Catechol-estrogen modified DNA: a better antigen for cancer autoantibody

Estrogenized HSA induced high-affinity autoantibodies in breast cancer - Novel biomarker for early detection

Objective

Breast cancer (BC) is the second most prevalent cancer worldwide. Estrogen has been increasingly recognized as a major contributor to the development of BC, playing a more critical role than previously understood. Estrogen derived nucleic acid and protein adducts have been shown to play significant roles in BC development and progression. However, the alterations in molecular mechanism(s) and immune pathways arising as a result of estrogenization still remain elusive.

Patients and methods

4-hydroxyestradiol (4-OHE2) was used for adduct formation with protein human serum albumin (HSA) (4-OHE2-HSA). The affinity of antibodies for 4-OHE2-HSA was evaluated in breast cancer patients. Immunoassays (direct binding ELISA, inhibition ELISA, and quantitative precipitin titration assay) were used to assess autoantibodies against estrogenized HSA in BC patients (n = 85) and healthy controls (n = 45).

Results

Estrogenization of HSA altered both its structure and function and compromised its interactions with various HSA-binding proteins. BC patients demonstrated high-affinity antibodies against 4-OHE2-HSA as compared to HSA (p < 0.05). Additionally, cytokines Interleukin (IL)-1, IL-6 and tumor necrosis factor-alpha (TNF-α) were significantly elevated in BC patients as compared to the control group. Several factors, such as chemotherapy, estrogen receptors (ERs), and combination of surgery and chemotherapy, influenced the production of antibodies in cancer patients. The affinity constant for estrogenized HSA was 1.31 × 10-7 M, while for HSA and 4-OHE2, it was 1.68 × 10-6 M and 1.36 × 10-6 M, respectively.

Conclusions

Estrogenized HSA is highly immunogenic, resulting in functional alterations. High affinity antibodies were detected in BC patients against 4-OHE2-HSA. Consequently, 4-OHE2-HSA may serve as a novel molecular target for potential cancer therapeutics. Furthermore, autoantibodies against 4-OHE2-HSA could serve as a potential biomarker for early detection of BC.

Crotonaldehyde induced structural alterations in Low-Density Lipoprotein: Immunogenicity of the modified protein in experimental animals and auto-antibodies generation in various cancers

Crotonaldehyde (CA), a prominent component of cigarette smoke (CS) is a pervasive environmental pollutant that is a highly toxic, unsaturated aldehyde. Exposure to CA-rich pollutants has been linked to the emergence of many malignancies in humans. To better understand the role of CA in biomolecule modification, this study investigated the detailed structural alterations in low-density lipoprotein (LDL) modified by CA, as well as the immunogenicity of the modified protein in experimental animals and the search for autoantibodies in various cancers patients.In vitro, results indicated alterations in secondary and tertiary structures; examined using UV-visible, fluorescence, far-UV circular dichroism, and Fourier transform infrared spectroscopy techniques. Changes in the oxidation status of LDL were studied by carbonyl content assay and NBT assay. ThT binding assay, scanning, and transmission electron microscopy were used to study aggregate formation. The findings revealed significant structural damage in LDL modified by CA. The modification resulted in the unmasking of hydrophobic clusters, the loss of the protein α-helix, and the formation of β-pleated sheet structure. The amyloid aggregate formation was confirmed through ThT microscopy and electron spectroscopy. Rabbits immunized with crotonaldehyde; lead to structural changes in the LDL; that acted as extra antigenic determinants, eliciting strong antibody response. Immunoglobulin response is highly specific for modified LDL as demonstrated by the ELISA. The presence of antibodies against CA-modified LDL was confirmed by the immunoglobulin content of blood sera from human subjects with lung cancer, and competitive ELISA demonstrated the specificity of these antibodies. This study offers insights into the CA-mediated LDL modification and immunogenicity in lung cancer that will have diagnostic importance.

d-ribose-mediated glycation of fibrinogen: Role in the induction of adaptive immune response

A nonenzymatic reaction between reducing sugars and amino groups of proteins results in the formation of advanced glycation end products, which are linked to a number of chronic progressive diseases with macro- and microvascular complications. In this research, we sought to ascertain the immunological response to d-ibose-glycated fibrinogen. New Zealand White female rabbits were immunized with native and d-ribose-glycated (Rb-gly-Fb) fibrinogen and used for studying the immunological response. Serum from these rabbits analyzed using direct binding and competitive inhibition ELISA was found to contain a high titer of antibodies against Rb-gly-Fb; Rb-gly-Fb was much more immunogenic than its native form. The IgG against Rb-gly-Fb (Rb-gly-Fb-IgG) was highly specific against the immunogenic protein. Moreover, histopathology and immunofluorescence studies revealed the deposition of the Rb-gly-Fb-IgG immune complex in the glomerular basement membrane of the kidneys of immunized rabbits. Furthermore, immunization with Rb-gly-Fb increased the expression of genes encoding proinflammatory cytokines, tumour necrosis factor α, interleukin-6, interleukin-1β, and interferon-gamma, which is indicative of increased inflammation and the antigenic role of Rb-gly-Fb in provoking an immune response.

Differential Metabolome in Rheumatoid Arthritis: a Brief Perspective

PURPOSE OF REVIEW

Rheumatoid arthritis (RA) is a chronic autoimmune, inflammatory disease of the synovium that affects the movable joints. It develops due to the infiltration and invasion of the synovial joints by immune cells. Metabolism is anabolic or catabolic chemical reactions occurring in a cell. The biochemical pathways in synovial and immune cells are altered affecting the downstream metabolite formation. Changes in the metabolite levels alter signaling cascades which further intensify the disease. Despite current knowledge of metabolomics, there remain certain features that need to be elucidated to correlate the differential metabolite levels with RA.

RECENT FINDINGS

Metabolite profiling can be used to find altered patterns of metabolites in RA. Glucose, lipid, amino acid, and estrogen metabolism are the key pathways that are altered and contribute to the aggravation of RA. The altered metabolic pathways involved in different cells in RA results in complex interactions between metabolites and biomacromolecules; thus, it generates autoantigens. Moreover, understanding the correlation between differential metabolites and disease severity might help reveal potential new biomarkers and therapeutic targets for RA pathogenesis. So, considering the multi-faceted role of altered metabolites in the pathogenesis of RA, metabolic pathways of different cells are needed to be studied for a better understanding of their functions in the disease and thus, improving the present therapeutic strategies.

Anti-human serum albumin autoantibody may be involved in the pathogenesis of autoimmune bullous skin diseases

Although effective immunological diagnostic systems for autoimmune bullous skin diseases (AIBD) have been established, there are still unidentified cutaneous autoantigens. The purpose of this study is to investigative whether anti-human serum albumin (HSA) autoantibodies exist in AIBD sera and their potential pathogenesis. By immunoprecipitation-immunoblotting, immunofluorescence assay, anti-HSA autoantibodies could be detected in AIBD sera; by ELISAs, positive rates of AIBD sera for IgG and IgA anti-HSA autoantibodies were 29% and 34%, respectively. The IgG anti-HSA autoantibodies in ABID sera recognized a number of HSA antigen epitopes and therefore a polyclonal antibody against HSA were next employed to study its pathogenesis. In vitro cell and tissue culture models, anti-HSA antibody could influence DNA damage-related signaling proteins, via activation of phospho-p38 signaling pathway. This is the first report that an autoantibody may influence DNA damage-related signaling proteins. Statistical analyses also proved that anti-HSA autoantibodies were positively correlated with various known autoantibodies and clinical features of ABID patients. In summary, IgG and IgA autoantibodies to HSA may have diagnosis values for AIBD. DNA damage-related signaling proteins might be involved in the pathogenic role of anti-HSA autoantibodies in AIBD. Phospho-p38 signaling pathway is a potential target for treatment of AIBD positive for serum anti-HSA autoantibodies.

Recombinant interferon alpha 2b in rheumatoid arthritis: good antigen for rheumatoid arthritis antibodies

Aim of the study

Interferon alpha-induced arthritis and activation of the type 1 interferon pathway during rheumatoid arthritis (RA) has been well documented but the underlying mechanism remains unclear. This study addressed the binding specificity of antibodies with recombinant interferon alpha 2b (rIFN α-2b) in sera from different RA patients. Utilization of anti-hrIFN α-2b antibodies as a probe for estimation of interferon α-2b concentration in RA patients’ synovial fluid (SF) was also investigated.

Material and methods

Binding specificities of antibodies from the sera of 60 RA patients and 35 controls subjects were studied by direct binding, inhibition ELISA, and quantitative precipitation titration. Inhibition ELISA was also used to estimate patients’ SF interferon α-2b concentrations.

Results

RA IgG from patients’ sera showed strong recognition to hrIFN α-2b in comparison to commercially available interferon (IFN α-2b) (p < 0.05) or the gene encoding this interferon (IFN α-2b gene) (p < 0.05). The affinity of RA antibodies for rIFN α-2b (1.10 × 10^–7 M) was found to be high as assessed by Langmuir plot. No significant difference in the level of interferon α in the SF of RA patients was observed as compared to the healthy controls.

Conclusions

rIFN α-2b presents unique epitopes that might explain the possible antigenic role in the induction of RA antibodies and anti-rIFN α-2b antibodies represent an alternative immunological probe for the estimation of interferon α in the SF of RA patients.

SLE autoantibodies are well recognized by peroxynitrite-modified-HSA: Its implications in the pathogenesis of SLE

Systemic lupus erythematosus (SLE) is an autoimmune disorder where the role of inflammatory processes in the etiopathogenesis is well documented. Despite extensive research, the trigger for initiation of the disease has not been identified. Peroxynitrite, a strong nitrating/oxidizing agent has been reported in SLE and other autoimmune diseases. In this study, human serum albumin (HSA) was exposed to peroxynitrite for 30min at 37°C. The structure of HSA was grossly perturbed when examined by various physico-chemical techniques. Peroxynitrite mediated nitration of HSA was confirmed by LCMS/MS. Furthermore, increase in hydrodynamic radius of peroxynitrite-modified-HSA suggests the attachment of nitro group(s). Aggregation in peroxynitrite-modified-HSA was evident in a TEM scan. Nitration, oxidation, cross linking, aggregation etc conferred immunogenicity on peroxynitrite-modified-HSA. High titre antibodies were elicited in rabbits immunized with peroxynitrite-modified-HSA. Induced antibodies were highly specific for peroxynitrite-modified-HSA but showed considerable binding with other nitrated molecules. Direct binding/inhibition ELISA carried out with autoantibodies in SLE sera showed preferential binding with peroxynitrite-modified-HSA. Anti-nDNA positive IgG from SLE sera showed preference for peroxynitrite-modified-HSA when subjected to immunoassay (direct binding and inhibition) and mobility shift assay. Our results reinforce the role of augmented inflammation in SLE progression.

Immuno-chemistry of hydroxyl radical modified GAD-65: A possible role in experimental and human diabetes mellitus

The repertoire of known auto-antigens is limited to a very small proportion of all human proteins, and the reason why only some proteins become auto-antigens is unclear. The 65 kDa isoform of the enzyme glutamic acid decarboxylase (GAD-65) is a major auto-antigen in type I diabetes, and in various neurological diseases. Most patients with type I diabetes (70-80%) have auto-antibodies against GAD-65, which often appear years before clinical onset of the autoimmune diabetes. Thus, the aim of the study is to focus on the immunogenicity of GAD65 and its reactive oxygen species (ROS) conformer in STZ-induced diabetic rats and on human diabetic patients. In the present study, GAD-65 was modified by hydroxyl radical following Fenton's reaction. The modifications in the structure of the GAD-65 are supported by UV-vis and fluorescence spectral studies. Immunogenicity of both native and hydroxyl radical modified GAD-65 (ROS-GAD-65) was studied in experimental rabbits and was confirmed by inducing type I diabetes in experimental male albino rats using streptozotocin (45 mg/kg). We found that ROS-GAD-65 was a better immunogen as compared to the native GAD-65. A considerable high binding to ROS-GAD-65 was observed as compared to native GAD-65 in both the serum antibodies from diabetes animal models and as well as in the serum samples of type I diabetes. Hydrogen peroxide under the exposure of UV light produces hydroxyl radical (·OH) which is most potent oxidant, and could cause protein damage (GAD-65) to the extent of generating neo-epitopes on the molecule, thus making it immunogenic.

Glycoxidative damage to human DNA: Neo-antigenic epitopes on DNA molecule could be a possible reason for autoimmune response in type 1 diabetes

Advanced glycation end-products (AGEs) are known to be mutagenic, diabetogenic and vascular disease risk factors. Methylglyoxal (MG) is a dicarbonyl species that reacts with biological macromolecule (proteins, DNA and lipids) to give AGEs. Nonenzymatic glycation of MG with lysine (Lys) in the presence of copper (Cu(2+)) is reported to generate reactive oxygen species (ROS) capable of causing DNA damage. We show that DNA modification in MG-Lys-Cu(2+) system results in the generation of strand breaks, base modification, hyperchromicity and increased fluorescence intensity. Superoxide generation in the MG-Lys system was found to be significantly higher when compared with that in the MG and Lys alone. Moreover, d-penicillamine and pyridoxal phosphate significantly inhibited the formation of glycation products. The presence of a major DNA glycation adduct, N(2)-carboxyethyl-2'-deoxyguanosine (CEdG), was detected by high performance liquid chromatography (HPLC) and confirmed by nuclear magnetic resonance (NMR). As reported earlier, modified DNA (MG-Lys-Cu(2+)-DNA) was highly immunogenic in experimental animals. Furthermore, induced anti-MG-Lys-Cu(2+)-DNA antibodies were effective probe for detecting glycoxidative lesions in human genomic DNA of type I diabetes patients. Our results clearly imply that interaction of MG-Lys and Cu(2+) leads to the formation of AGEs and also the production of potent ROS, capable of causing DNA damage, thereby playing an important role in diabetes mellitus.

Cancer morbidity in rheumatoid arthritis: role of estrogen metabolites

Estrogen metabolites have been implicated in rheumatoid arthritis (RA) and cancer, although the mechanism remains unestablished. Some estrogen metabolites, which are used for the assessment of cancer risk, play an important role in RA. The pathways by which malignancies associated with RA remain elusive. Possible mechanism involves enzymatic or nonenzymatic oxidation of estrogen into catecholestrogen metabolites through semiquinone and quinone redox cycle to produce free radicals that can cause DNA modifications. Modifications of DNA alter its immunogenicity and trigger various immune responses leading to elevated levels of cancer and RA antibodies. However, the role of different estrogen metabolites as a mediator of immune response cannot be ruled out in various immune-related diseases.

Preferential recognition of catechol-estrogen modified DNA by circulating autoantibodies in cancer patients

Catecholestrogens [4-hydroxyestradiol (4-OHE(2))] have been implicated in human carcinogenesis, although the mechanism remains unestablished. In this study pUC 18 plasmid DNA was modified with 4-OHE(2) and nitric oxide (NO). The modification induced in native DNA exhibited hyperchromicity, single strand breaks, damage to restriction sites, modification of bases, decrease in Tm and change in ellipticity. Modified DNA was found to be highly immunogenic in experimental animal, eliciting high titer antibodies. Circulating cancer autoantibodies showed preferable recognition of 4-OHE(2)-NO-DNA over native form (p < 0.001) and the oxidative epitopes on the DNA isolates from cancer patients were immunochemically detected by using experimentally induced anti-4-OHE(2)-NO-DNA antibodies as a probe. Preferential recognition of 4-OHE(2)-NO-DNA by cancer autoantibodies coupled with enhanced binding of induced antibodies to DNA isolated from cancer patients is an indicative of oxidative stress induced DNA damage in cancer. Possible involvement of unique epitopes on modified DNA in cancer autoantibody induction has been suggested.

Mechanistic investigation of ROS-induced DNA damage by oestrogenic compounds in lymphocytes and sperm using the comet assay

Past research has demonstrated that oestrogenic compounds produce strand breaks in the DNA of sperm and lymphocytes via reactive oxygen species (ROS). In the current investigation, sperm and lymphocytes were treated in vitro with oestrogenic compounds (diethylstilboestrol, progesterone, 17β-oestradiol, noradrenaline and triiodotyronine) and several aspects of DNA damage were investigated. Firstly, mediation of DNA damage by lipid peroxidation was investigated in the presence of BHA (a lipid peroxidation blocker). BHA reduced the DNA damage generated by 17β-oestradiol and diethylstilboestrol in a statistically significant manner. No effects were observed for sperm. Secondly, the presence of oxidized bases employing FPG and EndoIII were detected for lymphocytes and sperm in the negative control and after 24 h recovery in lymphocytes but not immediately after treatment for both cell types. The successful detection of oxidized bases in the negative control (untreated) of sperm provides an opportunity for its application in biomonitoring studies. DNA repair at 24 h after exposure was also studied. A nearly complete recovery to negative control levels was shown in lymphocytes 24 h recovery after oestrogenic exposure and this was statistically significant in all cases. Rapid rejoining of DNA, in a matter of hours, is a characteristic of DNA damaged by ROS.

Biochemistry of nitric oxide

Nitric oxide (NO) a free radical having both cytoprotective as well as tumor promoting agent is formed from l-arginine by converting it to l-citrulline via nitric oxide synthase enzymes. The reaction product of nitric oxide with superoxide generates potent oxidizing agent, peroxynitrite which is the main mediator of tissue and cellular injury. Peroxynitrite is reactive towards many biomolecules which includes amino acids, nucleic acid bases; metal containing compounds, etc. NO metabolites may play a key role in mediating many of the genotoxic/carcinogenic effects as DNA damage, protein or lipid modification, etc. The basic reactions of nitric oxide can be divided as direct effect of the radical where it alone plays a role in either damaging or protecting the cell milieu and an indirect effect in which the byproducts of nitric oxide formed by convergence of two independent radical generating pathways play the role in biological reactions which mainly involve oxidative and nitrosative stress. Nitric oxide is also capable of directly interacting with mitochondria through inhibition of respiration or by permeability transition. Reaction of nitric oxide with metal ions include its direct interaction with the metals or with oxo complexes thereby reducing them to lower valent state. Excessive production of nitric oxide can be studied by inhibiting the synthetic pathway of nitric oxide using both selective or specific nitric oxide synthase inhibitor or non-selective nitric oxide synthase inhibitor with respect to isoforms of nitric oxide.

Optical biosensor-based characterization of anti-double-stranded DNA monoclonal antibodies as possible new standards for laboratory tests

The serum determination of circulating anti-double-stranded (ds)DNA autoantibodies is a routine measure for the laboratory diagnosis of systemic lupus erythematosus. Since available assays differ substantially and no feasible calibrator is available, the aim of this study was to evaluate a recently introduced surface plasmon resonance (SPR) biosensor chip for binding studies between dsDNA and anti-dsDNA autoantibodies and to demonstrate its usefulness for the characterization of new monoclonal antibody (mAb) standards and standardization of assays. We characterized two human and one murine monoclonal anti-dsDNA antibodies by measuring the kinetic on- and off-rates using the biosensor and calculating functional affinity (avidity) as the ratio of these. Obtained equilibrium dissociation constants were verified by an independent method and inhibition experiments were performed to determine reactivities to DNA of various length and composition. While all mAbs exhibited comparable avidities, which could be confirmed by gel shift experiments, one of them proved to have slower association and dissociation kinetics. This was the only mAb providing positive results in the Farr RIA. In inhibition experiments with ss- and ds-oligonucleotides 10, 24 and 42 bp in length, the mAbs acted substantially different. The study demonstrates how putative standards for the anti-dsDNA determination can be characterized using SPR biosensor technology. Our results suggest that kinetic rate constants seem to be decisive in explaining the behaviour of mAbs. Different reactivities to various DNA species should be taken into account with respect to varying DNA sources in commonly used laboratory assays.

Enhanced binding of circulating SLE autoantibodies to catecholestrogen-copper-modified DNA

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease characterized by circulating and tissue fixed autoantibodies reactive with self-antigens, including nucleic acid and other nuclear components. The pathways by which these autoantibodies act as a pathogenic factor remain elusive. Present study has investigated the role of estrogens in SLE etiopathogenesis. Estrogen-modified DNA [4-OHE(2)-Cu(II)-DNA] showed single- and double-strand breaks, hyperchromicity, decrease in Tm, and modification of bases. The 4-OHE(2)-Cu(II)-DNA exhibited increased binding with naturally occurring anti-DNA autoantibodies as compared to the unmodified native form (P < 0.001) as assessed by ELISA, quantitative precipitin titration, and gel retardation assay. The relative affinity of anti-DNA antibodies for modified and native DNA was in the order of 2.1 x 10(-7) M and 1.3 x 10(-6) M, respectively. The data suggested that DNA modified with 4-OHE(2) and Cu(II) may be one of the factors for the induction of circulating anti-DNA autoantibodies in SLE.

The temperature activated HtrA protease from pathogen Chlamydia trachomatis acts as both a chaperone and protease at 37 degrees C

Characterization of the protease, HtrA, from pathogen Chlamydia trachomatis is presented. The purified recombinant protein was a serine endoprotease, specific for unfolded proteins, and temperature activated above 34 degrees C. Chaperone activity was observed, although this appeared target-dependent. Inactive protease (S247A) was able to chaperone insulin B-chain, irrespective of temperature, but at 30 degrees C only HtrA and not S247A displayed significant chaperone activity for alpha-lactalbumin. These data demonstrate that chaperone activity may involve functional protease domain and that C. trachomatis HtrA functions as both a chaperone and protease at 37 degrees C. These properties are consistent with the developmental cycle of this obligate intracellular bacterium.