Role of hydrogen peroxide in neutrophil-mediated destruction of cultured endothelial cells

Evidence-based pathogenesis and treatment of ulcerative colitis: A causal role for colonic epithelial hydrogen peroxide

In this comprehensive evidence-based analysis of ulcerative colitis (UC), a causal role is identified for colonic epithelial hydrogen peroxide (H₂O₂) in both the pathogenesis and relapse of this debilitating inflammatory bowel disease. Studies have shown that H₂O₂ production is significantly increased in the non-inflamed colonic epithelium of individuals with UC. H₂O₂ is a powerful neutrophilic chemotactic agent that can diffuse through colonic epithelial cell membranes creating an interstitial chemotactic molecular “trail” that attracts adjacent intravascular neutrophils into the colonic epithelium leading to mucosal inflammation and UC. A novel therapy aimed at removing the inappropriate H₂O₂ mediated chemotactic signal has been highly effective in achieving complete histologic resolution of colitis in patients experiencing refractory disease with at least one (biopsy-proven) histologic remission lasting 14 years to date. The evidence implies that therapeutic intervention to prevent the re-establishment of a pathologic H₂O₂ mediated chemotactic signaling gradient will indefinitely preclude neutrophilic migration into the colonic epithelium constituting a functional cure for this disease. Cumulative data indicate that individuals with UC have normal immune systems and current treatment guidelines calling for the suppression of the immune response based on the belief that UC is caused by an underlying immune dysfunction are not supported by the evidence and may cause serious adverse effects. It is the aim of this paper to present experimental and clinical evidence that identifies H₂O₂ produced by the colonic epithelium as the causal agent in the pathogenesis of UC. A detailed explanation of a novel therapeutic intervention to normalize colonic H₂O₂, its rationale, components, and formulation is also provided.

Discrimination of Methionine Sulfoxide and Sulfone by Human Neutrophil Elastase

Human neutrophil elastase (HNE) is a uniquely destructive serine protease with the ability to unleash a wave of proteolytic activity by destroying the inhibitors of other proteases. Although this phenomenon forms an important part of the innate immune response to invading pathogens, it is responsible for the collateral host tissue damage observed in chronic conditions such as chronic obstructive pulmonary disease (COPD), and in more acute disorders such as the lung injuries associated with COVID-19 infection. Previously, a combinatorially selected activity-based probe revealed an unexpected substrate preference for oxidised methionine, which suggests a link to oxidative pathogen clearance by neutrophils. Here we use oxidised model substrates and inhibitors to confirm this observation and to show that neutrophil elastase is specifically selective for the di-oxygenated methionine sulfone rather than the mono-oxygenated methionine sulfoxide. We also posit a critical role for ordered solvent in the mechanism of HNE discrimination between the two oxidised forms methionine residue. Preference for the sulfone form of oxidised methionine is especially significant. While both host and pathogens have the ability to reduce methionine sulfoxide back to methionine, a biological pathway to reduce methionine sulfone is not known. Taken together, these data suggest that the oxidative activity of neutrophils may create rapidly cleaved elastase "super substrates" that directly damage tissue, while initiating a cycle of neutrophil oxidation that increases elastase tissue damage and further neutrophil recruitment.

Enhancement by Hydrogen Peroxide of Calcium Signals in Endothelial Cells Induced by 5-HT1B and 5-HT2B Receptor Agonists

Hydrogen peroxide, formed in the endothelium, acts as a factor contributing to the relaxation of blood vessels. The reason for this vasodilatory effect could be modulation by H₂O₂ of calcium metabolism, since mobilization of calcium ions in endothelial cells is a trigger of endothelium-dependent relaxation. The aim of this work was to investigate the influence of H₂O₂ on the effects of Ca²⁺-mobilizing agonists in human umbilical vein endothelial cells (HUVEC). We have found that H₂O₂ in concentration range 10-100 μM increases the rise of [Ca²⁺]_i induced by 5-hydroxytryptamine (5-HT) and carbachol and does not affect the calcium signals of ATP, agonist of type 1 protease-activated receptor SFLLRN, histamine and bradykinin. Using specific agonists of 5-HT1B and 5-HT2B receptors CGS12066B and BW723C86, we have demonstrated that H₂O₂ potentiates the effects mediated by these types of 5-HT receptors. Potentiation of the effect of BW723C86 can be produced by the induction of endogenous oxidative stress in HUVEC. We have shown that the activation of 5-HT2B receptor by BW723C86 causes production of reactive oxygen species (ROS). Inhibitor of NADPH oxidases VAS2870 suppressed formation of ROS and partially inhibited [Ca²⁺]_i rise induced by BW723C86. Thus, it can be assumed that vasorelaxation induced by endogenous H₂O₂ in endothelial cells partially occurs due to the potentiation of the agonist-induced calcium signaling.

Lung Defense through IL-8 Carries a Cost of Chronic Lung Remodeling and Impaired Function

IL-8-dependent inflammation is a hallmark of host lung innate immunity to bacterial pathogens, yet in many human lung diseases, including chronic obstructive pulmonary disease, bronchiectasis, and pulmonary fibrosis, there are progressive, irreversible, pathological changes associated with elevated levels of IL-8 in the lung. To better understand the duality of IL-8-dependent host immunity to bacterial infection and lung pathology, we expressed human IL-8 transgenically in murine bronchial epithelium, and investigated the impact of overexpression on lung bacterial clearance, host immunity, and lung pathology and function. Persistent IL-8 expression in bronchial epithelium resulted in neutrophilia, neutrophil maturation and activation, and chemotaxis. There was enhanced protection against challenge with Pseudomonas aeruginosa, and significant changes in baseline expression of innate and adaptive immunity transcripts for Ccl5, Tlr6, IL-2, and Tlr1. There was increased expression of Tbet and Foxp3 in response to the Pseudomonas antigen OprF, indicating a regulatory T-cell phenotype. However, this enhanced bacterial immunity came at a high price of progressive lung remodeling, with increased inflammation, mucus hypersecretion, and fibrosis. There was increased expression of Ccl3 and reduced expression of Claudin 18 and F11r, with damage to epithelial organization leading to leaky tight junctions, all of which resulted in impaired lung function with reduced compliance, increased resistance, and bronchial hyperreactivity as measured by whole-body plethysmography. These results show that IL-8 overexpression in the bronchial epithelium benefits lung immunity to bacterial infection, but specifically drives lung damage through persistent inflammation, lung remodeling, and damaged tight junctions, leading to impaired lung function.

Polymicrobial sepsis impairs bystander recruitment of effector cells to infected skin despite optimal sensing and alarming function of skin resident memory CD8 T cells

Sepsis is a systemic infection that enhances host vulnerability to secondary infections normally controlled by T cells. Using CLP sepsis model, we observed that sepsis induces apoptosis of circulating memory CD8 T-cells (TCIRCM) and diminishes their effector functions, leading to impaired CD8 T-cell mediated protection to systemic pathogen re-infection. In the context of localized re-infections, tissue resident memory CD8 T-cells (TRM) provide robust protection in a variety of infectious models. TRM rapidly 'sense' infection in non-lymphoid tissues and 'alarm' the host by enhancing immune cell recruitment to the site of the infection to accelerate pathogen clearance. Here, we show that compared to pathogen-specific TCIRCM, sepsis does not invoke significant numerical decline of Vaccinia virus induced skin-TRM keeping their effector functions (e.g., Ag-dependent IFN-γ production) intact. IFN-γ-mediated recruitment of immune cells to the site of localized infection was, however, reduced in CLP hosts despite TRM maintaining their 'sensing and alarming' functions. The capacity of memory CD8 T-cells in the septic environment to respond to inflammatory cues and arrive to the site of secondary infection/antigen exposure remained normal suggesting T-cell-extrinsic factors contributed to the observed lesion. Mechanistically, we showed that IFN-γ produced rapidly during sepsis-induced cytokine storm leads to reduced IFN-γR1 expression on vascular endothelium. As a consequence, decreased expression of adhesion molecules and/or chemokines (VCAM1 and CXCL9) on skin endothelial cells in response to TRM-derived IFN-γ was observed, leading to sub-optimal bystander-recruitment of effector cells and increased susceptibility to pathogen re-encounter. Importantly, as visualized by intravital 2-photon microscopy, exogenous administration of CXCL9/10 was sufficient to correct sepsis-induced impairments in recruitment of effector cells at the localized site of TRM antigen recognition. Thus, sepsis has the capacity to alter skin TRM anamnestic responses without directly impacting TRM number and/or function, an observation that helps to further define the immunoparalysis phase in sepsis survivors.

Elevated Leukocyte Azurophilic Enzymes in Human Diabetic Ketoacidosis Plasma Degrade Cerebrovascular Endothelial Junctional Proteins

OBJECTIVE

Diabetic ketoacidosis in children is associated with vasogenic cerebral edema, possibly due to the release of destructive polymorphonuclear neutrophil azurophilic enzymes. Our objectives were to measure plasma azurophilic enzyme levels in children with diabetic ketoacidosis, to correlate plasma azurophilic enzyme levels with diabetic ketoacidosis severity, and to determine whether azurophilic enzymes disrupt the blood-brain barrier in vitro.

DESIGN

Prospective clinical and laboratory study.

SETTING

The Children's Hospital, London Health Sciences Centre.

SUBJECTS

Pediatric type 1 diabetes patients; acute diabetic ketoacidosis or age-/sex-matched insulin-controlled.

MEASUREMENTS AND MAIN RESULTS

Acute diabetic ketoacidosis in children was associated with elevated polymorphonuclear neutrophils. Plasma azurophilic enzymes were elevated in diabetic ketoacidosis patients, including human leukocyte elastase (p < 0.001), proteinase-3 (p < 0.01), and myeloperoxidase (p < 0.001). A leukocyte origin of human leukocyte elastase and proteinase-3 in diabetic ketoacidosis was confirmed with buffy coat quantitative real-time polymerase chain reaction (p < 0.01). Of the three azurophilic enzymes elevated, only proteinase-3 levels correlated with diabetic ketoacidosis severity (p = 0.002). Recombinant proteinase-3 applied to human brain microvascular endothelial cells degraded both the tight junction protein occludin (p < 0.05) and the adherens junction protein VE-cadherin (p < 0.05). Permeability of human brain microvascular endothelial cell monolayers was increased by recombinant proteinase-3 application (p = 0.010).

CONCLUSIONS

Our results indicate that diabetic ketoacidosis is associated with systemic polymorphonuclear neutrophil activation and degranulation. Of all the polymorphonuclear neutrophil azurophilic enzymes examined, only proteinase-3 correlated with diabetic ketoacidosis severity and potently degraded the blood-brain barrier in vitro. Proteinase-3 might mediate vasogenic edema during diabetic ketoacidosis, and selective proteinase-3 antagonists may offer future vascular- and neuroprotection.

Phenylboronic acid-based (19)F MRI probe for the detection and imaging of hydrogen peroxide utilizing its large chemical-shift change

Herein, we report on a new (19)F MRI probe for the detection and imaging of H2O2. Our designed 2-fluorophenylboronic acid-based (19)F probe promptly reacted with H2O2 to produce 2-fluorophenol via boronic acid oxidation. The accompanying (19)F chemical-shift change reached 31 ppm under our experimental conditions. Such a large chemical-shift change allowed for the imaging of H2O2 by (19)F chemical-shift-selective MRI.

The heterogenic properties of monocytes/macrophages and neutrophils in inflammatory response in diabetes

Inflammation is a complicated biological process in response to harmful stimuli, which involves the cooperation of immune system and vascular system. Upon pathogen invasion or tissue injury, resident innate immune cells such as macrophages and dendritic cells are activated and release inflammatory mediators, which result in the vasodilation and recruitment of leukocytes, mainly monocytes and neutrophils. As two of the most important inflammation-mediating immune cells, macrophages and neutrophils have long been regarded to have a pro-inflammatory effect. However, increasing evidences suggest the role of macrophage and neutrophil in inflammation is more complicated and diversified than we thought. Differently activated macrophages and neutrophils lead to diverse even opposite activities. Precise understanding of the role of different subpopulations is critical to achieve the effective treatment for inflammatory diseases. In this review, we discuss the two potentially distinct activation routes of macrophages and neutrophils in obesity and diabetes.

Mechanisms of haptoglobin protection against hemoglobin peroxidation triggered endothelial damage

Extracellular hemoglobin (Hb) has been recognized as a disease trigger in hemolytic conditions such as sickle cell disease, malaria, and blood transfusion. In vivo, many of the adverse effects of free Hb can be attenuated by the Hb scavenger acute-phase protein haptoglobin (Hp). The primary physiologic disturbances that can be caused by free Hb are found within the cardiovascular system and Hb-triggered oxidative toxicity toward the endothelium has been promoted as a potential mechanism. The molecular mechanisms of this toxicity as well as of the protective activities of Hp are not yet clear. Within this study, we systematically investigated the structural, biochemical, and cell biologic nature of Hb toxicity in an endothelial cell system under peroxidative stress. We identified two principal mechanisms of oxidative Hb toxicity that are mediated by globin degradation products and by modified lipoprotein species, respectively. The two damage pathways trigger diverse and discriminative inflammatory and cytotoxic responses. Hp provides structural stabilization of Hb and shields Hb's oxidative reactions with lipoproteins, providing dramatic protection against both pathways of toxicity. By these mechanisms, Hp shifts Hb's destructive pseudo-peroxidative reaction to a potential anti-oxidative function during peroxidative stress.

Low-density granulocytes: a distinct class of neutrophils in systemic autoimmunity

Recent studies have renewed the interest on the potential role that neutrophils play in the development of systemic lupus erythematosus (SLE) and other autoimmune conditions. A distinct subset of proinflammatory, low-density granulocytes (LDGs) isolated from the peripheral blood mononuclear cell fractions of patients with SLE has been described. While the origin and role of LDGs needs to be fully characterized, there is evidence that these cells may contribute to lupus pathogenesis and to the development of end-organ damage through heightened proinflammatory responses, altered phagocytic capacity, enhanced ability to synthesize type I interferons, and to kill endothelial cells. Furthermore, these cells readily form neutrophil extracellular traps, a phenomenon that may promote autoantigen externalization and organ damage. This review examines the biology and potential origin of LDGs, describes the ultrastructural characteristics of these cells, and discusses their putative pathogenic role in systemic autoimmune diseases.

A sensitive H2O2 assay based on dumbbell-like PtPd-Fe3O4 nanoparticles

Dumbbell-like Pt(48)Pd(52)-Fe(3)O(4) nanoparticles are synthesized and functionalized with oleylamine-polyethyleneglycol to serve as an efficient catalyst for H(2)O(2) reduction and tetramethylbenzidine (TMB) oxidation in biological solutions. The Pt(48)Pd(52)-Fe(3)O(4)/TMB kit is even more active than the natural enzyme for H(2)O(2) detection with a detection limit reaching 2 μM, and is successfully used to quantitatively monitor the extracellular H(2)O(2) generated by neutrophils.

A new pharmacological agent (AKB-4924) stabilizes hypoxia inducible factor-1 (HIF-1) and increases skin innate defenses against bacterial infection

Hypoxia inducible factor-1 (HIF-1) is a transcription factor that is a major regulator of energy homeostasis and cellular adaptation to low oxygen stress. HIF-1 is also activated in response to bacterial pathogens and supports the innate immune response of both phagocytes and keratinocytes. In this work, we show that a new pharmacological compound AKB-4924 increases HIF-1 levels and enhances the antibacterial activity of phagocytes and keratinocytes against both methicillin-sensitive and methicillin-resistant strains of Staphylococcus aureus in vitro. AKB-4924 is also effective in stimulating the killing capacity of keratinocytes against the important opportunistic skin pathogens Pseudomonas aeruginosa and Acinetobacter baumanii. The effect of AKB-4924 is mediated through the activity of host cells, as the compound exerts no direct antimicrobial activity. Administered locally as a single agent, AKB-4924 limits S. aureus proliferation and lesion formation in a mouse skin abscess model. This approach to pharmacologically boost the innate immune response via HIF-1 stabilization may serve as a useful adjunctive treatment for antibiotic-resistant bacterial infections.

Structure-activity relationship of antioxidants for inhibitors of linoleic acid hydroperoxide-induced toxicity in cultured human umbilical vein endothelial cells

Structure-activity relationship of antioxidants for the protective effects on linoleic acid hydroperoxide (LOOH)-induced toxicity were examined in cultured human umbilical vein endothelial cells. alpha-Tocopherol, 2,2,5,7,8-pentamethylchroman-6-ol, butylated hydroxytoluene, probucol, and fatty acid esters of ascorbic acid provided efficient protection against the cytotoxicity of LOOH in pretreatment, but phenols without alkyl groups at the ortho positions and hydrophilic antioxidants such as Trolox and ascorbic acid provided no protection. Probably, the effectiveness of the protection against cytotoxicity by these antioxidants dependsprimarily on their rate of incorporation into cells due to their lipophilicity, secondly on their antioxidant activity, and thirdly on their orientation in biomembranes. On the other hand, flavones, such as baicalein and luteolin bearing 3 to 5 hydroxyl groups, and flavonols showed a protective effect against LOOH cytotoxicity when added together with LOOH,but not by pretreatment. Among catechins, (+)-catechin and (-)-epigallocatechin gallate monoglucoside and diglucoside were effective in suppressing LOOH-induced cytotoxicity, but their effects were not so strong. The structure-activity relationship of flavonoids revealed the presence of either theortho-dihydroxy structure in the B ring of flavonoids or the 3-hydroxyl and 4-oxo groups in the C ring to be important forthe protective activities. Furthermore, coumarins such as esculetin containing the ortho catechol structure had protective effects in both pretreatment and concurrent treatment. These results suggest that ortho catechol moiety of flavonoids, catechins, and coumarins is an important structure in the protection against LOOH-induced cytotoxicity,and that the alkyl groups of monophenols are critical for protection.

Formation, reactivity, and detection of protein sulfenic acids

It has become clear in recent decades that the post-translational modification of protein cysteine residues is a crucial regulatory event in biology. Evidence supports the reversible oxidation of cysteine thiol groups as a mechanism of redox-based signal transduction, while the accumulation of proteins with irreversible thiol oxidations is a hallmark of stress-induced cellular damage. The initial formation of cysteine-sulfenic acid (SOH) derivatives, along with the reactive properties of this functional group, serves as a crossroads whereby the local redox environment may dictate the progression of either regulatory or pathological outcomes. Protein-SOH are established as transient intermediates in the formation of more stable cysteine oxidation products both under basal conditions and in response to several redox-active extrinsic compounds. This review details both direct and multistep chemical routes proposed to generate protein-SOH, the spectrum of secondary reactions that may follow their initial formation and the arsenal of experimental tools available for their detection. Pioneering studies that have provided a framework for our current understanding of protein-SOH as well as state-of-the-art proteomic strategies designed for global assessments of this post-translational modification are highlighted.

Neutrophil elastase contributes to the development of ischemia/reperfusion-induced liver injury by decreasing the production of insulin-like growth factor-I in rats

Neutrophil elastase (NE) decreases the endothelial production of prostacyclin (PGI(2)) through the inhibition of endothelial nitric oxide synthase (NOS) activation and thereby contributes to the development of ischemia/reperfusion (I/R)-induced liver injury. We previously demonstrated that calcitonin gene-related peptide (CGRP) released from sensory neurons increases the insulin-like growth factor- I (IGF-I) production and thereby reduces I/R-induced liver injury. Because PGI(2) is capable of stimulating sensory neurons, we hypothesized that NE contributes to the development of I/R-induced liver injury by decreasing IGF-I production. In the present study, we examined this hypothesis in rats subjected to hepatic I/R. Ischemia/reperfusion-induced decreases of hepatic tissue levels of CGRP and IGF-I were prevented significantly by NE inhibitors, sivelestat, and L-658, 758, and these effects of NE inhibitors were reversed completely by the nonselective cyclooxygenase inhibitor indomethacin (IM) and the nonselective NOS inhibitor L-NAME but not by the selective inducible NOS inhibitor 1400W. I/R-induced increases of hepatic tissue levels of caspase-3, myeloperoxidase and the number of apoptotic cells were inhibited by NE inhibitors, and these effects of NE inhibitors were reversed by IM and L-NAME but not by 1400W. Administration of iloprost, a stable PGI(2) analog, produced effects similar to those induced by NE inhibitors. Taken together, these observations strongly suggest that NE may play a critical role in the development of I/R-induced liver injury by decreasing the IGF-I production through the inhibition of sensory neuron stimulation, which may lead to an increase of neutrophil accumulation and hepatic apoptosis through activation of caspase-3 in rats.

Superoxide dismutase mimetic drug tempol aggravates anti-GBM antibody-induced glomerulonephritis in mice

Oxidative stress plays an important role in the pathogenesis of anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM-GN). Superoxide dismutase (SOD) is the first line of defense against oxidative stress by converting superoxide to hydrogen peroxide (H(2)O(2)). We investigated the effect of the SOD mimetic drug tempol on anti-GBM-GN in mice. 129/svJ mice were challenged with rabbit anti-mouse-GBM sera to induce GN and subsequently divided into tempol (200 mg.kg(-1).day(-1), orally) and vehicle-treated groups. Routine histology, SOD and catalase activities, malondialdehyde (MDA), H(2)O(2), and immunohistochemical staining for neutrophils, lymphocytes, macrophages, p65-NF-kappaB, and osteopontin were performed. Mice with anti-GBM-GN had significantly reduced renal SOD and catalase activities and increased H(2)O(2) and MDA levels. Unexpectedly, tempol administration exacerbated anti-GBM-GN as evidenced by intensification of proteinuria, the presence of severe crescentic GN with leukocyte influx, and accelerated mortality in the treated group. Tempol treatment raised SOD activity and H(2)O(2) level in urine, upregulated p65-NF-kappaB and osteopontin in the kidney, but had no effect on renal catalase activity. Thus tempol aggravates anti-GBM-GN by increasing production of H(2)O(2) which is a potent NF-kappaB activator and as such can intensify inflammation and renal injury. This supposition is supported by increases seen in p65-NF-kappaB, osteopontin, and leukocyte influx in the kidneys of the tempol-treated group.

A distinct subset of proinflammatory neutrophils isolated from patients with systemic lupus erythematosus induces vascular damage and synthesizes type I IFNs

Neutrophil-specific genes are abundant in PBMC microarrays from lupus patients because of the presence of low-density granulocytes (LDGs) in mononuclear cell fractions. The functionality and pathogenicity of these LDGs have not been characterized. We developed a technique to purify LDGs from lupus PBMCs and assessed their phenotype, function, and potential role in disease pathogenesis. LDGs, their autologous lupus neutrophils, and healthy control neutrophils were compared with regard to their microbicidal and phagocytic capacities, generation of reactive oxygen species, activation status, inflammatory cytokine profile, and type I IFN expression and signatures. The capacity of LDGs to kill endothelial cells and their antiangiogenic potential were also assessed. LDGs display an activated phenotype, secrete increased levels of type I IFNs, TNF-alpha, and IFN-gamma, but show impaired phagocytic potential. LDGs induce significant endothelial cell cytotoxicity and synthesize sufficient levels of type I IFNs to disrupt the capacity of endothelial progenitor cells to differentiate into mature endothelial cells. LDG depletion restores the functional capacity of endothelial progenitor cells. We conclude that lupus LDGs are proinflammatory and display pathogenic features, including the capacity to synthesize type I IFNs. They may play an important dual role in premature cardiovascular disease development in systemic lupus erythematosus by simultaneously mediating enhanced vascular damage and inhibiting vascular repair.

PDK1 regulates chemotaxis in human neutrophils

Phosphoinositide-dependent kinase (PDK1) plays a central role in signal transduction mediated by phosphatidylinositol 3-kinases (PI3K) and regulates cellular functions in neutrophils. Neutrophils from individuals diagnosed with localized aggressive periodontitis (LAP) present an in vivo phenotype with depressed chemotaxis. The aim of this study was to test the hypothesis that PDK1 regulates chemotaxis in neutrophils and is responsible for the abnormal neutrophil chemotaxis LAP. Neutrophil chemotaxis was significantly suppressed by the PDK1 inhibitor staurosporine. When cells were transfected with PDK1 siRNA, there was a significant reduction in chemotaxis, while superoxide generation was not significantly affected. In primary neutrophils from persons with LAP, PDK1 expression and activation levels were significantly reduced, and this reduction was associated with the reduced phosphorylation of Akt (Thr308) and chemotaxis. Analysis of these data demonstrates that PDK1 is essential for the chemotactic migration of neutrophils, and in the absence of PDK1, neutrophil chemotaxis is impaired.

Increased Oxidative Stress in the Mouse Adriamycin Model of Glomerulosclerosis Is Accompanied by Deposition of Ferric Iron and Altered GGT Activity in Renal Cortex

Chronic renal failure evolves inevitable towards glomerular and tubulo-interstitial sclerosis. This pathological process involves a disturbed redox status of the kidney tissue, leading to irreversible damage. In this study we investigate in an adriamycin model of chronic renal failure in mice the evolution of in vivo hydrogen peroxide production, and the possible role of gamma-glutamyl transpeptidase and ferric iron in the process. Histological changes and ferric iron deposits are evaluated by histochemical staining. To evaluate oxidative stress residual catalase activity, TBARS formation and gamma-glutamyl transpeptidase activity are measured spectrophotometrically. While catalase activity remains the same, a decreased residual catalase activity indicates an increased formation of hydrogen peroxide. Both the activity of gamma-glutamyl transpeptidase and TBARS formation is increased at early stages of the disease. Ferric iron is clearly present in the proximal tubule. Twenty days after adriamycin injection all parameters decrease, probably due to the destruction of the tissue. Our data show the involvement of oxidative stress in the progression of adriamycin induced renal failure in mice. Both radical production and oxidative damage are measurable, while the altered activity of gamma-glutamyl transpeptidase and the deposition of ferric iron suggest the involvement of these factors in the development of a disturbed redox status in the kidney cortex.

Transepithelial migration of neutrophils: mechanisms and implications for acute lung injury

The primary function of neutrophils in host defense is to contain and eradicate invading microbial pathogens. This is achieved through a series of swift and highly coordinated responses culminating in ingestion (phagocytosis) and killing of invading microbes. While these tasks are usually performed without injury to host tissues, in pathologic circumstances such as sepsis, potent antimicrobial compounds can be released extracellularly, inducing a spectrum of responses in host cells ranging from activation to injury and death. In the lung, such inflammatory damage is believed to contribute to the pathogenesis of diverse lung diseases, including acute lung injury and the acute respiratory distress syndrome, chronic obstructive lung disease, and cystic fibrosis. In these disorders, epithelial cells are targets of leukocyte-derived antimicrobial products, including proteinases and oxidants. Herein, we review the mechanisms involved in the physiologic process of neutrophil transepithelial migration, including the role of specific adhesion molecules on the leukocyte and epithelial cells. We examine the responses of the epithelial cells to the itinerant leukocytes and their cytotoxic products and the consequences of this for lung injury and repair. This paradigm has important clinical implications because of the potential for selective blockade of these pathways to prevent or attenuate lung injury.

Sustained contraction and endothelial dysfunction induced by reactive oxygen species in porcine coronary artery

A combination of purine and xanthine oxidase (XOD) dose-dependently elicited sustained contraction of porcine coronary arterial rings and resulted in increased concentrations of superoxide anions and hydrogen peroxide. These contractile responses appeared, with a delay, after the application of purine and XOD, used as a reactive oxygen species (ROS)-generating system. Coronary arteries precontracted with prostaglandin F(2alpha) failed to relax in response to substance P after exposing the arterial preparation to this ROS-generating system. The contractile response of the coronary artery to the ROS-generating system was almost completely inhibited by catalase (130 U/ml), and was partially inhibited by superoxide dismutase (60 U/ml), or mannitol (30 mM). A voltage-dependent L-type Ca(2+) channel antagonist, nicardipine, had no effect on contraction. Dysfunction of endothelial cells was completely prevented by catalase, but not by superoxide dismutase or mannitol. These results suggest that superoxide anions, hydrogen peroxide and hydroxyl radicals might be involved in eliciting sustained, delayed-onset coronary artery contraction, which is not related to L-type Ca(2+) channels. They also suggest that hydrogen peroxide might play a major role in endothelial dysfunction of the porcine coronary artery.

Homocysteine stimulates NADPH oxidase-mediated superoxide production leading to endothelial dysfunction in rats

Elevation of blood homocysteine (Hcy) levels (hyperhomocysteinemia) is a risk factor for cardiovascular disorders. We previously reported that oxidative stress contributed to Hcy-induced inflammatory response in vascular cells. In this study, we investigated whether NADPH oxidase was involved in Hcy-induced superoxide anion accumulation in the aorta, which leads to endothelial dysfunction during hyperhomocysteinemia. Hyperhomocysteinemia was induced in rats fed a high-methionine diet. NADPH oxidase activity and the levels of superoxide and peroxynitrite were markedly increased in aortas isolated from hyperhomocysteinemic rats. Expression of the NADPH oxidase subunit p22phox increased significantly in these aortas. Administration of an NADPH oxidase inhibitor (apocynin) not only attenuated aortic superoxide and peroxynitrite to control levels but also restored endothelium-dependent relaxation in the aortas of hyperhomocysteinemic rats. Transfection of human endothelial cells or vascular smooth muscle cells with p22phox siRNA to inhibit NADPH oxidase activation effectively abolished Hcy-induced superoxide anion production, thus indicating the direct involvement of NADPH oxidase in elevated superoxide generation in vascular cells. Taken together, these results suggest that Hcy-stimulated superoxide anion production in the vascular wall is mediated through the activation of NADPH oxidase, which leads to endothelial dysfunction during hyperhomocysteinemia.

NADPH oxidase is required for neutrophil-dependent autoantibody-induced tissue damage

The contribution of phagocyte-derived reactive oxygen species to tissue injury in autoimmune inflammatory diseases is unclear. Here we report that granulocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase crucially contributes to tissue injury in experimental models of the antibody-mediated autoimmune disease epidermolysis bullosa acquisita. Neutrophil cytosolic factor 1-deficient mice lacking functional NADPH oxidase were resistant to skin blistering by the passive transfer of antibodies against type VII collagen. Pharmacological inhibition or deficiency of human NADPH oxidase abolished dermal-epidermal separation caused by autoantibodies and granulocytes ex vivo. In addition, recruitment of granulocytes into the skin was required for tissue injury, as demonstrated by the resistance to experimental blistering of wild-type mice depleted of neutrophils and of CD18-deficient mice. Transfer of neutrophil cytosolic factor 1-sufficient granulocytes into neutrophil cytosolic factor 1-deficient mice demonstrated that granulocytes provide the NADPH oxidase required for tissue damage. Our findings identify granulocyte-derived NADPH oxidase as a key molecular effector engaged by pathogenic autoantibodies and provide relevant targets for prevention of tissue damage in granulocyte-mediated autoimmune diseases.

Inhibition of neutrophil activation by lafutidine, an H2-receptor antagonist, through enhancement of sensory neuron activation contributes to the reduction of stress-induced gastric mucosal injury in rats

Sensory neuron activation reduces water-immersion restraint stress (WIR)-induced gastric mucosal injury by inhibiting neutrophil activation through increase in endothelial production of prostacyclin. This study was designed to examine whether lafutidine, which is an H(2)-receptor antagonist and activates sensory neurons, inhibits neutrophil activation, thereby reducing WIR-induced gastric mucosal injury. Lafutidine enhanced WIR-induced increases in gastric tissue levels of calcitonin gene-related peptide (CGRP) and 6-keto-PGF(1alpha), a stable metabolite of prostacyclin, whereas famotidine, another H(2)-receptor antagonist, did not. Such lafutidine-induced increases in gastric tissue levels of 6-keto-PGF(1alpha) were reversed by pretreatment with capsazepine, an inhibitor of sensory neuron activation, CGRP(8-37), a CGRP antagonist, and indomethacin. Lafutidine inhibited acid-induced exacerbation of gastric mucosal injury in animals subjected to WIR by inhibiting neutrophil activation, whereas famotidine did not. Lafutidine synergistically increased CGRP release from isolated rat dorsal root ganglion neurons in the presence of anandamide, but famotidine did not. These observations suggest that lafutidine might reduce WIR-induced gastric mucosal injury not only by inhibiting acid secretion but also by inhibiting neutrophil activation through enhancement of sensory neuron activation.

Platelet-leukocyte interactions in hemodialysis patients: culprit or bystander?

The formation of circulating platelet-leukocyte complexes has been observed in a variety of conditions and may be pathophysiologically significant. Platelet-leukocyte interactions in fact facilitate metabolic cooperation and mutual activation, which may be of relevance in many biological processes including inflammation, atherogenesis and hemostasis. During hemodialysis procedure, the series of reactions that can occur upon blood contact with the foreign membrane surface may involve a variety of changes affecting almost every cellular and plasmatic component of the blood. This article reviews the evidence for abnormal interactions between circulating platelets and leukocytes in uremic patients undergoing maintenance hemodialysis and the pathophysiologic implications which may stem from such interactions.

Upregulation of arginase by H2O2 impairs endothelium-dependent nitric oxide-mediated dilation of coronary arterioles

OBJECTIVE

Overproduction of reactive oxygen species such as hydrogen peroxide (H2O2) has been implicated in various cardiovascular diseases. However, mechanism(s) underlying coronary vascular dysfunction induced by H2O2 is unclear. We studied the effect of H2O2 on dilation of coronary arterioles to endothelium-dependent and endothelium-independent agonists.

METHODS AND RESULTS

Porcine coronary arterioles were isolated and pressurized without flow for in vitro study. All vessels developed basal tone and dilated dose-dependently to activators of nitric oxide (NO) synthase (adenosine and ionomycin), cyclooxygenase (arachidonic acid), and cytochrome P450 monooxygenase (bradykinin). Intraluminal incubation of vessels with H2O2 (100 micromol/L, 60 minutes) did not alter basal tone but inhibited vasodilations to adenosine and ionomycin in a manner similar as that by NO synthase inhibitor L-NAME. H2O2 affected neither endothelium-dependent responses to arachidonic acid and bradykinin nor endothelium-independent dilation to sodium nitroprusside. The inhibited adenosine response was not reversed by removal of H2O2 but was restored by excess L-arginine. Inhibition of L-arginine consuming enzyme arginase by alpha-difluoromethylornithine or N(omega)-hydroxy-nor-L-arginine also restored vasodilation. Administering deferoxamine, an inhibitor of hydroxyl radical production, prevented the H2O2-induced impairment of vasodilation to adenosine. Western blot and reverse-transcription polymerase chain reaction results indicated that arginase I was upregulated after treating vessels with H2O2.

CONCLUSIONS

H2O2 specifically impairs endothelium-dependent NO-mediated dilation of coronary microvessels by reducing L-arginine availability through upregulation of arginase. The formation of hydroxyl radicals from H2O2 may contribute to this process.

Neutrophil elastase contributes to the development of ischemia-reperfusion-induced liver injury by decreasing endothelial production of prostacyclin in rats

We previously reported that nitric oxide (NO) derived from endothelial NO synthase (NOS) increased endothelial prostacyclin (PGI(2)) production in rats subjected to hepatic ischemia-reperfusion (I/R). The present study was undertaken to determine whether neutrophil elastase (NE) decreases endothelial production of PGI(2), thereby contributing to the development of I/R-induced liver injury by decreasing hepatic tissue blood flow in rats. Hepatic tissue levels of 6-keto-PGF(1alpha), a stable metabolite of PGI(2), were transiently increased and peaked at 1 h after reperfusion, followed by a gradual decrease until 3 h after reperfusion. Sivelestat sodium hydrochloride and L-658,758, two NE inhibitors, reduced I/R-induced liver injury. These substances inhibited the decreases in hepatic tissue levels of 6-keto-PGF(1alpha) at 2 and 3 h after reperfusion but did not affect the levels at 1 h after reperfusion. These NE inhibitors significantly increased hepatic tissue blood flow from 1 to 3 h after reperfusion. Both hepatic I/R-induced increases in the accumulation of neutrophils and the microvascular permeability were inhibited by these two NE inhibitors. Protective effects induced by the two NE inhibitors were completely reversed by pretreatment with nitro-l-arginine methyl ester, an inhibitor of NOS, or indomethacin. Administration of iloprost, a stable derivative of PGI(2), produced effects similar to those induced by NE inhibitors. These observations strongly suggest that NE might play a critical role in the development of I/R-induced liver injury by decreasing endothelial production of NO and PGI(2), leading to a decrease in hepatic tissue blood flow resulting from inhibition of vasodilation and induction of activated neutrophil-induced microvascular injury.

Mechanical loading and injury induce human myotubes to release neutrophil chemoattractants

The purpose of this study was to 1) test the hypothesis that skeletal muscle cells (myotubes) after mechanical loading and/or injury are a source of soluble factors that promote neutrophil chemotaxis and superoxide anion (O(2)(-).) production and 2) determine whether mechanical loading and/or injury causes myotubes to release cytokines that are known to influence neutrophil responses [tumor necrosis factor-alpha (TNF-alpha), IL-8, and transforming growth factor-beta1 (TGF-beta1)]. Human myotubes were grown in culture and exposed to either a cyclic strain (0, 5, 10, 20, or 30% strain) or a scrape injury protocol. Protocols of 5, 10, and 20% strain did not cause injury, whereas 30% strain and scrape injury caused a modest and a high degree of injury, respectively. Conditioned media from strained myotubes promoted chemotaxis of human blood neutrophils and primed them for O(2)(-). production in a manner that was dependent on a threshold of strain and independent from injury. Neutrophil chemotaxis, but not priming, progressively increased with higher magnitudes of strain. Conditioned media only from scrape-injured myotubes increased O(2)(-). production from neutrophils. Concentrations of IL-8 and total TGF-beta1 in conditioned media were reduced by mechanical loading, whereas TNF-alpha and active TGF-beta1 concentrations were unaffected. In conclusion, skeletal muscle cells after mechanical loading and injury are an important source of soluble factors that differentially influence neutrophil chemotaxis and the stages of neutrophil-derived reactive oxygen species production. Neutrophil responses elicited by mechanical loading, however, did not parallel changes in the release of IL-8, TGF-beta1, or TNF-alpha from skeletal muscle cells.

Role of glutathione in the adaptive tolerance to H2O2

Endogenous antioxidant defense systems are enhanced by various physiological stimuli including sublethal oxidative challenges, which induce tolerance to subsequent lethal oxidative injuries. We sought to evaluate the contributions of catalase and the glutathione system to the adaptive tolerance to H2O2. For this purpose, H9c2 cells were stimulated with 100 microM H2O2, which was the maximal dose at which no significant acute cell damage was observed. Twenty-four hours after stimulation, control and pretreated cells were challenged with a lethal concentration of H2O2 (300 microM). Compared with the control cells, pretreated cells were significantly tolerant of H2O2, with reduced cell lysis and improved survival rate. In pretreated cells, glutathione content increased to 48.20 +/- 6.38 nmol/mg protein versus 27.59 +/- 2.55 nmol/mg protein in control cells, and catalase activity also increased to 30.82 +/- 2.64 versus 15.46 +/- 1.29 units/mg protein in control cells, whereas glutathione peroxidase activity was not affected. Increased glutathione content was attributed to increased gamma-glutamylcysteine synthetase activity, which is known as the rate-limiting enzyme of glutathione synthesis. To elucidate the relative contribution of the glutathione system and catalase to tolerance of H2O2, control and pretreated cells were incubated with specific inhibitors of gamma-glutamyl cysteine synthetase (L-buthionine sulfoximine) or catalase (3-amino-1,2,4-triazole), and challenged with H2O2. Cytoprotection by the low-dose H2O2 pretreatment was almost completely abolished by L-buthionine sulfoximine, while it was preserved after 3-amino-1,2,4-triazole treatment. From these results, it is concluded that both the glutathione system and catalase can be enhanced by H2O2 stimulation, but increased glutathione content rather than catalase activity was operative in the tolerance of lethal oxidative stress.

The Lung in Sepsis: Fueling the Fire

Advances in our understanding of the molecular mechanisms underlying the pathophysiology of sepsis have generated considerable efforts in manipulating the host response during this frequently lethal condition. While existing trials of immune modulation have been largely unsuccessful, an appreciation for the roles of individual organ systems in sepsis is important to enable clinicians to discern how each functions as both a target for injury and a contributor to the derangement in homeostasis seen in sepsis. Such awareness will encourage treatment decisions aimed at optimizing conventional therapy while minimizing the adverse effects of supportive care, and it may also guide the incorporation of newer immunomodulatory therapeutics into our existing modalities. This article discusses the lung's response to sepsis, from the standpoint of organ dysfunction related to sepsis as well as its participation in the generation and maintenance of the systemic inflammatory state.

Elevated levels of plasma homocysteine in hypertensive patients with diabetes mellitus

BACKGROUND

Homocysteine generates oxygen radicals (superoxide anion and hydrogen peroxide) that are known to produce vasoconstriction. Hypertension is a common problem in individuals with diabetes mellitus. It is possible that hypertension in diabetic patients may be due to increased levels of plasma homocysteine. We investigated the plasma levels of homocysteine, factors involved in homocysteine metabolism (serum folic acid and vitamin B12) and lipid peroxidation product in the serum of diabetic patients with hypertension.

METHODS AND RESULTS

The studies were conducted in three groups: 1) healthy controls, and diabetic patients who were 2) normotensive and 3) hypertensive. Plasma homocysteine, serum malondialdehyde (a lipid peroxidation product), vitamin B12, and folic acid were measured in these patients. Plasma homocysteine and serum malondialdehyde levels were elevated in diabetic patients compared to the control group. Plasma levels of homocysteine and serum levels of malondialdehyde were higher in the hypertensive diabetic patients than in those who were normotensive. Levels of serum folate were lower in hypertensive diabetic patients compared to the normotensive group. Levels of serum vitamin B12 were similar in both the normotensive and hypertensive diabetic patients.

CONCLUSIONS

Levels of plasma homocysteine and serum malondialdehyde are elevated in hypertensive diabetic patients. Hyperhomocysteinemia may be involved in the induction and sustaining of hypertension in diabetic patients.

Surface expression of neutrophil adhesion molecules in pregnant women at risk for hypertensive complications

OBJECTIVE

To determine if neutrophil activation is a pathogenetic factor in hypertensive disorders in pregnancy, the neutrophil expression of adhesion molecules was prospectively investigated in pregnant women at risk, prior to the development of hypertensive complications.

METHODS

Two neutrophil activation parameters, beta2-integrin (CD11b) and l-selectin (CD62L), were assessed at admission between 14 and 24 weeks of gestation in 82 pregnant women at risk of preeclampsia and other hypertensive complications. Results were compared to those in 20 healthy normotensive women.

RESULTS

Of the 82 women at risk, 23 (28%) developed hypertensive complications: 9 (11%) preeclampsia and 14 (17%) others, such as intrauterine growth restriction (n = 6), fetal or neonatal loss (n = 8), and preterm delivery (< or = 30 weeks of gestation) (n = 8). All pregnancy outcome measures were significantly worse in the patients with complications than in those at risk but without complications or the healthy controls. Expression of beta2-integrin was significantly higher in early stages of pregnancy in the women who eventually developed complications than the women who did not, P =.019, or the healthy controls, P =.049.

CONCLUSIONS

Surface expression of beta2-integrin is increased in pregnant women at risk for hypertensive complications before the clinical manifestations of the disorder.

Contribution of capsaicin-sensitive sensory neurons to stress-induced increases in gastric tissue levels of prostaglandins in rats

We examined whether capsaicin-sensitive sensory neurons might be involved in the increase in the gastric tissue level of prostaglandins, thereby contributing to the reduction of water immersion restraint stress (WIR)-induced gastric mucosal injury in rats. Gastric tissue levels of calcitonin gene-related peptide (CGRP), 6-keto-PGF1alpha, and PGE2 were transiently increased 30 min after WIR. These increases were significantly inhibited by subcutaneous injection of capsazepine (CPZ), a vanilloid receptor antagonist, and by functional denervation of capsaicin-sensitive sensory neurons induced by the administration of high-dose capsaicin. The administration of capsaicin (orally) and CGRP (intravenously) significantly enhanced the WIR-induced increases in the gastric tissue level of prostaglandins 30 min after WIR, whereas CGRP-(8-37), a CGRP receptor antagonist, significantly inhibited them. Pretreatment with Nomega-nitro-L-arginine methyl ester (L-NAME), a nonselective inhibitor of nitric oxide (NO) synthase (NOS), and that with indomethacin inhibited the WIR-induced increases in gastric tissue levels of prostaglandins, whereas either pretreatment with aminoguanidine (AG), a selective inhibitor of the inducible form of NOS, or that with NS-398, a selective inhibitor of cyclooxygenase (COX)-2, did not affect them. CPZ, the functional denervation of capsaicin-sensitive sensory neurons, and CGRP-(8-37) significantly increased gastric MPO activity and exacerbated the WIR-induced gastric mucosal injury in rats subjected to 4-h WIR. The administration of capsaicin and CGRP significantly increased the gastric tissue levels of prostaglandins and inhibited both the WIR-induced increases in gastric MPO activity and gastric mucosal injury 8 h after WIR. These effects induced by capsaicin and CGRP were inhibited by pretreatment with L-NAME and indomethacin but not by pretreatment with AG and NS-398. These observations strongly suggest that capsaicin-sensitive sensory neurons might release CGRP, thereby increasing the gastric tissue levels of PGI2 and PGE2 by activating COX-1 through activation of the constitutive form of NOS in rats subjected to WIR. Such activation of capsaicin-sensitive sensory neurons might contribute to the reduction of WIR-induced gastric mucosal injury mainly by inhibiting neutrophil activation.

Redox regulation of PI3K/Akt and p53 in bovine aortic endothelial cells exposed to hydrogen peroxide

To clarify the apoptotic and survival signal transduction pathways in activated vascular endothelial cells exposed to oxidative stress, the effects of inhibitors of signal transduction on hydrogen peroxide (H(2)O(2))-induced apoptosis in bovine aortic vascular endothelial cells (BAEC) were examined. Treatment of BAEC with 1 mM H(2)O(2) caused increases of DNA fragmentation, p53 expression, Bax/Bcl-2 ratio, and the activities of caspases 3 and 9. The increases of DNA fragmentation, Bax/Bcl-2 ratio, and caspase activities were abrogated by BAPTA-AM (an intracellular Ca(2+) chelator) and N-acetyl-L-cysteine (an antioxidant), and augmented by wortmannin [a phosphatidylinositol 3-kinase (PI3K) inhibitor]. The increase of the intracellular Ca(2+) concentration ([Ca(2+)](i)) observed in H(2)O(2)-stimulated cells was unaffected by wortmannin, suggesting that the potentiating effect of wortmannin on the apoptosis was not due to an alteration of [Ca(2+)](i). H(2)O(2) increased the levels of PI3K activity and Akt phosphorylation. Both were attenuated by wortmannin and, to a lesser extent, by genistein (a tyrosine kinase inhibitor) and suramin (a growth factor receptor inhibitor), but not affected by BAPTA-AM. These results suggest that H(2)O(2) induces Ca(2+)-dependent apoptosis and Ca(2+)-independent survival signals such as redox-regulated activation of PI3K/Akt, which is partly mediated by the activation of growth factor receptors in BAEC.

Protection of coumarins against linoleic acid hydroperoxide-induced cytotoxicity

Coumarins comprise a group of natural phenolic compounds found in a variety of plant sources. Protective effects of coumarins against cytotoxicity induced by linoleic acid hydroperoxide were examined in cultured human umbilical vein endothelial cells. When the cells were incubated in medium supplemented with linoleic acid hydroperoxide and coumarins, esculetin (6,7-dihydroxycoumarin) and 4-methylesculetin protected cells from injury by linoleic acid hydroperoxide. Fraxetin and caffeic acid showed weak, but significant, protection. Esculin as well as esculetin and 4-methylesculetin were effective for protecting cells against linoleic acid hydroperoxide-induced cytotoxicity in the case of pretreatment for 24 h, however fraxetin and caffeic acid showed no protection. Since esculetin was detected after 24 h treatment with esculin, a sugar moiety in the esculin molecule appears to be hydrolyzed during pretreatment. Coumarins such as umbelliferone containing only one hydroxyl group showed no protective effect in pretreatment or concurrent treatment. Esculetin and 4-methylesculetin provided synergistic protection against cytotoxicity induced by linoleic acid hydroperoxide with alpha-tocopherol. Furthermore, the radical-scavenging ability of coumarins was examined in electron spin resonance spectrometry. Esucletin, 4-methylesculetin, fraxetin, and caffeic acid showed the quenching effect on the 1,1-diphenyl-2-picrylhydrazyl radical. These results indicate that the presence of an ortho catechol moiety in the coumarin molecules plays an important role in the protective activities against linoleic acid hydroperoixde-induced cytotoxicity.

Ischemia/reperfusion-induced increase in the hepatic level of prostacyclin is mainly mediated by activation of capsaicin-sensitive sensory neurons in rats

Capsaicin-sensitive sensory neurons are nociceptive neurons that release calcitonin gene-related peptide (CGRP) on activation by various noxious stimuli. CGRP has been shown to increase the endothelial production of prostacyclin, which reduces ischemia/reperfusion (I/R)-induced liver injury. Therefore, if the sensory neurons can be activated by the pathologic process of hepatic I/R, they might help ameliorate I/R-induced liver injury by promoting the endothelial production of prostacyclin, also known as prostaglandin I(2). In this study, we examined these possibilities using a rat model of I/R-induced liver injury. Male Wistar rats were subjected to 60-minute hepatic ischemia and subsequent reperfusion. Hepatic levels of 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), a stable metabolite of prostacyclin, were significantly increased after hepatic I/R, peaking 1 hour after reperfusion. Administration of capsaicin and CGRP significantly enhanced I/R-induced increases in hepatic levels of 6-keto-PGF(1alpha), increased hepatic-tissue blood flow after reperfusion, and inhibited the I/R-induced increase in tissue levels of both tumor necrosis factor-alpha (TNF-alpha) and myeloperoxidase. Capsazepine, a vanilloid receptor antagonist; CGRP(8-37), a CGRP-receptor antagonist; l-nitro-arginine-methyl-ester (L-NAME), a nonselective inhibitor of nitric oxide (NO) synthase (NOS); and indomethacin, a nonselective inhibitor of cyclooxygenase, inhibited the I/R-induced increases in hepatic tissue levels of 6-keto-PGF(1alpha) and decreased hepatic-tissue blood flow after reperfusion. These compounds significantly enhanced the I/R-induced increases in hepatic tissue levels of both TNF-alpha and myeloperoxidase. Although I/R-induced liver injury was significantly reduced by capsaicin and CGRP, it was exacerbated by capsazepine, CGRP(8-37), L-NAME, and indomethacin. Administration of aminoguanidine, a selective inhibitor of the inducible form of NOS, and NS-398, a selective inhibitor of cyclooxygenase-2, demonstrated no effects on the liver injury or the hepatic levels of 6-keto-PGF(1alpha). These findings strongly suggest that the activation of the sensory neurons helps ameliorate I/R-induced liver injury both by increasing hepatic-tissue blood flow and by limiting inflammatory response through the enhancement of endothelial production of prostacyclin. In the sensory neuron-mediated enhancement of endothelial production of prostacyclin, CGRP-induced activation of both endothelial NOS and cyclooxygenase-1 may be critically involved.

Hypochlorite- and hypobromite-mediated radical formation and its role in cell lysis

Activated leukocytes generate the potent oxidants HOCl and HOBr via the formation of H(2)O(2) and the release of peroxidase enzymes (myeloperoxidase, eosinophil peroxidase). HOCl and HOBr are potent microbiocidal agents, but excessive or misplaced production can cause tissue damage and cell lysis. In this study it is shown that HOBr induces red blood cell lysis at approximately 10-fold lower concentrations than HOCl, whereas with monocyte (THP1) and macrophage (J774) cells HOCl and HOBr induce lysis at similar concentrations. The role of radical formation during lysis has been investigated by EPR spin trapping, and it is shown that reaction of both oxidants with each cell type generates cell-derived radicals. Red blood cells exposed to nonlytic doses of HOCl generate novel nitrogen-centered radicals whose formation is GSH dependent. In contrast, HOBr gives rise to nitrogen-centered, membrane-derived protein radicals. With lytic doses of either oxidant, protein (probably hemoglobin)-derived, nitrogen-centered radicals are observed. Unlike the red blood cells, treatment of monocytes and macrophages with HOCl gives significant radical formation only under conditions where cell lysis occurs concurrently. These radicals are nitrogen-centered, cell-protein-derived species and have parameters identical to those detected with red blood cells and HOBr. Exposure of these cells to HOBr did not give detectable radicals. Overall these experiments demonstrate that HOCl and HOBr react with different selectivity with cellular targets, and that this can result in radical formation. This radical generation can precede, and may play a role in, cell lysis.

p38 MAPK and Ca2+ contribute to hydrogen peroxide-induced increase of permeability in vascular endothelial cells but ERK does not

To examine the involvement of p38 mitogen-activated protein kinase (p38 MAPK) and extracellular signal-regulated kinase (ERK) in the oxidative stress-induced increase of permeability in endothelial cells, the effects of a p38 MAPK inhibitor (SB203580) and ERK inhibitor (PD90859) on the H2O2-induced increase of permeability in bovine pulmonary artery endothelial cells (BPAEC) were investigated using a two-compartment system partitioned by a semi-permeable filter. H2O2 at 1 mM caused an increase of the permeation rate of fluorescein isothiocyanate (FITC)-labeled dextran 40 through BPAEC monolayers. SB203580 inhibited the H2O2-induced increase of permeability but PD98059 did not, though activation (phosphorylation) of both p38 MAPK and ERK was observed in H2O2-treated cells in Western blot analysis. An H2O2-induced increase of the intracellular Ca2+ concentration ([Ca2+]i) was also observed and an intracellular Ca2+ chelator (BAPTA-AM) significantly inhibited the H2O2-induced increase of permeability. However, it showed no inhibitory effects on the H2O2-induced phosphorylation of p38 MAPK and ERK. The H2O2-induced increase of [Ca2+]i was not influenced by SB203580 and PD98059. These results indicate that the activation of p38 MAPK and the increase of [Ca2+]i are essential for the H2O2-induced increase of endothelial permeability and that ERK is not.

Effect of palmitic acid on neutrophil functions in vitro

BACKGROUND

It has been shown that in acne comedones the proportion of linoleic acid is markedly decreased, while palmitic acid is significantly increased. We previously reported that the decreased proportion of linoleic acid, which markedly suppresses neutrophil reactive oxygen species (ROS) generation and phagocytosis, contribute to the worsening of acne inflammation. The aim of this study was to examine the effect of palmitic acid on neutrophil functions in vitro.

METHODS

We investigated the effect of palmitic acid on inflammatory parameters such as neutrophil chemotaxis, phagocytosis, and ROS generation. Reactive oxygen species generation in a cell-free, xanthine-xanthine oxidase system was also assessed. The species examined were superoxide radical anion (O2-), hydrogen peroxide (H2O2), and hydroxyl radical (OH.).

RESULTS

Palmitic acid significantly decreased H2O2 generation both by neutrophils and in the xanthine-xanthine oxidase system, while neutrophil chemotaxis and phagocytosis as well as O2- and OH. generation by both systems were not markedly affected in the presence of palmitic acid.

CONCLUSIONS

The present study suggests that palmitic acid may be involved in the pathogenesis of acne inflammation from a standpoint of oxidative tissue injury.

Neutrophils injure cultured skeletal myotubes

The purpose of the study was to test the hypothesis that neutrophils can injure cultured skeletal myotubes. Human myotubes were grown and then cultured with human blood neutrophils. Myotube injury was quantitatively and qualitatively determined using a cytotoxicity (51Cr) assay and electron microscopy, respectively. For the 51Cr assay, neutrophils, under non-in vitro-stimulated and N-formylmethionyl-leucyl-phenylalanine (FMLP)-stimulated conditions, were cultured with myotubes at effector-to-target cell (E:T) ratios of 10, 30, and 50 for 6 h. Statistical analyses revealed that myotube injury was proportional to the E:T ratio and was greater in FMLP-stimulated conditions relative to non-in vitro-stimulated conditions. Transmission electron microscopy, using lanthanum as an extracellular tracer, revealed in cocultures a diffuse appearance of lanthanum in the cytoplasm of myotubes and a localized appearance within cytoplasmic vacuoles of myotubes. These observations and their absence in control cultures (myotubes only) suggest that neutrophils caused membrane rupture and increased myotube endocytosis, respectively. Myotube membrane blebs were prevalent in scanning and transmission electron micrographs of cultures consisting of neutrophils and myotubes (E:T ratio of 5) and were absent in control cultures. These data support the hypothesis that neutrophils can injure skeletal myotubes in vitro and may indicate that neutrophils exacerbate muscle injury and/or delay muscle regeneration in vivo.

The endothelium in sepsis: source of and a target for inflammation

OBJECTIVE

To discuss a possible role of the endothelium in sepsis.

DATA SOURCES

Studies published in biomedical journals and our own experimental results.

STUDY SELECTION

Studies on endothelial mechanisms in the context of sepsis.

DATA EXTRACTION AND SYNTHESIS

Changes in endothelial cells on activation by inflammatory stimuli are reviewed briefly; potential mechanisms that lead to endothelial damage during sepsis are discussed.

CONCLUSIONS

The endothelium is a key organ involved in the pathogenesis of sepsis. Dysfunction of or injury to the endothelium may be involved in the pathogenesis of multiple organ failure and should be discriminated from activation resulting from stimulation with inflammatory stimuli. Identification of the molecular mechanisms that contribute to endothelial dysfunction or damage is likely to provide novel targets for the treatment of sepsis.

Glycolipoprotein extract (G-90) from earthworm Eisenia foetida exerts some antioxidative activity

Antioxidants protect DNA, proteins and lipids in the body from damage. These types of damages are a major contributor to aging and to degenerative diseases such as cancer, cardiovascular disease, immune-system decline, brain dysfunction and cataracts. The effect of glycolipoprotein extract of Eisenia foetida (G-90) as an antioxidant was investigated in cultured human fibroblasts and epithelial cells. After treatment of the cells with H2O2 for 4 h, G-90 completely allows the cells to recover and stimulated their growth. When the cells were incubated with G-90 48 h before the treatment with H2O2, the oxidative damage of the cells did not occur. Thus, G-90 had an apparent protective effect against the toxicity of H2O2 and stimulated the growth of the cells. Ascorbic acid, a known antioxidant, did not allow the growth of the cells to recover after damage nor did it protect them, unless it was added simultaneously with H2O2. The antioxidative activity of G-90, together with its antibacterial and mitogen activities, could be useful in the study of G-90 as a wound-healing agent.

Effects of lactoferrin on rat dermal interstitial fluid pressure (Pif) and in vitro endothelial barrier function

We recently demonstrated that intravenous (i.v.) injection of the iron-binding protein lactoferrin (Lf) followed by antilactoferrin (aLf) antibodies or iron-saturated Lf alone increased albumin extravasation in vivo in several tissues including skin. Increased driving pressure for blood-tissue exchange or direct effects of Lf on the endothelial barrier are possible mechanisms. We therefore, firstly, measured interstitial fluid pressure (Pif) in dermis of rats given 1 mg Lf i.v. followed 30 min later by aLf or saline and circulatory arrest 1 or 5 min thereafter and compared with controls. Secondly, transmonolayer passage of Evans blue labelled albumin (EB-albumin) was evaluated in porcine pulmonary artery endothelial cells exposed to iron-free or iron-saturated Lf (both 100 microg mL-1) in the absence and presence of 0.5 mM hydrogen peroxide. Pif increased significantly at 11-30 min following Lf to +2.1 +/- 0.3 and +1.7 +/- 0.2 mmHg at 11-20 and 21-30 min, respectively, compared with +0.1 +/- 0.2 mmHg before Lf (P < 0.05, n=25). Endothelial transmonolayer passage of EB-albumin during 3 h was not affected by iron-free or iron-saturated Lf neither in the absence nor presence of hydrogen peroxide that increased passage 3.5 times compared with controls. In conclusion, Lf-induced increase in albumin extravasation in rat skin is not explained by changes in Pif (because Lf raised Pif significantly) or direct effects of Lf on the endothelial barrier.

Lactoferrin and anti-lactoferrin antibodies: effects of ironloading of lactoferrin on albumin extravasation in different tissues in rats

Lactoferrin is a cationic iron-binding protein, which is released from activated neutrophils in concert with reactive oxygen species. In vitro, lactoferrin has both anti- and proinflammatory effects; many of them dependent on iron-binding. In vivo, only iron-free lactoferrin reduced inflammatory hyperpermeability in the lung. We therefore examined whether 1 mg iron-free (Apo-Lf) or iron-saturated lactoferrin (Holo-Lf) alone or followed by anti-lactoferrin antibodies (aLf) affected permeability evaluated by extravasation of radiolabelled bovine serum albumin (CBSA) in different tissues of anaesthetized rats. Fifteen minutes after i.v. injection of Lf, aLf or saline was given and circulatory arrest was induced 20 min thereafter. Measurements were performed in control, after Apo-Lf, Holo-Lf, Apo-Lf + aLf, Holo-Lf + aLf and aLf alone (n=6-8 in each group). No intergroup differences were found for plasma volume and haematocrit at the start and end of the 37 min extravasation period or for total tissue water in any of the six different tissues studied, excluding larger transcapillary fluid shifts. However, increases in CBSA were seen without differences in tissue intravascular volume. Iron-free lactoferrin and aLf alone did not change CBSA significantly. Iron-saturated lactoferrin significantly increased CBSA in skin (neck), trachea and left ventricle of the heart to 249 +/- 9, 284 +/- 16 and 160 +/- 7% of control, respectively. When followed by aLf, both Apo- and Holo-Lf increased CBSA significantly in four and five of the tissues studied, respectively. However, no significant effect was seen for Holo-Lf + aLf compared with Holo-Lf alone. In conclusion, iron-saturated, but not iron-free lactoferrin increased CBSA, whereas antilactoferrin increased CBSA compared with lactoferrin alone only when following iron-free lactoferrin.