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Biomedical subjects

A Cerami

Publications and source records attributed to A Cerami.

At least 181 records · Page 10Linked to original sources
PubMed1988

Cachectin: a hormone that triggers acute shock and chronic cachexia.

Septic shock and invasive infection are diseases caused by humoral mediators of both exogenous and endogenous origin. The search for and identification of these factors has led to the discovery and molecular cloning of cachectin. This pyrogenic cytokine is identical to tumor necrosis factor (TNF) and, when released into the circulation, causes profound shock and multiple organ injury. Cachectin antibodies protect against the lethal effects of mice given endotoxin and baboons given E. coli, a result suggesting that this mediator is both necessary and sufficient to provoke septic shock. Cachectin is produced in humans after endotoxin infusion; the infusion of small doses of TNF is associated with fever, rigors, headache, and hypotension. Septicemic patients also produce cachectin, and during meningococcal infection, patients with the highest serum levels of cachectin die. Chronic cachectin production causes a potentially lethal syndrome of cachexia, anemia, and protein and lipid wasting. Future investigation is being directed toward the development of cachectin antibodies for use in treating the humorally mediated systemic complications of infectious disease.

Animals↗
PubMed1988

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.

Adrenocorticotropic Hormone↗
PubMed1988

Recombinant human cachectin/tumor necrosis factor but not interleukin-1 alpha downregulates lipoprotein lipase gene expression at the transcriptional level in mouse 3T3-L1 adipocytes.

Lipoprotein lipase (LPL) is synthesized primarily in muscle and adipose tissue and by hydrolyzing triglycerides in chylomicrons and very low density lipoprotein allows uptake of the resultant free fatty acids by these tissues. This report describes the cloning of the mouse LPL gene from which probes were derived to study the regulation of LPL synthesis in the 3T3-L1 adipocyte cell culture system. Preconfluent 3T3-L1 preadipocytes had very small amounts of LPL mRNA (less than 1 pg/micrograms of RNA). At confluency, LPL mRNA levels increased to 5 to 15 pg/micrograms of RNA. After insulin and dexamethasone were added, LPL activity and mRNA levels rose in parallel. Peak mRNA levels were reached within 4 to 10 days, achieving LPL mRNA concentrations of 150 to 500 pg/micrograms of RNA. This represents a 15- to 50-fold increase over confluent cells. Two cytokines known to diminish adipose tissue LPL activity were studied to see how their effects were regulated. Recombinant human cachectin/tumor necrosis factor diminished both LPL activity and LPL mRNA levels. The effect on LPL activity compared with mRNA levels was quicker, at a lower dose, and more complete (95 versus 75% maximum effect). The effect of recombinant human cachectin tumor necrosis factor on LPL mRNA levels was shown by nuclear run-on experiments to be exerted transcriptionally. It was also independent of new protein synthesis. Recombinant human interleukin-1 alpha diminished only LPL activity but not mRNA levels. This study suggests that during times of stress, cytokines secreted by activated macrophages can alter energy balance by affecting transcriptional and posttranscriptional processes in adipocytes.

Adipose Tissue↗
PubMed1988

Specific macrophage receptor activity for advanced glycosylation end products inversely correlates with insulin levels in vivo.

A high-affinity macrophage receptor has been shown to mediate the removal of proteins modified by advanced nonenzymatic glycosylation end products (AGEs) in both animals and humans. To characterize the effect of diabetes on this receptor system, resident peritoneal macrophages from experimentally induced and genetically diabetic mice were studied. Binding and degradation of radioiodinated AGE-bovine serum albumin (AGE-BSA) were determined from saturation kinetics and compared with glucose and insulin levels of each subgroup. Scatchard plot analysis of nondiabetic mouse macrophages has indicated 1.5 X 10(5) receptors/cell, with a binding affinity of 1.7 X 10(7) M-1. The in vitro exposure of macrophages to either elevated glucose or insulin concentrations failed to demonstrate a short-term regulatory effect on AGE-receptor function. However, macrophages from hypoinsulinemic alloxan-induced diabetic mice indicated a two- to threefold increase in AGE-receptor number per cell (2.98 +/- 0.25 X 10(5)/cell), and macrophages from C57BL/KsJ (db/db) mice showed an almost threefold greater receptor number (2.86 +/- 0.2 X 10(5)/cell), with binding affinity remaining essentially unchanged (1.24 +/- 0.05 X 10(7) and 1.21 +/- 0.07 X 10(7) M-1, respectively). In addition, a moderate increase (25-30%) of 125I-labeled AGE-BSA degradation was observed in these two insulin-deficient diabetic macrophage groups compared with the normal control group. In contrast, macrophages from hyperinsulinemic and hyperglycemic C57BL/6J (db/db) mice demonstrated a distinct reduction in both AGE-receptor number (0.67 +/- 0.03 X 10(5)/cell) and binding affinity (0.37 +/- 0.03 X 10(7) M-1), with a decrease of AGE-BSA degradation of approximately 50% compared with the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Tumor necrosis factor and endotoxin induce similar metabolic responses in human beings.

After injury, infection, or major operations a number of predictable metabolic responses occur. It has been proposed that the cytokine tumor necrosis factor (TNF)/cachectin is a primary mediator of these host responses. To test this hypothesis, we studied 16 tumor-bearing humans with normal renal and hepatic function, who received 24-hour continuous intravenous infusions of escalating doses of recombinant TNF (4 to 636/micrograms/m2/24 h). Serial measurements were made of vital signs and plasma concentrations of TNF, interleukin-1, adrenocorticotropic hormone, cortisol, iron, glucose, and C-reactive protein. Low doses of TNF had minimal metabolic effects, but infusions of greater than or equal to 545 micrograms/m2/24 hr (n = 8) resulted in fever, pituitary, and stress hormone release and acute phase changes. These alterations were compared with the changes that occurred in healthy humans (n = 13) receiving intravenous bolus injections of Escherichia coli endotoxin (4 ng/kg). TNF infusion in doses greater than or equal to 545 micrograms/m2/24 hr produced peak plasma TNF concentrations and metabolic responses that were similar to those after endotoxin injection. Interleukin-1 concentrations remained basal after TNF or endotoxin administration. TNF may represent the primary afferent signal that initiates many of the metabolic responses associated with sepsis and endotoxemia.

Acute-Phase Proteins↗
PubMed1988

Cytokine appearance in human endotoxemia and primate bacteremia.

The results of recent work have demonstrated that endotoxin elicits the production of several immunopeptide cytokines that likely mediate the development of septic shock. Bolus injection of endotoxin (20 units per kilogram of body weight) to four volunteers resulted in peak serum cachetin/tumor necrosis factor (TNF) levels of 358 +/- 166 picograms per milliliter within 90 minutes after challenge (p less than 0.05 versus base line) and peak serum interleukin-1 levels of 2.14 +/- 0.89 units per milliliter within two hours after challenge. By contrast, the infusion of a lethal dose of live Escherichia coli to four baboons revealed peak serum cachectin/TNF levels of 20,500 +/- 9,890 picograms per milliliter within 90 minutes after bacteria were given (p less than 0.05 versus base line) and peak interleukin-1 levels of 14.2 +/- 10.1 units per milliliter three hours after bacterial challenge. No detectable monokine levels were observed in either model six hours after challenge. Interferon-gamma levels reached a peak of 2.67 +/- 1.66 nanograms per milliliter in baboon sera at eight hours after bacterial infusion and was no longer detectable by 12 hours. Interferon-gamma was not detected in the sera of humans. These results suggest that the transient release of cachectin/TNF, followed by interleukin-1 and interferon-gamma, may participate in the cascade of events noted in overwhelming bacterial invasion.

Adult↗
PubMed1987

Advanced glycosylation endproducts on erythrocyte cell surface induce receptor-mediated phagocytosis by macrophages. A model for turnover of aging cells.

Glucose can react nonenzymatically with amino groups of proteins to form covalent Amadori products. With time these adducts undergo further rearrangements to form irreversible advanced glycosylation endproducts (AGE), which accumulate with protein age. A specific AGE, 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI), has been identified on proteins in vivo. We have recently shown that a macrophage receptor specifically recognizes and internalizes proteins modified by AGE such as FFI, thus preferentially degrading senescent macromolecules. Reasoning that cellular turnover may be mediated by macrophage recognition of AGE-membrane proteins, we prepared human RBCs with FFI attached chemically. Human monocytes were incubated with either FFI-RBCs, IgG-opsonized RBCs, or PBS-treated RBCs. Erythrophagocytosis of FFI-RBCs was significantly higher than that of PBS-RBCs (55 vs. 4%; p less than 0.0025) and almost as high as that of IgG-RBCs (70%), and was competitively inhibited by AGE-BSA. AGE-RBCs were also prepared by incubating RBCs with various sugars. Human monocytes showed a 15% ingestion of glucose-RBCs, and a 26% ingestion of glucose-6-phosphate-RBCs, compared to 6% for PBS-RBCs. Similarly, diabetic mouse RBCs were phagocytosed by nearly three times more cells (21%) than normal mouse RBCs when exposed to syngeneic mouse macrophages. This phagocytosis was competitively inhibited (70%) by addition of excess AGE-BSA. The in vivo half-life of 51Cr-labeled mouse FFI-RBCs injected into syngeneic mice was reduced to 7 d, as compared to a half-life of 20 d for the controls. These data suggest that the macrophage receptor for the removal of glucose-modified proteins may also mediate the endocytosis of RBCs with AGE formed on their surface, and thus be responsible in part for the removal of some populations of aging cells.

Animals↗
PubMed1987

Substrate specificity of the flavoprotein trypanothione disulfide reductase from Crithidia fasciculata.

The substrate specificity of the trypanosomatid enzyme trypanothione reductase has been studied by measuring the ability of the enzyme to reduce a series of chemically synthesized cyclic and acyclic derivatives of N1,N8-bis(glutathionyl)spermidine disulfide (trypanothione). Kinetic analysis of the enzymatic reduction of these synthetic substrates indicates that the mutually exclusive substrate specificity observed by the NADPH-dependent trypanothione disulfide reductase and the related flavoprotein glutathione disulfide reductase is due to the presence of a spermidine binding site in the substrate binding domain of trypanothione reductase. Trypanothione reductase will reduce the disulfide form of N1-monoglutathionylspermidine and also the mixed disulfide of N1-monoglutathionylspermidine and glutathione. The Michaelis constants for these reactions are 149 microM and 379 microM, respectively. Since the disulfide form of N1-monoglutathionylspermidine and the mixed disulfide of N1-monoglutathionylspermidine and glutathione could be formed in trypanosomatids, the binding constants and turnover numbers for the enzymatic reduction of these acyclic disulfides are consistent with these being potential alternative substrates for trypanothione reductase in vivo.

Animals↗
PubMed1987

Leishmania promastigotes are recognized by the macrophage receptor for advanced glycosylation endproducts.

In this paper we demonstrate the involvement of the macrophage receptor for advanced glycosylation endproducts (AGE) in the phagocytosis of Leishmania major promastigotes. Blocking of this receptor with the ligand, AGE-BSA, leads to a 50% decrease in phagocytosis relative to controls, and a comparable decrease in the respiratory burst. The inhibition of phagocytosis by AGE-BSA was specific to leishmania. The binding of zymosan or C3bi-RBC and the phagocytosis of IgG-RBC or latex beads was not affected by the presence of AGE-BSA. Blocking of both the AGE receptor and CR3 decreases leishmania binding by nearly 90%, and reduces the respiratory burst by 80%, indicating that the two receptors account for the bulk of L. tropica promastigote recognition and uptake by the macrophage.

Animals↗
PubMed1987

Physiological responses to cachectin.

Mammals infected with parasitic, bacterial or viral organisms or bearing tumours characteristically display a catabolic state and weight loss which can advance to cachexia (or wasting), shock and death. Although the phenomenon is commonly observed in many parasitic diseases its mechanism is not understood. We have identified and isolated a macrophage protein, cachectin, as the molecule that may be responsible for cachexia and shock. Cachectin is produced by macrophages in response to endotoxin or a number of other bacterial or protozoal products. The released cachectin acts as a hormone, binding to specific high affinity receptors and eliciting biological responses. In the adipocyte anabolic enzymes such as lipoprotein lipase are suppressed through the selective inhibition of mRNA production. An intriguing aspect of cachectin is its pivotal role in the pathogenesis of endotoxin-induced shock. Cachectin causes fever and anorexia and can induce lethal shock and tissue injury in experimental animals. During its chemical characterization cachectin was shown to be identical to tumour necrosis factor (TNF), a macrophage protein that kills tumour cells. This finding emphasizes the extensive range of effects associated with this protein. Cachectin has many properties in common with interleukin 1 but binds to a different receptor and lacks structural homology. Presumably, low levels of cachectin help the host in its battle to remove invasive pathogens, but extensive production of cachectin can lead to shock and catabolic stress hormone responses. These findings have added a new dimension to the biological properties of cachectin, its production, and its role in cachexia and shock.

Animals↗
PubMed1987

The formation of reactive intermediate(s) of glucose 6-phosphate and lysine capable of rapidly reacting with DNA.

Glucose has been shown to react nonenzymatically in vitro with DNA, to form products with spectral properties similar to those observed with the nonenzymatic glycosylation of proteins in vivo. The incubation in vitro of glucose or glucose 6-phosphate with f1 phage DNA results in a time- and concentration-dependent loss of transfection efficiency. It has also been shown that incubation in vitro of pBR322 DNA with glucose 6-phosphate prompts a loss in transformation capability as well as gross DNA alterations. In the present communication, we have investigated a model reaction of glucose 6-phosphate with the amino groups of lysine to form reactive intermediates which are capable of forming covalent adducts with DNA. The preincubation of glucose 6-phosphate and [3H]lysine leads to a time- and concentration-dependent formation of reactive intermediates. These intermediates, which accumulate with time, can subsequently react with single- or double-stranded DNA to form acid-stable complexes. Studies done with synthetic polynucleotides suggest low reactivity of the intermediate with thymidine. The formation of the reactive intermediates is saturated by the addition of excess unlabeled lysine. Once formed the intermediates are insensitive to the addition of aminoguanidine and to reduction by sodium borohydride. The chemical reactions between sugars and lysine reported here and the reactivity of that product with DNA provide a model for exploring the classes of DNA damage that may contribute to the loss of DNA function during aging.

DNA, Bacterial↗