Ten-Year Experience with Sevelamer and Calcium Salts as Phosphate Binders

Most patients with chronic kidney disease experience abnormalities in serum calcium, phosphorus, parathyroid hormone, and vitamin D metabolism. These can lead to vascular calcification (VC), which has been associated with increased risk for cardiovascular disease and mortality. Although hyperphosphatemia is believed to be a risk factor for mortality and VC, no randomized trial was ever designed to demonstrate that lowering phosphate reduces mortality. Nonetheless, binders have been used extensively, and the preponderance of evidence shows that sevelamer slows the development of VC whereas calcium salts do not. Four studies have demonstrated a slower progression of VC with sevelamer than with calcium-containing binders, although a fifth study showed nonsuperiority. Conversely, the results on mortality with sevelamer have been variable, and data on calcium-based binders are nonexistent. Improved survival with sevelamer was demonstrated in a small randomized clinical trial, whereas a larger randomized trial failed to show a benefit. In addition, preclinical models of renal failure and preliminary clinical data on hemodialysis patients suggest a potential benefit for bone with sevelamer. Meanwhile, several randomized and observational studies suggested no improvement in bone density and fracture rate, and a few noted an increase in total and cardiovascular mortality in the general population given calcium supplements. Although additional studies are needed, there are at least indications that sevelamer may improve vascular and bone health and, perhaps, mortality in hemodialysis patients, whereas data on calcium-based binders are lacking. Clin J Am Soc Nephrol 5: S31-S40, 2010. doi: 10.2215/CJN.05880809

Vitamin D Receptor and Calcium-Sensing Receptor Gene Polymorphisms in Hypercalciuric Stone-Forming Patients

Background/Aim: Some studies have identified an association of kidney stone formation with vitamin D receptor (VDR) or calcium-sensing receptor (CaSR) polymorphisms. We aimed to evaluate the association between these polymorphisms with urinary calcium excretion (uCa) in calcium-stone-forming patients. Methods: VDR polymorphism, detected by BsmI digestion, and 3 CaSR polymorphisms (G/T at codon 986, G/A at codon 990 and C/G at codon 1011), detected by direct sequencing, were evaluated in 100 hypercalciuric (HCa) and 101 normocalciuric (NCa) calcium-stone-forming patients. Results: The total allelic frequency of VDR polymorphism was: 16% BB, 49% Bb and 35% bb. The prevalence of bb genotype was significantly higher in the HCa when compared to the NCa group (43 vs. 27%). With respect to CaSR polymorphisms, 986S, 990G and 1011E variant alleles were detected, respectively, in 5, 4 and 3% of the whole sample and 5 CaSR haplotypes were identified: 94% ARQ (wildtype), 3% SRQ, 1.5% AGQ, 1.0% ARE and 0.5% AGE. No statistical differences have been observed between NCa and HCa with respect to these CaSR haplotypes. Conclusions: The present study suggested that bb homozygous for VDR polymorphism was overrepresented in hypercalciuric stone formers. Urinary calcium excretion was not associated with CaSR polymorphism in the present sample. Copyright (C) 2009 S. Karger AG, Basel

Study of the discovery potential of light custodians in a clean decay channel at the LHC

Models of warped extra dimensions with custodial symmetry usually predict the existence of a light Kaluza-Klein fermion arising as a partner of the right-handed top quark, sometimes called light custodians which we will denote (b) over tilde (R). The production of these particles at the LHC can give rise to multi-W events which could be observed in same-sign dilepton channels, but its mass reconstruction is challenging. In this paper we study the possibility of finding a signal for the pair production of this new particle at the LHC focusing on a rarer, but cleaner decay mode of a light custodian into a Z boson and a b-quark. In this mode it would be possible to reconstruct the light custodian mass. In addition to the dominant standard model QCD production processes, we include the contribution of a Kaluza-Klein gluon first mode. We find that (b) over tilde (R) stands out from the background as a peak in the bZ invariant mass. However, when taking into account only the electronic and muonic decay modes of the Z boson and b-tagging efficiencies, the LHC will have access only to the very light range of masses, m((b) over tilde) = O(500) GeV.

Angiotensin II Binding to Angiotensin I-Converting Enzyme Triggers Calcium Signaling

Angiotensin (Ang) I-converting enzyme (ACE) is involved in the control of blood pressure by catalyzing the conversion of Ang I into the vasoconstrictor Ang II and degrading the vasodilator peptide bradykinin. Human ACE also functions as a signal transduction molecule, and the binding of ACE substrates or its inhibitors initiates a series of events. In this study, we examined whether Ang II could bind to ACE generating calcium signaling. Chinese hamster ovary cells transfected with an ACE expression vector reveal that Ang II is able to bind with high affinity to ACE in the absence of the Ang II type 1 and type 2 receptors and to activate intracellular signaling pathways, such as inositol 1,4,5-trisphosphate and calcium. These effects could be blocked by the ACE inhibitor, lisinopril. Calcium mobilization was specific for Ang II, because other ACE substrates or products, namely Ang 1-7, bradykinin, bradykinin 1-5, and N-acetyl-seryl-aspartyl-lysyl-proline, did not trigger this signaling pathway. Moreover, in Tm5, a mouse melanoma cell line endogenously expressing ACE but not Ang II type 1 or type 2 receptors, Ang II increased intracellular calcium and reactive oxygen species. In conclusion, we describe for the first time that Ang II can interact with ACE and evoke calcium and other signaling molecules in cells expressing only ACE. These findings uncover a new mechanism of Ang II action and have implications for the understanding of the renin-Ang system. (Hypertension. 2011;57:965-972.) . Online Data Supplement

Sildenafil inhibits duodenal contractility via activation of the NO-K+ channel pathway

Phosphodiesterase type-5 (PDE5) specifically cleaves cyclic guanosine monophosphate (cGMP), a key intracellular secondary messenger. The PDE5 inhibitor sildenafil is a well-known vasodilator that also has gastrointestinal myorelaxant properties. In the present study, we further investigated sildenafil-induced myorelaxation in rat isolated duodenum, assessing its interaction with nitric oxide (NO) synthase and K+ channel opening. The spontaneous contractions of duodenal strips were reversibly inhibited by sildenafil (0.1-300 mu M) in a concentration-dependent manner [mean (95% confidence interval); EC50 = 6.8 (2.7-17.3) mu M]. The sildenafil-induced myorelaxation was significantly decreased by the NO synthase inhibitor N-nitro-L-arginine methyl ester [increasing the EC50 value to 41.9 (26.1-67.3) mu M]. Sodium nitroprusside or forskolin pretreatments enhanced the sildenafil-induced myorelaxation. In isolated strips pretreated with BaCl2 (0.2 mM), 4-aminopyridine (4-AP, 3 mM), or glybenclamide (1 mu M), the sildenafil-induced EC50 value was significantly increased to 32.8 (19.1-56.4), 27.1 (15.2-48.3) and 20.1 (16.4-24.7) mu M, respectively. Minoxidil (50 mu M) or diazoxide (100 mu M) also significantly attenuated the sildenafil-induced potency. In conclusion, the NO synthase/cyclic nucleotide pathway activation is involved in sildenafil-induced inhibition of spontaneous duodenal contractions. Its pharmacological action seems to be influenced by K+ channel opening, especially the voltage-sensitive ones, being inhibited by 4-AP and K-ATP channels, sensitive to glybenclamide.

The peripheral pro-nociceptive state induced by repetitive inflammatory stimuli involves continuous activation of protein kinase A and protein kinase C epsilon and its Na(v)1.8 sodium channel functional regulation in the primary sensory neuron

In the present study, the participation of the Na(v)1.8 sodium channel was investigated in the development of the peripheral pro-nociceptive state induced by daily intraplantar injections of PGE(2) in rats and its regulation in vivo by protein kinase A (PKA) and protein kinase C epsilon (PKC epsilon) as well. In the prostaglandin E(2) (PGE(2))-induced persistent hypernociception, the Na(v)1.8 mRNA in the dorsal root ganglia (DRG) was up-regulated. The local treatment with dipyrone abolished this persistent hypernociception but did not alter the Na(v)1.8 mRNA level in the DRG. Daily intrathecal administrations of antisense Na(v)1.8 decreased the Na(v)1.8 mRNA in the DRG and reduced ongoing persistent hypernociception. once the persistent hypernociception had been abolished by dipyrone, but not by Na(v)1.8 antisense treatment, a small dose of PGE(2) restored the hypernociceptive plateau. These data show that, after a period of recurring inflammatory stimuli, an intense and prolonged nociceptive response is elicited by a minimum inflammatory stimulus and that this pro-nociceptive state depends on Na(v)1.8 mRNA up-regulation in the DRG. in addition, during the persistent hypernociceptive state, the PKA and PKC epsilon expression and activity in the DRG are up-regulated and the administration of the PKA and PKC epsilon inhibitors reduce the hypernociception as well as the Na(v)1.8 mRNA level. In the present study, we demonstrated that the functional regulation of the Na(v)1.8 mRNA by PKA and PKC epsilon in the primary sensory neuron is important for the development of the peripheral pro-nociceptive state induced by repetitive inflammatory stimuli and for the maintenance of the behavioral persistent hypernociception. (C) 2008 Elsevier Inc. All rights reserved.

Hydrogen Sulfide Improves Neutrophil Migration and Survival in Sepsis via K(ATP)(+) Channel Activation

Rationale Recovering the neutrophil migration to the infectious focus improves survival in severe sepsis. Recently, we demonstrated that the cystathionine gamma-lyase (CSE)/hydrogen sulfide (H(2)S) pathway increased neutrophil recruitment to inflammatory focus during sterile inflammation. Objectives: To evaluate if H(2)S administration increases neutrophil migration to infectious focus and survival of mice. Methods. Sepsis was induced by cecal ligation and puncture (CLP) Measurements and Main Results. The pretreatments of mice with H2S donors (NaHS or Lawesson`s reagent) improved leukocyte rolling/adhesion in the mesenteric microcirculation as well as neutrophil migration. Consequently, bacteremia levels were reduced, hypotension and lung lesions were prevented, and the survival rate increased from approximately 13% to approximately 80% Even when treatment was delayed (6 h after CLP), a highly significant reduction in mortality compared with untreated mice was observed Moreover, H(2)S pretreatment prevented the down-regulation of CXCR2 and L-selectin and the up-regulation of CD11b and G protein-coupled receptor kinase 2 in neutrophils during sepsis. H(2)S also prevented the reduction of intercellular adhesion molecule-1 expression in the endothelium of the mesenteric microcirculation in severe sepsis Confirming the critical role of H(2)S on sepsis outcome, pretreatment with dl-propargylglycine (a CSE inhibitor) inhibited neutrophil migration to the infectious focus, enhanced lung lesions, and induced high mortality in mice subjected to nonsevere sepsis (from 0 to similar to 80%). The beneficial effects of H(2)S were blocked by glibenclamide (a ATP-dependent K(+) channel blocker). Conclusions: These results showed that H(2)S restores neutrophil migration to the infectious focus and improves survival outcome in severe sepsis by an ATP-dependent K(+) channel-dependent mechanism.

STIM and Orai proteins: players in sexual differences in hypertension-associated vascular dysfunction?

Sex-associated differences in hypertension have been observed repeatedly in epidemiological studies; however, the mechanisms conferring vascular protection to females are not totally elucidated. Sex-related differences in intracellular Ca(2+) handling or, more specifically, in mechanisms that regulate Ca(2+) entry into vascular smooth muscle cells have been identified as players in sex-related differences in hypertension-associated vascular dysfunction. Recently, new signalling components that regulate Ca(2+) influx, in conditions of intracellular store depletion, were identified: STIM1 (stromal interaction molecule 1), which works as an intracellular Ca(2+) sensor; and Orai1, which is a component of the CRAC (Ca(2+) release-activated Ca(2+)) channels. Together, these proteins reconstitute store-operated Ca(2+) channel function. Disturbances in STIM1/Orai1 signalling have been implicated in pathophysiological conditions, including hypertension. In the present article, we analyse evidence for sex-related differences in Ca(2+) handling and propose a new hypothesis where sex-related differences in STIM/Orai signalling may contribute to hypertension-associated vascular differences between male and female subjects.

Luteinizing hormone (LH) acts through PKA and PKC to modulate T-type calcium currents and intracellular calcium transients in mice Leydig cells

LH increases the intracellular Ca(2+) concentration ([Ca(2+)](i)) in mice Leydig cells, in a process triggered by calcium influx through T-type Ca(2+) channels. Here we show that LH modulates both T-type Ca(2+) currents and [Ca(2+)]; transients through the effects of PKA and PKC. LH increases the peak calcium current (at -20 mV) by 40%. A similar effect is seen with PMA. The effect of LH is completely blocked by the PKA inhibitors H89 and a synthetic inhibitory peptide (IP-20), but only partially by chelerythrine (PKC inhibitor). LH and the blockers induced only minor changes in the voltage dependence of activation, inactivation or deactivation of the currents. Staurosporine (blocker of PKA and PKC) impaired the [Ca(2+)](i) changes induced by LH. A similar effect was seen with H89. Although PMA slowly increased the [Ca(2+)](i) the subsequent addition of LH still triggered the typical transients in [Ca(2+)](i). Chelerythrine also does not avoid the Ca(2+) transients, showing that blockage of PKC is not sufficient to inhibit the LH induced [Ca(2+)](i) rise. In summary, these two kinases are not only directly involved in promoting testosterone synthesis but also act on the overall calcium dynamics in Leydig cells, mostly through the activation of PKA by LH. (c) 2011 Elsevier Ltd. All rights reserved.

Volume-activated chloride channels in mice Leydig cells

Production and secretion of testosterone in Leydig cells are mainly controlled by the luteinizing hormone (LH). Biochemical evidences suggest that the activity of Cl(-) ions can modulate the steroidogenic process, but the specific ion channels involved are not known. Here, we extend the characterization of Cl(-) channels in mice Leydig cells (50-60 days old) by describing volume- activated Cl(-) currents (I(Cl,swell)). The amplitude of I(Cl,swell) is dependent on the osmotic gradient across the cell membrane, with an apparent EC(50) of similar to 75 mOsm. These currents display the typical biophysical signature of volume- activated anion channels (VRAC): dependence on intracellular ATP, outward rectification, inactivation at positive potentials, and selectivity sequence (I(-)>Cl(-)>F(-)). Staurosporine (200 nM) did not block the activation of I(Cl), swell. The block induced by 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB; 128 mu M), SITS (200 mu M), ATP (500 mu M), pyridoxalphosphate-6- azophenyl-2`,4`-disulfonate (PPADS; 100 mu M), and Suramin (10 mu M) were described by the permeant blocker model with apparent dissociation constant at 0 mV K(d)(0) and fractional distance of the binding site (delta) of 334 mu M and 47%, 880 mu M and 35%, 2,100 mu M and 49%, 188 mu M and 27%, and 66.5 mu M and 49%, respectively. These numbers were derived from the peak value of the currents. We conclude that ICl, swell in Leydig cells are activated independently of purinergic stimulation, that Suramin and PPADS block these currents by a direct interaction with VRAC and that ATP is able to permeate this channel.

Insights on calcium-independent phospholipid membrane damage by Lys49-PLA(2) using tryptophan scanning mutagenesis of bothropstoxin-I from Bothrops jararacussu

Bothropstoxin-I (BthTx-I) is a homodimerie Lys49-PLA(2) from the venom of the snake Bothrops jararacussu, which lacks hydrolytic activity against phospholipid substrates, yet permeabilizes membranes by a Ca2+- independent mechanism. The interaction of the BthTx-I with model membranes has been studied by intrinsic tryptophan fluorescence emission (ITFE) spectroscopy. Nine separate mutants have been created each with a unique tryptophan residue located at a different position in the interfacial recognition site (IRS) of the protein. The rapid and efficient Ca2+-independent membrane damage against unilamellar liposomes composed of DPPC/DMPA in a 9:1 molar ratio was unaffected by these substitutions. Binding studies revealed low protein affinity for these liposomes and no changes were observed in the ITFE properties. In contrast, the binding of all mutants to DPPC/DMPA liposomes in a 1:1 molar ratio was stronger, and was correlated with altered ITFE properties. The blue-shifted emission spectra and increased emission intensity of mutants at positions 31, 67 and 115-117 in the interface recognition surface of the protein suggest these regions are partially inserted into the membrane. These results are consistent with a model for the Ca2+-independent membrane damaging mechanism that involves a transient interaction of the protein with the outer phospholipid leaflet of the target membrane. (C) 2007 Elsevier Masson SAS. All rights reserved.

Comparison of different irrigants on calcium hydroxide medication removal: microscopic cleanliness evaluation

Calcium hydroxide dressing residuals can compromise endodontic sealing. This study evaluated the cleaning efficacy of different endodontic irrigants in removing calcium hydroxide by SEM image analysis. Fifty-four single-rooted mandibular premolars were instrumented to a master apical file #60 and dressed with calcium hydroxide. After 36 hours, the teeth were reopened and Ca(OH)(2) medication was removed by 5 different experimental groups: 0.5% NaOCl (G1), EDTA-C (G2), citric acid (G3), EDTA-T (G4), and re-instrumentation with MAF using NaOCl and lubrificant, followed by EDTA-T (G5). The roots were split in the buccal-lingual direction and prepared for SEM analysis in cervical, middle, and apical thirds (9, 6, and 3 mm from the apex). Five blinded examiners evaluated the wall cleanliness using a scale from 1 to 5. Statistical analysis was performed using Kruskal-Wallis at 5% level of significance. Group G5 had the best results in all thirds, with significant statistical differences compared to all other groups in the middle and coronal third, and to G1 in the apical third. On the other hand, G1, only flushed with NaOCl, had the worst results, with statistical differences in all thirds compared to the other groups. The best cleanliness was achieved by G4 and G5 groups. The recapitulation of MAF in combination with irrigants improved the removal of calcium hydroxide medication better than an irrigant flush alone. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: 580-584)

Response of human dental pulp capped with MTA and calcium hydroxide powder

Objectives: To compare the response of human dental pulp capped with a mineral trioxide aggregate (MTA) and Ca(OH)(2) powder. Methods and Material: Pulp exposures were performed on the occlusal floor of 40 permanent premolars. The pulp was then capped with either Ca(OH)(2) powder (CH) or MTA and restored with resin composite. After 30 days (groups CH30 and MTA30) and 60 days (groups CH60 and MTA60), the teeth were extracted and processed for HE and categorized in a histological score system. The data were subjected to Kruskal-Wallis and Conover tests (alpha=0.05). Results: In regard to dentin bridge formation, CH30 showed a tendency towards superior performance compared to MTA30 (p>0.05), although the products showed comparable results at day 60. In the item ""Inflammation"" and ""General State of the Pulp"" (p>0.05), CH showed a tendency towards presenting a higher inflammatory response. In the item ""Other Pulpal Findings,"" MTA and Ca(OH)(2) showed equal and excellent performance after 30 and 60 days (p>0.05). Conclusion: After 30 days, Ca(OH)(2) powder covered with calcium hydroxide cement showed faster hard tissue bridge formation compared to MTA. After 60 days, Ca(OH)(2) powder or NITA materials showed a similar and excellent histological response with the formation of a hard tissue bridge in almost all cases with low inflammatory infiltrate.

Influence of dentin on pH of 2% chlorhexidine gel and calcium hydroxide alone or in combination

The aims of endodontic treatment in cases of apical periodontitis are to reduce as much as possible the number of microorganisms inside the root canal system and to inactivate toxins produced by them. Most of the times, these objectives are not achieved solely by chemomechanical preparation, and intracanal dressing may be necessary. In these cases, calcium hydroxide is used as a root canal dressing due to its well-known and recognized antimicrobial activity. Chlorhexidine has a wide spectrum of antimicrobial activity and its association with calcium hydroxide has been recommended in an attempt to amplify antimicrobial effects of calcium hydroxide. It is also known that dentin exerts a buffering effect under wide pH variations, and may be responsible for decreasing the antimicrobial activity of drugs inside the root canal. The objectives of this study were to assess the pH of 2% chlorhexidine gel and calcium hydroxide alone or in combination, as well as the influence of dentin on the pH of these compounds. Dentin powder was obtained from bovine teeth and added as 1.8% to the volume of the medications. All substances were individually stored in plastic flasks, in triplicate. A pH meter was used at five different moments to assess pH in viscous medium: immediately after preparation and after 24 h, and 7, 14, and 21 days. Results were analyzed by paired Student`s t-test. Statistically significant differences were observed in the 2% chlorhexidine gel group alone or associated with calcium hydroxide and added of dentin powder (P < 0.05). Mean pH values indicated the influence of dentin powder because of a significant increase in pH. Calcium hydroxide with propylene glycol as the vehicle always showed high pH, demonstrating that this compound was not affected by the presence of dentin.

pH, Calcium Ion Release, and Setting Time of an Experimental Mineral Trioxide Aggregate-based Root Canal Sealer

Introduction: An experimental mineral trioxide aggregate sealer (MTAS) has been developed for use as a root canal sealer. The aim of this study was to evaluate the setting time, pH, and calcium ion release of MTAS compared with white Portland cement (CPB-40; Votorantin Cimentos, Camargo Correa SA, Pedro Leopoldo, MG, Brazil), white MTA Angelus (MTA; Angelus, Londrina, PR, Brazil), and AH Plus (Dentsply DeTrey, Konstanz, Germany). Methods: For the evaluation of setting time, each material was analyzed using Gilmore-type needles. Polyethylene tubes with the materials were immersed in distilled water for the measurement of pH (digital pH meter) and calcium release (atomic absorption spectrophotometry). The evaluations were performed at 3, 6, 12, 24, and 48 hours and 7, 14, and 28 days. Data were analyzed by analysis of variance and the Tukey test at 5% significance level. Results: MTAS showed higher calcium release at all experimental periods, a greater increase in pH up to 48 hours and the longest setting time. Conclusions: MTAS presented favorable properties for its indication as a root canal sealer. (J Endod 2011;37:844-846)