Protein tyrosine phosphatase CD45 as a molecular biosensor of hydrogen peroxide generation in cell culture media

Redox Regulation of LAT Enhances T Cell-Mediated Inflammation

The positional cloning of single nucleotide polymorphisms (SNPs) of the neutrophil cytosolic factor 1 (Ncf1) gene, advocating that a low oxidative burst drives autoimmune disease, demands an understanding of the underlying molecular causes. A cellular target could be T cells, which have been shown to be regulated by reactive oxygen species (ROS). However, the pathways by which ROS mediate T cell signaling remain unclear. The adaptor molecule linker for activation of T cells (LAT) is essential for coupling T cell receptor-mediated antigen recognition to downstream responses, and it contains several cysteine residues that have previously been suggested to be involved in redox regulation. To address the possibility that ROS regulate T cell-dependent inflammation through LAT, we established a mouse strain with cysteine-to-serine mutations at positions 120 and 172 (LATSS). We found that redox regulation of LAT through C120 and C172 mediate its localization and phosphorylation. LATSS mice had reduced numbers of double-positive thymocytes and naïve peripheral T cells. Importantly, redox insensitivity of LAT enhanced T cell-dependent autoimmune inflammation in collagen-induced arthritis (CIA), a mouse model of rheumatoid arthritis (RA). This effect was reversed on an NCF1-mutated (NCF1m1j), ROS-deficient, background. Overall, our data show that LAT is redox-regulated, acts to repress T cell activation, and is targeted by ROS induced by NCF1 in antigen-presenting cells (APCs).

Cis-[Cr(C2O4)(pm)(OH2)2]+ coordination ion as a specific sensing ion for H2O2 detection in HT22 cells

The purpose of this study was to examine the application of the coordinated cis-[Cr(C₂O₄)(pm)(OH)₂]⁺ cation where pm denotes pyridoxamine, as a specific sensing ion for the detection of hydrogen peroxide (H₂O₂). The proposed method for H₂O₂ detection includes two key steps. The first step is based on the nonenzymatic decarboxylation of pyruvate upon reaction with H₂O₂, while the second step is based on the interaction of cis-[Cr(C₂O₄)(pm)(OH₂)₂]⁺ with the CO₂ released in the previous step. Using this method H₂O₂ generated during glutamate-induced oxidative stress was detected in HT22 hippocampal cells. The coordination ion cis-[Cr(C₂O₄)(pm)(OH₂)₂]⁺ and the spectrophotometric stopped-flow technique were applied to determine the CO₂ concentration in cell lysates, supernatants and cell-free culture medium. Prior to CO₂ assessment pyruvate was added to all samples studied. Pyruvate reacts with H₂O₂ with 1:1 stoichiometry, and consequently the amount of CO₂ released in this reaction is equivalent to the amount of H₂O₂.

The effects of nitroxyl (HNO) on H₂O₂ metabolism and possible mechanisms of HNO signaling

Nitroxyl (HNO) possesses unique and potentially important biological/physiological activity that is currently mechanistically ill-defined. Previous work has shown that the likely biological targets for HNO are thiol proteins, oxidized metalloproteins (i.e. ferric heme proteins) and, most likely, selenoproteins. Interestingly, these are the same classes of proteins that interact with H2O2. In fact, these classes of proteins not only react with H2O2, and thus potentially responsible for the signaling actions of H2O2, but are also responsible for the degradation of H2O2. Therefore, it is not unreasonable to speculate that HNO can affect H2O2 degradation by interacting with H2O2-degrading proteins possibly leading to an increase in H2O2-mediated signaling. Moreover, considering the commonality between HNO and H2O2 biological targets, it also seems likely that HNO-mediated signaling can also be due to reactivity at otherwise H2O2-reactive sites. Herein, it is found that HNO does indeed inhibit H2O2 degradation via inhibition of H2O2-metaboilizing proteins. Also, it is found that in a system known to be regulated by H2O2 (T cell activation), HNO behaves similarly to H2O2, indicating that HNO- and H2O2-signaling may be similar and/or intimately related.

Activation of hydrogen peroxide to peroxytetradecanoic acid is responsible for potent inhibition of protein tyrosine phosphatase CD45

Hydrogen peroxide induces oxidation and consequently inactivation of many protein tyrosine phosphatases. It was found that hydrogen peroxide, in the presence of carboxylic acids, was efficiently activated to form even more potent oxidant - peroxy acid. We have found that peroxytetradecanoic acid decreases the enzymatic activity of CD45 phosphatase significantly more than hydrogen peroxide. Our molecular docking computational analysis suggests that peroxytetradecanoic acid has a higher binding affinity to the catalytic center of CD45 than hydrogen peroxide.