPx is played during the maturation of spermatozoa from precursor cells, but not anymore in the mature cells. The enzymatic activity is fully restored by treatment of spermatozoa with high concentration of disulfide-reduc-ing agents. Thus, the loss of activity could be reasonably ascribed to the formation in the active site of the enzyme of species more oxidized than during the usual catalytic cycle.
Spermatozoa contain highly oxidized proteins, which, following thorough reduction, can be tracked by monobromobimane labelling and SDS-PAGE. The observation that some of these proteins undergo a thiol- disulfide transition in the presence of PCOOH and PHGPx, argue for the selenoperoxidase as the catalyst of the protein-thiol oxidation in maturating germ cells. This reaction maybe relevant for the formation of the mitochondrial sheath of spermatozoa.
1. Wallace, E., et al.(1987) In ıSelenium in Biology and Medicineı, part A (Combs G.F,, Spallholz J.E., Levander.O.A., Oldfield, J.E eds). AVI Publishing Co, Wesport, CT. p.181-196.
2. Pushpa-Rekha, T.R., et al. J. Biol. Chem. 270, 26993-26999.
3. Arai, M., et al.(1996) Biochem. Biophys. Res. Comm. 227, 433-439.
Oxidative damage precedes the formation of cytopathological lesions in Alzheimer disease
George Perry, Kiesuke Hirai, Lawrence M. Sayre, and Mark A. Smith
Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106 USA
The etiology of neuronal death in Alzheimer disease (AD) remains elusive. However, recent compelling lines of evidence including an association of defects in energy metabolism, compensatory upre gulation of antioxidant enzymes and various macromolecular oxidative modifications, indicate that neuronal death is tied to oxidative stress and free radical damage. Nonetheless, to have therapeutic relevance, it is extremely important to determine whether oxidative damage represents an early or late change in the pathophysiology of the disease.
In this study, we characterized the time course of the oxidative stress response of neurons in AD by comparing HO-1, an oxidative stress response marker, and four markers of oxidative damage (hydro xynonenal adducts, 8-hydroxydeoxyguanosine (8OHdG), nitrotyro sine and free carbonyls) with a monoclonal antibody (Alz50) that recognizes one of the earliest known changes of as it is incorporated into neurofibrillary tangles (NFT). Adjacent serial sections were immunostained with Alz50 or either of the other antibodies. We found that the same neurons are recognized by Alz50 and anti-HO-1 but the other markers of oxidative damage recognized all neurons at risk of death in AD, whether or not they contained an NFT, in cases of AD but none in the brains of controls.
These findings not only support oxidative damage preceding lesion formation but also that the source of ROS is in the cell bodies. In light of numerous studies showing mitochondrial abnormalities in AD, and from our finding of cytoplasmic 8OHdG, it seems very likely that mitochondria may be an important ROS source in initiating damage. Indeed, recent studies demonstrating mitochondrial abnormalities in AD and increased caloric consumption in cases of AD just prior to disease onset support the hypothesis that early metabolic abnormalities are important in the etiology of AD.
Supported by the NIH and the American Health Assistance Foundation.
Oxidative damage to DNA and other biomolecules in neurodegenerative diseases
Barry Halliwell
Neurodegenerative Disease Research Centre, Kingıs College, London, UK
There are frequent suggestions that oxidative damage contributes to the pathology of neurodegenerative diseases. In Parkinsonıs disease, the substantia nigra shows elevated SOD, depleted GSH, increased lipid peroxidation (measured as HPLC-detectable peroxides or as HNE) and rises in levels of 8OHdG and protein carbonyls. Whereas elevated lipid peroxidation and 8OHdG are unique to substantia nigra, protein carbonyls are increased in many brain regions. It is possible that treatment of patients with L-DOPA can increase oxidative damage in the brainf, as suggested by the fact that brain protein carbonyl levels are normal in incidental Lewy body disease (ILBD). L-DOPA and dopamine react with O2. and RO2. radicals to generate quinones/semi-quinones that can combina with GSH: increased levels of cysteinyl adducts are found in substantia nigra but not elsewhere in the brain in PD.
Nevertheless, ILBD tissues still show depleted GSH and rises in the level of the antiapoptotic protein bcl-2. The rise in 8OHdG in PD is not accompanied by rises in other oxidation/deamination products and so is unlikely to involve DNA attack by OH. or by species such as ONOO. Part of the rise may be due to a redox shift in the tissue that favours 8OHdG over other guanine damage products, rather than a marked elevation in total oxidative damage to guanine. By contrast, in senile dementia of the Lwy body type total guanine damage products are elevated and there is evidence for both increased oxidation and deamination.
Possible confounding effects in the study of DNA and other oxidative damage in human brain include post mortem interval and storage time: data on the effects of these will be presented.