DNA methylation maintains allele-specific KIR gene expression in human natural killer cells

Killer immunoglobulin-like receptors (KIR) bind self-major histocompatibility complex class I molecules, allowing natural killer (NK) cells to recognize aberrant cells that have down-regulated class I. NK cells express variable numbers and combinations of highly homologous clonally restricted KIR genes, but uniformly express KIR2DL4. We show that NK clones express both 2DL4 alleles and either one or both alleles of the clonally restricted KIR 3DL1 and 3DL2 genes. Despite allele-independent expression, 3DL1 alleles differed in the core promoter by only one or two nucleotides. Allele-specific 3DL1 gene expression correlated with promoter and 5' gene DNA hypomethylation in NK cells in vitro and in vivo. The DNA methylase inhibitor, 5-aza-2'-deoxycytidine, induced KIR DNA hypomethylation and heterogeneous expression of multiple KIR genes. Thus, NK cells use DNA methylation to maintain clonally restricted expression of highly homologous KIR genes and alleles.

Antidepressant mechanisms: functional and molecular correlates of excitatory amino acid neurotransmission

Specific targeting of the serotonergic and noradrenergic systems for the development of antidepressant compounds has resulted in drugs with more favourable side-effect profiles but essentially no greater efficacy than those compounds discovered more than 40 years ago. Alternative targets are now being considered in the hope that they will have a faster onset of action and be useful for those patients currently unresponsive to conventional treatments. Excitatory amino acid neurotransmission has been attributed various roles in both normal and abnormal brain function. The N-methyl-D-aspartate receptor in particular has long been postulated to play a role in the formation of memories. Major depressive disorder is characterised by alterations in cognitive function, as well as affect. Although there is evidence that early adverse events and stress can have a causal influence on depression, the underlying neurobiology of the disorder is poorly understood. This review will document current evidence for the involvement of excitatory amino acid neurotransmission in the pathophysiology of the affective disorders. The preclinical literature suggests that both electroconvulsive stimulation and antidepressant drugs can affect hippocampal long-term potentiation and the expression of excitatory amino acid receptor subtypes. Exposing animals to stress, including the kind that produces learned helplessness, can also affect synaptic plasticity in the hippocampus. There is clinical evidence that patients with chronic depression have structural brain abnormalities, including hippocampal atrophy, and a preliminary study has shown that an N-methyl-D-aspartate receptor antagonist may have antidepressant efficacy.

Regional osteoporosis in women who have a complete spinal cord injury

BACKGROUND

Regional bone loss in patients who have a spinal cord injury has been evaluated in males. In addition, there have been reports on groups of patients of both genders who had an acute or chronic complete or incomplete spinal cord injury. Regional bone loss in females who have a complete spinal cord injury has not been reported, to our knowledge.

METHODS

In a study of thirty-one women who had a chronic, complete spinal cord injury, we assessed bone mineral density in relation to age, weight, and time since the injury. The results were compared with the bone mineral density in seventeen healthy, able-bodied women who had been age-matched by group (thirty years old and less, thirty-one to fifty years old, and more than fifty years old). Dual-energy x-ray absorptiometry was used to measure the bone mineral density of the lumbar spine, hip, and knee; Z-scores for the hip and spine were calculated.

RESULTS

The mean bone mineral density in the spine in the youngest, middle, and oldest spinal-cord-injury groups was 98%, 108%, and 115% of the densities in the respective age-matched control groups (p < 0.0001), and the mean bone mineral density in the oldest spinal-cord-injury group was equal to that in the youngest control group. This gain in bone mineral density in the spine was reflected by the spine Z-scores, as the mean score in the oldest injured group averaged more than one standard deviation above both the norm and the mean score in the control group. The mean loss of bone mineral density in the knee in the youngest, middle, and oldest spinal-cord-injury groups was 38%, 41%, and 47% compared with the densities in the corresponding control age-groups (p < 0.0001). Furthermore, the oldest injured group had a mean reduction of knee bone mineral density of 54% compared with the youngest control group. The mean loss of bone mineral density in the hips of the injured patients was 18%, 25%, and 25% compared with the densities in the control subjects in the respective age-groups (p < 0.0001).

CONCLUSIONS

The bone mineral density in the spine either was maintained or was increased in relation to the time since the injury. This finding is unlike that seen in healthy women, in whom bone mineral density decreases with age. The bone mineral density in the hips of the injured patients initially decreased approximately 25%; thereafter, the rate of loss was similar to that in the control group. The bone mineral density in the knees of the injured patients rapidly decreased 40% to 45% and then further decreased only minimally.

Specific repression of beta-globin promoter activity by nuclear ferritin

Developmental hemoglobin switching involves sequential globin gene activations and repressions that are incompletely understood. Earlier observations, described herein, led us to hypothesize that nuclear ferritin is a repressor of the adult beta-globin gene in embryonic erythroid cells. Our data show that a ferritin-family protein in K562 cell nuclear extracts binds specifically to a highly conserved CAGTGC motif in the beta-globin promoter at -153 to -148 bp from the cap site, and mutation of the CAGTGC motif reduces binding 20-fold in competition gel-shift assays. Purified human ferritin that is enriched in ferritin-H chains also binds the CAGTGC promoter segment. Expression clones of ferritin-H markedly repress beta-globin promoter-driven reporter gene expression in cotransfected CV-1 cells in which the beta-promoter has been stimulated with the transcription activator erythroid Krüppel-like factor (EKLF). We have constructed chloramphenicol acetyltransferase reporter plasmids containing either a wild-type or mutant beta-globin promoter for the -150 CAGTGC motif and have compared the constructs for susceptibility to repression by ferritin-H in cotransfection assays. We find that stimulation by cotransfected EKLF is retained with the mutant promoter, whereas repression by ferritin-H is lost. Thus, mutation of the -150 CAGTGC motif not only markedly reduces in vitro binding of nuclear ferritin but also abrogates the ability of expressed ferritin-H to repress this promoter in our cell transfection assay, providing a strong link between DNA binding and function, and strong support for our proposal that nuclear ferritin-H is a repressor of the human beta-globin gene. Such a repressor could be helpful in treating sickle cell and other genetic diseases.

The genomic context of natural killer receptor extended gene families

The two sets of inhibitory and activating natural killer (NK) receptor genes belong either to the Ig or to the C-type lectin superfamilies. Both are extensive and diverse, comprising genes of varying degrees of relatedness, indicative of a process of iterative duplication. We have constructed gene maps to help understand how and when NK receptor genes developed and the nature of their polymorphism. A cluster of over 15 C-type lectin genes, the natural killer complex is located on human chromosome 12p13.1, syntenic with a region in mouse that borders multiple Ly49 loci. The equivalent locus in man is occupied by a single pseudogene, LY49L. The immunoglobulin superfamily of loci, the leukocyte receptor complex (LRC), on chromosome 19q13.4, contains many polymorphic killer cell immunoglobulin-like receptor (KIR) genes as well as multiple related sequences. These include immunoglobulin-like transcript (ILT) (or leukocyte immunoglobulin-like receptor genes), leukocyte-associated inhibitory receptor genes (LAIR), NKp46, Fc alphaR and the platelet glycoprotein receptor VI locus, which encodes a collagen-binding molecule. KIRs are expressed mostly on NK cells and some T cells. The other LRC loci are more widely expressed. Further centromeric of the LRC are sets of additional loci with weak sequence similarity to the KIRs, including the extensive CD66(CEA) and Siglec families. The LRC-syntenic region in mice contains no orthologues of KIRs. Some of the KIR genes are highly polymorphic in terms of sequence as well as for presence/absence of genes on different haplotypes. Some anchor loci, such as KIR2DL4, are present on most haplotypes. A few ILT loci, such as ILT5 and ILT8, are polymorphic, but only ILT6 exhibits presence/absence variation. This knowledge of the genomic organisation of the extensive NK superfamilies underpins efforts to understand the functions of the encoded NK receptor molecules. It leads to the conclusion that the functional homology of human KIR and mouse Ly49 genes arose by convergent evolution. NK receptor immunogenetics has interesting parallels with the major histocompatibility complex (MHC) in which some of the polymorphic genes are ligands for NK molecules. There are hints of an ancient genetic relationship between NK receptor genes and MHC-paralogous regions on chromosomes 1, 9 and 19. The picture that emerges from both complexes is of eternal evolutionary restlessness, presumably in response to resistance to disease.

How antidepressants work: new perspectives on the pathophysiology of depressive disorder

BACKGROUND

New research in animals is beginning to change radically our understanding of the biology of stress and the effects of antidepressant agents.

AIMS

To relate recent findings from the basic neurosciences to the pathophysiology of depressive disorder.

METHOD

Drawing together findings from molecular and physiological studies in rats, social studies in primates and neuropsychological studies in humans, we review the neurotrophic and neuroplastic effects of antidepressants and stress.

RESULTS

Stress and antidepressants have reciprocal actions on neuronal growth and vulnerability (mediated by the expression of neurotrophins) and synaptic plasticity (mediated by excitatory amino acid neurotransmission) in the hippocampus and other brain structures. Stressors have the capacity to progressively disrupt both the activities of individual cells and the operating characteristics of networks of neurons throughout the life cycle, while antidepressant treatments act to reverse such injurious effects.

CONCLUSIONS

We propose a central role for the regulation of synaptic connectivity in the pathophysiology of depressive disorder.

Repeated electroconvulsive stimulation, but not antidepressant drugs, induces mossy fibre sprouting in the rat hippocampus

Electroconvulsive stimulation (ECS) has been shown recently to induce axonal sprouting of granule cells in the rodent hippocampus. This may relate to the clinical efficacy of electroconvulsive therapy (ECT) in humans. We compared the effects of three different clinically effective antidepressant treatments on mossy fibre sprouting in the rat dentate gyrus using Timm's histochemistry: (1) repeated spaced ECS; (2) daily administration for 4 weeks of the serotonin re-uptake inhibitor fluoxetine (1 mg/kg); and (3) daily administration for 4 weeks of the noradrenaline re-uptake inhibitor desipramine (5 mg/kg). The effect of subconvulsive electrical stimulation was also examined. Repeated ECS-induced sprouting while subconvulsive stimulation (which is ineffective clinically) did not. The two well-established chemical antidepressant therapies were also ineffective, indicating that induction of mossy fibre sprouting is not a common property of effective antidepressant agents. It is possible that the ability to induce sprouting might relate to the superior efficacy of ECT when compared to chemical antidepressants in clinical practice. Alternatively, it may contribute to the transient cognitive impairment that accompanies ECS in humans and other species.

Liver transplantation at the University of Pennsylvania and the Children's Hospital of Philadelphia

The liver transplant program at the University of Pennsylvania and the Children's Hospital of Philadelphia experienced healthy growth in its clinical activity in the past 5 years. Patterns of referral and patient evaluation were established, care of patients while waiting on the list or being followed after transplantation was streamlined. We are now achieving excellent outcomes while transplanting relatively sicker patients. Innovative surgical procedures are implemented resulting in more efficient utilization of cadaveric and living-donor liver grafts. The protocols that are used for patient care are more standard, yet flexible and accommodate recent advancement in transplantation immunobiology. This progress of the clinical program was enhanced by careful preservation of the academic mission of the institution, which encourages the liver transplant faculty to be involved in NIH-supported clinical and basic science research.

Chronic infection with hepatitis C virus in patients with elevated or persistently normal serum alanine aminotransferase levels: comparison of hepatic histology and response to interferon therapy

Ninety-five patients with chronic hepatitis C virus (HCV) infection, 35 with persistently normal serum alanine aminotransferase (ALT) levels, were randomized to treatment with daily interferon (IFN) for 3 months, followed by IFN 3 times weekly (TIW) for 12 months (group A) or TIW for 18 months (group B). Patients with elevated versus normal ALT levels had similar demographic and virologic characteristics but significantly (P<.05) more advanced liver histology (bridging fibrosis and cirrhosis, 37.9% vs. 11.4%). After 3 months of treatment, 38.3% of patients in group A were HCV RNA negative versus 18.8% in group B (P<.05). When the IFN dose was reduced from daily to TIW in group A, the percentage of patients who remained HCV RNA negative declined; sustained virologic response was similar in both groups (10.6% vs. 8.3%). Response to treatment was similar in patients with elevated or normal ALT levels. Persons with chronic HCV infection and persistently normal serum ALT levels have milder liver disease than, and respond to IFN therapy similarly to, persons with elevated ALT levels.

Tansley Review No. 115: Impact of ozone on the reproductive development of plants

Sexual reproductive development is a crucial stage in the life cycle of higher plants as any impairment of the processes involved might have significant implications for the productivity of crop plants and the survival of native species. There is considerable evidence that exposure to ozone, even at current ambient levels in many industrialized countries, reduces grain and fruit yields and adversely affects yield quality. It is also well established that sensitivity to ozone may differ not only between species, but also between cultivars and populations of individual species, and that the impact of exposure is highly dependent on ozone concentration and the duration and timing of exposure. However, few studies have attempted to distinguish between the direct effects of air pollutants on reproductive development, and indirect effects mediated by injury to the vegetative organs and associated changes in the supply of assimilates and other essential resources to support reproductive growth, or the levels of endogenous growth regulators. This review considers the impact of ozone on the reproductive biology of agricultural and native species, and examines its direct effects on specific reproductive processes. The extent to which compensatory responses redress the adverse effects of exposure is also explored, with particular reference to recent studies of Brassica napus (oilseed rape), Brassica campestris (Wisconsin Fast Plants), Plantago major (greater plantain) and Triticum aestivum (wheat). contents Summary 421 I. introduction 421 II. effects of ozone on reproduction 423 III. influence of reproductive habit and implications for field-grown plants 438 IV. conclusions and future research 441 Acknowledgements 442 References 442.

The N-methyl-D-aspartate receptor, synaptic plasticity, and depressive disorder. A critical review

The roles of the N-methyl-D-aspartate (NMDA) receptor and NMDA receptor-mediated synaptic plasticity are reviewed in the context of depressive disorder and its treatment. The mode of action of antidepressant treatment is poorly understood. Animal studies have suggested that many antidepressant drugs show activity at the NMDA receptor and that NMDA antagonists have antidepressant profiles in preclinical models of depression. A post-mortem study in humans has suggested that certain binding characteristics of the NMDA receptor may be down-regulated in the brains of suicide victims. "Depressogenic" stressors in animals and chronic administration of antidepressant agents perturb NMDA-dependent synaptic plasticity in the hippocampus.

The effect of pulsed electromagnetic fields on osteoporosis at the knee in individuals with spinal cord injury

The purpose of this study was to determine the effects of pulsed electromagnetic fields on osteoporotic bone at the knee in individuals with chronic spinal injury. The study consisted of 6 males with complete spinal cord injury at a minimum of 2 years duration. Bone mineral density (BMD) was obtained at both knees at initiation, 3 months, 6 months, and 12 months using dual energy X-ray absorptiometry. In each case, 1 knee was stimulated using The Bone Growth Stimulator Model 3005 from American Medical Electronics, Incorporated and the opposite knee served as the control. Stimulation ceased at 6 months. At 3 months BMD increased in the stimulated knees 5.1% and declined in the control knees 6.6% (p < .05 and p < .02, respectively). By 6 months the BMD returned to near baseline values and at 12 months both knees had lost bone at a similar rate to 2.4% below baseline for the stimulated knee and 3.6% below baseline for the control. There were larger effects closer to the site of stimulation. While the stimulation appeared useful in retarding osteoporosis, the unexpected exaggerated decline in the control knees and reversal at 6 months suggests underlying mechanisms are more complex than originally anticipated. The authors believe a local as well as a systemic response was created.

Dietary choline restriction causes complex I dysfunction and increased H(2)O(2) generation in liver mitochondria

Removal of choline from the diet results in accumulation of triglycerides in the liver, and chronic dietary deficiency produces a non-genotoxic model of hepatocellular carcinoma. An early event in choline deficiency is the appearance of oxidized lipid, DNA and protein, suggesting that increased oxidative stress may facilitate neoplasia in the choline deficient liver. In this study, we find that mitochondria isolated from rats fed a choline-deficient, L-amino acid defined diet (CDAA) demonstrate impaired respiratory function, particularly in regard to complex I-linked (NADH-dependent) respiration. This impairment in mitochondrial electron transport occurs coincidentally with alterations in phosphatidylcholine metabolism as indicated by an increased ratio of long-chain to short-chain mitochondrial phosphatidylcholine. Moreover, hydrogen peroxide (H(2)O(2)) generation is significantly increased in mitochondria isolated from CDAA rats compared with mitochondrial from normal rats, and the NADH-specific yield of H(2)O(2) is increased by at least 2.5-fold. These findings suggest an explanation for the rapid onset of oxidative stress and energy compromise in the choline deficiency model of hepatocellular carcinoma and indicate that dietary choline withdrawal may be a useful paradigm for the study of mitochondrial pathophysiology in carcinogenesis.

A broad spectrum secreted chemokine binding protein encoded by a herpesvirus

Chemokines are a family of small proteins that interact with seven-transmembrane domain receptors and modulate the migration of immune cells into sites of inflammation and infection. The murine gammaherpesvirus 68 M3 gene encodes a secreted 44-kD protein with no sequence similarity to known chemokine receptors. We show that M3 binds a broad range of chemokines, including CC, CXC, C, and CX(3)C chemokines, but does not bind human B cell-specific nor mouse neutrophil-specific CXC chemokines. This herpesvirus chemokine binding protein (hvCKBP) blocks the interaction of chemokines with high-affinity cellular receptors and inhibits chemokine-induced elevation of intracellular calcium levels. hvCKBP is the first soluble chemokine receptor identified in herpesviruses; it represents a novel protein structure with the ability to bind all subfamilies of chemokines in solution and has potential therapeutic applications.

Repeated ECS and fluoxetine administration have equivalent effects on hippocampal synaptic plasticity

RATIONALE

Recent studies have implicated intracellular transduction pathways and neurotrophic factors in the action of antidepressants. Adaptation in these pathways may ultimately affect electrophysiological and morphological properties of neurones. We have previously shown that repeated electroconvulsive stimulation, a safe and effective antidepressant treatment, has profound effects on hippocampal synaptic connectivity and plasticity in the rat. Here, we investigated whether these electrophysiological properties were shared by the chemical antidepressant, fluoxetine.

OBJECTIVES

To compare the electrophysiological and cognitive effects of two very different antidepressant treatments: repeated electroconvulsive stimulation (rECS); and chronic administration of the serotonin specific re-uptake inhibitor (SSRI), fluoxetine.

METHODS

Rats were exposed to either rECS or daily fluoxetine administration for 15 days. The animals were then anaesthetised and dentate field excitatory post-synaptic potential (fEPSP) characteristics were measured before and after the induction of long-term potentiation (LTP) by high frequency perforant path stimulation. In a separate experiment, the effects of rECS and chronic fluoxetine administration on acquisition and retention of a spatial learning task in the Morris watermaze were determined.

RESULTS

Chronic fluoxetine administration and rECS produced equivalent increases in dentate fEPSP compared to respective control groups. LTP induction was attenuated in both groups. Spatial learning was, in contrast, unaffected by fluoxetine treatment but significantly impaired following rECS.

CONCLUSIONS

Given that fluoxetine and rECS share antidepressant properties, but differ in their effects on learning and memory, we propose that the common effects on dentate connectivity and synaptic plasticity described here are more likely to relate to affective rather than cognitive function. This result is consistent with other experiments showing that a reduction in dentate connectivity correlates with stress susceptibility in animals.

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

Reversible protein phosphorylation regulates a wide array of cellular functions. Cells respond to cytokines and various stressors via phosphorylation and thus activation of one or more of the mitogen-activated protein kinase (MAPK) pathways. Involvement of these signal transduction pathways has been implicated in numerous pathologies, including inflammation. Using a primary glia cell culture, we show here that the antioxidant N-acetylcysteine (NAC) and the nitrone-based free radical trap, alpha-phenyl-N-tert-butyl nitrone (PBN), reduce total basal protein phosphorylation in a concentration-dependent manner as assessed by phosphotyrosine analysis and by [gamma-32P]ATP transfer radioassay. In addition we show that NAC inhibits H2O2-induced phosphatase inactivation in glia cell lysate. The PBN- and NAC-induced reduction in protein phosphorylation is accompanied by an increase in phosphatase activity, suggesting that PBN and NAC reduce protein phosphorylation by globally augmenting oxidant-sensitive phosphatase activities. These results partly explain why certain antioxidants also possess anti-inflammatory actions.

p38 kinase is activated in the Alzheimer's disease brain

The p38 mitogen-activated protein kinase is a stress-activated enzyme responsible for transducing inflammatory signals and initiating apoptosis. In the Alzheimer's disease (AD) brain, increased levels of phosphorylated (active) p38 were detected relative to age-matched normal brain. Intense phospho-p38 immunoreactivity was associated with neuritic plaques, neuropil threads, and neurofibrillary tangle-bearing neurons. The antibody against phosphorylated p38 recognized many of the same structures as an antibody against aberrantly phosphorylated, paired helical filament (PHF) tau, although PHF-positive tau did not cross-react with the phospho-p38 antibody. These findings suggest a neuroinflammatory mechanism in the AD brain, in which aberrant protein phosphorylation affects signal transduction elements, including the p38 kinase cascade, as well as cytoskeletal components.

Phenyl-N-tert-butylnitrone demonstrates broad-spectrum inhibition of apoptosis-associated gene expression in endotoxin-treated rats

Systemic exposure to gram-negative bacterial substances such as lipopolysaccharide (LPS, or endotoxin) induces an uncontrolled, massive inflammatory reaction which culminates in multiple system organ failure and death. Septic shock often does not respond to corticosteroids; however, certain low-molecular-weight antioxidant compounds have been discovered to possess potent anti-inflammatory action, and some of these novel compounds can rescue animals from experimentally induced septic shock. Phenyl-N-tert-butylnitrone (PBN) is the archetype of the nitrone class of antioxidants which we have previously shown to suppress LPS-induced cytokine biosynthesis in vivo. Using a multiprobe ribonuclease protection assay, we now demonstrate the ability of PBN to suppress proapoptotic gene expression in the LPS-induced model of endotoxic shock. The broad-spectrum gene-suppressive affects of PBN are discussed in the context of inflammatory signal transduction and models are proposed to explain why certain antioxidants may also possess anti-inflammatory and antiapoptotic properties.

Redox-sensitive protein phosphatase activity regulates the phosphorylation state of p38 protein kinase in primary astrocyte culture

Reactive oxygen species (ROS) have been implicated as second messengers that activate protein kinase cascades, although the means by which ROS regulate signal transduction remains unclear. In the present study, we show that interleukin 1beta (IL1beta), H2O2, and sorbitol-induced hyperosmolarity mediate a 5- to 10-fold increase in phosphorylation (activation) of the p38 protein kinase in rat primary glial cells as measured by analyses of Western blots using an antibody directed against the dually phosphorylated (active) p38. Additionally, IL1beta was found to elicit H2O2 synthesis in these cells. Concurrent with p38 phosphorylation, all three stimulation paradigms caused an inhibition of protein phosphatase activity. Phenyl-tert-butyl nitrone (PBN), a nitrone-based free radical trap and N-acetyl-cysteine (NAC), a thiol reducing agent, were examined for their effects on the phosphorylation of p38 as well as phosphatase activity. Pretreatment of cells with either PBN or NAC at 1.0 mM suppressed IL1beta H2O2, and sorbitol-mediated activation of p38 and significantly increased phosphatase activity. These data suggest that ROS, particularly H2O2, are used as second messenger substances that activate p38 in part via the transient inactivation of regulatory protein phosphatases.

Expression of cytokines and activation of transcription factors in lipopolysaccharide-administered rats and their inhibition by phenyl N-tert-butylnitrone (PBN)

The spin-trapping compound phenyl N-tert-butylnitrone (PBN) affords protection from the lethality of septic shock in rodents. Previous studies have shown that PBN elicits its protection by inhibiting inducible nitric oxide synthase (iNOS) induction. In the present study, using the lipopolysaccharide (LPS) rat septic shock model, we determined the expression of various cytokine genes (tumor necrosis factor (TNF)-alpha, TNF-beta, interferon (IFN)-gamma, interleukin (IL)-1alpha, IL-1beta, IL-2, IL-3, IL-4, IL-5, IL-6, and IL-10) and the activation of transcription factors nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1) in the liver tissue, 30 min and 3 h after LPS administration. The effects of PBN preadministration on the production levels were also investigated. The results show that LPS (4 mg/kg, ip) induced the production of the cytokine genes and increased the nuclear protein level of NF-kappaB within 30 min after LPS administration. Preadministration of PBN (150 mg/kg, ip) significantly down-regulated the production of cytokine genes (TNF-alpha by 94%, IL-1 by 63%, and IL-1 by 70%) and reduced the nuclear protein level of NF-kappaB by 75% and AP-1 by 72% at 3 h after LPS injection. These results demonstrate that PBN, in addition to its iNOS induction inhibition, also has multiple anti-inflammatory effects in septic shock, via modulation of the production of the key inflammatory mediators.

Interaction of alpha-phenyl-N-tert-butyl nitrone and alternative electron acceptors with complex I indicates a substrate reduction site upstream from the rotenone binding site

Mitochondrial complexes I, II, and III were studied in isolated brain mitochondrial preparations with the goal of determining their relative abilities to reduce O2 to hydrogen peroxide (H2O2) or to reduce the alternative electron acceptors nitroblue tetrazolium (NBT) and diphenyliodonium (DPI). Complex I and II stimulation caused H2O2 formation and reduced NBT and DPI as indicated by dichlorodihydrofluorescein oxidation, nitroformazan precipitation, and DPI-mediated enzyme inactivation. The O2 consumption rate was more rapid under complex II (succinate) stimulation than under complex I (NADH) stimulation. In contrast, H2O2 generation and NBT and DPI reduction kinetics were favored by NADH addition but were virtually unobservable during succinate-linked respiration. NADH oxidation was strongly suppressed by rotenone, but NADH-coupled H2O2 flux was accelerated by rotenone. Alpha-phenyl-N-tert-butyl nitrone (PBN), a compound documented to inhibit oxidative stress in models of stroke, sepsis, and parkinsonism, partially inhibited complex I-stimulated H2O2 flux and NBT reduction and also protected complex I from DPI-mediated inactivation while trapping the phenyl radical product of DPI reduction. The results suggest that complex I may be the principal source of brain mitochondrial H2O2 synthesis, possessing an "electron leak" site upstream from the rotenone binding site (i.e., on the NADH side of the enzyme). The inhibition of H2O2 production by PBN suggests a novel explanation for the broad-spectrum antioxidant and antiinflammatory activity of this nitrone spin trap.

Inhibition by phenyl N-tert-butyl nitrone of early phase carcinogenesis in the livers of rats fed a choline-deficient, L-amino acid-defined diet

Male Wistar rats were fed a choline-deficient, L-amino acid-defined (CDAA) diet alone or in combination with a nitrone-based free radical trapping agent, phenyl N-tert-butyl nitrone (PBN) in the drinking water at the concentrations of 0.013, 0.065, and 0.130% for 12 weeks. PBN inhibited the changes that are normally induced in the livers of rats by the CDAA diet feeding, i.e., development of putative preneoplastic lesions, proliferation of connective tissue, reduction of glutathione S-transferase activity, formation of 8-hydroxyguanine in DNA, and an increase in inducible cyclo-oxygenase (COX2) activity. PBN, however, did not prevent the increases in the COX2 mRNA or protein levels brought on by the CDAA diet These results indicate that the loss of glutathione S-transferase activity and COX2 induction may play significant roles in rat liver carcinogenesis by the CDAA diet and that PBN prevents neoplasia not only by its radical scavenging activity but also by inhibiting COX2 activity at the catalytic level.

Transfer of human serum IgG to nonobese diabetic Igmu null mice reveals a role for autoantibodies in the loss of secretory function of exocrine tissues in Sjögren's syndrome

The NOD (nonobese diabetic) mouse has been studied as an animal model for autoimmune insulin-dependent diabetes and Sjögren's syndrome. NOD.Igmu null mice, which lack functional B lymphocytes, develop progressive histopathologic lesions of the submandibular and lachrymal glands similar to NOD mice, but in the absence of autoimmune insulitis and diabetes. Despite the focal appearance of T cells in salivary and lachrymal tissues, NOD.Igmu null mice fail to lose secretory function as determined by stimulation of the muscarinic/cholinergic receptor by the agonist pilocarpine, suggesting a role for B cell autoantibodies in mediating exocrine dryness. Infusion of purified serum IgG or F(ab')2 fragments from parental NOD mice or human primary Sjögren's syndrome patients, but not serum IgG from healthy controls, alters stimulated saliva production, an observation consistent with antibody binding to neural receptors. Furthermore, human patient IgG fractions competitively inhibited the binding of the muscarinic receptor agonist, [3H]quinuclidinyl benzilate, to salivary gland membranes. This autoantibody activity is lost after preadsorption with intact salivary cells. These findings indicate that autoantibodies play an important part in the functional impairment of secretory processes seen in connection with the autoimmune exocrinopathy of Sjögren's syndrome.