Effect of hyperglycemia and hyperinsulinemia on the response of IL-6, TNF-alpha, and FFAs to low-dose endotoxemia in humans

Insulin therapy to maintain euglycemia increases survival in critically ill patients. To explore possible mechanisms of action, we investigated the effect of endotoxin on circulating cytokines, free fatty acids (FFA), and leukocytes during manipulated plasma glucose and insulin concentrations. Ten volunteers underwent three trials each, receiving an intravenous bolus of endotoxin (0.2 ng/kg) during normoglycemia (trial A, control), during a hyperglycemic clamp at 15 mM (trial B), and during a hyperinsulinemic euglycemic clamp (trial C). Endotoxin induced an increase in neutrophil count, a decrease in lymphocyte count, and an increase in serum levels of TNF-alpha, IL-6, and FFA. There was no difference in the TNF response between the three trials; the IL-6 levels were increased during the late phase of trials B and C compared with trial A. The endotoxin-induced elevation in FFA in trial A was suppressed during trials B and C. Clamping (trials B and C) caused a reduction in lymphocyte count that persisted after endotoxin injection. We conclude that low-dose endotoxemia triggers a subclinical inflammatory response and an elevation in FFA. The finding that high insulin serum concentrations induce a more prolonged increase in the anti-inflammatory cytokine IL-6 and suppress the levels of FFA suggests that insulin treatment of patients with sepsis may exert beneficial effects by inducing anti-inflammation and protection against FFA toxicity, and thereby inhibit FFA-induced insulin resistance.     

Effect of intralipid infusion on lecithin:cholesterol acyltransferase and lipoprotein lipase in young rats

We compared the effects of Intralipid and dextrose infusion on plasma lecithin:cholesterol acyltransferase (LCAT), plasma lipid profiles and lipolytic activity. We used 5-week-old male Sprague-Dawley rats which were given total parenteral nutrition (TPN) with either Intralipid (3 g/kg body weight) or an equicaloric amount of 25% dextrose in the presence or absence of heparin (1 or 10 IU/ml of TPN). 40 min after the end of 4 h of infusion, plasma LCAT activity was significantly decreased (P less than 0.001), while total cholesterol and free fatty acid levels were significantly (P less than 0.05) increased in rats given Intralipid as compared to those given dextrose. We found associations (P less than 0.005) between LCAT activity and total cholesterol and between LCAT and free fatty acid levels; the coefficients of negative correlation were 0.543 and 0.607, respectively. Concomitantly to the increment in plasma total cholesterol levels, there was a decrease in the high-density lipoprotein (HDL) cholesterol fraction; the latter, which was 40% of the total plasma cholesterol in control and dextrose-infused rats, declined to 9% in rats given Intralipid. Administration of heparin during Intralipid infusion, even up to 10 IU/ml of TPN, did not affect any of these changes. After dextrose infusion, the values of all three parameters were similar to those of the control group. Plasma lipolytic activity was not significantly different between rats given infusion (Intralipid or dextrose) and controls. However, in the presence of heparin, plasma lipolytic activity increased similarly in both infused groups. These data indicate that in young rats, Intralipid infusion leads to an increase in plasma total cholesterol and free fatty acid levels, which correlates with a decrease in LCAT activity; the concurrent decrease in HDL cholesterol levels might account, in part, for the loss of LCAT activity. The administration of heparin results in an elevation of plasma lipolytic activity; however, it does not prevent the hypercholesterolemia, nor the decline in LCAT activity associated with Intralipid infusion.     

Glucocorticoid-attenuated response genes induced in the lung during endotoxemia

Cytokines and other mediators whose induction in inflammatory lung disease is attenuated by glucocorticoids are potential targets for development of selective anti-inflammatory treatments. We refer to genes with these regulatory characteristics as glucocorticoid-attenuated response genes, or GARGs. Systematic identification of GARGs has not been attempted previously in vivo. Using an endotoxemia model in adrenalectomized mice, we constructed a subtracted lung library enriched in endotoxemia-induced genes and identified candidate GARGs by differential hybridization screening. Northern analysis confirmed induction in the lung during endotoxemia and attenuation by glucocorticoids of 36 genes of diverse types. The majority were genes of unknown function not previously implicated in the pulmonary response to inflammation, including a new member of a 2'-5'-oligoadenylate synthetase-like family and a novel lung inducible Neuralized-related C3HC4 RING protein. Our results suggest that a full understanding of glucocorticoid effects on lung inflammation will require elucidation of the roles of an extensive network of glucocorticoid-modulated genes.     

Effect of low-dose total-body radiotherapy on immune microenvironment

The history of low-dose total-body irradiation (LTBI) as a means of radiotherapy for treating malignant tumors can be traced back to the 1920s. Despite this very low total dose, LTBI can induce long-term remissions. Tumor cells are known to change and maintain their own survival and development conditions through autocrine and paracrine signaling. LTBI can change the tumor microenvironment, enhance the infiltration of activated T cells, and trigger inflammatory processes. LTBI-mediated immune response can exert systemic long-term anti-tumor effects, and can induce tumor regression at the primary site and metastatic sites. With a continuous improvement in the anti-tumor immune microenvironment in the field of tumor therapy, LTBI provides more choices to comprehensively treat of tumors. The present study aimed to explore the experimental research mechanism of LTBI and immune microenvironment, and discuss the difficulties and development prospects of applying LTBI to tumor treatment.     

Metabolic alterations in adipose tissue during the early phase of experimental endotoxemia in humans

Adipose tissue plays an important role in energy homeostasis; however, there is only little knowledge about its metabolic activity during critical illness or sepsis. We assessed adipose tissue metabolic activity and local blood flow during experimental endotoxemia in otherwise healthy humans. In a prospective, placebo controlled and randomized experiment we measured changes in lactate, glycerol, and pyruvate concentrations in microdialysate samples of femoral adipose tissue after an intravenous bolus of lipopolysaccharide (LPS, 4 ng/kg). Intravenous endotoxin caused an early and constant increase in interstitial pyruvate, while formation of lactate in adipose tissue was not affected. In contrast, lactate levels in serum were elevated significantly after 90 min (p<0.05) and likewise, serum glycerol concentrations rose 90 min after LPS treatment (p<0.05) and 60 min earlier than in adipose tissue. Subcutaneous adipose tissue blood perfusion increased 2-fold while there was a strong decline in skin blood flow. Pyruvate accumulation in subcutaneous adipose tissue is an early marker of endotoxemia. While adipose tissue is a major source of serum glycerol and lactate in humans during physiological conditions, it contributes only little to increased serum lactate and glycerol levels during endotoxemia.     

Effect of prior exercise on maximal short-term power output in humans

The effect of prior exercise (PE) on subsequent maximal short-term power output (STPO) was examined during cycling exercise on an isokinetic ergometer. In the first series of experiments the duration of PE at a power output equivalent to 98% maximum O2 uptake (VO2max) was varied between 0.5 and 6 min before measurement of maximal STPO. As PE duration increased subsequent STPO fell to approximately 70% of control values after 3-6 min. In series ii the effect of varying the intensity of PE of fixed 6-min duration was studied in five subjects. After PE less than 60% VO2max there was an increase of 12% in STPO, but after greater than 60% VO2max there was a progressive fall in STPO as PE intensity increased, indicating a reduction of approximately 35% at 100% VO2max compared with control values. In series iii we examined the effect on STPO of allowing a recovery period after a fixed intensity (mean = 87% VO2max) of 6 min PE before measurement of STPO. This indicated a rapid recovery of dynamic function with a half time of approximately 32 s, which is similar to the kinetics of PC resynthesis and taken with the other findings suggests the dominant role that PC exerts on the STPO under these conditions.     

Effect of intravenous catalase on the pulmonary vascular response to endotoxemia in goats

Neutrophils have been implicated in the pathogenesis of acute lung injury associated with clinical and experimental sepsis. Data from in vitro systems and experimental animals have suggested that neutrophil-derived oxidants, particularly H2O2, may be primarily responsible for endothelial damage, vasoconstriction, and lung edema. With the use of endotoxin infusion as an in vivo model of sepsis we tested the hypothesis that pretreatment with catalase, a peroxide scavenger, would ameliorate the resultant changes in pulmonary vasoconstriction and lung fluid balance. Paired experiments were performed in 16 goats with chronic lung lymph fistulas. One group of animals (n = 7) received endotoxin first alone and then again, several days later, after pretreatment with Ficoll-linked catalase. As a control, identical experiments were performed in a separate group (n = 6) with Ficoll-linked albumin substituted for Ficoll-catalase. A third group (n = 3) was given endotoxin alone and then again during a continuous infusion of catalase. Plasma and lymph levels of catalase were comparable to or exceeded those previously shown to be completely protective in isolated perfused lung preparations and in vitro systems. Endotoxin caused neutropenia, pulmonary arterial hypertension, decreased cardiac output, and increases in lymph flow to approximately three times base line, with a return of all variables toward control values by 6 h. Catalase pretreatment produced no significant differences in any of these variables. These experiments do not support a role for H2O2 as a mediator of acute lung injury due to endotoxemia.     

Influence of Naloxone on the cellular immune response to head-up tilt in humans

To evaluate a possible role for β-endorphin in the stress-induced modulation of natural killer (NK) cells, immunologically competent blood cells were followed in eight male volunteers administered either Naloxone or saline (control) during head-up tilt maintained until the appearance of presyncopal symptoms (PS). The PS appeared more rapidly with Naloxone compared to control [5.7 (SEM 1.1) vs 22.3 (SEM 5.1) min; P = 0.01]. The NK cell activity increased threefold during PS partly due to an increase in CD16⁺ and CD56⁺ NK cells in blood. In support, NK cell activity boosted with interferon-α and interleukin 2 rose in parallel with unboosted NK cell activity and NK cell concentration and activities returned to the baseline level after 105 min. The total lymphocyte count and the concentrations of CD3⁺, CD4⁺, CD8⁺, CD16⁺, and CD56⁺ cells increased during PS. Head-up tilt also induced an increase in plasma adrenaline concentration during control PS and a rise in plasma cortisol and adrenocorticotropic hormone concentrations up to 30 min thereafter, whereas no significant changes were found in plasma concentrations of noradrenaline, growth hormone, or β-endorphin. The results would indicate an influence of endorphin on the increase in plasma adrenaline concentration during head-up tilt and at the same time contra-indicate a significant role for adrenaline in the provocation of PS. The influence of head-up tilt on plasma β-endorphin was too small to influence the modulation of the cellular immune system. Accepted: 22 May 1997     

Skeletal muscle proteolysis in response to short-term unloading in humans.

Skeletal muscle atrophy is evident after muscle disuse, unloading, or spaceflight and results from decreased protein content as a consequence of decreased protein synthesis, increased protein breakdown or both. At this time, there are essentially no human data describing proteolysis in skeletal muscle undergoing atrophy on Earth or in space, primarily due to lack of valid and accurate methodology. This particular study aimed at assessing the effects of short-term unloading on the muscle contractile proteolysis rate. Eight men were subjected to 72-h unilateral lower limb suspension (ULLS) and intramuscular interstitial levels of the naturally occurring proteolytic tracer 3-methylhistidine (3MH) were measured by means of microdialysis before and on completion of this intervention. The 3MH concentration following 72-h ULLS (2.01 +/- 0.22 nmol/ml) was 44% higher (P < 0.05) than before ULLS (1.56 +/- 0.20 nmol/ml). The present experimental model and the employed method determining 3MH in microdialysates present a promising tool for monitoring skeletal muscle proteolysis or metabolism of specific muscles during conditions resulting in atrophy caused by, e.g., disuse and real or simulated microgravity. This study provides evidence that the atrophic processes are evoked rapidly and within 72 h of unloading and suggests that countermeasures should be employed in the early stages of space missions to offset or prevent muscle loss during the period when the rate of muscle atrophy is the highest.     

The suppressive effect of continuous infusion of bilirubin on the immune response in mice

Mice (strains Balb/c and A/J) received an intravenous infusion of bilirubin for a 1 d period. The infusion was delivered at various phases of the primary reaction; the degree of the immune response was expressed as the number of antibody-forming cells against sheep erythrocytes. Bilirubin infusion during both the inductive and productive phase of the primary reaction decreased significantly the immune response. We assume that bilirubin influences the differentiation of immunocompetent cells immediately after their contact with the antigen; in addition it acts in the period of the quantitative increase of the number of antibody-producing cells.     

Involvement of eicosanoids in the hypothermic response to lipopolysaccharide during endotoxemia in rats

Hypothermia is one of the prominent features of the acute phase response to endotoxin (LPS). This study was undertaken to elucidate the effects of the COX-inhibitor Indomethacin (INDO) and the selective FLAP inhibitor MK-886 on LPS-induced hypothermia, mortality and increase in production of hypothalamic prostaglandin E(2) (PGE(2)) and leukotriene during endotoxemia.It has been demonstrated that INDO and MK-886 significantly attenuate the hypothermia induced by LPS, but MK-886 has a lesser (protective) effect than INDO. Only INDO was found to attenuate significantly the hyperthermic response to LPS. Furthermore, INDO significantly reduced the elevation in hypothalamic PGE(2) levels. MK-886 significantly reduced the elevation in hypothalamic leukotriene production only when LPS was given in a dose of 1mg/kg. Both drugs failed to reduce the elevation in plasma TNF-alpha and mortality induced by LPS.We conclude that in rats, febrile response to endotoxin involves many inflammatory mediators. However, it seems that PGE(2) and leukotrienes do not have a pivotal role in the mechanism of LPS-induced mortality.     

Effect of neutrophilokines on the immune response in mice

The influence of different peptide fractions obtained from the intact and latex-stimulated neutrophils on the immune response was studied. It was demonstrated that neutrophils after stimulation synthesize the factors activating immune response, the intact neutrophils synthesize the suppressor factors of peptide nature.     

Effect of sulfatide on acute lung injury during endotoxemia in rats

Experimental studies have shown that intrapulmonary leukocyte sequestration and activation is implicated in the pathogenesis of acute lung injury during endotoxemia. Selectins are involved in the adhesion of leukocyte to the endothelium. Sulfatide is recognized by P selectin and blocks this adhesion molecule. We studied the effects of sulfatide on endotoxin-induced lung damage in rats. Endotoxin shock was produced in male rats by a single intravenous (i.v.) injection of 20 mg/kg of Salmonella enteritidis lipopolysaccharide (LPS). LPS administration reduced survival rate (0%, 72 h after endotoxin challenge) decreased mean arterial blood pressure (MAP), produced leukopenia (Controls = 11,234+/-231 cells/mL, LPS = 4,567+/-123 cells/mL) and increased lung myeloperoxidase activity (MPO; a marker of leukocyte accumulation) in the lung (Controls = 0.35+/-0.1 U/g/tissue; LPS = 10+/-1.2 U/g/tissue). Furthermore LPS administration markedly impaired the concentration-response curves for acetylcholine and sodium nitroprusside in isolated pulmonary arterial rings. There was also an increased staining for P-selectin in the pulmonary arteries. Sulfatide treatment (10 mg/kg, 30 min. after LPS challenge), significantly protected against LPS-induced lethality (90% survival rate and 70% survival rate 24 h and 72 h after LPS injection), reduced LPS induced hypotension, reverted leukopenia (8,895+/-234 cells/ml) and lowered lung MPO activity (1.7+/-0.9 U/g/tissue). Furthermore sulfatide restored to control values the LPS-induced impairment in arterial pulmonary vasorelaxation and reduced P-selectin immunostaining. Our data indicate that sulfatide attenuates LPS-induced lung injury and protects against endotoxin shock.