Effects of transmitters and interleukin-10 on rat hepatic fibrosis induced by CCl4

Rebamipide retards CCl4-induced hepatic fibrosis in rats: Possible role for PGE2

Prostaglandin E2 (PGE2) is a potent physiological suppressor of liver fibrosis. Because the anti-ulcer drug rebamipide can induce the formation of endogenous PGE2, this study investigated the potential effects of rebamipide on development of a hepatic fibrosis that was inducible by carbon tetrachloride (CCl4). Groups of Wistar rats received intraperitoneal (IP) injections of CCl4 (0.45 ml/kg [0.72 g CCl4/kg]) over the course of for 4 weeks. Sub-sets of CCl4-treated rats were also treated concurrently with rebamipide at 60 or 100 mg/kg. At 24 h after the final treatments, liver function and oxidative stress were indirectly assessed. The extent of hepatic fibrosis was evaluated using two fibrotic markers, hyaluronic acid (HA) and pro-collagen-III (Procol-III); isolated liver tissues underwent histology and were evaluated for interleukin (IL)-10 and PGE2 content. The results indicated that treatment with rebamipide significantly inhibited CCl4-induced increases in serum ALT and AST and also reduced oxidative stress induced by CCl4. Fibrotic marker assays revealed that either dose of rebamipide decreased the host levels of Procol-III and HA that had become elevated due to the CCl4. At the higher dose tested, rebamipide appeared to be able to permit the hosts to have a normal liver histology and to minimize any CCl4-induced collagen precipitation in the liver. Lastly, the use of rebamipide was seen to be associated with significant increases in liver levels of both PGE2 and the anti-inflammatory cytokine IL-10. Based on these findings, it is concluded that rebamipide can retard hepatic fibrosis induced by CCl4 and that this effect may, in part, be mediated by an induction of PGE2 and IL-10 in the liver itself.

Renin-angiotensin system and fibrosis in non-alcoholic fatty liver disease

BACKGROUND & AIMS

Therapeutic options are limited for patients with non-alcoholic fatty liver disease (NAFLD). One promising approach is the attenuation of necroinflammation and fibrosis by inhibition of the renin-angiotensin system (RAS). We explored whether the risk of fibrosis was associated with the use of commonly used medications in NAFLD patients with hypertension. Specifically, we sought to determine the association between RAS blocking agents and severity of hepatic fibrosis in NAFLD patients with hypertension.

METHODS

Cross-sectional study where clinical information including demographics, anthropometry, medical history, concomitant medication use, biochemical and histological features were ascertained in 290 hypertensive patients with biopsy proven NAFLD followed at two hepatology outpatient clinics. Stage of hepatic fibrosis was compared in patients with and without RAS blocker use. Other risk factors for fibrosis were evaluated from the electronic medical records and patient follow-up.

RESULTS

Baseline characteristics of hypertensive patients treated with and without RAS blockers were similar except for less ballooning (1.02 vs. 1.31, P = 0.001) and lower fibrosis stage (1.63 vs. 2.16, P = 0.002) in patients on RAS blockers On multivariate analysis, advancing age (OR: 1.04; 95%CI: 1.01-1.06, P = 0.012) and presence of diabetes (OR: 2.55; 95%CI: 1.28-5.09, P = 0.008) had an independent positive association, while use of RAS blockers (OR: 0.37; 95%CI: 0.21-0.65, P = 0.001) and statins (OR: 0.52; 95%CI: 0.29-0.93, P = 0.029) had a negative association with advanced fibrosis.

CONCLUSION

Hypertensive patients with NAFLD on baseline RAS blockers had less advanced hepatic fibrosis suggesting a beneficial effect of RAS blockers in NAFLD.

Interleukin-10 gene modification attenuates hepatocyte activation of rat hepatic stellate cells in vitro

Activation of hepatic stellate cells (HSCs) plays a key role in the progression of liver fibrosis. Interleukin-10 (IL-10), a potential anti-fibrosis cytokine, has an unfavorable pharmacokinetic profile, which limits its clinical applications. A liver-targeting gene delivery system may maintain a longer-lasting concentration in hepatic tissue with fewer side‑effects in non-target tissues. In the present study, when delivered by asialoglycoprotein receptor-mediated liposomes, the IL-10 gene was highly expressed in BRL cells (a rat hepatocyte line) and attenuated the apoptosis of BRL cells induced by plasmid transfection. In a co-culture system, BRL cells demonstrated a marked ability to stimulate the proliferation of primary HSCs and their expression of α-SMA and procollagen type I. Following modification of the BRL cells with the IL-10 gene, this stimulation was attenuated and an accelerated apoptosis of the HSCs was induced. These results suggest that hepatocyte‑targeting gene delivery may be an ideal technique for the IL-10 gene therapy of liver fibrosis, which requires further confirmation by in vivo studies.

Gene therapy for hepatic fibrosis

Hepatic fibrosis is a common pathological process of chronic liver diseases, characterized by increased synthesis and relatively low degradation of extracellular matrix (ECM) resulting from their dynamic imbalance. Recent progress in molecular biology techniques has made it possible to treat hepatic fibrosis with gene therapy. At present, the commonly used method is to induce the expression of exogenous genes by transducing enough therapeutic genes into injured liver to delay or cure liver fibrosis.

Liver fibrosis: a balance of ACEs?

There is an increasing body of evidence to suggest that the RAS (renin–angiotensin system) contributes to tissue injury and fibrosis in chronic liver disease. A number of studies have shown that components of a local hepatic RAS are up-regulated in fibrotic livers of humans and in experimental animal models. Angiotensin II, the main physiological effector molecule of this system, mediates liver fibrosis by stimulating fibroblast proliferation (myofibroblast and hepatic stellate cells), infiltration of inflammatory cells, and the release of inflammatory cytokines and growth factors such as TGF (transforming growth factor)-β1, IL (interleukin)-1β, MCP (monocyte chemoattractant protein)-1 and connective tissue growth factor. Furthermore, blockade of the RAS by ACE (angiotensin-converting enzyme) inhibitors and angiotensin type 1 receptor antagonists significantly attenuate liver fibrosis in experimental models of chronic liver injury. In 2000 ACE2 (angiotensin-converting enzyme 2), a human homologue of ACE, was identified. ACE2 efficiently degrades angiotensin II to angiotensin-(1–7), a peptide which has recently been shown to have both vasodilatory and tissue protective effects. This suggests that ACE2 and its products may be part of an alternate enzymatic pathway in the RAS, which counterbalances the generation and actions of angiotensin II, the ACE2–angiotensin-(1–7)–Mas axis. This review focuses on the potential roles of the RAS, angiotensin II and ACE2 in chronic liver injury and fibrogenesis.

Roles of activin A and hepatocellular apoptosis in the anti-liver fibrosis process induced by Ginkgo biloba extract in rats

AIM: To investigate the effects of Ginkgo biloba extract (GBE) on CCl₄-induced liver fibrosis as well as the underlying mechanisms.

METHODS: Thirty adult male Sprague Dawley rats were randomized into 3 groups: control group (n = 10), model group (n = 10) and treatment group (n = 10). Except the rats in the control group, the others were intraperitoneally injected with 500 mL/L CCl₄ (1 mL/kg) to induce liver cirrhosis (twice a week, for 8 weeks). Moreover, the rats in treatment group were intragastrically administered with GBE (0.4 g/kg) for 8 weeks. At the end of the 8^th week, all the rats were sacrificed. Blood samples were collected for the determination of biochemical indicators. Tissue samples were used for histopathological examinations. The expression of activin A was determined by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). Hepatocellular apoptosis was determined by the method of terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method.

RESULTS: The grade of liver fibrosis in treatment group was lower than that in the model group (P < 0.05). The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and albumin (ALB) in treatment group were significantly improved as compared with those in the model group (ALT: 2806.9 ±576.1 nkat/L vs 4452.9 ± 709.5 nkat/L; AST: 5314.2 ± 1042 nkat/L vs 15 743.4 ± 625.8 nkat/L; ALB: 31.0 ± 2.1 g/L vs 21.7 ± 1.8 g/L; all P < 0.05). GBE treatment markedly reduced mRNA and protein levels of activin A (mRNA: 0.42 ± 0.09 vs 0.78 ± 0.15; protein: 4.2 ± 0.8 vs 11.4 ± 1.2; both P < 0.01). In comparison with that in the model group, the apoptosis index was decreased in treatment groups (7.56 ± 3.36 vs 16.06 ± 8.84, P < 0.01).

CONCLUSION: GBE can markedly attenuate the degrees of hepatic fibrosis, and the mechanism may be correlated with the expression of activin A and hepatocellular apoptosis.

Relationship between transforming growth factor β1 and anti-fibrotic effect of interleukin-10

AIM: To study the effect of interleukin-10 (IL-10) on the expression of transforming growth factor β1 (TGF-β1) in hepatic fibrosis rats and the anti-fibrotic role of exo-genous IL-10.

METHODS: Hepatic fibrosis was induced by carbon tetrachloride administered (CCl₄) intraperitoneally. The experiment was performed in two stages. In the first stage, 60 SD rats were divided randomly into normal control group 1(GN₁, n = 8), hepatic fibrosis group(GC, n = 28)and IL-10 intervened group(GI, n = 24). At the beginning of the 7^th and 11^th wk, hepatic stellate cells (HSCs) were isolated, reverse transcription-polymerase chain reation (RT-PCR) and immunocytochemistry were performed to detect the expression of TGF-β1 in HSCs. Histological examination was used to determine the degree of hepatic fibrosis. In the second stage, 47 SD rats were divided randomly into normal control group 2(GN₂, n = 6)and CCl₄ group(GZ, n = 41). At the end of the 9th week, rats in GZ group were allocated randomly into model group(GM, n = 9), IL-10 treatment group(GT, n = 9)and recovered group(GR, n = 9). At the end of the 12^th week, all rats were sacrificed. RT-PCR and immunohistochemistry were performed to detect the expression of TGF-β1 in liver tissue. ELISA was used to assay serum TGF-β1 levels.

RESULTS: Hepatic fibrosis developed in rats with the increase of the injection frequency of CCl₄. In the first stage, hepatic fibrosis developed and HSCs were isolated successfully. At the 7^th and 11^th week, TGF-β1 mRNA in GC group increased significantly compared with that in GN₁(P = 0.001/0.042)and GI groups(P = 0.001/0.007), whereas there was no significant difference between the two groups. The levels of TGF-β1 at the beginning of the 7^th wk was higher than that of the 11^th wk(P = 0.049). Immunocytochemistry results of TGF-β1 were consistent with the above findings. In the second stage, TGF-β1 increased significantly in GM group compared to GN₂. After treatment with IL-10, TGF-β1 declined obviously. The expression of TGF-β1 decreased in GR group but was still higher than that in GT group.

CONCLUSION: The levels of TGF-β1 are increased in hepatic fibrosis rats and decreased after treatment with exogenous IL-10. IL-10 may play an anti-fibrotic role by suppressing TGF-β1 expression.

Interleukin-10 and chronic liver disease

Interleukin (IL)-10 is an important immunoregulatory cytokine produced by many cell populations. Numerous investigations suggest that IL-10 plays a major role in chronic liver diseases. IL-10 gene polymorphisms are possibly associated with liver disease susceptibility or severity. Recombinant human IL-10 has been produced and is currently tested in clinical trials. These trials may give new insights into the immunobiology of IL-10 and suggest that the IL-10/IL-10 receptor system may become a new therapeutic target.

Effects of sleep deprivation on gastric mucosal blood flow and gastric mucosal lesions in rats

AIM: To observe the changes of gastric mucosal blood flow and gastric mucosal lesions in rats after sleep deprivation.

METHODS: Sleep deprivation was induced in male Sprague-Dawley rats housed on small platform over water. Control mice were housed either in normal cages or on large platform over water. Laser Doppler blood flow meter was used to measure the gastric mucosal blood flow, and index of gastric mucosal lesions was quantified. The arterial plasma levels of endotoxin (ET) and calcitonin gene related peptide (CGRP) were measured by radioimmunoassay.

RESULTS: Compared with control mice in normal cage, on big platform, or the mice on the 1st day of sleep deprivation, the gastric mucosal blood flow of mice on the 3rd, 5th and 7th day of sleep deprivation (54.2±2.5, 53.7±3.0, 48.3±2.5 mv, respectively) were significantly lower. The gastric mucosal injury became more and more serious: the injury indices were 29.8±3.2, 3.7±3.6 and 34.8±3.5 on the 3rd, 5th and 7th day of sleep deprivation, respectively. The serum levels of ET were 123±28, 139±36 and 149±38 ng/L in mice on the 3rd, 5th and 7th day of sleep deprivation, and the levels of CGRP were 193±32 and 221±40 ng/L in the mice on the 5th and 7th day of sleep deprivation. All were significantly higher than those in control mice.

CONCLUSION: Sleep deprivation can cause the decrease of gastric mucosal blood flow and the gastric mucosal injury, which are accompanied by the elevation of serum ET and CGRP.

Effect of prostaglandin E2 and prostaglandin I2 on PDGF-induced proliferation of LI90, a human hepatic stellate cell line

Hepatic stellate cells (HSC) are central to liver fibrosis. The eicosanoid pathway and cyclooxygenase-2 (COX-2) may be an important signaling mechanism in HSC. We investigated the role of COX-2, prostaglandin E(2) (PGE(2)) and prostaglandin I(2) (PGI(2)) in proliferation of LI90, an immortalized cell line of HSC. Our results showed that COX-2 was upregulated by platelet-derived growth factor (PDGF), a mitogen in HSC. COX-2 was responsible for the production of PGE(2) and PGI(2) in PDGF-stimulated LI90 cells. Furthermore, we demonstrated that COX-2 and PGE(2) mediated the proliferative response of LI90 to PDGF while synthetic analogue of PGI(2) exhibited anti-proliferative effect. Our findings suggest complex interactions of prostaglandins in liver fibrogenesis. In vivo studies using animal models are needed to elucidate the effect of COX-2 inhibition by non-steroidal anti-inflammatory drugs or COX-2 inhibitor in hepatic fibrosis.

Gene expression profiles in liver cirrhosis and normal liver tissues

AIM: To describe liver specific gene expression profiles and to identify genes with differential expression between liver cirrhotic tissues and normal liver tissues.

METHODS: The cDNA probes which were labeled with α-³²P dATP were synthesized from total RNAs of liver cirrhosis and normal liver tissues and hybridized to two identical Atlas human cDNA expression arrays membranes containing 588 known genes respectively.

RESULTS: Autoradiographic results were analyzed by specific AtlasImage^TM (version1.01a) software. Among the 588 genes analyzed, 17 genes were found up-regulated in cirrhosis, including integrin beta 7 and collagen type XVIII, and 98 genes were down-regulated in cirrhosis, including TFDP2, BAK and ABL. Expression of the genes was associated with the regulation of cell proliferation, apoptosis, differen-tiation, cell-cell interaction, invasion regulators and cytokines altered.

CONCLUSION: The results obtained from Atlas microarray provide a comprehensive liver cirrhosis specific expression profile. These results may be helpful for identification of target genes for diagnosis and designing rational therapeutic strategies.

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Expression of insulin-like growth factor 1 and insulin-like growth factor 1 receptor and its intervention by interleukin-10 in experimental hepatic fibrosis

AIM: To study the expression of IGF-1 and IGF-1R and its intervention by interleukin-10 in the course of experimental hepatic fibrosis.

METHODS: Hepatic fibrosis was induced in rats by carbon tetrachloride intoxication and liver specimens were taken from the rats administered CCl₄ with or without IL-10 treatment and the animals of the control group. Immunoreactivities for insulin-like growth factor-1 (IGF-1) and IGF-1 receptor(IGF-1R) were demonstrated by immunohistochemistry, and their intensities were evaluated in different animal groups.

RESULTS: The positive levels for IGF-1 and IGF-1R were increased with the development of hepatic fibrosis, with the positive signals localized in cytoplasm and/or at the plasmic membrane of hepatocytes. The positive signals of IGF-1 and IGF-1R were observed more frequently (P < 0.01) in the CCl₄-treated group (92.0% and 90.0%) compared to those in the control group. The positive signals decreased significantly (P < 0.05) in IL-10-treated group. The responses in IGF-1 and IGF-1R expression correlated with the time of IL-10 treatment.

CONCLUSION: The expression of IGF-1 and IGF-1R immunoreactivities in liver tissue seems to be up-regulated during development of hepatic fibrosis induced by CCl₄, and exogenic IL-10 inhibits the responses.