The acute splanchnic and peripheral tissue metabolic response to endotoxin in humans

Evaluation of hepatosplanchnic circulation and intestinal oxygenation in dogs with a condition that mimicked septic shock induced by continuous infusion of a low dose of lipopolysaccharide

OBJECTIVE

To determine whether continuous infusion of a low dose of lipopolysaccharide (LPS) to induce a condition mimicking septic shock in dogs would affect systemic and hepatosplanchnic circulation and oxygenation.

ANIMALS

12 healthy adult Beagles.

PROCEDURE

Dogs received a low dose of LPS (Escherichia coli O55:B5) by continuous IV infusion at a rate of 1 microg/kg/h for 8 hours. Systemic hemodynamics; systemic oxygenation; blood flow in the cranial mesenteric artery, common hepatic artery, and portal vein; intestinal and hepatic tissue blood flow; mesenteric oxygenation; and intramucosal Pco2 were examined before and at selected time points after onset of the LPS infusion.

RESULTS

After onset of the LPS infusion, cardiac index increased and mean arterial pressure (MAP) and systemic vascular resistance decreased, which is characteristic of the hyperdynamic state in septic patients. Hepatosplanchnic blood flow increased during the hyperdynamic state. Intestinal Pco2 was increased even when blood flows increased. During the latter half of the experimental period, MAP was maintained but hepatosplanchnic blood flows decreased and intestinal Pco2 increased further.

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of the results suggested that hepatosplanchnic blood flow enters the hyperdynamic state during the early stages of sepsis and that intestinal tissue oxygenation is threatened even when hepatosplanchnic blood flow is increased or maintained. Hence, improvement of hepatosplanchnic circulation and intestinal tissue oxygenation is important in dogs with clinical evidence of a septic condition.

Genomic and proteomic determinants of outcome in patients undergoing thoracoabdominal aortic aneurysm repair

Thoracoabdominal aortic aneurysm repair, with its requisite intraoperative mesenteric ischemia-reperfusion, often results in the development of systemic inflammatory response syndrome, multiorgan dysfunction syndrome (MODS), and death. In the present study, an adverse clinical outcome following thoracoabdominal aortic aneurysm repair was identified by blood leukocyte genomic and plasma proteomic responses. Time-dependent changes in the expression of 146 genes from blood leukocytes were observed (p < 0.001). Expression of 138 genes (p < 0.001) and the concentration of seven plasma proteins discriminated between patients who developed MODS and those who did not, and many of these differences were evident even before surgery. These findings suggest that changes in blood leukocyte gene expression and plasma protein concentrations can illuminate pathophysiological processes that are subsequently associated with the clinical sequelae of systemic inflammatory response syndrome and MODS. These changes in gene expression and plasma protein concentrations are often observed before surgery, consistent with either a genetic predisposition or pre-existing inflammatory state.

Hypoxic suppression of E. coli-induced NF-κB and AP-1 transactivation by oxyradical signaling

Transactivation of the DNA-binding proteins nuclear factor-κB (NF-κB) and activator protein (AP)-1 by de novo oxyradical generation is a stereotypic redox-sensitive process during hypoxic stress of the liver. Systemic trauma is associated with splanchnic hypoxia-reoxygenation (H/R) followed by intraportal gram-negative bacteremia, which collectively have been implicated in posttraumatic liver dysfunction and multiple organ damage. We hypothesized that hypoxic stress of the liver before stimulation by Escherichia coli serotype O55:B5 (EC) amplifies oxyradical-mediated transactivation of NF-κB and AP-1 as well as cytokine production compared with noninfectious H/R or gram-negative sepsis without prior hypoxia. Livers from Sprague-Dawley rats underwent perfusion for 180 min with or without 0.5 h of hypoxia (perfusate Po2, 40 ± 5 mmHg) followed by reoxygenation and infection with 109 EC or 0.9% NaCl infusion. In H/R + EC livers, nuclear translocation of NF-κB and AP-1 was unexpectedly reduced in gel shift assays vs. normoxic EC controls, as were perfusate TNF-α and IL-1β levels. Preceding hypoxic stress paradoxically increased postbacteremic reduced-to-oxidized glutathione ratios plus nuclear localization of IκBα and phospho-IκBα, but not JunB/FosB profiles. Notably, xanthine oxidase inhibition increased transactivation as well as cytokine production in H/R + EC livers. Thus brief hypoxic stress of the liver before intraportal gram-negative bacteremia potently suppresses activation of canonical redox-sensitive transcription factors and production of inflammatory cytokines by mechanisms including xanthine oxidase-induced oxyradicals functioning in an anti-inflammatory signaling role. These results suggest a novel multifunctionality of oxyradicals in decoupling hepatic transcriptional activity and cytokine biosynthesis early in the posttraumatic milieu.

Glutamine decreases lipopolysaccharide-induced intestinal inflammation in infant rats

Using a gastrostomy-fed (GF) rat infant "pup-in-a-cup" model, the effects of protein deprivation and supplemental glutamine (Gln) and glutamate (Glu) were examined to test the hypothesis that Gln decreases the proinflammatory response induced by LPS in the developing infant rat small intestine. Four groups of 6- to 7-day-old pups were fed a rat milk substitute (RMS), one providing 100% and three providing 25% of normal protein intake for another 6 days. Two of the 25% protein-fed groups received supplemental Gln or Glu. GF and LPS treatment blunted body growth and intestinal villus height and increased intestinal cytokine-induced neutrophil chemoattractant (CINC) mRNA in the protein-deprived, non-Gln-treated group compared with mother-fed pups (P < 0.05). Gln blunted intestinal CINC mRNA (P < 0.05), but Glu did not. Intestinal CINC peptide in the LPS-treated pups provided 100 and 25% protein was elevated approximately 13-fold compared with the mother-reared pups (P < 0.001). Gln and Glu decreased intestinal CINC peptide by 73 and 80%, respectively. GF, LPS-treated pups also had a higher level of plasma CINC peptide (P < 0.05). Gln but not Glu decreased plasma CINC peptide (P < 0.05). An approximate sixfold elevation of intestinal MPO activity in the GF, LPS-treated rats was decreased by Gln and Glu by 92% (P < 0.001) and 54% (P < 0.05), respectively. Intestinal and plasma TNF-alpha were increased in GF, LPS-treated pups (P < 0.01), and Gln and Glu both blunted this increase (P < 0.05) in the intestine but not in the plasma. The results indicate that Gln decreases the LPS-induced inflammatory response in infant rat intestine under different conditions of protein intake.

Acute effect of drinking red and white wines on circulating levels of inflammation-sensitive molecules in men with coronary artery disease

There is evidence that moderate consumption of red wine with its high content of polyphenolic antioxidants may be more protective than white wine against development of coronary artery disease (CAD). The aim of this study was to compare the acute effects of ingestion of red wine and white wine on markers of inflammation in men with CAD. Thirteen men with angiographically-proven CAD were studied in a cross-over trial. The men consumed 4 mL/kg (2 to 3 glasses) red wine and white wine in random order during a light meal and with at least a week between interventions. Later, the men also consumed an isoenergetic nonalcoholic beverage (control) in the same study protocol. Venous blood was taken at baseline, 1 hour, and 6 hours after the drinks. Plasma interleukin-6 (IL-6), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), blood alcohol, plasma lipids, and plasma polyphenols were measured. Mean +/- SD blood alcohol was 6.5 +/- 2.2 mmol/L and 6.9 +/- 1.1 mmol/L at 1 hour and returned to baseline at 6 hours after intake of red wine and white wine, respectively. Plasma IL-6 concentration increased significantly (P =.01) during 6 hours after ingestion of red wine (56%) and white wine (63%). The increase in plasma IL-6 concentration after ingestion of wine was significantly higher (P =.045) compared with the corresponding increase (11%) following intake of the nonalcoholic beverage. Plasma IL-6 levels at 6 hours (r =.631, P =.02) were correlated significantly with plasma alcohol levels at 1 hour after ingestion of red wine. These data suggest that moderate wine intake may acutely increase plasma levels of IL-6 in men with CAD. It is possible that this increase in plasma IL-6 is a response to alcohol-induced oxidative stress in the liver.

Continuous Therapeutic Epinephrine but not Norepinephrine Prolongs Splanchnic IL-6 Production in Porcine Endotoxic Shock

Catecholamines play a central role in the treatment of sepsis-associated hypotension. However, these hormones have also been shown to modulate the lipopolysaccharide (LPS)-induced induction of cytokines such as tumor necrosis factor alpha, interleukin (IL)-10, and IL-6 in vitro and in human endotoxemia. We hypothesized that catecholamines applied therapeutically in septic shock also influence cytokine patterns. We studied the cytokine response in tissues of the splanchnic compartment in a porcine endotoxin shock model up to 4 h. Shock was induced by a short infusion of LPS, and animals were treated either with fluid resuscitation alone or in combination with continuous epinephrine or norepinephrine. Animals, receiving epinephrine therapy, showed a significantly prolonged upregulation of IL-6 mRNA expression at 4 h after LPS application in liver (P = 0.0014), spleen (P < 0.0001), and mesenteric lymph nodes (P = 0.0078) as compared with animals treated with norepinephrine or fluid resuscitation. Serum IL-6 increased over time in all groups. The total concentration of the cytokine (area under the curve) was significantly higher in the epinephrine group as compared with the norepinephrine and fluid resuscitation groups (P = 0.017). The peak of serum tumor necrosis factor alpha at 1 h after LPS application was already significantly reduced by epinephrine, which was only administered at a mean of less than 0.05 microg/kg/min at this time point (P < 0.01). None of the catecholamines had a significant effect on IL-10 serum levels when compared with animals receiving fluid resuscitation alone. Our data suggest that the therapeutic application of epinephrine but not of norepinephrine is associated with a profound effect on the IL-6 response of splanchnic reticuloendothelial tissues.

Molecular characterization of the acute inflammatory response to infections with gram-negative versus gram-positive bacteria

Sepsis caused by gram-negative bacteria and that caused by gram-positive bacteria often manifest similar clinical features. We investigated plasma proinflammatory cytokine profiles in patients with sepsis due to gram-positive and gram-negative bacteria and studied the cytokine production and differential gene regulation of leukocytes stimulated ex vivo with Escherichia coli lipopolysaccharide or heat-killed Staphylococcus aureus. Concentrations of tumor necrosis factor alpha, interleukin 1 receptor antagonist (IL-1Ra), IL-8, IL-10, IL-18 binding protein, procalcitonin, and protein C in plasma did not differ between patients with sepsis due to gram-negative and gram-positive bacteria. However, plasma IL-1beta, IL-6, and IL-18 concentrations were significantly higher in patients with sepsis due to gram-positive bacteria. Ex vivo stimulation of whole blood with heat-killed S. aureus markedly increased IL-1beta and IL-18 levels more than E. coli lipopolysaccharide stimulation. Microarray analysis revealed at least 359 cross-validated probe sets (genes) significant at the P < 0.001 level whose expression discriminated among gram-negative-organism-stimulated, gram-positive-organism-stimulated, and unstimulated whole-blood leukocytes. The host inflammatory responses to gram-negative and gram-positive stimuli share some common response elements but also exhibit distinct patterns of cytokine appearance and leukocyte gene expression.

Metabolic alterations in sepsis and vasoactive drug-related metabolic effects

The main clinical characteristics of sepsis and septic shock are derangements of cardiocirculatory and respiratory function. Additionally, profound alterations in metabolic pathways occur leading to hypermetabolism, enhanced energy expenditure, and insulin resistance. The clinical hallmarks are hyperglycemia, hyperlactatemia, and enhanced protein catabolism. These metabolic alterations are even more pronounced during sepsis as a result of cytokine release and subsequent induction of inflammatory pathways. Increased oxygen demands from mitochondrial oxygen utilization and oxygen consumption related to oxygen radical formation may contribute to hypermetabolism. In addition, mitochondrial dysfunction with impaired cellular respiration may be present. Mainstay therapeutic interventions for hemodynamic stabilization are adequate volume resuscitation and vasoactive agents, which, however, have additional impact on metabolic activity. Therefore, beyond hemodynamic effects, specific drug-related metabolic alterations need to be considered for optimal treatment during sepsis. This review gives an overview of the typical metabolic alterations during sepsis and septic shock and highlights the impact of vasoactive therapy on metabolism.

A single intravenous dose of endotoxin rapidly alters serum lipoproteins and lipid transfer proteins in normal volunteers

Endotoxemia is associated with rapid and marked declines in serum levels of LDL and HDL by unknown mechanisms. Six normal volunteers received a single, small intravenous (iv) dose of endotoxin (Escherichia coli 0113, 2 ng/kg) or saline in a random order, cross-over design. After endotoxin treatment, volunteers had mild, transient flu-like symptoms and markedly increased serum levels of tumor necrosis factor and its soluble receptors, interleukin-6, cortisol, serum amyloid A, and C-reactive protein. Triglyceride (TG), VLDL-TG, and nonesterified fatty acid increased (peak at 3-4 h), then TG declined (nadir at 9 h), and then cholesterol, LDL cholesterol, apolipoprotein B (apoB), and phospholipid declined (nadirs at 12-24 h). HDL cholesterol and apoA-I levels were not affected, but half of the decrease in phospholipid was HDL phospholipid. Lipopolysaccharide binding protein (LBP) rose 3-fold (peak at 12 h), with smaller and later decreases in the activities of phospholipid transfer protein and cholesteryl ester transfer protein. In conclusion, a decline in LDL was rapidly induced in normal volunteers with a single iv dose of endotoxin. The selective loss of phospholipid from HDL may have been mediated by LBP and, after more intense or prolonged inflammation, could result in increased HDL clearance and reduced HDL levels.

Gastrointestinal disorders of the critically ill. Shock liver

Shock liver describes a collecting pool of critically ill patients in whom the elevation of liver function tests or overt hepatic dysfunction is apparent. Different grades of shock liver affect about 50% of all intensive-care patients, varying from a mild elevation of serum aminotransferase and bilirubin levels in septic patients to an acute onset of high serum aminotransferases after haemodynamic shock. Abnormalities can subside within days or progressively deteriorate when persistent hepatic microcirculatory failure is present. Although hepatic injury in critically ill patients influences mortality rates it is underdiagnosed. The underlying pathophysiology involves changes in the portal and arterial blood supply as well as in microcirculation. Cross-talk between hepatocytes, Kupffer cells and endothelial cells, leading to an inflammatory response mediated primarily by tumour necrosis factor-alpha (TNF-alpha), is central to shock liver. The liver is a victim of shock inducers, and can also be the orchestrator of the inflammatory response syndrome (IRS). Hepatic injury by TNF-alpha is modulated by the prevalent pro-inflammatory or anti-inflammatory mediator profile elaborated by Kupffer cells. Kupffer cells additionally participate in the clearance of endotoxin, bacteria and inflammatory mediators and are thereby capable of preventing IRS. The hepatocyte undergoes dramatic alterations in synthetic activity, biliary transport, bile flow and glucose metabolism. Although standard determinations of aminotransferases, coagulation studies, glucose, lactate and bilirubin can detect hepatic injury they only partially reflect the cellular mechanisms driving shock liver. The management of shock liver is focused on the prevention of precipitating causes by controlling sepsis, circulation parameters and metabolism in addition to the cautious monitoring of therapeutic measures that can increase hepatic injury, which include intravenous nutrition, mechanical ventilation and catecholamine administration.

Intermittent flow increases endotoxin-induced adhesion of human erythrocytes to vascular endothelial cells

OBJECTIVE

To investigate the effects of different conditions of flow on endotoxin induced adhesion of human red blood cells (RBC) to human umbilical vein endothelial cells (HUVEC).

DESIGN AND SETTING

Prospective, randomized, controlled in vitro study in a university-affiliated cell biology laboratory. SUBJECTS. Human erythrocytes, human vascular endothelial cells.

INTERVENTIONS

Superfusion of HUVEC monolayers with human erythrocytes incubated with either saline (CON) or endotoxin (ETX) with different flow pattern (basic flow rates of 0.65 or 1.3 ml/min; intermittent flow, IMF). The CON/0.6, CON/1.3, CON-IMF/1.3 ( n=7/group) groups served as control, and in test groups ETX/0.6, ETX/1.3, ETX-IMF/0.6, and ETX-IMF/1.3 ( n=7/group) both RBC and HUVECs were incubated with ETX and flow pattern and rates varied. In the IMF experiments flow rates of 0.65 and 1.3 ml/min were combined with stop-and-go flow pattern.

MEASUREMENTS AND RESULTS

At continuous flow of 0.65 ml/min erythrocyte adhesion was 61+/-5 cells/mm(2) in CON and 172+/-25 cells/mm(2) after ETX. When flow rate was increased to 1.3 ml/min, adhesion decreased to 27+/-4 cells/mm(2) in CON and 93+/-18 cells/mm(2) after ETX. IMF conditions had no effect on RBC adhesion of naive RBC but increased the number of adhesive erythrocytes after incubation with ETX both at 0.65 ml/min (287+/-33 cells/mm(2)) and at 1.3 ml/min (148+/-13 cells/mm(2)).

CONCLUSIONS

RBC adhesion to vascular endothelium is affected by rate and pattern of blood flow. Higher flow rates or shear forces reduce RBC adhesion while stop-and-go flow pattern favored adhesion of ETX-treated erythrocytes to HUVECs. These findings suggest that altered RBCs interact with altered flow patterns potentially contributing to the microcirculatory injury observed in sepsis.

Neonatal necrotizing enterocolitis: clinical considerations and pathogenetic concepts

Necrotizing enterocolitis (NEC), a disease affecting predominantly premature infants, is a leading cause of morbidity and mortality in neonatal intensive care units. Although several predisposing factors have been identified, such as prematurity, enteral feeding, and infection, its pathogenesis remains elusive. In the past 20 years, we have established several animal models of NEC in rats and found several endogenous mediators, especially platelet-activating factor (PAF), which may play a pivotal role in NEC. Injection of PAF induces intestinal necrosis, and PAF antagonists prevent the bowel injury induced by bacterial endotoxin, hypoxia, or challenge with tumor necrosis factor-a (TNF) plus endotoxin in adult rats. The same is true for lesions induced by hypoxia and enteral feeding in neonatal animals. Human patients with NEC show high levels of PAF and decreased plasma PAF-acetylhydrolase, the enzyme degrading PAF. The initial event in our experimental models of NEC is probably polymorphonuclear leukocyte (PMN) activation and adhesion to venules in the intestine, which initiates a local inflammatory reaction involving proinflammatory mediators including TNF, complement, prostaglandins, and leukotriene C4. Subsequent norepinephrine release and mesenteric vasoconstriction result in splanchnic ischemia and reperfusion. Bacterial products (e.g., endotoxin) enter the intestinal tissue during local mucosal barrier breakdown, and endotoxin synergizes with PAF to amplify the inflammation. Reactive oxygen species produced by the activated leukocytes and by intestinal epithelial xanthine oxidase may be the final pathway for tissue injury. Protective mechanisms include nitric oxide produced by the constitutive (mainly neuronal) nitric oxide synthase, and indigenous probiotics such as Bifidobacteria infantis. The former maintains intestinal perfusion and the integrity of the mucosal barrier, and the latter keep virulent bacteria in check. The development of tissue injury depends on the balance between injurious and protective mechanisms.

Effect of sepsis syndrome on neonatal oxygen consumption and energy expenditure

OBJECTIVE

To evaluate oxygen consumption (VO2), carbon dioxide production, and energy expenditure (EE) in full-term neonates with early-onset neonatal septicemia daily for 7 days beginning at the day of clinical diagnosis of sepsis.

METHODS

A total of 17 spontaneously breathing full-term neonates, 10 with clinical signs of sepsis and 7 healthy neonates (control group), were enrolled in the study. Age at first study day was 3 +/- 0.9 days in both groups. Sepsis syndrome was defined as a systemic response to a bacterial infection with clinical signs of infection, elevated values of interleukins 6 and 8 and C-reactive protein, and abnormal white blood cell count and positive blood cultures (9 group B streptococci, 1 Escherichia coli). Measurements of VO2 and carbon dioxide production were performed daily for 7 days by means of indirect calorimetry.

RESULTS

In the septic infants, VO2 and EE were increased by about 20% at days 1 to 3 and by 15% at day 4 when compared with the controls. From days 1 to 3, EE averaged 57 +/- 3 kcal/kg/d in the septic neonates and 47 +/- 2 kcal/kg/d in the controls. At day 4, EE was 55 +/- 2 and 47 +/- 2 kcal/kg/d, respectively. Energy intake was about the same in both groups, whereas weight gain during the 7 study days was significantly lower in the sick patients than in the control group (19 +/- 2 g/d vs 33 +/- 9 g/d and 5.4 +/- 0.5 g/kg/d vs 9.4 +/- 2.6 g/kg/d, respectively). Increased EE was associated with increased heart rate (126 +/- 4 vs 112 +/- 4 min(-1) at day 1) and respiratory rate (56 +/- 6 vs 40 +/- 4 min(-1) at day 1). There were no differences in rectal temperature (37.3 +/- 0.4 degrees C vs 37.4 +/- 0.2 degrees C), skin temperature (36.5 +/- 0.4 degrees C vs 36.6 +/- 0.3 degrees C), and oxygen saturation (96 +/- 3% vs 96 +/- 3%) between the 2 groups.

CONCLUSIONS

Neonates with sepsis syndrome have elevated VO2 and EE values that could explain impaired growth during the illness period and may make the infants vulnerable to insufficient calorie supply during the acute phase of septic disease.

Pro- and antiinflammatory cytokine production after radiofrequency ablation of unresectable hepatic tumors

BACKGROUND

Experience using radiofrequency ablation (RFA) for treating unresectable hepatic malignancies is expanding, with promising outcomes and fewer complications compared with cryotherapy.

STUDY DESIGN

This study examined systemic inflammatory responses after RFA as measured by the appearance of postoperative symptoms and cytokine production. Seventeen patients (11 men, 6 women) aged 40 to 85 years (mean 64.2 years) with unresectable primary and metastatic hepatic tumors underwent RFA. Mean liver volume treated with RFA was 35.3% +/- 3.6% (SEM) (median 36.8%). Plasma cytokines (tumor necrosis factor-alpha, interleukin [IL]-1beta, IL-1ra, IL-6, IL-8, IL-10, p55, and p75) were measured from anesthesia induction through 48 hours after RFA. Ex vivo whole-blood cytokine production was measured at baseline, 24 hours, and 48 hours after RFA.

RESULTS

Cytokine and cytokine-receptor production were not notably altered by RFA. Ex vivo whole-blood endotoxin stimulation indicated that intrinsic cellular immune function remained intact after treatment, although modest decreases in stimulated tumor necrosis factor alpha production were observed 24 to 48 hours after RFA. Variceal bleeding, hepatic failure, and death occurred in one patient 30 days after RFA. None of the remaining patients exhibited tachycardia or hypotension. Fevers (> or = 38.5 degrees C) developed in three patients during the first 48 hours postoperatively. There was no association between plasma cytokines and postoperative complications.

CONCLUSIONS

In contrast to previous reports using cryotherapy, systemic inflammatory responses as measured by increased cytokines were not observed after RFA. The cryotherapy-induced "cryoshock" phenomenon was not observed in patients undergoing RFA in our study. We conclude that RFA ablation is fundamentally different than cryotherapy and apparently does not stimulate Kupffer and other hepatic macrophages to produce proinflammatory cytokines.

Euglycemic hyperinsulinemia augments the cytokine and endocrine responses to endotoxin in humans

Type 2 diabetes is associated with biochemical evidence of low-grade inflammation, and experimental studies have suggested that both insulin and glucose affect inflammatory responses. To determine the effect of in vivo changes in glucose availability and plasma insulin concentrations in humans, we administered 20 U/kg Escherichia coli lipopolysaccharide (LPS) or saline (control) to 14 subjects during a euglycemic hyperinsulinemic clamp (n = 6) or an infusion of sterile saline (n = 8). Parallel in vitro studies on human whole blood were undertaken to determine whether there was a direct effect of glucose, insulin, and leptin on proinflammatory cytokine production. Infusion of glucose and insulin significantly amplified and/or prolonged the cardiovascular, plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and counterregulatory hormone responses to LPS, whereas the effects on fever, plasma norepinephrine concentrations, and oxygen consumption were unaffected. In vitro studies showed no modulation of LPS-stimulated IL-6 or TNF-alpha production by glucose, insulin, or leptin at physiologically relevant concentrations. Hyperinsulinemia indirectly enhances key components of the systemic inflammatory and stress responses in this human model of infection.

Nitric oxide in liver diseases: friend, foe, or just passerby?

Research on the free radical gas, nitric oxide (NO), during the past twenty years is one of the most rapid growing areas in biology. NO seems to play a part in almost every organ and tissue. However, there is considerable controversy and confusion in understanding its role. The liver is one organ that is clearly influenced by NO. Acute versus chronic exposure to NO has been associated with distinct patterns of liver disease. In this paper we review and discuss the involvement of NO in various liver diseases collated from observations by various researchers. Overall, the important factors in determining the beneficial versus harmful effects of NO are the amount, duration, and site of NO production. A low dose of NO serves to maximize blood perfusion, prevent platelet aggregation and thrombosis, and neutralize toxic oxygen radicals in the liver during acute sepsis and reperfusion events. NO also demonstrates antimicrobial and antiapoptosis properties during acute hepatitis infection and other inflammatory processes. However, in the setting of chronic liver inflammation, when a large sustained amount of NO is present, NO might become genotoxic and lead to the development of liver cancer. Additionally, during prolonged ischemia, high levels of NO may have cytotoxic effects leading to severe liver injury. In view of the various possible roles that NO plays, the pharmacologic modulation of NO synthesis is promising in the future treatment of liver diseases, especially with the emergence of selective NO synthase inhibitors and cell-specific NO donors.

Accelerated recovery after endotoxic challenge in heat shock-pretreated mice

The inflammatory response induced by bacterial lipopolysaccharide (LPS) has profound metabolic and physiological effects. Thus hepatic glucose production is depressed after LPS administration, which is, at least in part, due to the downregulation of phosphoenolpyruvate carboxykinase (PEPCK) expression. PEPCK is a key regulatory enzyme of the gluconeogenic pathway. Expression of heat shock proteins (hsps) is a well-conserved response to stress correlated with protection from subsequent insults including inflammation. In this study, the expression of PEPCK was observed to be preserved after injection of LPS in heat shock-pretreated mice. Protection of PEPCK expression was limited to the time after heat shock treatment that displayed hsp70. Comparison of the transcription rate and mRNA levels of PEPCK after LPS injection between mice that were heat shock pretreated or not indicated that the preservation of PEPCK expression was not due to initial protection from the LPS challenge. On the contrary, it was mediated by a rapid recovery after the LPS insult at the level of transcription. These observations suggest that the mechanism of heat shock-mediated protection (stress tolerance) after LPS challenge is due to an increase in the capacity of the organism to recover rather than deterrence from the insult.

Clinical review: splanchnic ischaemia

Inadequate splanchnic perfusion is associated with increased morbidity and mortality, particularly if liver dysfunction coexists. Heart failure, increased intra-abdominal pressure, haemodialysis and the presence of obstructive sleep apnoea are among the multiple clinical conditions that are associated with impaired splanchnic perfusion in critically ill patients. Total liver blood flow is believed to be relatively protected when gut blood flow decreases, because hepatic arterial flow increases when portal venous flow decreases (the hepatic arterial buffer response [HABR]). However, there is evidence that the HABR is diminished or even abolished during endotoxaemia and when gut blood flow becomes very low. Unfortunately, no drugs are yet available that increase total hepato-splanchnic blood flow selectively and to a clinically relevant extent. The present review discusses old and new concepts of splanchnic vasoregulation from both experimental and clinical viewpoints. Recently published trials in this field are discussed.

Hepatic response to sepsis: interaction between coagulation and inflammatory processes

OBJECTIVES

a) To review the hepatic response to sepsis and to establish how this response contributes to coagulation and inflammatory processes; b) to review the physiologic and biochemical mechanisms that suggest hepatic dysfunction may occur during sepsis, enhance procoagulant and proinflammatory activities, and participate in the potential evolution to multiple organ dysfunction syndrome.

DATA SOURCES

A summary of published medical literature from MEDLINE search files and published reviews on liver function in experimental and human sepsis.

DATA SUMMARY

In sepsis, the liver plays a major role in host defense mechanisms. Kupffer cells are responsible for bacterial scavenging, bacterial products inactivation, and inflammatory mediators clearance and production. Hepatocytes, via receptors for many proinflammatory cytokines, modify their metabolic pathway toward gluconeogenesis, amino-acid uptake, and increased synthesis of coagulant and complement factors and protease inhibitors. The acute-phase protein (APP) response also contributes to the procoagulant state, especially by enhancing the inhibition of protein C (alpha1-antitrypsin and alpha2-macroglobulin) and by decreasing liver synthesis of protein C and antithrombin (negative APPs). Elevated C-reactive protein levels (positive APPs) promote the expression of tissue factor by mononuclear cells. Increased liver production of thrombin-activatable fibrinolytic inhibitor (positive APPs) enhances fibrinolysis inhibition. Conversely, such hepatic inflammatory and coagulation processes in sepsis may alter the function of this organ. Indeed, the liver can be injured by activated Kupffer cells that release chemokines, attract blood neutrophils into the liver, and activate them. Neutrophils up-regulate their surface adhesion molecules, tissue factor, and Kupffer cells, whereas tissue factor pathway inhibitor and thrombomodulin are almost undetectable in endothelial cells. This may lead to microcirculatory disturbances, fibrin deposition, hepatocyte injury, endotoxin and bacteria spillover, and multiple organ failure.

CONCLUSIONS

In sepsis, the liver participates in host defense and tissue repair through hepatic cell cross-talk that controls most of the coagulation and inflammatory processes. When this control is not adequate, a secondary hepatic dysfunction may occur and may sometimes lead to bacterial products spillover, enhanced procoagulant and inflammatory processes, and in turn, multiple organ failure and death.

A role for parathyroid hormone-related protein in the pathogenesis of inflammatory/autoimmune diseases

Our increased understanding of the critical role of cytokines in chronic inflammatory/autoimmune diseases has led to the recent development of effective anti-cytokine treatments. In particular, agents blocking the function of TNF-alpha, a cytokine first identified as an endotoxin-inducible mediator of tumor cell necrosis, are now licensed for the treatment of rheumatoid arthritis (RA) and inflammatory bowel disease. However, TNF-alpha is but one member of a cytokine network that is responsible for mediating these inflammatory disorders. Therefore, as our understanding of the pathophysiologic role of other members of this inflammatory network increases, other cytokines may similarly be identified as effective targets for treatment. In this article, we will review evidence which suggests that parathyroid hormone-related protein (PTHrP), a peptide which, like TNF-alpha, was first identified because of its effects in the setting of malignancy, may in fact serve an important non-neoplastic, physiologic function by mediating the inflammatory/autoimmune host response. Data identifying PTHrP as a member of the cytokine network induced in multi-organ inflammation and rheumatoid arthritis will be summarized, initial evidence comparing the therapeutic efficacy of PTHrP- vs. TNF-alpha-blockade in the treatment of endotoxemia will be reviewed, and potential future areas of research, including assessment of the effects of PTHrP blockade in the treatment of RA, will be discussed.

Osteonecrosis induced by a single administration of low-dose lipopolysaccharide in rabbits

We succeeded in developing a novel rabbit model of nonsteroid and nontraumatic osteonecrosis (ON) by use of a single- and low-dose lipopolysaccharide (LPS) injection. This model is simple and highly reproducible for the frequent development of multifocal and widespread ON lesions. Male adult Japanese white rabbits intravenously injected with a single injection of 10 microg/kg body weight of LPS were histopathologically examined in the early phase (3 [n = 3], 5 [n = 3], and 24 h [n = 3]) and at 4 weeks (n = 22). Seventy-seven percent of the rabbits developed multifocal ON 4 weeks after LPS injection. ON was also observed in the femoral and humeral condyle. The average percentage of necrotic area/total area examined was 86.7 +/- 29.1% and 78.8 +/- 16.7% in the proximal one third of both the femoral and humeral bones, respectively. Organized thrombi in the intraosseous small-sized arteries and arterioles were frequently seen in and around the necrotic tissues. In the early phase, LPS treatment prominently induced thrombocytopenia, hyperlipidemia, and increased plasma levels of plasminogen activator inhibitor-1 (PAI-1). The plasma level of PAI-1 was significantly higher in the rabbits with ON than in those without ON (p < 0.01). The immunohistochemical expression of tissue factor was exaggerated in monocytes/macrophages and adipocytes in both the femoral and humeral bones of the LPS-treated rabbits. Histologically, marrow necrosis and fibrin thrombi could be observed at 24 h. In addition, pretreatment with an anticoagulant, warfarin potassium, significantly decreased the incidence of LPS-induced ON (33%, n = 9, p < 0.05) associated with elongation of prothrombin time. The results of our study show that a single administration of low-dose lipopolysaccharide induces multifocal and widespread ON characterized by the pathophysiological participation of hypercoagulability in ON development. Therefore, this model would be useful for elucidating the pathogenesis of nonsteroid ON in humans especially inflammatory hypercoagulability-induced as well as for developing preventive and therapeutic strategies.

Carbohydrate ingestion attenuates the increase in plasma interleukin-6, but not skeletal muscle interleukin-6 mRNA, during exercise in humans

1. The present study was undertaken to examine the effects of exercise and carbohydrate (CHO) ingestion on interleukin-6 (IL-6) gene expression in skeletal muscle and plasma IL-6 concentration. 2. Seven moderately trained men completed 60 min of exercise at a workload corresponding to each individual's lactate threshold on four randomised occasions. Two trials were conducted on a bicycle ergometer (Cyc) and two on a running treadmill (Run) either with (CHO) or without (Con) the ingestion of a CHO beverage throughout the exercise. Muscle biopsies were obtained from the vastus lateralis before and immediately after exercise and IL-6 gene expression in these samples was determined using real-time PCR. In addition, venous blood samples were collected at rest, and after 30 min during and at the cessation of exercise. These samples were analysed for plasma IL-6. 3. Irrespective of exercise mode or CHO ingestion, exercise resulted in a 21 +/- 4-fold increase (P < 0.01; main exercise effect) in IL-6 mRNA expression. In contrast, while the mode of exercise did not affect the exercise-induced increase in plasma IL-6, CHO ingestion blunted (P < 0.01) this response. 4. These data demonstrate that CHO ingestion attenuates the plasma IL-6 concentration during both cycling and running exercise. However, because IL-6 mRNA expression was unaffected by CHO ingestion, it is likely that the ingestion of CHO during exercise attenuates IL-6 production by tissues other than skeletal muscle.

Liver-lung interactions following Escherichia coli bacteremic sepsis and secondary hepatic ischemia/reperfusion injury

We hypothesized that ischemia/reperfusion (I/R) injury of the liver during normotensive gram-negative bacteremic sepsis alters the kinetics of circulating endotoxin, tumor necrosis factor-alpha (TNF-alpha), and coinduced mediators, thereby exacerbating sepsis-induced lung inflammation. Liver and lung dysfunction were studied after hematogenous infection of Sprague-Dawley rats with 10(9) Escherichia coli serotype O55:B5 (EC) and 90 min of secondary hepatic ischemia in EC + I/R and saline-infused (normal saline NS) x I/R rats, followed by brief (1 h) or longer reperfusion (24 h). TNF- alpha:leukotriene interactions in this model were examined using the 5-lipoxygenase-activating protein inhibitor MK-886. Compared with sham-operated EC + Sham animals, peak serum endotoxin, TNF-alpha, alanine aminotransferase, interleukin-6 (IL-6), and hepatic neutrophil (PMN) influx were higher in EC + I/R rats through 24 h (p < 0.05) despite comparable arterial pressure. Lung PMN influx and wet/dry weight ratios were likewise enhanced in EC + I/R versus EC + Sham or NS + I/R rats. MK-886 attenuated TNF-alpha concentrations and ischemic liver injury but not mortality. Thus, focal hepatic I/R augments circulating endotoxin, TNF-alpha, and postbacteremic lung inflammation early after normotensive E. coli bacteremic sepsis.

The hepatosplanchnic area is not a common source of lactate in patients with severe sepsis

OBJECTIVE

To investigate the role of the splanchnic region in the hyperlactatemia of septic patients.

DESIGN

Prospective, observational study.

SETTING

Thirty-one-bed mixed medicosurgical intensive care unit.

PATIENTS

Ninety invasively monitored and mechanically ventilated patients with severe sepsis.

MEASUREMENTS AND MAIN RESULTS

Splanchnic lactate balance was measured in all patients. Splanchnic blood flow was determined by using the primed continuous indocyanine green infusion technique in 69 patients. In 71 patients, gastric mucosal Pco2 and the Pco2 gap (the difference between gastric and arterial Pco2) also were determined by using gas tonometry with an automated gas analyzer. In each patient, arterial, mixed-venous, and hepatic venous blood samples were obtained to determine hemoglobin oxygen saturations and lactate concentrations. Arterial and hepatic venous lactate concentrations were determined in triplicate and were averaged, and the arterial hepatic venous difference in lactate and lactate consumption were calculated. The splanchnic region produced lactate in only six of the 90 patients. Mean arterial pressure, cardiac index, arterial lactate, hepatic venous oxygen saturation, and catecholamine use were similar in the six patients with splanchnic lactate production and in the 84 others. The arterial hepatic venous differences in lactate and splanchnic lactate consumption were related directly to arterial lactate concentrations (y = 0.073x + 0.209, r(2) =.06, p <.05, and y = 0.06x + 0.183, r(2) =.08, p <.05, respectively) but were not related to Pco2 gap, to the gradient between mixed-venous and hepatic venous oxygen saturations, or to bilirubin concentrations.

CONCLUSIONS

Splanchnic lactate release is uncommon in septic patients, even when hyperlactatemia is severe.

Therapeutic Options for the Treatment of Impaired Gut Function

Abstract. Tissue hypoxia, especially in the splanchnic area, is still considered to be an important cofactor in the pathogenesis of multiple organ failure. Therefore, the specific effects of the various therapeutic interventions on splanchnic perfusion and oxygenation are of particular interest. Restoring and maintaining oxygen transport and tissue oxygenation is the most important step in the supportive treatment of patients with sepsis and impaired gut perfusion. Therefore, supportive treatment should be focused on an adequate volume resuscitation and appropriate use of vasoactive drugs. Adequate volume loading may be the most important step in the treatment of patients with septic shock. An elevated oxygen delivery may be beneficial in some patients, but the increase of oxygen delivery should be guided by the measurement of parameters assessing global and regional oxygenation. Forcing an elevation in oxygen delivery by the use of very high dosages of catecholamines can be harmful. Vasopressors should be used for achieving an adequate perfusion pressure. For norepinephrine, no negative effects on gut perfusion have been demonstrated. Epinephrine and dopamine should be avoided because they seem to redistribute blood flow away from the splanchnic region. There are no convincing data yet to support the routine use of low-dose dopamine or dopexamine to improve an impaired gut perfusion. There is even evidence that low-dose dopamine may reduce the mucosal perfusion in the gut in some patients. It has been suggested that dopexamine can improve splanchnic perfusion, but because these effects remain somewhat controversial, a general recommendation for dopexamine to improve gut perfusion is not justified.

Exposure to febrile temperature modifies endothelial cell response to tumor necrosis factor-alpha

Fever is an important regulator of inflammation that modifies expression and bioactivity of cytokines, including tumor necrosis factor (TNF)-alpha. Pulmonary vascular endothelium is an important target of TNF-alpha during the systemic inflammatory response. In this study, we analyzed the effect of a febrile range temperature (39.5 degrees C) on TNF-alpha-stimulated changes in endothelial barrier function, capacity for neutrophil binding and transendothelial migration (TEM), and cytokine secretion in human pulmonary artery endothelial cells (EC). Permeability for [(14)C]BSA tracer was increased by treatment with TNF-alpha, and this effect was augmented by incubating EC at 39.5 degrees C. Treating EC with 2. 5 U/ml TNF-alpha stimulated an increase in subsequent neutrophil adherence and TEM. Incubating EC at 39.5 degrees C caused a 30% increase in TEM but did not modify the enhancement of neutrophil adherence or TEM by TNF-alpha treatment. Analysis of cytokine expression in EC cultures exposed to TNF-alpha at either 37 degrees or 39.5 degrees C revealed three patterns of temperature and TNF-alpha responsiveness. Granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin (IL)-8 were not detectable in untreated EC but were increased after TNF-alpha exposure, and this increase was enhanced at 39.5 degrees C. IL-6 expression was also increased with TNF-alpha exposure, but IL-6 expression was lower in 39.5 degrees C EC cultures. Transforming growth factor-beta(1) was constitutively expressed, and its expression was not influenced either by TNF-alpha or exposure to 39.5 degrees C. These data demonstrate that clinically relevant shifts in body temperature might cause important changes in the effects of proinflammatory cytokines on the endothelium.

Brief hypoxic stress suppresses postbacteremic NF-kappaB activation and TNF-alpha bioactivity in perfused liver

Reductions in hepatic O(2) delivery are common early after gram-negative bacteremic sepsis owing to cardiopulmonary dysfunction and derangements in sinusoidal perfusion. Although gram-negative endotoxin and cellular hypoxia independently enhance activation of nuclear factor-kappaB (NF-kappaB) via generation of reactive O(2) species (ROS), the combination of these stimuli downregulates hepatic TNF-alpha gene expression. Here we tested the hypothesis that hypoxic suppression of postbacteremic TNF-alpha gene expression is transcriptionally mediated by reduced activation of NF-kappaB. Buffer-perfused rat livers (n = 52) were studied over 180 min after intraportal infection at t = 0 with 10(9) live Escherichia coli (EC), serotype O55:B5, or 0.9% NaCl controls under normoxic conditions, compared with 0.5 h of constant-flow hypoxia (PO(2) approximately 41 +/- 7 Torr) beginning at t = 30 min, followed by 120 min of reoxygenation. In parallel studies, tissue was obtained at peak hypoxia (t = 60 min). To determine the role of xanthine oxidase (XO)-induced ROS in modulating NF-kappaB activity after hypoxia/reoxygenation (H/R), livers were pretreated with the XO inhibitor allopurinol, with results confirmed in organs of tungstate-fed animals. Electrophoretic mobility shift assays were performed on nuclear extracts of whole liver lysates using (32)P-labeled oligonucleotides specific for NF-kappaB. Compared with normoxic EC controls, hypoxia reduced postbacteremic NF-kappaB nuclear translocation and TNF-alpha bioactivity, independent of reoxygenation, tissue levels of reduced glutathione, or posthypoxic O(2) consumption. XO inhibition reversed the hypoxic suppression of NF-kappaB nuclear translocation and ameliorated decreases in cell-associated TNF-alpha. Thus decreases in hepatic O(2) delivery reduce postbacteremic nuclear translocation of NF-kappaB and hepatic TNF-alpha biosynthesis by signaling mechanisms involving low-level generation of XO-mediated ROS.

Differential effects of hemorrhage and LPS on tissue TNF-alpha, IL-1 and associate neuro-hormonal and opioid alterations

LPS administration and hemorrhage are frequently used models for the in vivo study of the stress response. Both challenges stimulate cytokine production as well as activate opiate and neuro-endocrine pathways; which in turn modulate the inflammatory process. Differences in the magnitude and tissue specificity of the proinflammatory cytokine and neuro-hormonal responses to these stressors are not well established. We contrasted the tissue specificity and magnitude of the increase in circulating and tissue cytokine (TNF-alpha, IL-1alpha and IL-1beta) content in response to either fixed-pressure hemorrhage (approximately 40 mm Hg) followed by fluid resuscitation (HEM) or lipopolysaccharide (LPS; 100 microg/100 g BW) administration. LPS and HEM elevated circulating levels of TNF-alpha, while neither stress altered circulating IL-1-alpha and IL-beta. LPS-induced increases in TNF-alpha content were greater than those elicited by HEM in all tissues studied except for the lung, where both stressors produced similar increases. Tissue (lung, spleen and heart) content of IL-1alpha was increased by HEM but was not affected by LPS. Tissue (lung, spleen, and heart) content of IL-1beta was increased by LPS but was not affected by HEM. HEM produced greater increases than LPS in epinephrine (16- vs. 4-fold) and norepinephrine (4-fold vs. 60%) levels and similar elevations in beta-endorphin. LPS produced greater elevation in corticosterone levels (2-fold) than HEM (50%). These results suggest differential tissue cytokine modulation to HEM and LPS, both with respect to target tissue and cytokine type. The hormonal milieu to HEM is characterized by marked catecholaminergic and moderate glucocorticoid while that of LPS is characterized by marked glucocorticoid with moderate catecholaminergic influence.

Spontaneous high systemic oxygen delivery increases survival rate in awake sheep during sustained endotoxemia

OBJECTIVE

To study the natural evolution of systemic oxygen delivery (Do2) and oxygen consumption (Vo2) in sheep infused with low or high doses of endotoxin.

DESIGN

Prospective, controlled experimental study.

SETTING

Animal research laboratory at a medical university.

SUBJECTS

Twenty-nine chronically instrumented awake sheep (25-35 kg).

INTERVENTIONS

Awake animals were continuously infused with saline (n = 8) or two doses of Escherichia coli endotoxin (20 or 40 ng/kg/min; n = 21) for 72 hrs. No attempt was made to increase Do2, but respiratory failure was treated by mechanical ventilation and metabolic acidosis was corrected.

MEASUREMENTS AND MAIN RESULTS

The mortality rate was 25% in the group infused with the low dose and 89% in the group infused with the high dose of endotoxin. During the first 12 hrs of endotoxemia, both surviving (S group; n = 10) and nonsurviving (NS group; n = 11) sheep developed similar pulmonary hypertension, left ventricular failure, and hypotension with low systemic vascular resistance. However, S sheep had less interstitial lung edema (pulmonary lymph protein clearance at 8 hrs was 13+/-3 mL/hr vs. 27+/-6 mL/hr in the NS group and 4+/-1 mL/hr in the control group). During this early phase of endotoxemia, Do2, Vo2, and oxygen extraction ratio did not change significantly in any group. After this phase, animals that ultimately survived had a persistent hyperdynamic syndrome with high cardiac output and hypotension. In this group, the Do2 increase was greater than the Do2 measured in controls and remained steady up to 48 hrs after the start of the endotoxin infusion. Because systemic Vo2 did not change significantly, oxygen extraction ratio decreased progressively to values less than those measured in controls. In contrast, animals that ultimately died had a hypotensive and normokinetic syndrome associated with pulmonary hypertension, persistent depressed left ventricular function, hypothermia, and a progressive deterioration of gas exchange. Systemic Do2 was not significantly different from that in the control group. In contrast, Vo2 decreased progressively to values significantly lower than those measured in controls and remained low until death.

CONCLUSIONS

Our results indicate that in the absence of treatment such as fluid challenge or inotropic drugs in sheep infused with endotoxin, the occurrence of spontaneous hyperdynamic syndrome and high Do2 improves the survival rate.

Enhanced monocyte activation and hepatotoxicity in response to endotoxin in portal hypertension

BACKGROUND/AIMS

Septic shock is a systemic response to infection, and it causes a high mortality rate in cirrhotic patients. The mechanisms responsible for this susceptibility in cirrhosis are poorly understood. The aim of this study was to investigate whether monocyte activation and hepatic function are altered in portal hypertension after endotoxin administration.

METHODS

Portal-hypertensive and sham-operated rats were used. Plasma levels of tumor necrosis factor-alpha after lipopolysaccharide stimulation (both in vivo and in vitro) were measured by ELISA. CD11b/CD18 integrin expression on leukocyte membrane was measured by flow cytometry. Plasma transaminase activities were also determined.

RESULTS

The levels of tumor necrosis factor-alpha in plasma and the expression of CD11b/CD18 on leukocytes in portal-hypertensive rats was similar to that in sham-operated rats. Injection of 150 microg/kg of lipopolysaccharide produced a 9-fold increase in plasma levels of tumor necrosis factor-alpha in portal-hypertensive compared with sham-operated rats, together with a significant up-regulation of CD11b/CD18 expression on monocytes and an elevation in plasma transaminase activity. Blood leukocytes incubated in vitro with lipopolysaccharide (0.5 microg/ml) induced a hypersecretion of tumor necrosis factor-alpha in portal-hypertensive rats, as compared to sham-operated rats.

CONCLUSIONS

This study shows that monocytes from portal-hypertensive rats have an enhanced response to endotoxin, leading to hepatotoxicity.

Dose-dependent effects of recombinant human interleukin-6 on the pituitary-testicular axis

Inflammatory cytokines are soluble mediators of immune function that also regulate intermediate metabolism and several endocrine axes. To examine the effects of interleukin-6 (IL-6), the main circulating cytokine, on the hypothalamic-pituitary-testicular axis in men, we performed dose-response studies of recombinant human IL-6 (rHuIL-6) in normal volunteers. Increasing single doses of IL-6 (0.1, 0.3, 1.0, 3.0, and 10.0 microg/kg body weight) were injected subcutaneously into 15 healthy male volunteers (3 at each dose) in the morning. We measured the circulating levels of testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and sex hormone binding globulin (SHBG) at baseline and then at 24 h, 48 h, and 7 days after the IL-6 injection. LH and FSH levels were also measured half-hourly for the first 4 h after the IL-6 injection. All IL-6 doses were tolerated well and produced no significant adverse effects. Mean peak plasma IL-6 levels achieved after IL-6 administration were 8 +/- 1, 22 +/- 5, 65 +/- 22, 290 +/- 38, and 4050 +/- 149 pg/ml, respectively for the five doses. We observed no significant changes in plasma testosterone levels after the two smaller IL-6 doses. The three higher IL-6 doses, however, caused significant decreases in testosterone levels by 24 h, which persisted at 48 h and returned to baseline by 7 days. The higher testosterone suppression was after the 3.0 microg/kg dose, making the dose-response curve bell-shaped. There also appeared to be small but not significant increases in LH levels after the three higher IL-6 doses, which were not acute and seemed to follow temporally the testosterone decreases. The concurrent plasma levels of FSH and SHBG were not appreciably affected by any IL-6 dose. In conclusion, subcutaneous IL-6 administration, which caused acute elevations in circulating IL-6 levels of a similar magnitude to those observed in severe inflammatory and noninflammatory stress, induced prolonged suppression in testosterone levels in healthy men without apparent changes in gonadotropin levels. This suggests that IL-6 might induce persistent testicular resistance to LH action or suppression of Leydig cell steroidogenesis or both, with potential adverse effects on male reproductive function.

Evaluation of oxygen consumption and resting energy expenditure in critically ill patients with systemic inflammatory response syndrome

OBJECTIVE

To determine whether oxygen consumption VO2), CO2 production, and resting energy expenditure (REE) in critically ill patients differ in varying grades of systemic inflammatory response syndrome (SIRS).

DESIGN

Prospective, clinical study.

SETTING

Intensive care unit at a university hospital.

PATIENTS

Twenty-six critically ill patients requiring mechanical ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 100 metabolic measurements were performed. The grade of SIRS and the Acute Physiology and Chronic Health Evaluation II score were evaluated at the time of the metabolic cart study. VO2 and REE differed among the groups inadequate for SIRS (non-SIRS), with SIRS without infection (nonseptic SIRS), and with SIRS with infection (septic SIRS) (125 +/- 37 mL/min/m2 and 855 +/- 204 kcal/day/m2, 135 +/- 33 mL/min/m2 and 948 +/- 214 kcal/day/m2, and 166 +/- 55 mL/min/m2 and 1149 +/- 339 kcal/day/m2, respectively; p < .005). Patients with septic SIRS had higher VO2 and REE than patients with non-SIRS and nonseptic SIRS.

CONCLUSION

VO2 and REE differ among groups of patients with non-SIRS, nonseptic SIRS, and septic SIRS. Patients with septic SIRS have higher VO2 and REE than patients with non-SIRS or nonseptic SIRS. The present study shows that classifying patients into three grades (non-SIRS, nonseptic SIRS, and septic SIRS) is a valid predictor of metabolic stress in critically ill patients.

New insights into the biology of the acute phase response

Innate or natural immunity is a highly conserved defense mechanism against infection found in all multicellular organisms. The acute phase response is the set of immediate inflammatory responses initiated by pattern recognition molecules. These germ cell-encoded proteins recognize microbial pathogens based on shared molecular structures and induce host responses that localize the spread of infection and enhance systemic resistance to infection. Innate immunity also influences the initiation and type of adaptive immune response by regulating T cell costimulatory activity and antigen presentation by antigen presenting cells and by influencing mediator production, which affects lymphocyte function and trafficking. Acute phase protein concentrations rapidly increase after infection, and their production is controlled primarily by IL-6- and IL-1-type cytokines. The acute phase proteins provide enhanced protection against microorganisms and modify inflammatory responses by effects on cell trafficking and mediator release. For example, serum amyloid A has potent leukocyte activating functions including induction of chemotaxis, enhancement of leukocyte adhesion to endothelial cells, and increased phagocytosis. The constellation of inflammatory responses seen after endotoxin administration to humans represents an in vivo model of the acute phase response. Studies with inflammatory modifying agents, such as soluble dimeric TNF receptor and IL-10, show that these responses are not dependent on a single mediator but result from multiple overlapping inflammatory pathways. Understanding the factors that initiate and alter the magnitude and duration of the acute phase response represents an important step in the development of new therapies for infectious and inflammatory diseases.

Febrile-range temperature modifies early systemic tumor necrosis factor alpha expression in mice challenged with bacterial endotoxin

Fever improves survival in acute infections, but the effects of increased core temperature on host defenses are poorly understood. Tumor necrosis factor alpha (TNF-alpha) is an early activator of host defenses and a major endogenous pyrogen. TNF-alpha expression is essential for survival in bacterial infections but, if disregulated, can cause tissue injury. In this study, we show that passively increasing core temperature in mice from the basal (36.5 to 37.5 degrees C) to the febrile (39.5 to 40 degrees C) range modifies systemic TNF-alpha expression in response to bacterial endotoxin (lipopolysaccharide). The early TNF-alpha secretion rate is enhanced, but the duration of maximal TNF-alpha production is shortened. We identified Kupffer cells as the predominant source of the excess TNF-alpha production in the warmer animals. The enhanced early TNF-alpha production observed at the higher temperature in vivo could not be demonstrated in isolated Kupffer cells or in precision-cut liver slices in vitro, indicating the participation of indirect pathways. Therefore, expression of the endogenous pyrogen TNF-alpha is regulated by increments in core temperature during fever, generating an enhanced early, self-limited TNF-alpha pulse.

Elevated resting energy expenditure in adolescents with sickle cell anemia

OBJECTIVE

To assess the reliability of standard prediction equations in estimating resting energy expenditure (REE) values in adolescents with sickle cell anemia.

SUBJECTS/DESIGN

Body composition and metabolic measurements were performed in 8 adolescents, aged 11 to 18 years, with homozygous sickle cell anemia. REE was measured by indirect calorimetry under standard conditions, and measurements were compared with 4 prediction formulas (Harris-Benedict, Schofield, Mayo Clinic, and Food and Agriculture Organization/World Health Organization/United Nations University). Fat-free mass was measured to assess REE per unit of actively metabolizing tissue. Fat-free mass was expressed as a mean of values obtained by densitometry, deuterium dilution, 40K-counting, and total body electrical conductivity.

STATISTICAL ANALYSES

Repeated measures analysis of variance was performed to determine whether measured REE values and predicted values differed. The Fischer test was used to identify which predicted values differed significantly from the measured REE.

RESULTS

All 4 prediction formulas significantly underestimated REE. Group mean values for the prediction formulas ranged from 83% to 89% of the measured value. REE averaged 47.7 +/- 10.0 kcal/kg fat-free mass per day, which is 30% to 50% higher than reported values in healthy adolescent populations.

CONCLUSIONS

These data suggest that REE is elevated in adolescents with sickle cell anemia. Standard equations used to predict REE are unreliable in these patients.

APPLICATIONS

REE in patients with sickle cell anemia is best determined by indirect or direct measurement of energy expenditure. Clinically useful formulas to estimate REE should be developed for patients with conditions, including sickle cell anemia, where the metabolic rate may be altered.

The opiate sufentanil alters the inflammatory, endocrine, and metabolic responses to endotoxin in dogs

Sufentanil is a synthetic mu-opioid receptor agonist frequently used in anesthesia and critically ill patients. To evaluate the effects of sufentanil on the inflammatory, neuroendocrine, and metabolic responses to endotoxin, we studied six dogs during saline infusion (control), during sufentanil infusion (1.5 microg . kg-1 . h-1), after endotoxin injection (1.0 microg/kg iv), and during combined endotoxin and sufentanil administration. The rate of appearance of glucose was determined by infusion of [6,6-2H2]glucose. Sufentanil depressed the endotoxin-induced increase in body temperature (36.9 +/- 0.3 vs. 40.6 +/- 0.5 degrees C, P < 0.05). Sufentanil depressed the tumor necrosis factor (TNF) response to endotoxin by approximately 60% (P < 0.01) but increased the interleukin-6 (IL-6) response by approximately 70% (P < 0.01). Sufentanil per se induced a transient neuroendocrine activation. Sufentanil also increased plasma concentrations of insulin and catecholamines after endotoxin (P < 0.05 vs. endotoxin alone) and increased plasma glucose levels by approximately 36% (from 6.1 +/- 0.1 to 8.3 +/- 0.6 mmol/l, P < 0.05 vs. endotoxin alone). Endotoxin stimulated glucose production transiently by 95% (24.2 +/- 3.2 vs. control 12.4 +/- 1.0 micromol . kg-1 . min-1, P < 0.05). Paradoxically, sufentanil inhibited this endotoxin-induced stimulation of glucose production (P < 0.05 vs. endotoxin alone). In conclusion, sufentanil modulates the response to intravenous endotoxin by dissociating the TNF and IL-6 response, increasing insulin and catecholamine levels, and depressing the increase in glucose production. Therefore, opiates alter inflammatory, endocrine, and metabolic regulation in endotoxemia.

Chemical structure of lipid A isolated from Flavobacterium meningosepticum lipopolysaccharide

The chemical structure of the lipid A of the lipopolysaccharide component isolated from Flavobacterium meningosepticum IFO 12535 was elucidated. Methylation and nuclear magnetic resonance analyses showed that two kinds of hydrophilic backbone exist in the free lipid A: a beta (1-->6)-linked 2-amino-2-deoxy-D-glucose, which is usually present in enterobacterial lipid A's, and a 2-amino-6-O-(2, 3-diamino-2,3-dideoxy-beta-D-glucopyranosyl)-2-deoxy-D-glucose, in a molar ratio of 1.00:0.35. Both backbones were alpha-glycosidically phosphorylated in position 1, and the hydroxyl groups at positions 4, 4', and 6' were unsubstituted. Liquid secondary ion-mass spectrometry revealed a pseudomolecular ion at m/z 1673 [M-H]- as a major monophosphoryl lipid A component carrying five acyl groups. Fatty acid analysis showed that the lipid A contained 1 mol each of amide-linked (R)-3-OH iC17:0, ester-linked (R)-3-OH iC15:0, amide-linked (R)-3-O-(iC15:0)-iC17:0, and both amide- and ester-linked (R)-3-OH C16:0. Fatty acid distribution analyses using several mass spectrometry determinations demonstrated that the former two constituents were distributed on positions 2 and 3 of the reducing terminal unit of the backbones and that the latter two were attached to the 2' and 3' positions in the nonreducing terminal residue.

Effect of increased cardiac output on liver blood flow, oxygen exchange and metabolic rate during longterm endotoxin-induced shock in pigs

We investigated hepatic blood flow, O2 exchange and metabolism in porcine endotoxic shock (Control, n = 8; Endotoxin, n = 10) with administration of hydroxyethylstarch to maintain arterial pressure (MAP)>60 mmHg. Before and 12, 18 and 24 h after starting continuous i.v. endotoxin we measured portal venous and hepatic arterial blood flow, intracapillary haemoglobin O2 saturation (Hb-O2%) of the liver surface and arterial, portal and hepatic venous lactate, pyruvate, glycerol and alanine concentrations. Glucose production rate was derived from the plasma isotope enrichment during infusion of [6,6-2H2]-glucose. Despite a sustained 50% increase in cardiac output endotoxin caused a progressive, significant fall in MAP. Liver blood flow significantly increased, but endotoxin affected neither hepatic O2 delivery and uptake nor mean intracapillary Hb-O2% and Hb-O2% frequency distributions. Endotoxin nearly doubled endogenous glucose production rate while hepatic lactate, alanine and glycerol uptake rates progressively decreased significantly. The lactate uptake rate even became negative (P<0.05 vs Control). Endotoxin caused portal and hepatic venous pH to fall significantly concomitant with significantly increased arterial, portal and hepatic venous lactate/pyruvate ratios. During endotoxic shock increased cardiac output achieved by colloid infusion maintained elevated liver blood flow and thereby macro- and microcirculatory O2 supply. Glucose production rate nearly doubled with complete dissociation of hepatic uptake of glucogenic precursors and glucose release. Despite well-preserved capillary oxygenation increased lactate/pyruvate ratios reflecting impaired cytosolic redox state suggested deranged liver energy balance, possibly due to the O2 requirements of gluconeogenesis.

Nutritional modulation of cytokine biology

The pro-inflammatory cytokines and oxidant molecules produced during the inflammatory response, which follows infection and injury, may be beneficial, or detrimental to the patient, depending on the amounts and contexts in which they are produced. Aberrant or excessive production has been implicated in inflammatory disease, and sepsis. The upregulation of cytokine production by NF kappa B and NFIL-6 activation by oxidants increases the likelihood of cytokine-induced mortality and morbidity. Complex systems exist for the control of cytokine production and oxidant actions. The former include the hormones of the hypothalamo-pituitary-adrenal axis, acute phase proteins, and endogenous inhibitors of interleukin (IL)-1 and tumor necrosis factor (TNF). The latter include endogenously synthesized antioxidants, such as glutathione and dietary antioxidants, such as tocopherols, ascorbates and cachectins. Nutrients change cytokine production and potency by influencing tissue concentrations of many of the molecules involved in cytokine biology. Monounsaturated fatty acids and omega-3 polyunsaturated fatty acids (PUFAs) suppress TNF and IL-1 production and actions, while n-6 PUFAs exert the opposite effect. Changes in eicosanoid production are more likely to underlie this effect than alterations in membrane fluidity. Low antioxidant intake results in enhanced cytokine production and effects. The anorexia that follows infection and injury, may be purposeful to permit release of substrate from endogenous sources to support and control the inflammatory process. Therefore, prior as well as concurrent nutrient intake are of importance in determining the outcome of the inflammatory response.

Growth hormone and insulinlike growth factor 1 promote intestinal uptake and hepatic release of glutamine in sepsis

OBJECTIVE

To study the effects of growth hormone (GH) and insulinlike growth factor 1 (IGF-1) on whole body and gastrointestinal (GI), hepatic, femoral, and renal glutamine (GLN) uptake and release in septic piglets.

SUMMARY BACKGROUND DATA

The GI metabolism of GLN is impaired during sepsis, and this may contribute to a breakdown of the gut's mucosal barrier. GH treatment has produced increased GI GLN uptake in surgical stress. Little is known about the effects of GH and IGF-1 in sepsis.

METHODS

Twenty-four piglets were randomized to three groups of eight each: a GH group received a bolus of 16 IU of Genotropin; an IGF-1 group received a continuous infusion of 1.3 mg/hour of IGF-1; and a control group received saline. After surgical preparation, sepsis was induced with live Escherichia coli bacteria. Using isotope technique, whole body turnover and organ-specific absolute uptake and release were measured before and 4 hours after sepsis.

RESULTS

After sepsis, both GH and IGF-1 treatment increased GI GLN uptake compared with controls and induced hepatic release of GLN. GLN release from skeletal muscle was diminished in all groups after sepsis. Whole body GLN turnover was increased in the GH and IGF-1 groups compared with the controls, before and after sepsis.

CONCLUSIONS

GH and IGF-1 treatment induced increased GI net uptake of GLN. GH and IGF-1 treatment also promoted absolute and net release of GLN from the liver. This release might facilitate increased GI uptake despite reduced hindleg release in the early phase of sepsis.

Role of glutamine in immunologic responses

Glutamine has traditionally been thought of as a nonessential amino acid, but laboratory and clinical data suggests that it may be essential during certain inflammatory conditions, such as infection and injury. Glutamine is a necessary nutrient for cell proliferation, serves as a specific fuel for inflammatory cells and enterocytes, and, when present in appropriate concentrations, enhances cell function. During inflammatory states, glutamine consumption may outstrip endogenous production and a relative glutamine deficiency state may exist. Animal and clinical studies suggest that improved outcome may be possible by providing the appropriate dose of this nutrient by the appropriate route to achieve adequate tissue concentrations. Such an approach prevents patients from being exposed to some of the inadequacies of present day conventional nutrition. The overall benefit of providing an appropriate glutamine-supplemented diet to all metabolically compromised patients arises from the multiple anabolic and host protective effects of this amino acid, of which immunomodulation is only one important facet of glutamine's essential nature.

Immunonutrition: role of sulfur amino acids, related amino acids, and polyamines

Pro-inflammatory cytokines mediate widespread changes in protein metabolism. Amino acids released from peripheral tissues fulfill a number of functions. They act as substrate for acute phase protein and immunoglobulin synthesis and, together with polyamines, in the replication of immune cells. Demands for specific amino acids may outstrip the supply from endogenous sources. A number of strands of evidence suggest that sulphur amino acids, and amino acids that are metabolically related to them, may be required in increased amounts. Protein deficiency impairs the acute phase response. However, sulfur amino acid insufficiency compromises glutathione synthesis, to a greater extent than hepatic protein synthesis, in the presence and absence of an inflammatory stimulus. The resulting effect may be compromised antioxidant defences. Functioning of T cells is dependent on intracellular glutathione concentrations and may also be affected by sulphur amino acid insufficiency. It has been suggested that the increased N excretion, which occurs during the immune response, is a reflection of a relative imbalance in the profile of amino acids released from peripheral tissues and the requirements imposed by the synthesis of substances involved in the acute phase response. Phenylalanine, tyrosine, tryptophan serine, and cysteine are released in amounts closest to requirements. Polyamine synthesis may be important for the fidelity of the enhanced level DNA transcription and RNA translation that occurs in response to infection and during tissue repair, gut growth after surgery, and in gut barrier functions. Although synthesized de novo from ornithine, arginine and S-adenosyl methionine (SAM), substantial recycling is a key feature of polyamine metabolism. The recycling may be a reflection of the need to maintain adequate tissue SAM during periods of rapid cell growth. During an immune/inflammatory response the combination of enhanced utilization of cysteine for glutathione synthesis and cell replication may lead to depletion of cellular SAM. A relatively small addition of polyamines to the diet may improve gut-associated aspects of the hosts' antibacterial defenses.

Early Preferential Stimulation of γδ T Cells by TNF-α

Although recent findings indicate that γδ T cells influence both early innate and Ag-specific adaptive host responses, it has remained unclear what triggers γδ T cell reactivity. Investigating very early T cell activation in mouse and human models of bacterial infection, we measured CD69 expression as an indicator of early cellular activation. Both murine αβ and γδ T cells responded polyclonally to systemic bacterial infections, and to LPS. However, γδ T cells responded more strongly to the bacteria and to LPS. In vitro LPS-stimulated human T cells showed a similar differential response pattern. We identified TNF-α as mediator of the early differential T cell activation, and of differential proliferative responses. The stronger response of γδ T cells to TNF-α was correlated with higher inducible expression levels of TNF-Rp75. Among unstimulated splenocytes, more γδ T cells than αβ T cells expressed CD44 at high levels. The data suggest that TNF-Rp75 determines the differential T cell reactivity, and that most γδ T cells in the normal spleen are present in a presensitized state. As TNF-α stimulates activated T cells, it may early preferentially connect γδ T cell functions with those of cells that produce this cytokine, including activated innate effector cells and Ag-stimulated T lymphocytes.

Effect of MTP on TNF-alpha in perfused rat liver after bacteremia and ischemia/reperfusion

INTRODUCTION

Muramlytripeptide phosphatidylethanolamine (MTP) stimulates synthesis of cytokines by hepatic Kupffer cells. We have shown in a perfused rat liver model that secondary ischemia/reperfusion (I/R) downregulates tumor necrosis factor alpha (TNF-alpha) expression after Escherichia coli (EC) bacteremia. Here, we tested the hypothesis that pretreatment with MTP restores cytokine response after sequential bacteremia and I/R.

METHODS

Thirty-eight livers were studied in eight groups after intraportal injection of 10(9) live EC or normal saline (NS): (1) normoxic EC; (2) EC + I/R (ischemia began 30 min after EC followed by 2 h of reperfusion); (3) normoxic NS controls; and (4) NS + I/R. Four groups of rats received 300 micrograms of MTP i.v. 24 h prior to liver harvesting; (5) MTP + EC; (6) MTP + EC + I/R; (7) MTP + NS; and (8) MTP + NS + I/R. Bioactive and antigenic TNF-alpha, PGE2 and bacterial clearance were assessed.

RESULTS

MTP increased bioactive TNF-alpha response to EC (MTP + EC vs EC controls: 685 +/- 255 U/ml vs 250 +/- 180 U/ml, P < 0.02). I/R did not downregulate TNF-alpha in animals treated with MTP (MTP + NS vs MTP + NS +I/R, P = 0.83). Pretreatment with MTP restored TNF-alpha after I/R MTP + EC + I/R vs EC + I/R: 671 +/- 215 U/ml vs 27 +/- 14 U/ml, P < 0.001) to levels similar to those found in the MTP + EC group (MTP + EC + I/R vs MTP + EC: 671 +/- 215 U/ml vs 685 +/- 255 U/ml, P = 0.75). Finally, bacterial clearance was increased in groups which received MTP.

CONCLUSION

In vivo administration of MTP increases hepatic TNF-alpha response to intraportal EC bacteremia by a PGE2 independent mechanism. This response is maintained even after subsequent ischemia and reperfusion.