Production Of Oxygen Metabolites Research Articles

Features of cellular and molecular inflammatory mechanisms involvement in hormone-mediated myocardial experimental injury

Aim. To study the features of inflammatory effector mechanisms variation in Wistar rats with metabolic non-coronary myocardial infarction. Methods. Metabolic myocardial infarction was reproduced in Wistar rats by adrenalin injection. Metabolic myocardial infarction was verified by electrocardiography and histological examination. Biocidal activity of blood neutrophils was determined by nitro blue tetrazolium test and chemiluminescence, cytokine serum levels (interleukin-1β, interleukin 6 and tumor necrosis factor alpha) were determined by ELISA. Lipid peroxidation was assessed by measuring malondialdehyde, diene conjugates and diketones blood concentrations. Catalase activity and reduced glutathione level were determined in erythrocyte hemolysate, serum activity of superoxide dismutase was also measured. Intact animals were examined as a control group. Results. In rats with metabolic myocardial infarction, oxygen-dependent leukocyte biocidity (determined by nitro blue tetrazolium test and chemiluminescence) increased dramatically from the first day of the adrenalin administration and continued to increase until the end of the experiment (day 14). Accordingly, the production of active oxygen metabolites, which intensified the lipid peroxidation, was increasing. Simultaneously an imbalance between pro-and antioxidant system parameters was detected. Serum concentration of pro-inflammatory cytokines (tumor necrosis factor alpha, interleukin-1β, interleukin-6) increased. Conclusion. Long-term administration of adrenalin to experimental animals causes an increase in the neutrophils biocidal activity, accompanied by release of reactive oxygen species, pro-inflammatory cytokines, lipid peroxidation intensifying and decreased compensation by antioxidant defense system, which together can be a powerful trigger of myocardial damage.

Taurine chloramine produced from taurine under inflammation provides anti-inflammatory and cytoprotective effects

Taurine is one of the most abundant non-essential amino acid in mammals and has many physiological functions in the nervous, cardiovascular, renal, endocrine, and immune systems. Upon inflammation, taurine undergoes halogenation in phagocytes and is converted to taurine chloramine (TauCl) and taurine bromamine. In the activated neutrophils, TauCl is produced by reaction with hypochlorite (HOCl) generated by the halide-dependent myeloperoxidase system. TauCl is released from activated neutrophils following their apoptosis and inhibits the production of inflammatory mediators such as, superoxide anion, nitric oxide, tumor necrosis factor-α, interleukins, and prostaglandins in inflammatory cells at inflammatory tissues. Furthermore, TauCl increases the expressions of antioxidant proteins, such as heme oxygenase 1, peroxiredoxin, thioredoxin, glutathione peroxidase, and catalase in macrophages. Thus, a central role of TauCl produced by activated neutrophils is to trigger the resolution of inflammation and protect macrophages and surrounding tissues from being damaged by cytotoxic reactive oxygen metabolites overproduced during inflammation. This is achieved by attenuating further production of proinflammatory cytokines and reactive oxygen metabolites and also by increasing the levels of antioxidant proteins that are able to scavenge and diminish the production of cytotoxic oxygen metabolites. These findings suggest that TauCl released from activated neutrophils may be involved in the recovery processes of cells affected by inflammatory oxidative stresses and thus TauCl could be used as a potential physiological agent to control pathogenic symptoms of chronic inflammatory diseases.

Immunomodulatory effects of antileishmanial drugs

The commonly used antileishmanial drugs are sodium antimony gluconate (SAG), amphotericin B, miltefosine and paromomycin. There are a number of reports that antileishmanial drugs show immunomodulatory properties. Here, we attempt to understand how the innate arm of the immune system is modulated in response to these antileishmanial drugs. BALB/c peritoneal macrophages were treated with miltefosine, SAG, amphotericin B or paromomycin. The membrane fluidity of macrophages following drug treatment was studied in terms of fluorescence anisotropy. The T cell-stimulating ability, production of cytokines and nitrogen and oxygen metabolite production in drug-treated macrophages were also studied. The study was also carried out using peritoneal macrophages from drug-treated BALB/c mice. The antileishmanial drugs altered macrophage membrane fluidity, except amphotericin B. The drug-treated macrophages showed enhanced T cell-stimulating ability and generation of reactive oxygen species, nitrite, interleukin-12 and tumour necrosis factor-α. Antileishmanial drugs can stimulate the innate arm of the immune system, which may have a significant bearing on the cellular arm of the immune system.

A Phosphatidylinositol Species Acutely Generated by Activated Macrophages Regulates Innate Immune Responses

Activation of macrophages with stimuli of the innate immune response results in the intense remodeling of arachidonate-containing phospholipids, leading to the mobilization of large quantities of this fatty acid for conversion into biologically active eicosanoids. As a consequence of this process, the arachidonate levels in membrane phospholipids markedly decrease. We have applied mass spectrometry-based lipid profiling to study the levels of arachidonate-containing phospholipids under inflammatory activation of macrophages. We identify an unusual inositol phospholipid molecule, PI(20:4/20:4), the levels of which do not decrease but actually increase by 300% after activation of the macrophages. PI(20:4/20:4) is formed and degraded rapidly, suggesting a role for this molecule in regulating cell signaling events. Using a metabolipidomic approach consisting in exposing the cells to deuterium-labeled arachidonate at the time they are exposed to stimuli, we show that PI(20:4/20:4) biosynthesis occurs via the sequential incorporation of arachidonate, first into the sn-2 position of a preformed phosphatidylinositol (PI) molecule, followed by the rapid introduction of a second arachidonate moiety into the sn-1 position. Generation requires the participation of cytosolic phospholipase A2α and CoA-dependent acyltransferases. PI(20:4/20:4) formation is also detected in vivo in murine peritonitis exudates. Elevating the intracellular concentration of PI(20:4/20:4) by introducing the lipid into the cells results in enhancement of the microbicidal capacity of macrophages, as measured by reactive oxygen metabolite production and lysozyme release. These findings suggest that PI(20:4/20:4) is a novel bioactive inositol phospholipid molecule that regulates innate immune responses in macrophages.

Antibacterial effect of microvesicles released from human neutrophilic granulocytes

AbstractCell-derived vesicles represent a recently discovered mechanism for intercellular communication. We investigated their potential role in interaction of microbes with host organisms. We provide evidence that different stimuli induced isolated neutrophilic granulocytes to release microvesicles with different biologic properties. Only opsonized particles initiated the formation of microvesicles that were able to impair bacterial growth. The antibacterial effect of neutrophil-derived microvesicles was independent of production of toxic oxygen metabolites and opsonization or engulfment of the microbes, but depended on β2 integrin function, continuous actin remodeling, and on the glucose supply. Neutrophil-derived microvesicles were detected in the serum of healthy donors, and their number was significantly increased in the serum of bacteremic patients. We propose a new extracellular mechanism to restrict bacterial growth and dissemination.

Abstract 62: Direct Comparison of the Effect of Mild Hypothermia and Controlled Normothermia on Reactive Oxygen Metabolites Production and Antioxidant Potential After Cardiac Arrest in a Porcine Model

Introduction . Mild therapeutic hypothermia was implemented in the management of post cardiac arrest syndrome (PCAS) after publication of clinical trials comparing hypothermia with common practice, i.e. usually with hyperthermia. Current evidence on the comparison of mild hypothermia (HT) and controlled normothermia (NT) is, however, still insufficient. We tested the hypothesis that HT is superior to NT in suppression of oxidative stress, which plays probably an important role in the pathogenesis of PCAS. Methods. We worked on porcine model (females, 45 kg) in general anesthesia and mechanical ventilation (HT and NT groups, four animals per group). Veno-arterial extracorporeal membrane oxygenation (ECMO) was introduced and on minimal ECMO flow (0.5 L/min) ventricular fibrillation was induced by rapid ventricular pacing. After 20 min of cardiac arrest, circulation was restored by increase of ECMO flow to 4.5 L/min and 90 min of reperfusion followed. Target core temperature (33°C in HT and 36.8°C in NT) was maintained using heat exchanger on oxygenator. Blood levels of reactive oxygen metabolites (ROM) and biological antioxidant potential (BAP) were assessed before cardiac arrest, immediately after restoration of blood flow and at 30, 60, and 90 minutes of reperfusion. Results . While the pre-arrest and early post-arrest ROM levels were comparable in both groups, we observed significant differences between HT and NT groups later during the reperfusion: at 30 minutes (HT vs. NT: 277.8 ± 11.4 vs. 363.3 ± 13.4 U Carr, p < 0.01), at 60 minutes (292.8 ± 6.6 vs. 355.8 ± 10.9 U Carr, p < 0.05), and at 90 minutes (278.5 ± 12.3 vs. 340.8 ± 14.1 U Carr, p < 0.05). The levels of BAP were comparable in both groups in all measurements. Conclusion . Our results indicate superiority of mild therapeutic hypothermia over controlled normothermia in the suppression of oxidative stress after cardiac arrest.

1790 Oxidative Stress and Clinical Outcome of Preterm Infants Resuscitated with Different Concentrations of Oxygen

Background and AimsPreterm infants are more sensitive to oxidative stress than older humans. Hyperoxic exposure, although essential for survival of neonates, induces excessive production of reactive oxygen metabolites which could...

Augmentation of antileishmanial efficacy of miltefosine in combination with tuftsin against experimental visceral leishmaniasis

Current drugs for the treatment of visceral leishmaniasis are inadequate, and their efficacies are also compromised due to suppression of immune function during the course of infection. Miltefosine is the only promising orally active antileishmanial drug, but due to its long half-life, there is risk of development of resistance. To overcome these problems, efforts are needed to develop combination therapy of miltefosine with effective immunostimulating agents where a decrease of parasitic burden and simultaneous enhancement of adaptive immunity can be achieved. In the present study, we have explored the antileishmanial efficacy of a subcurative dose of miltefosine in combination with free as well as liposomal palmitoyl tuftsin (p-tuftsin) using a Leishmania donovani/BALB/c mouse model. When miltefosine (2.5 mg/kg for 5 days) was given with free p-tuftsin, the inhibitory effect was significantly increased from 49.6% to 66% (P < 0.01), which was further enhanced up to 81% (P < 0.001) when given after liposomal encapsulation of p-tuftsin. Significant enhancement in parasitic inhibition (93%, P < 0.01) was witnessed when animals were co-administered with liposomal p-tuftsin + 5 mg/kg × 5 days dose of miltefosine (72.1%). Enhancement in the production of Th1 cytokines (IL-12, TNF-α, and IFN-γ), reactive oxygen, and nitrogen metabolites was witnessed in the combination group. A remarkable increase in phagocytosis index was also observed indicating overall immunological enhancement to antileishmanial activity of miltefosine by p-tuftsin.

In vitro NADH-oxidase, NADPH-oxidase and myeloperoxidase activity of macrophages after Tinospora cordifolia (guduchi) treatment

It is believed that the enhanced microbicidal and tumoricidal capability of activated macrophages is related to the remarkable increase in the production of oxygen metabolites. Both the production of H2O2 and the oxidation of NAD(P)H are directly dependent upon NAD(P)H-oxidase. It has been established that the respiratory burst is due to activation of NAD(P)H-oxidase localised in the plasmalemma. Myeloperoxidase is believed to be involved in augmenting the cytotoxic activity of H2O2. It was observed that the macrophage cell line J774A.1 when treated with Tinospora cordifolia (guduchi) and LPS showed enhanced NADH-oxidase, NADPH-oxidase and myeloperoxidase production as compared to macrophages treated with medium alone. The direct drug treatment to J774A cells showed activation as assessed by biochemical assays. These results suggest that high NADH-oxidase, NADPH-oxidase and myeloperoxidase activities may account for tumoricidal and microbicidal properties via macrophage activation.

Effects of indomethacin and diclofenac on some functions of polymorphonuclear neutrophils

The effects in-vitro of two non-steroidal anti-inflammatory drugs, diclofenac and indomethacin, have been studied on human polymorphonuclear functions. Adhesivity and chemotaxis were decreased by the two drugs, but in a manner that varied with the attractant used. As shown by the nitro blue tetrazolium slide test, all cells remained active but the production of oxygen metabolites by opsonized zymosan was decreased in the presence of diclofenac.

The purinergic receptor P2Y2 receptor mediates chemotaxis of dendritic cells and eosinophils in allergic lung inflammation

Extracellular ATP contributes to the pathogenesis of asthma via signalling at purinergic receptors. However, the precise purinergic receptors subtypes mediating the pro-asthmatic effects of ATP have not been identified, yet. In vivo studies were performed using the OVA-alum model. Functional expression of the P2Y(2) purinergic receptor subtype on human monocyte-derived dendritic cells and eosinophils was investigated using real-time PCR, migration assays, and production of reactive oxygen species. Compared to wild-type animals P2Y(2) -/- mice showed reduced allergic airway inflammation which can be explained by defective migration of blood myeloid DCs towards ATP in vitro and in vivo, whereas the influence of ATP on maturation and cytokine production was not changed. Additionally, ATP failed to induce migration of bone marrow-derived eosinophils from P2Y(2) R-deficient animals. The relevance of our findings for humans was confirmed in functional studies with human monocyte-derived DCs and eosinophils. Interestingly, stimulation of human DCs derived from allergic individuals with house dust mite allergen induced functional up-regulation of the P2Y(2) R subtype. Furthermore, eosinophils isolated from asthmatic individuals expressed higher levels of P2Y(2) R compared to healthy controls. This was of functional relevance as these eosinophils were more sensitive to ATP-induced migration and production of reactive oxygen metabolites. In summary, P2Y(2) R appears to be involved in asthmatic airway inflammation by mediating ATP-triggered migration of mDCs and eosinophils, as well as reactive oxygen species production. Together our data suggest that targeting P2Y(2) R might be a therapeutic option for the treatment of asthma.

The IgG-specific endoglycosidase EndoS inhibits both cellular and complement-mediated autoimmune hemolysis

AbstractEndoS from Streptococcus pyogenes is an immunomodulating enzyme that specifically hydrolyzes glycans from human immunoglobulin G and thereby affects antibody effector functions. Autoimmune hemolytic anemia is caused by antibody-mediated red blood cell (RBC) destruction and often resists treatment with corticosteroids that also cause frequent adverse effects. We show here that anti-RhD (anti-D) and rabbit anti–human-RBC antibodies (anti-RBC) mediated destruction of RBC, ie, phagocytosis, complement activation, and hemolysis in vitro and in vivo was inhibited by EndoS. Phagocytosis by monocytes in vitro was inhibited by pretreatment of anti-D with EndoS before sensitization of RBCs and abrogated by direct addition of EndoS to blood containing sensitized RBCs. The toxic effects of monocytes stimulated with anti-D–sensitized RBCs, as measured by interleukin-8 secretion and oxygen metabolite production, was restrained by EndoS. Agglutination of RBCs and complement-mediated hemolysis in vitro in whole human blood caused by rabbit anti-RBCs was inhibited by EndoS. Development of anemia in mice caused by a murine anti-RBC immunoglobulin G2a monoclonal autoantibody and complement activation and erythrophagocytosis by Kupffer cells in the liver were reduced by EndoS. Our data indicate that EndoS is a potential therapeutic agent that might be evaluated as an alternative to current treatment regimens against antibody-mediated destruction of RBCs.

COMBINED IMMUNOSUPPRESSIVE AND ANTIBIOTIC THERAPY IMPROVES BACTERIAL CLEARANCE AND SURVIVAL OF POLYMICROBIAL SEPTIC PERITONITIS

Effective immunosuppressive therapy is essential to prevent transplant rejection but renders patients vulnerable to opportunistic infections. The present study investigates the effects of common immunosuppressive drugs on the course of septic peritonitis in an experimental mouse model. We show that treatment with a combination of tacrolimus, mycophenolate mofetil, and methylprednisolone resulted in highly elevated lethality of septic peritonitis. When immunosuppressive drugs were combined with antibiotic therapy, however, mice were almost completely protected. The combination of mycophenolate mofetil and methylprednisolone was shown to be required and sufficient to improve outcome of septic peritonitis in the presence of antibiotic therapy. Combined immunosuppressive and antibiotic therapy, but not antibiotic therapy alone, resulted in enhanced bacterial clearance. These beneficial effects were linked to an elevated expression of activation markers and an increased production of reactive oxygen metabolites by peritoneal neutrophils and correlated with a reduced messenger RNA expression of the inhibitory cytokine IL-22. In contrast, systemic or peritoneal levels of IL-10, IL-12, TNF-alpha, keratinocyte chemoattractant, and monocyte chemoattractant protein 1, and splenic messenger RNA levels of IFN-gamma were not influenced by the immunosuppressive therapy. These results therefore suggest that combined immunosuppressive and antibiotic therapy may improve bacterial clearance and survival of septic peritonitis by a mechanism that involves enhanced activation and antimicrobial activity of neutrophils and reduced production of IL-22.

Effect of Yeast Superoxide Dismutase Treatment on Some Mediators of Infl ammation during Adjuvant-Induced Arthritis in Mice

* Author for correspondence and reprint requests Z. Naturforsch. 65c, 141-147 (2010); received June 17/July 21, 2009 The superoxide radical (O2-), hydrogen peroxide (H2O2) and nitric oxide (NO) are pleiotropic inflammatory mediators which play an important role in inflammatory joint diseases. They are overproduced during rheumatoid arthritis and its experimental model - adjuvant-induced arthritis in rodents--and may be detected both systemically and intra-articularly. Their secretion is up-regulated by proinflammatory cytokines such as IFN-gamma, IL-12, IL-6 and TNF-alpha, and they are responsible for the destruction of joint tissue. In this work, the effect of superoxide dismutase (SOD) from a thermotolerant yeast strain, Kluyveromyces marxianus, on the production of proinflammatory cytokines, reactive oxygen and nitrogen species was studied. Mice received three intraperitoneal injections of yeast SOD at a dose of 10 mg/ kg body weight (30,000 U/kg) on consecutive days starting on the day after arthritic induction. On days 3, 8 and 14 post induction peritoneal macrophages were isolated and both spontaneous and stimulated production of reactive oxygen and nitrogen metabolites were measured. Early in arthritic development yeast SOD treatment did not influence the O2- production, but on day 14 both spontaneous and PMA-induced secretion were dramatically reduced. Spontaneous H2O2 release was inhibited on day 14, while PMA-stimulated production was decreased from the beginning of the arthritic development. Yeast SOD treatment effectively suppressed the spontaneous and recombinant mouse IFN-gamma + LPS induced release of NO as well. Serum levels of proinflammatory cytokines, IL-12, IFN-gamma, IL-6 and TNF-alpha, were also significantly reduced. The obtained results show some of the mechanisms of action of SOD in reducing the severity of arthritic inflammation. Besides direct inhibition of joint tissue destruction exogenous SOD substantially limits the existing positive feedback between secretion of reactive oxygen species and inflammatory cytokine production.

Actinomyces in Chronic Granulomatous Disease: An Emerging and Unanticipated Pathogen

Chronic granulomatous disease (CGD) is a rare inherited disease of the phagocyte NADPH oxidase system that causes defective production of toxic oxygen metabolites, impaired bacterial and fungal killing, and recurrent life-threatening infections, mostly by catalase-producing organisms. We report for the first time, to our knowledge, chronic infections with Actinomyces species in 10 patients with CGD. Actinomycosis is a chronic granulomatous condition that commonly manifests as cervicofacial, pulmonary, or abdominal disease, caused by slowly progressive infection with oral and gastrointestinal commensal Actinomyces species. Treatment of actinomycosis is usually simple in immunocompetent individuals, requiring long-term, high-dose intravenous penicillin, but is more complicated in those with CGD because of delayed diagnosis and an increased risk of chronic invasive or debilitating disease. Actinomyces was identified by culture, staining, 16S ribosomal DNA polymerase chain reaction, and/or a complement fixation test in 10 patients with CGD. All 10 patients presented with a history of fever and elevated inflammatory signs without evident focus. Diagnosis was delayed and clinical course severe and protracted despite high-dose intravenous antibiotic therapy and/or surgery. These results suggest an unrecognized and unanticipated susceptibility to weakly pathogenic Actinomyces species in patients with CGD because these are catalase-negative organisms previously thought to be nonpathogenic in CGD. Actinomycosis should be vigorously sought and promptly treated in patients with CGD presenting with uncommon and prolonged clinical signs of infection. Actinomycosis is a catalase-negative infection important to consider in CGD.

No relationship between neutrophil granulocyte activation and the myeloperoxidase gene −129 G&gt;A and −463 G&gt;A promoter polymorphisms: implications for investigations of cardiovascular disease

Myeloperoxidase catalyzes the formation of reactive oxygen metabolites in neutrophils and monocytes. Increased plasma myeloperoxidase concentrations are linked to coronary artery stenosis and may be useful for risk prediction following acute coronary syndromes. We studied the influence of the - 129 G>A and - 463 G>A myeloperoxidase gene promoter polymorphisms on myeloperoxidase concentrations and reactive oxygen metabolite production after neutrophil stimulation. Neutrophils from 305 healthy blood donors were stimulated with N-Formyl-Met-Leu-Phe or phorbol-myristate-acetate. Plasma myeloperoxidase concentrations were quantified by enzyme immunoassay and reactive oxygen metabolites by flow cytometry. Genotyping was performed by PCR and restriction fragment length analysis. The - 129 A allele was associated with lower myeloperoxidase concentrations in unstimulated blood (P< 0.05), but the variation among the genotypes was small. Plasma myeloperoxidase was unrelated to the - 463 G> A polymorphism. Baseline myeloperoxidase was associated with use of sex hormones in women, but not with sex, age, smoking habits or use of nonsteroid anti-inflammatory medication. The polymorphisms were not associated with the change from baseline in myeloperoxidase or reactive oxygen metabolites after neutrophil stimulation. Control experiments on myeloperoxidase function in cell lysates from 50 additional donors confirmed the results. The - 129 A allele was associated with slightly lower myeloperoxidase plasma concentrations. The - 129 G>A and - 463 G>A polymorphisms did not affect myeloperoxidase degranulation or reactive oxygen metabolite production after neutrophil activation. It therefore seems unlikely that they are mechanistically related to the risk for atherosclerosis. Our findings may explain why associations between these polymorphisms and cardiovascular disease have been difficult to reproduce.

Punica Granatum Peel Extract Protects Against Ionizing Radiation-Induced Enteritis And Leukocyte Apoptosis In Rats

Radiation-induced enteritis is a well-recognized sequel of therapeutic irradiation. Therefore we examined the radioprotective properties of Punica granatum peel extract (PPE) on the oxidative damage in the ileum. Rats were exposed to a single whole-body X-ray irradiation of 800 cGy. Irradiated rats were pretreated orally with saline or PPE (50 mg/kg/day) for 10 days before irradiation and the following 10 days, while control rats received saline or PPE but no irradiation. Then plasma and ileum samples were obtained. Irradiation caused a decrease in glutathione and total antioxidant capacity, which was accompanied by increases in malondialdehyde levels, myeloperoxidase activity, collagen content of the tissue with a concomitant increase 8-hydroxy-2'-deoxyguanosine (an index of oxidative DNA damage). Similarly, pro-inflammatory cytokines (TNF-alpha, IL-1beta and IL-6) and lactate dehydrogenase were elevated in irradiated groups as compared to control. PPE treatment reversed all these biochemical indices, as well as histopathological alterations induced by irradiation. Furthermore, flow cytometric measurements revealed that leukocyte apoptosis and cell death were increased in irradiated animals, while PPE reversed these effects. PPE supplementation reduced oxidative damage in the ileal tissues, probably by a mechanism that is associated with the decreased production of reactive oxygen metabolites and enhancement of antioxidant mechanisms. Adjuvant therapy of PPE may have a potential to support a successful radiotherapy by protecting against radiation-induced enteritis.

Bacillus Calmette-Guérin (BCG) and immunoglobulins synergistically enhance mineral dust-induced production of reactive oxygen metabolites by human monocytes.

The modulating effect of BCG and polyclonal immunoglobulin on mineral dust-induced production of reactive oxygen metabolites (ROM) by human monocytes was studied using luminol-dependent chemiluminescence. BCG and immunoglobulin synergistically amplified the ROM production induced by chrysotile asbestos and quartz particles, and BCG caused a sharper dose response for poly-immunoglobulin added to the mineral dusts. Immunoglobulins did not affect zymosan yeast-induced ROM production, which was enhanced strongly by BCG. As there is evidence that phagocyte-derived ROM are of importance in mineral dust-induced lung injury, we suggest that the observed synergism between host response inflammatory mediators (poly-immunoglobulin) and exogenic irritants (BCG) may contribute to the outcome of exposure of mineral dusts, and thus in part explain the individual variations in susceptibility to mineral dust-induced diseases.

Tumour necrosis factor enhances the asbestos-induced production of reactive oxygen metabolites by human polymorphonuclear leucocytes (PMN).

We studied the effect of recombinant tumour necrosis factor-alpha (TNF-alpha) on the production of reactive oxygen metabolites (ROM) by human PMN exposed in vitro to chrysotile and crocidolite asbestos fibres, quartz dusts and opsonized zymosan. TNF caused a significant increase in ROM release by PMN, and significantly and dose-dependently amplified the ROM production induced by asbestos fibres. The amplification of ROM production by TNF can be of crucial importance in the process of lung inflammation and fibrogenesis in pneumoconioses.

Thyroid follicular cell function after non-lethal complement membrane attack

Terminal complement complexes have been identified around thyroid follicles in Graves' disease and Hashimoto's thyroiditis, and the concentrations of such complexes are increased in the sera of these patients, suggesting a role for complement activation and membrane attack complexes (MAC) in autoimmune thyroiditis. This has been investigated further using cultured human and rat thyroid cells. Thyrocytes were resistant to lysis by homologous complement, in contrast to the effects of heterologous (rabbit) complement. The formation of non-lethal amounts of MAC, using reactive lysis or classical pathway activation, significantly reduced cAMP production by these cells in response to thyroid-stimulating hormone (TSH) (P less than 0.01); similar effects were seen with thyroid-stimulating antibodies. Thyroid cells were able to recover rapidly from complement attack after washing and incubation for 30 min. Non-lethal MAC formation also resulted in reactive oxygen metabolite production, detected by luminol-dependent chemiluminescence in three out of five thyroid cell preparations tested. Ionomycin, but not TSH, also stimulated reactive oxygen metabolite production. These results suggest that repeated or continuous sub-lethal complement attack on thyroid cells may exacerbate hypothyroidism in Hashimoto's thyroiditis, or partially counter the effects of thyroid-stimulating antibodies in Graves' disease. Furthermore, the production of reactive oxygen metabolites in these circumstances could increase the intra-thyroidal inflammatory response; oxygen radical scavenging by anti-thyroid drugs (which are concentrated by thyrocytes) may account in part for the amelioration of thyroiditis observed with such treatment.