Akitoshi Douhara

The Effect of Inflammatory Cytokines in Alcoholic Liver Disease

Alcohol is the most common cause of liver disease in the world. Chronic alcohol consumption leads to hepatocellular injury and liver inflammation. Inflammatory cytokines, such as TNF-α and IFN-γ, induce liver injury in the rat model of alcoholic liver disease (ALD). Hepatoprotective cytokines, such as IL-6, and anti-inflammatory cytokines, such as IL-10, are also associated with ALD. IL-6 improves ALD via activation of the signal transducer and activator of transcription 3 (STAT3) and the subsequent induction of a variety of hepatoprotective genes in hepatocytes. IL-10 inhibits alcoholic liver inflammation via activation of STAT3 in Kupffer cells and the subsequent inhibition of liver inflammation. Alcohol consumption promotes liver inflammation by increasing translocation of gut-derived endotoxins to the portal circulation and activating Kupffer cells through the LPS/Toll-like receptor (TLR) 4 pathways. Oxidative stress and microflora products are also associated with ALD. Interactions between pro- and anti-inflammatory cytokines and other cytokines and chemokines are likely to play important roles in the development of ALD. The present study aims to conduct a systemic review of ALD from the aspect of inflammation.

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

BackgroundDipeptidyl 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).MethodsThe 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.ResultsDPP4-I significantly attenuated liver fibrosis development along with the suppression of hepatic transforming growth factor (TGF)-β1, 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-β1 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.ConclusionsDPP4-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.

Reduction of endotoxin attenuates liver fibrosis through suppression of hepatic stellate cell activation and remission of intestinal permeability in a rat non-alcoholic steatohepatitis model

Previous clinical studies have demonstrated that endotoxin/toll-like receptor 4 (TLR4) signaling is critical in the inflammatory pathways associated with non-alcoholic steatohepatitis (NASH). In human and animal studies, NASH was associated with portal lipopolysaccharide (LPS) and the plasma LPS level was hypothesized to be associated with small intestinal bacterial overgrowth, change in composition of the microbiota and increased intestinal permeability. The aim of the present study was to investigate the roles of endogenous endotoxin and TLR4 in the pathogenesis of NASH. The effects of antibiotics were assessed in vivo using a choline deficiency amino acid (CDAA)-induced experimental liver fibrosis model. Antibiotics, including polymyxins and neomycins, were orally administered in drinking water. Antibiotics attenuated hepatic stellate cell (HSC) activation and liver fibrosis via TGF-β and collagen in an experimental hepatic fibrosis model. The mechanism by which antibiotics attenuated LPS-TLR4 signaling and liver fibrosis was assessed. Notably, TLR4 mRNA level in the liver was elevated in the CDAA group and the CDAA-induced increase was significantly reduced by antibiotics. However, no significant differences were observed in the intestine among all groups. Elevated mRNA levels of LPS binding protein, which was correlated with serum endotoxin levels, were recognized in the CDAA group and the CDAA-induced increase was significantly reduced by antibiotics. The intestinal permeability of the CDAA group was increased compared with the choline-supplemented amino acid group. The tight junction protein (TJP) in the intestine, determined by immunohistochemical analysis was inversely associated with intestinal permeability. Antibiotics improved the intestinal permeability and enhanced TJP expression. Inhibition of LPS-TLR4 signaling with antibiotics attenuated liver fibrosis development associated with NASH via the inhibition of HSC activation. These results indicated that reduction of LPS and restoration of intestinal TJP may be a novel therapeutic strategy for treatment of liver fibrosis development in NASH.

Cross talk between toll-like receptor-4 signaling and angiotensin-II in liver fibrosis development in the rat model of non-alcoholic steatohepatitis

The innate immune system, including toll‐like receptor‐4 (TLR4) signaling cascade and angiotensin‐II (AT‐II) play important roles in the progression of liver fibrosis development; the cross talk between TLR4 and AT‐II has not been elucidated yet. The aim of the current study was to elucidate the effect of AT‐II type 1 receptor blocker (ARB), on the liver fibrosis development, especially in conjunction with the interaction of TLR4 and AT‐II in the rat model of non‐alcoholic steatohepatitis.

Possible Involvement of Angiogenesis in Chronic Liver Diseases: Interaction Among Renin-Angiotensin-Aldosterone System, Insulin Resistance and Oxidative Stress

Angiogenesis plays a pivotal role in many pathological processes including chronic liver diseases. Various factors, such as renin-angiotensin-aldosterone system (RAAS), insulin resistance (IR), and reactive oxygen species (ROS) contribute reciprocally to promote angiogenesis. Blockade of RAAS by angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin II (AngII) receptor blocker (ARB) markedly attenuates liver fibrosis and hepatocellular carcinoma (HCC) along with suppression of angiogenesis, IR, and ROS. Aldosterone (Ald), a downstream component of AngII, is also involved in these processes, and a selective Ald blocker (SAB) significantly suppressed the progression of chronic liver diseases. The IR status itself has shown to directly accelerate the progression of chronic liver diseases whereas inhibition of ROS by iron chelator suppressed it through augmentation and inhibition of neovascularization. The combination therapy of ACE-I/ARB/SAB with other clinically used agents, such as interferon, imatinib mesylate, vitamin K, iron chelator, and branched-chain amino acids (BCAA) exerted more potent inhibitory effects on the development of liver fibrosis and HCC than the treatment using a single agent alone. Collectively, the anti-angiogenic treatment targeting RAAS, IR, ROS with clinically available agents may become a new therapeutic strategy against the progression of chronic liver diseases.

Direct renin inhibitor, aliskiren, attenuates the progression of non‐alcoholic steatohepatitis in the rat model

Renin is a rate‐limiting enzyme of the renin–angiotensin system (RAS), and several reports have shown that renin plays an important role in several pathological processes. Although RAS is known to play a pivotal role in the progression of non‐alcoholic steatohepatitis (NASH), the role of renin is still obscure. The aim of the current study was to examine the effect of the clinically used direct renin inhibitor (DRI), aliskiren, on the progression of NASH in a rat model.

Cholangiocarcinoma developed in a patient with IgG4-related disease

A 77-year-old man with jaundice and a pancreatic head tumor was referred to our hospital in August 2006. The initial laboratory tests, computed tomography (CT) scan, magnetic resonance imaging (MRI), and endoscopic retrograde cholangiopancreatography suggested IgG4-related cholangitis and autoimmune pancreatitis. Oral prednisolone (PSL) was then administered. This treatment reduced the size of the pancreatic parenchyma, and the lower common bile duct (CBD) returned to its normal size. Thus, the oral PSL was gradually tapered to a maintenance dose. In February 2010, a CT scan and MRI showed segmental wall thickening and stenosis of the middle CBD, the progression of which led to extrahepatic obstructive jaundice. We suspected the emergence of a cholangiocarcinoma rather than the exacerbation of the IgG4-related sclerosing cholangitis because the stricture of the CBD was short and localized. Then, a percutaneous transhepatic biliary drainage was performed. The biopsy specimens obtained via the percutaneous transhepatic tract indicated an abnormal glandular formation, suggesting the presence of a moderate, well-differencated adenocarcinoma. The gross examination, microscopic examination and immunohistochemical analysis of the pancreaticoduodenectomy specimen suggested that a cholangiocarcinoma developed from the IgG4-related sclerosing cholangitis.

Dual blockade of angiotensin-II and aldosterone suppresses the progression of a non-diabetic rat model of steatohepatitis.

Both angiotensin‐II (AT‐II) and aldosterone (Ald) play pivotal roles in the pathogenesis of diseases in several organs including the liver. We previously reported that suppression of AT‐II and Ald with angiotensin‐converting enzyme inhibitor (ACE‐I) and selective Ald blocker (SAB), respectively, attenuated the rat liver fibrogenesis and hepatocarcinogenesis. The aim of our current study was to elucidate the combined effects of ACE‐I and SAB in the progression of a non‐diabetic rat model of steatohepatitis, and the possible mechanisms involved.

Combination of branched-chain amino acid and angiotensin‑converting enzyme inhibitor improves liver fibrosis progression in patients with cirrhosis

An effective therapeutic strategy for suppressing liver fibrosis should improve the overall prognosis of patients with chronic liver diseases. Although enormous efforts are ongoing to develop anti-fibrotic agents, no drugs have yet been approved as anti-fibrotic agents for humans. Insulin resistance (IR) is reportedly involved in the progression of liver fibrosis. The aim of the present study was to evaluate the effect of combination treatment with a clinically used branched-chain amino acid (BCAA) and an angiotensin-converting enzyme inhibitor (ACE-I) on several fibrotic indices in patients with liver cirrhosis under the condition of IR. BCAA granules (Livact; 12 g/day) and/or ACE-I (perindopril; 4 mg/day) were administered, and several indices were analyzed. A 48-month follow-up revealed that the combination treatment with BCAA and ACE-I markedly improved the progression of serum fibrosis markers, whereas single treatment with either BCAA or ACE-I did not exert these inhibitory effects. The plasma level of transforming growth factor-β was significantly attenuated almost in parallel with the suppression of serum fibrosis markers. Furthermore, the combined treatment with BCAA and ACE-I improved the serum albumin level and IR, which was evaluated using the homeostasis model assessment method for IR. Taken together, since both BCAA and ACE-I are widely used with safety in clinical practice, these results indicate that this combination therapy may represent a potential new future strategy against liver fibrosis development in patients with liver cirrhosis under the condition of IR.

Branched-chain amino acids suppress the cumulative recurrence of hepatocellular carcinoma under conditions of insulin-resistance

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). We previously reported that BCAAs exert a chemopreventive effect against HCC under IR conditions in rats. The aim of the present study was to examine the effect of BCAAs on the cumulative recurrence of HCC under IR conditions in the clinical practice. BCAA granules (Livact®, 12 g/day) were administered for 60 months following the local curative therapy for HCC, and several indices were determined. Treatment with BCAAs markedly inhibited the cumulative recurrence of HCC in patients with a high IR index [homeostasis model assessment (HOMA)-IR >2.5], but not in patients with HOMA-IR of ≤2.5. BCAA also improved the HOMA-IR, and the inhibitory effect was observed regardless of the serum albumin (Alb) levels. Similarly, BCAA treatment revealed a marked suppressive effect in patients with high fasting insulin [immune reactive insulin (IRI) >15 U/ml], but not with IRI of ≤15. BCAA treatment did not result in differences in HCC recurrence in patients with high and low glucose levels [fasting blood sugar (FBS) >110 and ≤110, respectively]. Furthermore, serum levels of the soluble form of vascular endothelial growth factor receptor 2 (sVEGFR2) were significantly inhibited along with these clinical effects. Our findings indicate that the inhibitory effect of BCAAs was achieved, at least partly, by coordinated effects of anti-angiogenesis and IR improvement. Since BCAAs are widely and safely used in clinical practice to treat patients with chronic liver diseases, BCAAs may represent a new strategy for secondary chemoprevention for HCC patients with IR. Moreover, our findings suggest that sVEGFR2 may be a useful clinical predictive marker for BCAA treatment under IR conditions.