Hepatic fibrosis--new therapeutic approaches

Induced hypothyroidism accelerates the regression of liver fibrosis in rats

BACKGROUND AND AIM

It has been shown in previous studies that hypothyroidism prevents the development of liver fibrosis in bile duct ligated rats and in rats chronically treated with thioacetamide (TAA). In recent years, regression of liver fibrosis (occurring spontaneously or during treatment) has been demonstrated in rodent models such as bile duct ligation and CCl(4) administration. Therefore, in the present study, the potential therapeutic effect of hypothyroidism on liver fibrosis was investigated.

METHODS

Liver fibrosis was induced in rats by administration of TAA (200 mg/kg, i.p., twice weekly) for 12 weeks. Hypothyroidism was then induced by either methimazole (0.04%) or propylthiouracil (0.05%) administered in drinking water for 8 weeks. Control euthyroid rats received normal drinking water. Hypothyroidism was confirmed by a significant elevation of serum thyroid-stimulating hormone levels.

RESULTS

Eight weeks after the cessation of TAA administration, spleen weight, histological score of liver fibrosis, and hepatic hydroxyproline content were significantly lower in both groups of hypothyroid rats as compared to euthyroid controls (P < 0.001). In vitro studies using the rat hepatic stellate cell line HSC-T6 using northern blot analysis and zymography, respectively, showed that high concentrations of triiodotyronine (T(3)) enhanced transforming growth factor (TGF)-beta-induced collagen I gene expression, and reduced metalloproteinase (MMP)-2 secretion, implying that reducing the levels of T(3) may contribute to resolution of fibrosis. Additionally, low T(3) concentration inhibited HSC-T6 proliferation.

CONCLUSION

Pharmacologically induced hypothyroidism accelerates the resolution of liver fibrosis in rats. This beneficial effect may in part be due to prevention of T(3)-induced stimulation of collagen synthesis and reduction of MMP-2 secretion.

Pirfenidone inhibits dimethylnitrosamine-induced hepatic fibrosis in rats

1. In the present study, we investigated the preventive effects of pirfenidone (PFD), an antifibrotic agent, on experimental hepatic fibrosis induced by dimethylnitrosamine (DMN) in rats. 2. Treatment with DMN caused a significant decrease in bodyweight and liver weight. Oral PFD (500 mg/kg daily for 4 weeks) essentially prevented this DMN-induced loss in bodyweight and tended to suppress the loss in liver weight. There were no significant differences in liver weight and serum L-alanine aminotransferase levels between PFD-treated and -untreated groups. Pirfenidone has no major side effects in vivo. 3. Pirfenidone suppressed the induction of hepatic fibrosis determined by histological evaluation and reduced hepatic hydroxyproline levels. Expression of mRNA for type I collagen and transforming growth factor-beta in the liver was also suppressed by PFD treatment. 4. Because hepatic stellate cells (HSC) are the major cellular source of extracellular matrix in hepatic fibrosis, we examined the effects of PFD on type I collagen production in vitro using rat primary HSC cultures. Pirfenidone inhibited collagen production in HSC culture in a dose-dependent manner. 5. These results demonstrate that the inhibitory effects of PFD against hepatic fibrosis may be due, at least in part, to blockade of collagen production by HSC and suggest that PFD may be potentially useful in the prevention of the development of hepatic fibrosis.

The Ras antagonist, farnesylthiosalicylic acid (FTS), inhibits experimentally-induced liver cirrhosis in rats

BACKGROUND/AIMS

Protooncogenes may play an important role, not only in carcinogenesis, but also in the regulation of normal cellular proliferation and differentiation. Several studies have indicated increased expression of the Ras protooncogenes in the liver in animal models and in patients with liver cirrhosis. The aim of the present study was to examine whether a synthetic Ras antagonist, S-farnesylthiosalicylic acid (FTS), which specifically dislodges Ras from the membrane of Ras-transformed fibroblasts (EJ cells), can prevent experimentally-induced liver cirrhosis in rats.

METHODS

Cirrhosis was induced in male Wistar rats by intraperitoneal administration of thioacetamide (200 mg/kg twice weekly for 12 weeks). The Ras antagonist, farnesylthiosalicylic acid (FTS, 5 mg/kg), was administered during the study period 3 times a week. Ras expression in the liver was determined by Western blot analysis with pan anti-Ras antibodies and by immunohistochemistry.

RESULTS

Rats treated with thioacetamide and the Ras antagonist, farnesylthiosalicylic acid (FTS), for 12 weeks had lower histopathologic scores of fibrosis and inflammation (p-values of 0.003 and 0.008, respectively) than those treated with thioacetamide only. There were no differences between the histopathologic scores in vehicle (control) and in Ras-antagonist (FTS) only treatments. Analysis of hepatic hydroxyproline levels from the two thioacetamide-treated groups and controls confirmed the histopathologic scores (7.7+/-0.9 mg/g protein in the TAA-treated vs. 3.8+/-0.5 mg/g protein in the TAA+FTS treated group, p = 0.007). Ras levels, determined by Western blot analysis, were markedly increased in the livers treated with TAA (17-fold over control) and significantly decreased (by about 70%) in the livers of rats treated with TAA and FTS. Studies in isolated human hepatic stellate cells demonstrated that FTS inhibited both DNA synthesis and migration of those cells (p<0.05).

CONCLUSION

These results indicate that inhibition of Ras expression in the liver during fibrogenesis, prevents the development of experimentally-induced hepatic cirrhosis.

Liver function in cirrhotic patients in the euthyroid versus the hypothyroid state

We recently showed that some decrease in thyroid hormone blood levels can effectively and significantly prevent the development of cirrhosis and fulminant hepatic failure and decrease portal pressure in three different rat models. This study was conducted to determine whether hypothyroidism has a beneficial effect over euthyroidism on patients with active liver cirrhosis of different etiologies. The medical files of hypothyroid patients with cirrhosis who were referred to the Tel-Aviv Medical Center between the years 1980 and 1995 were retrospectively evaluated. Of 3,528 patients with biopsy-proven cirrhosis and 4,738 hypothyroid patients who were identified, only 46 (25 female, 54%; mean age, 52.3 +/- 9.1) met the eligibility criteria. The patients suffered from cirrhosis (mean, 9.5 +/- 4.3 years; range, 4-23) and had hypothyroidism (mean, 12 +/- 6 years; range, 4-31). Most patients suffered from hypothyroidism of unknown etiology (85%), whereas the rest had hypothyroidism after surgical/iodine ablation of the gland. In the hypothyroid versus the euthyroid state, a significant negative correlation was found between thyroid-stimulating hormone blood levels and both functional and synthetic liver function tests (p < 0.001). A significant negative correlation was also found between thyroid-stimulating hormone blood levels and clinical deterioration manifested as bleeding varices, the development of ascites, and episodes of encephalopathy. We conclude that in patients with liver cirrhosis, the liver function in the hypothyroid state tend to be better than in the euthyroid state. A mild controlled decreased thyroid function may be beneficial for euthyroid cirrhotic patients.

Changes in liver fibrosis at the end of alpha interferon therapy and 6 to 18 months later in patients with chronic hepatitis C: quantitative assessment by a morphometric method

BACKGROUND/AIMS

The aims of the study were to determine, in patients with chronic hepatitis C treated with alpha interferon: (i) changes in the morphometric evaluation of liver fibrosis at the end of treatment and 6, 12 and 18 months after treatment; (ii) the predictive value of histologic lesions for the response to treatment, in particular the predictive value of morphometric evaluation of liver fibrosis.

METHODS

Seventy patients with chronic hepatitis C who participated in two trials of recombinant interferon alpha 2b treatment were studied. Liver specimens were obtained before and at the end of treatment and 6, 12 or 18 months later. Histologic lesions were assessed according to the Knodell system. Quantitative study of total fibrosis and of Disse space collagen was done by the computerized automated morphometric method.

RESULTS

A significant decrease in morphometric Disse space collagen was observed at the end of treatment and 6 months later. This decrease was also observed, although it was not significant, 12 and 18 months after treatment. There was no relationship between this decrease and the biochemical and virological responses or the dose of interferon. The pretreatment Knodell activity score, but not the morphometric evaluation of fibrosis, was a significant predictor of sustained response.

CONCLUSION

A decrease in Disse space collagen, as assessed by the sensitive morphometric method, was observed at the end of and 6 months after treatment. This observation is consistent with an anti-fibrogenetic effect of alpha interferon. Mild or moderate histologic activity was associated with a sustained response to therapy.

Inhibition of experimentally-induced liver cirrhosis in rats by a nonpeptidic mimetic of the extracellular matrix-associated Arg-Gly-Asp epitope

AIMS/METHODS

In the present study, we examined whether a nonpeptidic mimetic of Arg-Gly-Asp (RGD), which specifically inhibits RGD-dependent adhesion of CD4+ T lymphocytes or fibroblasts to fibronectin, can prevent thioacetamide-induced liver cirrhosis in rats. The nonpeptidic RGD mimetic, rather than the RGD peptide was utilized, since the peptide is rapidly degraded, and therefore, relatively ineffective for in vivo use.

RESULTS

We now report that rats treated with thioacetamide and the RGD analogue SF-6,5 for 12 weeks had lower histopathologic scores than those treated with thioacetamide alone. Further improvement in liver histology was observed after another 8 weeks of treatment with the analogue SF-6,5. Quantitative microscopic analysis by computerized imaging morphometry of liver biopsies from the three groups and controls confirmed the semi-quantitative histopathologic scores (p < 0.001). After 3 months of treatment, the spleen weights in the SF-6,5-treated rats were 30% less than those of rats that received only thioacetamide, which indicated that the analogue-treated rats were less portal hypertensive.

CONCLUSIONS

The observed inhibition of the progression of cirrhosis in rats by the nonpeptidic RGD analogue suggests that RGD mimetics may be useful therapeutically in inhibiting pathological processes that involve RGD recognition.

Improvement of liver fibrosis in chronic hepatitis C patients treated with natural interferon alpha

To investigate the histological change (change of liver fibrosis) produced by the anti-viral effect of interferon on hepatitis C virus, 40 patients with chronic hepatitis C treated with natural interferon alpha were divided according to the existence of viremia at the end of treatment and 6 months after the end of treatment. The condition of liver fibrosis was scored numerically with a new "hepatic fibrosis score" which is sensitive to more subtle changes than Knodell's fibrosis score. Each portal zone was evaluated separately. End-of-treatment biopsy for the HCV RNA-negative group (negative for HCV RNA at the end of treatment) showed a significant improvement of the "hepatic fibrosis score" as well as the alleviation of necrosis and inflammation. At the end of treatment and 6 months after that, serum procollagen type III peptide levels and serum type IV collagen-7s levels had also decreased significantly in the HCV RNA-negative group. The present study showed that treatment with interferon alpha could alleviate fibrosis in addition to necrosis and inflammation.

Detection of liver fibrosis with magnetic cross-relaxation

The utility of MRI using magnetization transfer (MT) enhanced pulse sequences to diagnose hepatic cirrhosis in a rat model was investigated. Hepatic T1 was measured with and without MT off-resonance RF pulses in 17 treated and six control rats. The livers were evaluated histologically, and the hydroxyproline content quantitatively measured. We did not find a statistically significant linear correlation between the MR relaxation times and the degree of tissue injury. However, the MR measurements performed with MT were superior to those without differentiating the treated and control groups. Specifically, the T1 times were 695 +/- 76 ms for the treated group, versus 748 +/- 61 ms in the controls; P = 0.095. The T1sat times were also lower in the treated group, with statistical significance: 367 +/- 51 ms versus 421 +/- 38 ms, P = 0.016. Finally, the change in the relaxation rates (the inverse of the relaxation times) with and without saturation were 1.31 +/- 0.22 s-1 (treated group) versus 1.05 +/- 0.12 s-1 (controls), which differed significantly, P = 0.001.

The effect of interferon alpha and prednisolone on the serum concentrations of the aminoterminal domain of procollagen type III(PIIIP) and type IV (7-S collagen) in patients with chronic hepatitis B

Since interferons are reported to inhibit collagen synthesis in vivo and in vitro, they are possible anti-fibrogenic drugs. However, little is known about the effect of interferons on connective tissue metabolism in liver disease. To investigate the effect, serum concentrations of the aminoterminal domain of procollagen type III and type IV (7-S collagen) were measured in 16 patients with chronic hepatitis B during alpha interferon treatment. The levels were also determined during prednisolone withdrawal treatment to investigate the effect on hepatic collagen turnover. In patients with chronic hepatitis B, the serum levels of both markers were significantly elevated before any treatment (procollagen type III: 1.10 +/- 0.39 U/ml, 7-S collagen: 6.69 +/- 3.71 ng/ml) compared with levels in 41 healthy volunteers (pro-collagen type III: 0.53 +/- 0.13 U/ml, P < 0.001; 7-S collagen: 4.72 +/- 0.57 ng/ml, P < 0.001). Both levels were even more elevated during interferon therapy (procollagen type III: 1.36 +/- 0.58 U/ml, P < 0.05; 7-S collagen: 8.77 +/- 4.68 ng/ml, P < 0.01). On the other hand, serum procollagen type III and 7-S collagen levels were both decreased during prednisolone treatment (procollagen type III: 0.62 +/- 0.13 U/ml, P < 0.001; 7-S collagen: 4.66 +/- 1.69 ng/ml, P < 0.01). These preliminary data suggest that interferon alpha enhanced, but prednisolone inhibited the turnover of procollagen type III and IV in the liver. Further study is required to interpret this observation in relation to anti-fibrotic therapy.

alpha-Interferon in the treatment of chronic viral hepatitis: effects on fibrogenesis serum markers

Forty patients with chronic viral hepatitis or active cirrhosis (33 anti-HCV positive) entered a recombinant human alpha 2A interferon randomized trial. Twenty-one subjects were treated with 6 million units (MU) three times per week for 6 months. Nineteen were not treated. Six months later in 12 patients of the treated group (60% of the evaluable 20) with normalized serum aminotransferases levels (responders), fibrogenesis serum markers (NPIIIP and laminin) were significantly lower than baseline. In the untreated patients and in non-responders NPIIIP and laminin were unchanged. Semi quantitative histological evaluation (allotting scores for inflammation, necrosis and fibrosis) confirmed a significant improvement of necro-inflammation in the responders. These data suggest that alpha-IFN treatment may decrease stimuli for fibrogenesis by reducing liver inflammation and necrosis, thus preventing evolution to cirrhosis.