Regulation of intracellular Ca2+ release in corpus cavernosum smooth muscle: synergism between nitric oxide and cGMP

Crocus Sativus Linnaeus (Saffron) intake does not affect physiological and perceptual responses during a repeated sprint test in healthy active young males

The study aimed to investigate the effects of acute ingestion of saffron (SAF) on physiological (i.e., heart rate and blood lactate) and perceptual (i.e., ratings of perceived exertion [RPE] and feeling scale) measures in response to a repeated-sprint ability test (RSS) in healthy young males (N = 22; mean ± SD: age, 21.7 ± 1.24 yrs.). All participants completed two experimental trials with a one-week washout period using a double-blind, placebo-controlled, crossover design. In each session, the participants were randomly chosen to receive either a capsule of saffron (300 mg) (SAF session) or a capsule of lactose (PLB session) two hours before performing the RSS.No significant differences (p > 0.05) were found for heart rate, RPE, and feeling scale between the SAF or PLB sessions at pre- and post-RSS. There were no significant changes (p > 0.05) in peak time, total time, fatigue index, and blood lactate in either the SAF or PLB sessions. Acute SAF ingestion did not significantly improve RSS performance nor physiological and perceptual measures in active young males. Future trials should address the topic by using shortened/prolonged higher doses of SAF on biological, physical, physiological, and perceptual responses to acute and chronic exercise.

Effect of Crocus sativus L. (saffron) and crocin in the treatment of patients with type-2 diabetes mellitus: A systematic review and meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Crocus sativus L. (saffron, Iridaceae) has been traditionally used for thousands of years as herbal medicine for many diseases, including type-2 diabetes mellitus (T2DM), especially in Sri Lanka. Systematic reviews and meta-analysis on C. sativus for T2DM value traditional knowledge about this species.

AIM OF THE STUDY

To assess the effectiveness of C. sativus powdered plant, hydroethanolic extract and crocin in reducing fasting blood sugar (FBG), glycated hemoglobin (HbA1c), blood pressure, and other metabolic parameters in patients with T2DM.

MATERIAL AND METHODS

Systematic review and meta-analysis based on searches in PubMed, Embase, and Cochrane, including all randomized clinical trials (RCTs) published before January 2, 2023. Two independent reviewers extracted the data and assessed the risks of bias. The effects of C. sativus and crocin were assessed on glycemic, metabolic, and blood pressure parameters. Weighted (WMD) or standardized (SMD) mean differences (before-after) and 95% confidence intervals (95%CI) of the outcomes were extracted or estimated and meta-analyses were conducted using RevMan 5.4 (Cochrane Collaboration). This protocol was registered in PROSPERO (#CRD42023390073).

RESULTS

Fifteen of 29 studies were included. Saffron powdered plant decreased AST (WMD -1.19, 95%CI -2.24, -0.13), but increased BMI (WMD 0.56, 95%CI 0.07, 1.05); saffron extract decreased HbA1c (WMD -0.35, 95%CI -0.65, -0.06), FBG (WMD -26.90, 95%CI -38.87, -14.93), creatinine (WMD -0.12, 95%CI -0.19, -0.05), and total cholesterol (WMD -9.29, 95%CI -18.25, -0.33); and crocin decreased HbA1c (WMD -0.43, 95%CI -0.66, -0.20), FBG (WMD -14.10, 95%CI -22.91, -5.30), and systolic blood pressure (WMD -8.18, 95%CI -12.75, -3.61), but increased creatinine levels (WMD 0.24, 95%CI 0.17, 0.32). Of the 15 included studies, 14 had a moderate risk of bias, and one study had a low risk of bias.

CONCLUSION

C. sativus (saffron) powdered plant, extract, and crocin have potential as an adjunct treatment for T2DM, improving control of metabolic and clinical parameters. However, C. sativus extract seems to be superior because it was effective in more parameters and did not induce adverse effects. Since many studies were at moderate risk of bias, further high-quality research is needed to firmly establish the clinical efficacy of this plant.

Glutathione-S-Transferases as Potential Targets for Modulation of Nitric Oxide-Mediated Vasodilation

Glutathione-S-transferases (GSTs) are highly promiscuous in terms of their interactions with multiple proteins, leading to various functions. In addition to their classical detoxification roles with multi-drug resistance-related protein-1 (MRP1), more recent studies have indicated the role of GSTs in cellular nitric oxide (NO) metabolism. Vasodilation is classically induced by NO through its interaction with soluble guanylate cyclase. The ability of GSTs to biotransform organic nitrates such as nitroglycerin for NO generation can markedly modulate vasodilation, with this effect being prevented by specific GST inhibitors. Recently, other structurally distinct pro-drugs that generate NO via GST-mediated catalysis have been developed as anti-cancer agents and also indicate the potential of GSTs as suitable targets for pharmaceutical development. Further studies investigating GST biochemistry could enhance our understanding of NO metabolism and lead to the generation of novel and innovative vasodilators for clinical use.

The therapeutic potential of Crocus sativus Linn.: A comprehensive narrative review of clinical trials

Crocus sativus Linn. (Saffron) is valued worldwide for its potential use in the management of various degenerative disorders, including cardiovascular diseases (CVDs), diabetes, cancer, metabolic syndrome (MetS), neurodegenerative diseases, immune disorders, and sexual dysfunction. Previous reports, based on clinical trials, suggest that crocetin, crocin, picrocrocin, and safranal are the main bioactive components of saffron with antioxidant, anti-inflammatory, and anti-apoptotic effects. In this comprehensive narrative review, we studied the recent clinical trials, investigating the medicinal applications of saffron and/or its components. The present results can provide important insights into the potential of saffron in preventing and treating different disorders, with a special focus on the underlying cellular and molecular mechanisms. However, further high-quality studies are needed to firmly establish the clinical efficacy of saffron in treating some degenerative diseases.

The Relaxant Effect of Crocin on Rat Tracheal Smooth Muscle and Its Possible Mechanisms

Crocin, a component of saffron, showed hypotensive activity which is perhaps due to vascular smooth muscle relaxant effect. The relaxant effects of saffron on tracheal smooth muscle also could be due to its constituent, crocin. In the present study, the relaxant effects of crocin and its possible mechanisms on rat tracheal smooth muscle were investigated. The relaxant effects of three cumulative concentrations of crocin (30, 60, and 120 μM) or theophylline (0.2, 0.4, 0.6 mM) as positive control were examined on pre-contracted tracheal smooth muscle by methacholine or KCl in non-incubated or incubated conditions with different agents including atropine, chlorpheniramine, indomethacin, diltiazem, glibenclamide, and propranolol. In non-incubated tracheal smooth muscle, crocin showed significant relaxant effects on KCl induced muscle contraction (p < 0.001 for two higher concentrations). However, crocin did not show relaxant effect on methacholine induced tissue contraction. In incubated tissues with chlorpheniramine, indomethacin, diltiazem and propranolol, there were no significant differences in the relaxant effects of crocin between non-incubated and incubated tissues. However, the relaxant effects of crocin obtained in incubated tissues with atropine and glibenclamide were significant lower than non-incubated tracheal smooth muscle (p < 0.05 to p < 0.001). The EC₅₀ value obtained in incubated tissue with propranolol was significantly increased. Theophylline showed significant relaxant effect on both KCl and methacholine induced tissue contraction (p < 0.01 to p < 0.001). A relatively potent relaxant effect of crocin on tracheal smooth muscle, lower than that of theophylline was shown. Muscarinic receptor blocking, potassium channels opening and ß₂-adrenoreceptors stimulation were also suggested as possible mechanisms of this effect.

Anti-hypertensive effect of crocin and hesperidin combination in high-fat diet treated rats

Cardiovascular diseases are the leading cause of death worldwide. Hypertension is the most important cause of such conditions. The use of medicinal herbs is of particular importance due to their lower cost and side effects. The aim of the present study was to compare the effect of hesperidin (HES) and crocin (CRO) alone and in combination, on blood pressure in a rat model of high-fat diet (HFD)-induced hypertension, using invasive carotid artery measurements. Animals were randomly assigned to the following groups: control group (received standard chow diet), HFD control group (received HFD containing 32% kcal of fat and 0.1% cholesterol), and three groups of HFD-treated animals that were treated with a single dose of CRO (20 mg/kg), HES (20 mg/kg), or CRO + HES (20 + 20 mg/kg). Except for the control group, rats received HFD for 7 weeks. On day 50, CRO, HES and normal saline were administered intraperitoneally and carotid arteries of the rats were cannulated. Three hours after the carotid artery cannulation, mean arterial blood pressure (MAP), systolic and diastolic blood pressure (SBP and DBP), and heart rate (HR) were measured using an intra-arterial catheter with the use of a Power Lab system. Data was analyzed using SPSS software. Rats that received HFD for 49 days presented a significant increase in SBP, HR and MAP compared to the control group (P<0.001). Whereas, HFD-treated rats of the CRO + HES group showed lower levels of SBP, HR and MAP; however, DBP remained unaffected. HES administration in HFD treated rats resulted in a significant decrease in SBP compared to the HFD control group with no significant differences in MAP. The hypotensive effects of the simultaneous administration of CRO and HES in HFD-hypertensive rats suggest the need for further study of these two natural products as a potential preventive measure against hypertension development, especially in patients with high normal blood pressure.

Ion Channels and Intracellular Calcium Signalling in Corpus Cavernosum

The corpus cavernosum smooth muscle is important for both erection of the penis and for maintaining penile flaccidity. Most of the time, the smooth muscle cells are in a contracted state, which limits filling of the corpus sinuses with blood. Occasionally, however, they relax in a co-ordinated manner, allowing filling to occur. This results in an erection. When contractions of the corpus cavernosum are measured, it can be deduced that the muscle cells work together in a syncytium, for not only do they spontaneously contract in a co-ordinated manner, but they also synchronously relax. It is challenging to understand how they achieve this.In this review we will attempt to explain the activity of the corpus cavernosum, firstly by summarising current knowledge regarding the role of ion channels and how they influence tone, and secondly by presenting data on the intracellular Ca²⁺ signals that interact with the ion channels. We propose that spontaneous Ca²⁺ waves act as a primary event, driving transient depolarisation by activating Ca²⁺-activated Cl^- channels. Depolarisation then facilitates Ca²⁺ influx via L-type voltage-dependent Ca²⁺ channels. We propose that the spontaneous Ca²⁺ oscillations depend on Ca²⁺ release from both ryanodine- and inositol trisphosphate (IP₃)-sensitive stores and that modulation by signalling molecules is achieved mainly by interactions with the IP₃-sensitive mechanism. This pacemaker mechanism is inhibited by nitric oxide (acting through cyclic GMP) and enhanced by noradrenaline. By understanding these mechanisms better, it might be possible to design new treatments for erectile dysfunction.

Saffron; An updated review on biological properties with special focus on cardiovascular effects

OBJECTIVE

Saffron as a natural product has long been used to impede and treat different disorders including cardiovascular disease (CVDs). Stigma is the most principal part of saffron. Various compounds such as carotenoids and flavonoids are the essential components of saffron stigma. The health benefits of saffron have been shown in previous studies; however, there is a lack of comprehensive data on the mechanistic aspects of its cardiovascular-health properties. This current comprehensive review focuses on the medicinal applications of saffron, and then the new findings regarding its cardiovascular-health effects and various cellular and molecular mechanisms of action will be debated.

METHODS

The literature search of MEDLINE, Embase, PubMed, Google Scholar and Cochrane Library was performed for all comparative studies since 2000-2018 with the limitations of the English language.

RESULTS

The results provided new evidence about antioxidant, anti-inflammatory, anti- atherogenic, anti- apoptotic, anti- hypertensive, and hypolipidemic effects of saffron. Pharmacological effects of saffron are due to a number of ingredients contained within this spice, including safranal, crocetin and crocins.

CONCLUSIONS

Our study concludes that saffron with wide range of usefulness in medicine may be the potent candidate in the process of new drug production for the treatment of CVDs.

Pharmacological characterization of the relaxant effect induced by adrenomedullin in rat cavernosal smooth muscle

The aim of the present study was to determine the mechanisms underlying the relaxant effect of adrenomedullin (AM) in rat cavernosal smooth muscle (CSM) and the expression of AM system components in this tissue. Functional assays using standard muscle bath procedures were performed in CSM isolated from male Wistar rats. Protein and mRNA levels of pre-pro-AM, calcitonin receptor-like receptor (CRLR), and Subtypes 1, 2 and 3 of the receptor activity-modifying protein (RAMP) family were assessed by Western immunoblotting and quantitative real-time polymerase chain reaction, respectively. Nitrate and 6-keto-prostaglandin F_1α (6-keto-PGF_1α; a stable product of prostacyclin) levels were determined using commercially available kits. Protein and mRNA of AM, CRLR, and RAMP 1, -2, and -3 were detected in rat CSM. Immunohistochemical assays demonstrated that AM and CRLR were expressed in rat CSM. AM relaxed CSM strips in a concentration-dependent manner. AM_22-52, a selective antagonist for AM receptors, reduced the relaxation induced by AM. Conversely, CGRP_8-37, a selective antagonist for calcitonin gene-related peptide receptors, did not affect AM-induced relaxation. Preincubation of CSM strips with N^G-nitro-L-arginine-methyl-ester (L-NAME, nitric oxide synthase inhibitor), 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, quanylyl cyclase inhibitor), Rp-8-Br-PET-cGMPS (cGMP-dependent protein kinase inhibitor), SC560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethyl pyrazole, selective cyclooxygenase-1 inhibitor], and 4-aminopyridine (voltage-dependent K⁺ channel blocker) reduced AM-induced relaxation. On the other hand, 7-nitroindazole (selective neuronal nitric oxide synthase inhibitor), wortmannin (phosphatidylinositol 3-kinase inhibitor), H89 (protein kinase A inhibitor), SQ22536 [9-(tetrahydro-2-furanyl)-9H-purin-6-amine, adenylate cyclase inhibitor], glibenclamide (selective blocker of ATP-sensitive K⁺ channels), and apamin (Ca²⁺-activated channel blocker) did not affect AM-induced relaxation. AM increased nitrate levels and 6-keto-PGF_1α in rat CSM. The major new contribution of this research is that it demonstrated expression of AM and its receptor in rat CSM. Moreover, we provided evidence that AM-induced relaxation in this tissue is mediated by AM receptors by a mechanism that involves the nitric oxide-cGMP pathway, a vasodilator prostanoid, and the opening of voltage-dependent K⁺ channels.

Is there a rationale for penile rehabilitation following radical prostatectomy?

Erectile function recovery after radical prostatectomy (RP) is an increasingly prominent quality-of-life outcome following surgery. Following RP many men, despite the advent of cavernous nerve-sparing surgical technique, have moderately or significantly impaired erectile function (EF). The term penile rehabilitation (PR) is used to define interventions that maintain the health of erectile tissue in the context of nervous, vascular, and structural tissue injury. The goal of PR is to regain, as closely re-approximate, preoperative erectile function. PR is based on an increasing volume of preclinical and clinical data, but conclusive evidence of efficacy has not been established, and therefore the concept of PR remains controversial. The optimal PR regimen has not been established, but all strategies rely on one or more erectile dysfunction treatments to be administered on a regular basis regardless of actual use for sexual activity. This review highlights recent studies and evidence related to PR.

Phosphodiesterase type 5 inhibitors as adjunctive therapy in the management of systolic heart failure

OBJECTIVE

To review the efficacy and safety of phosphodiesterase-5 (PDE5) inhibitors in the treatment of patients with chronic systolic heart failure (HF).

DATA SOURCES

Literature was retrieved through MEDLINE (1966-September 2011) and EMBASE (1980-September 2011), using the medical subject heading terms heart failure and phosphodiesterase-5 inhibitors, sildenafil, tadalafil, and vardenafil. Focus was placed on multidose trials of patients with systolic HF, because of these trials' greater strength of clinical evidence.

STUDY SELECTION AND DATA EXTRACTION

All English-language, peer-reviewed publications were analyzed for relevance. Studies appropriate to the objective were evaluated, including 4 multidose trials investigating the effect of sildenafil on cardiovascular function.

DATA SYNTHESIS

In patients with New York Heart Association class II or III HF, treatment with sildenafil was associated with improvements in cardiac index, right ventricular ejection fraction, and other markers of cardiovascular function, as well as reduced pulmonary arterial pressure. Study durations ranged from 4 weeks to 1 year, and the studies used varying doses of sildenafil, ranging from 75 to 225 mg/day, in divided doses. The most common adverse effects associated with sildenafil therapy were headache and flushing.

CONCLUSIONS

Based on current studies, sildenafil appears to be well tolerated and can improve markers of cardiovascular and pulmonary function in patients with HF. PDE5 inhibitors may be a therapeutic option for patients who cannot tolerate standard therapy for HF or who remain symptomatic with standard therapy. Larger long-term trials are necessary to better understand the role of PDE5 inhibitors in HF.

Putative role of carbon monoxide signaling pathway in penile erectile function

INTRODUCTION

Erectile response depends on nitric oxide (NO) generated by NO synthase (NOS) enzyme of the nerves and vascular endothelium in the cavernous tissue. NO activates soluble guanylate cyclase (sGC), leading to the production of cyclic guanosine monophosphate (cGMP). cGMP activates cGMP-dependent protein kinase that activates Ca(2+)/ATPase pump that activates Ca(2+)/K efflux pump extruding Ca(2+) across the plasma membrane with consequent smooth muscle cell relaxation. A role similar to that of NOS/NO signaling has been postulated for carbon monoxide (CO) produced in mammals from heme catabolism by heme oxygenase (HO) enzyme.

AIM

To assess CO signaling pathway for erectile function by reviewing published studies.

METHODS

A systematic review of published studies on this affair based on Pubmed and Medical Subject Heading databases, with search for all concerned articles.

MAIN OUTCOME MEASURES

Documentation of positive as well as negative criteria of CO/HO signaling focused on penile tissue.

RESULTS

The concept that HO-derived CO could play a role in mediating erectile function acting in synergism with, or as a potentiator for, NOS/NO signaling pathway is gaining momentum. CO/HO signaling pathway has been shown to partially mediate the actions of oral phosphodiesterase type 5 inhibitors. In addition, it was shown that the use of CO releasing molecules potentiated cavernous cGMP levels. However, increased CO production or release was reported to be associated, in some studies, with vasoconstriction.

CONCLUSION

This review sheds a light on the significance of cavernous tissue CO signaling pathway that may pave the way for creation of therapeutic modalities based on this pathway.

RhoA GTPase and F-actin dynamically regulate the permeability of Cx43-made channels in rat cardiac myocytes

Gap junctions are clusters of transmembrane channels allowing a passive diffusion of ions and small molecules between adjacent cells. Connexin43, the main channel-forming protein expressed in ventricular myocytes, can associate with zonula occludens-1, a scaffolding protein linked to the actin cytoskeleton and to signal transduction molecules. The possible influence of Rho GTPases, major regulators of cellular junctions and of the actin cytoskeleton, in the modulation of gap junctional intercellular communication (GJIC) was examined. The activation of RhoA by cytoxic necrotizing factor 1 markedly enhanced GJIC, whereas its specific inhibition by the Clostridium botulinum C3 exoenzyme significantly reduced it. RhoA activity affects GJIC without major cellular redistribution of junctional plaques or changes in the Cx43 phosphorylation pattern. As these GTPases frequently act via the cortical cytoskeleton, the importance of F-actin in the modulation of GJIC was investigated by means of agents interfering with actin polymerization. Cytoskeleton stabilization by phalloidin slowed down the kinetics of channel rundown in the absence of ATP, whereas its disruption by cytochalasin D rapidly and markedly reduced GJIC despite ATP presence. Cytoskeleton stabilization by phalloidin markedly reduced the consequences of RhoA activation or inactivation. This mechanism appears to be the first described capable to both up- or down-regulate GJIC through RhoA activation or, conversely, inhibition. The inhibition of Rho downstream kinase effectors had no effect on GJIC. The present results provide further insight into the gating and regulation of junctional channels and identify a new downstream target for the small G-protein RhoA.

Phosphodiesterase-5 inhibition abolishes neuron apoptosis induced by chronic hypoxia independently of hypoxia-inducible factor-1alpha signaling

Exposure to hypoxia triggers a variety of adverse effects in the brain that arise from metabolic stress and induce neuron apoptosis. Overexpression of the hypoxia-inducible factor-1alpha (HIF-1alpha) is believed to be a major candidate in orchestrating the cell's defense against stress. To test the impact of HIF-1alpha on apoptosis during chronic hypoxia in vivo, we examined the protective effect of modulating the nitric oxide (NO)/cGMP pathway by sildenafil, a selective inhibitor of phosphodiesterase-5 (PDE-5). Male ICR/CD-1 mice were divided into 3 groups (n = 6/group): normoxic (21% O(2)), hypoxic (9.5% O(2)), and hypoxic with sildenafil (1.4-mg/kg intraperitoneal injections daily). At the end of the 8-day treatment period, the mice were euthanized and cerebral cortex biopsies were harvested for analyses. We found that sildenafil: (1) did not significantly alter the hypoxia-induced weight loss and hemoglobin increase, but did augment plasma nitrates+nitrites and the tissue content of cGMP and phosphorylated (P) NO synthase III; (2) reversed the hypoxia-induced neuron apoptosis (terminal deoxynucleotidyl transferase positivity and double-staining immunofluorescence, P = 0.009), presumably through increased bcl-2/Bax (P = 0.0005); and (3) did not affect HIF-1alpha, but rather blunted the hypoxia-induced increase in P-ERK1/2 (P = 0.0002) and P-p38 (P = 0.004). We conclude that upregulating the NO/cGMP pathway by PDE-5 inhibition during hypoxia reduces neuron apoptosis, regardless of HIF-1alpha, through an interaction involving ERK1/2 and p38.

The effect of saffron, Crocus sativus stigma, extract and its constituents, safranal and crocin on sexual behaviors in normal male rats

In this study, the aphrodisiac activities of Crocus sativus stigma aqueous extract and its constituents, safranal and crocin, were evaluated in male rats. The aqueous extract (80, 160 and 320mg/kg body wt.), crocin (100, 200 and 400mg/kg body wt.), safranal (0.1, 0.2 and 0.4ml/kg), sildenafil (60mg/kg body wt., as a positive control) and saline were administered intraperitoneally to male rats. Mounting frequency (MF), intromission frequency (IF), erection frequency (EF), mount latency (ML), intromission latency (IL) and ejaculation latency (EL) were the factors evaluated during the sexual behavior study. Crocin, at all doses, and the extract, especially at doses 160 and 320mg/kg body wt., increased MF, IF and EF behaviors and reduced EL, IL and ML parameters. Safranal did not show aphrodisiac effects. The present study reveals an aphrodisiac activity of saffron aqueous extract and its constituent crocin.

Hypercontractility and impaired sildenafil relaxations in the BKCa channel deletion model of erectile dysfunction

Erectile dysfunction (ED) can be elicited by a variety of pathogenic factors, particularly impaired formation of and responsiveness to nitric oxide (NO) and the downstream effectors soluble guanylate cyclase (sGC) and cGMP-dependent protein kinase I (PKGI). One important target of PKGI in smooth muscle is the large-conductance, Ca2+ -activated potassium (BKCa) channel. In our previous report (42), we demonstrated that deletion of the BKCa channel in mice induced force oscillations and led to reduced nerve-evoked relaxations and ED. In the current study, we used this ED model to explore the role of the BKCa channel in the NO/sGC/PKGI pathway. Electrical field stimulation (EFS)-induced contractions of corpus cavernosum smooth muscle strips were significantly enhanced in the absence of BKCa channel function. In strips precontracted with phenylephrine, EFS-induced relaxations were converted to contractions by inhibition of sGC, and this was further enhanced by loss of BK channel function. Sildenafil-induced relaxations were decreased to a similar extent by inhibition of sGC or BKCa channels. At concentrations >1 microM, sildenafil caused relaxations independent of inhibition of sGC or BKCa channels. Sildenafil did not affect the enhanced force oscillations that were induced by the loss of BKCa channel function. Yet, these oscillations could be completely eliminated by blocking L-type voltage-dependent Ca2+ channels (VDCCs). These results suggest that therapeutically relevant concentrations of sildenafil act through cGMP and BKCa channels, and loss of BKCa channel function leads to hypercontractility, which depends on VDCCs and cannot be modified by the cGMP pathway.

Rehabilitation of erectile function following radical prostatectomy

The concept of muscle rehabilitation after nerve injury is not a novel idea and is practiced in many branches of medicine, including urology. Bladder rehabilitation after spinal cord injury is universally practiced. The erectile dysfunction (ED) experienced after radical prostatectomy (RP) is increasingly recognized as being primarily neurogenic followed by secondary penile smooth muscle (SM) changes. There is unfortunately no standard approach to penile rehabilitation after RP because controlled prospective human studies are not available. This article reviews the epidemiology, experimental pathophysiological models, rationale for penile rehabilitation, and currently published rehabilitation strategies.

Cell signal transduction mechanism for nitric oxide regulating lymphatic stomata and its draining capability

We have previously demonstrated that nitric oxide (NO) is involved in the regulation of the lymphatic stomata. However, the related mechanisms are still unknown. The present study was designed to test the hypothesis that NO-cyclic guanosine monophosphate (cGMP) -mediated cytosolic Ca(2+) concentration ([Ca(2+)]i) signaling may contribute to the regulation of the lymphatic stomata and lymph drainage. Using trypan blue as a tracer, the effects of NO-cGMP-Ca(2+) signal cascade on the lymphatic stomata and lymph absorption were examined by means of scanning electron microscopy. Then, the role of NO in cGMP and [Ca(2+)]i of rat peritoneal mesothelial cells (RPMCs) was measured by radioimmunoassay and a confocal laser scanning microscope. Our results showed that NO-donor spermine/nitric oxide complex (Sper/NO) could broaden the opening area of the lymphatic stomata and enhance lymph absorption in a dose-dependent manner. These NO-mediated changes could be blocked by 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), a specific inhibitor of soluble guanylyl cyclase, and mimicked by calcium channel blocker nifedipine. Furthermore, Sper/NO enhanced the cGMP level and lessened [Ca(2+)](i) in RPMCs, which was completely abrogated at the presence of ODQ. Nifedipine induced an immediate and marked decrease of [Ca(2+)](i) in the RPMCs, which was not attenuated by addition of Sper/NO, indicating that the Sper/NO-cGMP signaling system induced [Ca(2+)](i) change was related to the L-type voltage-gated calcium channel in the RPMCs. Our results suggest that NO enlarges the opening area of the lymphatic stomata to strengthen the lymph drainage of tracer by means of NO-cGMP-[Ca(2+)]i signal transduction pathway in the RPMCs.

Sphincter of Oddi dysfunction in hypercholesterolemic rabbits

BACKGROUND AND OBJECTIVES

The mechanisms that trigger gallbladder evacuation dysfunction, the key risk factor for gallstone formation, have not yet been fully elucidated. The sphincter of Oddi (SO) plays important roles in the regulation of gallbladder evacuation and maintenance of normal hydraulic pressure of the biliary tract. The aim of our study was to investigate the effects of hypercholesterolemia on the motility function of SO and the underlying mechanisms of SO dysfunction (SOD).

METHODS

Forty New Zealand white rabbits were divided randomly into the control group fed with standard chow and the experimental (Ch) group fed with a high-cholesterol diet for 8 weeks. Changes in the maximal gallbladder emptying rate, gallbladder evacuation with cholecystokinin-octapeptide (CCK-8) stimulation and SO functions of both groups were measured in vivo; B ultrasound examination was used for dynamic observation of peristaltic movements in vivo; SO pressure was measured using manometry; morphological characteristics were observed by electronic microscope; laser scanning confocal fluorescence microscopy was used to identify changes in [Ca]i and Ca oscillation in primary SO smooth muscle cells (SMCs).

RESULTS

Gallbladder cholestasis was observed during early stages of gallstone formation in Ch rabbits. CCK-8 could not improve the gallbladder cholestatic state in Ch group. Passive dilation of SO significantly improved the cholestatic state in Ch rabbits (P<0.05), although the maximal gallbladder emptying rate was still lower than that of the control group. Manometry data indicted a significant increase in the base pressure of the SO low-pressure ampulla segment and high-pressure segment (P<0.05) in Ch group. laser scanning confocal fluorescence microscopy assay data indicated that [Ca]i in SO cells of Ch group significantly increased and were in a state of overload (P<0.05); Ca oscillation signals in SO cells of Ch group were also abnormal.

CONCLUSION

Hypercholesterolemia initially induced SOD, leading to increased gallbladder evacuation resistance and cholestasis. We suggested that [Ca]i overload and/or Ca oscillation abnormality potentially play important roles in the pathogenesis of SOD.

Rho kinase is involved in Ca2+ entry of rat penile small arteries

Tonic physiological activity of RhoA/Rho kinase contributes to the maintenance of penile flaccidity through its involvement in the Ca(2+) sensitization of erectile tissue smooth muscle. The present study hypothesized that Rho kinase is also involved in the modulation of Ca(2+) entry induced by alpha(1)-adrenoceptor stimulation of penile arteries. Rat penile arteries were mounted in microvascular myographs for simultaneous measurements of intracellular Ca(2+) ([Ca(2+)](i)) and force. The Rho-kinase inhibitor Y-27632 markedly reduced norepinephrine-mediated electrically induced contractions and the increases in both [Ca(2+)](i) and tension elicited by the alpha(1)-adrenoceptor agonist phenylephrine (Phe). In contrast, the protein kinase C (PKC) inhibitor Ro-31-8220 reduced tension without altering the Phe-induced increase in [Ca(2+)](i). In the presence of nifedipine, Y-27632 still inhibited the non-L-type Ca(2+) signal and blunted Phe contraction. Y-27632 did not impair the capacitative Ca(2+) entry evoked by store depletion with cyclopiazonic acid but largely reduced the Ba(2+) influx stimulated by Phe in fura-2 AM-loaded arteries. The addition of Y-27632 to arteries depolarized with high KCl markedly reduced tension without changing [Ca(2+)](i). In alpha-toxin-permeabilized penile arteries stimulated with threshold Ca(2+) concentrations, Y-27632 inhibited the sensitization induced by either guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) or Phe in the presence of GTPgammaS. However, Y-27632 failed to alter contractions induced by a maximal concentration of free Ca(2+). These results suggest that Rho kinase, besides its contribution to the Ca(2+) sensitization of the contractile proteins, is also involved in the regulation of Ca(2+) entry through a nonselective cation channel activated by alpha(1)-adenoceptor stimulation in rat penile arteries.

Relaxant effects of an alkaloid-rich fraction from Aspidosperma ulei root bark on isolated rabbit corpus cavernosum

We described earlier that an alkaloid-rich fraction (F(3-5)) from Aspidosperma ulei (Markgr) induces penile erection-like behavioral responses in mice. This study verified a possible relaxant effect of this fraction on isolated rabbit corpus cavernosum (RbCC) strips precontracted by phenylephrine (1 microM) or K+ 60 mM. F(3-5) (1-300 microg ml(-1)) relaxed the RbCC strips in a concentration-dependent and reversible manner. The relaxant effect of F(3-5) (100 microg ml(-1)) on phenylephrine contraction was unaffected in the presence of atropine, N-omega-nitro-L-arginine methyl ester or 1H-[1,2,4]oxadiazole[4,3-a] quinoxalin-1-one and by preincubation with tetrodotoxin, glibenclamide, apamine and charybdotoxin suggesting that mechanisms other than cholinergic, nitrergic, sGC activation or potassium channel opening are probably involved. However, the phasic component of the contraction induced by K+ 60 mM as well as the maximal contraction elicited by increasing external Ca2+ concentrations in depolarized corpora cavernosa was inhibited by F(3-5). We conclude that F(3-5) relaxes the RbCC smooth muscle, at least in part, through a blockade of calcium influx or its function.

Inhibition of pacemaker currents by nitric oxide via activation of ATP-sensitive K+ channels in cultured interstitial cells of Cajal from the mouse small intestine

We investigated the role of nitric oxide (NO) in pacemaker activity and signal mechanisms in cultured interstitial cells of Cajal (ICC) of the mouse small intestine using whole cell patch-clamp techniques at 30 degrees C. ICC generated pacemaker potential in the current clamp mode and pacemaker currents at a holding potential of -70 mV. (+/-)-S-nitroso-N-acetylpenicillamine (SNAP; a NO donor) produced membrane hyperpolarization and inhibited the amplitude and frequency of the pacemaker currents, and increased resting currents in the outward direction. These effects were blocked by the use of glibenclamide (an ATP-sensitive K+ channel blocker), but not by the use of 5-hydroxydecanoic acid (a mitochondrial ATP-sensitive K+ channel blocker). Pretreatment with ODQ (a guanylate cyclase inhibitor) almost blocked the NO-induced effects. The use of cell-permeable 8-bromo-cyclic GMP also mimicked the action of SNAP. However, the use of KT-5823 (a protein kinase G inhibitor) did not block the NO-induced effects. Spontaneous [Ca2+]i oscillations in ICC were inhibited by the treatment of SNAP, as seen in recordings of intracellular Ca2+ ([Ca2+]i). These results suggest that NO inhibits pacemaker activity by the activation of ATP-sensitive K+ channels via a cyclic GMP dependent mechanism in ICC, and the activation of ATP-sensitive K+ channels mediates the inhibition of spontaneous [Ca2+]i oscillations.

Calcium sparks activate calcium-dependent Cl− current in rat corpus cavernosum smooth muscle cells

Spontaneous transient currents, due to activation of Ca2+-dependent K+ and Cl− channels, occur in corpus cavernosum smooth muscle cells (CCSMC) of the penis. The Ca2+ events responsible for triggering Ca2+-dependent Cl− channels have never been identified in vascular muscle. We used high-speed fluorescence imaging combined with patch-clamp electrophysiology to provide the first characterization of Ca2+ events underlying these currents. Freshly isolated rat CCSMC loaded with fluo-4 exhibited localized, spontaneous elevations of intracellular Ca2+ (Ca2+ sparks) in 57% of cells. There was an average of 6.4 ± 0.5 release sites/cell with a frequency of 0.9 ± 1 Hz/cell and peak amplitude ΔF/Fo of 67 ± 10%. We addressed the controversy of whether these events are mediated by ryanodine or inositol 1,4,5 trisphosphate (IP3) receptors. Caffeine caused either a global Ca2+ rise at high concentrations or an increase in spark frequency at lower concentrations, whereas ryanodine dramatically reduced the amplitude and frequency of sparks. 2-Aminoethoxydiphenyl borate, an inhibitor of IP3 receptors, had no effect on spark frequency. Combined imaging and electrophysiological recording revealed strong coupling between Ca2+ sparks and biphasic transient currents, a relationship never before shown in vascular muscle. Moreover, spark frequency increased on depolarization, an effect abolished with the blockade of Ca2+ channels, consistent with Ca2+ influx regulating Ca2+ release from stores. We establish for the first time that Ca2+ sparks occur in CCSMC and arise from Ca2+ release through ryanodine receptors. Moreover, the voltage dependence of spark frequency demonstrated here provides novel functional evidence for voltage-dependent Ca2+ influx in CCSMC.

Physiological regulation of penile arteries and veins

Recent experimental evidence suggests that arterial insufficiency precedes the structural and functional changes in corpora cavernosa (CC) leading to organic erectile dysfunction (ED). The present review gives an overview of the physiological factors involved in the regulation of penile vasculature. Sympathetic nerves maintain flaccidity and tonically released noradrenaline induces vasoconstriction of both arteries and veins through alpha(1)- and alpha(2)-postsynaptic receptors and downregulates its own release and that of nitric oxide (NO) through alpha(2)-presynaptic receptors. The sympathetic cotransmitter neuropeptide Y (NPY) modulates noradrenergic vasoconstriction in penile small arteries by both enhancing and depressing noradrenaline contractions through Y(1)- and Y(2)-postsynaptic and a NO-independent atypical endothelial receptor, respectively. Activation of alpha(1)-adrenoceptors involves both Ca(2+) influx through L-type and receptor-operated Ca(2+) channels (ROC) and Ca(2+) sensitization mechanisms mediated by protein kinase C (PKC), tyrosine kinases (TKs) and Rho kinase (RhoK). In addition, RhoK can regulate Ca(2+) entry in penile arteries upon receptor stimulation. Vasodilatation of penile arteries and large veins during erection is mediated by neurally released NO. The subsequent increased arterial inflow to the cavernosal sinoids and shear stress on the endothelium lining penile arteries activates endothelial NO production through Akt phosphorylation of endothelial NO synthase (eNOS). NO stimulates guanylate cyclase and increased cyclic guanin 3'-monophosphate (cGMP) levels in turn activate protein kinase G (PKG), which enhances K(+) efflux through Ca(2+)-activated (K(Ca)) and voltage-dependent Ca(2+) (K(v)) channels in penile arteries and veins, respectively. PKG-mediated decrease in Ca(2+) sensitivity and its regulation by RhoK remains to be clarified in penile vasculature. Phosphodiesterase type 5 (PDE5) inhibitors are potent vasodilators of penile resistance arteries and increase the content and effects of basally released endothelial NO. Endothelium-dependent relaxations of penile small arteries also include an endothelium-derived hyperpolarizing factor (EDHF)-type response, which is impaired in diabetes and hypertension-associated ED. Locally produced contractile and relaxant prostanoids regulate penile venous and arterial tone, respectively. The latter activates prostaglandin I (IP) and prostaglandin E (EP) receptors coupled to adenylate cyclase and to the increase of cyclic adenosine monophosphate (cAMP) levels, which in turn stimulates K(+) efflux through ATP-sensitive K(+) (K(ATP)) channels. There is a crosstalk between the cGMP and cAMP signaling pathways in penile small arteries. Relevant issues such as the mechanisms underlying the excitation-secretion coupling of the endothelial cells, as well as those involved in cell proliferation and vascular remodeling of the penile vasculature remain to be elucidated. In addition, only few studies have investigated the changes in structure and function of penile arteries in cardiovascular risk situations leading to ED.

Regulator of G-protein signalling 3 redirects prototypical Gi-coupled receptors from Rac1 to RhoA activation

The small GTPases, Rac1 and RhoA, are pivotal regulators of several essential, but distinct cellular processes. Numerous G-protein-coupled receptors signal to these GTPases, but with different specificities. Specifically, Gi-coupled receptors (GiPCRs) are generally believed to activate Rac1, but not RhoA, a process involving Gbetagamma-dimers and phosphatidylinositol 3-kinase (PI3K). Here we show that, depending on the expression level of the 519 amino acid isoform of regulator of G-protein signalling 3 (RGS3L), prototypical GiPCRs, like M2 muscarinic, A1 adenosine, and alpha2-adrenergic receptors, activate either Rac1 or RhoA in human embryonic kidney cells and neonatal rat cardiomyocyte-derived H10 cells. The switch from Rac1 to RhoA activation in H10 cells was controlled by fibroblast growth factor-2 (FGF-2), lowering the expression of RGS3L. Activation of both, Rac1 and RhoA, seen at low and high expression levels of RGS3L, respectively, was sensitive to pertussis toxin and the PI3K inhibitor LY294002 and mediated by Gbetagamma-dimers. We conclude that RGS3L functions as a molecular switch, redirecting GiPCRs via Gbetagamma-dimers and PI3K from Rac1 to RhoA activation. Considering the essential roles of Rac1 and RhoA in many signalling pathways, this additional function of RGS3L indicates a specific role of this protein in cellular signalling networks.

Effect of nitric oxide on histamine-induced cytological transformations in parietal cells in isolated human gastric glands

Previous studies have shown that nitric oxide (NO) inhibits histamine-induced gastric acid secretion in isolated human gastric glands. NO synthase has been found to be present in the human oxyntic mucosa and has been suggested to serve as a paracrine regulator of gastric acid secretion. Histamine stimulation of parietal cells induces cytoskeletal rearrangements, recruitment of H+/K+-ATPase-rich tubulovesicles to the apical membrane and expansion of intracellular canaliculi. The aim of the present study was thus to investigate (i) the effect of an NO donor on histamine-induced cytological transformations and (ii) the influence of increased [Ca2+]i on NO-induced morphological changes in human parietal cells. Human gastric glands were isolated and subjected to the NO donor SNAP prior to histamine administration. [Ca2+]i was increased by photolysis of the caged Ca2+ compound NP-EGTA. The distribution of F-actin, ezrin, and H+/K+-ATPase was assessed by confocal microscopy. Ultrastructural analysis was performed using transmission electron microscopy. SNAP did not influence the histamine-induced translocation of F-actin, ezrin, and H+/K+-ATPase but prevented an increase in the canalicular size. Elevation of [Ca2+]i in resting cells was found to mimic histamine-induced intraparietal cell transformations; however, NO-induced parietal cell morphology was unaffected by a rise in [Ca2+]i. These results indicate that NO inhibits secretion of fluid into the canalicular lumen without affecting membrane recruitment and that this effect is Ca2+-insensitive.

Contribution of both Ca2+ entry and Ca2+ sensitization to the alpha1-adrenergic vasoconstriction of rat penile small arteries

Sympathetic adrenergic nerves maintain the flaccid state of the penis through the tonic release of norepinephrine that contracts trabecular and arterial smooth muscle. Simultaneous measurements of intracellular Ca(2+) concentration ([Ca(2+)](i)) and tension and experiments with alpha-toxin-permeabilized arteries were performed in branches of the rat dorsal penile artery to investigate the intracellular Ca(2+) signaling pathways underlying alpha(1)-adrenergic vasoconstriction. Phenylephrine increased both [Ca(2+)](i) and tension, these increases being abolished by extracellular Ca(2+) removal and reduced by about 50% by the L-type Ca(2+) channel blocker nifedipine (0.3 microM). Non-L-type Ca(2+) entry through store-operated channels was studied by inhibiting the sarcoplasmic reticulum Ca(2+)-ATPase with cyclopiazonic acid (CPA). CPA (30 microM) induced variable phasic contractions that were abolished by extracellular Ca(2+) removal and by the store-operated channels antagonist 2-aminoethoxydiphenyl borate (2-APB, 50 microM) and largely inhibited by nifedipine (0.3 microM). CPA induced a sustained increase in [Ca(2+)](i) that was reduced in a Ca(2+)-free medium. Under conditions of L-type channels blockade, Ca(2+) readmission after store depletion with CPA evoked a sustained and marked elevation in [Ca(2+)](i) not coupled to contraction. 2-APB (50 microM) inhibited the rise in [Ca(2+)](i) evoked by CPA and the nifedipine-insensitive increases in both [Ca(2+)](i) and contraction elicited by phenylephrine. In alpha-toxin-permeabilized penile arteries, activation of G proteins with guanosine 5'-O-(3-thiotriphosphate) and of the alpha(1)-adrenoceptor with phenylephrine both enhanced the myofilament sensitivity to Ca(2+). This Ca(2+) sensitization was reduced by selective inhibitors of PKC, tyrosine kinase (TK), and Rho kinase (RhoK) by 43%, 67%, and 82%, respectively. As a whole, the present data suggest the alpha(1)-adrenergic vasoconstriction in penile small arteries involves Ca(2+) entry through both L-type and 2-APB-sensitive receptor-operated channels, as well as Ca(2+) sensitization mechanisms mediated by PKC, TK, and RhoK. A capacitative Ca(2+) entry coupled to noncontractile functions of the smooth muscle cell is also demonstrated.

Rapid translocation and insertion of the epithelial Na+ channel in response to RhoA signaling

Activity of the epithelial Na+ channel (ENaC) is limiting for Na+ absorption across many epithelia. Consequently, ENaC is a central effector impacting systemic blood volume and pressure. Two members of the Ras superfamily of small GTPases, K-Ras and RhoA, activate ENaC. K-Ras activates ENaC via a signaling pathway involving phosphatidylinositol 3-kinase and production of phosphatidylinositol 3,4,5-trisphosphate with the phospholipid directly interacting with the channel to increase open probability. How RhoA increases ENaC activity is less clear. Here we report that RhoA and K-Ras activate ENaC through independent signaling pathways and final mechanisms of action. Activation of RhoA signaling rapidly increases the membrane levels of ENaC likely by promoting channel insertion. This process dramatically increases functional ENaC current, resulting in tight spatial-temporal control of these channels. RhoA signals to ENaC via a transduction pathway, including the downstream effectors Rho kinase and phosphatidylinositol-4-phosphate 5-kinase. Phosphatidylinositol 4,5-biphosphate produced by activated phosphatidylinositol 4-phosphate 5-kinase may play a role in targeting vesicles containing ENaC to the plasma membrane.