Binding of circulating antibodies to reactive oxygen species modified-DNA and detecting DNA damage by a monoclonal antibody probe

Autoantibodies to Peroxiredoxin I and IV in Patients with Systemic Autoimmune Diseases

Anti-oxidative enzymes protect living bodies from various oxidative stresses. In the systemic autoimmune diseases, autoantibodies to oxidized molecules and to anti-oxidative enzymes have been reported. To promote understanding of the relationships between autoimmunity and oxidative stress, we here investigate whether autoimmunity to the anti-oxidative peroxiredoxin (Prxs) enzymes exists in patients with systemic autoimmune diseases. Specifically, we detected autoantibodies to recombinant Prx I and Prx IV respectively by ELISA and western blotting. Next, clinical parameters were compared between the anti-Prx I or IV-positive and-negative patients. We found that 33% of the 92 patients with autoimmune diseases tested possessed autoantibodies to Prx I (57% in systemic lupus erythematosus (SLE), 19% in rheumatoid arthritis (RA), 5% in Behçet disease, and 46% in primary vasculitis syndrome). In contrast, autoantibodies to Prx IV were detected in only 17% of the same patients. No significant correlation was found between occurrence of the two autoantibodies. Clinically, possession of anti-Prx I autoantibodies correlated with lower serum levels of CH50, C3, and C4. Taken together, our data demonstrate the existence of autoantibodies to Prxs for the first time. The autoantibodies to Prx I may be involved in the pathophysiology of systemic autoimmune diseases such as SLE and vasculitis.

Biochemical markers of aging for longitudinal studies in humans

Much progress has been made in the past decades in unraveling the mechanisms that are responsible for aging. The discovery that particular gene mutations in experimental species such as yeast, flies, and nematodes are associated with longevity has led to many important insights into pathways that regulate aging processes. However, extrapolating laboratory findings in experimental species to knowledge that is valid for the complexity of human physiology remains a major challenge. Apart from the restricted experimental possibilities, studying aging in humans is further complicated by the development of various age-related diseases. The availability of a set of biomarkers that really reflect underlying aging processes would be of much value in disentangling age-associated pathology from specific aging mechanisms. In this review, we survey the literature to identify promising biochemical markers of aging, with a particular focus on using them in longitudinal studies of aging in humans that entail repeated measurements on easily obtainable material, such as blood samples. Our search strategy was a 2-pronged approach, one focused on general mechanisms of aging and one including studies on clinical biomarkers of age-related diseases.

Potential biomarkers of ageing

Life span in individual humans is very heterogeneous.Thus, the ageing rate, measured as the decline of functional capacity and stress resistance, is different in every individual. There have been attempts made to analyse this individual age, the so-called biological age, in comparison to chronological age. Biomarkers of ageing should help to characterise this biological age and, as age is a major risk factor in many degenerative diseases,could be subsequently used to identify individuals at high risk of developing age-associated diseases or disabilities. Markers based on oxidative stress, protein glycation,inflammation, cellular senescence and hormonal deregulation are discussed.

Characterization of chromatin modified with reactive oxygen species: recognition by autoantibodies in cancer

OBJECTIVES

To study the binding of chromatin modified with reactive oxygen species (ROS) with circulating autoantibodies present in cancer patients.

DESIGN AND METHODS

Chromatin isolated from goat liver was modified by superoxide radical plus singlet oxygen and hydroxyl radicals. Sera from 47 patients with various types of cancers were tested for binding to native and modified chromatin by direct binding and competition ELISA.

RESULTS

Maximum modification of thymine (54%) was found in case of chromatin modified with hydroxyl radical whereas by the combined action of singlet oxygen and superoxide anion radical, guanine was modified most (72%). Autoantibodies in cancer sera recognized modified chromatin in preference to native chromatin. Band shift assay with affinity-purified IgG from sera of cancer patients reiterated the results obtained with serum samples.

CONCLUSION

Greater recognition of ROS-modified chromatin with the autoantibodies in cancer sera is indicative of reactive-oxygen-species-induced chromatin damage in cancer patients.

Acquired antigenicity of DNA after modification with peroxynitrite

There are many contaminants affecting human beings, the most important being the metabolites of gases in air around us or certain deleterious by products from metabolic activity. They are reactive species of nitrogen, oxygen and their derivatives. Nitrogen is taken into body as nitrates, nitrites, peptides, proteins, etc. and its metabolites include higher oxides of nitrogen and peroxynitrite. Although NO is a free radical, it is probably insufficiently reactive to attack DNA directly. By contrast its derivatives N2O3, HNO2, ONOO- can nitrate, deaminate, cause strand breaks in DNA leading to serious consequences including mutations. The study exploits this property of ONOO-, such that on modification DNA which in its native form is non-immunogenic acquires the ability to elicit immune response in experimental animals. The extent of modifications, characterization of induced antibodies along with antigen-antibody interactions are studied and analyzed through different techniques.

Aging research in India

Research on aging in India has been well documented since ancient times. As way back as 3000-1500 BC, the Indian medical system of Ayurveda was used as a means for the prevention of the effects of aging and generation of disease in organs or the whole organism, respectively. In recent years, the focus has been demographic studies on different aspects of aging and has been in isolation. Molecular aspects of aging have been addressed only by a few groups of scientists which has focused on regulation of gene expression, DNA damage and repair, development of immunochemical reagents to detect oxidative DNA damage and assessing the levels of circulating antibodies to reactive oxygen species modified DNA (ROS-DNA), etc. This review aims to recapitulate various research studies on aging since 3000 BC to date.

In vitro study on the genotoxicity of dichloromethane extracts of valerian (DEV) in human endothelial ECV304 cells and the effect of vitamins E and C in attenuating the DEV-induced DNA damages

To study the genotoxicity of valepotriates in vitro, the degree of DNA damage in human endothelial cell line ECV304 treated with 5-60 microg/mL of dichloromethane extracts of valerian (DEV) was analyzed by the Comet assay. No DNA damage was observed in ECV304 cells after culture for 48 h in the presence of 5,10, and 20 microg/mL of DEV. But a moderate degree of DNA damage was observed in the cells treated with 40 or 60 microg/mL of DEV. Quantitative analyses of DNA damage in the presence of antioxidants vitamin E (VE) and vitamin C (VC) were also carried out. The study revealed that both VE and VC exhibited a biphasic effect, reducing DEV-induced DNA damages at low concentrations but increasing them at high concentrations. We concluded that (1). the observed DNA damage in ECV304 cells induced by high concentrations of DEV was mainly through epigenetic mechanisms, i.e., reactive oxygen species mediated oxidative DNA damage (2). at the low doses, DEV did not appear to have any significant genotoxicity in ECV304 cells, and (3). VE and VC, at proper concentrations, can reduce or eliminate the adverse effects derived from high doses of DEV. This study should serve as scientific guidance for clinical therapy of valerian preparation.

Oxygen free radicals and systemic autoimmunity

Reactive oxygen species generated during various metabolic and biochemical reactions have multifarious effects that include oxidative damage to DNA leading to various human degenerative and autoimmune diseases. The highly reactive hydroxy radical (*OH) can interact with chromatin and result in a wide range of sugar and base-derived products, DNA-protein cross-links and strand breaks. Studies from our laboratory have demonstrated that after modification the DNA becomes highly immunogenic and the induced antibodies exhibit variable antigen-binding characteristics. Systemic lupus erythematosus, a prototype autoimmune disease, is characterized by the presence of autoantibodies to multiple nuclear antigens. The detection of 8-hydroxyguanosine in the immune complex derived DNA of systemic lupus erythematosus patients reinforces the evidence that reactive oxygen species may be involved in its pathogenesis. Increased apoptosis and decreased clearance of apoptotic cells as observed in systemic lupus erythematosus (SLE) might well be a contributory factor in systemic autoimmunity. Clinically, titres of autoantibodies are closely related to the degree of renal inflammation. Anti-DNA antibodies may combine with circulating antigen and contribute to the deposition of immune complexes in renal glomeruli.

Antigenicity of poly(I) and ROS-poly(I) and their recognition of human anti-DNA autoantibodies

The effect of hydroxyl radicals on polyinosinic acid [poly(I)] was studied. Strand breaks, base alteration and a decrease in absorbance at 248 nm (lambda max) were observed upon *OH modification of poly(I). The broad antigen specificity of the induced anti-poly(I) and anti-ROS-poly(I) antibodies showed diverse antigen binding characteristics similar to those of SLE autoantibodies. Recognition of both poly(I) and ROS-poly(I) by human SLE anti-DNA autoantibodies was observed. The possible significance of these findings in the etiology of SLE has been discussed.

The aging paradox: free radical theory of aging

There are more than 300 theories to explain the aging phenomenon. Many of them originate from the study of changes that accumulate with time. Among all the theories, the free radical theory of aging, postulated first by Harman, is the most popular and widely tested, and is based on the chemical nature and ubiquitous presence of free radicals. This review aims to recapitulate various studies on the role of free radicals in DNA damage-both nuclear as well as mitochondrial-the oxidative stress they impose on cells, the role of antioxidants, the presence of autoantibodies, and their overall impact on the aging process.

Immunochemical detection of oxidative DNA damage in cancer and aging using anti-reactive oxygen species modified DNA monoclonal antibody

The formation of reactive oxygen species (ROS), although a normal cellular activity, is considerably enhanced under chronic inflammatory conditions and ischemia. These species have been implicated in various disorders, mutagenesis, carcinogenesis and aging. Of many macromolecules, DNA is the most susceptible to hydroxyl radical, the most reactive of the ROS. The present study is designed to detect oxidative DNA damage in cancer patients and healthy aged humans using an anti-ROS-DNA monoclonal antibody (mAb). Purified calf thymus DNA fragments (approximate size 400 bp) were modified with OH, generated by UV-irradiation (254 nm) of hydrogen peroxide. ROS-modified DNA was characterized by UV-spectroscopy, melting temperature, alkaline sucrose density gradient ultracentrifugation and ion-exchange chromatography. ROS-DNA showed single strand breaks, decrease in Tm, modification of thymine (58.3%) and guanine (20%). The mAb generated against ROS-DNA was characterized for antigen binding specificity by competition ELISA. Monoclonal antibody showed strong binding to ROS-modified DNA, its modified fragments, polynucleotides and bases. With the exception of native DNA, binding of unmodified polynucleotides and bases was much lower. The mAb distinctly recognized DNA samples from lymphocytes of healthy aged humans and gave maximum inhibitions of 49, 53, 64 and 70%, while not reacting with DNA from young population. Similarly, oxidative lesions in DNA from cancer patients were also efficiently recognized by the mAb. DNA from healthy controls served as negative control. The studies demonstrate that the mAb, although cross-reactive, preferentially binds ROS-modified epitopes on DNA. High reactivity of mAb to DNA samples from cancer patients and healthy aged humans indicates increased oxidative stress leading to DNA damage.