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R Porat

Publications and source records attributed to R Porat.

At least 37 records · Page 2Linked to original sources
PubMed1994

Interleukin-1 induces interleukin-8 secretion from endothelial cells by a juxtacrine mechanism.

Inflammation is characterized by migration of neutrophils through the endothelium, and the chemokine interleukin-8 (IL-8) appears to be involved. We asked whether adherence of cells bearing a membrane-form of interleukin 1 (IL-1) induces IL-8 secretion from human umbilical vein endothelial cells (HUVEC) and fibroblasts. Human peripheral blood mononuclear cells (PBMC) were stimulated with endotoxin for 12 hours and then fixed for 4 hours with paraformaldehyde. When these cells were added to HUVEC or fibroblasts, IL-8 production was induced. This stimulation by fixed PBMC was attributed to IL-1, because pretreatment of HUVEC or fibroblasts with IL-1 receptor antagonist (IL-1Ra) reduced the induction by 95% and 80%, respectively, P < .005. Using anti-IL-1 alpha monoclonal antibodies, reduction was complete, whereas anti-IL-1 beta had no effect. IL-1 alpha was shown on the surface of monocytes by fluorescence-activated cell sorter (FACS) analysis. Blockade of IL-1 receptors on PBMC did not affect the activity of membrane-associated IL-1 alpha, indicating that IL-1 is not anchored to the membrane through its receptors. However, PBMC treated with D-mannose before fixation resulted in a loss of activity; this loss of activity was associated with release of IL-1 alpha, not IL-1 beta, into the supernatant. Thus, anchoring of IL-1 alpha to the membrane may be via a lectin or mannose receptor-like interaction. Blockade of membrane IL-1 alpha required a 30-fold and fivefold excess of IL-1Ra compared with the amount required to block soluble IL-1 beta and IL-1 alpha, respectively. We conclude that the fixed PBMC IL-8 inducing activity is almost entirely caused by IL-1, that this represents IL-1 alpha bound to a surface lectin or mannose receptor on the monocyte, and that it functions in inflammation via juxtacrine interactions.

Cell Membrane↗
PubMed1993

Hematologic and immunomodulatory effects of an interleukin-1 receptor antagonist coinfusion during low-dose endotoxemia in healthy humans.

Endotoxin is a component of gram-negative bacteria that causes hematologic and immunologic changes through its induction of cytokines. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring inhibitor of IL-1 that competes with IL-1 for occupancy of cell-surface receptors but possesses no agonist activity. We investigated the ability of human recombinant IL-1Ra to block the effects of low-dose endotoxin. Fourteen healthy male volunteers between 18 and 30 years old were injected intravenously with 3 ng/kg Escherichia coli endotoxin. Concurrent with the injections, nine volunteers received a 3-hour continuous intravenous infusion of IL-1Ra. The other five subjects were given a 3-hour infusion of saline. Volunteers injected with endotoxin experienced a threefold increase in circulating neutrophils over baseline. This neutrophilia was significantly reduced by 48% in subjects administered endotoxin plus IL-1Ra (P = .0253). Ex vivo mitogen-induced peripheral blood mononuclear cell proliferation decreased by greater than 60% at 3 and 6 hours after endotoxin injection (P = .0053). This endotoxin-induced reduction in mitogen response was reversed in subjects coinjected with IL-1Ra (P = .0253). Endotoxin-induced symptoms, fever, and tachycardia were unaffected by IL-1Ra. IL-1 appears to be an important mediator in endotoxemia because some of its hematologic and immunomodulatory effects can be blocked by IL-1Ra.

Adolescent↗
PubMed1993

Intravenous endotoxin suppresses the cytokine response of peripheral blood mononuclear cells of healthy humans.

When administered parenterally, endotoxin stimulates the synthesis of IL-1, TNF-alpha, and IL-6. However, this initial injection induces tolerance; a second injection of endotoxin results in lower levels of circulating cytokines. In our study, five healthy male volunteers between the ages of 18 and 30 were injected with Escherichia coli endotoxin. Four subjects received only saline. Immediately before the injection and 3, 6, and 24 h afterward, PBMC were isolated and stimulated in vitro with endotoxin, IL-1, or toxic shock syndrome toxin-1. Inasmuch as CD14+ monocytes are the primary source of the cytokines induced by these stimuli, results are expressed as cytokine production per 10(6) CD14+ cells. Six h after endotoxin injection, endotoxin-stimulated CD14+ cells synthesized 66% less IL-1 beta (p < 0.01), 47% less TNF-alpha (p < 0.001), 56% less IL-6 (p < 0.01), and 49% less IL-8 (p < 0.01) than cells obtained before the injection. This suppression was not specific for endotoxin; IL-1 beta-induced IL-1 alpha and TNF-alpha were reduced by 84% (p = 0.01) and 68% (p < 0.001), respectively. A decrease in cytokine synthesis was also observed using toxic shock syndrome toxin-1 as a stimulus: 57% for IL-1 beta (p = 0.06), 70% for TNF-alpha (p < 0.01), 56% for IL-6 (p < 0.05), and 71% for IL-8 (p = 0.001). When data were expressed as cytokine production per 10(6) PBMC, cells isolated 3 h after endotoxin injection synthesized significantly less stimulus-induced IL-1, TNF-alpha, IL-6, and IL-8 than did PBMC from saline-injected controls. We conclude that endotoxin tolerance is due, in part, to changes in the stimulus-induced cytokine response of circulating CD14+ cells.

Antigens, CD↗
PubMed1993

Activated platelets induce endothelial secretion of interleukin-8 in vitro via an interleukin-1-mediated event.

Migration of neutrophils through endothelial cells (EC) and induction of cytokine secretion are two well-documented events during the inflammatory reaction. The inflammatory, chemotactic cytokine interleukin-8 (IL-8) is secreted by EC in response to IL-1 stimulation. In this study, we show that platelets activated with either adenosine-5'-diphosphate or epinephrine induce IL-8 secretion by EC. This stimulatory activity was found to be associated with sedimented platelets after activation. Blockade of IL-1 receptors on EC with IL-1 receptor antagonist (IL-1Ra) decreased the stimulatory effect of whole activated platelet preparations by 59% (P < .05). Similarly, IL-1Ra pretreatment of EC reduced the stimulatory effect of sedimented activated platelets by 60% (P < .01). In addition, we treated human blood donors with 750 mg of oral aspirin, and evaluated the stimulatory effect of epinephrine-activated platelets on IL-8 secretion by EC. IL-8 synthesis after aspirin ingestion was inhibited by 90% (P < .01) as compared with the preaspirin stimulation. These observations show that activated platelets induce IL-8 secretion via membrane-associated IL-1 activity, and provide a novel relationship between coagulation and inflammation that could be relevant to several diseases.

Adenosine Diphosphate↗
PubMed1992

Pharmacokinetics, safety and immunomodulatory effects of human recombinant interleukin-1 receptor antagonist in healthy humans.

A phase I study of human recombinant interleukin-1 receptor antagonist (IL-1ra) was conducted in healthy males between the ages of 18 and 30. Twenty-five volunteers received a single, 3 h continuous intravenous infusion of doses ranging between 1 mg/kg and 10 mg/kg IL-1ra. At 3 h into the infusion, plasma IL-1ra levels were 3.1 micrograms/ml and 29 micrograms/ml for the 1 mg/kg and 10 mg/kg doses, respectively. Post-infusion plasma IL-1ra levels declined rapidly, exhibiting an initial half-life of 21 min and a terminal half-life of 108 min. Clinical, hematological, biochemical, endocrinological and immunomodulatory effects were monitored over 72 h and compared to those of four subjects receiving a 3 h infusion of saline. There were no clinically significant differences between the drug and saline groups in symptoms, physical examinations, complete blood counts, mononuclear cell phenotypes, blood chemistry profiles, serum iron and serum cortisol levels. Peripheral blood mononuclear cells (PBMC) obtained after completion of the IL-1ra infusion synthesized significantly less interleukin 6 ex vivo than PBMC from saline-injected controls. These data suggest that transient blockade of interleukin 1 receptors is safe and does not significantly affect homeostasis.

Cytokines↗
PubMed1992

Distribution of polysaccharide side chains of lipopolysaccharide determine resistance of Escherichia coli to the bactericidal activity of serum.

The lipopolysaccharide (LPS) of serum-sensitive strains of Escherichia coli was compared with LPS derived from serum-resistant clones. Polysaccharide O-antigen side chains (PSSC) of LPS from serum-resistant clones contained 12%-40% more of the longer carbohydrate molecules (L-PSSC) than did LPS from serum-sensitive parent strains; in contrast, 12%-27% more of the shorter PSSC (S-PSSC) were found in LPS from serum-sensitive strains. The sensitivity or resistance to the bactericidal activity of human serum correlated with the distribution and the length of PSSC fractions of LPS. This was demonstrated in a liposome model in which LPS was incorporated into simulated bacterial membranes. The incubation of serum with liposomes incorporated with various ratios of S-PSSC-to-L-PSSC concentrations resulted in liposomal lysis at S-PSSC-to-L-PSSC ratios greater than 2:1. These findings demonstrate the importance of the length of carbohydrate side chains of LPS in determining sensitivity or resistance to the bactericidal activity of human serum.

Blood Bactericidal Activity↗
PubMed1992

Interleukin-1 (IL-1) receptor blockade reduces endotoxin and Borrelia burgdorferi-stimulated IL-8 synthesis in human mononuclear cells.

Interleukin-1 (IL-1) is a potent stimulator of IL-8 production by fibroblasts and monocytes. In the present study, we asked how much of endotoxin (LPS)-induced IL-8 production by human peripheral blood mononuclear cells was due to IL-1 induced by LPS. Cells were stimulated with either IL-1 beta, LPS, or Borrelia burgdorferi, and total IL-8 was determined by a specific radioimmunoassay. The addition of saturating concentrations of IL-1 receptor antagonist protein (IRAP) reduced the IL-1 beta-, LPS-, and B. burgdorferi-induced IL-8 synthesis by 85, 50, and 40%, respectively. Increasing the concentration of LPS did not affect the reduction in IL-8 synthesis observed in the presence of IRAP. Significant inhibition of the IL-1 beta-induced IL-8 synthesis was observed when IRAP was added 60 or 90 min after IL-1 beta; similarly, IL-8 synthesis after LPS was also reduced by delayed addition of IRAP. These data suggest that the ameliorative effects of IL-1 receptor blockade in models of inflammation and infection may be due, in part, to suppression of IL-1-induced IL-8.

Borrelia burgdorferi Group↗
PubMed1992

Effects of endotoxin-associated protein on hematopoiesis.

Endotoxin-associated protein (EAP), a gram-negative bacterial cell wall component, was evaluated for its effects on hematopoietic colony formation in vitro. Colony-stimulating activity, induced by EAP on circulating and bone marrow progenitor cells, was found to be partially mediated by T cells and augmented by interleukin-3. The addition of anti-human interleukin-1 (IL-1) antibodies reduced EAP activity, suggesting that EAP may induce IL-1 production. However, EAP was shown to promote the growth of mature progenitor cells independently, unlike the effects of IL-1 on the hematopoietic system. These studies demonstrate that bacterial components other than lipopolysaccharide, such as EAP, may have hematopoietic activity.

Bacterial Proteins↗
PubMed1991

Enhancement of growth of virulent strains of Escherichia coli by interleukin-1.

Interleukin-1 (IL-1) is a polypeptide cytokine that mediates many physiological responses to infection and inflammation and is a growth factor for certain mammalian cells. Virulent and avirulent clinical isolates of Escherichia coli were grown in culture media in the presence of human IL-1. IL-1 beta, but not tumor necrosis factor or IL-4, enhanced the growth of virulent, but not avirulent, E. coli. This enhancement was blocked by the IL-1 receptor antagonist (IL-1ra). Radiolabeled IL-1 bound to virulent but not avirulent E. coli in a specific and saturable fashion; IL-1ra inhibited this binding. Thus, human IL-1 may recognize a functional IL-1-like receptor structure on virulent E. coli and may be a virulence factor for bacterial pathogenicity.

Culture Media↗
PubMed1991

Restoration of in vitro hematopoiesis in B-chronic lymphocytic leukemia by antibodies to tumor necrosis factor.

Hematopoiesis was evaluated in 15 B-CLL patients using the mixed colony formation assay. The mean growth of all types of colonies in B-CLL peripheral blood was significantly lower than that of 10 normal controls (p less than 0.05). To investigate whether TNF is the cytokine involved in the reduced growth of hematopoietic progenitors in B-CLL, neutralizing anti-TNF antibodies (anti-TNF Abs) were added to the cultures. Anti-TNF Abs optimized in vitro hematopoiesis in 11 out of 15 B-CLL patients and a significant growth increase in all types of colonies was noted as compared to baseline cultures (p less than 0.05). In patients with stage IV disease, the increase in both mixed and erythroid colonies was more prominent than in patients with earlier disease stages. This optimization of growth was also observed in normal control cultures containing accessory cells. However, high TNF levels were measured in conditioned media from CLL patients and suppressed normal bone marrow hematopoietic progenitors growth. In contrast no TNF was detected in normal conditioned media. It is concluded that TNF and other cytokines, among them IL-3, play a role in the regulation of hematopoietic function in some B-CLL cases. These findings may have clinical applicability.

Aged↗
PubMed1991

Cocaine: a risk factor for necrotizing enterocolitis.

Necrotizing enterocolitis occurs most often in the small preterm infant, usually with birthweight less than 1.5 kg. Necrotizing enterocolitis has also been described in more mature infants, however, often the result of reduced gastrointestinal blood flow. We describe four relatively large infants from our nursery with varying severity of necrotizing enterocolitis. None had any of the known risk factors; all had a history of maternal cocaine use. Two were initially cared for in the term nursery. All four presented with abdominal distention, bloody stools, vomiting, or residuals. One infant presented with fulminant deterioration and subsequently died; the other three infants were treated medically and survived. It is suggested that a high index of suspicion be maintained for the possibility of necrotizing enterocolitis and feeding intolerance in term and near-term infants exposed in utero to cocaine.

Cocaine↗
PubMed1989

Inaccuracy in the doses of injectable medications dispensed from rubber-stoppered vials.

The literature of pharmacology often assumes that a full dosage is utilized when the contents of a vial have been administered by syringe. Five hundred discarded medication vials were assayed. The residues amounted to 1.98% to 8.81% of the listed dosages. An additional 0.7% to 8.66% remained in the syringes and needles used to aspirate the vials. Routine preparation techniques do not recover medication trapped on glass and rubber surfaces; losses are greatest when small diluent volumes are added to prepare intramuscular injections. The mean dose of gentamicin recovered from 80-mg ampules was 78.65 mg, and comparable vials of tobramycin yielded 76.01 mg. The discrepancy may contribute to the "increased toxicity" of gentamicin. Each year, more than $40,000,000 worth of antibiotics are lost to a biopharmaceutical dead space. Used antibiotic and controlled substance vials pose a potential threat to the environment. Although the amount of drug lost during preparation and administration may be of little therapeutic consequence, the discrepancy between intended and administered dosage is reflected in economic loss and pharmacological confusion. Pharmacological data should be adjusted for such losses. Medication wastage could be reduced by redesign of vials and alterations in practice of the administration.

Anti-Bacterial Agents↗
PubMed1989

Effect of sustained pharmacologic vitamin E levels on incidence and severity of retinopathy of prematurity: a controlled clinical trial.

The incidence and severity of retinopathy of prematurity (ROP) as affected by vitamin E prophylaxis at pharmacologic serum levels (5 mg/dl) were evaluated in a double-masked clinical trial of infants with a birth weight less than or equal to 2000 gm or a gestational age less than or equal to 36 weeks. The infants were enrolled by age 5 days and randomly assigned to receive parenterally administered, and later orally administered, free alpha-tocopherol (vitamin E) or its placebo. Study medication was continued until retinal vascularization was complete or active ROP had subsided, except in infants with a diagnosis of severe disease, in whom vitamin E was substituted for study medication. Acute ROP data were collected on 755 infants. Logistic regression analysis, with control for immaturity, oxygen exposure, and other illness risk factors, showed a decrease in incidence of ROP in vitamin E-treated infants (p = 0.003, all infants; p = 0.035, infants weighing less than or equal to 1500 gm at birth). Among the 424 infants weighing less than or equal to 1500 gm at birth, the age at enrollment influenced treatment effect (age day 0 to 1, p = 0.006 (n = 288) vs age day 2 to 5, p greater than 0.1 (n = 136]. Overall, 77.6% of infants with ROP had mild disease. Moderate to severe ROP was confined to infants weighing greater than or equal to 1500 gm at birth (25 given placebo, 25 given vitamin E), with progression to severe disease in nine placebo-treated versus three vitamin E-treated infants (p = 0.048). The incidence of severe ROP per se was not significantly decreased (all birth weights, p = 0.086; less than or equal to 1500 gm birth weight, p = 0.080); the sample size was too small, however, to assess this end point adequately. An increased incidence of sepsis and late-onset necrotizing enterocolitis was found among vitamin E-treated infants weighing less than or equal to 1500 gm at birth who received study medication for greater than or equal to 8 days (p = 0.006). Because most ROP is mild in degree and regresses completely, the risk/benefit ratio of pharmacologic prophylaxis for ROP is unfavorable. Treatment of moderate and severe ROP with vitamin E above physiologic serum levels (greater than 3 mg/dl) appears promising and should be further investigated. The interpretation of cicatricial outcome was confounded by the small number of patients involved and by subsequent treatment of severe ROP in placebo-treated infants with vitamin E.

Age Factors↗
PubMed1989

Randomized clinical trial of aztreonam and aminoglycoside antibiotics in the treatment of serious infections caused by gram-negative bacilli.

Aztreonam was compared with aminoglycoside antibiotics (tobramycin and amikacin) in a randomized, prospective, clinical trial in serious infections caused by gram-negative bacilli (GNB). A total of 43 evaluable patients with 47 infected sites were treated with aztreonam, and 41 evaluable patients were treated with aminoglycosides for 43 infections. Of patients treated with aztreonam, 17 were bacteremic, as were 12 of those treated with aminoglycosides. Clinical and microbiologic response rates were similar, except that only 5 of 11 patients with pneumonia were considered to be clinically cured with aminoglycoside therapy, while 5 of 6 patients with pneumonia treated with aztreonam were cured. Renal impairment was observed in 9 of 54 patients who received aminoglycoside antibiotics, but in only 2 of 53 patients treated with aztreonam. Hearing impairment developed in one patient treated with tobramycin. Transient elevations of serum transaminase levels occurred in 9 of 53 patients treated with aztreonam and in only 2 of 54 aminoglycoside-treated patients. Diarrhea and superinfection occurred with equal frequency in both groups. Serum concentrations of bactericidal activity could not be correlated with the outcome of therapy. Aztreonam appears to have comparable clinical efficacy with aminoglycoside antibiotics for the treatment of serious infections caused by aerobic and facultative GNB. Its use as a single agent for the treatment of serious lower respiratory infections caused by GNB warrants further evaluation.

Adult↗