Study of heteroserum-induced rat liver fibrosis model and its mechanism

Parkin-Mediated Mitophagy by TGF-β Is Connected with Hepatic Stellate Cell Activation

Hepatic stellate cells (HSCs) are the main contributors to the development and progression of liver fibrosis. Parkin is an E3 ligase involved in mitophagy mediated by lysosomes that maintains mitochondrial homeostasis. Unfortunately, there is little information regarding the regulation of parkin by transforming growth factor-β (TGF-β) and its association with HSC trans-differentiation. This study showed that parkin is upregulated in fibrotic conditions and elucidated the underlying mechanism. Parkin was observed in the cirrhotic region of the patient liver tissues and visualized using immunostaining and immunoblotting of mouse fibrotic liver samples and primary HSCs. The role of parkin-mediated mitophagy in hepatic fibrogenesis was examined using TGF-β-treated LX-2 cells with mitophagy inhibitor, mitochondrial division inhibitor 1. Parkin overexpression and its colocalization with desmin in human tissues were found. Increased parkin in fibrotic liver homogenates of mice was observed. Parkin was expressed more abundantly in HSCs than in hepatocytes and was upregulated under TGF-β. TGF-β-induced parkin was due to Smad3. TGF-β facilitated mitochondrial translocation, leading to mitophagy activation, reversed by mitophagy inhibitor. However, TGF-β did not change mitochondrial function. Mitophagy inhibitor suppressed profibrotic genes and HSC migration mediated by TGF-β. Collectively, parkin-involved mitophagy by TGF-β facilitates HSC activation, suggesting mitophagy may utilize targets for liver fibrosis.

LncRNA-MIAT activates hepatic stellate cells via regulating Hippo pathway and epithelial-to-mesenchymal transition

Long non-coding RNA-myocardial infarction-associated transcript (lncRNA-MIAT) has been reported to play an important role in the development of multiple cancers. However, the biological roles of MIAT in liver fibrosis are still unknown. In this study, the expression of MIAT is up-regulated during liver fibrosis. Silencing MIAT leads to the suppression of hepatic stellate cell (HSC) proliferation and collagen expression. Double immunofluorescence analysis additionally demonstrates that MIAT inhibition leads to the suppression of type I collagen and α-SMA in vitro. In vivo, MIAT knockdown contributes to the inhibition of fibrosis progression and collagen accumulation. MIAT is confirmed as a target of miR-3085-5p, and the co-location of MIAT and miR-3085-5p is found in HSC cytoplasm. Interestingly, there is a negative correlation between MIAT expression and miR-3085-5p level in cirrhotic patients as well as activated HSCs. In addition, the effects of MIAT inhibition on HSC inactivation are blocked down by miR-3085-5p inhibitor. YAP is a target of miR-3085-5p. Reduced YAP caused by loss of MIAT is reversed by miR-3085-5p inhibitor. Notably, YAP knockdown results in the suppression of MIAT-mediated epithelial-to-mesenchymal transition (EMT) process. In conclusion, we demonstrate that MIAT enhances the activation of HSCs, at least in part, via miR-3085-5p/YAP/EMT signaling pathway.

Mast Cells in Liver Fibrogenesis

Mast cells (MCs) are immune cells of the myeloid lineage that are present in the connective tissue throughout the body and in mucosa tissue. They originate from hematopoietic stem cells in the bone marrow and circulate as MC progenitors in the blood. After migration to various tissues, they differentiate into their mature form, which is characterized by a phenotype containing large granules enriched in a variety of bioactive compounds, including histamine and heparin. These cells can be activated in a receptor-dependent and -independent manner. Particularly, the activation of the high-affinity immunoglobulin E (IgE) receptor, also known as FcεRI, that is expressed on the surface of MCs provoke specific signaling cascades that leads to intracellular calcium influx, activation of different transcription factors, degranulation, and cytokine production. Therefore, MCs modulate many aspects in physiological and pathological conditions, including wound healing, defense against pathogens, immune tolerance, allergy, anaphylaxis, autoimmune defects, inflammation, and infectious and other disorders. In the liver, MCs are mainly associated with connective tissue located in the surrounding of the hepatic arteries, veins, and bile ducts. Recent work has demonstrated a significant increase in MC number during hepatic injury, suggesting an important role of these cells in liver disease and progression. In the present review, we summarize aspects of MC function and mediators in experimental liver injury, their interaction with other hepatic cell types, and their contribution to the pathogenesis of fibrosis.

Dynamic Changes in MMP1 and TIMP1 in the Antifibrotic Process of Dahuang Zhechong Pill in Rats with Liver Fibrosis

On the basis of carbon tetrachloride (CCl4)induced liver fibrosis in rats, this study aims to investigate the dynamic changes in matrix metalloproteinase 1 (MMP1) and the tissue inhibitor of metalloproteinase 1 (TIMP1) in the antifibrotic process of Dahuang Zhechong Pill (DHZCP). A total of 50 male Sprague Dawley rats, aged 8 weeks, were randomly divided into 3 groups: the control group, the model group (the group treated with CCl4), and the treatment group (the group treated with CCl4 and DHZCP). Rats were sacrificed at Weeks 4 and 8. Liver tissues were separated for RNA sequencing and bioinformatics analysis. Real-time PCR, Western blot analysis, and histological staining were conducted to confirm the gene expression and pathological change in liver tissues. Compared with control group, rats in model group showed poor mental state and slow weight gain. The liver tissues of the rats in the model group exhibited a damaged hepatic lobule structure, fibrous connective tissue hyperplasia, and inflammatory cell infiltration among the hyperplastic tissues. DHZCP could significantly improve the appearance of rats and alleviate CCl4-induced fibrosis. Compared to model group, 798 differentially expressed mRNAs were found in the treatment group, of which 120 were up-regulated and 678 were down-regulated. Differentially expressed mRNAs between the CCl4-induced group and the DHZCP-treated group were mainly focused on the following KEGG pathways: focal adhesion, phagosome, tight junction, and ECM–receptor interactions. Relative to those in the control group, MMP1 was downregulated, whereas, TIMP1 and Col1A1 were upregulated in the CCl4-induced group at Weeks 4 and 8. DHZCP could reverse MMP1, TIMP1, and Col1A1 expression.DHZCP protects against liver injury and exerts an antifibrotic effect on liver fibrosis induced by CCl4 in rats. Its mechanism may be related to the upregulation of MMP1, downregulation of TIMP1, and promotion of collagen degradation.

Genome‑wide identification of long noncoding RNAs in CCl4‑induced liver fibrosis via RNA sequencing

Liver fibrosis occurs as a result of chronic liver lesions, which may subsequently develop into liver cirrhosis and hepatocellular carcinoma. The involvement of long noncoding RNAs (lncRNAs) in liver fibrosis is being increasingly recognized. However, the exact mechanisms and functions of the majority of lncRNAs are poorly characterized. In the present study, the hepatotoxic substance carbon tetrachloride (CCl4) was employed to induce liver fibrosis in an animal model and agenome‑wide identification of lncRNAs in fibrotic liver tissues compared with CCl4 untreated liver tissues was performed using RNA sequencing. Sprague‑Dawley rats were treated with CCl4 for 8 weeks. Histopathogical alterations were observed in liver tissues, and serum levels of alanine aminotransferase, aspartate aminotransferase, transforming growth factor‑β1 and tumor necrosis factor‑α were significantly higher, in the CCl4‑treated group compared with the CCl4 untreated group. RNA sequencing of liver tissues demonstrated that 231 lncRNAs and 1,036 mRNAs were differentially expressed between the two groups. Furthermore, bioinformatics analysis demonstrated that the differentially expressed mRNAs were predominantly enriched in 'ECM‑receptor interaction', 'PI3K‑Akt signaling pathway' and 'focal adhesion' pathways, all of which are essential for liver fibrosis development. Validation of 12 significantly aberrant lncRNAs by reverse transcription‑quantitative polymerase chain reaction indicated that the expression patterns of 11 lncRNAs were consistent with the sequencing data. Furthermore, overexpression of lncRNA NR_002155.1, which was markedly downregulated in CCl4‑treated liver tissues, was demonstrated to inhibit HSC‑T6 cell proliferation in vitro. In conclusion, the present study determined the expression patterns of mRNAs and lncRNAs in fibrotic liver tissue induced by CCl4. The identified differentially expressed lncRNAs may serve as novel diagnostic biomarkers and therapeutic targets for liver fibrosis.

Mechanisms of CCl4-induced liver fibrosis with combined transcriptomic and proteomic analysis

The classic toxicity of carbon tetrachloride (CCl4) is to induce liver lesion and liver fibrosis. Liver fibrosis is a consequence of chronic liver lesion, which can progress into liver cirrhosis even hepatocarcinoma. However, the toxicological mechanisms of CCl4-induced liver fibrosis remain not fully understood. We combined transcriptomic and proteomic analysis and biological network technology, predicted toxicological targets and regulatory networks of CCl4 in liver fibrosis. Wistar rats were treated with CCl4 for 9 weeks. Histopathological changes, hydroxyproline (Hyp) contents, serum ALT and AST in the CCl4-treated group were significantly higher than that of CCl4-untreated group. CCl4-treated and -untreated liver tissues were examined by microarray and iTRAQ. The results showed that 3535 genes (fold change ≥ 1.5, P < 0.05) and 1412 proteins (fold change ≥ 1.2, P < 0.05) were differentially expressed. Moreover, the integrative analysis of transcriptomics and proteomics data showed 523 overlapped proteins, enriched in 182 GO terms including oxidation reduction, response to oxidative stress, inflammatory response, extracellular matrix organization, etc. Furthermore, KEGG pathway analysis showed that 36 pathways including retinol metabolism, PPAR signaling pathway, glycolysis/gluconeogenesis, arachidonic acid metabolism, metabolism of xenobiotics by cytochrome P450 and drug metabolism. Network of protein-protein interaction (PPI) and key function with their related targets were performed and the degree of network was calculated with Cytoscape. The expression of key targets such as CYP4A3, ALDH2 and ALDH7A1 decreased after CCl4 treatment. Therefore, the toxicological mechanisms of CCl4-induced liver fibrosis may be related with multi biological process, pathway and targets which may provide potential protection reaction mechanism for CCl4 detoxication in the liver.

Protective effects of Rhodiola sachalinesis A Bor on CCl4-induced liver fibrosis in rats

AIM

To study the protective effects of Rhodiola schalinensis A Bor on CCl4-induced liver fibrosis.

METHODS: Male SD rats were divided into 3 groups: normal(N), Rhodiola sachalinesis A Bor(R) and model(M) group. The M and R group were given 300 ml/L CCl₄(3ml/kg, 2 times/week) for 15 weeks and Rhodiola sachalinesis A Bor (0.5g/kg, p.o., daily for 15 weeks) was administered to rats of R group. Histopathological changes were examined. The changes of hepatic content of hydroxyproline and expression of α1(Ⅰ)mRNA were observed.

RESULTS

Rhodiola sachalinesis A Bor decreased the hepatic content of hydroxyproline (657±74 μg/g vs 1 257±98 μg/g, P<0.05) and severity of hepatic fibrosis, improved the liver histopathological changes and inhibited the expression of α1(Ⅰ) mRNA and decreased the level of HA, CⅣ, PCⅢ and TGFβ1 (164±46 μg/L, 97±15 μg/L, 289±76 μg/L, 60±20 mg/L vs 265±98 μg/L, 160±30 μg/L, 456±113 μg/L, 89±23 mg/L. P<0.05, P<0.01).

CONCLUSION

Rhodiola sachalinesis A Bor is effective in protecting against CCl4-induced liver fibrosis in rats, its machenisms appear to be associated with the inhibition of collagen production and protection of hepatic cells.

Preparation and identification of anti-transforming growth factor β1 U1 small nuclear RNA chimeric ribozyme in vitro

AIM: To study the preparation and cleavage activity of anti-transforming growth factor (TGF)β1 U1 small nuclear (sn) RNA chimeric hammerhead ribozymes in vitro.

METHODS: TGFβ1 partial gene fragment was cloned into T-vector at the downstream of T7 promoter. ³²p-labeled TGFβ1 partial transcripts as target RNA were transcribed in vitro and purified by denaturing polyacrylamide gel electrophoresis (PAGE). Anti-TGFβ1 ribozymes were designed by computer, then synthetic ribozyme fragments were cloned into the U1 ribozyme vector pZeoU1EcoSpe containing U1 snRNA promoter/enhancer and terminator. ³²p-labeled U1 snRNA chimeric ribozyme transcripts were gel-purified, incubated with target-RNAs at different conditions and autoradiographed after running denaturing PAGE.

RESULTS: Active U1snRNA chimeric ribozyme (U1Rz803) had the best cleavage activity at 50 °C; at 37 °C, it was active, K_m = 34.48 nmol/L, K_cat = 0.14 min^-1; while the point mutant ribozyme U1Rz803_m had no cleavage activity, so these indicated the design of U1Rz803 was correct.

CONCLUSION: U1Rz803 prepared in this study possessed the perfect specific catalytic cleavage activity. These results indicate U1 snRNA chimeric ribozyme U1Rz803 may suppress the expression of TGFβ1 in vivo, therefore it may provide a new avenue for the treatment of liver fibrosis in the future.

Effect of Chinese herb Shuangjiawuling on expression of TIMPs in rat with liver fibrosis

AIM: To explore the effect of Chinese herb Shuangjiawuling in preventing hepatic fibrosis in rat with liver fibrosis.

METHODS: Rat immunogenic liver fibrosis model was induced by administration human serum albumin (HSA 200 g/L) intravenously, 80 rats were randomly divided into 5 groups. Shuangjiawuling was taken orally simultaneously with (group A), immediately after (group B), or 3 months after (group C) administration of HAS intravenously. Colchine tablets were taken orally with the administration of HAS (group D), normal rats were used as control (Group E). The pathological changes of liver tissue were observed by HE and Von-Gieson staining. The hepatic mRNA and protein of TIMP-1 and TIMP-2 were analyzed by in site hybridization and immunohistochemistry.

RESULTS: Hepatic fibrosis developed gradually and became obviously on the third month after administration of HAS. And strong expressions of TIMP-1 and TIMP-2 were observed, however, its expression and hepatic fibrosis were reduced dramatically following administration of Shuangjiawuling and colchine tablets. The effect of Shuangjiawuling in preventing fibrosis was superior to that of colchine tablets (P<0.05), and its effect in group A, B, and C decreased in order.

CONCLUSION: Chinese herb Shuangjiawuling can inhibit the development of hepatic fibrosis and the expression of TIMPs, and promoted the effect of the degradation of the extracellular matrix.

Inhibition on the production of collagen type I, III of activated hepatic stellate cells by antisense TIMP-1 recombinant plasmid

AIM

To investigate the inhibition effects on the production of collagen type I, III secreted by activated rat hepatic stellate cells (rHSCs) by antisense tissue inhibitors of metalloproteinase 1 (TIMP-1) recombinant plasmid through elevating interstitial collagenase activity.

METHODS

rHSCs were extracted from normal rat liver by pronase and collagenase digestion and purified by centrifugal elutriation, and were cultured on plastic dishes until they were activated to a myofibroblastic phenotype after 7-10 days. RT-Nest-PCR and gene recombinant techniques were used to construct the rat antisense TIMP-1 recombinant plasmids which can express in eucaryotic cells. The recombinant plasmid and the pcDNA3 empty plasmid were transfected in rHSCs by Effectene (QIAGEN) separately. Cells were selected after growing in DMEM containing 400 microg/ml G418 for 2-3 weeks. Expression of exogenous gene was assessed by Northern blot, and expression of TIMP-1 in rHSCs was determined by Northern blot and Western blot. We tested the interstitial collagenase activity with FITC-labled type I collagen as substrate. Ultimately, we quantified the type I, III collagen by Western blot.

RESULTS

The exogenous antisense TIMP-1 recombinant plasmid could be expressed in rHSCs well, which could block the expression of TIMP-1 greatly, the ratio of TIMP-1/GAPDH was 0.67, 2.41, and 2.97 separately at mRNA level (P<0.05); the ratio of TIMP-1/beta-actin was 0.31, 0.98 and 1.32 separately at protein level (P<0.05); It might elevate active and latent interstitial collagenase activity, the collagenase activity was 0.3049, 0.1411 and 0.1196 respectively. (P<0.05), which led to promotion the degradation of type I, III collagen, the ratio of collagen I/beta-actin was 0.63, 1.78 and 1.92 separately (P<0.05); and the ratio of collagen III/beta-actin was 0.59, 1.81 and 1.98 separately (P<0.05).

CONCLUSION

These data shows that the antisense TIMP-1 recombinant plasmid has the inhibitory effects on the production of type I, III collagens secreted by activated rHSCs in vitro. It could be a novel method to reverse hepatic fibrosis in the future.

Methodologic research on TIMP-1, TIMP-2 detection as a new diagnostic index for hepatic fibrosis and its significance

AIM

To set up a new method to detect tissue inhibitors of metalloproteinase-1 and -2(TIMP-1 and TIMP-2) in sera of patients with hepatic cirrhosis, and to investigate the expression and location of TIMP-1 and TIMP-2 in liver tissue of patients with hepatic cirrhosis, and the correlation between TIMPs in liver and those in sera so as to discuss whether TIMPs can be used as a diagnosis index of hepatic fibrosis.

METHODS

The monoclonal antibodies (McAbs) of TIMP-1 and TIMP-2 were used to sensitize erythrocytes, and solid-phase absorption to sensitized erythrocytes (SPASE) was used to detect TIMP-1 and TIMP-2 in the sera of patients with hepatic cirrhosis. Meanwhile, with the method of in situ hybridization and immunohistochemistry, we studied the mRNA expression and antigen location of TIMP-1 and TIMP-2 in the livers of 40 hepatic cirrhosis patients with pathologic diagnosis.

RESULTS

With SPASE, they were 16.4% higher in the acute hepatitis group, 33.3% higher in the chronic hepatitis group, and the positive rates were 73.6% and 61.2% respectively in sera of hepatic cirrhosis patients, which were remarkably higher than those in chronic hepatitis and acute hepatitis group (P<0.001). In 40 samples of hepatic cirrhosis tissues, all of them showed positive expression of TIMP-1 and TIMP-2 mRNA detected with immunohistochemistry or in situ hybridization (positive rate was 100%). Expression of TIMPs in different degrees could be found in liver tissue with cirrhosis. TIMPs were located in cytoplasm of liver cells of patients with hepatic cirrhosis. There was a significant correlation between serum TIMPs level and liver TIMPs level.

CONCLUSION

SPASE is a useful method to detect the TIMP-1 and TIMP-2 in sera of patients with hepatic cirrhosis, and TIMP-1 and TIMP-2 can be considered as a useful diagnostic index of hepatic fibrosis, especially TIMP-1.

Influence of BOL on hyaluronic acid, laminin and hyperplasia in hepatofibrotic rats

AIM

To study the anti-hepatofibrosis mechanism of Bie Jia Jian oral liquid (BOL).

METHODS

The model was induced by subcutaneous injection of CCl(4). BOL was administered and the change of serum hyaluronic acid (HA) and laminin (LN) was observed and the degeneration of liver cells and the degree of fibre hyperplasia analyzed. Changes of ultra micro-structure in liver cells were observed in some samples.

RESULTS

HA was reduced in both the groups with low and high dosage of BOL, which showed a remarkable difference as compared with that of the model group (low dosage group: 376.15 microg/L+/-35.48 microg/L vs 806.07 microg/L+/-98.49 microg/L P<0.05; high dosage group: 340.14 microg/L+/-30.18 microg/L vs 806.07 microg/L+/-98.49 microg/L P<0.05). The LN content of low and high dosage group of BOL was lower than that of model group (low dosage group: 71.99 microg/L+/-8.15 microg/L vs 133.94 microg/L+/-14.45 microg/L P <0.01; high dosage group: 71.68 microg/L+/-11.62 microg/L vs 133.94 microg/L+/-14.45 microg/L P<0.01) and colchicine group (low dosage group: 71.99 microg/L+/-8.15 microg/L vs 118.28 microg/L+/-16.13 microg/L P < 0.05; high dosage group: 71.68 microg/L+/-11.62 microg/L vs 118.28 microg/L+/-16.13 microg/L P <0.05). Examined by Ridit, BOL could reduce the degeneration and necrosis of liver cells (chi(2)=11.99 P<0.05), the degree of fibre hyperplasia (chi(2)=13.24 P<0.05) and the pathological change of ultra micro-structure as well.

CONCLUSION

The BOL has certain therapeutic effect on the experiment hepatofibrosis. Its mechanisms might include: protecting the function of liver cells, inhibiting excessive synthesis and secretion of extracellular matrix from hepatic stellate cells, relieving the capillarization of hepatic sinusoid, improving liver micro-circulation, and regulating immune function.

Inhibiting effect of antisense oligonucleotides phosphorthioate on gene expression of TIMP-1 in rat liver fibrosis

AIM

To observe the inhibition of antisense oligonucleotides (asON) phosphorthioate to the tissue inhibitors metalloproteinase-1 (TIMP-1) gene and protein expression in the liver tissue of immunologically induced hepatic fibrosis rats. The possibility of reversing hepatic fibrosis through gene therapy was observed.

METHODS

Human serum albumin (HSA) was used to attack rats, as hepatic fibrosis model, in which asONs were used to block the gene and protein expressing TIMP-1. According to the analysis of modulator, structure protein, coding series of TIMP-1 genome, we designed four different asONs. These asONs were injected into the hepatic fibrosis models through coccygeal vein. The results was observed by RT-PCR for measuring TIMP-1 mRNA expression, immunohistochemistry and in situ hybridization for collagen I, II, special staining of collagen fiber, and electron microscopic examination.

RESULTS

Hepatic fibrosis could last within 363 days in our modified model. The expressing level of TIMP-1 was high during hepatic fibrosis process. It has been proved by the immunohistochemical and the electron microscopic examination that the asON phosphorthioate of TIMP-1 could exactly express in vivo. The effect of colchicine was demonstrated to inhibit the expressing level of mRNA and the content of collagen I, III in the liver of experimental hepatic fibrosis rats. However, the electron microscopy research and the pathologic grading of hepatic fibrosis showed that there was no significant difference between the treatment group and the model group (P> 0.05).

CONCLUSION

The experimental rat model of hepatic fibrosis is one of the preferable models to estimate the curative effect of anti-hepatic fibrosis drugs. The asON phosphorthioate of TIMP-1 could block the gene and protein expression of TIMP-1 in the liver of experimental hepatic fibrosis rats at the mRNA level. It is possible to reverse hepatic fibrosis, and it is expected to study a new drug of antihepatic fibrosis on the genetic level. Colchicine has very limited therapeutic effect on hepatic fibrosis, furthermore, its toxicity and side effects are obvious.

Expression changes of activin A in the development of hepatic fibrosis

AIM: To examine the expression of activin A, a member of the transforming growth factor (TGF-β) superfamily, recently has been reported to beoverexpressed in liver cirrhosis, in the course of carbon tetrachloride-induced rat hepatic fibrosis.

METHODS: Hepatic fibrosis was induced in rats by subcutaneous injections of 40% carbon tetrachloride oily solution for a period of 1 to 7 weeks. At the end of 1, 2, 3, 4, 5, 6 and 7 weeks after carbon tetrachloride injections, the rats were killed in group (6-10 rats each time) for study. The activin A messenger RNA expression and its protein localization were assessed by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS: The normal rat liver expressed activin A mRNA and protein, and its expression was transiently decreased and became undetectable after carbon tetrachloride injections for 2 or 3 weeks and then increased gradually. After injection of carbon tetrachloride for 6 and 7 weeks, activin A mRNA and protein expressions were significantly enchanced in rat liver. Compared with that of the normal rat liver. Activin A mRNA expression levels in rats receiving carbon tetrachloride injections for 6 and 7 weeks were 1.6 and 2.2 times that of those in normal rat liver respectively (0.456 ± 0.094 vs 0.286 ± 0.0670, P < 0.01; 0.620 ± 0.134 vs 0.286 ± 0.0670, P < 0.01). Immunohistochemistry showed that activin A expressed in hepatocytes of normal liver, and its expression was decreased in rats receiving carbon tetrachloride for 2 or 3 weeks. Compared with normal liver, activin A expression distribution mode changed in fibrotic liver, being increased significantly in hepatocytes around fibrotic areas.

CONCLUSION: Activin A expression was increased in late stage of hepatic fibrosis, and this may be involved in hepatic fibrosis formation in this period.

The regulatory role of AT1 receptor on activated HSCs in hepatic fibrogenesis: Effects of RAS inhibitors on hepatic fibrosis induced by CCl4

AIM: To assess the effect of ACE inhibitor and AngII type 1 (AT1) receptor antagonist in preventing hepatic fibrosis caused by CCl₄ administration in rats; to investigate whether or not there are expression of AT1 receptors on hepatic stellate cells; and to observe the effect of AngII on proliferation and ECM synthesis of cultured HSCs.

METHODS: Studies were conducted in male Sprague-Dawley rats. Except for the hepatofibrotic model group and the control group, in three treated groups, either enalapril (5 mg/kg), or losartan (10 mg/kg), or enalapril + losartan were given to the fibrotic rats by daily gavage, and saline vehicle was given to model and normal control rats. After 6 wk, liver fibrosis was assessed directly by hepatic morphometric analysis, which has been considered the gold standard for the quantification of fibrosis. The expressions of AT1 receptors and (α-mooth muscle actin, α-SMA) in liver tissue or isolated hepatic stellate cells (HSCs) were detected by immunohistochemical techniques. The effect of AngII on HSC proliferation was determined by MTT method. Effect of AngII on collagen synthesis of HSCs was de termined by ³H-proline incorporation.

RESULTS: Contrasted to the fibrosis in rats of the model group, groups of rats treated with either enalapril or losartan, or a combination of two drugs showed a limited expansion of the interstitium (4.23 ± 3.70 vs 11.22 ± 4.79, P < 0.05), but no difference was observed among three treated groups (5.38 ± 3.43, 4. 96 ± 2.96, 4.23 ± 2.70, P > 0.05). Expression of AT1 receptors was found in fibrotic interstitium of fibrotic rats, whereas in normal control rats they were limited to vasculature only to a very slight degree. AT1 receptors were also expressed on activated HSCs in the culture. At concentrations from 10^-9 to 10^-5 mol/L, AngII stimulated HSC proliferation in culture in a dose-dependent manner. Increasing AngII concentrations produced corresponding increases in ³H-proline incorporation. Differences among groups were significant.

CONCLUSION: Angiotensin-converting enzyme inhibitors and AT 1 blocker may slow the progression of hepatic fibrosis; activated HSCs express AT1 receptors, and AngII can stimulate the proliferation and collagen synthesis of HSCs in a dose-dependent manner; and activation of RAS may be related to hepatic fibrogenesis induced by CCl₄.

Effects of AT1 receptor antagonist, losartan, on rat hepatic fibrosis induced by CCl4

AIM: To investigate effect o f losartan, an AT1 receptor antagonist, on hepatic fibrosis induced by CCl₄; and to determine whether or not AT1 receptors are expressed on hepatic stellate cells.

METHODS AND RESULTS: Fifty male Sprague-Dawley rats, weighing (180 ± 20) g, were randomized into five groups (control group, model group, and three los artan treated groups), in which all rats were given the subcutaneous injection o f 40% CCl₄ (every 3 days for 6 weeks) except for rats of control group. Rats of losartan-treated groups were treated with losartan (20 mg/kg, 10 mg/kg, 5 mg/kg, daily gavage). After 6 weeks liver tissue and serum samples of all rats were examined. Serum hyaluronic acid (HA), procollagen type III (PC III) were detected by radioimmunoassays. van Giesion collagen staining was used to evaluate the extracellular matrix of rats with liver fibrosis. The expression of AT1 receptors, transforming growth factor-beta (TGF-β), and alpha-smooth muscle actin (α-SMA) in liver tissue were determined by immunohistochemical techniques. Compared with model group, serum ALT and AST of losartan-treated groups were significantly reduced (t = 4. 20, P < 0.01 and t = 4.57, P < 0.01). Serum HA and PC III also had significant differences (t = 3.53, P < 0.01 and t = 2.20, P < 0.05). The degree of fibrosis was improved by losartan and correlated with the expressions of AT1 receptors, TGF-β, and α-SMA in liver tissue.

CONCLUSION: AT1 receptor antagonist, losartan, could limit the progression of the hepatic fibrosis induced by CCl₄. The mechanism may be relat ed to the decrease in the expression of AT1 receptors and TGF-β, a meliorating the injury of hepatocytes; activation of local renin-angiotensin system might relate to hepatic fibrosis; and during progression of fibrosis, activated hepatic stellate cells might express AT1 receptors.