Effect of corticosteroids on the production of superoxide and hydrogen peroxide and the appearance of chemiluminescence by phagocytosing polymorphonuclear leukocytes

Kidney Transplant Recipients Show Limited Lung Diffusion Capacity but Similar Hydrogen Peroxide Exhalation as Healthy Matched Volunteers: A Pilot Study

Patients with end-stage chronic kidney disease show higher systemic oxidative stress and exhale more hydrogen peroxide (H2O2) than healthy controls. Kidney transplantation reduces oxidative stress and H2O2 production by blood polymorphonuclear leukocytes (PMNs). Kidney transplant recipients (KTRs) may be predisposed to an impairment of lung diffusing capacity due to chronic inflammation. Lung function and H2O2 concentration in the exhaled breath condensate (EBC) were compared in 20 KTRs with stable allograft function to 20 healthy matched controls. Serum interleukin eight (IL-8) and C-reactive protein (CRP), blood cell counts, and spirometry parameters did not differ between groups. However, KTRs showed lower total lung diffusing capacity for carbon monoxide, corrected for hemoglobin concentration (TLCOc), in comparison to healthy controls (92.1 ± 11.5% vs. 102.3 ± 11.9% of predicted, p = 0.009), but similar EBC H2O2 concentration (1.63 ± 0.52 vs. 1.77 ± 0.50 µmol/L, p = 0.30). The modality of pre-transplant renal replacement therapy had no effect on TLCOc and EBC H2O2. TLCOc did not correlate with time after transplantation. In this study, TLCOc was less reduced in KTRs in comparison to previous reports. We suggest this fact and the non-elevated H2O2 exhalation exhibited by KTRs, may result perhaps from the evolution of the immunosuppressive therapy.

Stress doses of hydrocortisone in septic shock: beneficial effects on opsonization-dependent neutrophil functions

OBJECTIVE

To assess the effects of stress doses of hydrocortisone (HC) on clinical parameters and neutrophil functions in patients with septic shock.

DESIGN

Prospective, double-blind, randomized, placebo-controlled study.

SETTING

Intensive care units of a university hospital.

PATIENTS AND PARTICIPANTS

30 adult patients with septic shock.

INTERVENTIONS

Patients were allocated to receive either HC (intravenous bolus of 100 mg preceding a continuous infusion 10 mg/h, n = 15) or placebo (n = 15), respectively. The effects of HC were assessed at baseline and after 24 h.

MEASUREMENTS AND RESULTS

As compared with placebo-treated patients, administration of HC significantly decreased norepinephrine requirements (from 1.5 to 0.8 mg/h; p < 0.001), interleukin-6 serum concentrations (from 388.8 to 88.8 pg/ml; p < 0.02), and the spontaneous release of hydrogen peroxide (H2O2) by neutrophils (-33.0%; p < 0.05). Additionally, HC treatment preserved the autologous plasma-induced amplification of phagocytosis of zymosan particles [factor of opsonin-induced amplification of phagocytosis of unopsonized particles: 1.80 for placebo vs. 1.75 for HC at baseline (not significant between groups) and 0.50 for placebo vs. 1.75 for HC after 24 h of treatment (p < 0.05)]. These effects were paralleled by respective changes in the phagocytosis-associated H2O2 production.

CONCLUSIONS

In patients with septic shock stress doses of HC exert beneficial effects in terms of improvements in hemodynamics, decrease in pro-inflammatory mediators, and oxidative stress without the compromise of opsonization-dependent phagocytic neutrophil functions; thus, HC treatment does not aggravate non-specific immunosuppression but instead improves innate immunity in the early stage of septic shock.

Is there any relationship between plasma antioxidant capacity and lung function in smokers and in patients with chronic obstructive pulmonary disease?

BACKGROUND

It has been suggested that oxidative stress is an important factor in the pathogenesis of chronic obstructive pulmonary disease (COPD). We have shown that an oxidant/antioxidant imbalance occurs in the distal air spaces of smokers and in patients with COPD which is reflected systemically in the plasma. A study was undertaken to determine whether plasma antioxidant status correlated with lung function as assessed by forced expiratory volume in one second (FEV(1)) and forced vital capacity (FVC) in smokers and patients with COPD.

METHODS

Plasma antioxidant capacity, assessed by the Trolox equivalent antioxidant capacity (TEAC) as an index of overall systemic oxidative stress, and protein thiol levels were measured in 95 patients with stable COPD, in 82 healthy smokers, and in 37 healthy non-smokers.

RESULTS

Mean (SE) plasma TEAC levels were significantly decreased in patients with COPD (0.81 (0.03) mmol/l, p<0.001) and in healthy smokers (0.87 (0.04) mmol/l, p<0. 001) compared with healthy non-smokers (1.31 (0.11) mmol/l). The mean differences in plasma antioxidant capacity (mM) were (0.81, 95% confidence interval (CI) 0.22 to 1.48), (0.87, 95% CI 0.2 to 1.46), and (1.31, 95% CI 1.09 to 1.58) in patients with COPD, healthy smokers, and healthy non-smokers, respectively. This reduction was associated with a 29% (95% CI 18 to 38) and a 30% (95% CI 19 to 40) decrease in plasma protein thiol levels in COPD patients and smokers, respectively. Current smoking was not the main contributor to the reduction in antioxidant capacity in patients with COPD as those patients who were still smokers had similar TEAC levels (mean (SE) 0. 78 (0.05); n = 25) to those who had stopped smoking (0.84 (0.02); n = 70). No significant correlations were found between spirometric data measured as FEV(1) % predicted or FEV(1)/FVC % predicted and the plasma levels of TEAC in patients with COPD, healthy smokers, or healthy non-smokers. Similarly, there was no significant correlation between FEV(1) % predicted or FEV(1)/FVC % predicted and the levels of plasma protein thiols in the three groups.

CONCLUSIONS

These data confirm decreased antioxidant capacity in smokers and patients with COPD, indicating the presence of systemic oxidative stress. However, no relationship was found between protein thiols or TEAC levels and measurements of airflow limitation in either smokers or in patients with COPD.

Antioxidant effects of aminosalicylates and potential new drugs for inflammatory bowel disease: assessment in cell-free systems and inflamed human colorectal biopsies

BACKGROUND

The therapeutic efficacy of 5-aminosalicylic acid in inflammatory bowel disease may be related to its antioxidant properties.

AIM

To compare in vitro the antioxidant effects of conventional drugs (5-aminosalicylic acid, corticosteroids, metronidazole), with new aminosalicylates (4-aminosalicylic acid, balsalazide) and other potential therapies (ascorbate, N-acetylcysteine, glutathione, verapamil).

METHODS

Compounds were assessed for efficacy in reducing the in vitro production of reactive oxygen species by cell-free systems (using xanthine/xanthine oxidase, with or without myeloperoxidase) and by colorectal biopsies from patients with ulcerative colitis using luminol-amplified chemiluminescence.

RESULTS

5-aminosalicylic acid and balsalazide were more potent antioxidants than 4-aminosalicylic acid or N-acetyl-5-aminosalicylic acid in cell-free systems. 5-aminosalicylic acid (20 mM) and balsalazide (20 mM) inhibited rectal biopsy chemiluminescence by 93% and 100%, respectively, compared with only 59% inhibition by 4-aminosalicylic acid (20 mM). Hydrocortisone, metronidazole and verapamil had no significant effect on chemiluminescence in any system. Ascorbate (20 mM) inhibited chemiluminescence by 100% in cell-free systems and by 60% in rectal biopsies. N-acetyl cysteine (10 mM), and both oxidized and reduced glutathione (10 mM), completely inhibited chemiluminescence in cell-free systems, but not with rectal biopsies.

CONCLUSIONS

The antioxidant effects of compounds varies between cell-free systems and inflamed colorectal biopsies. The effect of drugs on the chemiluminescence produced by these two assay systems is useful for screening potentially new antioxidant treatments for inflammatory bowel disease. Ascorbate seems worth further study as a novel therapy.

The effect of prednisolone on canine neutrophil function: in vivo and in vitro studies

The in vivo effect of a therapeutic dose of prednisolone on canine neutrophil adherence, random migration, chemotaxis, phagocytosis of IgG and C3b opsonized yeast cells, chemiluminescence, Fc- and CR3-receptor expression was investigated. Prednisolone was also added in vitro to neutrophils as isolated cells and in whole blood. In the in vivo study, prednisolone increased the IgG mediated ingestion of yeast cells and the number of activated neutrophils in the phagocytosis assay, while flow cytometric investigation of the IgG-receptor Fc gamma RIII with a monoclonal antibody showed similar expression before, during and after treatment. Prednisolone also increased the ingestion of C3b-opsonized yeast cells, while the expression of CR3-receptors (CD11b CD18) measured by flow cytometry was unchanged. Chemiluminescence and the chemotactic response towards zymosan activated serum were increased, while adherence to nylon wool was decreased. The in vitro studies revealed that prednisolone had no or a dampening effect on neutrophils in cell suspensions. Adherence as well as IgG mediated ingestion was decreased at the highest prednisolone concentration (800 ng/ml) in whole blood. The present study suggests that the part of the antiinflammatory effect of corticosteroids mediated through their influence on neutrophils, besides reduced adherence, may be exerted by increased clearance of microorganisms and IgG-complexes through an elevated functional capacity.

Comparative in vitro phagocytosis and F-actin polymerization of bovine neonatal neutrophils

Analysis of neonatal neutrophil (PMN) functions should help to reveal factors which could contribute to the impaired host defense system of neonates. We analysed functional parameters of PMN from newborn calves (N-PMN) and adult bovines (A-PMN): cellular volume and F-actin content upon stimulation with complement factors, by cytofluorometry and phagocytosis of E. coli 78:80B with a colorimetric assay. Polymerization of F-actin was rapid in both N- and A-PMN, but reached higher levels in N-PMN. N-PMN are significantly smaller than A-PMN throughout the whole activation time. Percentage of phagocytosing PMN, the rate of phagocytosis, and the rate of killing are similar between A- and N-PMN after opsonization of bacteria with adult serum (AS). Opsonization with newborn serum (NS) reduced all three examined parameters: in A-PMN more (P < 0.001) than in N-PMN (P < 0.05). However, when phagocytosis was compared following age-matched opsonization (N-PMN and NS; A-PMN and AS), N-PMN phagocytosed less (P < 0.001) bacteria per PMN than A-PMN. Additionally, steroidal (dexamethasone) and non-steroidal (phenylbutazone) anti-inflammatory drugs inhibited phagocytosis by N-PMN less than by A-PMN. Higher relative F-actin content of N-PMN can be correlated with the documented functional hyperactivity of bovine N-PMN. However, the exaggerated impairment of phagocytosis in calves observed after age-matched opsonization of bacteria could potentially indicate a specific host defence defect.

Inhibition of inflammatory cell-mediated myelin oxidation and interleukin-1 beta generation by a 21-aminosteroid, U74500A

Inflammatory cell-mediated myelin injury may be an important cause of tissue damage in both acute and chronic central nervous system (CNS) disorders. The 21-aminosteroids are novel derivatives of methylprednisolone without obvious glucocorticoid or mineralocorticoid side effects. We evaluated the ability of 21-aminosteroid, U74500A, to inhibit oxidation of rat brain myelin by human polymorphonuclear leukocytes (PMN) and monocytes. Myelin samples, as confirmed by SDS-PAGE, were incubated with PMN or monocytes and 100 microM U74500A or vehicle. Myelin oxidation by both PMN and monocytes was significantly reduced by U74500A. These observations demonstrate that U74500A can inhibit myelin oxidation by inflammatory cells. Additionally, 100 microM U74500A significantly reduced production of interleukin 1-beta by monocytes exposed to myelin. The aminosteroids may be beneficial in CNS disorders where myelin injury by inflammatory cells appears to contribute, such as acute focal ischemia or multiple sclerosis.

Chemiluminescence assay of mucosal reactive oxygen metabolites in inflammatory bowel disease

Previous studies suggesting increased reactive oxygen metabolite (ROM) production in inflammatory bowel disease have been restricted to peripheral blood and isolated intestinal phagocytes. In the current study, chemiluminescence and the effect of various scavengers, enzymes, and enzyme inhibitors were used to show that ROMs account for the increased production of oxidants by colorectal mucosal biopsy specimens in inflammatory bowel disease. Luminol-amplified chemiluminescence was increased in active ulcerative colitis [macroscopic grade 1: 25 photons.mg-1.min.10(-3) (median), 8-47 (95% confidence intervals), n = 40; grade 2: 89, 65-156, n = 30; grade 3: 247, 133-562, n = 13] and Crohn's disease [mild: 9, 3-84, n = 6; severe: 105, 25-789 (range), n = 5] compared with normal-looking mucosa (ulcerative colitis: 0.8, 0.4-1.4, n = 22, P less than 0.01; Crohn's disease: 0.8, 0.1-2, n = 6, P less than 0.05) and controls (0.6, 0.04-1.4, n = 52, P less than 0.01). In ulcerative colitis, luminol chemiluminescence correlated with microscopic inflammation (Spearman's p = 0.74, P = 0.0001) and was decreased by sodium azide (-89%, P less than 0.05), taurine (-31%, P less than 0.05), catalase (-23%, P less than 0.05), and dimethyl sulfoxide (-29%, P less than 0.05). Superoxide dismutase and oxypurinol decreased lucigenin chemiluminescence in ulcerative colitis by -63% (P less than 0.05) and -27% (P less than 0.05), respectively. Luminol chemiluminescence correlated with lucigenin chemiluminescence (Spearman's rho = 0.72, P = 0.003). These results suggest that neutrophil-derived oxidants (superoxide, hydrogen peroxide, hydroxyl radical, and hypochlorite) are generated in colorectal mucosa in active inflammatory bowel disease and support the hypothesis that production of such metabolites by neutrophils is of major pathogenetic importance.

Inhibition of stimulated human leukocyte hydrogen peroxide generation by a novel antioxidant, OPC-14117

Oxygen free radicals generated by leukocytes may contribute to tissue injury after central nervous system (CNS) focal ischemia or trauma. Inhibiting oxygen free radicals has improved outcome in experimental models of these conditions and antioxidant therapy appears promising. We evaluated the ability of a novel antioxidant, OPC-14117, to reduce hydrogen peroxide (H2O2) production by stimulated human polymorphonuclear (PMN) leukocytes and monocytes. Stimulated PMN and monocytes were incubated with several concentrations of OPC-14117 for 20 min and H2O2 production, nmol/1 x 10(6) cells/30 min, was measured. OPC-14117 significantly reduced PMN H2O2 production (P less than 0.001) and monocyte H2O2 production (P less than 0.05). A dose response relationship was observed for both leukocytes, as the 100 microM drug concentration was significantly (P less than 0.05) more effective than the 10 microM concentration. These results demonstrate that OPC-14117 inhibits H2O2 generation by stimulated human leukocytes and support further studies of its effects in disorders such as CNS focal ischemia and trauma, conditions where antioxidant therapy may be beneficial.

Methylprednisolone prophylaxis protects against endotoxin-induced death in rabbits

Endotoxemia in patients can lead to sepsis and shock by activation of cellular and plasmatic systems. Corticosteroids are described to have a beneficial effect on these phenomena. In this study of controlled endotoxic shock, we investigated the protective effects of prophylactic corticosteroid treatment against activation of cellular and plasmatic systems. In this respect, a low-dose methylprednisolone (1 mg/kg body wt) treatment was compared with that of a high-dose methylprednisolone (40 mg/kg body wt) treatment. Endotoxin infusion induced death of all rabbits, which was associated with leukopenia, thrombopenia, increased levels of beta-glucuronidase, and leukotriene B4 (LTB4) and decreased levels of complement total hemolytic activity (CH50) and tissue plasminogen activator (t-PA) activity. Both methylprednisolone regimens prevented death of the rabbits after endotoxin infusion, which correlated with a significant decrease of the granulocyte release product beta-glucuronidase (P less than 0.01). The early leukopenia and thrombopenia were not prevented; however, both cell numbers returned more rapidly to baseline values than in the placebo group (P less than 0.01, P less than 0.05). The LTB4 and CH50 concentration and t-PA activity did not differ significantly between the treated and placebo groups. These results indicate that although methylprednisolone has no inhibitory effect on the activation of the complement, arachidonic acid, and fibrinolytic systems, it protected the animals from the deleterious effects of endotoxin shock by inhibition of leukocyte activation. In this regard a low dosage of methylprednisolone is equally effective as the most often recommended high dose.

Oxygen radicals, inflammation, and arthritis: pathophysiological considerations and implications for treatment

A vast amount of circumstantial evidence implicates oxygen-derived free radicals, especially superoxide and hydroxyl radical (and to lesser extent, hydrogen peroxide), as mediators of inflammation and/or tissue destruction in inflammatory and arthritic disorders. The substrates for radical generation, namely properly stimulated phagocytic cells, transition metal catalysts, and (to a limited extent) ischemia, are all amply present, although there is no particular rheumatic disease in which a consistent abnormality of radical generation has been identified. These radical species can clearly degrade hyaluronic acid, modify collagen and perhaps proteoglycan structure and/or synthesis, alter and interact with immunoglobulins, activate enzymes and inactivate their inhibitors, and possibly participate in chemotaxis. In most situations, however, there is ample scavenging ability to detoxify these radicals before they hit their target, and many rheumatic disease drugs can decrease their production and/or effects. Despite the apparent sufficiency of natural scavengers and the lack of direct evidence that oxygen radicals are pathogenetically important, substantial pharmaceutical effort is still being made to develop free radical scavengers as therapeutic agents. Although individual free radicals die out quickly, rheumatologic interest in them has been sustained for nearly two decades.

A 21-aminosteroid reduces hydrogen peroxide generation by and chemiluminescence of stimulated human leukocytes

Leukocytes recruited to regions of focal cerebral ischemia may contribute to tissue injury by their ability to promote inflammation. A novel group of drugs, the 21-aminosteroids, have been observed to reduce neurologic damage and vasogenic cerebral edema in animal models of stroke by inhibiting lipid peroxidation. Production of hydrogen peroxide and free radicals by leukocytes during the inflammatory response may contribute to lipid peroxidation and other consequences of free radical-mediated tissue injury. We assessed the effect of U74500A, a 21-aminosteroid, on the generation of hydrogen peroxide by and on the chemiluminescence of stimulated polymorphonuclear leukocytes and monocytes from normal humans. U74500A significantly reduced the generation of hydrogen peroxide by polymorphonuclear leukocytes (p less than 0.001) and monocytes (p less than 0.01) in a dose-dependent manner. Monocyte chemiluminescence was also significantly inhibited (p less than 0.05), but polymorphonuclear leukocyte-associated chemiluminescence was unchanged. Our results indicate that U74500A can reduce the concentration of oxygen metabolites associated with stimulated human leukocytes, and this effect may explain in part how 21-aminosteroids reduce lipid peroxidation, ischemic injury, and vasogenic edema.

Methylprednisolone inhibits granulocytopenia induced by infusion of complement-activated serum but not of complement-activated plasma in rabbits

The effect of methylprednisolone was examined on complement-induced granulocytopenia in vivo following infusion of zymosan-activated autologous plasma or serum into rabbits. Methylprednisolone only inhibited granulocytopenia and thrombocytopenia when zymosan-activated serum or fibrinogen-depleted plasma were infused. It was ineffective at preventing granulocytopenia in animals infused with zymosan-activated plasma. Only zymosan-activated plasma contained fibrin monomers which could directly cause granulocytopenia independently of the generation of C5a. Hence, during complement activation in whole blood in vivo, little or no effect of methylprednisolone should be expected in preventing granulocytopenia.

Monocyte and polymorphonuclear leukocyte toxic oxygen metabolite production in multiple sclerosis

Lipid-laden macrophages, which are predominantly derived from blood monocytes, are present at sites of active multiple sclerosis demyelination and are assumed to be involved in the demyelinating process. These inflammatory cells produce a variety of toxic oxygen metabolites which can mediate host tissue destruction. We measured production of two oxygen metabolites by monocytes and polymorphonuclear leukocytes in MS patients and controls. Stimulated monocytes produced significantly more hydrogen peroxide, superoxide, and chemiluminescence in the MS group than controls. The polymorphonuclear leukocyte, an inflammatory cell that appears to contribute little to MS demyelination, did not demonstrate increased production of toxic oxygen metabolites in the MS patients as compared to controls. These results suggest that blood monocytes in MS patients are primed to produce increased amounts of cytotoxic oxygen metabolites when exposed to inflammatory stimuli.

Linoleic acid levels in white blood cells, platelets, and serum of multiple sclerosis patients

We found a small but statistically significant reduction in the linoleic acid concentration of white blood cells and platelets in MS patients. The percent linoleic acid concentration (mean +/- S.D.) in the white blood cells if 24 MS patients was 8.8 +/- 1.8% as compared with 11.4 +/- 4.9 in 24 age and sex-matched controls (p less than 0.05). Platelet levels were 8.5 +/- 2.4% and 10.6 +/- 3.8% respectively (P less than 0.05). Serum linoleic acid levels were not significantly different in the two groups. The possible role of linoleic acid in the pathogenesis of MS has yet to be defined.

Inhibition of the phagocytosis-induced respiratory burst by the fungal metabolite wortmannin and some analogues

The sterol-like fungal metabolite wortmannin and a number of natural and chemically-derived analogues were found to block the induction of the respiratory burst during phagocytosis. 17-Hydroxy wortmannin, the most active compound tested, showed a 50% inhibition of the burst in neutrophils and mononuclear phagocytes at concentrations ranging between 0.8 and 17 nM, while wortmannin itself was about half as potent. Chemical derivation showed that a furane structure between ring A and B with adjacent carbonyl functions is essential for activity. At concentrations that entirely prevented superoxide or hydrogen peroxide production, the wortmannins were not cytotoxic and did not inhibit phagocytosis. At even higher concentrations (10 microM), 17-hydroxy wortmannin had no effect on the NADPH oxidase, once activated. This suggests that the wortmannins interfere with the signal transduction sequence initiated by the particulate stimulus and leading to the activation of the respiratory burst oxidase.

Effects of dietary fish oil supplementation on polymorphonuclear leukocyte inflammatory potential

Polymorphonuclear leukocytes (PMNLs) are an important contributor to inflammation and are thus a part of the pathophysiology of many human diseases. We assessed the effect of fish oil on PMNL inflammatory potential by measuring chemiluminescence and superoxide production before and after six weeks of daily cod liver oil ingestion by healthy volunteers. Phagocytosing PMNLs demonstrated a 27% decrease in chemiluminescence (P less than 0.05) and a 64% decrease in superoxide production (P less than 0.01), following the cod liver oil supplementation. Analysis of PMNL and platelet fatty acids revealed the appearance of eicosapentaenoic acid and a significant decrease in arachidonic acid in both types of cells.

Mechanism by which methylprednisolone inhibits acute immune complex-induced changes in vascular permeability

Intravital microscopy was used to quantitate protein leakage which resulted from the deposition of immune complexes in the vasculature of the rat cremaster muscle. Immune complex deposition was initiated by the addition of 80 micrograms/ml of ovalbumin to the bath surrounding the muscle, followed by the intravenous administration of antiovalbumin. Administration of 25 mg/kg of antiovalbumin produced significant leakage of protein from the third-order venules, while 7.5 and 2.5 mg/kg had no effect. Administration of methylprednisolone (MP), 30 mg/kg, 1 h prior to the deposition of immune complexes significantly inhibited protein leakage. In separate experiments, MP inhibited intradermal edema formation and protein exudation induced in rats by histamine, platelet activating factor, or C5a. However, MP had no effect on protein exudation or edema produced by xanthine oxidase or glucose oxidase. Intravenous administration of MP inhibited the ability of polymorphonuclear leukocytes (PMNs) to phagocytize bacteria, but failed to alter hydrogen peroxide production. These results suggest that MP prevents acute changes in vascular permeability following immune complex deposition by inhibiting the effects of soluble mediators of edema on vascular endothelium and by inhibiting PMN phagocytosis.

Prophylactic and delayed treatment with high-dose methylprednisolone in a porcine model of early ARDS induced by endotoxaemia

The effects of prophylactic and delayed treatment with high-dose methylprednisolone were evaluated in a porcine model of early adult respiratory distress syndrome induced by endotoxaemia. Spontaneously breathing pigs under ketamine anaesthesia were infused i.v. with E. coli endotoxin (10 micrograms . h-1 . kg-1) over 6h. Twenty animals received endotoxin without treatment. Eight animals were pretreated with methylprednisolone i.v., 60 mg . kg-1, followed by an i.v. infusion at a rate of 10 mg . h-1 . kg-1. Ten animals received the same dosage of methylprednisolone beginning 2 h after the start of endotoxin infusion. Pretreatment with methylprednisolone prevented the endotoxin-induced impairment in pulmonary gas exchange and the development of pulmonary oedema. The pulmonary hypertension was counteracted. Cardiac output (Qt) and O2 delivery were improved. Mean arterial blood pressure (MAP) increased and was higher than in the untreated endotoxin group. The profound fall in PMN count was inhibited, while the accumulation of these cells in the lung was still substantial. Survival was improved. Delayed methylprednisolone treatment prevented further deterioration in pulmonary gas exchange and tended to restore it towards baseline. The pulmonary oedema and pulmonary hypertension were reduced. Qt and O2 delivery did not improve. MAP was higher than in the untreated endotoxin group towards the end of the observation period. The decline in PMN count and the pulmonary accumulation of these cells were not significantly influenced. Survival was improved. These results indicate that high-dose methylprednisolone, when given early in the course of sepsis, might be of clinical value in prevention of the devastating pulmonary and circulatory complications of this disease.

The immunologic effects, kinetics, and use of glucocorticosteroids

This article describes our current understanding of the immunologic effects of glucocorticosteroids and uses this information in an attempt to place the therapeutic dosing of glucocorticosteroids on a more rational basis.

Pharmacology of free radicals; recent views on their relation to inflammatory mechanisms

Production of free radicals from molecular oxygen during the inflammatory process can exhibit beneficial effects against the phlogistic stimulus and may act as a defence mechanism. Nevertheless, in many cases this production is associated with toxic reactions related to inflammatory response. Many compounds including bovine superoxide dismutase, non steroidal anti-inflammatory drugs, radical scavengers (e.g. acetaminophen), corticoids etc., have been shown to counteract this phenomenon. Their beneficial effects and mechanism of action are reviewed.

In vitro effect of hydrocortisone on the attachment and ingestion phases of immunoglobulin G- and complement component 3b-mediated phagocytosis by human neutrophils

The fluorescence quenching method (FQ method) was used to investigate the effect of hydrocortisone on the attachment and ingestion phases of immunoglobulin G (IgG)- and complement component 3b (C3b)-mediated phagocytosis by human neutrophils (PMNs). The results were compared with metabolic activity (O2- release) of the phagocytes. When the PMNs were treated with 5 X 10(-5) M hydrocortisone or more, both IgG-mediated and C3b-mediated interactions decreased. The number of intracellular particles decreased as the total number of PMN-associated particles decreased, indicating an effect mainly on particle attachment. This was substantiated by the fact that pretreatment of the PMN with cytochalasin B resulted in a hydrocortisone dose-related decrease of interacting particles. The FQ method made it possible to quantify the stimulus-phagocyte interaction in relation to the metabolic response. Superoxide anion release decreased at the highest concentration of hydrocortisone used (5 X 10(-3) M), which merely reflected the decreased number of interacting particles. No reduction in metabolic activation was obtained when the superoxide anion release was correlated with the number of interacting yeast-IgG particles. The results indicate that hydrocortisone primarily affects the binding capacity of Fc and C3b receptors, resulting in decreased metabolic activation. The effector functions, e.g., ingestion and metabolic activation, were not affected by hydrocortisone in this study.

Effect of metal chelators and antiinflammatory drugs on the degradation of hyaluronic acid

Degradation of hyaluronic acid (measured viscometrically) by oxygen-derived free radicals (ODFR) generated 1) by autoxidation of ferrous EDTA chelates and 2) enzymatically by xanthine oxidase and hypoxanthine (XO/HX) was studied. Degradation of hyaluronic acid by XO/HX was strongly inhibited by superoxide dismutase and catalase, whereas degradation of hyaluronic acid by autoxidation of ferrous ions was weakly inhibited by catalase and unaffected by superoxide dismutase. Both ODFR-producing systems were inhibited by hydroxyl radical scavengers, suggesting that hydroxyl radical was the proximate damaging species in both systems. Penicillamine at concentrations of 1-5 mM stimulated hyaluronic acid degradation by ferrous EDTA chelates but inhibited degradation by the XO/HX system. Higher concentrations of penicillamine and all concentrations studied (1-100 mM) of other antiinflammatory drugs (chloroquine, gold sodium thiomalate, and salicylate) inhibited hyaluronic acid degradation by both the autoxidation and enzymatic ODFR-producing systems, with inhibitory potency similar to that seen with known hydroxyl radical scavengers. Both systems serve as in vitro models of ODFR-mediated tissue damage which may occur in vivo at sites of inflammation.