Biomedical subjects

P Boon Chock

Publications and source records attributed to P Boon Chock.

24 records · Page 2Linked to original sources

PubMed2002

Manganese(II) induces apoptotic cell death in NIH3T3 cells via a caspase-12-dependent pathway.

Under physiological conditions, manganese(II) exhibits catalase-like activity. However, at elevated concentrations, it induces apoptosis via a non-mitochondria-mediated mechanism (Oubrahim, H., Stadtman, E. R., and Chock, P. B. (2001) Proc. Natl. Acad. Sci. U. S. A. 98, 9505-9510). In this study, we show that the Mn(II)-induced apoptosis, as monitored by caspase-3-like activity, in NIH3T3 cells was inhibited by calpain inhibitors I and II or the p38 MAP kinase inhibitor, SB202190. The control experiments showed that each of these inhibitors in the concentration ranges used exerted no effect on activated caspase-3-like activity. Furthermore, caspase-12 was cleaved in Mn(II)-treated cells, suggesting that the Mn(II)-induced apoptosis is mediated by caspase-12. This notion is confirmed by the observations that pretreatment of NIH3T3 cells with either caspase-12 antisense RNA or dsRNA corresponding to the full-length caspase-12 led to a dramatic decrease in caspase-3-like activity induced by Mn(II). The precise mechanism by which Mn(II) induced the apoptosis is not clear. Nevertheless, Mn(II), in part, exerts its effect via its ability to replace Ca(II) in the activation of m-calpain, which in turn activates caspase-12 and degrades Bcl-xL. In addition, the dsRNA(i) method serves as an effective technique for knocking out caspase-12 in NIH3T3 cells without causing apoptosis.

3T3 Cells↗

PubMed2002

Free radicals and disease.

Free radicals and reactive oxygen species (ROS) have been associated with the etiology and/or progression of a number of diseases and in aging. Many of the proteins oxidatively modified by free radicals contain side-chain carbonyl derivatives, which can be used as markers for protein oxidation. The protein carbonyl content has been quantitated as a function of age for human cultured dermal fibroblasts, lens, and brain tissue. These data were analyzed using a simple autocatalytic model with the assumption that free radicals randomly oxidize proteins or peptides to form carbonyl derivatives and lead to their inactivation. The carbonylated proteins and peptides are highly susceptible to proteolytic degradation. Implication of free radicals in aging and in age-dependent susceptibility to neurodegenerative diseases will be discussed in light of this simplified kinetic model.

Aging↗

PubMed2002

Tyrosine phosphatase CD45 regulates hydrogen peroxide-induced calcium mobilization in B cells.

By taking advantage of established CD45-deficient DT40 cells, the roles of CD45 in oxidative stress signaling were investigated. Using p-nitrophenyl phosphate as substrate, it was found that CD45 constituted nearly 40% of the total protein-tyrosine phosphatase activity. Almost 90% of the phosphatase activity was rapidly inactivated upon hydrogen peroxide treatment. Hydrogen peroxide-induced tyrosine phosphorylation of cellular proteins and c-Jun N-terminal kinase activation were markedly enhanced in CD45-deficient cells relative to that in its parental cells. In comparison, hydrogen peroxide-induced inositol 1,4,5-trisphosphate production and Ca(2+) mobilization were impaired in CD45-deficient DT40 cells. However, hydrogen peroxide-induced tyrosine phosphorylation of phospholipase Cgamma2 (PLCgamma2), phosphatidylinositol 3-kinase activity precipitated by anti-phosphotyrosine antibody, and activation of Bruton's tyrosine kinase appeared intact in CD45-deficient DT40 cells. This suggests that CD45 mediates the ability of hydrogen peroxide-activated PLCgamma2 to hydrolyze its substrate via a mechanism independent of both tyrosine phosphorylation of PLCgamma2 and phosphatidylinositol 3-kinase, as well as activation of Bruton's tyrosine kinase. Taken together, our observations demonstrated that, in addition to its negative regulatory or phosphatase activity, CD45 has a positive role in oxidative stress signaling.

Agammaglobulinaemia Tyrosine Kinase↗

PubMed2002

Preconditioning-mediated neuroprotection: role of nitric oxide, cGMP, and new protein expression.

Preconditioning adaptation induced by transient ischemia can increase brain tolerance to oxidative stress, but the underlying neuroprotective mechanisms are not fully understood. Recently, we developed a human brain-derived cell model to investigate preconditioning mechanism in SH-SY5Y neuroblastoma cells.(1) Our results demonstrate that a non-lethal serum deprivation-stress for 2 h (preconditioning stress) enhanced the tolerance to a subsequent lethal oxidative stress (24 h serum deprivation) and also to 1-methyl-4-phenyl-pyridinium (MPP(+)).(2) Two-hour non-lethal preconditioning stress increased the expression of neuronal nitric oxide (NOS1/nNOS) mRNA, Fos, Ref-1, NOS protein, and then nitric oxide (*NO) production. As well as MnSOD expression, the *NO-cGMP-PKG pathway mediated the preconditioning-induced upregulation of antiapoptotic protein Bcl-2 and the downregulation of adaptor protein p66(shc). We also propose that cGMP-mediated preconditioning-induced adaptation against oxidative stress may be due to the synthesis of a new protein, such as thioredoxin (Trx) since the protective effect can be blocked by Trx reductase inhibitor.(3) The antioxidative potency of Trx was approximately 100 and 1,000 times greater than GSNO and GSH, respectively. These results suggest that *NO-cGMP-PKG signaling pathway plays an important role in the preconditioning-induced neuroprotection, and perhaps cardioprotection, against oxidative stress.

Central Nervous System↗

PubMed2001

The roles of thioredoxin in protection against oxidative stress-induced apoptosis in SH-SY5Y cells.

Using models of serum deprivation and 1-methyl-4-phenylpyridinium (MPP(+)), we investigated the mechanism by which thioredoxin (Trx) exerts its antiapoptotic protection in human neuroblastoma cells (SH-SY5Y) and preconditioning-induced neuroprotection. We showed that SH-SY5Y cells are highly sensitive to oxidative stress and responsive to both extracellularly administered and preconditioning-induced Trx. Serum deprivation and MPP(+) produced an elevation in the hydroxyl radicals, malondialdehyde and 4-hydroxy-2,3-nonenal (HNE), causing the cells to undergo mitochondria-mediated apoptosis. Trx in the submicromolar range blocked the observed apoptosis via a multiphasic protection mechanism that includes the suppression of cytochrome c release (most likely via the induction of Bcl-2), the inhibition of procaspase-9 and procaspase-3 activation, and the elevated level of Mn-SOD. The reduced form of Trx suppresses the serum-free-induced hydroxyl radicals, lipid peroxidation, and apoptosis, indicating that H(2)O(2) is removed by Trx peroxidase. The participation of Trx in preconditioning-induced neuroprotection is supported by the observation that inhibition of Trx synthesis with antisense oligonucleotides or of Trx reductase drastically reduced the hormesis effect. This effect of Trx-mediated hormesis against oxidative stress-induced apoptosis is striking. It induced a 30-fold shift in LD(50) in the MPP(+)-induced neurotoxicity.

Animals↗

PubMedDate not supplied

Glutaredoxin: role in reversible protein s-glutathionylation and regulation of redox signal transduction and protein translocation.

Reversible posttranslational modifications on specific amino acid residues can efficiently regulate protein functions. O-Phosphorylation is the prototype and analogue to the rapidly emerging mechanism of regulation known as S-glutathionylation. The latter is being recognized as a potentially widespread form of modulation of the activities of redox-sensitive thiol proteins, especially those involved in signal transduction pathways and translocation. The abundance of reduced glutathione in cells and the ready conversion of sulfenic acids and S-nitroso derivatives to S-glutathione mixed disulfides support the notion that reversible S-glutathionylation is likely to be the preponderant mode of redox signal transduction. The glutaredoxin enzyme has served as a focal point and important tool for evolution of this regulatory mechanism because of its characterization as a specific and efficient catalyst of protein-SSG de-glutathionylation (akin to phosphatases). Identification of specific mechanisms and enzyme(s) that catalyze formation of protein-SSG intermediates, however, is largely unknown and represents a prime objective for furthering understanding of this evolving mechanism of cellular regulation. Several proteomic approaches, including the use of cysteine-reactive fluorescent and radiolabel probes, have been developed to detect arrays of proteins whose cysteine residues are modified in response to oxidants, thus identifying them as potential interconvertible proteins to be regulated by redox signaling (glutathionylation). Specific criteria were used to evaluate current data on cellular regulation via S-glutathionylation. Among many proteins under consideration, actin, protein tyrosine phosphatase-1B, and Ras stand out as the best current examples for establishing this regulatory mechanism.

Animals↗