Biomedical subjects

X Meng

Publications and source records attributed to X Meng.

At least 37 records · Page 2Linked to original sources

PubMed2001

Suppression of tumor necrosis factor alpha production by cAMP in human monocytes: dissociation with mRNA level and independent of interleukin-10.

BACKGROUND: Elevation of cellular cAMP inhibits lipopolysaccharide(LPS)-stimulated tumor necrosis factor alpha (TNF-alpha) production and increases the expression of interleukin (IL)-10 in mononuclear cells. TNF-alpha gene expression obligates activation of the transcription factor nuclear factor kappaB (NF-kappaB). Exogenous IL-10 inhibits NF-kappaB in monocytes and thus attenuates TNF-alpha production. We examined the role of endogenous IL-10 in the regulation of NF-kappaB activation and TNF-alpha production in human monocytes by cAMP. METHODS: Human monocytes were stimulated with Escherichia coli LPS (100 ng/ml) with and without forskolin (FSK, 50 microM) or dibutyryl cyclic AMP (dbcAMP, 100 microM). Cytokine (TNF-alpha and IL-10) release was measured by immunoassay. TNF-alpha mRNA was measured by reverse transcription polymerase chain reaction, and NF-kappaB DNA binding activity was assessed by gel mobility shift assay. RESULTS: cAMP-elevating agents inhibited LPS-stimulated TNF-alpha release (0.77 +/- 0.13 ng/10(6) cells in LPS + dbcAMP and 0.68 +/- 0.19 ng/10(6) cells in LPS + FSK, both P < 0.05 vs 1.61 +/- 0.34 ng/10(6) cells in LPS alone). Conversely, cAMP enhanced LPS-stimulated IL-10 release (100 +/- 21.5 pg/10(6) cells in LPS + dbcAMP and 110 +/- 25.2 pg/10(6) cells in LPS + FSK, both P < 0.05 vs 53.3 +/- 12.8 pg/10(6) cells in LPS alone). Neither TNF-alpha mRNA expression nor NF-kappaB activation stimulated by LPS was inhibited by the cAMP-elevating agents. Neutralization of IL-10 with a specific antibody did not attenuate the effect of cAMP-elevating agents on TNF-alpha production. CONCLUSION: The results indicate that cAMP inhibits LPS-stimulated TNF-alpha production through a posttranscriptional mechanism that is independent of endogenous IL-10.

Antibodies↗

PubMed2001

TNF receptor I mediates chemokine production and neutrophil accumulation in the lung following systemic lipopolysaccharide.

BACKGROUND: Tumor necrosis factor (TNF)-alpha is a critical effector of lipopolysaccharide (LPS)-induced acute lung injury, and its effects are mediated by two structurally related receptors, RI and RII. Cellular adhesion molecules and C-X-C chemokines (Keratinocyte chemoattractant (KC) and macrophage inflammatory protein [MIP]-2) regulate tissue neutrophil polymorphonuclear neutrophil (PMN) accumulation in a multitude of inflammatory states. We hypothesized that TNFRI signaling dictates PMN accumulation in the lung via regulation of chemokine molecule production. Therefore, the purposes of this study were to (1) delineate LPS-induced lung TNF-alpha production and (2) characterize the contribution of both TNF receptors to lung chemokine production and neutrophil influx following systemic LPS. METHODS: Wild-type or TNFRI and TNFRII knockout (KO) mice were injected with vehicle (saline) or LPS (Escherichia coli 0.5 mg/kg intraperitoneally). After 2, 4, 6, or 24 h, lungs were analyzed for TNF-alpha and chemokine (KC and MIP-2) protein expression (enzyme-linked immunosorbent assay) and PMN accumulation (myeloperoxidase assay). RESULTS: There was an increase in total lung TNF-alpha (vehicle, 5.0 +/- 1.2 pg/mg total protein vs LPS, 950 +/- 318; P < 0.05) after LPS. Lung chemokine production and PMN accumulation were also increased compared to vehicle-injected mice. Lung chemokine production and PMN accumulation were significantly lower in TNFRI KO, but not TNFRII KO, mice, despite no difference in TNF-alpha production (TNFRI KO, 925 +/- 301 vs TNFRII KO, 837 +/- 267, P = 0.82). CONCLUSIONS: Acute lung injury following systemic LPS administration is characterized by increased lung (1) TNF-alpha production, (2) C-X-C chemokine production, and (3) neutrophil accumulation. The maximal effect of LPS-induced lung neutrophil accumulation appears to be dependent upon the TNFRI receptor but not the TNFRII receptor. .

Animals↗

PubMed2001

Inhibition of cyclic-3',5'-nucleotide phosphodiesterase abrogates the synergism of hypoxia with lipopolysaccharide in the induction of macrophage TNF-alpha production.

BACKGROUND: Local tumor necrosis factor (TNF)-alpha production by resident macrophages (M phi) contributes to posttraumatic tissue injury. Hypoxia decreases cellular cyclic adenosine monophosphate (cAMP) levels and enhances M phi secretion of TNF-alpha following lipopolysaccharide (LPS) stimulation. Thus, tissue hypoxia associated with trauma likely synergizes with proinflammatory mediators in the induction of M phi TNF-alpha production through an influence on cAMP generation or degradation. It is unclear whether elevation of cellular cAMP inhibits LPS-stimulated TNF-alpha production by hypoxic M phi. Moreover, it is unknown whether the synergism of hypoxia with LPS can be abrogated by promotion of cAMP generation or inhibition of cAMP degradation. METHODS: Rat peritoneal M phi were stimulated with Escherichia coli LPS (20 ng/ml) in a normoxic (room air with 5% CO(2)) or hypoxic (95% N(2) with 5% CO(2)) condition. TNF-alpha levels in cell-free supernatants were measured by enzyme-linked immunoassay. The beta-adrenoceptor agonist isoproterenol (ISP; 5.0 microM) and the adenylate cyclase activator forskolin (FSK; 50 microM) were applied to promote cAMP generation. The nonselective cyclic-3',5'-nucleotide phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX; 1.0 mM) and the PDE III-specific inhibitor milrinone (200 microM) were used to inhibit cAMP degradation. The nondegradable cAMP analogue dibutyryl cAMP (dbcAMP; 100 microM) was applied to further determine the role of PDE. RESULTS. Although hypoxia alone had a minimal effect on TNF-alpha production, it dramatically enhanced LPS-stimulated TNF-alpha production (4.08 +/- 0.28 ng/10(6) cells in hypoxia plus LPS vs 1.63 +/- 0.26 ng/10(6) cells in LPS, 2.5-fold, P < 0.01). Promotion of cAMP generation by either ISP or FSK reduced TNF-alpha production by hypoxic cells. However, neither of these two agents abolished the synergism of hypoxia with LPS (1.68 +/- 0.13 ng/10(6) cells in ISP plus hypoxia plus LPS vs 0.55 +/- 0.04 ng/10(6) cells in ISP plus LPS, threefold; 1.17 +/- 0.03 ng/10(6) cells in FSK plus hypoxia plus LPS vs 0.33 +/- 0.02 ng/10(6) cells in FSK plus LPS, 3.5-fold; both P < 0.01). Inhibition of cAMP degradation with IBMX reduced TNF-alpha production in hypoxic cells and abrogated the synergism (0.31 +/- 0.11 ng/10(6) cells in IBMX plus hypoxia plus LPS vs 0.27 +/- 0.04 ng/10(6) cells in IBMX plus LPS, P > 0.05), and the PDE III inhibitor milrinone had a comparable effect. Moreover, dbcAMP also attenuated TNF-alpha production with abrogation of the synergistic effect of hypoxia (0.56 +/- 0.08 ng/10(6) cells in dbcAMP plus hypoxia plus LPS vs 0.46 +/- 0.04 ng/10(6) cells in dbcAMP plus LPS, P > 0.05). CONCLUSIONS: The results show that elevation of cellular cAMP, either by promotion of generation or by inhibition of degradation, suppresses LPS-stimulated TNF-alpha production in hypoxic M phi. It appears that hypoxia synergizes with LPS in the induction of M phi TNF-alpha production through PDE-mediated cAMP degradation. Inhibition of PDE may be a therapeutic approach for suppression of synergistic induction of M phi TNF-alpha production by hypoxia and LPS in posttraumatic tissue.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2001

Generalized dimension of the intersection between EEGs.

The generalized dimension defined by [Mandelbrot (1995) J Fourier Anal Appl special J.P. Kahane issue: 409-432] was applied to studying the interrelationship between various parts of human cerebral cortex in different functional conditions. Taking EEG signals from different brain areas as different sets, the generalized dimensions of their intersections were calculated to describe the interrelationship between them. The results showed that the generalized dimensions of intersections in different brain states decreased according to the following order: rest with eyes open, closed, light sleep, and deep sleep. The generalized dimensions of intersections related to the left or right temporal lobe were higher than the others when the subjects was doing mental arithmetic, and there was a decrease when the subjects listened to soft classical music. In addition, it was found that there was a noticeable difference in singular spectra between epileptic patients and normal subjects, irrespective of whether the epileptic patient was experiencing a seizure or not.

Adult↗

PubMed2001

Treatment of arsenic in Bangladesh well water using a household co-precipitation and filtration system.

Laboratory and field tests were conducted to evaluate the effectiveness of a household filtration process and investigate the effects of phosphate and silicate on the removal of arsenic from Bangladesh groundwater by ferric hydroxides. Fe/As ratios of greater than 40 (mg/mg) were required to reduce arsenic to less than 50 microg/L in Bangladesh well water due to the presence of elevated phosphate and silicate concentrations. The household filtration process included co-precipitation of arsenic by adding a packet (approximately 2 g) of ferric and hypochlorite salts to 20 L of well water and subsequent filtration of the water through a bucket sand filter. A field demonstration study was performed to test the treatment system in seven households in Bangladesh in March and April 2000. Experimental results obtained from the participating families proved that the household treatment process removed arsenic from approximately 300 microg/L in the well water to less than 50 microg/L. The participating families liked this simple and affordable process and used it to prepare clean water for drinking and cooking. A larger scale field test is currently underway.

Adsorption↗

PubMed2001

The electrochemical and spectroelectrochemical behaviors of SOD at cysteine modified gold electrode.

Different promoters were used to enhance the rate of the electron transfer process of superoxide dismutase (SOD). A quasi-reversible cyclic voltammogram (CV) of SOD was observed on the cysteine-modified gold wire electrode. The coupled adsorption/desorption processes and the characteristic Raman spectra of different states of SOD molecules on the electrode surface were studied with electrochemical quartz crystal microbalance (EQCM) and in-situ Raman spectroelectrochemical techniques. The possible promotion mechanism was discussed.

Adsorption↗

PubMed2001

Analysis of urinary metabolites of tea catechins by liquid chromatography/electrospray ionization mass spectrometry.

Tea has been proposed to have beneficial health effects which have been attributed to the polyphenolic compounds known as catechins. The bioavailability and biotransformation of these compounds, however, are not clearly understood. In this study, we used liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) to determine urinary glucuronidated and sulfated tea catechins and their metabolites (including methylated and ring-fission metabolites) based on the detection of deprotonated molecular ions and aglycone fragment ions. The compound resolution was achieved both chromatographically and mass spectroscopically. After green tea administration, the major conjugates appeared in human, mouse, and rat urine samples were identified as monoglucuronides and monosulfates of (-)-epigallocatechin (EGC) and (-)-epicatechin. We also found O-methyl-EGC-O-glucuronides and -O-sulfates and O-methyl-epicatechin-O-sulfates in human urine. (-)-5-(3',4',5'-Trihydroxyphenyl)-gamma-valerolactone (M4) and (-)-5-(3',4'-dihydroxyphenyl)-gamma-valerolactone (M6), the ring-fission metabolites of EGC and (-)-epicatechin, respectively, were also predominantly in monoglucuronide and monosulfate forms in the urine. In comparison to rats, the urinary metabolite profiles of tea catechins in mice resemble more closely to those in humans. This is the first report describing direct simultaneous analysis of multiple tea catechin conjugates in urine samples. This method will allow more thorough investigations of the biotransformation of tea polyphenols.

Adult↗

PubMed2001

Keratinocyte gene therapy: inducible promoters and in vivo control of transgene expression.

Modulation of transgene expression by exogenous agents is an optimal goal in gene therapy. Successful keratinocyte gene therapy requires a promoter-enhancer cassette to regulate expression of the therapeutic gene in vivo. In this study, we first transferred plasmids, constructed by introducing inducible promoters fused to the beta-galactosidase gene (LAC Z), into keratinocytes in vitro. Metallothionein (MT) and 1,24-vitamin D(3)(OH)(2) dehydroxylase (VDH) promoters responded to the inducing agents, Cadmium and 1,25-vitamin D(3)(OH)(2) (VitD(3)), respectively. The plasmids were then introduced in vivo using a naked DNA method and the inducible promoters were evaluated by measuring beta-gal activity in rat keratinocytes. Zinc induced the transferred MT promoter activity by approximately 2-fold or 10-fold when administered systemically and topically, respectively. In addition, VitD(3) induced the transferred VDH promoter activity approximately 10-fold when administered topically. These data are useful for developing inducible promoters for keratinocyte gene therapy.

Animals↗

PubMed2001

Differential cellular immunolocalization of renal tumour necrosis factor-alpha production during ischaemia versus endotoxaemia.

Both renal ischaemia and endotoxaemia provoke renal dysfunction and cellular injury. Although the clinical manifestation of each insult is similar (global renal dysfunction), ischaemia and endotoxaemia induce different patterns of cellular injury. Tumour necrosis factor-alpha (TNF-alpha) has been implicated in both types of renal injury; however, it remains unknown whether differential cellular TNF-alpha expression accounts for these changes. We hypothesized that renal glomerular cells and tubular cells differentially express TNF-alpha in response to ischaemia compared with endotoxaemia. To investigate this hypothesis, male Sprague-Dawley rats were anaesthetized and exposed to various time-periods of renal ischaemia, with or without reperfusion (sham operation=negative control), or lipopolysaccharide (LPS) 0.5 mg/kg intraperitoneally (i.p.). The kidneys were harvested following renal injury, and rat TNF-alpha protein expression was determined (by enzyme-linked immunosorbent assay), as were TNF-alpha bioactivity (by WEHI-164 cell clone cytotoxicity assay) and TNF-alpha cellular localization (by immunohistochemistry). TNF-alpha protein expression and TNF-alpha bioactivity peaked following 1 hr of ischaemia and 2 hr of reperfusion (48 +/- 11 pg/mg of protein, P < 0.05, and 12 +/- 0.5 x 10-3 units/mg of protein, P < 0.05, respectively). The concentration of TNF-alpha increased to a similar extent following exposure to LPS; however, while TNF-alpha production following ischaemia-reperfusion injury localized predominantly to renal tubular epithelial cells, animals exposed to LPS demonstrated a primarily glomerular distribution of TNF-alpha production. Hence, the cellular localization of renal TNF-alpha production appears to be injury specific, i.e. renal tubular cells are the primary source of TNF-alpha following an ischaemic insult, whereas LPS induces glomerular TNF-alpha production. The cellular source of TNF-alpha following different insults may have therapeutic implications for targeted inhibition of TNF-alpha production.

Animals↗

PubMed2001

Vascular cell adhesion molecule--1 expression is obligatory for endotoxin-induced myocardial neutrophil accumulation and contractile dysfunction.

BACKGROUND: Sepsis-induced cardiac dysfunction occurs commonly in critically ill patients and is associated with high mortality rates. Neutrophils play a central role in sepsis-induced lung and liver injury; however, the mechanism of sepsis-induced cardiac dysfunction remains unclear. Vascular cell adhesion molecule-1 (VCAM-1) has been implicated in neutrophil-mediated liver injury during endotoxemia and is also expressed in myocardium. The purposes of this study were to examine the temporal relationship of myocardial VCAM-1 expression with neutrophil accumulation during endotoxemia and to determine whether VCAM-1 mediates neutrophil accumulation and cardiac dysfunction during endotoxemia. METHODS: Mice were subjected to lipopolysaccharide (LPS; 0.5 mg/kg, intraperitoneally). Myocardial VCAM-1 expression and neutrophil accumulation were determined by immunofluorescence staining. Cardiac performance with or without VCAM-1 blocking antibody (5 mg/kg, intravenously) was determined by the Langendorff technique. RESULTS: LPS caused a time-dependent increase in both myocardial VCAM-1 expression and neutrophil accumulation. At 6 hours after LPS, the immunofluorescent intensity for VCAM-1 increased from 2.5 +/- 0.6 x 10(6) in saline solution controls to 19.9 +/- 3.5 x 10(6) (P <.05, analysis of variance), and neutrophil count increased from 2.4 +/- 1.7/mm(2) in saline solution controls to 13.0 +/- 2.5/mm(2) (P <.05). Left ventricular developed pressure was decreased maximally at 6 hours after LPS compared with saline solution controls (29.1 +/- 1.1 mm Hg vs 53.1 +/- 3.9 mm Hg; P <.05). Treatment with VCAM-1 monoclonal antibody abrogated both myocardial neutrophil accumulation and cardiac dysfunction during endotoxemia. CONCLUSIONS: LPS-induced myocardial dysfunction is associated with increased expression of VCAM-1 and with neutrophil accumulation. Blockade of VCAM-1 abrogates myocardial neutrophil accumulation and preserves cardiac function during endotoxemia, which supports a role for VCAM-1 as a therapeutic target for myocardial protection during sepsis.

Animals↗

PubMed2001

Divergence of volatile anesthetic effects in inhibitory neurotransmitter receptors.

BACKGROUND: The mechanism of volatile anesthetic (VA) action is unknown. Inhibitory receptors for the neurotransmitters gamma-aminobutyric acid (GABA) or glycine are typically positively modulated by VAs and may be important targets for their action. The existence of a GABA receptor subtype (p), which is uniquely inhibited by VAs, suggested a chimeric receptor approach to identify portions of these proteins that may be necessary for anesthetic effects. METHODS: A silent mutation resulting in the addition of a unique restriction enzyme recognition site was introduced in GABA receptor type A alpha2, glycine alpha1, and p subunit cDNAs. Chimeras were constructed by rejoining restriction digest fragments and were expressed in Xenopus oocytes. Modulation of submaximal agonist-evoked peak currents by the VAs chloroform, enflurane, halothane, or isoflurane was measured using two-electrode voltage clamp. RESULTS: Four chimeras were constructed and designated glyrho, rhogly, alpha2rho, and rhoalpha2. Glyrho formed glycine-gated receptors with currents that were enhanced by chloroform or halothane but were inhibited by enflurane or isoflurane. Chimeras rhogly and rhoalpha2 each formed GABA-gated receptors with currents that were inhibited by chloroform or halothane but enhanced by enflurane or isoflurane. CONCLUSIONS: These data show, for the first time, functional divergence of VA action on a single protein target. The VAs in this study fall into two distinct groups with respect to their effects on these receptors. This grouping parallels the chemistry of these compounds. Our results support the involvement of multiple protein domains in the mechanism of VA modulation of GABA and glycine receptors.

Amino Acid Sequence↗

PubMed2001

Post-hemorrhagic shock mesenteric lymph lipids prime neutrophils for enhanced cytotoxicity via phospholipase A2.

Hemorrhagic shock induced mesenteric hypoperfusion has long been implicated as a key event in the pathogenesis of the adult respiratory distress syndrome (ARDS) and multiple organ failure (MOF). Previous work links post-hemorrhagic shock mesenteric lymph (PHSML) lipids and neutrophil (PMN) priming in the pathogenesis of ARDS. We hypothesize that gut phospholipase A2 (PLA2) liberates proinflammatory lipids following hemorrhagic shock, which are responsible for enhanced PMN cytotoxicity. Mesenteric lymph was collected from rats (n > or = 5) before hemorrhagic shock, during hemorrhagic shock (MAP 40 mm Hg x 30 min), and after resuscitation (shed blood + 2x lactated Ringers). PMNs were incubated with physiologic concentrations (1-5%, v:v) of (a) buffer control, (b) sham (c) pre-shock lymph, (c) PHSML, (d) PHSML lipid extracts, (e) heat-denatured PSHML, and (f) PHSML harvested after i.v. pretreatment with a known PLA2 inhibitor (quinacrine, 10 mg/kg). PMNs were activated with fMLP (1 micromol), and the maximal rate of superoxide production measured by reduction of cytochrome c. Gut morphology was assessed histologically using hematoxalin and eosin (HE) staining. PHSML and PHSML lipid extracts (5%, v:v) primed for enhanced superoxide production compared to buffer controls (2.5-fold and 3.6-fold), sham (2.5-fold) and pre-shock lymph (2.0-fold). Lymph collected after systemic PLA2 inhibition, in contrast, abrogated the PMN priming response. Gut mucosal morphology, at end-resuscitation, was intact on HE staining both with and without PLA2 inhibition. Heat denaturing the PHSML (eliminating cytokines and complement), on the other hand, did not reduce PMN priming. Physiologic concentrations of PHSML lipids prime the PMN respiratory burst. Lymph priming is diminished with systemic PLA2 inhibition, implicating gut PLA2 as a source of proinflammatory lipids that may be central in the pathogenesis of hemorrhagic shock induced ARDS/MOF.

Animals↗

PubMed2001

Differential cardiopulmonary recruitment of neutrophils during hemorrhagic shock: a role for ICAM-1?

Hemorrhagic shock and subsequent resuscitation can result in acute lung injury and cardiac dysfunction. Previous studies have demonstrated that tissue neutrophil accumulation contributes to cardiopulmonary injury associated with trauma. Thus, suppression of tissue neutrophil recruitment in an early therapeutic window after hemorrhagic shock may protect the cardiopulmonary system. It is unclear whether hemorrhagic shock induces cardiopulmonary recruitment of neutrophils before resuscitation. Intercellular adhesion molecule-1 (ICAM-1) is one of the important factors that mediate tissue neutrophil recruitment. The physiologic significance of ICAM-1 expression after hemorrhage before resuscitation is not well delineated. The present study examined the role of ICAM-1 in neutrophil accumulation in the heart and lung after severe hemorrhage without resuscitation. Mice were subjected to hemorrhagic shock by removal of 30% of total blood volume. Lung neutrophil number as determined by immunofluorescent staining increased by 1 h after hemorrhage and was maximal at 4 h whereas myocardial neutrophil number was not changed. Lung neutrophil accumulation was not associated with an up-regulation of ICAM-1 expression or an alteration in ICAM-1 subcellular distribution. Surprisingly, deletion of the ICAM-1 gene enhanced hemorrhagic shock-induced lung neutrophil accumulation. These results suggest that hemorrhagic shock induces preferential neutrophil accumulation to the lung that appears to occur independent of ICAM-1-expression.

Animals↗

PubMed2001

TNF receptor I is required for induction of macrophage heat shock protein 70.

Expression of heat shock proteins (HSP) is an adaptive response to cellular stress. Stress induces tumor necrosis factor (TNF)-alpha production. In turn, TNF-alpha induces HSP70 expression. However, osmotic stress or ultraviolet radiation activates TNF-alpha receptor I (TNFR-I) in the absence of TNF-alpha. We postulated that TNF-alpha receptors are involved in the induction of HSP70 by cellular stress. Peritoneal Mphi were isolated from wild-type (WT), TNF-alpha knockout (KO), and TNFR (I or II) KO mice. Cells were cultured overnight and then heat stressed at 43 +/- 0.5 degrees C for 30 min followed by a 4-h recovery at 37 degrees C. Cellular HSP70 expression was induced by heat stress or exposure to endotoxin [lipopolysaccharide (LPS)] as determined by immunoblotting. HSP70 expression induced by either heat or LPS was markedly decreased in TNFR-I KO Mphi, whereas TNFR-II KO Mphi exhibited HSP70 expression comparable to that in WT mice. Expression of HSP70 after heat stress in TNF-alpha KO Mphi was also similar to that in WT mice, suggesting that induction of HSP70 by TNFR-I occurs independently of TNF-alpha. In addition, levels of steady-state HSP70 mRNA were similar by RT-PCR in WT and TNFR-I KO Mphi despite differences in protein expression. Furthermore, the effect of TNFR-I appears to be cell specific, since HSP70 expression in splenocytes isolated from TNFR-I KO was similar to that in WT splenocytes. These studies demonstrate that TNFR-I is required for the synthesis of HSP70 in stressed Mphi by a TNF-independent mechanism and support an intracellular role for TNFR-I.

Animals↗

PubMed2001

L-arginine attenuates lipopolysaccharide-induced lung chemokine production.

Chemokines stimulate the influx of leukocytes into tissues. Their production is regulated by nuclear factor-kappaB (NF-kappaB), an inducible transcription factor under the control of inhibitory factor kappaB-alpha (IkappaB-alpha). We have previously demonstrated that L-arginine (L-Arg) attenuates neutrophil accumulation and pulmonary vascular injury after administration of lipopolysaccharide (LPS). We hypothesized that L-Arg would attenuate the production of lung chemokines by stabilizing IkappaB-alpha and preventing NF-kappaB DNA binding. We examined the effect of L-Arg on chemokine production, IkappaB-alpha degradation, and NF-kappaB DNA binding in the lung after systemic LPS. To block nitric oxide (NO) production, a NO synthase inhibitor was given before L-Arg. LPS induced the production of chemokine protein and mRNA. L-Arg attenuated the production of chemokine protein and mRNA, prevented the decrease in IkappaB-alpha levels, and inhibited NF-kappaB DNA binding. NO synthase inhibition abolished the effects of L-Arg on all measured parameters. Our results suggest that L-Arg abrogates chemokine protein and mRNA production in rat lung after LPS. This effect is dependent on NO and is mediated by stabilization of IkappaB-alpha levels and inhibition of NF-kappaB DNA binding.

Animals↗

PubMed2001

A low level of TNF-alpha mediates hemorrhage-induced acute lung injury via p55 TNF receptor.

Acute lung injury after hemorrhagic shock (HS) is associated with the expression of tumor necrosis factor (TNF)-alpha in the lung. However, the role of TNF-alpha and its receptors in this pulmonary disorder remains obscure. This study examined the temporal relationship of pulmonary TNF-alpha production to neutrophil accumulation during HS and determined the role of TNF-alpha in neutrophil accumulation and lung leak. HS was induced in mice by removal of 30% of total blood volume. Lung TNF-alpha was measured by ELISA. Neutrophil accumulation was detected by immunofluorescent staining, and microvascular permeability was assessed using Evans blue dye. Although HS induced a slight and transient increase in lung TNF-alpha, neutrophil accumulation preceded the increase in TNF-alpha. However, lung neutrophil accumulation and lung leak were abrogated in TNF-alpha knockout mice, and both were restored by administration of recombinant TNF-alpha to TNF-alpha knockout mice before HS. Neutrophil accumulation and lung leak were abrogated in mice lacking the p55 TNF-alpha receptor, but neither was influenced by p75 TNF-alpha receptor knockout. This study demonstrates that a low level of pulmonary TNF-alpha is sufficient to mediate HS-induced acute lung injury during HS and that the p55 TNF-alpha receptor plays a dominant role in regulating the pulmonary inflammatory response to HS.

Acute Disease↗

PubMed2001

[Expression of rasp21, C-myc, C-erbB-2, and AFP in 2-FAA induced experimental hepatocarcinogenesis].

OBJECTIVE: To investigate the distribution of oncogenes and their relationships in 2-FAA induced experimental hepatocarcinogenesis. METHODS: Rasp21, C-myc, C-erbB-2, and AFP were detected and analyzed by the SP method of immunohistochemistry. RESULTS: Some cells expressed rasp21, C-myc, and AFP in peripheral liver lobules and alternated hepatocyte foci in the early stage of the experiment. And with the formation and progression of hyperplastic hepatocytic nodules, expressed cells increased and often accompanied each other. Expression of C-erbB-2 appeared in the middle stage of the hepatocarcinogenesis. CONCLUSIONS: Expression of rasp21, C-myc, and AFP in the experimental hepatocarcinogenesis is an early molecule change, which may relate to the initiation of hepatocarcinogenesis and be considered to be one of the molecular bases for the morphogenesis of hepatocarcinogenesis. During the development of lesion, C-erbB-2 may have promoting effects. It is also clear that malignant transformation of hepatocyte needs the cooperation of multiple oncogenes.

2-Acetylaminofluorene↗

PubMed2001

Formation and identification of 4'-O-methyl-(-)-epigallocatechin in humans.

The possible beneficial effects of tea consumption have attracted a great deal of attention. Many of the biological effects have been attributed to tea catechins, but the metabolic fate of these compounds is not clear. In the present study, a major metabolite observed in human blood and urine samples after green tea administration was identified as a O-methylated derivative of (-)-epigallocatechin (EGC) by comparison with products from chemical and enzymatic O-methylation of EGC. The structure of this metabolite was elucidated as 4'-O-methyl-(-)-epigallocatechin (4'-O-MeEGC) by (1)H and (13)C NMR and heteronuclear multiple bond connectivity experiment. The human plasma level of 4'-O-MeEGC reached its peak value within the first 2 h following tea ingestion. Its maximum concentration was 4 to 6 times higher than that of EGC. The half-lives of EGC and 4'-O-MeEGC in the blood were 1.02 +/- 0.07 and 4.39 +/- 1.14 h, respectively. The amount of 4'-O-MeEGC excreted in urine was about 3 times higher than that of EGC, and 88% of 4'-O-MeEGC was excreted in urine within 8 h. The present structural information and concentration-time profile of this metabolite provide the basis for understanding the biotransformation of EGC and for future elucidation of its biological activities.

Catechin↗