New base-altered adenosine analogues: Synthesis and affinity at adenosine A1 and A2A receptors

N⁶-Substituted adenosine analogues containing cyclic hydrazines or chiral hydroxy (ar)alkyl groups, designed to interact with the S2 and S3 receptor subregions, have been synthesized and their binding to the adenosine A₁ and A_2A receptors have been investigated. Examples of both types of compounds were found to exhibit highly selective binding (K_i in low nM range) to the rat A₁ receptor.     

Rationale and design of the SMART Heart study

Left ventricular hypertrophy (LVH) is an independent risk factor for the development of heart failure, coronary heart disease and stroke. LVH develops in response to haemodynamic overload, e.g. hypertension. LVH was originally thought to start as an adaptive and beneficial response required to normalise wall stress. However, this concept has been challenged by recent animal experiments suggesting that any degree of LVH is detrimental for the preservation of cardiac function and survival. If confirmed in humans, these findings imply that an increase in LV mass should be prevented, e.g. by lifestyle or pharmacological interventions. To facilitate and optimise interventions, the SMART Heart study was recently set up to develop a prediction model, also involving single nucleotide polymorphism data, for the identification of subjects at high risk of developing LVH in hypertension. For this purpose 1000 subjects with chronic hypertension will undergo cardiac MR imaging. In addition, this study allows the extrapolation of animal experimental genetic research into the human situation. (Neth Heart J 2007;15:295-8).     

An LQT mutant minK alters KvLQT1 trafficking

Cardiac I_Ks, the slowly activated delayed-rectifier K⁺ current, is produced by the protein complex composed of - and -subunits: KvLQT1 and minK. Mutations of genes encoding KvLQT1 and minK are responsible for the hereditary long QT syndrome (loci LQT1 and LQT5, respectively). MinK-L51H fails to traffic to the cell surface, thereby failing to produce effective I_Ks. We examined the effects that minK-L51H and an endoplasmic reticulum (ER)-targeted minK (minK-ER) exerted over the electrophysiology and biosynthesis of coexpressed KvLQT1. Both minK-L51H and minK-ER were sequestered primarily in the ER as confirmed by lack of plasma membrane expression. Glycosylation and immunofluorescence patterns of minK-L51H were qualitatively different for minK-ER, suggesting differences in trafficking. Cotransfection with the minK mutants resulted in reduced surface expression of KvLQT1 as assayed by whole cell voltage clamp and immunofluorescence. MinK-L51H reduced current amplitude by 91% compared with wild-type (WT) minK/KvLQT1, and the residual current was identical to KvLQT1 without minK. The phenotype of minK-L51H on I_Ks was not dominant because coexpressed WT minK rescued the current and surface expression. Collectively, our data suggest that ER quality control prevents minK-L51H/KvLQT1 complexes from trafficking to the plasma membrane, resulting in decreased I_Ks. This is the first demonstration that a minK LQT mutation is capable of conferring trafficking defects onto its associated -subunit. potassium channel; hereditary arrhythmia; electrophysiology; protein interaction     

S641 contributes HERG K+ channel inactivation

The kinetics of voltage-dependent inactivation of the rapidly activating delayed rectifier, IKr, are unique among K+ channels. The human ether-a-gogo-related gene (HERG) encodes the pore-forming subunit of IKr and shares a high degree of homology with ether-a-gogo (EAG) channels that do not inactivate. Within those segments thought to contribute to the channel pore, HERG possesses several serine residues that are not present in EAG channels. Two of these serines, S620 and S631, are known to be required for inactivation. We now show that a third serine, S641, which resides in the outer portion of the sixth transmembrane segment, is also critical for normal inactivation. As with the other serines, S641 is also involved in maintaining ion selectivity of the HERG channel and alters sensitivity to block by E4031. Larger charged or polar substitutions (S641D and S641T) disrupted C-type inactivation in HERG. Smaller aliphatic and more conservative substitutions (S641A and S641C) facilitated C-type inactivation. Our data show that, like S620 and S631, S641 is another key residue for the rapid inactivation. The altered inactivation of mutations at S620, S631, and S641 were dominant, suggesting that a network of hydroxyl side chains is required for the unique inactivation, permeation, and rectification of HERG channels.     

Design,synthesis and binding affinity of 3'-fluoro analogues of Cl-IB-MECA as adenosine A3 receptor ligands

Several 3'-fluoro analogues, 1a, 1b, and 1c of selective and potent adenosine A(3) receptor agonist, Cl-IB-MECA were synthesized from D-xylose via highly regioselective opening of lyxo-epoxides, 8a and 8b with fluoride anion. Compared to the high binding affinity of Cl-IB-MECA to the A(3) adenosine receptor, the corresponding 3'-fluoro derivative showed remarkably decreased binding affinity, indicating that 3'-hydroxyl group acts as hydrogen bonding acceptor, not hydrogen bonding donor like fluorine atom in binding to the A(3) adenosine receptor.     

Bladder injection of "naked" hSlo/pcDNA3 ameliorates detrusor hyperactivity in obstructed rats in vivo

The goal of these studies was to examine the potential utility of bladder instilled K+ channel gene therapy with hSlo cDNA (i.e., the maxi-K channel) to ameliorate bladder overactivity in a rat model of partial urinary outlet obstruction. Twenty-two female Sprague-Dawley rats were subjected to partial urethral (i.e., outlet) obstruction, with 17 sham-operated control rats run in parallel. After 6 wk of obstruction, suprapubic catheters were surgically placed in the dome of the bladder in all rats. Twelve obstructed rats received bladder instillation of 100 microg of hSlo/pcDNA in 1 ml PBS during catheterization, and another 10 obstructed rats received 1 ml PBS (7 rats) or 1 ml PBS containing pcDNA only (3 rats). Two days after surgery cystometry was performed on all animals to examine the characteristics of the micturition reflex in conscious and unrestrained rats. Obstruction was associated with a three- to fourfold increase in bladder weight and alterations in virtually every micturition parameter estimate. PBS-injected obstructed rats routinely displayed spontaneous bladder contractions between micturitions. In contrast, hSlo injection eliminated the obstruction-associated bladder hyperactivity, without detectably affecting any other cystometric parameter. Presumably, expression of hSlo in rat bladder functionally antagonizes the increased contractility normally observed in obstructed animals and thereby ameliorates bladder overactivity. These initial observations indicate a potential utility of gene therapy for urinary incontinence.     

Synthesis and antiproliferating activity of iron chelators of hydroxyamino-1,3,5-triazine family

We synthesized and evaluated new specific tridentate iron(III) chelators of 2,6-bis[hydroxyamino]-1,3,5-triazine (BHT) family for use in iron deprivation cancer therapy. Physical properties of BHT chelators are easily customizable allowing easy penetration through cellular membranes. Antiproliferative activity of new BHT chelators was studied on MDA-MB-231 and MiaPaCa cells and compared to a clinically available new oral iron chelator, deferasirox (DFX). The antiproliferative activity of new chelators was found to correlate with iron(III) chelation ability and some of analogs showed substantially higher antiproliferative activity than DFX.     

Radical perineal prostatectomy: a more optimal treatment approach than laparoscopic radical prostatectomy in obese patients?

In comparison with laparoscopic radical prostatectomy (LRP), the perineal approach to radical prostatectomy offers specific technical advantages related to obesity and its unique surgical challenges. Radical perineal prostatectomy (RPP) reduces operative time and its associated risk of complication, which may be more pronounced in obese men. It allows for low blood loss, low postoperative use of narcotics for pain, short hospital stays, and requires only 1 small perineal incision. With a proven history of success, RPP presents obese men with an advantageous surgical option.     

Cyclic AMP regulates the HERG K(+) channel by dual pathways

Lethal cardiac arrhythmias are a hallmark of the hereditary Long QT syndrome (LQTS), a disease produced by mutations of cardiac ion channels [1]. Often these arrhythmias are stress-induced, suggesting a relationship between beta-adrenergic activation of adenylate cyclase and cAMP-dependent alteration of one or more of the ion channels involved in LQTS. Second messengers modulate ion channel activity either by direct interaction or through intermediary kinases and phosphatases. Here we show that the second messenger cAMP regulates the K(+) channel mutated in the LQT2 form of LQTS, HERG [2], both directly and indirectly. Activation of cAMP-dependent protein kinase (PKA) causes phosphorylation of HERG accompanied by a rapid reduction in current amplitude, acceleration of voltage-dependent deactivation, and depolarizing shift in voltage-dependent activation. In a parallel pathway, cAMP directly binds to the HERG protein with the opposing effect of a hyperpolarizing shift in voltage-dependent activation. The summation of cAMP-mediated effects is a net diminution of the effective current, but when HERG is complexed with with the K(+) channel accessory proteins MiRP1 or minK, the stimulatory effects of cAMP are favored. These findings provide a direct link between stress and arrhythmia by a unique mechanism where a single second messenger exerts complex regulation of an ion channel via two distinct pathways.