Akmal Taher

Characterization of cyclic nucleotide phosphodiesterase isoenzymes in the human ureter and their functional role in vitro

SummaryAn increase in cyclic nucleotide monophosphate levels is suggested to play a prominent role in mediating smooth-muscle relaxation. Cyclic nucleotide phosphodiesterase (PDE) influences smooth-muscle tone by decreasing the level of cyclic nucleotides. At present, five different families of isoenzymes of PDE exist that show a distinct species- and organ-specific distribution. Our study was done to evaluate the existence of specific PDE isoenzymes and its functional role in human ureteral tissue. Normal ureteral tissue was homogenized and centrifuged and the supernatant fraction was separated using anioin-exchange diethylaminoethyl (DEAE)-Sephacel chromatography. A PDE assay was then performed and the peak fractions were added to different specific PDE activators and inhibitors. In vitro, longitudinal ureteral strips were precontracted and different selective and nonselective PDE inhibitors were added incremently. Three different PDE isoenzymes were characterized: PDE I (calmodulin-sensitive), PDE II (cGMP-stimulated), and PDE IV (cAMP-specific). All PDE inhibitors relaxed the strips dose-dependently, with the 50% effective concentrations (EC50) being 30 μM for papaverine, 40 μM for zaprinast, 25 μM for quazinone, and 0.1 μM for rolipram. The ureter-relaxing effect of the PDE IV inhibitor at low concentrations, combined with its low-level effect on the systemic circulatory parameters, may open the possibility of using selective PDE IV- inhibitors in the treatment of ureteral colics or for ureteral stone passage.

Phosphodiesterase Isoenzymes in Human Ureteral Smooth Muscle: Identification, Characterization, and Functional Effects of Various Phosphodiesterase Inhibitors in vitro

Phosphodiesterases (PDE) are key enzymes regulating intracellular cyclic nucleotide metabolism and, thus, contraction and relaxation of the muscle. At present, five different families of isoenzymes of PDE exist that show a distinct species-specific and organ-specific distribution. The aim of the present study was to analyze the PDE isoenzymes present in the human ureter and to evaluate the functional effects of isoenzyme-specific inhibitors in this tissue. Normal ureteral tissue was obtained during radical nephrectomies, homogenized, centrifuged, and the supernatant fraction was separated using DEAE-Sephacel anion-exchange chromatography. PDE assay was then performed and the isoenzymes characterized on the basis of their kinetic characteristics and their sensitivity to allosteric modulators and inhibitors. In vitro, longitudinal ureteral strips as well as ureteral rings were precontracted, and different selective and nonselective PDE inhibitors were added incrementally. Three different PDE isoenzymes were identified: PDE I (Ca/calmodulin-stimulated), PDE II (cyclic guanosine monophosphate-stimulated), and PDE IV (cyclic adenosine monophosphate-specific). All PDE inhibitors relaxed the strips dose-dependently with an EC50 of 30 microM for papaverine, 40 microM for zaprinast, 25 microM for quazinone, and 0.1 microM for rolipram. The existence of three different PDE isoenzymes was shown in this study. The ureter-relaxing effect of the PDE IV inhibitor at low concentrations, combined with its low effect on the systemic circulatory parameters, may open a possibility of using selective PDE IV inhibitors in the treatment of ureteral colics or ureteral stones.

Endogenous Vasoactive Peptides and the Human Vagina—A Molecular Biology and Functional Study

INTRODUCTION Endogenous peptides, such as vasoactive intestinal polypeptide (VIP), C-type natriuretic peptide (CNP), and bradykinin (BK), have been proposed to play a role in the female sexual arousal response by exerting relaxation of clitoral, labial, and vaginal smooth muscle. While the effects of endogenous peptides on the human male erectile tissue have already been described, only very few studies have been conducted to investigate the peptidergic control of female genital tissues, including the vagina. AIMS To elucidate the expression of mRNA specifically encoding for peptide receptors in the human vagina and the effects of VIP, CNP, and BK on the tension induced by endothelin-1 (ET-1) of isolated human vaginal wall smooth muscle. The production of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in response to exposure of the tissue to the peptides was also measured. METHODS The expression of mRNA encoding for receptor proteins specific for VIP, CNP, and BK were investigated by means of molecular biology (reverse transcriptase polymerase chain reaction [RT-PCR] analysis). Using the organ bath technique, the effects of VIP, CNP, and BK (0.1 nM to 1 µM) on the tension induced by 0.1 µM ET-1 of human vaginal strips were investigated. The tissue was also exposed to three different concentrations of VIP, CNP, and BK (0.01 µM, 0.1 µM, 1 µM) and the production of cAMP and cGMP determined by means of radioimmunoassays. MAIN OUTCOME MEASURES Characterize the expression of peptide receptors in the human vagina and measure the relaxation exerted by BK, CNP, and VIP on the contraction induced by ET-1 of isolated human vaginal tissue. In addition, the effects of the peptides on the production of cAMP and cGMP were also elucidated. RESULTS RT-PCR analysis revealed the expression of mRNA transcripts encoding for the VIP receptors VIP1R/vasoactive intestinal polypeptide receptor type 1 (VPAC1) and VIP2R/VPAC2, CNP receptors natriuretic peptide receptor type A (NPRA), natriuretic peptide receptor type B (NPRB) and natriuretic peptide receptor type C (NPRC), and BK receptor B2R. The tension induced by ET-1 was reversed by the peptides with the following rank order of efficacy: BK (21.7%) > VIP (20.9%) > CNP (13.3%). The relaxing effects of VIP and BK were paralleled by a 4.8-fold and fivefold increase in cAMP, while the production of cGMP was stimulated 38-fold and 119-fold in the presence of CNP or BK, respectively. CONCLUSION Our results are in support of the hypothesis that endogenous peptides may contribute to the control of human vaginal smooth muscle tone through the involvement of the cyclic nucleotide-dependent pathways.

Efficacy and tolerability of vardenafil in Asian men with erectile dysfunction

AIM To evaluate the efficacy and tolerability of vardenafil, a phosphodiesterase type-5 (PDE-5) inhibitor, in men of Asian ethnicity with erectile dysfunction (ED). METHODS In this prospective, double-blind, multinational study, Asian men were randomized to receive vardenafil (10 mg) or placebo (4:1 ratio) for 12 weeks. The primary efficacy variables were the International Index of Erectile Function erectile function domain (IIEF-EF), and Sexual Encounter Profile (SEP) questions related to penetration and intercourse completion. Significant mean improvements were required in all three measures to show positive benefits of vardenafil treatment. Secondary efficacy variables included the Global Assessment Question (GAQ) on erection improvement. RESULTS Least-squares mean baseline IIEF-EF domain scores (vardenafil 14.6, placebo 13.4) were consistent with moderate ED. After 12 weeks, vardenafil treatment was associated with significant increases from the baseline in IIEF-EF domain scores compared with the placebo (22.4 vs. 14.3; P<0.001). Vardenafil was associated with significant improvements from baseline in least squares (LS) mean success rates for SEP-2 (vardenafil 82.2 vs. placebo 43.6; P<0.001) and SEP-3 (vardenafil 66.1 vs. placebo 24.0; P<0.001). Positive GAQ responses were reported by 81.8% of vardenafil recipients vs. 24.3% of placebo recipients. Adverse events were reported by 25.4% of the vardenafil group, the majority mild and transient. CONCLUSION Vardenafil (10 mg) is a highly effective and well-tolerated treatment for moderate ED in Asian men. These results add to the increasing amount of data demonstrating the safety and efficacy of vardenafil for the treatment of ED in a range of patient populations.

The renal paracrine peptide system - possible urologic implications of urodilatin

SummaryCardiodilatin/atrial natriuretic peptide (CDD/ANP) is a hormone system of great clinical importance. The prohormone CDD/ANP-1-126 is a peptide synthesized in the heart and cleaved during exocytosis into the circulating form CDD/ANP-99-126. Urodilatin (CDD/ANP-95-126) is a homologue natriuretic peptide that differs from CDD/ANP-99-126 by four amino acids. Whereas CDD/ANP-99-126 circulates in blood plasma and is not excreted into the urine, urodilatin is detected only in urine. Urodilatin exerts its renal effects in a paracrine fashion. After its secretion from cells in the distal tubule, it interacts with luminally located receptors in the collecting duct, resulting in increased diuresis and natriuresis. Results suggest that urodilatin plays an important role in the physiologic regulation of fluid balance and sodium homeostasis. Pharmacology studies reveal significant differences when urodilatin and CDD/ANP-99-126 are given intravenously, showing that stronger diuresis and natriuresis are induced by urodilatin as compared with those induced by CDD/ANP-99-126. Clinical studies indicate the prophylactic and therapeutic effect of urodilatin in patients suffering from acute renal failure following heart and liver transplantation. A significant reduction in requirements for hemodialysis/hemofiltration can be achieved using urodilatin. Postobstructive diuresis and natriuresis is probably due to a defective urinary concentrating mechanism and is usually resistant to treatment with antidiuretic hormone. The distal tubule and collecting duct have often been considered to be the site of altered sodium and water excretion following relief of obstruction. Since circulating CDD/ANP-99-126 levels are markedly elevated during obstruction and decrease upon relief of the obstruction, natriuretic peptides may play an important role in this clinical feature. On the basis of recent findings attributing an important role in sodium homeostasis to urodilatin in contrast to CDD/ANP-99-126, future studies have to clarify whether urodilatin, not CDD/ANP-99-126, might be responsible for the altered renal sodium excretion observed in postobstructive diuresis.

Effects of Endopeptidase Inhibition on the Contraction–Relaxation Response of Isolated Human Vaginal Tissue

INTRODUCTION.: Vasoactive peptides, such as bradykinin, C-type natriuretic peptide (CNP), vasoactive intestinal polypeptide (VIP), and endothelin 1 (ET-1), are assumed to be involved in the control of female genital vascular and nonvascular smooth muscle. Tissue levels of said peptides are controlled by the activity of endopeptidase enzymes. Theoretically, in female genital tissues, inhibiting the degradation of bradykinin, CNP, and VIP, or the conversion of Big ET-1 into ET-1 should result in an enhancement in smooth muscle relaxation and, thus, an improvement in sexual response. AIM.: Elucidate the effects of the endopeptidase inhibitor KC 12615 on the contraction/relaxation response of isolated human vaginal smooth muscle to Big ET-1, bradykinin, CNP, or VIP. METHODS.: Tissue bath experiments were carried out to ascertain the responses of human vaginal tissue challenged by ET-1 (0.1 μM) to increasing concentrations of bradykinin, CNP, and VIP (0.01 μM, 0.1 μM, and 1 μM, respectively). The effects were also evaluated following preexposure to KC 12615 (10 μM, for 20 minutes). MAIN OUTCOME MEASURES.: Measure the effects of KC 12615 on the relaxation of isolated human vaginal smooth muscle brought about by bradykinin, CNP, or VIP and the contraction mediated by Big ET-1. RESULTS.: The tension induced by ET-1 was reversed by bradykinin, CNP, or VIP (-25 ± 6.6%, -13.3 ± 2.2%, and -17.6 ± 10%, respectively). Big ET-1 induced contraction of the vaginal tissue. Preexposure of the tissue to KC 12615 increased the relaxation exerted by bradykinin, CNP, or VIP (to -39.2 ± 5.8%, -40.7 ± 7.3%, and -44.6 ± 19%, respectively). The contraction induced by Big ET-1 was attenuated in the presence of KC 12615 (to approximately 25% of the initial response). CONCLUSION.: Inhibition of endopeptidase activity can antagonize the contraction of human vaginal tissue induced by Big ET-1 and increase the relaxation induced by vasoactive endogenous peptides.

The role of autosuggestion in geriatric patients' quality of life: a study on psycho-neuro-endocrine-immunology pathway.

ABSTRACT Background: There has been no study conducted about the effect of autosuggestion on quality of life for geriatric patients. Our aim was to evaluate the efficacy of autosuggestion for geriatric patients’ quality of life and its impact on psycho-neuro-endocrine-immune pathway. Methods: Sixty geriatric patients aged ≥60 years in a ward were randomly assigned to either receive autosuggestion or not. Autosuggestion was recorded in a tape to be heard daily for 30 days. Both groups received the standard medical therapy. Primary outcome was quality of life by COOP chart. Secondary outcomes were serum cortisol level, interleukin-2, interleukin-6, interferon-γ, and N-acetylaspartate/creatine ratio in limbic/paralimbic system by magnetic resonance spectroscopy. The study was single blinded due to the nature of the intervention studied. Results: Out of 60 subjects, 51 finished the study. The autosuggestion group reported better scores than the control one for quality of life, COOP chart 1.95 vs. 2.22 (95% CI, p = 0.02). There were increments of serum cortisol (p = 0.03) and interleukin-6 in the autosuggestion group (p = 0.04). Interleukin-2, interferon-γ, and N-acetylaspartate/creatine ratio in prefrontal cortex showed a tendency to increase in the autosuggestion groups. Conclusion: Autosuggestion is associated with improvement of geriatrics’ quality of life, serum cortisol level, and adaptive immunity. There is a better trend for neuroplasticity in prefrontal cortex in the autosuggestion group.