Inhibition of prostate smooth muscle contraction and prostate stromal cell growth by the inhibitors of Rac, NSC23766 and EHT1864.

BACKGROUND AND PURPOSE: Medical therapy of lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH) targets smooth muscle contraction in the prostate, or prostate growth. However, current therapeutic options are insufficient. Here, we investigated the role of Rac in the control of smooth muscle tone in human prostates and growth of prostate stromal cells. EXPERIMENTAL APPROACH: Experiments were performed using human prostate tissues from radical prostatectomy and cultured stromal cells (WPMY-1). Expression of Rac was examined by Western blot and fluorescence staining. Effects of Rac inhibitors (NSC23766 and EHT1864) on contractility were assessed in the organ bath. The effects of Rac inhibitors were assessed by pull-down, cytotoxicity using a cell counting kit, cytoskeletal organization by phalloidin staining and cell growth using an 5-ethynyl-2'-deoxyuridine assay. KEY RESULTS: Expression of Rac1-3 was observed in prostate samples from each patient. Immunoreactivity for Rac1-3 was observed in the stroma, where it colocalized with the smooth muscle marker, calponin. NSC23766 and EHT1864 significantly reduced contractions of prostate strips induced by noradrenaline, phenylephrine or electrical field stimulation. NSC23766 and EHT1864 inhibited Rac activity in WPMY-1 cells. Survival of WPMY-1 cells ranged between 64 and 81% after incubation with NSC23766 (50 or 100 µM) or EHT1864 (25 µM) for 24 h. NSC23766 and EHT1864 induced cytoskeletal disorganization in WPMY-1 cells. Both inhibitors impaired the growth of WPMY-1 cells. CONCLUSIONS AND IMPLICATIONS: Rac may be a link connecting the control of prostate smooth muscle tone with proliferation of smooth muscle cells. Improvements in LUTS suggestive of BPH by Rac inhibitors appears possible.

Reduction of obstruction related bladder overactivity by the guanylyl cyclase modulators BAY 41-2272 and BAY 60-2770 alone or in combination with a phosphodiesterase type 5 inhibitor.

AIMS: To assess the urodynamic effects of soluble guanylyl cyclase (sGC) stimulator, BAY 41-2272, and activator, BAY 60-2770, (which both are able to induce cGMP synthesis even in the absence of nitric oxide (NO)) alone or in combination with a phosphodiesterase type 5 (PDE5) inhibitor, vardenafil, in a model of partial urethral obstruction (PUO) induced bladder overactivity (BO). METHODS: Fifty-six male Sprague-Dawley rats were used, 31 of them underwent PUO. Fourteen rats were used for Western blots to assess PDE5 and sGC expression. For drug evaluation cystometry without anesthesia was performed three days following bladder catheterization. RESULTS: Obstructed rats showed higher micturition frequency and bladder pressures than non-obstructed animals (Intermicturition Interval, IMI, 2.28 ± 0.55 vs. 3.60 ± 0.60 min (± standard deviation, SD); maximum micturition pressure, MMP, 70.1 ± 8.0 vs. 48.8 ± 7.2 cmH2O; both P < 0.05). In obstructed rats vardenafil, BAY 41-2272, and BAY 60-2770 increased IMI (2.77 ± 1.12, 2.62 ± 0.52, and 3.22 ± 1.04 min; all P < 0.05) and decreased MMP (54.4 ± 2.8, 61.5 ± 11.3, and 51.2 ± 6.3 cmH2O; all P < 0.05). When vardenafil was given following BAY 41-2272 or BAY 60-2770 no further urodynamic effects were observed. PDE5 as well as sGC protein expression was reduced in obstructed bladder tissue. CONCLUSIONS: Targeting sGC via stimulators or activators, which increase the levels of cGMP independent of endogenous NO, is as effective as vardenafil to reduce urodynamic signs of BO. Targeting the NO/cGMP pathway via compounds acting on sGC might become a new approach to treat BO.

Inhibition of adrenergic human prostate smooth muscle contraction by the inhibitors of c-Jun N-terminal kinase, SP600125 and BI-78D3.

BACKGROUND AND PURPOSE α(1) -Adrenoceptor-induced contraction of prostate smooth muscle is mediated by calcium- and Rho kinase-dependent mechanisms. In addition, other mechanisms, such as activation of c-jun N-terminal kinase (JNK) may be involved. Here, we investigated whether JNK participates in α(1)-adrenoceptor-induced contraction of human prostate smooth muscle. EXPERIMENTAL APPROACH Prostate tissue was obtained from patients undergoing radical prostatectomy. Effects of the JNK inhibitors SP600125 (50 µM) and BI-78D3 (30 µM) on contractions induced by phenylephrine, noradrenaline and electric field stimulation (EFS) were studied in myographic measurements. JNK activation by noradrenaline (30 µM) and phenylephrine (10 µM), and the effects of JNK inhibitors of c-Jun phosphorylation were assessed by Western blot analyses with phospho-specific antibodies. Expression of JNK was studied by immunohistochemistry and fluorescence double staining. KEY RESULTS The JNK inhibitors SP600125 and BI-78D3 reduced phenylephrine- and noradrenaline-induced contractions of human prostate strips. In addition, SP600125 reduced EFS-induced contraction of prostate strips. Stimulation of prostate tissue with noradrenaline or phenylephrine in vitro resulted in activation of JNK. Incubation of prostate tissue with SP600125 or BI-78D3 reduced the phosphorylation state of c-Jun. Immunohistochemical staining demonstrated the expression of JNK in smooth muscle cells of human prostate tissue. Fluorescence staining showed that α(1A)-adrenoceptors and JNK are expressed in the same cells. CONCLUSIONS AND IMPLICATIONS Activation of JNK is involved in α(1)-adrenoceptor-induced prostate smooth muscle contraction. Models of α(1)-adrenoceptor-mediated prostate smooth muscle contraction should include this JNK-dependent mechanism.

Vascular hyporesponsiveness to angiotensin II in rats with CCl(4)-induced liver cirrhosis.

BACKGROUND: Portal hypertension is triggered by vasodilation due to impaired contraction of extrahepatic vessels. Angiotensin II type 1 (AT(1)) receptor-induced vasocontraction is mediated by G proteins and may be desensitized by recruitment of beta-arrestin-2 to the receptor. In this study, we analysed the interaction of AT(1) receptors with beta-arrestin-2 in the context of vascular hypocontractility in rats with CCl(4)-induced cirrhosis. METHODS: Micronodular liver cirrhosis in rats (n = 15) was induced by regular CCl(4) exposure. Age-matched rats (n = 15) served as controls. Contractility of aortic rings was measured by myography. Protein expressions and phosphorylations were assessed by Western blot analysis, and AT(1) receptor interaction with beta-arrestin-2 by co-immunoprecipitation. RESULTS: Aortic rings from CCl(4) rats were hypocontractile to angiotensin II independent of nitric oxide synthases (Nomega-nitro-l-arginine methyl ester 200 microM). Expression of the AT(1) receptor, Galpha(q/11) and the contraction-mediating effector Rho kinase was similar in aortas from both groups. Expression and AT(1) receptor binding of beta-arrestin-2 were up-regulated in aortas from CCl(4) rats. Stimulation of isolated aortas with exogenous angiotensin II caused recruitment of beta-arrestin-2 in aortas from noncirrhotic rats, but no further interaction of AT(1) receptors with beta-arrestin-2 was found in aortas from CCl(4) rats. While angiotensin II stimulation resulted in Rho kinase activation in aortas from noncirrhotic rats but not in aortas from CCl(4) rats, extracellular signal-regulated kinase activation in response to angiotensin II was observed in aortas from both groups. CONCLUSIONS: Vascular hyporesponsiveness to angiotensin II in CCl(4) rats is due to enhanced interaction of the AT(1) receptor with beta-arrestin-2 and consecutively changed receptor function.

Sorafenib targets dysregulated Rho kinase expression and portal hypertension in rats with secondary biliary cirrhosis.

BACKGROUND AND PURPOSE: Extrahepatic vasodilation and increased intrahepatic vascular resistance represent attractive targets for the medical treatment of portal hypertension in liver cirrhosis. In both dysfunctions, dysregulation of the contraction-mediating Rho kinase plays an important role as it contributes to altered vasoconstrictor responsiveness. However, the mechanisms of vascular Rho kinase dysregulation in cirrhosis are insufficiently understood. They possibly involve mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK)-dependent mechanisms in extrahepatic vessels. As the multikinase inhibitor sorafenib inhibits ERK, we tested the effect of sorafenib on haemodynamics and dysregulated vascular Rho kinase in rats with secondary biliary cirrhosis. EXPERIMENTAL APPROACH: Secondary biliary cirrhosis was induced by bile duct ligation (BDL). Sorafenib was given orally for 1 week (60 mg.kg(-1).d(-1)). Messenger RNA levels were determined by quantitative real time polymerase chain reaction, protein expressions and protein phosphorylation by Western blot analysis. Aortic contractility was studied by myographic measurements, and intrahepatic vasoregulation by using livers perfused in situ. In vivo, haemodynamic parameters were assessed invasively in combination with coloured microspheres. KEY RESULTS: In BDL rats, treatment with sorafenib decreased portal pressure, paralleled by decreases in hepatic Rho kinase expression and Rho kinase-mediated intrahepatic vascular resistance. In aortas from BDL rats, sorafenib caused up-regulation of Rho kinase and an improvement of aortic contractility. By contrast, mesenteric Rho kinase remained unaffected by sorafenib. CONCLUSIONS AND IMPLICATIONS: Intrahepatic dysregulation of vascular Rho kinase expression is controlled by sorafenib-sensitive mechanisms in rats with secondary biliary cirrhosis. Thus, sorafenib reduced portal pressure without affecting systemic blood pressure.

Mechanisms of extrahepatic vasodilation in portal hypertension.

In liver cirrhosis, abnormal persistent extrahepatic vasodilation leads to hyperdynamic circulatory dysfunction which essentially contributes to portal hypertension. Since portal hypertension is a major factor in the development of complications in cirrhosis, the mechanisms underlying this vasodilation are of paramount interest. Extensive studies performed in cirrhotic patients and animals revealed that this vasodilation is associated on the one hand with enhanced formation of vasodilators, and on the other hand with vascular hyporesponsiveness to vasoconstrictors. The latter phenomenon has been termed "vascular hypocontractility". It is caused by a combination of different mechanisms and factors described in this review.

Intrahepatic upregulation of RhoA and Rho-kinase signalling contributes to increased hepatic vascular resistance in rats with secondary biliary cirrhosis.

BACKGROUND AND AIMS: Portal hypertension in cirrhosis is mediated in part by increased intrahepatic resistance, reflecting an increased sensitivity of the hepatic microvasculature to vasoconstrictors. Activation of the RhoA/Rho-kinase pathway is essential for contraction of vascular smooth muscle. The aim of this study was to investigate RhoA/Rho-kinase mediated regulation of the intrahepatic vascular tone in cirrhotic rats. METHODS: Cirrhosis was induced by bile duct ligation (BDL). Hepatic RhoA and Rho-kinase expressions were studied by real time reverse transcription polymerase chain reaction and western blot analysis. Hepatic Rho-kinase activity in rat and human livers was assessed as phosphorylation of the Rho-kinase substrate moesin. The effect of the Rho-kinase inhibitor Y-27632 on hepatic perfusion pressure was measured in livers perfused at constant flow. The in vivo effect of intravenous application of Y-27632 was studied by haemodynamic measurements. RESULTS: Hepatic expressions of RhoA and Rho-kinase were increased at mRNA and protein level in BDL rats. Intrahepatic moesin phosphorylation was increased in livers from cirrhotic rats and patients with alcohol induced cirrhosis. Y-27632 reduced the basal perfusion pressure of in situ perfused livers in BDL rats but not in sham operated rats. Y-27632 reduced the sensitivity to methoxamine in isolated perfused livers in sham operated rats more than in BDL rats. In vivo, Y-27632 reduced portal pressure to a greater extent in BDL rats than in sham operated rats. Intrahepatic vascular resistance was decreased in response to bolus injection of Y-27632 in BDL rats but not in sham operated rats. CONCLUSIONS: Upregulation of RhoA and Rho-kinase contributes to increased intrahepatic resistance in cirrhotic rats and to an increased sensitivity of cirrhotic livers to vasoconstrictors.

Acute haemodynamic effects of losartan in anaesthetized cirrhotic rats.

BACKGROUND: Portal hypertension in cirrhosis is the result of increased intrahepatic vascular resistance to portal outflow as well as increased portal tributary blood flow. The angiotensin II type 1 receptor antagonist losartan has been suggested as a portal pressure-lowering drug in patients with cirrhosis. AIM: To investigate the systemic and splanchnic haemodynamic effects of different doses of losartan. METHODS: In 35 anaesthetized rats with secondary biliary cirrhosis, 3, 10 or 30 mg of losartan kg(-1) or solvent were administered intravenously. Ten sham-operated rats served as controls. Mean arterial pressure and portal pressure were measured by catheters in the femoral artery or portal vein. Systemic and splanchnic haemodynamics and mesenterico-systemic shunt rate were determined by the coloured microsphere method. RESULTS: Losartan reduced portal pressure (sham: 9.1 +/- 0.4. cirrhosis: 19.3 +/- 1.1, after 3 mg kg(-1) of losartan 16.4 +/- 0.4, after 10 mg kg(-1) of losartan 15.6 +/- 0.6, after 30 mg kg(-1) of losartan 14.9 +/- 0.6 mmHg) without reducing portal sinusoidal resistance. However, in cirrhotic rats it reduced portal tributary blood flow (sham: 4.3 +/- 0.6. cirrhosis: 8.6 +/- 1.4, after 3 mg kg(-1) of losartan 3.8 +/- 0.7, after 10 mg kg(-1) of losartan 4.7 +/- 0.5, after 30 mg kg(-1) of losartan 5.9 +/- 0.9 mmHg). This was owing either to an increase in splanchnic vascular resistance at the 3 mg kg(-1) dose or to a reduction in the splanchnic perfusion-pressure gradient secondary to a reduction in mean arterial pressure at the 10 and 30 mg kg(-1) doses (mean arterial pressure: sham: 109.7 +/- 4.8. cirrhosis: 109.4 +/- 2.8, after 3 mg kg(-1) of losartan 99.7 +/- 2.9, after 10 mg kg(-1) of losartan 89.9 +/- 3.4, after 30 mg kg(-1) of losartan 81.0 +/- 2.9 mmHg). CONCLUSIONS: Low doses of losartan reduce portal hypertension by an increase in splanchnic vascular resistance without hypotensive side-effects on arterial pressure.

Coupled capillary and gravity-driven instability in a liquid film overlying a porous layer.

In this work, we study the problem of onset of thermal convection in a fluid layer overlying a porous layer, the whole system being heated from below. We use Brinkman's model to describe the porous medium and determine the corresponding linear stability equations. The eigenvalue problem is solved by means of a modified Galerkin method. The behavior of the critical wave number and temperature gradient is discussed in terms of the various parameters of the system. We also emphasize the influence of the boundary conditions at the upper surface of the fluid layer; in particular, we examine the role of a free surface whose surface tension is temperature dependent (Marangoni effect). Comparison with earlier works is also made.

On the Earnshaw and the Van den Tempel-Lucassen Compositional Viscoelastic Theories.

We consider a diffusion-controlled solute transfer and discuss the reasons to study the complete convective-diffusive equation to determine the coupling resonant domain between capillary and longitudinal waves in terms of viscoelastic compositional behavior. A perturbation of the surface tension due to solute transfer has two contributions. One is proportional to the surface area change while the other, not considered in the Van den Tempel-Lucassen theory, is due to the surface velocity. Copyright 2000 Academic Press.

Stationary Solutal Marangoni Instability in a Two-Layer System.

The effect of different mass transfer mechanisms on the Marangoni instability in a two-layer system of finite width is studied. A dilute soluble surfactant is transferred across the interface between two immiscible fluid phases. A linear stability analysis is developed, and the corresponding eigenvalue problem is solved analytically for the onset of monotonic instability. Mass transfer is assumed to be controlled by bulk diffusion or/and by the adsorption-desorption mechanism. The influences of the diffusivity ratio and the layer width ratio on the instability of the system are examined. Copyright 1998 Academic Press.

Kinetorheological aspects of biorheology.

The relationship between stress and strain is the rheological equation of state. In the case of sophisticated systems such as biological tissue, this is rarely a simple relationship. The relationship is seen to be even more complex when it is recalled that in most living tissues, the tissue is not in chemical equilibrium, but is at best in some controlled steady state. At worst, it is undergoing major fluctuations or transitions because the chemical reactions or fluxes are altering the system. It is shown, in particular, that in addition to the changes in composition, the effective rheological relaxation times of the system are shortened due to contributions deriving from the reaction rate constants. These and other points are illustrated by considering a process of irreversible monomolecular degradation of a large macromolecular species.