11beta-Hydroxysteroid Dehydrogenase Type 1 Regulation by Intracellular Glucose 6-Phosphate Provides Evidence for a Novel Link between Glucose Metabolism and Hypothalamo-Pituitary-Adrenal Axis Function

Microsomal glucose-6-phosphatase-alpha (G6Pase-alpha) and glucose 6-phosphate transporter (G6PT) work together to increase blood glucose concentrations by performing the terminal step in both glycogenolysis and gluconeogenesis. Deficiency of the G6PT in liver gives rise to glycogen storage disease type 1b (GSD1b), whereas deficiency of G6Pase-alpha leads to GSD1a. G6Pase-alpha shares its substrate (glucose 6-phosphate; G6P) with hexose-6-phosphate-dehydrogenase (H6PDH), a microsomal enzyme that regenerates NADPH within the endoplasmic reticulum lumen, thereby conferring reductase activity upon 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). 11beta-HSD1 interconverts hormonally active C11beta-hydroxy steroids (cortisol in humans and corticosterone in rodents) to inactive C11-oxo steroids (cortisone and 11-dehydrocorticosterone, respectively). In vivo reductase activity predominates, generating active glucocorticoid. We hypothesized that substrate (G6P) availability to H6PDH in patients with GSD1b and GSD1a will decrease or increase 11beta-HSD1 reductase activity, respectively. We investigated 11beta-HSD1 activity in GSD1b and GSD1a mice and in two patients with GSD1b and five patients diagnosed with GSD1a. We confirmed our hypothesis by assessing 11beta-HSD1 in vivo and in vitro, revealing a significant decrease in reductase activity in GSD1b animals and patients, whereas GSD1a patients showed a marked increase in activity. The cellular trafficking of G6P therefore directly regulates 11beta-HSD1 reductase activity and provides a novel link between glucose metabolism and function of the hypothalamo-pituitary-adrenal axis.     

Renal responses to the kappa-opioid-receptor agonist U-50488H in conscious lambs

In adult animals and humans, activation of kappa-opioid receptors results in a diuresis. The aim of the present study was to investigate whether kappa-opioids are also diuretic early in life and whether this is altered during postnatal maturation. Therefore, the renal effects of the kappa-opioid-receptor agonist U-50488H were measured in two separate age groups of conscious lambs at two stages of postnatal maturation (approximately 1 wk and approximately 6 wk) under physiological conditions. To evaluate whether the renal responses to U-50488H resulted from receptor-dependent effects, responses to U-50488H were also tested in the presence of the specific kappa-opioid-receptor antagonist 5'-guanidinonaltrindole (GNTI). Urinary flow rate, free water clearance, and electrolyte excretions and clearances were measured for 30 min before and for 90 min after intravenous injection of U-50488H or vehicle. An increase in urinary flow rate accompanied by an increase in free water clearance occurred in response to administration of U-50488H but not vehicle. There were no effects of U-50488H on electrolyte excretions or clearances at either 1 or 6 wk of postnatal life. Although there were no effects of GNTI on any of the measured or calculated variables, the aforementioned diuretic response to U-50488H was abolished by pretreatment with GNTI in both age groups. We conclude that kappa-opioid receptors are diuretic early in life and that this response does not appear to be altered as postnatal maturation proceeds. Therefore, these data provide evidence that activation of kappa-opioid receptors early in life may lead to alterations in fluid balance.     

Integrin-mediated mechanotransduction in renal vascular smooth muscle cells: activation of calcium sparks

Integrins are transmembrane heterodimeric proteins that link extracellular matrix (ECM) to cytoskeleton and have been shown to function as mechanotransducers in nonmuscle cells. Synthetic integrin-binding peptide triggers Ca(2+) mobilization and contraction in vascular smooth muscle cells (VSMCs) of rat afferent arteriole, indicating that interactions between the ECM and integrins modulate vascular tone. To examine whether integrins transduce extracellular mechanical stress into intracellular Ca(2+) signaling events in VSMCs, unidirectional mechanical force was applied to freshly isolated renal VSMCs through paramagnetic beads coated with fibronectin (natural ligand of alpha(5)beta(1)-integrin in VSMCs). Pulling of fibronectin-coated beads with an electromagnet triggered Ca(2+) sparks, followed by global Ca(2+) mobilization. Paramagnetic beads coated with low-density lipoprotein, whose receptors are not linked to cytoskeleton, were minimally effective in triggering Ca(2+) sparks and global Ca(2+) mobilization. Preincubation with ryanodine, cytochalasin-D, or colchicine substantially reduced the occurrence of Ca(2+) sparks triggered by fibronectin-coated beads. Binding of VSMCs with antibodies specific to the extracellular domains of alpha(5-) and beta(1)-integrins triggered Ca(2+) sparks simulating the effects of fibronectin-coated beads. Preincubation of microperfused afferent arterioles with ryanodine or integrin-specific binding peptide inhibited pressure-induced myogenic constriction. In conclusion, integrins transduce mechanical force into intracellular Ca(2+) signaling events in renal VSMCs. Integrin-mediated mechanotransduction is probably involved in myogenic response of afferent arterioles.     

Caveolin-1 abolishment attenuates the myogenic response in murine cerebral arteries

Intravascular pressure-induced vasoconstriction (the "myogenic response") is intrinsic to smooth muscle cells, but mechanisms that underlie this response are unresolved. Here we investigated the physiological function of arterial smooth muscle cell caveolae in mediating the myogenic response. Since caveolin-1 (cav-1) ablation abolishes caveolae formation in arterial smooth muscle cells, myogenic mechanisms were compared in cerebral arteries from control (cav-1(+/+)) and cav-1-deficient (cav-1(-/-)) mice. At low intravascular pressure (10 mmHg), wall membrane potential, intracellular calcium concentration ([Ca(2+)](i)), and myogenic tone were similar in cav-1(+/+) and cav-1(-/-) arteries. In contrast, pressure elevations to between 30 and 70 mmHg induced a smaller depolarization, [Ca(2+)](i) elevation, and myogenic response in cav-1(-/-) arteries. Depolarization induced by 60 mM K(+) also produced an attenuated [Ca(2+)](i) elevation and constriction in cav-1(-/-) arteries, whereas extracellular Ca(2+) removal and diltiazem, an L-type Ca(2+) channel blocker, similarly dilated cav-1(+/+) and cav-1(-/-) arteries. N(omega)-nitro-l-arginine, an nitric oxide synthase inhibitor, did not restore myogenic tone in cav-1(-/-) arteries. Iberiotoxin, a selective Ca(2+)-activated K(+) (K(Ca)) channel blocker, induced a similar depolarization and constriction in pressurized cav-1(+/+) and cav-1(-/-) arteries. Since pressurized cav-1(-/-) arteries are more hyperpolarized and this effect would reduce K(Ca) current, these data suggest that cav-1 ablation leads to functional K(Ca) channel activation, an effect that should contribute to the attenuated myogenic constriction. In summary, data indicate that cav-1 ablation reduces pressure-induced depolarization and depolarization-induced Ca(2+) influx, and these effects combine to produce a diminished arterial wall [Ca(2+)](i) elevation and constriction.     

The inhibition of endocytosis affects HDL-lipid uptake mediated by the human scavenger receptor class B type I

The scavenger receptor SR-BI plays an important role in the hepatic clearance of HDL cholesterol and other lipids, driving reverse cholesterol transport and contributing to protection against atherosclerosis in mouse models. We characterized the role of endocytosis in lipid uptake from HDL, mediated by the human SR-BI, using a variety of approaches to inhibit endocytosis, including hypertonic shock, potassium or energy depletion and disassembly of the actin cytoskeleton. Our studies revealed that unlike mouse SR-BI, human SR-BI-mediated HDL-lipid uptake was reduced by inhibition of endocytosis. This was not dependent on the cytoplasmic C-terminus of SR-BI. Monitoring the uptake of both the protein and lipid components of HDL revealed that although overall lipid uptake was decreased, the degree of selective lipid uptake was increased. These data suggest that that endocytosis is a dynamic regulator of SR-BI's selective lipid uptake activity.     

Impact of hemodialysis on P-wave amplitude, duration, and dispersion

Atrial fibrillation (AF) is a frequent arrhythmia in patients undergoing hemodialysis (HD). P wave duration (PWdu) and P wave dispersion (PWdi) have been shown to be predictors of emerging AF in different clinical conditions. We sought to study the impact of HD on PWdu, PWdi, and P wave amplitude in a cohort of patients undergoing HD. Seventeen patients (8 men, 31+/-10 years) were studied. Echocardiography parameters, the sum of the amplitude of P waves in all 12 ECG leads (SP), mean PWdu, and PWdi, along with a host of other parameters (body weight, heart rate, electrolytes and hemoglobin/hematochrit) were measured 1/2h, before and after, HD. SP increased (11.8+/-3.9 vs 15.3+/-4.0 mm, p = 0.004), mean PWdu remained stable (82.7+/-11.1 vs 81.6+/-10.5 ms, p = 0.606), PWdi decreased (51.7+/-19.1 vs 41.7+/-19.1 ms, p = 0.03), and left atrial dimension decreased (37.96+/-3.90 vs 30.62+/-3.38 mm, p = 0.0001), after HD. The change in PWdi correlated with fluid removed by HD (r = -0.55, p = 0.022). Re-measurements of P-wave parameters in a random group of 11 of the 17 patients revealed augmented SP (p = 0.01), and stable mean PWdu (p = 0.36), and PWdi (p = 0.31), after HD. Fluid removed by HD leads to an increase in SP, a stable mean PWdu, and decrease (or stability on re-measurement in a subgroup of patients) in PWdi. Stability of PWdu may be due to the effects of augmentation of the P-wave amplitude and the reduction of the left atrial volume, cancelling each other. Variability of PWdi may stem from the occasional impossibility to measure PWdu (or measure it correctly) in minute P-waves in certain ECG leads, which in turn profoundly affects the PWdi.     

Synthesis, structure analysis, and antibacterial activity of some novel 10-substituted 2-(4-piperidyl/phenyl)-5,5-dioxo[1,2,4]triazolo[1,5-b][1,2,4]benzothiadiazine derivatives

A new series of 10-substituted 5,5-dioxo-5,10-dihydro[1,2,4]triazolo[1,5-b]-[1,2,4]benzothiadiazine arylsulfonamide derivatives (10a-j and 13a-f) was synthesized. The structures of these compounds were confirmed on the basis of spectral data, elemental analysis, X-ray analysis, and quantum chemical calculations. These compounds were evaluated for their efficacy as antibacterial agents against various Gram-positive and Gram-negative strains of bacteria. Amongst these compounds 10f and 10i were the most active compounds against Escherichia coli and 13e against E. coli as well as Bacillus subtilis. Moreover, other compounds also showed potent inhibitory activity in comparison to the standard drugs.     

Sulfatide mediates attachment of Pseudomonas aeruginosa to human pharyngeal epithelial cells

Pseudomonas aeruginosa infections are particularly common in people with cystic fibrosis and despite regular treatment with antibiotics, lung damage due to chronic infection with P. aeruginosa remains the major cause of death in those patients. In order to initiate an infection, P. aeruginosa needs contact with the respiratory epithelial surface and by means of its adhesins i.e., fimbria, hemagglutinins,etc., it recognizes and adheres to the corresponding epithelial receptors. We treated P. aeruginosa strains isolated from sputum of cystic fibrosis patients with several glycolipids such as sulfatide, sulfated ganglioside mixture (GM1a, GD1b, GT1b), asialo-GM1 and galactocerebrosides to determine their effect on attachment with pharyngeal epithelial cells. Sulfated ganglioside mixture and sulfatide inhibited the attachment of P. aeruginosa significantly, whereas asialo-GM1, Gal-Cer and sodium sulfite had no effect on attachment inhibition. This finding suggests that sulfated glycoconjugates found in the extracellular matrix, in mucus and on the surface of epithelial cells of human trachea and lung mediates attachment of P. aeruginosa.     

Incidences de la restriction calorique et du Nickel sur l’aromatase testiculaire du rat

This study was designed to determine whether intermittent fasting induces malnutrition that, according to many authors, accentuates the cytotoxic effects of environmental pollutants, or caloric restriction that reduces these effects. Ninety six male Wistar rats (180g) were divided into two groups: one group was fed daily (N) and the other group was fed every second day (J) for one month. At the end of one month, each group was then divided into two subgroups, one subgroup received an injection of 0.9% NaCI (groups NO and JO), the other subgroup received an injection of 4 mg/kg NiCI^b2 (groups NNi and JNi). Intermittent fasting was continued in parallel to treatment for 1, 3, 5 and 10 days. Under these experimental conditions, nickel increased testicular aromatase activity and altered total RNA, while no alteration of these biomarkers was observed with intermittent fasting. The combination of these two factors, nickel and intermittent fasting, did not amplify these effects. In contrast, protection of RNA by intermittent fasting was observed, especially overexpression of aromatase mRNA.     

Association analysis of interleukin gene polymorphisms in autoimmune thyroid diseases in the Tunisian population

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and autoimmune hypothyroidism (AH), are inherited as complex traits. Among the genes contributing to AITDs susceptibility are genes of the IL-1 family. IL-1 regulates T and B lymphocyte maturation, including the induction of several cytokines and cytokine receptors. Therefore, disturbances of this balance may not only play a role in inflammation but also in the pathogenesis of autoimmunity. In order to investigate genetic association of IL-1 gene polymorphisms with AITDs, we performed both a familial study in a large Tunisian pedigree with high prevalence of AITDs (64 patients and 176 controls), and a case-control study (131 GD unrelated patients and 225 healthy controls). PCR and PCR-RFLP methods were used to analyse respectively a VNTR in the IL-1RN gene and three SNPs in both IL-1B genes (-511 C/T and +3954 C/T) and IL-1A (-889 C/T). The family-based association study showed an association of the IL-1B+3954 C/T polymorphism (p=0.02) and two haplotypes IL-1RN*3/C/T/T and IL-1RN*1/C/T/T (p=0.009 and p=0.047 respectively) with AITDs. The case-control study is the first study revealing a significant association of the IL-1A-889 C/T polymorphism (chi2=10.23; p=0.0014) with susceptibility to GD. Our data suggest that the IL-1 gene cluster may harbour susceptibility genes for AITDs and GD pathogenesis in the Tunisian population.