Unlocking the mechanisms of transcription factor YY1: are chromatin modifying enzymes the key?

The transcription factor YY1 is a complex protein that is involved in repressing and activating a diverse number of promoters. Numerous studies have attempted to understand how this one factor can act both as a repressor and an activator in such a wide set of different contexts. The fact that YY1 interacts with a number of key regulatory proteins (e.g. TBP, TFIIB, TAFII55, Sp1, and E1A) has suggested that these interactions are important for determining which particular function of YY1 is displayed at a specific promoter. Two groups of proteins, previously known to function as corepressors and coactivators, that now seem likely to modulate YY1's functions, are the histone deacetylases (HDAC) and histone acetyltransferases (HAT). These two groups of enzymes modify histones, and this modification is proposed to alter chromatin structure. Acetylated histones are typically localized to active chromatin while deacetylated histones colocalize with transcriptionally inactive chromatin. When these enzymes are directed to a promoter through a DNA binding factor such as YY1, that promoter can be activated or repressed. This review will discuss the recent work dealing with the different proteins that interact with YY1, with particular emphasis on ones that modify chromatin, and how they could be involved in regulating YY1's activities.

Acetaldehyde (CH3CHO) production in rodent lung after exposure to metal-rich particles

Epidemiological reports demonstrate an association between increased human morbidity and mortality with exposure to air pollution particulate matter (PM). Metal-catalyzed oxidative stress has been postulated to contribute to lung injury in response to PM exposure. We studied the effects of residual oil fly ash (ROFA), a component of ambient air PM, on the formation of lung carbonyls that are indicators of lipid peroxidation. Rats were instilled intratracheally with ROFA (62.5-1000 micrograms) and underwent lung lavage. Lavage fluid carbonyls were derivatized with 2,4-dinitrophenylhydrazine, and measured by high performance liquid chromatography with UV detection. Dose-dependent increases in a peak that eluted with the same retention time as the acetaldehyde (CH3CHO) derivative was observed in rats treated with ROFA 15 min after instillation (up to 25-fold greater than saline treated controls). The identification of CH3CHO was confirmed using gas chromatography-mass spectroscopy. ROFA-induced increases in other lavage fluid carbonyls were not seen. Increased CH3CHO in lavage fluid was observed as late as 8 h later. No increase in CH3CHO was observed in plasma from ROFA-treated rats. An increased formation of CH3CHO was observed in a human airway epithelial cell line incubated with ROFA suggesting a pulmonary source of CH3CHO production. Instillation of solutions of metals (iron, vanadium, nickel) contained in ROFA, or instillation of another ROFA-type particle containing primarily iron, also induced a specific increase in CH3CHO. These data support the hypothesis that metals were involved in the increased CH3CHO formation. Thus metals on PM may mediate lung responses through induction of lipid peroxidation and carbonyl formation.

Lipid exchange between mixed micelles of phospholipid and triton X-100

If phospholipase catalyzed hydrolysis of phospholipid dissolved in a detergent mixed micelle is limited to the phospholipid carried by a single micelle, then hydrolysis ceases upon exhaustion of that pool. However, if the rate of phospholipid exchange between micelles exceeds the catalytic rate then all of the phospholipid is available for hydrolysis. To determine phospholipid availability we studied the exchange of 1,2-dioleoyl-sn-glycero-3-phosphocholine between mixed micelles of phospholipid and non-ionic Triton detergents by both stopped-flow fluorescence-recovery and nuclear magnetic resonance-relaxation techniques. Stopped-flow analysis was performed by combining mixed micelles of Triton and phospholipid with mixed micelles that contained the fluorescent phospholipid 1-palmitoyl-2-(12-[{7-nitro-2-1, 3-benzoxadiazo-4-yl}amino]dodecanoyl)-sn-glycero-3-phosphocholine (P-2-NBD-PC). The concentration dependence of fluorescence recovery suggested a second-order exchange mechanism that was saturable. The true second-order rate constant depends on the specific mechanism for exchange, which was not determined in this study, but the rate constant will be on the order of 106 to 107 M-1s-1. Incorporation of 1-palmitoyl-2-(16-doxylstearoyl)phosphatidylcholine into micelles increased the rate of proton relaxation and gave a limiting relaxation time of 1.3 ms. The results demonstrate that phospholipid exchange was rapid and that the phospholipid content of a single micelle did not limit the rate of phospholipid hydrolysis by phospholipases.

Receptors for the 5-oxo class of eicosanoids in neutrophils

5-Hydroxy- and 5-oxo-eicosatetraenoate (5-HETE and 5-oxoETE) activate polymorphonuclear neutrophils (PMNs) through a common, receptor-like recognition system. To define this system, we examined the interaction of these eicosanoids with human PMNs. PMNs esterified 5-[3H]HETE to glycerolipids at 37 and 4 degreesC. At 37 but not 4 degreesC, the cells also hydroxylated the label to 5, 20-[3H]diHETE. The acyl:CoA synthetase blocker, triacsin C, inhibited esterification but also led to an increase in the hydroxylation of the label. PMNs processed 5-[3H]oxoETE through the same pathways but only or principally after reducing it to 5-[3H]HETE (37 or 4 degreesC). In the presence of these varying metabolic reactions, PMNs (37 or 4 degreesC; +/- triacsin C) could not be shown to receptor bind either radiolabel. Plasma membranes isolated from PMNs esterified but unlike whole cells did not reduce or hydroxylate 5-[3H]oxoETE. Triacsin C blocked esterification, thereby rendering the membranes unable to metabolize this radiolabel. Indeed, triacsin C-treated membranes bound (Kd = 3.8 nM) 5-[3H]oxoETE specifically and reversibly to 86 pmol of sites per 25 micrograms of membrane protein. 5-OxoETE, 5-HETE, and 5,15-diHETE displaced this binding at concentrations correlating with their potency in eliciting PMN Ca2+ transients. GTP and GTPgammaS, but not ATP or ATPgammaS, also reduced 5-[3H]oxoETE binding, whereas 15-HETE, leukotriene B4, platelet-activating factor, IL-8, C5a, and N-formyl-Met-Leu-Phe lacked this effect. We conclude that PMNs and their plasma membranes use an acyl:CoA synthetase-dependent route to esterify 5-HETE and 5-oxoETE into lipids. Blockade of the synthetase uncovers cryptic plasmalemma sites that bind 5-oxoETE with exquisite specificity. These sites apparently mediate responses to the 5-oxo class of eicosanoids and are likely members of the serpentine superfamily of G protein-linked receptors.

[Markers of lipid peroxidation, inflammatory proteins and plasma tocopherols in homozygotic and heterozygotic sickle cell anemia]

Lipoperoxidation final products represented by the TBARS (substances reacting with the Thiobarbituric acid), inflammatory reaction proteins and sera tocopherol have been studied in homozygous forms as well as in heterozygous forms of sickle cell diseases. The significant increase of TBARS (P < 0.001) measured by spectrofluorimetry, the considerable decrease of the sera alpha gamma tocopherol, measured by HPLC (P < 0.005) in all sickle cell patients, especially in crisis homozygous form, reinforce our previous study (22, 23, 24). The absence of links between the TBARS and the tocopherols (fig. 1) suggests that other defence mechanisms occur without vitamin E. The collapse of haptoglobinemia in homozygous sickle cell patients associated with the fall of hemoglobinemia indicates a severe tissue and intravascular hemolysis as a consequence of LPO. Furthermore, the simultaneous decrease of cholesterolemia seems to indicate important lipoperoxide activity detected in sickle cell patients.

Postsynaptic complex spike bursting enables the induction of LTP by theta frequency synaptic stimulation

Long-term potentiation (LTP), a persistent enhancement of synaptic transmission that may be involved in some forms of learning and memory, is induced at excitatory synapses in the CA1 region of the hippocampus by coincident presynaptic and postsynaptic activity. Although action potentials back-propagating into dendrites of hippocampal pyramidal cells provide sufficient postsynaptic activity to induce LTP under some in vitro conditions, it is not known whether LTP can be induced by patterns of postsynaptic action potential firing that occur in these cells in vivo. Here we report that a characteristic in vivo pattern of action potential generation in CA1 pyramidal cells known as the complex spike burst enables the induction of LTP during theta frequency synaptic stimulation in the CA1 region of hippocampal slices maintained in vitro. Our results suggest that complex spike bursting may have an important role in synaptic processes involved in learning and memory formation, perhaps by producing a highly sensitive postsynaptic state during which even low frequencies of presynaptic activity can induce LTP.

The place of electron spin resonance methods in the detection of oxidative stress in type 2 diabetes with poor glycemic control

OBJECTIVE

Chronic production of reactive oxygen species (ROS) and/or deficiency in the antioxidant defense system are observed in non-insulin-dependent diabetes mellitus (NIDDM) patients. As an adjunct to the usual indirect parameters for evaluating oxidative stress, we assessed the feasibility of oxyradicals detection in venous blood by electron spin resonance spectroscopy (ESR). Detection of the ascorbate pool was also performed using the validated ESR analysis of the ascorbyl free radial (AFR)-dimethyl sulfoxide (DMSO) complex.

METHODS AND RESULTS

Plasma lipoperoxidation was characterized by higher levels of total MDA (1.50 +/- 0.08 nmol/L), lower levels of GSH (0.54 +/- 0.02 mmol/L) and of vitamin A (2.13 +/- 0.52 mumol/L) in the NIDDM group than in the controls (0.75 +/- 0.05 nmol/L, 0.90 +/- 0.05 mmol/L, 3.52 +/- 1.04 mumol/L, respectively). Improvement of the ESR measurement of oxyradical adducts has been previously obtained by addition of a new sensitive nitrone (DEPMPO), which acts as a spin-trap. However, in our experiment the ESR signal-to-noise ratio was too low to detect significative oxyradicals adducts in total venous blood of NIDDM patients having a weak production of ROS. A significant difference (p < 0.002) was observed in DMSO/AFR index between controls (24.00 +/- 4.10 nmol/L) and NIDDM patients (7.28 +/- 2.36 nmol/L) suggesting ascorbate depletion related to the free radical production.

CONCLUSION

The DMSO/AFR index could be an interesting additional marker of oxidative stress during a chronic production of ROS.

5-Hz stimulation of CA3 pyramidal cell axons induces a beta-adrenergic modulated potentiation at synapses on CA1, but not CA3, pyramidal cells

In mouse hippocampal slices, long-term potentiation (LTP) at Schaffer collateral fiber synapses onto CA1 pyramidal cells could be induced by brief trains of 5-Hz synaptic stimulation (30 s) or by longer trains of 5-Hz stimulation (3 min) delivered during beta-adrenergic receptor activation. In contrast, 5-Hz stimulation, either alone or in the presence of the beta-adrenergic receptor agonist isoproterenol, failed to induce LTP at associational-commissural (assoc-com) fiber synapses onto CA3 pyramidal cells. Our results suggest that although CA3 pyramidal cells give rise to both the Schaffer collateral fiber synapses in CA1 and the assoc-com fiber synapses in CA3, the induction of LTP at these synapses may be regulated by different activity- and modulatory neurotransmitter-dependent processes.

Transcriptional fidelity and proofreading by RNA polymerase II

We have addressed whether the intrinsic 3'-->5' nuclease activity of human RNA polymerase II (pol II) can proofread during transcription in vitro. In the presence of SII, a protein that stimulates the nuclease activity, pol II quantitatively removed misincorporated nucleotides from the nascent transcript during rapid chain extension. The basis of discrimination between the correct and incorrect base was the slow addition of the next nucleotide to the mismatched terminus. Incorporation of inosine monophosphate inhibited next nucleotide addition by a similar magnitude as a mismatched base. We used this finding to demonstrate that addition of SII to a transcription reaction dramatically altered the RNA base content, reflecting the stable incorporation of more "correct" (GMP) and fewer "incorrect" (IMP) nucleotides.

The hydrophobic face orientation of apolipoprotein A-I amphipathic helix domain 143-164 regulates lecithin:cholesterol acyltransferase activation

Apolipoprotein A-I (apoA-I) activates the plasma enzyme lecithin:cholesterol acyltransferase (LCAT), catalyzing the rapid conversion of lipoprotein cholesterol to cholesterol ester. Structural mutants of apoA-I have been used to study the details of apoA-I-LCAT-catalyzed cholesterol ester formation. Several studies have shown that the alpha-helical segments corresponding to amino acids 143-164 and 165-186 (repeats 6 and 7) are essential for LCAT activation. In the present studies, we examined how the orientation of the hydrophobic face, independent of an increase in overall hydrophobicity, affects LCAT activation. We designed, expressed, and characterized a mutant, reverse of 6 apoA-I (RO6 apoA-I), in which the primary amino acid sequence of repeat 6 (amino acids 143-164) was reversed from its normal orientation. This mutation rotates the hydrophobic face of repeat 6 approximately 80 degrees. Lipid-free RO6 apoA-I showed a marked stabilization when denatured by guanidine hydrochloride, but showed significant destabilization to guanidine hydrochloride denaturation in the lipid-bound state compared with wild-type apoA-I. Recombinant high density lipoprotein discs (rHDL) formed from RO6 apoA-I, sn-1-palmitoyl-sn-2-oleoyl phosphati-dylcholine, and cholesterol were approximately 12 A smaller than wild-type apoA-I rHDL. The reduced size suggests that one of the repeats did not effectively participate in phospholipid binding and organization. The sn-1-palmitoyl-sn-2-oleoyl phosphatidylcholine RO6 rHDL were a less effective substrate for LCAT. Mapping the entire lipid-free and lipid-bound RO6 apoA-I with a series of monoclonal antibodies revealed that both the lipid-free and lipid-bound RO6 apoA-I displayed altered or absent epitopes in domains within and adjacent to repeat 6. Together, these results suggest that the proper alignment and orientation of the hydrophobic face of repeat 6 is an important determinant for maintaining and stabilizing helix-bilayer and helix-helix interactions.

Corticosteroid metabolism in human granulosa-lutein cells

OBJECTIVE

The aims of this study were to determine the type and level of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) in human granulosa-leutein cells (GLE) shortly before ovulation and to correlate activity with the outcome of treatment in patients undergoing in vitro fertilization and embryo transfer (IVF/ET).

DESIGN

GLC from 32 patients undergoing IVF/ET were tested for type and level of 11 beta HSD activity in relation to treatment outcome.

PATIENTS

Periovulatory follicles were aspirated by ultrasound guided transvaginal puncture following a standard controlled ovarian stimulation protocol, approximately 36 h after administering an ovulation-inducing dose of human chorionic gonadotrophin (HCG). GLC were separated from follicular fluid by density-gradient centrifugation and taken for measurement of 11 beta HSD activity in vitro; oocytes were used for IVF/ET.

MEASUREMENTS

Interconversion of cortisol (F) and cortisone (E), and dexamethasone (D) and 11-dehydrodexamethasone (DHD) was measured in standardized assays comprising incubation of GLC with 3H-labelled substrate, with separation of substrate and product by thin-layer radiochromatography.

RESULTS

Conversion of F to E varied from 10.5 to 30.9% while that of E to F was between 2.4 and 44.6%. In the GLC of 25 patients in whom both activities were measured, dehydrogenase (F to E) activity predominated in 13 and reductase (E to F) in 12. By contrast, D (substrate for 11 beta HSD2 but not 11 beta HSD1) showed less than 1% metabolism in this system while DHD (substrate for 11 beta HSD1 and 11 beta HSD2) was converted significantly (65.6-90.5%) to D in the four patients tested. There was no significant difference in the interconversion of F and E between patients who became pregnant and those who did not.

CONCLUSIONS

The dehydrogenase and oxoreductase reactions catalysed by 11 beta HSD both occur in granulosa-lutein cells at the time of follicular rupture, probably due to 11 beta HSD1. A lack of measurable conversion of dexamethasone to 11-dehydrodexamethasone suggests that dehydrogenation due to 11 beta HSD2 is low or absent. Neither type nor level of 11 beta HSD activity measured under the present assay conditions correlates with IVF outcome.

Insulin sensitivity and cardiovascular risk factors in ovariectomized monkeys with estradiol alone or combined with nomegestrol acetate

We have previously shown that medroxyprogesterone acetate (MPA), either alone or combined with conjugated equine estrogens (CEE), significantly decreased insulin sensitivity (SI), compared with both untreated controls and those treated with CEE alone. The purpose of this study was to determine the effects of estradiol (E2), with and without nomegestrol acetate (NA; a potent progestin that lacks androgenic activity), on SI and arterial antioxidant activity, as determined by F2-isoprostanes. Thirty-six adult female cynomolgus monkeys (Macaca fascicularis) were ovariectomized and fed a moderately atherogenic diet, with one of the following three treatments added to the diet, for 12 weeks: 1) no treatment (control); 2) E2; or 3) continuous combined E2 + NA (E2+NA). SI and glucose effectiveness were assessed by the frequently sampled i.v. glucose tolerance test using a third-phase insulin infusion after 10 weeks of treatment. Cholesterol content and F2-isoprostanes were measured in the thoracic aorta after 12 weeks of treatment. E2 treatment resulted in a significantly greater SI, compared with control or E2+NA-treated monkeys (10.03 +/- 0.91 vs. 6.35 and 6.49 x 10(-4) min(-1) microU(-1) mL; P < 0.05). In contrast to our studies of CEE and MPA, E2+NA treatment, though reducing the SI below that of the E2 group, did not reduce the SI below that of control monkeys. As expected, the short period of treatment resulted in no significant differences in aortic cholesterol content. There was no treatment effect on total F2-isoprostanes (representing F2-isoprostane formation caused primarily by autooxidation), suggesting minimal antioxidant activity. However, there was a treatment difference in the prostaglandin F2alpha (PGF2alpha) isomer (a prostaglandin (PG) isomer formed by both autooxidation of arachidonate and cyclooxygenase activity). PGF2alpha concentrations were 32% lower with E2 treatment, compared with controls, and 36% lower, compared with E2+NA treatment (0.48 +/- 0.08 vs. 0.71 +/- 0.12 and 0.75 +/- 0.06; P < 0.05), suggesting differences in PG synthesis between hormone treatments. In conclusion, NA, a progestin without androgenic activity, may still affect some cardiovascular risk factors differently than estrogen-only therapy. However, it seems to be less detrimental than MPA.

The molecular basis of growth hormone action

Recent studies have begun to elucidate the molecular actions of growth hormone, a major regulator of somatic growth and metabolic functions. The cell surface growth hormone receptor, a member of the cytokine receptor superfamily, binds as a dimer to a single growth hormone molecule. Receptor dimerization precedes signal transduction, which is predominantly mediated by the non-receptor tyrosine kinase, Jak2. Activation of Jak2 leads to mitogenic proliferation, phosphorylation of intracellular proteins, MAP kinase activation, activation of Stats 1, 3, and 5, and induction of target gene expression. Specific cytoplasmic domains of the growth hormone receptor mediate Jak2 activation, metabolic actions of growth hormone, Stat activation, and calcium influx.

Effect of TNF-alpha on SMIT mRNA levels and myo-inositol accumulation in cultured endothelial cells

Previously we have shown that hyperosmolarity increases Na(+)-myo-inositol cotransporter (SMIT) activity and mRNA levels in cultured endothelial cells. Because hyperosmolarity and cytokines, such as tumor necrosis factor-alpha (TNF-alpha), activate similar signal transduction pathways, we examined the effect of TNF-alpha on SMIT mRNA levels and myo-inositol accumulation. In contrast to the effect of hyperosmolarity, TNF-alpha caused a time- and concentration-dependent decrease in SMIT mRNA levels and myo-inositol accumulation. The effect of TNF-alpha on myo-inositol accumulation was found in large-vessel endothelial cells (derived from the aorta and pulmonary artery) and cerebral microvessel endothelial cells. In bovine aorta and bovine pulmonary artery endothelial cells, TNF-alpha activated nuclear factor (NF)-kappa B. TNF-alpha also increased ceramide levels, and C2-ceramide mimicked the effect of TNF-alpha on SMIT mRNA levels and myo-inositol accumulation in bovine aorta endothelial cells. Pyrrolidinedithiocarbamate, genistein, and 7-amino-1-chloro-3-tosylamido-2-hepatanone, compounds that can inhibit NF-kappa B activation, partially prevented the TNF-alpha-induced decrease in myo-inositol accumulation. The effect of TNF-alpha on myo-inositol accumulation was also partially prevented by the protein kinase C inhibitor calphostin C but not by staurosporine. These studies demonstrate that TNF-alpha causes a decrease in SMIT mRNA levels and myo-inositol accumulation in cultured endothelial cells, which may be related to the activation of NF-kappa B.

Effect of porcine somatotropin administration in young pigs during the growth phase from 10 to 25 kilograms

We conducted two experiments to determine the efficacy of exogenous porcine somatotropin (pST) on enhancing performance during an early phase of growth (10 kg initial BW) when pigs are already growing efficiently and have high rates of lean deposition and low rates of lipid deposition. In Exp. 1, performance was measured on 45 barrows that received one of five daily doses (0, 50, 100, 150 and 200 microg/kg BW) of recombinant pST. In Exp. 2, 27 barrows were used in a slaughter-balance study in which two groups received daily either buffer (control) or 120 microg/kg BW of pST and the third group was slaughtered for initial body composition. In both experiments, pigs received daily i.m. injections of their respective dose for 20 d. The diet was fed for ad libitum consumption and calculated to contain 3.5 Mcal DE/kg, 22.3% CP, and 1.5% lysine. Administration of pST failed to alter overall growth rate or efficiency of gain in either experiment. However, in Exp. 2 pigs treated with pST had increased deposition rates of protein and water but reduced lipid deposition rates. Furthermore, pST treatment resulted in characteristic reductions in plasma urea nitrogen and elevations in glucose and NEFA. Plasma concentrations of insulin and IGF-I were also increased, but pST reduced IGF-II and IGF binding protein-2. Overall, the data demonstrated that very young pigs respond to pST with enhanced lean tissue accretion and metabolic changes, but the response is attenuated compared with previous studies in older growing pigs.

Blood transfusion in disasters, war, and emergencies

Historically, the needs of those wounded in war have led to many major advances in blood transfusion. The most important of these is probably the ability to draw blood in one location and transfuse it, at a later time, in a distant location. Another important lesson is the need for meticulous planning. Every hospital and blood center should have a disaster plan consisting of five components. What fluids to use, from where are they to be obtained, to what degree are they to be tested, how will they be transported to the disaster scene, and, once there, how will they be stored. Once drawn up, this plan must be regularly exercised and periodically revised. This will ensure rapid and efficient implementation when an emergency arises. Triage is vital in mass casualty situations, ensuring that scarce resources are used for those with the best chance of recovery. Although patients survive with low hemoglobin levels for considerable periods, speedy treatment of hypovolemia is imperative. When perflourochemicals and hemoglobin solutions are available for general clinical use, they will have a major role to play in disasters. Similarly, a simple method for the cryopreservation of red cells will allow stockpiles to be established. Unfortunately, none of these are presently available, although some are undergoing clinical trials.

Effects of leptin on insulin sensitivity in normal rats

To determine whether leptin has insulin sensitizing effects in normal rodents, we measured plasma glucose and insulin concentrations in male Sprague-Dawley rats treated with leptin or vehicle by continuous s.c. infusion for 48 h. In additional experiments, we examined the acute effect of i.v. leptin upon insulin sensitivity under conditions of clamped glycemia. Subcutaneous leptin was administered at 10.0 and 1.0 microg/h. To avoid confounding effects of differences in food intake, both leptin- and vehicle-treated rats were fasted during the 48-h period of infusion. Infusion of leptin, 10 microg/h, significantly reduced both plasma glucose and insulin. Leptin, 1.0 microg/h, also decreased plasma glucose and insulin, although the effects on insulin did not achieve statistical significance. Leptin at either dose did not alter body weight or epididymal fat mass compared with vehicle treated controls. Leptin, 10 microg/h, decreased circulating insulin-like growth factor-1 levels. No differences in GLUT-4 content in either in brown or epididymal fat were observed as a result of leptin-treatment. Leptin, 10 microg/h, significantly decreased urine osmolality, increased water intake, and reduced renal potassium excretion compared with vehicle-infused rats. In additional rats, we measured the acute effect of i.v. leptin on insulin sensitivity determined as whole body glucose utilization during hyperinsulinemic glucose clamps performed at glucose targets of 60 and 90 mg/100 ml. Glucose utilization was increased by 29% during the last 135 min of glycemia clamped at 60 mg/100 ml (P < 0.05) and by 30% during the last 135 min of glycemia clamped at 90 mg/dl (P < 0.01) in rats infused with leptin compared with vehicle. In summary, leptin increased insulin sensitivity in normal rats both under fasting conditions and in the presence of hyperinsulinemia at clamped glucose. These effects did not appear dependent on altered body weight. Leptin also altered salt and water metabolism under fasting conditions resulting in increased water intake and more dilute urine.

Differential expression of messenger ribonucleic acids encoding 11beta-hydroxysteroid dehydrogenase types 1 and 2 in human granulosa cells

In glucocorticoid target organs 11beta-hydroxysteroid dehydrogenase (11betaHSD) regulates the levels of active glucocorticoids available to glucocorticoid receptors. To date two isoforms of 11betaHSD, NADP-dependent type 1 11betaHSD (11betaHSD1) with predominant reductase activity and NAD-dependent type 2 11betaHSD (11betaHSD2) with dehydrogenase activity have been identified. Human ovarian granulosa cells have been shown to possess both dehydrogenase and reductase 11betaHSD activities and express 11betaHSD1 mRNA. However, whether 11betaHSD2 mRNA is also present or if the expression of either mRNA is developmentally regulated in the human ovary is unknown. We therefore used northern analysis to examine 11betaHSD1 and 11betaHSD2 mRNA levels in non-luteinized and luteinizing granulosa cells, corpora lutea (CL) and ovarian stroma obtained from human ovaries. Here we show that non-luteinized granulosa cells express relatively high levels of 11betaHSD2 mRNA but not 11betaHSD1. Conversely, luteinizing granulosa cells abundantly express 11betaHSD1 mRNA but not 11betaHSD2. CL also expresses 11betaHSD2 to lesser extent. Neither 11betaHSD mRNA is detectable in ovarian stroma. These results indicate that mRNAs encoding both 1lbetaHSD isozymes are present in human granulosa cells and they are developmentally--but differentially--regulated during preovulatory follicular development. The existence of developmentally regulated 11betaHSD in human granulosa cells is important new evidence that glucocorticoids, acting directly on the ovary, serve physiologically significant roles in the regulation of folliculogenesis.

Alteration in apolipoprotein A-I 22-mer repeat order results in a decrease in lecithin:cholesterol acyltransferase reactivity

Apolipoprotein A-I contains eight 22-amino acid and two 11-amino acid tandem repeats that comprise 80% of the mature protein. These repeating units are believed to be the basic motif responsible for lipid binding and lecithin:cholesterol acyltransferase (LCAT) activation. Computer analysis indicates that despite a fairly high degree of compositional similarity among the tandem repeats, significant differences in hydrophobic and amphipathic character exist. Our previous studies demonstrated that deletion of repeat 6 (143-164) or repeat 7 (165-186) resulted in a 98-99% reduction of LCAT activation as compared with wild-type apoA-I. To determine the effects of substituting one of these repeats with a more hydrophobic repeat we constructed a mutant apoA-I protein in which residues 143-164 (repeat 6) were replaced with repeat 10 (residues 220-241). The cloned mutant protein, 10F6 apoA-I, was expressed and purified from an Sf-9 cell baculoviral system and then analyzed using a number of biophysical and biochemical techniques. Recombinant complexes prepared at a 100:5:1 molar ratio of L-alpha-dimyristoylphosphatidylcholine:cholesterol:wild-type or 10F6 apoA-I showed a doublet corresponding to Stokes diameters of 114 and 108 A on nondenaturing 4-30% polyacrylamide gel electrophoresis. L-alpha-Dimyristoylphosphatidylcholine 10F6 apoA-I complexes had a 5-6-fold lower apparent Vmax/apparent Km as compared with wild-type apoA-I containing particles. As expected, monoclonal antibody epitope mapping of the lipid-free and lipid-bound 10F6 apoA-I confirmed that a domain expressed between residues 143 and 165 normally found in wild-type apoA-I was absent. The region between residues 119 and 144 in 10F6 apoA-I showed a marked reduction in monoclonal antibody binding capacity. Therefore, we speculate that the 5-6-fold lower LCAT reactivity in 10F6 compared with wild-type apoA-I recombinant particles results from increased stabilization within the 121-165 amino acid domain due to more stable apoprotein helix phospholipid interactions as well as from conformational alterations among adjacent amphipathic helix repeats.

Short-term insulin therapy and normoglycemia. Effects on erythrocyte lipid peroxidation in NIDDM patients

OBJECTIVE

To evaluate erythrocyte lipid peroxidation (LPO) before and after an adaptive short-term insulin therapy in NIDDM patients who were chronically hyperglycemic.

RESEARCH DESIGN AND METHODS

Twenty-six patients with NIDDM (mean HbA1c, 11.28%) aged 53.04 +/- 2.03 years were submitted for 3 days to constant intravenous glucose and continuous insulin perfusion at an adaptable rate to maintain glycemia within the normal range. An evaluation of LPO at baseline and after euglycemic insulin therapy was determined by erythrocyte free and total malondialdehyde (MDA) levels, polyunsaturated fatty acid (PUFA) percentage, vitamin E and glutathione content, and the following antioxidant enzymatic activity determinations: glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT). Fasting serum glucose, HbA1c, triglycerides, cholesterol, and HDL cholesterol levels were also determined at these time points.

RESULTS

At baseline, erythrocyte free and total MDA were significantly higher in NIDDM patients than in control subjects (11.14 +/- 0.80 vs. 1.74 +/- 0.11 nmol/g Hb [P < 0.0001] for free MDA; 18.04 +/- 1.79 vs. 7.85 +/- 0.55 nmol/g Hb [P < 0.0001] for total MDA). PUFAs, particularly C20:4 and C22:5, were increased (14.69 +/- 0.34 vs. 12.03 +/- 0.31 and 2.31 +/- 0.04 vs. 1.71 +/- 0.03% of total fatty acids, respectively). Vitamin E and glutathione were reduced significantly (6.16 +/- 0.61 vs. 14.84 +/- 0.64 nmol/g Hb and 0.42 +/- 0.04 vs. 0.97 +/- 0.06 mmol/l, respectively). No difference was observed for the enzymatic activities. After euglycemic insulin therapy, triglycerides significantly decreased compared with baseline concentrations (1.55 +/- 0.13 vs. 2.42 +/- 0.22 mmol/l; P < 0.001), whereas other lipidic parameters were unchanged. Free MDA significantly decreased (8.60 +/- 0.76 vs. 11.14 +/- 0.80 nmol/g Hb [P < 0.01]), while vitamin E increased (7.93 +/- 0.73 vs. 6.16 +/- 0.61 nmol/g Hb [P < 0.05]). No difference was observed for PUFAs, glutathione, or total MDA.

CONCLUSIONS

The observed erythrocyte LPO in NIDDM decreased after a short-term adaptive insulin therapy. This decrease could be principally attributed to the normalized glycemia that reduces reactive oxygen species (ROS) production, which in turn may explain the increase in erythrocyte membrane vitamin E and the decrease in MDA. This study shows the value of a euglycemic environment in NIDDM to reduce LPO and, at long range, to minimize clinical diabetes complications.

Antioxidant effects of a supplemented very low protein diet in chronic renal failure

Increased peroxidation of lipids in red blood cells (RBC) in patients with advanced chronic renal failure (CRF) reflects increased generation of reactive oxygen species (ROS), which may contribute to the metabolic damage induced by CRF and to its progression. We have evaluated parameters indicative of lipoperoxidation (LPO) of RBC at baseline in patients with CRF compared to controls, and the effects of a very low protein diet supplemented with amino and keto acids and vitamins A, C, E (VLPD) over a 6-month period. The presence of peroxidation damage in CRF patients before the administration VLPD was demonstrated by elevated levels of free malondialdehyde (MDA) (p < .0003) and decreased levels of polyunsaturated fatty acids (PUFA), particularly C20:4 (p < .001), C22:4 (p < .0001) and C22:5 (p < .0001) when compared to controls. Similarly, RBC vitamin E content was significantly decreased (p < .0001) while enzymatic activities were unalterated. VLPD reduced erythrocyte LPO as suggested by (a) decreased levels of free and total RBC MDA (p < .003 and p < .03, respectively), (b) increased levels of PUFA, particularly C22:4 and C22:5 (p < .003 and p < .03, respectively), and (c) increased levels of vitamins A and E (p < .001 and p < .04, respectively) as compared to prediet results. Antioxidant enzyme activities were not modified. These results suggest that VLPD has a protective role against LPO of erythrocytes in patients with CRF.

A comparison of the kinetics of low-density lipoprotein oxidation initiated by copper or by azobis (2-amidinopropane)

This article describes the kinetics of low density lipoprotein (LDL) oxidation catalyzed by azobis (2-amidinopropane) dihydrochloride, ABAP, or by copper. The LDLs were isolated from nonhuman primates fed diets enriched in one of three types of fatty acids: saturated fatty acids, monounsaturated fatty acids, predominantly, oleic acid, or polyunsaturated fatty acids, predominantly linoleic acid. Oxidation was followed by monitoring the formation of conjugated diene hydroperoxides from polyunsaturated fatty acids (PUFA). For both copper and ABAP-initiated oxidation, the rate of LDL oxidation depended on the concentrations of initiator, PUFA, and LDL. Except for the dependence on PUFA concentration the rate of LDL oxidation was not directly influenced by the fatty acid composition of the LDL particle. The two initiators had very different dependence on initiator concentration. Because LDL particles are essentially small, lipid-rich droplets, the kinetic descriptions of LDL oxidation assumed: (1), that there was only one chain per particle, and (2) that the radical chain was terminated when a second radical either entered or was formed in the particle. When two LDL samples having very different lag times were mixed, the oxidation profile was bimodal. This finding demonstrated that the oxidation of native LDL particles was independent of the oxidation state of the other native LDL particles in solution, i.e., LDL particles do not rapidly exchange radicals, for example, hydroperoxyl radicals. Oxidation initiated by ABAP was proportional to [ABAP]0.5, suggesting that hydroperoxyl radical recombination between the lipid hydroperoxyl radical and the ABAP-hydroperoxyl radical was the chain-terminating step. The reciprocal of the rate of copper oxidation was linearly related to the reciprocal copper concentration, demonstrating that the binding of copper to LDL was necessary to initiate oxidation. This binding constant showed considerable variability among LDL samples. The kinetic descriptions of LDL oxidation reflect the differences in the mechanisms of initiation and termination.

Identification of the cAMP response element that controls transcriptional activation of the insulin-like growth factor-I gene by prostaglandin E2 in osteoblasts

Insulin-like growth factor-I (IGF-I), a multifunctional growth factor, plays a key role in skeletal growth and can enhance bone cell replication and differentiation. We previously showed that prostaglandin E2 (PGE2) and other agents that increase cAMP activated IGF-I gene transcription in primary rat osteoblast cultures through promoter 1 (P1), the major IGF-I promoter, and found that transcriptional induction was mediated by protein kinase A. We now have identified a short segment of P1 that is essential for full hormonal regulation and have characterized inducible DNA-protein interactions involving this site. Transient transfections of IGF-I P1 reporter genes into primary rat osteoblasts showed that the 328-base pair untranslated region of exon 1 was required for a full 5.3-fold response to PGE2; mutation in a previously footprinted site, HS3D (base pairs +193 to +215), reduced induction by 65%. PGE2 stimulated nuclear protein binding to HS3D. Binding, as determined by gel mobility shift assay, was not seen in nuclear extracts from untreated osteoblast cultures, was detected within 2 h of PGE2 treatment, and was maximal by 4 h. This DNA-protein interaction was not observed in cytoplasmic extracts from PGE2-treated cultures, indicating nuclear localization of the protein kinase A-activated factor(s). Activation of this factor was not blocked by cycloheximide (Chx), and Chx did not impair stimulation of IGF-I gene expression by PGE2. In contrast, binding to a consensus cAMP response element (CRE; 5'-TGACGTCA-3') from the rat somatostatin gene was not modulated by PGE2 or Chx. Competition gel mobility shift analysis using mutated DNA probes identified 5'-CGCAATCG-3' as the minimal sequence needed for inducible binding. All modified IGF-I P1 promoterreporter genes with mutations within this CRE sequence also showed a diminished functional response to PGE2. These results identify the CRE within the 5'-untranslated region of IGF-I exon 1 that is required for hormonal activation of IGF-I gene transcription by cAMP in osteoblasts.