Expression of Rho-kinase (ROCK-1 and ROCK-2) and its substantial role in the contractile activity of the sheep ureter

Genome-wide evaluation of copy gain and loss variations in three Afghan sheep breeds

Copy number variation (CNV) is one of the main sources of variation between different individuals that has recently attracted much researcher interest as a major source for heritable variation in complex traits. The aim of this study was to identify CNVs in Afghan indigenous sheep consisting of three Arab, Baluchi, and Gadik breeds using genomic arrays containing 53,862 single nucleotide polymorphism (SNP) markers. Data were analyzed using the Hidden Markov Model (HMM) of PennCNV software. In this study, out of 45 sheep studied, 97.8% (44 animals) have shown CNVs. In total, 411 CNVs were observed for autosomal chromosomes and the entire sequence length of around 144 Mb was identified across the genome. The average number of CNVs per each sheep was 9.13. The identified CNVs for Arab, Baluchi, and Gadik breeds were 306, 62, and 43, respectively. After merging overlapped regions, a total of 376 copy number variation regions (CNVR) were identified, which are 286, 50, and 40 for Arab, Baluchi, and Gadik breeds, respectively. Bioinformatics analysis was performed to identify the genes and QTLs reported in these regions and the biochemical pathways involved by these genes. The results showed that many of these CNVRs overlapped with the genes or QTLs that are associated with various pathways such as immune system development, growth, reproduction, and environmental adaptions. Furthermore, to determine a genome-wide pattern of selection signatures in Afghan sheep breeds, the unbiased estimates of FST was calculated and the results indicated that 37 of the 376 CNVRs (~ 10%) have been also under selection signature, most of those overlapped with the genes influencing production, reproduction and immune system. Finally, the statistical methods used in this study was applied in an external dataset including 96 individuals of the Iranian sheep breed. The results indicated that 20 of the 114 CNVRs (18%) identified in Iranian sheep breed were also identified in our study, most of those overlapped with the genes influencing production, reproduction and immune system. Overall, this is the first attempts to develop the genomic map of loss and gain variation in the genome of Afghan indigenous sheep breeds, and may be important to shed some light on the genomic regions associated with some economically important traits in these breeds.

Biomimetic in vitro respiratory system using smooth muscle cells on ECIS chips for anti-asthma TCMs screening

Airway smooth muscle (ASM) contraction is a major pathophysiological characteristic of asthma. Although β2-adrenoceptor (β2-AR) agonists are currently used as bronchodilators, they cause rapid effect and long-term agonist-induced desensitization. Thus, it is necessary to search for more effective and safer relaxant agents for ASM cells. In this work, bitter taste receptors (TAS2Rs) were demonstrated to be expressed in primary mouse ASM cells endogenously, and they were considered as new drug targets for asthma treatment. Traditional Chinese medicines (TCMs) contained a wide range of TAS2R agonists and some of them had the efficacy of relieving cough and asthma with less toxic side effects. Then the electronic cell-substrate impedance sensor (ECIS) was used for the first time to establish a method to detect the contraction/relaxation effects of ASM cells. Therefore, we introduced a biomimetic in vitro respiratory system using ASM cells on ECIS chips to screen for potential TCMs against asthma. Quinine, nobiletin, and picfeltarraenin IA screened in this study could effectively inhibit the ASM contraction in a concentration-dependent manner, showing potential value as novel anti-asthma drugs. Furthermore, the effective screening of anti-asthma drugs was realized based on 3D ASM cell arrays and gel imaging system. Consistent results were found and the reliability of the biomimetic in vitro respiratory system for the screening of TCMs against asthma was further verified. The biomimetic system designed in this study has the advantages of operation simplicity, high throughput, non-invasive, real-time, and high sensitivity, and therefore provides a promising drug screening platform for asthma disease.

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.

A role of the endothelial nitric oxide system in acute renal colic caused by ureteral stone

BACKGROUND AND AIMS

Endothelial nitric oxide synthase gene polymorphisms play a role in some pathophysiological processes. In this study, the possible effects of endothelial nitric oxide synthase gene polymorphisms on ureteral stone disease in patients who were admitted to the emergency department with severe pain due to renal colic are examined.

MATERIALS AND METHODS

The study groups were designed as controls and patients. The control group was formed from the healthy volunteers who applied to the blood center next to the emergency service. The patient group comprised patients who were diagnosed with ureteral stone disease with severe pain. All of the genetic studies were based on extracted peripheral blood samples using the necessary procedures from the Genome and Stem Cell Center at Erciyes University (GENKOK). The data were analyzed with SPSS (IBM, ver 20, United Sate).

RESULTS

The study group comprised 62 females and 138 males, and the control group comprised 64 females and 136 males. All of the stones that caused renal colic were found to be localized in the ureters and the ureterovesical junction. The genotypes of the intron 4 polymorphism were found to be as follows: 4a/4a in 10 people, 4b/4a in 115, and 4b/4b in 275 people. The GG genotype of the eNOS-G894T polymorphism was found in 108 patients in the study group and in117 of the healthy individuals. There was no statistically significant difference between the two groups regarding these data.

CONCLUSION

Although this study is the first in the literature to examine the relationship between renal colic and endothelial nitric oxide synthase gene polymorphisms, our study demonstrated that no relation was found.

Rho/rho-kinase signalling in chronically alcohol-fed mice

BACKGROUND/AIM

The effects of chronic ethanol consumption on male sexual function are debateable, and its effects on the Rho/Rho-kinase pathway are unknown. Therefore, we investigated smooth muscle reactivity and Rho/Rho-kinase signalling in the corpus cavernosum of ethanol-fed mice.

MATERIALS AND METHODS

Ethanol was added to drinking water at 5% concentration in the first 2 days with 5% increment every subsequent 2 days, up to a final concentration of 20% for 45 days. Corpora cavernosa were isolated and a cumulative dose-response curve to phenylephrine was obtained. Acetylcholine (10-6 M), electrical field stimulation (EFS, 40 V, 8-16 Hz) and Y-27632 (10^-6-10^-5 M)-induced relaxations were compared in the control and ethanol groups.

RESULTS

Blood ethanol levels in the control and ethanol-treated mice were 1.5 ± 0.3 mg/dL and 37.4 ± 4.1 mg/dL (P < 0.001), respectively. Phenylephrine-induced contractile responses were potentiated in the ethanol group, with pD₂ values of 4.92 ± 0.18 and 5.71 ± 0.21 (P < 0.01) in the corpus cavernosum obtained from control and alcohol-fed mice, respectively. The relaxant responses to acetylcholine and EFS, but not Y-27632, were significantly augmented in the corpus cavernosum obtained from ethanol-treated mice. However, expression and activation of Rho-kinase remained unchanged in the alcohol group.

CONCLUSION

Ethanol drinking may increase sensitivity to both vasoconstrictors and vasodilators in the mouse corpus cavernosum without any alteration in Rho/Rho-kinase signalling.

The Role of Rho/Rho-Kinase Pathway in the Pathogenesis of Cholesteatoma

OBJECTIVE

To assess the role of Rho/Rho-kinase pathway in the pathogenesis of cholesteatoma.

MATERIALS AND METHODS

Thirty-eight patients with cholesteatoma, who had gone mastoidectomies were enrolled in this prospective study. Cholesteatomas matrix (CM) and a piece of the external ear canal skin (EECS as control) were taken and transferred to the liquid nitrogen and kept at -86 °C for Rho A and Rho-kinase (ROCK) analysis with Western blotting and commercial ELISA kits (Cell Biolabs Inc., San Diego, CA). The tissues were homogenized by an appropriate ice-cold lysis buffer. Following centrifugation, the supernatant was taken and total protein amount was detected by the Bradford method. Thereafter, tissue homogenates were subjected to sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis electrophoresis then transferred to nitrocellulose membrane where it was treated with specific monoclonal primary antibody against to ROCK-2 and HRP-conjugated seconder antibody, respectively. The protein blots were visualized with commercial x-ray film and dansitometrically analyzed by the Scion Image Program (Cell Biolabs Inc., San Diego, CA). In another series of experiments, Rho-kinase activities were assessed by ROCK-2 ELISA kits.

RESULTS

There were no statistical differences in Rho A translocation between CM and EECS. However, ROCK activity was found to be lower in CM than EECS as detected by ELISA kits. Furthermore, ROCK protein expression was also significantly lower in CM than EECS as demonstrated by Western blotting.

CONCLUSION

Given Rho-kinase could take essential roles in cell differentiation, the results of this study implicate that down-regulated Rho-kinase could be responsible for the keratinocyte undifferentiation seen in cholesteatoma pathogenesis.

Effects of ethanol on RhoA/Rho-kinase-mediated calcium sensitization in mouse lung parenchymal tissue

Calcium sensitization by the RhoA/Rho-kinase (ROCK) pathway contributes to the contraction in smooth muscle. Contractile stimuli can sensitize myosin to Ca(2+) by activating RhoA/Rho-kinase that inhibits myosin light chain phosphatase activity. The present study was aimed at investigating the possible involvement of RhoA/Rho-kinase pathway in contractile responses to agonist (phenylephrine) and depolarizing (KCl) of mouse lung parenchymal tissues. Also, we investigated the effect of ethanol on RhoA/Rho-kinase pathway. Phenylephrine (10(-8)-10(-4) M) and KCl (10-80 mM) induced sustained contractions in parenchymal strips. Ethanol significantly attenuated the contractions to phenylephrine and KCl. The Rho-kinase inhibitors fasudil (5×10(-5) M) and Y-27632 (5×10(-5) M) inhibited contractions to in both control and ethanol-treated parenchymal strips. In addition, the relaxations induced by fasudil (10(-4) M) and Y-27632 (5×10(-4) M) on parenchymal strips contracted by phenylephrine but not KCl was decreased in ethanol-treatment group. Also, RhoA, ROCK1 and ROCK2 expressions were detected in mouse lung parenchymal tissue. In ethanol-treated group, expression of RhoA and ROCK1 but not ROCK2 decreased compared to control. Furthermore, ethanol causes apoptotic changes in alveolar type I epithelial cells of parenchymal tissue. These results suggest that RhoA/Rho-kinase signaling pathway plays an important role in phenylephrine- and KCl-induced Ca(2)(+) sensitization in mouse lung parenchymal tissue. Also, ethanol may be decrease phenylephrine- and KCl-induced contraction due to lowering the RhoA/Rho-kinase-mediated Ca(2+)-sensitizing by inhibiting RhoA/Rho-kinase pathway in parenchymal tissue. These results may be lead to important insights into the mechanisms of lung diseases due to alcohol consumption.

The functional significance of the rho/rho-kinase pathway in human erythrocytes

Objective: Erythrocyte deformability, which can be influenced by various intracellular signaling mechanisms, such as nitric oxide, cAMP, cGMP, and protein kinases, is the most important physiological factor providing the blood flow in microcirculation. However, the functional significance of the Rho/Rho-kinase pathway, which contributes cell shape changes and the reorganization of the actin cytoskeleton, has yet to be explored in erythrocytes. Therefore, we examined the influence of several activators and inhibitors of Rho/Rho-kinase signaling on human erythrocyte deformability.

Materials and Methods: RhoA and ROCK-2 proteins were studied by western blotting. Influences of 2 Rho-kinase inhibitors, fasudil and Y-27632 (both 10-7 to 10-4 M), on erythrocyte deformability was determined by ektacytometer at various shear stresses (0-30 Pa) in the presence or absence of a known Rho activator, lysophosphatidic acid (LPA, 10-5 to 5x10-5 M, 1-15 min).

Results: LPA incubation reduced deformability with concomitant RhoA-GTP inhibition. Y-27632 and fasudil also decreased deformability, but had no effect on LPA-induced reduction of deformability. Rho inhibitor C3 had no effect on RhoA activation. Reduction in RhoA activation was induced by sub-hemolytic mechanical stress.

Conclusion: Our findings may indicate that the Rho/Rho-kinase pathway could contribute to the regulation of deformability of human erythrocytes.

Control of urinary drainage and voiding

Urine differs greatly in ion and solute composition from plasma and contains harmful and noxious substances that must be stored for hours and then eliminated when it is socially convenient to do so. The urinary tract that handles this output is composed of a series of pressurizable muscular compartments separated by sphincteric structures. With neural input, these structures coordinate the delivery, collection, and, ultimately, expulsion of urine. Despite large osmotic and chemical gradients in this waste fluid, the bladder maintains a highly impermeable surface in the face of a physically demanding biomechanical environment, which mandates recurring cycles of surface area expansion and increased wall tension during filling, followed by rapid wall compression during voiding. Afferent neuronal inflow from mucosa and submucosa communicates sensory information about bladder fullness, and voiding is initiated consciously through coordinated central and spinal efferent outflow to the detrusor, trigonal internal sphincter, and external urethral sphincter after periods of relative quiescence. Provocative new findings suggest that in some cases, lower urinary tract symptoms, such as incontinence, urgency, frequency, overactivity, and pain may be viewed as a consequence of urothelial defects (either urothelial barrier breakdown or inappropriate signaling from urothelial cells to underlying sensory afferents and potentially interstitial cells). This review describes the physiologic and anatomic mechanisms by which urine is moved from the kidney to the bladder, stored, and then released. Relevant clinical examples of urinary tract dysfunction are also discussed.

Hepatoprotective activity of Tribulus terrestris extract against acetaminophen-induced toxicity in a freshwater fish (Oreochromis mossambicus)

The potential protective role of Tribulus terrestris in acetaminophen-induced hepatotoxicity in Oreochromis mossambicus was investigated. The effect of oral exposure of acetaminophen (500 mg/kg) in O. mossambicus at 24-h duration was evaluated. The plant extract (250 mg/kg) showed a remarkable hepatoprotective activity against acetaminophen-induced hepatotoxicity. It was judged from the tissue-damaging level and antioxidant levels in liver, gill, muscle and kidney tissues. Further acetaminophen impact induced a significant rise in the tissue-damaging level, and the antioxidant level was discernible from the enzyme activity modulations such as glutamate oxaloacetic transaminase, glutamate pyruvic transaminase, alkaline phosphatase, acid phosphatase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, lipid peroxidase and reduced glutathione. The levels of all these enzymes have significantly (p < 0.05) increased in acetaminophen-treated fish tissues. The elevated levels of these enzymes were significantly controlled by the treatment of T. terrestris extract (250 kg/mg). Histopathological changes of liver, gill and muscle samples were compared with respective controls. The results of the present study specify the hepatoprotective and antioxidant properties of T. terrestris against acetaminophen-induced toxicity in freshwater fish, O. mossambicus.

The importance of Rho-associated kinase-induced Ca2+ sensitization as a component of electromechanical and pharmacomechanical coupling in rat ureteric smooth muscle

Ureteric peristalsis, which occurs via alternating contraction and relaxation of ureteric smooth muscle, ensures the unidirectional flow of urine from the kidney to the bladder. Understanding of the molecular mechanisms underlying ureteric excitation-contraction coupling, however, is limited. To address these knowledge deficits, and in particular to test the hypothesis that Ca2+ sensitization via activation of the RhoA/Rho-associated kinase (ROK) pathway plays an important role in ureteric smooth muscle contraction, we carried out a thorough characterization of the electrical activity, Ca2+ signaling, MYPT1 (myosin targeting subunit of myosin light chain phosphatase, MLCP) and myosin regulatory light chain (LC20) phosphorylation, and force responses to membrane depolarization induced by KCl (electromechanical coupling) and carbachol (CCh) (pharmacomechanical coupling). The effects of ROK inhibition on these parameters were investigated. We conclude that the tonic, but not the phasic component of KCl- or CCh-induced ureteric smooth muscle contraction is highly dependent on ROK-catalyzed phosphorylation of MYPT1 at T855, leading to inhibition of MLCP and increased LC20 phosphorylation.

Proton pump inhibitors omeprazole, lansoprazole and pantoprazole induce relaxation in the rat lower oesophageal sphincter

Objectives

We aimed to investigate effects of the proton pump inhibitors (PPIs) omeprazole, lansoprazole and pantoprazole, which are currently used for the treatment of hyperacidity and gastro-oesophageal reflux, on the reactivity of the isolated rat lower oesophageal sphincter.

Methods

Omeprazole, lansoprazole and pantoprazole (all 10–9–10–3m, cumulatively) were tested on carbachol-induced (10–6m) contraction. In addition, the effects of PPI preincubation (all 10–3m) on the contractions induced by cumulative carbachol (10−9–10−5m), angiotensin-2 (10−9–10–5m) or electrical field stimulation (EFS; 40 V, 32 Hz, 1 ms, 10 s) were assessed. Finally, the effects of PPI on the spontaneous contractile activity of the tissue were also evaluated.

Key findings

PPI relaxed precontracted lower oesophageal sphincter in a concentration-dependent manner and suppressed carbachol-, angiotensin- and EFS-induced contractions. Furthermore, PPI attenuated spontaneous contractile activity of the tissue.

Conclusions

Omeprazole, lansoprazole and pantoprazole had a suppressor effect on lower oesophageal sphincter contractions.

CDP-choline-induced contractions in the mouse gastric fundus through purinoceptors and Rho/Rho-kinase signalling

AIMS

This study aimed to investigate the effects of cytidine-5'-diphosphocholine (CDP-choline), an endogenous lipid precursor, on the reactivity of the mouse gastric fundus and to determine the mechanism(s) mediating its effects.

MAIN METHODS

Possible contractile effect of CDP-choline (10(-5)-10(-2)M) was investigated in the absence and presence of a muscarinic receptor antagonist, atropine (3 × 10(-6)M), an acetylcholine esterase inhibitor, physostigmine (10(-6)M), a Na(+) channel blocker, tetrodotoxin (TTX, 3 × 10(-6)M), a Rho-kinase inhibitor, Y-27632 (10(-5) M), a purinoceptor antagonist, suramin (2 × 10(-4)M), a nitric oxide synthase inhibitor, N(G)-nitro-L-arginine (L-NA, 3 × 10(-4)M), a Ca(2+) channel blocker, nifedipine (10(-6)M), an α(7) nicotinic receptor antagonist, methyllycaconitine citrate (MLA, 10(-6)M) and a G protein (G(i/o)) inhibitor, pertussis toxin (PTX, 2 μg/ml). The metabolites of CDP-choline, namely choline (10(-4)-10(-2)M), cytidine 5'-triphosphate (CTP, 10(-5)-10(-2)M), cytidine (10(-5)-10(-2)M) and cytidine monophosphate (CMP, 10(-3)-10(-2)M) were also tested. Besides, phosphorylation of MYPT1, which indicates Rho-kinase activity, was also detected.

KEY FINDINGS

CDP-choline produced contractions in a concentration-dependent manner. The contractions were not affected by atropine, physostigmine, TTX, PTX, MLA or L-NA. However, Y-27632, suramin or nifedipine partly reduced these contractions. CDP-choline increased phosphorylation of MYPT1. Among CDP-choline metabolites, cytidine had no contractile effects. However, choline induced considerable contractions, which were sensitive to atropine. CMP and CTP had also contractile activity, comparable to that of CDP-choline.

SIGNIFICANCE

These results suggest that CDP-choline produced contraction through, at least in part, purinoceptors and Rho/Rho-kinase signalling in the mouse gastric fundus.

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.

Role of Rho-kinase in mediating contraction of chicken embryo femoral arteries

Rho-kinase-dependent Ca2+ sensitization is an essential process for contraction of mammalian vascular smooth muscle but the information about its effects in non-mammalian vessels is scarce. We aimed to investigate, using the Rho-kinase inhibitor hydroxyfasudil, the potential role of the Rho-kinase pathway of Ca2+ sensitization in depolarization- and agonist-mediated contraction of chicken embryo (at day 19 of the 21 days of incubation) femoral arteries. Contraction elicited by KCl (125 mM) comprised two phases (phasic and tonic contraction), both of which were abolished in the absence of extracellular Ca2+. Hydroxyfasudil (10 microM) left the initial phasic component nearly intact but abolished the tonic component. Hydroxyfasudil also induced a marked impairment of the contractions elicited by phenylephrine (PE), the thromboxane A2 mimetic U46619, and endothelin-1. In contrast, inhibition of protein kinase C (PKC) by chelerythrine did not affect KCl- or PE-induced contractions, indicating lack of participation of PKC-mediated Ca2+ sensitization. Incubation under chronic hypoxia (15% O2 from day 0) impaired embryonic growth but did not significantly affect hydroxyfasudil-mediated relaxation. In summary, our findings are indicative of a role for Rho-kinase activity in depolarization- and agonist-induced force generation in chicken embryo femoral arteries.

Ureteral motility

The pyeloureteral function is to transport urine from the kidneys into the ureter toward the urinary bladder for storage until micturition. A set of mechanisms collaborates to achieve this purpose: the basic process regulating ureteral peristalsis is myogenic, initiated by active pacemaker cells located in the renal pelvis. Great emphasis has been given to hydrodynamic factors, such as urine flow rate in determining the size and pattern of urine boluses which, in turn, affect the mechanical aspects of peristaltic rhythm, rate, amplitude, and baseline pressure. Neurogenic contribution is thought to be limited to play a modulatory role in ureteral peristalsis. The myogenic theory of ureteral peristalsis can be traced back to Engelmann (1) who was able to localize the peristaltic pressure wave's origin in the renal pelvis and suggested that the ureteral contraction impulse passes from one ureteral cell to another, the whole ureter working as a functional syncitium. Recent studies of ureteral biomechanics, smooth muscle cell electrophysiology, membrane ionic currents, cytoskeletal components and pharmacophysiology much improved our understanding of the mechanism of how the urine bolus is propelled, how this process is disturbed in pathological states, and what could be done to improve it.

Rho kinase as a therapeutic target in the treatment of asthma and chronic obstructive pulmonary disease

Asthma is a complex inflammatory disease of the airways involving reversible bronchoconstriction. Chronic obstructive pulmonary disease is typified by inflammation and airflow limitation that has an irreversible component. There is now substantial evidence that Rho kinase is involved in many of the pathways that contribute to the pathologies associated with these respiratory diseases including bronchoconstriction, airway inflammation, airway remodelling, neuromodulation and exacerbations due to respiratory tract viral infection. Indeed the Rho kinase inhibitor Y-27632 causes bronchodilatation and reduces pulmonary eosinophilia trafficking and airways hyperresponsiveness. Furthermore, accumulating evidence suggests that inhibition of Rho kinase could have a major beneficial impact on symptoms and disease progression in asthma and COPD by modulating several other systems and processes. Thus, the Rho kinase pathway may indeed be a worthwhile therapeutic target in the treatment of asthma and chronic obstructive pulmonary disease.

Antiepileptic effects of two Rho-kinase inhibitors, Y-27632 and fasudil, in mice

BACKGROUND AND PURPOSE

Rho/Rho-kinase signalling is involved in many cellular events, including some in the CNS. However, the role of this pathway in epilepsy has not yet been assessed. Therefore, we determined the effects of two Rho-kinase inhibitors, Y-27632 and fasudil, on seizures induced by pentylenetetrazole (PTZ) or maximal electroconvulsive shock (MES).

EXPERIMENTAL APPROACH

Effects of Y-27632 (5-10 mg kg(-1)) and fasudil (5-25 mg kg(-1)) on duration of myoclonic jerks, clonic and tonic convulsions, tonic hindlimb extensions and percentage of tonic convulsion index, as well as recovery latency for righting reflex were investigated in mice stimulated with PTZ (65 mg kg(-1)) or MES (50 Hz, 50 mA and 0.4 s). These inhibitors were also tested on a model of kindling induced by PTZ (35 mg kg(-1), for 11 days). Membrane and cytosolic levels of RhoA protein were measured in brain homogenates from kindled mice.

KEY RESULTS

Y-27632 and fasudil diminished onset of myoclonic jerks, clonic convulsions and tonic hindlimb extensions in mice given PTZ. These inhibitors suppressed the percentage of tonic convulsion index and recovery latency for righting reflex in the mice excited with MES. Western blotting demonstrated that Rho translocation to plasma membrane increased in the brain homogenates obtained from PTZ-kindled mice. However, the Rho-kinase inhibitors at the given doses did not change motor coordination of the mice.

CONCLUSIONS AND IMPLICATIONS

Rho/Rho-kinase signalling may play a role in epilepsy induced by PTZ and MES. Furthermore, Rho-kinase inhibitors could be novel important antiepileptic agents.

Role of Rho-kinase in contractions of ureters from rabbits with unilateral ureteric obstruction

OBJECTIVE

To investigate the expression of two isoforms of Rho-kinase (ROCK) and its functional role in the pathophysiological control of smooth muscle contraction in rabbits with unilateral ureteric obstruction (UUO).

MATERIAL AND METHODS

Left UUO was created in 14 rabbits and eight other rabbits (controls) had sham operations. After 2 weeks all the rabbits were killed. Ureteric strips suspended in an organ bath were used for functional studies and the effects of Y-27632, a specific inhibitor of Rho-kinase, on spontaneous contractions and electrical field stimulation (EFS; 50 V, 1 ms, 16 Hz, for 20 s), carbachol- (10(-7)-10(-4)m), phenylephrine- (10(-7)-10(-4)m) and KCl- (50 mm) induced contractions were analysed. Western blotting was used to determine expression levels of Rho-kinase protein in the ureters of UUO and control rabbits.

RESULTS

In the functional analysis, the contractions induced by EFS, KCl, phenylephrine and carbachol in the ureteric strips from rabbits with UUO were significantly greater than those from the control rabbits. Y-27632 considerably suppressed the ureter contractile responses in both UUO and control rabbits. Western blot analysis showed that both ROCK-1 and ROCK-2 proteins were expressed in the rabbit ureter. In accordance with the functional studies, the expression levels of both ROCK-1 and ROCK-2 were significantly greater in the ureters of UUO rabbits than in the controls.

CONCLUSIONS

Y-27632 suppressed ureteric contractions in the rabbits with UUO. Western blot analysis also confirmed greater expression levels of ROCK-1 and ROCK-2 in the ureters of UUO rabbits. It is important to elucidate by which mechanisms the Rho-kinase pathway affects ureteric function after obstruction.

Physiology and pharmacology of the human ureter: basis for current and future treatments

INTRODUCTION

This article sets out to be a review regarding agents that affect contraction and relaxation of the ureter in order to establish a basis for current and future treatments for upper urinary tract obstruction.

MATERIAL AND METHODS

A complete review of the English literature using MEDLINE was performed between 1960 and 2007 on ureter physiology and pharmacology with special emphasis on signal transduction mechanisms involved in the contractile regulation of the human ureter.

RESULTS

Activation of muscarinic and adrenergic receptors increases the amplitude of ureteral contractions. The sympathetic nerves modulate the contractions by alpha-adrenoceptors and relaxation by beta-adrenoceptors. The purinergic system is important in sensory/motor functions and ATP is an important non-adrenergic non-cholinergic (NANC) agent causing contraction. Nitric oxide (NO) is a major inhibitory NANC neurotransmitter causing relaxation. Serotonin causes contraction. Prostaglandin-F(2)alpha contracts whereas prostaglandin-E(1)/E(2) relaxes the ureter. Phosphodiesterases (PDE) and the Rho-kinase pathway have recently been identified in the human ureter. PDE-IV inhibitors, K(+) channel openers, calcium antagonists, alpha(1)-adrenoceptor antagonists and NO donors seem to be promising drugs in relieving obstruction and facilitating stone passage.

CONCLUSIONS

Further understanding of the ureteral function and pharmacology may lead to the discovery of promising new drugs that could be useful in relieving ureteral colic, facilitating spontaneous stone passage, preparing the ureter for ureteroscopy as well as acting adjunctive to extracorporeal shock-wave lithotripsy.

Rho-kinase inhibition suppresses potassium chloride-induced bladder hyperactivity in a rat model

OBJECTIVES

The molecular mechanisms by which potassium induces urinary bladder hyperactivity are not clear. In the present study, we tested our hypothesis that potassium chloride (KCl)-induced bladder hyperactivity might be mediated through a calcium-sensitizing RhoA-Rho-kinase pathway in an in vivo animal model using urodynamic parameters.

METHODS

Two groups of adult male rats (n = 8) were anesthetized, their bladder exteriorized, and a saline-filled Intracath fixed into the bladder dome. This Intracath was connected to a pressure transducer and an infusion pump. Continuous filling cystometrograms were performed by infusing warm saline (0.04 mL/min) to obtain baseline data on each rat. The number of contractions per unit time (intercontractile intervals in seconds), pressure threshold, and peak pressure during micturition were recorded. To create bladder hyperactivity, protamine sulfate (30 mg/mL) followed by KCl (500 mM) was infused intravesically, and a continuous filling cystometrogram was again recorded. Y-27632, a specific RhoA-Rho-kinase inhibitor, was administered either intra-arterially (group 1) or intravesically (group 2) to each rat, and an additional continuous filling cystometrogram was recorded with KCl (500 mM) to observe the effects of Rho-kinase inhibition on bladder contractility.

RESULTS

Intravesical KCl infusion after protamine exposure resulted in significantly greater contractions and decreased the intercontractile interval (P <0.05). Y-27632 administration attenuated the effect of KCl on the contractions and intercontractile interval and decreased the mean pressure threshold.

CONCLUSIONS

Suppression of KCl-induced bladder contractility by the Rho-kinase inhibitor Y-27632 confirmed the involvement of this novel calcium-sensitizing RhoA-Rho-kinase pathway in mediating these smooth muscle contractions.

A Rho-kinase inhibitor, Y-27632, reduces cholinergic contraction but not neurotransmitter release

This study examined the effects of the selective Rho-kinase inhibitor Y-27632 [(+)-(R)-trans-4-(1-aminoethyl)-(4-pyridyl)cyclohexanecarboxamide dihydrochloride]) on cholinergic nerve-mediated contraction and neurotransmitter release in murine and guinea-pig isolated tracheal preparations. In tracheal preparations obtained from both species, Y-27632 shifted carbachol concentration-effect curves to the right and reduced the maximal contractile response. Repeated electrical field stimulation (EFS) evoked transient, consistent and reproducible contractions in murine and guinea-pig tracheal preparations. Y-27632 inhibited these cholinergic nerve-mediated contractions in a concentration-dependent manner. EFS (0.1-30 Hz) elicited frequency-dependent cholinergic nerve-mediated contractile responses. In murine tracheal preparations, Y-27632 (3 microM and 10 microM) shifted frequency-response curves to EFS to the right by 5.5 and 13.0 fold respectively and markedly reduced the maximal contractile response. In murine and guinea-pig tracheal preparations loaded with [(3)H]-choline, Y-27632 (10 microM) significantly increased the EFS-induced outflow of radioactivity from airway cholinergic nerves by 27% and 54% respectively. Thus, Y-27632 inhibited both carbachol-induced and cholinergic nerve-mediated contractile responses. Conversely, Y-27632 increased neurotransmitter release from airway cholinergic nerves. However, since antagonism of acetylcholine-induced contraction by Y-27632 overwhelmed the increased neurotransmitter release, the overall effect of this Rho-kinase inhibitor was to inhibit cholinergic nerve-mediated contraction.

Contribution of Rho-kinase in human gallbladder contractions

Rho/Rho-kinase-mediated pathway has been involved in a variety of physiological processes, including Ca2+ sensitization, which enhances smooth muscle contraction. In this study, first of all we investigated the expression of Rho-kinase (ROCK-2) and then the role of this protein in the control of smooth muscle contraction in the isolated human gallbladder. For this purpose, we examined the effects of a selective Rho-kinase inhibitor, (+)- (R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632, 10(-8)-3x10(-5) M) on carbachol (10(-8)-10(-4) M), cholecystokinin-8 (10(-8) M), endothelin-1 (10(-8) M), histamine (10(-5) M), neurokinin A (10(-7)-10(-6) M), 5-hydroxytryptamine (10(-6)-10(-5) M) and potassium chloride (KCl, 25-50 mM)-induced contractions as well as spontaneous contractile activity. Y-27632 (10(-5) M) significantly reduced 5-hydroxytryptamine, neurokinin A and KCl-induced contractions. Moreover, this Rho-kinase inhibitor (10(-8)-3x10(-5) M, cumulatively) relaxed the contractions produced by cholecystokinin-8, endothelin-1 and histamine in a concentration-dependent manner, being the pEC50 values for Y-27632 5.74+/-0.12, 5.33+/-0.09 and 5.95+/-0.18, respectively. Carbachol (10(-8)-10(-4) M) produced concentration-dependent contractions, which were also inhibited significantly by Y-27632. In addition, the spontaneous contractile activity was suppressed in the presence of Y-27632 (10(-6)-10(-5) M). Moreover, Western blot analysis has revealed that Rho-kinase is expressed in homogenates of the human gallbladder. Taken together, these results show that Rho-kinase is expressed in the human gallbladder, and it has an essential role in agonists and depolarization-induced contractions as well as spontaneous contractile activity.

Role of Rho-kinase in guinea-pig gallbladder smooth muscle contraction

Guinea-pig gallbladder smooth muscle contractions can be elicited pharmacologically by a range of mechanisms. The involvement of Rho-kinase in contractions mediated by receptor-dependent and receptor-independent mechanisms was investigated using the Rho-kinase inhibitor (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexane carboxamide (Y-27632). In a separate series of experiments, the role of Rho-kinase in the contractile response to Ca2+ entry through store-operated Ca2+ channels and to electrical field stimulation was also examined. Y-27632 (10 microM), which caused a significant decrease (P<0.0005) in basal resting tone, significantly inhibited gallbladder contractions evoked by cumulative additions of the G-protein-coupled agonists, carbachol (1 nM-100 microM; P<0.05) and cholecystokinin (10 nM-1 microM; P<0.005). Y-27632 also inhibited the contractions evoked by a single addition of the sarcoplasmic reticulum ATPase inhibitor, thapsigargin (1 microM; P<0.0005) and cumulative additions of KCl (10-85 mM; P<0.0005). The contractile response to Ca2+ entry through store-operated Ca2+ channels was significantly inhibited by Y-27632 (P<0.05) as were the contractile responses evoked by electrical field stimulation (2-25 Hz; P<0.0005). In contrast, Y-27632 had no significant effect on contractions evoked by phorbol 12,13-dibutyrate (0.1 nM-1 microM; a protein kinase C activator) or by the phosphatase inhibitor, cantharidin (100 microM). In conclusion, Rho-kinase contributes to the contractile response in guinea-pig gallbladder smooth muscle evoked by both G-protein-coupled and non-G-protein-coupled mechanisms in addition to contributing to the maintenance of basal tone. It also contributes to the contractile responses resulting from electrical field stimulation and store-operated Ca2+ channel entry.

Rho kinase expression and its central role in ovine gallbladder contractions elicited by a variety of excitatory stimuli

Rho kinase has contractile activity, which induces Ca2+ sensitization in various cells. Several receptors are linked to the Rho/Rho-kinase pathway. Therefore, in this study we aimed to demonstrate the central importance of this novel pathway for diverse excitatory stimuli in the smooth muscle of the sheep gallbladder. Accordingly, the effects of a Rho kinase inhibitor, (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632, 10(-8)-3 x 10(-5) M), were investigated on cholecystokinin-8 (CCK-8, 10(-8) M), endothelin-1 (10(-8) M), carbachol (10(-6)-10(-5) M), 5-hydroxytryptamine (5-HT, 10(-6)-10(-5) M), histamine (10(-6)-10(-5) M), phenylephrine (10(-5)-10(-4) M), neurokinin A (10(-7)-10(-6) M), electrical field stimulation (40 V, 0.5 ms, 2, 4, 8, 16, 32 Hz, 15 s, 3 min intervals) and potassium chloride (KCl, 25-50 mM)-induced contractions as well as spontaneous contractile activity. Electrical field stimulation evoked tetrodotoxin (3 x 10(-6) M)-sensitive reproducible contractions, which were inhibited by atropine (2 x 10(-6) M) and potentiated by eserine (5 x 10(-7) M). EFS-induced contraction was significantly inhibited by Y-27632 (10(-5) M). In addition, spontaneous contractile activity was suppressed in the presence of the compound (10(-6)-10(-5) M). This Rho kinase inhibitor also dramatically decreased the contractions elicited by 5-HT, neurokinin A and carbachol. KCl-induced contraction, which was not atropine-sensitive, was also conspicuously attenuated by Y-27632. Moreover, Y-27632 (10(-8)-3 x 10(-5) M) relaxed gallbladder strips that were contracted by histamine, endothelin-1, CCK-8 and phenylephrine in a concentration-dependent manner. pEC50 values for Y-27632 were 6.25+/-0.10, 5.79+/-0.12, 5.83+/-0.09 and 5.70+/-0.13 for the contraction elicited by histamine, CCK-8, endothelin-1 and phenylephrine, respectively. Furthermore, we also demonstrated Rho kinase protein expression (ROCK-1 and ROCK-2) by Western blot analysis. In conclusion, ROCK is expressed in the smooth muscle of the ovine gallbladder, and it has a central role in the contractile activity induced by diverse excitatory stimuli.

Anti-apoptotic effects of muscarinic receptor activation are mediated by Rho kinase

Activation of muscarinic receptors has been shown to be neuroprotective in several different models of apoptosis, but the mechanism of this action is unknown. Therefore, we investigated the intermediate signals mediating the anti-apoptotic action of muscarinic receptor activation in SH-SY5Y cells. Inhibition of most muscarinic receptor-coupled actions had no effect on protection, but inhibition of Rho kinase with HA-1077 concentration-dependently was able to completely block the protection against H(2)O(2)- and camptothecin-induced apoptosis produced by stimulation of muscarinic receptors. These results demonstrate that the anti-apoptotic effect provided by muscarinic receptor stimulation is dependent on the activity of Rho kinase.

Regulation of smooth muscle calcium sensitivity: KCl as a calcium-sensitizing stimulus

KCl has long been used as a convenient stimulus to bypass G protein-coupled receptors (GPCR) and activate smooth muscle by a highly reproducible and relatively “simple” mechanism involving activation of voltage-operated Ca2+channels that leads to increases in cytosolic free Ca2+([Ca2+]i), Ca2+-calmodulin-dependent myosin light chain (MLC) kinase activation, MLC phosphorylation and contraction. This KCl-induced stimulus-response coupling mechanism is a standard tool-set used in comparative studies to explore more complex mechanisms generated by activation of GPCRs. One area where this approach has been especially productive is in studies designed to understand Ca2+sensitization, the relationship between [Ca2+]iand force produced by GPCR agonists. Studies done in the late 1980s demonstrated that a unique relationship between stimulus-induced [Ca2+]iand force does not exist: for a given increase in [Ca2+]i, GPCR activation can produce greater force than KCl, and relaxant agents can produce the opposite effect to cause Ca2+desensitization. Such changes in Ca2+sensitivity are now known to involve multiple cell signaling strategies, including translocation of proteins from cytosol to plasma membrane, and activation of enzymes, including RhoA kinase and protein kinase C. However, recent studies show that KCl can also cause Ca2+sensitization involving translocation and activation of RhoA kinase. Rather than complicating the Ca2+sensitivity story, this surprising finding is already providing novel insights into mechanisms regulating Ca2+sensitivity of smooth muscle contraction. KCl as a “simple” stimulus promises to remain a standard tool for smooth muscle cell physiologists, whose focus is to understand mechanisms regulating Ca2+sensitivity.

Lysophosphatidic acid-mediated augmentation of cardiomyocyte lipoprotein lipase involves actin cytoskeleton reorganization

The lipoprotein lipase (LPL)-augmenting property of lysophosphatidylcholine requires the formation of lysophosphatidic acid (LPA) (J Mol Cell Cardiol 37: 931-938, 2004). Given that the actin cytoskeleton has been implicated in regulating cardiomyocyte LPL, we examined whether LPL secretion after LPA involves actin cytoskeleton reassembly. Incubation of myocytes with LPA (1-100 nM) increased basal and heparin-releasable LPL (HR-LPL), an effect that was independent of shifts in LPL mRNA. The influence of LPA on myocyte LPL was reflected at the coronary lumen, with substantial increases of the enzyme at this location. Incubation of myocytes with cytochalasin D not only blocked LPA-induced augmentation of HR-LPL but also abrogated filamentous actin formation. These effects of LPA were likely receptor mediated. Exposure of myocytes to LPA facilitated significant membrane translocation of RhoA and its downstream effector Rho kinase I (ROCK I), and blocking this effect with Y-27632 appreciably reduced basal and HR-LPL activity. Incubation of adipose tissue with LPA also significantly enhanced basal and HR-LPL activity, suggesting that sarcomeric actin likely has a limited role in influencing the LPL secretory function of LPA in the myocyte. Comparable to LPA, hyperglycemia also caused significant membrane translocation of RhoA and ROCK I in hearts isolated from diazoxide-treated animals, effects that were abrogated using insulin. Overall, our data suggest that comparable to hyperglycemia, LPA-induced increases in cardiac LPL occurred via posttranscriptional mechanisms and processes that likely required RhoA activation and actin polymerization. Whether this increase in LPL augments triglyceride deposition in the heart leading to eventual impairment in contractile function is currently unknown.