Interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor alpha (TNF alpha) regulate insulin-like growth factor binding protein-1 (IGFBP-1) levels and mRNA abundance in vivo and in vitro.

TNF alpha and IL-1 alpha are thought to contribute to impaired anabolism in a variety of clinical states, including sepsis, cancer cachexia and the AIDS wasting syndrome. We asked whether cytokines exert direct effects on hepatic production of IGFBP-1, an important modulator of IGF bioavailability. C57BL/6 mice were treated with 100 micrograms/kg of recombinant IL-1 alpha or TNF alpha by intraperitoneal injection. Western ligand blotting and immunoprecipitation with specific antisera revealed that serum levels of IGFBP-1 (but not IGFBP-2, -3, -4, -5 or -6) are increased approximately 4 fold 2 h after treatment and then decline. Northern blotting confirms that hepatic IGFBP-1 mRNA abundance also is increased acutely in both IL-1 alpha- and TNF alpha-treated animals. Similar results obtained in adrenalectomized mice indicate that adrenal activation is not required for this effect. Cell culture studies show that cytokines exert direct effects on the production of IGFBP-1 by HepG2 hepatoma cells, increasing IGFBP-1 levels in conditioned medium and the abundance of IGFBP-1 mRNA approximately 3-fold. In contrast, transient transfection studies with IGFBP-1 promoter/luciferase reporter gene constructs show that IGFBP-1 promoter activity is reduced after 18 hr cytokine treatment. We conclude that IL-1 alpha and TNF alpha increase circulating levels of IGFBP-1, reflecting direct effects on hepatic IGFBP-1 mRNA abundance. Stimulation of hepatic IGFBP-1 production may contribute to alterations in IGF bioactivity and impaired anabolism in clinical conditions where cytokine production is high. Additional studies are required to identify specific mechanisms mediating effects of cytokines on hepatic production of IGFBP-1.     

A rationale for administering leukocyte endogenous mediator to protein malnourished,hospitalized patients

Leukocyte endogenous mediator is a low molecular-weight protein synthesized by circulating monocytes and fixed macrophages of the reticuloendothelial system. Exogenous administration of leukocyte endogenous mediator to a well-nourished animal stimulates both specific and nonspecific immune function and replicates the protein metabolic response to infection, characterized by fever and increased amino acid oxidation, skeletal protein degradation and synthesis of “acute-phase” proteins. Leukocyte endogenous mediator administration also affords protection against semilethal doses of bacteremia in the well-nourished animal.In the protein-depleted host, synthesis or release of leukocyte endogenous mediator in response to infection appears to be reduced and the attenuated metabolic response may be attributed, in part, to a deficit in its production. However, nutritional repletion of the malnourished patient results in restoration of the capacity to produce leukocyte endogenous mediator usually within three to seven days, if adequate dietary protein is provided.Since protein malnutrition is associated with increased incidence and severity of bacterial infections, we postulate that the reduced synthesis and/or release of leukocyte endogenous mediator in protein malnutrition is detrimental. In those critically-ill, malnourished patients who cannot endogenously synthesize leukocyte endogenous mediator, and for clinical reasons cannot be repleted rapidly or are already infected and/or undergoing operative stress, exogenous administration of leukocyte endogenous mediator should be considered along with nutritional support. Administration of this protein to a seriously-ill malnourished individual should produce a metabolic profile of fever, increased urinary nitrogen excretion and falls in serum albumin concentrations that are generally considered pathologic. However, administration of leukocyte endogenous mediator over short periods of time should also provide the anabolic impetus for the augmented synthesis of proteins beneficial to recovery. In most cases, these countervailing forces of anabolism and catabolism should be of benefit to the host if the response to infection and injury is viewed as a physiologic redistribution of endogenous nutrients to meet the more critical and immediate needs of the stressed patient.     

Identification and interpretation of longitudinal gene expression changes in trauma

Rationale

The relationship between leukocyte gene expression and recovery of respiratory function after injury may provide information on the etiology of multiple organ dysfunction.

Objectives

To find a list of genes for which expression after injury predicts respiratory recovery, and to identify which networks and pathways characterize these genes.

Methods

Blood was sampled at 12 hours and at 1, 4, 7, 21 and 28 days from 147 patients who had been admitted to the hospital after blunt trauma. Leukocyte gene expression was measured using Affymetrix oligonucleotide arrays. A linear model, fit to each probe-set expression value, was used to impute the gene expression trajectory over the entire follow-up period. The proportional hazards model score test was used to calculate the statistical significance of each probe-set trajectory in predicting respiratory recovery. A list of genes was determined such that the expected proportion of false positive results was less than 10%. These genes were compared to the Gene Ontology for ‘response to stimulus’ and, using Ingenuity software, were mapped into networks and pathways.

Measurements and Main Results

The median time to respiratory recovery was 6 days. There were 170 probe-sets representing 135 genes that were found to be related to respiratory recovery. These genes could be mapped to nine networks. Two known pathways that were activated were antigen processing and presentation and JAK- signaling.

Conclusions

The examination of the relationship of gene expression over time with a patient''s clinical course can provide information which may be useful in determining the mechanism of recovery or lack of recovery after severe injury.     

Sepsis induces early alterations in innate immunity that impact mortality to secondary infection

Sepsis, the systemic inflammatory response to microbial infection, induces changes in both innate and adaptive immunity that presumably lead to increased susceptibility to secondary infections, multiorgan failure, and death. Using a model of murine polymicrobial sepsis whose severity approximates human sepsis, we examined outcomes and defined requirements for survival after secondary Pseudomonas aeruginosa pneumonia or disseminated Listeria monocytogenes infection. We demonstrate that early after sepsis neutrophil numbers and function are decreased, whereas monocyte recruitment through the CCR2/MCP-1 pathway and function are enhanced. Consequently, lethality to Pseudomonas pneumonia is increased early but not late after induction of sepsis. In contrast, lethality to listeriosis, whose eradication is dependent upon monocyte/macrophage phagocytosis, is actually decreased both early and late after sepsis. Adaptive immunity plays little role in these secondary infectious responses. This study demonstrates that sepsis promotes selective early, impaired innate immune responses, primarily in neutrophils, that lead to a pathogen-specific, increased susceptibility to secondary infections.     

Urinary cytokines for assessing inflammation in HIV-associated wasting

The relationship between cytokines and HIV-related weight loss has not been well established. Unlike most cytokines that are secreted in a paracrine manner, IL-6, sTNFR-II, and IL-1ra are readily detected in the systemic circulation and serve as markers of the inflammatory response. Twenty-four-hour urine concentrations of these proteins are believed to provide an integrative assessment of their systemic levels over the preceding hours. We sought to determine whether spot measurements of IL-6, sTNFR-II, and IL-1ra could be related to subsequent 24 h concentrations and prior weight loss. Eighteen subjects with severe wasting (average BMI=18+/-3 kg/m2with 19+/-13 kg of weight loss) and six HIV-negative healthy subjects were tested. Compared to values in controls, 24-h urinary concentrations of the three proteins adjusted for creatinine excreted were elevated in 44%, 89%, and 72% of patients, respectively. Twenty-four-hour concentrations were highly correlated with the spot concentrations (r=0.80, 0.87, 0.84, respectively, P<0.001). IL-1ra concentrations (24 h and spot) were correlated with weight loss in the previous 6 months, lifetime rate of weight loss and the 6 month rate of weight loss (spot: r=0.66, 0.73, 0.68, respectively, P< or =0.001). These data suggest that spot urinary collections can be used to estimate 24 h excretion rates. This strategy may be useful in assessing the inflammatory response in HIV-associated wasting.     

Appearance of hybridoma growth factor/interleukin-6 in the serum of mice bearing a methylcholanthrene-induced sarcoma

Serum concentrations of hybridoma growth factor/interleukin-6 progressively increased in mice bearing a transplantable methylcholanthrene-induced sarcoma with tumor growth. Elevated HGF/interleukin-6 concentrations were also positively correlated with increased serum concentrations of the hepatic acute phase reactant protein, amyloid P. Daily Indomethacin treatment of sarcoma-bearing mice prolonged survival and reduced the magnitude of the serum amyloid P response, but failed to attenuate either tumor growth or serum HGF/interleukin-6 responses. Since previous studies have demonstrated that neither interleukin-1 nor tumor necrosis factor-alpha can be detected in the serum of these sarcoma-bearing mice, and that HGF/interleukin-6 is a principal mediator of the hepatic acute phase response, we conclude that circulating HGF/interleukin-6 may contribute significantly to the host responses which accompany experimentally-introduced cancer. Furthermore, prostanoid inhibition does not appear to regulate the synthesis and release of HGF/interleukin-6 during tumor growth.     

Effects of intravenous IL-8 administration in nonhuman primates.

IL-8, a cytokine known for its potent and specific neutrophil activation and chemoattractant properties, has been recently detected in the circulation during septic shock, endotoxemia, and after IL-1 alpha administration. Because of its observed in vitro actions, it has been hypothesized that IL-8 may contribute to the dynamics of circulating granulocytes and to the pathologic sequelae seen in sepsis. Here, human rIL-8 is administered to healthy nonhuman primates as a single i.v. injection or as a continuous 8-h i.v. infusion. We demonstrate that both methods of i.v. administration result in a rapid but transient, severe granulocytopenia, followed by a granulocytosis that persists as long as IL-8 levels are detectable in the circulation. There were no hemodynamic changes after IL-8 administration, and animals remained clinically stable during the 24-h observation period. No detectable circulating TNF-alpha, IL-1 beta, or IL-6 response was induced by either IL-8 administration regimen. Histopathologic examination revealed mild to moderate neutrophilic margination in lung, liver, and spleen, of greater severity in baboons receiving the 8-h infusion. There was no associated neutrophilic infiltration or tissue injury. Thus, IL-8 modulates circulating granulocyte dynamics and likely directs their actions, but when administered i.v. to healthy animals, either as a bolus dose or as a continuous infusion for up to 8 h, does not induce the hemodynamic and metabolic aberrations or the acute organ damage seen during sepsis.     

Cachectin/tumor necrosis factor-alpha alters red blood cell kinetics and induces anemia in vivo

Chronic inflammatory diseases are often associated with decreased red blood cell (RBC) mass. The cytokines cachectin/tumor necrosis factor-alpha (TNF) and interleukin 1 (IL 1) are produced by monocytes/macrophages in response to many inflammatory stimuli and have been implicated in the anemia of chronic disease. This study was undertaken to evaluate the mechanisms by which cachectin/TNF, IL 1, or endotoxin induce anemia. Hematologic parameters and RBC kinetics were quantitated in rats given chronic sublethal quantities of either recombinant human cachectin/TNF, recombinant human IL 1 alpha, or Salmonella endotoxin for 7 days. Cachectin/TNF or endotoxin treatment resulted in a 25 or 31% decrease, respectively, in total RBC mass, whereas RBC mass was unchanged by IL 1 administration. Anemia associated with either chronic cachectin or endotoxin administration was characterized by normal mean corpuscular volume, mean corpuscular hemoglobin content, and reticulocyte numbers. [59Fe]RBC survival was significantly shortened in animals given cachectin, IL 1 or endotoxin, but the magnitude of the response was greatest in cachectin/TNF-or endotoxin-treated rats. Although cachectin/TNF-IL 1-, or endotoxin treatment resulted in similar hypoferremia and shortened plasma iron half-life, endotoxin or cachectin/TNF treatment (but not IL 1) significantly reduced the incorporation of plasma 59Fe into newly synthesized RBCs. We conclude that chronic cachectin/TNF administration produces anemia by decreasing RBC synthesis and reducing the life span of circulating RBCs. An endogenous cachectin/TNF response during inflammatory disease may contribute to an associated anemic state, whereas the modestly reduced red cell life span induced by IL 1 does not lead to a net reduction in RBC mass, presumably owing to a preserved RBC synthetic rate.     

Apoptosis in sepsis: a new target for therapeutic exploration.

The treatment of sepsis and septic shock remains a clinical conundrum, and recent prospective trials with biological response modifiers aimed at the inflammatory response have shown only modest clinical benefit. Recently, interest has shifted toward therapies aimed at reversing the accompanying periods of immune suppression. Studies in experimental animals and critically ill patients have demonstrated that increased apoptosis of lymphoid organs and some parenchymal tissues contributes to this immune suppression, anergy, and organ system dysfunction. During sepsis syndromes, lymphocyte apoptosis can be triggered by the absence of IL-2 or by the release of glucocorticoids, granzymes, or the so-called 'death' cytokines: tumor necrosis factor alpha or Fas ligand. Apoptosis proceeds via auto-activation of cytosolic and/or mitochondrial caspases, which can be influenced by the pro- and anti-apoptotic members of the Bcl-2 family. In experimental animals, not only can treatment with inhibitors of apoptosis prevent lymphoid cell apoptosis; it may also improve outcome. Although clinical trials with anti-apoptotic agents remain distant due in large part to technical difficulties associated with their administration and tissue targeting, inhibition of lymphocyte apoptosis represents an attractive therapeutic target for the septic patient.     

A novel type I IFN-producing cell subset in murine lupus

Excess type I IFNs (IFN-I) have been linked to the pathogenesis of systemic lupus erythematosus (SLE). Therapeutic use of IFN-I can trigger the onset of SLE and most lupus patients display up-regulation of a group of IFN-stimulated genes (ISGs). Although this "IFN signature" has been linked with disease activity, kidney involvement, and autoantibody production, the source of IFN-I production in SLE remains unclear. 2,6,10,14-Tetramethylpentadecane-induced lupus is at present the only model of SLE associated with excess IFN-I production and ISG expression. In this study, we demonstrate that tetramethylpentadecane treatment induces an accumulation of immature Ly6C(high) monocytes, which are a major source of IFN-I in this lupus model. Importantly, they were distinct from IFN-producing dendritic cells (DCs). The expression of IFN-I and ISGs was rapidly abolished by monocyte depletion whereas systemic ablation of DCs had little effect. In addition, there was a striking correlation between the numbers of Ly6C(high) monocytes and the production of lupus autoantibodies. Therefore, immature monocytes rather than DCs appear to be the primary source of IFN-I in this model of IFN-I-dependent lupus.