The role of oxidative stress during inflammatory processes

Abstract The production of various reactive oxidant species in excess of endogenous antioxidant defense mechanisms promotes the development of a state of oxidative stress, with significant biological consequences. In recent years, evidence has emerged that oxidative stress plays a crucial role in the development and perpetuation of inflammation, and thus contributes to the pathophysiology of a number of debilitating illnesses, such as cardiovascular diseases, diabetes, cancer, or neurodegenerative processes. Oxidants affect all stages of the inflammatory response, including the release by damaged tissues of molecules acting as endogenous danger signals, their sensing by innate immune receptors from the Toll-like (TLRs) and the NOD-like (NLRs) families, and the activation of signaling pathways initiating the adaptive cellular response to such signals. In this article, after summarizing the basic aspects of redox biology and inflammation, we review in detail the current knowledge on the fundamental connections between oxidative stress and inflammatory processes, with a special emphasis on the danger molecule high-mobility group box-1, the TLRs, the NLRP-3 receptor, and the inflammasome, as well as the transcription factor nuclear factor-κB.

Testosterone and oxidative stress: the oxidation handicap hypothesis

Secondary sexual traits (SST) are usually thought to have evolved as honest signals of individual quality during mate choice. Honesty of SST is guaranteed by the cost of producing/maintaining them. In males, the expression of many SST is testosterone-dependent. The immunocompetence handicap hypothesis has been proposed as a possible mechanism ensuring honesty of SST on the basis that testosterone, in addition to its effect on sexual signals, also has an immunosuppressive effect. The immunocompetence handicap hypothesis has received mixed support. However, the cost of testosterone-based signalling is not limited to immunosuppression and might involve other physiological functions such as the antioxidant machinery. Here, we tested the hypothesis that testosterone depresses resistance to oxidative stress in a species with a testosterone-dependent sexual signal, the zebra finch. Male zebra finches received subcutaneous implants filled with flutamide (an anti-androgen) or testosterone, or kept empty (control). In agreement with the prediction, we found that red blood cell resistance to a free radical attack was the highest in males implanted with flutamide and the lowest in males implanted with testosterone. We also found that cell-mediated immune response was depressed in testosterone-treated birds, supporting the immunocompetence handicap hypothesis. The recent finding that red blood cell resistance to free radicals is negatively associated with mortality in this species suggests that benefits of sexual signalling might trade against the costs derived from oxidation.

Immune cells: free radicals and antioxidants in sepsis

The excessive production of reactive oxygen species (ROS), associated with inflammation, leads to a condition of oxidative stress. Oxidative stress is a major contributing factor to the high mortality rates associated with several diseases such as endotoxic shock. This condition can be controlled to a certain degree by antioxidant therapies. Immune cells use ROS in order to support their functions and therefore need adequate levels of antioxidant defenses in order to avoid the harmful effect of an excessive production of ROS. This review discusses the toxic effects of endotoxin, paying particular attention to immune function. It continues by analyzing the mechanism to which specific cells of the immune system recognize endotoxin, and the resulting pathways leading to nuclear factor-kappaB activation and proinflammatory gene transcription. We also focus on the involvement of reactive oxygen and nitric oxide (NO) and the protective role of antioxidants. The potential clinical use of antioxidants in the treatment of sepsis and the effects on the redox state of the immune cells are discussed.

Role of cytochrome P4502E1-dependent formation of hydroxyethyl free radical in the development of liver damage in rats intragastrically fed with ethanol

We have previously shown that the treatment with diallyl sulfide (DAS) and phenylethyl isothiocyanate (PIC) of rats receiving ethanol in the alcohol tube-feeding model effectively suppressed the induction of cytochrome P4502E1 (CYP2E1) by ethanol. Here we report that rat treatment with DAS and PIC significantly decreased the trapping of hydroxyethyl free radicals in liver microsomes incubated in vitro with ethanol. Furthermore, these inhibitors also greatly reduced the production of hydroxyethyl radical-derived epitopes detectable in vivo in the liver of ethanol-fed rats. The action of DAS and PIC on the formation of hydroxyethyl radicals paralleled their inhibitory effect on lipid peroxidation as monitored using, respectively, liver malonildialdehyde (MDA) and plasma lipid hydroperoxide levels as well as by the titers of antibodies versus MDA adducts to proteins. Thus, these results indicated a link between the induction of CYP2E1 by ethanol, the formation of hydroxyethyl radicals and the stimulation of lipid peroxidation. The pathological scores in the livers of rats fed with ethanol plus or minus DAS and PIC also correlated with levels of hydroxyethyl radical-derived epitopes. Rats fed intragastrically with ethanol developed antibodies and the formation of these antibodies was greatly reduced by DAS and PIC. Taken together these results suggest that CYP2E1 plays an important role in the generation of hydroxyethyl radicals during chronic alcohol feeding and that ethanol-derived free radicals might play a role in the onset of liver injury in this model of alcohol administration.

Comparison of the roles of reactive oxygen and nitrogen intermediates in the host response to Mycobacterium tuberculosis using transgenic mice

OBJECTIVE

To study the role of reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) in host response to Mycobacterium tuberculosis.

DESIGN

M. tuberculosis infection (i.v.) was compared in B6 control and two strains of knockout (KO) mice. X-CGD mice with a nonfunctional allele for the gp91phox subunit of the phagocyte oxidase cytochrome b are unable to produce ROI whereas iNOS KO mice lack a functional inducible nitric oxide synthase (iNOS) gene and fail to make RNI.

RESULTS

M. tuberculosis growth was markedly enhanced in the lungs of X-CGD mice compared to B6 mice, but was controlled in the spleen and liver. In iNOS KO mice, M. tuberculosis growth was exacerbated in the spleen, but was unremarkable in the lungs compared to B6 mice until later (Day 60) in the infection. In vitro, X-CGD alveolar and peritoneal macrophages (M phi) produced no ROI, but did produce RNI and inhibited growth of M. tuberculosis when activated with interferon gamma. iNOS KO M phi produced ROI, but failed to produce RNI and could not cope with M. tuberculosis in vitro when activated. The inhibition of M. tuberculosis growth observed in activated B6 and X-CGD M phi) was reversed in the presence of aminoguanidine.

CONCLUSION

These KO mouse strains demonstrate the relative potent effects of ROI and RNI in resistance to M. tuberculosis and should prove useful for the study of regulatory and compensatory mechanisms of immunity.

Extensive peroxynitrite activity during progressive stages of central nervous system inflammation

Nitric oxide (NO) production has been associated with disease activity in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). This free radical can be transformed by superoxide to peroxynitrite, an extremely toxic oxidant which causes lipid peroxidation. In addition, peroxynitrite nitrates tyrosine residues, resulting in nitrotyrosine, which can be identified immunohistochemically. The results of this study indicate that peroxynitrite is formed very early during EAE development, correlating with clinical disease activity. Nitrotyrosine-positive cells display a widespread distribution in brain and spinal cord during severe disease and are associated with both perivascular infiltrates and parenchymal sites. Double-staining procedures demonstrated that a subpopulation of CD11b-positive cells (macrophages/microglia) reacted with nitrotyrosine antibodies. Immunostaining for inducible NO synthase demonstrated a similar distribution as nitrotyrosine staining. These experiments indicate that peroxynitrite is formed during progressive stages of disease activity.

Free radical mediated peroxidative damage in systemic lupus erythematosus

Free radicals and damage caused by these molecular species are implicated in the pathogenesis of a variety of diseases, including autoimmune. Here we have examined oxidative damage, SOD activity and autoantibodies against SOD in systemic lupus erythematosus (SLE), a multifactorial disease with autoantibody production as an universal feature. We found significantly increased amounts of conjugated dienes in the SLE patients compared to normals (mean value of 0.917 vs 0.627, p = 0.0001) and MDA formation (6.96 vs 4.17 nmoles/microl, p = 0.0006) as well as decreased SOD activity. In addition, we found autoantibodies binding SOD by both ELISA and immunoblot. The presence of anti-SOD antibodies was associated with increased free radical damage in SLE patients. Heat inactivated anti-SOD autoantibodies were able to inhibit the activity of the enzyme. We propose that the inhibition of SOD by autoantibodies is, in part, responsible for the increased free radical damage seen in the disease.

Heterogeneity of macrophage activation in fish

In this review, we focus on four different activation states of fish macrophages. In vitro, stimulation with microbial ligands induces the development of innate activated macrophages whereas classically activated macrophages can be induced by stimulation with LPS in combination with (recombinant) IFNγ. Both types of macrophages show elevated phagocytic activity, expression of pro-inflammatory cytokine genes and radical production. Alternatively activated macrophages require the cytokines IL-4/IL-13 for induction of, among others, arginase activity. Until in vitro studies identify the effects of putative IL-4 and IL-13 homologues on fish macrophages, arginase enzyme activity remains the most reliable marker for the presence of alternatively activated macrophages in fish. The best evidence for the existence of regulatory macrophages, associated with the presence of IL-10, comes from in vivo studies, for example during parasitic infections of carp. Altogether, differentially activated macrophages in fish largely resemble the phenotypes of mammalian macrophages. However, the presence of fish-specific ligand recognition by TLRs and of duplicated genes coding for proteins with particular activities, poses additional challenges for the characterization of phenotype-specific gene signatures and cell surface markers.

Critical advances in septicemia and septic shock

Recent advances suggest that toll-like receptors, various cytokines, cicosanoids, free radicals and macrophage migration inhibitory factor (MIF) play an important role in the pathobiology of septicemia and septic shock. Anti-MIF antibodies can decrease the plasma concentrations of tumor necrosis factor (TNF), lower bacterial circulating counts and enhance survival of animals with septicemia and septic shock. Monocyte expression of MHC-class II antigens, neutrophil expression of the integrin CD11b/CD18 and neutrophil activation can be related to the development of, and/or recovery from, post-operative sepsis. Thus, biological variations in the response of an individual to a given stimulus, appears to determine his/her ability or inability to develop and also recover from sepsis and septic shock. This suggests that it may be possible to predict the development of septicemia and septic shock in a given individual and take appropriate action both to prevent and treat them adequately.

T-cell-based immunity counteracts the potential toxicity of glutamate in the central nervous system

Injuries to the central nervous system (CNS) evoke self-destructive processes, which eventually lead to a much greater loss of tissue than that caused by the trauma itself. The agents of self-destruction include physiological compounds, such as glutamate, which are essential for the proper functioning of the CNS, but become cytotoxic when their normal concentrations are exceeded. The CNS is equipped with buffering mechanisms that are specific for each compound. Here we show, using Balb/c mice (a strain resistant to induction of experimental autoimmune encephalomyelitis), that after intravitreal injection of any concentration of glutamate (a neurotransmitter that becomes toxic when in excess) or ammonium-ferrous sulfate hexahydrate (which increases the formation of toxic oxygen species), the loss of retinal ganglion cells in mice devoid of mature T cells (nude mice) is significantly greater than in matched wild-type controls. We further show that this outcome can be partially reversed by supplying the T cell-defective mice with splenocytes derived from the wild-type mice. The results suggest that potentially toxic physiological compounds, when present in excessive amounts, can recruit and activate a T-cell-dependent self-protective immune mechanism. This may represent a prototype mechanism for the physiological regulation of potentially destructive CNS events by T-cell-mediated immune activity, when the local buffering mechanisms cannot adequately cope with them.

Adverse effects of neutrophils on the lung

Studies of both emphysema and adult respiratory distress syndrome (ARDS) support the premise that lung injury is due to unregulated host defense mechanisms. A major mediator of host defense and injury is the neutrophil, which is relatively incapable of regulating its own function. Accordingly, defects in regulatory mechanisms allow neutrophils to damage the lungs. Emphysema serves as a prime example of this link between host defense and injury. Hereditary emphysema is caused by a deficiency in alpha 1-antitrypsin (alpha 1-AT), a protease inhibitor. The decreased levels of this enzyme in affected individuals result in inadequate protection against neutrophil elastase and other proteolytic enzymes, leading to lung damage. Patients with acquired emphysema, associated with cigarette smoking, have normal levels of alpha 1-AT in their lungs. However, the alpha 1-AT in these patients has a reduced ability to associate with and inhibit the action of neutrophil elastase. Thus, both types of emphysema involve an alteration in the balance between proteases and antiproteases. The lung damage observed in patients with ARDS also appears to involve neutrophils, but in this case elastase may not be the culprit. In these patients, neutrophil elastase appears to be inactivated by high levels of alpha 1-AT, thus preventing excess protease action. It is hoped that a more complete understanding of the mechanisms involved in host defense and injury will enable the development of specific therapeutic interventions, such as the alpha 1-AT replacement therapy that is being used to treat patients with hereditary emphysema.

Free radical release and HSP70 expression in two human immune-relevant cell lines after exposure to 1800 MHz radiofrequency radiation

The goal of this study was to investigate whether radiofrequency (RF) electromagnetic-field (EMF) exposure at 1800 MHz causes production of free radicals and/or expression of heat-shock proteins (HSP70) in human immune-relevant cell systems. Human Mono Mac 6 and K562 cells were used to examine free radical release after exposure to incubator control, sham, RF EMFs, PMA, LPS, heat (40 degrees C) or co-exposure conditions. Several signals were used: continuous-wave, several typical modulations of the Global System for Mobile Communications (GSM): GSM-non DTX (speaking only), GSM-DTX (hearing only), GSM-Talk (34% speaking and 66% hearing) at specific absorption rates (SARs) of 0.5, 1.0, 1.5 and 2.0 W/kg. Heat and PMA treatment induced a significant increase in superoxide radical anions and in ROS production in the Mono Mac 6 cells when compared to sham and/or incubator conditions. No significant differences in free radical production were detected after RF EMF exposure or in the respective controls, and no additional effects on superoxide radical anion production were detected after co-exposure to RF EMFs+PMA or RF EMFs+LPS. The GSM-DTX signal at 2 W/kg produced a significant difference in free radical production when the data were compared to sham because of the decreasing sham value. This difference disappeared when data were compared to the incubator controls. To determine the involvement of heat-shock proteins as a possible inhibitor of free radical production, we investigated the HSP70 expression level after different RF EMF exposures; no significant effects were detected.

The neuregulin GGF2 attenuates free radical release from activated microglial cells

The neuregulin glial growth factor 2 (GGF2) is a neural growth factor that is best known for its ability to promote the survival and proliferation of oligodendrocytes and Schwann cells. While it has been shown in recent years that GGF2 is effective in the treatment of autoimmune models of brain injury, it is not known if the beneficial effects of GGF2 are based in part on modulation of brain inflammation. In this report, we document the anti-inflammatory effects of recombinant human GGF2 (rhGGF2) on microglial free radical production in vitro. The presence of the neuregulin receptors ErbB2, 3, and 4 was confirmed in N9 microglial cells by Western blot analysis. Pretreatment of N9 cells with 10-100 ng/ml rhGGF2 24 h before either phorbol 12-myristate 3-acetate (PMA) or interferon gamma (IFNgamma) caused dose-dependent decreases in oxidative burst activity and nitrite release, respectively, with 50 and 100 ng/ml causing significant effects. When cells were co-treated with increasing doses of rhGGF2 and PMA or IFNgamma, only concentrations of 50 ng/ml, but not 10 or 100 ng/ml, were able to decrease oxidative burst activity and nitrite release. Finally, when microglial cell viability following treatment of cells with IFNgamma with or without rhGGF2 was evaluated, it was observed that 50 and 100 ng/ml rhGGF2 conferred significant protection against IFNgamma-induced cell death in microglial cells. Overall, these results indicate that the neuregulin rhGGF2 may have anti-inflammatory and antioxidant properties in the brain, and may also provide trophic support for brain-resident microglial cells.

Hemorrhagic-ischemic cerebral injury in the preterm infant: current concepts

PV-IVH and adjacent white matter injury remains a significant problem in the premature infant. The potential mechanisms contributing to injury are complex and involve factors related to blood flow and its regulation, as well as cellular mediators including cytokines, free radical formation, and excitotoxin release. Although a reduction in the occurrence of severe IVH can be achieved with indomethacin, it does translate into long-term neurodevelopmental benefit. This reinforces the concept of a more diffuse injury to brain in sick premature infants than is apparent from the appearance of current neuroimaging techniques.

Allopurinol and superoxide dismutase protect against leucocyte-endothelium interactions in a novel model of colonic ischaemia-reperfusion

BACKGROUND

Leucocyte recruitment is a key feature in ischaemia-reperfusion (I/R)-triggered tissue injury. However, the mechanisms underlying leucocyte-endothelium interactions in the large bowel remain elusive because of a previous lack of models to examine the colonic microcirculation. The aim of this study was to develop and validate a novel method for studying reperfusion-induced leucocyte-endothelium interactions in the colon.

METHODS

The superior mesenteric artery was occluded for 30 min in male C57/Bl6 mice and leucocyte responses were analysed in colonic venules after 30-240 min of reperfusion. Analysis of leucocyte rolling and adhesion in colonic venules was made possible by an inverted approach using intravital fluorescence microscopy.

RESULTS

Thirty minutes of ischaemia and 120 min of reperfusion induced the strongest and most reproducible increase in leucocyte rolling and adhesion. This was associated with a significant increase in colonic levels of malondialdehyde (MDA). Administration of allopurinol and superoxide dismutase reduced I/R-induced leucocyte responses in a dose-dependent manner. Pretreatment with allopurinol attenuated the tissue content MDA in the colon by more than 60 per cent.

CONCLUSION

A new method for examining I/R-induced leucocyte responses in the colonic microcirculation is described. Oxygen free radicals play an important role in triggering leucocyte rolling and adhesion in colonic venules.

Immuno-spin trapping of a post-translational carboxypeptidase B1 radical formed by a dual role of xanthine oxidase and endothelial nitric oxide synthase in acute septic mice

Post-translational modification of proteins due to exposure to radicals and other reactive species are markers of metabolic and inflammatory oxidative stress such as sepsis. This study uses the nitrone spin-trap DMPO and a combination of immuno-spin trapping and mass spectrometry to identify in vivo products of radical reactions in mice. We report the detection of dose-dependent production of DMPO-carboxypeptidase B1 (CPB1) adducts in the spleens of mice treated with lipopolysaccharide (LPS). Additionally, we report significant detection of DMPO-CPB1 adducts in mice experiencing normal physiological conditions. Treatments with inhibitors and experiments with knock-out mice indicate that xanthine oxidase and endothelial nitric oxide synthase are important sources of the reactive species that lead to CPB1 adduct formation. We also report a significant loss of CPB1 activity following LPS challenge in conjunction with an increase in CPB1 protein accumulation. This suggests the presence of a possible mechanism for CPB1 activity loss with compensatory protein production.

In vitro immunogenicity of silicon-based micro- and nanostructured surfaces

The increasing use of micro- and nanostructured silicon-based devices for in vivo therapeutic or sensing applications highlights the importance of understanding the immunogenicity of these surfaces. Four silicon surfaces (nanoporous, microstructured, nanochanneled, and flat) were studied for their ability to provoke an immune response in human blood derived monocytes. The monocytes were incubated with the surfaces for 48 h and the immunogenicity was evaluated based on the viability, shape factors, and cytokine expression. Free radical oxygen formation was measured at 18 h to elicit a possible mechanism invoking immunogenicity. Although no cytokines were significantly different comparing the response of monocytes on the tissue culture polystyrene surfaces to those on the micropeaked surfaces, on average all cytokines were elevated on the micropeaked surface. The monocytes on the nanoporous surface also displayed an elevated cytokine response, overall, but not to the degree of those on the micropeaked surface. The nanochanneled surface response was similar to that of flat silicon. Overall, the immunogenicity and biocompatibility of flat, nanochanneled, and nanoporous silicon toward human monocytes are approximately equivalent to tissue culture polystyrene.

Antioxidants attenuate anthralin-induced skin inflammation in BALB/c mice: role of specific proinflammatory cytokines

Anthralin is the most common therapeutic agent among a small number of pro-oxidant, 9-anthrones effective in the topical treatment of psoriasis. However, the usefulness of this drug is diminished by toxic side effects, including skin irritation and inflammation. The activities of anthralin are believed to be mediated by the generation of reactive oxygen intermediates and anthrone radicals produced in the skin. In this study, the dermal inflammatory response to anthralin was determined using a mouse ear swelling test. Maximum ear swelling induced by anthralin coincided with the elevation of cytokine mRNA expression in the skin, including interleukin-6, granulocyte-macrophage colony-stimulating factor, macrophage inflammatory protein-2, and tumor necrosis factor alpha at 24 h post challenge. The role of free radical generation in ear swelling and cytokine modulation were examined by systemic administration of cell permeable and impermeable antioxidants before anthralin challenge. Superoxide dismutase and alpha-tocopherol acetate, but not the glutathione precursor N-acetyl cysteine, were effective inhibitors of anthralin-induced ear swelling and cytokine elevation. Maximum inflammatory cell infiltration occurred 72-96 h post anthralin challenge and was also reduced by antioxidants. These data suggest that oxidative stress, generated at the site of anthralin treatment, alters the expression of dermal chemokines and other cytokines resulting in the recruitment of inflammatory cells. Systemic antioxidant administration may provide opportunities for therapeutic intervention against anthralin-associated toxicities.

Wine modifies the effects of alcohol on immune cells of mice

Ethanol may be detrimental to immune cells due to the generation of free radicals during detoxification. If this is true, then alcoholic beverages that contain antioxidants, like red wine, should be protective against immune cell damage. We investigated this by giving mice either a red muscadine wine (Vitis rotundifolia), a cabernet sauvignon (Vitis vinifera), ethanol (all at 6% alcohol) or water in the water bottles as the sole fluid for 8 wk. Plasma antioxidant capacity was measured with alphaalpha-diphenyl-beta-picrylhydrazyl and was more than doubled in the mice that consumed wine compared to control mice that consumed water or ethanol. Cytochrome P450-2E1 levels and glutathione-S-transferase activity were modified in such a way as to be interpreted as protective. An immune response was elicited by an intraperitoneal injection of lipopolysaccharide. Later (24 h), natural killer cells and T-lymphocytes derived from the circulation were quantitated in the leukocyte fraction by flow cytometry. Ethanol consumption, as ethanol, significantly suppressed baseline cell numbers relative to the other groups. However, the mice that consumed the same amount of alcohol as wine had baseline cell numbers not different from the water-consuming controls. The lymphocyte response to lipopolysaccharide challenge was inhibited in the mice that consumed ethanol, but was normal in those that consumed the same amount of alcohol in the form of wine. We conclude that there are phytochemicals acting as antioxidants and impacting on the detoxification pathway in the wine that offset the detrimental effects of ethanol on immunity.

Impairment of blood-cerebrospinal fluid barrier properties by retrovirus-activated T lymphocytes: reduction in cerebrospinal fluid-to-blood efflux of prostaglandin E2

The choroid plexus epithelium forms the interface between the blood and the CSF. In conjunction with the tight junctions restricting the paracellular pathway, polarized specific transport systems in the choroidal epithelium allow a fine regulation of CSF-borne biologically active mediators. The highly vascularized stroma delimited by the choroidal epithelium can be a reservoir for retrovirus-infected or activated immune cells. In this work, new insight in the implication of the blood-CSF barrier in neuroinfectious and inflammatory diseases is provided by using a differentiated cellular model of the choroidal epithelium, exposed to infected T lymphocytes. We demonstrate that T cells activated by a retroviral infection, but not non-infected cells, reduce the transporter-mediated CSF-to-blood efflux of organic anions, in particular that of the potent pro-inflammatory prostaglandin PGE2, via the release of soluble factors. A moderate alteration of the paracellular permeability also occurs. We identified the viral protein Tax, oxygenated free radicals, matrix-metalloproteinases and pro-inflammatory cytokines as active molecules released during the exposure of the epithelium to infected T cells. Among them, tumour necrosis factor and interleukin 1 are directly involved in the mechanism underlying the decrease in some choroidal organic anion efflux. Given the strong involvement of CSF-borne PGE2 in sickness behaviour syndrome, these data suggest that the blood-CSF barrier plays an important role in the pathophysiology of neuroinflammation and neuroinfection, via changes in the transport processes controlling the CSF biodisposition of PGE2.

Effects of in-vivo generation of oxygen free radicals on immune responsiveness in rabbits

Oxygen free radicals (OFRs) generated during biological processes are reportedly involved in the pathogenesis of several disease states and various reports have indicated that oxidative stress may alter immune competence. Hence, effects of in-vivo generation of OFRs by using xanthine/xanthine oxidase (X/XO) system on immune responsiveness were evaluated in rabbits. Intravenous injections of xanthine (0.14 mg/kg) along with xanthine oxidase (2 U/Kg) following primary and secondary immunizations of animals with sheep red blood cells (SRBC) significantly attenuated the primary and secondary antibody responses respectively. In tests for cell-mediated immunity, tuberculin sensitivity and leucocyte migration inhibition were also decreased significantly in sensitized animals following X/XO treatment. The observed changes in both humoral and cell-mediated immune responses following such in-vivo generation of OFRs indicate a possible nexus between OFR generation and immune suppression.

ICAM-1 upregulation in the spinal cords of PLSJL mice with experimental allergic encephalomyelitis is dependent upon TNF-alpha production triggered by the loss of blood-brain barrier integrity

Urate (UA) selectively scavenges peroxynitrite-dependent radicals and suppresses CNS inflammation through effects that are manifested at the blood-brain barrier (BBB). ICAM-1 upregulation in the spinal cord tissues of myelin basic protein (MBP) immunized mice is selectively inhibited by UA treatment. In contrast, the expression of ICAM-1 and other adhesion molecules by circulating cells is unchanged. Moreover, TNF-alpha expression in the CNS tissues of MBP-immunized mice is suppressed by UA treatment but TNF-alpha-induced ICAM-1 expression on neurovascular endothelial cells is not. Therefore the effect of UA on ICAM-1 upregulation in the CNS tissues is likely due to its known contribution to the maintenance of BBB integrity in MBP-immunized mice which in turn inhibits cell invasion into the CNS and prevents TNF-alpha production in CNS tissues.

Free radicals in antigen formation: reduction of contact allergic response to hydroperoxides by epidermal treatment with antioxidants

BACKGROUND

For patients with allergic contact dermatitis, the main therapy is anti-inflammatory steroids, a non-specific and symptomatic treatment. In contact allergy, the antigen formation is considered to be the binding of a chemical (hapten) to a biological macromolecule, e.g. a protein. Limonene-2-hydroperoxide (Lim-OOH) is a hapten with a known allergenic effect. It is likely to bind to proteins in the skin via a radical mechanism. It might be possible to inhibit the allergic reaction by epidermal application of substances that can trap free radicals, e.g. antioxidants such as ascorbic acid or alpha-tocopherol, prior to the application of the hapten.

OBJECTIVES

To study the influence of antioxidants on the allergenic effect of Lim-OOH in sensitization experiments on guinea pigs.

METHODS

Pretreatment with the antioxidants was performed before induction to study the effect on sensitization as well as before challenge testing to study the effect on elicitation.

RESULTS

A reduction in the response rate was found both at sensitization and at elicitation. The antioxidants had no effect on cobalt allergy or on the allergenic effect of haptens that form antigens via nucleophilic-electrophilic reactions. No reduction of the effect was seen for irritants.

CONCLUSIONS

The protective effect of antioxidants in elicitation could be of practical therapeutic value, as it indicates a possibility for the treatment of patients who have become sensitized to haptens that form full antigens via a radical mechanism.

Suppression of hyperacute and passively transferred experimental autoimmune encephalomyelitis by the anti-oxidant, butylated hydroxyanisole

Butylated hydroxyanisole (BHA) was used to treat hyperacute, ordinary passive, and hyperacute passive experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. The anti-oxidant, delivered via mini-osmotic pumps, reduced the incidence, severity and mortality in hyperacute EAE and also reduced the incidence, severity and duration of disease in passively induced EAE and hyperacute passive EAE. In all cases, cellular infiltration by both mononuclear and polymorphonuclear leukocytes were significantly reduced in treated rats. BHA appears therefore to act at the effector stage of EAE, reducing cellular infiltration in the brain and spinal cord and minimising clinical signs without blocking sensitisation or activation. This was supported by the finding that spleen cells from BHA-treated donors immunised for hyperacute EAE transferred disease at least as well as cells recovered from untreated donors.

Evidence of oxygen free radical damage in human otitis media

Recent work with a guinea pig model of otitis media has demonstrated evidence of oxygen free radical damage to the middle ear mucosa. However, the relevance of an animal model to human disease is uncertain. Accordingly, the following pilot study was conducted to examine human middle ear fluid for lipid hydroperoxides as evidence of free radical damage. Thirty-five specimens of middle ear fluid from children with chronic otitis media were collected and described as mucoid (n = 19), purulent (n = 10), or serous (n = 6); specimens were weighed and analyzed for lipid hydroperoxide content. The results demonstrated the presence of lipid hydroperoxide in all 3 types of middle ear fluid. Additionally, there was a statistically significant elevation of total lipid hydroperoxide content in mucoid effusions compared with serous effusions, as well as a significant elevation of lipid hydroperoxide divided by weight of purulent effusions compared with serous effusions. This is the first study to document free radical damage in human otitis media.