Dipeptidyl peptidase-4 inhibitor attenuates hepatic fibrosis via suppression of activated hepatic stellate cell in rats.

BACKGROUND: Dipeptidyl peptidase-4 inhibitor (DPP4-I) is clinically used as a new oral antidiabetic agent. Although DPP4 is reportedly associated with the progression of chronic liver diseases, the effect of DPP4-I on liver fibrosis development is still obscure. This study was designed to elucidate the effect of DPP4-I on liver fibrosis development in conjunction with the activated hepatic stellate cells (Ac-HSCs). METHODS: The antifibrotic effect of DPP4-I was assessed in vivo and in vitro using porcine serum-induced experimental liver fibrosis model. DPP4-I, sitagliptin, at a clinically comparable low dose was administered by gavage daily. RESULTS: DPP4-I significantly attenuated liver fibrosis development along with the suppression of hepatic transforming growth factor (TGF)-ß1, total collagen, and tissue inhibitor of metalloproteinases-1 in a dose-dependent manner. These suppressive effects occurred almost concurrently with the attenuation of HSCs activation. Our in vitro studies showed that DPP4-I inhibited platelet-derived growth factor-BB-mediated proliferation of the Ac-HSCs as well as upregulation of TGF-ß1 and α1(I)-procollagen at magnitudes similar to those of the in vivo studies. The inhibitory effects of DPP4-I against HSCs proliferation and fibrogenic gene expression are mediated through the inhibition of the phosphorylation of ERK1/2, p38 and Smad2/3, respectively. CONCLUSIONS: DPP4-I markedly inhibits liver fibrosis development in rats via suppression of HSCs proliferation and collagen synthesis. These suppressive effects are associated with dephosphorylation of ERK1/2, p38 and Smad2/3 in the HSCs. Since DPP4-I is widely used in clinical practice, this drug may represent a potential new therapeutic strategy against liver fibrosis in the near future.

Cocktail therapy with a combination of interferon, ribavirin and angiotensin-II type 1 receptor blocker attenuates murine liver fibrosis development.

An effective therapeutic strategy for suppressing liver fibrosis development should improve the overall prognosis of patients with chronic liver diseases. Despite efforts to develop anti-fibrotic agents, no drugs have yet been approved as anti-fibrotic treatments for humans. An alternative strategy may be to employ a clinically available agent that also exhibits anti-fibrotic activities, for which the safety of long-term administration has been proven. The aim of the current study was to elucidate the combined effect of clinically used interferon (IFN), ribavirin (Rib) and angiotensin-II receptor blocker (ARB) on liver fibrosis development in mice. A model of CCl4-induced hepatic fibrosis was used to assess the effect of IFN, Rib and ARB. IFN, Rib and ARB were administered after a two-week treatment with CCl4, and the hepatic indices of fibrosis were assessed at eight weeks. Single treatment with IFN, Rib or ARB at the clinically available comparable doses significantly attenuated the liver fibrogenesis associated with the suppression of the number of α-smooth muscle actin positive cells, and the hepatic transforming growth factor-ß (TGF-ß) mRNA. Hepatic neovascularization, which is also known to play a pivotal role in liver fibrogenesis, and vascular endothelial growth factor (VEGF), a potent angiogenic factor, were also markedly inhibited. Combination treatment with any two agents exerted a more potent inhibitory effect than any single treatment. Moreover, the triple cocktail treatment revealed further suppressive effects than any two agent combination. Furthermore, in vitro studies showed that similar combined effects were observed on the proliferation and TGF-ß mRNA expression of activated hepatic stellate cells and endothelial cell tube formation. These results indicate that the cocktail combination treatment of clinically used IFN, Rib and ARB may provide a new strategy for anti-liver fibrosis therapy.

Combination treatment of angiotensin II type I receptor blocker and new oral iron chelator attenuates progression of nonalcoholic steatohepatitis in rats.

Angiotensin II type I receptor blocker and iron chelator reportedly exert suppressive effects on nonalcoholic steatohepatitis (NASH) progression, including liver fibrosis and hepatocarcinogenesis. The aim of this study was to elucidate the combined effect of losartan (LOS), an angiotensin II type I receptor blocker, and deferasirox (DSX), a newly developed oral iron chelator, on the progression of NASH in rats. To induce NASH, F344 rats were fed a choline-deficient l-amino acid-defined diet for 12 wk, and the effects of LOS and DSX at clinically comparable low doses were elucidated in conjunction with oxidative stress, neovascularization, and hepatic stellate cells (HSC) activation, all known to play important roles in the progression of NASH. Treatment with both LOS and DSX suppressed choline-deficient L-amino acid-defined diet-induced liver fibrosis development and hepatocarcinogenesis. This combination treatment exerted a stronger inhibitory effect compared with treatment with a single agent. These inhibitory effects occurred almost concurrently with the suppression of oxidative stress, neovascularization, and HSC activation. Our in vitro study demonstrated that LOS and DSX inhibited angiotensin II-induced proliferation, transforming growth factor-ß(1) expression of activated HSC, and in vitro angiogenesis. These results indicated that dual inhibition by combined treatment of LOS and DSX attenuated the progression of NASH. Since both agents are widely used in clinical practice, this combination therapy may represent a potential new strategy against NASH in the near future.

The vascular endothelial growth factor (VEGF) receptor-2 is a major regulator of VEGF-mediated salvage effect in murine acute hepatic failure.

Although administration of the vascular endothelial growth factor (VEGF), a potent angiogenic factor, could improve the overall survival of destroyed sinusoidal endothelial cells (SEC) in chemically induced murine acute hepatic failure (AHF), the mechanistic roles of the VEGF receptors have not been elucidated yet. The respective roles of VEGF receptors; namely, Flt-1 (VEGFR-1: R1) and KDR/Flk-1 (VEGFR-2: R2), in the D-galactosamine (Gal-N) and lipopolysaccharide (LPS)-induced AHF were elucidated with specific neutralizing monoclonal antibody against R1 and R2 (R1-mAb and R2-mAb, respectively). The serum ALT elevation, with a peak at 24 h after Gal-N+LPS intoxication, was markedly augmented by means of the R1-mAb and R2-mAb. The aggregative effect of R2-mAb was more potent than that of R1-mAb, and the survival rate was 70% in the R2-mAb-treated group and 100% in the other groups. The results of SEC destruction were almost parallel to those of the ALT changes. Our in-vitro study showed that R1-mAb and R2-mAb significantly worsened the Gal-N+LPS-induced cytotoxicity and apoptosis of SEC mediated by caspase-3, which were almost of similar magnitude to those in the in-vivo study. In conclusion, these results indicated that R2 is a major regulator of the salvage effect of VEGF on the maintenance of SEC architecture and the anti-apoptotic effects against chemically-induced murine AHF.

Selective aldosterone blocker ameliorates the progression of non-alcoholic steatohepatitis in rats.

Although non-alcoholic steatohepatitis (NASH) may progress to cirrhosis and hepatocellular carcinoma (HCC), no effective therapeutic modalities have been fully established yet. Recent studies have shown that the renin-angiotensin-aldosterone-system plays an important role in NASH. The aim of our current study was to elucidate the effects of aldosterone (Ald) inhibition on the progression of NASH. In the choline-deficient L-amino acid-defined diet-induced rat NASH model, the effects of a clinically used selective Ald blocker (SAB) were elucidated in conjunction with the activated hepatic stellate cells (HSC) and neovascularization, which are both known to play important roles in liver fibrosis development and hepatocarcinogenesis, respectively. Liver fibrosis development and the glutathione-S-transferase placental form-positive pre-neoplastic lesions were both markedly attenuated by SAB along with the suppression of the activated HSC and neovascularization. SAB inhibited the hepatic expression of transforming growth factor-beta 1 and also that of the vascular endothelial growth factor. Our in vitro study showed that SAB also inhibited the Ald-induced HSC proliferation and in vitro angiogenesis in a dose-dependent manner. These results indicated that Ald plays a pivotal role in the progression of NASH. Considering that SAB is already widely used in clinical practice, this drug could represent a potential new strategy against NASH in the future.

Selective aldosterone blocker, eplerenone, attenuates hepatocellular carcinoma growth and angiogenesis in mice.

AIM: The renin-angiotensin-aldosterone system (RAAS) has become known as a prerequisite for tumor angiogenesis, including hepatocellular carcinoma (HCC). Although angiotensin II is known to play an important role in tumor growth and angiogenesis, the role of aldosterone (Ald) is still obscure. The aim of our current study was to elucidate the effect of eplerenone, a clinically used selective Ald blocker (SAB), on murine HCC development especially in conjunction with angiogenesis. METHODS: To create an allograft model, we injected 1 x 10(6) of BNL-HCC cells into the flanks of BALB/c mice. After the tumor was established, SAB was administrated at dose of 100 mg/kg per day. RESULTS: Administration of SAB significantly suppressed HCC development along with inhibition of angiogenesis and expression of the vascular endothelial growth factor (VEGF), a potent angiogenic factor. SAB treatment resulted in a marked increase of apoptosis in the tumor, whereas tumor cell proliferation was not altered. Our in vitro study showed that SAB significantly suppressed the Ald-induced endothelial proliferation and tubular formation through inhibition of phosphorylation of the extracellular signal-regulated kinase 1/2. On the contrary, neither Ald nor SAB affected the proliferation of HCC cells in vitro. CONCLUSION: Ald plays a pivotal role in HCC development through VEGF-mediated tumor angiogenesis, and SAB may be a potential new strategy in HCC therapy in the future.

Synergistic inhibitory effect of gemcitabine and angiotensin type-1 receptor blocker, losartan, on murine pancreatic tumor growth via anti-angiogenic activities.

Pancreatic cancer is one of the leading causes of cancer death, and represents a challenging chemotherapeutic problem. The crucial role of angiogenesis in tumor growth has been widely recognized, and several reports have revealed that the combination treatment of the conventional chemotherapeutic drugs and anti-angiogenic agents exerted synergistic anti-cancerous effects. It has been reported that the clinically used angiotensin type-1 receptor blocker (ARB) exerted potent anti-angiogenic activity. The aim of our current study was to examine the combination effect of gemcitabine (GEM), a widely used conventional chemotherapeutic drug against pancreas cancer, and losartan (Lo), an ARB, on murine pancreatic tumor growth, especially in conjunction with angiogenesis. When used individually, GEM and Lo at clinically comparable low doses moderately suppressed pancreatic tumor development. The combination treatment with GEM and Lo exerted a marked inhibitory effect as compared with single agent treatments even after the tumor was fully established. Neovascularization and the expression of the vascular endothelial growth factor (VEGF), a central angiogenic factor, in the tumor were both markedly suppressed in a magnitude similar to the inhibitory effects against the tumor growth. Since both agents are widely used in the clinical practice, the combination regimen of GEM and Lo may represent a potential new therapeutic strategy for pancreatic cancer in the future.

Losartan, an angiotensin-II type 1 receptor blocker, attenuates the liver fibrosis development of non-alcoholic steatohepatitis in the rat.

BACKGROUND: Apart from simple steatosis, the non-alcoholic steatohepatitis (NASH) can progress into liver fibrosis and cirrhosis. To date, however, no widely accepted therapeutic modalities have been established against NASH in the clinical practice. To find out promising new therapeutic agents, it is important to employ an appropriate experimental model of NASH, such as association with insulin resistance. FINDINGS: In the current study, we found that losartan, a clinically used angiotensin-II type 1 receptor blocker, significantly attenuated a choline-deficient L-amino acid-defined (CDAA) diet-induced steatohepatitis in obese diabetic- and insulin resistance-associated Otsuka Long-Evans Tokushima Fatty (OLETF) rats. The transforming growth factor-beta, a well-known major fibrogenic cytokine, was also suppressed in a similar magnitude to that of the fibrosis area. Noteworthy was the finding that these inhibitory effects were achieved even at a clinically comparable low dose. CONCLUSION: Since losartan is widely used without serious side effects in the clinical practice, this agent may be an effective new therapeutic strategy against NASH.

Branched-chain amino acids suppress insulin-resistance-based hepatocarcinogenesis in obese diabetic rats.

BACKGROUND: Branched-chain amino acids (BCAAs) reportedly inhibit the incidence of hepatocellular carcinoma (HCC) in patients with liver cirrhosis and obesity that is frequently associated with insulin resistance (IR). However, the possible mechanism is still obscure. The aim of the present study was to examine the effect of BCAAs, especially in conjunction with angiogenesis, on hepatocarcinogenesis under the condition of IR. METHODS: The effect of BCAAs on the development of liver enzyme-altered preneoplastic lesions and angiogenesis was examined in obese diabetic Otsuka Long-Evans Tokushima Fatty rats. We also performed an in vitro study to elucidate the possible mechanisms involved. RESULTS: Treatment with BCAAs markedly inhibited glutathione-S-transferase placental form (GST-P)-positive preneoplastic lesions along with suppression of neovascularization in the liver. The hepatic expression of vascular endothelial growth factor (VEGF), a potent angiogenic factor, was also attenuated. BCAA treatment significantly suppressed glucose- and insulin-induced in vitro angiogenesis in the presence of VEGF. CONCLUSIONS: In obese diabetic rats BCAAs exerted a chemopreventive effect against HCC, associated with the suppression of VEGF expression and hepatic neovascularization. Since BCAA preparations are widely used in clinical practice for patients with chronic liver diseases, this agent may represent a new strategy for chemoprevention against HCC in the future.

Impact of insulin resistance on the progression of chronic liver diseases.

Recent studies have revealed a close relationship between insulin resistance (IR) and the progression of chronic liver diseases, although relatively little is known regarding the possible mechanisms involved. The aim of this study was to elucidate the impact of IR on the development of liver fibrosis and hepatocarcinogenesis using obese diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Liver fibrosis development and glutathione-S-transferase placental form (GST-P)-positive pre-neoplastic lesions were both markedly accelerated in OLETF rats, being induced by pig serum and diethylnitrosamine (DEN), respectively. In the fibrosis experiment, alpha-smooth muscle actin-positive activated hepatic stellate cells (HSCs) also significantly increased in OLETF rats along with augmentation of the hepatic collagen content and transforming growth factor-beta1. Our in vitro study showed that both glucose and insulin stimulated the proliferation of activated HSCs, and the combination treatment exerted an additive effect. In the DEN model, neovascularization, which plays a pivotal role in hepatocarcinogenesis, was up-regulated in OLETF rats almost in parallel with pre-neoplastic lesion development and a potent angiogenic factor, vascular endothelial growth factor. High glucose and insulin also significantly augmented the in vitro neovascularization via extracellular signal-regulated kinase 1/2 phosphorylation. Similar to the effect on the activated HSCs, co-existence of both factors exerted a more potent effect than either single factor. In conclusion, these results indicated that the IR status directly accelerated liver fibrosis development and hepatocarcinogenesis at least partly through the stimulation of activated HSC proliferation and hepatic neovascularization, respectively, in the rat.

Neovascularization and oxidative stress in the progression of non-alcoholic steatohepatitis.

Reactive oxygen species (ROS) is known to play an important role in the pathogenesis of non-alcoholic steatohepatitis (NASH); however, as we previously reported, angiogenesis also plays a pivotal role in NASH progression - the development of liver fibrosis and hepatocellular carcinoma - in rats. The aim of the current study was to elucidate the role of angiogenesis in the development of fibrosis in NASH. Twenty-six patients with NASH and 11 with simple fatty liver (FL) disease were enrolled in the study and underwent clinicopathological examination. Immunohistochemical analysis of 4-hydroxy-2-noneal (4-HNE) and CD34 was employed for the detection of ROS and angiogenesis in the liver tissues, respectively. Both the NASH and FL samples displayed a marked staining of 4-HNE as compared to the healthy liver. Similar levels of 4-HNE were observed in NASH regardless of the grade of liver fibrosis. In sharp contrast, hepatic neovascularization developed significantly in NASH alone, whereas almost no neovascularization was observed in FL or the healthy liver. The degree of angiogenesis was almost parallel with the development of liver fibrosis. In conclusion, simple FL and NASH cases were both affected by ROS. However, only NASH was associated with marked neovascularization, proportional to the increase in the grade of liver fibrosis development. These results indicate that hepatic neovascularization may play an important role in the onset and progression of NASH.

Crosstalk between high-molecular-weight adiponectin and T-cadherin during liver fibrosis development in rats.

Adiponectin, a circulating adipocyte-derived secretory protein, reportedly plays an important role in liver fibrosis development, although the biological role of adiponectin in liver fibrogenesis is still controversial. Adiponectin is present in the serum as three oligometric complexes; namely, high-, middle-, and low-molecular weight (HMW, MMW, and LMW, respectively). Adiponectin exerts different biological activities in an oligomerization-dependent manner. The aim of our current study was to examine the alteration of each isoform of adiponectin and its receptors (AdipoR1, AdipoR2, and T-cadherin) during the choline-deficient L-amino acid-defined (CDAA) diet-induced rat liver fibrosis development. We also elucidated the methylation status of all receptors. The serum level of total adiponectin significantly increased during the liver fibrosis development. Among the three isoforms, only HMW adiponectin was significantly up-regulated whereas MMW and LMW were not. The expression of T-cadherin, which exclusively binds with HMW adiponectin, was significantly augmented as well. The AdipoR2 expression was markedly decreased and showed no marked difference from that of AdipoR1. No obvious methylation change was observed in all three receptors, suggesting that another mechanism is involved in the alteration of receptor gene expression. Collectively, since the specific ligand and receptor were augmented together, crosstalk between HMW adiponectin and T-cadherin may play an important role during liver fibrosis development in rats.

Synergistic inhibition of hepatocellular carcinoma growth and hepatocarcinogenesis by combination of 5-fluorouracil and angiotensin-converting enzyme inhibitor via anti-angiogenic activities.

Therapies aimed at destruction of the tumor vasculature are now recognized as a promising approach against cancer, and it has been reported that the combination treatment with an angiogenic inhibitor and conventional chemotherapeutic drug exerted synergistic anti-cancerous effects. We previously reported that the clinically used angiotensin-converting enzyme inhibitor (ACE-I) exerted potent-anti-angiogenic activities. The aim of our current study was to examine the combined effect of ACE-I and 5-fluorouracil (5-FU), which is widely used for hepatogastrointestinal tumors, on hepatocellular carcinoma (HCC) growth and hepatocarcinogenesis. When used individually at low doses, neither 5-FU nor ACE-I exerted significant inhibitory effects on the HCC growth. However, the combination treatment of 5-FU and ACE-I showed a potent inhibitory effect on HCC growth along with suppression of neovascularization in the tumor. The expression level of the vascular endothelial growth factor, a potent angiogenic factor, was also suppressed, almost in conjunction with tumor growth inhibition. Furthermore, 5-FU and ACE-I treatment resulted in a marked increase of apoptosis in the tumor. In the hepatocarcinogenesis model, the combination treatment with 5-FU and ACE-I also showed a marked inhibitory effect on the development of preneoplastic lesions. The in vitro study demonstrated that this combination treatment inhibited endothelial cell tubular formation. Collectively, the combination treatment of 5-FU and ACE-I exerted a marked synergistic inhibitory effect on HCC growth via suppression of angiogenesis. This regimen also showed a chemopreventive effect against hepatocarcinogenesis. Since both 5-FU and ACE-I are widely used in clinical practice, this combination therapy may be an effective new therapeutic strategy against HCC in the future.

Leptin-mediated neovascularization is a prerequisite for progression of nonalcoholic steatohepatitis in rats.

Nonalcoholic steatohepatitis (NASH) may cause fibrosis, cirrhosis, and hepatocellular carcinoma (HCC); however, the exact mechanism of disease progression is not fully understood. Angiogenesis has been shown to play an important role in the progression of chronic liver disease. The aim of this study was to elucidate the role of angiogenesis in the development of liver fibrosis and hepatocarcinogenesis in NASH. Zucker rats, which naturally develop leptin receptor mutations, and their lean littermate rats were fed a choline-deficient, amino acid-defined diet. Both Zucker and littermate rats showed marked steatohepatitis and elevation of oxidative stress markers (e.g., thiobarbital acid reactive substances and 8-hydroxydeoxyguanosine). In sharp contrast, liver fibrosis, glutathione-S-transferase placental form (GST-P)-positive preneoplastic lesions, and HCC developed in littermate rats but not in Zucker rats. Hepatic neovascularization and the expression of vascular endothelial growth factor (VEGF), a potent angiogenic factor, only increased in littermate rats, almost in parallel with fibrogenesis and carcinogenesis. The CD31-immunopositive neovessels were mainly localized either along the fibrotic septa or in the GST-P-positive lesions. Our in vitro study revealed that leptin exerted a proangiogenic activity in the presence of VEGF. In conclusion, these results suggest that leptin-mediated neovascularization coordinated with VEGF plays an important role in the development of liver fibrosis and hepatocarcinogenesis in NASH.

Angiotensin-II and vascular endothelial growth factor interaction plays an important role in rat liver fibrosis development.

Both angiotensin-II (AT-II) and vascular endothelial growth factor (VEGF) have been shown to play important roles in the progression of liver fibrosis. However, the interaction of AT-II with VEGF in the liver fibrosis has not been elucidated yet. The aim of the current study was to elucidate a possible association between these molecules, especially in conjunction with the hepatic stellate cells (HSC). The effect of AT-II type 1 receptor blocker (ARB) was assessed on several indices of choline-deficient l-amino acid-defined (CDAA)-induced liver fibrogenesis. This ARB significantly suppressed liver fibrosis development along with suppression of the VEGF expression and neovascularization in the liver. In the cultured activated HSC, AT-II induced VEGF in a dose- and time-dependent manner. ARB and LY333531, a protein kinase C (PKC) inhibitor, attenuated this augmentation. These results indicated that AT-II and VEGF interaction played an important role in liver fibrosis development, and that in the activated HSC, AT-II utilized type 1 receptor and PKC as an intracellular signaling pathway to induce VEGF.

A potent angiogenic factor, vascular endothelial growth factor, improves the survival of the on-going acute hepatic failure in rats.

Although it has been shown that a simultaneous administration of the vascular endothelial growth factor (VEGF); a potent angiogenic factor, could improve the overall survival of chemically induced acute hepatic failure (AHF) in rats, it has not been elucidated yet whether this salvage effect can be observed in the on-going AHF or not. For future clinical application, we examined the effect of VEGF on the on-going AHF. A combination of d-galactosamine (Gal-N) and lipopolysaccharide (LPS) was administered to induce AHF in rats. The survival rate and several indices were compared with or without VEGF treatment at 12 and 24h after the intoxication. Even after the establishment of severe liver injury, the overall survival and the serum ALT elevation were significantly improved by treatment with VEGF. The proliferation of the hepatocytes and sinusoidal endothelial cells (SEC) was also stimulated by VEGF. Furthermore, VEGF prevented the destruction of the architecture of the hepatic sinusoids. Since VEGF significantly improved the survival of the on-going AHF, the exogenous VEGF administration may represent a feasible new therapeutic strategy for AHF in the future.

Amelioration of liver fibrogenesis by dual inhibition of PDGF and TGF-beta with a combination of imatinib mesylate and ACE inhibitor in rats.

Both platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) are known to be pivotal cytokines in liver fibrosis development. The aim of our current study was to elucidate the effects of dual inhibition of PDGF and TGF-beta by combination of the clinically used imatinib mesylate (STI-571) and perindopril (an ACE-inhibitor; ACE-I), respectively, on ongoing liver fibrosis development in rats. The effects of STI-571 and ACE-I at clinically comparable low doses were examined in a rat model of CCl4-induced liver fibrogenesis. Treatment with both STI-571 and ACE-I inhibited liver fibrogenesis and suppressed activation of hepatic stellate cells (HSCs). Administration of both agents exerted a more potent inhibitory effect than administration of either single agent. Our in vitro study demonstrated that STI-571 and ACE-I suppressed PDGF receptor (PDGFR) phosphorylation and TGF-beta expression in activated HSCs, respectively. Dual suppression of PDGF and TGF-beta with a combination of clinically comparable low doses of STI-571 and ACE-I exerted a significant inhibitory effect on ongoing liver fibrosis development. Since both agents are widely used in clinical practice, this combination therapy may provide a new strategy against liver fibrosis in the future.

Amelioration of carcinogenesis and tumor growth in the rat liver by combination of vitamin K2 and angiotensin-converting enzyme inhibitor via anti-angiogenic activities.

Recent studies have revealed that angiogenesis plays a pivotal role in carcinogenesis and tumor growth. We previously reported that the clinically used vitamin K(2) (VK) and angiotensin-converting enzyme inhibitor (ACE-I) exerted potent anti-angiogenic activities. The aim of our current study was to examine the combination effect of VK and ACE-I on hepatocarcinogenesis induced by diethyl-nitrosamine, and orthotopic hepatocellular carcinoma (HCC) growth in rats. When used individually, both VK and ACE-I at clinically comparable low doses exerted significant inhibitory effects on tumor development in the liver. A combination treatment of VK and ACE-I showed a more potent suppressive effect against hepatocarcinogenesis. Neovascularization increased during hepatocarcinogenesis, and VK and ACE-I significantly attenuated angiogenesis in the tumor. In orthotopic HCC transplantation, VK and ACE-I also showed marked suppressive effects against HCC development similar to those against hepatocarcinogenesis. In both experiments, the suppressive effects of VK and ACE-I against angiogenesis were similar in magnitude to their inhibitory effects against hepatocarcinogenesis and orthotopic HCC development. In the orthotopic model, VK and ACE-I treatment resulted in a marked increase of apoptosis in the tumor, whereas tumor cell proliferation itself was not altered. Since both VK and ACE-I are widely used in clinical practice without serious side effects, this combination therapy may be an effective new therapeutic strategy against hepatocarcinogenesis and HCC growth in the future.

Salvage effect of the vascular endothelial growth factor on chemically induced acute severe liver injury in rats.

BACKGROUND/AIMS: The role of the vascular endothelial growth factor (VEGF), a potent angiogenic factor, in liver regeneration following acute severe liver injury (ALI) has not been elucidated. The aims of the current study were to investigate the role of VEGF, and to find out whether VEGF can improve the outcome of ALI in rats. METHODS: ALI was induced in male rats by combination of D-galactosamine (Gal-N) and lipopolysaccharide (LPS). The survival rate and several indices were chronologically compared with or without VEGF treatment. RESULTS: The overall survival rate of the VEGF-treated group significantly improved as compared with the untreated group (100 vs. 27%, respectively). The serum ALT elevation, with a peak at 24 h after Gal-N+LPS intoxication, was markedly attenuated with VEGF treatment. The proliferation of hepatocytes and sinusoidal endothelial cells (SEC) was stimulated by VEGF with a peak at 36 and 96 h, respectively. The immunohistochemical analysis revealed that VEGF drastically prevented destruction of the SEC architecture in ALI. Our in vitro study showed that VEGF significantly prevented the Gal-N+LPS-induced cytotoxicity and apoptosis of SEC. CONCLUSIONS: VEGF treatment significantly reduced the mortality rate of ALI in the rat, and it may provide a new therapeutic strategy for ALI.

Suppression of renin-angiotensin system attenuates hepatocarcinogenesis via angiogenesis inhibition in rats.

Recent studies have shown that the renin-angiotensin system (RAS) as well as angiogenesis is involved in tumor development. The aim of the present study was to examine the interaction of RAS, angiogenesis and a potent angiogenic factor, namely the vascular endothelial growth factor (VEGF), in the hepatocarcinogenesis process. In a diethylnitrosamine-induced rat hepatocarcinogenesis model, a clinically used angiotensin-converting enzyme inhibitor, perindopril (PE), significantly suppressed glutathione S-transferase placental form (GST-P)-positive preneoplastic lesions along with inhibition of neovascularization in the liver. The hepatic expression of VEGF was also attenuated. The degree of angiogenesis correlated well with the development of preneoplastic lesions. Our in vitro study showed that PE significantly suppressed VEGF-induced tubular formation and the migration of endothelial cells (EC), whereas it did not affect the proliferation of EC. These results suggested that RAS plays an important role in hepatocarcinogenesis, at least partly through VEGF-mediated angiogenesis.