Hitoshi Yoshiji

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. (HEPATOLOGY 2006;44:983–991.)

Angiopoietin 2 displays a vascular endothelial growth factor dependent synergistic effect in hepatocellular carcinoma development in mice

Background: Orchestration of two major classes of angiogenic factors—namely, vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang-2)—has been shown to play a pivotal role in tumour angiogenesis, including hepatocellular carcinoma (HCC). However, few studies have focused on the direct interaction of these factors on in vivo tumour development and angiogenesis. Aim: To examine the interaction between both factors in murine HCC. Methods: We examined the combination effect of VEGF and Ang-2 overexpression by means of a combination of a retroviral tetracycline (tet) regulated gene manipulating system in vivo, by providing tet in the drinking water, and a conventional plasmid gene expression system. Results: Neither Ang-2 nor VEGF overexpression induced proliferation of HCC cells in vitro. In vivo, although overexpression of Ang-2 did not increase tumour development, simultaneous expression of Ang-2 and VEGF synergistically augmented tumour growth and angiogenesis in murine HCC. Ang-2 plus VEGF induced tumour development was markedly attenuated by treatment with neutralising monoclonal antibodies against VEGF receptors. Ang-2 plus VEGF overexpression significantly increased the activities of matrix metalloproteinase (MMP)-2 and MMP-9 in the tumour. Suppression of intratumoral VEGF almost completely abolished this augmentation of MMPs. Conclusions: These results suggest that Ang-2 synergistically augments VEGF mediated HCC development and angiogenesis. This proangiogenic activity was exerted only in the presence of VEGF, at least partly mediated via induction of MMP-2 and MMP-9 in the tumour.

Blockade of renin–angiotensin system in antifibrotic therapy

Recent studies have shown that the renin–angiotensin system (RAS) plays a pivotal role in liver fibrosis. An intrahepatic RAS is expressed in chronically damaged livers, and angiotensin‐II (AT‐II) reportedly stimulates contraction and proliferation of the activated hepatic stellate cells (Ac‐HSC), and increases the transforming growth factor‐β (TGF‐β) expression through angiotensin type‐I receptors (AT1‐R). Some studies have demonstrated that the clinically used angiotensin‐converting enzyme (ACE) inhibitor (ACE‐I), and AT1‐R blockers (ARB) significantly attenuated experimental liver fibrosis along with suppression of the Ac‐HSC and hepatic TGF‐β expression. Angiotensin‐II also stimulates the tissue inhibitor of metalloproteinases‐1 (TIMP‐1) in a dose‐ and time‐dependent manner via protein kinase‐C as an intracellular signaling cascade in the Ac‐HSC, and these effects are completely suppressed by ARB. Combination treatment with low‐dose interferon (IFN) and ACE‐I exerts a stronger inhibitory effect than either single agent on its own. In humans it has been reported that ARB markedly improved the liver fibrosis score and TGF‐β expression in patients with chronic hepatitis C and non‐alcoholic steatohepatitis. Serum fibrosis markers also significantly improved by treatment with low‐dose IFN and ACE‐I in patients with chronic hepatitis C, refractory to IFN monotherapy. Collectively, these data suggest that the interaction between AT‐II and AT1‐R plays a pivotal role in liver fibrosis development. Because both ACE‐I and ARB are widely used in clinical practice without serious side‐effects, these drugs in combination with IFN may provide a new strategy for antifibrosis therapy.

Renin-angiotensin system inhibitors as therapeutic alternatives in the treatment of chronic liver diseases.

The renin-angiotensin system (RAS) is frequently activated in the patients with chronic liver diseases, and recent studies have shown that RAS plays a pivotal role in the progression of chronic liver diseases, i.e., liver fibrosis and hepatocellular carcinoma (HCC). Angiotensin-II (AT-II) reportedly stimulates contractility and proliferation of the activated hepatic stellate cells, and increases the transforming growth factor-beta (TGF-betabeta expression through angiotensin type-I receptors (AT1-R). Many studies have demonstrated that the clinically used angiotensin-converting enzyme inhibitors (ACE-I) and AT1-R blockers (ARB) significantly attenuated the liver fibrosis development in the experimental studies and clinical practice. AT-II also strongly promotes neovascularization, which plays a pivotal role in tumor development. AT-II induces a potent angiogenic factor; namely, the vascular endothelial growth factor (VEGF). It has been reported that ACE-I significantly attenuated the experimental HCC growth and hepatocarcinogenesis along with suppression of neovascularization. The VEGF expression in the tumor was suppressed by ACE-I, too. The combined treatment of ACE-I with other clinically used agents, such as interferon, imatinib mesylate, and vitamin K, shows more potent inhibitory effects on the development of liver fibrosis and HCC. Since RAS inhibitors are widely used in the clinical practice without serious side effects, they may represent a potential new therapeutic strategy against the progression of chronic liver diseases.

Combined effect of an ACE inhibitor, perindopril, and interferon on liver fibrosis markers in patients with chronic hepatitis C

ous report,2 several factors are involved in the occurrence of depletion syndrome due to villous tumor; i.e., the villous tumor is large, ranging from 7 to 18 cm in maximum diameter, and is located in the rectum. The large size allows an increase in surface area for secretion, and the distal location limits the colon’s ability to reabsorb the fluid. Although the mechanisms underlying the occurrence of secretory villous tumor are unknown, prostaglandin E2 (PGE2) has been assumed to be involved. Steven et al.3 reported that indomethacin treatment reduced rectal PGE2 excretion and decreased rectal fluid loss. Prostaglandin (PG) inhibitors suppress secretion, but secretion resumes after the discontinuation of the PG inhibitor. Therefore, at present, surgery is assumed to be the only basic treatment. The present patient represents a very uncommon case of villous tumor that started secreting after an operation for peritonitis caused by perforation of the large intestine. However, the factors related to the start of secretion from the villous tumor are not clear. Because severe inflammation presented at the initial operation in this patient, one possible reason for the start of secretion may have been an increase in endogenous PG production, due to preand post-operative inflammation, which may have triggered the secretion.