Endotoxemia and acute-phase proteins in major abdominal surgery

BACKGROUND: Translocation of endotoxin is a controversial issue. The ability of plasma to inactivate endotoxin is an indirect measure of endotoxemia. Endotoxin is a potent stimulator of the inflammatory response and affects the innate immune system. OBJECTIVE: To elucidate the kinetics of endotoxemia and the ability of plasma to inactivate endotoxin in patients with major abdominal operations. To demonstrate the early time course of the acute-phase proteins C-reactive protein (CRP), serum amyloid A (SAA), alpha(1)-antitrypsin, alpha(2)-macroglobulin, transferrin, and interleukin 6 (IL-6), and to correlate them with the amount of endotoxemia. METHODS: Twenty patients with elective major abdominal operation and 10 healthy controls were investigated. Blood was collected preoperatively, during the operation and regularly up to 12 days after surgery. Endotoxin was measured by Limulus amebocyte lysate test (LAL), the ability of plasma to inactivate endotoxin by modified LAL, the acute-phase proteins nephelometrically, and IL-6 by enzyme-linked immunosorbent assay (ELISA). RESULTS: Preoperative endotoxin plasma level (0.026 +/- 0.004 EU/mL) did not differ from healthy volunteers but increased during operation (0.09 +/- 0.02 EU/mL, P = 0.02). Endotoxemia peaked 1 hour after the surgical procedure (0.16 +/- 0.03 EU/mL; P <0.0001 versus preoperative) and decreased to almost normal values after 48 hours. The capability of plasma to inactivate endotoxin was significantly reduced during (recovery, 0.16 +/- 0.03 EU/mL), 1 hour (0.25 +/- 0.04 EU/mL) and 24 hours (0.16 +/- 0.02 EU/mL) after the operation compared with preoperative (0.068 +/- 0.01 EU/mL) values. Plasma IL-6 was significantly increased for 48 hours with a peak 1 hour after surgery (470 +/- 108 pg/mL). CRP peaked at 210 +/- 19 mg/L (P <0.0001 versus preoperative) 48 hours after operation and was significantly elevated for the rest of the observation period. SAA was significantly increased 24 hours after surgery (249 +/- 45 mg/L) and peaked additional 48 hours later (456 +/- 86 mg/L). alpha(1)-Antitrypsin, although a positive acute-phase protein, decreased initially to 1.38 +/- 0.1 g/L (preoperative, 2.33 +/- 0.18 g/L; P <0.0001) and increased thereafter until day 12 (3.05 +/- 0.35 g/L, P = 0.11 versus preoperative). The same was true for alpha(2)-macroglobulin (preoperative, 2.2 +/- 0.16 g/L; intraoperative, 1.36 +/- 0.13 g/L; day 5, 2.8 +/- 0.4 g/L). Transferrin decreased already during surgery (1.6 +/- 0.1 g/L versus preoperative 2.8 +/- 0.17 g/L, P <0.0001) and remained on this level for 5 days. Correlation analysis revealed a relationship between endotoxemia and the ability of plasma to inactivate endotoxin (r = 0.67, P <0.0001) and also a relation between intraoperative endotoxemia on one hand and alpha(2)-macroglobulin (-0.53 > r > -0.6, P <0.05) as well as alpha(1)-antitrypsin (0.64 > r >0.55, P <0.05) on the other. CONCLUSION: Major abdominal surgery is associated with transient endotoxemia and a transient reduced endotoxin inactivation capacity of the plasma. Endotoxemia correlates with the endotoxin inactivation capacity. The surgical procedure causes substantial changes in plasma concentrations of acute-phase proteins. alpha(2)-Macroglobulin and alpha(1)-antitrypsin correlate moderately with endotoxemia.     

Recombinant bactericidal/permeability-increasing protein attenuates the systemic inflammatory response syndrome in lower limb ischemia-reperfusion injury

OBJECTIVES: Hind limb ischemia-reperfusion (I/R) injury increases gut permeability, and resultant endotoxemia is associated with an amplified systemic inflammatory response syndrome leading to multiple organ dysfunction syndrome. We studied the potential role of recombinant bactericidal/permeability-increasing protein (rBPI(21) ), a novel antiendotoxin therapy, in modulating endotoxin-enhanced systemic inflammatory response syndrome in hind limb I/R injury. METHODS: In this prospective, randomized, controlled, experimental animal study, 48 male Wistar rats, weighing 300 to 350 g, were randomized to a control group (sham) and five groups undergoing 3 hours bilateral hind limb ischemia with 2 hours reperfusion (I/R) (n = 8 per group). The control and untreated I/R groups received thaumatin, a control-protein preparation, at 2 mg/kg. Treatment groups were administered rBPI(21) intravenously at 1, 2, or 4 mg/kg body weight at the beginning of reperfusion; an additional group was administered rBPI(21) intravenously at 2 mg/kg after 1 hour of reperfusion. Plasma interleukin-6 concentration was estimated by bioassay as a measure of systemic inflammation. Plasma endotoxin concentration was determined by use of an amebocyte lysate chromogenic assay. Crossreactive immunoglobulin G and M antibodies to the highly conserved inner core region of endotoxin were measured by use of an enzyme-linked immunosorbent assay. The lung tissue wet-to-dry weight ratio and myeloperoxidase concentration were used as markers of edema and neutrophil sequestration, respectively. RESULTS: I/R provoked highly significant elevation in plasma interleukin-6 concentrations (1351.20 pg/mL [860.16 - 1886.40 pg/mL]) compared with controls (125.32 pg/mL [87.76-157.52 pg/mL; P <.0001]), but treatment with rBPI(21) 2 mg/kg at onset of reperfusion (715.89 pg/mL [573.36-847.76 pg/mL]) significantly decreased interleukin-6 response compared with the nontreatment group ( P <.016). I/R increased plasma endotoxin concentrations significantly (21.52 pg/mL [6.20-48.23 pg/mL]), compared with control animals (0.90 pg/mL [0.00-2.30 pg/mL; P <.0001]), and treatment with rBPI(21) 4 mg/kg at reperfusion significantly decreased endotoxemia (1.30 pg/mL [1.20-2.20 pg/mL]), compared with the untreated group ( P <.001). The lung tissue myeloperoxidase level was significantly increased in the untreated I/R group (208.18% [128.79%-221.81%]), compared with in controls (62.00% [40.45%-80.92%; P <.0001]), and attenuated in those treated with rBPI(21) 2 mg/kg (129.54% [90.49%-145.78%; P <.05]). Data represent median and interquartile range, comparisons made with the nonparametric Mann-Whitney U test. CONCLUSIONS: These findings show that hind limb ischemia-reperfusion injury is associated with endotoxemia, elevations in plasma interleukin-6, and pulmonary leukosequestration. Treatment with rBPI(21) after ischemia reduces endotoxemia, the interleukin-6 response, and attenuates pulmonary leukosequestration in response to hind limb reperfusion injury.     

Effect of internal biliary drainage on plasma levels of endotoxin,cytokines, and C-reactive protein in patients with obstructive jaundice

Preoperative biliary drainage may improve the cytokine and acute-phase response derangements observed in patients with obstructive jaundice. We conducted a prospective longitudinal, before-after trial in our 600-bed teaching hospital. Twenty-four patients with obstructive jaundice were investigated, 11 with benign obstruction and 13 with malignant disease. Endoscopic internal biliary drainage was performed in all patients (7 by papillotomy and 17 by endoprostheses). Endotoxin, tumor necrosis factor alpha (TNF-a), interleukin-6 (IL-6), nitric oxide production, and C-reactive protein (CRP) were determined at admission and on days 2 and 7 after internal biliary drainage was accomplished. Bile cultures were obtained before and at the time of drainage. Endotoxin, IL-6, TNF-a, and CRP were significantly higher in patients with cancer. After internal drainage, endotoxin (11.4 vs. 2 EU/L; p <0.05), TNF-a (87.5 vs. 48 pg/ml; p = 0.03), and IL-6 (324 vs. 232 pg/ml; p <0.05) plasma levels decreased significantly in the early postdrainage period in patients with cancer. Endotoxin, cytokines, as well as the CRP plasma values, however, increased again on day 7 after drainage. This trend was less marked in patients with benign obstruction. Patients with positive bile cultures after drainage displayed higher levels of CRP (115 vs. 62 mg/L; p = 0.03), IL-6 (598 vs. 330 pg/ml; p = 0.04), and endotoxin (10.6 vs. 4.8 EU/L; p = 0.02) than those with negative bile cultures. Biliary tract obstruction is associated with an increase in endotoxin levels, a positive acute-phase response, and plasma cytokine elevation. After biliary drainage a transitory improvement of these alterations was observed, although values remained high 1 week postdrainage. These findings were associated with positive bile cultures.     

Endotoxin-induced renal failure. II. A role for tubular hypoxic damage

Endotoxin-induced hypotension and altered renal microcirculation could lead to tubular injury, particularly at the physiologically hypoxic outer medulla. We explored this hypothesis in isolated perfused kidneys and in vivo in rats subjected to endotoxemia. Rat kidneys were removed 15 min after endotoxin injection in vivo (from Escherichia coli 0127:B8, 1 mg/kg i.p.) and perfused with oxygenated medium supplemented with 20 amino acids and endotoxin. Glomerular filtration rate and filtration fraction markedly declined (0.4 +/- 0. 1 ml/min and 1.1 +/- 0.1, respectively) as compared with control kidneys (0.7 +/- 0.1 ml/min and 1.8 +/- 0.1, n = 8-12 per group; p < 0.05). Hypoxic injury to medullary thick ascending limbs in the innermost outer medulla increased (47 +/- 9% of tubules vs. 16 +/- 8% in controls, p < 0.05). When rats were preconditioned with an additional endotoxin injection 16 h earlier (a manipulation that markedly reduces cortical and medullary blood flow), glomerular filtration rate and filtration fraction further declined to 0.1 +/- 0.0 ml/min and 0.4 +/- 0.1, respectively (p < 0.01), and tubular sodium reabsorption fell to 81 +/- 12 vs 98 +/- 0% in controls (p < 0.05). Tubular damage, however, did not increase (20 +/- 7%), probably reflecting a decline in reabsorptive workload and oxygen requirement. In rats subjected to a single or two repeated daily doses of endotoxin (1 mg/kg i.p.) plasma creatinine comparably rose 41% on the average over 24 h, creatinine clearance fell by 27% (p < 0.0001), but tubular damage was absent. By contrast, in rats preconditioned with indomethacin and the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (10 mg/kg), the addition of endotoxin markedly augmented outer medullary hypoxic tubular damage both in S(3) segments (27 +/- 10 vs 1 +/- 1%) and in medullary thick ascending limbs (38 +/- 11 vs. 10 +/- 5%, n = 7-8; p < 0.05). It is concluded that under special conditions, such as altered medullary oxygen balance or defective nitric oxide or prostaglandin synthesis, endotoxin may predispose to hypoxic outer medullary tubular damage.     

Immunoglobulin Enriched Colostral Milk Reduces Gut-Derived Endotoxemia in a Rat Hemorrhage Model

Background: Several studies indicate that a breakdown of mucosal barrier is often a major cause of endotoxemia and septic complications after hemorrhagic/traumatic insults. The aim of this study was to investigate, whether enteral administration of an immunoglobulin enriched colostral milk preparation (ICM) is able to affect endotoxemia as well as survival in a hemorrhagic shock model in rats. Materials and Methods: Rats were orally pre-treated with either 5 ml of 0.9% saline (CON) or ICM (3 g/kg body weight) once a day for 5 days (ICM). Laboratory control animals were not treated (LAB-CON). On day 6, intestinal endotoxin contents were assessed. In a separate set of animals treated similarly, hemorrhage was induced on the 6th day by bleeding the animals to a mean arterial pressure of 30-35 mm Hg for 3 h followed by resuscitation over 1 h. Results: Pre-treatment with ICM significantly reduced intraluminal endotoxin contents in the duodenum when compared with CON (0.43 - 0.27 vs.. 1.03 - 0.67 EU/mg contents; p = 0.03). Hemorrhage for 3 h resulted in a significant rise in plasma endotoxin concentrations in CON animals compared with LAB-CON (0.30 - 0.20 vs. 0.06 - 0.04 EU/ml). ICM pre-treatment attenuated plasma endotoxin levels after hemorrhage(0.11 - 0.12 EU/ml). The 6-day-survival rate after hemorrhage tended to be higher in the ICM pre-treated animals when compared with CON (66.7% vs. 40%). Conclusion: A passive immunization of the gut together with the reduction of the intraluminal endotoxin contents by enteral administration of immunoglobulin-enriched preparations might prove to be a prophylactic approach towards preventing gut-derived endotoxemia after hemorrhagic/traumatic insults.     

Perioperative change of plasma endotoxin levels in early infants

As a preliminary study to elucidate the relationship of endotoxemia to postoperative morbidity, the plasma endotoxin levels in 64 surgical neonates were quantitated by the chromogenic limulus test (Toxicolor test; Seikagaku Kogyo, Tokyo, Japan). The preoperative levels of plasma endotoxin were 64 +/- 59 pg/mL in the group of infants with perforated peritonitis (n = 9), 63 +/- 51 pg/mL in the group of infants with gastroschisis (n = 7), and 15 +/- 16 pg/mL in the group of infants with ileus (n = 28), while the mean level was 6 +/- 5 pg/mL in the remaining 20 surgical neonates who had no signs of ileus or peritonitis. In the serial determination of plasma endotoxin in 28 neonates, the levels on the first postoperative day increased significantly compared with the preoperative levels (16 +/- 18 pg/mL to 46 +/- 25 pg/mL, P less than .01). They decreased gradually to 8 +/- 5 pg/mL within a week in 15 neonates who had no postoperative complications. However, in 13 neonates who had postoperative complications such as wound infection or postoperative ileus, the postoperative levels of plasma endotoxin increased to a much higher level and remained there. In this article the relationship of clinical endotoxemia to postoperative thrombocytopenia and hyperbilirubinemia is analyzed, and the usefulness of evaluating endotoxemia in surgical neonates is discussed.     

Interleukin-2 initiates metabolic responses associated with critical illness in humans.

The cytokine interleukin-2 is a primary modulator of the immune response that occurs after infection, trauma, and transplant rejection, yet its role as a mediator of associated metabolic changes in surgical illness is unknown. We studied clinical and metabolic responses in eleven tumor-bearing humans with normal renal and hepatic function receiving bolus intravenous (I.V.) interleukin-2 (30,000 U/kg). Additional subjects (n = 6) were pretreated with the cyclooxygenase inhibitor, ibuprofen (1600 mg, orally), before interleukin-2 administration. Serial measurements were made of vital signs, symptoms, hematology, and plasma concentrations of pituitary and stress hormones and selected cytokines. Administration of interleukin-2 resulted in fever, tachyacardia, "flu-like" symptoms, and neurohormonal elaboration. The responses observed were quantitatively similar to those that occurred after endotoxin administration in healthy subjects (n = 13), but differed in the following manner: 1) the onset of fever and endocrine changes occurred after a longer latent interval (180-240 minutes vs. 60-90 minutes after endotoxin), 2) peak responses after the administration of interleukin-2 also occurred later, 3) no increased circulating tumor necrosis factor was detected after administration of interleukin-2 (peak plasma concentration was greater than 35 pg/ml vs. 270 +/- 70 pg/ml after endotoxin administration), and 4) administration of interleukin-2 but not of endotoxin was associated with increased circulating concentrations of gamma interferon (peak plasma concentration 1.7 +/- 0.2 NIH U/ml vs. less than 0.1 NIH U/ml after endotoxin administration). Fever and neurohormonal responses after interleukin-2 administration were greatly attenuated by ibuprofen administration. Interleukin-2 induces other cytokines that exert their effects largely through the cyclooxygenase pathway. Interleukin-2 may be an important signal, initiating the integrated host responses to infection and injury.     

Reduced amino acid transport in skeletal muscle caused by a circulating factor during endotoxemia.

The present study was designed to determine whether reduced amino acid uptake in skeletal muscle during endotoxemia is due to associated hypotension or is caused by a factor present in plasma. Three series of experiments were performed. In the first series of experiments, mean arterial pressure (MAP), heart rate, and amino acid uptake in incubated soleus muscles were measured after intravenous injection of endotoxin (1 mg/kg) in male Sprague-Dawley rats (40 to 60 g). Amino acid transport was measured by determining intracellular uptake of [3H]-alpha-amino-isobutyric acid (AIB) during 2 hours of incubation. In the second series of experiments, hypotension was induced by bleeding and muscle amino acid uptake was measured. In the third series of experiments, whole plasma or a low molecular weight fraction (less than 10,000 d) of plasma from endotoxin-injected rats was added in vitro to incubated muscles and amino acid uptake was determined. One hour after injection of endotoxin, MAP was reduced from 80 +/- 2 mmHg to 54 +/- 4 mmHg (p less than 0.05). AIB uptake was reduced by 20% (p less than 0.05) 2 hours after endotoxin injection. When MAP was maintained at 50 mmHg for 1 hour by bleeding, no changes in muscle AIB uptake were noted. When plasma obtained from rats 2 hours after endotoxin injection was added to incubated soleus muscles, AIB uptake was reduced by 22%. This effect was duplicated by a fraction of endotoxic plasma containing substances with a molecular weight less than 10,000 d. The present results suggest that reduced muscle amino acid uptake during endotoxemia is not due to associated hypotension, but may be caused by a circulating factor(s) with a molecular weight less than 10,000 d.     

Total parenteral nutrition and bowel rest modify the metabolic response to endotoxin in humans.

Intestinal mucosal atrophy, as induced by total parenteral nutrition (TPN) and/or prolonged bowel rest, is hypothesized to enhance bowel endotoxin (LPS) translocation and may alter host responses to infection. To examine the effect of TPN-induced bowel atrophy on the response to LPS, 12 healthy volunteers were randomized to receive either enteral feedings (ENT, n = 6) or seven days of TPN without oral intake (TPN, n = 6). Enteral or TPN feedings were terminated 12 hours before the study period when a constant dextrose infusion (50 mg/kg/hour) was initiated and continued throughout the subsequent study period. After placement of arterial, hepatic vein, and femoral vein catheters, metabolic parameters were determined before and for six hours after an intravenous E. coli LPS challenge (20 U/kg). Subsequent peak levels of arterial glucagon (ENT, 189 +/- 39 pg/mL; TPN, 428 +/- 48; p less than 0.01), arterial epinephrine (ENT, 236 +/- 52 pg/mL; TPN, 379 +/- 49; p less than 0.05) and hepatic venous cachectin/tumor necrosis factor (cachectin/TNF) (ENT, 250 +/- 56 pg/mL; TPN, 479 +/- 136; p less than 0.05) were significantly higher in the TPN group than in the ENT group. The extremity efflux of lactate (ENT, -16 +/- 4 micrograms/min-100cc tissue; TPN, -52 +/- 13; t = 2 hours; p less than 0.05) and of amino acids (ENT, -334 +/- 77 nmol/min-100cc tissue; TPN, -884 +/- 58; t = 4 hours; p less than 0.05) were higher in the TPN subjects after the endotoxin challenge. Circulating C-reactive Protein (CRP) levels measured 24 hours postendotoxin were also significantly higher in the TPN subjects (ENT, 1.7 +/- 0.2 mg/dL; TPN, 3.2 +/- 0.3; p less than 0.01). Hence the counter-regulatory hormone and splanchnic cytokine responses to LPS were enhanced after TPN and bowel rest. This is associated with a magnified acute-phase response, peripheral amino acid mobilization, and peripheral lactate production. Thus antecedent TPN may influence the metabolic alterations seen in infection and sepsis via both an exaggerated counter-regulatory hormone response as well as an enhanced systemic and splanchnic production of cytokines.     

Reactive Oxygen Species Scavengers Attenuate Endotoxin-induced Impairment of Hypoxic Pulmonary Vasoconstriction in Mice

Background: Sepsis and endotoxemia attenuate hypoxic pulmonary vasoconstriction (HPV), thereby impairing systemic oxygenation. Reactive oxygen species (ROS) are implicated in the pathogenesis of sepsis-induced lung injury. The authors investigated whether treatment with scavengers of ROS prevents impairment of HPV in mice challenged with endotoxin.

Methods: The pulmonary vasoconstrictor response to left mainstem bronchus occlusion (LMBO) was studied in anesthetized mice 22 h after an intraperitoneal challenge with saline solution or 10 mg/kg Escherichia coli endotoxin. In some mice, challenge with saline solution or endotoxin was followed after 1 h with intraperitoneal or intratracheal administration of the ROS scavengers N-acetylcysteine or EUK-8. Myeloperoxidase activity and nitric oxide synthase-2 gene expression were measured in lung tissues.

Results: The LMBO increased left pulmonary vascular resistance by 106 +/- 24% in saline-challenged control mice but by only 23 +/- 12% (P < 0.05) in endotoxin-challenged mice. Intraperitoneal administration of N-acetylcysteine or EUK-8 1 h after endotoxin challenge attenuated the endotoxin-induced impairment of HPV (58 +/- 6% and 68 +/- 10%, respectively; both P < 0.05 vs. endotoxin-challenged mice). Intratracheal administration of ROS scavengers 1 h after endotoxin challenge was equally effective but required lower doses than systemic treatment. Administration of the ROS scavengers 22 h after endotoxin challenge did not restore HPV.     

Cardiac interleukin-6 release and myocardial recovery after aortic crossclamping. Crystalloid versus blood cardioplegia

BACKGROUND: Pro-inflammatory cytokines may play an important role in patient response to cardiopulmonary bypass (CPB). Since the myocardium is proposed to be a major source of cytokines, we studied the influence of the cardiolpegia type on interleukin-6 release and early myocardial recovery. METHODS: Experimental design: prospective, randomized study. Setting: university hospital, operative and intensive care. Patients: 20 consecutive patients (3 females) scheduled for elective coronary artery bypass grafting (CABG), mean age 62.8+/-5 years, history of myocardial infarction 11/20, left ventricular ejection fraction 62.9+/-15%. Interventions: patients were operated on using randomly either cold blood cardioplegia (B, n = 10) or cold crystalloid cardioplegia (C, n = 10). Measures: plasma levels of interleukin-6 (IL-6) were measured prior to CPB, after aortic declamping, after CPB, 1 hour, 6 hours and 12 hours postoperatively. RESULTS: Groups were comparable with respect to demographic data, left ventricular function, number of grafts, CPB and aortic crossclamp time. Group B patients demonstrated significant lower IL-6 levels after 1 hour (210+/-108 vs. 578+/-443 pg/ml), 6 hours (204+/-91 vs. 1210+/-671 pg/ml) and 12 hours (174+/-97 vs. 971+/-623 pg/ml). Post-CPB cardiac index was superior in group B (3.9+/-0.3 vs. 3.2+/-0.3 l/min/m2, p<0.05) with similar doses of inotropes. Group B patients could earlier be weaned off respirator (10+/-4 vs. 13+/-4 hours, p<0.05) and showed minor blood loss (635+/-211 vs. 918+/-347 ml, p<0.05). CONCLUSIONS: Inflammatory response to CPB is associated with delayed myocardial recovery. The use of blood cardioplegia may attenuate inflammatory reactions.     

Adaptive regulation of alanine transport in hepatic plasma membrane vesicles from the endotoxin-treated rat

The mechanisms by which hepatic alanine consumption is increased during endotoxemia were investigated to gain further insight into the altered amino acid metabolism which characterizes critical illness. Rats were studied 12 hr after receiving endotoxin (ENDO) or saline. Hepatic alanine delivery was determined in vivo and hepatic alanine content was measured. Hepatocyte transport activity was studied by evaluation of [3H]-alanine accumulation in hepatocyte plasma membrane vesicles (HPMVs). Vesicle integrity was demonstrated by electron microscopy and a 14-fold enrichment in 5'-nucleotidase. Endotoxin treatment resulted in a state of hyperalaninemia and a threefold increase in hepatic alanine delivery (2.79 +/- 0.17 mu mole/100 g body weight/min in controls vs 8.13 +/- 0.98 in ENDO animals; P less than 0.001). Data from HPMVs revealed the presence of a high- and low-affinity component of alanine transport. Endotoxin treatment resulted in a 30% decrease in the Vmax of the high-affinity transport component (3355 +/- 177 pmole/mg protein/10 sec in controls vs 2338 +/- 270 in the ENDO group; P less than 0.05). Concomitant with the observed changes in alanine delivery and transport activity, endotoxin treatment resulted in a 56% rise in hepatic alanine content (2.53 +/- 0.29 mu mole/g liver in controls vs 3.95 +/- 0.23 in ENDO; P less than 0.005). These data indicate that the accelerated hepatic alanine consumption which occurs during endotoxemia is primarily the result of increased hepatic substrate delivery. Despite the resultant repression of transport activity, delivery begins to outdistance the metabolic capacity of the hepatocyte to utilize alanine and intracellular alanine levels rise.     

The complex pattern of cytokines in sepsis. Association between prostaglandins, cachectin, and interleukins.

Although the cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1), and interleukin-6 (IL-6) are important mediators of hemodynamic, metabolic, and immunologic alterations in the host during sepsis, it is not known whether there is any association between the release of these cytokines and prostanoids during sepsis. Sepsis induced by cecal ligation and puncture in rats led to a persistent elevation (p less than 0.05) of plasma TNF until 10 hours, steadily increasing (p less than 0.05) IL-1 plasma levels, and enhanced (p less than 0.05) IL-6 plasma levels at all time points compared to the sham group. Prostaglandin E2 plasma levels were elevated (p less than 0.05) at 5 hours (153 +/- 29 pg/mL; control: 47 +/- 11 pg/mL) and 10 hours (96 +/- 16 pg/mL; control: 21 +/- 5 pg/mL). Prostaglandin E2 production by splenic macrophages (sM phi) from septic animals was increased (p less than 0.05) at 5 hours (9.1 +/- 2.2 ng/mL) and 10 hours (5.6 +/- 1.5 ng/mL) compared to controls (3.3 +/- 0.3 ng/mL at 5 hours; 1.3 +/- 1.3 ng/mL at 10 hours). Incubation of sM phi from septic animals with ibuprofen enhanced (p less than 0.05) IL-1 and TNF synthesis, while IL-6 production was reduced (p less than 0.05). These results indicate that the alterations in prostanoid release and elevated plasma prostanoids may regulate the release and consequently the circulating levels of cytokines during sepsis.     

Microendoscopic discectomy, a less traumatic procedure for lumbar disk herniation

OBJECTIVE: To investigate the change of serum levels of interleukin-6 (IL-6), C-reactive protein (CRP) and creatine kinase (CK) in patients undergoing microendoscopic discectomy (MED) and open discectomy. METHODS: Forty-four patients with single level lumbar disk herniation were treated, either by MED (Group A, n equal to 22) or open discectomy (Group B, n equal to 22). Peripheral venous blood samples were taken before surgery and at 24 and 48 hours postoperatively. The operating time, intraoperative blood loss, postoperative hospital stay were recorded. The pain severity of incision was evaluated by visual analog scale after operation and the clinical outcome was evaluated by Oswestry disability index. Statistical comparison was performed by the analysis of variance and Student's t test. RESULTS: The data showed that patients in Group A had a less intraoperative blood loss (P < 0.05), shorter operating length (P < 0.05), shorter postoperative hospital stay (P < 0.05) and less postoperative pain of incision than those in Group B. Serum levels of IL-6 (mean, 31.60 ng/L +/- 9.88 ng/L vs 39.16 ng/L +/- 11.14 ng/L, P < 0.05) and CK (mean, 167.91 U/L +/- 51.85 U/L vs 401.55 U/L +/- 108.86 U/L, P < 0.05) all get to the peak at 24 hours after operation and Group A with the response statistically less than Group B. Serum level of CRP peaked at 24 hours in Group A (mean, 12.68 mg/L +/- 7.10 mg/L vs 20.82 mg/L +/- 8.79 mg/L, P less than 0.05)and peaked at 48 hours after surgery in Group B (mean, 10.77 mg/L +/- 5.25 mg/L vs 29.95 mg/L +/- 14.85 mg/L, P < 0.05). The clinical outcomes of both groups were the same at 6 months after surgery. CONCLUSIONS: Both MED and open discectomy have made good clinical outcomes, however, the less change of IL-6, CRP and CK after operation proves that MED procedure is less traumatic to patients than open discectomy.     

Different role of antioxidants in endotoxin-induced late myocardial protection

Previous studies have proposed that endogenous antioxidants play a protective role against cardiac ischemia-reperfusion injury in endotoxin pretreatment. However, the mechanism underlying this effect remains elusive. We therefore evaluated the role of endogenous antioxidants in delayed myocardial protection after different doses of endotoxin administration using cultured rat neonatal cardiomyocytes. Myocytes were treated with normal saline (control) or lipopolysaccharide (Escherichia coli, serotype O111) at doses of 40 and 80 microg/ml (ET40 and ET80). Also, antisense oligodeoxyribonucleotide (1.5 micromol/L) to manganese superoxide dismutase (Mn-SOD) and 3-amino-1,2,4-triazole (25 mg/ml) were added along with a 40 or 80 microg/ml endotoxin pretreatment in the IET40 and IET80 groups. Twenty-four hours later, Cells were subjected to hypoxia (pO2 < 1 kPa, 3 h) and reoxygenation (pO2: 19 kPa, 1 h). Compared with controls, cell viability enhanced significantly (65.3 +/- 5.9, 63.8 +/- 4.6, and 69.7 +/- 5.2% vs 47.2 +/- 4.3%, P < 0.05) and creatine kinase release decreased (7.34 +/- 1.76, 7.11 +/- 1.49, and 6.27 +/- 1.24 U/mg protein vs 11.23 +/- 2.49 U/mg protein, P < 0. 05) in ET40, IET40, and ET80 groups following reoxygenation. No statistically significant difference was found between the control and the IET80 groups. Furthermore, the levels of Mn-SOD (1.12 +/- 0. 31 vs 0.75 +/- 0.15 U/mg. protein, P < 0.05) and catalase activity (1265 +/- 109 vs 996 +/- 85 U/mg. protein, P < 0.05) were higher only in the ET80 group. The results suggest that at a dose of 40 microg/ml, cells were protected by mechanisms other than the augmentation of endogenous antioxidant activity which were more evident at a dose of 80 microg/ml. It seems that different doses of endotoxin pretreatment may induce delayed myocardial protection through various mechanisms.     

Increased oxygen cost of contractility in the endotoxemic porcine left ventricle

OBJECTIVE: Myocardial oxygen consumption (MVO) in the septic myocardium is comparatively high in relation to the sepsis-induced reduction in ventricular work. Our previous studies indicate that this energetic inefficiency is due to increased energy consumption in excitation-contraction (EC) coupling, i.e. myocardial calcium handling. DESIGN: To further confirm this observation, we assessed the oxygen cost of contractility in anesthetized pigs before and 2 h after induction of endotoxemia (1 microg/kg endotoxin infusion over 1 h, Escherichia coli toxin, n=6). Baroreceptor reflexes were blocked by hexamethonium. Contractility was increased by stepwise dopamine infusions at baseline and 2 h after induction of endotoxemia. Oxygen cost of contractility was assessed as the relationship between myocardial contractility (E or elastance) and non-mechanical oxygen consumption (unloaded MVO), a measure of energy consumption in EC coupling or calcium handling. RESULTS: Non-mechanical oxygen consumption (unloaded MVO) was higher after endotoxin infusions than at baseline (0.641 +/- 0.05 vs 0.383 +/- 0.07 J/beat/100 g, p < 0.05). The relationship between unloaded MVO and E, constructed by the dopamine response, was highly linear both at baseline and endotoxemia (r2 =0.76-0.99). However, endotoxin increased oxygen cost of contractility by approximately 45% (baseline 0.06 +/- 0.03 vs endotoxin 0.09 +/- 0.04 J ml/mmHg/beat/100 g). CONCLUSION: Acute endotoxemia increases oxygen cost of contractility, a measure of energy consumed in EC coupling or myocardial calcium handling.     

Interleukin-1 and the acute-phase response: induction of mouse liver serum amyloid A mRNA by murine recombinant interleukin-1

Traumatic tissue injury of infection provokes a systemic inflammatory response, termed the acute-phase response, which is accompanied by hepatic synthesis of certain plasma proteins. Increased levels of serum amyloid A (SAA), C-reactive protein (CRP), and fibrinogen have been observed during the acute-phase response. One possible mediator of the acute-phase response is interleukin-1, a pro-inflammatory monokine released in response to traumatic tissue injury or infection. There is evidence that partially purified macrophage supernatants containing interleukin-1 activity stimulate hepatocyte secretion of SAA, CRP, and fibrinogen. The effect of interleukin-1 on mouse liver serum amyloid A mRNA levels was investigated. The acute-phase response was induced in mice by intraperitoneal injection of interleukin-1 obtained from cloned murine recombinant DNA. We monitored SAA mRNA levels using DNA/RNA dot blot hybridization. Interleukin-1 stimulated a dose-dependent increase in SAA mRNA levels compared to unstimulated controls. In contrast, mRNA levels for apolipoprotein E (a constitutive hepatic protein not produced as part of the acute-phase response) were unchanged under identical conditions. Interleukin-1 also induced SAA mRNA in an endotoxin-resistant strain of mice (C3H/HeJ), indicating that this stimulation was not due to endotoxin contamination since endotoxin alone was unable to induce SAA mRNA in these mice. These results indicate that recombinant interleukin-1, when injected intraperitoneally into mice, induced specific production of SAA mRNA and hence one phase of the acute-phase response.     

Effects of activated protein C on the mesenteric microcirculation and cytokine release during experimental endotoxemia

PURPOSE: Activated protein C (APC) is the first anti-inflammatory drug to be approved for the treatment of severe sepsis. However, the underlying mechanisms are not completely elucidated. Therefore, the aim of our study was to evaluate the effects of APC on the microcirculation (mesenteric leukocyte-endothelial interaction, plasma extravasation) using intravital microscopy (IVM) and on cytokine release during experimental endotoxemia in rats. METHODS: We divided forty, male, Lewis rats into four groups (n = 10 per group): Controls, LPS (15 mg x kg(-1) lipopolysaccharide iv), APC (2 mg x kg(-1) APC iv), and LPS+APC. We determined mesenteric leukocyte-endothelial interactions and plasma extravasation at zero, one and two hours following administration of LPS and APC by IVM. Plasma levels of tumour necrosis factor-alpha, IL-1beta, interleukin (IL)-6, and IL-10 were measured at zero and at two hours. RESULTS: Leukocyte adherence (-74%) and plasma extravasation (-28%) during endotoxemia were diminished significantly following APC treatment, compared to untreated LPS animals (P = 0.0001 and P = 0.0004, respectively). Interleukin-1ss release was also significantly reduced by APC treatment (2567.4 +/- 320.9 pg x mL(-1) in the LPS group vs 1626.1 +/- 427.2 pg x mL(-1) in the LPS+APC group; P = 0.001).Conclusion: These rodent experiments showed that APC treatment significantly attenuated deterioration of the mesenteric microcirculation and systemic IL-1ss release caused by endotoxin challenge. Because of the crucial role of the microcirculation in ongoing sepsis pathogenesis and multiple organ dysfunction syndrome, these effects may be of clinical importance.     

Development and reversal of endotoxemia and endotoxin-related death in obstructive jaundice

Gut-derived endotoxemia has been implicated in postoperative complications in patients with jaundice. It is thought that absence of bile in the gut predisposes to portal absorption of endotoxin and endotoxemia is reversed by oral bile salt replacement or internal biliary drainage and return of bile to the gut, but not by external drainage. We believe that the importance of gastrointestinal bile flow has been overestimated and biliary obstruction and the integrity of hepatocyte and Kupffer cell function are more important in the development and reversal of endotoxemia. In experiment 1, serum endotoxin concentrations were measured in control rats (n = 10) after choledochovesical fistula (n = 15) and bile duct ligation (n = 15) and after relief of biliary obstruction by internal drainage (choledochoduodenostomy; n = 8) and sterile external drainage (choledochovesical fistula; n = 8), with a quantitative limulus assay. In experiment 2, mortality rates were measured in similar groups 48 hours after administration of oral endotoxin (5 mg/100 gm) and intravenous lead acetate (5 mg/100 gm). Bilirubin levels were elevated in bile duct ligation (192 +/- 13 mumols/L) compared with control animals and those with choledochovesical fistula, internal drainage, and external drainage (10.6 +/- 1.5 mumols/L). In experiment 1, significant portal endotoxemia and systemic endotoxemia occurred in bile duct ligation (portal, 130.4 +/- 12.9 pg/ml; systemic, 91.8 +/- 11.0 pg/ml) but not in choledochovesical fistula (portal, 49.3 +/- 17.1 pg/ml; systemic, 27.2 +/- 11.5 pg/ml). Relief of obstruction by both internal and external drainage reversed endotoxemia. In experiment 2, significant death occurred in bile duct ligation (13 of 15) but not in choledochovesical fistula (3 of 15), and relief of obstruction by both internal and external drainage prevented death. These results confirm that biliary obstruction is a more important factor than is gastrointestinal bile flow in the development and reversal of endotoxemia.