Reactive oxygen species (ROS) mediate apoptosis in a number of cell types. We studied the role that ROS play in activated T cell apoptosis by activating T cells in vivo and then culturing them for a short time. Activated T cells died independently of Fas and TNF alpha. Their death was characterized by rapid loss of mitochondrial transmembrane potential (delta psi(m)), caspase-dependent DNA fragmentation, and superoxide generation. A superoxide dismutase mimetic, Mn (III) tetrakis (5, 10, 15, 20-benzoic acid) porphyrin (MnTBAP), protected T cells from superoxide generation, caspase-dependent DNA loss, loss of delta psi(m), and cell death. These results indicate that ROS can regulate signals involved in caspase activation and apoptosis and may contribute to peripheral T cell deletion.

Highly active antiretroviral therapy (HAART) regimes based on nucleoside reverse transcriptase inhibitors (NRTIs) have revolutionized the treatment of AIDS in recent years. Although HAART can successfully suppress viral replication in the long term, it is not without significant toxicity, which can seriously compromise treatment effectiveness. A major toxicity that has been recognized for more than a decade is NRTI-related mitochondrial toxicity, which manifests as serious side effects such as hepatic failure and lactic acidosis. However, a lack of understanding of the mechanisms underlying mitochondrial toxicity has hampered efforts to develop novel drugs with better side-effect profiles. This review characterizes the pharmacological mechanisms and pathways that are involved in mitochondrial dysfunction caused by NRTIs, and suggests opportunities for future pharmacological research.

Reactive oxygen species (ROS) have been implicated in a wide range of degenerative processes including amyotrophic lateral sclerosis, ischemic heart disease, Alzheimer disease, Parkinson disease and aging. ROS are generated by mitochondria as the toxic by-products of oxidative phosphorylation, their energy generating pathway. Genetic inactivation of the mitochondrial form of superoxide dismutase in mice results in dilated cardiomyopathy, hepatic lipid accumulation and early neonatal death. We report that treatment with the superoxide dismutase (SOD) mimetic Manganese 5, 10, 15, 20-tetrakis (4-benzoic acid) porphyrin (MnTBAP) rescues these Sod2tm1Cje(-/-) mutant mice from this systemic pathology and dramatically prolongs their survival. The animals instead develop a pronounced movement disorder progressing to total debilitation by three weeks of age. Neuropathologic evaluation reveals a striking spongiform degeneration of the cortex and specific brain stem nuclei associated with gliosis and intramyelinic vacuolization similar to that observed in cytotoxic edema and disorders associated with mitochondrial abnormalities such as Leighs disease and Canavans disease. We believe that due to the failure of MnTBAP to cross the blood brain barrier progressive neuropathology is caused by excessive mitochondrial production of ROS. Consequently, MnTBAP-treated Sod2tm1Cje(-/-) mice may provide an excellent model for examining the relationship between free radicals and neurodegenerative diseases and for screening new drugs to treat these disorders.

We tested the pathogenic role of O2-) radicals in excitotoxic injury. Inactivation of the TCA cycle enzyme, aconitase, was used as a marker of intracellular O2- levels, and a porphyrin SOD mimetic was used to scavenge O2-. The selective, reversible, and SOD-sensitive inactivation of aconitase by known O2- generators was used to validate aconitase activity as a marker of O2- generation. Treatment of rat cortical cultures with NMDA, KA, or the intracellular O2- generator PQ2+ produced a selective and reversible inactivation of aconitase, which closely correlated with subsequent cell death produced by these agents. The SOD mimetic, but not its less active congener, attenuated both aconitase inactivation and cell death produced by NMDA, KA, and PQ2+. These results provide direct evidence implicating O2(-) generation in the pathway to excitotoxic injury.

There is substantial evidence that protein S-nitrosylation provides a significant route through which nitric oxide (NO)-derived bioactivity is conveyed. However, most examples of S-nitrosylation have been characterized on the basis of analysis in vitro, and relatively little progress has been made in assessing the participant forms of nitric-oxide synthase (NOS) or the dynamics of protein S-nitrosylation in situ. Here we utilize antibodies specific for the nitrosothiol (SNO) moiety to provide an immunohistochemical demonstration that protein Snitrosylation is coupled to the activity of each of the major forms of NOS. In cultured endothelial cells, SNOprotein immunoreactivity increases in response to Ca 2؉ -stimulated endothelial NOS (eNOS) activity, and in aortic rings, endothelium-derived and eNOS-mediated relaxation (EDRF) is coupled to increased protein Snitrosylation in both endothelial and associated smooth muscle cells. In cultured macrophages, SNO-protein levels increase upon cytokine induction of induced NOS (iNOS), and in PC12 cells, increased protein S-nitrosylation is linked to nerve growth factor induction of neuronal NOS (nNOS). In addition, we describe developmental and pathophysiological increases in SNOprotein immunoreactivity within human lung. These results, which demonstrate Ca 2؉ , neurohumoral, growth factor, cytokine, and developmental regulation of protein S-nitrosylation that is coupled to NOS expression and activity, provide unique evidence for the proposition that this ubiquitous NO-derived post-translational protein modification serves as a major effector of NOrelated bioactivity.Nitric oxide (NO), 1 generated by cell type-specific NO synthases (NOSs), has classically been characterized as a freely diffusible intercellular messenger that functions in target cells to subserve NOS-dependent signaling, which includes generation of endothelium-derived relaxing factor (EDRF) via eNOS, synaptic transmission and plasticity via nNOS, and antimicrobial activity via iNOS (see Ref. 1 for review). More recently, it has been proposed that S-nitrosylation of cysteine thiols may constitute a major route of NO trafficking through which NOrelated bioactivity is effected, serving as a ubiquitous posttranslational modification that regulates dynamically a broad functional spectrum of proteins (2-4). However, the analysis of protein S-nitrosylation in situ, originating with endogenous NOS activity, has been impeded by substantial technical barriers, and there is little direct evidence for cellular protein S-nitrosylation that can be ascribed specifically to the activity of any NOS isoform (4 -7). Here we show that S-nitrosylated proteins can be identified, on membrane blots and with immunohistochemistry, by antibodies that recognize the SNO moiety. We exploit this capacity to demonstrate ongoing and physiologically regulated protein S-nitrosylation that is coupled to the activity of each of the major forms of NOS in NO-generating cells and (in the case of endothelial NOS) their functional cellular partner...

Why are groupoids such special categories? The obvious answer is because all arrows have inverses. Yet this is precisely what is needed mathematically to model symmetry in nature. The relation between the groupoid and the physical object is expressed by an action. The presence of inverses means that actions of a groupoid G behave much better than actions of an arbitrary category. The totality of actions of G on vector spaces forms a category Mod G of modules. The feature of Mod G which epitomises the fact that G is a groupoid is that the internal hom in Mod G is calculated in a particularly simple way. More precisely, the functor out of Mod G which forgets the actions preserves, not only the monoidal structure but also, the closed structure. With this as a guiding principle, we develop a general concept of``autonomous pseudomonoid'' which includes ordinary Hopf algebras (indeed, Hopf algebroids) and autonomous (=compact=rigid) monoidal categories. This is intended to elucidate the interaction between Hopf algebras and autonomous monoidal categories in Tannaka duality as appearing in [JS2; D2], for example.Given a topological monoid M, it is explained in [JS2, Section 8] why the monoidal category of finite-dimensional representations of M is equivalent to the monoidal category of finite-dimensional comodules over the bialgebra R(M ) of representative functions on M. This provides evidence that, when regarding a Hopf algebra as a quantum group, it is the finitedimensional comodules (rather than modules) which should be regarded as the representations of the group. In dealing with comodules, we are using the coalgebra structure of the Hopf algebra H. A Hopf algebroid is an additive category (that is,``algebra with several objects''; that is, algebroid) with a comonoidal structure: modules over a Hopf algebroid make sense but comodules are not appropriate. What we need is a notion where the article no. AI971649 99

No abstract

No abstract