Urine hydrogen peroxide during adult respiratory distress syndrome in patients with and without sepsis

Parenteral Cysteine Supplementation in Preterm Infants: One Size Does Not Fit All

Due to their gastrointestinal immaturity or the severity of their pathology, many neonates require parenteral nutrition (PN). An amino acid (AA) solution is an important part of PN. Cysteine is a key AA for protein and taurine synthesis, as well as for glutathione synthesis, which is a cornerstone of antioxidant defenses. As cysteine could be synthesized from methionine, it is considered a nonessential AA. However, many studies suggest that cysteine is a conditionally essential AA in preterm infants due to limitations in their capacity for cysteine synthesis from methionine and the immaturity of their cellular cysteine uptake. This critical review discusses the endogenous synthesis of cysteine, its main biological functions and whether cysteine is a conditionally essential AA. The clinical evidence evaluating the effectiveness of the current methods of cysteine supplementation, between 1967 and 2023, is then reviewed. The current understanding of cysteine metabolism is applied to explain why these methods were not proven effective. To respond to the urgent need for changing the current methods of parenteral cysteine supplementation, glutathione addition to PN is presented as an innovative alternative with promising results in an animal model. At the end of this review, future directions for research in this field are proposed.

Association of Vegetable and Fruit Consumption with Urinary Oxidative Biomarkers in Teenaged Girls: A School-Based Pilot Study in Japan

Hexanoyl-lysine (HEL), 8-hydroxy-2'deoxyguanosine (8-OHdG), and dityrosine (DT) have served as potential biomarkers for detecting oxidative modified lipids, DNA, and proteins in biological samples, respectively. Whether regular higher levels of consumption of vegetables/fruit (V/F) would decrease oxidative modification of these biomolecules in the body remain unelucidated. To examine the association of regular V/F consumption with the generation of these reactive oxygen species-induced biomarkers, this study evaluated V/F consumption in a school-based sample of teenaged girls (mean age 15.6 ± 1.7 years, n = 103), and quantified the formation of oxidative stress biomarkers in their urine. Only 19.4% and 23.3% of participants reported that they consumed the recommended daily amount of vegetables and fruits, respectively. Individuals who consumed lower levels of fruit (<100g/day) or vegetables (<250g/day) had significantly higher HEL excretion in their urine than those who consumed higher levels of fruit (≥100g/day) (p < 0.05) or vegetables (≥250g/day) (p = 0.057). The results of a multiple regression analysis showed that vegetable consumption was an important inhibiting factor of early lipid peroxidation measured as HEL in urine, independent of various confounders (β = - 0.332, p < 0.05). The findings suggest that relatively higher consumption of vegetables would help in the prevention of early lipid peroxidation in adolescents.

Urine Hydrogen Peroxide Levels and Their Relation to Outcome in Patients with Sepsis, Septic Shock, and Major Burn Injury

Hydrogen peroxide (H2O2) and oxidative stress have been suggested as possible instigators of both the systemic inflammatory response and the increased vascular permeability associated with sepsis and septic shock. We measured H2O2 concentrations in the urine of 82 patients with severe infections, such as sepsis, septic shock, and infections not fulfilling sepsis-3 criteria, in patients with major burn injury with associated systemic inflammation, and healthy subjects. The mean concentrations of H2O2 were found to be lower in patients with severe infections compared to burn injury patients and healthy subjects. Patients with acute kidney injury (AKI), vs. those without AKI, in all diagnostic groups displayed higher concentrations of urine H2O2 (p < 0.001). Likewise, urine concentrations of H2O2 were higher in non-survivors as compared to survivors (p < 0.001) at day 28 in all diagnostic groups, as well as in patients with severe infections and burn injury (p < 0.001 for both). In this cohort, increased H2O2 in urine is thus associated with mortality in patients with sepsis and septic shock as well as in patients with burn injury.

Radiation exposure and mitochondrial insufficiency in chronic fatigue and immune dysfunction syndrome

Chronic fatigue and Immune Dysfunction Syndrome (CFIDS) is a heterogeneous disease that may be promoted by various environmental stressors, including viral infection, toxin uptake, and ionizing radiation exposure. Previous studies have identified mitochondrial dysfunction in CFIDS patients, including modulation of mitochondrial respiratory chain activity, deletions in the mitochondrial genome, and upregulation of reactive oxygen species (ROS). This paper focuses on radiation effects and hypothesizes that CFIDS is primarily caused by stressor-induced mitochondrial metabolic insufficiency, which results in decreased energy production and anabolic metabolites required for normal cellular metabolism. Furthermore, tissues neighbouring or distant from directly perturbed tissues compensate for this dysfunction, which causes symptoms associated with CFIDS. This hypothesis is justified by reviewing the links between radiation exposure and CFIDS, cancer, immune dysfunction, and induction of oxidative stress. Moreover, the relevance of mitochondria in cellular responses to radiation and metabolism are discussed and putative mitochondrial biomarkers for CFIDS are introduced. Implications for diagnosis are then described, including a potential urine assay and PCR test for mitochondrial genome mutations. Finally, future research needs are offered with an emphasis on where rapid progress may be made to assist the afflicted.

The effect of Myrtus communis L. ethanol extract on the small intestine and lungs in experimental thermal burn injury

Thermal trauma can damage organs away from the skin burn site and lead to multiple organ dysfunction. Following thermal injury, all tissues are exposed to ischemia, and as a result, resuscitation and reperfusion occur during the burning shock. Burn damage starts systemic inflammatory reactions that produce toxins and reactive oxygen radicals that lead to peroxidation. This study aimed to investigate, for the first time, the possible antioxidant effects of Myrtus communis ethanol extract on burn-induced oxidative distant organ injury orally. The thermal trauma was generated under ether anesthesia by exposing the dorsum of rats to 90 ^°C water bath for 10 s. 100 mg/kg/day Mrytus communis ethanol extract was applied orally for two days. Malondialdehyde (MDA) and glutathione (GSH) levels, glutatinone-S-transferase (GST), superoxidedismutase (SOD) and catalase (CAT) activities were determined to detect the possible antioxidant effects of myrtle on small intestine and lung tissues. Burn damage significantly increased MDA levels in lung and small intestine tissues, and significantly decreased GSH levels, CAT and GST activities in the small intestine and lung tissues compared to control group. Mrytus communis ethanol extract decreased MDA level and increased GSH level, SOD, CAT and GST activities significantly in either small intestine or lung tissues. Mrytus communis extract may be an ideal candidate to be used as an antioxidant adjunct to improve oxidative distant organ damage to limit the systemic inflammatory response and decreasing the recovery time after thermal injury.

Catalase-Containing Silica Particles as Ultrasound-Based Hydrogen Peroxide Sensors to Determine Infected From Noninfected Fluid Collections in Humans

OBJECTIVE. Hydrogen peroxide (H₂O₂) plays a key role in neutrophil oxidative defense against infection. Catalase-containing silica nanoshells are nanoparticles that generate O₂ microbubbles imaged with ultrasound in the presence of elevated H₂O₂. We aimed to determine whether ultrasound-detectable O₂ microbubbles produced by catalase-containing silica nanoshells can determine whether fluid collections drained from patients are infected. SUBJECTS AND METHODS. During this HIPAA-compliant, institutional review board-approved study, 52 human fluid samples were collected from clinically required image-guided percutaneous drainage procedures. Catalase-containing silica nanoshells were added to the fluid samples during imaging in real time using a Sequoia-512 15L8-S linear transducer (Siemens Healthcare). Production of detectable microbubbles was graded subjectively as negative (noninfected) or positive (infected) with low, moderate, or high confidence by a single observer blinded to all clinical data. The truth standard was microbiology laboratory culture results. Performance characteristics including ROC curves were calculated. RESULTS. Microbubble detection to distinguish infected from noninfected fluids was 84% sensitive and 72% specific and offered negative and positive predictive values of 89% and 64%, respectively. The AUC was 0.79. Six of nine false-positive samples were peritoneal fluid collections that were all collected from patients with decompensated cirrhosis. CONCLUSION. The presence of elevated H₂O₂ indicated by microbubble formation in the presence of catalase-containing silica nanoshells is sensitive in distinguishing infected from noninfected fluids and offers a relatively high negative predictive value. False-positive cases may result from noninfectious oxidative stress. Catalase-containing silica nanoshells may constitute a novel point-of-care test performed at time of percutaneous drainage, potentially obviating placement of drains into otherwise sterile collections and minimizing risk of secondary infection or other complication.

Biomarkers for Acute Respiratory Distress syndrome and prospects for personalised medicine

Acute lung injury (ALI) affects over 10% of patients hospitalised in critical care, with acute respiratory distress syndrome (ARDS) being the most severe form of ALI and having a mortality rate in the region of 40%. There has been slow but incremental progress in identification of biomarkers that contribute to the pathophysiology of ARDS, have utility in diagnosis and monitoring, and that are potential therapeutic targets (Calfee CS, Delucchi K, Parsons PE, Thompson BT, Ware LB, Matthay MA, Thompson T, Ware LB, Matthay MA, Lancet Respir Med 2014, 2:611–-620). However, a major issue is that ARDS is such a heterogeneous, multi-factorial, end-stage condition that the strategies for “lumping and splitting” are critical (Prescott HC, Calfee CS, Thompson BT, Angus DC, Liu VX, Am J Respir Crit Care Med 2016, 194:147–-155). Nevertheless, sequencing of the human genome, the availability of improved methods for analysis of transcription to mRNA (gene expression), and development of sensitive immunoassays has allowed the application of network biology to ARDS, with these biomarkers offering potential for personalised or precision medicine (Sweeney TE, Khatri P, Toward precision medicine Crit Care Med; 2017 45:934-939).

Biomarker panels have potential applications in molecular phenotyping for identifying patients at risk of developing ARDS, diagnosis of ARDS, risk stratification and monitoring. Two subphenotypes of ARDS have been identified on the basis of blood biomarkers: hypo-inflammatory and hyper-inflammatory. The hyper-inflammatory subphenotype is associated with shock, metabolic acidosis and worst clinical outcomes. Biomarkers of particular interest have included interleukins (IL-6 and IL-8), interferon gamma (IFN-γ), surfactant proteins (SPD and SPB), von Willebrand factor antigen, angiopoietin 1/2 and plasminogen activator inhibitor-1 (PAI-1). In terms of gene expression (mRNA) in blood there have been found to be increases in neutrophil-related genes in sepsis-induced and influenza-induced ARDS, but whole blood expression does not give a robust diagnostic test for ARDS.

Despite improvements in management of ARDS on the critical care unit, this complex disease continues to be a major life-threatening event. Clinical trials of β₂-agonists, statins, surfactants and keratinocyte growth factor (KGF) have been disappointing. In addition, monoclonal antibodies (anti-TNF) and TNFR fusion protein have also been unconvincing. However, there have been major advances in methods of mechanical ventilation, a neuromuscular blocker (cisatracurium besilate) has shown some benefit, and stem cell therapy is being developed. In the future, by understanding the role of biomarkers in the pathophysiology of ARDS and lung injury, it is hoped that this will provide rational therapeutic targets and ultimately improve clinical care (Seymour CW, Gomez H, Chang CH, Clermont G, Kellum JA, Kennedy J, Yende S, Angus DC, Crit Care 2017, 21:257).

A new 3D printed radial flow-cell for chemiluminescence detection: Application in ion chromatographic determination of hydrogen peroxide in urine and coffee extracts

A new polymer flow-cell for chemiluminescence detection (CLD) has been designed and developed by diverging multiple linear channels from a common centre port in a radial arrangement. The fabrication of radial flow-cell by 3D PolyJet printing and fused deposition modeling (FDM) has been evaluated, and compared with a similarly prepared spiral flow-cell design commonly used in chemiluminescence detectors. The radial flow-cell required only 10 h of post-PolyJet print processing time as compared to ca. 360 h long post-PolyJet print processing time required for the spiral flow-cell. Using flow injection analysis, the PolyJet 3D printed radial flow-cell provided an increase in both the signal magnitude and duration, with an average increase in the peak height of 63% and 58%, peak area of 89% and 90%, and peak base width of 41% and 42%, as compared to a coiled-tubing spiral flow-cell and the PolyJet 3D printed spiral flow-cell, respectively. Computational fluid dynamic (CFD) simulations were applied to understand the origin of the higher CLD signal obtained with the radial flow-cell design, indicating higher spatial coverage near the inlet and lower linear velocities in the radial flow-cell. The developed PolyJet 3D printed radial flow-cell was applied in a new ion chromatography chemiluminescence based assay for the detection of H₂O₂ in urine and coffee extracts.

Antioxidant strategies in respiratory medicine

Pulmonary oxidant stress plays an important pathogenetic role in disease conditions including acute lung injury/adult respiratory distress syndrome (ALI/ARDS), hyperoxia, ischemia-reperfusion, sepsis, radiation injury, lung transplantation, COPD, and inflammation. Reactive oxygen species (ROS), released from activated macrophages and leukocytes or formed in the pulmonary epithelial and endothelial cells, damage the lungs and initiate cascades of pro-inflammatory reactions propagating pulmonary and systemic stress. Diverse molecules including small organic compounds (e.g. gluthatione, tocopherol (vitamin E), flavonoids) serve as natural antioxidants that reduce oxidized cellular components, decompose ROS and detoxify toxic oxidation products. Antioxidant enzymes can either facilitate these antioxidant reactions (e.g. peroxidases using glutathione as a reducing agent) or directly decompose ROS (e.g. superoxide dismutases [SOD] and catalase). Many antioxidant agents are being tested for treatment of pulmonary oxidant stress. The administration of small antioxidants via the oral, intratracheal and vascular routes for the treatment of short- and long-term oxidant stress showed rather modest protective effects in animal and human studies. Intratracheal and intravascular administration of antioxidant enzymes are being currently tested for the treatment of acute oxidant stress. For example, intratracheal administration of recombinant human SOD is protective in premature infants exposed to hyperoxia. However, animal and human studies show that more effective delivery of drugs to cells experiencing oxidant stress is needed to improve protection. Diverse delivery systems for antioxidants including liposomes, chemical modifications (e.g. attachment of masking pegylated [PEG]-groups) and coupling to affinity carriers (e.g. antibodies against cellular adhesion molecules) are being employed and currently tested, mostly in animal and, to a limited extent, in humans, for the treatment of oxidant stress. Further studies are needed, however, in order to develop and establish effective applications of pulmonary antioxidant interventions useful in clinical practice. Although beyond the scope of this review, antioxidant gene therapies may eventually provide a strategy for the management of subacute and chronic pulmonary oxidant stress.

Metabolic theory of septic shock

Septic shock is a life threatening condition that can develop subsequent to infection. Mortality can reach as high as 80% with over 150000 deaths yearly in the United States alone. Septic shock causes progressive failure of vital homeostatic mechanisms culminating in immunosuppression, coagulopathy and microvascular dysfunction which can lead to refractory hypotension, organ failure and death. The hypermetabolic response that accompanies a systemic inflammatory reaction places high demands upon stored nutritional resources. A crucial element that can become depleted early during the progression to septic shock is glutathione. Glutathione is chiefly responsible for supplying reducing equivalents to neutralize hydrogen peroxide, a toxic oxidizing agent that is produced during normal metabolism. Without glutathione, hydrogen peroxide can rise to toxic levels in tissues and blood where it can cause severe oxidative injury to organs and to the microvasculature. Continued exposure can result in microvascular dysfunction, capillary leakage and septic shock. It is the aim of this paper to present evidence that elevated systemic levels of hydrogen peroxide are present in septic shock victims and that it significantly contributes to the development and progression of this frequently lethal condition.

The pathophysiology of perioperative lung injury

The degree of perioperative lung injury that patients sustain results from a complex interaction between their current physiologic state, comorbidities, lifestyle choices, underlying surgical diagnosis, operative, and ultimately their cardiopulmonary interaction with a mechanical ventilator. This review addresses primarily the pathophysiology of perioperative lung injury with reference to ventilator-induced lung injury and acute respiratory distress syndrome.

Pseudomonas aeruginosa is associated with increased lung cytokines and asymmetric dimethylarginine compared with methicillin-resistant Staphylococcus aureus

The objective of the study was to investigate pulmonary responses to Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) using ovine and mice models of sepsis with emphasis on lung cytokine expression, asymmetric dimethylarginine (ADMA) concentration, and the arginase pathway. Sheep were instilled with either MRSA, P. aeruginosa, or saline under deep anesthesia; mechanically ventilated; resuscitated with fluid; and killed after 24 h. Mice were instilled with either MRSA, P. aeruginosa, or saline under deep anesthesia and killed after 8 h. Lungs were assessed for ADMA concentration, arginase activity, oxidative stress, and cytokine expression, and plasma was assessed for nitrate/nitrite concentrations. The severity of lung injury was more pronounced in P. aeruginosa sepsis compared with MRSA. The significant changes in sheep lung function after P. aeruginosa sepsis were associated with significantly increased ADMA concentrations and arginase activity compared with MRSA. However, the plasma concentration of nitrites and nitrates were significantly increased in MRSA sepsis compared with P. aeruginosa sepsis. In the mice model, P. aeruginosa significantly increased lung cytokine expression (IL-1 and IL-13), protein oxidation, and arginase activity compared with MRSA. Our data suggest that the greater expression of cytokines and ADMA concentrations may be responsible for severity of acute lung injury in P. aeruginosa sepsis. The lack of arginase activity may explain the greater nitric oxide production in MRSA sepsis.

Changes of markers of oxidative stress during menstrual cycle

The levels of urinary hydrogen peroxide and thiobarbituric acid reactive substances have been compared during the menstrual cycle of 12 regularly menstruating women. Higher level of both indices of oxidative stress (normalized with respect to creatinine content) were found in the luteal phase of the cycle. These results give further evidence for the usefulness of urinary hydrogen peroxide and thiobarbituric acid reactive substances as potential biomarkers of oxidative stress and for the antioxidant action of estrogens.

The effect of ethyl pyruvate on oxidative stress in intestine and bacterial translocation after thermal injury

BACKGROUND

Thermal injury causes a breakdown in the intestinal mucosal barrier due to ischemia reperfusion injury, which can induce bacterial translocation (BT), sepsis, and multiple organ failure in burn patients. The aim of this study was to investigate the effect of ethyl pyruvate (EP) on intestinal oxidant damage and BT in burn injury.

MATERIALS AND METHODS

Thirty-two rats were randomly divided into four groups. The sham group was exposed to 21 degrees C water and injected intraperitoneal with saline (1 mL/100 g). The sham + EP group received EP (40 mg/kg) intraperitoneally 6 h after the sham procedure. The burn group was exposed to thermal injury and given intraperitoneal saline injection (1 mL/100 g). The burn + EP group received EP (40 mg/kg) intraperitoneally 6 h after thermal injury. Twenty-four hours later, tissue samples were obtained from mesenteric lymph nodes, spleen, and liver for microbiological analysis and ileum samples were harvested for biochemical analysis.

RESULTS

Thermal injury caused severe BT in burn group. EP supplementation decreased BT in mesenteric lymph nodes and spleen in the burn + EP group compared with the burn group (P < 0.05). Also, burn caused BT in liver, but this finding was not statistically significant among all groups. Thermal injury caused a statistically significant increase in malondialdehyde and myeloperoxidase levels, and EP prevented this effects in the burn + EP group compared with the burn group (P < 0.05).

CONCLUSION

Our data suggested that EP can inhibit the BT and myeloperoxidase and malondialdehyde production in intestine following thermal injury, suggesting anti-inflammatory and anti-oxidant properties of EP.

Efficient protection by cationized catalase against H2O2 injury in primary cultured alveolar epithelial cells

Increasing evidence suggests that hydrogen peroxide plays an important role in alveolar epithelial injury produced during many inflammatory lung diseases. In this study, the successful prevention of hydrogen peroxide (H(2)O(2))-induced injury in primary cultured rabbit alveolar epithelial cells by cationized catalase is described. Cationized catalase was synthesized by direct chemical modification to enhance its association with alveolar epithelial cells. Cationized catalase exhibited a 22.3-fold higher cellular association at 2 h than native catalase, and incubation of cationized catalase with the cells produced a 2.19-fold intracellular catalase activity, which suggested that cationized catalase distributed both to the cell membrane and into the cell interior. Cationized catalase markedly suppressed H(2)O(2)-induced cell injury. In addition, electron spin resonance spectrometry analysis revealed that cationized catalase effectively eliminated H(2)O(2) produced in the medium by glucose plus glucose oxidase. On the other hand, polyethylene glycol-modified catalase (PEG-catalase) did not have any protective effect against H(2)O(2)-induced cell injury although PEG-catalase exhibited a 2.49-fold higher cellular association at 2 h than native catalase. These results suggest that cationization of catalase is a promising strategy for the treatment of many of inflammatory lung diseases.

Urinary Metabolites of Oxidative Stress and Nitric Oxide in Preterm and Term Infants

BACKGROUND

Many neonatal diseases have been associated with oxidative stress and altered nitric oxide status.

OBJECTIVE

To determine the effects of clinical interventions on the levels of urinary peroxides, a marker of oxidative stress, and urinary nitrate/nitrites, indices of nitric oxide production and metabolism, in the first 72 h of life in premature infants.

METHODS

A single, spot urine sample was collected from 82 premature and 20 healthy term infants within the first 72 h of life. The peroxide levels were quantified using a fluorometric method, and nitrate/nitrite levels were quantified by chemiluminescence.

RESULTS

Premature infants had a median peroxide level of 10.0 micromol/mmol creatinine (Cr) (interquartile range 4.8-20.0 micromol/mmol Cr). These values were significantly higher than term infants (median 5.0 micromol/mmol Cr, interquartile range 2.7-10.0 micromol/mmol Cr). Urinary nitrate/nitrite levels were not significantly different between preterm (220.5 micromol/mmol Cr, interquartile range 161-287 micromol/mmol Cr) and healthy term infants (244 micromol/mmol Cr, interquartile range 194-316 micromol/mmol Cr). For urinary peroxides, infants on TPN had significantly higher urinary peroxide levels than infants who were not on TPN at the time of urine collection (p = 0.006). Administration of indomethacin was associated with lower levels of urinary nitrate/nitrites (p = 0.0003). Both effects remained significant after controlling for gestational age, degree of respiratory distress and day of urine collection.

CONCLUSION

Monitoring the level of both peroxides and nitrate/nitrite may offer added information about the degree of oxidative stress experienced by a newborn but needs to account for clinical and therapeutic interventions.

Higher urine nitric oxide is associated with improved outcomes in patients with acute lung injury

RATIONALE

Nitrogen oxide (NO) species are markers for oxidative stress that may be pathogenic in acute lung injury (ALI).

OBJECTIVES

We tested two hypotheses in patients with ALI: (1) higher levels of urine NO would be associated with worse clinical outcomes, and (2) ventilation with lower VT would reduce urine NO as a result of less stretch injury.

METHODS

Urine NO levels were measured by chemiluminescence in 566 patients enrolled in the National Heart Lung and Blood Institute Acute Respiratory Distress Syndrome Network trial of 6 ml/kg versus 12 ml/kg VT ventilation. The data were expressed corrected and uncorrected for urine creatinine (Cr).

RESULTS

Higher baseline levels of urine NO to Cr were associated with lower mortality (odds ratio, 0.43 per log(10) increase in the ratio), more ventilator-free days (mean increase, 1.9 d), and more organ-failure-free days (mean increase, 2.3 d) on multivariate analysis (p < 0.05 for all analyses). Similar results were obtained using urine NO alone. NO to Cr levels were higher on Day 3 in the 6 ml/kg than in the 12 ml/kg VT group (p = 0.04).

CONCLUSIONS

Contrary to our hypothesis, higher urine NO was associated with improved outcomes in ALI at baseline and after treatment with the 6 ml/kg VT strategy. Higher endogenous NO may reflect less severe lung injury and better preservation of the pulmonary and systemic endothelium or may serve a protective function in patients with ALI.

Hypercapnia via reduced rate and tidal volume contributes to lipopolysaccharide-induced lung injury

Appreciating that CO2 modifies the chemical reactivity of nitric oxide (NO)-derived inflammatory oxidants, we investigated whether hypercapnia would modulate pulmonary inflammatory responses. Rabbits (n = 72) were ventilated with approximately 7-ml/kg tidal volume for 6 hours. Animals were randomized to one of the following conditions: eucapnia (Pa(CO2) at approximately 35-40 mm Hg), eucapnia + lipopolysaccharide (LPS), eucapnia + LPS + inhaled NO (iNO delivered at approximately 20 ppm), hypercapnia (Pa(CO2) at approximately 60 mm Hg), hypercapnia + LPS, and hypercapnia + LPS + iNO. The hypercapnia + LPS groups compared with groups exposed to eucapnia + LPS displayed significantly increased bronchoalveolar lavage fluid protein concentrations (p < 0.05), lung wet-to-dry ratios (p < 0.05), bronchoalveolar lavage fluid cell counts (p < 0.05), and lung histologic alterations consistent with greater injury. Furthermore, expression of inducible nitric oxide synthase (p < 0.05), tissue myeloperoxidase content (p < 0.05), and formation of lung protein 3-nitrotyrosine derivatives (p < 0.05) was greatest under conditions of hypercapnia + LPS. Groups exposed to hypercapnic conditions without LPS did not manifest these changes. The inhalation of iNO attenuated selected indices of lung injury. We conclude that hypercapnia induced by means of reduced rate and tidal volume amplifies pulmonary inflammatory responses.

Modulation of bone marrow-derived neutrophil signaling by H2O2: disparate effects on kinases, NF-kappaB, and cytokine expression

Reactive oxygen species (ROS), including hydrogen peroxide (H2O2), are generated in increased amounts in pathological, biological processes and can play a role in signal transduction. Neutrophils often accumulate in acute inflammatory reactions, at sites where elevated concentrations of ROS are present. ROS have been demonstrated to participate in the activation of intracellular signaling pathways, including those involved in modulating nuclear accumulation and transcriptional activity of NF-kappaB. However, the role of ROS in affecting such events in neutrophils has not been examined. Using exposure of murine bone marrow neutrophils to H2O2 as a model of oxidative stress, we found both strong and persistent activation of ERK1/2, p38, JNK, and PKB, but not the p21-activated kinase. Stimulating the bone marrow-derived neutrophils with H2O2 did not affect nuclear translocation of NF-kappaB. However, production and secretion of the proinflammatory cytokine TNF-alpha in LPS-stimulated neutrophils were inhibited by H2O2. Exposure of LPS- or TNF-alpha-stimulated neutrophils to H2O2 decreased nuclear translocation of NF-kappaB. LPS-induced activation of the transcriptional factor AP-1 was also inhibited by H2O2. This inhibition of nuclear accumulation of NF-kappaB by H2O2 was not caused by an impaired capacity of LPS to stimulate the IKK pathway or to direct oxidative effects on NF-kappaB but rather reflected diminished degradation of IkappaB-alpha. These results indicate that oxidative stress, despite being able to selectively activate intracellular kinases in bone marrow-derived neutrophils, also inhibits NF-kappaB activation and associated TNF-alpha expression. Such inhibitory effects on neutrophil activation may limit tissue damage produced by oxidative stress.

Oxidant-induced hypertrophy of A549 cells is accompanied by alterations in eukaryotic translation initiation factor 4E and 4E-binding protein-1

Control of protein synthesis resides at the level of eukaryotic translation initiation (eIF) complex formation. Complex formation is regulated by the mRNA cap-binding protein, eIF4E, whose activity is influenced by phosphorylation and binding to 4E-binding protein 1 (4E-BP1). To provide a link between alterations in protein synthesis and the pathogenesis of oxidant-mediated lung disease, we investigated the effect of hydrogen peroxide (H2O2) on actively growing A549 cells. Cells were exposed to 200 or 400 microM H2O2 for 4 h and then assessed for changes in proliferation, protein synthesis, and eIF4E and 4E-BP1 status over 72 h. We found that both concentrations of H2O2 inhibited [3H]thymidine incorporation and cell division while inducing a G2/M-predominant growth arrest within 24 h. In addition, H2O2 increased cell size, [3H]leucine incorporation/cell, and total cell protein. Although time had little effect on eIF4E and 4E-BP1 expression and phosphorylation state of control cells, H2O2 induced a 2- to 3-fold increase in eIF4E and 4E-BP1 expression, a 5-fold increase in eIF4E phosphorylation, and a shift in the distribution of 4E-BP1 phosphorylation favoring lesser phosphorylated forms. These findings suggest that oxidant-mediated alterations in protein synthesis and cell morphology occur in concert with changes in factors known to regulate translation kinetics.

Multivitamin solutions for enteral supplementation: a source of peroxides

OBJECTIVE

We investigated whether solutions of enteral vitamin supplementation are involved in the generation of peroxides and whether that contamination is biologically significant.

METHODS

Peroxide contents of oral multivitamin preparations were measured over 3 wk after the initial opening of the containers. In selected premature infants (younger than 35 wk gestation), urinary peroxides were measured after initiating oral multivitamin supplementation.

RESULTS

Peroxides in multivitamin solutions for enteral use are predominantly organic peroxides because they resist catalase. After the initial opening of the containers, there was a two-fold increase in total peroxides levels (P < 0.05) even in the preparation without riboflavin, a catalyst for the generation of peroxides. Initiation of oral vitamin supplementation was associated with increased (P < 0.05) urine peroxide levels. The high organic peroxide load did not correlate with its urinary excretion, mostly in the form of H(2)O(2). The excretion of H(2)O(2) corresponded to its oral intake from the multivitamin solution.

CONCLUSIONS

Compared with parenteral multivitamin solutions, the enteral preparations contained higher organic peroxide levels starting with the initial opening of the bottles. The increased urinary excretion of H(2)O(2) after enteral multivitamin supplementation suggested a systemic diffusion of peroxides or of components of the multivitamin preparation responsible for the generation of peroxides. This oxidant load was not quenched by the immature antioxidant defenses of premature infants.

Resuscitation from hemorrhagic shock with Ringer's ethyl pyruvate solution improves survival and ameliorates intestinal mucosal hyperpermeability in rats

We previously showed that pretreatment with a solution of ethyl pyruvate in a calcium-containing balanced salt solution, Ringer's ethyl pyruvate solution (REPS), ameliorates gut mucosal damage in rats subjected to mesenteric ischemia/reperfusion. Herein, we sought to test the hypothesis that REPS would be beneficial as a post-treatment (i.e., resuscitation fluid) for hemorrhagic shock. Anesthetized Sprague-Dawley rats were bled to a mean arterial pressure (MAP) of 40 mmHg until 40% of shed blood was returned. The animals then were resuscitated over 60 min with the remaining shed blood plus twice the shed blood volume as either Ringer's lactate solution (RLS) or REPS. In Experiment 1, RLS or REPS was then infused for 3 h more (or until death) at 3 mL/kg/h. Read-outs were post-resuscitation ileal mucosal permeability to fluorescein-labeled Dextran with an average molecular mass of 4000 Da (FD4) and survival. Permeability, determined just before death (MAP < 40 mmHg) or after 4 h of resuscitation, was assessed using an ex vivo everted gut sac technique and is expressed as a clearance (nL/cm/min). In Experiment 2, the read-outs were ileal FD4 permeability measured at 60 min after starting resuscitation and gut and liver malondialdehyde (MDA) formation. FD4 clearance data were logarithmically transformed prior to performing statistical analyses. In Experiment 1, 4/8 (50%) of RLS-treated rats survived 4 h after resuscitation whereas 7/7 (100%) of REPS-treated rats survived (P< 0.05). Ileal FD4 clearances were 105 +/- 30*, 85 +/- 34*, and 38 +/- 7 for all rats treated with RLS, surviving rats treated with RLS, and rats treated with REPS, respectively (the asterisk indicates P < 0.05 vs. REPS). In Experiment 2, ileal FD4 clearances were 71 +/- 13* and 34 +/- 8 for rats treated with RLS and REPS (n = 5 each), respectively. Post-resuscitation levels of MDA in the ileum and liver were significantly lower in rats treated with REPS as compared with RLS. Resuscitation with REPS, a stable and nontoxic antioxidant solution, improves survival and ameliorates ileal mucosal permeability in a rat model of severe hemorrhagic shock.

Oxidative stress and endothelial activation

The vascular endothelial surface is a major target of oxidative stress, but we are only now beginning to understand the molecular sources and physiologic consequences of such oxidative activity. Along with exogenous oxidants, provided by professional phagocytes or circulating enzymes, vascular cells generate oxidants in response to cytokine and growth factor stimulation, and these endogenous oxidants participate in vascular cell signal transduction. Endothelial cells express at least four of the five principal subunits of an NADPH oxidase, and we review evidence that such an oxidase is tightly regulated in both activity and in subcellular targeting. Both of these features are likely to contribute to the signal specificity of unstable oxidants.

Role of reactive oxygen and nitrogen species in acute respiratory distress syndrome

Reactive oxygen species are reactive, partially reduced derivatives of molecular oxygen (O 2 ). Important reactive oxygen species in biologic systems include superoxide radical anion, hydrogen peroxide, and hydroxyl radical. Closely related species include the hypohalous acids, particularly hypochlorous acid; chloramine and substituted chloramines; and singlet oxygen. Reactive nitrogen species are derived from the simple diatomic gas, nitric oxide. Peroxynitrite and its protonated form, peroxynitrous acid, are the most significant reactive nitrogen species in biologic systems. A variety of enzymatic and nonenzymatic processes can generate reactive oxygen species and reactive nitrogen species in mammalian cells. An extensive body of experimental evidence from studies using animal models supports the view that reactive oxygen species and reactive nitrogen species are important in the pathogenesis of acute respiratory distress syndrome. This view is further supported by data from clinical studies that correlate biochemical evidence of reactive oxygen species-mediated or reactive nitrogen species-mediated stress with the development of acute respiratory distress syndrome. Despite these data, pharmacologic strategies directed at minimizing reactive oxygen species-mediated or reactive nitrogen species-mediated damage have yet to be successfully introduced into clinical practice. The most extensively studied compound in this regard is N -acetylcysteine; unfortunately, clinical trials with this compound in patients with acute respiratory distress syndrome have yielded disappointing results.

Ringer's ethyl pyruvate solution ameliorates ischemia/reperfusion-induced intestinal mucosal injury in rats

OBJECTIVE

Pyruvate has been shown to be protective in numerous in vitro and in vivo models of oxidant-mediated cellular or organ system injury. Unfortunately, the usefulness of pyruvate as a therapeutic agent is abrogated by its very poor stability in solution. In an effort to take advantage of the ability of pyruvate to scavenge reactive oxygen species while avoiding the problems associated with the instability of pyruvate in solution, we sought to determine whether a simple derivative, ethyl pyruvate, would be protective in an animal model of reactive oxygen species-mediated tissue injury, namely mesenteric ischemia and reperfusion in rats.

DESIGN

Prospective, randomized trial.

SETTING

Animal research center.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Under general anesthesia, rats were subjected to 60 mins of mesenteric ischemia followed by 60 mins of reperfusion. Controls (n = 6) received intravenous lactated Ringer's solution according this dosing schedule: 1.5 mL/kg bolus before ischemia, 3.0 mL/kg bolus before resuscitation, and 1.5 mL.kg-1.hr-1 by continuous infusion. Two experimental groups received similar volumes of either pyruvate (n = 6 each) or ethyl pyruvate (n = 9) solution made up exactly like lactated Ringer's solution except for the substitution of either pyruvate or ethyl pyruvate for lactate, respectively.

MEASUREMENTS AND MAIN RESULTS

To obtain tissues for assessing mucosal permeability and histology, five 10-cm long segments of small intestine were obtained at the following time points: baseline, after 30 and 60 mins of ischemia, and after 30 and 60 mins of reperfusion. Mucosal permeability to fluorescein isothiocyanate dextran (molecular weight 4000 Da) was assessed ex vivo by using an everted gut sac method. Compared with controls, treatment of rats with either pyruvate solution or ethyl pyruvate solution significantly ameliorated the development of intestinal mucosal hyperpermeability during the reperfusion. Treatment with ethyl pyruvate solution also significantly decreased the extent of histologic mucosal damage after mesenteric reperfusion.

CONCLUSIONS

Treatment with Ringer's ethyl pyruvate solution ameliorated structural and functional damage to the intestinal mucosa in a rat model of mesenteric ischemia/reperfusion. Ethyl pyruvate solution warrants further evaluation as a novel therapeutic agent for preventing oxidant-mediated injury in various disease states.

Photoprotection of solutions of parenteral nutrition decreases the infused load as well as the urinary excretion of peroxides in premature infants

Light exposure and multivitamins are contributing factors to the generation of peroxides in solutions of parenteral nutrition. This article verifies if peroxides infused with parenteral nutrition are of biological significance in neonates. The mechanisms responsible for the generation of peroxides in total parenteral nutrition solutions are reviewed. The consequences of infused peroxides on an index of oxidant stress and on levels of a central antioxidant are evaluated in an animal model. The effect of photoprotection of parenteral nutrition on a biological marker of redox imbalance is evaluated in the urine of premature infants. Parenteral multivitamins produce a drop in glutathione and an oxidant stress similar to peroxides in the lungs of newborn guinea pigs. Infused peroxides elicited an increased urinary peroxide excretion in infants receiving parenteral nutrition exposed to light. Photoprotection reduced levels of infused and excreted peroxides. The results suggest that peroxides infused with total parenteral nutrition are not fully quenched by premature infants.

Parenteral multivitamin supplementation induces both oxidant and antioxidant responses in the liver of newborn guinea pigs

BACKGROUND

The multivitamin solution is a major component of photo-induced generation of peroxides in parenteral nutrition. The aim of this study was to determine whether the parenteral multivitamin preparation induces in the liver a peroxide-induced oxidant challenge or an antioxidant protection associated with the antiradical components of the solution.

METHODS

Newborn guinea pigs were infused with dextrose supplemented with peroxides (250 micromol/L H2O2 or 350 micromol/L tert-butylhydroperoxide) or with a multivitamin preparation (MVP, 1% vol/vol). After 4 days, total glutathione and a free radical-sensitive eicosanoid marker (prostaglandin I2 [PGI2]/total prostaglandins) were measured in livers.

RESULTS

There was a significant decrease in the PGI2/total prostaglandin ratio (mean +/- SEM) [dextrose: 0.068 +/- 0.007 vs. (dextrose + H2O2: 0.048 +/- 0.001, dextrose + TBH: 0.043 +/- 0.001)] and glutathione concentrations decreased [dextrose: 55 +/- 7 vs. (dextrose + H2O2: 37 +/- 7, dextrose + TBH: 18 +/- 7 nmol/mg protein)] after infusion of peroxides. Despite the peroxide load in the multivitamin solution, it did not alter the measured variables as prostanoid ratio remained at control concentrations (dextrose: 0.066 +/- 0.008 vs. dextrose + MVP: 0.065 +/- 0.006), as did glutathione levels (dextrose: 52 +/- 6 vs. dextrose + MVP: 45 +/- 7 nmol/mg prot).

CONCLUSION

In the liver of guinea pig pups, infused peroxides cause oxidation of membrane-derived prostanoids. The decrease in glutathione in response to administration of peroxides suggests consumption rather than a response to a free radical attack. Despite the oxidant load associated with peroxides generated in MVP, the multivitamin preparation protected membranes as the prostanoid ratio, and glutathione levels remained at control levels.

Increased levels of nitrate and surfactant protein a nitration in the pulmonary edema fluid of patients with acute lung injury

Levels of nitrite (NO2-) and nitrate (NO3-) were measured in pulmonary edema fluid and plasma from 34 patients with early acute lung injury (ALI) and 20 patients with hydrostatic pulmonary edema. Pulmonary edema fluid from patients with ALI had significantly higher levels of NO2- + NO3- compared with pulmonary edema fluid from patients with hydrostatic pulmonary edema (108 +/- 13 microM versus 66 +/- 9 microM; means +/- SEM; p < 0.05). In addition, patients with shock had higher plasma NO2- + NO3- levels than those without shock (79 +/- 11 microM versus 53 +/- 12 microM, p < 0.05). Acidemia and increased anion gap, markers of systemic hypoperfusion, were also associated with twofold higher plasma NO2- + NO3- levels (p < 0.01). Increased levels of NO2- + NO3- in edema fluid samples were associated with slower rates of alveolar fluid clearance. Nitrated pulmonary surfactant protein A (SP-A) was also detected in the edema fluid of patients with ALI after immunoprecipitation with a specific antibody against this protein. Previously, we have shown that nitration of SP-A impairs its host- defense properties. In aggregate, the results of this study indicate that reactive oxygen-nitrogen species may play a role in the pathogenesis of human ALI.

Hydrogen peroxide in the human body

Hydrogen peroxide (H(2)O(2)) is widely regarded as a cytotoxic agent whose levels must be minimized by the action of antioxidant defence enzymes. In fact, H(2)O(2) is poorly reactive in the absence of transition metal ions. Exposure of certain human tissues to H(2)O(2) may be greater than is commonly supposed: substantial amounts of H(2)O(2) can be present in beverages commonly drunk (especially instant coffee), in freshly voided human urine, and in exhaled air. Levels of H(2)O(2) in the human body may be controlled not only by catabolism but also by excretion, and H(2)O(2) could play a role in the regulation of renal function and as an antibacterial agent in the urine. Urinary H(2)O(2) levels are influenced by diet, but under certain conditions might be a valuable biomarker of 'oxidative stress'.

Hypercapnia induces injury to alveolar epithelial cells via a nitric oxide-dependent pathway

Ventilator strategies allowing for increases in carbon dioxide (CO(2)) tensions (hypercapnia) are being emphasized to ameliorate the consequences of inflammatory-mediated lung injury. Inflammatory responses lead to the generation of reactive species including superoxide (O(2)(-)), nitric oxide (.NO), and their product peroxynitrite (ONOO(-)). The reaction of CO(2) and ONOO(-) can yield the nitrosoperoxocarbonate adduct ONOOCO(2)(-), a more potent nitrating species than ONOO(-). Based on these premises, monolayers of fetal rat alveolar epithelial cells were utilized to investigate whether hypercapnia would modify pathways of.NO production and reactivity that impact pulmonary metabolism and function. Stimulated cells exposed to 15% CO(2) (hypercapnia) revealed a significant increase in.NO production and nitric oxide synthase (NOS) activity. Cell 3-nitrotyrosine content as measured by both HPLC and immunofluorescence staining also increased when exposed to these same conditions. Hypercapnia significantly enhanced cell injury as evidenced by impairment of monolayer barrier function and increased induction of apoptosis. These results were attenuated by the NOS inhibitor N-monomethyl-L-arginine. Our studies reveal that hypercapnia modifies.NO-dependent pathways to amplify cell injury. These results affirm the underlying role of.NO in tissue inflammatory reactions and reveal the impact of hypercapnia on inflammatory reactions and its potential detrimental influences.

Peroxide-like oxidant response in lungs of newborn guinea pigs following the parenteral infusion of a multivitamin preparation

The multivitamin solution is a major component responsible for the photo-induced generation of peroxides in parenteral nutrition. The lung is a target of oxidant injury; however, the specific role of infused peroxides is unknown. The aim of this study was to determine if parenteral multivitamins induce in the lung an oxidant challenge similar to that of peroxides. Newborn guinea pigs were infused with dextrose plus relevant concentrations of H(2)O(2) (0,250,500 microM) or multivitamins (0,1%), as well as parenteral nutrition supplemented with multivitamins (0,1%). After 4 days, total glutathione, glutathione-related enzymes, and oxidant-sensitive eicosanoids were measured in the lungs. Peroxides as well as multivitamins led to a significant decrease in glutathione and the activity of glutathione synthase, indicating that infused peroxides were not entirely transformed into free radicals, which would have stimulated glutathione synthesis. The multivitamin solution induced a response in oxidant-sensitive eicosanoids similar to the response to peroxides, suggesting an oxidant stress that was not alleviated by the antiradical properties of its components. The effects on prostaglandins occurred independently from the stimulation in glutathione levels induced by parenteral nutrition. The multivitamin solution carries an oxidant load and causes effects similar to those of peroxides in the lungs of newborn guinea pigs.

Thirty years of clinical trials in acute respiratory distress syndrome

OBJECTIVE

To systematically review clinical trials in acute respiratory distress syndrome (ARDS).

DATA SOURCES

Computerized bibliographic search of published research and citation review of relevant articles.

STUDY SELECTION

All clinical trials of therapies for ARDS were reviewed. Therapies that have been compared in prospective, randomized trials were the focus of this analysis.

DATA EXTRACTION

Data on population, interventions, and outcomes were obtained by review. Studies were graded for quality of scientific evidence.

MAIN RESULTS

Lung protective ventilator strategy is supported by improved outcome in a single large, prospective trial and a second smaller trial. Other therapies for ARDS, including noninvasive positive pressure ventilation, inverse ratio ventilation, fluid restriction, inhaled nitric oxide, almitrine, prostacyclin, liquid ventilation, surfactant, and immune-modulating therapies, cannot be recommended at this time. Results of small trials using corticosteroids in late ARDS support the need for confirmatory large clinical trials.

CONCLUSIONS

Lung protective ventilator strategy is the first therapy found to improve outcome in ARDS. Trials of prone ventilation and fluid restriction in ARDS and corticosteroids in late ARDS support the need for large, prospective, randomized trials.

Determination of hydrogen peroxide by micro-flow injection-chemiluminescence using a coupled flow cell reactor chemiluminometer

A novel flow cell reactor was developed for micro-flow injection determination of hydrogen peroxide (H(2)O(2)) using horseradish peroxide (HRP)-catalysed luminol chemiluminescence. The newly developed flow cell reactor for a chemiluminometer allowed mixing of the chemiluminescent reagents in front of a photomultiplier for maximum detection of the emitted light. The rapid mixing allowed a decrease in the flow rate of the pump to 0.1-0.01 mL/min, resulting in increased sensitivity of detection of light. The flow cell reactor was made by packing HRP-immobilized gels into a flow cell (Teflon tube; 6 cm x 0.98 mm i.d.) located in the cell holder of a chemiluminometer (flow-through type). The HRP-immobilized gels were made by immobilizing HRP onto the Chitopearl gel by the periodate method. H(2)O(2) specimens (50 microL) were injected into a stream of water delivered at a flow rate of 0.1 mL/min and mixed with a luminol solution (0.56 mmol/L in Tricine buffer, pH 9.2) delivered at 0.1 mL/min in the flow cell reactor. Within-run reproducibility of the assay of H(2)O(2) was 2.4% (4.85 micromol/L; flow rate 0.1 mL/min, injection interval 10 min). The reproducibility of the H(2)O(2) assay was influenced by the flow rates and the injection intervals of the H(2)O(2) specimens. As the flow rates decreased, both the light intensity and the light duration increased. Optimal light intensity was obtained at a luminol concentration of 3-8 mmol/L, but 0.56 mmol/L was sufficient for assay of H(2)O(2) in clinical specimens. At a luminol concentration of 0.56 mmol/L, the regression equation of the standard curve for H(2)O(2) (0-9.7 micromol/L) was Y = 27.5 X(2) + 394 X + 58.9 (Y = light intensity; X = concentration of H(2)O(2)) and the detection limit of H(2)O(2) was 0.2 micromol/L. This method was used to assay glucose (2.7-16.7 mmol/L) based on a glucose oxidase (20 U/mL, pH 7.4) reaction. The standard curve for glucose was Y = 167 X(2) - 351 X + 1484 (Y = light intensity; X = glucose). The within-run reproducibility for an aqueous glucose standard (2.7 mmol/L) and a control serum (glucose, 5 mmol/L) was 4.48% (n = 5) and 5.70% (n = 9), respectively.

Plasma proteins modified by tyrosine nitration in acute respiratory distress syndrome

The present study identifies proteins modified by nitration in the plasma of patients with ongoing acute respiratory distress syndrome (ARDS). The proteins modified by nitration in ARDS were revealed by microsequencing and specific antibody detection to be ceruloplasmin, transferrin, alpha(1)-protease inhibitor, alpha(1)-antichymotrypsin, and beta-chain fibrinogen. Exposure to nitrating agents did not deter the chymotrypsin-inhibiting activity of alpha(1)-antichymotrypsin. However, the ferroxidase activity of ceruloplasmin and the elastase-inhibiting activity of alpha(1)-protease inhibitor were reduced to 50.3 +/- 1.6 and 60.3 +/- 5.3% of control after exposure to the nitrating agent. In contrast, the rate of interaction of fibrinogen with thrombin was increased to 193.4 +/- 8.5% of the control value after exposure of fibrinogen to nitration. Ferroxidase activity of ceruloplasmin and elastase-inhibiting activity of the alpha(1)-protease inhibitor in the ARDS patients were significantly reduced (by 81 and 44%, respectively), whereas alpha(1)-antichymotrypsin activity was not significantly altered. Posttranslational modifications of plasma proteins mediated by nitrating agents may offer a biochemical explanation for the reported diminished ferroxidase activity, elevated levels of elastase, and fibrin deposits detected in patients with ongoing ARDS.

Increased urinary peroxides in newborn infants receiving parenteral nutrition exposed to light

OBJECTIVES

To determine whether peroxide loads infused with total parenteral nutrition (TPN) are fully quenched by premature infants.

STUDY DESIGN

After baseline urine peroxide levels were established, the effect of various parenteral regimens was correlated with urinary peroxide levels in 64 newborn infants </=32 weeks' gestation. This correlation was achieved with the properties of light and of various parenteral nutrient admixtures on the generation of peroxides. Peroxides were measured by the ferrous oxidation of xylenol orange.

RESULTS

The level of urinary peroxides measured for infants given a fat-free TPN regimen unprotected from light (74.5 +/- 15.3 micromol/L) was similar to levels found in infants given a lipid-containing regimen (88.1 +/- 10.3 micromol/L). When photoprotected, the fat-free alimentation was associated with peroxide levels (28.8 +/- 2.8 micromol/L) similar to those measured before TPN (27.6 +/- 4.1 micromol/L).

CONCLUSIONS

Because urine peroxide levels are changed by various nutritional procedures, antioxidant systems of premature infants are unable to fully quench the oxidant load associated with TPN.

Acute lung injury and acute respiratory distress syndrome in sepsis and septic shock

Sepsis remains the leading cause of ARDS, and ARDS is still an often fatal condition. With our expanding knowledge of the pathobiologic mechanisms and the relationship between these two entities, early recognition, treatment, and prevention of sepsis may prevent or hasten recovery from ARDS. Understanding the biologic markers involved in the complex inflammatory response of sepsis and acute lung injury offers the possibility of future investigations to target treatment based on these mediators.

Contribution of multivitamins, air, and light in the generation of peroxides in adult and neonatal parenteral nutrition solutions

OBJECTIVE

To compare the concentrations of peroxides between adult and neonatal total parenteral nutrition (TPN) solutions in response to protection against inducers of peroxidation such as multivitamins and exposure to light or air.

METHODS

Peroxide concentrations were measured in freshly prepared adult and neonatal solutions of fat-free TPN in four settings: with or without an air inlet, and protected or unprotected from ambient light. An oxygen washout was performed by exposing a fat-free neonatal TPN solution to a continuous flow of nitrogen.

RESULTS

Globally, light was the main inducer of peroxides in adult and neonatal solutions. However, in adult solutions the concentration of peroxides remained <15 micromol/L, while in neonatal solutions the peroxide concentration was as high as 300 micromol/L in ambient light. Although the oxygen washout did prevent the generation of peroxides, avoiding air inlet was not as effective as was photoprotection in decreasing the important peroxide load in the neonatal TPN solution.

CONCLUSIONS

The higher concentration of peroxides found in neonatal solutions compared with adult solutions is explained by the differences in nutrient composition between the two solutions. Contamination of parenteral solutions by air during compounding accounts for the photoinduced generation of peroxides in TPN solutions. It is more convenient to protect TPN solutions from light exposure after the admixture of the multivitamin solution than to avoid contact with oxygen.

Reactive oxygen species induced smooth muscle responses in the intestine, vessels and airways and the effect of antioxidants

Numerous experimental data confirm the importance of reactive oxygen species (ROS) in physiological activities of smooth muscles and in the pathogenesis of various diseases with altered function of smooth muscles. The present study shows that smooth muscles of the intestine, airways and vessels, as well as their epithelium, endothelium and innervations, might be important targets of the ROS action. We demonstrated differences among the actions of various ROS (endogenous, exogenous, produced enzymatically, non-enzymatically) as well as among their actions in different smooth muscle tissues. Our results indicate that ROS are involved in changes in muscle tone, membrane conductance, calcium homeostasis, calcium-dependent processes, as well as in eicosanoid and nitric oxide metabolism. The effects of antioxidative enzymes (superoxide dismutase, catalase), of several drugs of natural origin (e.g. Kampo Medicines) and synthetic agents (e.g. stobadine, nitrosopine, ACE inhibitors) suggest that smooth muscle tissues are useful models to study ROS action and drug intervention in ROS induced injuries.

The influence of liposome-encapsulated prostaglandin E1 on hydrogen peroxide concentrations in the exhaled breath of patients with the acute respiratory distress syndrome

Hydrogen peroxide (H2O2) levels are increased in the exhaled breath of patients with the acute respiratory distress syndrome (ARDS). Because liposome-encapsulated prostaglandin E1 (PGE1) downregulates the CD11/CD18 receptor of the neutrophil, thereby limiting endothelial adhesion, the use of this drug should decrease the excretion of H2O2 in the expiratory condensate of patients with ARDS. Patients > 11 yr of age with ARDS (diffuse, patchy infiltrates by chest radiograph; Pao2/fraction of inspired oxygen [P/F] ratio < or = 200 mm Hg; pulmonary capillary wedge pressure < or = 18 mm Hg; and the requirement for mechanical ventilation) were randomized to receive placebo (n = 14) or escalating doses (0.15-3.6 micrograms/kg) of liposomal PGE1 (n = 14) every 6 h for up to 7 days. Condensate was collected every morning from the expiratory tubing that was submerged in an ice saltwater bath (-5 degrees C). H2O2 levels were measured by using a horseradish peroxidase assay. Other data collected included white blood cell count and P/F ratios. There was no significant difference in the concentration of H2O2 in the expiratory condensate between the liposomal PGE1 group and the control group either before (0.99 +/- 0.52 vs 0.93 +/- 0.48 mumol/L) or during treatment (1.04 +/- 0.45 vs 0.76 +/- 0.25 mumol/L). Liposomal PGE1 treatment improved the P/F ratio and decreased the white blood cell count over time. Despite its ability to downregulate the CD11/CD18 neutrophil receptor, liposomal PGE1 did not reduce exhaled H2O2 excretion.

IMPLICATIONS

White blood cells (WBC) are thought to be part of the cause of the acute respiratory distress syndrome, a lung disease. WBC in the lung produce hydrogen peroxide, which is exhaled. Liposomal PGE1 inhibits WBC function but was found to have no effect in decreasing exhaled hydrogen peroxide in patients with the acute respiratory distress syndrome.

Leucocyte activation markers in clinical practice

The response against tissue injury and infection begins with the early activation of molecular and cellular elements of the inflammatory and immune response. Severe tissue injury, necrosis, and infection induce imbalanced inflammation associated with leukocyte over-stimulation and excessive or dysregulated release of cellular mediators. Clinical and experimental studies have shown that these mediators are directly related to progressive post-injury complications. Persistent increased levels of pro-inflammatory mediators produce tissue injury. Excessive production and activity of anti-inflammatory mediators cause anergy and/or immune dysfunction with increased susceptibility to infection. Leukocyte activation is assessed by cell surface phenotype expression, cellular mediators determination, or by measuring functional responses using isolated cells. Potential routine clinical uses are: evaluation of severity and prognosis in critically ill patients, immunomonitoring of sepsis, and detection of tissue injury, necrosis, and infection. In practice, the determination of cellular activation markers is restricted by a limited number of automated methods and by the cost of reagents. The availability of flow cytometry and immunoassay automated systems can contribute to a wider use in practice. Here we review the immunopathophysiology of polymorphonuclear neutrophil, monocyte, macrophage, and lymphocyte activation in response to tissue injury and infection. In addition, laboratory methods for their determination, and clinical applications in practice, are discussed.

Protecting solutions of parenteral nutrition from peroxidation

BACKGROUND

Light exposure induces the generation of peroxides in solutions of total parenteral nutrition (TPN). Peroxide toxicity has been documented in cell, in tissue, and in isolated organs. To decrease the infused peroxide load and to protect the quality of the parenteral nutrients, we tested the photoprotective properties of different infusion sets.

METHODS

Solutions of fat-free TPN and all-in-one total nutrient admixture (TNA) were run through sets of bags (clear and covered) and tubings (clear and colored: black, orange, and yellow) offering different levels of protection against light. Peroxide levels were determined by ferrous oxidation of xylenol orange, thiol functions by the 5,5,-dithiobis(2-nitrobenzoic acid) technique, and absorbance of tubings by spectroscopy.

RESULTS

Protection of only the bag had little effect on peroxide generation. In fat-free TPN solutions kept in covered bags, peroxide concentrations were 1.5 to 2 times higher when run through clear compared with colored tubings. When exposed to phototherapy or in the presence of lipids, peroxides were two to three times higher with the clear compared with the black tubing; meanwhile, orange and yellow tubings offered varying levels of protection related to their light-absorbing properties. Colored tubings offered a greater protection against the disappearance of thiol functions.

CONCLUSIONS

Covering bags and using orange and yellow tubings may be a practical solution to reduce infused peroxide loads from about 400 to 100 microM. This is especially relevant in patients with an immature or a compromised antioxidant capacity or when phototherapy or preparations of TNA are used.

Has the mortality of septic shock changed with time

OBJECTIVES

To determine whether a systematic review of the literature could identify changes in the mortality of septic shock over time.

DATA SOURCES

A review of all relevant papers from 1958 to August 1997, identified through a MEDLINE search and from the bibliographies of articles identified.

DATA SYNTHESIS

The search identified 131 studies (99 prospective and 32 retrospective) involving a total of 10,694 patients. The patients' mean age was 57 yrs with no change over time. The overall mortality rate in the 131 studies was 49.7%. There was an overall significant trend of decreased mortality over the period studied (r=.49, p < .05). The mortality rate in those patients with bacteremia as an entry criterion was greater than that rate in patients whose entry criterion was sepsis without definite bacteremia (52.1% vs. 49.1%; chi2=6.1 and p< .05). The site of infection altered noticeably over the years. Chest-related infections increased over time, with Gram-negative infections becoming proportionately less common. If all other organisms and mixed infections are included with the Gram-positives, the result is more dramatic, with these organisms being causative in just 10% of infections between 1958 and 1979 but in 31% of infections between 1980 and 1997.

CONCLUSIONS

The present review showed a slight reduction in mortality from septic shock over the years, although this result should be approached with caution. The heterogeneity of the articles and absence of a severity score for most of the studies limited our analysis. Furthermore, there was an increasing prevalence of Gram-positive causative organisms, and a change of the predominant origin of sepsis from the abdomen to the chest.

Activation of the JAK-STAT pathway by reactive oxygen species

Reactive oxygen species (ROS) play an important role in the pathogenesis of many human diseases, including the acute respiratory distress syndrome, Parkinson's disease, pulmonary fibrosis, and Alzheimer's disease. In mammalian cells, several genes known to be induced during the immediate early response to growth factors, including the protooncogenes c-fos and c-myc, have also been shown to be induced by ROS. We show that members of the STAT family of transcription factors, including STAT1 and STAT3, are activated in fibroblasts and A-431 carcinoma cells in response to H2O2. This activation occurs within 5 min, can be inhibited by antioxidants, and does not require protein synthesis. STAT activation in these cell lines is oxidant specific and does not occur in response to superoxide- or nitric oxide-generating stimuli. Buthionine sulfoximine, which depletes intracellular glutathione, also activates the STAT pathway. Moreover, H2O2 stimulates the activity of the known STAT kinases JAK2 and TYK2. Activation of STATs by platelet-derived growth factor (PDGF) is significantly inhibited by N-acetyl-L-cysteine and diphenylene iodonium, indicating that ROS production contributes to STAT activation in response to PDGF. These findings indicate that the JAK-STAT pathway responds to intracellular ROS and that PDGF uses ROS as a second messenger to regulate STAT activation.

Low-dose N-acetylcysteine protects rats against endotoxin-mediated oxidative stress, but high-dose increases mortality

We evaluated the effect of the antioxidant N-acetylcysteine (NAC) on oxidative stress, lung damage, and mortality induced by an endotoxin (lipopolysaccharide, or LPS) in the rat. Continuous intravenous infusion of 275 mg NAC/kg in 48 h, starting 24 h before LPS challenge, decreased hydrogen peroxide (H2O2) concentrations in whole blood (p < 0.01). This decrease was accompanied by fewer histologic abnormalities of the lung and decreased mortality (p < 0.025), compared with rats receiving LPS alone. N-Acetylserine, which has no sulfhydryl group, did not protect rats against LPS toxicity. Improved survival was not associated with an increase in pulmonary reduced glutathione, nor with inhibition of serum tumor necrosis factor (TNF) activity. In vitro, TNF production and DNA binding of nuclear factor kappa B (NF-kappaB) in human Mono Mac 6 cells was only inhibited at concentrations of NAC above 20 mM. High-dose NAC treatment (550 and 950 mg/kg in 48 h) decreased lung GSH (p < 0.05) and resulted in a significantly smaller number of surviving animals when compared with the low-dose NAC group (p < 0.025). In vitro, NAC increased hydroxyl radical generation in a system with Fe(III)-citrate and H2O2 by reducing ferric iron to its catalytic, active Fe2+ form. We conclude that low-dose NAC protects against LPS toxicity by scavenging H2O2, while higher doses may have the opposite effect.

Dimethylthiourea protects rats against gram-negative sepsis and decreases tumor necrosis factor and nuclear factor kappaB activity

The thiol-containing compound dimethylthiourea (DMTU) is a known protectant in various models of oxidant-mediated tissue damage. Protective effects of DMTU have also been reported in studies on endotoxin-induced (LPS-induced) tissue injury. DMTU may exert this protective effect by reducing oxidative stress. In this study we investigated the effect of DMTU on survival, oxidative stress, and tumor necrosis factor (TNF) activity in two rat models of gram-negative bacterial sepsis. Intraperitoneal injection of 500 mg DMTU/kg protected against the lethal effects of intraperitoneally injected LPS (5 mg/kg) and live Salmonella typhimurium (3.3 x 10(10) CFU/kg). LPS injection resulted in oxidative stress, as indicated by an elevated concentration of hydrogen peroxide (H(2)O(2)) in normal and carbon monoxide-treated deproteinized blood. We also observed increased H(2)O(2) levels in animals injected with live Salmonella typhimurium. Although DMTU improved survival in both models, H(2)O(2) concentrations were not affected by it. This is consistent with our in vitro observation that DMTU is a weak H(2)O(2) scavenger. Serum TNF activity, however, was substantially decreased by DMTU, and this was associated with a reduced activation of nuclear factor kappaB in the peritoneal cells of LPS-treated rats. In addition, LPS-induced TNF production in vitro by rat peritoneal macrophages was inhibited by DMTU (p < 0.05). These results suggest that the protective effect of DMTU in gram-negative bacterial sepsis may be the result of a reduction in TNF activity. DMTU does not exert this effect by H(2)O(2) scavenging but may inactivate toxic H(2)O(2) metabolites.

A profile of amino acid and catecholamine levels during endotoxin-induced acute lung injury in sheep: searching for potential markers of the acute respiratory distress syndrome

The identification of plasma markers of the course of the acute respiratory distress syndrome (ARDS) is needed to improve its treatment and to further advance the development of new therapeutic agents. The status of markers of lung injury in ARDS is reviewed and some new potential markers are proposed. This study focused on plasma amino acids, related amino compounds, and catecholamine levels during the acute phase of endotoxin-induced lung injury in 8 sheep characterized by the onset of pulmonary edema caused by increased microvascular permeability. A number of significant changes from baseline values were found. During the sixth hour of a 12-hour period of endotoxin infusion, norepinephrine, epinephrine, and alanine levels increased whereas the isoleucine level decreased. During the sixth hour of the immediate postendotoxin period, the taurine level increased while the levels of arginine, citrulline, glycine, isoleucine, methionine, ornithine, serine, threonine, and tryptophan decreased. These findings are compared with prior studies in human subjects detailing the amino acid profile characteristic of advanced sepsis. We conclude that the present profile of catecholamine and amino acid changes during endotoxemia in sheep deserves further study in human subjects to determine its significance as a marker of the early stage of ARDS.