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W Hsueh

Publications and source records attributed to W Hsueh.

At least 37 records · Page 2Linked to original sources
PubMed1997

Regulation of platelet-activating factor receptor gene expression in vivo by endotoxin, platelet-activating factor and endogenous tumour necrosis factor.

A competitive PCR assay was developed to quantify platelet-activating factor (PAF) receptor (PAF-R) transcripts in rat tissues using a synthetic RNA as a competitor. We found PAF-R mRNA constitutively expressed in the eight organs tested, with the ileum containing the highest concentration [(3.49+/-0.15) x 10(7) molecules/microg of RNA]. Significant but lower levels were also detected in the jejunum, spleen, lungs, kidneys, heart, stomach and liver. Furthermore we defined the regulatory role of inflammatory mediators in ileal PAF-R gene expression using a rat model of intestinal injury induced by PAF or lipopolysaccharide (LPS). Injection of LPS or low-dose PAF resulted in a marked increase in ileal PAF-R mRNA within 30 min. The up-regulation on PAF-R elicited by PAF was biphasic, peaking first at 90 min, then again at 6 h. In contrast, LPS elicited a weak monophasic response. The second phase of PAF-R mRNA increase after PAF administration was completely abolished by WEB 2170, a PAF antagonist, and partially inhibited by antitumour necrosis factor (TNF) antibody. These observations indicate the involvement of endogenous PAF and TNF in this event. In conclusion, we found: (a) preferential PAF-R expression in the ileum, suggesting a role for PAF in intestinal inflammation; (b) induction of PAF-R expression in vivo by its own agonist; (c) a complex regulation of PAR-R gene expression in vivo involving a network of various pro-inflammatory mediators.

Animals↗
PubMed1997

The platelet-activating factor receptor antagonist WEB 2170 prevents neonatal necrotizing enterocolitis in rats.

UNLABELLED: To evaluate the role of platelet-activating factor (PAF) in a neonatal rat model of necrotizing enterocolitis (NEC). METHODS: NEC was reproduced in newborn rats following exposure to formula feeding, asphyxia, and bacterial colonization. The role of endogenous PAF in neonatal NEC was studied by pretreating animals with PAF receptor antagonists (WEB 2170 and WEB 2086) and by measuring intestinal PAF content in animals with NEC, WEB-treated animals, and controls. RESULTS: We found that WEB 2170 (dosed using 10 mg/kg in a.m. and 30 mg/kg in p.m.) markedly reduced the incidence of NEC (3/17 vs. 14/18 control: p < 0.001) and death (6/17 vs. 17/18 control; p < 0.001) compared with saline-treated animals. Although lower WEB 2170 doses prevented NEC, neither fourfold higher dosing with WEB 2170 nor similar dosing with WEB 2086 affected the incidence of disease in this study. PAF content in intestine was elevated in NEC animals (270 +/- 80 pg/g) compared with WEB 2170-treated animals (0 pg/g) and maternally fed controls (70 +/- 50 pg/g). CONCLUSIONS: The data support the role of PAF in the final common pathway of neonatal NEC.

Animals↗
PubMed1997

P-selectin-deficient mice are protected from PAF-induced shock, intestinal injury, and lethality.

In a previous study, we showed that anti-CD11b or anti-CD18 antibody markedly attenuated platelet-activating factor (PAF)-induced shock and intestinal necrosis in rats, whereas anti-P-selectin anti-body was ineffective. Here we used genetically altered mice to study the mechanism of PAF in mice. We found that P-selectin-deficient mice are completely protected from the adverse effects of PAF with no mortality or intestinal injury and only mild hemoconcentration and transient hypotension. In contrast, CD18- or intercellular adhesion molecule 1 (ICAM-1)-deficient mice were not protected from PAF-induced tissue injury and death. However, when ICAM-1-, but not CD18-, deficient mice were pretreated with fucoidin, the adverse effects of PAF were markedly reduced; survival was 100%, although hypotension still developed. Neutrophil-depleted mice were protected from PAF-induced intestinal injury but still developed hypotension and hemoconcentration. PAF increases peripheral blood neutrophil counts, probably by inducing granulopoiesis, since neutrophil-depleted mice still showed granulocytosis 60 min after PAF. Thus P-selectin plays an important role in PAF-induced injury in mice, and the selectins and the integrin-ICAM-1 system work in concert to mediate the inflammatory response to PAF in vivo.

Animals↗
PubMed1997

Platelet-activating factor (PAF) up-regulates plasma and tissue PAF-acetylhydrolase activity in the rat: effect of cycloheximide.

Platelet-activating factor (PAF) is a proinflammatory phospholipid mediator implicated in necrotizing enterocolitis. Regulation of PAF-acetylhydrolase (AH), the enzyme degrading PAF, is poorly understood. In this study we found that administration of a dose of PAF (1.5 microg/kg, i.v.), which does not cause gross intestinal injury, increased plasma and intestinal PAF-AH in the rat. Cycloheximide (CHX, 5 mg/kg, i.v.) reduced the activity of plasma (but not intestinal tissue) AH in control, as well as in PAF-injected rats, and aggravated systemic inflammation and tissue injury in the latter. The intestinal necrosis induced by PAF and CHX was ameliorated by posttreatment with WEB2170 (a PAF antagonist), indicating a role of endogenous PAF in mediating injury. Both WEB2170 and anti-TNF antibody reduced PAF-induced AH activity in intestinal tissue, but not in the plasma. Allopurinol largely prevented the injury induced by PAF and CHX, but had no effect on the up-regulation of AH. We conclude: 1) de novo protein synthesis is required to maintain physiologic AH level in the plasma; 2) PAF up-regulates plasma and intestinal AH activity; 3) CHX enhances the injurious effect of PAF; 4) endogenous PAF and TNF also play a role in the up-regulation of intestinal AH; the former probably mediating the intestinal injury by PAF; and 5) reactive oxygen species may mediate the injurious effect of PAF plus CHX, but do not contribute to the regulation of AH by PAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1996

Platelet activating factor and endotoxin increase the enzyme activity and gene expression of type II phospholipase A2 in the rat intestine. Role of polymorphonuclear leukocytes.

Type II phospholipase A2 (PLA2-II) may regulate eicosanoid synthesis; is involved in various inflammatory processes, septic shock, and inflammatory bowel disease; and is up-regulated by LPS and inflammatory cytokines in vitro. We have previously shown that the platelet-activating factor (PAF)-induced intestinal injury is attenuated by peptido-leukotriene antagonists, suggesting a role of PLA2. The purpose of this study is to examine the regulation of intestinal PLA2-II by PAF and LPS. Using synthesized competitor RNA as competitor, we quantified PLA2-II transcripts by competitive reverse transcription-PCR. We found that PLA2-II gene is constitutively expressed in the rat ileum. PAF at a dose (1.5 micrograms/kg) below that causing intestinal injury rapidly up-regulated intestinal PLA2-II at both transcriptional and post-transcriptional levels, almost tripling its transcripts and significantly increasing enzyme activity in 30 min. LPS (5 mg/kg) also up-regulated PLA2-II. This effect could not be blocked by PAF antagonist. Depletion of circulating polymorphonuclear leukocytes (PMNs) abolished the effect of PAF on PLA2-II gene expression and enzyme activation. In contrast, PMN depletion prevented LPS-induced PLA2-II enzyme activity but enhanced the gene expression. We conclude that: 1) both PAF and LPS induce gene transcription and enzyme activation of PLA2-II in the small intestine; 2) PAF up-regulates PLA2-II via PMN activation; 3) LPS effect is independent of endogenous PAF formation; and 4) different pathways exist for PAF and LPS in the regulation of intestinal PLA2-II gene expression in vivo.

Animals↗
PubMed1996

Endotoxin induces PAF production in the rat ileum: quantitation of tissue PAF by an improved method.

PAF (platelet-activating factor) is an endogenous mediator of endotoxin (LPS) shock and intestinal injury. In the present study we used an improved method to quantitate intestinal PAF after LPS injection. Both column and thin layer chromatography (TLC) were used to purify PAF. We found that using C18 column eluted sequentially with 10% acetic acid, ethyl acetate and 70% ethanol, yielded consistent results. TLC yielded falsely high PAF values, possibly from an unknown tissue lipid which co-migrated with PAF, or from toxic ingredients in the silica gel. Moreover, addition of optimal amounts of Tween-20 or ethanol in the bioassay samples enhanced PAF solubility and markedly improved PAF recovery. Lastly, dilution and heparinization of platelet-rich plasma greatly improved the sensitivity of the bioassay. The overall PAF recovery under these optimal conditions was 70-80%. We found that LPS (2-10 mg/kg, iv, 90 min) stimulated PAF production in the rat ileum, but not in the jejunum and colon. The difference in PAF production did not correlate to the numbers of sequestered neutrophils (reflected by myeloperoxidase levels) after LPS injection. This selective PAF production may account for the special vulnerability of the ileum to develop injury during endotoxemia.

Animals↗
PubMed1996

Role of leukocyte beta 2-integrin in PAF-induced shock and intestinal injury.

Leukocyte adhesion and diapedesis, critical steps in the inflammatory process, depend on the expression of integrin CD11b/CD18. In this study, we examined the preventive effect of monoclonal antibodies (MAb) against CD11b (1B6), CD11a, or CD18 (CL26) on platelet-activating factor (PAF)-induced bowel injury. Young male Sprague-Dawley rats were anesthetized and injected with either of two doses of PAF (2.5 or 3 micrograms/kg iv) to induce transient hypotension and irreversible shock. Some rats wee also injected intravenously with 1B6 (anti-CD11b), anti-CD11a, CL26 (anti-CD18), or combined anti-CD11a and 1B6, 30 min before PAF. Animals receiving a low dose of PAF developed mild hypotension, hemoconcentration, increased intestinal myeloperoxidase, and bowel injury after 1 h. These effects were completely prevented by pretreatment with 1B6. A high dose of PAF induced irreversible shock and gross intestinal necrosis. Both CL26 and 1B6 were partially effective in attenuating PAF-induced bowel injury. Addition of anti-CD11a to 1B6 in the treatment further ameliorated the systemic adverse effects of PAF and intestinal injury. However, focal minor injury still developed. Anti-CD11a alone, fucoidin, or anti-P-selectin was ineffective. Rats depleted of neutrophils were also largely protected from the adverse effects of PAF at high doses, although minor intestinal injury often persisted. We conclude that leukocyte beta 2-integrins play an important role in PAF-induced hypotension, leukopenia, hemoconcentration, and intestinal necrosis, and that CD11b/CD18 is the main adhesion molecule involved in the pathogenesis of injury. However, CD11/CD18- and neutrophil-independent pathways exist for mediating PAF-induced bowel injury, although their role is probably a minor one.

Animals↗
PubMed1995

Endotoxin-resistant mice are protected from PAF-induced bowel injury and death. Role of TNF, complement activation, and endogenous PAF production.

C3H/HeJ (endotoxin-resistant) mice have been used widely in biological research. However, the mechanism of endotoxin (LPS) resistance is only partially understood. In this study, we first investigated the differences in response to PAF, a mediator of endotoxin shock, between normal and C3H/HeJ mice. We found that in control mice, PAF (2.5 micrograms/kg) caused shock, hemoconcentration, complement activation, intestinal hypoperfusion, and necrosis with 75% mortality, whereas all C3H/HeJ mice survived, without complement activation or intestinal injury, and manifesting only mild hypotension and hemoconcentration. PAF also caused elevated serum TNF-alpha in some control mice but not in C3H/HeJ mice. We also observed that PAF induces endogenous PAF production and intestinal phospholipase A2 activation in normal mice, whereas PAF production and phospholipase A2 are suppressed in C3H/HeJ mice. The low endogenous PAF production may account, at least in part, for the resistance to LPS and PAF of C3H/HeJ mice.

Animals↗
PubMed1995

Endogenous bacterial toxins are required for the injurious action of platelet-activating factor in rats.

BACKGROUND & AIMS: Platelet-activating factor (PAF), an endogenous mediator for experimental sepsis, has been shown to induce shock and intestinal necrosis in vivo. However, it is unclear whether PAF exerts its injurious effects on the intestinal tissue directly or via synergism with other endogenous products. The aim of this study was to examine the role of endogenous bacterial products, such as endotoxin, in PAF-induced intestinal injury. METHODS: PAF (3 micrograms/kg) was injected intravenously into normally colonized rats, germfree rats, and normal rats pretreated with a combination of antibiotics, and the systemic response and intestinal injury were assessed. RESULTS: PAF did not cause prolonged shock, leukopenia, hemoconcentration, and bowel necrosis in germfree rats. When germfree rats were primed with a low dose (0.5 mg/kg) of endotoxin, the protection was lost. Combined treatment of the normally colonized rats with neomycin, polymyxin B, and metronidazole for 7 days largely protected the animal from PAF-induced shock and intestinal necrosis. CONCLUSIONS: PAF does not directly induce prolonged hypotension, hemoconcentration, persistent leukopenia, and gross intestinal necrosis but causes these changes via a synergism with endogenous bacterial toxins, presumably from the gut flora.

Analysis of Variance↗
PubMed1994

PAF and TNF increase the precursor of NF-kappa B p50 mRNA in mouse intestine: quantitative analysis by competitive PCR.

NF-kappa B, a nuclear transcription factor, is involved in the regulation of inflammatory cytokines. We have previously reported that PAF and TNF induce intestinal injury in rats and mice and the interaction of TNF and PAF probably plays a central role in its pathogenesis. In the present study, we developed a competitive PCR method to quantitate the transcripts of NF-kappa B p50/p105 gene, and investigated the effects of PAF and TNF on p50/p105 gene expression in the small intestine of C3H/HeN mice - p105 is the precursor of the p50 subunit of NF-kB. We found that NF-kappa B p50/p105 gene is constitutively expressed in the normal small intestine in small quantities (7.05 +/- 1.04 attomol/micrograms total RNA). PAF at a dose (1 microgram/kg) causing no systemic changes (e.g., hypotension, hemoconcentration), markedly increased intestinal p50/p105 transcripts within 30 min. TNF, at dose (1 mg/kg) also insufficient to induce systemic changes, increased intestinal p50/p105 gene expression, although its effect was much slower than PAF. The effect of TNF was not blocked by WEB 2086, a PAF antagonist. Our results indicate that both PAF and TNF stimulate the expression of NF-kappa B p50/p105 in vivo. However, the mechanisms of their respective actions are probably different.

Animals↗
PubMed1994

Molecular and phenotypic variability in the congenital alveolar proteinosis syndrome associated with inherited surfactant protein B deficiency.

Congenital alveolar proteinosis (CAP) is an often fatal cause of respiratory failure in term newborn infants, which has been associated with a genetic deficiency of surfactant protein B (SP-B) as a result of a frameshift mutation (121ins2) in a family with three affected siblings. In the index cases the deficiency of SP-B was associated with qualitative and quantitative abnormalities of the surfactant proteins A and C. Immunostaining for lung surfactant proteins and a search for the 121ins2 mutation by restriction enzyme analysis of DNA extracted from paraffin-embedded lung tissue was performed for 7 additional affected infants from 6 families, bringing to 10 the total number of patients with CAP who have been studied. In six infants, the surfactant protein immunostaining pattern was similar to that of the index cases. Of these, three patients were homozygous for the 121ins2 mutation; one was a compound heterozygote with the 121ins2 in one allele and a different mutation in the other; and three patients lacked the mutation in both alleles. One infant had an abundance of SP-B, suggesting phenotypic heterogeneity in CAP. Lung ultrastructural abnormalities, such as a reduced number of lamellar bodies, absent tubular myelin, and basal secretion of surfactant lipids and proteins, suggest a significant derangement of surfactant metabolism. The phenotypic heterogeneity in infants with CAP raises the possibility that variable degrees of SP-B deficiency may be more common than previously suspected.

Female↗
PubMed1994

Tumour necrosis factor and endotoxin synergistically activate intestinal phospholipase A2 in mice. Role of endogenous platelet activating factor and effect of exogenous platelet activating factor.

Previous studies have shown that: (a) platelet activating factor induces shock and intestinal injury, (b) exogenous platelet activating factor stimulates synthesis of endogenous platelet activating factor, and (c) tumour necrosis factor alpha and endotoxin synergise to induce shock and bowel injury in animals. These last two effects are largely mediated by platelet activating factor forming phospholipase A2 A2, a key enzyme for platelet activating factor synthesis, was examined in mouse intestine. It was found that tumour necrosis factor alpha and endotoxin synergise to stimulate platelet activating factor forming phospholipase A2 activity in the intestine, as well as platelet activating factor production, and these effects were blocked by pretreatment with platelet activating factor antagonists, SRI-63-441 and WEB 2086. In addition, exogenous platelet activating factor stimulates intestinal phospholipase A2 activity. These results show that tumour necrosis factor alpha and lipopolysaccharide synergistically activate the phospholipase A2 that participates in platelet activating factor formation, and this activation is largely mediated by endogenous platelet activating factor. Furthermore, platelet activating factor itself increases phospholipase A2 activity, suggesting that platelet activating factor induces its own synthesis, probably by phospholipase A2 activation.

Animals↗
PubMed1994

Potentiation of isosorbide dinitrate effects with N-acetylcysteine in patients with chronic heart failure.

BACKGROUND: Supply of sulfhydryl groups with the administration of N-acetylcysteine (NAC) has been reported to reverse tolerance to nitroglycerin but not to isosorbide dinitrate (ISDN). Lack of interaction between NAC and ISDN was suggested as an explanation for these findings. The present study was therefore designed to further evaluate this hypothesis. For this purpose, we compared the hemodynamic and hormonal effects of ISDN when given alone and in combination with NAC. METHODS AND RESULTS: We performed a randomized, cross-over design evaluation of the hemodynamic and hormonal effects of ISDN and ISDN + NAC in 14 patients with chronic congestive heart failure due to left ventricular systolic dysfunction. The findings of this study demonstrated a substantial NAC-mediated potentiation of ISDN effect on mean right atrial pressure (-11 +/- 21% versus -38 +/- 27%, -17 +/- 20% versus -34 +/- 27%, and -7 +/- 20% versus -25 +/- 26% at 2, 3, and 4 hours, respectively; all P < .05), mean pulmonary artery wedge pressure (-18 +/- 16% versus -33 +/- 14%, -15 +/- 25% versus -33 +/- 19%, -14 +/- 22% versus -25 +/- 22%, and -16 +/- 16% versus -26 +/- 16% at 2, 3, 4, and 5 hours, respectively; all P < .05), mean pulmonary artery pressure (-8 +/- 11% versus -20 +/- 15% at 3 hours, P < .05), and cardiac output (an increase of 2 +/- 16% versus 25 +/- 20% at 4 hours, P < .05). Although there were no significant changes in serum catecholamine levels and plasma renin concentration with both regimens, ISDN + NAC resulted in a greater fall in plasma levels of atrial natriuretic peptide (296 +/- 251 pg/mL after ISDN versus 202 +/- 118 pg/mL after ISDN + NAC, P < .05). CONCLUSIONS: The results of this study provide strong evidence for the existence of an interaction between thiols and ISDN and further support the role of sulfhydryl groups in the activation and therapeutic action of organic nitrates. The discrepancy between the results of this study demonstrating NAC-induced potentiation of ISDN effects and a previous study showing failure to reverse ISDN tolerance with NAC may suggest that ISDN-NAC interaction requires normal intracellular levels of sulfhydryl groups and does not occur after intracellular sulfhydryl group depletion.

Acetylcysteine↗
PubMed1994

Chronic insulin administration elevates blood pressure in rats.

To examine the relative contribution of dietary glucose and infused insulin on blood pressure, we administered a 4% glucose supplement (in drinking water) with and without insulin infusion (15.8 nmol [2.2 U]/d via osmotic minipump) to male Sprague-Dawley rats (n = 6). We also tested the effect of the sympatholytic agent clonidine on rats receiving glucose and insulin. Blood pressure and heart rate were recorded via a novel radio telemetry system. Experiments were performed using a crossover design with three animals receiving treatment and three receiving vehicle for 10 days. After a 10-day washout period, the groups were reversed, and the experiment was repeated. Blood samples for insulin and glucose were drawn throughout the study. Systolic and diastolic blood pressures increased (by 6.0 +/- 1.2 and 2.2 +/- 1.3 mm Hg, respectively) in the animals given glucose alone in association with an increase in plasma insulin. However, blood pressure increased more rapidly and to a greater extent, systolic by 8.6 +/- 0.7 mm Hg and diastolic by 2.9 +/- 1.1 mm Hg, during the insulin treatment that raised plasma insulin above the levels observed during glucose feeding alone. Heart rate increased equally during both treatments. The average change in blood pressure and average plasma insulin during the infusion were correlated (r = .72, P = .009). Blood pressure dropped during the week following discontinuation of the insulin infusion. On rechallenge with insulin and glucose, blood pressure again rose and then decreased after termination of the insulin and glucose administration. Clonidine prevented the rise in blood pressure and heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Platelet-activating factor and endotoxin induce tumour necrosis factor gene expression in rat intestine and liver.

We have shown previously that endotoxin, tumour necrosis factor (TNF) and platelet-activating factor (PAF) are important in the pathogenesis of bowel injury, and that endotoxin and TNF induce PAF formation in bowel tissue. In the present study we investigated the effects of endotoxin and PAF on TNF gene expression. Adult rats were injected with endotoxin (2 mg/kg), PAF (1 microgram/kg) or endotoxin plus PAF, and were killed after 30 min. Endotoxin had little systemic effect. PAF induced transient hypotension and mild bowel injury. Endotoxin plus PAF caused profound shock, severe haemoconcentration, leukopenia and intestinal necrosis. Sham-operated rats had barely detectable TNF mRNA in the liver or intestine. Endotoxin or PAF induced a marked increase in TNF mRNA, especially in the distal ileum and in the liver, but much less in the jejunum. Endotoxin plus PAF did not further increase TNF mRNA, probably due to development of tissue injury. Serum TNF levels in animals treated with endotoxin, PAF and endotoxin plus PAF were elevated. Endotoxin induces TNF gene expression probably via both PAF-dependent and PAF-independent pathways, since TNF mRNA formation was only partially blocked by PAF antagonist.

Animals↗
PubMed1993

Plasma cyclic guanosine monophosphate in chronic heart failure: hemodynamic and neurohormonal correlations and response to nitrate therapy.

This study evaluated the relation between plasma cyclic guanosine monophosphate (cGMP) and hemodynamic and neurohormonal parameters in patients with chronic congestive heart failure and assessed the effect of organic nitrate on plasma cGMP levels. Plasma cGMP was fourfold higher in 18 patients with congestive heart failure compared with 15 control subjects (16.7 +/- 9.7 versus 4.0 +/- 1.0 pmol/ml; p < 0.0001) but did not correlate with plasma levels of catecholamines, renin, atrial natriuretic peptide, or with baseline hemodynamic values. The administration of a hemodynamically effective dose of oral isosorbide dinitrate (40 mg) resulted in a transient reduction in plasma cGMP from 16.7 +/- 9.7 pmol/ml at baseline to 13.0 +/- 6.6 pmol/ml at 1 hour (p < 0.05). This change was associated with small and statistically insignificant changes in neurohormonal values and had no relation to any of the hemodynamic changes. We concluded that (1) elevated plasma cGMP in congestive heart failure does not correlate with other neurohormonal or hemodynamic parameters and may be an independent parameter of heart failure, (2) in contrast to previously documented nitrate-mediated increases in intracellular cGMP, nitrate therapy results in a reduction in plasma cGMP, and (3) changes in plasma cGMP cannot serve as a surrogate measurement of changes in intracellular cGMP.

Administration, Oral↗