MitoVitE, a mitochondria-targeted antioxidant, limits paclitaxel-induced oxidative stress and mitochondrial damage in vitro, and paclitaxel-induced mechanical hypersensitivity in a rat pain model

BACKGROUND

Neuropathic pain is a common side-effect of chemotherapy. Although precise mechanisms are unclear, oxidative stress and mitochondrial damage are involved. We investigated whether the mitochondria targeted antioxidant, MitoVitE, provided better protection against paclitaxel-induced mitochondrial damage in rat dorsal root ganglion (DRG) cells, than a non-targeted form of vitamin E, Trolox. We also determined whether MitoVitE, compared with duloxetine, could limit paclitaxel-induced mechanical hypersensitivity in rats.

METHODS

Mitochondrial function was measured in DRG cells exposed to paclitaxel with and without MitoVitE or Trolox. The effect of MitoVitE or Trolox on paclitaxel-induced cell killing in cancer cell lines was also determined. Rats received a cumulative dose of 8 mg kg^-1 paclitaxel plus either MitoVitE (2 mg^-1 kg day^-1), duloxetine (10 mg kg^-1 day^-1) or vehicle control daily. Mechanical hind paw withdrawal thresholds were measured every two days.

RESULTS

Paclitaxel caused loss of membrane potential in DRG cells. At 100 µM paclitaxel median [range] change was 61[44-78]%, P < 0.0001, which was ameliorated by MitoVitE (86[62-104]%) but not Trolox (46[46-57]%). Similarly, loss of metabolic activity and glutathione induced by paclitaxel (both P < 0.0001) were reduced by MitoVitE but not Trolox. Cytotoxicity of paclitaxel was not affected by co-exposure of ovarian cancer cells to either MitoVitE or Trolox, but was slightly reduced against breast cancer cells, in the presence of Trolox. Mean (SD) areas under the curve of withdrawal thresholds at 6 h after injection in rats given paclitaxel + control, or + MitoVitE (P < 0.0001) or + duloxetine (P < 0.0001) were 110 (5), 145 (10) and 156 (13) respectively.

CONCLUSIONS

Paclitaxel affected mitochondrial function and glutathione in DRG cells, which was abrogated by MitoVitE but not Trolox, without decreasing cancer cell cytotoxicity. In rats, paclitaxel-induced mechanical hypersensitivity was ameliorated by MitoVitE treatment to an extent similar to duloxetine. These data confirm mitochondria as a mechanistic target for paclitaxel-induced damage and suggest mitochondria targeted antioxidants as future therapeutic strategies.

Pharmacological activation of endogenous protective pathways against oxidative stress under conditions of sepsis

BACKGROUND

Mitochondrial oxidative stress has a role in sepsis-induced organ dysfunction. The endogenous mechanisms to initiate protective pathways are controlled by peroxisome proliferator-activated receptor gamma co-activator 1-alpha (PGC1α) and nuclear factor erythroid 2-like 2 (NFE2L2). Activation of these pathways are potential therapeutic targets in sepsis. We used pharmacological activators to determine the effects on markers of mitochondrial damage and inflammation in human endothelial cells under conditions of sepsis.

METHODS

Human endothelial cells were exposed to lipopolysaccharide plus peptidoglycan G to mimic a sepsis environment, with a range of concentrations of a selective synthetic agonist of silent information regulator-1 (SIRT-1) which activates PGC1α, or bis(2-hydroxy-benzylidene) acetone (2HBA) which activates NFE2L2, with and without inhibitors of these pathways. Cells were cultured for up to seven days and we measured mitochondrial membrane potential, metabolic activity, and density (as a marker of biogenesis), interkeukin-6 (to reflect inflammation) and glutathione (as a measure of antioxidant status).

RESULTS

Under conditions mimicking sepsis, activation of the PGC1α and NFE2L2 pathways protected cells from LPS/PepG-induced loss of mitochondrial membrane potential (P=0.0002 and P=0.0009, respectively) and metabolic activity (P=0.05 and P<0.0001, respectively), and dampened interleukin-6 responses (P=0.003 and P=0.0001, respectively). Mitochondrial biogenesis (both P=0.0001) and glutathione (both P<0.0001) were also increased. These effects were blunted by the respective inhibitors.

CONCLUSIONS

The development of organ dysfunction during human sepsis is linked to mitochondrial dysfunction, and so activation of PGC1α/NFE2L2 is likely to be beneficial. These pathways are attractive therapeutic targets for sepsis.

Low zinc and selenium concentrations in sepsis are associated with oxidative damage and inflammation

BACKGROUND

Oxidative stress with dysregulated inflammation are hallmarks of sepsis. Zinc and selenium have important antioxidant functions, such that they could be important in patients with sepsis. We used an in vitro approach to assess the effect of zinc and selenium on oxidative stress, mitochondrial function, and inflammatory responses in conditions mimicking sepsis and related the findings to plasma concentrations and biomarkers in patients with and without sepsis.

METHODS

Human endothelial cells were exposed to a range of zinc and selenium concentrations in conditions mimicking sepsis. Zinc, selenium, and a series of biomarkers of oxidative stress and inflammation were measured in plasma from critically ill patients with and without sepsis.

RESULTS

Culturing cells with different concentrations of zinc caused altered zinc transporter protein expression and cellular zinc content, and selenium affected glutathione peroxidase 3 activity. Although zinc or selenium at physiological concentrations had no effect on interleukin-6 release in vitro, higher concentrations of the trace elements were associated with improved mitochondrial function. Plasma zinc and selenium concentrations were low in patients [zinc: median (range) 4.6 (2.1-6.5) μM in control patients without sepsis and 3.1 (1.5-5.4) μM in patients with sepsis, P=0.002; and selenium: 0.78 (0.19-1.32) μM in control patients and 0.42 (0.22-0.91) μM in sepsis patients, P=0.0009]. Plasma concentrations of interleukin-6, other biomarkers of inflammation, and markers of oxidative damage to proteins and lipids were elevated, particularly in patients with sepsis, and were inversely related to plasma zinc and selenium concentrations.

CONCLUSIONS

Zinc and selenium concentrations were reduced in critically ill patients, with increased oxidative stress and inflammatory biomarkers, particularly in patients with sepsis. Oxidative stress as a result of suboptimal selenium and zinc concentrations might contribute to damage of key proteins.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: registration number NCT01328509.

Antioxidants that protect mitochondria reduce interleukin-6 and oxidative stress, improve mitochondrial function, and reduce biochemical markers of organ dysfunction in a rat model of acute sepsis

Background

Sepsis-induced organ failure is the major cause of death in critical care units, and is characterized by a massive dysregulated inflammatory response and oxidative stress. We investigated the effects of treatment with antioxidants that protect mitochondria (MitoQ, MitoE, or melatonin) in a rat model of lipopolysaccharide (LPS) plus peptidoglycan (PepG)-induced acute sepsis, characterized by inflammation, mitochondrial dysfunction and early organ damage.

Methods

Anaesthetized and ventilated rats received an i.v. bolus of LPS and PepG followed by an i.v. infusion of MitoQ, MitoE, melatonin, or saline for 5 h. Organs and blood were then removed for determination of mitochondrial and organ function, oxidative stress, and key cytokines.

Results

MitoQ, MitoE, or melatonin had broadly similar protective effects with improved mitochondrial respiration (P<0.002), reduced oxidative stress (P<0.02), and decreased interleukin-6 levels (P=0.0001). Compared with control rats, antioxidant-treated rats had lower levels of biochemical markers of organ dysfunction, including plasma alanine amino-transferase activity (P=0.02) and creatinine concentrations (P<0.0001).

Conclusions

Antioxidants that act preferentially in mitochondria reduce mitochondrial damage and organ dysfunction and decrease inflammatory responses in a rat model of acute sepsis.

Regulation of pentraxin-3 by antioxidants

BACKGROUND

Pentraxin-3 (PTX3) may be a useful biomarker in sepsis, but its regulatory mechanisms are still unclear. Oxidative stress is well defined in patients with sepsis and has a role in regulation of inflammatory pathways which may include PTX3. We undertook an in vitro study of the effect of antioxidants on regulation of PTX3 in endothelial cells combined with a prospective observational pilot study of PTX3 in relation to markers of antioxidant capacity and oxidative stress in patients with sepsis.

METHODS

Human endothelial cells were cultured with lipopolysaccharide 2 microg ml(-1), peptidoglycan G 20 microg ml(-1), tumour necrosis factor (TNF) alpha 10 ng ml(-1), interleukin-1 (IL-1) beta 20 ng ml(-1), or killed Candida albicans yeast cells plus either N-acetylcysteine (NAC) 25 mM, trolox 100 mM, or idebenone 1 microM. Plasma samples were obtained from 15 patients with sepsis and 11 healthy volunteers.

RESULTS

PTX3 levels in plasma were higher in patients with sepsis than in healthy people [26 (1-202) ng ml(-1) compared with 6 (1-12) ng ml(-1), P=0.01]. Antioxidant capacity was lower in patients with sepsis than healthy controls [0.99 (0.1-1.7) mM compared with 2.2 (1.3-3.3) mM, P=0.01]. In patients with sepsis, lipid hydroperoxide levels were 3.32 (0.3-10.6) nM and undetectable in controls. We found no relationship between PTX3 and antioxidant capacity or lipid hydroperoxides. Cell expression of PTX3 increased with all inflammatory stimulants but was highest in cells treated with TNFalpha plus IL-1beta. PTX3 concentrations were lower in cells co-treated with antioxidants (all P<0.05), associated with lower nuclear factor kappaB expression for NAC and trolox (P<0.05).

CONCLUSIONS

PTX3 expression is down-regulated in vitro by antioxidants. Plasma levels of PTX3 are elevated in sepsis but seem to be unrelated to markers of oxidant stress or antioxidant capacity.

Immunomodulation in the critically ill

Immunotherapy in the critically ill is an appealing notion because of the apparent abnormal immune and inflammatory responses seen in so many patients. The administration of a medication that could alter immune responses and decrease mortality in patients with sepsis could represent a ‘magic bullet’. Various approaches have been tried over the last 20 yr: steroids; anti-endotoxin or anti-cytokine antibodies; cytokine receptor antagonists; and other agents with immune-modulating side-effects. However, in some respects, research along these lines has been unsuccessful or disappointing at best. The current state of knowledge is summarized with particular reference to sepsis and the acute respiratory distress syndrome.

Inhibition of neuronal nitric oxide synthase reduces the propofol requirements in wild-type and nNOS knockout mice

BACKGROUND AND OBJECTIVE

The glutamate-nitric oxide-cyclic guanosine monophosphate pathway has been identified as a potential target for anaesthetic agents. However, mice deficient in neuronal nitric oxide synthase have a similar susceptibility to volatile anaesthetic agents to wild-type mice and are not affected by non-isoform selective inhibitors. We hypothesized that the neuronal nitric oxide synthase selective inhibitor, 7-nitroindazole, would also reduce the propofol requirements in wild-type mice but would have no effect in neuronal nitric oxide synthase knockout mice.

METHODS

We determined the time to loss of righting reflex, time to painful stimulus and time to regaining the righting reflex in neuronal nitric oxide synthase knockout and wild-type mice following the intraperitoneal injection of propofol in untreated, 7-nitroindazole and vehicle only treated animals (n = 6 per group). Propofol (200 mg kg(-1)) resulted in loss of righting reflex in the untreated and vehicle only groups but was lethal in 7-nitroindazole pre-treated mice, requiring a reduced dose of propofol (100 mg kg(-1)).

RESULTS

7-nitroindazole pre-treatment significantly reduced the loss of righting reflex (P < 0.001) in both wild-type and knockout mice when compared to untreated and vehicle only pre-treated animals, but had no effect on time to painful stimulus or regaining of the righting reflex. 7-nitroindazole reduced the propofol requirements in knockout mice to the same extent as in wild-type animals.

CONCLUSIONS

Propofol exerts its anaesthetic effects at least partially via the glutamate-nitric oxide-cyclic guanosine monophosphate pathway. The neuronal nitric oxide synthase knockout mice are sensitive to neuronal nitric oxide synthase selective inhibition suggesting that compensatory pathways in neuronal nitric oxide synthase knockout mice exist.

Inhibition of neuronal nitric oxide synthase reduces isoflurane MAC and motor activity even in nNOS knockout mice

BACKGROUND

The glutamate-nitric oxide-cyclic GMP pathway has been identified as a potential target for volatile anaesthetic agents as acute inhibition of nitric oxide synthase (NOS) reduces the minimum alveolar concentration (MAC) in most animal studies. However, mice deficient in the type I NOS isoform (nNOS) are reported to have a similar MAC for isoflurane and are not affected by non-isoform specific inhibitors.

METHODS

We determined whether the nNOS specific inhibitor, 7-nitroindazole (7-NI), had an effect on isoflurane MAC and righting reflex (RRF) and investigated spontaneous motor activity in an open-field study in wild-type (WT) and knockout (KO) mice.

RESULTS

7-NI reduced isoflurane MAC and RRF in both WT and KO animals (all P<0.04). 7-NI profoundly reduced spontaneous motor activity in both the WT and KO animals in the open-field study as indicated by a reduction in the number of line crossings and rearings in both WT and KO mice (both P<0.001).

CONCLUSION

We conclude that isoform specific inhibition of nNOS reduces MAC and spontaneous motor activity even in nNOS KO animals. Our results indicate that the NMDA receptor-nitric oxide-cyclic GMP pathway remains a credible target in modulating the effects of isoflurane.

Physiology of the endothelium

In the past, the endothelium was considered to be inert, described as a 'layer of nucleated cellophane', with only non-reactive barrier properties, such as presentation of a non-thrombogenic surface for blood flow and guarding against pro-inflammatory insults. However, it is now becoming clear that endothelial cells actively and reactively participate in haemostasis and immune and inflammatory reactions. They regulate vascular tone via production of nitric oxide, endothelin and prostaglandins and are involved in the manifestations of atherogenesis, autoimmune diseases and infectious processes. They produce and react to various cytokines and adhesion molecules and it is now clear that they can mount anti- and pro-inflammatory and protective responses depending on environmental conditions and are key immunoreactive cells. Endothelial dysfunction or activation also contributes to a variety of disease states.

Genotype and interleukin-10 responses after cardiopulmonary bypass

BACKGROUND

The pro- and anti-inflammatory cytokine balance has been implicated in outcome from inflammatory conditions, and cardiopulmonary bypass is associated with a marked inflammatory response. Interleukin-10 (IL-10) is an anti-inflammatory cytokine and levels have been shown to be highest in those patients who develop sepsis after trauma or surgery. IL-10 levels vary between individuals and genotype may dictate the IL-10 response. We therefore investigated IL-10 genotype, circulating IL-10 concentrations and outcome in terms of organ dysfunction 24 h after cardiopulmonary bypass.

METHODS

Blood samples were obtained from 150 patients before, and 3, and 24 h after cardiopulmonary bypass. IL-10 was measured by enzyme immunoassay. The single nucleotide polymorphism at -1082 base pairs was detected by restriction fragment length polymorphism analysis. Post-bypass organ system dysfunction was defined prospectively.

RESULTS

IL-10 concentrations were increased 3 h after bypass (P<0.0001) and were still increased at 24 h (P<0.0001). Homozygosity for the G allele was associated with lower median (range) maximal IL-10 levels at 3 h (44 (13-136) pg ml(-1)) compared with the A allele (118 (39-472) pg ml(-1); P=0.042). Those patients who developed at least one organ dysfunction (n=33) had higher IL-10 levels 3 h after surgery (242 (18-694) pg ml(-1)) compared with those without organ dysfunction (77 (7-586) pg ml(-1); P=0.001, n=117).

CONCLUSIONS

The G allele of the -1082 base pair single nucleotide polymorphism in the IL-10 gene is associated with lower IL-10 release after cardiopulmonary bypass. High levels of IL-10 secretion are associated with organ dysfunction 24 h after surgery.

Oxidative stress and gene expression in sepsis

Dysregulation of the immuno-inflammatory response, as seen in sepsis, may culminate in host cell and organ damage. Lipopolysaccharide from Gram-negative bacterial cell walls induces gene activation and subsequent inflammatory mediator expression. Gene activation is regulated by a number of transcription factors at the nuclear level, of which nuclear factor kappaB appears to have a central role. The redox (reduction-oxidation) cellular balance is important for normal cellular function, including transcription factor regulation. In sepsis, a state of severe oxidative stress is encountered, with host endogenous antioxidant defences overcome. This has implications for cellular function and the regulation of gene expression. This review gives an overview of the mechanisms by which transcription factor activation and inflammatory mediator overexpression occur in sepsis, together with the events surrounding the state of oxidative stress encountered and the effects on the host's antioxidant defences. The effect of oxidative stress on transcription factor regulation is considered, together with the role of antioxidant repletion in transcription factor activation and in sepsis in general. Other interventions that may modulate transcription factor activation are also highlighted.

Saliva cyclic GMP increases during anaesthesia

BACKGROUND

Cyclic GMP (cGMP) has been implicated in modulating the effects of general anaesthesia. Changes in cGMP in humans undergoing anaesthesia have not been reported previously.

METHODS

In this pilot study we measured cGMP in the saliva of six healthy volunteers and eight patients undergoing general anaesthesia for minor gynaecological procedures. Samples were obtained using a commercially available sampling device and cGMP was determined with an enzyme immunoassay and results expressed as a cGMP per mg protein.

RESULTS

There was no statistically significant variation in salivary cGMP either day-to-day or between time points in healthy volunteers. Analysis of variance of salivary cGMP of patients undergoing general anaesthesia showed that cGMP increased significantly intraoperatively and returned to preoperative levels after surgery (P=0.03).

CONCLUSIONS

This is the first time that real time in vivo changes in salivary cGMP levels during general anaesthesia in humans have been demonstrated and may allow an alternative technique for measuring depth of anaesthesia in the future.

Matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-1 and tumour necrosis factor alpha release during cardiopulmonary bypass

An inflammatory response occurs during cardiac surgery involving cardiopulmonary bypass. Matrix metalloproteinase-9 is an enzyme involved in cytokine processing and leucocyte extravasation. It is secreted as a pro-enzyme in response to several inflammatory mediators and is inhibited by endogenous tissue inhibitor of metalloproteinase-1. The interaction between matrix metalloproteinase-9 and its inhibitor during cardiopulmonary bypass is not known. We measured tumour necrosis factor alpha, and matrix metalloproteinase-9 and its inhibitor using enzyme immunoassay at three time points in 20 patients undergoing elective coronary artery bypass grafting with cardiopulmonary bypass. Tumour necrosis factor and matrix metalloproteinase concentrations increased in all patients during bypass (both p < 0.0001), whereas the inhibitor in contrast, decreased (p < 0.0001). We conclude that matrix metalloproteinase-9 is released as part of the inflammatory response during cardiac surgery. Levels of the endogenous inhibitor of metalloproteinase, however, show a different pattern of release, suggesting independent regulation.

Differential modulation of interleukin-6 and interleukin-10 by diclofenac in patients undergoing major surgery

BACKGROUND

Prostaglandins modulate cytokine release though increases in cAMP, regulating interleukin (IL) 6 and IL-10. Diclofenac inhibits cyclo-oxygenase activity and hence prostaglandin production. We hypothesized that diclofenac would affect release of IL-6 and IL-10 and modulate the immune response.

METHODS

In a randomized, double-blind, placebo-controlled study, we investigated the effect of diclofenac in patients undergoing major urological surgery. Patients were randomized to receive either diclofenac (50 mg orally every 8 h the day before surgery and 75 mg i.m. every 12 h on the day of surgery, n = 23) or placebo (n = 23). Standardized combined general anaesthesia and epidural analgesia was administered. Serum IL-6, IL-10 and cortisol were measured before surgery and 30 min and 2, 6, 12 and 24 h after skin incision. Temperature, leucocyte count and C-reactive protein concentration were measured before surgery and after 24 h.

RESULTS

IL-6 and IL-10 concentrations increased, reaching peak levels at 12 and 6 h respectively in both groups. At 12 h, the IL-6 concentration was significantly lower in patients receiving diclofenac than in those receiving placebo (P = 0.003). In contrast, IL-10 concentration at 6 h was higher in diclofenac-treated patients (P = 0.008), and this was associated with less pyrexia (P = 0.03), a lower leucocyte count (P = 0.0002) and a lower C-reactive protein concentration (P = 0.0039). Serum cortisol concentration was similar in the two groups of patients until 24 h, when the concentration was lower in patients who received diclofenac (P = 0.002). Cortisol concentration correlated with IL-6 concentration at 24 h.

CONCLUSIONS

Administration of diclofenac was associated with lower IL-6 and higher IL-10 concentrations, and lower leucocyte count, C-reactive protein concentration and temperature. Diclofenac may have an anti-inflammatory role in major surgery.

Matrix metalloproteinase-9 concentrations in critically ill patients

Matrix metalloproteinase-9 is involved in the processing of cytokines during sepsis. We studied 10 critically ill patients within 12 h of fulfilling the American Consensus Conference criteria for severe sepsis and compared the results with 12 critically ill non-septic control patients and eight healthy subjects. Total matrix metalloproteinase-9 concentrations were measured on days 1, 2 and 3. The median admission Acute Physiological and Chronic Health Evaluation II score was 19.5 (range 13-27) in the septic patients and 20.5 (range 7-28) in the non-septic patients. Four patients from each group died within 28 days. Matrix metalloproteinase-9 concentrations were elevated significantly in both groups of patients compared with healthy subjects (p = 0.0004) but there was no difference between patients with and without sepsis. Matrix metalloproteinase-9 levels did not change with time, and there was no difference between survivors and those who died. We conclude that matrix metalloproteinase-9 represents a non-specific marker of systemic inflammation.

Circulating tetrahydrobiopterin concentrations in patients with septic shock

Nitric oxide synthase requires tetrahydrobiopterin for its activity. In animal models of sepsis, changes in circulating tetrahydrobiopterin concentrations precede increases in nitrate. We measured plasma tetrahydrobiopterin and nitrate concentrations on three consecutive days in 10 patients with septic shock and 10 critically ill control patients. Total nitrate concentration was measured after reduction of nitrite to nitrate. Tetrahydrobiopterin concentrations were measured using HPLC. The median (range) APACHE II score was 22 (13-27) in the patients with septic shock and 25 (7-28) in the control group. The nitrate concentration was significantly higher in patients with septic shock than in controls (P = 0.01) on all days but did not change with time. Tetrahydrobiopterin concentrations were highest in the patients with septic shock on day 1 only (P = 0.037). In the seven patients with renal failure, both nitrate and tetrahydrobiopterin concentrations tended to be higher than in the 13 patients without renal failure. The nitrate concentration correlated with tetrahydrobiopterin concentration on day 1 only (P = 0.05). In patients with septic shock, both tetrahydrobiopterin and total nitrate concentrations were higher than those in critically ill controls but were increased mainly in patients with renal failure. In summary, tetrahydrobiopterin concentration increases during septic shock, in line with increases in nitrate concentration. However, as for nitrate, concentrations

Differential nitric oxide synthase activity, cofactor availability and cGMP accumulation in the central nervous system during anaesthesia

We investigated the effects of anaesthesia on dynamic nitric oxide production, concentrations of tetrahydrobiopterin and the accumulation of cyclic GMP (cGMP) in the rat central nervous system (CNS). Rats were assigned to anaesthesia with halothane, isoflurane, pentobarbital, diazepam, ketamine or xenon (n=6 per group). After 30 min, [14C]L-arginine (i.v.) was given and, after a further 60 min of anaesthesia, rats were killed and exposed immediately to focused microwave radiation. After removal of the brain and spinal cord, nitric oxide production from radiolabelled arginine (and hence nitric oxide synthase activity during anaesthesia) was measured as [14C]L-citrulline by scintillation counting. cGMP was determined by enzyme immunoassay and tetrahydrobiopterin by fluorescence HPLC, in brain regions and the spinal cord. Nitric oxide synthase activity was similar in all brain regions but was lower in the spinal cord, and was unaffected by anaesthesia. cGMP was similar in all areas of the CNS and was significantly decreased in rats anaesthetized with halothane. Isoflurane produced similar effects. In contrast, ketamine and xenon anaesthesia increased cGMP in the spinal cord, brainstem and hippocampus. Diazepam and pentobarbital had no effect. Tetrahydrobiopterin concentrations were similar in all areas of the CNS and were increased in the cortex and hippocampus after anaesthesia. We have shown profound differential effects of anaesthesia on the nitric oxide pathway in the rat CNS.

Nutrition in the critically ill patient

Critically ill patients are hypermetabolic and have increased nutrient requirements. Although it is assumed that nutritional support is beneficial in this group of patients there are no well designed clinical trials to test this hypothesis. The rationale for nutritional support, therefore, is based upon clinical judgement. Although it is not known how long a critically ill patient can tolerate what is effectively starvation, the loss of lean tissue which occurs in catabolic patients (20-40 g nitrogen/day) suggests that depletion to a critical level may occur after 14 days. Total parenteral nutrition given to malnourished patients with gastrointestinal cancer for 7 to 10 days before surgery has been shown to decrease complications by about 10%. Wound healing and normal immune responses are dependent upon adequate nutrient intake, and it seems reasonable, therefore, to commence feeding as soon as possible. Earlier feeding may decrease length of stay and complication rates in both critically ill patients and following surgery. It has been shown in randomised controlled trials of both enteral and parenteral feeding in the critically ill, that current regimens are sub-optimal. Calorie intake was shown to be often considerably in excess of metabolic requirements alone, and variable study design has made comparisons impossible. Despite the lack of knowledge regarding even the most simple of nutritional requirements in these patients, the administration of specific micronutrients and specialised supplements has attracted attention. Again, many of these more recent studies are limited because of poor study design.

Effect of ciprofloxacin on the activation of the transcription factors nuclear factor kappaB, activator protein-1 and nuclear factor-interleukin-6, and interleukin-6 and interleukin-8 mRNA expression in a human endothelial cell line

Quinolone antibiotics such as ciprofloxacin modify immune and inflammatory responses in some cells. We have shown previously that ciprofloxacin decreases the accumulation of interleukin (IL)-6 protein from a human endothelial cell line, whilst IL-8 protein production was increased. It is not known whether this occurs through effects on transcription and mRNA expression. We therefore investigated the effect of ciprofloxacin on mRNA for IL-6 and IL-8, and on three transcription factors known to be involved in the regulation of these cytokines. We investigated the effect of ciprofloxacin on tumour necrosis factor alpha- and IL-1beta-mediated activation of the transcription factors nuclear factor kappaB (NFkappaB), activator protein-1 (AP-1) and nuclear factor IL-6 (NF-IL-6) using an electrophoretic mobility shift assay, and the effect on expression of mRNA for IL-6 and IL-8 by reverse transcriptase-PCR in the EAhy926 endothelial cell line. Ciprofloxacin decreased IL-6 mRNA (P<0.05) and increased IL-8 mRNA (P<0.05) expression. Ciprofloxacin did not modulate activation of NFkappaB or AP-1. However, NF-IL-6 binding was decreased in the presence of 100 microg/ml ciprofloxacin (P<0.05). The study shows that ciprofloxacin-mediated decreased IL-6 release by a human endothelial cell line is reflected by decreased mRNA expression and decreased NF-IL-6 but not NFkappaB or AP-1 activation. Increased IL-8 mRNA in response to ciprofloxacin was not reflected by altered transcription factor activation and may represent increased mRNA stability.

Variability in E-selectin expression, mRNA levels and sE-selectin release between endothelial cell lines and primary endothelial cells

Endothelial cell lines express markers and are assumed to exhibit other endothelial cell responses. We investigated E-selectin expression from human umbilical vein endothelial cells, the spontaneously transformed ECV304 line and the hybrid line EA.hy926 by flow cytometry and immunofluorescence, mRNA and soluble E-selectin release. In cells exposed to tumour necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta), median (range) percentage of E-selectin-positive HUVECs increased from 1.6(0.9-6. 2)% to 91.4(83.0-96.1)%, (P=0.001) using flow cytometry. In contrast, E-selectin expression by ECV304 and EA.hy926 cell lines was 100-fold lower. E-selectin mRNA was detectable after 2 h, maximal at 6 h in HUVECs and undetectable in EA.hy926 and ECV304 cell lines after exposure to TNF-alpha/IL-1beta. sE-selectin accumulation increased (P=0.004) in HUVECs only. Neutrophil adherence to ECV304 and EA.hy926 cells was poor compared to HUVECs (P=0.004). The cell lines ECV304 and EA.hy926 do not exhibit normal endothelium expression of E-selectin, and may not be appropriate for studies of adhesion.

Effect of inhaled nitric oxide on key mediators of the inflammatory response in patients with acute lung injury

OBJECTIVE

Inhaled nitric oxide is used to treat hypoxia associated with acute lung injury. Endogenous nitric oxide regulates inflammatory responses, but the effect of inhaled nitric oxide therapy is unknown. We hypothesized that inhaled nitric oxide may alter inflammatory responses and endogenous nitric oxide synthase activity.

DESIGN

A randomized, prospective interventional study.

SETTING

A university hospital's general intensive care unit.

PATIENTS

Thirty-two patients with acute lung injury.

INTERVENTIONS

Patients who responded to test doses of nitric oxide were randomized to ventilator therapy with and without inhaled nitric oxide. The inhaled concentration of nitric oxide was determined by dose titration at 0, 2, 10, and 40 ppm and the minimum concentration used, which resulted in an increase in the PaO2/FIO2 ratio of at least 25%.

MEASUREMENTS AND MAIN RESULTS

Patients were followed up for 30 days or until death, and bronchoalveolar lavage (BAL) was performed at 0, 24, and 72 hrs. Nitric oxide synthase activity was measured spectrophotometrically, and myeloperoxidase, elastase, interleukin-8, and leukotrienes were measured in BAL fluid by enzyme immunoassay. Total nitrite and lipid peroxides in serum were measured colorimetrically. Nitric oxide synthase activity decreased (p = .01) and total nitrite increased (p = .02) in patients receiving inhaled nitric oxide. Other markers of inflammation in BAL fluid did not change. Lipid peroxide concentrations also did not alter.

CONCLUSIONS

The decrease in activity of nitric oxide synthase in patients receiving nitric oxide is likely to be the result of feedback inhibition of the enzyme. This study shows that inhaled nitric oxide has no effect on several markers of the inflammatory response system and does not lead to increased oxidant stress.

Increased nuclear factor kappa B activation in critically ill patients who die

OBJECTIVES

To determine nuclear factor kappa B (NF-kappa B) activation in mononuclear and neutrophils from critically ill patients and to compare NF-kappa B activation with circulating concentrations of interleukin (IL)-6, IL-8, and soluble intercellular adhesion molecule (sICAM)-1.

DESIGN

Observational study.

SETTING

University Teaching Hospital, eight-bed intensive care unit in northeast Scotland.

PATIENTS

Ten patients admitted to the intensive care unit who fulfilled the criteria for systemic inflammatory response syndrome were studied at 0, 24, 48, and 72 hrs. Six healthy volunteers were also studied.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

NF-kappa B activation was significantly higher in patients compared to healthy volunteers in both neutrophils (p = .001) and mononuclear leukocytes (p = .013). In the six patients who survived to 96 hrs, the level of NF-kappa B activation in mononuclear cells remained constant (p = .9). However, in the four patients who died before 96 hrs, mononuclear cell NF-kappa B activation increased markedly and was significantly higher before death than in those who survived to 96 hrs (p = .0105). NF-kappa B activation in neutrophils similarly remained constant in patients who survived to 96 hrs (p = .4) but did not show the same increase before death. Circulating concentrations of IL-6, IL-8, and sICAM-1 were elevated but were unrelated to leukocyte NF-kappa B activation.

CONCLUSIONS

We found NF-kappa B activation in mononuclear and neutrophils in patients with systemic inflammatory response syndrome, which increased markedly before death in mononuclear leukocytes and was not related to plasma IL-6, IL-8, and sICAM-1 concentrations. These data support the need for further study of the role of NF-kappa B activation in mortality from systemic inflammatory response syndrome and sepsis.

Can acute renal failure be prevented?

Correction of salt and volume depletion is paramount in the prevention of renal damage. Measures which stimulate intense filtration of glomeruli in acute renal failure, such as the use of atrial natriuretic peptide analogues, theophylline, dopamine, or growth factors should be regarded with caution, since they all increase metabolic workload in the outer medulla and hence aggravate medullary hypoxia. Neither frusemide, dopamine nor dopexamine have been shown to be better than aggressive saline loading in preventing acute renal failure in at risk patients. Until new clinical studies emerge, avoidance of nephrotoxic insults where possible, monitoring of circulating concentrations of potentially nephrotoxic drug levels and volume loading coupled with supportive measures is recommended. When volume depletion persists, usual blood pressure cannot be restored and patients remain oliguric, early referral to the intensive care unit is paramount. The mortality rate in patients with acute renal failure is high; therefore, measures which reduce the incidence and progression of renal dysfunction will be of benefit.

Mitochondrial redox state in the critically ill

Abnormal oxygen use and organ failure in the critically ill may result from 'poisoning' of mitochondrial function. Measurement of arterial ketone body ratio (AKBR) has been proposed to reflect mitochondrial redox state and may provide a useful marker to monitor mitochondrial function in the critically ill. We measured AKBR (acetoacetate to beta-hydroxybutyrate) and plasma lactate concentrations in 20 critically ill patients, on 3 consecutive days after admission to the intensive care unit. Nine (45%) patients died (five with sepsis) within the 30-day follow-up period. AKBR increased significantly over the 3 days of the study in patients who died (P = 0.034) and decreased in those who survived (P < 0.0001). In addition, there was a significant difference between survivors and non-survivors (P = 0.015). We conclude that serial AKBR measurement may be useful in the management of septic patients.

Effect of the nitric oxide inhibitor, L-N(G)-monomethylarginine, on accumulation of interleukin-6 and interleukin-8, and nuclear factor-kappaB activity in a human endothelial cell line

OBJECTIVE

To determine the effect of the nitric oxide synthase inhibitor, L-N(G)-monomethylarginine, on interleukin-6 and interleukin-8 accumulation, and nuclear factor-kappaB expression in an endothelial cell model of sepsis.

DESIGN

Controlled cell culture experiments examining the immunomodulatory effects of nitric oxide synthase inhibition.

SUBJECTS

A human endothelial cell line (EA.hy926).

MEASUREMENTS AND RESULTS

Cells were incubated with tumor necrosis factor-alpha and interleukin (IL)-1beta in the presence of L-N(G)-monomethylarginine (L-NMMA). IL-6 and IL-8 were measured in culture supernatants using enzyme immunoassay. Nuclear factor-kappaB was measured using electrophoretic mobility shift assay and was quantified using phosphorimaging. IL-6 accumulation was decreased (p < .05) and IL-8 accumulation increased (p < .01) with L-NMMA. Increased nuclear factor-kappaB expression in stimulated cells was unaltered on exposure to L-NMMA. Cell viability was unaffected.

CONCLUSIONS

Excessive production of nitric oxide has been implicated in septic shock, and the use of nitric oxide synthase inhibitors has been suggested. The immunoregulatory actions of nitric oxide synthase inhibitors affects the profile of cytokine release. This effect is not mediated through modulation of nuclear factor-kappaB. These findings have implications for the use of nitric oxide synthase inhibiting agents in septic shock.

Acidosis and tissue hypoxia in the critically ill: how to measure it and what does it mean

We routinely monitor blood gases to determine the adequacy of ventilation and the presence of acid-base abnormalities. Changes in the blood are easily assessed, but of more importance is the abnormality at tissue level. Defects in acid-base homoeostasis have major effects on protein function, thus affecting tissue and organ performance. We concentrate on the changes seen in critically ill patients with acidosis because they form a large portion of the workload of the average intensive care unit. In addition, such patients have significant morbidity and mortality. The development of acidemia in the critically ill is often attributed to reductions in oxygen utilization, which in the past has generally been regarded as dysregulation of tissue blood supply. Resulting tissue hypoperfusion leads to anaerobic metabolism and lactic acidosis. Carbon dioxide production increases as anaerobically produced hydrogen ions are buffered by extracellular bicarbonate. The effectiveness of tissue perfusion is the target of much research, and in this review we outline factors that affect tissue acid-base status, techniques to measure tissue acid-base status, and explore the relationship between tissue acidosis and hypoxia in the critically ill. However, things are not always as simple as they may first appear.

T helper cell subset ratios in patients with severe sepsis

BACKGROUND

T helper 1 (Thl) lymphocytes produce interferon gamma (IFNgamma), favouring cell mediated immunity; Th2 cells secrete interleukin-4 (IL-4), favouring humoral immunity. Cytokines produced in sepsis may effect Th subset predominance and subsequent immune responses.

METHODS

We measured Th subsets in ten patients with severe sepsis, seven APACHE II score-matched non-septic critically ill control patients, and ten healthy subjects. Mononuclear leukocytes were isolated and Th subsets identified by flow cytometry.

RESULTS

The median (range) Th1/Th2 ratio was 0.46 (0.2-2.5) in patients with sepsis, which was significantly lower than both non-septic controls (median 2.5 (0.2-5.9), p = 0.050) and healthy subjects (median 3.9 (1.2-10.8), p = 0.01).

CONCLUSIONS

In patients with sepsis, Th2 antibody mediated (humoral) immune responses predominate. This type of response may lead to fibroblast activation and ultimately immunosuppression. Modulation of Th cell subset predominance may present a novel therapeutic option in the treatment of severe sepsis.

Spinal but not general anesthesia increases the ratio of T helper 1 to T helper 2 cell subsets in patients undergoing transurethral resection of the prostate

Surgical stress and anesthesia cause immunosuppression that may predispose patients to postoperative infections. T helper lymphocytes play a major role in the immune response by controlling cell-mediated and humoral immunity. The type of immune response generated is determined by the differentiation of precursor T helper cells into Th1 or Th2 cells. Each cell subset secretes a particular array of cytokines that further augment the differentiation into that subset. Th1 cells produce interferon gamma and are responsible for cell-mediated immunity. Th2 cells produce interleukin-4 and are more effective in inducing humoral immunity. Cytokine concentrations are altered during surgery and anesthesia, which may effect Th cell predominance and, therefore, subsequent immune responses. We determined Th1 to Th2 cell ratios in patients undergoing transurethral resection of the prostate (TURP) using either spinal or general anesthesia. Mononuclear cells were isolated before anesthesia, immediately after surgery, and after 24 h from patients undergoing TURP, 10 under general anesthesia and 9 under spinal anesthesia. T helper cell subsets were quantified by using flow cytometry, and the ratio of Th1 to Th2 cells was calculated. Th1 to Th2 ratios in patients receiving spinal anesthesia increased over the three time points studied (P = 0.029) but did not change in patients who had general anesthesia (P = 0.11). At 24 h, Th1 to Th2 ratios were significantly higher in the spinal group than in patients who received general anesthesia (P = 0.0157). Total T helper cell numbers remained constant. These data suggest that, from an immunological viewpoint, spinal anesthesia, but not general anesthesia, benefits the patient by maintaining Th1 cell numbers, thereby promoting cellular immunity.

IMPLICATIONS

Spinal anesthesia may result in less immunosuppression after surgery. We found that the ratio of T helper 1 to T helper 2 cells was higher in patients undergoing prostate surgery by spinal rather than general anesthesia. Th1 cells promote protective immune responses that may result in fewer postoperative infections.

The effect of nitric oxide and peroxynitrite on apoptosis in human polymorphonuclear leukocytes

In acute lung injury, neutrophil apoptosis may be important in regulating the inflammatory process by controlling neutrophil numbers and thus activity. Exogenous inhaled nitric oxide is now a widely used therapy in patients with acute lung injury, and its effects on apoptosis may be important. We investigated the effect of nitric oxide and peroxynitrite on apoptosis in lipopolysaccharide stimulated polymorphonuclear leukocytes as a model of nitric oxide-treated lung injury. Cells were incubated for up to 16 h with and without 1.7 microg/ml lipopolysaccharide and the nitric oxide donor GEA-3162 or the peroxynitrite donor SIN-1. Apoptosis was assessed using flow cytometry following annexin-V staining, after 4, 6, 8, and 16 h. Data were assessed using Kruskal-Wallis analysis of variance or Mann-Whitney U-test as appropriate. Annexin-V staining increased spontaneously over 16 h in untreated cells (p = .0002) and incubation with either 1000 microM SIN-1 or 10 microM GEA-3162 increased annexin staining at early time points in nonactivated cells. Apoptosis was attenuated when cells were exposed to lipopolysaccharide and both nitric oxide and peroxynitrite dose dependently inhibited this suppression at all time points and was most apparent at 16 h (p = .004 and .001, respectively). Exposure of activated neutrophils to exogenous nitric oxide or peroxynitrite has marked influences on apoptosis. This work has implications for the modulation of neutrophil function within the lung in patients with lung injury who receive inhaled nitric oxide therapy.

Nitric oxide synthase activity is increased in relation to the severity of liver dysfunction

1. Nitric oxide is a potent vasodilator which plays a major role in the control of blood pressure. The hyperdynamic circulation of cirrhosis has been linked to nitric oxide.2. We measured neutrophil nitric oxide synthase activity in relation to the level of hepatic dysfunction in patients with liver disease of varying aetiology and severity.3. Neutrophils were isolated from 21 patients (7 Child-Pugh score A, 6 grade B and 8 grade C) aged 28-76 (median 49) years. Nitric oxide synthase activity was measured using the conversion of oxyhaemoglobin to methaemoglobin by nitric oxide and expressed in terms of cell protein. Blood pressure and biochemical indices were recorded. Data were assessed using Kruskal-Wallis one-way analysis of variance, Mann-Whitney U-test or Pearson correlation as appropriate.4.Systolic, mean arterial and diastolic blood pressures decreased with increasing hepatic damage (P=0.031, P=0.01 and P=0. 038 respectively). Nitric oxide synthase activity increased with the degree of liver dysfunction (P=0.033) and was highest in patients with Child-Pugh score C. Systolic blood pressure correlated with nitric oxide synthase activity in patients with Child-Pugh score C (P=0.029).5. Our results show that nitric oxide synthase activity increases with increasing Child-Pugh score and is associated with the development of systemic hypotension. These data may support the involvement of nitric oxide in the haemodynamic disturbances seen in liver disease.

The effect of midazolam and propofol on interleukin-8 from human polymorphonuclear leukocytes

Anesthetics and sedatives contribute to postoperative immunosuppression. Interleukin-8 (IL-8) is a chemotactic and activating factor that mediates neutrophil adhesion and margination and is essential for host defense. We investigated the effect of anesthetics on isolated human polymorphonuclear leukocyte production of IL-8. Healthy human polymorphonuclear leukocytes were isolated using a single-step density gradient and stimulated with lipopolysaccharide in the presence of varying concentrations of propofol or midazolam for up to 20 h. IL-8 was measured in both culture supernatants and cell lysates using enzyme immunoassay, and IL-8 mRNA in cells was measured using Northern blotting and phosphorimaging. Data were analyzed using Kruskal-Wallis analysis of variance or the Mann-Whitney U-test as appropriate. Lipopolysaccharide increased extracellular accumulation of interleukin-8, which was suppressed by both propofol (P = 0.025) and midazolam (P = 0.028). However, intracellular IL-8 increased with exposure to lipopolysaccharide (P = 0.028) and remained increased with both anesthetics. Northern blot analysis also revealed increased IL-8 mRNA levels in the presence of both midazolam and propofol, which was confirmed by molecular imaging. These data strongly suggest that the anesthetics modulate transport or secretion of IL-8 protein from the cell. Suppression of IL-8 by anesthetics and sedatives may predispose postoperative and intensive care patients to infection.

IMPLICATIONS

Anesthesia causes immune suppression and alters neutrophil function. We investigated the effect of propofol and midazolam on interleukin-8, a neutrophil chemotactic agent in human neutrophils. Both anesthetics decreased extracellular interleukin-8 accumulation, but intracellular levels and mRNA remained high. This suggests that propofol and midazolam alter interleukin-8 secretion from cells.

The effects of nitric oxide and peroxynitrite on interleukin-8 and elastase from lipopolysaccharide-stimulated whole blood

Inhaled nitric oxide is now widely used in the treatment of hypoxemia and pulmonary hypertension in critically ill patients. Interleukin-8 (IL-8) and neutrophil elastase are important markers of the onset and severity of acute lung injury. We studied the effects of nitric oxide and peroxynitrite on IL-8) and elastase accumulation in lipopolysaccharide-activated whole blood. The nitric oxide donor (GEA-3162) did not affect IL-8 accumulation (P = 0.195) but did cause an increase in elastase accumulation (P = 0.007). The peroxynitrite donor (SIN-1) caused an increase in both IL-8 accumulation (P = 0.0004) and elastase accumulation (P = 0.007). The lack of effect of nitric oxide could be explained by the scavenging of nitric oxide by hemoglobin. These results suggest that modulation of the inflammatory response may occur during inhaled nitric oxide therapy in the critically ill.

IMPLICATIONS

Inhaled nitric oxide, used in lung injury, reacts within the lung, forming peroxynitrite. We investigated the effect of nitric oxide and peroxynitrite on interleukin-8 and elastase release by white cells during inflammation. Nitric oxide and peroxynitrite had marked effects on elastase and interleukin-8, which suggests modulation of the inflammatory response.

Changes in inflammatory mediators during orthotopic liver transplantation

Transplantation is associated with an inflammatory rejection response. Graft reperfusion causes typical haemodynamic and biochemical responses. In this study we have investigated the relationship between these haemodynamic responses and changes in circulating inflammatory mediators after graft reperfusion in 10 consecutive patients undergoing orthotopic liver transplantation. After reperfusion, systemic vascular resistance index decreased (P = 0.011) and cardiac index increased (P = 0.038). These characteristic haemodynamic changes of the reperfusion syndrome were accompanied by global increases in cytokine concentrations. Plasma concentrations of leukotrienes decreased, while thromboxane B2 and platelet activating factor remained increased throughout. Reperfusion-mediated changes in inflammatory mediators may account for the haemodynamic disturbance.

Effect of ciprofloxacin on the accumulation of interleukin-6, interleukin-8, and nitrite from a human endothelial cell model of sepsis

OBJECTIVE

To determine the effect of the quinolone antibiotic ciprofloxacin, on interleukin-6, interleukin-8, and nitrite production by human endothelial cells.

DESIGN

Controlled cell culture experiments examining the immunomodulatory effects of an antibiotic.

SETTING

University research laboratory attached to a large teaching hospital.

SUBJECTS

A human endothelial cell line.

MEASUREMENTS AND MAIN RESULTS

Cells were incubated with tumor necrosis factor-alpha and interleukin-1beta in the presence of a range of ciprofloxacin concentrations. Interleukin-6, interleukin-8, and nitrite concentrations were measured in culture supernatants after 24 hrs using enzyme immunoassay. Ciprofloxacin decreased interleukin-6 accumulation (p = .001). Interleukin-8 was decreased at lower ciprofloxacin concentrations (p = .017) but was increased at 100 microg/mL (p = .0039). Ciprofloxacin had no effect on nitrite accumulation (p = .38).

CONCLUSIONS

Ciprofloxacin differentially modulates interleukin-6 and interleukin-8 expression. The response to infection is coordinated by a cascade of cytokines and other mediators. The widespread use of ciprofloxacin in patients with severe infections is likely to result in alterations in local concentrations of cytokines. Selective control of cytokine concentrations by antibacterial agents will clearly have important therapeutic implications and may be a future research consideration in antibiotic drug design.

Effect of exogenous nitric oxide and superoxide on interleukin-8 from human polymorphonuclear leucocytes

Patients with acute inflammatory lung injury are commonly treated with inhaled nitric oxide. Nitric oxide has profound immunoregulatory effects. Increased concentrations of the cytokine interleukin-8 (IL-8) in bronchoalveolar lavage fluid has been associated with disease severity. We have investigated the effects of a nitric oxide donor and a combined nitric oxide-superoxide donor on lipopolysaccharide-mediated accumulation of IL-8 from cultured human neutrophils. Interleukin-8 was measured in culture supernatant after 20 h using enzyme immunoassay. The combined nitric oxide-superoxide donor, 3-morpholinosydnonimine (SIN-1), dose-dependently decreased lipopolysaccharide-mediated IL-8 accumulation (P < 0.01). SIN-1 also decreased IL-8 accumulation from unstimulated neutrophils (P < 0.001). In contrast, the pure nitric oxide donor, 1,2,3,4-oxatriazolium 5-amino chloride (GEA-3162), increased stimulated IL-8 accumulation (P < 0.01) and also increased IL-8 accumulation in unstimulated cells (P < 0.002). Nitric oxide and superoxide have profound effects on IL-8. These results have important implications for the treatment of patients with acute lung injury with inhaled nitric oxide.

Combination oral antioxidant supplementation reduces blood pressure

1. Hypertension affects 30% of adults and low intakes of antioxidants have been associated with increased risk of hypertension and cardiovascular disease. To investigate the effect of short-term high-dose antioxidant supplementation on blood pressure in hypertensive and normotensive outpatients, we undertook a randomized, double-blind, crossover design placebo-controlled study. 2. Forty subjects were recruited from medical outpatient clinics, of whom 38 completed the study. Twenty-one were attending for treatment of hypertension and 17 were normotensive, attending for minor gastrointestinal complaints. Subjects were randomly assigned to receive either 8 weeks placebo followed by 2 weeks washout then 8 weeks antioxidants or vice versa. The combination of antioxidants consisted of 200 mg of zinc sulphate, 500 mg of ascorbic acid, 600 mg of alpha-tocopherol (sodium succinate salt) and 30 mg of beta-carotene daily. 3. Systolic blood pressure fell at the end of the antioxidant phase compared with the placebo phase both in subjects receiving anti-hypertensive therapy (P < 0.01) and those who were normotensive (P = 0.067). Circulating levels of beta-carotene and alpha-tocopherol increased in all subjects during supplementation (P < 0.01) and urine nitrite increased in hypertensive patients (P < 0.05). 4. Short-term oral high-dose combination antioxidant therapy reduces blood pressure, possibly via increased availability of nitric oxide. This study may have implications for the innovative use of antioxidants as an adjunct to anti-hypertensive therapy.

The effects of intravenous antioxidants in patients with septic shock

Oxidative stress is implicated in septic shock. We investigated the effect of intravenous antioxidant therapy on antioxidant status, lipid peroxidation, hemodynamics and nitrite in patients with septic shock. Thirty patients randomly received either antioxidants (n-acetylcysteine 150 mg/kg for 30 min then 20 mg/kg/h plus bolus doses of 1 g ascorbic acid and 400 mg alpha-tocopherol) or 5% dextrose. Basal vitamin C was low and redox-reactive iron was elevated in all patients. In the 16 patients receiving antioxidants, vitamin C increased (p = .0002) but total antioxidant capacity was unaffected. Lipid peroxides were elevated in all patients but did not increase further in the patients receiving antioxidants. Plasma total nitrite also increased (p = .007) in the antioxidant group. Heart rate increased in patients receiving antioxidants at 60 min (p = .018) and 120 min (p = .004). Cardiac index also increased at 60 min (p = .007) and 120 min (p = .05). Systemic vascular resistance index decreased at 120 min in the antioxidant treated patients (p = .003). The effect of antioxidants on hemodynamic variables has not previously been reported. Antioxidant administration may be a useful adjunct to conventional approaches in the management of septic shock.

Xanthine oxidase activity and free radical generation in patients with sepsis syndrome

OBJECTIVE

To determine xanthine oxidase activity, free radical concentrations, and lipid peroxidation in patients with sepsis syndrome compared with noninfected critically ill patients.

DESIGN

A prospective observational study.

SETTING

A nine-bed intensive care unit in a university teaching hospital trust.

PATIENTS

Fourteen consecutive patients who met the established criteria for sepsis syndrome with multiple organ dysfunction syndrome, and ten noninfected critically ill patients were studied.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Xanthine oxidase activity was increased in septic patients compared with both healthy volunteers (p < .01) and noninfected patients (p < .05), and was highest in the six patients who survived (p < .05). Lipid peroxides were increased in both septic patients (p < .001) and nonseptic controls (p < .001). Xanthine oxidase activity did not relate to the Acute Physiology and Chronic Health Evaluation (APACHE) II score or to the presence of organ dysfunction. The mean ascorbyl radical concentration (arbitrary units) determined by electron paramagnetic resonance following spin trapping was increased in patients compared with healthy subjects (p < .05).

CONCLUSIONS

Patients with sepsis have xanthine oxidase activation, high free-radical concentrations, and evidence of free radical damage. The finding that xanthine oxidase activity was lower in those patients who died, coupled with increased lactate concentrations implies more severe ischemia with incomplete reperfusion resulting in less xanthine oxidase "wash out" into the circulation. Increased ascorbyl radical concentrations may be due to an increased radical generation and oxidant scavenging, but appears to be unrelated to xanthine oxidase activity within the circulation.

Brain nitric oxide synthase activity is decreased by intravenous anesthetics

Nitric oxide is produced from L-arginine in a variety of cells, and in neuronal tissue, by the action of nitric oxide synthase. Inhibitors to nitric oxide synthase reduce the threshold for anesthesia and anesthetics reduce nitric oxide synthase activity in neutrophils. We investigated the effect of four intravenous anesthetics and an anticonvulsant on rat brain nitric oxide synthase activity using the stoichiometric conversion of oxyhemoglobin to methemoglobin by nitric oxide. Enzyme activity was assayed in the presence of 0, 0.01, 0.1, and 1.00 microM thiopental, ketamine, etomidate, midazolam, and phenytoin. Thiopental (P = 0.001), ketamine (P = 0.0002), midazolam (P = 0.0024), and etomidate (P = 0.0006) caused a decrease in nitric oxide synthase activity. Phenytoin had no effect on enzyme activity. We conclude that the intravenous anesthetics, but not the nonsedative anticonvulsant tested, have a significant effect on neuronal nitric oxide synthase activity.