Rapid endotoxin-induced alterations in myocardial calcium handling: obligatory role of cardiac TNF-alpha.

BACKGROUND: Bacterial endotoxin (lipopolysaccharide [LPS]) induces septic shock and depressed myocardial contractility. The mechanism of LPS-mediated cardiac dysfunction remains controversial. We hypothesized that LPS exerts significant effects on myocardial excitation-contraction coupling by rapid stimulation of tumor necrosis factor alpha (TNF-alpha) expression in the heart. METHODS: Isolated rat hearts were studied with and without recirculation of cell-free perfusate. The effects of LPS, exogenous TNF-alpha, anti-TNF-alpha antibody, and ceramidase inhibition were examined. Measurements included myocardial uptake of LPS, left ventricular contractility, myocardial oxygen consumption, intracellular calcium [Ca2+] cycling, and TNF-alpha concentrations in coronary perfusate and myocardium. RESULTS: Lipopolysaccharide was rapidly taken up by the perfused heart. With non-recirculating perfusion, LPS had no effect on contractility, oxygen consumption, coronary vascular resistance, or intracellular free calcium concentration ([Ca2+]i). However, with recirculating perfusion contractility was significantly impaired after 30 min of LPS, associated with lower [Ca2+]i levels and attenuated systolic rise in [Ca2+]i. Significant amounts of TNF-alpha accumulated in recirculating perfusate and myocardial tissue from LPS-perfused hearts. Ceramidase inhibition or neutralizing anti-TNF-alpha antibody inhibited the effects of LPS on contractility and [Ca2+]i. Recombinant rat TNF-alpha mimicked the LPS effects with faster onset. CONCLUSIONS: Lipopolysaccharide exerts rapid, negative inotropic effects on the isolated whole rat heart. The reduction in contractility is associated with depressed intracellular calcium cycling. In response to LPS, TNF-alpha is rapidly released from the heart and mediates the effects of LPS via the sphingomyelinase pathway. The present study for the first time directly links LPS-stimulated TNF-alpha production, abnormal calcium cycling, and decreased contractility in intact hearts.

Inhibition of tumor necrosis factor-alpha improves postischemic recovery of hypertrophied hearts.

BACKGROUND: Tumor necrosis factor (TNF)-alpha has been implicated in the pathogenesis of heart failure and ischemia-reperfusion injury. Effects of TNF-alpha are initiated by membrane receptors coupled to sphingomyelinase signaling and include altered metabolism and calcium cycling, contractile dysfunction, and cell death. We postulate that pressure-overload hypertrophy results in increased myocardial TNF-alpha expression and that it contributes to decreased contractility in hypertrophied infant hearts subjected to ischemia-reperfusion. METHODS AND RESULTS: Neonatal rabbits underwent aortic banding to induce LV hypertrophy. Myocardial TNF-alpha protein expression increased progressively with LV hypertrophy. Serum TNF-alpha was detected only after the onset of heart failure. Before onset of ventricular dilatation and heart failure (determined by serial echocardiograms), hearts from aortic banded and age-matched control rabbits were perfused in the Langendorff mode and subjected to 45 minutes of ischemia and 30 minutes of reperfusion. Postischemic recovery was impaired in hypertrophied hearts, but addition of neutralizing anti-rabbit TNF-alpha antibody to cardioplegia and perfusate solutions restored postischemic function. This effect was mimicked by treatment with the ceramidase inhibitor N-oleoyl ethanolamine. TNF-alpha inhibition also was associated with faster postischemic recovery of phosphocreatine, ATP, and pH as assessed by (31)P nuclear magnetic resonance spectroscopy. Intracellular calcium handling, measured by Rhod 2 spectrofluorometry, demonstrated lower diastolic calcium levels and higher systolic calcium transients in anti-TNF-alpha treated hearts. CONCLUSIONS: TNF-alpha is expressed in myocardium during compensated pressure-overload hypertrophy and contributes to postischemic myocardial dysfunction. Inhibition of TNF-alpha signaling significantly improves postischemic contractile function, myocardial energetics, and intracellular calcium handling.

Post-ischemic PKC inhibition impairs myocardial calcium handling and increases contractile protein calcium sensitivity.

OBJECTIVE: Protein kinase C (PKC) activation impairs contractility in the normal heart but is protective during myocardial ischemia. We hypothesized that PKC remains activated post-ischemia and modulates myocardial excitation-contraction coupling during early reperfusion. METHODS: Langendorff-perfused rabbit hearts where subjected to 25 min unmodified ischemia and 30 min reperfusion. Total PKC activity was measured, and the intracellular translocation pattern of PKC-alpha, -delta, -epsilon, and -eta assessed by immunohistochemistry and fractionated Western immunoblotting. The PKC-inhibitors chelerythrine and GF109203X were added during reperfusion and also given to non-ischemic hearts. Measurements included left ventricular function, intracellular calcium handling measured by Rhod-2 spectrofluorometry, myofibrillar calcium responsiveness in beating and tetanized hearts, and metabolic parameters. RESULTS: Total PKC activity was increased at end-ischemia and remained elevated after 30 min of reperfusion. The translocation pattern indicated PKC-epsilon as the main active isoform during reperfusion. Post-ischemic PKC inhibition affected mainly diastolic relaxation, with lesser effect on contractility. Both PKC inhibitors increased the Ca(2+) responsiveness of the myofilaments as indicated by a leftward shift of the calcium-to-force relationship and increased maximum calcium activated tetanic pressure. Diastolic Ca(2+) removal was delayed and the post-ischemic [Ca(2+)](i) overload further exacerbated. Depressed systolic function was associated with a lower amplitude of [Ca(2+)](i) transients. CONCLUSION: PKC is activated during ischemia and remains activated during early reperfusion. Inhibition of PKC activity post-ischemia impairs functional recovery, delays diastolic [Ca(2+)](i) removal, and increases Ca(2+) sensitivity of the contractile apparatus, resulting in impaired diastolic relaxation. Thus, post-ischemic PKC activity may serve to restore post-ischemic Ca(2+) homeostasis and attenuate contractile protein calcium sensitivity during the period of post-ischemic [Ca(2+)](i) overload.

Lipopolysaccharide internalization activates endotoxin-dependent signal transduction in cardiomyocytes.

We tested the hypothesis that bacterial lipopolysaccharide (LPS) must be internalized to facilitate endotoxin-dependent signal activation in cardiac myocytes. Fluorescently labeled LPS was used to treat primary cardiomyocyte cultures, perfused heart preparations, and the RAW264.7 macrophage cell line. Using confocal microscopy and spectrofluorometry, we found that LPS was rapidly internalized in cardiomyocyte cultures and Langendorff-perfused hearts. Although LPS uptake was also observed in macrophages, only a fraction of these cells were found to internalize endotoxin to the extent seen in cardiomyocytes. Colocalization experiments with organelle or structure-specific fluorophores showed that LPS was concentrated in the Golgi apparatus, lysosomes, and sarcomeres. Similar intracellular localization was demonstrated in cardiomyocytes by transmission electron microscopy using gold-labeled LPS. The internalization of LPS was dependent on endosomal trafficking, because an inhibitor of microfilament reorganization prevented uptake in both cardiomyocytes and whole hearts. Inhibition of endocytosis specifically restricted early activation of extracellular signal-regulated kinase proteins and nuclear factor-kappaB as well as later tumor necrosis factor-alpha production and inducible nitric oxide synthase expression. In conclusion, we have demonstrated that bacterial endotoxin is internalized and transported to specific intracellular sites in heart cells and that these events are obligatory for activation of LPS-dependent signal transduction.

Ischemic dysfunction in transgenic mice expressing troponin I lacking protein kinase C phosphorylation sites.

To determine the in vivo functional significance of troponin I (TnI) protein kinase C (PKC) phosphorylation sites, we created a transgenic mouse expressing mutant TnI, in which PKC phosphorylation sites at serines-43 and -45 were replaced by alanine. When we used high-perfusate calcium as a PKC activator, developed pressures in transgenic (TG) perfused hearts were similar to wild-type (WT) hearts (P = not significant, NS), though there was a 35% and 32% decrease in peak-systolic intracellular calcium (P < 0.01) and diastolic calcium (P < 0.005), respectively. The calcium transient duration was prolonged in the TG mice also (12-27%, ANOVA, P < 0.01). During global ischemia, TG hearts developed ischemic contracture to a greater extent than WT hearts (41 +/- 18 vs. 69 +/- 10 mmHg, perfusate calcium 3.5 mM, P < 0.01). In conclusion, expression of mutant TnI lacking PKC phosphorylation sites results in a marked alteration in the calcium-pressure relationship, and thus susceptibility to ischemic contracture. The reduced intracellular calcium and prolonged calcium transients suggests that a potent feedback mechanism exists between the myofilament and the processes controlling calcium homeostasis.

Vesnarinone restores contractility and calcium handling in early endotoxemia.

BACKGROUND: Endotoxin (lipopolysaccharide, LPS) is a trigger of the systemic inflammatory response. We have previously found that vesnarinone and amrinone, when given before LPS, prevented cytokine production and LPS-related cardiac dysfunction. We tested the hypothesis that vesnarinone would improve intracellular Ca(2+) handling and calcium-activated contractile force after the onset of endotoxemia. METHODS AND RESULTS: Adult rabbits received a bolus injection of LPS or vehicle. Vesnarinone (3 mg/kg) was given intravenously 90 minutes later. Two hours after LPS administration, hearts were perfused in the isolated Langendorff mode. Peak left ventricular developed pressure, +/-dp/dt, oxygen consumption (MVO(2)), and ratexpressure product were evaluated in conjunction with fluorescent spectroscopic determinations of intracellular calcium concentrations (Ca(i)) and the rate of Ca(i) transient decline during diastole (tauCa). Peak left ventricular developed pressure and +/-dp/dt were significantly lower in the LPS group. These were completely restored by vesnarinone. There was significantly slower diastolic calcium removal (increased tauCa) in LPS hearts that was also corrected by vesnarinone; however, the cytosolic calcium overload characteristic of LPS hearts was only partially improved. Reduced mechanical inefficiency (the ratio of rate-pressure product to MVO(2)) and myofilament sensitivity to Ca(i) were also significantly improved by vesnarinone. CONCLUSIONS: Acute endotoxemia caused contractile protein calcium insensitivity, oxygen wastage, and abnormal calcium cycling. Vesnarinone, given in the rescue mode, normalized LPS-induced myocardial dysfunction and partially restored abnormal calcium cycling. Although the mechanisms responsible for these effects require further clarification, it appears that agents such as vesnarinone may be useful to treat inflammatory-induced myocardial dysfunction.

CD14-independent activation of cardiomyocyte signal transduction by bacterial endotoxin.

In the heart, lipopolysaccharide (LPS) induces the production of proinflammatory cytokines that cause myocardial dysfunction; however, the signaling pathways involved in cardiomyocyte responses are poorly understood. We studied LPS-induced signaling by treating cardiomyocyte cultures with 0.01-10 microgram/ml LPS for 0-24 h in the presence or absence of 2.5% serum. Cytosolic and nuclear proteins were analyzed for expression and activation of protein kinases. Members of the extracellular signal-regulated kinase (ERK) and signal transducer and activators of transcription (STAT) protein families were uniformly expressed and specifically phosphorylated in response to LPS. Activation was biphasic; peaking at 5-10 min and 24 h after treatment. Inhibitor experiments provided evidence that ERK proteins may regulate STAT activity. Serum did not augment endotoxin-induced phosphorylation. Although cardiomyocytes expressed low levels of CD14 and LPS-binding protein, specific enzymatic removal of glycosyl phosphatidylinositol-linked receptors or incubation with an anti-CD14 antibody had no effect on kinase activation. Treatment of cells with an excess of detoxified LPS attenuated endotoxin-induced signaling. In addition, endotoxin stimulated specific binding of nuclear factors to AP-1, nuclear factor-kappaB (NF-kappaB), STAT1 (SIE, sis-inducible element), and STAT3 consensus-binding sequences. Finally, inhibition of ERK phosphorylation reduced, and NF-kappaB nuclear translocation prevented, tumor necrosis factor-alpha production. Our results indicate that LPS-induced activation of signal transduction in cardiomyocytes occurs by a CD14-independent mechanism.

The Process of Family Reconstruction after DNA Testing for Huntington Disease.

The needs of families to reconstruct their relationships in response to the DNA testing for Huntington disease of one or more of their asymptomatic members are presented. Data were collected from family interviews with 18 families, and from their responses on a post interview questionnaire. Findings are that families need to (a) address "unfinished business" associated with the decision for testing; (b) bring family members, peripheral in the decision for testing, into the loop; (c) reorganize patterns of communication and roles altered by the testing and heal ruptures in family membership; and (d) revise family stories about illness to provide a meaning for HD and explain the test results in a way that leaves them with a sense of mastery. Findings suggest that families should be more involved in the initial decision for testing of a member and that protocols should be established to provide help for their ongoing adjustment.

Impact of genetic testing for Huntington disease on the family system.

The psychological impact of DNA predictive testing on asymptomatic individuals at risk for Huntington disease (HD) has received considerable attention since the advent of the procedure in 1993. This study examined the impact of such testing on families from the families' perspective. Individuals asymptomatic at the time of testing, together with their families, were interviewed in their homes with a semi-structured interview. Eighteen families with a total of 55 individuals participated. Defining the family as the unit of analysis was consistent with Systems Theory that links interactions of individuals, families, and the social environment. Areas of affected family functioning noted by the respondents included: 1) family membership; 2) family patterns of communication; and 3) future care giving concerns as they influenced current relationships. Eighty-one percent of families experienced changes in family membership. Members in 50% of families experienced changes in patterns of communication, and 56% percent of persons reported changes in current relationships in response to test results and their implications for future caregiving. The data support the conclusion that genetic testing is a family, as opposed to an individual, matter and that family involvement in the decision making process should be strongly encouraged in order to help families adjust. The data imply that families will benefit in pre-test sessions from an examination of their patterns of dealing with illness issues, both past and present.

Transient and steady-state effects of shear stress on endothelial cell adherens junctions.

Endothelial cells exhibit profound changes in cell shape in response to altered shear stress that may require disassembly/reassembly of adherens junction protein complexes that mediate cell-cell adhesion. To test this hypothesis, we exposed confluent porcine aortic endothelial cells to 15 dyne/cm(2) of shear stress for 0, 8.5, 24, or 48 hours, using a parallel plate flow chamber. Cells were fixed and stained with antibodies to vascular endothelial (VE) cadherin, alpha-catenin, beta-catenin, or plakoglobin. Under static conditions, staining for all proteins was intense and peripheral, forming a nearly continuous band around the cells at cell-cell junctions. After 8.5 hours of shear stress, staining was punctate and occurred only at sites of continuous cell attachment. After 24 or 48 hours of shear, staining for VE-cadherin, alpha-catenin, and beta-catenin was intense and peripheral, forming a band of "dashes" (adherens plaques) that colocalized with the ends of stress fibers that inserted along the lateral membranes of cells. Staining for plakoglobin was not observed after 24 hours of shear stress, but returned after 48 hours. Western blot analysis indicated that protein levels of VE-cadherin, alpha-catenin, and plakoglobin decreased, whereas beta-catenin levels increased after 8.5 hours of shear stress. As cell shape change reached completion (24 to 48 hours), all protein levels were upregulated except for plakoglobin, which remained below control levels. The partial disassembly of adherens junctions we have observed during shear induced changes in endothelial cell shape may have important implications for control of the endothelial permeability barrier and other aspects of endothelial cell function.

Increased myocardial calcium cycling and reduced myofilament calcium sensitivity in early endotoxemia.

BACKGROUND: Mechanisms of cardiac dysfunction during endotoxemia are multiple and their targets uncertain. This study tested the hypothesis that endotoxin (LPS) induces abnormal calcium-activated contractile force in the heart. METHODS: Adult rabbits were given LPS intravenously; 2 hours later hearts were studied in the Langendorff mode. Measurements included peak developed pressure (PDP), myocardial oxygen consumption (MVO2), high-energy phosphates by 31P-NMR, and beat-to-beat intracellular calcium (Cai) by fluorescence spectroscopy. Myofibrillar calcium sensitivity was assessed from the relationship of PDP to Cai and the rate of diastolic Cai removal (tau Ca) was quantified. RESULTS: Force-calcium relationships were markedly depressed in LPS hearts despite increased Cai. MVO2 was increased in parallel with increased Cai. Taken together, these data denote myofilament calcium insensitivity and mechanical inefficiency. tau Ca was markedly prolonged in LPS hearts, indicating impaired calcium reuptake and/or extrusion. High-energy phosphates and intracellular pH were unaffected by LPS; however, inorganic phosphate (Pi) was significantly increased. Dobutamine further increased Cai and MVO2 in LPS hearts without significantly improving calcium-activated force. Pyruvate, an inotrope that reduces Pi, significantly improved contractility in LPS hearts. CONCLUSIONS: Endotoxemia rapidly induced futile calcium cycling and reduced myofibrillar calcium sensitivity. This state was resistant to beta-agonist inotropic stimulation; inotropes that normalize the calcium-force relationship may be more effective.

Vesnarinone and amrinone reduce the systemic inflammatory response syndrome.

OBJECTIVE: The systemic inflammatory response is an important cause of organ dysfunction. The present study tested the hypothesis that 2 clinically used agents, amrinone and vesnarinone, would decrease inflammation and cardiac dysfunction in a relevant model of systemic inflammatory response activation. METHODS: Rabbits received intravenous endotoxin, alone or in conjunction with amrinone or vesnarinone. Systemic effects were assessed by death, fever, behavior, and acidosis. Measures of inflammatory signaling were (1) plasma tumor necrosis factor-alpha and interleukin-1 beta production, (2) lung tissue myeloperoxidase activity, and (3) myocardial inducible nitric oxide synthase activity. Indices of systolic and diastolic myocardial function were measured in Langendorff-perfused hearts. RESULTS: Vesnarinone, in particular, reduced mortality rates (19% vs 61% for lipopolysaccharide alone, P =.01) and acidosis in lipopolysaccharide-treated rabbits. Both agents markedly reduced systemic tumor necrosis factor and interleukin-1 concentrations, lipopolysaccharide-mediated effects on myocardial systolic and diastolic function and on myocardial inducible nitric oxide synthase activity. Vesnarinone, but not amrinone, (1) decreased fever and lethargy, consistent with decreased central nervous system effects of endotoxin, and (2) decreased lung leukocyte infiltration. CONCLUSIONS: Vesnarinone and amrinone, which are used clinically for their inotropic and vasodilating properties, may be useful to limit inflammatory activation and consequent organ dysfunction. Structure-activity and/or pharmacokinetic between the compounds may be important, particularly in preventing inflammatory signaling within certain tissues.

Regulation of vascular connexin43 gene expression by mechanical loads.

Vascular tissues respond to changes in the mechanical forces imposed on them with changes in vasomotor tone in the short term and with structural remodeling in the long term. Since these responses involve intercellular communication, we have investigated regulation of the gap junction proteins, connexin26 (Cx26), connexin37 (Cx37), connexin40 (Cx40), and connexin43 (Cx43), by mechanical loads. Results were compared with parallel experiments on c-fos and GAPDH. Twenty percent stretch of cultured vascular smooth muscle cells caused a 3-fold increase in Cx43 mRNA levels by 2 hours. Cx26 was expressed at low levels but failed to respond to stretch, and Cx37 and Cx40 were not detected. c-fos mRNA levels increased after 30 minutes of stretch, whereas GAPDH mRNA did not change. Protein levels of Cx43 increased by 4 hours and remained elevated for 16 hours. Nuclear run-on experiments confirmed that Cx43 and c-fos were transcriptionally regulated by stretch. New protein synthesis was not a requirement for the stretch-induced rise in Cx43 expression, since mRNA levels were unaffected by treatment with cycloheximide. To examine transcriptional control of Cx43, stretched and unstretched vascular smooth muscle cells were transfected with a variety of promoter-reporter gene constructs. Cx43 sequences extending from within exon 1 (+162) to -1686 in the 5'-flanking region were coupled to the chloramphenicol acetyl transferase reporter gene. Deletions from the 5' end of these sequences differentially regulated reporter gene expression and indicated multiple potential regulatory sites. In particular, a putative activator protein-1 site at the -42 to -48 region was required for basal reporter activity. None of the promoter constructs revealed stretch sensitivity, indicating that the site of transcriptional control by stretch lies outside the -1686 to +162 region. Finally, Cx43 mRNA levels were assessed in cultured endothelial cells subjected to laminar shear stress of 15 dynes/cm2. Cx43 mRNA levels increased by approximately 4-fold at 1 hour and remained elevated for the duration of shear force. In conclusion, both mechanical strain and fluid shear stress caused increased expression of the gap junction protein Cx43.

A bridge to intracytoplasmic sperm injection--high insemination concentrations benefit patients who have a reduced chance of fertilization with standard in-vitro fertilization.

This study was carried out to determine whether high insemination concentrations (HIC) could improve fertilization and pregnancy rates in patients who had either previously demonstrated poor fertilization rates in vitro using standard protocols (Group 1) or in whom a reduced chance of fertilization was indicated at semen assessment prior to in-vitro fertilization (IVF) (Groups 2 and 3). Forty nine patients were recruited for the study. Standard IVF was carried out in 1 ml volumes using 10(5) spermatozoa/ml. HIC treatment involved co-culture of spermatozoa and oocytes in microdroplets with insemination concentrations increased 10-50 fold higher than standard IVF. Fertilization and pregnancy rates were compared between standard IVF and HIC in individual patients either in consecutive cycles (Group 1) or using sibling oocytes in the same cycle (Group 2). Group 3 patients were treated with HIC for their first treatment cycle. HIC significantly improved the fertilization rate compared with standard IVF for Groups 1 (59.7 +/- 10.7 versus 19.6 +/- 5.4% respectively) and 2 (54.9 +/- 8.5 versus 34.0 +/- 8.5% respectively). HIC increased the pregnancy rate from 0% with standard IVF to 20% per embryo transfer in Group 1 patients. A single pregnancy derived from the transfer of HIC and IVF embryos occurred in Group 2. The fertilization rate (47.2 +/- 7.6%) and pregnancy rate (31.3% per embryo transfer) for Group 3 patients was higher than predicted. There was no increase in the rate of polyploidy with HIC. Provided there are sufficient numbers of motile spermatozoa, HIC may be offered as an initial form of treatment, thus permitting referral of only the poorest responders for intracytoplasmic sperm injection (ICSI).

Cellular and molecular biology of vascular remodeling.

The vascular system undergoes remodeling throughout life, first as primitive vessels form and reorganize, then as the circulation accommodates changing tissue perfusion requirements. Recent investigations that have targeted receptor tyrosine kinases have elucidated fundamental mechanisms that are involved in early formation and restructuring of blood vessels. Distinct receptors for vascular endothelial growth factor, and other receptor tyrosine kinases, appear to regulate very different aspects of early vessel formation including endothelial cell differentiation, tube formation and differentiation of blood vessels into microvasculature versus large vessels. In later development and in the adult circulation, remodeling adapts arteries to chronic changes in hemodynamic function. Furthermore, novel findings of how vascular cells transduce the hemodynamic forces to which they respond have been reported. Force-sensitive gene transcription occurs by previously characterized transcription factors that bind to both established and novel responsive elements in promoter regions of relevant genes. There now is evidence that more than one of these factors can regulate gene expression in response to a single physical force (shear stress). Recent studies have emphasized the role of matrix degradation and cell death, in addition to matrix synthesis and cell proliferation, in arterial remodeling. The importance of cell death and matrix degradation has also been emphasized in the pathogenesis of vascular pathologies. As a result of these and other findings, the role tissue remodeling is being examined closely as a primary factor in the pathogenesis of atherosclerosis, hypertension and restenosis after angioplasty.

Effect of vitamin E on human glutathione peroxidase (GSH-PX1) expression in cardiomyocytes.

To determine the effect of vitamin E on cellular antioxidant enzymes, human ventricular cardiomyocytes were incubated with 200 microM all-racemic-alpha-tocopheryl acetate for 14 d at pO2s of 150 and 40 mm Hg. Cellular Cu, Zn superoxide dismutase, catalase, and GSH-Px1 activities were measured. Although SOD and catalase activities were unaffected by alpha-tocopherol, GSH-Px1 activities increased (p < .0001) as much as twofold. This increase was independent of oxygen tension and selenium. The increase in GSH-Px1 activity became significant (p < .01) by day 4. A nonantioxidant analog of alpha-tocopherol, 200 microM RRR-alpha-tocopherol methyl ether, did not affect GSH-Px1 activities. Although GSH-Px1 mRNA levels mirrored the changes in enzyme activities, the de novo nuclear GSH-Px1 transcript synthesis was unaffected by alpha-tocopherol. Because the increase in GSH-Px1 activities also occurred after cellular alpha-tocopherol levels had plateaued, the above results were most consistent with posttranscriptional stabilization of GSH-Px1 mRNA by alpha-tocopherol or an alpha-tocopherol-related metabolic product.

Identification of oxygen responsive elements in the 5'-flanking region of the human glutathione peroxidase gene.

The -1389 to +588 region of the human genomic glutathione peroxidase gene (hgpx1) was amplified using the polymerase chain reaction. This DNA fragment was cloned and sequenced, and various deletion constructs derived from the hgpx1 5'-flanking region were fused to the chloramphenicol acetyltransferase gene. These reporter genes were analyzed in transient transfection assays using primary cultured human ventricular cardiomyocytes obtained from patients with tetralogy of Fallot. Two distinct regions upstream from the transcription start site, which was determined using S1 nuclease analysis, were identified to be responsive to the oxygen tension in culture (pO2 values of 150 or 40 mm Hg). Methylation interference footprinting assays revealed proteins closely apposed to two sequences located at -1232 to -1213 and -282 to -275. We have designated these oxygen responsive elements ORE1 and ORE2, respectively. Gel mobility shift assays using double-stranded oligonucleotides corresponding to each site have demonstrated the formation of specific complexes using both cultured human cardiomyocyte and HeLa nuclear extracts. ORE1 and ORE2 bind disparate proteins with equal precision as bound complexes could be competed away with identical sequences but not with either the other ORE or an unrelated sequence. Insertion of these oxygen responsive elements into a reporter gene governed by a SV40 promoter similarly regulated chloramphenicol acetyltransferase activity according to the oxygen tension in culture.

The regulation of glutathione peroxidase gene expression by oxygen tension in cultured human cardiomyocytes.

In earlier studies we have shown that the activity of the antioxidant enzyme glutathione peroxidase is regulated by oxygen tension in cultured tetralogy of Fallot (TOF) ventricular myocytes and in the ventricles of TOF patients having corrective cardiac surgery. The present study was undertaken to determine the mechanism of this regulation. Northern and slot blot analysis was performed using RNA isolated from TOF myocytes cultured at oxygen tensions of 150 and 40 mmHg for 3, 7, 14, 21, and 28 days. As was found for enzyme activities, glutathione peroxidase mRNA levels were lower in the cells cultured at a pO2 of 40 mmHg than at 150 mmHg and could be elevated with an increase in oxygen tension. These results were standardized against house-keeping gene hexosaminidase B which showed no difference in mRNA levels between the two oxygen tensions throughout the time course. Nuclear run-off assays indicated that glutathione peroxidase was regulated by oxygen tension at the transcriptional level, while hexosaminidase B and total mRNA synthesis levels remained unchanged.

The DNA-binding properties of a rat nuclear phosphoprotein.

The non-histone nuclear phosphoprotein B2 (Mr 68,000; pI 6.5-8.2) was found to bind specifically defined fragments of DNA. With the use of monoclonal IgG2A antibodies prepared against this nuclear antigen, nucleosomal DNA fragments associated with phosphoprotein B2 were isolated and cloned. Nine cloned fragments were sequenced and analysed for similarity. The clone having the most similarity to the others was chosen to serve as a model in gel shift and footprinting assays. Subsequently, the DNA binding site was found to reside within a 30 bp region. Synthetic oligonucleotides corresponding to this site confirmed the specificity of DNA binding exhibited by the nuclear antigen as demonstrated in competition assays. Moreover, a 5'-TATTAG/C-3' motif was found to exist within the binding site and in the other sequenced clones, possibly implicating the involvement of this motif in protein binding.

The perinatal database: content and collection.

Recent advances in computer technology provide improved means for the collection of information for the perinatal database. They depend principally upon online entry via a computer terminal which allows immediate checking of the data input. The availability of such effective procedures for information gathering demands a careful review of the purposes, content, and structure of a computerized perinatal questionnaire.