The effect of a Rho kinase inhibitor Y-27632 on superoxide production, aggregation and adhesion in human polymorphonuclear leukocytes

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.

Antitumoral effect of a selective Rho-kinase inhibitor Y-27632 against Ehrlich ascites carcinoma in mice

BACKGROUND

The Rho proteins and Rho-kinase (ROCK) enzymes are responsible for signal transduction, and cause cell permeability, contractility, differentiation, migration, proliferation or apoptosis depending on cell types. All of these functions are vital for cancer initiation and progression. In this study, the preventive and protective effects of a selective ROCK inhibitor Y-27632 against Ehrlich ascites carcinoma in Swiss albino mice were investigated.

METHODS

Adult male albino mice were divided into five equal groups, and Y-27632 (0.1, 1, and 10 mg/kg) was given to groups as two steps; before (pre-carcinoma) and after inoculation of carcinoma cell suspensions (post-carcinoma). At the end of the experiments (at day 15), cardiac blood samples, the ascitic fluid, and intestinal specimens were collected for histopathology and biochemical investigation.

RESULTS

Significant decreases in the body weight and immunostaining scores in small and large intestine for ROCK2, preservation of serum glutathione (GSH) levels, and an increase in tumor level of nitric oxide were recorded in groups pretreated with Y-27632. However, treatment with Y-27632 after tumor inoculation did not affect body weight and ROCK2 immunostaining scores, increased serum MDA levels, and decreased GSH levels.

CONCLUSIONS

This is the first study on the effectiveness of Y-27632 in this experimental tumor model. Our findings provided direct evidence for ROCK involvement in tumor development. These data suggest that pretreatment with Y-27632 has a protective effect against tumor formation.

Protective effects of Y-27632 on hypoxia/reoxygenation-induced intestinal injury in newborn rats

BACKGROUND/PURPOSE

Necrotizing enterocolitis (NEC) is a major cause of mortality in neonates and is associated with a disruption in the protective intestinal barrier. The precise cause of NEC is elusive. However, ischemia/reperfusion injury of the intestine has been considered a major contributing factor. We examined the role of Y-27632, a selective Rho-kinase inhibitor, on a hypoxia/reoxygenation (H/R)-induced intestinal injury of newborn rat pups.

METHODS

Hypoxia/reoxygenation was achieved by placing rat pups in an airtight chamber aerated with 95% N(2) + 5% CO(2) for 10 minutes followed by 10-minute 100% oxygen. Forty newborn rat pups were randomly allocated into 4 groups. Group 1 served as untreated controls. The pups in group 2 were subjected to H/R only. In groups 3 and 4, the rats were treated with intraperitoneal injection of 0.3 and 3 mg kg(-1) day(-1) of Y-27632 for 5 days following H/R, respectively. The pups were killed 6 days following the H/R injury. Intestine specimens were evaluated for histopathology and biochemical investigation.

RESULTS

The microscopic lesions in H/R rat pups were virtually the same as those seen in neonatal NEC, with severe destruction of villi and crypts. Hypoxia/reoxygenation resulted in significant elevation in malondialdehyde levels, but decreased tissue nitric oxide levels (P < .05). Protective effects of Y-27632 on H/R-induced intestinal injury of newborn rat pups were observed with a significant decrease in the intestinal injury score, suppression in malondialdehyde levels, and increase in nitric oxide levels (P < .05).

CONCLUSIONS

In this experimental study, Y-27632 significantly attenuated H/R-induced intestinal injury. These findings indicate that inhibition of Rho-kinase may offer a novel therapeutic approach in the treatment of NEC.

ROCK inhibitor improves survival of cryopreserved serum/feeder-free single human embryonic stem cells

BACKGROUND

Efficient slow freezing protocols within serum-free and feeder-free culture systems are crucial for the clinical application of human embryonic stem (hES) cells. Frequently, however, hES cells must be cryopreserved as clumps when using conventional slow freezing protocols, leading to lower survival rates during freeze-thaw and limiting their recovery and growth efficiency after thawing, as well as limiting downstream applications that require single cell suspensions. We describe a novel method to increase freeze-thaw survival and proliferation rate of single hES cells in serum-free and feeder-free culture conditions.

METHODS

hES cells maintained on Matrigel-coated dishes were dissociated into single cells with Accutase and slow freezing. After thawing at 37 degrees C, cells were cultured in mTeSR medium supplemented with 10 microM of Rho-associated kinase inhibitor Y-27632 for 1 day.

RESULTS

The use of Y-27632 and Accutase significantly increases the survival of single hES cells after thawing compared with a control group (P < 0.01). Furthermore, by treatment of hES cell aggregates with EGTA to disrupt cell-cell interaction, we show that Y-27632 treatment does not directly affect hES cell apoptosis. Even in the presence of Y-27632, hES cells deficient in cell-cell interaction undergo apoptosis. Y-27632-treated freeze-thawed hES cells retain typical morphology, stable karyotype, expression of pluripotency markers and the potential to differentiate into derivatives of all three germ layers after long-term culture.

CONCLUSIONS

The method described here allows for cryopreservation of single hES cells in serum-free and feeder-free conditions and therefore we believe this method will be ideal for current and future hES cell applications that are targeted towards a therapeutic end-point.

Rho-kinase signalling mediates endotoxin hypersensitivity after partial hepatectomy

BACKGROUND

Excessive loss of functional liver mass results in hepatic dysfunction and is associated with an increased sensitivity to infection. This experimental study investigated the role of Rho-kinase in hepatectomy-induced sensitization to endotoxin.

METHODS

Male C57BL/6J mice underwent 68 per cent hepatectomy and were injected 24 h later with 100 microg Escherichia coli lipopolysaccharide (LPS). Simultaneously, animals received either fasudil or Y-27632 for Rho-kinase inhibition, or phosphate-buffered saline. Untreated hepatectomized animals served as positive controls and sham-operated animals as negative controls. Liver injury and inflammatory parameters were assessed 6 h after LPS challenge by serum alanine aminotransferase (ALT) levels, histomorphology and enzyme-linked immunosorbent assay.

RESULTS

Hepatectomy resulted in a significant susceptibility to LPS, as indicated by inflammatory leucocyte recruitment (mean(s.e.m.) 10(1) leucocytes per high-power field), hepatocellular disintegration (ALT 22.4(3.1) microkat/l) and apoptotic cell death (3.8(0.2) per cent). Rho-kinase inhibition reduced leucocytic infiltration by more than 33 per cent, abolished hepatocellular apoptosis entirely, and reduced tumour necrosis factor alpha expression by more than 48 per cent and CXC chemokine expression by more than 36 per cent.

CONCLUSION

Hepatectomy increased susceptibility to LPS by Rho-kinase-dependent mechanisms. Blocking Rho-kinase signalling decreased LPS-induced liver injury in hepatectomized mice.

Wide therapeutic time window for Rho-kinase inhibition therapy in ischemic brain damage in a rat cerebral thrombosis model

The aim of this study was to investigate the influence of delayed Rho-kinase inhibition with fasudil on second ischemic injury in a rat cerebral thrombosis model. Cerebral ischemia was induced in rats by injecting 150 mug of sodium laurate into the left internal carotid artery on day 1. In the ischemic group, the regional cerebral blood flow (rCBF) was significantly decreased 6.5 h after the injection. Fasudil (3 mg/kg/30 min i.v. infusion) significantly increased rCBF. The viscosity of whole blood was significantly increased 48 h after the injection of sodium laurate. Fasudil (10 mg/kg, i.p.) significantly decreased blood viscosity. To clarify the therapeutic time window of fasudil, rats received their first i.p. administration of fasudil (10 mg/kg) 6 h after an injection of sodium laurate. Administration of fasudil twice daily was continued until day 4. Fasudil prevented the accumulation of neutrophils within the brain as seen from measurements taken on day 3, and improved neuronal functions and reduced the infarction area as seen on day 5. Fasudil and hydroxyfasudil, an active metabolite of fasudil, concentration-dependently inhibited phosphorylation of myosin binding subunit of myosin phosphatase in neutrophils. The present results indicate that inhibition of Rho-kinase activation with fasudil is effective for the treatment of ischemic brain damage with a wide therapeutic time window by improving hemodynamic function and preventing the inflammatory responses. These results suggest that fasudil will be a novel and efficacious approach for the treatment of acute ischemic stroke.

Wide therapeutic time window for fasudil neuroprotection against ischemia-induced delayed neuronal death in gerbils

The neuroprotective potential and therapeutic time window for fasudil, a Rho-kinase inhibitor (RKI), were evaluated for delayed neuronal death in gerbils. A preliminary screening was done on fasudil, ozagrel, and edaravone using a single administration in a delayed neuronal death study. Intraperitoneal (i.p.) administration of edaravone, a free radical scavenger (3, 10 mg/kg) immediately after re-circulation did not reduce neuronal degeneration. We previously reported that ozagrel, a thromboxane A(2) synthetase inhibitor (30 mg/kg) also did not reduce neuronal degeneration, while fasudil (3, 30 mg/kg) significantly protected against the ischemia-induced neuronal loss. To clarify the therapeutic time window of fasudil, which showed a positive effect in a preliminary screening, animals received their first i.p. administration of fasudil (10 mg/kg) 24 or 48 h after ischemia. Administration of fasudil twice daily was continued until day 6. Fasudil significantly protected against the ischemia-induced delayed neuronal death when the treatment was started 24 h after ischemia. In gerbils, hydroxyfasudil, an active metabolite of fasudil, was found following an i.p. administration of fasudil (10 mg/kg), and the value of the area under the plasma level curve of hydroxyfasudil was 7 times higher than that of fasudil. Hydroxyfasudil may contribute to the potency of fasudil. The present findings indicate that the RKI fasudil reduces ischemic neuronal damage with a wide therapeutic time window in gerbil, and may be useful in the treatment of acute ischemic stroke in humans.

[Rho/Rho kinase signal transduction pathway in cardiovascular disease and cardiovascular remodeling]

The small guanosine triphosphatase Rho and its target, Rho kinase, play important roles in both blood pressure regulation and vascular smooth muscle contraction. Rho is activated by agonists of receptors coupled to cell membrane G protein, such as angiotensin II and phenylephrine. Once Rho is activated, it translocates to the cell membrane where it, in turn, activates Rho kinase. Activated Rho kinase phosphorylates myosin light chain phosphatase, which is then inhibited. This sequence stimulates vascular smooth muscle contraction, stress fiber formation,and cell migration. In this way, Rho and Rho kinase activation have important effects on several cardiovascular diseases. Currently available substances that specifically inhibit this signaling pathway could offer clinical benefits in several cardiovascular, as well as noncardiovascular diseases, such as arterial hypertension, pulmonary hypertension, cerebral or coronary spasm, post-angioplasty restenosis, and erectile dysfunction.

Prolonged lesional expression of RhoA and RhoB following spinal cord injury

Inhibition of the small GTPase ras homology protein (Rho) or its downstream target, the Rho-associated kinase (ROCK), has been shown to promote axon regeneration and to improve functional recovery following spinal cord injury (SCI) in the adult rat. Here, we have analyzed the expression of RhoA and RhoB following spinal cord injury in order to assess whether Rho is a possible target for late pharmacological intervention. In control spinal cords, RhoA(+) cells were almost absent, whereas RhoB was localized to some ependymal cells, a few microglia, and some dissociated neurons. In injured spinal cords, RhoA(+) and RhoB(+)cells accumulated at perilesional areas and in the developing necrotic core early after injury at day 1. After reaching their maximum levels (RhoA at day 3; RhoB at day 1), RhoA(+) and RhoB(+) cell numbers remained significantly elevated until day 28. In areas remote from the lesion (> or =0.75 mm), a more discrete accumulation of RhoA(+) and RhoB(+) cells was observed, primarily in areas of ongoing Wallerian degeneration. RhoA and RhoB were predominantly expressed by polymorphonuclear granulocytes, ED1(+) microglia/macrophages, oligodendrocytes, some neurons, and swollen axons/neurites. Furthermore, expression was located to lesional, reactive astrocytes and fibroblastoid cells confined to areas of scar formation. Our experiments have determined that most RhoA(+) and RhoB(+) cells (>70%) are of mononuclear origin. The persistent presence of lesional RhoA(+) and RhoB(+) axon/neurite fibers over a period of 4 weeks after injury suggests that Rho inhibition is a putative therapeutic concept also for delayed intervention after SCI.

Effects of fasudil in acute ischemic stroke: results of a prospective placebo-controlled double-blind trial

BACKGROUND

A multicenter, double-blind, placebo-controlled study was conducted to assess the efficacy and safety of fasudil, a Rho-kinase inhibitor (RKI), in the treatment of acute ischemic stroke.

METHODS

A total of 160 patients, who were able to receive drug treatment within 48 h of acute ischemic stroke onset were enrolled. Patients received either 60 mg fasudil or a placebo (saline) by intravenous injection over 60 min, twice daily for 14 days. The primary end points were neurological status at 2 weeks after the start of treatment, and clinical outcome at 1 month after the onset of symptoms.

RESULTS

Fasudil treatment resulted in significantly greater improvements in both neurological functions (p=0.0013), and clinical outcome (p=0.0015). There were no serious adverse events reported in the fasudil group. The average trough value (12 h values) of active metabolite hydroxyfasudil, another RKI, in healthy elderly volunteers receiving 60 mg of fasudil was 0.077 microM-a concentration well above that needed to inhibit Rho-kinase (0.025-0.05 microM).

CONCLUSION

Treatment with fasudil within 48 h of acute ischemic stroke onset significantly improved the patient's clinical outcome. This study found fasudil to be a useful and safe drug for patients with acute ischemic stroke. Further evaluations, for example, 3-month functional outcomes in a larger clinical trial, may help to define the efficacy of fasudil in acute ischemic stroke.

Role of Rho-kinase in reexpansion pulmonary edema in rabbits

Reexpansion of a collapsed lung increases the microvascular permeability and causes reexpansion pulmonary edema. Neutrophils and their products have been implicated in the development of this phenomenon. The small GTP-binding proteins Rho and its target Rho-kinase (ROCK) regulate endothelial permeability, although their roles in reexpansion pulmonary edema remain unclear. We studied the contribution of ROCK to pulmonary endothelial and epithelial permeability in a rabbit model of this disorder. Endothelial and epithelial permeability was assessed by measuring the tissue-to-plasma (T/P) and bronchoalveolar lavage (BAL) fluid-to-plasma (B/P) ratios with (125)I-labeled albumin. After intratracheal instillation of (125)I-albumin, epithelial permeability was also assessed from the plasma leak (PL) index, the ratio of (125)I-albumin in plasma/total amount of instilled (125)I-albumin. T/P, B/P, and PL index were significantly increased in the reexpanded lung. These increases were attenuated by pretreatment with Y-27632, a specific ROCK inhibitor. However, neutrophil influx, neutrophil elastase activity, and malondialdehyde concentrations in BAL fluid collected from the reexpanded lung were not changed by Y-27632. In endothelial monolayers, Y-27632 significantly attenuated the H(2)O(2)-induced increase in permeability and mitigated the morphological changes in the actin microfilament cytoskeleton of endothelial cells. These in vivo and in vitro observations suggest that the Rho/ROCK pathway contributes to the increase in alveolar barrier permeability associated with reexpansion pulmonary edema.

Lysophosphatidic acid induces histamine release from mast cells and skin fragments

The present study examined whether lysophosphatidic acid (LPA) induces histamine release and the role of Rho-associated protein kinase (ROCK) in histamine release utilizing Y-27632, an inhibitor of ROCK. Rat peritoneal mast cells and mouse skin fragments were challenged with LPA; subsequently, histamine contents were measured by spectrofluorometric assay. LPA-induced histamine release from mast cells and skin fragments occurred in a time- and dose-dependent manner Pretreatment with Y-27632 inhibited LPA-induced histamine release in a dose-dependent fashion. LPA-induced histamine release was not influenced by calcium-free conditions; however, A23187-induced histamine release decreased significantly. TMB-8, an intracellular calcium antagonist, dose-dependently inhibited the histamine release under these conditions. Additionally, Y-27632 scarcely affected A23187-induced histamine release. These findings suggest that LPA-induced histamine release may be attributable to calcium release from intracellular stores. Moreover, ROCK participates in the extracellular calcium-independent process of LPA-induced histamine release.

Effects of Y-27632, a selective Rho-kinase inhibitor, on myocardial preconditioning in anesthetized rats

The objective of this study was to examine the effects of Y-27632, a selective Rho-kinase inhibitor, on ischemic preconditioning (IP) and carbachol preconditioning (CP) in anesthetized rats. Administration of Y-27632 (0.1 mg/kg) produced slight, but not significant, reduction in mean arterial blood pressure and suppressed the total number of ventricular ectopic beats (VEBs). IP, induced by 5 min coronary artery occlusion and 5 min reperfusion, decreased the incidence of ventricular tachycardia (VT) from 100 (n=30) to 25% (n=24) and abolished the occurrence of ventricular fibrillation (VF) (40% in control group) during 30 min of ischemia. The incidences of VT and VF in Y-27632+IP group were found to be similar to IP group. Carbachol (4 microg/kg/min for 5 min) induced marked depressions in mean arterial blood pressure, heart rate and attenuated the total number of VEBs, but significant reductions in VT and VF incidences were noted in Y-27632+CP group. Y-27632 infusion for 5 min abolished VF occurrence. Marked reductions in plasma lactate levels were observed in all treatment and preconditioning groups. IP led to marked decrease in malondialdehyde levels. Decreases in infarct size were also observed with all groups when compared to control. These results suggest that infusion of Y-27632 was able to produce cardioprotective effects on myocardium against arrhythmias, infarct size or biochemical parameters and mimic the effects of ischemic preconditioning in anesthetized rats. Therefore, it is likely that inhibition of Rho-kinase is involved in the signaling cascade of myocardial preconditioning.

Role of protein kinase C in Ca channel blocker-induced renal arteriolar dilation in spontaneously hypertensive rats

The present study examined the role of L-/T-type Ca channels and the interaction between these channels and protein kinase C (PKC) in hypertension. The isolated perfused hydronephrotic rat kidney model was used to visualize directly the renal microvascular effects of L-/T-type Ca channel blockers (nifedipine and mibefradil, respectively). Nifedipine reversed the angiotensin II-induced constriction of afferent, but not efferent, arterioles in kidneys from Wistar-Kyoto rats (WKY), and similar magnitude in dilation was observed in spontaneously hypertensive rats (SHR). Although mibefradil elicited dilation of both arterioles, the afferent arteriolar dilation was less in SHR than in WKY (57+/-5% vs. 80+/-4% reversal at 1 micrommol/L). The pretreatment with staurosporine did not alter the angiotensin II-induced afferent arteriolar constriction in WKY, but attenuated this response in SHR. Furthermore, staurosporine enhanced the nifedipine-induced afferent arteriolar dilation (62+/-3% vs. 50+/-3% reversal at 10 nmol/L), and restored the attenuated afferent arteriolar response to mibefradil in SHR. The pretreatment with thapsigargin (a blocker of IP3-mediated intracellular calcium release) prevented the angiotensin II-induced afferent arteriolar constriction in WKY, but caused a significant constriction of afferent arterioles in SHR and efferent arterioles in WKY and SHR; in this setting, mibefradil did not alter efferent arteriolar tone. In conclusion, although both L-type (nifedipine) and T-type Ca channel blockers (mibefradil) exerted potent vasodilation of rat renal microvessels, these actions were modified by PKC, which determined the afferent arteriolar sensitivity to these blockers in SHR. Furthermore, the enhancement in nifedipine-induced afferent arteriolar dilation by staurosporine in SHR suggests that L-type Ca channel activity is augmented in hypertensive animals.

Comparison of effects of Y-27632 and Isoproterenol on release of cytokines from human peripheral T cells

Y-27632 selectively inhibits Rho-associated protein kinases (ROCKs), an effector for RhoA. The RhoA system is involved in T cell activation. Y-27632 mimicked effects of beta agonists on human cells. We examined the effects of both Y-27632 and Isoproterenol (Iso) on the release of T helper type 1 (Th-1) cytokines (interleukin (IL)-2 and interferon (IFN)-gamma) and Th-2 cytokines (IL-4 and IL-5) from activated human T cells. Peripheral T cells obtained from seven healthy volunteers were incubated in the presence of Y-27632 (0.1-10 micro M) for 30 min, and stimulated with 50 micro g/ml of Concanavalin A (Con A) for 24 h. Concomitantly, after an incubation with medium alone, cells were stimulated with Con A in the presence of Iso (0.1-10 micro M). The concentration of these cytokines in supernatants was measured by ELISA. Both Y-27632 and Iso suppressed release of Th-1 cytokines, decreased release of Th-2 cytokines weakly, and reduced ratio of Th-1/Th-2 cytokine release from Con A-activated T cells. These inhibitory effects of Y-27632 closely resembled those of Iso at each concentration tested. Y-27632 mimicked effects of Iso on secretion of Th-1 and Th-2 cytokines from human peripheral T cells activated with Con A. It is suggested that the RhoA/ROCK system plays an important role in the release of Th-1 cytokines and is partially involved in the release of Th-2 cytokines from human T cells activated through T cell receptor (TCR).

Lesional Expression of RhoA and RhoB following Traumatic Brain Injury in Humans

Inhibition of the small GTPase Rho or of its downstream target Rho-associated kinase (ROCK) has been shown to promote axon regeneration and to improve functional recovery following traumatic CNS lesions in the adult rat. In order to determine the expression pattern of RhoA and RhoB following human traumatic brain injury (TBI) and to assess whether Rho is a possible target for pharmacological intervention in humans, we investigated expression patterns of RhoA and RhoB in brain specimens from 25 patients who died after closed TBI in comparison to brain tissue derived from four neuropathologically unaffected control patients by immunohistochemistry. A highly significant lesional upregulation of both RhoA and RhoB was observed beginning several hours after the traumatic event and continuing for months after TBI. The cellular sources of both molecules included polymorphonuclear granulocytes, monocytes/macrophages, and reactive astrocytes. Additionally, expression of RhoA was also detected in neuronal cells in some of the cases. From our data, we conclude that inhibition of Rho is a promising mechanism for the development of new pharmacological interventions in human TBI. As the observed upregulation of RhoA and RhoB was still detectable months after TBI, we speculate that even delayed treatment with Rho inhibitors might be a therapeutic option.

Partial protective effect of Y-27632, a Rho kinase inhibitor, against hepatic ischemia–reperfusion injury in rats

(+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)-cyclohexanecarboxamide dihydrochloride (Y-27632), a Rho kinase inhibitor, has a suppressive effect on the functions of polymorphonuclear leukocytes. In this study, the influence of Y-27632 on ischemia-reperfusion injury of the liver was examined in rats. Y-27632 (3 mg/kg) or vehicle alone was intravenously injected into rats 60 min before occlusion. Blood samples were obtained for 48 h after reperfusion. At the end of the experiment, the hepatic content of myeloperoxidase, which reflects the number of polymorphonuclear leukocytes in liver tissues, was determined. The increases in serum hepatic aminotransferases and inflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6] after reperfusion were partially, but significantly, inhibited by Y-27632. The increased hepatic myeloperoxidase content was significantly lowered by Y-27632. These results suggest that Y-27632 has a partial protective effect against hepatic ischemia-reperfusion injury through the suppression of polymorphonuclear leukocytes and inflammatory cytokines.

Enhancement of migration and invasion of hepatoma cells via a Rho GTPase signaling pathway

AIM: Intrahepatic extension is the main cause of liver failure and death in hepatocellular carcinoma patients. The small GTPase Rho and one of its effector molecules ROCK regulate cytoskeleton and actomyosin contractility, and play a crucial role in cell adhesion and motility. We investigated the role of small GTPase Rho in biological behaviors of hepatocellular carcinoma to demonstrate the importance of Rho in cancer invasion and metastasis.

METHODS: Using Western blotting, we quantitated Rho protein expression in SMMC-7721 cells induced by Lysophosphatidic acid (LPA). Furthermore, we examined the role of Rho signaling in regulating the motile and invasive properties of tumor cells.

RESULTS: Rho protein expression was stimulated by LPA. Using the Rhotekin binding assay to assess Rho activation, we observed that the level of GTP-bound Rho was elevated transiently after the addition of LPA, and Y-27632 decreased the level of active Rho. LPA enhanced the motility of tumor cells and facilitated their invasion. Rho played an essential role in the migratory process, as evidenced by the inhibition of migration and motility of cancer cells by a specific inhibitor of ROCK, Y-27632.

CONCLUSION: The finding that invasiveness of hepatocellular carcinoma is facilitated by the Rho/Rho-kinase pathway is likely to be relevant to tumor progression and Y-27632 may be a new potential effective agent for the prevention of intrahepatic extension of human liver cancer.

Rho inhibition decreases TNF-induced endothelial MAPK activation and monolayer permeability

Our laboratory previously demonstrated that MAPK activation is an important signal during cytokine-induced endothelial permeability (Nwariaku FE, Liu Z, Terada L, Duffy S, Sarosi G, and Turnage R. Shock 18: 82-85, 2002). Because GTP-binding proteins have been implicated in MAPK activation, we now hypothesize that the GTP-binding protein Rho is a mediator of TNF-induced MAPK activation and increased endothelial permeability. Transmonolayer permeability was assessed in human lung microvascular cells by measuring transmonolayer electrical resistance. MAPK activity was assessed by using a phospho-specific immunoprecipitation kinase assay and by comparing Western blots for phospho-MAPK with total MAPK. MAPK inhibitors used were SB-202190 and PD-098059, whereas Clostridium botulinum C3 transferase was used as a Rho inactivator. Rho-associated coiled-coil kinase was inhibited with Y-27632. TNF increased pulmonary endothelial permeability in vitro and caused a rapid, sustained increase in endothelial p38 and extracellular signal-regulated kinase MAPK activity. Inhibition of p38 and extracellular signal-regulated kinase MAPK with SB-202190 and PD-098059, respectively, decreased TNF-induced endothelial permeability. C3 transferase attenuated TNF-induced MAPK activation and blocked TNF-induced endothelial permeability. Finally, inhibition of Rho-associated coiled-coil kinase with Y-27632 prevented both MAPK activation and TNF-induced decreases in transmonolayer resistance. Rho acts upstream of mitogen-activated protein kinases in mediating TNF-induced pulmonary endothelial leak.

Inhibition of small-conductance Cl- channels by the interleukin-1beta-stimulated production of superoxide in rabbit gastric parietal cells

We have shown previously that the G protein-coupled production of superoxide anion (O2-) leads to closure of small-conductance Cl- channels (0.3-0.4 pS) in the basolateral membrane of rabbit parietal cells. In the present study, effects of interleukin-1beta (IL-1beta) on the Cl- channel were investigated. In the whole-cell patch-clamp recording, IL-1beta (0.3-10 ng ml-1) inhibited the whole-cell Cl- current recorded from a parietal cell within isolated rabbit gastric glands. Variance noise analysis of the whole-cell Cl- current showed that the single channel conductance of the Cl- channel that is sensitive to IL-1beta is 0.37 pS. The IL-1beta (1 ng ml-1)-induced decrease of the Cl- current was abolished by anti-IL-1beta antibody (2 microg ml-1), recombinant IL-1 receptor antagonist (500 ng ml-1), GDPbetaS (500 microM) and superoxide dismutase (100 units ml-1), a scavenger of O2-. Northern blot analysis showed that the mRNA of the IL-1 receptor was selectively expressed in rabbit gastric parietal cells. In the dihydrofluorescein diacetate-loaded single parietal cells in gastric glands, IL-1beta (0.3-10 ng ml-1) stimulated the production of oxygen radicals. Y-27632 (1-10 microM), a specific Rho-kinase inhibitor, and fluvastatin (10 microM), an indirect inhibitor for Rho proteins, significantly inhibited the IL-1beta-induced effects on the channel activity and production of oxygen radicals. IL-1beta (0.3-10 ng ml-1) activated Rho in the parietal cells. These results indicate that IL-1beta binds to the IL-1 receptor of gastric parietal cells and inhibits the small-conductance Cl- channel via the G protein-mediated Rho/Rho-kinase-dependent production of O2-.

Rho-dependent Rho kinase activation increases CD44 surface expression and bone resorption in osteoclasts

Osteoclasts from osteopontin-deficient mice exhibit decreased CD44 surface expression [corrected]. Osteopontin (OPN)/alphavbeta3 generated Rho signaling pathway is required for the surface expression of CD44. In this work we show the Rho effector, Rho kinase (ROK-alpha), to be a potent activator of CD44 surface expression. ROK-alpha activation was associated with autophosphorylation, leading to its translocation to the plasma membrane, as well as its association with CD44. ROK-alpha promoted CD44 surface expression through phosphorylation of CD44 and ezrin-radixin-moesin (ERM) proteins and CD44.ERM.actin complex formation. Osteoclasts from OPN-/- mice exhibited an approximately 55-60% decrease in basal level ROK-alpha phosphorylation as compared with wild type osteoclasts. Furthermore, RhoVal-14 transduction was only partially effective in stimulating ROK-alpha/CD44 phosphorylation, as well as CD44 surface expression, in these osteoclasts. Studies on the inhibition of Rho by C3 transferase or ROK-alpha by the specific inhibitor, Y-27632, showed a decrease in the phosphorylation mediated by ROK-alpha and CD44 surface expression. Neutralizing antibodies to alphav, beta3, or CD44 inhibited the migration and bone resorption of wild type osteoclasts. However, only anti-alphav or -beta3 antibodies blocked OPN-induced phosphorylation of ROK-alpha, CD44, and the ERM proteins. Our results strongly suggest a role for ROK-alpha in alphavbeta3-mediated Rho signaling, which is required for the phosphorylation events and CD44 surface expression. The functional deficiencies in the Rho effector(s) because of the lack of OPN were associated with decreased CD44 surface expression and hypomotility in the OPN-/- osteoclasts. Finally, we find that cooperativity exists between alphavbeta3 and CD44 for osteoclast motility and bone resorption.

Reduction of hepatic ischemia/reperfusion-induced injury by a specific ROCK/Rho kinase inhibitor Y-27632

BACKGROUND

The low-molecular-weight GTPase Rho is known to act as a molecular switch by activating several downstream effectors, one of which is Rho-associated coiled-coil forming protein kinase (ROCK). ROCK/Rho kinase mediates cytoskeleton-dependent cell functions, such as actomyosin-based smooth muscle contraction and integrin-mediated cell adhesion. A specific inhibitor of ROCK/Rho kinase, Y-27632, was recently developed. The present study examined whether Y-27632 could provide a beneficial effect on hepatic ischemia/reperfusion (I/R)-induced injury through the attenuation of microcirculatory disturbance.

MATERIALS AND METHODS

In male Sprague-Dawley rats, normothermic partial ischemia was induced by clamping the hepatic pedicle to the left and median lobes for 90 min, followed by 2 h of reperfusion. In the treatment group, Y-27632 was intravenously administered prior to ischemic insult. Hepatic microcirculation was investigated by using intravital fluorescence microscopy. Liver enzyme release and histological changes of the liver tissue were also evaluated.

RESULTS

Y-27632 significantly improved sinusoidal perfusion and reduced the number of leukocytes sticking in hepatic sinusoids and adhering in postsinusoidal venules. The postischemic narrowing of both sinusoids and postsinusoidal venules was also markedly suppressed. Consequently, liver enzyme release was reduced and postischemic histological damage was suppressed.

CONCLUSIONS

A specific ROCK/Rho kinase inhibitor, Y-27632, was useful to alleviate hepatic I/R-induced injury through ameliorating postischemic microcirculation. The administration of Y-27632 may be a novel strategy for conquering hepatic I/R-induced injury.

Inhibition of Rho-kinase reduces renal Na-H exchanger activity and causes natriuresis in rat

Rho-kinase regulates the actin cytoskeleton and therefore modulates transport. The role of Rho-kinase in Na-H exchanger (NHE) activity of rat proximal convoluted tubules (PCTs) was investigated using (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632), a specific inhibitor of Rho-kinase. In spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats, apical and basolateral NHE activities were determined by measuring cell pH recovery following luminal NH4+ prepulse and basolateral sodium removal, respectively. Apical NHE activity was greater in 8 to 9 week old hypertensive SHR compared with WKY. Although Y-27632 suppressed pH(i) recovery in both strains, sensitivity was 50-fold higher in adult SHR. Y-27632 suppressed basolateral NHE in both strains with similar sensitivity. Apical NHE activity was not greater in 5-week-old, not yet hypertensive, SHR rats compared with WKY. In clearance studies, Na excretion was less in SHR than in WKY rats. Y-27632 increased Na excretion and fractional excretion Na in both strains but more so in SHR. (22)Na uptake of the brush border membrane vesicle taken from Y-27632-treated rats decreased more than that from vehicle-treated animals in both adult SHR and WKY. We conclude that apical NHE activity is increased in SHR PCT compared with controls and that inhibition of Rho-kinase reduces PCT NHE activities and causes natriuresis.

A novel inhibitor of Rho-associated protein kinase, Y-27632, ameliorates hepatic ischemia and reperfusion injury in rats

BACKGROUND

A Rho-ROCK signal system induces vascular contraction and neutrophil migration, both of which are characteristic features found with ischemia and reperfusion injury of the liver. We tested our hypothesis that a novel ROCK I inhibitor, Y-27632, attenuates hepatic ischemia and reperfusion injury.

METHODS

Rats underwent 70% partial hepatic ischemia for 120 minutes and subsequent reperfusion. Y-27632 of 10mg/kg was given orally 1 hour before ischemia, while distilled water was given to the control animals. One week animal survival, systemic hemodynamics, hepatic tissue blood flow, liver function tests, plasma endothelin-1, serum hyaluronic acid levels, myeloperoxidase activity and malondialdehyde level in liver tissue, membrane attack complex-1 and intracellular adhesion molecule-1 staining, and histological architecture were analyzed.

RESULTS

Y-27632 prolonged 1-week animal survival from 25% of untreated animals to 75% accompanied with significant amelioration of hepatic tissue blood flow, liver function tests and histological architecture without any adverse effects on systemic hemodynamics. In addition, plasma endothelin-1 and serum hyaluronic acid levels decreased markedly compared to the control, concomitant with remarkable suppression of membrane attack complex-1 stain positive neutrophils infiltration, myeloperoxidase activity and malondialdehyde level.

CONCLUSION

Present study suggests that activation of a Rho-ROCK signal system is associated with ischemia and reperfusion injury of the liver, and that Y-27632 may be an attractive agent for application in major liver resection using temporary inflow occlusion and hepatic preservation.

Lysophosphatidic acid enhances in vivo infiltration and activation of guinea pig eosinophils and neutrophils via a Rho/Rho-associated protein kinase-mediated pathway

Lysophosphatidic acid (LPA) has been shown to be a chemoattractant in in vitro studies. The present study was carried out to determine whether LPA enhances infiltration of inflammatory cells in in vivo studies with guinea pigs. LPA (1 - 10 microg/ml), when by guinea pigs for 5 min, substantially increased the numbers of eosinophils and neutrophils in the bronchoalveolar lavege fluid (BALF), which was recovered at over 4 h after the inhalation of LPA. Infiltration in BALF was significantly inhibited by inhalation of Y-27632, an inhibitor of Rho-associated protein kinase (ROCK). LPA also increased superoxide production of eosinophils and neutrophils. In contrast, Y-27632 inhibited superoxide production. These findings suggest that LPA may contribute to infiltration and activation of inflammatory cells in bronchial asthma; furthermore, the Rho/ROCK-mediated pathway may be involved.

Role of Rho-associated protein kinase and histamine in lysophosphatidic acid-induced airway hyperresponsiveness in guinea pigs

Inhalation of oleoyl lysophosphatidic acid (LPA) induced airway hyperresponsiveness to acetylcholine (ACh). In contrast, palmitoyl and stearoyl LPA exerted minimal effects. Airway hyperresponsiveness was inhibited by inhalation of Y-27632, an inhibitor of Rho-associated protein kinase (ROCK). Mepyramine, an H1 histamine receptor antagonist and ketotifen, an inhibitor of histamine release and H1 histamine receptor antagonist, also inhibited airway hyperresponsiveness induced by LPA; however, aspirin failed to attenuate this response. The incubation of lung fragments with LPA gave rise to releases in histamine. On the other hand, LPA produced no significant changes on the smooth muscle contraction evoked by ACh. These findings suggest that LPA-induced airway hyperresponsiveness is attributable to activation of the Rho/ROCK-mediated pathway via endothelial cell differentiation gene (EDG) receptors, probably EDG 7. Moreover, histamine release may be involved.

Vitamin E-bonded hemodialyzer improves neutrophil function and oxidative stress in patients with end-stage renal failure

We evaluated the biocompatibility of a newly developed vitamin E hemodialyzer (CL-EE; Terumo Co Ltd, Tokyo, Japan) by neutrophil function and oxidant stress in patients with end-stage renal failure in a randomized crossover study. Ten patients underwent hemodialysis using either the CL-EE or a control dialyzer membrane identical to the CL-EE except for vitamin E binding for 12 weeks in a crossover fashion after a 1-month washout period with hemophane membranes. White blood cell counts, serum oxidized low-density lipoprotein (Ox-LDL) levels, and malondialdehyde (MDA) levels during hemodialysis sessions were measured at the initiation and end of the CL-EE and control trials. Superoxide anion production by neutrophils just before and 4 hours after starting the session also was measured. Leukocytopenia at 1 hour after starting the session was detected to a similar extent in both membranes. However, the degree of reduction was less in the CL-EE trial after repeated use. Superoxide anion production by neutrophils just before a hemodialysis session was reduced after repeated use of the CL-EE membrane. Serum Ox-LDL levels increased, whereas serum MDA levels decreased during sessions to a similar extent in both trials. However, these parameters were significantly lower in the CL-EE trial after repeated use. Serum LDL concentrations significantly decreased with repeated use of the CL-EE membrane. These data suggest that repeated use of the CL-EE membrane for 3 months improves neutrophil function, oxidant stress, and LDL concentrations in patients with renal failure. This membrane may be useful to reduce the incidence of cardiovascular events in patients with renal failure.

The functional role of rho and rho-associated coiled-coil forming protein kinase in eotaxin signaling of eosinophils

The CC chemokine eotaxin plays a pivotal role in local accumulation of eosinophils. Very little is known about the eotaxin signaling in eosinophils except the activation of the mitogen-activated protein (MAP) kinase family. The p21 G protein Rho and its substrate Rho-associated coiled-coil forming protein kinase (ROCK) regulate the formation of stress fibers and focal adhesions. In the present study, we studied the functional relevance of Rho and ROCK in eosinophils using the ROCK inhibitor (Y-27632) and exoenzyme C3, a specific Rho inhibitor. Eotaxin stimulates activation of Rho A and ROCK II in eosinophils. Exoenzyme C3 almost completely inhibited the ROCK activity, indicating that ROCK is downstream of Rho. We then examined the role of Rho and ROCK in eosinophil chemotaxis. The eotaxin-induced eosinophil chemotaxis was significantly inhibited by exoenzyme C3 or Y-27632. Because extracellular signal-regulated kinase (ERK)1/2 and p38 MAP kinases are activated by eotaxin and are critical for eosinophil chemotaxis, we investigated whether Rho and ROCK are upstream of these MAP kinases. C3 partially inhibited eotaxin-induced phosphorylation of ERK1/2 but not p38. In contrast, neither ERK1/2 nor p38 phosphorylation was abrogated by Y-27632. Both C3 and Y-27632 reduced reactive oxygen species production from eosinophils. We conclude that both Rho and ROCK are important for eosinophil chemotaxis and reactive oxygen species production. There is a dichotomy of downstream signaling pathways of Rho, namely, Rho-ROCK and Rho-ERK pathways. Taken together, eosinophil chemotaxis is regulated by multiple signaling pathways that involve at least ROCK, ERK, and p38 MAP kinase.