5 results on '"Ramkumar, V."'
Search Results
2. Expression of the kidney injury molecule 1 in the rat cochlea and induction by cisplatin
- Author
-
Mukherjea, D., primary, Whitworth, C.A., additional, Nandish, S., additional, Dunaway, G.A., additional, Rybak, L.P., additional, and Ramkumar, V., additional
- Published
- 2006
- Full Text
- View/download PDF
3. Reduced basal and lipopolysaccharide-stimulated adenosine A1 receptor expression in the brain of nuclear factor-κB p50−/− mice
- Author
-
Jhaveri, K.A., Reichensperger, J., Toth, L.A., Sekino, Y., and Ramkumar, V.
- Subjects
- *
ADENOSINES , *LIMBIC system , *DEHYDROGENASES , *CEREBRAL cortex - Abstract
Abstract: Adenosine promotes cytoprotection under conditions of infection, ischemic preconditioning and oxidative stress. Previous studies from our laboratory indicate that the expression of the adenosine A1 receptor (A1AR) is induced by oxidative stress via activation of nuclear factor (NF)-κB. The prototypic transcription factor is composed of homo- or heterodimers of p50 and p65 subunits. To determine the role of NF-κB in the regulation of the A1AR in vivo, we compared the A1AR RNA and protein levels in the brains of mice lacking the p50 subunit of NF-κB (p50−/− mice) and age-matched B6129PF2/J (F2) controls. Radioligand binding assays in the cortex revealed a significantly lower number of A1AR (maximal binding capacity, B max) in the cortex of p50−/− mice (151±62 fmol/mg protein) versus 479±181 fmol/mg protein in the F2 (N=5 per strain, P<0.05), but no change in the equilibrium dissociation constant. Similar reductions in A1AR were measured in the hippocampus, brain stem and hypothalamus and in peripheral tissues, such as the adrenal gland, kidney and spleen. Estimation of the A1AR following purification by antibody affinity columns also indicated reduced A1AR in the p50−/− mice cortex, as compared with the F2 mice. A1AR immunocytochemistry indicates distinct neuronal labeling in the F2 cortex, which was substantially reduced in similar sections obtained from p50−/− mice. The p50−/− mice expressed lower levels of A1AR mRNA than F2 mice, as determined by real time PCR. Quantitation of the A1AR transducing G proteins by Western blotting show significantly less Gαi3, no change in Gαi1, but higher levels of Gαo and Gβ in the cortices of p50−/−, as compared with F2 mice. Administration of bacterial lipopolysaccharide (LPS), an activator of NF-κB, increased A1AR expression in the cortices of F2 mice but not p50−/− mice. Cortical neurons cultures prepared from p50−/− mice showed a greater degree of apoptosis, compared with neurons from F2 mice. Activation of the A1AR reduced apoptosis with greater efficacy in cultures from F2 than p50−/− mice. Taken together, these data support a role for NF-κB in determining both the basal and LPS-stimulated A1AR expression in vivo which could contribute to neuronal survival. [Copyright &y& Elsevier]
- Published
- 2007
- Full Text
- View/download PDF
4. Pertussis toxin B-oligomer suppresses human immunodeficiency virus-1 Tat-induced neuronal apoptosis through feedback inhibition of phospholipase C-beta by protein kinase C.
- Author
-
Jajoo S, Mukherjea D, Brewer GJ, and Ramkumar V
- Subjects
- Adenosine Diphosphate Ribose physiology, Animals, Calcium metabolism, Cerebral Cortex cytology, Cerebral Cortex drug effects, Electrophoresis, Polyacrylamide Gel, Feedback, Physiological, GTP-Binding Protein alpha Subunits, Gi-Go physiology, Immunohistochemistry, Neurons pathology, PC12 Cells, Rats, Apoptosis drug effects, Enzyme Inhibitors pharmacology, Neurons drug effects, Pertussis Toxin pharmacology, Phospholipase C beta antagonists & inhibitors, Protein Kinase C physiology, tat Gene Products, Human Immunodeficiency Virus antagonists & inhibitors, tat Gene Products, Human Immunodeficiency Virus toxicity
- Abstract
Human immunodeficiency virus (HIV)-1 Tat is a multifunctional protein involved in viral replication, inflammation and apoptosis. Tat activates phospholipase C-beta (PLC-beta), presumably via a pertussis toxin (PTX) sensitive G(i) protein, which is critical for neuronal apoptosis. In this study, we show that Tat-mediated intracellular Ca(2+) release in rat pheochromocytoma (PC-12) cells and rat primary cortical neuronal cultures was abrogated by pretreatment with either pertussis toxin and/or its B-oligomer subunit (PTX-B), devoid of ADP ribosyltransferase activity. PTX-B pretreatment also inhibited intracellular Ca(2+) release by bradykinin and 2,4,6-trimethyl-N-(m-3-trifluoromethylphenyl) benzenesulfonamide (m-3M3FBS), a director activator of phospholipase C. Activation of protein kinase C (PKC) by phorbol 12,13-dibutyrate (PdBu) mimicked the PTX-B-mediated inhibition of m-3M3FBS-stimulated intracellular Ca(2+) increase, while inhibition of PKC by bisindolylmaleimide I hydrochloride (BIM) reversed the inhibitory action of PTX-B. Functionally, PTX-B reduced Tat-induced Bax and caspase-3 proteins and reduced cell apoptosis. We conclude that PTX inhibition of Tat-mediated intracellular Ca(2+) release is independent of ADP ribosylation of the G(i) protein via the A protomer, but mediated by the B-oligomer. Furthermore, PTX-B suppresses HIV-1 Tat-mediated apoptosis by reducing its activation of PLC-beta through a PKC activation pathway.
- Published
- 2008
- Full Text
- View/download PDF
5. Reduced basal and lipopolysaccharide-stimulated adenosine A1 receptor expression in the brain of nuclear factor-kappaB p50-/- mice.
- Author
-
Jhaveri KA, Reichensperger J, Toth LA, Sekino Y, and Ramkumar V
- Subjects
- Analysis of Variance, Animals, Brain ultrastructure, Cell Membrane drug effects, Cell Membrane metabolism, GTP-Binding Proteins metabolism, Immunoprecipitation methods, In Situ Nick-End Labeling methods, Male, Mice, Mice, Knockout, Protein Binding drug effects, RNA, Messenger metabolism, Radioligand Assay methods, Receptor, Adenosine A1 genetics, Reverse Transcriptase Polymerase Chain Reaction methods, Xanthines pharmacokinetics, Brain metabolism, Gene Expression Regulation drug effects, Lipopolysaccharides pharmacology, NF-kappa B p50 Subunit deficiency, Receptor, Adenosine A1 metabolism
- Abstract
Adenosine promotes cytoprotection under conditions of infection, ischemic preconditioning and oxidative stress. Previous studies from our laboratory indicate that the expression of the adenosine A1 receptor (A1AR) is induced by oxidative stress via activation of nuclear factor (NF)-kappaB. The prototypic transcription factor is composed of homo- or heterodimers of p50 and p65 subunits. To determine the role of NF-kappaB in the regulation of the A1AR in vivo, we compared the A1AR RNA and protein levels in the brains of mice lacking the p50 subunit of NF-kappaB (p50-/- mice) and age-matched B6129PF2/J (F2) controls. Radioligand binding assays in the cortex revealed a significantly lower number of A(1)AR (maximal binding capacity, Bmax) in the cortex of p50-/- mice (151+/-62 fmol/mg protein) versus 479+/-181 fmol/mg protein in the F2 (N=5 per strain, P<0.05), but no change in the equilibrium dissociation constant. Similar reductions in A1AR were measured in the hippocampus, brain stem and hypothalamus and in peripheral tissues, such as the adrenal gland, kidney and spleen. Estimation of the A1AR following purification by antibody affinity columns also indicated reduced A1AR in the p50-/- mice cortex, as compared with the F2 mice. A1AR immunocytochemistry indicates distinct neuronal labeling in the F2 cortex, which was substantially reduced in similar sections obtained from p50-/- mice. The p50-/- mice expressed lower levels of A1AR mRNA than F2 mice, as determined by real time PCR. Quantitation of the A1AR transducing G proteins by Western blotting show significantly less Galphai3, no change in Galphai1, but higher levels of Galphao and Gbeta in the cortices of p50-/-, as compared with F2 mice. Administration of bacterial lipopolysaccharide (LPS), an activator of NF-kappaB, increased A1AR expression in the cortices of F2 mice but not p50-/- mice. Cortical neurons cultures prepared from p50-/- mice showed a greater degree of apoptosis, compared with neurons from F2 mice. Activation of the A1AR reduced apoptosis with greater efficacy in cultures from F2 than p50-/- mice. Taken together, these data support a role for NF-kappaB in determining both the basal and LPS-stimulated A1AR expression in vivo which could contribute to neuronal survival.
- Published
- 2007
- Full Text
- View/download PDF
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