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

The effects of sorafenib on the portal hypertensive syndrome in patients with liver cirrhosis and hepatocellular carcinoma--a pilot study

BACKGROUND

Increased intrahepatic vascular resistance and hyperperfusion in the splanchnic circulation are the principal mechanisms leading to portal hypertension in cirrhosis. Several preclinical studies have demonstrated a beneficial effect of the multikinase inhibitor sorafenib on the portal hypertensive syndrome.

AIM

To investigate the effect of sorafenib on hepatic venous pressure gradient (HVPG), systemic hemodynamics and intrahepatic mRNA expression of proangiogenic, profibrogenic and proinflammatory genes.

METHODS

Patients with liver fibrosis/cirrhosis and hepatocellular carcinoma were treated with sorafenib 400 mg b.d. HVPG measurement and transjugular liver biopsy were performed at baseline and at week 2. Changes in HVPG and intrahepatic mRNA expression of vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), RhoA, tumour necrosis factor-alpha (TNF-α) and placental growth factor (PlGF) were evaluated.

RESULTS

Thirteen patients (m/f = 12/1; Child-Pugh class A/B = 10/3) were included. The most common aetiology of liver disease was alcohol consumption (n = 7). Eleven patients had an elevated portal pressure, including eight patients with clinically significant portal hypertension. A significant decrease of HVPG (≥ 20% from baseline) was observed in four subjects. In HVPG responders, we observed mRNA downregulation of VEGF, PDGF, PlGF, RhoA kinase and TNF-α, while no substantial mRNA decrease was found in nonresponders in any of the five genes. In two of the four HVPG responders we observed a dramatic (43-85%) mRNA decrease of all five investigated genes.

CONCLUSION

Larger controlled clinical trials are needed to demonstrate any potential beneficial effect of sorafenib on portal hypertension in patients with cirrhosis.

Complementary vascular and matrix regulatory pathways underlie the beneficial mechanism of action of sorafenib in liver fibrosis

Paracrine signaling between hepatic stellate cells (HSCs) and liver endothelial cells (LECs) modulates fibrogenesis, angiogenesis, and portal hypertension. However, mechanisms regulating these processes are not fully defined. Sorafenib is a receptor tyrosine kinase inhibitor that blocks growth factor signaling in tumor cells but also displays important and not yet fully characterized effects on liver nonparenchymal cells including HSCs and LECs. The aim of this study was to test the hypothesis that sorafenib influences paracrine signaling between HSCs and LECs and thereby regulates matrix and vascular changes associated with chronic liver injury. Complementary magnetic resonance elastography, micro-computed tomography, and histochemical analyses indicate that sorafenib attenuates the changes in both matrix and vascular compartments that occur in response to bile duct ligation-induced liver injury in rats. Cell biology studies demonstrate that sorafenib markedly reduces cell-cell apposition and junctional complexes, thus reducing the proximity typically observed between these sinusoidal barrier cells. At the molecular level, sorafenib down-regulates angiopoietin-1 and fibronectin, both released by HSCs in a manner dependent on the transcription factor Kruppel-like factor 6 , suggesting that this pathway underlies both matrix and vascular changes associated with chronic liver disease.

CONCLUSION

Collectively, the results of this study demonstrate that sorafenib inhibits both matrix restructuring and vascular remodeling that accompany chronic liver diseases and characterize cell and molecular mechanisms underlying this effect. These data may help to refine future therapies for advanced gastrointestinal and liver diseases characterized by abundant fibrosis and neovascularization.

Hepatic and HSC-specific sorafenib effects in rats with established secondary biliary cirrhosis

Portal hypertension in cirrhosis depends on increased intrahepatic vascular resistance, which is explained by fibrosis and intrahepatic hyperresponsiveness to vasoconstrictors. Both are caused by activation and proliferation of hepatic stellate cells (HSCs). Portal hypertension of cirrhotic rats can be reduced by the multikinase inhibitor sorafenib, due to a reduction of intrahepatic vascular resistance. Therefore, the hepatic effects of sorafenib require further understanding. Here, we investigated hepatic and HSC-specific sorafenib effects in cirrhotic rats. Animal models of bile duct ligation-induced secondary biliary cirrhosis in rats were studied. The rats were treated with sorafenib (60 mg/kg/day) for 1 week, starting after established cirrhosis. Histological evaluation was carried out using hemalaun and eosin (HE) staining. Apoptosis was studied by PARP cleavage, colorimetric caspase-3 assay, and electrophoretic DNA detection. HSC activation was studied by hepatic Sirius red and immunohistochemical αSMA (α-smooth muscle actin) staining, and by in vitro experiments with culture-activated primary HSCs. Biochemical serum parameters suggested the occurrence of sorafenib-induced liver damage. HE staining revealed histological changes in livers of sham-operated and bile duct-ligated (BDL) rats in response to sorafenib, which were different in both groups. In BDL rats and isolated HSCs, the treatment with sorafenib reduced hepatic αSMA and procollagen-1α mRNA expression. As shown by immunohistochemical staining, perisinusoidal αSMA expression was reduced by sorafenib in BDL rats. This was associated with reduced perisinusoidal deposition of extracellular matrix, as revealed by Sirius red staining. Although no change in PARP cleavage and only a minor increase in hepatic caspase-3 activity were detected in BDL rats in response to sorafenib, livers of sorafenib-treated BDL rats contained small DNA fragments, which were not observed in untreated BDL rats. In conclusion, sorafenib treatment reduces the number of activated HSCs in cirrhotic livers. This leads to the decrease in intrahepatic vascular resistance, but also to liver damage in the dosage we used. Therefore, any translation to portal hypertensive patients who may profit from sorafenib should be done with particular care.

Intrahepatic angiogenesis and sinusoidal remodeling in chronic liver disease: new targets for the treatment of portal hypertension?

Portal hypertension accounts for the majority of morbidity and mortality that is encountered in patients with cirrhosis. Portal hypertension is initiated in large part through increases in intrahepatic vascular resistance. Fibrosis, regenerative nodule formation, and intrahepatic vasoconstriction are classical mechanisms that account for increased intrahepatic vascular resistance in cirrhosis. Recent data suggest that intrahepatic angiogenesis and sinusoidal remodeling could also be involved in sinusoidal resistance, fibrosis, and portal hypertension. While angiogenesis is defined as the formation of new vessels deriving from existing ones, sinusoidal remodeling in its pathological form associated with cirrhosis is characterized by increased mural coverage of vessels by contractile HSC. Most attention on the mechanisms of these processes has focused on the liver sinusoidal endothelial cell (SEC), the hepatic stellate cell (HSC), and the paracrine signaling pathways between these two cell types. Interventions that target these vascular structural changes have beneficial effects on portal hypertension and fibrosis in some animal studies which has stimulated interest for pursuing parallel studies in humans with portal hypertension.

Toxicity of sorafenib: clinical and molecular aspects

IMPORTANCE OF THE FIELD

Sorafenib is a novel oral bis-aryl urea compound originally developed as an inhibitor of RAF kinase for its anti-proliferative property. Sorafenib also inhibits receptor tyrosine kinases of multiple pro-angiogenic factors such as VEGFR-1/2/3, Flt-3 and PDGFR-beta. The combination of both its anti-proliferative and anti-angiogenic properties makes sorafenib an attractive agent in cancer treatment. Sorafenib has been approved for the treatment of metastatic renal cell carcinoma as well as hepatocellular cancer. Despite its inherent selectivity, sorafenib can cause unusual adverse events whose the management represents a challenge for oncologists.

AREAS COVERED IN THIS REVIEW

Relevant literature was identified using a Pubmed search of articles published up to June 2009. Search terms included 'sorafenib' and 'toxicity'. Original articles were reviewed and relevant citations from these articles were also considered.

WHAT THE READER WILL GAIN

The clinical aspect of sorafenib-induced adverse events and the molecular basis behind this toxicity are discussed. Finally, recommendations for the management of these adverse events are proposed.

TAKE HOME MESSAGE

Although not life-threatening, toxicity of sorafenib can severely impact the physical, psychological and social well-being of patients. The management of this unusual toxicity highlights the particular need of new pluridisciplinarities linking oncologist, cardiologist and dermatologist.

Measurement of porto-systemic shunting in mice by novel three-dimensional micro-single photon emission computed tomography imaging enabling longitudinal follow-up

BACKGROUND AND AIMS

The reference method for diagnosing porto-systemic shunting (PSS) in experimental portal hypertension involves measuring (51)Chrome ((51)Cr)-labelled microspheres. Unfortunately, this technique necessitates the sacrifice of animals. Alternatively, (99m)technetium-macroaggregated albumin ((99m)Tc-MAA) has been used; however, planar scintigraphy imaging techniques are not quantitatively accurate and adequate spatial information is not attained. Here, we describe a reliable, minimally invasive and rapid in vivo imaging technique, using three-dimensional single photon emission computed tomography (3D SPECT) modus, that allows more accurate quantification, serial measurements and spatial discrimination.

METHODOLOGY

Partial portal vein ligation, common bile duct ligation and sham were induced in male mice. A mixture of (51)Cr microspheres and (99m)Tc-macroaggregated albumin particles was injected into the splenic pulpa. All mice were scanned in vivo with microSPECT (1 mm spatial resolution) and, when mandatory for localisation, a microSPECT-CT was acquired. A relative quantitative analysis was performed based on the 3D reconstructed datasets. Additionally, (51)Cr was measured in the same animals to calculate the correlation coefficient between the (99m)Tc detection and the gold standard (51)Cr. In each measuring modality, the PSS fraction was calculated using the formula: [(lung counts)/(lung counts+liver counts)] x 100.

RESULTS

A significant correlation between the (99m)Tc detection and (51)Cr was demonstrated in partial portal vein ligation, common bile duct ligation and sham mice and there was a good agreement between the two modalities. MicroSPECT scanning delivers high spatial resolution and 3D image reconstructions.

CONCLUSION

We have demonstrated that quantitative high-resolution microSPECT imaging with (99m)Tc-MAA is useful for detecting the extent of PSS in a non-sacrificing set-up. This technology permits serial measurements and high-throughput screening to detect baseline PSS, which is especially important in pharmacological studies.

Intraperitoneal LPS amplifies portal hypertension in rat liver fibrosis

Recent studies have shown that the risk of variceal bleeding in patients with liver cirrhosis increases with infections such as spontaneous bacterial peritonitis (SBP). In this study, we hypothesized that pretreatment with intraperitoneal LPS may escalate portal hypertension. In fibrotic livers (4 weeks after bile duct ligation, BDL), the activation of Kupffer cells (KCs) by zymosan (150 microg/ml) in the isolated non-recirculating liver perfusion system resulted in a transient increase in portal perfusion pressure. Pretreatment with intraperitoneal LPS (1 mg/kg body weight (b.w.) for 3 h) increased basal portal perfusion pressure, and prolonged the zymosan-induced increase from transient to a long-lasting increase that was sustained until the end of the experiments in BDL but not in sham-operated animals. Pretreatment with gadolinium chloride (10 mg/kg b.w.), MK-886 (0.6 mg/kg b.w.), Ly171883 (20 microM) or BM 13.177 (20 microM) reduced the maximal and long-lasting pressure increase in BDL animals by approximately 50-60%. The change in portal perfusion pressure was paralleled by a long-lasting production of cysteinyl leukotriene (Cys-LT) and thromboxane (TX) after LPS pretreatment. However, the response to vasoconstrictors was not altered by intraperitoneal LPS. Western blot analyses showed an increased Toll-like receptor (TLR)4 and MyD88 expression after LPS pretreatment. In vivo experiments confirmed that intraperitoneal LPS increased basal portal pressure, and extended the portal pressure increase produced by intraportal zymosan or by LPS infusion. In conclusion, upregulation of TLR4 and MyD88 expression in fibrotic livers confers hypersensitivity to LPS. This may lead to escalation of portal hypertension by production of TX and Cys-LT after endotoxin-induced KC activation. Therefore, LT inhibitors may represent a promising treatment option in addition to early administration of antibiotics in SBP.

Paediatric cholestatic liver disease: Diagnosis, assessment of disease progression and mechanisms of fibrogenesis

Cholestatic liver disease causes significant morbidity and mortality in children. The diagnosis and management of these diseases can be complicated by an inability to detect early stages of fibrosis and a lack of adequate interventional therapy. There is no single gold standard test that accurately reflects the presence of liver disease, or that can be used to monitor fibrosis progression, particularly in conditions such as cystic fibrosis. This has lead to controversy over how suspected liver disease in children is detected and diagnosed. This review discusses the challenges in using commonly available methods to diagnose hepatic fibrosis and monitor disease progression in children with cholestatic liver disease. In addition, the review examines the mechanisms hypothesised to be involved in the development of hepatic fibrogenesis in paediatric cholestatic liver injury which may ultimately aid in identifying new modalities to assist in both disease detection and therapeutic intervention.

Treatment with the leukotriene inhibitor montelukast for 10 days attenuates portal hypertension in rat liver cirrhosis

The mechanisms underlying intrahepatic vasoconstriction are not fully elucidated. Here we investigated the Kupffer cell (KC)-dependent increase in portal pressure by way of actions of vasoconstrictive cysteinyl leukotrienes (Cys-LTs). Liver cirrhosis was induced in rats by bile duct ligation (BDL for 4 weeks; controls: sham-operation) and thioacetamide application (18 weeks). Infusion of leukotriene (LT) C(4) or LTD(4) in isolated perfused livers (20 nM, BDL and sham) demonstrated that LTC(4) is a more relevant vasoconstrictor. In BDL animals the Cys-LT(1) receptor inhibitor montelukast (1 microM) reduced the maximal portal perfusion pressure following LTC(4) or LTD(4) infusion. The infusion of LTC(4) or D(4) in vivo (15 microg/kg b.w.) confirmed LTC(4) as the more relevant vasoconstrictor. Activation of KCs with zymosan (150 microg/mL) in isolated perfused BDL livers increased the portal perfusion pressure markedly, which was attenuated by LT receptor blockade (Ly171883, 20 microM). Cys-LTs in the effluent perfusate increased with KC activation but less with additional blockade of KCs with gadolinium chloride (10 mg/kg body weight, 48 and 24 hours pretreatment). KCs were isolated from normal rat livers and activated with zymosan or lipopolysaccharide at different timepoints. This resulted in an increase in Cys-LT production that was not influenced by preincubation with montelukast (1 microM). Infusion of LTC(4) (20 nM) and the thromboxane analog U46619 (0.1 microM) further enhanced portal pressure, indicating additive effects. Treatment with montelukast for 10 days resulted in an impressive reduction in the basal portal pressure and an attenuation of the KC-dependent increase in portal pressure.

CONCLUSION

Activation of isolated KCs produced Cys-LTs. Infusion of Cys-LTs increased portal pressure and, vice versa, treatment with montelukast reduced portal pressure in rat liver cirrhosis. Therefore, montelukast may be of therapeutic benefit for patients with portal hypertension.

Upregulation of early growth response factor-1 by bile acids requires mitogen-activated protein kinase signaling

Cholestasis results when excretion of bile acids from the liver is interrupted. Liver injury occurs during cholestasis, and recent studies showed that inflammation is required for injury. Our previous studies demonstrated that early growth response factor-1 (Egr-1) is required for development of inflammation in liver during cholestasis, and that bile acids upregulate Egr-1 in hepatocytes. What remains unclear is the mechanism by which bile acids upregulate Egr-1. Bile acids modulate gene expression in hepatocytes by activating the farnesoid X receptor (FXR) and through activation of mitogen-activated protein kinase (MAPK) signaling. Accordingly, the hypothesis was tested that bile acids upregulate Egr-1 in hepatocytes by FXR and/or MAPK-dependent mechanisms. Deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA) stimulated upregulation of Egr-1 to the same extent in hepatocytes isolated from wild-type mice and FXR knockout mice. Similarly, upregulation of Egr-1 in the livers of bile duct-ligated (BDL) wild-type and FXR knockout mice was not different. Upregulation of Egr-1 in hepatocytes by DCA and CDCA was prevented by the MEK inhibitors U0126 and SL-327. Furthermore, pretreatment of mice with U0126 prevented upregulation of Egr-1 in the liver after BDL. Results from these studies demonstrate that activation of MAPK signaling is required for upregulation of Egr-1 by bile acids in hepatocytes and for upregulation of Egr-1 in the liver during cholestasis. These studies suggest that inhibition of MAPK signaling may be a novel therapy to prevent upregulation of Egr-1 in liver during cholestasis.

Sorafenib attenuates the portal hypertensive syndrome in partial portal vein ligated rats

BACKGROUND/AIMS

Angiogenesis plays a key role in development of portal hypertension (PHT) and represents a potential therapeutic target. We aimed to evaluate the molecular effects of sorafenib, a multiple tyrosine kinase inhibitor, on splanchnic hemodynamics in rats with partial portal vein ligation (PPVL).

METHODS

The following four groups of rats were treated orally with sorafenib (10mg/kg per day; SORA group) or placebo (PLAC group) for 7 days, beginning at the day of PPVL or sham operation (SO): (1) PPVL-SORA, (2) PPVL-PLAC, (3) SO-SORA and (4) SO-PLAC. Measurements of mean arterial pressure (MAP), portal pressure (PP), and superior mesenterial artery blood flow (SMABF) were performed. Portosystemic collateral blood flow (PSCBF) was determined by radioactive microspheres. Splanchnic protein expression of CD31, alpha-smooth muscle actin (alphaSMA), phospho-extracellular signal-regulated kinase (pERK), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), tumor necrosis factor alpha (TNFalpha), and endothelial nitric oxide synthetase (eNOS) was assessed by Western blot. Gene expression was studied by angiogenesis-focused real-time reverse transcription polymerase chain reaction microarray.

RESULTS

PP, SMABF, and PSCBF were significantly higher in PPVL rats than in SO rats. MAP and heart rate were similar in all groups. Treatment with sorafenib resulted in a significant decrease of PP (p<0.001) and SMABF (p<0.05) in PPVL-SORA rats compared to PPVL-PLAC rats. PPVL-SORA rats had markedly less PSCBF than PPVL-PLAC rats (p<0.001). Superior mesenteric artery resistance (SMAR) was significantly lower in both PPVL groups compared to both SO groups, but PPVL-SORA rats showed significantly higher SMAR than PPVL-PLAC rats (p<0.05). The increased protein expression of CD31, alphaSMA, pERK, VEGF, PDGF, TNFalpha, and eNOS in rats with PHT was markedly decreased by sorafenib treatment. Sorafenib decreased mRNA levels of TNFalpha, VEGF receptor 2, VEGF receptor 1, transforming growth factor beta, cyclooxygenase 1, and expression of various genes that are involved in pathways of cellular proliferation, fibrogenesis, tissue remodeling, inflammation, and angiogenesis.

CONCLUSIONS

Treatment with sorafenib reduced PP, SMABF, and PSCBF in noncirrhotic rats with prehepatic PHT, without affecting systemic hemodynamics. Additional antiproliferative, anti-inflammatory, and antiangiogenic effects of sorafenib were identified.

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

BACKGROUND

Portal hypertension is triggered by vasodilation due to impaired contraction of extrahepatic vessels. Angiotensin II type 1 (AT(1)) receptor-induced vasocontraction is mediated by G proteins and may be desensitized by recruitment of beta-arrestin-2 to the receptor. In this study, we analysed the interaction of AT(1) receptors with beta-arrestin-2 in the context of vascular hypocontractility in rats with CCl(4)-induced cirrhosis.

METHODS

Micronodular liver cirrhosis in rats (n = 15) was induced by regular CCl(4) exposure. Age-matched rats (n = 15) served as controls. Contractility of aortic rings was measured by myography. Protein expressions and phosphorylations were assessed by Western blot analysis, and AT(1) receptor interaction with beta-arrestin-2 by co-immunoprecipitation.

RESULTS

Aortic rings from CCl(4) rats were hypocontractile to angiotensin II independent of nitric oxide synthases (Nomega-nitro-l-arginine methyl ester 200 microM). Expression of the AT(1) receptor, Galpha(q/11) and the contraction-mediating effector Rho kinase was similar in aortas from both groups. Expression and AT(1) receptor binding of beta-arrestin-2 were up-regulated in aortas from CCl(4) rats. Stimulation of isolated aortas with exogenous angiotensin II caused recruitment of beta-arrestin-2 in aortas from noncirrhotic rats, but no further interaction of AT(1) receptors with beta-arrestin-2 was found in aortas from CCl(4) rats. While angiotensin II stimulation resulted in Rho kinase activation in aortas from noncirrhotic rats but not in aortas from CCl(4) rats, extracellular signal-regulated kinase activation in response to angiotensin II was observed in aortas from both groups.

CONCLUSIONS

Vascular hyporesponsiveness to angiotensin II in CCl(4) rats is due to enhanced interaction of the AT(1) receptor with beta-arrestin-2 and consecutively changed receptor function.

Rho proteins and hepatic stellate cells

The Rho family small GTPases can act as molecular switches in eukaryotic signal transduction and exert diverse biological effects through a variety of downstream effector proteins. The actin cytoskeleton is important in maintaining cell shape, mediating many important biological functions in eukaryotic cells and controlling cell contraction, movement and survival. Hepatic stellate cells (HSCs) activation plays a key role in the formation of liver fibrosis and the regulation of portal blood flow. Rho proteins can direct activation-associated changes in HSC morphology via regulation of the actin cytoskeleton. In this article, we will review the mechanisms underlying the roles of Rho family small GTPases in regulating actin cytoskeleton remodeling and cell contractility, movement and survival in HSC cells. Furthermore, we explore the possibility that the Rho family small GTPase-associated signal pathway is used as a new target for treating hepatic fibrosis and portal hypertension.