PubMed Health⌕ Search

Biomedical subjects

D Keppler

Publications and source records attributed to D Keppler.

At least 127 records · Page 7Linked to original sources
PubMed1989

Prevention of endogenous leukotriene production during anaphylaxis in the guinea pig by an inhibitor of leukotriene biosynthesis (MK-886) but not by dexamethasone.

Leukotriene C4 (LTC4) underwent rapid elimination from the circulating blood and was extensively converted to LTD4 within the vascular space of the guinea pig. To mimic the elimination and metabolism of endogenous LTC4 generated during anaphylaxis, 14,15-3H-labeled LTC4 was infused intravenously over a period of 15 min, leading to a recovery in bile of 85% of the infused LT radioactivity within 2 h. Corresponding to the tracer studies, LTD4 and, to a lesser extent, LTC4 were the predominant endogenous cysteinyl LTs in guinea pig bile. The biliary production rate of endogenous LTD4 increased from 0.3 +/- 0.1 to 6.2 +/- 1.8 pmol x min-1 x kg-1 (p less than 0.001) during anaphylactic shock induced by intravenous injection of OVA (0.2 mg/kg) into sensitized guinea pigs. A novel LT biosynthesis inhibitor (MK-886; 10 mg/kg, i.v., 15 min before antigen challenge) suppressed the antigen-induced cysteinyl LT production by greater than 92% (p less than 0.001). This inhibition of systemic LTC4 formation was associated with a complete protection against lethal anaphylactic shock in animals pretreated in addition with the H1 receptor antagonist pyrilamine. Pretreatment with either the inhibitor of LT synthesis or the histamine receptor antagonist reduced the lethality during anaphylactic shock from 100 to 60 and 78%, respectively. In artificially ventilated, pyrilamine-pretreated animals, the antigen-induced decrease in dynamic lung compliance and the rise in hematocrit were significantly reduced (p less than 0.05) by pretreatment with the inhibitor of LT synthesis. Dexamethasone at high doses (10 mg/kg, i.p., once daily for 7 d, or in a single dose of 10 mg/kg, i.v., 3.5 h before challenge) had no inhibitory effect on LT generation during anaphylaxis in vivo. However, in resident peritoneal macrophages, harvested from these dexamethasone-treated sensitized guinea pigs and stimulated with zymosan, both cysteinyl LT and 6-keto-PGF1 alpha formation were strongly suppressed. These studies indicate an important role of cysteinyl LTs in systemic anaphylaxis in vivo and demonstrate the blockade of anaphylactic LT generation by a novel inhibitor of LT biosynthesis (MK-886) but not by dexamethasone.

Anaphylaxis↗
PubMed1989

Ethanol-induced inhibition of leukotriene degradation by omega-oxidation.

omega-Oxidation of leukotrienes is a major pathway in the degradation and inactivation of these proinflammatory mediators. Ethanol inhibited this process in vivo and in vitro. In rat liver in vivo the catabolism of LTE4 to omega-carboxylated leukotrienes was inhibited by 57% by an ethanol dose of 25 mmol/kg body mass administered intragastrically. The site of inhibition was the oxidation of omega-hydroxy-N-acetyl-LTE4 to omega-carboxy-N-acetyl-LTE4 resulting in an accumulation of omega-hydroxy-N-acetyl-LTE4 and of N-acetyl-LTE4. Analogous results were obtained for the oxidative degradation of LTB4 and omega-hydroxy-LTB4 in rat hepatocyte suspensions. Ethanol, at a concentration of 12.5 mmol/l (0.07%; by vol.), caused 68% inhibition of the oxidation of omega-hydroxy-LTB4 by 50% in hepatocyte suspensions. The conversion of omega-hydroxy-LTB4 to omega-carboxy-LTB4 by rat and human liver cytosol was inhibited by ethanol with half maximal concentrations of 100 mumols/l and 300 mumols/l, respectively. Our measurements indicate that direct interference by ethanol of the omega-oxidation of leukotrienes as well as an increased NADH/NAD+ ratio induced by ethanol led to the inhibition of leukotriene degradation. The impairment of leukotriene inactivation in the liver by ethanol may contribute to the development of the inflammatory reaction in acute alcoholic liver disease.

Animals↗
PubMed1989

Metabolic inactivation of leukotrienes.

The metabolic inactivation of the cysteinyl leukotrienes LTC4 and LTD4 and of the chemotactic LTB4 was studied in the rat in vivo and in hepatocyte suspensions, respectively. 1. Deactivation of LTC4 via LTD4 to LTE4 was a most active process in the blood circulation, catalyzed mainly by ectoenzymes located on the internal wall of blood vessels. Uptake of cysteinyl leukotrienes by hepatocytes and kidney cells contributed to the rapid elimination of these potent mediators whenever they were released into the blood circulation. The initial half-life of LTC4 in vivo was 12 seconds. 2. omega-Oxidation leads to the formation of omega-hydroxylated and omega-carboxylated cysteinyl leukotrienes which were detected in bile and urine. Biliary metabolites included those formed by stepwise beta-oxidative degradation of omega-carboxy-N-acetyl-LTE4, yielding the dinor, tetranor, and hexanor derivative. 3. The peroxisome proliferator clofibrate strongly increased the degradation of LTE4 by omega-oxidation and subsequent beta-oxidation in vivo. The generation of new polar metabolites was detected by HPLC methods and by the use of 3H8-labeled cysteinyl leukotrienes in comparison with the 3H2-labeled precursor. 4. The metabolic degradation and inactivation of cysteinyl leukotrienes in vivo and of LTB4 in isolated hepatocytes was potently inhibited by ethanol. The site of inhibition was the oxidation of omega-hydroxy-N-acetyl-LTE4 and of omega-hydroxy-LTB4 to the respective omega-carboxylated metabolite. This inhibition led to an accumulation of the biologically active LTB4 and of N-acetyl-LTE4. The interference of leukotriene inactivation in the liver may provide a novel explanation for the ethanol-induced inflammatory reaction in acute alcoholic liver disease.

Animals↗
PubMed1989

Analysis of cysteinyl leukotrienes in human urine: enhanced excretion in patients with liver cirrhosis and hepatorenal syndrome.

The cysteinyl leukotrienes, comprising leukotriene C4 and its metabolites, are biologically most active mediators, eliminated from the blood circulation by the liver and the kidneys. The urine of normal subjects and of patients with hepatic and/or renal failure was analysed for endogenous cysteinyl leukotrienes. The leukotriene metabolites were separated by reversed-phase high-performance liquid chromatography and subsequently quantified by radioimmunoassay. Leukotriene E4 was detected in all urine samples analysed. Its mean concentration increased from 0.3 nmol l-1 in healthy subjects to 0.8 nmol l-1 in patients with liver cirrhosis. In patients with hepatorenal syndrome leukotriene E4 averaged 7.8 nmol l-1; in addition, N-acetyl-leukotriene E4 was detected in an average amount of 1.5 nmol l-1. The mean leukotriene E4/creatinine ratio in urine increased from 0.02 in healthy subjects to 0.11 in patients with liver cirrhosis and to 1.2 mumol leukotriene E4 mol-1 creatinine in patients with hepatorenal syndrome. These results indicate that cysteinyl leukotrienes may play an important role in the mediator network responsible for the development of the hepatorenal syndrome in patients with severe liver disease.

Adolescent↗
PubMed1988

Immunohistochemical and biochemical study of a cathepsin B-like proteinase in human colonic cancers.

An immunohistological study was carried out on 51 human colorectal adenocarcinomas and eight samples of histologically normal colonic mucosa removed far from tumors, using anti-rabbit cathepsin B and anti-human cathepsin B immunoglobulins. Positive reactions were obtained on tumor cells and macrophage-like cells. However, as these immunoglobulins could not discriminate between cathepsin B and cathepsin B-like proteinases, and as they cross-reacted with cathepsins H and L, a partial characterization of the proteinase activities was performed in order to identify the type of enzyme present in the positive cells. The levels of cathepsins H and L were very low in extracts of colorectal tumors and normal colonic mucosa. A peculiar cathepsin B-like proteinase activity with pH optimum at 6.8 was found in tumor extracts together with the lysosomal cathepsin B, whereas normal colonic mucosa showed only cathepsin B activity (pH optimum, 6.0). These results indicate that lysosomal cathepsin B is responsible for staining of macrophage-like cells found in the lamina propria of colonic mucosa and in the peritumoral stroma. Immunohistochemical staining of colonic tumor cells observed in 29/51 cases seems on the other hand to be primarily due to a cathepsin B-like proteinase. Three colonic tumor cell lines, Colo-205, HT-29, and SW-1116, were also studied using the same methods. These cells produced a latent cathepsin B-like proteinase which, after activation, was similar to that found in tumor extracts. This latent proteinase was detected mainly in the culture media. The cultured colonic tumor cells, after staining by anti-cathepsin B antibodies, showed strongly positive granules. In conclusion, this work demonstrates that malignant colonic cells are the source of a cathepsin B-like proteinase, with optimal activity near neutrality. Its secretion into the extracellular space indicates furthermore, that it may be an important component of the "proteinase cascade" associated with tumor invasion and metastasis.

Cathepsin B↗
PubMed1988

[The Heinrich-Wieland Prize presentation. Metabolism and analysis of leukotrienes in vivo].

Leukotrienes are potent mediators of inflammatory and allergic reactions involved, among others, in endotoxin action and shock, tissue trauma, acute liver injury, hepatorenal syndrome, inflammatory bowel disease, acute pancreatitis, and asthma. Studies on metabolism and analysis of these arachidonate metabolites in vivo are a prerequisite for an improved understanding of their role under physiological and pathophysiological conditions and for the development of inhibitors of leukotriene synthesis and of receptor antagonists. Leukotriene C4 and its metabolites, collectively termed the cysteinyl leukotrienes, are predominantly inactivated by the liver. Rapid hepatocellular uptake is followed by partial metabolic inactivation, comprising omega-oxidation and N-acetylation of leukotriene E4, and excretion into bile. A minor portion of the cysteinyl leukotrienes undergoes enterohepatic circulation. In all species investigated so far, hepatobiliary elimination of cysteinyl leukotrienes predominates over renal excretion. Analysis of the systemic production of cysteinyl leukotrienes in vivo has been accomplished by radioimmunological determination of species-characteristic index metabolites in bile after their separation by high-performance liquid chromatography. The mercapturate N-acetyl-leukotriene E4 is the index metabolite of choice in the rat. In man, leukotriene E4 is the predominant endogenous cysteinyl leukotriene in both bile and urine. The amounts of cysteinyl leukotrienes detected under various pathophysiological conditions may be sufficient to induce known phenomena associated with the respective disease. As shown under experimental conditions, inhibition of leukotriene synthesis or receptor antagonism can serve as therapeutic approaches.

Animals↗
PubMed1988

Tumor necrosis factor alpha stimulates leukotriene production in vivo.

Tumor necrosis factor alpha, or cachectin (TNF), is a polypeptide mediator with proinflammatory and antitumor actions. It is produced in large amounts by lipopolysaccharide (LPS)-activated macrophages. TNF as well as LPS stimulated the arachidonate cascade leading to the synthesis of leukotrienes (LT) in vivo. Production of endogenous cysteinyl LT was measured in anesthetized rat using the biliary excretion of N-acetyl-LTE4 as an indicator. Infusion of TNF over a 1-h period greatly increased the rate of cysteinyl LT production during the subsequent 3 h. Pretreatment with anti-TNF antibody F(ab')2 fragments prevented enhanced LT generation as well as tachypnea (a sign of the in vivo action of TNF). LT production elicited by TNF was similar to that evoked by infusion of LPS. Our results indicate that lipoxygenase products are involved in the network of pathophysiological events induced by TNF. The proinflammatory and shock-inducing LT may mediate many of the adverse effects of TNF in vivo as well as its antitumor action.

Animals↗
PubMed1988

Leukotriene C4 metabolism during its action on glucose and lactate balance and flow in perfused rat liver.

Rat livers were perfused in a non-recirculating mode at constant pressure via the portal vein with media containing 5 mM glucose, 2 mM lactate, and 0.2 mM pyruvate. [3H]LTC4 was infused for a period of 5 min to a final concentration of 20 nM; it increased glucose and lactate output and reduced perfusion flow. 1) Leukotriene radioactivity was recovered 10 min after the onset of [3H]LTC4 infusion to about 40% in the effluent, to 20% in the bile, and to 40% in the liver. 2) Radioactivity in the effluent increased to a maximum 4-5 min after the onset and decreased again to essentially zero 3 min after completion of [3H]LTC4 infusion. [3H]LTC4 and [3H]LTD4 were the major labeled components in the effluent accounting for 45% and 38%, respectively, of the effluent radioactivity. 3) [3H]LTC4 and [3H]LTD4 were also the major components in bile; they accounted for 50% and 30%, respectively, of the radioactivity excreted, while more polar [3H]leukotriene metabolites accounted for the remainder. 4) In the liver, [3H]LTC4 and [3H]LTD4 were the major and [3H]LTE4, N-acetyl-[3H]LTE4 as well as omega-hydroxy-N-acetyl-[3H]LTE4 and omega-carboxy-N-acetyl-[3H]LTE4 were minor components detected 5 min after completion of [3H]LTC4 infusion. It is concluded from the present findings that during a 5 min infusion period about one third each of the infused LTC4 remained unchanged, was converted to LTD4, and was further degraded to LTE4 and polar metabolites including omega-oxidation products of N-acetyl-LTE4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Purification and characterization of two different precursor forms of the cathepsin B-like proteinase from human malignant ascitic fluid.

We have purified two different precursors of a cathepsin B-like proteinase (PCBT) from malignant ascitic fluid. The molecular mass of these proteins were 45-47 kDa and 36 kDa, respectively. This report is the first which shows cathepsin-B precursors as purified proteins. By using sheep immunoglobulins directed against denatured lysosomal cathepsin B, we have found that both precursors, together with the 33-kDa pepsin generated cathepsin B-like proteinase, reacted in immunoblotting: the three components are thus cathepsin B-related. These antibodies allow us the show that during pepsin activation the 45-47 kDa precursor is converted to the 33-kDa cathepsin B-like proteinase together with the 36-kDa PCBT. We have also prepared sheep immunoglobulins directed against the 36-kDa precursor. The generation of the cathepsin B-like proteinase by pepsin digestion of purified precursors followed a time and dose dependent process. This latter result argues for activation through peptide bond cleavages.

Ascitic Fluid↗
PubMed1987

w-oxidation products of leukotriene E4 in bile and urine of the monkey.

The intravenous administration of [3H]leukotriene C4 in the monkey Macaca fascicularis results in the biliary and urinary elimination of [3H]leukotriene D4 and [3H]leukotriene E4 in addition to more-polar metabolites. Separation of these polar metabolites and chromatographic comparison with synthetic w-oxidized leukotrienes indicated the in vivo formation of w-hydroxy-[3H]leukotriene E4 and w-carboxy-[3H]leukotriene E4. Time course studies of the [3H]leukotriene metabolite pattern in bile and urine showed that w-hydroxy-leukotriene E4 was decreasing as w-carboxy-leukotriene E4 and additional polar derivatives were increasing.

Animals↗
PubMed1987

Inhibition of leukotriene D4 catabolism by D-penicillamine.

Inhibition of the catabolism of the most biologically potent cysteinyl leukotriene, LTD4, was studied in rat hepatoma cells in vitro and in the rat in vivo. LTD4 dipeptidase, an ectoenzyme on the surface of AS-30D hepatoma cells, exhibited an apparent Km value of 6.6 microM for LTD4. D-Penicillamine and L-penicillamine inhibited this enzyme activity with apparent Ki values of 0.46 mM and 0.21 mM respectively. Bestatin, an inhibitor of the aminopeptidase activity of hepatoma cells, did not affect LTD4 hydrolysis at concentrations as high as 5 mM, indicating that the aminopeptidase did not contribute to LTD4 catabolism. In the rat in vivo, D-penicillamine also inhibited LTD4 catabolism. After intravenous injection of [3H]LTC4 an accumulation of [3H]LTD4 and a retarded formation of [3H]LTE4 were observed in the circulating blood after D-penicillamine pretreatment. Within 1 h after intravenous [3H]LTC4 injection, about 80% of the administered radioactivity was recovered in bile. After D-penicillamine pretreatment [3H]LTD4 was the major biliary leukotriene metabolite, whereas in untreated controls leukotriene metabolites more polar than LTC4 predominated in bile. After stimulation of endogenous leukotriene production in vivo by platelet-activating factor, N-acetyl-LTE4 was the major cysteinyl leukotriene detected in bile. D-Penicillamine treatment prior to platelet-activating factor resulted in the accumulation of LTD4, which under these circumstances was the major endogenous leukotriene metabolite detected in bile.

Animals↗
PubMed1987

Leukotriene C4 metabolism by hepatoma cells and liver.

The metabolism of the glutathionyl leukotriene LTC4 in the mercapturic acid pathway was studied in suspensions of AS-30D hepatoma cells and hepatocytes, as well as in vivo in the bile duct-cannulated rat and in primates. 1. Isolated hepatocytes actively took up cysteinyl leukotrienes and metabolized LTC4 not only to LTD4 and LTE4 but also to N-acetyl-LTE4 and to metabolites more polar than LTC4. 2. AS-30D hepatoma cells are deficient in the transport system for the uptake of cysteinyl leukotrienes. Peptide cleavage of LTC4 to LTD4 and LTE4 was catalyzed by ectoenzymes of these cells. Inactivation of gamma-glutamyltransferase by acivicin and inhibition of LTD4 dipeptidase by penicillamine largely prevented further catabolism of LTC4 and LTD4, respectively. 3. [3H]LTC4 injected i.v. into rats was rapidly eliminated from the circulating blood, taken up by the liver, and excreted into bile where 77% of the administered radioactivity was recovered within 1 hr. The biliary LTC4 metabolites included LTD4, N-acetyl-LTE4, and metabolites more polar than LTC4. 4. Inhibition of [3H]LTC4 metabolism in vivo by i.v. penicillamine shifted the pattern of biliary cysteinyl leukotrienes; an extended half-life of [3H]LTD4 was associated with a retarded formation of N-acetyl-LTE4 and of polar metabolites. 5. Endogenous cysteinyl leukotrienes elicited by trauma were measured after HPLC separation by radioimmunologic analysis in plasma and bile of rats. The biliary concentration of these leukotrienes was up to 100 times as great as in plasma. N-Acetyl-LTE4 was the predominant endogenous metabolite in rat bile. 6. In the monkey Macaca fascicularis, cysteinyl leukotrienes were predominantly eliminated from blood via the liver into bile; renal excretion amounted to about 50% of the hepatobiliary elimination. Absorption of cysteinyl leukotrienes from the intestine resulted in enterohepatic circulation of these mediators. 7. Metabolites of [3H]LTC4 injected i.v. in the monkey were analyzed in bile and urine. In addition to polar metabolites and a small percentage of [3H]LTD4, [3H]LTE4 was a predominant metabolite particularly in bile. LTE4 was also the major endogenous cysteinyl leukotriene detected by radioimmunologic analysis in monkey bile. 8. LTE4 was the predominant endogenous cysteinyl leukotriene measured in human bile in patients suffering from acute pancreatitis. The detected amounts of LTE4 may be sufficient to induce known phenomena associated with acute pancreatitis including the shock-like reaction.

Animals↗
PubMed1987

Enterohepatic circulation of N-acetyl-leukotriene E4.

N-Acetyl-leukotriene E4, the end product of leukotriene C4 metabolism in the mercapturic acid pathway, was rapidly eliminated from the blood circulation into the bile of rats. Part of the N-acetyl-leukotriene E4 secreted from bile into the intestine underwent enterohepatic circulation. Leukotriene absorption occurred from the small intestine and from the colon. Biliary and urinary excretion within 5.5 h amounted to 15 and 2%, respectively, of the intraduodenally administered N-acetyl- 3H leukotriene E4 in animals anesthetized with ketamine. HPLC analyses indicated that 35% of the biliary radioactivity corresponded to unchanged N-acetyl-3H leukotriene E4, while 65% in bile and 100% in urine were polar metabolites. Enterohepatic circulation extends the biological half-life of N-acetyl-leukotriene E4.

Animals↗
PubMed1987

Cysteinyl leukotrienes as mediators of staphylococcal enterotoxin B in the monkey.

The role of cysteinyl leukotrienes (LTs) in the action of staphylococcal enterotoxin B (SEB) was investigated in unsensitized monkeys using inhibitors of prostanoid synthesis and LT action and by measuring generation of LT in vivo. LY 171883, a selective LTD4/LTE4 receptor antagonist, proved highly efficient in inhibiting immediate-type hypersensitivity reactions in the skin and protecting against the emetic response provoked by SEB in a concentration-dependent manner. Inhibition of prostanoid formation by pretreatment of monkeys with indomethacin or aspirin did not influence SEB responses. Based on chromatographic and radioimmunologic analysis, the generation of endogenous cysteinyl LTs was demonstrated in vivo. The concentration of LTE4, the major biliary cysteinyl LT detected, increased ten-fold and a novel cysteinyl LT metabolite in urine indicated strongly enhanced LT generation upon challenge with SEB. Cysteinyl LTs are important mediators in the pathophysiology of SEB-induced enteric intoxication. Therefore, cysteinyl LT antagonists may be of therapeutic value in the treatment of this intestinal disorder.

Acetophenones↗
PubMed1987

Staphylococcal enterotoxin B as a nonimmunological mast cell stimulus in primates: the role of endogenous cysteinyl leukotrienes.

The immediate-type skin reaction and the emetic response in unsensitized monkeys on challenge with staphylococcal enterotoxin B (SEB) were studied to define the role of cysteinyl leukotrienes (LTs) in the action of the toxin. LY 171883, a selective LTD4/LTE4 receptor inhibitor, antagonized SEB-induced skin reactions and emetic responses completely. Inhibition of prostanoid formation by indomethacin, however, and pretreatment with BW 755C, a dual lipoxygenase and cyclooxygenase inhibitor, did not influence these reactions. The generation of endogenous cysteinyl LTs upon intragastric SEB administration was established in vivo. There was a tenfold increase in LTE4, the major biliary cysteinyl LT, and a novel cysteinyl LT metabolite in urine occurred, indicating strongly enhanced LT generation on SEB challenge. These results provide the first evidence that cysteinyl LTs may be important mediators in the pathophysiology of SEB-induced effects, as a model for pseudo-allergic reactions.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗