Preferential recognition of methylglyoxal-modified calf thymus DNA by circulating antibodies in cancer patients

290-296Methylglyoxal (MG) has been implicated in mutagenesis and cancer. Present study probes the antigenicity of MG damaged DNA in cancer patients. Purified calf thymus DNA was damaged by the synergistic action of MG, lysine (Lys) and CuSO4 for 24 h at 37oC. DNA modifications produced single-strand breaks, hyperchromicity in UV spectrum and increased fluorescence intensity. Binding characteristics of auto-antibodies in cancer patients were assessed by direct binding and inhibition ELISA. These antibodies exhibited enhanced binding with the modified DNA, as compared to the native form. The effect was more pronounced when affinity-purified IgG was used in place of the serum. In conclusion, MG-modified DNA presents unique epitopes which are recognized as non-self by the immune system and may, therefore, be one of the factors for the autoantibody induction in cancer patients

Oxidative Modification of LDL by Various Physicochemical Techniques: Its Probable Role in Diabetes Coupled with CVDs

Background. Pro- and antiatherogenic properties of oxidised low density lipoprotein (Ox-LDL) are responsible for different chronic diseases including diabetes and cardiovascular diseases (CVD). The constant attack on the body from oxidative stress makes the quantification of various oxidation products necessary. In this study, the oxidative stress causing the structural and chemical changes occurring in the LDL molecule is comprehensively done. Moreover, the prevalence of the autoantibodies against the oxidised LDL is also determined. Methods. Our study made an attempt to see the effect of Ox-LDL as an enhancer of type 2 diabetes mellitus (T2DM) coupled with CVD. Primarily, we detected the oxidation of LDL with different concentration of Fenton reaction. The biochemical parameters were assessed for the changes occurring in the LDL molecule. In a clinical set up, 20 sera samples were taken from patients who are healthy, 30 from those with diabetes, 20 from those with CVD, and 30 from diabetes with CVD patients. Results. In biochemical assays there were markedly increased TBARS, carbonyl, and HMF content in Ox-LDL as compared to native LDL. The prevalence of autoantibodies against the T2DM was recorded to be 36%, while for CVD it was recorded to be 29%. However, it was found that 50% of the sera samples showed autoantibodies against oxidized LDL in the sera of T2DM with CVD complications as compared to the native analogue. Conclusion. There is significant change in the LDL molecule as revealed by various physicochemical analysis. The change in the LDL macromolecule as a result of oxidation triggered the development of the autoantibodies against it

Therapeutic Efficacy of Natural Product ‘C-Phycocyanin’ in Alleviating Streptozotocin-Induced Diabetes via the Inhibition of Glycation Reaction in Rats

Diabetes is a long-term metabolic disorder characterized by persistently elevated blood sugar levels. Chronic hyperglycemia enhances glucose–protein interactions, leading to the formation of advanced glycation end products (AGEs), which form irreversible cross-links with a wide variety of macromolecules, and accumulate rapidly in the body tissues. Thus, the objective of this study was to assess the therapeutic properties of C-phycocyanin (C-PC) obtained from Plectonema species against oxidative stress, glycation, and type 2 diabetes mellitus (T2DM) in a streptozotocin (STZ)-induced diabetic Wistar rat. Forty-five days of C-PC administration decreased levels of triglycerides (TGs), blood glucose, glycosylated hemoglobin, (HbA1c), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), liver and kidney function indices, and raised body weight in diabetic rats. C-PC suppressed biochemical glycation markers, as well as serum carboxymethyllysine (CML) and fluorescent AGEs. Additionally, C-PC maintained the redox state by lowering lipid peroxidation and protein-bound carbonyl content (CC), enhancing the activity of high-density lipoprotein cholesterol (HDL-C) and renal antioxidant enzymes, and preserving retinal and renal histopathological characteristics. Thus, we infer that C-PC possesses antidiabetic and antiglycation effects in diabetic rats. C-PC may also act as an antidiabetic and antiglycation agent in vivo that may reduce the risk of secondary diabetic complications

Autoimmune response to AGE modified human DNA: Implications in type 1 diabetes mellitus

Aims: Non-enzymatic glycation of DNA both in vivo and in vitro results in generation of free radicals, known as glycoxidation. Glycoxidation leads to structural perturbation of DNA resulting in generation of neo-antigenic epitopes having implication in autoimmune disorders like diabetes mellitus. In this study human placental DNA was glycated with methylglyoxal (MG) and lysine (Lys) in the presence of Cu2+ and its auto-antibody binding was probed in Type 1 diabetes patients. Methods: Glycation was carried out by incubating DNA with MG, Lys and Cu2+ for 24 h at 37 °C. Carboxyethyl deoxyguanosine (CEdG) formed in glycation reaction was studied by LC-MS and the pathway for Amadori formation was studied by ESI-MS techniques. Furthermore, binding characteristics of auto-antibodies in diabetes patients were assessed by direct binding, competitive ELISA and band shift assay. Results: DNA glycation with MG, Lys and Cu2+ results in the formation of CEdG (marker of DNA glycation) which was confirmed by LC-MS. The intermediate stages of glycation were confirmed by ESI-MS technique. Serum from diabetes patients exhibited enhanced binding and specificity for glycated DNA as compared to native form. Conclusions: Glycation of DNA has resulted in structural perturbation causing generation of neo-antigenic epitopes thus recognizing auto-antibodies in diabetes

Genotoxic effect of N-hydroxy-4-acetylaminobiphenyl on human DNA: implications in bladder cancer.

BackgroundThe interaction of environmental chemicals and their metabolites with biological macromolecules can result in cytotoxic and genotoxic effects. 4-Aminobiphenyl (4-ABP) and several other related arylamines have been shown to be causally involved in the induction of human urinary bladder cancers. The genotoxic and the carcinogenic effects of 4-ABP are exhibited only when it is metabolically converted to a reactive electrophile, the aryl nitrenium ions, which subsequently binds to DNA and induce lesions. Although several studies have reported the formation of 4-ABP-DNA adducts, no extensive work has been done to investigate the immunogenicity of 4-ABP-modified DNA and its possible involvement in the generation of antibodies in bladder cancer patients.Methodology/principal findingsHuman DNA was modified by N-hydroxy-4-acetylaminobiphenyl (N-OH-AABP), a reactive metabolite of 4-ABP. Structural perturbations in the N-OH-AABP modified DNA were assessed by ultraviolet, fluorescence, and circular dichroic spectroscopy as well as by agarose gel electrophoresis. Genotoxicity of N-OH-AABP modified DNA was ascertained by comet assay. High performance liquid chromatography (HPLC) analysis of native and modified DNA samples confirmed the formation of N-(deoxyguanosine-8-yl)-4-aminobiphenyl (dG-C8-4ABP) in the N-OH-AABP damaged DNA. The experimentally induced antibodies against N-OH-AABP-modified DNA exhibited much better recognition of the DNA isolated from bladder cancer patients as compared to the DNA obtained from healthy individuals in competitive binding ELISA.Conclusions/significanceThis work shows epitope sharing between the DNA isolated from bladder cancer patients and the N-OH-AABP-modified DNA implicating the role of 4-ABP metabolites in the DNA damage and neo-antigenic epitope generation that could lead to the induction of antibodies in bladder cancer patients

Hydroxyl Radical Modification of Collagen Type II Increases Its Arthritogenicity and Immunogenicity

Background: The oxidation of proteins by endogenously generated free radicals causes structural modifications in the molecules that lead to generation of neo-antigenic epitopes that have implications in various autoimmune disorders, including rheumatoid arthritis (RA). Collagen induced arthritis (CIA) in rodents (rats and mice) is an accepted experimental model for RA. Methodology/Principal Findings: Hydroxyl radicals were generated by the Fenton reaction. Collagen type II (CII) was modified by N OH radical (CII-OH) and analysed by ultraviolet-visible (UV-VIS), fluorescence and circular dichroism (CD) spectroscopy. The immunogenicity of native and modified CII was checked in female Lewis rats and specificity of the induced antibodies was ascertained by enzyme linked immunosorbent assay (ELISA). The extent of CIA was evaluated by visual inspection. We also estimated the oxidative and inflammatory markers in the sera of immunized rats. A slight change in the triple helical structure of CII as well as fragmentation was observed after hydroxyl radical modification. The modified CII was found to be highly arthritogenic and immunogenic as compared to the native form. The CII-OH immunized rats exhibited increased oxidative stress and inflammation as compared to the CII immunized rats in the control group. Conclusions/Significance: Neo-antigenic epitopes were generated on N OH modified CII which rendered it highly immunogenic and arthritogenic as compared to the unmodified form. Since the rodent CIA model shares many feature

Antioxidant and α-Amylase Inhibitory Property of Phyllanthus virgatus L.: An In Vitro and Molecular Interaction Study

The present study on Phyllanthus virgatus, known traditionally for its remedial potential, for the first time provides descriptions of the antioxidant and inhibition of α-amylase enzyme activity first by in vitro analyses, followed by a confirmatory in silico study to create a stronger biochemical rationale. Our results illustrated that P. virgatus methanol extract exhibited strong antioxidant and oxidative DNA damage protective activity than other extracts, which was well correlated with its total phenolic content. In addition, P. virgatus methanol extract strongly inhibited the α-amylase activity (IC50 33.20 ± 0.556 μg/mL), in a noncompetitive manner, than acarbose (IC50 76.88 ± 0.277 μg/mL), which showed competitive inhibition. Moreover, this extract stimulated the glucose uptake activity in 3T3-L1 cells and also showed a good correlation between antioxidant and α-amylase activities. The molecular docking studies of the major bioactive compounds (9,12-octadecadienoic acid, asarone, 11-octadecenoic acid, and acrylic acid) revealed via GC-MS analysis from this extract mechanistically suggested that the inhibitory property may be due to the synergistic effect of these bioactive compounds. These results provide substantial basis for the future use of P. virgatus methanol extract and its bioactive compound in in vivo system for the treatment and management of diabetes as well as in the related condition of oxidative stress