PubMed Health⌕ Search

Biomedical subjects

Rashid Ali

Publications and source records attributed to Rashid Ali.

16 recordsLinked to original sources
PubMed2007

Immunogenicity of DNA modified by singlet oxygen: implications in systemic lupus erythematosus and cancer.

Activation, proliferation and programmed cell death of immune cells are dependent on controlled production of ROS (reactive oxygen species). However, under chronic inflammatory conditions, large amounts of ROS generated are a major cause of many human degenerative diseases. ROS are known to cause DNA damage, leading to strand breaks, base damage and conformational changes. (1)O(2) (singlet oxygen), being one of the most potent ROS, is known to selectively react with the deoxyguanosine moiety in DNA. The effect of (1)O(2), generated by UV irradiation of Methylene Blue, on plasmid DNA was studied by UV spectroscopy and electrophoresis. The antibodies raised against the modified DNA in experimental animals induced a high titre. IgG was purified on a Protein A-Sepharose matrix, and oxidative lesions in DNA of SLE (systemic lupus erythematosus) and cancer patients were probed using anti-((1)O(2)-plasmid DNA) [anti-((1)O(2)-modified plasmid DNA)]. The DNA isolated from the sera of SLE and cancer patients was found to inhibit anti-(1)O(2)-plasmid DNA IgG activity, reiterating the results obtained with serum samples. These binding results indicate the presence of oxidative lesions in the SLE and cancer patients' genome caused by excessive production of ROS. The results confirm the damaging effect ROS has on DNA. The excessive production of reactive oxygen intermediates may be one of the factors responsible for the induction of autoimmune response seen in SLE and cancer.

Animals↗
PubMed2006

Characterization of plant phenotypes associated with loss-of-function of AtCNGC1, a plant cyclic nucleotide gated cation channel.

Of the 57 cation channel genes in the Arabidopsis genome, over a third encode cyclic nucleotide gated cation channels (CNGCs). CNGCs are ion channels regulated by cytosolic signaling molecules (cyclic nucleotides, calmodulin, and Ca(2+)), and which conduct Ca(2+) as well as K(+) and in some cases Na(+). Little is currently known about the role CNGCs may play in plant growth and development. Here, we examined the hypothesis that an Arabidopsis thaliana genotype containing a null mutation in one of the CGNC genes (AtCNGC1) would display cation uptake-related growth phenotype differences from wild type (WT) plants. We determined that AtCNGC1 protein is primarily expressed in the roots of Arabidopsis seedlings. Seedlings lacking this protein had slightly (6-22%) lower shoot Ca(2+) than WT plants. Primary roots of Atcngc1 mutant seedlings grew faster than roots of WT plants, and had larger angles of gravicurvature and less nitric oxide generation upon gravistimulation. We conclude that channels formed (at least in part) by AtCNGC1 contribute (along with other channels) to Ca(2+) uptake into plants, and that Ca(2+) uptake into roots through AtCNGC1 affects some aspects of growth in the primary root of Arabidopsis seedlings.

Arabidopsis↗
PubMed2006

Reactive oxygen species damaged human serum albumin in patients with type 1 diabetes mellitus: biochemical and immunological studies.

The role of hydroxyl radical (.OH) damaged human serum albumin (HSA) in type 1 diabetes has been investigated in the present study. Hydroxyl radical induced modification on HSA has been studied by UV absorption spectroscopy, ANS fluorescence and carbonyl estimation. Hydroxyl radical modified HSA was found to be highly immunogenic in rabbits as compared to native HSA. The binding characteristics of circulating autoantibodies in type 1 diabetes patients against native and modified HSA were assessed. Diabetes patients (n=31) were examined by direct binding ELISA and the results were compared with healthy age-matched controls (n=22). High degree of specific binding by 54.8% of patients sera towards .OH modified HSA, in comparison to its native analogue (p<0.05) was observed. Sera from those type 1 diabetes patients having smoking history, high aging with high degree of disease showed substantially stronger binding to .OH modified HSA over native HSA in particular. Normal human sera showed negligible binding with either antigen. Competitive inhibition ELISA reiterates the direct binding results. Gel retardation assay further substantiated the enhanced recognition of modified HSA by circulating autoantibodies in diabetes patients. The increase in total serum protein carbonyl levels in the diabetes patients was largely due to an increase in oxidized albumin. HSA of diabetes mellitus patients (DM-HSA) and normal subjects (normal-HSA) were purified on a Sephacryl S-200 HR column. Spectroscopic analysis confirmed that the DM-HSA samples contained higher levels of carbonyls than normal-HSA (p<0.001). DM-HSA was conformationally altered, with more exposure of its hydrophobic regions. Collectively, the oxidation of plasma proteins, especially HSA, might enhance oxidative stress in type 1 diabetes mellitus patients.

Adult↗
PubMed2006

Antibodies against nitric oxide damaged poly L-tyrosine and 3-nitrotyrosine levels in systemic lupus erythematosus.

Alterations in the amino acid structure or sequence can generate neo-epitopes from self-proteins causing autoaggressive immune attack. Reactive nitrogen species are an important factor that induces post-translational modification of proteins by cellular reduction and oxidation mechanism; cysteinyl-nitrosylation or tyrosine nitration leading to potentially pathogenic pathways. It was thought of interest to investigate the immunogenicity of nitrated poly L-tyrosine vis-á-vis its possible role in the induction of antibodies in systemic lupus erythematosus (SLE). Commercially available poly L-tyrosine was exposed to nitrating species and the damage was monitored by UV spectroscopy and alkaline gel electrophoresis. The results indicated the formation of 3-nitrotyrosine. Nitrated poly L-tyrosine induced higher titre antibodies as compared to the native form. Nitrated poly L-tyrosine was recognized by the autoantibodies present in the sera of patients suffering from SLE by enzyme immunoassays and band shift assay. The possible role of nitrated self-proteins has been discussed in the production of circulating anti-DNA antibodies in SLE.

Antibody Specificity↗
PubMed2006

Peroxynitrite-modified DNA: a better antigen for systemic lupus erythematosus anti-DNA autoantibodies.

Native human DNA was modified by ONOO- (peroxynitrite), generated by the synergistic action of sodium nitroprusside [Na2Fe(CN)5NO], an NO donor, and pyrogallol, a superoxide donor. The modifications were analysed by UV absorption characteristics, fluorescence emission transitions, nuclease S1 digestibility and melting-temperature studies. Modified DNA was found to be highly immunogenic, inducing high-titre immunogen-specific antibodies in experimental animals. A maximum of 85% inhibition of the antibody binding was observed in competition ELISA with immunogen as inhibitor. SLE (systemic lupus erythematosus) anti-DNA autoantibodies recognized modified DNA as a better antigen than the native analogue. Modification of native DNA by ONOO-, forming neo-epitopes on the molecule, may be one of the factors for the induction of the autoimmune response seen in SLE.

Animals↗
PubMed2006

Hydroxyl radical modification of human serum albumin generated cross reactive antibodies.

Hydroxyl radical-mediated in vitro modification of human serum albumin (HSA) showed 59.2% hyperchromicity at lambdamax, 30% loss of alpha helical structure and 71.4% loss of tryptophan fluorescence. The reactive oxygen species (ROS)-modified HSA was highly immunogenic in rabbits as compare to native HSA. The antibody binding was inhibited to the extent of 97% with the immunogen as inhibitor, indicating the induction of immunogen specific antibodies. Experimentally induced antibodies against modified HSA exhibited diverse antigen binding characteristics. Native plasmid DNA, ROS-modified plasmid DNA and ROS-chromatin were found to be an effective inhibitor of induced antibody-immunogen interaction. Induced antibodies against native HSA showed negligible binding to the above mentioned nucleic acid antigens. Band shift assay reiterated the recognition towards nucleic acid antigens. Thus, the induced antibodies against *OH modified HSA resembled the diverse antigen-binding characteristics of naturally occurring systemic lupus erythematosus (SLE) anti-DNA autoantibodies.

Animals↗
PubMed2006

Plasmid DNA acquires immunogenicity on exposure to singlet oxygen.

In the present study, the effect of singlet oxygen (1O2) (generated by ultraviolet (UV) irradiation of methylene blue) on plasmid DNA has been analyzed by UV spectroscopy, fluorescence spectroscopy, and S1 nuclease digestibility. Both native and 1O2-modified plasmid DNA were treated with a number of restriction enzymes to map out the sites damaged by 1O2. It was also observed that, on exposure to 1O2, native plasmid DNA that is non-immunogenic acquired the ability to elicit an immune response in experimental animals. However, the induced antibodies exhibited appreciable cross reactivity with various polynucleotides and nucleic acids. The data indicate that the antibodies, though cross-reactive, preferentially bind 1O2-modified epitopes on plasmid DNA. Gel retardation assay further substantiated the enhanced recognition of 1O2-modified plasmid DNA over the native form. The antibodies developed were then subjected to competition ELISA with sera from various diseases such as systemic lupus erythematosus, rheumatoid arthritis, and cancer. These results suggest that upon exposure of DNA to 1O2, neo-epitopes are generated, which may be one of the factors for the induction of circulating autoantibodies in the three diseases.

Animals↗
PubMed2005

Expression of plant cyclic nucleotide-gated cation channels in yeast.

The functional properties of inwardly conducting plant cyclic nucleotide-gated cation channels (CNGCs) have not been thoroughly characterized due in part to the recalcitrance of their functional expression in heterologous systems. Here, K+ uptake-deficient mutants of yeast (trk1,2) and Escherichia coli (LB650), as well as the Ca2+-uptake yeast mutant mid1,cch1, were used for functional characterization of Arabidopsis thaliana CNGCs, with the aim of identifying some of the cultural and physiological conditions that impact on plant CNGC function in heterologous systems. Use of the Ca2+-uptake yeast mutant provided the first evidence consistent with Ca2+ conduction by the A. thaliana CNGC AtCNGC1. Expression of AtCNGC1 in LB650 demonstrated that mutants of Escherichia coli (which has no endogenous calmodulin) can also be used to study functional properties of CNGCs. Expression of AtCNGC2 and AtCNGC4 enhanced growth of trk1,2 in the presence of hygromycin; AtCNGC1 has less of an effect. Deletion of the AtCNGC1 calmodulin-binding domain enhanced growth of trk1,2 at low external K+ but not of LB650, suggesting that yeast calmodulin may bind to, and down-regulate this plant channel. In vitro binding studies confirmed this physical interaction. Northern analysis, green fluorescent protein:AtCNGC1 fusion protein expression, as well as an antibody raised against a portion of AtCNGC1, were used to monitor expression of AtCNGC1 and deletion constructs of the channel in the heterologous systems. In the presence of the activating ligand cAMP, expression of the AtCNGC1 channel with the calmodulin-binding domain deleted increased intracellular [K+] of trk1,2. Trk1,2 is hypersensitive to the toxic cations spermine, tetramethylamine, and NH4+. These compounds, as well as amiloride, inhibited trk1,2 growth and thereby improved the efficacy of this yeast mutant as a heterologous expression system for CNGCs. In addition to characterizing mutants of yeast and E. coli as assay systems for plant CNGCs, work presented in this report demonstrates, for the first time, that a plant CNGC can retain ion channel function despite (partial) deletion of its calmodulin-binding domain and that yeast calmodulin can bind to and possibly down-regulate a plant CNGC.

Arabidopsis↗
PubMed2005

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.

Animals↗
PubMed2005

Binding of circulating SLE autoantibodies to oxygen free radical damaged chromatin.

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease characterized by various immunologic disorders, including production of autoantibodies, formation of immune complexes, decreased serum complement levels, and lymphocytopenia. One of the hallmarks of this disease is the loss of tolerance to nuclear antigens. The dominant presence of antibodies against the exposed conformational epitopes on chromatin strongly suggests that the pathogenic immune response in lupus is driven by chromatin. In the present study, the binding of SLE autoantibodies with native chromatin and oxygen free radical damaged chromatin was studied. As assessed by direct binding and inhibition ELISA, circulating SLE autoantibodies exhibited a high degree of specificity towards the reactive oxygen species (ROS)-modified chromatin in comparison to native chromatin and this binding specificity was reiterated visually by gel retardation assay. The data suggested possible role of modified chromatin in the induction of SLE autoantibodies and higher recognition of oxidatively damaged chromatin by antibodies in sera of SLE patients. It is indicated that free radical modified chromatin or nucleosomes might be the antigen for the production of circulating autoantibodies in SLE.

Animals↗
PubMed2004

Yeast hygromycin sensitivity as a functional assay of cyclic nucleotide gated cation channels.

Cyclic nucleotide gated cation channels (CNGCs) are a large (20 genes in Arabidopsis thaliana) family of plant ligand gated (i.e. cyclic nucleotides activate currents) ion channels, however, little is known about their functional properties. One reason for this is the recalcitrance of plant CNGC expression in heterologous systems amenable to patch clamp studies. Here, we show results demonstrating the efficacy of using growth of a K+ uptake-deficient yeast (trk1,2) as a functional assay of CNGCs as inwardly-conducting cell membrane cation (K+) transporters. Prior work demonstrated that trk1,2 is hypersensitive to the antibiotic hygromycin (hyg) and that expression of an inwardly conducting K+ transporter suppresses hyg hypersensitivity. We find that increasing [hyg] in solid YPD medium inhibits trk1,2 growth around a filter disk saturated with 3 M K+. Northern analysis indicated that message is transcribed in trk1,2 transformed with the CNGC coding sequences. Confocal imaging of yeast expressing CNGC-fluorescent fusion proteins indicated channel targeting to the cell membrane. Trk1,2 expressing several plant CNGCs grown in the presence of hyg demonstrated (a) greater growth than trk1,2 transformed with empty plasmid, and (b) enhanced growth when cAMP was added to the medium. Alternatively, cAMP inhibited growth of yeast transformed with either the empty plasmid, or the plant K+ channel KAT1; this channel is not a CNGC. Growth of trk1,2 was dependent on filter disk [K+]; suggesting that complementation of hyg hypersensitivity due to presence of a functional plant CNGC was dependent on K+ movement into the cytosol. We conclude that plant CNGC functional characterization can be facilitated by this assay system.

Arabidopsis↗
PubMed2003

Inhibition of sodium/proton exchange by a Rab-GTPase-activating protein regulates endosomal traffic in yeast.

Endosomal Na+/H+ exchangers are important for salt and osmotolerance, vacuolar pH regulation, and endosomal trafficking. We show that the C terminus of yeast Nhx1 interacts with Gyp6, a GTPase-activating protein for the Ypt/Rab family of GTPases, and that Gyp6 colocalizes with Nhx1 in the endosomal/prevacuolar compartment (PVC). The gyp6 null mutant exhibits novel phenotypes consistent with loss of negative regulation of Nhx1, including increased tolerance to hygromycin, increased vacuolar pH, and decreased plasma membrane potential. In contrast, overexpression of Gyp6 increases sensitivity to hygromycin, decreases vacuolar pH, and results in a slight missorting of vacuolar carboxypeptidase Y to the cell surface. We conclude that Gyp6 is a negative regulator of Nhx1-dependent trafficking out of the PVC. Taken together with its GTPase-activating protein-dependent role as a negative regulator of Ypt6-mediated retrograde traffic to the Golgi, we propose that Gyp6 coordinates upstream and downstream events in the PVC to Golgi pathway. Our findings provide a possible molecular link between intraendosomal pH and regulation of vesicular trafficking.

Base Sequence↗
PubMed2003

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.

Aged↗
PubMed2003

Hydroxyl radical modification of polyguanylic acid: role of modified guanine in circulating SLE anti-DNA autoantibodies.

The hydroxyl radical generated by UV irradiation of hydrogen peroxide cause an extensive damage to guanine residues of ribohomopolymer, polyguanylic acid, poly (G) as investigated by spectrophotometric measurements, agarose gel electrophoresis, Sephadex G-200 gel filtration and DEAE Sephadex A-25 column chromatography. Native and ROS-poly (G) were highly immunogenic inducing high titre antibodies in rabbits. The antibodies showed wide range of cross reactivity with various synthetic polynucleotides exhibiting B-, A-, and allied conformations. The diverse antigen binding characteristics of the induced antibodies resembles to those of naturally occurring lupus anti-DNA autoantibodies. Sera from various SLE patients showed preferential binding to ROS-poly (G) than native poly (G), indicating that oxidatively modified guanine residues are better recognised. The significance of these findings in the induction of SLE anti-DNA autoantibodies by oxygen free radicals modified guanine residues in DNA has been discussed.

Animals↗
PubMed1997

Comparative physiology of salt tolerance in Candida tropicalis and Saccharomyces cerevisiae.

The salt tolerance of the respiratory yeast Candida tropicalis and the fermentative yeast Saccharomyces cerevisiae have been compared in glucose media. C. tropicalis showed a better adaptation to Na+ and Li+ and maintained higher intracellular K+:Na+ and K+:Li+ ratios than S. cerevisiae. However, C. tropicalis showed a poorer adaptation to osmotic stress (produced by KCl and sorbitol) and exhibited reduced glycerol production as compared to S. cerevisiae. In media with the non-repressing sugar galactose as carbon source, S. cerevisiae exhibited reduced glycerol production and increased sensitivity to osmotic stress. Under these conditions, S. cerevisiae, but not C. tropicalis, utilized trehalose as a more important osmolyte than glycerol. These results suggest that the relative tolerance of yeast to the osmotic and cation toxicities of NaCl, and the underlying relative capabilities for osmolyte synthesis and cation transport, are modulated by the general catabolite control exerted by glucose.

Adaptation, Physiological↗