gamma-Glutamyl transpeptidase is increased by oxidative stress in rat alveolar L2 epithelial cells

The tripeptide glutathione (GSH) is used by cells to detoxify hydroperoxides, produced during oxidative stress, and is consumed in the process. Previous studies have indicated that cells can be protected against oxidative stress by extracellular GSH through its degradation catalyzed by the exoenzyme gamma-glutamyl transpeptidase (gamma GT) and its de novo synthesis within the cytosol. We hypothesized that gamma GT would be increased as part of the adaptation of cells to oxidative stress. We examined whether oxidative stress could increase gamma GT activity, protein, and mRNA in a lung epithelial cell line (L2). Cultures were subjected to H2O2-mediated toxicity by 15 min of exposure to the redox cycling quinone, menadione. Menadione (50 microM) caused an initial decrease (27 +/- 9% of baseline after 15 min) in intracellular GSH, followed by resynthesis to levels significantly higher than baseline (335 +/- 40% after 24 h, P < 0.001). This elevation was prevented by acivicin, a gamma GT inhibitor. Menadione also caused a dose-dependent increase in gamma GT enzymatic activity (715 +/- 125% of control at 24 h after 15 min of exposure to 100 microM menadione, P < 0.001) that was prevented by actinomycin D. Western blot analysis indicated increased levels of gamma GT protein with increasing menadione. A concentration-dependent increase in gamma GT-mRNA was also observed. Previous investigation has demonstrated that an increase in gamma GT activity enhances the capacity of cells to utilize extracellular GSH. The findings presented here are consistent with a role for gamma GT in cellular adaptation to oxidative stress.

Deletion of 3 basepairs resulting in the loss of lysine-121 in the insulin receptor alpha-subunit in a patient with leprechaunism: binding, phosphorylation, and biological activity

We have identified a novel mutation of the human insulin receptor gene in a previously unreported patient with leprechaunism, leprechaun Rochester. This mutation consists of deletion of three nucleotides (GAA) in exon 2 and results in loss of the lysine-121 in the putative ligand-binding domain of the alpha-subunit. To analyze this mutation, we prepared a corresponding mutant insulin receptor by site-directed mutagenesis and expressed the receptor in Chinese hamster ovary cells. Although the mutant receptor displayed normal insulin binding, abnormalities were found in autophosphorylation and in phosphorylation of endogenous and exogenous protein substrates. These abnormalities consisted of increased basal kinase activity, but blunted insulin-stimulated responsiveness. Importantly, cells that expressed the mutant receptor showed markedly decreased insulin- and serum-stimulated DNA synthesis compared to untransfected control cells and cells transfected with the wild-type insulin receptor. These findings suggest that deletion of lysine-121 in conjunction with a presumed, but thus far unidentified, second mutant allele contributed significantly to the lethal insulin-resistant state in this patient with leprechaunism.

Fetal renal vein thrombosis, hydrops fetalis, and maternal lupus anticoagulant. A case report

Hydrops fetalis with fetal renal vein thrombosis in a mother with antiphospholipid antibody syndrome detected post-partum suggests an underlying pathogenetic association that may provide new strategies for treatment of a lethal disorder.

The transcription factor YY1 binds to negative regulatory elements in the human cytomegalovirus major immediate early enhancer/promoter and mediates repression in non-permissive cells

We have previously shown that repression of human cytomegalovirus (HCMV) major immediate early (IE) gene expression in non-permissive human teratocarcinoma (T2) cells is associated with a number of nuclear factors which bind to the imperfect dyad symmetry located in the modulator region upstream of the major IE enhancer as well as to the 21 bp repeat elements within the enhancer. Differentiation of T2 cells with retinoic acid (RA) results in a decrease in binding of some of these nuclear factors to these sites and deletion of these specific binding sites from major IE promoter/reporter constructs results in increased IE promoter activity in normally non-permissive cells. In this study, we demonstrate that the transcription factor YY1, which can negatively regulate the adeno-associated virus P5 promoter, directly binds to both the imperfect dyad symmetry and the 21 bp repeat elements in the HCMV major IE promoter/regulatory region and mediates repression of HCMV IE gene expression. This strongly suggests that YY1 plays an important role in regulating HCMV expression in non-permissive cells.

Regulation of neuropeptide-processing enzymes by nitric oxide in cultured astrocytes

Nitric oxide (NO), a recently discovered neurotransmitter, has been shown to have a cytostatic effect on cultured glia. A NO-generating agent, S-nitroso-N-acetyl-penicillamine (SNAP), was used to treat C6 glioma and primary cortical astrocytes. The levels of a monobasic peptide-processing enzyme activity and carboxypeptidase E activity were examined. The cellular levels of these two enzymes are specifically reduced in response to treatment with SNAP. A decrease of approximately 30-50% in these two enzyme activities was seen in both primary astrocytes and C6 glioma cells. This decrease in cellular enzyme activities is not due to increased secretion because the secreted activity is also reduced in response to SNAP treatment in both the glioma cells and the primary astrocytes. Removal of SNAP treatment causes the carboxypeptidase enzyme activity to return to control levels within 3 days. Northern and western blot analyses indicate that the reduced cellular level of carboxypeptidase E is not due to reduced expression of the messenger RNA or protein, suggesting that the SNAP treatment is affecting factors that influence carboxypeptidase E activity. Taken together, these results imply that NO is involved in the regulation of peptide biosynthetic enzymes and this could lead to the antimitogenic action of SNAP on glia.

Rat fibroblasts transfected with the human 70-kDa heat shock gene exhibit altered translation and eukaryotic initiation factor 2 alpha phosphorylation following heat shock

Heat shock inhibits translation in a wide variety of cells. After heating, eukaryotic initiation factor 2-alpha (eIF-2 alpha) becomes phosphorylated which prevents the binding of Met-tRNA to the 40s ribosomal subunit inhibiting initiation of translation. Thermotolerant cells demonstrate resistance to inhibition of translation by additional heating suggesting that heat shock proteins may help to maintain translational integrity following thermal stress. Here we have examined the effects of increased intracellular levels of hsp70 protein on translation and eIF-2 alpha phosphorylation using rat fibroblasts stably transfected with a cloned human hsp70 gene. We observed a decrease in the rate of translational inhibition following heat shock in both hsp70-transfected and thermotolerant cells. Upon recovery at 37 degrees C, both hsp70-transfected and thermotolerant cells exhibit a faster rate of translational recovery. Utilizing slab gel isoelectric focusing coupled with immunoblotting we demonstrate that 45 degrees C heat shock leads to a rapid 4-5-fold increase in eIF-2 alpha phosphorylation, with little difference seen between control cells and hsp70-transfected cells. However, dephosphorylation of eIF-2 alpha occurs faster in the hsp70-transfected cells. These results suggest that hsp70 may play a role in facilitating the dephosphorylation of eIF-2 alpha as well as reversing the inhibition of translation following heat shock.

Effects of background stress and anxiety on postoperative recovery

The effects of background stress and anxiety on both short- and long-term recovery were measured in 30 healthy patients undergoing general anaesthesia for day-case dental extractions. Standardised questionnaires presented pre-operatively, assessed psychological status in terms of trait and state anxiety and stress levels. State anxiety was again measured postoperatively; recovery was assessed with pre- and postoperative batteries of cognitive tasks. Correlation coefficients revealed that the level of background stress in the preceding 6 months correlated with physical parameters of recovery such as time taken for patients to open their eyes, perceived pain and increased postoperative morbidity. The study also demonstrated that high levels of state anxiety after surgery correlated with postoperative pain. Trait and state anxiety before surgery did not correlate with any parameters of recovery or postoperative morbidity.

Differential signal transduction of epidermal-growth-factor receptors in hormone-dependent and hormone-independent human breast cancer cells

In breast cancer, hormone dependency is inversely correlated with the number of surface epidermal-growth-factor (EGF) receptors on the tumor cells. In vitro, EGF stimulated only hormone-dependent immortalized human breast cancer cells to grow with an increased rate whereas hormone-independent cells were not affected by EGF. The number of EGF surface receptors is about 5-10-times smaller on hormone-dependent cells than on hormone-independent cells. Two cell lines representing the two cell types were used to demonstrate the signal-transduction capabilities of the EGF receptors. The two cell lines were the hormone-dependent MCF-7 cells and the hormone-independent MDA-MB-231 cells. Incubation at 37 degrees C for 15 min with 10(-8) M EGF increased the surface EGF-receptor density substantially on MCF-7 cells (50%) and reduced the number of these receptors on MDA-MB-231 cells to about 65% of the control. Both cell lines internalized a fluorescein-isothiocyanate-labeled EGF with similar kinetics. EGF triggered tyrosine phosphorylation of several targets in isolated MCF-7 cell membranes. One of these targets was shown by immunoprecipitation to be the EGF receptor. In MDA-MB-231 cell membranes, the EGF receptor was demonstrated to be the main target for tyrosine phosphorylation. The mRNA expression of the immediate early proto-oncogene c-fos was stimulated by EGF only in MCF-7 cells. In contrast, the mRNA of the EGF receptors was stimulated by EGF in both cell lines. These results demonstrate that, although EGF-binding sites are present on both cell lines, their signal-transduction capacity and activities are substantially different and resulted in a divergent response of the two cell types to EGF.

Plasma HDL levels are regulated by the catabolic rate of large particles of lipoprotein containing apo-A-I

Lp-A-I was isolated by immunoaffinity chromatography and then separated into two fractions of large and small Lp-A-I particles by conventional ultracentrifugation with a cut-off density of 1.125 g/ml. The large and small particle-rich fractions were then radiolabeled with [125I]-Na and [131I]-Na, respectively. Both of the labeled lipoproteins were injected (20 microCi, i.v.) simultaneously into normolipidemic rabbits. The FCR of the large Lp-A-I particles was much less than that of the small Lp-A-I particles (0.801 +/- 0.026/day vs. 2.227 +/- 0.067/day, P < 0.0001). These data indicate that the two particles have distinctly different metabolic pathways and that the lower FCR of larger Lp-A-I particles can effectively raise plasma HDL levels.

Role of tumor necrosis factor in neonatal sepsis

In order to assess the role of tumor necrosis factor (TNF) in neonatal sepsis, plasma TNF levels were determined by a method using L929 cells at the time of septic work-up in 67 neonates. Thirty-three patients with sepsis were found to have significantly higher TNF levels (533.33 +/- 468.74 U/ml; 1 U corresponding to 1.67 pg recombinant TNF) as compared with 34 non-sepsis patients (100.0 +/- 188.97 U/ml) and 30 healthy newborns (27.33 +/- 16.17 U/ml, P < 0.05, respectively). The upper limit of normal plasma TNF levels was 60 U/ml and the best cutoff value for predicting neonatal sepsis was 160 U/ml. This had remarkable sensitivity (88%), specificity (82%), positive predictive value (83%), and negative predictive value (88%). Plasma TNF levels were significantly associated with the occurrence of shock, organ failure, scleroma and outcome. Thus, anti-TNF antibodies might be used in protecting newborns from septic death.

Quantitative characterization of insulin-glucose response in Watanabe heritable hyperlipidemic and cholesterol-fed rabbits and the effect of cilazapril

A great deal of evidence suggests that insulin resistance, via hyperinsulinemia, contributes to hyperlipoproteinemia and coronary atherosclerosis. When Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of familial hypercholesterolemia (FH), are compared with normolipidemic Japanese White (JW) rabbits, an elevated fasting plasma insulin level and a heightened plasma insulin response to an intravenous (i.v.) glucose challenge are found. To elucidate the mechanism behind this phenomenon, a two-compartment model of the glucose/insulin system was fitted to empirical time courses of glucose and insulin concentrations during an i.v. glucose tolerance test (IVGTT) by nonlinear least-square regression, and the model parameters such as the glucose utilization rate constant, insulin degradation rate constant, and pancreas sensitivity were determined. WHHL rabbits showed decreased values of glucose utilization and insulin degradation rate constants and slightly higher values of pancreas sensitivity. This suggests that insulin resistance occurs in extrapancreatic tissues, and that this may be attributable to insulin receptor and/or post-insulin receptor abnormalities. Cholesterol feeding did not significantly change glucose tolerance or insulin action in JW rabbits. The effects of an angiotensin-converting enzyme (ACE) inhibitor, cilazapril, on insulin resistance were also examined in WHHL and JW rabbits. A decreased insulin response to an i.v. glucose challenge and increased glucose utilization and insulin degradation rate constants were observed in WHHL rabbits that had been treated with cilazapril, indicating that cilazapril improved insulin resistance in WHHL rabbits, possibly by increasing the number of insulin receptors. No significant differences were found in glucose tolerance and insulin action in JW rabbits before and after cilazapril administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative molecular field analysis combined with physicochemical parameters for prediction of polydimethylsiloxane membrane flux in isopropanol

Comparative molecular field analysis (CoMFA) combined with various physicochemical parameters were used to develop three-dimensional quantitative structure-transportability relationships (3-D QSTR) to predict membrane flux for 108 aromatic and heteroaromatic compounds through polydimethylsiloxane (PDMS) membranes in isopropyl alcohol (IPA). Sybyl, a comprehensive computational molecular modeling package, was used to analyze the data. Optimized molecular models were selected using molecular modeling techniques. Partial least-squares (PLS) regression combined with crossvalidation or bootstrapping was used as the statistical method to establish the predictive models. Prediction was good for the steady-state flux using both steric and electrostatic field descriptors combined with a functional group classification technique. Predictive ability was substantially increased in a model using CoMFA descriptors along with log mole fraction solubility for the penetrants in isopropanol, a hydrophobic term, fchex, which is used to estimate the partition coefficient between cyclohexane and water, and the addition of an intramolecular hydrogen bonding (IHB) term. The crossvalidated r2 and the conventional r2 for this model were 0.951 and 0.973, respectively. Excellent predictions are demonstrated for the membrane flux of the compounds both inside and outside the data domain.

In vitro conversion of recombinant human proapolipoprotein A-I to apolipoprotein A-I

We recently investigated the in vivo conversion of recombinant human proapolipoprotein A-I (rh-Met-proapo A-I) from E. coli to apolipoprotein (apo) A-I in rabbits. In vitro incubation of rh-Met-proapo A-I with rabbit serum produced mature apo A-I3 isoproteins, as determined by the immunoblotting method. However, at the time we were unable to chemically confirm a newly produced protein band which appeared at the position of human apo A-I3. Since then, we have confirmed the amino acid sequence of the protein using a membrane protein sequence technique, and have concluded that it corresponds to human apo A-I3.

Association of the insulin receptor and phosphatidylinositol 3-kinase requires a third component

We have studied the interactions between the insulin receptor and PtdIns 3-kinase by a reconstitution system in vitro composed of highly purified PtdIns 3-kinase from rat liver and highly purified insulin receptors bound to insulin-agarose or to antibodies against insulin receptors. As a positive control, receptors for platelet-derived growth factor, which bind and phosphorylate PtdIns 3-kinase, were studied in parallel with insulin receptors. Our results indicate that the insulin receptor, regardless of its phosphorylation state, does not directly associate with purified PtdIns 3-kinase, whereas the autophosphorylated receptor does associate with PtdIns 3-kinase present in the crude CHO-cell lysate. Also, we could not detect phosphorylation of PtdIns 3-kinase by the insulin receptor, even through the receptor readily underwent autophosphorylation and phosphorylated an insulin-receptor substrate, poly(Glu-Tyr) (4:1). These findings argue that one or more cytosolic components link the receptor and the enzyme. Insulin-receptor substrate-1 (IRS-1) was evaluated as a potential linking protein. In the absence of ATP, IRS-1 did not facilitate the coupling of the phosphorylated insulin receptor to PtdIns 3-kinase. Thus IRS-1 is unlikely to be the component in crude CHO-cell lysate that couples PtdIns 3-kinase to the phosphorylated insulin receptor. However, the addition of ATP, which allows phosphorylation of IRS-1 by the insulin receptor, also enhances the coupling of PtdIns 3-kinase to the insulin receptor. In support of this idea, immunoprecipitates of IRS-1 from insulin-treated CHO cells were found to contain both the insulin receptor and PtdIns 3-kinase. In conclusion, the insulin receptor does not appear to phosphorylate or bind directly to PtdIns 3-kinase, regardless of the receptor's state of phosphorylation. Association of PtdIns 3-kinase with the insulin receptor is mediated by one or more components, one of which may involve an unidentified factor in cell lysate and another that apparently involves phosphorylated IRS-1.

Polymorphic site study at codon 347 of apolipoprotein A-IV in a Japanese population

In a population of Japanese subjects, we surveyed codon 347 of the apolipoprotein (apo) A-IV gene and found that the frequency of a rare allele at this point was extremely low compared to that in western populations. Only one of 850 unrelated samples showed mutation at the enzyme recognition site by agarose gel electrophoresis. However, direct sequencing of the coding region revealed that it did not result from the ACT (Thr) to TCT (Ser) mutation which has been reported in western countries, but from an ACT to ACG (Thr) mutation, which does not affect the primary structure of apo A-IV. Two additional family members showed the same point mutation at codon 347.

Plasma nitric oxide levels in newborn infants with sepsis

Nitric oxide is thought to play an important role in the mediation of the cardiovascular features of septic shock. We determined plasma levels of nitrite and nitrate (not differentiated in measurement) in neonates with sepsis and found these levels to be elevated at the time of entry compared with those of control subjects (p < 0.05); the levels were significantly higher in the patients with sepsis and shock than in those without shock (p < 0.05). Elevations of nitrite plus nitrate were correlated with tumor necrosis factor and severity of illness judged by pediatric risk of mortality (PRISM) scores at onset (p < 0.05). Of 8 newborn infants with a nitrite-plus-nitrate value > 200 mumol/L, 6 had septic shock; none of 12 not reaching that cutoff value had septic shock (p < 0.05). Levels of nitrite plus nitrate were elevated as much in gram-positive as in gram-negative sepsis. We conclude that the determination of circulating plasma levels of nitrite plus nitrate may be useful in forecasting the severity of illness and the occurrence of septic shock; therapeutic approaches associated with inhibition of nitric oxide synthesis may be worth trying in infants with septic shock.

Association between protective efficacy of antibodies to tumor necrosis factor and suppression of nitric oxide production in neonatal rats with fatal infection

In a rat model of fatal infection caused by Pseudomonas aeruginosa, the circulating level of nitrite/nitrate (NO2-/NO3-), a good indicator for nitric oxide production, was remarkably increased after elevation of circulatory tumor necrosis factor (TNF). Anti-TNF MAb cotreatment was shown to blunt hypoglycemia and hyperlacticemia and was associated with decreased mortality of septic animals. Moreover, anti-TNF MAb significantly reduced not only plasma TNF but also plasma NO2-/NO3- levels. Dexamethasone had a similar effects, and when anti-TNF MAb was used in combination with dexamethasone, the suppression of nitric oxide production and the protective efficacy were more remarkable compared with therapy with either anti-TNF MAb or dexamethasone alone. Our present data suggested that the protective efficacy of anti-TNF MAb may correlate with the suppression of nitric oxide production and also with a modulation in metabolic abnormalities in the septic newborn rats.

In vivo kinetics of lipoprotein(a) in homozygous Watanabe heritable hyperlipidaemic rabbits

In vivo kinetics of lipoprotein(a) [Lp(a)] were investigated in homozygous Watanabe heritable hyperlipidaemic (WHHL) rabbits (an animal model of familial hypercholesterolemia (FH)), and in normolipidemic Japanese White rabbits (controls). 125I-labelled Lp(a) and 131I-labelled LDL were simultaneously injected intravenously. Blood samples were then taken periodically. Kinetic parameters were calculated from the plasma radioactivity decay curves. The fractional catabolic rates (FCRs) of both Lp(a) and LDL (1.355 +/- 0.189 pools per day and 1.278 +/- 0.397 pools per day, respectively) in the WHHL rabbits were significantly (P < 0.005) smaller than those in the control rabbits (2.008 +/- 0.083 pools per day and 2.855 +/- 0.759 pools per day, respectively). In WHHL rabbits, the FCRs of Lp(a) and LDL were similar. However, in control rabbits, the FCR of Lp(a) was significantly (P < 0.01) smaller than that of LDL. In WHHL rabbit organs, the mean ratio of 125I-Lp(a): 131I-LDL, 48 h after injection, normalized to the corresponding isotope ratio in plasma, were 1.525, 1.020, 1.819 and 1.967, in liver, kidney, spleen and bile, respectively. These values were significantly higher than the corresponding values in control rabbits (0.590, 0.677, 0.862 and 0.766, respectively). Our data strongly suggest that Lp(a) clearance is not entirely dependent upon LDL receptors and may be mediated by some other mechanisms.

Combined therapy with probucol and pravastatin in hypercholesterolaemia. One year follow-up study

The effect of co-administration of low doses of pravastatin to hypercholesterolaemic patients already receiving long-term probucol treatment (mean 500-1,000 mg/day for 350 days) were investigated. Pravastatin 5 mg/day (Group 1; 12 m, 13 f; mean age 59.1 y) or 10 mg/day (Group 2; 8 m, 11 f; mean age 60.8 y) was administered, and blood was taken after 0, 3, 6, and 12 months. Both groups showed a significant reduction in serum total cholesterol (TC), phospholipid (PL), low density lipoprotein-cholesterol (LDL-C), LDL-triglyceride (TG), LDL-PL, apolipoprotein (apo) B, and apo E after the combined therapy. These levels were reduced more in Group 2 than in Group 1 subjects. In Group 2, significant falls in serum TG and apo CII were also observed. The changes in TC, PL, LDL-C, apo B, apo CII and apo E were dependent upon the dose of pravastatin, as assessed by two-way analysis of variance. Serum high density lipoprotein (HDL)3-C, apo AI and apo AII were slightly but significantly increased in both groups after 12 months of combined therapy, but the increase was not sufficient to reverse the probucol-induced lowering of the HDL level. We conclude that combined therapy resulted in a significant reduction in atherogenic lipoproteins and apolipoproteins, and an increasing dose of pravastatin (5 mg to 10 mg daily) made the lipid lowering effect more prominent. The reduction in serum HDL-C due to long-term probucol administration was not reversed by the addition of pravastatin.

The influence of phthalate esters on Leydig cell structure and function in vitro and in vivo

Phthalate esters are widely used in the manufacture of plastics and have been shown to cause testicular toxicity, purportedly, by targeting the Sertoli cell alone. Recent evidence, however, indicates that a paracrine control exists between Sertoli and Leydig cells and the breakdown of one component of this relationship is therefore detrimental to normal function. However, no data that explore the influence of testicular toxins on Leydig cell structure and function have been published hitherto. The preliminary studies reported here were initiated to test the hypothesis that phthalate intoxication may adversely alter Leydig cell structural and functional integrity. Four phthalate esters, namely, di(2-ethylhexyl) phthalate (DEHP, di-n-pentyl phthalate (DPP)., di-n-octyl phthalate (DOP), and diethyl phthalate (DEP) were investigated in vivo and their monoesters (MEHP, MPP, MOP, and MEP, respectively) in vitro for indications of Leydig cell toxicity in the rat. Rats were dosed by oral gavage with 2 g phthalate diester/kg/day in corn oil vehicle for 2 days, while Leydig cell primary cultures were incubated with 1,000 microM monoester for 2 hr. Light and electron microscopy were undertaken to determine the type and degree of any changes. Phthalate esters exerted a direct effect on Leydig cell structure and function (as determined by testosterone output) with correlation of the in vitro and in vivo effects of MEHP (DEHP) and MOP (DOP). No effects on Leydig cell structure or function were seen with MPP (DPP), although Sertoli cell cytoplasmic rarefaction and vacuolation were observed in vivo. DEP produced Leydig cell ultrastructural alterations in vivo. We conclude that individual phthalate esters may exert effects on both Sertoli and Leydig cells or one cell type alone.