Effects of tempol, a free radical scavenger, on long-term hyperdynamic porcine bacteremia*

Renal arterial infusion of tempol prevents medullary hypoperfusion, hypoxia, and acute kidney injury in ovine Gram-negative sepsis

AIM

Renal medullary hypoperfusion and hypoxia precede acute kidney injury (AKI) in ovine sepsis. Oxidative/nitrosative stress, inflammation, and impaired nitric oxide generation may contribute to such pathophysiology. We tested whether the antioxidant and anti-inflammatory drug, tempol, may modify these responses.

METHODS

Following unilateral nephrectomy, we inserted renal arterial catheters and laser-Doppler/oxygen-sensing probes in the renal cortex and medulla. Noanesthetized sheep were administered intravenous (IV) Escherichia coli and, at sepsis onset, IV tempol (IVT; 30 mg kg-1  h-1 ), renal arterial tempol (RAT; 3 mg kg-1  h-1 ), or vehicle.

RESULTS

Septic sheep receiving vehicle developed renal medullary hypoperfusion (76 ± 16% decrease in perfusion), hypoxia (70 ± 13% decrease in oxygenation), and AKI (87 ± 8% decrease in creatinine clearance) with similar changes during IVT. However, RAT preserved medullary perfusion (1072 ± 307 to 1005 ± 271 units), oxygenation (46 ± 8 to 43 ± 6 mmHg), and creatinine clearance (61 ± 10 to 66 ± 20 mL min-1 ). Plasma, renal medullary, and cortical tissue malonaldehyde and medullary 3-nitrotyrosine decreased significantly with sepsis but were unaffected by IVT or RAT. Consistent with decreased oxidative/nitrosative stress markers, cortical and medullary nuclear factor-erythroid-related factor-2 increased significantly and were unaffected by IVT or RAT. However, RAT prevented sepsis-induced overexpression of cortical tissue tumor necrosis factor alpha (TNF-α; 51 ± 16% decrease; p = 0.003) and medullary Thr-495 phosphorylation of endothelial nitric oxide synthase (eNOS; 63 ± 18% decrease; p = 0.015).

CONCLUSIONS

In ovine Gram-negative sepsis, renal arterial infusion of tempol prevented renal medullary hypoperfusion and hypoxia and AKI and decreased TNF-α expression and uncoupling of eNOS. However, it did not affect markers of oxidative/nitrosative stress, which were significantly decreased by Gram-negative sepsis.

Therapeutic Potential of Small Molecules Targeting Oxidative Stress in the Treatment of Chronic Obstructive Pulmonary Disease (COPD): A Comprehensive Review

Chronic obstructive pulmonary disease (COPD) is an increasing and major global health problem. COPD is also the third leading cause of death worldwide. Oxidative stress (OS) takes place when various reactive species and free radicals swamp the availability of antioxidants. Reactive nitrogen species, reactive oxygen species (ROS), and their counterpart antioxidants are important for host defense and physiological signaling pathways, and the development and progression of inflammation. During the disturbance of their normal steady states, imbalances between antioxidants and oxidants might induce pathological mechanisms that can further result in many non-respiratory and respiratory diseases including COPD. ROS might be either endogenously produced in response to various infectious pathogens including fungi, viruses, or bacteria, or exogenously generated from several inhaled particulate or gaseous agents including some occupational dust, cigarette smoke (CS), and air pollutants. Therefore, targeting systemic and local OS with therapeutic agents such as small molecules that can increase endogenous antioxidants or regulate the redox/antioxidants system can be an effective approach in treating COPD. Various thiol-based antioxidants including fudosteine, erdosteine, carbocysteine, and N-acetyl-L-cysteine have the capacity to increase thiol content in the lungs. Many synthetic molecules including inhibitors/blockers of protein carbonylation and lipid peroxidation, catalytic antioxidants including superoxide dismutase mimetics, and spin trapping agents can effectively modulate CS-induced OS and its resulting cellular alterations. Several clinical and pre-clinical studies have demonstrated that these antioxidants have the capacity to decrease OS and affect the expressions of several pro-inflammatory genes and genes that are involved with redox and glutathione biosynthesis. In this article, we have summarized the role of OS in COPD pathogenesis. Furthermore, we have particularly focused on the therapeutic potential of numerous chemicals, particularly antioxidants in the treatment of COPD.

Bioinspired copper single-atom nanozyme as a superoxide dismutase-like antioxidant for sepsis treatment

Sepsis is a systemic inflammatory response syndrome with high morbidity and mortality mediated by infection-caused oxidative stress. Early antioxidant intervention by removing excessively produced reactive oxygen and nitrogen species (RONS) is beneficial to the prevention and treatment of sepsis. However, traditional antioxidants have failed to improve patient outcomes due to insufficient activity and sustainability. Herein, by mimicking the electronic and structural characteristics of natural Cu-only superoxide dismutase (SOD5), a single-atom nanozyme (SAzyme) featuring coordinately unsaturated and atomically dispersed Cu-N4 site was synthesized for effective sepsis treatment. The de novo-designed Cu-SAzyme exhibits a superior SOD-like activity to efficiently eliminate O2 •-, which is the source of multiple RONS, thus blocking the free radical chain reaction and subsequent inflammatory response in the early stage of sepsis. Moreover, the Cu-SAzyme effectively harnessed systemic inflammation and multi-organ injuries in sepsis animal models. These findings indicate that the developed Cu-SAzyme possesses great potential as therapeutic nanomedicines for the treatment of sepsis.

Therapeutic potential of megadose vitamin C to reverse organ dysfunction in sepsis and COVID-19

Sepsis induced by bacteria or viruses can result in multiorgan dysfunction, which is a major cause of death in intensive care units. Current treatments are only supportive, and there are no treatments that reverse the pathophysiological effects of sepsis. Vitamin C has antioxidant, anti‐inflammatory, anticoagulant and immune modulatory actions, so it is a rational treatment for sepsis. Here, we summarise data that support the use of megadose vitamin C as a treatment for sepsis and COVID‐19. Megadose intravenous sodium ascorbate (150 g per 40 kg over 7 h) dramatically improved the clinical state and cardiovascular, pulmonary, hepatic and renal function and decreased body temperature, in a clinically relevant ovine model of Gram‐negative bacteria‐induced sepsis. In a critically ill COVID‐19 patient, intravenous sodium ascorbate (60 g) restored arterial pressure, improved renal function and increased arterial blood oxygen levels. These findings suggest that megadose vitamin C should be trialled as a treatment for sepsis and COVID‐19.

Microcirculation vs. Mitochondria-What to Target?

Circulatory shock is associated with marked disturbances of the macro- and microcirculation and flow heterogeneities. Furthermore, a lack of tissue adenosine trisphosphate (ATP) and mitochondrial dysfunction are directly associated with organ failure and poor patient outcome. While it remains unclear if microcirculation-targeted resuscitation strategies can even abolish shock-induced flow heterogeneity, mitochondrial dysfunction and subsequently diminished ATP production could still lead to organ dysfunction and failure even if microcirculatory function is restored or maintained. Preserved mitochondrial function is clearly associated with better patient outcome. This review elucidates the role of the microcirculation and mitochondria during circulatory shock and patient management and will give a viewpoint on the advantages and disadvantages of tailoring resuscitation to microvascular or mitochondrial targets.

Distinct Myocardial Mechanisms Underlie Cardiac Dysfunction in Endotoxemic Male and Female Mice

In male mice, sepsis-induced cardiomyopathy develops as a result of dysregulation of myocardial calcium (Ca) handling, leading to depressed cellular Ca transients (ΔCai). ΔCai depression is partially due to inhibition of sarcoplasmic reticulum Ca ATP-ase (SERCA) via oxidative modifications, which are partially opposed by cGMP generated by the enzyme soluble guanylyl cyclase (sGC). Whether similar mechanisms underlie sepsis-induced cardiomyopathy in female mice is unknown.Male and female C57Bl/6J mice (WT), and mice deficient in the sGC α1 subunit activity (sGCα1), were challenged with lipopolysaccharide (LPS, ip). LPS induced mouse death and cardiomyopathy (manifested as the depression of left ventricular ejection fraction by echocardiography) to a similar degree in WT male, WT female, and sGCα1 male mice, but significantly less in sGCα1 female mice. We measured sarcomere shortening and ΔCai in isolated, externally paced cardiomyocytes, at 37°C. LPS depressed sarcomere shortening in both WT male and female mice. Consistent with previous findings, in male mice, LPS induced a decrease in ΔCai (to 30 ± 2% of baseline) and SERCA inhibition (manifested as the prolongation of the time constant of Ca decay, τCa, to 150 ± 5% of baseline). In contrast, in female mice, the depression of sarcomere shortening induced by LPS occurred in the absence of any change in ΔCai, or SERCA activity. This suggested that, in female mice, the causative mechanism lies downstream of the Ca transients, such as a decrease in myofilament sensitivity for Ca. The depression of sarcomere shortening shortening after LPS was less severe in female sGCα1 mice than in WT female mice, indicating that cGMP partially mediates cardiomyocyte dysfunction.These results suggest, therefore, that LPS-induced cardiomyopathy develops through distinct sex-specific myocardial mechanisms. While in males LPS induces sGC-independent decrease in ΔCai, in female mice LPS acts downstream of ΔCai, possibly via sGC-dependent myofilament dysfunction.

Renal Hemodynamics in AKI: In Search of New Treatment Targets

Novel therapeutic interventions are required to prevent or treat AKI. To expedite progress in this regard, a consensus conference held by the Acute Dialysis Quality Initiative was convened in April of 2014 to develop recommendations for research priorities and future directions. Here, we highlight the concepts related to renal hemodynamics in AKI that are likely to reveal new treatment targets on investigation. Overall, we must better understand the interactions between systemic, total renal, and glomerular hemodynamics, including the role of tubuloglomerular feedback. Furthermore, the net consequences of therapeutic maneuvers aimed at restoring glomerular filtration need to be examined in relation to the nature, magnitude, and duration of the insult. Additionally, microvascular blood flow heterogeneity in AKI is now recognized as a common occurrence; timely interventions to preserve the renal microcirculatory flow may interrupt the downward spiral of injury toward progressive kidney failure and should, therefore, be investigated. Finally, development of techniques that permit an integrative physiologic approach, including direct visualization of renal microvasculature and measurement of oxygen kinetics and mitochondrial function in intact tissue in all nephron segments, may provide new insights into how the kidney responds to various injurious stimuli and allow evaluation of new therapeutic strategies.

Vasoplegia in septic shock: do we really fight the right enemy?

Vasoplegia is a key factor for the death of patients with septic shock in intensive care unit owing to persistent and irreversible hypotension. Impairment of vascular reactivity has been attributed to a combination of endothelial injury, arginine-vasopressin system dysfunction, release of other vasodilatory inflammatory mediators, and muscle hyperpolarizaton. Nitric oxide induced by a Ca(+2) independent isoform of nitric oxide synthase has been suggested to play an important role in sepsis-induced vasoplegia. However, inhibition of nitric oxide synthase only partially restores the endotoxin-induced vascular hyporeactivity. The aim of this review is to discuss in detail the recent suggested alternative mechanisms of vasoplegia and to briefly outline the current therapeutic strategies and the novel therapeutic options based on those mechanisms.

Edaravone, a novel free radical scavenger, reduces high-mobility group box 1 and prolongs survival in a neonatal sepsis model

Free radicals play an important role in the inflammatory process of sepsis. We hypothesized that edaravone, a novel free radical scavenger, can suppress pathophysiological events and prolong survival in a neonatal sepsis cecal ligation and perforation (CLP) model. Of 32 3-day-old anesthetized and mechanically ventilated piglets, 11 received CLP only, 10 received CLP and edaravone treatment starting 30 min after CLP, and 11 constituted a sham (control) group. Mean arterial pressure (MAP), heart rate, cardiac output, arterial blood gas, serum total hydroperoxide, nitrite and nitrate, TNF-alpha, and high-mobility group box 1 (HMGB1) were measured before CLP and at 1, 3, and 6 h after CLP. Compared with the CLP group, the edaravone group showed higher MAP at 6 h, lower heart rate at 1 and 3 h, lower total hydroperoxide at 1 h, lower nitrite and nitrate at 3 and 6 h, and higher (although not significantly so) mean cardiac output at 1, 3, and 6 h. TNF-alpha elevation was delayed from 1 h in the CLP group to 3 h in the edaravone group. In the edaravone group, HMGB1 did not change significantly at any time, whereas in the CLP group, it increased at 6 h. Survival times were longer in the edaravone group than in the CLP group (15.4 +/- 1.4 vs. 10.2 +/- 1 h; P < 0.005). In addition, each of the serial dilutions of edaravone had a higher biological antioxidant potential than tempol does. In conclusion, edaravone suppressed free radicals, delayed the TNF-alpha surge, and prevented HMGB1 elevation, thereby maintaining MAP and prolonging survival time in a neonatal sepsis CLP model.

Effects of levosimendan and dobutamine on experimental acute lung injury in rats

The effects of levosimendan on acute lung injury induced by peritonitis and abdominal hypertension in the early stages of sepsis in rats were investigated. Twenty-four adult male Wistar rats were randomized into: (1) sham, (2) subjected to abdominal hypertension and peritonitis induced lung injury using cecal ligation and puncture, then treated by dobutamine, (3) subjected to abdominal hypertension and peritonitis induced lung injury using cecal ligation and puncture, then treated by levosimendan, and (4) controls subjected to abdominal hypertension and peritonitis induced lung injury using cecal ligation and puncture with no treatment. In the control and levosimendan groups, cecal ligation and puncture resulted in moderate IL-1beta immunolabelling in lung tissue; marked IL-1beta immunolabelling was demonstrated in the dobutamine group. TNF-alpha immunolabelling was negative in both the sham and levosimendan groups, but moderate and weak immunoreactivities were observed in the dobutamine and control groups, respectively. There were almost no TUNEL positive cells in the sham, but they were prominent in the control. TUNEL positive cells were significantly less in the levosimendan treated lungs when compared to control and dobutamine groups. Immunoreactivity of eNOS was stronger in the dobutamine group when compared with the levosimendan group. In addition, iNOS immunoreactivity was strongly detected in the control group; this immunoreactivity was less in the levosimendan group than the dobutamine group. In this experimental sepsis model, treatment with levosimendan had a marked effect on attenuating or decreasing apoptosis and inflammation in the lung.

Coupled plasma filtration adsorption in experimental peritonitis-induced septic shock

The coupled plasma filtration adsorption (CPFA) was developed as an adsorptive hemopurification method aimed at nonselective removal of circulating soluble mediators potentially involved in the pathogenesis of sepsis. We hypothesized that this nonselective hemopurification could protect from detrimental consequences of long-term, volume-resuscitated porcine septic shock. In 16 anesthetized, mechanically ventilated, and instrumented pigs, the hyperdynamic septic shock secondary to peritonitis was induced by intraperitoneally inoculating feces and maintained for 22 h with fluid resuscitation and norepinephrine infusion as needed to maintain MAP above 65 mmHg. After 12 h of peritonitis, animals were randomized to receive either supportive treatment (control, n = 8) or CPFA treatment (CPFA, n = 8). Systemic, hepatosplanchnic, and renal hemodynamics; oxygen exchange; energy metabolism (lactate/pyruvate and ketone body ratios); ileal mucosal and renal cortex microcirculation; systemic inflammation (TNF-alpha, IL-6); nitrosative/oxidative stress (thiobarbituric acid reactive species, nitrates + nitrites); and endothelial/coagulation dysfunction (asymmetric dimethylarginine, von Willebrand factor, thrombin-antithrombin complexes, platelet count) were assessed before and 12, 18, and 22 h of peritonitis. Coupled plasma filtration adsorption neither delayed the development of hypotension nor reduced the dose of norepinephrine. The treatment failed to attenuate sepsis-induced alterations in microcirculation, surrogate markers of cellular energetics, endothelial injury, and systemic inflammation. Similarly, CPFA did not protect from lung and liver dysfunction and even aggravated sepsis-induced disturbances in coagulation and oxidative/nitrosative stress. In this porcine model of septic shock, the early treatment with CPFA was not capable of reversing the sepsis-induced disturbances in various biological pathways and organ systems. Both the efficacy and safety of this method require further rigorous experimental validation in clinically relevant models.

Altered plasma proteome during an early phase of peritonitis-induced sepsis

Sepsis is a systemic response to infection commonly found in critically ill patients and is associated with multi-organ failure and high mortality rate. Its pathophysiology and molecular mechanisms are complicated and remain poorly understood. In the present study, we performed a proteomics investigation to characterize early host responses to sepsis as determined by an altered plasma proteome in a porcine model of peritonitis-induced sepsis, which simulated several clinical characteristics of human sepsis syndrome. Haemodynamics, oxygen exchange, inflammatory responses, oxidative and nitrosative stress, and other laboratory parameters were closely monitored. Plasma samples were obtained from seven pigs before and 12 h after the induction of sepsis, and plasma proteins were resolved with two-dimensional gel electrophoresis (n=7 gels/group; before being compared with during sepsis). The resolved proteins were stained with the SYPRO Ruby fluorescence dye and subjected to quantitative and comparative analyses. From approx. 1500 protein spots visualized in each gel, levels of 36 protein spots were significantly altered in the plasma of animals with sepsis (sepsis/basal ratios or degrees of change ranged from 0.07 to 21.24). Q-TOF (quadrupole–time-of-flight) MS and MS/MS (tandem MS) identified 30 protein forms representing 22 unique proteins whose plasma levels were increased, whereas six forms of five unique proteins were significantly decreased during sepsis. The proteomic results could be related to the clinical features of this animal model, as most of these altered proteins have important roles in inflammatory responses and some of them play roles in oxidative and nitrosative stress. In conclusion, these findings may lead to a better understanding of the pathophysiology and molecular mechanisms underlying the sepsis syndrome.

Renal haemodynamic, microcirculatory, metabolic and histopathological responses to peritonitis-induced septic shock in pigs

Introduction

Our understanding of septic acute kidney injury (AKI) remains incomplete. A fundamental step is the use of animal models designed to meet the criteria of human sepsis. Therefore, we dynamically assessed renal haemodynamic, microvascular and metabolic responses to, and ultrastructural sequelae of, sepsis in a porcine model of faecal peritonitis-induced progressive hyperdynamic sepsis.

Methods

In eight anaesthetised and mechanically ventilated pigs, faecal peritonitis was induced by inoculating autologous faeces. Six sham-operated animals served as time-matched controls. Noradrenaline was administered to maintain mean arterial pressure (MAP) greater than or equal to 65 mmHg. Before and at 12, 18 and 22 hours of peritonitis systemic haemodynamics, total renal (ultrasound Doppler) and cortex microvascular (laser Doppler) blood flow, oxygen transport and renal venous pressure, acid base balance and lactate/pyruvate ratios were measured. Postmortem histological analysis of kidney tissue was performed.

Results

All septic pigs developed hyperdynamic shock with AKI as evidenced by a 30% increase in plasma creatinine levels. Kidney blood flow remained well-preserved and renal vascular resistance did not change either. Renal perfusion pressure significantly decreased in the AKI group as a result of gradually increased renal venous pressure. In parallel with a significant decrease in renal cortex microvascular perfusion, progressive renal venous acidosis and an increase in lactate/pyruvate ratio developed, while renal oxygen consumption remained unchanged. Renal histology revealed only subtle changes without signs of acute tubular necrosis.

Conclusion

The results of this experimental study argue against the concept of renal vasoconstriction and tubular necrosis as physiological and morphological substrates of early septic AKI. Renal venous congestion might be a hidden and clinically unrecognised contributor to the development of kidney dysfunction.

High versus standard-volume haemofiltration in hyperdynamic porcine peritonitis: effects beyond haemodynamics?

OBJECTIVE

The role of haemofiltration as an adjunctive treatment of sepsis remains a contentious issue. To address the role of dose and to explore the biological effects of haemofiltration we compared the effects of standard and high-volume haemofiltration (HVHF) in a peritonitis-induced model of porcine septic shock.

DESIGN AND SETTING

Randomized, controlled experimental study.

SUBJECTS

Twenty-one anesthetized and mechanically ventilated pigs.

INTERVENTIONS

After 12 h of hyperdynamic peritonitis, animals were randomized to receive either supportive treatment (Control, n = 7) or standard haemofiltration (HF 35 ml/kg per h, n = 7) or HVHF (100 ml/kg per hour, n = 7).

MEASUREMENTS AND RESULTS

Systemic and hepatosplanchnic haemodynamics, oxygen exchange, energy metabolism (lactate/pyruvate, ketone body ratios), ileal and renal cortex microcirculation and systemic inflammation (TNF-alpha, IL-6), nitrosative/oxidative stress (TBARS, nitrates, GSH/GSSG) and endothelial/coagulation dysfunction (von Willebrand factor, asymmetric dimethylarginine, platelet count) were assessed before, 12, 18, and 22 h of peritonitis. Although fewer haemofiltration-treated animals required noradrenaline support (86, 43 and 29% animals in the control, HF and HVHF groups, respectively), neither of haemofiltration doses reversed hyperdynamic circulation, lung dysfunction and ameliorated alterations in gut and kidney microvascular perfusion. Both HF and HVHF failed to attenuate sepsis-induced alterations in surrogate markers of cellular energetics, nitrosative/oxidative stress, endothelial injury or systemic inflammation.

CONCLUSIONS

In this porcine model of septic shock early HVHF proved superior in preventing the development of septic hypotension. However, neither of haemofiltration doses was capable of reversing the progressive disturbances in microvascular, metabolic, endothelial and lung function, at least within the timeframe of the study and severity of the model.

Effects of a cantaloupe melon extract/wheat gliadin biopolymer during aortic cross-clamping

OBJECTIVE

We previously reported in healthy volunteers that a cantaloupe melon extract chemically combined with wheat gliadin (melon extract/gliadin) and containing SOD, catalase and residual glutathione peroxidase (GPx), protected against DNA strand-break damage induced by hyperbaric oxygen (HBO), a well-established model of DNA damage resulting from oxidative stress. Aortic cross-clamping is a typical example of ischemia/reperfusion injury-related oxidative stress, and therefore we investigated whether this melon extract/gliadin would also reduce DNA damage after aortic cross-clamping and reperfusion.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

Animal laboratory.

PATIENTS AND PARTICIPANTS

18 anesthetized, mechanically ventilated and instrumented pigs.

INTERVENTIONS

After 14 days of oral administration of 1250 mg of the melon extract/gliadin (n=9) or vehicle (n=9), animals underwent 30 min of thoracic aortic cross-clamping and 4 h of reperfusion.

MEASUREMENTS AND RESULTS

Before clamping, immediately before declamping, and at 2 and 4 h of reperfusion, we measured blood isoprostane (immunoassay) and malondialdehyde concentrations (fluorimetric thiobarbituric acid test), SOD, catalase and GPx activities (spectrophotometric kits), NO formation (nitrate+nitrite; chemoluminescence), DNA damage in whole blood samples and isolated lymphocytes exposed to hyperbaric oxygen (comet assay). Organ function was also evaluated. Kidney and spinal cord specimen were analysed for apoptosis (TUNEL assay). The melon extract/gliadin blunted the DNA damage, reduced spinal cord apoptosis and attenuated NO release, however, without any effect on lipid peroxidation and organ function.

CONCLUSIONS

Pre-treatment with the oral melon extract/gliadin may be a therapeutic option to reduce oxidative cell injury affiliated with aortic cross-clamping.

EFFECTS OF COMBINING INDUCIBLE NITRIC OXIDE SYNTHASE INHIBITOR AND RADICAL SCAVENGER DURING PORCINE BACTEREMIA

Complex interactions of nitric oxide and other free radicals have been implicated in the pathogenesis of sepsis and organ dysfunction. We hypothesized that simultaneous inducible nitric oxide synthase inhibition (L-N6-[1-iminoethyl]-lysine [L-NIL]) and neutralization of superoxide (O2-) (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl [Tempol]) would protect from detrimental consequences of long-term, volume-resuscitated, hyperdynamic porcine bacteremia. In this prospective, randomized, controlled experimental study, 16 anesthetized, mechanically ventilated and instrumented pigs were exposed to 24 h of continuous infusion of live Pseudomonas aeruginosa. After 12 h of hyperdynamic sepsis, animals were randomized to receive either vehicle (control, n = 8) or combination of L-NIL and Tempol (n = 8). Systemic and hepatosplanchnic hemodynamics, oxygen exchange, metabolism, ileal mucosal microcirculation and tonometry, oxidative stress and coagulation parameters were assessed before, 12, 18, and 24 h of P. aeruginosa infusion. Combined treatment inhibited sepsis-induced increase in plasma nitrate/nitrite, 8-isoprostane, and thiobarbituric acid reactive species concentrations, prevented hypotension, and reversed hyperdynamic circulation. Despite lower intestinal macrocirculation, combined regimen attenuated the otherwise progressive deterioration in ileal mucosal microcirculation and prevented mucosal acidosis. Treatment substantially attenuated mesenteric and hepatic venous acidosis, preserved sepsis-induced impairment of hepatosplanchnic redox state, and prevented the development of renal dysfunction. Finally, coinfusion of L-NIL and Tempol largely attenuated the sepsis-induced rise in plasma von Willebrand factor and thrombin-antithrombin complexes. Thus, hemodynamic, microcirculatory, metabolic, renal, and coagulation data indicate that combining inducible inhibition with cell permeable O2(-) radical scavenger afforded significant protection in porcine sepsis, thus suggesting an important interactive role of O2(-) and nitric oxide in mediating organ dysfunction.

Role of oxidative stress in experimental sepsis and multisystem organ dysfunction

Massive increase in radical species can lead to oxidative stress, promoting cell injury and death. This review focuses on experimental evidence of oxidative stress in critical illnesses, sepsis and multisystem organ dysfunction. Oxidative stress could negatively affect organ injury and thus overall survival of experimental models. Based on this experimental evidence, we could improve the rationale of supplementation of antioxidants alone or in combination with standard therapies aimed to reduce oxidative stress as novel adjunct treatment in critical care.

OLEUROPEIN

Oleuropein, a novel immunomodulator derived from olive tree, was assessed in vitro and in experimental sepsis by Pseudomonas aeruginosa. After addition in monocyte and neutrophil cultures, malondialdehyde, TNF-alpha, IL-6, and bacterial counts were estimated in supernatants. Acute pyelonephritis was induced in 70 rabbits after inoculation of pathogen in the renal pelvis. Intravenous therapy was administered in four groups postchallenge by one multidrug-resistant isolate (A, controls; B, oleuropein; C, amikacin; D, both agents) and in three groups postchallenge by one susceptible isolate (E, controls; F, oleuropein; G, amikacin). Survival was recorded; bacterial growth in blood and organs was counted; endotoxins (LPS), malondialdehyde, total antioxidant status, and TNF-alpha in serum were estimated. TNF-alpha and IL-6 of cell supernatants were not increased compared with controls when triggered by LPS and P. aeruginosa. Counts of multidrug-resistant P. aeruginosa were decreased in monocyte supernatants. Median survival of groups A, B, C, D, E, F, and G were 3.00, 6.00, 2.00, 10.00, 1.00, 5.00, and 1.00 days, respectively. Bacteria in blood were lower at 48 h in groups B and D compared with A and in groups F and G compared with E. Total antioxidant status decreased steadily over time in groups A, C, D, and G, but not in groups B and F. TNF-alpha of groups B, C, and D was lower than A at 48 h. Tissue bacteria decreased in group F compared with E. Oleuropein prolonged survival in experimental sepsis probably by promoting phagocytosis or inhibiting biosynthesis of proinflammatory cytokines.

Catecholamines and vasopressin during critical illness

In critical care medicine, catecholamines are most widely used to reverse circulatory dysfunction and thus to restore tissue perfusion. However, catecholamines not only influence systemic and regional hemodynamics, but also exert a variety of significant metabolic, endocrine, and immunologic effects. Arginine vasopressin is a vasomodulatory hormone with potency to restore vascular tone in vasodilatory hypotension. Although the evidence supporting the use of low doses of vasopressin or its analogs in vasodilatory shock is increasing, lack of data regarding mortality and morbidity prevent their implementation in critical care protocols.

Polyethylene glycol-superoxide dismutase prevents endotoxin-induced cardiac dysfunction

RATIONALE

Sepsis produces significant mitochondrial and contractile dysfunction in the heart, but the role of superoxide-derived free radicals in the genesis of these abnormalities is not completely understood.

OBJECTIVES

The study was designed to test the hypothesis that superoxide scavenger administration prevents endotoxin-induced cardiac mitochondrial and contractile dysfunction.

METHODS

Four groups of rats were studied, and animals were injected with either saline, endotoxin, endotoxin plus polyethylene glycol-adsorbed-superoxide dismutase (PEG-SOD; a free-radical scavenger), or PEG-SOD alone. Animals were killed 48 h after injections. We then measured cardiac mitochondrial generation of reactive oxygen species (ROS), formation of free-radical reaction products (protein carbonyls, lipid aldehydes, nitrotyrosine), mitochondrial function, and cardiac contractile function.

MEASUREMENTS AND MAIN RESULTS

Endotoxin elicited increases in cardiac mitochondrial ROS formation (p < 0.001), increases in cardiac levels of free-radical reaction products, reductions in mitochondrial ATP generation (p < 0.001), and decrements in cardiac pressure-generating capacity (p < 0.01). Administration of PEG-SOD blocked formation of free-radical reaction products, prevented mitochondrial dysfunction, and preserved cardiac contractility. For example, mitochondrial ATP generation was 923 +/- 50, 392 +/- 32, 753 +/- 25, and 763 +/- 36 nmol/min/mg, respectively, for control, endotoxin, endotoxin + PEG-SOD, and PEG-SOD groups (p < 0.001). In addition, cardiac systolic pressure generation at a diastolic pressure of 15 mm Hg averaged 110 +/- 11, 66 +/- 7, 129 +/- 10 and 124 +/- 5 mm Hg, respectively, for control, endotoxin, endotoxin + PEG-SOD, and PEG-SOD groups (p < 0.01).

CONCLUSION

These data indicate that superoxide-derived oxidants play a critical role in the development of cardiac mitochondrial and contractile dysfunction in endotoxin-induced sepsis.