Expression of RhoA mRNA and activated RhoA in urothelium and smooth muscle, and effects of a rho-kinase inhibitor on contraction of the porcine urinary 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.

Deleterious impact of nerve growth factor precursor (proNGF) on bladder urothelial and smooth muscle cells

The nerve growth factor precursor (proNGF) activates p75^NTR receptor and promotes cell death in different tissues, yet this pathophysiological effect is not fully described in the bladder. The aim of this study was to identify the biological effect of proNGF/p75^NTR activation on urothelial and smooth muscle (SM) cells of rodents' bladder. Cell viability was assessed by MTT assay which showed a significant reduction in urothelial viability after 24 h of incubation with proNGF in culture medium [5 or 10 nM], an effect not seen in SM cells. Western blot analysis on cellular protein extracts showed increased expression of the transmembrane TNF-α and activation of RhoA in urothelial cells exposed to proNGF with no evidence of a nuclear translocation of NF-κB assessed by western blotting on nuclear extracts and immunofluorescence. The activation of p75^NTR-death domain related pathways in urothelial cells such as TNF-α or RhoA had a downstream effect on NO release and the junctional protein occludin, as estimated respectively by colorimetric and western blotting. On the other hand, proNGF did not induce TNF-α or RhoA expression in SM cells, but induced a significant NF-κB nuclear translocation. ProNGF had a different impact on SM as evidenced by a significant dose- and time-dependent increase in SM proliferation and migration examined by MTT test and cell migration assay. Together, our results indicate that activation of proNGF/p75^NTR axis induces degenerative changes to the urothelial layer impacting its barrier and signaling integrity, while promoting adaptive proliferative changes in detrusor SM cells that can interfere with the contractile phenotype essential for proper bladder function.

Effects of hypoxia and glucose-removal condition on muscle contraction of the smooth muscles of porcine urinary bladder

To elucidate the dependence of aerobic energy metabolism and utilization of glucose in contraction of urinary bladder smooth muscle, we investigated the changes in the reduced pyridine nucleotide (PNred) fluorescence, representing glycolysis activity, and determined the phosphocreatine (PCr) and ATP contents of the porcine urinary bladder during contractions induced by high K⁺ or carbachol (CCh) and with and without hypoxia (achieved by bubbling N₂ instead of O₂) or in a glucose-free condition. Hyperosmotic addition of 65 mM KCl (H-65K⁺) and 1 µM CCh induced a phasic contraction followed by a tonic contraction. A glucose-free physiological salt solution (PSS) did not change the subsequent contractile responses to H-65K⁺ and CCh. However, hypoxia significantly attenuated H-65K⁺- and CCh-induced contraction. H-65K⁺ and CCh induced a sustained increase in PNred fluorescence, representing glycolysis activity. Hypoxia enhanced H-65K⁺- and CCh-induced increases in PNred fluorescence, whereas glucose-free PSS decreased these increases, significantly. In the presence of H-65K⁺, hypoxia decreased the PCr and ATP contents; however, the glucose-free PSS did not change the PCr contents. In conclusion, we demonstrated that high K⁺- and CCh-induced contractions depend on aerobic metabolism and that an endogenous substrate may be utilized to maintain muscle contraction in a glucose-free PSS in the porcine urinary bladder.

Pre- and post-junctional bradykinin B2 receptors regulate smooth muscle tension to the pig intravesical ureter

AIMS

Neuronal and non-neuronal bradykinin (BK) receptors regulate the contractility of the bladder urine outflow region. The current study investigates the role of BK receptors in the regulation of the smooth muscle contractility of the pig intravesical ureter.

METHODS

Western blot and immunohistochemistry were used to show the expression of BK B1 and B2 receptors and myographs for isometric force recordings.

RESULTS

B2 receptor expression was consistently detected in the intravesical ureter urothelium and smooth muscle layer, B1 expression was not detected where a strong B2 immunoreactivity was observed within nerve fibers among smooth muscle bundles. On ureteral strips basal tone, BK induced concentration-dependent contractions, were potently reduced by extracellular Ca(2+) removal and by B2 receptor and voltage-gated Ca(2+) (VOC) channel blockade. BK contraction did not change as a consequence of urothelium mechanical removal or cyclooxygenase and Rho-associated protein kinase inhibition. On 9,11-dideoxy-9a,11a-methanoepoxy prostaglandin F2α (U46619)-precontracted samples, under non-adrenergic non-cholinergic (NANC) and nitric oxide (NO)-independent NANC conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. Kallidin, a B1 receptor agonist, failed to increase preparation basal tension or to induce relaxation on U46619-induced tone.

CONCLUSIONS

The present results suggest that BK produces contraction of pig intravesical ureter via smooth muscle B2 receptors coupled to extracellular Ca(2+) entry mainly via VOC (L-type) channels. Facilitatory neuronal B2 receptors modulating NO-dependent or independent NANC inhibitory neurotransmission are also demonstrated.

The Rho-kinase inhibitor HA-1077 suppresses proliferation/migration and induces apoptosis of urothelial cancer cells

Background

Activation of Rho, one of the small GTPases, and its major downstream target Rho-kinase (ROCK) promotes the development and metastasis of cancer. We previously showed that elevation of Rho and ROCK expression was associated with tumor invasion, metastasis, and an unfavorable prognosis in patients with urothelial cancer of the bladder or upper urinary tract.

Methods

We investigated the effects of a ROCK inhibitor on the growth, migration, and apoptosis of bladder cancer cells. We also examined phosphorylation of RhoA (RhoA activity) by measuring its GTP-bound active form and assessed the expression of ROCK to explore the underlying molecular mechanisms.

Results

Lysophosphatidic acid (LPA) and geranylgeraniol (GGOH) induced an increase of cell proliferation and migration in association with promotion of RhoA activity and upregulation of ROCK expression. The ROCK inhibitor fasudil (HA-1077) suppressed cell proliferation and migration, and also induced apoptosis in a dose-dependent manner. HA-1077 dramatically suppressed the expression of ROCK-I and ROCK-II, but did not affect RhoA activity.

Conclusions

These findings suggest that ROCK could be a potential molecular target for the treatment of urothelial cancer.

Sickling cells, cyclic nucleotides, and protein kinases: the pathophysiology of urogenital disorders in sickle cell anemia

Sickle cell anemia is one of the best studied inherited diseases, and despite being caused by a single point mutation in the HBB gene, multiple pleiotropic effects of the abnormal hemoglobin S production range from vaso-occlusive crisis, stroke, and pulmonary hypertension to osteonecrosis and leg ulcers. Urogenital function is not spared, and although priapism is most frequently remembered, other related clinical manifestations have been described, such as nocturia, enuresis, increased frequence of lower urinary tract infections, urinary incontinence, hypogonadism, and testicular infarction. Studies on sickle cell vaso-occlusion and priapism using both in vitro and in vivo models have shed light on the pathogenesis of some of these events. The authors review what is known about the deleterious effects of sickling on the genitourinary tract and how the role of cyclic nucleotides signaling and protein kinases may help understand the pathophysiology underlying these manifestations and develop novel therapies in the setting of urogenital disorders in sickle cell disease.

Increased alpha-taxilin protein expression is associated with the metastatic and invasive potential of renal cell cancer

Intracellular vesicle trafficking is the principal transportation system in eukaryotic cells, and is considered to be involved in a variety of processes related to cell proliferation. A protein named alpha-taxilin has been identified as a binding partner of the syntaxin family, which coordinates intracellular vesicle trafficking. To clarify the role of alpha-taxilin in renal cell carcinoma (RCC), we investigated alpha-taxilin protein expression in clear cell RCC tissues. We analyzed alphataxilin protein in matched sets of tumor and non-tumor tissues from the surgical specimens of 52 Japanese RCC patients by Western blotting. We also studied the relation between alpha-taxilin protein expression in tumor tissues and various clinicopathological features. The alpha-taxilin protein level was higher in tumor tissues than in non-tumor tissues (P < 0.05). Increased expression of alpha-taxilin protein in primary tumors was related to local invasion (P < 0.001), pathological vessel invasion (P < 0.001), and metastasis (P < 0.0001). Kaplan-Meier plots of survival for patients with low versus high alpha-taxilin expression revealed that high expression in tumor tissues was associated with shorter overall survival in all patients (P < 0.05) and with shorter disease-free survival in patients without metastasis (P < 0.01). These findings suggest that alpha-taxilin influences the metastatic and invasive potential of RCC.

Rho-kinase, a common final path of various contractile bladder and ureter stimuli

Normal urinary bladder function is based on the proper contraction and relaxation of smooth muscle (SM), which constitutes the majority of the bladder wall. The contraction and relaxation of all SM involves a phosphorylation-dephosphorylation pathway involving the enzymes smooth muscle myosin light chain kinase (SMMLCK) and smooth muscle myosin light chain phosphatase (SMMLCP), respectively. Although originally thought to function just as a passive opposition to SMMLCK-driven SM contraction, it is now clear that SMMLCP activity is under an extremely complex molecular regulation via which SMMLCP inhibition can induce "calcium sensitization." This review provides a thorough summary of the literature regarding the molecular regulation of the SMMLCP with a focus on one of its major inhibitory pathways that is RhoA/Rho-kinase (ROK) including its activation pathways, effector molecules, and its roles in various pathological conditions associated with bladder dysfunction. Newly emerging roles of ROK outside of SM contractility are also discussed. It is concluded that the RhoA/ROK pathway is critical for the maintenance of basal SM tone of the urinary bladder and serves as a common final pathway of various contractile stimuli in rabbits, rats, mice, and pigs as well as humans. In addition, this pathway is upregulated in response to a number of pathological conditions associated with bladder SM dysfunction. Similarly, RhoA/Rho-kinase signaling is essential for normal ureteral function and development and is upregulated in response to ureteral outlet obstruction. In addition to its critical role in bladder SM function, a role of ROK in the urothelium is also beginning to emerge as well as roles for ROK in bladder infection and invasion and metastasis of bladder cancer.

Increased Rac1 activity and Pak1 overexpression are associated with lymphovascular invasion and lymph node metastasis of upper urinary tract cancer

Background

Lymphovascular invasion (LVI) and lymph node metastasis are conventional pathological factors associated with an unfavorable prognosis of urothelial carcinoma of the upper urinary tract (UC-UUT), but little is known about the molecular mechanisms underlying LVI and nodal metastasis in this disease. Rac1 small GTPase (Rac1) is essential for tumor metastasis. Activated GTP-bound Rac1 (Rac1 activity) plays a key role in activating downstream effectors known as Pak (21-activated kinase), which are key regulators of cytoskeletal remolding, cell motility, and cell proliferation, and thus have a role in both carcinogenesis and tumor invasion.

Methods

We analyzed Rac1 activity and Pak1 protein expression in matched sets of tumor tissue, non-tumor tissue, and metastatic lymph node tissue obtained from the surgical specimens of 108 Japanese patients with UC-UUT.

Results

Rac1 activity and Pak1 protein levels were higher in tumor tissue and metastatic lymph node tissue than in non-tumor tissue (both P < 0.0001). A high level of Rac1 activity and Pak1 protein expression in the primary tumor was related to poor differentiation (P < 0.05), muscle invasion (P < 0.01), LVI (P < 0.0001), and lymph node metastasis (P < 0.0001). Kaplan-Meier survival analysis showed that an increase of Rac1 activity and Pak1 protein was associated with a shorter disease-free survival time (P < 0.01) and shorter overall survival (P < 0.001). Cox proportional hazards analysis revealed that high Rac1 activity, Pak1 protein expression and LVI were independent prognostic factors for shorter overall and disease-free survival times (P < 0.01) on univariate analysis, although only Pak1 and LVI had an influence (P < 0.05) according to multivariate analysis.

Conclusions

These findings suggest that Rac1 activity and Pak1 are involved in LVI and lymph node metastasis of UC-UUT, and may be prognostic markers for this disease.

Effects of fasudil, a Rho-kinase inhibitor, on contraction of pig bladder tissues with or without urothelium

OBJECTIVES

To investigate the effects of fasudil, a Rho-associated serine-threonine protein kinase inhibitor, on contraction of the pig urinary bladder tissues with or without urothelium.

METHODS

Cumulative concentration-response curves (CRCs) to carbachol were obtained with and without 3-10 microM fasudil. Drug effects were evaluated in detrusor with and without urothelium. Inhibitory responses to fasudil were also examined in tissues precontracted with KCl and carbachol, and in response to electrical field stimulation, in pig bladder with and without urothelium.

RESULTS

In detrusor without urothelium, maximum contraction (E(max)) decreased after administration of fasudil at 3 or 10 micromol/L (both P < 0.01), or 30 micromol/L (72.5 + or - 7.43%, 58.4 + or - 8.04% and 68.4 + or - 9.6%, respectively, of the first curve). In detrusor with urothelium, E(max) decreased significantly (all P < 0.05) after the addition of 3, 10 or 30 micromol/L of fasudil (84.9 + or - 6.7%, 67.9 + or - 5.2% and 35.2 + or - 4.1%, respectively). In tissues precontracted with 80 mmol/L KCl or 100 micromol/L carbachol, tension after administration of fasudil (1 nmol/L to 100 micromol/L) decreased (by approximately 40%), only after administration of fasudil at high concentration (>1 micromol/L), in detrusor both with and without urothelium. In tissues with and without urothelium, responses to electrical field stimulation at 1-50 Hz decreased significantly in a concentration-dependent manner after addition of fasudil (3 to 30 micromol/L).

CONCLUSIONS

Fasudil seems to provoke relaxation of the bladder detrusor via both urothelium-dependent and independent pathways.

Effect of diabetes on cooling-induced detrusor muscle contraction: mediation via Rho-kinase activation

OBJECTIVES

To investigate the possible involvement of Rho-kinase in cooling-induced contraction of the detrusor muscle. The etiology of diabetic cystopathy is not clear. It may be due to various changes in bladder innervation and/or detrusor muscle dysfunction. Because cooling of urinary bladder smooth muscle normally is a potent stimulus to micturition due to increase in muscle tone, we studied the effects of cooling on normal and diabetic bladder specimens.

METHODS

Urinary detrusor muscle strips isolated from rats were suspended in organ baths containing Krebs solution for isometric tension recording. Tissue responses to stepwise cooling were examined from normal and 12-week streptozocin-induced diabetic rats. We examined the effects of calcium-free, ethylene glycol bis (beta-aminoethylether)-N,N,N,N,-tetraacetic acid (1 mm)-containing Krebs solution, and the Rho-kinase inhibitor Y-27632 on the cooling responses.

RESULTS

Stepwise cooling from 37 degrees C to 5 degrees C induced a rapid and reproducible increase in basal tone, proportional to cooling temperature. This response was more pronounced in diabetic specimens. Cooling-induced contractions were significantly inhibited in calcium-free solutions in both control and diabetic bladders. Our investigation showed that the influx of extracellular calcium is important in inducing the cooling response. The Rho-kinase inhibitor Y-27632 (1 microm) inhibited cooling (20 degrees C)-induced contraction. It reduced the response by 52.1% +/- 10.0% in control and by 70.0% +/- 12.0% in diabetic rats.

CONCLUSIONS

Cooling-induced contractions in control and diabetic detrusor muscle preparations are highly calcium dependant. It also involves activation of Rho-kinase, which might be upregulated in the diabetic detrusor muscle. These results may help in the management of diabetes-induced incontinence due to involuntary detrusor muscle activity.

Effect of the rho-kinase inhibitor hydroxyfasudil on bladder overactivity: an experimental rat model

OBJECTIVES

To investigate the effects of the rho-kinase inhibitor hydroxyfasudil on bladder overactivity in cyclophosphamide (CYP)-induced cystitis.

METHODS

Female Sprague-Dawley rats received a single intraperitoneal injection of CYP (200 mg/kg). Four days later, bladder function was evaluated by: (i) monitoring micturition behavior in metabolic cages between hydroxyfasudil- and vehicle-treated animals; (ii) measuring changes in continuous cystometrograms in response to intravenous hydroxyfasudil under anesthesia; and (iii) conducting a functional study examining the effect of hydroxyfasudil on the concentration-response curves to carbachol in bladder tissue strips.

RESULTS

Intraperitoneal injection of hydroxyfasudil (10 mg/kg) significantly increased both the average and maximal voided volumes. Hydroxyfasudil significantly decreased the maximal detrusor pressure, whereas the intercontraction interval was not significantly affected. After administration of 0.1, 0.3, 1, and 3 microM hydroxyfasudil, the maximal contraction of the concentration-response curves to carbachol was significantly reduced to 74.5 +/- 4.2%, 55.2 +/- 5.6%, 29.4 +/- 5.6%, and 21.6 +/- 8.2% of the control values, respectively.

CONCLUSIONS

The present findings indicate that hydroxyfasudil might be a new treatment option for CYP-induced detrusor overactivity.