Basal protein phosphorylation is decreased and phosphatase activity increased by an antioxidant and a free radical trap in primary rat glia

Concurrent suppression of NF-κB, p38 MAPK and reactive oxygen species formation underlies the effect of a novel compound isolated from Curcuma comosa Roxb. in LPS-activated microglia

OBJECTIVE

We investigated the molecular mechanisms underlying the effect of (3S)-1-(3,4-dihydroxyphenyl)-7-phenyl-(6E)-6-hepten-3-ol, also known as compound 092, isolated from Curcuma comosa Roxb on the production of pro-inflammatory mediators and oxidative stress in lipopolysaccharide (LPS)-activated highly aggressive proliferating immortalized (HAPI) microglial cell lines.

METHOD

Nitric oxide (NO) production was determined using the Griess reaction, and reverse transcription polymerase chain reaction was used to measure the expression of inducible nitric oxide synthase (iNOS) mRNA. Western blotting was used to determine the levels of pro-inflammatory mediators and their related upstream proteins.

KEY FINDING

Compound 092 suppressed NO production and iNOS expression in LPS-stimulated HAPI cells. These effects originated from the ability of compound 092 to attenuate the activation of nuclear factor (NF)-κB as determined by the reduction in p-NF-κB and p-IκB kinase (IKK) protein levels. Compound 092 also significantly lowered LPS-activated intracellular reactive oxygen species production and p38 mitogen-activated protein kinase (MAPK) activation.

CONCLUSION

Compound 092 suppresses microglial activation through attenuation of p38 MAPK and NF-κB activation. Compound 092 thus holds the potential to treat neurodegenerative disorders associated with neuroinflammation and oxidative stress.

Hierarchical regulation of wound healing by NOD-like receptors in cardiovascular disease

SIGNIFICANCE

Persistent nonmicrobial tissue injury leads to the nonlinear activation of integrated wound-healing pathways. In chronic cardiovascular diseases, local tissue undergoes dynamic remodeling involving both structural cells and professional innate immune cells in attempts to limit burden of injury. While the final effector mechanisms by which these different cellular populations participate in wound healing are functionally distinct, their upstream molecular signaling pathways can often be shared.

RECENT ADVANCES

The NOD-like receptors (NLRs) are intracellular pattern recognition receptors that have been well characterized as key regulators of pro-inflammatory cytokine production in innate immune cells. However, recent evidence has shown that some NLR proteins are additionally expressed by resident structural cells despite negligible cytokine production. These results indicate the potential for noncanonical routes of innate immune signaling by NLRs within solid organ systems.

CRITICAL ISSUES

Here, we review the emerging functions of NLR proteins in professional immune and tissue-resident cells, and discuss the implications in wound healing during chronic cardiovascular diseases. Emphasis is placed on NLRP3 and its regulation of cardiac structure and function in response to injury. Specific cellular and subcellular signaling paradigms are also discussed.

FUTURE DIRECTIONS

The characterization of how NLRs participate in homeostasis during cellular injury is essential to develop their potential utility for therapeutic intervention in cardiovascular disease.

A role for glutathione, independent of oxidative stress, in the developmental toxicity of methanol

Oxidative stress and reactive oxygen species (ROS) have been implicated in the teratogenicity of methanol (MeOH) in rodents, both in vivo and in embryo culture. We explored the ROS hypothesis further in vivo in pregnant C57BL/6J mice. Following maternal treatment with a teratogenic dose of MeOH, 4 g/kg via intraperitoneal (ip) injection on gestational day (GD) 12, there was no increase 6h later in embryonic ROS formation, measured by 2',7'-dichlorodihydrofluorescin diacetate (DCFH-DA) fluorescence, despite an increase observed with the positive control ethanol (EtOH), nor was there an increase in embryonic oxidatively damaged DNA, quantified as 8-oxo-2'-deoxyguanosine (8-oxodG) formation. MeOH teratogenicity (primarily ophthalmic anomalies, cleft palate) also was not altered by pre- and post-treatment with varying doses of the free radical spin trapping agent alpha-phenyl-N-tert-butylnitrone (PBN). In contrast, pretreatment with L-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, depleted maternal hepatic and embryonic GSH, and enhanced some new anomalies (micrognathia, agnathia, short snout, fused digits, cleft lip, low set ears), but not the most common teratogenic effects of MeOH (ophthalmic anomalies, cleft palate) in this strain. These results suggest that ROS did not contribute to the teratogenic effects of MeOH in this in vivo mouse model, in contrast to results in embryo culture from our laboratory, and that the protective effect of GSH in this model may arise from its role as a cofactor for formaldehyde dehydrogenase in the detoxification of formaldehyde.

Respiratory syncytial virus infection: mechanisms of redox control and novel therapeutic opportunities

Respiratory syncytial virus (RSV) is one of the most important causes of upper and lower respiratory tract infections in infants and young children, for which no effective treatment is currently available. Although the mechanisms of RSV-induced airway disease remain incompletely defined, the lung inflammatory response is thought to play a central pathogenetic role. In the past few years, we and others have provided increasing evidence of a role of reactive oxygen species (ROS) as important regulators of RSV-induced cellular signaling leading to the expression of key proinflammatory mediators, such as cytokines and chemokines. In addition, RSV-induced oxidative stress, which results from an imbalance between ROS production and airway antioxidant defenses, due to a widespread inhibition of antioxidant enzyme expression, is likely to play a fundamental role in the pathogenesis of RSV-associated lung inflammatory disease, as demonstrated by a significant increase in markers of oxidative injury, which correlate with the severity of clinical illness, in children with RSV infection. Modulation of ROS production and oxidative stress therefore represents a potential novel pharmacological approach to ameliorate RSV-induced lung inflammation and its long-term consequences.

Influence of green tea on enzymes of carbohydrate metabolism, antioxidant defense, and plasma membrane in rat tissues

OBJECTIVE

Green tea, consumed worldwide since ancient times, is considered beneficial to human health. We hypothesized that green tea would enhance antioxidant defenses and specific metabolic activities of rat intestine, liver, and kidney to improve their functions.

METHODS

The effect of green tea given to rats in the diet or drinking water for 25 d was determined on blood chemistry and on activities of enzymes of carbohydrate metabolism, brush border membrane, and antioxidant defense.

RESULTS

Serum glucose, cholesterol, phosphate, and body weight decreased, whereas the activities of lactate and malate dehydrogenases and glucose-6- and fructose 1,6-bis-phosphatases increased in the intestine and kidney but slightly changed in the liver. Activity of glucose-6-phosphate dehydrogenase profoundly increased in the renal cortex but decreased in other tissues. Lipid peroxidation increased in the intestine and renal medulla and decreased in the renal cortex and liver; catalase increased in all tissues but the medulla. Superoxide dismutase activity decreased in the intestine but increased in renal tissues. Activities of brush border membrane enzymes in general increased in the intestine and kidney.

CONCLUSION

Green tea consumption resulted in enhanced enzyme activities of carbohydrate metabolism and antioxidant defenses, which may lead to improved health.

Nitrone-related therapeutics: potential of NXY-059 for the treatment of acute ischaemic stroke

At present, none of the neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease and stroke are treatable with compounds that slow or halt neuronal cell death. However, the prototype nitrone radical trap alpha-phenyl-tert-butylnitrone (PBN) has been shown to be an effective neuroprotective agent in various models of neurodegeneration. Some of these data are briefly reviewed as an introduction to an examination of the effect of the novel nitrone radical trapping agent disodium 2,4-disulfophenyl-N-tert-butylnitrone (NXY-059) in various animal models of stroke. NXY-059 has been shown to be an effective neuroprotective agent in both transient (reperfusion) and permanent focal ischaemia models in rats. In both types of model, NXY-059 has a large window of opportunity, providing effective neuroprotection when given up to 5 hours after the start of the occlusion in transient ischaemia and 4 hours after the start of permanent ischaemia. The compound is also effective in a marmoset permanent ischaemia model when administered up to 4 hours after the start of the occlusion. In this model it has been found to attenuate the problem of spatial neglect and maintain function to the paretic arm. NXY-059 administration also improves motor function in a rat haemorrhagic stroke model and has a neuroprotective effect in a rabbit thromboembolic stroke model. The compound is also well tolerated in stroke patients at plasma levels shown to provide a maximum neuroprotective effect in animal models of stroke.NXY-059, like PBN, is a nitrone with free radical trapping properties and this may be the basis of its neuroprotective action. However, experiments with PBN and NXY-059 suggest the possibility of other mechanisms being involved and these are also reviewed. Further experiments are required to fully elucidate the mechanism of action of these very effective neuroprotective agents.

Reactive Oxygen Species Mediate Virus-induced STAT Activation

Respiratory syncytial virus (RSV) is the leading cause of epidemic respiratory tract illness in children in the United States and worldwide. RSV infection of airway epithelial cells induces formation of reactive oxygen species (ROS), whose production mediates the expression of cytokines and chemokines involved the immune/inflammatory responses of the lung. In this study, we have investigated the role of ROS in RSV-induced signal transducers and activators of transcription (STAT) activation and interferon regulatory factor (IRF) gene expression in human airway epithelial cells. Our results indicate that RSV replication induces IRF-1 and -7 gene transcription, a response abrogated by antioxidants. RSV infection induces binding of STAT to the IRF-1 gamma-interferon-activated sequence (GAS) and IRF-7 interferon-stimulated responsive element (ISRE). STAT1 and STAT3 bind IRF-1 GAS, whereas STAT1, STAT2, IRF-1, and IRF-9 bind IRF-7 ISRE. Antioxidant treatment blocks RSV-induced STAT binding to both the IRF-1 GAS and IRF-7 ISRE by inhibition of inducible STAT1 and STAT3 tyrosine phosphorylation, suggesting that RSV-induced ROS formation is required for STAT activation and IRF gene expression. Although protein tyrosine phosphorylation is necessary for RSV-induced STAT activation, Janus kinase and Src kinase activation do not mediate this effect. Instead, RSV infection inhibits intracellular tyrosine phosphatase activity, which is restored by antioxidant treatment. Pharmacological inhibition of tyrosine phosphatases induces STAT activation. Together, these results suggest that modulation of phosphatases could be an important mechanism of virus-induced STAT activation. Treatment of alveolar epithelial cells with the NAD(P)H oxidase inhibitor diphenylene iodonium abolishes RSV-induced STAT activation, indicating that NAD(P)H oxidase-produced ROS are required for downstream activation of the transcription factors IRF and STAT in virus-infected airway epithelial cells.

Free radical trap phenyl-N-tert-butylnitrone protects against light damage but does not rescue P23H and S334ter rhodopsin transgenic rats from inherited retinal degeneration

Phenyl-N-tert-butylnitrone (PBN) protects rat retinas against light damage. Because the degenerative process involved in light damage and inherited retinal degeneration both lead to a common final cell death, apoptosis, we used transgenic rats with a P23H or S334ter rhodopsin mutation to test the effects of PBN on retinal degeneration and light damage and the susceptibility of the transgenic rats to light damage. In the first study, 3-week-old mutant and wild-type rats were given no drug, 0.25% PBN in drinking water, or 0.25% PBN in drinking water plus three daily intraperitoneal injections of PBN (100 mg/kg, i.p., every 8 hr). Electroretinograms were recorded at postnatal day 49, after which the rats were killed for morphometric analysis. There was no photoreceptor rescue by PBN in P23H or S334ter rats, as evidenced by equivalent loss of function and photoreceptor cells in the three treatment groups. In the second study, P23H, S334ter, and wild-type rats were exposed for 24 hr to 2700 lux light. The rats were untreated or treated with PBN (50 mg/kg per injection, every 6 hr, starting before exposure). ERGs were recorded before and 1 d after exposure. Animals were killed 6 d later for morphometric analysis. PBN protected wild-type and P23H but not S334ter retinas from light damage. S334ter retinas were relatively less susceptible to light damage than P23H and wild-type rats. The results suggest that the initiating event(s) that causes photoreceptor cell death in the mutated rats is different from that which occurs in light damage, although both ultimately undergo an apoptotic cell death.

Phenyl N-tert-butylnitrone down-regulates interleukin-1 beta-stimulated matrix metalloproteinase-13 gene expression in human chondrocytes: suppression of c-Jun NH2-terminal kinase, p38-mitogen-activated protein kinase and activating protein-1

Cytokine-mediated induction and overexpression of matrix metalloproteinases (MMPs) is recognized as an important factor in the pathogenesis of arthritis. Interleukin (IL)-1 beta is a proinflammatory cytokine that is known to superinduce the expression and production of MMP-13 in many cell types. Phenyl N-tert-butylnitrone (PBN), a spin trap agent, inhibited the IL-1 beta-induced expression of MMP-13 in human osteoarthritis (OA) chondrocytes. Down-regulation of MMP-13 expression correlated with the inhibition of mitogen-activated protein kinase (MAPK) subgroups c-Jun NH2-terminal kinase (JNK) and p38-MAPK activation, accumulation of phospho-c-jun, and the DNA binding activity of activating protein-1 (AP-1). Results of in vitro kinase assays showed that exogenously added PBN completely blocked the c-Jun phosphorylating activity of JNK. Interestingly, using in vitro kinase assay, we also found that chondrocyte p38-MAPK phosphorylate c-Jun and that PBN was not very effective in inhibiting c-Jun phosphorylating activity of p38-MAPK. In addition, PBN did not block the ATF-2 phosphorylating activity of p38-MAPK and Elk-1 phosphorylating activity of extracellular regulated kinase p44/p42 in vitro, indicating that PBN may act selectively to inhibit the phosphorylation of c-Jun in OA chondrocytes. Together, our results for the first time demonstrate that PBN suppresses the IL-1 beta-stimulated expression of MMP-13 in OA chondrocytes and that this was achieved by inhibiting the activation of JNK and AP-1. These results suggest that use of PBN or compounds derived from it may be of potential benefit in inhibiting signaling events associated with cartilage degradation in arthritis.

Epigallocatechin gallate, a constituent of green tea, represses hepatic glucose production

Herbs have been used for medicinal purposes, including the treatment of diabetes, for centuries. Plants containing flavonoids are used to treat diabetes in Indian medicine and the green tea flavonoid, epigallocatechin gallate (EGCG), is reported to have glucose-lowering effects in animals. We show here that the regulation of hepatic glucose production is decreased by EGCG. Furthermore, like insulin, EGCG increases tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 (IRS-1), and it reduces phosphoenolpyruvate carboxykinase gene expression in a phosphoinositide 3-kinase-dependent manner. EGCG also mimics insulin by increasing phosphoinositide 3-kinase, mitogen-activated protein kinase, and p70(s6k) activity. EGCG differs from insulin, however, in that it affects several insulin-activated kinases with slower kinetics. Furthermore, EGCG regulates genes that encode gluconeogenic enzymes and protein-tyrosine phosphorylation by modulating the redox state of the cell. These results demonstrate that changes in the redox state may have beneficial effects for the treatment of diabetes and suggest a potential role for EGCG, or derivatives, as an antidiabetic agent.

Nitrones as neuroprotectants and antiaging drugs

Specific nitrones have been used for more than 30 years in analytical chemistry and biochemistry to trap and stabilize free radicals for the purpose of their identification and characterization. PBN (alpha-phenyl-tert-butyl nitrone), one of the more widely used nitrones for this purpose, has been shown to have potent pharmacologic activities in models of a number of aging-related diseases, most notably the neurodegenerative diseases of stroke and Alzheimer's disease. Studies in cell and animal models strongly suggest that PBN has potent antiaging activity. A novel nitrone, CPI-1429, has been shown to extend the life span of mice when administration was started in older animals. It has also shown efficacy in the prevention of memory dysfunction associated with normal aging in a mouse model. Mechanistic studies have shown that the neuroprotective activity of nitrones is not due to mass-action free radical-trapping activity, but due to cessation of enhanced signal transduction processes associated with neuroinflammatory processes known to be enhanced in several neurodegenerative conditions. Enhanced neuroinflammatory processes produce higher levels of neurotoxins, which cause death or dysfunction of neurons. Therefore, quelling of these processes is considered to have a beneficial effect allowing proper neuronal functioning. The possible antiaging activity of nitrones may reside in their ability to quell enhanced production of reactive oxygen species associated with age-related conditions. On the basis of novel ideas about the action of secretory products formed by senescent cells on bystander cells, it is postulated that nitrones will mitigate these processes and that this may be the mechanism of their antiaging activity.

Protein kinases activities in erythrocyte membranes of asphyxiated newborns

OBJECTIVES

Perinatal asphyxia represents a major cause of acute brain impairment and mortality in neonates. To develop the effective therapies able to reduce post-asphyxial damages, the understanding of biochemical processes accompanying asphyxia appears to be of the great relevance.

DESIGN AND METHODS

The activities of protein kinases A and C, and tyrosine kinases in erythrocyte membranes of healthy and asphyxiated neonatals were compared. Using monoclonal antibodies the band 3 presence and its phosphotyrosine levels were assayed.

RESULTS

In asphyxiated erythrocyte membranes the activities of PKA and tyrosine kinases increased, whereas the activity of PKC was reduced in relation to healthy newborns. Under asphyxia the band 3 has been overphosphorylated; however, its amount decreased.

CONCLUSION

These findings may provide some evidence for a potential role of asphyxia in disturbance of phosphorylation processes in erythrocytes, as reflected by altered protein kinases activities. The diminished band 3 presence may be partially responsible for the impairment of erythrocyte function.

Reactive oxygen species and protein oxidation in aging: a look back, a look ahead

The existence of free radicals, as chemical entities, was inferred 100 years ago but not universally accepted for some 30-40 years. The existence and importance of free radicals in biological systems was not recognized until the mid 1950s, by a small number of visionary scientists who can be credited with founding the field of reactive oxygen biochemistry. For most of the remaining 20th century, reactive oxygen species (ROS) were considered a type of biochemical "rusting agent" that caused stochastic tissue damage and disease. As we enter the 21st century, reactive oxygen biochemistry is maturing as a discipline and establishing its importance among the biomedical sciences. It is now recognized that virtually every disease state involves some degree of oxidative stress. Moreover, we are now beginning to recognize that ROS are produced in a well-regulated manner to help maintain homeostasis on the cellular level in normal, healthy tissue. This review summarizes the history of reactive oxygen biochemistry, outlining major paradigm shifts that the field has undergone and continues to experience. The contributions of Earl Stadtman to the recent history of the field (1980-present) are especially highlighted. The role of ROS in signal transduction is presented in some detail as central to the latest paradigm shift. Emerging technologies, particularly proteomic technologies, are discussed that will facilitate further evolution in the field of reactive oxygen biochemistry.

Redox paradox: effect of N-acetylcysteine and serum on oxidation reduction-sensitive mitogen-activated protein kinase signaling pathways

The thiol reducing agent N-acetylcysteine (NAC) is commonly used as an "antioxidant" in studies examining gene expression, signaling pathways, and outcome in acute and chronic models of lung injury. It is less widely appreciated that NAC can also undergo auto-oxidation and behave as an oxidant. We showed previously that NAC can have opposite effects on the activation of nuclear factor-kappaB depending on whether or not serum is present, and that the effects of NAC in the absence of serum are mimicked by various oxidants. Here we show that in a serum-depleted environment (0.1% fetal bovine serum), NAC substantially inhibited lipopolysaccharide (LPS) activation of the mitogen-activated protein kinases (MAPKs), namely extracellular signal-regulated kinase (ERK), p38mapk, and c-Jun NH2-terminal kinase (JNK). By contrast, in the presence of 10% serum, NAC had no effect on LPS activation of p42 and p44 ERK and in fact enhanced LPS induction of p38mapk and JNK phosphorylation. Because serum can significantly alter the redox state, these findings highlight the importance of the local redox milieu in signal transduction.

Update on oxygen radical disease in neonatology

An increasing number of articles related to free radicals in the newborn period is published. The hypothesis that there exists a socalled 'Oxygen radical disease of neonatology' has not been proven but an increasing body of evidence seems to indicate that free radicals are involved in several disease processes leading to conditions such as chronic lung disease, retinopathy of prematurity, necrotizing enterocolitis and periventricular leukomalacia. There are also accumulating data implying the involvement of reactive oxygen species and oxidative stress in signal transduction and they therefore perhaps affect growth and development. In the last year there have been no new breakthroughs in antioxidant therapy.

Reactive oxygen species, cell signaling, and cell injury

Oxidative stress has traditionally been viewed as a stochastic process of cell damage resulting from aerobic metabolism, and antioxidants have been viewed simply as free radical scavengers. Only recently has it been recognized that reactive oxygen species (ROS) are widely used as second messengers to propagate proinflammatory or growth-stimulatory signals. With this knowledge has come the corollary realization that oxidative stress and chronic inflammation are related, perhaps inseparable phenomena. New pharmacological strategies aimed at supplementing antioxidant defense systems while antagonizing redox-sensitive signal transduction may allow improved clinical management of chronic inflammatory or degenerative conditions, including Alzheimer's disease. Introduction of antioxidant therapies into mainstream medicine is possible and promising, but will require significant advances in basic cell biology, pharmacology, and clinical bioanalysis.

Evidence for enhanced neuro-inflammatory processes in neurodegenerative diseases and the action of nitrones as potential therapeutics

A brief review is presented on observations leading to the current notions regarding neuro-inflammatory processes. The greatest focus is on Alzheimer's disease (AD) since this is where the most convincing data has been obtained. A brief summary of observations on the neuroprotective action of alpha-phenyl-tert-butyl-nitrone (PBN) as well as results of research designed to understand its mechanism of action is presented. We hypothesize that the mechanism of action of PBN involves inhibition of signal transduction processes, which are involved in the upregulation of genes mediated by pro-inflammatory cytokines and H2O2 that cause formation of toxic gene products. Results from recent experiments on Kainic acid (KA) mediated brain damage are provided to suggest the validity of the in vivo action of PBN to inhibit neuro-inflammatory processes. The accumulating scientific facts are helping to provide concepts that may become the basis for novel therapeutic approaches to the treatment of several neurodegenerative diseases.

Pharmacologic properties of phenyl N-tert-butylnitrone

Phenyl N-tert-butylnitrone (PBN) is the parent of a family of nitrones used as spin-trapping agents to trap free radicals. PBN's pharmacological effects in animal models are extensive, ranging from protection against death after endotoxin shock, protection from ischemia-reperfusion injury, to increasing the life span of mice. Recent additions to the list include protection from bacterial meningitis, thalidomide-induced teratogenicity, drug-induced diabetogenesis, and choline-deficient hepatocarcinogenesis. Because PBN reacts with oxygen radicals to produce less reactive species, it has been suggested that this is the basis of its pharmacological effects. However, there has been no hard evidence for this notation. Nevertheless, many investigators have used the presence of PBN's pharmacologic effect as evidence for free radical involvement in their models. Mechanistic studies on the PBN's antisepsis action revealed that PBN inhibits expression of various pro-inflammatory genes, suggesting that the protective action involves more than a straightforward free radical-scavenging mechanism. Previous and recent developments in the investigations on the pharmacologic properties of PBN are described in this review.