Pivotal role of glutathione depletion in plasma-induced endothelial oxidative stress during sepsis. Crit Care Med. 2008;36:2328-2334. [PMID: 18664787 DOI: 10.1097/ccm.0b013e3181800387]

The Role of Iron Metabolism in Sepsis-associated Encephalopathy: a Potential Target

Sepsis-associated encephalopathy (SAE) is an acute cerebral dysfunction secondary to infection, and the severity can range from mild delirium to deep coma. Disorders of iron metabolism have been proven to play an important role in a variety of neurodegenerative diseases by inducing cell damage through iron accumulation in glial cells and neurons. Recent studies have found that iron accumulation is also a potential mechanism of SAE. Systemic inflammation can induce changes in the expression of transporters and receptors on cells, especially high expression of divalent metal transporter1 (DMT1) and low expression of ferroportin (Fpn) 1, which leads to iron accumulation in cells. Excessive free Fe2+ can participate in the Fenton reaction to produce reactive oxygen species (ROS) to directly damage cells or induce ferroptosis. As a result, it may be of great help to improve SAE by treatment of targeting disorders of iron metabolism. Therefore, it is important to review the current research progress on the mechanism of SAE based on iron metabolism disorders. In addition, we also briefly describe the current status of SAE and iron metabolism disorders and emphasize the therapeutic prospect of targeting iron accumulation as a treatment for SAE, especially iron chelator. Moreover, drug delivery and side effects can be improved with the development of nanotechnology. This work suggests that treating SAE based on disorders of iron metabolism will be a thriving field.

Role of toll-like receptor-mediated pyroptosis in sepsis-induced cardiomyopathy

Sepsis, a life-threatening dysregulated status of the host response to infection, can cause multiorgan dysfunction and mortality. Sepsis places a heavy burden on the cardiovascular system due to the pathological imbalance of hyperinflammation and immune suppression. Myocardial injury and cardiac dysfunction caused by the aberrant host responses to pathogens can lead to cardiomyopathy, one of the most critical complications of sepsis. However, many questions about the specific mechanisms and characteristics of this complication remain to be answered. The causes of sepsis-induced cardiac dysfunction include abnormal cardiac perfusion, myocardial inhibitory substances, autonomic dysfunction, mitochondrial dysfunction, and calcium homeostasis dysregulation. The fight between the host and pathogens acts as the trigger for sepsis-induced cardiomyopathy. Pyroptosis, a form of programmed cell death, plays a critical role in the progress of sepsis. Toll-like receptors (TLRs) act as pattern recognition receptors and participate in innate immune pathways that recognize damage-associated molecular patterns as well as pathogen-associated molecular patterns to mediate pyroptosis. Notably, pyroptosis is tightly associated with cardiac dysfunction in sepsis and septic shock. In line with these observations, induction of TLR-mediated pyroptosis may be a promising therapeutic approach to treat sepsis-induced cardiomyopathy. This review focuses on the potential roles of TLR-mediated pyroptosis in sepsis-induced cardiomyopathy, to shed light on this promising therapeutic approach, thus helping to prevent and control septic shock caused by cardiovascular disorders and improve the prognosis of sepsis patients.

Neutrophil, neutrophil extracellular traps and endothelial cell dysfunction in sepsis

Sepsis is a persistent systemic inflammatory condition involving multiple organ failures resulting from a dysregulated immune response to infection, and one of the hallmarks of sepsis is endothelial dysfunction. During its progression, neutrophils are the first line of innate immune defence against infection. Aside from traditional mechanisms, such as phagocytosis or the release of inflammatory cytokines, reactive oxygen species and other antibacterial substances, activated neutrophils also release web-like structures composed of tangled decondensed DNA, histone, myeloperoxidase and other granules called neutrophil extracellular traps (NETs), which can efficiently ensnare bacteria in the circulation. In contrast, excessive neutrophil activation and NET release may induce endothelial cells to shift toward a pro-inflammatory and pro-coagulant phenotype. Furthermore, neutrophils and NETs can degrade glycocalyx on the endothelial cell surface and increase endothelium permeability. Consequently, the endothelial barrier collapses, contributing to impaired microcirculatory blood flow, tissue hypoperfusion and life-threatening organ failure in the late phase of sepsis.

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.

Is Selenium Supplementation Beneficial in Acute Ischemic Stroke?

BACKGROUND

Selenium (Se) plays a significant role in brain physiology. The existing human data demonstrate that stroke is associated with significantly reduced Se levels and glutathione peroxidase (GPx) activity. This study proposed to investigate the effect of intravenous Se (Selenase) administration in patients with acute ischemic stroke (AIS) on neurological outcomes, antioxidant enzyme activity, and inflammatory marker levels.

METHODS

AIS patients (n=50) were recruited from a neurology unit of a university-affiliated hospital. Patients were randomly assigned to receive either Selenase or placebo (saline) for 5 days. The modified ranking scale, the national institute of health stroke scale, and the mini-mental state examination, as primary outcomes, and the serum GPx concentration, total antioxidant activity, and tumor necrosis factor-α levels, as secondary outcomes, were measured at the baseline and on day 30.

RESULTS

Eventually, 44 patients with AIS completed the intervention study. A notable increase in GPx and total antioxidant activity levels was detected in the treatment group compared with the placebo group (110.63±52.48 m/mL, 1.34±0.30 mmol/L, P<0.05), whereas the serum tumor necrosis factor-α level in the Selenase group was significantly lower than that of the placebo group (58.58±61.33 pg/mL, P<0.05). In addition, Selenase improved the modified ranking scale and national institute of health stroke scale scores significantly (P<0.05 and <0.04, respectively), but no statistical difference was observed between the 2 groups in the mini-mental state examination score.

CONCLUSION

Selenase, plausibly due to its antioxidant function, results in positive outcomes in terms of neurological deficits, antioxidant enzyme activity, and inflammatory marker levels.

Oxidative Stress and Endothelial Dysfunction in Sepsis and Acute Inflammation

Significance: Under homeostatic conditions, the endothelium dynamically regulates vascular barrier function, coagulation pathways, leukocyte adhesion, and vasomotor tone. During sepsis and acute inflammation, endothelial cells (ECs) undergo multiple phenotypic and functional modifications that are initially adaptive but eventually become harmful, leading to microvascular dysfunction and multiorgan failure. Critical Issues and Recent Advances: Sepsis unbalances the redox homeostasis toward a pro-oxidant state, characterized by an excess production of reactive oxygen species and reactive nitrogen species, mitochondrial dysfunction, and a breakdown of antioxidant systems. In return, oxidative stress (OS) alters multiple EC functions and promotes a proinflammatory, procoagulant, and proadhesive phenotype. The OS also induces glycocalyx deterioration, cell death, increased permeability, and impaired vasoreactivity. Thus, during sepsis, the ECs are both a significant source and one of the main targets of OS. Future Directions: This review aims at covering the current understanding of the role of OS in the endothelial adaptive or maladaptive multifaceted response to sepsis and to outline the therapeutic potential and issues of targeting OS and endothelial dysfunction during sepsis and septic shock. One of the many challenges in the management of sepsis is now based on the detection and correction of these anomalies of endothelial function.

Selenocompounds and Sepsis: Redox Bypass Hypothesis for Early Diagnosis and Treatment: Part A-Early Acute Phase of Sepsis: An Extraordinary Redox Situation (Leukocyte/Endothelium Interaction Leading to Endothelial Damage)

Significance: Sepsis is a health disaster. In sepsis, an initial, beneficial local immune response against infection evolves rapidly into a generalized, dysregulated response or a state of chaos, leading to multiple organ failure. Use of life-sustaining supportive therapies creates an unnatural condition, enabling the complex cascades of the sepsis response to develop in patients who would otherwise die. Multiple attempts to control sepsis at an early stage have been unsuccessful. Recent Advances: Major events in early sepsis include activation and binding of leukocytes and endothelial cells in the microcirculation, damage of the endothelial surface layer (ESL), and a decrease in the plasma concentration of the antioxidant enzyme, selenoprotein-P. These events induce an increase in intracellular redox potential and lymphocyte apoptosis, whereas apoptosis is delayed in monocytes and neutrophils. They also induce endothelial mitochondrial and cell damage. Critical Issues: Neutrophil production increases dramatically, and aggressive immature forms are released. Leukocyte cross talk with other leukocytes and with damaged endothelial cells amplifies the inflammatory response. The release of large quantities of reactive oxygen, halogen, and nitrogen species as a result of the leukocyte respiratory burst, endothelial mitochondrial damage, and ischemia/reperfusion processes, along with the marked decrease in selenoprotein-P concentrations, leads to peroxynitrite damage of the ESL, reducing flow and damaging the endothelial barrier. Future Directions: Endothelial barrier damage by activated leukocytes is a time-sensitive event in sepsis, occurring within hours and representing the first step toward organ failure and death. Reducing or stopping this event is necessary before irreversible damage occurs.

Is Pyroglutamic Acid a Prognostic Factor Among Patients with Suspected Infection? A Prospective Cohort Study

Pyroglutamic acid (PGA) is a compound that accumulates during oxidative stress and hence, elevated levels may be associated with poor prognosis in patients with infection or sepsis. To examine this hypothesis, patients presenting with acute infection were recruited in the emergency department and prospectively followed for 30 days. Sport urine samples were quantified for PGA. Outcomes were mortality and composite outcome of death or organ failure. Thirty two (32%) patients had qSOFA≥2. Median urine PGA was 22.9 (IQR 17.64, 33.53) µmol/mmol creatinine. Four patients demonstrated PGA values ≥ 63 µmol/mmol creatinine. Univariate analysis showed that PGA concentration ≥ 75^th percentile (i.e. 33.53 µmol/mmol creatinine) was associated with higher rates of in-hospital mortality (p = 0.041) with similar trend for PGA ≥ 63 µmol/mmol creatinine (p = 0.04). However, multivariate analysis showed that PGA was not associated with worse outcomes, whereas heart rate was associated with both composite outcomes (HR 1.0, p = 0.008 and HR 1.02, p = 0.001 for composite outcome with 30 days and in-hospital mortality, respectively). Among low risk patients, high PGA levels were consistently associated with worse outcomes. In conclusion, urine PGA concentration was not associated with worse outcomes among septic patients. Nevertheless, future studies should evaluate this association in larger cohorts.

The clinical outcomes of selenium supplementation on critically ill patients: A meta-analysis of randomized controlled trials

PURPOSE

Selenium supplementation is a potentially promising adjunctive therapy for critically ill patients, but the results are controversy among studies. Accordingly, we performed this meta-analysis to more clearly detect the efficacy and safety of selenium supplementation on critically ill patients.

METHODS

Systematic literature retrieval was carried out to obtain RCTs on selenium supplementation for critically ill patients up to August 2017. Data extraction and quality evaluation of these studies were performed by 2 investigators. Statistical analyses was performed by RevMan 5.3. Trial sequential analysis (TSA) was conducted to control the risks of type I and type II errors and calculate required information size (RIS).

RESULTS

Totally 19 RCTs involving 3341 critically ill patients were carried out in which 1694 participates were in the selenium supplementation group, and 1647 in the control. The aggregated results suggested that compared with the control, intravenous selenium supplement as a single therapy could decrease the total mortality (RR = 0.86, 95% CI: 0.78-0.95, P = .002, TSA-adjusted 95% CI = 0.77-0.96, RIS = 4108, n = 3297) and may shorten the length of stay in hospital (MD -2.30, 95% CI -4.03 to -0.57, P = .009), but had no significant treatment effect on 28-days mortality (RR = 0.96, 95% CI: 0.85-1.09, P = .54) and could not shorten the length of ICU stay (MD -0.15, 95% CI -1.68 to 1.38, P = .84) in critically ill patients. Our results also showed that selenium supplementation did not increase incidence of drug-induced side effect compared with the control (RR 1.04, 95% CI 0.83 to 1.30, P = .73).

CONCLUSIONS

The current evidence suggests that the use of selenium could reduce the total mortality, and TSA results showed that our outcome is reliable and no more randomized controlled trials are needed. But selenium supplementation might have no effect on reducing 28-days mortality as well as the incidence of new infections, or on length of stay in ICU or mechanical ventilation. However, the results should be used carefully because of potential limitations.

Clinical Trial Assessment of Intermittent and Continuous Infusion Dose of N-Acetylcysteine on Redox Status of the Body in Patients with Sepsis Admitted to the ICU

PURPOSE

Conflicting results exist regarding the efficacy of N-acetyl cysteine (NAC) in sepsis treatment. A pivotal factor affecting the therapeutic potency of NAC in sepsis is timing and dosing of its infusion. We aimed to assess the effect of NAC on redox status of patients with sepsis and to compare its efficacy in intermittent and continuous infusion with the objective of developing the infusion regimen and optimizing the timing.

MATERIALS AND METHODS

A prospective, randomized clinical trial was designed to compare the antioxidative effect of NAC in intermittent infusion group (IV: 25 mg/kg bolus and then 25 mg/kg/8 hours 3 times) and continuous infusion group (IV: 25 mg/kg bolus and then 75 mg/kg over 24 hours) in 60 critically ill patients with sepsis (20 patients in each group). Blood samples were collected immediately before and after intervention for total antioxidant capacity (TAC) and malondialdehyde (MDA) assessment.

RESULTS

N-acetyl cysteine considerably increased TAC levels in both intermittent (0.68 ± 0.60; P value = .036) and continuous (0.69 ± 0.64; P value = .015) infusion groups when compared to placebo (0.61 ± 0.10); however, the difference in TAC levels between the intermittent and the continuous infusion did not reach statistical significance (P value = .942). Likewise, NAC treatment decreased MDA levels in both intermittent (19.45 ± 4.18; P value = 0.001) and continuous (22.47 ± 6.68; P value = .002) infusion groups when compared to placebo (31.76 ± 11.06), while the difference in MDA levels between the intermittent and the continuous infusion did not reach statistical significance (P value = .481).

CONCLUSION

Our data confirmed the antioxidative effect of NAC treatment in patients with sepsis, with no significant difference in intermittent and continuous infusion.

Intensive insulin therapy increases glutathione synthesis rate in surgical ICU patients with stress hyperglycemia

Objective

The glutathione system plays an essential role in antioxidant defense after surgery. We assessed the effects of intensive insulin treatment (IIT) on glutathione synthesis rate and redox balance in cancer patients, who had developed stress hyperglycemia after major surgery.

Methods

We evaluated 10 non-diabetic cancer patients the day after radical abdominal surgery combined with intra-operative radiation therapy. In each patient, a 24-hr period of IIT, aimed at tight euglycemic control, was preceded, or followed, by a 24-hr period of conventional insulin treatment (CIT) (control regimen). Insulin was administered for 24 hours, during total parenteral nutrition, at a dosage to maintain a moderate hyperglycemia in CIT, and normoglycemic blood glucose levels in IIT (9.3±0.5 vs 6.5±0.3 mmol/L respectively, P<0.001; coefficient of variation, 9.7±1.4 and 10.5±1.1%, P = 0.43). No hypoglycemia (i.e., blood glucose < 3.9 mmol/L) was observed in any of the patients. Insulin treatments were performed on the first and second day after surgery, in randomized order, according to a crossover experimental design. Plasma concentrations of thiobarbituric acid reactive substances (TBARS) and erythrocyte glutathione synthesis rates (EGSR), measured by primed-constant infusion of L-[²H₂]cysteine, were assessed at the end of each 24-hr period of either IIT or CIT.

Results

Compared to CIT, IIT was associated with higher EGSR (2.70±0.51 versus 1.18±0.29 mmol/L/day, p = 0.01) and lower (p = 0.04) plasma TBARS concentrations (2.2±0.2 versus 2.9±0.4 nmol/L).

Conclusions

In patients developing stress hyperglycemia after major surgery, IIT, in absence of hypoglycemia, stimulates erythrocyte glutathione synthesis, while decreasing oxidative stress.

N-Acetylcysteine's Role in Sepsis and Potential Benefit in Patients With Microcirculatory Derangements

OBJECTIVE

To review the data surrounding the utility of N-acetylcysteine (NAC) in sepsis and identify areas needed for additional research.

DATA SOURCES

A review of articles describing the mechanisms of action and clinical use of NAC in sepsis.

SUMMARY OF REVIEW

Despite many advances in critical care medicine, still as many as 50% of patients with septic shock die. Treatments thus far have focused on resuscitation and restoration of macrocirculatory targets in the early phases of sepsis, with less focus on microcirculatory dysfunction. N-acetylcysteine, due to its anti-inflammatory and antioxidative properties, has been readily investigated in sepsis and has yielded largely incongruous and disappointing results. In addition to its known anti-inflammatory and antioxidative roles, one underappreciated property of NAC is its ability to vasodilate the microcirculation and improve locoregional blood flow. Some investigators have sought to capitalize on this mechanism with promising results, as evidenced by microcirculatory vasodilation, improvements in regional blood flow and oxygen delivery, and reductions in lactic acidosis, organ failure, and mortality.

CONCLUSION

In addition to its antioxidant and anti-inflammatory properties, N-acetylcysteine possesses vasodilatory properties that could benefit the microcirculation in sepsis. It is imperative that we investigate these properties to uncover NAC's full potential for benefit in sepsis.

Neurologic complications of sepsis

Over the past decades, the incidence of sepsis and resultant neurologic sequelae has increased, both in industrialized and low- or middle-income countries, by approximately 5% per year. Up to 300 patients per 100 000 population per year are reported to suffer from sepsis, severe sepsis, and septic shock. Mortality is up to 30%, depending on the precision of diagnostic criteria. The increasing incidence of sepsis is partially explained by demographic changes in society, with aging, increasing numbers of immunocompromised patients, dissemination of multiresistant pathogens, and greater availability of supportive medical care in both industrialized and middle-income countries. This results in more septic patients being admitted to intensive care units. Septic encephalopathy is a manifestation especially of severe sepsis and septic shock where the neurologist plays a crucial role in diagnosis and management. It is well known that timely treatment of sepsis improves outcome and that septic encephalopathy may precede other signs and symptoms. Particularly in the elderly and immunocompromised patient, the brain may be the first organ to show signs of failure. The neurologist diagnosing early septic encephalopathy may therefore contribute to the optimal management of septic patients. The brain is not only an organ failing in sepsis (a "sepsis victim" - as with other organs), but it also overwhelmingly influences all inflammatory processes on a variety of pathophysiologic levels, thus contributing to the initiation and propagation of septic processes. Therefore, the best possible pathophysiologic understanding of septic encephalopathy is essential for its management, and the earliest possible therapy is crucial to prevent the evolution of septic encephalopathy, brain failure, and poor prognosis.

Effects of N-acetylcysteine (NAC) supplementation in resuscitation fluids on renal microcirculatory oxygenation, inflammation, and function in a rat model of endotoxemia

Background

Modulation of inflammation and oxidative stress appears to limit sepsis-induced damage in experimental models. The kidney is one of the most sensitive organs to injury during septic shock. In this study, we evaluated the effect of N-acetylcysteine (NAC) administration in conjunction with fluid resuscitation on renal oxygenation and function. We hypothesized that reducing inflammation would improve the microcirculatory oxygenation in the kidney and limit the onset of acute kidney injury (AKI).

Methods

Rats were randomized into five groups (n = 8 per group): (1) control group, (2) control + NAC, (3) endotoxemic shock with lipopolysaccharide (LPS) without fluids, (4) LPS + fluid resuscitation, and (5) LPS + fluid resuscitation + NAC (150 mg/kg/h). Fluid resuscitation was initiated at 120 min and maintained at fixed volume for 2 h with hydroxyethyl starch (HES 130/0.4) dissolved in acetate-balanced Ringer’s solution (Volulyte) with or without supplementation with NAC (150 mg/kg/h). Oxygen tension in the renal cortex (CμPO₂), outer medulla (MμPO₂), and renal vein was measured using phosphorimetry. Biomarkers of renal injury, inflammation, and oxidative stress were assessed in kidney tissues.

Results

Fluid resuscitation significantly improved the systemic and renal macrohemodynamic parameters after LPS. However, the addition of NAC further improved cortical renal oxygenation, oxygen delivery, and oxygen consumption (p < 0.05). NAC supplementation dampened the accumulation of NGAL or L-FABP, hyaluronic acid, and nitric oxide in kidney tissue (p < 0.01).

Conclusion

The addition of NAC to fluid resuscitation may improve renal oxygenation and attenuate microvascular dysfunction and AKI. Decreases in renal NO and hyaluronic acid levels may be involved in this beneficial effect. A therapeutic strategy combining initial fluid resuscitation with antioxidant therapies may prevent sepsis-induced AKI.

Pancreatic injury in patients with septic shock: A literature review

Sepsis and septic shock are life threatening condition associated with high mortality rate in critically-ill patients. This high mortality is mainly related to the inadequacy between oxygen delivery and cellular demand leading to the onset of multiorgan dysfunction. Whether this multiorgan failure affect the pancreas is not fully investigated. In fact, pancreatic injury may occur because of ischemia, overwhelming inflammatory response, oxidative stress, cellular apoptosis and/or metabolic derangement. Increased serum amylase and/or lipase levels are common in patients with septic shock. However, imaging test rarely reveal significant pancreatic damage. Whether pancreatic dysfunction does affect the prognosis of patients with septic shock or not is still a matter of debate. In fact, only few studies with limited sample size assessed the clinical relevance of the pancreatic injury in this group of patients. In this review, we aimed to describe the epidemiology and the physiopathology of pancreatic injury in septic shock patients, to clarify whether it requires specific management and to assess its prognostic value. Our main finding is that pancreatic injury does not significantly affect the outcome in septic shock patients. Hence, increased serum pancreatic enzymes without clinical features of acute pancreatitis do not require further imaging investigations and specific therapeutic intervention.

Plasmonic nanoparticle-film calipers for rapid and ultrasensitive dimensional and refractometric detection

In this study, we develop an ultrasensitive nanoparticle (NP)-film caliper that functions with high resolution (angstrom scale) in response to both the dimensions and refractive index of the spacer sandwiched between the NPs and the film. The anisotropy of the plasmonic gap mode in the NP-film caliper can be characterized readily using spectroscopic ellipsometry (SE) without the need for further optical modeling. To the best of our knowledge, this paper is the first to report the use of SE to study the plasmonic gap modes in NP-film calipers and to demonstrate that SE is a robust and convenient method for analyzing NP-film calipers. The high sensitivity of this system originates from the plasmonic gap mode in the NP-film caliper, induced by electromagnetic coupling between the NPs and the film. The refractometric sensitivity of this NP-film caliper reaches up to 314 nm per RIU, which is superior to those of other NP-based sensors. The NP-film caliper also provides high dimensional resolution, down to the angstrom scale. In this study, the shift in wavelength in response to the change in gap spacing is approximately 9 nm Å(-1). Taking advantage of the ultrasensitivity of this NP-film caliper, we develop a platform for discriminating among thiol-containing amino acids.

Septic acute kidney injury: molecular mechanisms and the importance of stratification and targeting therapy

The most common cause of acute kidney injury (AKI) in hospitalized patients is sepsis. However, the molecular pathways and mechanisms that mediate septic AKI are not well defined. Experiments performed over the past 20 years suggest that there are profound differences in the pathogenesis between septic and ischemic AKI. Septic AKI often occurs independently of hypoperfusion, and is mediated by a concomitant pro- and anti-inflammatory state that is activated in response to various pathogen-associated molecular patterns, such as endotoxin, as well as damage-associated molecular patterns. These molecular patterns are recognized by Toll-like receptors (TLRs) found in the kidney, and effectuate downstream inflammatory pathways. Additionally, apoptosis has been proposed to play a role in the pathogenesis of septic AKI. However, targeted therapies designed to mitigate the above aspects of the inflammatory state, TLR-related pathways, and apoptosis have failed to show significant clinical benefit. This failure is likely due to the protean nature of septic AKI, whereby different patients present at different points along the immunologic spectrum. While one patient may benefit from targeted therapy at one end of the spectrum, another patient at the other end may be harmed by the same therapy. We propose that a next important step in septic AKI research will be to identify where patients lie on the immunologic spectrum in order to appropriately target therapies at the inflammatory cascade, TLRs, and possibly apoptosis.

Elements of margin of safety, toxicity and action of sodium selenite in a lipopolysaccharide rat model

PROJECT

Both septic shock and sodium selenite (Na2SeO3) lead to multiple organ failure through oxidation. Na2SeO3 has direct oxidant effects above the nutritional level and indirect anti-oxidant properties. In a lipopolysaccharide (LPS) rat model we assessed margin of safety, toxicity and beneficial effect of pentahydrate Na2SeO3 (5H2O·Na2SeO3) at oxidant doses.

PROCEDURE

In a three-step study on 204 rats we: (i) observed toxic effects of Na2SeO3 injected intraperitoneously (IP) and determined its Minimum Dose Without Toxic effect (MDWT) 0.25-0.35 mg/kg selenium (Se) content; (ii) injected IP LPS at 70% lethal dose (LD) followed, or not, one hour later by IP Na2SeO3 at MDWT and (iii) by doses>MDWT. At 48 h, in survivors, we measured plasma creatinine, lactate, aspartate and alanine aminotransferase (AST, ALT), nitric oxide (NO) and Se concentrations.

RESULTS

(i) Na2SeO3 alone did not increase NO and lactate. Encephalopathy appeared at 1mg Se/kg. Creatinine increased at 1-1.75 mg Se/kg, AST, ALT at 3-4.5 mg Se/kg, and the minimum LD was 3 mg Se/kg. (ii) Mortality after LPS was 37/50 (74%, [62-86%]) vs. 20/30 (67%, [50-84%]) when followed by Na2SeO3 at MDWT (p=0.483) with a decreased in NO (-31%, p=0.038) a trend for lactate decrease (-19%, p=0.068) and an increased Se in plasma of survivals. (iii) All rats died at doses ≥0.6 mg/kg (p<0.001).

CONCLUSION

Mechanisms of LPS and Na2SeO3 toxicity differ (i.e. NO, lactate). In septic shock 5H2O·Na2SeO3 toxicity increased, margin of safety decrease, but IP administration of dose considered as oxidant of 5H2O·Na2SeO3 showed beneficial effects.

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.

Interleukin 10 antioxidant effect decreases leukocytes/endothelial interaction induced by tumor necrosis factor α

Little is known about the endothelial mechanisms involved in the anti-inflammatory effects of interleukin 10 (IL-10). The goal of this study was to evaluate the effects of IL-10 on endothelial oxidative stress and endothelial inflammation induced by tumor necrosis factor α (TNF-α). Production of reactive oxygen species (ROS) in perfused human umbilical vein endothelial cells (HUVECs) was studied by fluorescent microscopy using dichlorodihydrofluorescein diacetate. Tumor necrosis factor α (1 ng/mL) was added to the perfusion medium in the absence and presence of IL-10 (1 ng/mL). The role of phosphatidylinositol 3-kinase (PI3-kinase) was assessed using wortmannin and LY 2940002 (inhibitors of PI3-kinase). Specific inhibition of p110 α and p110 γ/δ PI3-kinase subunits was studied using A66 and TG100-115. As well, levels of ceramide and intercellular adhesion molecule 1 (ICAM-1) expression were measured. Finally, the effect of IL-10 on TNF-α-induced leukocyte/endothelium interaction was examined using an ex vivo perfused vessel model. Interleukin 10 significantly reduced dichlorodihydrofluorescein diacetate fluorescence induced by TNF-α in HUVECs (12.5% ± 3.2% vs. 111.7% ± 21.6% at 60 min). Pretreatment by LY2940002 or wortmannin restored ROS production induced by TNF-α in the presence of IL-10. In HUVECs treated by TNF-α + IL-10, inhibition of p110 α PI3-kinase subunit significantly increased ROS production, whereas p110 γ/δ inhibition did not have a significant effect. Pretreatment with IL-10 significantly decreased TNF-α-induced increased levels of ceramide (TNF-α vs. TNF-α + IL-10: 6,278 ± 1,013 vs. 1,440 ± 130 pmol/mg prot), as well as ICAM-1 expression and leukocyte adhesion (TNF-α vs. TNF-α + IL-10: 26.8 ± 2.6 vs. 6.7 ± 0.4 adherent leukocytes/field at 15 min). Interleukin 10 decreases the level of inflammation induced by TNF-α in endothelial cells by reducing the TNF-α-induced ROS production, ICAM-1 expression, and leukocyte adhesion to the endothelium. The antioxidant effect of IL-10 is mediated through PI3-kinase and is paralleled by a decrease in ceramide synthesis induced by TNF-α.

Glutamine treatment decreases plasma and lymph cytotoxicity during sepsis in rats

Glutamine (Gln) is considered as a conditionally essential amino acid. Pharmacological supplementation of Gln helps to maintain the intestinal mucosal barrier, modulate cytokine production, and prevent organ injury during sepsis. Our previous study demonstrated the different effects of Gln on macrophage cytokine production in vitro or in vivo. The purpose of this study was to investigate the potential mechanism of Gln treatment to protect cells and modulate inflammation during sepsis in vivo. The results showed that administration of Gln significantly attenuated plasma-induced macrophage cytokine production and endothelial cell necrosis after cecal ligation and puncture in rats. In addition, it preserved human umbilical vein endothelial cell (HUVEC) viability and migration ability. Gln treatment also reduced lymph cytotoxicity by restoring macrophage tumor necrosis factor-α production, maintaining HUVEC viability, and decreasing endothelial cell necrosis. Mesenteric lymph duct ligation did not alleviate plasma cytotoxicity. Plasma lipopolysaccharide and d-lactate levels were suppressed after Gln treatment. Taken together, these results indicated that Gln administration can protect cells by attenuating the cytotoxicity of plasma and mesenteric lymph during sepsis.

Postresuscitation syndrome: potential role of hydroxyl radical-induced endothelial cell damage

OBJECTIVE

After out of hospital cardiac arrest, it has been reported that endothelium dysfunction may occur during the postresuscitation syndrome. However, the consequences of the reperfusion phase on endothelial reactive oxygen species production and redox homeostasis have not been explored in out of hospital cardiac arrest patients.

DESIGN

Prospective, observational study.

SETTING

Medical intensive care unit in a university hospital.

PATIENTS

Twenty successfully resuscitated out of hospital cardiac arrest patients, seven septic shock patients, and ten healthy volunteers.

INTERVENTION

Plasma was collected from patients at admission and 12, 24, 36, 48, and 72 hrs after cardiac arrest. We studied the production of reactive oxygen species and cell survival during plasma perfusion using perfused endothelial cells (human umbilical vein endothelial cells) as a model. Cell antioxidant response was studied by measuring superoxide dismutase, glutathione peroxidase, and glutathione reductase activities and reduced and oxidized glutathione levels. Mitochondrial respiratory chain activity was assessed by measuring complex I, II, III, and IV activities and anaerobic glycolysis by measuring glucose-6-phosphate dehydrogenase activity.

MEASUREMENTS AND MAIN RESULTS

Using perfused endothelial cells as a model, we demonstrate that plasma from out of hospital cardiac arrest patients induced on naive human umbilical vein endothelial cells a significant and massive cell death compared to plasma from septic shock patients and healthy volunteers. An increase of reactive oxygen species production with a decrease in antioxidant defenses (superoxide dismutase, glutathione peroxidase, and glutathione reductase activities, reduced and oxidized glutathione levels) was observed. The metabolic consequence of plasma exposure showed that mitochondrial respiratory chain activity was significantly impaired and anaerobic glycolysis was significantly increased. Inhibiting hydroxyl radical production significantly decreased cell death, suggesting that plasma from out of hospital cardiac arrest induced significant cell death by triggering the Fenton reaction.

CONCLUSION

Plasma from out of hospital cardiac arrest induces major endothelial toxicity with an acute pro-oxidant state in the cells and impairment of mitochondrial respiratory chain activity. This toxicity could be due to hydroxyl radical production by activation of the Fenton reaction.

Mitochondrial antioxidants alleviate oxidative and nitrosative stress in a cellular model of sepsis

PURPOSE

Mitochondrial dysfunction plays a key role in sepsis.

METHODS

We used a sepsis model of human endothelial cells (HUVEC) to study mitochondrial function during normoxic (21% O(2)) and hypoxic (1% O(2)) conditions.

RESULTS

When stimulated with a LPS cocktail, HUVEC displayed an increase of nitric oxide (NO) in normoxic and hipoxic conditions, being higher at 21% O(2). LPS-activation for 24 h at 1% O(2) increased ROS production, which was reversed with the mitochondrial antioxidant Mitoquinone (MQ) and Glutathione Ethyl Ester (GEE). Activated cells displayed diminished mitochondrial O(2) consumption with specific inhibition of Complex I, accompanied by increase in tyrosine nitration and Type II NOS protein expression, effects which were recovered by antioxidants and/or with L-NAME. These parameters varied with O(2) environment, namely inhibition of respiration observed in both O(2) environments at 24 h was very similar, whereas O(2) consumption rate fell earlier in 1% O(2)-exposed cells. While no significant differences were detected at earlier time points, at 24 h tyrosine nitration was higher in normoxic vs. hypoxic cells.

CONCLUSIONS

Mitochondria are heavily implicated in sepsis. Mitochondrial antioxidants provide a mechanistic model for the development of potential therapies.

γ-glutamylcysteine ethyl ester protects cerebral endothelial cells during injury and decreases blood-brain barrier permeability after experimental brain trauma

Oxidative stress is a pathway of injury that is common to almost all neurological conditions. Hence, methods to scavenge radicals have been extensively tested for neuroprotection. However, saving neurons alone may not be sufficient in treating CNS disease. In this study, we tested the cytoprotective actions of the glutathione precursor gamma-glutamylcysteine ethyl ester (GCEE) in brain endothelium. First, oxidative stress was induced in a human brain microvascular endothelial cell line by exposure to H(2)O(2). Addition of GCEE significantly reduced formation of reactive oxygen species, restored glutathione levels which were reduced in the presence of H(2)O(2), and decreased cell death during H(2)O(2)-mediated injury. Next, we asked whether GCEE can also protect brain endothelial cells against oxygen-glucose deprivation (OGD). As expected, OGD disrupted mitochondrial membrane potentials. GCEE was able to ameliorate these mitochondrial effects. Concomitantly, GCEE significantly decreased endothelial cell death after OGD. Lastly, our in vivo experiments using a mouse model of brain trauma show that post-trauma (10 min after controlled cortical impact) administration of GCEE by intraperitoneal injection results in a decrease in acute blood-brain barrier permeability. These data suggest that the beneficial effects of GCEE on brain endothelial cells and microvessels may contribute to its potential efficacy as a neuroprotective agent in traumatic brain injury.

Colorimetric assay of glutathione based on the spontaneous disassembly of aggregated gold nanocomposites conjugated with water-soluble polymer

This article describes the glutathione-triggered disassembly of gold nanocomposites composed of gold cores and water-soluble copolymers [poly(N-n-isopropylacrylamide-co-acryloyldiethyletriamine)] attached to the surfaces of gold cores. The gold nanocomposites exhibit a bluish purple color because of the assembled gold cores that are conjugated with the diethylenetriamine groups incorporated into the copolymers. Glutathione added to the gold nanocomposite solution adsorbs onto the surface of the gold cores to liberate diethylenetriamine groups, resulting in spontaneous disassembly that changes the color of the solution to a reddish shade. Increasing the glutathione concentration facilitates the spontaneous disassembly of the gold nanocomposites. For the determination of glutathione, the colorimetric change of the gold nanoparticles is quantified with the a* value of the L*a*b* color coordinates defined by the CIE (Commission Internationale de l'Eclairage) chromaticity diagram. A linear relationship between the a* value and the glutathione concentration of up to 6 x 10(-6) mol/L is obtained 15 min after the addition of glutathione that has a detection limit (defined as 3sigma) of 2.9 x 10(-8) mol/L. The colorimetric assay is successfully applied to the determination of glutathione in eye drops and health supplements.

The response of the host microcirculation to bacterial sepsis: does the pathogen matter?

Sepsis results from the interaction between a host and an invading pathogen. The microcirculatory dysfunction is now considered central in the development of the often deadly multiple organ dysfunction syndrome in septic shock patients. The microcirculatory flow shutdown and flow shunting leading to oxygen demand and supply mismatch at the cellular level and the local activation of inflammatory pathways resulting from the leukocyte–endothelium interactions are both features of the sepsis-induced microcirculatory dysfunction. Although the host response through the inflammatory and immunologic response appears to be critical, there are also evidences that Gram-positive and Gram-negative bacteria can exert different effects at the microcirculatory level. In this review we discuss available data on the potential bacterial-specific microcirculatory alterations observed during sepsis.