Expression and functional role of Rho-kinase in rat urinary bladder smooth muscle

Intracellular signaling pathways of muscarinic acetylcholine receptor-mediated detrusor muscle contractions

Acetylcholine plays an essential role in the regulation of detrusor muscle contractions, and antimuscarinics are widely used in the management of overactive bladder syndrome. However, several adverse effects limit their application and patients' compliance. Thus, this study aimed to further analyze the signal transduction of M2 and M3 receptors in the murine urinary bladder to eventually find more specific therapeutic targets. Experiments were performed on adult male wild-type, M2, M3, M2/M3, or Gαq/11 knockout (KO), and pertussis toxin (PTX)-treated mice. Contraction force and RhoA activity were measured in the urinary bladder smooth muscle (UBSM). Our results indicate that carbamoylcholine (CCh)-induced contractions were associated with increased activity of RhoA and were reduced in the presence of the Rho-associated kinase (ROCK) inhibitor Y-27632 in UBSM. CCh-evoked contractile responses and RhoA activation were markedly reduced in detrusor strips lacking either M2 or M3 receptors and abolished in M2/M3 KO mice. Inhibition of Gαi-coupled signaling by PTX treatment shifted the concentration-response curve of CCh to the right and diminished RhoA activation. CCh-induced contractile responses were markedly decreased in Gαq/11 KO mice; however, RhoA activation was unaffected. In conclusion, cholinergic detrusor contraction and RhoA activation are mediated by both M2 and M3 receptors. Furthermore, whereas both Gαi and Gαq/11 proteins mediate UBSM contraction, the activation at the RhoA-ROCK pathway appears to be linked specifically to Gαi. These findings may aid the identification of more specific therapeutic targets for bladder dysfunctions.NEW & NOTEWORTHY Muscarinic acetylcholine receptors are of utmost importance in physiological regulation of micturition and also in the development of voiding disorders. We demonstrate that the RhoA-Rho-associated kinase (ROCK) pathway plays a crucial role in contractions induced by cholinergic stimulation in detrusor muscle. Activation of RhoA is mediated by both M2 and M3 receptors as well as by Gi but not Gq/11 proteins. The Gi-RhoA-ROCK pathway may provide a novel therapeutic target for overactive voiding disorders.

The role of rhoA/rho-kinase and PKC in the inhibitory effect of L-cysteine/H2S pathway on the carbachol-mediated contraction of mouse bladder smooth muscle

We investigated the role of RhoA/Rho-kinase (ROCK) and PKC in the inhibitory effect of L-cysteine/hydrogen sulfide (H2S) pathway on the carbachol-mediated contraction of mouse bladder smooth muscle. Carbachol (10-8-10-4 M) induced a concentration-dependent contraction in bladder tissues. L-cysteine (H2S precursor; 10-2 M) and exogenous H2S (NaHS; 10-3 M) reduced the contractions evoked by carbachol by ~ 49 and ~ 53%, respectively, relative to control. The inhibitory effect of L-cysteine on contractions to carbachol was reversed by 10-2 M PAG (~ 40%) and 10-3 M AOAA (~ 55%), cystathionine-gamma-lyase (CSE) and cystathionine-β-synthase (CBS) inhibitor, respectively. Y-27632 (10-6 M) and GF 109203X (10-6 M), a specific ROCK and PKC inhibitor, respectively, reduced contractions evoked by carbachol (~ 18 and ~ 24% respectively), and the inhibitory effect of Y-27632 and GF 109203X on contractions was reversed by PAG (~ 29 and ~ 19%, respectively) but not by AOAA. Also, Y-27632 and GF 109203X reduced the inhibitory responses of L-cysteine on the carbachol-induced contractions (~ 38 and ~ 52% respectively), and PAG abolished the inhibitory effect of L-cysteine on the contractions in the presence of Y-27632 (~ 38%). Also, the protein expressions of CSE, CBS, and 3-MST enzymes responsible for endogenous H2S synthesis were detected by Western blot method. H2S level was increased by L-cysteine, Y-27632, and GF 109203X (from 0.12 ± 0.02 to 0.47 ± 0.13, 0.26 ± 0.03, and 0.23 ± 0.06 nmol/mg respectively), and this augmentation in H2S level decreased with PAG (0.17 ± 0.02, 0.15 ± 0.03, and 0.07 ± 0.04 nmol/mg respectively). Furthermore, L-cysteine and NaHS reduced carbachol-induced ROCK-1, pMYPT1, and pMLC20 levels. Inhibitory effects of L-cysteine on ROCK-1, pMYPT1, and pMLC20 levels, but not of NaHS, were reversed by PAG. These results suggest that there is an interaction between L-cysteine/H2S and RhoA/ROCK pathway via inhibition of ROCK-1, pMYPT1, and pMLC20, and the inhibition of RhoA/ROCK and/or PKC signal pathway may be mediated by the CSE-generated H2S in mouse bladder.

The role of intracellular calcium and Rho kinase pathways in G protein-coupled receptor-mediated contractions of urinary bladder urothelium and lamina propria

The influence of extracellular and intracellular calcium on smooth muscle contractile activity varies between organs. In response to G protein-coupled receptor (GPCR) stimulation, the urinary bladder detrusor muscle has shown a 70% dependence on extracellular calcium, whereas the urothelium and lamina propria (U&LP) has a 20%-50% dependence. However, as this only accounts for partial contractile activity, the contribution of intracellular calcium and calcium sensitization pathways remains unclear. This study assessed the role of intracellular signaling pathways on GPCR-mediated urinary bladder U&LP contraction. Porcine U&LP responses to activation of the G_q/11-coupled muscarinic, histamine, 5-hydroxytryptamine (serotonin), neurokinin, prostaglandin, and angiotensin II receptors were assessed with three selective inhibitors of store-released intracellular calcium, 2-aminoethyl diphenylborinate (2-APB), cyclopiazonic acid (CPA), and ruthenium red, and three Rho kinase inhibitors, fasudil, Y-27632, and GSK269962. There was no discernible impact on receptor agonist-induced contractions of the U&LP after blocking intracellular calcium pathways, suggesting that this tissue is more sensitive to alterations in the availability of extracellular calcium. However, an alternative mechanism of action for GPCR-mediated contraction was identified to be the activation of Rho kinase, such as when Y-27632 significantly reduced the GPCR-mediated contractile activity of the U&LP by approximately 50% (P < 0.05, n = 8). This suggests that contractile responses of the bladder U&LP do not involve a significant release of calcium from intracellular stores, but that G_q/11-coupled receptor activation causes calcium sensitization via Rho kinase. This study highlights a key role for Rho kinase in the urinary bladder, which may provide a novel target in the future pharmaceutical management of bladder contractile disorders.

Signaling Pathways Mediating Bradykinin-Induced Contraction in Murine and Human Detrusor Muscle

Bradykinin (BK) has been proposed to modulate urinary bladder functions and implicated in the pathophysiology of detrusor overactivity. The present study aims to elucidate the signaling pathways of BK-induced detrusor muscle contraction, with the goal of better understanding the molecular regulation of micturition and identifying potential novel therapeutic targets of its disorders. Experiments have been carried out on bladders isolated from wild-type or genetically modified [smooth muscle-specific knockout (KO): Gαq/11-KO, Gα12/13-KO and constitutive KO: thromboxane prostanoid (TP) receptor-KO, cyclooxygenase-1 (COX-1)-KO] mice and on human bladder samples. Contractions of detrusor strips were measured by myography. Bradykinin induced concentration-dependent contractions in both murine and human bladders, which were independent of secondary release of acetylcholine, ATP, or prostanoid mediators. B2 receptor antagonist HOE-140 markedly diminished contractile responses in both species, whereas B1 receptor antagonist R-715 did not alter BK's effect. Consistently with these findings, pharmacological stimulation of B2 but not B1 receptors resembled the effect of BK. Interestingly, both Gαq/11- and Gα12/13-KO murine bladders showed reduced response to BK, indicating that simultaneous activation of both pathways is required for the contraction. Furthermore, the Rho-kinase (ROCK) inhibitor Y-27632 markedly decreased contractions in both murine and human bladders. Our results indicate that BK evokes contractions in murine and human bladders, acting primarily on B2 receptors. Gαq/11-coupled and Gα12/13-RhoA-ROCK signaling appear to mediate these contractions simultaneously. Inhibition of ROCK enzyme reduces the contractions in both species, identifying this enzyme, together with B2 receptor, as potential targets for treating voiding disorders.

Increased expression of Rho-associated protein kinase 2 confers astroglial Stat3 pathway activation during epileptogenesis

Patients with TLE are prone to tolerance to antiepileptic drugs. Based on the perspective of molecular targets for drug resistance, it is necessary to explore effective drug resistant genes and signaling pathways for the treatment of TLE. We performed gene expression profiles in hippocampus of patients with drug-resistant TLE and identified ROCK2 as one of the 20 most significantly increased genes in hippocampus. In vitro and in vivo experiments were performed to identify the potential role of ROCK2 in epileptogenesis. In addition, the activity of Stat3 pathway was tested in rat hippocampal tissues and primary cultured astrocytes. The expression levels of ROCK2 in the hippocampus of TLE patients were significantly increased compared with the control group, which was due to the hypomethylation of ROCK2 promoter. Fasudil, a specific Rho-kinase inhibitor, alleviated epileptic seizures in the pilocarpine rat model of TLE. Furthermore, ROCK2 activated the Stat3 pathway in pilocarpine-treated epilepsy rats, and the spearman correlation method confirmed that ROCK2 is associated with Stat3 activation in TLE patients. In addition, ROCK2 was predominantly expressed in astrocytes during epileptogenesis, and induced epileptogenesis by activating astrocyte cell cycle progression via Stat3 pathway. The overexpressed ROCK2 plays an important role in the pathogenesis of drug-resistant epilepsy. ROCK2 accelerates astrocytes cell cycle progression via the activation of Stat3 pathway likely provides the key to explaining the process of epileptogenesis.

ATP as a cotransmitter in sympathetic and parasympathetic nerves - another Burnstock legacy

Geoff Burnstock created an outstanding scientific legacy that includes identification of adenosine 5'-triphosphate (ATP) as an inhibitory neurotransmitter in the gut, the discovery and characterisation of a large family of purine and uridine nucleotide-sensitive ionotropic P2X and metabotropic P2Y receptors and the demonstration that ATP is as an excitatory cotransmitter in autonomic nerves. The evidence for cotransmission includes that: 1) ATP is costored with noradrenaline in synaptic vesicles in postganglionic sympathetic nerves innervating smooth muscle tissues, including the vas deferens and most arteries. 2) When coreleased with noradrenaline, ATP acts at postjunctional P2X1 receptors to elicit depolarisation, Ca²⁺ influx, Ca²⁺ sensitisation and contraction. 3) ATP is also coreleased with acetylcholine from postganglionic parasympathetic nerves innervating the urinary bladder, where it stimulates postjunctional P2X1 receptors, and a second, as yet unidentified site to evoke contraction of detrusor smooth muscle. In both systems membrane-bound ecto-enzymes and soluble nucleotidases released from postganglionic nerves dephosphorylate ATP and so terminate its neurotransmitter actions. Currently, the most promising potential area of therapeutic application relating to cotransmission is treatment of dysfunctional urinary bladder. This family of disorders is associated with the appearance of a purinergic component of neurogenic contractions. This component is an attractive target for drug development and targeting it may be a rewarding area of research.

The effect of testosterone replacement therapy on bladder functions, histology, apoptosis, and Rho-kinase expression in bladder outlet obstruction and hypogonadism rat model

Background/aim

The effect of testosterone replacement therapy was investigated on bladder functions, histology, apoptosis as well as Rho-kinase expression in the rat bladder outlet obstruction (BOO) and hypogonadism models.

Materials and methods

30 mature male rats divided into 4 groups: sham group (n = 8), BOO group (n = 8), BOO + orchiectomy group (n = 7), BOO + orchiectomy + testosterone (T) treatment group (n = 7). Cystometric findings, apoptosis index, Rho-kinase (ROCK-2) expression, and smooth muscle/collagen ratio were compared.

Results

BOO did not change ROCK-2 expression level, compared to sham group (P > 0.05). However, when compared to BOO group (P < 0.01), BOO + orchiectomy led ROCK-2 increase. The testosterone treatment failed to reverse the up-regulation of ROCK-2 induced by orchiectomy although it tended to lower ROCK-2 level. Compared to sham group (P = 0.002), changes in maximal bladder capacity and leak point pressure were higher (P = 0.026, P = 0.001), and bladder compliance was lower in BOO group. Also, the apoptosis index was different between the two groups (P = 0.380). Smooth muscle/collagen ratio was higher in BOO + orchiectomy + T group than in BOO + orchiectomy group (P = 0.010).

Conclusions

The research draws attention to alternating treatment approaches in case of the presence of hypogonadism and BOO.

Is medicinal ketamine associated with urinary dysfunction issues? Assessment of both the European Medicines Agency (EMA) and the UK Yellow Card Scheme pharmacovigilance database-related reports

OBJECTIVE

A range of ketamine-induced uropathy (KIU) issues have been typically described in ketamine misusers. Conversely, more knowledge is needed in terms of medicinal ketamine-related urological disturbances, since ketamine prescribing is being increasingly considered for a range of medical and psychopathological conditions.

METHODS

To assess medicinal KIU issues, we aimed at analyzing both the 2005-2017 European Medicines Agency (EMA) and the 2006-2018 UK Yellow Card Scheme (YCS) pharmacovigilance databases.

RESULTS

A total number (eg, all categories) of 11 632 EMA ketamine-related adverse drug reaction (ADR) reports were here identified. Out of these, some 9971 ADRs (eg, 85.7% of the total) were judged as "suspect" and were here analyzed. Some 1758 ADRs (17.7% of 9971, corresponding to 194 individual patients) referred to urological issues, relating to either kidney/ureter (922 ADRs) or bladder/urethra (837 ADRs). Ketamine was the sole drug administered in 156/194 (80.4%) cases/patients. Although most cases occurred in the 1 month-1 year time frame following the start of ketamine prescribing, in 30 cases the ADR occurred within 48 hours. Most ADR-related cases resolved, although both sequelae (18 cases) and fatalities (79/1758; 4.5%) were recorded. Overall, YCS data were consistent with EMA findings, with some 50/217 (23%) ADRs referring to renal/urinary disorders.

CONCLUSIONS

Current data may only represent a gross underestimate of the KIU real prevalence issues. It is here suggested that chronic treatment involving higher doses/repeated exposure to ketamine be restricted to the context of controlled trials or clinical audits.

Hydrogen sulfide dilates the isolated retinal artery mainly via the activation of myosin phosphatase

AIMS

Hydrogen sulfide (H₂S) is shown in ocular tissues and suggested to involve in the regulation of retinal circulation. However, the mechanism of H₂S-induced relaxation on retinal artery is not clarified yet. Herein, we aimed to evaluate the role of several calcium (Ca²⁺) signaling and Ca²⁺ sensitization mechanisms in the relaxing effect of H₂S donor, NaHS, on retinal arteries.

MATERIALS AND METHODS

Relaxing effects of NaHS (10^-5-3 × 10^-3M) were determined on precontracted retinal arteries in Ca²⁺ free medium as well as in the presence of the inhibitors of Ca²⁺ signaling and Ca²⁺ sensitization mechanisms. Additively, Ca²⁺ sensitivity of the contractile apparatus were evaluated by CaCl₂-induced contractions in the presence of NaHS (3 × 10^-3M). Functional experiments were furtherly assessed by protein and/or mRNA expressions, as appropriate.

KEY FINDINGS

The relaxations to NaHS were preserved in Ca²⁺ free medium while NaHS pretreatment decreased the responsiveness to CaCl₂. The inhibitors of plasmalemmal Ca²⁺-ATPase, sarcoplasmic-endoplasmic reticulum Ca²⁺-ATPase, Na⁺-Ca²⁺ ion-exchanger and myosin light chain kinase (MLCK) unchanged the relaxations to NaHS. Likewise, Ca²⁺ sensitization mechanisms including, rho kinase, protein kinase C and tyrosine kinase were unlikely to mediate the relaxation to NaHS in retinal artery. Whereas, a marked reduction was determined in NaHS-induced relaxations in the presence of MLCP inhibitor, calyculin A. Supportively, NaHS pretreatment significantly reduced phosphorylation of MYPT1-subunit of MLCP.

SIGNIFICANCE

The relaxing effect of NaHS in retinal artery is likely to be related to the activation of MLCP and partly, to decrement in Ca²⁺ sensitivity of contractile apparatus.

Low androgen status inhibits erectile function by up-regulating the expression of P2X receptors in rat corpus cavernosum

The aim of our study was to investigate whether low androgen level inhibits the erectile function of rats by regulating the expression of P2X receptors. Thirty-six 8-week-old male SD rats were randomly divided into six groups: sham-operated groups (4w-sham, 8w-sham), castration groups (4w-cast, 8w-cast) and androgen replacement after castration groups (4w-cast + T, 8w-cast + T). The maximum intracavernous pressure/mean arterial pressure (ICPmax/MAP), the levels of serum testosterone (T) and nitric oxide (NO), and the expression of P2X1, P2X2, P2X3, eNOS, p-eNOS, ROCK1 and ROCK2 in the cavernous tissue of rats were determined. The serum T, ICPmax/MAP and NO levels in penile corpus cavernosum in the castration groups were significantly lower than those in other groups (p < .01). The protein expression of P2X1, P2X2, P2X3, ROCK1 and ROCK2 in the castration groups was significantly higher than those in other groups (p < .01). P-eNOS/eNOS of the castration groups were significantly lower than those of other groups (p < .01). The serum T level was negatively correlated with the expression of P2X1, P2X2 and P2X3 in the corpus cavernosum. Low androgen level inhibits erectile function by up-regulating the expression of P2X1, P2X2, P2X3 and RhoA/Rho-kinase resulting in reducing the ratio of p-eNOS/eNOS and the level of NO in corpus cavernosum of rats.

NK2 receptor-mediated detrusor muscle contraction involves Gq/11-dependent activation of voltage-dependent Ca2+ channels and the RhoA-Rho kinase pathway

Tachykinins (TKs) are involved in both the physiological regulation of urinary bladder functions and development of overactive bladder syndrome. The aim of the present study was to investigate the signal transduction pathways of TKs in the detrusor muscle to provide potential pharmacological targets for the treatment of bladder dysfunctions related to enhanced TK production. Contraction force, intracellular Ca²⁺ concentration, and RhoA activity were measured in the mouse urinary bladder smooth muscle (UBSM). TKs and the NK2 receptor (NK2R)-specific agonist [β-Ala⁸]-NKA(4-10) evoked contraction, which was inhibited by the NKR2 antagonist MEN10376. In Gα_q/11-deficient mice, [β-Ala⁸]-NKA(4-10)-induced contraction and the intracellular Ca²⁺ concentration increase were abolished. Although G_q/11 proteins are linked principally to phospholipase Cβ and inositol trisphosphate-mediated Ca²⁺ release from intracellular stores, we found that phospholipase Cβ inhibition and sarcoplasmic reticulum Ca²⁺ depletion failed to have any effect on contraction induced by [β-Ala⁸]-NKA(4-10). In contrast, lack of extracellular Ca²⁺ or blockade of voltage-dependent Ca²⁺ channels (VDCCs) suppressed contraction. Furthermore, [β-Ala⁸]-NKA(4-10) increased RhoA activity in the UBSM in a G_q/11-dependent manner and inhibition of Rho kinase with Y-27632 decreased contraction force, whereas the combination of Y-27632 with either VDCC blockade or depletion of extracellular Ca²⁺ resulted in complete inhibition of [β-Ala⁸]-NKA(4-10)-induced contractions. In summary, our results indicate that NK2Rs are linked exclusively to G_q/11 proteins in the UBSM and that the intracellular signaling involves the simultaneous activation of VDCC and the RhoA-Rho kinase pathway. These findings may help to identify potential therapeutic targets of bladder dysfunctions related to upregulation of TKs.

Pharmacological modulation of the spatiotemporal disposition of micromotions in the intact resting urinary bladder of the rabbit; their pattern is under both myogenic and autonomic control

OBJECTIVES

To explore and characterize the disposition and dynamics of micromotions in the wall of the intact resting teradotoxinized urinary bladder of the rabbit before and after the administration of adrenergic and cholinergic pharmaceutical agents.

METHODS

Spatiotemporal maps and related intravesical pressure were used to analyse propagating patches of contractions (PPCs) and their component individual myogenic contractions [propagating individual contractions (PICs)] in the wall of the tetradotoxinized urinary bladder.

RESULTS

The bladder wall exhibited two contractile states that were of similar frequencies to those of the two types of electrophysiological discharge described in previous studies; the first, in which cyclic PPCs predominated, the second in which small irregular PICs predominated. The addition of carbachol increased the size, frequency, speed and distance of propagation of PPCs, whereas the addition of isoprenaline temporarily halted the incorporation of PICs into PPCs, and reduced patch size and total area undergoing contraction. The RhoA kinase (ROCK) inhibitor Y-27632 reduced both largest patch index and mean patch size. Both carbenoxolone and ROCK inhibition decreased the duration of PPCs. Carbenoxolone also prolonged duration and accelerated PPC propagation velocity. The authors postulate that these differences arise from differing effects of these agents on myocytes and interstitial cells within the stress environment of the bladder, influencing the development, coordination and propagation of PPCs.

CONCLUSIONS

The timings and structure of spontaneous micromotions in the wall of the isolated bladder change when it is treated with sympathetic/parasympathetic agonists and with myogenically active agents. Correspondingly, disorders of bladder wall contraction may result from disorders of either neurogenic or myogenic signalling and may be amenable to treatment with combinations of agents that influence both.

Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease

Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.

Calcium sensitization mechanisms in detrusor smooth muscles

The contraction of detrusor smooth muscles depends on the increase in intracellular calcium. The influx of calcium from the plasma membrane calcium channels and calcium release from the sarcoplasmic reticulum give rise to intracellular calcium. Under the pathophysiological conditions, the increased sensitivity of regulatory and contractile proteins to calcium also plays an important role in maintaining the spontaneous detrusor smooth muscle activity. Many proteins have been identified to play a role in calcium sensitization. Both the protein kinase C (PKC) and Rho-kinase (ROCK) signaling pathways are responsible for the induction of calcium sensitization in the detrusor smooth muscles. The balance between the myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP) regulates the intracellular calcium-contractile force relationship. The inhibition of MLCP by PKC-mediated phosphatase inhibitor (CPI-17) and myosin phosphatase target subunit (MYPT-1) phosphorylation by both the PKC and ROCK are responsible for calcium sensitization in the detrusor smooth muscles. However, the ROCK pathway predominantly participates in the calcium sensitization induction under pathophysiological situations. Many kinases are well known nowadays to play a role in calcium sensitization. This review aims to enlighten the current understanding of the regulatory mechanisms of calcium sensitization with special reference to the PKC and ROCK pathways in the detrusor smooth muscles. It will also aid in the development of new pharmacological strategies to prevent and treat bladder diseases.

The effect of extracellular ATP on rat uterine contraction from different gestational stages and its possible mechanisms of action

BACKGROUND

The mechanisms underlying the onset of labor are not fully understood. Extracellular adenosine 5'-triphosphate (ATP) is known to cause uterine contractions in different species but the exact underlying mechanisms are poorly investigated to date. The aims of this study were to investigate the effect of extracellular ATP on spontaneous uterine contractions from different gestational stages and to elucidate its possible underlying mechanisms.

METHODS

Longitudinal uterine strips were obtained from rats in different gestational stages (nonpregnant, late-pregnant, and term-pregnant). The effects of 1 mM ATP were examined on uterine contractions generated spontaneously, depolarized by high-KCl (60 mM), induced by oxytocin (5 nM), in the presence of high external Ca2+, or in the absence of external Ca2+.

RESULTS

Application of 1 mM extracellular ATP significantly increased the force of spontaneous contraction in uterine strips obtained from all gestational stages with prominent increase in term-pregnant rats compared to other gestations. ATP significantly increased the force induced by depolarization (122%, p=0.010, n=6), oxytocin (129%, p=0.001, n=7), high-Ca2+ (145%, p=0.005, n=6) and it was able to cause transient contraction in the absence of external Ca2+ (33%, p<0.01).

CONCLUSIONS

Extracellular ATP is able to increase the force and frequency of uterine contractions and its effect increases with the progression of pregnancy and it involves Ca2+ influx and release. These findings open a new window for clinicians to consider ATP as a therapeutic target to control the uterine activity during difficult labors.

Role of rho-kinase (ROCK) in tonic but not phasic contraction in the frog stomach smooth muscle

AIMS

Rho/Rho-kinase (ROCK) signaling has extensively been shown to take part in mammalian smooth muscle contractions in response to diverse agents yet its role in the contraction of amphibian smooth muscle has not been investigated. Therefore, we aimed to explore any role of this pathway in the contractions of frog stomach smooth.

MAIN METHODS

The strips were prepared and suspended in organ baths filled with Ringer solution. Changes in the circular strips of the frog stomach muscle length were recorded isotonically with a force transducer in organ baths.

KEY FINDINGS

Carbachol (CCh) exerted both phasic and tonic contractions. In contrast, atropin abolished all types of contractions by CCh. The phasic contractions were suppressed by a Ca²⁺ channel blocker, nifedipine but not by the ROCK inhibitor, Y-27632. However, the tonic contractions were markedly attenuated by Y-27632. Selective M₁ receptor blocker, pirenzepin, selective M₃ receptor blocker and DAMP had no effects on CCh-elicited contractions. On the other hand, selective M₂ receptor blocker, AF-DX suppressed all types of contractile activity by CCh.

SIGNIFICANCE

These data suggest that M₂ receptor activation could mainly mediate CCh-induced phasic and tonic contractions, and ROCK seems to be involved in the CCh-induced tonic but not phasic contractions of the frog stomach smooth muscle.

Investigational Drug Therapies for Overactive Bladder Syndrome: The Potential Alternatives to Anticolinergics

Background

Overactive bladder is a high prevalent and quality of life affecting disease. The mainstay of the medical therapy is represented by antimuscarinic drugs, but their side effects markedly affect patient compliance and prompt studies on novel investigational drugs.

Methods

A systematic literature search of peer-reviewed papers and meeting abstracts published by December 2008 was performed. PubMed databank was searched for original English articles, by using the following search terms: “overactive bladder” or “detrusor overactivity” or “urinary incontinence” and “treatment”, alone and linked to any potential molecular target or novel drug cited in the literature.

Results

Effective alternative pharmacological treatments are currently scarce, but many new promising compounds are emerging which target key molecular pathways involved in micturition control. The most promising potential therapeutic targets include central nervous system GABAergic inhibitory pathway, dopaminergic and serotoninergic systems, b-adrenoceptors and cAMP metabolism, nonadrenergic-noncholinergic mechanisms such as purinergic and neuropeptidergic systems, vanilloid receptor, bladder sensory nervous terminals, nonneuronal bladder signalling systems including urothelium and interstitial cells, prostanoids, Rho-kinase and different subtypes of potassium and calcium channels.

Conclusions

Despite the enormous amount of new biologic insight, very few novel pharmacological therapies seems to have passed the proof-of-concept clinical stage. The ultimate clinical utility of new drugs will depend on the ability to exploit tissue-specific differences and disease-related changes in molecular expression/function and to improve storage phase dysfunctions without interfering with the emptying phase. Further preclinical investigations and controlled clinical trials are urgently needed in this challenging field.

Lower urinary tract symptoms/benign prostatic hypertrophy and vascular function: Role of the nitric oxide-phosphodiesterase type 5-cyclic guanosine 3',5'-monophosphate pathway

It is well known that there is an association of lower urinary tract symptoms/benign prostatic hypertrophy with cardiovascular disease, suggesting that lower urinary tract symptoms/benign prostatic hypertrophy is a risk factor for cardiovascular events. Vascular function, including endothelial function and vascular smooth muscle function, is involved in the pathogenesis, maintenance and development of atherosclerosis, leading to cardiovascular events. Vascular dysfunction per se should also contribute to lower urinary tract symptoms/benign prostatic hypertrophy. Both lower urinary tract symptoms/benign prostatic hypertrophy and vascular dysfunction have cardiovascular risk factors, such as hypertension, dyslipidemia, diabetes mellitus, aging, obesity and smoking. Inactivation of the phosphodiesterase type 5-cyclic guanosine 3',5'-monophosphate-nitric oxide pathway causes lower urinary tract symptoms/benign prostatic hypertrophy through an enhancement of sympathetic nervous activity, endothelial dysfunction, increase in Rho-associated kinase activity and vasoconstriction, and decrease in blood flow of pelvic viscera. Both endogenous nitric oxide and exogenous nitric oxide act as vasodilators on vascular smooth muscle cells through an increase in the content of cyclic guanosine 3',5'-monophosphate, which is inactivated by phosphodiesterase type 5. In a clinical setting, phosphodiesterase type 5 inhibitors are widely used in patients with lower urinary tract symptoms/benign prostatic hypertrophy. Phosphodiesterase type 5 inhibitors might have beneficial effects on vascular function through not only inhibition of cyclic guanosine 3',5'-monophosphate degradation, but also increases in testosterone levels and nitric oxide bioavailability, increase in the number and improvement of the function of endothelial progenitor cells, and decrease in insulin resistance. In the present review, the relationships between lower urinary tract symptoms/benign prostatic hypertrophy, the phosphodiesterase type 5-nitric oxide-cyclic guanosine 3',5'-monophosphate pathway, vascular function and cardiovascular outcomes are examined.

Rho kinase inhibition ameliorates cyclophosphamide-induced cystitis in rats

Hemorrhagic cystitis often develops in patients treated with cyclophosphamide (CYP). Studies have indicated that Rho kinase (ROCK) inhibitors may suppress detrusor overactivity symptoms and possess anti-inflammatory properties. The aim of the present study was to investigate whether inhibition of ROCK reduces cystometric and histopathological changes associated with CYP-induced cystitis. The rats received GSK 269962, a ROCK inhibitor, at a dose of 30 mg/kg daily, or vehicle for 7 days. Then, acute chemical cystitis leading to bladder overactivity was induced by CYP injection (200 mg/kg i.p.). Following CYP injection, cystometric studies with physiological saline were performed. Moreover, bladder edema (by the Evans Blue dye leakage technique) and urothelium thickness were measured. CYP injection resulted in a significant increase in cystometric parameters: basal pressure, threshold pressure, bladder contraction duration, relaxation time, detrusor overactivity index, non-voiding contractions amplitude, and non-voiding contractions frequency as well as increased Evans Blue extravasation into bladder tissue, whereas micturition voiding pressure, voided volume, post-void residual, volume threshold, intercontraction interval, bladder compliance, and volume threshold to elicit non-voiding contractions as well as urothelium thickness were significantly decreased in CYP-injected rats. Administration of GSK 269962 normalized the abovementioned CYP injection-induced changes. Inhibition of ROCK was found to ameliorate CYP-induced detrusor overactivity and bladder inflammation. Our data indicate uroprotective effects following ROCK inhibition, which further suggests that this strategy may become an interesting pharmacological tool to prevent urinary adverse effects in patients treated with chemotherapy using CYP.

Regulation of pulmonary endothelial barrier function by kinases

The pulmonary endothelium is the target of continuous physiological and pathological stimuli that affect its crucial barrier function. The regulation, defense, and repair of endothelial barrier function require complex biochemical processes. This review examines the role of endothelial phosphorylating enzymes, kinases, a class with profound, interdigitating influences on endothelial permeability and lung function.

The influence of Rho-kinase inhibition on acetic acid-induced detrusor overactivity

AIMS

Accumulating evidence has shown that Rho-kinase (ROCK) is involved in the regulation of bladder contraction. Our objective was to examine whether the ROCK inhibitor, GSK 269962, could prevent acetic acid (AA)-induced detrusor overactivity and to assess its influence on urine production (UP) and mean arterial pressure (MAP).

METHODS

The bladder was catheterized from the external urethral orifice. 0.25 % (AA) solution was infused into the bladder for 5 min. In the same session a catheter was inserted into the apex of the bladder dome. In order to measure the blood pressure, the carotid artery was cannulated. Three days after the intravesical instillation of AA, the ROCK-GSK 269962 inhibitor was administered in a single dose of 10 mg/kg and a cystometry was carried out, along with a 24 hr measurement of UP and MAP.

RESULTS

GSK 269962 reversed the changes induced by AA causing a drop in basal pressure, threshold pressure, micturition voiding pressure, bladder contraction duration, relaxation time, detrusor overactivity index, amplitude, and frequency of nonvoiding contractions while an increase in voided volume, post-void residual, volume threshold, voiding efficiency, intercontraction interval, bladder compliance, and volume threshold to elicit nonvoiding contractions. ROCK inhibition did not show any significant changes in UP and MAP.

DISCUSSION

The results obtained indicate that ROCK inhibition may ameliorate AA-induced bladder overactivity.

CONCLUSION

ROCK inhibitors appear to represent a potentially attractive pharmacological option for the treatment of lower urinary tract disorders associated with changes in detrusor contractility. Neurourol. Urodynam. 36:263-270, 2017. © 2015 Wiley Periodicals, Inc.

Protective effect of hydroxyfasudil, a Rho kinase inhibitor, on ventral prostatic hyperplasia in the spontaneously hypertensive rat

BACKGROUND

Rho kinase (ROCK) pathway is associated with various cellular functions, such as smooth muscle contraction, inflammatory response, and cell proliferation. The spontaneously hypertensive rat (SHR) is commonly used genetically hypertensive rat model which develops hyperplastic morphological abnormalities in the ventral prostate. We investigated whether administration of hydroxyfasudil, a ROCK inhibitor, could reduce the levels of growth factors, inflammatory markers, and morphological abnormalities in the ventral prostate of the SHR.

METHODS

Twelve-week-old SHRs were treated with hydroxyfasudil (1 mg/kg/day, i.p.) or vehicle once daily for another 6 weeks. Wistar Kyoto (WKY) rats treated with vehicle were used as normotensive controls. At 18 weeks of age, blood pressure and heart rate were measured by the tail cuff method. Then the rats were sacrificed, and the ventral prostates were removed. The levels of ROCK activity, growth factors (TGF-β1 and bFGF), a smooth muscle differentiation marker (α-SMA) and an inflammatory cytokine (IL-6) in the ventral prostate were measured by ELISA and western blot. A histological evaluation in each group was also performed.

RESULTS

There were significant increases in blood pressure, prostate weight, prostate body weight ratio, and tissue levels of ROCK activity, TGF-β1, bFGF, α-SMA, and IL-6 in the SHR compared to the WKY rat. Histological examination of the ventral prostate showed morphological abnormalities such as a higher degree of proliferation in the glandular epithelial and stromal area in the SHR compared to the WKY rat. Treatment with hydroxyfasudil reduced the elevated ROCK activity, TGF-β1, bFGF, α-SMA, and IL-6 found in the ventral prostate of the SHR. Moreover, treatment with hydroxyfasudil decreased the morphological abnormalies in the SHR ventral prostate.

CONCLUSIONS

Treatment with hydroxyfasudil decreased the growth factors, an inflammatory cytokine, and morphological abnormalies in the SHR ventral prostate. These results suggest that chronic treatment with hydroxyfasudil may inhibit the progression of prostatic hyperplasia in the SHR.

Inverse relationship of Rho kinase and myosin-light chain kinase expression in the aging human detrusor smooth muscle

Background

Rho kinase (ROCK) and myosin-light chain kinase (MLCK) are key enzymes in smooth muscle contraction. Previous data have suggested that ROCK contribution to human detrusor contraction is increasing with age. Here, we have analyzed the transcriptional expression of Rho kinase isoforms (ROCK1 and ROCK2) as well as MLCK in the aging human detrusor smooth muscle obtained from resected tissue.

Methods

Small pieces of macroscopically healthy human detrusor smooth muscle (urothelium-free) were prepared for quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR). Transcript expression (mRNA level) of the target genes ROCK1, ROCK2 and MLCK was normalized to three common reference genes (glyceraldehyde-3-phosphate dehydrogenase, β-actin, phosphoglycerate kinase 1).

Results

We found that across all ages the expression level of ROCK (i.e. ROCK1 and ROCK2 together) was almost equal to that of MLCK in the human bladder. Further, ROCK2 showed a significantly higher expression level than ROCK1. Among all subjects, there was no significant correlation of any single target gene to age, but expression levels of ROCK and MLCK were inversely correlated. Moreover, the within-subject analysis revealed that the ROCK-to-MLCK ratio showed a significantly negative correlation to age. Thus, within a given subject, there is a relative ROCK down-regulation and concomitant MLCK up-regulation.

Conclusions

Together with previous data in human detrusor specimens showing increased ROCK contribution to detrusor contraction, we speculate that the drop of the ROCK-to-MLCK ratio may occur as an attempt to compensate for the increased Rho kinase activity.

Aging changes agonist induced contractile responses in permeabilized rat bladder

Aging alters bladder functions where a decrease in filling, storage and emptying is observed. These changes cause urinary incontinence, especially in women. The aim of this study is to examine how aging affects the intracellular calcium movements due to agonist-induced contractions in permeabilized female rat bladder. Urinary bladder isolated from young and old female Sprague-Dawley rats were used. Small detrusor strips were permeabilized with β-escin. The contractile responses induced with agonists were compared between young and old groups. Carbachol-induced contractions were decreased in permeabilized detrusor from old rats compared to young group. Heparin and ryanodine decreased carbachol-induced contractions in young rats where only heparin inhibited these contractions in olds. Caffeine-induced contractions but not inositol triphosphate (IP3)-induced contractions were decreased in old group compared to youngs. The cumulative calcium response curves (pCa 8-4) were also decreased in old rats. Carbachol-induced calcium sensitization responses did not alter by age where GTP-β-S and GF-109203X but not Y-27632 inhibited these responses. Carbachol-induced contractions decrease with aging in rat bladder detrusor. It can be postulated as IP3-induced calcium release (IICR) is primarily responsible for the contractions in older rats where the decrease in carbachol contractions in aging may be as a result of a decrease in calcium-induced calcium release (CICR), rather than carbachol-induced calcium sensitization.

Pioneering drugs for overactive bladder and detrusor overactivity: Ongoing research and future directions

The ongoing research on pioneering drug candidates for the overactive bladder (OAB) aimed to overcome the limitations of currently licensed pharmacotherapies, such as antimuscarinics, β3-adrenergic agents, and botulinum neurotoxin, has been reviewed performing a systematic literature review and web search. The review covers the exploratory agents alternative to available medications for OAB and that may ultimately prove to be therapeutically useful in the future management of OAB patients based on preclinical and early clinical data. It emerges that many alternative pharmacological strategies have been discovered or are under investigation in disease-oriented studies. Several potential therapeutics are known for years but still find obstacles to pass the clinical stages of development, while other completely novel compounds, targeting new pharmacological targets, have been recently discovered and show potential to translate into clinical therapeutic agents for idiopathic and neurogenic OAB syndrome. The global scenario of investigational drugs for OAB gives promise for the development of innovative therapeutics that may ultimately prove effective as first, combined or second-line treatments within a realistic timescale of ten years.

ATP as a cotransmitter in the autonomic nervous system

The role of adenosine 5'-triphosphate (ATP) as a major intracellular energy source is well-established. In addition, ATP and related nucleotides have widespread extracellular actions via the ionotropic P2X (ligand-gated cation channels) and metabotropic P2Y (G protein-coupled) receptors. Numerous experimental techniques, including myography, electrophysiology and biochemical measurement of neurotransmitter release, have been used to show that ATP has several major roles as a neurotransmitter in peripheral nerves. When released from enteric nerves of the gastrointestinal tract it acts as an inhibitory neurotransmitter, mediating descending muscle relaxation during peristalsis. ATP is also an excitatory cotransmitter in autonomic nerves; 1) It is costored with noradrenaline in synaptic vesicles in postganglionic sympathetic nerves innervating smooth muscle preparations, such as the vas deferens and most arteries. When coreleased with noradrenaline, ATP acts at postjunctional P2X1 receptors to evoke depolarisation, Ca(2+) influx, Ca(2+) sensitisation and contraction. 2) ATP is also coreleased with acetylcholine from postganglionic parasympathetic nerves innervating the urinary bladder and again acts at postjunctional P2X1 receptors, and possibly also a P2X1+4 heteromer, to elicit smooth muscle contraction. In both cases the neurotransmitter actions of ATP are terminated by dephosphorylation by extracellular, membrane-bound enzymes and soluble nucleotidases released from postganglionic nerves. There are indications of an increased contribution of ATP to control of blood pressure in hypertension, but further research is needed to clarify this possibility. More promising is the upregulation of P2X receptors in dysfunctional bladder, including interstitial cystitis, idiopathic detrusor instability and overactive bladder syndrome. Consequently, these roles of ATP are of great therapeutic interest and are increasingly being targeted by pharmaceutical companies.

Proteomic profile of an acute partial bladder outlet obstruction

INTRODUCTION

Partial bladder outlet obstruction (pBOO) is a ubiquitous problem in urology. From posterior urethral valves to prostatic hypertrophy, pBOO results in significant morbidity and mortality. However, the pathophysiology is not completely understood. Proteomics uses mass spectrometry to accurately quantify change in tissue protein concentration. Therefore, we have applied proteomic analysis to a rodent model to assess for protein changes after a surgically induced pBOO. We hypothesize that proteomic analysis after an acute obstruction will determine the most prevalent initial protein response and, potentially, novel molecular pathways.

METHODS

Sprague Dawley rats underwent a surgically induced pBOO (n = 3 per group) for 3, 7, or 14 days. Bladders were assessed for weight and urodynamic parameters. Proteomics used liquid-chromatography based mass spectrometry. Polymerase chain reaction (PCR) was performed on tissue samples to confirm increased mRNA transcription.

RESULTS

Bladder weight and capacity increased over the experimental period, but no changes were seen in bladder pressure. Statistically significant increases in protein quantities were seen in 3 proteins related to endoplasmic reticulum stress: GRP-78 (3.66-fold), RhoA (1.90-fold), and RhoA-GDP (1.95-fold), and 2 cytoskeleton molecules: actin (1.7-fold) and tubulin a/b (3.01-fold). Decorin and lumican, members of the small leucine rich proteoglycan (SLRP) family, were also elevated (0.35- and 0.34-fold, respectively). Real-time PCR data confirmed protein elevation.

CONCLUSION

Our experiment confirms that molecular changes occur very soon after the initiation of pBOO, and implicates several molecular pathways. We believe these insights may provide insight into novel prevention and treatment strategies targeted at the pathophysiology of pBOO.

Protective Effect and Mechanism of Total Flavones from Rhododendron simsii Planch Flower on Cultured Rat Cardiomyocytes with Anoxia and Reoxygenation

Many flavonoids have cardioprotection against myocardial ischemia/reperfusion (I/R) injury. Total flavones from Rhododendron simsii Planch flower (TFR) can protect myocardial ischemic injuries. However, its protective mechanism is still unknown. The present study was designed to investigate the mechanism of TFR on myocardial I/R and anoxia/reoxygenation (A/R) injuries. Rat model of myocardial I/R injury was made, and myocardial infarction was determined. A/R injury was induced in cultured rat cardiomyocytes; cellular damage was evaluated by measuring cell viability, LDH and cTnT releases, and MDA content. Expressions of ROCK₁ and ROCK₂ protein were examined by Western blot analysis, and K⁺ currents were recorded by using whole-cell patch clamp technique. TFR 20~80 mg/kg markedly reduced I/R-induced myocardial infarction. TFR 3.7~300 mg/L significantly inhibited A/R-induced reduction of cell viability, LDH and cTnT releases, and MDA production. Exposure to A/R significantly increased ROCK₁ and ROCK₂ expressions in rat cardiomyocytes, but TFR 33.3~300 mg/L obviously inhibited this increase. 300 mg/L TFR significantly augmented inward rectifier K⁺ current and other K⁺ currents in rat cardiomyocytes. These results indicate that TFR has a protective effect on rat cardiomyocytes A/R damage, and the protective mechanism may be engaged with the inhibition of ROCK₁ and ROCK₂ and activation of K⁺ channels.

Rho-kinase as a therapeutic target in vascular diseases: striking nitric oxide signaling

Rho GTPases are a globular, monomeric group of small signaling G-protein molecules. Rho-associated protein kinase/Rho-kinase (ROCK) is a downstream effector protein of the Rho GTPase. Rho-kinases are the potential therapeutic targets in the treatment of cardiovascular diseases. Here, we have primarily discussed the intriguing roles of ROCK in cardiovascular health in relation to nitric oxide signaling. Further, we highlighted the biphasic effects of Y-27632, a ROCK inhibitor under shear stress, which acts as an agonist of nitric oxide production in endothelial cells. The biphasic effects of this inhibitor raised the question of safety of the drug usage in treating cardiovascular diseases.

Tadalafil effect on metabolic syndrome-associated bladder alterations: an experimental study in a rabbit model

INTRODUCTION

Metabolic syndrome (MetS) and lower urinary tract symptoms (LUTS) are often associated. Bladder detrusor hyper-contractility-a major LUTS determinant-is characterized by increased Ras homolog gene family, member A/Rho-associated protein kinase (RhoA/ROCK) signaling, which is often upregulated in MetS.

AIM

This study investigated the effects of tadalafil dosing on RhoA/ROCK signaling in bladder, in a rabbit model of high-fat diet (HFD)-induced MetS.

METHODS

Adult male rabbits feeding a HFD for 12 weeks. A subset of HFD animals was treated with tadalafil (2 mg/kg/day, 1 week: the last of the 12 weeks) and compared with HFD and control (feeding a regular diet) rabbits.

MAIN OUTCOME MEASURES

In vitro contractility studies to evaluate the relaxant effect of the selective ROCK inhibitor, Y-27632, in carbachol precontracted bladder strips. Evaluation of RhoA activation by its membrane translocation. Immunohistochemistry for ROCK expression has been performed to evaluate ROCK expression in bladder from the different experimental groups. mRNA expression of inflammation, pro-fibrotic markers by quantitative RT-PCR has been performed to evaluate the effect of tadalafil on MetS-induced inflammation and fibrosis within the bladder. The in vitro effect of tadalafil on RhoA/ROCK signaling in bladder smooth muscle cells was evaluated by using chemotaxis assay.

RESULTS

Bladder strips from HFD rabbits showed hyper-responsiveness to Y-27632, indicating RhoA/ROCK overactivity in HFD bladder compared with matched controls. Accordingly, the fraction of activated (translocated to the membrane) RhoA as well as ROCK expression are increased in HFD bladder. Tadalafil dosing normalized HFD-induced bladder hypersensitivity to Y-27632, by reducing RhoA membrane translocation and ROCK overexpression. Tadalafil dosing reduced mRNA expression of inflammatory, pro-fibrotic, and hypoxia markers. A direct inhibitory effect of tadalafil on RhoA/ROCK signaling in bladder smooth muscle cell was demonstrated by using chemotaxis assay. Pre-treatment with tadalafil inhibited both basal and PDGF-induced migration of bladder smooth muscle cells.

CONCLUSIONS

Tadalafil dosing reduced RhoA/ROCK signaling and smooth muscle overactivity in an animal model of MetS-associated bladder alterations. Our findings suggest a novel mechanism of action of tadalafil in alleviating LUTS in MetS patients.

Tachykinins and their receptors: contributions to physiological control and the mechanisms of disease

The tachykinins, exemplified by substance P, are one of the most intensively studied neuropeptide families. They comprise a series of structurally related peptides that derive from alternate processing of three Tac genes and are expressed throughout the nervous and immune systems. Tachykinins interact with three neurokinin G protein-coupled receptors. The signaling, trafficking, and regulation of neurokinin receptors have also been topics of intense study. Tachykinins participate in important physiological processes in the nervous, immune, gastrointestinal, respiratory, urogenital, and dermal systems, including inflammation, nociception, smooth muscle contractility, epithelial secretion, and proliferation. They contribute to multiple diseases processes, including acute and chronic inflammation and pain, fibrosis, affective and addictive disorders, functional disorders of the intestine and urinary bladder, infection, and cancer. Neurokinin receptor antagonists are selective, potent, and show efficacy in models of disease. In clinical trials there is a singular success: neurokinin 1 receptor antagonists to treat nausea and vomiting. New information about the involvement of tachykinins in infection, fibrosis, and pruritus justifies further trials. A deeper understanding of disease mechanisms is required for the development of more predictive experimental models, and for the design and interpretation of clinical trials. Knowledge of neurokinin receptor structure, and the development of targeting strategies to disrupt disease-relevant subcellular signaling of neurokinin receptors, may refine the next generation of neurokinin receptor antagonists.

Age-dependent contribution of Rho kinase in carbachol-induced contraction of human detrusor smooth muscle in vitro

AIM

Activation of muscarinic receptors on the detrusor smooth muscle is followed by contraction, which involves both myosin light chain kinase (MLCK) and Rho kinase (ROCK). The aim of this study was to determine the relative contributions of MLCK and ROCK to carbachol-induced contraction of human detrusor smooth muscle in vitro.

METHODS

Detrusor smooth muscle strips were prepared from the macroscopically unaffected bladder wall of patients underwent cystectomy. The strips were fixed in an organ bath, and carbachol or KCl-induced isometric contractions were measured by force transducers.

RESULTS

Addition of carbachol (0.4-4 μmol/L) into the bath induced concentration-dependent contractions of detrusor specimens, which was completely abolished by atropine (1 μmol/L). Pre-incubation of detrusor specimens with either the MLCK inhibitor ML-9 or the ROCK inhibitors HA1100 and Y-27632 (each at 10 μmol/L) significantly blocked carbachol-induced contractions as compared to the time-control experiments. Moreover, MLCK and ROCK inhibition were equally effective in reducing carbachol-induced contractions. The residual carbachol-induced contractions in the presence of both MLCK and ROCK inhibitors were significantly smaller than the contractions obtained when only one enzyme (either MLCK or ROCK) was inhibited, suggesting an additive effect of the two kinases. Interestingly, ROCK-mediated carbachol-induced contractions were positively correlated to the age of patients (r=o.52, P<0.05).

CONCLUSION

Both MLCK and ROCK contribute to carbachol-induced contractions of human detrusor smooth muscle. ROCK inhibitors may be a new pharmacological approach to modulate human bladder hyperactivity.

Coptisine protects rat heart against myocardial ischemia/reperfusion injury by suppressing myocardial apoptosis and inflammation

OBJECTIVE

Protecting the heart from myocardial ischemia and reperfusion (I/R) damage is the focus of intense research. Coptisine is an isoquinoline alkaloid isolated from Coptidis Rhizoma. The present study investigated the potential effect of coptisine on myocardial I/R damage in rats and the underlying mechanisms.

METHODS AND RESULTS

Electrocardiogram examination showed that the administration of coptisine 10 min before ischemia significantly decreased I/R-induced arrhythmia after 30 min ischemia followed by 3 h reperfusion. The release of cardiac markers was also limited. Echocardiography was performed before ischemia and 24 h post-I/R, separately. The M-mode records showed that the reductions of ejection fraction (EF) and fractional shortening (FS) were attenuated in coptisine-treated rats compared with the I/R rats. Similar results were obtained with Evans Blue/triphenyl tetrazolium chloride (TTC) staining, in which coptisine notably reduced infarct size. Moreover, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay demonstrated coptisine suppressed myocardial apoptosis, which may be related to the upregulation of Bcl-2 protein and inhibition of caspase-3 activation. Coptisine treatment also attenuated the proinflammatory cytokines including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in heart tissue. Additionally, Western blot and immunohistochemical analysis showed that coptisine markedly reduced Rho, Rho-kinase 1 (ROCK1), and ROCK2 expression and attenuated the phosphorylation of myosin phosphatase targeting subunit-1, a downstream target of ROCK.

CONCLUSIONS

Coptisine exerts pronounced cardioprotection in rats subjected to myocardial I/R likely through suppressing myocardial apoptosis and inflammation by inhibiting the Rho/ROCK pathway.

Acute Rho-kinase inhibition improves coronary dysfunction in vivo, in the early diabetic microcirculation

OBJECTIVES

Activation of RhoA/Rho-kinase (ROCK) is increasingly implicated in acute vasospasm and chronic vasoconstriction in major organ systems. Therefore we aimed to ascertain whether an increase in ROCK activity plays a role in the deterioration of coronary vascular function in early stage diabetes.

METHODS

Synchrotron radiation microangiography was used to determine in vivo coronary responses in diabetic (3 weeks post streptozotocin 65 mg/kg ip) and vehicle treated male Sprague-Dawley rats (n = 8 and 6). Changes in vessel number and calibre during vasodilator stimulation before and after blockade of nitric oxide synthase and cyclooxygenase were compared between rats. Acute responses to ROCK inhibitor, fasudil (10 mg/kg iv) was evaluated. Further, perivascular and myocardial fibrosis, arterial intimal thickening were assessed by histology, and capillary density, nitrotyrosine and ROCK1/2 expressions were evaluated by immunohistochemical staining.

RESULTS

Diabetic rats had significantly elevated plasma glucose (P < 0.001 vs control), but did not differ in fibrotic scores, media to lumen ratio, capillary density or baseline visible vessel number or calibre. Responses to acetylcholine and sodium nitroprusside stimulation were similar between groups. However, in comparison to control rats the diabetic rats showed more segmental constrictions during blockade, which were not completely alleviated by acetylcholine, but were alleviated by fasudil. Further, second order vessel branches in diabetic rats were significantly more dilated relative to baseline (37% vs 12% increase, P < 0.05) after fasudil treatment compared to control rats, while visible vessel number increased in both groups. ROCK2 expression was borderline greater in diabetic rat hearts (P < 0.053).

CONCLUSIONS

We found that ahead of the reported decline in coronary endothelial vasodilator function in diabetic rats there was moderate elevation in ROCK expression, more widespread segmental constriction when nitric oxide and prostacyclin production were inhibited and notably, increased calibre in second and third order small arteries-arterioles following ROCK inhibition. Based on nitrotyrosine staining oxidative stress was not significantly elevated in early diabetic rats. We conclude that tonic ROCK mediated vasoconstriction contributes to coronary vasomotor tone in early diabetes.

PDE5-Is for the Treatment of Concomitant ED and LUTS/BPH

Epidemiologic data in adult men exhibit a strong relationship between erectile dysfunction (ED) and lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH), indicating that men affected by ED should also be investigated for LUTS/BPH and those presenting with storage or voiding LUTS should be investigated for co-morbid ED. Common pathophysiolgical mechanisms underlying both LUTS/BPH and ED, including alteration of NO/cGMP or RhoA/Rho-kinase signaling and/or vascular or neurogenic dysfunction, are potential targets for proposed phosphodiesterase type 5 inhibitors (PDE5-Is). Several randomized controlled trials and only a few reviews including all commercially available PDE5-Is demonstrated the safety and efficacy of these drugs in the improvement of erectile function and urinary symptoms, in patients affected either by ED, LUTS, or both conditions.

Cyclic guanosine monophosphate-enhancing reduces androgenic extracellular regulated protein kinases-phosphorylation/Rho kinase II-activation in benign prostate hyperplasia

OBJECTIVES

To investigate whether 7-[2-[4-(2-chlorophenyl) piperazinyl] ethyl]-1,3-di-methylxanthine (KMUP-1) inhibits the effects of testosterone on the development of benign prostatic hyperplasia and sensitizes prostate contraction.

METHODS

A benign prostatic hyperplasia animal model was established by subcutaneous injections of testosterone (3 mg/kg/day, s.c.) for 4 weeks in adult male Sprague-Dawley rats. Animals were divided into six groups: control, testosterone, testosterone with KMUP-1 (2.5, 5 mg/kg/day), sildenafil (5 mg/kg/day) or doxazosin (5 mg/kg/day). After 4 weeks, the animals were killed, and prostate tissues were prepared for isometric tension measurement and western blotting analysis. KMUP-1, Y27632, zaprinast, doxazosin or tamsulosin were used at various concentrations to determine the contractility sensitized by phenylephrine (10 μmol/L).

RESULTS

KMUP-1 inhibited testosterone-induced phosphorylation of extracellular signal-regulated phosphorylated protein kinase and mitogen-activated protein kinase kinase and Rho kinase-II activation. Sildenafil and doxazosin significantly decreased benign prostatic hyperplasia-induced mitogen-activated protein kinase kinase and Rho kinase-II activation. The decreased expressions of soluble guanylate cyclase α1 was reversed by KMUP-1, doxazosin and sildenafil. Soluble guanylate cyclase β1 and protein kinase G were increased by KMUP-1, doxazosin, and sildenafil in the testosterone-treated benign prostatic hyperplasia group. Phosphodiesterase-5A was increased by testosterone and inhibited by KMUP-1 (5 mg/kg/day) or sildenafil (5 mg/kg/day). KMUP-1 inhibited phenylephrine-sensitized prostate contraction of rats treated with testosterone.

CONCLUSIONS

Mitogen-activated protein kinase 1/extracellular regulated protein kinases kinase, soluble guanylate cyclase/cyclic guanosine monophosphate, protein kinase/protein kinase G and Rho kinase-II are related to prostate smooth muscle tone and proliferation induced by testosterone. KMUP-1 inhibits testosterone-induced prostate hyper-contractility and mitogen-activated protein kinase 1/extracellular regulated protein kinases kinase-phosphorylation, and it inactivates Rho kinase-II by cyclic guanosine monophosphate, protein kinase and α1A-adenergic blockade. Thus, KMUP-1 might be a beneficial pharmacotherapy for benign prostatic hyperplasia.

Effects of vitamin D analog on bladder function and sensory signaling in animal models of cystitis

OBJECTIVE

To measure the effects of nonhypercalcemic vitamin D receptor agonist elocalcitol on bladder function in rats with cyclophosphamide-induced cystitis and on bladder function and sensory nerve activity in a mouse with acetic acid-evoked bladder irritation.

MATERIALS AND METHODS

Female Wistar rats and male Balb/C mice were gavaged once daily with elocalcitol diluted in miglyol 812 (treatment group) or miglyol alone (control group). On experimental day 12, polyethylene tubing was implanted into the urinary bladder in all the animals. In the mice, a bipolar electrode was positioned under a single postganglionic bladder nerve. At 48 hours after surgery, bladder function was measured in awake, freely moving rats during bladder filling with 0.9% NaCl and both bladder function and sensory nerve activity was measured in awake, restrained mice during continuous intravesical infusion of 0.9% NaCl followed by 0.25% acetic acid.

RESULTS

In rats, the treatment group showed a significant increase in bladder capacity and decrease in number of nonvoiding bladder contractions. In mice, the filling pressure during saline infusion was similar in both groups; however, during acetic acid infusion, the average filling pressure was significantly increased (47%) in the control group but not in the elocalcitol treatment group. The firing rate at filling pressure for the treatment group was 3.6-fold and 2.7-fold lower than that in the control group during the saline and acetic acid infusion, respectively.

CONCLUSION

Oral treatment with elocalcitol suppressed signs of detrusor overactivity in both animal models and exerted strong suppressive effect on urinary bladder sensory signaling during filling in mice.

Effects of the Rho kinase inhibitor, hydroxyfasudil, on bladder dysfunction and inflammation in rats with HCl-induced cystitis

OBJECTIVE

To evaluate the effect of the Rho kinase inhibitor, hydroxyfasudil, on bladder function in a rat model of HCl-induced chemical cystitis, and to elucidate the possible mechanisms associated with its therapeutic effect.

METHODS

Female Sprague-Dawley rats with HCl-induced cystitis were given hydroxyfasudil (10 mg/kg, i.p.) for 7 days. Treatment efficacy was determined by comparing bladder function and histopathology to sham and untreated control rats. Bladder function was determined by cystometric analysis. Rho kinase activity was determined by quantitative reverse transcription polymerase chain reaction and signal inhibition of downstream Ras homolog member A/Rho kinase signaling molecules by western blot and immunohistochemistry.

RESULTS

Treatment with hydroxyfasudil significantly improved bladder intercontraction intervals. Rats treated with hydroxyfasudil also showed a significant reduction of histopathological features associated with cystitis. Western blot and immunohistochemistry findings showed that hydroxyfasudil inhibited downstream molecules of Rho kinase that ameliorated changes associated with HCl-induced chemical cystitis, such as inflammatory cell recruitment and smooth muscle cell proliferation.

CONCLUSION

The findings from the present study suggest a promising therapeutic role for hydroxyfasudil in bladder inflammation associated with cystitis.

Autonomic nervous control of the urinary bladder

The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β(3) -adrenoceptors in the detrusor and on α(1) (A) -adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M(3) receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non-neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post-junctional smooth muscle level until now. The implications of such plasticity are being discussed.

Sensory dysfunction of bladder mucosa and bladder oversensitivity in a rat model of metabolic syndrome

Purpose

To study the role of sensory dysfunction of bladder mucosa in bladder oversensitivity of rats with metabolic syndrome.

Materials and Methods

Female Wistar rats were fed a fructose-rich diet (60%) or a normal diet for 3 months. Based on cystometry, the fructose-fed rats (FFRs) were divided into a group with normal detrusor function or detrusor overactivity (DO). Acidic adenosine triphosphate (ATP) solution (5mM, pH 3.3) was used to elicit reflex micturition. Cystometric parameters were evaluated before and after drug administration. Functional proteins of the bladder mucosa were assessed by western blotting.

Results

Compared to the controls, intravesical acidic ATP solution instillation induced a significant increase in provoked phasic contractions in both FFR groups and a significant decrease in the mean functional bladder capacity of group DO. Pretreatment with capsaicin for C-fiber desentization, intravesical liposome for mucosal protection, or intravenous pyridoxal 5-phosphate 6-azophenyl-2′,4′-disulfonic acid for antagonized purinergic receptors can interfere with the urodynamic effects of intravesical ATP in FFRs and controls. Over-expression of TRPV1, P2X₃, and iNOS proteins, and down-regulation of eNOS proteins were observed in the bladder mucosa of both fructose-fed groups.

Conclusions

Alterations of sensory receptors and enzymes in the bladder mucosa, including over-expression of TRPV1, P2X₃, and iNOS proteins, can precipitate the emergence of bladder phasic contractions and oversensitivity through the activation of C-afferents during acidic ATP solution stimulation in FFRs. The down-regulation of eNOS protein in the bladder mucosa of FFRs may lead to a failure to suppress bladder oversensitivity and phasic contractions. Sensory dysfunction of bladder mucosa and DO causing by metabolic syndrome are easier to elicit bladder oversensitivity to certain urothelium stimuli.

Distinct distribution and localization of Rho-kinase in mouse epithelial, muscle and neural tissues

The small GTP-binding protein Rho plays a crucial role in a wide variety of cellular functions through various effector proteins. Rho-kinase is a key effector protein of Rho, which is composed of two isoforms, ROCK1 and ROCK2. To clarify the site of action of ROCK1 and ROCK2, we performed immunofluorescence and immunoelectron microscopic analyses using isoform-specific antibodies in mouse tissues. In the large and small intestines, ROCK1 immunoreactivity was predominantly identified in epithelial cells, and ROCK2 immunoreactivity was negligible. In these epithelial cells, ROCK1 immunoreactivity was distributed on plasma membranes, while ROCK1 immunogold signals were localized at cell-cell contacts and cell adhesion sites, especially at the adherens junctions at the ultrastructural level. In the bladder epithelium, however, ROCK1 and ROCK2 signals were identified at intermediate filaments, and ROCK2 signals were also observed in nuclei. In the three types of muscular cells-smooth, cardiac, and skeletal muscle cells-ROCK1 and ROCK2 also showed differential distribution. ROCK1 signals were localized at actin filaments, plasma membranes, and vesicles near plasma membranes in smooth muscle cells; at the lysosomes in skeletal muscle cells; and were undetectable in cardiac muscle cells. ROCK2 signals were localized at actin filaments and centrosomes in smooth muscle cells, at intercalated discs in cardiac muscle cells, and at Z-discs and sarcoplasmic reticulum in skeletal muscle cells. In the brain, ROCK1 immunoreactivity was distributed in glia, whereas ROCK2 immunoreactivity was observed in neurons. These results indicate that the two isoforms of Rho-kinase distribute differentially to accomplish their specific functions.

The effect of hypercholesterolemia on carbachol-induced contractions of the detrusor smooth muscle in rats: increased role of L-type Ca2+ channels

To investigate a possible relation between hypercholesterolemia and detrusor smooth muscle function, we studied the contractile response to potassium challenge, carbachol (CCh), and the components of CCh-induced contractile mechanism in high-cholesterol diet-fed rats. Adult male Sprague-Dawley rats were fed with standard (control group, N = 17) or 4 % cholesterol diet (hypercholesterolemia group (HC), N = 16) for 4 weeks. Spontaneous contractions of detrusor muscle strips and their responses to potassium chloride (KCl) or cumulative dose-contraction curves to CCh were recorded. The effects of muscarinic receptor antagonists (methoctramin and/or 4-diphenylacetoxy-N-methylpiperidine), L-type Ca(+2) channel blocker (nifedipine), and/or rho-kinase inhibitor Y-27632 were investigated. Blood cholesterol level was increased in the HC group with no sign of atherosclerosis. The KCl-induced detrusor smooth muscle contractions were higher in HC, whereas spontaneous and CCh-induced responses were similar in both groups. Preincubation with receptor antagonist for M(3) but not for M(2) attenuated contraction significantly, shifting the dose-response curve to the right. This response was similar in both groups. Among two effector mechanisms of M(3)-mediated detrusor smooth muscle contraction, rho-kinase pathway was not affected by hypercholesterolemia, whereas blockade of L-type Ca(+2) channels potently reduced contractions. The results of this study point out a relation between hypercholesterolemia and contractile mechanism of detrusor smooth muscle likely to change urinary bladder function, via altering L-type Ca(+2) channels. Taken together with escalating incidence of hypercholesterolemia and lower urinary tract symptoms, it is a field which deserves to be investigated further.

Contractile responses of isolated equine digital arteries under hypoxic or hyperoxic conditions in vitro: role of reactive oxygen species and Rho kinase

The underlying pathophysiological triggers for equine acute laminitis are unknown, although digital vasoconstriction, ischaemia, hypoxia and reperfusion injury may be involved. The contractile responses of isolated equine digital arteries (EDAs), harvested from the hindlimbs of normal horses postmortem at an abattoir, were studied acutely (up to 3 h) under hyperoxic (95% oxygen, 5% CO2 ) and hypoxic (95% nitrogen, 5% CO2 ) conditions in organ baths. Phenylephrine (PHE; 10(-6) m), 5-hydroxytryptamine (5-HT; 10(-7) m) and high potassium (K(+) ; 118 mm) caused contraction in EDAs which was significantly (P<0.0001) enhanced under hypoxic conditions. In contrast, contraction stimulated by 9,11-dideoxy-9α,11α-epoxymethanoprostaglandin F2α (U44069; 3 × 10(-8) m) was not significantly enhanced by hypoxia (P=0.75). Hypoxia-enhanced contraction in response to K(+) was greater (P<0.03) in vessels with a functional endothelium than in vessels in which the endothelium was removed by rubbing. Fasudil (10(-6) to 10(-5) m), a Rho kinase inhibitor, and apocynin (10(-3) to 3 × 10(-3) m), an NADPH oxidase inhibitor, significantly (P ≤ 0.05) inhibited hypoxia-enhanced contraction in response to PHE and 5-HT. In conclusion, hypoxia-enhanced contraction occurred in EDAs. This appears to be partially mediated by reactive oxygen species produced by NAPDH oxidase, which activate Rho kinase to increase calcium sensitisation and enhance smooth muscle contraction.