The role of superoxide and nuclear factor-kappaB signaling in N-methyl-D-aspartate-induced necrosis and apoptosis

Resveratrol Prevents Cell Swelling Through Inhibition of SUR1 Expression in Brain Micro Endothelial Cells Subjected to OGD/Recovery

The SUR1-TRPM4-AQP4 complex is overexpressed in the initial phase of edema induced after cerebral ischemia, allowing the massive internalization of Na+ and water within the brain micro endothelial cells (BMEC) of the blood-brain barrier. The expression of the Abcc8 gene encoding SUR1 depends on transcriptional factors that are responsive to oxidative stress. Because reactive oxygen species (ROS) are generated during cerebral ischemia, we hypothesized that antioxidant compounds might be able to regulate the expression of SUR1. Therefore, the effect of resveratrol (RSV) on SUR1 expression was evaluated in the BMEC cell line HBEC-5i subjected to oxygen and glucose deprivation (OGD) for 2 h followed by different recovery times. Different concentrations of RSV were administered. ROS production was detected with etidine, and protein levels were evaluated by Western blotting and immunofluorescence. Intracellular Na+ levels and cellular swelling were detected by imaging; cellular metabolic activity and rupture of the cell membrane were detected by MTT and LDH release, respectively; and EMSA assays measured the activity of transcriptional factors. OGD/recovery increased ROS production induced the AKT kinase activity and the activation of SP1 and NFκB. SUR1 protein expression and intracellular Na+ concentration in the HBEC-5i cells increased after a few hours of OGD. These effects correlated with cellular swelling and necrotic cell death, responses that the administration of RSV prevented. Our results indicate that the ROS/AKT/SP1-NFκB pathway is involved in SUR1 expression during OGD/recovery in BMEC of the blood-brain barrier. Thus, RSV prevented cellular edema formation through modulation of SUR1 expression.

Application of Nonhuman Primate Models in the Studies of Pediatric Anesthesia Neurotoxicity

Numerous animal models have been used to study developmental neurotoxicity associated with short-term or prolonged exposure of common general anesthetics at clinically relevant concentrations. Pediatric anesthesia models using the nonhuman primate (NHP) may more accurately reflect the human condition because of their phylogenetic similarity to humans with regard to reproduction, development, neuroanatomy, and cognition. Although they are not as widely used as other animal models, the contribution of NHP models in the study of anesthetic-induced developmental neurotoxicity has been essential. In this review, we discuss how neonatal NHP animals have been used for modeling pediatric anesthetic exposure; how NHPs have addressed key data gaps and application of the NHP model for the studies of general anesthetic-induced developmental neurotoxicity. The appropriate application and evaluation of the NHP model in the study of general anesthetic-induced developmental neurotoxicity have played a key role in enhancing the understanding and awareness of the potential neurotoxicity associated with pediatric general anesthetics.

Magnesium acetyltaurate prevents retinal damage and visual impairment in rats through suppression of NMDA-induced upregulation of NF-κB, p53 and AP-1 (c-Jun/c-Fos)

Magnesium acetyltaurate (MgAT) has been shown to have a protective effect against N-methyl-D-aspartate (NMDA)-induced retinal cell apoptosis. The current study investigated the involvement of nuclear factor kappa-B (NF-κB), p53 and AP-1 family members (c-Jun/c-Fos) in neuroprotection by MgAT against NMDA-induced retinal damage. In this study, Sprague-Dawley rats were randomized to undergo intravitreal injection of vehicle, NMDA or MgAT as pre-treatment to NMDA. Seven days after injections, retinal ganglion cells survival was detected using retrograde labelling with fluorogold and BRN3A immunostaining. Functional outcome of retinal damage was assessed using electroretinography, and the mechanisms underlying antiapoptotic effect of MgAT were investigated through assessment of retinal gene expression of NF-κB, p53 and AP-1 family members (c-Jun/c-Fos) using reverse transcription-polymerase chain reaction. Retinal phospho-NF-κB, phospho-p53 and AP-1 levels were evaluated using western blot assay. Rat visual functions were evaluated using visual object recognition tests. Both retrograde labelling and BRN3A immunostaining revealed a significant increase in the number of retinal ganglion cells in rats receiving intravitreal injection of MgAT compared with the rats receiving intravitreal injection of NMDA. Electroretinography indicated that pre-treatment with MgAT partially preserved the functional activity of NMDA-exposed retinas. MgAT abolished NMDA-induced increase of retinal phospho-NF-κB, phospho-p53 and AP-1 expression and suppressed NMDA-induced transcriptional activity of NF-κB, p53 and AP-1 family members (c-Jun/c-Fos). Visual object recognition tests showed that MgAT reduced difficulties in recognizing the visual cues (i.e. objects with different shapes) after NMDA exposure, suggesting that visual functions of rats were relatively preserved by pre-treatment with MgAT. In conclusion, pre-treatment with MgAT prevents NMDA induced retinal injury by inhibiting NMDA-induced neuronal apoptosis via downregulation of transcriptional activity of NF-κB, p53 and AP-1-mediated c-Jun/c-Fos. The experiments were approved by the Animal Ethics Committee of Universiti Teknologi MARA (UiTM), Malaysia, UiTM CARE No 118/2015 on December 4, 2015 and UiTM CARE No 220/7/2017 on December 8, 2017 and Ethics Committee of Belgorod State National Research University, Russia, No 02/20 on January 10, 2020.

Nonhormonal Treatment for Endometriosis Focusing on Redox Imbalance

The aim of this review is to investigate the oxidant/antioxidant status and its regulatory mechanisms in patients with endometriosis and to summarize the antioxidant therapy as an alternative to hormonal therapy for endometriosis. Each keyword alone or in combination was used to search from PubMed and Embase by applying the filters of the title and the publication years between January 2000 and March 2020. Endometriosis is a chronic inflammatory disease characterized by repeated episodes of hemorrhage. Methemoglobin in repeated hemorrhage produces large amounts of superoxide anion via the autoxidation of hemoglobin. Excessive free-radical production causes redox imbalance, leading to inadequate antioxidant defenses and damage to endometrial cells, but may contribute to endometrial cell growth and survival through activation of various signaling pathways. In addition, to overcome excessive oxidative stress, estradiol participates in the induction of antioxidants such as superoxide dismutase in mitochondria. Several antioxidants that suppress free radicals may be effective in endometriosis-related pain. We searched for 23 compounds and natural substances that could reduce the pain caused by superoxide/reactive oxygen species in basic research and animal models. Next, we built a list of 16 drugs that were suggested to be effective against endometriosis other than hormone therapy in preclinical studies and clinical trials. Of the 23 and 16 drugs, 4 overlapping drugs could be potential candidates for clinically reducing endometriosis-related pain caused by superoxide anion/reactive oxygen species. These drugs include polyphenols (resveratrol and polydatin), dopamine agonists (cabergoline), and statins (simvastatin). However, no randomized controlled trials have evaluated the efficacy of these drugs. In conclusion, this review summarizes the following 2 points: superoxide anion generation by methemoglobin is enhanced in endometriosis, resulting in redox imbalance; and some compounds and natural substances that can suppress free radicals may be effective in endometriosis-related pain. Further randomized clinical trials based on larger series are mandatory to confirm the promising role of antioxidants in the nonhormonal management of endometriosis.

Propofol inhibits the expression of Abelson nonreceptor tyrosine kinase without affecting learning or memory function in neonatal rats

OBJECTIVE

Propofol is one of the most commonly used intravenous drugs to induce and maintain general anesthesia. In vivo and in vitro studies have shown that propofol can affect neuronal growth, leading to apoptosis and impairing cognitive function. The Abelson nonreceptor tyrosine kinase (c-Abl) is associated with both neuritic plaques and neurofibrillary tangles in the brains of patients with Alzheimer's disease and other neurodegenerative diseases. This study aimed to explore the effect of propofol on apoptosis and neurocognition through its regulation of c-Abl expression in vivo and in vitro.

MATERIALS AND METHODS

In this study, primary hippocampal neurons were cultured and exposed to propofol at different concentrations. Protein expression was measured by Western blotting and coimmunoprecipitation. The c-Abl transcription level was verified by fluorescence quantitative PCR. Reactive oxygen species (ROS) levels were detected by flow cytometry. In addition, an animal experiment was conducted to assess neuronal apoptosis by immunofluorescence staining for caspase-3 and to evaluate behavioral changes by the Morris water maze (MWM) test.

RESULTS

The in vitro experiment showed that propofol significantly decreased c-Abl expression and ROS levels. In addition, propofol has no cytotoxic effect and does not affect cell activity. Moreover, in the animal experiment, intraperitoneal injection of 50 mg/kg propofol for 5 days obviously decreased the expression of c-Abl in the neonatal rat brain (p < .05) but did not significantly increase the number of caspase-3-positive cells. Propofol treatment did not significantly reduce the number of platform crossings (p > .05) or prolong the escape latency of neonatal rats (p > .05) in the MWM test.

CONCLUSIONS

The present data suggest that reduced expression of this nonreceptor tyrosine kinase through consecutive daily administration of propofol did not impair learning or memory function in neonatal rats.

Potential mechanisms for phencyclidine/ketamine-induced brain structural alterations and behavioral consequences

Evidence of structural abnormalities in the nervous system of recreational drug [e.g., phencyclidine (PCP) or ketamine] users and/or preclinical animal research models suggests interference with the activity of multiple neurotransmitters, particularly glutamate neurotransmission. The damage to the central nervous system (CNS) may include neuronal loss, synaptic changes, disturbed neural network formation and reduced projections to subcortical fields. Notably, the reduced projections may considerably compromise the establishment of the subcortical areas, such as the nucleus accumbens located in the basal forebrain. With its abundant dopaminergic innervation, the nucleus accumbens is believed to be directly associated with addictive behaviors and mental disorders. This review seeks to delineate the relationship between PCP/ketamine-induced loss of cortical neurons and the reduced level of polysialic acid neural cell adhesion molecule (PSA-NCAM) in the striatum, and the likely changes in striatal synaptogenesis during development. The basic mechanism of how PSA-NCAM cell surface expression may be regulated will also be discussed, as well as the hypothesis that PSA-NCAM activity is critical to the regulation of synaptic protein expression. Overall, the present review will address the general hypothesis that damage/interruption of cortico-striatal communication and subcortical synaptogenesis could underlie the erratic/sensitization or addictive states produced by chronic or prolonged PCP/ketamine usage.

Inhibition of Spinal Oxidative Stress by Bergamot Polyphenolic Fraction Attenuates the Development of Morphine Induced Tolerance and Hyperalgesia in Mice

Citrus Bergamia Risso, commonly known as Bergamot, is a fruit whose Essential Oil and Bergamot Polyphenolic Fraction have numerous medicinal properties. It is also an excellent antioxidant and in this study, for the first time, its potential effect on morphine induced tolerance in mice has been investigated. Our studies revealed that development of antinociceptive tolerance to repeated doses of morphine in mice is consistently associated with increased formation of superoxide, malondialdehyde and tyrosine-nitrated proteins in the dorsal horn of the spinal cord such as the enzyme glutamine synthase. Nitration of this protein is intimately linked to inactivation of its biological function and resulting increase of glutamate levels in the spinal cord. Administration of Bergamot Polyphenolic Fraction (5–50 mg/kg) attenuated tolerance development. This effect was accompanied by reduction of superoxide and malondialdehyde production, prevention of GS nitration, re-establishment of its activity and of glutamate levels. Our studies confirmed the main role of free radicals during the cascade of events induced by prolonged morphine treatment and the co-administration of natural derivatives antioxidant such as Bergamot Polyphenolic Fraction can be an important therapeutic approach to restore opioids analgesic efficacy.

Ketamine is toxic to chondrocyte cell cultures

Ketamine has been used in combination with a variety of other agents for intra-articular analgesia, with promising results. However, although it has been shown to be toxic to various types of cell, there is no available information on the effects of ketamine on chondrocytes.

We conducted a prospective randomised controlled study to evaluate the effects of ketamine on cultured chondrocytes isolated from rat articular cartilage. The cultured cells were treated with 0.125 mM, 0.250 mM, 0.5 mM, 1 mM and 2 mM of ketamine respectively for 6 h, 24 hours and 48 hours, and compared with controls. Changes of apoptosis were evaluated using fluorescence microscopy with a 490 nm excitation wavelength. Apoptosis and eventual necrosis were seen at each concentration. The percentage viability of the cells was inversely proportional to both the duration and dose of treatment (p = 0.002 and p = 0.009). Doses of 0.5 mM, 1 mM and 2mM were absolutely toxic.

We concluded that in the absence of solid data to support the efficacy of intra-articular ketamine for the control of pain, and the toxic effects of ketamine on cultured chondrocytes shown by this study, intra-articular ketamine, either alone or in combination with other agents, should not be used to control pain.

Cite this article: Bone Joint J 2014; 96-B:989–94.

Posttranslational nitration of tyrosine residues modulates glutamate transmission and contributes to N-methyl-D-aspartate-mediated thermal hyperalgesia

Activation of the N-methyl-D-aspartate receptor (NMDAR) is fundamental in the development of hyperalgesia. Overactivation of this receptor releases superoxide and nitric oxide that, in turn, forms peroxynitrite (PN). All of these events have been linked to neurotoxicity. The receptors and enzymes involved in the handling of glutamate pathway—specifically NMDARs, glutamate transporter, and glutamine synthase (GS)—have key tyrosine residues which are targets of the nitration process causing subsequent function modification. Our results demonstrate that the thermal hyperalgesia induced by intrathecal administration of NMDA is associated with spinal nitration of GluN1 and GluN2B receptor subunits, GS, that normally convert glutamate into nontoxic glutamine, and glutamate transporter GLT1. Intrathecal injection of PN decomposition catalyst FeTM-4-PyP⁵⁺ prevents nitration and overall inhibits NMDA-mediated thermal hyperalgesia. Our study supports the hypothesis that nitration of key proteins involved in the regulation of glutamate transmission is a crucial pathway used by PN to mediate the development and maintenance of NMDA-mediated thermal hyperalgesia. The broader implication of our findings reinforces the notion that free radicals may contribute to various forms of pain events and the importance of the development of new pharmacological tool that can modulate the glutamate transmission without blocking its actions directly.

Is age-dependent, ketamine-induced apoptosis in the rat somatosensory cortex influenced by temperature?

General anesthetics have long been thought to be relatively safe but recent clinical studies have revealed that exposure of very young children (4 years or less) to agents that act by blocking the N-methyl-D-aspartate receptor (NMDAR) can lead to cognitive deficits as they mature. In rodent and non-human primate studies, blockade of this receptor during the perinatal period leads to a number of molecular, cellular and behavioral pathologies. Despite the overwhelming evidence from such studies, doubt remains as to their clinical relevance. A key issue is whether the primary injury (apoptotic cell death) is specific to receptor blockade or due to non-specific, patho-physiological changes. Principal to this argument is that loss of core body temperature following NMDAR blockade could explain why injury is observed hours later. We therefore examined the neurotoxicity of the general anesthetic ketamine in P7, P14 and P21 rats while monitoring core body temperature. We found that, at P7, ketamine induced the pro-apoptotic enzyme activated caspase-3 in a dose-dependent manner. As expected, injury was greatly diminished by P14 and absent by P21. However, contrary to expectations, we found that core body temperature was not a factor in determining injury. Our data imply that injury is directly related to receptor blockade and is unlikely to be overcome by artificially changing core body temperature.

NMDA-receptor activation and nitroxidative regulation of the glutamatergic pathway during nociceptive processing

The role of peroxynitrite (PN) as a mediator of nociceptive signaling is emerging. We recently reported that the development of central sensitization that follows the intraplantar injection of carrageenan in rats is associated with spinal PN synthesis. We now demonstrate that a significant pathway through which spinal PN modulates central sensitization is post-translational tyrosine nitration of key proteins involved in the glutamatergic pathway, namely glutamate transporter GLT-1 and glutamine synthetase (GS). We also reveal that spinal activation of the N-methyl-d-aspartate (NMDA) receptor provides a source of PN in this setting. Intraplantar injection of carrageenan led to the development of thermal hyperalgesia as well as nitration of GLT-1 and GS in dorsal horn tissues. Pretreatment with the PN decomposition catalyst FeTM-4-PyP(5+) [Fe(III)5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin] or the NMDA receptor antagonist MK-801 blocked the development of hyperalgesia. Carrageenan-induced hyperalgesia was also associated with nitration and inactivation of spinal mitochondrial superoxide dismutase (MnSOD) known to provide a critical source of PN during central sensitization. Nitration of GLT-1 and GS contributes to central sensitization by enhancing glutamatergic neurotransmission. Our results support the critical role of nitroxidative stress in the development of hyperalgesia and suggest that post-translational nitration of enzymes and transporters linked to glutamatergic neurotransmission represent a novel mechanism of central sensitization.

Laminar xanthine oxidase, superoxide dismutase and catalase activities in the prodromal stage of black-walnut induced equine laminitis

REASONS FOR STUDY: Xanthine oxidase (XO)-dependent production of superoxide anion and hydrogen peroxide, a characteristic of ischaemia-reperfusion injury, may contribute to the development of equine laminitis.

OBJECTIVE

To determine the levels of XO and antioxidant enzymes (catalase, superoxide dismutase [SOD]) in the digital laminae of normal horses (CON) and horses in the developmental stage of laminitis using the black walnut extract (BWE) model.

METHODS

Healthy horses (n = 12) were administered BWE (BWE group, n = 6), or water (CON group, n = 6) through a nasogastric tube. At the onset of leucopenia in the BWE-treated animals, all horses were anaesthetised, digital laminae and other samples collected rapidly and flash frozen, and the animals subjected to euthanasia. Extracts of the frozen tissues were assayed for the 2 conformational forms of xanthine: oxygen oxidoreductase (XOR), namely, xanthine dehydrogenase (XDH) and xanthine oxidase (XO), as well as the antioxidant enzymes, SOD and catalase.

RESULTS

Extracts of liver, lungs and skin, but not digital laminae, from either CON or BWE-treated horses had endogenous SOD, whereas all had endogenous XO and catalase. The levels of XDH, XO and catalase were similar in extracts of laminae from CON and BWE-treated horses as was the ratio of XDH to XO in extracts.

CONCLUSIONS AND POTENTIAL RELEVANCE

The absence of increased XO activity suggest against the involvement of this reactive oxygen intermediate-generating system in the development of laminar pathology in BWE-treated horses. Conversely, the absence of SOD from extracts of equine digital laminae, but not other tissues, suggests that the equine digital laminae are highly susceptible to damage by superoxide anion, produced, for example, by emigrant inflammatory leucocytes.

Cytotoxicity of methoctramine and methoctramine-related polyamines

Methoctramine and its analogues are polymethylene tetramines that selectively bind to a variety of receptor sites. Although these compounds are widely used as pharmacological tools for receptor characterization, the toxicological properties of these polyamine-based structures are largely unknown. We have evaluated the cytotoxic effects of methoctramine and related symmetrical analogues differing in polymethylene chain length between the inner nitrogens against a panel of cell lines. Methoctramine caused cell death only at high micromolar concentrations, whereas its pharmacological action is exerted at nanomolar level. Increasing the spacing between the inner nitrogen atoms resulted in a significative increase in cytotoxicity. In particular, an elevated cytotoxicity is associated to a methylene chain length of 12 units dividing the inner amine functions (compound 5). H9c2 cardiomyoblasts were the most sensitive cells, followed by SH-SY5Y neuroblastoma, whereas HL60 leukaemia cells were much more resistant. Methoctramine and related compounds down-regulated ornithine decarboxylase, the first enzyme of polyamine biosynthesis even at non-toxic concentration. Further, methoctramine and compound 5 caused a limited up-regulation of spermine/spermidine N-acetyltransferase, suggesting that interference in polyamine metabolism is not a primary mechanism of toxicity. Methoctramine and its analogues bound to DNA with a higher affinity than spermine, but the correlation with their toxic effect was poor. The highly toxic compound 5 killed the cells in the absence of caspase activation and caused an increase in p53 expression and ERK1/2 phosphorylation. Compound 5 was directly oxidized by cell homogenates producing hydrogen peroxide and its toxic effect was partially subdued by the inhibition of its uptake, by the NMDA ligand MK-801, and by the antioxidant N-acetylcysteine, suggesting that compound 5 can act at different cellular levels and lead to oxidative stress.

Gene expression profiles of neurotrophic factors in rat cultured spinal cord cells under cyclic tensile stress

STUDY DESIGN

An experimental study to investigate the in vitro gene expression of neurotrophic factors and receptors in cultured rat spinal cord cells subjected to cyclic mechanical stretch forces.

OBJECTIVE

We evaluated in vitro expression of neurotrophic factors and receptors in cultured rat spinal cord cells under cyclic tensile stress.

SUMMARY OF BACKGROUND DATA

Application of compressive mechanical stress to the spinal cord results in multiple changes making it difficult to examine the expression of neurotrophic factors and their receptors. There are no in vitro studies that investigated the biologic responses of cultured spinal cord cells to tensile stress.

METHODS

Spinal cord cells were isolated for culture from 15-day Sprague-Dawley rat embryos. We used the FX3000 Flexercell Strain Unit to induce mechanical stress. We analyzed the effects of mechanical stress on cell morphology, mRNA expression levels of various neurotrophic factors, and their immunoreactivities at 0, 2, 6, 12, 24, and 36 hours.

RESULTS

Tensile stress for 6 hours resulted in reduction of spinal cord cells and loss of neurites. Cells that survived 24-hours stress showed swollen irregular-shaped soma, bleb formation, and fragmented neurites. The cell survival rate decreased, whereas lactate dehydrogenase release increased significantly at 6 hours. There were significant increases in mRNA expression levels of nerve growth factor, brain-derived neurotrophic factor, trkB, p75 neurotrophin receptor (p75), glial cell line-derived neurotrophic factor, and caspase-9 during the early period after application of tensile stress.

CONCLUSION

Our results suggest survival of spinal cord neuronal cells under injurious tensile stress with increased synthesis and utilization of several neurotrophic factors, receptors, and expression of proteins related to cell apoptosis.

Cyclooxygenases 1 and 2 contribute to peroxynitrite-mediated inflammatory pain hypersensitivity

Peroxynitrite (ONOO(-)), the reaction product of the interaction between superoxide (O(2)(*-)) and nitric oxide (*NO), is a potent proinflammatory and cytotoxic nitrooxidative species. Its role as a mediator of hyperalgesia (clinically defined as an augmented sensitivity to painful stimuli) is not known. In light of the known proinflammatory properties of ONOO(-), our study addressed its potential involvement in the development of hyperalgesia associated with tissue damage and inflammation. Intraplantar injection in rats of the ONOO(-) precursor O(2)(*-) (1 microM) led to the development of thermal hyperalgesia associated with a profound localized inflammatory response. Both events were blocked by L-NAME (N(G)-nitro-L-arginine methyl ester, 3-30 mg/kg), a nitric oxide synthase inhibitor, or by FeTM-4-PyP(5+) [Fe(III)5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin, 3-30 mg/kg], an ONOO(-) decomposition catalyst. These results suggested that locally synthesized ONOO(-) produced in situ by O(2)(*-) and *NO is key in the development of inflammatory hyperalgesia. The direct link between ONOO(-) and hyperalgesia was further supported by demonstrating that intraplantar injection of soluble ONOO(-) itself (1 microM) similarly led to inflammatory hyperalgesia. ONOO(-) generated by the interaction between exogenous administration of O(2)(*-) and endogenous *NO, or provided by direct injection of ONOO(-), activated the transcription factor NF-kappaB in paw tissues, enhancing expression of the inducible but not the constitutive cyclooxygenase enzyme (COX-2 and COX-1, respectively). ONOO(-)-mediated hyperalgesia was blocked in a dose-dependent manner by intraperitoneal injections of indomethacin (10 mg/kg), a nonselective COX-1/COX-2 inhibitor, or NS398 [N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; 10 mg/kg] a selective COX-2 inhibitor, as well as by an anti-prostaglandin (PG) E(2) antibody (200 microg). In another established model of inflammation-related hyperalgesia by intraplantar injection of carrageenan in rats, inhibition of ONOO(-) with FeTM-4-PyP(5+) (3-30 mg/kg) inhibited the development of hyperalgesia and the release of PGE(2) in paw tissue exudates. Furthermore, FeTM-4-PyP(5+) synergized with indomethacin and NS397 (1-10 mg/kg) to block both hyperalgesia and edema. Taken together, these data show for the first time that ONOO(-) is a potent mediator of inflammation-derived hyperalgesia operating via the COX-to-PGE(2) pathway. These results provide a pharmacological rationale for the development of inhibitors of peroxynitrite biosynthesis as novel nonnarcotic analgesics. The broad implications of our study are that dual inhibition of both ONOO(-) formation and COX activity may provide an alternative therapeutic approach to the management of pain: effective analgesia with reduced side-effects typically associated with the use of COX inhibitors.

Dual roles of NF-kappaB in cell survival and implications of NF-kappaB inhibitors in neuroprotective therapy

NF-kappaB is a well-characterized transcription factor with multiple physiological and pathological functions. NF-kappaB plays important roles in the development and maturation of lymphoids, regulation of immune and inflammatory response, and cell death and survival. The influence of NF-kappaB on cell survival could be protective or destructive, depending on types, developmental stages of cells, and pathological conditions. The complexity of NF-kappaB in cell death and survival derives from its multiple roles in regulating the expression of a broad array of genes involved in promoting cell death and survival. The activation of NF-kappaB has been found in many neurological disorders, but its actual roles in pathogenesis are still being debated. Many compounds with neuroprotective actions are strongly associated with the inhibition of NF-kappaB, leading to speculation that blocking the pathological activation of NF-kappaB could offer neuroprotective effects in certain neurodegenerative conditions. This paper reviews the recent developments in understanding the dual roles of NF-kappaB in cell death and survival and explores its possible usefulness in treating neurological diseases. This paper will summarize the genes regulated by NF-kappaB that are involved in cell death and survival to elucidate why NF-kappaB promotes cell survival in some conditions while facilitating cell death in other conditions. This paper will also focus on the effects of various NF-kappaB inhibitors on neuroprotection in certain pathological conditions to speculate if NF-kappaB is a potential target for neuroprotective therapy.

Differential regulation of the NMDA receptor by acute and sub-chronic phencyclidine administration in the developing rat

Neurodegeneration induced by the NMDA receptor antagonist, phencyclidine (PCP), has been used to model the pathogenesis of schizophrenia in the developing rat. Acute and sub-chronic administration of PCP in perinatal rats results in different patterns of neurodegeneration. The potential role of an alteration in the membrane expression of NMDA receptors in PCP-induced degeneration is unknown. Acute PCP treatment on postnatal day 7 increased membrane levels of both NMDA receptor subunit 1 (NR1) and NMDA receptor subunit 2B (NR2B) proteins in the frontal cortex; conversely, NR1 and NR2B protein levels in the endoplasmic reticulum fraction were decreased. Acute PCP administration also resulted in increased membrane cortical protein levels of post-synaptic density-95, as well as the activation of calpain, which paralleled the observed increase in membrane expression of NR1 and NR2B. Further, administration of the calpain inhibitor, MDL28170, prevented PCP-induced up-regulation of NR1 and NR2B. On the other hand, sub-chronic PCP treatment on postnatal days 7, 9 and 11 caused an increase in NR1 and NR2A expression, which was accompanied by an increase in both NR1 and NR2A in the endoplasmic reticulum fraction. Sub-chronic PCP administration did not alter levels of post-synaptic density-95 and had no effect on activation of calpain. These data suggest that increased trafficking accounts for up-regulation of cortical NR1/NR2B subunits following acute PCP administration, while increased protein synthesis likely accounts for the increased expression of NR1/NR2A following sub-chronic PCP treatment of the developing rat. These results are discussed in the context of the differential neurodegeneration caused by acute and subchronic PCP administration in the developing rat brain.

The role of caspase-3 activation in phencyclidine-induced neuronal death in postnatal rats

This study determined the role of caspase-3 in phencyclidine (PCP)-induced neurodegeneration in postnatal rats. PCP administration to postnatal day 7 rats induced a dose-dependent increase in caspase-3 enzymatic activity in frontal cortex, striatum, and hippocampus. Enzymatic activation was present at 4 h, peaked between 6 and 12 h, and disappeared by 24 h. Further, cleaved caspase-3-immunoreactive neurons were detected as early as 2 h in the cortex, and were found throughout the brain, including, in addition, the thalamus and striatum. Within the cingulate, frontal, parietal, and retrosplenial cortices, immunoreactivity was specific for layers II-IV (especially layer II). Neurons positive for both silver staining and terminal deoxynucleotidyl transferase biotin-d-UTP nick-end labeling (TUNEL) were found in the same brain regions and subregions. Double labeling experiments confirmed that cleaved caspase-3 and TUNEL were coexpressed in many neurons in all brain regions and subregions studied. Temporal studies revealed that procaspase-3 cleavage preceded TUNEL staining by about 3 h, with many neurons being positive for both caspase-3 and TUNEL 9 h after PCP treatment. In organotypic corticostriatal slices, PCP caused a concentration- and time-dependent cleavage of procaspase-3 that was also colocalized with TUNEL staining in layers II-IV of the parietal cortex. Caspase-3 activation again preceded PCP-induced DNA damage assessed by TUNEL. PCP-induced neuronal death in vitro as measured by TUNEL staining was blocked 85% by Ac-AAVALLPAVLLALLAPDEVD-CHO, a cell-permeable selective caspase-3 inhibitor. These data demonstrate that caspase-3 activation plays a necessary role in the regionally selective neuronal death induced by PCP in the developing rat brain.

Systems biology approaches for toxicology

Systems biology/toxicology involves the iterative and integrative study of perturbations by chemicals and other stressors of gene and protein expression that are linked firmly to toxicological outcome. In this review, the value of systems biology to enhance the understanding of complex biological processes such as neurodegeneration in the developing brain is explored. Exposure of the developing mammal to NMDA (N-methyl-D-aspartate) receptor antagonists perturbs the endogenous NMDA receptor system and results in enhanced neuronal cell death. It is proposed that continuous blockade of NMDA receptors in the developing brain by NMDA antagonists such as ketamine (a dissociative anesthetic) causes a compensatory up-regulation of NMDA receptors, which makes the neurons bearing these receptors subsequently more vulnerable (e.g. after ketamine washout), to the excitotoxic effects of endogenous glutamate: the up-regulation of NMDA receptors allows for the accumulation of toxic levels of intracellular Ca(2+) under normal physiological conditions. Systems biology, as applied to toxicology, provides a framework in which information can be arranged in the form of a biological model. In our ketamine model, for example, blockade of NMDA receptor up-regulation by the co-administration of antisense oligonucleotides that specifically target NMDA receptor NR1 subunit mRNA, dramatically diminishes ketamine-induced cell death. Preliminary gene expression data support the role of apoptosis as a mode of action of ketamine-induced neurotoxicity. In addition, ketamine-induced cell death is also prevented by the inhibition of NF-kappaB translocation into the nucleus. This process is known to respond to changes in the redox state of the cytoplasm and has been shown to respond to NMDA-induced cellular stress. Although comprehensive gene expression/proteomic studies and mathematical modeling remain to be carried out, biological models have been established in an iterative manner to allow for the confirmation of biological pathways underlying NMDA antagonist-induced cell death in the developing nonhuman primate and rodent. Published in 2007 John Wiley & Sons, Ltd.

L-carnitine protects neurons from 1-methyl-4-phenylpyridinium-induced neuronal apoptosis in rat forebrain culture

1-Methyl-4-phenylpyridinium ion (MPP+), an inhibitor of mitochondrial complex I, has been widely used as a neurotoxin because it elicits a severe Parkinson's disease-like syndrome with an elevation of intracellular reactive oxygen species (ROS) and apoptosis. L-carnitine plays an integral role in attenuating the brain injury associated with mitochondrial neurodegenerative disorders. The present study investigates the effects of L-carnitine against the toxicity of MPP+ in rat forebrain primary cultures. Cells in culture were treated for 24 h with 100, 250, 500 and 1000 microM MPP+ alone or co-incubated with L-carnitine. MPP+ produced a dose-related increase in DNA fragmentation as measured by cell death ELISA (enzyme-linked immunosorbent assay), an increase in the number of TUNEL (terminal dUTP nick-end labeling)-positive cells and a reduction in the mitochondrial metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). No significant effect was observed with the release of lactate dehydrogenase (LDH), indicating that cell death presumably occurred via apoptotic mechanisms. Co-incubation of MPP+ with L-carnitine significantly reduced MPP+-induced apoptosis. Western blot analyses showed that neurotoxic concentrations of MPP+ decreased the ratio of BCL-X(L) to Bax and decreased the protein levels of polysialic acid neural cell adhesion molecules (PSA-NCAM), a neuron specific marker. L-carnitine blocked these effects of MPP+ suggesting its potential therapeutic utility in degenerative disorders such as Parkinson's disease, Alzheimer's disease, ornithine transcarbamylase deficiency and other mitochondrial diseases.

Superoxide, peroxynitrite and oxidative/nitrative stress in inflammation

A considerable body of evidence suggests that formation of potent reactive oxygen species and resulting oxidative/nitrative stress play a major role in acute and chronic inflammation and pain. Much of the knowledge in this field has been gathered by the use of pharmacological and genetic approaches. In this mini review, we will evaluate recent advances made towards understanding the roles of reactive oxygen species in inflammation, focusing in particular on superoxide and peroxynitrite. Given the limited space to cover this broad topic, here we will refer the reader to comprehensive review articles whenever possible.

Involvement of TNF-alpha in glutamate-induced apoptosis in a differentiated neuronal cell line

We examined the involvement of tumor necrosis factor (TNF)-alpha on glutamate-induced cytotoxicity in a differentiated neuronal cell line. In this study, we used nerve growth factor (NGF)-differentiated PC12h cells. Glutamate cytotoxicity was assessed using the MTS and TUNEL assays. To detect TNF-alpha levels in culture supernatants after glutamate exposure, we used ELISA methods. The involvement of caspase-8, which is downstream from TNF receptor 1 (TNF-R1) in glutamate-induced cytotoxicity, was determined by Western blot analysis. The MTS assay showed that the addition of glutamate resulted in dose-dependent cell death, while the TUNEL assay showed that glutamate induced apoptosis in differentiated PC12h cells in a dose-dependent manner. TNF-alpha levels in the supernatant of glutamate-exposed cells were significantly increased compared with those in unexposed cells. In addition, glutamate caused increases in the levels of caspase-8 protein. The increases in caspase-8 levels were ameliorated by pretreatment with soluble TNF-R1. Moreover, soluble TNF-R1 significantly ameliorated the cell death induced by glutamate. These results suggest that TNF-alpha released from neuronal cells may be associated with glutamate-induced neuronal cell death.

Histamine protects against NMDA-induced necrosis in cultured cortical neurons through H receptor/cyclic AMP/protein kinase A and H receptor/GABA release pathways

Using histamine and the H3 receptor antagonist thioperamide, the roles of histamine receptors in NMDA-induced necrosis were investigated in rat cultured cortical neurons. Within 3 h of intense NMDA insult, most neurons died by necrosis. Histamine reversed the neurotoxicity in a concentration-dependent manner and showed peak protection at a concentration of 10(-7) m. This protection was antagonized by the H2 receptor antagonists cimetidine and zolantidine but not by the H1 receptor antagonists pyrilamine and diphenhydramine. In addition, the selective H2 receptor agonist amthamine mimicked the protection by histamine. This action was prevented by cimetidine but not by pyrilamine. 8-Bromo-cAMP also mimicked the effect of histamine. In contrast, both the adenylyl cyclase inhibitor 9-(tetrahydro-2-furanyl)-9H-purine-6-amine and the cAMP-dependent protein kinase inhibitor N-[2-(p-bromocinnamylamino) ethyl]-5-isoquinolinesulfonamide reversed the protection by histamine. Thioperamide also attenuated NMDA-induced excitotoxicity, which was reversed by the H3 receptor agonist (R)-alpha-methylhistamine but not by pyrilamine and cimetidine. In addition, the protection by thioperamide was inhibited by the GABA(A) receptor antagonists picrotoxin and bicuculline. Further study demonstrated that the protection by thioperamide was due to increased GABA release in NMDA-stimulated samples. These results indicate that not only the H2 receptor/cAMP/cAMP-dependent protein kinase pathway but also the H3 receptor/GABA release pathway can attenuate NMDA-induced neurotoxicity.

Blockade of N-methyl-D-aspartate receptors by ketamine produces loss of postnatal day 3 monkey frontal cortical neurons in culture

Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, is used as a general pediatric anesthetic. Recent data suggest that anesthetic drugs may cause neurodegeneration during development. The purpose of this study was to determine the robustness of ketamine-induced developmental neurotoxicity using rhesus monkey frontal cortical cultures and also to determine if dysregulation of NMDA receptor subunits promotes ketamine-induced cell death. Frontal cortical cells collected from the neonatal monkey were incubated for 24 h with 1, 10, or 20 microM ketamine alone or with ketamine plus either NR1 antisense oligonucleotides or the nuclear factor kB translocation inhibitor, SN-50. Ketamine caused a marked reduction in the neuronal marker polysialic acid neural cell adhesion molecule and mitochondrial metabolism, as well as an increase in DNA fragmentation and release of lactate dehydrogenase. Ketamine-induced effects were blocked by NR1 antisenses and SN-50. These data suggest that NR1 antisenses and SN-50 offer neuroprotection from the enhanced degeneration induced by ketamine in vitro.

Hyperglycemia, insulin, and acute ischemic stroke: a mechanistic justification for a trial of insulin infusion therapy

BACKGROUND AND PURPOSE

Hyperglycemia is associated with increased mortality and morbidity in acute ischemic stroke.

SUMMARY OF REVIEW

Hyperglycemia induces a pro-oxidative and proinflammatory state that can cause direct neuronal toxicity. Hyperglycemia-mediated increase in matrix metalloproteinase-9 can cause neuronal damage by an increase in cerebral edema. Moreover, hyperglycemia may be responsible for a procoagulant state that can further compromise blood supply to the penumbral areas in acute ischemic stroke. Insulin infusion has an effect that is opposite to that of hyperglycemia. It not only lowers blood glucose levels but also exerts an antioxidant and anti-inflammatory effect. Insulin also improves NO production and results in improved blood circulation to the ischemic areas. This article focuses on the potential mechanisms underlying the injurious effects of glucose and the beneficial effects of insulin.

CONCLUSIONS

In the absence of other potential beneficial therapies, there is an urgency to institute trials with insulin infusion in acute ischemic stroke.

Inhibition of apoptosis-inducing factor translocation is involved in protective effects of hepatocyte growth factor against excitotoxic cell death in cultured hippocampal neurons

Although hepatocyte growth factor (HGF) and its receptor are expressed in various regions of the brain, their effects and mechanism of action under pathological conditions remain to be determined. Over-activation of the N-methyl-d-aspartate (NMDA) receptor, an ionotropic glutamate receptor, has been implicated in a variety of neurological and neurodegenerative disorders. We investigated the effects of HGF on the NMDA-induced cell death in cultured hippocampal neurons and sought to explore their mechanisms. NMDA-induced cell death and increase in the number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were prevented by HGF treatment. Although neither the total amounts nor the mitochondrial localization of Bax, Bcl-2 and Bcl-xL were affected, caspase 3 activity was increased after NMDA exposure. Treatment with HGF partially prevented this NMDA-induced activation of caspase 3. Although the amount of apoptosis-inducing factor (AIF) was not altered, translocation of AIF into the nucleus was detected after NMDA exposure. This NMDA-induced AIF translocation was reduced by treatment with HGF. In addition, increased poly(ADP-ribose) polymer formation after NMDA exposure was attenuated by treatment with HGF. These results suggest that the protective effects of HGF against NMDA-induced neurotoxicity are mediated via the partial prevention of caspase 3 activity and the inhibition of AIF translocation to the nucleus.

Glioma cells under hypoxic conditions block the brain microvascular endothelial cell death induced by serum starvation

Angiogenesis is one of essential components for the growth of neoplasms, including malignant gliomas. However, tumor vascularization is often poorly organized and marginally functional due to tumor structural abnormalities, inducing regional or temporal hypoxic conditions and nutritional shortages in tumor tissues. We investigated how during angiogenesis migrating endothelial cells survive in these hypoxic and reduced nutritional conditions. Human brain microvascular endothelial cells (HBMECs) underwent apoptosis and necrosis after serum withdrawal. This endothelial cell death was blocked by recombinant VEGF protein or the culture medium of U251 glioma cells exposed to hypoxia (H-CM). Hypoxic treatment increased vascular endothelial growth factor (VEGF) and tumor necrosis factor alpha (TNF-alpha) expression in U251 glioma cells. H-CM activated nuclear factor-kappaB (NFkappaB) protein and increased the gene expression of antiapoptotic factors including Bcl-2, Bcl-X(L), survivin and X-chromosome-linked inhibitor of apoptosis protein (XIAP) in endothelial cells. The survival activity of H-CM for endothelial cells was abolished by two kinds of VEGF inhibitors {Cyclopeptidic VEGF inhibitor and a VEGF receptor tyrosine kinase inhibitor (4-[(4'-chloro-2'-fluoro) phenylamino]-6, 7-dimethoxyquinazoline)} or NFkappaB inhibitors (ALLN and BAY 11-7082). These VEGF inhibitors did not block the activation of NFkappaB induced by H-CM in endothelial cells. On the contrary, TNF-alpha antagonist WP9QY enhanced the survival activity of H-CM for endothelial cells and blocked NFkappaB activation induced by H-CM under serum-starved conditions. Taken together, our data suggest that both the secretion of VEGF from glioma cells and activation of NFkappaB in endothelial cells induced by TNF-alpha are necessary for endothelial cell survival as they increase the expression of antiapoptotic genes in endothelial cells under conditions of serum starvation. These pathways may be one of the mechanisms by which angiogenesis is maintained in glioma tissues.

Application of a systems biology approach to developmental neurotoxicology

Systems biology can be applied to enhance the understanding of complex biological processes such as apoptosis in the developing brain. Systems biology, as applied to toxicology, provides a structure to arrange information in the form of a biological model. The approach allows for the subsequent and iterative perturbation of the initial model with the use of toxicants, and the comparison of the resulting data against the proposed biological model. It is postulated that the exposure of the developing rat to NMDA antagonists, e.g., ketamine or phencyclidine (PCP), causes a compensatory up-regulation of NMDA receptors, thereby making cells bearing these receptors more vulnerable to excitotoxic effects of endogenous glutamate. Although comprehensive gene expression/proteomic studies and mathematical modeling remain to be accomplished, a biological model has been established and perturbed in an iterative manner to allow confirmation of the biological pathway for NMDA antagonist-induced brain cell death in the developing rat.

The role of NMDA receptor upregulation in phencyclidine-induced cortical apoptosis in organotypic culture

Phencyclidine (PCP) is an N-methyl-D-aspartate receptor (NMDAR) antagonist known to cause selective neurotoxicity in the cortex following subchronic administration. The purpose of this study was to test the hypothesis that upregulation of the NMDAR plays a role in PCP-induced apoptotic cell death. Corticostriatal slice cultures were used to determine the effects of NMDAR subunit antisense oligodeoxynucleotides (ODNs) on PCP-induced apoptosis and NMDAR upregulation. NR1, NR2A or NR2B antisense ODNs were incubated alone or with PCP for 48h. One day following washout, it was observed that PCP treatment caused an increase in NR1, NR2A and Bax polypeptides in the cortex, but had no effect on Bcl-xL. These increases were associated with an increase in cortical histone-associated DNA fragments. Co-incubation of PCP with either NR1 or NR2A antisense significantly reduced PCP-induced apoptosis, while neither NR2B antisense ODN nor NR1 sense ODN used as a control had an effect. This effect was exactly correlated with the ability of the antisense ODNs to prevent PCP-induced upregulation of NR subunit proteins and the pro-apoptotic protein, Bax. That is, western analysis showed that antisense ODNs directed against either NR1 or NR2A prevented PCP-induced increases in Bax in addition to preventing the upregulation of the respective receptor proteins. On the other hand, the NR2B antisense ODN had no effect on either NR2B protein or on Bax. These data suggest that NR1 and NR2A antisense ODNs offer neuroprotection from apoptosis, and that upregulation of the NR1 and NR2A subunits following PCP administration is at least partly responsible for the observed apoptotic DNA fragmentation.

Creatine enhances survival of glutamate-treated neuronal/glial cells, modulates Ras/NF-kappaB signaling, and increases the generation of reactive oxygen species

The protective effects of creatine against glutamate cytotoxicity have been demonstrated in neuronal cells and animal models of neurodegenerative diseases. The mechanisms underlying creatine neuroprotection against glutamate-induced cell death are understood poorly. For the first time, we demonstrate a correlation between the protective effect of creatine and the modulation of Ras-mediated redox-dependent signaling pathways, which involve nuclear factor kappaB (NF-kappaB) and reactive oxygen species (ROS). In primary cerebrocortical cultures of mixed neurons and glia, creatine significantly reduced glutamate-induced cell death. The increase in cell survival was accompanied by increased generation of oxygen radicals and decreased levels of farnesylated Ras and IkappaB, an inhibitor of NF-kappaB. Non-farnesylated Ras and ROS-dependent activation of NF-kappaB have been shown to promote neuronal survival. Our data suggest that creatine may enhance survival signaling via activation of the Ras/NF-kappaB system. Possible mechanisms underlying the protective effect of creatine are discussed, including normalization of cellular GTP levels.

Nuclear factor-kappa B p65 in NMDA-induced retinal neurotoxicity

Transcription factors of the nuclear factor-kappa B (NF-kappaB)/Rel family may be involved in neuronal cell death or survival. We examined the role of NF-kappaB p65 in N-methyl-D-aspartate (NMDA)-induced neurotoxicity in the rat retina. Western blot analysis showed that elevated levels of retinal NF-kappaB p65 protein at days 1 and 5 after intravitreal NMDA injection. Immunohistochemistry localized increased NF-kappaB p65 immunoreactivity in the ganglion cell layer (GCL) and the inner nuclear layer (INL) after NMDA injection especially in retinal ganglion cells (RGCs), displaced amacrine cells, and amacrine cells. Concomitant with the early increase in NF-kappaB p65 protein levels, there was an increase in NF-kappaB DNA binding activity after NMDA injection as shown by electrophoretic mobility shift assay (EMSA). These increases in NF-kappaB p65 protein levels and NF-kappaB DNA binding activity were totally abolished by simultaneous injection of NF-kappaB p65 antisense oligodeoxynucleotide (AS ODN). A partial but significant protective effect on the inner retina was noted when the AS ODN was given together with NMDA as shown by morphological analysis, morphometry of cells in the GCL and morphometry of inner plexiform layer thickness as well as quantitative real-time PCR of Thy-1 mRNA levels. These results suggest that activated NF-kappaB p65 may participate in NMDA-induced retinal neuronal cell death and that inhibition of NF-kappaB activation such as the use of AS ODN may be a viable neuroprotective strategy for protective RGCs and other inner retinal neurons.

Catalytic antioxidants: a radical approach to new therapeutics

In humans, several pathologies involve the overproduction of reactive oxygen species. Metal-containing catalytic antioxidants have emerged as a novel class of potential therapeutic agents that scavenge a wide range of reactive oxygen species. There are three structural classes of manganese-containing catalytic antioxidants that have efficacy in several oxidative stress models of human disease. The classes are divided based on their in vitro selectivity towards the scavenging of superoxide. The selective catalytic antioxidants include the macrocyclics, whereas the non-selective catalytic antioxidants include the salens and porphyrins. Cardiovascular, neurodegenerative and inflammatory lung disorders are all potentially important targets for catalytic antioxidant therapy.

Superoxide-mediated nitration of spinal manganese superoxide dismutase: a novel pathway in N -methyl-d-aspartate-mediated hyperalgesia

N-methyl-D-aspartate (NMDA) receptors serve prominent roles in vast physio-pathological conditions including hyperalgesia (defined as augmented pain intensity in response to painful stimuli) associated with central sensitization. Using M40403 a synthetic low molecular weight superoxide dismutase mimetic that removes superoxide we show for the first time that this radical plays a key role in NMDA-mediated hyperalgesia. Intrathecal administration of NMDA in rats led to a time-dependent development of thermal hyperalgesia. Removal of superoxide with M40403 abolished NMDA-mediated hyperalgesia, while its inactive congener had no effect. Thus NMDA-mediated hyperalgesic response to heat is mediated through spinal release of superoxide. At time of near-to-maximal hyperalgesia, we observed that spinal endogenous manganese superoxide dismutase (MnSOD), the enzyme that normally keeps superoxide under well-controlled condition was nitrated, as shown by immunoprecipitation. Subsequently and as determined by biochemical analysis, nitration of MnSOD led to its deactivation as shown by the loss of the enzyme's ability to dismute and hence remove superoxide. M40403 by preventing MnSOD nitration restored its activity and inhibited the hyperalgesic response to intrathecal NMDA. Thus, superoxide-mediated nitration and deactivation of spinal MnSOD is a novel pathway of NMDA-mediated spinal hyperalgesia and hence central sensitization since it helps to maintain high levels of superoxide that in turn maintains nociceptive signaling. The broader implication of our findings is that superoxide may contribute to various forms of pain events that are driven by NMDA-receptor activation.

Superoxide-related signaling cascade mediates nuclear factor-kappaB activation in acute inflammation

The nuclear factor-kappaB (NF-kappaB) is a transcription factor that plays a pivotal role in the induction of genes involved in physiological processes, as well as in the response to inflammation. In this study, we used a selective nonpeptidyl superoxide dismutase mimetic, M40403, to investigate the role of superoxide anion in NF-kappaB activation during acute inflammation in mice. Injection of carrageenan into the pleural cavity of mice induced an acute inflammatory response characterized by fluid accumulation in the pleural cavity that contained a large number of neutrophils, as well as an increased production of tumor necrosis factor-alpha and interleukin-1beta. All parameters of inflammation were attenuated by M40403 (10 mg/kg i. p., 30 min prior to carrageenan administration). These inflammatory events were associated with the activation of NF-kappaB in the lung. In particular, the appearance of inhibitory protein kappaB-alpha (IkappaB-alpha) in homogenates of lung tissues was investigated by immunoblot analysis at 4 h after carrageenan administration. IkappaB-alpha levels were substantially reduced in the lung tissue from carrageenan-treated mice in comparison with sham-treated mice. Furthermore, to detect NF-kappaB/DNA binding activity, whole extracts from lung tissue of each mouse were analyzed by electrophoretic mobility-shift assay. The DNA binding activity significantly increased in whole extracts obtained from lung tissues of vehicle-treated mice 4 h after carrageenan administration. Treatment of mice with M40403 caused a significant inhibition of carrageenan-induced IkappaB-alpha degradation and NF-kappaB/DNA binding activity. These data confirm that M40403 exerts a potent antiinflammatory activity and clearly demonstrate that the reduction of the inflammatory process is associated with modification of the activation of signal transduction pathways.

Blockade of N-methyl-D-aspartate receptors by phencyclidine causes the loss of corticostriatal neurons

Perinatal administration of the N-methyl-Dd-aspartate (NMDA) receptor antagonist phencyclidine (PCP) has been reported to produce regionally selective apoptotic cell death in the frontal cortex. The development of certain behavioral abnormalities following PCP treatment suggested that extracortical regions such as the striatum also could be affected. In this study, perinatal PCP treatment caused a marked reduction in striatal, but not hippocampal, staining for polysialic acid-neural cell adhesion molecule (PSA-NCAM), an NMDA-regulated molecule important in synaptogenesis. In order to isolate striatal influences to the cortex, this investigation was continued in vitro using corticostriatal slices. For these experiments we cultured coronal corticostriatal slices from postnatal day 7 rats. After 4 days in vitro, PCP was added for 48 h and then washed out for 24 h before harvesting the tissue. Similar to what was observed in vivo, we found that PCP treatment results in a marked reduction in striatal staining for PSA-NCAM. No change was observed in the mature form of NCAM. In striatal synaptoneurosomes, immunoblot analysis confirmed that the levels of PSA-NCAM and synaptophysin, a molecule often used as a marker of synaptogenesis, were substantially down-regulated by PCP. These effects were prevented by M40403, a superoxide dismutase mimetic that also prevented the PCP-induced terminal dUTP nick-end labeling of DNA fragments that was observed selectively in the cortex. These data suggest that PCP causes cell death by apoptosis selectively in the cortex, but not in the striatum, following either in vivo treatment of perinatal rat pups or in vitro treatment of corticostriatal slices. Further, cortical apoptosis induced by PCP negatively impacts striatal synaptogenesis, a process important in normal neural development. This deficit is probably caused by a reduction in corticostriatal neurotransmission. It is possible that the dysregulation of striatal synaptogenesis contributes to the behavioral abnormalities observed following perinatal PCP administration in vivo.

On the selectivity of superoxide dismutase mimetics and its importance in pharmacological studies

The list of pathophysiological conditions associated with the overproduction of superoxide expands every day. Much of the knowledge compiled on the role of this radical in disease has been gathered using the native superoxide dismutase enzyme and, more recently, by the use of superoxide dismutase knockout models or transgenic models that overexpress the various isoforms of the enzyme. Although the native enzyme has shown promising anti-inflammatory properties in both preclinical and clinical studies, there were drawbacks and issues associated with its use as a therapeutic agent and pharmacological tool. Based on the concept that removal of superoxide modulates the course of inflammation, synthetic, low-molecular-weight mimetics of the superoxide dismutase enzymes that could overcome some of the limitations associated with the use of the native enzyme have been designed. In this review, we will discuss the advances made using various superoxide dismutase mimetics that led to the proposal that superoxide (and/or the product of its interaction with nitric oxide, peroxynitrite) is an important mediator of inflammation, and to the conclusion that superoxide dismutase mimetics can be utilized as therapeutic agents in diseases of various etiologies. The importance of the selectivity of such compounds in pharmacological studies will be discussed.

Stabilization of p53 is a novel mechanism for proapoptotic function of NF-kappaB

Both pro- and antiapoptotic activities of NF-kappaB transcription factor have been observed; however, less is known about the mechanism by which NF-kappaB induces apoptosis. To elucidate how NF-kappaB regulates proapoptotic signaling, we performed functional analyses using wild-type, ikk1(-/-), ikk2(-/-), rela(-/-) murine fibroblasts, MDAPanc-28/Puro, MDAPanc-28/IkappaBalphaM, and HCT116/p53(+/+) and HCT116/p53(-/-) cells with investigational anticancer agent doxycycline as a superoxide inducer for generating apoptotic stimulus. In this report, we show that doxycycline increased superoxide generation and subsequently activated NF-kappaB, which in turn up-regulated p53 expression and increased the stability and DNA binding activity of p53. Consequently, NF-kappaB-dependent p53 activity induced the expression of p53-regulated genes PUMA and p21(waf1) as well as apoptosis. Importantly, lack of RelA, IKK, and p53 as well as expression of a dominant negative IkappaBalpha (IkappaBalphaM) inhibited NF-kappaB-dependent p53 activation and apoptosis. The doxycycline-induced NF-kappaB activation was not inhibited in HCT116/p53(-/-) cells. Our results demonstrate that NF-kappaB plays an essential role in activation of wild-type p53 tumor suppressor to initiate proapoptotic signaling in response to overgeneration of superoxide. Thus, these findings reveal a mechanism of NF-kappaB-regulated proapoptotic signaling.

Activated protein C prevents neuronal apoptosis via protease activated receptors 1 and 3

Activated protein C (APC), a serine protease with anticoagulant and anti-inflammatory activities, exerts direct cytoprotective effects on endothelium via endothelial protein C receptor-dependent activation of protease activated receptor 1 (PAR1). Here, we report that APC protects mouse cortical neurons from two divergent inducers of apoptosis, N-methyl-D-aspartate (NMDA) and staurosporine. APC blocked several steps in NMDA-induced apoptosis downstream to nitric oxide, i.e., caspase-3 activation, nuclear translocation of apoptosis-inducing factor (AIF), and induction of p53, and prevented staurosporine-induced apoptosis by blocking caspase-8 activation upstream of caspase-3 activation and AIF nuclear translocation. Intracerebral APC infusion dose dependently reduced NMDA excitotoxicity in mice. By using different anti-PARs antibodies and mice with single PAR1, PAR3, or PAR4 deletion, we demonstrated that direct neuronal protective effects of APC in vitro and in vivo require PAR1 and PAR3. Thus, PAR1 and PAR3 mediate anti-apoptotic signaling by APC in neurons, which may suggest novel treatments for neurodegenerative disorders.

The epidermal platelet-activating factor receptor augments chemotherapy-induced apoptosis in human carcinoma cell lines

Most chemotherapeutic agents exert their cytotoxic effects in part through the induction of apoptosis. In addition, many chemotherapeutic agents are potent pro-oxidative stressors. Although the lipid mediator platelet-activating factor (PAF) is synthesized in response to oxidative stress, and many epidermal carcinomas express PAF receptors, it is not known whether PAF is involved in chemotherapeutic agent-induced apoptosis. These studies examined the role of the PAF system in chemotherapy-mediated cytotoxicity using model systems created by retroviral mediated transduction of the PAF receptor-negative human epidermal carcinoma cell line KB with the human PAF receptor (PAF-R) and ablation of the endogenous PAF-R in the carcinoma cell line HaCaT with a retroviral mediated inducible antisense PAF-R vector. The presence of the PAF-R in these models resulted in an augmentation of apoptosis induced by chemotherapeutic agents etoposide and mitomycin C but not by tumor necrosis factor-related apoptosis-inducing ligand or by C(2) ceramide. Oxidative stress and the transcription factor nuclear factor kappaB (NF-kappaB) are found to be involved in this augmentative effect because it was blocked by antioxidants and inhibition of the NF-kappaB pathway using a super-repressor form of inhibitor B. These studies provide evidence for a novel pathway whereby the epidermal PAF-R can augment chemotherapy-induced apoptotic effects through an NF-kappaB-dependent process.