Effect of pentoxifylline on early proliferation and phenotypic modulation of fibrogenic cells in two rat models of liver fibrosis and on cultured hepatic stellate cells

Roles of hepatic stellate cells in NAFLD: From the perspective of inflammation and fibrosis

Non-alcoholic fatty liver disease (NAFLD) has become one of the most common diseases and severe problems worldwide because of the global increase in obesity, dyslipidemia, hypertension, and type 2 diabetes mellitus. NAFLD includes a wide spectrum of liver diseases, the histological forms of which range from non-alcoholic fatty liver (NAFL), which is generally nonprogressive, to non-alcoholic steatohepatitis (NASH), which can progress to chronic hepatitis, liver cirrhosis (LC), and sometimes hepatocellular carcinoma (HCC). Unlike NAFL, as the progressive form of NAFLD, NASH is characterized by the presence of inflammation with or without fibrosis in addition to hepatic steatosis. Although it is widely known and proved that persistent hepatic injury and chronic inflammation in the liver activate quiescent hepatic stellate cells (HSCs) and lead to hepatic fibrosis, the three-step process of “inflammation-fibrosis-carcinoma” in NAFLD has not been investigated and clarified clearly. In this process, the initiation of inflammation in the liver and the function of various liver inflammatory cells have been discussed regularly, while the activated HSCs, which constitute the principal cells responsible for fibrosis and their cross-talk with inflammation, seem not to be investigated specifically and frequently. Also, accumulated evidence suggests that HSCs can not only be activated by inflammation but also participate in the regulation of liver inflammation. Therefore, it is necessary to investigate the unique roles of HSCs in NAFLD from the perspective of inflammation and fibrosis. Here, we review the pivotal effects and mechanisms of HSCs and highlight the potential value of HSC-targeted treatment methods in NAFLD.

New Drugs for Hepatic Fibrosis

The morbidity and mortality of hepatic fibrosis caused by various etiologies are high worldwide, and the trend is increasing annually. At present, there is no effective method to cure hepatic fibrosis except liver transplantation, and its serious complications threaten the health of patients and cause serious medical burdens. Additionally, there is no specific drug for the treatment of hepatic fibrosis, and many drugs with anti-hepatic fibrosis effects are in the research and development stage. Recently, remarkable progress has been made in the research and development of anti-hepatic fibrosis drugs targeting different targets. We searched websites such as PubMed, ScienceDirect, and Home-ClinicalTrials.gov and found approximately 120 drugs with anti-fibrosis properties, some of which are in phase Ⅱ or Ⅲ clinical trials. Additionally, although these drugs are effective against hepatic fibrosis in animal models, most clinical trials have shown poor results, mainly because animal models do not capture the complexity of human hepatic fibrosis. Besides, the effect of natural products on hepatic fibrosis has not been widely recognized at home and abroad. Furthermore, drugs targeting a single anti-hepatic fibrosis target are prone to adverse reactions. Therefore, currently, the treatment of hepatic fibrosis requires a combination of drugs that target multiple targets. Ten new drugs with potential for development against hepatic fibrosis were selected and highlighted in this mini-review, which provides a reference for clinical drug use.

Effects of Pentoxifylline on Peritoneal Fibroblasts and Silica-Induced Peritoneal Fibrosis

♦ Background

Peritoneal fibrosis is a long-term complication following continuous ambulatory peritoneal dialysis (CAPD). Peritoneal fibroblasts may play an important role in peritoneal fibrosis. Up to now, the treatment of peritoneal fibrosis in patients with CAPD remains unsatisfactory. Pentoxifylline (PTX) is a xanthine derivative and is used in the treatment of peripheral vascular and cerebrovascular diseases. Several studies have demonstrated that PTX can ameliorate fibrosis of the skin, liver, and kidney.

♦ Objective

To investigate the effect of PTX on in vitro growth and collagen synthesis of human peritoneal fibroblasts (HPFBs), and to evaluate the effects of PTX on silica-induced peritoneal fibrosis in vivo.

♦ Design and Measurements

In the in vitro study, HPFBs were cultured from human omentum. The effect of PTX on the growth of serum-stimulated HPFBs was evaluated by MTT assay. The effect of PTX on the collagen synthesis of HPFB was measured by [3H]-proline incorporation. Expression of type I and type III collagen mRNA was evaluated by Northern blotting. The effects of PTX on matrix metalloproteinase (MMP) activity and cAMP level in HPFBs were measured by immunoassays. In the in vivo study, Wistar rats were randomly divided into five groups. All rats received intraperitoneal (IP) injection of silica suspension (250 mg/100 g body weight) on day 0. The rats of group 1 (control group) were injected with vehicle IP every day for 14 days. The rats of groups 2, 3, and 4 were injected with PTX (4 mg/100 g body weight) IP every day for 3, 7, and 14 days, respectively. The rats in group 5 received an intravenous infusion of PTX (8 mg/100 g body weight) every day for 7 days. On the 15th day after silica injection, all rats were sacrificed. Their parietal and visceral peritoneums were removed and processed for pathology, and the severity of fibrosis was measured and scored. ♦ Results: In vitro, PTX inhibited serum-stimulated HPFB growth (maximum was 93% at 1 mg PTX/mL) in a dose-dependent manner. Collagen synthesis by HPFB was reduced (47% at 1 mg PTX/mL), and collagen I and III mRNA expression in HPFBs was suppressed by PTX. The PTX did not affect the MMP (including MMP-1, MMP-8, and MMP-13) activities of HPFBs. The mechanism of PTX was through increasing cAMP by its phosphodiesterase inhibiting activity. In vivo, the severity of fibrosis was significantly reduced in groups 4 and 5 compared to group 1 ( p < 0.05).

♦ Conclusion

These results suggest that PTX can inhibit growth of and collagen synthesis by HPFBs in vitro. The fibrosis derived from silica-induced peritonitis in vivo was also ameliorated by PTX. Therefore, pentoxifylline may have the potential to be used to treat peritoneal fibrosis in patients on CAPD.

Biliary Atresia Relevant Human Induced Pluripotent Stem Cells Recapitulate Key Disease Features in a Dish

Biliary atresia (BA) is the most common cause of pediatric end-stage liver disease and the etiology is poorly understood. There is no effective therapy for BA partly due to lack of human BA models. Towards developing in vitro human models of BA, disease-specific induced pluripotent stem cells (iPSCs) from 6 BA patients were generated using non-integrating episomal plasmids. In addition, to determine the functional significance of BA-susceptibility genes identified by genome-wide association studies (GWAS) in biliary development, a genome-editing approach was used to create iPSCs with defined mutations in these GWAS BA loci. Using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 system, isogenic iPSCs deficient in BA-associated genes (GPC1 and ADD3) were created from healthy iPSCs. Both the BA patient-iPSCs and the knock out (KO) iPSCs were studied for their in vitro biliary differentiation potential. These BA-specific iPSCs demonstrated significantly decreased formation of ductal structures, decreased expression of biliary markers including CK7, EpCAM, SOX9, CK19, AE2, and CFTR and increased fibrosis markers such as alpha smooth muscle actin, Loxl2, and Collagen1 compared to controls. Both the patient- and the KO-iPSCs also showed increased yes-associated protein (YAP, a marker of bile duct proliferation/fibrosis). Collagen and YAP were reduced by treatment with the anti-fibrogenic drug pentoxifylline. In summary, these BA-specific human iPSCs showed deficiency in biliary differentiation along with increased fibrosis, the 2 key disease features of BA. These iPSCs can provide new human BA models for understanding the molecular basis of abnormal biliary development and opportunities to identify drugs that have therapeutic effects on BA.

Role of cAMP and phosphodiesterase signaling in liver health and disease

Liver disease is a significant health problem worldwide with mortality reaching around 2 million deaths a year. Non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) are the major causes of chronic liver disease. Pathologically, NAFLD and ALD share similar patterns of hepatic disorders ranging from simple steatosis to steatohepatitis, fibrosis and cirrhosis. It is becoming increasingly important to identify new pharmacological targets, given that there is no FDA-approved therapy yet for either NAFLD or ALD. Since the evolution of liver diseases is a multifactorial process, several mechanisms involving parenchymal and non-parenchymal hepatic cells contribute to the initiation and progression of liver pathologies. Moreover, certain protective molecular pathways become repressed during liver injury including signaling pathways such as the cyclic adenosine monophosphate (cAMP) pathway. cAMP, a key second messenger molecule, regulates various cellular functions including lipid metabolism, inflammation, cell differentiation and injury by affecting gene/protein expression and function. This review addresses the current understanding of the role of cAMP metabolism and consequent cAMP signaling pathway(s) in the context of liver health and disease. The cAMP pathway is extremely sophisticated and complex with specific cellular functions dictated by numerous factors such abundance, localization and degradation by phosphodiesterases (PDEs). Furthermore, because of the distinct yet divergent roles of both of its effector molecules, the cAMP pathway is extensively targeted in liver injury to modify its role from physiological to therapeutic, depending on the hepatic condition. This review also examines the behavior of the cAMP-dependent pathway in NAFLD, ALD and in other liver diseases and focuses on PDE inhibition as an excellent therapeutic target in these conditions.

Extracellular adenosine: a critical signal in liver fibrosis

Extracellular adenosine nucleoside is a potent, endogenous mediator that signals through specific G protein-coupled receptors, and exerts pleiotropic effects on liver physiology, in health and disease. Particularly, adenosinergic or adenosine-mediated signaling pathways impact the progression of hepatic fibrosis, a common feature of chronic liver diseases, through regulation of matrix deposition by liver myofibroblasts. This review examines the current lines of evidence on adenosinergic regulation of liver fibrosis and myofibroblasts, identifies unanswered research questions, and proposes important future areas of investigation.

MicroRNA-125b Promotes Hepatic Stellate Cell Activation and Liver Fibrosis by Activating RhoA Signaling

miR-125b is frequently dysregulated in different diseases. Activation of hepatic stellate cells (HSCs) is a critical event during liver fibrogenesis. However, the function and its underlying mechanism of miR-125b in HSC activation and liver fibrosis are still unknown. Here, we showed that miR-125b was upregulated in HSCs, but not in hepatocytes, during hepatic fibrogenesis in vivo and upon culture activation in vitro. Inhibition of miR-125b suppressed the expression of profibrogenic genes in culture-activated primary HSCs and reduced the basal and transforming growth factor β (TGF-β)-induced alpha-smooth muscle actin (α-SMA) expression and cell contraction of the immortalized HSC cell line. In contrast, ectopic expression of miR-125b promoted α-SMA expression and HSC contraction. Moreover, antagonizing miR-125b in vivo significantly alleviated liver fibrosis in CCl₄-treated mice. Mechanistically, overexpression of miR-125b in HSCs enhanced RhoA activity by directly targeting StAR-related lipid transfer (START) domain containing 13 (Stard13), a RhoA-specific GTPase-activating protein, whereas knockdown of miR-125b abrogated RhoA activation. Furthermore, inhibition of RhoA or its downstream molecules, Mrtf-A and Srf, attenuated the miR-125b-induced α-SMA expression and HSC contraction. Therefore, our findings identify a miR-125b-Stard13-RhoA-α-SMA signaling cascade in HSCs and highlight its importance in hepatic fibrosis.

The stellate cell system (vitamin A-storing cell system)

Past, present, and future research into hepatic stellate cells (HSCs, also called vitamin A-storing cells, lipocytes, interstitial cells, fat-storing cells, or Ito cells) are summarized and discussed in this review. Kupffer discovered black-stained cells in the liver using the gold chloride method and named them stellate cells (Sternzellen in German) in 1876. Wake rediscovered the cells in 1971 using the same gold chloride method and various modern histological techniques including electron microscopy. Between their discovery and rediscovery, HSCs disappeared from the research history. Their identification, the establishment of cell isolation and culture methods, and the development of cellular and molecular biological techniques promoted HSC research after their rediscovery. In mammals, HSCs exist in the space between liver parenchymal cells (PCs) or hepatocytes and liver sinusoidal endothelial cells (LSECs) of the hepatic lobule, and store 50-80% of all vitamin A in the body as retinyl ester in lipid droplets in the cytoplasm. SCs also exist in extrahepatic organs such as pancreas, lung, and kidney. Hepatic (HSCs) and extrahepatic stellate cells (EHSCs) form the stellate cell (SC) system or SC family; the main storage site of vitamin A in the body is HSCs in the liver. In pathological conditions such as liver fibrosis, HSCs lose vitamin A, and synthesize a large amount of extracellular matrix (ECM) components including collagen, proteoglycan, glycosaminoglycan, and adhesive glycoproteins. The morphology of these cells also changes from the star-shaped HSCs to that of fibroblasts or myofibroblasts.

Use of pentoxifylline and tocopherol in radiation-induced fibrosis and fibroatrophy

Radiation-induced fibrosis in the head and neck is a well-established pathophysiological process after radiotherapy. Recently pentoxifylline and tocopherol have been proposed as treatments to combat the late complications of radiation-induced fibrosis and a way of dealing with osteoradionecrosis. They both have a long history in the management of radiation-induced fibrosis at other anatomical sites. In this paper we review their use in sites other than the head and neck to illustrate the potential benefit that they offer to our patients.

Pentoxifylline Inhibits Epidural Fibrosis in Post-Laminectomy Rats

BACKGROUND

The aim of this experimental study was to investigate the effectiveness of intramuscular pentoxifylline in the prevention of postoperative fibrosis.

MATERIAL/METHODS

We divided 16 adult Wistar albino rats into 2 equal groups: treatment and control. Both groups underwent L1 vertebral total laminectomy to expose the dura. The intramuscular treatment group received pentoxifylline. Four weeks later, epidural fibrosis was studied in both groups using electron microscopy, light microscopy, histology, biochemistry, and macroscopy.

RESULTS

The evaluation of epidural fibrosis in the 2 groups according to macroscopic (p<0.01) assessment and light microscopy revealed that epidural scar tissue formation was lower in the treatment group compared to the control group (p<0.001) and the number of fibroblasts was also decreased significantly in the pentoxifylline-treated group (p<0.05). More immature fibers were demonstrated in the treatment group by electron microscopy in comparison with the control group. In biochemical analysis, a statistically significant decrease was detected in hydroxyproline, which indicates fibrosis and myeloperoxidase activity, and shows an inflammatory response (P<0.001).

CONCLUSIONS

Systemic pentoxifylline application prevents postoperative epidural fibrosis and adhesions with various mechanisms. Our study is the first to present evidence of experimental epidural fibrosis prevention with pentoxifylline.

Pentoxifylline Increases Antiadhesion Effect of Streptokinase on Postoperative Adhesion Formation: Involvement of Fibrinolytic Pathway

Pentoxifylline reduces peritoneal adhesions and increases peritoneal fibrinolysis in rodents. Furthermore, the activation of the fibrinolytic system by streptokinase leading to degradation of fibrin is effective in the prevention of adhesion formation. We have investigated the effects of pentoxifylline and streptokinase alone and/or coadministration on postoperative intra-abdominal adhesion formation in adult female NMRI mice. Drugs were administered from the day of surgery until 10 days after surgery. At relaparotomy 11 days after surgery, the abdomen was opened, and the adhesions were graded in a blinded fashion utilizing the classification system described. Oral gavage administration of lower doses of pentoxifylline (3.125, 6.25, and 12.5 mg/kg) had no significant effect on postsurgical adhesion formation, while the higher doses of pentoxifylline (25 and 50 mg/kg) significantly decreased postsurgical adhesion formation. Moreover, intraperitoneal injection of lower doses of streptokinase (9.375, 18.75, and 37.5 unit/kg, i.p.) had no significant effect on postsurgical adhesion formation, while the higher doses of streptokinase (75 and 150 unit/kg) significantly decreased postsurgical adhesion formation. In other series of experiments, coadministration of lower doses of pentoxifylline and streptokinase doses, which were ineffective when given alone, significantly decreased postsurgical intra-abdominal adhesion formation compared with streptokinase control group. The results suggest that pentoxifylline may interfere with streptokinase in the reduction of postoperative intra-abdominal adhesion formation by enhancing local fibrinolytic activity.

Rolipram attenuates bile duct ligation-induced liver injury in rats: a potential pathogenic role of PDE4

Anti-inflammatory and antifibrotic effects of the broad spectrum phosphodiesterase (PDE) inhibitor pentoxifylline have suggested an important role for cyclic nucleotides in the pathogenesis of hepatic fibrosis; however, studies examining the role of specific PDEs are lacking. Endotoxemia and Toll-like receptor 4 (TLR4)-mediated inflammatory and profibrotic signaling play a major role in the development of hepatic fibrosis. Because cAMP-specific PDE4 critically regulates lipopolysaccharide (LPS)-TLR4-induced inflammatory cytokine expression, its pathogenic role in bile duct ligation-induced hepatic injury and fibrogenesis in Sprague-Dawley rats was examined. Initiation of cholestatic liver injury and fibrosis was accompanied by a significant induction of PDE4A, B, and D expression and activity. Treatment with the PDE4-specific inhibitor rolipram significantly decreased liver PDE4 activity, hepatic inflammatory and profibrotic cytokine expression, injury, and fibrosis. At the cellular level, in relevance to endotoxemia and inflammatory cytokine production, PDE4B was observed to play a major regulatory role in the LPS-inducible tumor necrosis factor (TNF) production by isolated Kupffer cells. Moreover, PDE4 expression was also involved in the in vitro activation and transdifferentiation of isolated hepatic stellate cells (HSCs). Particularly, PDE4A, B, and D upregulation preceded induction of the HSC activation marker α-smooth muscle actin (α-SMA). In vitro treatment of HSCs with rolipram effectively attenuated α-SMA, collagen expression, and accompanying morphologic changes. Overall, these data strongly suggest that upregulation of PDE4 expression during cholestatic liver injury plays a potential pathogenic role in the development of inflammation, injury, and fibrosis.

Pentoxifylline and propentofylline prevent proliferation and activation of the mammalian target of rapamycin and mitogen activated protein kinase in cultured spinal astrocytes

Astrocyte activation is an important feature in many disorders of the central nervous system, including chronic pain conditions. Activation of astrocytes is characterized by a change in morphology, including hypertrophy and increased size of processes, proliferation, and an increased production of proinflammatory mediators. The xanthine derivatives pentoxifylline and propentofylline are commonly used experimentally as glial inhibitors. These compounds are generally believed to attenuate glial activity by raising cyclic AMP (cAMP) levels and inhibiting glial tumor necrosis factor (TNF) production. In the present study, we show that these substances inhibit TNF and serum-induced astrocyte proliferation and signaling through the mammalian target of rapamycin (mTOR) pathway, demonstrated by decreased levels of phosphorylated S6 kinase (S6K), commonly used as a marker of mTOR complex (mTORC) activation. Furthermore, we show that pentoxifylline and propentofylline also inhibit JNK and p38, but not ERK, activation induced by TNF. In addition, the JNK antagonist SP600125, but not the p38 inhibitor SB203580, prevents TNF-induced activation of S6 kinase, suggesting that pentoxifylline and propentofylline may regulate mTORC activity in spinal astrocytes partially through inhibition of the JNK pathway. Our results suggest that pentoxifylline and propentofylline inhibit astrocyte activity in a broad fashion by attenuating flux through specific pathways.

Systematic review on the treatment of pentoxifylline in patients with non-alcoholic fatty liver disease

Background

As an anti-TNF agent that targets inflammatory process directly, Pentoxifylline has been investigated for treatment of NASH in individual studies and pilot trials for years. We summarized the available information and generating hypotheses for future research.

Data Sources

Google, Cochrane, MEDLINE, and EMBASE and the Chinese Biomedical data bases for studies restricted to pentoxifylline treatment in humans with NAFLD in all languages until June 2010. Six studies (2 randomized, double-blind, placebo-controlled trials; 4 prospective cohort studies) extracted from 11604 references.

Results

Pentoxifylline-treated patients showed a significant decrease AST (n = 37, P = 0.01) and ALT (n = 50, P = 0.03), but no significant effect on IL-6 (n = 36, P = 0.33) and TNF-α (n = 68, P = 0.26) compared with Placebo or UDCA-controlled groups. Improvement in one or more histological variables was reported in two trails, only 1 study showed a reduction in of one or two points in fibrosis stage.

Limitations

The trails did not consistently report all of the outcomes of interest. Sample sizes (117 patients totally) were small and only 2 out of 6 studies had a randomized, controlled design.

Conclusion

Pentoxifylline reduce AST and ALT levels and may improve liver histological scores in patients with NALFD/NASH, but did not appear to affect cytokines. Large, prospective, and well-designed randomized, controlled studies are needed to address this issue. Novel therapeutic targets for activation of inflammatory signaling pathways by fat also merit investigation.

Combined itraconazole-pentoxifylline treatment promptly reduces lung fibrosis induced by chronic pulmonary paracoccidioidomycosis in mice

Fibrosis is a severe and progressive sequel of many pulmonary diseases, has no effective therapy at present and, consequently, represents a serious health problem. In Latin America, chronic pulmonary paracoccidioidomycosis (PCM) is one of the most important, prevalent and systemic fungal diseases that allows the development of lung fibrosis, with the additional disadvantage that this sequel may appear even after an apparently successful course of antifungal therapy. In this study, was propose the pentoxifylline as complementary treatment in the pulmonary PCM due to its immunomodulatory and anti-fibrotic properties demonstrated in vitro and in vivo in liver, skin and lung. Our objective was to investigate the possible beneficial effects that a combined antifungal (Itraconazole) and immunomodulatory (Pentoxifylline) therapy would have in the development of fibrosis in a model of experimental chronic pulmonary PCM in an attempt to simulate the naturally occurring events in human patients. Two different times post-infection (PI) were chosen for starting therapy, an "early time" (4 weeks PI) when fibrosis was still absent and a "late time" (8 weeks PI) when the fibrotic process had started. Infected mice received the treatments via gavage and were sacrificed during or upon termination of treatment; their lungs were then removed and processed for immunological and histopathologic studies in order to assess severity of fibrosis. When pulmonary paracoccidioidomycosis had evolved and reached an advanced stage of disease before treatment began (as normally occurs in many human patients when first diagnosed), the combined therapy (itraconazole plus pentoxifylline) resulted in a significantly more rapid reduction of granulomatous inflammation and pulmonary fibrosis, when compared with the results of classical antifungal therapy using itraconazole alone.

Modification of sleep architecture in an animal model of experimental cirrhosis

AIM: To analyze the polygraphic sleep patterns during cirrhosis progression in a rat model by repeated CCl₄ administration.

METHODS: Male Wistar rats received three weekly injections of CCl₄ for 11 wk, and were analyzed before and during the induction of cirrhosis. Rats were implanted with electrodes to record their sleep patterns. Polygraph recordings were made weekly over 11 wk for 8 h, during the light period. After a basal recording, rats received three weekly injections of CCl₄. Histological confirmation of cirrhosis was performed after 11 wk.

RESULTS: The results showed a progressive decrease in total wake time that reached statistical significance from the second week of treatment. In addition, there was an increase in total time of slow wave sleep (SWS) II and rapid eye movement sleep (REM sleep) in most of the 11 wk. SWS I showed no significant variations. During the final weeks, a significant increase in REM sleep frequency was also observed. Histological analyses of the livers showed unequivocal signs of cirrhosis.

CONCLUSION: These data suggest that hepatic failure produced by CCl₄ administration is capable of modifying the sleep pattern even after only a few doses.

Targeting liver myofibroblasts: a novel approach in anti-fibrogenic therapy

Chronic liver disease results in a liver-scarring response termed fibrosis. Excessive scarring leads to cirrhosis, which is associated with high morbidity and mortality. The only treatment for liver cirrhosis is liver transplantation; therefore, much attention has been directed toward therapies that will slow or reverse fibrosis. Although anti-fibrogenic therapies have been shown to be effective in experimental animal models, licensed therapies have yet to emerge. A potential problem for any anti-fibrogenic therapy in the liver is the existence of the body’s major drug metabolising cell (the hepatocyte) adjacent to the primary fibrosis-causing cell, the myofibroblast. This article reviews the development of a human recombinant single-chain antibody (scAb) that binds to the surface of myofibroblasts. This antibody binds specifically to myofibroblasts in fibrotic mouse livers. When conjugated with a compound that stimulates myofibroblast apoptosis, the antibody directs the specific apoptosis of myofibroblasts with greater specificity and efficacy than the free compound. The antibody also reduces the adverse effect of liver macrophage apoptosis and—in contrast to the free compound—reversed fibrosis in the sustained injury model used. These data suggest that specifically stimulating the apoptosis of liver myofibroblasts using a targeting antibody has potential in the treatment of liver fibrosis.

Prevention and treatment of functional and structural radiation injury in the rat heart by pentoxifylline and alpha-tocopherol

PURPOSE

Radiation-induced heart disease (RIHD) is a severe side effect of thoracic radiotherapy. This study examined the effects of pentoxifylline (PTX) and alpha-tocopherol on cardiac injury in a rat model of RIHD.

METHODS AND MATERIALS

Male Sprague-Dawley rats received fractionated local heart irradiation with a daily dose of 9 Gy for 5 days and were observed for 6 months after irradiation. Rats were treated with a combination of PTX, 100 mg/kg/day, and alpha-tocopherol (20 IU/kg/day) and received these compounds either from 1 week before until 6 months after irradiation or starting 3 months after irradiation, a time point at which histopathologic changes become apparent in our model of RIHD.

RESULTS

Radiation-induced increases in left ventricular diastolic pressure (in mm Hg: 35 +/- 6 after sham-irradiation, 82 +/- 11 after irradiation) were significantly reduced by PTX and alpha-tocopherol (early treatment: 48 +/- 7; late treatment: 53 +/- 6). PTX and alpha-tocopherol significantly reduced deposition of collagen types I (radiation only: 3.5 +/- 0.2 mum(2) per 100 mum(2); early treatment: 2.7 +/- 0.8; late treatment: 2.2 +/- 0.2) and III (radiation only: 13.9 +/- 0.8; early treatment: 11.0 +/- 1.2; late treatment: 10.6 +/- 0.8). On the other hand, radiation-induced alterations in heart/body weight ratios, myocardial degeneration, left ventricular mast cell densities, and most echocardiographic parameters were not significantly altered by PTX and alpha-tocopherol.

CONCLUSIONS

Treatment with PTX and alpha-tocopherol may have beneficial effects on radiation-induced myocardial fibrosis and left ventricular function, both when started before irradiation and when started later during the process of RIHD.

Pentoxifylline downregulates alpha (I) collagen expression by the inhibition of Ikappabalpha degradation in liver stellate cells

Overproduction of collagen (I) by activated hepatic stellate cells is a critical step in the development of liver fibrosis. It has been established that these cells express interleukin (IL)-6 and respond to this cytokine with an increase in alpha(I) collagen. Pentoxifylline, a methylxanthine derivate, has been reported to have antifibrotic properties, but the mechanism responsible for this effect is unknown. The aim of this study was to determine the effect of pentoxifylline on acetaldehyde-induced collagen production in a rat hepatic stellate cell line (CFSC-2G cells). Cells were treated with 100 microM acetaldehyde and 200 microM pentoxifyline for 3 h. IL-6 and alpha(I) collagen messenger RNA (mRNA) were determined by reverse transcriptase polymerase chain reaction (RT-PCR) assay. NFkappaB activation was determined by electrophoretic mobility shift assay. To corroborate NFkappaB participation in pentoxifylline effect, cells were pretreated with 10 microM TPCK, a NFkappaB inhibitor. IkappaBalpha was determined by Western blot. IL-6 expression decreased significantly in acetaldehyde-pentoxifylline-treated cells. Acetaldehyde-treated cells pretreated with an anti-IL-6 monoclonal antibody did not show any increase in alpha (I) collagen expression. Acetaldehyde-treated cells increased 1.48 times NFkappaB activation, whereas acetaldehyde-pentoxifylline-treated cells decreased NFkappaB activation to control values. TPCK pretreated acetaldehyde cells did not present NFkappaB activation. To corroborate NFkappaB participation in pentoxifylline effect, IkappaBalpha was determined. IkappaBalpha protein level decreased 50% in acetaldehyde-treated cells, while acetaldehyde-pentoxifylline-treated cells showed IkappaBalpha control cells value. The data suggest that acetaldehyde induced alpha(I) collagen and IL-6 expression via NFkappaB activation. Pentoxifylline prevents acetaldehyde-induced alpha(I) collagen and IL-6 expression by a mechanism dependent on IkappaBalpha degradation, which in turn blocks NFkappaB activation.

Liver fibrosis in vitro: Cell culture models and precision-cut liver slices

Chronic liver injury of various etiologies can cause liver fibrosis, which is characterized by the progressive accumulation of connective tissue in the liver. As no effective treatment for liver fibrosis is available yet, extensive research is ongoing to further study the mechanisms underlying the development of disease- or toxicity-induced liver fibrosis and to identify potential pro- or anti-fibrotic properties of compounds. This review gives an overview of the in vitro methods that are currently available for this purpose. The first focus is on cell culture models, since the majority of in vitro research uses these systems. Both primary cells and cell lines as well as the use of different culture matrices and co-culture models are discussed. Second, the use of precision-cut liver slices, which recently came into attention as in vitro model for the study of fibrosis, is discussed. The overview clearly shows that continuous optimization and adaptation have extended the potential of in vitro models for liver fibrosis during the past years. By combining the use of the different cell and tissue culture models, the mechanisms underlying multicellular fibrosis development can be studied in vitro and potential pro- or anti-fibrotic properties of compounds can be identified both on single liver cell types and in human liver tissue.

Pharmacodynamics of pentoxifylline and/or praziquantel in murine schistosomiasis mansoni

Pentoxifylline (PTX) was proved to exert both anti-inflammatory and anti-fibrotic effects, and was used therapeutically in this experimental model to investigate its role alone or with praziquantel (PZQ) in Schistosoma mansoni-infected mice, and to explore its impact on the tissue expression of transforming growth factor-beta1 (TGF-beta1). S. mansoni-infected mice were divided into seven groups: Control untreated (I), treated with curative dose of PZQ, 500 mg/kg/day for 2 consecutive days (II), or subcurative dose, 100 mg/kg/day for 2 consecutive days (III), treated with PTX (10 mg/kg/day for 5 days/wk) alone for 4 weeks (IV) or in addition to subcurative dose of PZQ (V), and treated with PTX alone for 8 weeks (VI) or in addition to subcurative dose of PZQ (VII). All animals were killed 10 weeks post infection. Parasitological assessment of worm burden, tissue egg load and oogram pattern was carried out. The degree of granulomatous fibrosis and eosinophilic cell population was quantified in Sirius-red-stained sections and tissue transforming growth factor beta-1 expression was estimated immunohistochemically. Serum ALAT and GGT, as well as hepatic content of reduced GSH, were measured. The results revealed the highest percent of worm reduction and dead ova in groups (II) and (VII) accompanied by significant diminution in granulomatous parameters, collagen content and TGF-beta1 tissue expression. Moreover, treatments with PTX and/or PZQ ameliorated the liver functions. In conclusion, prolonged treatment with PTX has a potent anti-fibrogenic role especially when used in the early stages of infection, with limited toxic effects on schistosome worms and eggs. Thus, PTX can be used as an adjuvant therapeutic tool with anti-helminthic drugs in the treatment of human schistosomiasis.

Precision-cut fibrotic rat liver slices as a new model to test the effects of anti-fibrotic drugs in vitro

BACKGROUND/AIMS

Current cell culture models contributed significantly to the study of liver fibrosis and the testing of anti-fibrotic drugs but mimic the complex in vivo milieu poorly. Therefore, we evaluated fibrotic rat liver slices as a new, more physiologic in vitro model to test anti-fibrotic compounds.

METHODS

Precision-cut slices (8 mm diameter, 250 microm thickness) were prepared from fibrotic rat livers three weeks after bile-duct ligation and incubated for 0-48 h, during which viability and progression of the fibrotic process was evaluated. In addition, the effects of pentoxifylline, gleevec, and dexamethasone on mRNA expression of markers for fibrosis were determined.

RESULTS

Fibrotic liver slices remained viable during 48 h of incubation, with increasing alphaSMA and pro-collagen 1a1 mRNA expression, and alphaSMA and collagen protein content after prolonged incubation. Addition of pentoxifylline, gleevec, or dexamethasone during incubation dose-dependently inhibited pro-collagen-1a1 and alphaSMA mRNA expression after 24h of incubation without influencing slice viability.

CONCLUSIONS

Fibrotic liver slices are a promising tool to test anti-fibrotic drugs in vitro in a multicellular, fibrotic milieu, which cannot be achieved in vitro using other models. Importantly, this method may provide the opportunity to study anti-fibrotic compounds not only in animal but also in fibrotic human liver tissue.

Effect of pentoxifylline on levels of pro-inflammatory cytokines during chronic hepatitis C

The cellular and humoral natural immune response induced by hepatitis C virus (HCV) is commonly unable to eradicate the virus. HCV is a highly mutable, hepatotropic RNA virus that causes acute and chronic hepatitis, an infection that involves the production of various cytokines. The aim of the study is to analyse the expression of pro-inflammatory cytokines IL-1beta, TNF-alpha, IFN-gamma and the chemokine CXCL8 (IL-8) in liver tissue and their expression and secretion in PBMC of patients with chronic hepatitis C (CHC), in response to pentoxyfilline (PTX). We studied six CHC patients, naive to treatment. Patients received PTX 400 mg twice a day/8 weeks. Pentoxyfilline resulted in decreased expression of mRNA of liver IL-1beta, TNF-alpha and IFN-gamma: 144.2 versus 83.5 molecules of IL-1beta (P < 0.05), TNF-alpha 194.3 versus 17.6 molecules (P = 0.03) and IFN-gamma 26.1 versus 0.5 molecules (P = 0.04). Following PTX, PBMC exhibited a decrease in IFN-gamma mRNA 12.2 versus 1.5 molecules (P = 0.028) and CXCL8 4.2 versus 2.5 molecules (P = 0.027). In PBMC, only the secretion of TNF-alpha was decreased 1109 versus 933.5 pg/ml, P = 0.046. Production of cytokines both locally (within the liver) and systemically (PBMC) may serve as biomarkers of the infection with hepatitis C. PTX inhibits the expression of several pro-inflammatory cytokines in the liver. These results indicate that it is worth exploring PTX in hepatitis in future clinical trials in nonresponders to antiviral treatment.

Comparison of the effects of melatonin and pentoxifylline on carbon tetrachloride-induced liver toxicity in mice

The purpose of the study was to determine whether along and in combination melatonin (MLT) and pentoxifylline (PTX) exerted beneficial effects on histopathological changes and changes in oxidant and antioxidant systems in liver caused by CCl4-induced liver toxicity in mice. Mice were randomly divided into six groups: control, olive oil, toxicity, MLT, PTX, PTX+MLT. MLT 10 mg/kg/day, PTX 50 mg/kg/day, and the same individual doses in MLT+PTX combination were given intraperitoneally to mice for 7 day. CCl4 0.8 mg/kg/day was administered on the 4th, 5th, and 6th days of therapy in all groups except the control and olive oil groups. In the toxicity group, increased concentrations of malondialdehyde (MDA) and lipid hydroperoxides (LOOH) and decreased glutathione peroxidase (GSH-Px) and catalase (CAT) activities were found compared to the control and olive oil groups (p < 0.05). Compared to the toxicity group, both the PTX group and the PTX+MLT group had decreased MDA and LOOH levels, whereas MLT reduced only LOOH levels (p < 0.01). MLT, PTX and MLT+PTX increased the GSH-Px and CAT activities compared to the toxicity group (p < 0.05). MLT increased CAT activity compared to PTX and MLT+PTX (p < 0.05). Superoxide dismutase enzyme activity did not change in any group (p < 0.05). Histopathologically, ballooning, degeneration, apoptosis, and bridging necrosis were seen in the toxicity group. MLT, PTX and MLT+PTX decreased the apoptosis and bridging necrosis (p < 0.01), and PTX and MLT+PTX decreased balloon degeneration compared to the toxicity group (p < 0.01). These results indicate that administration of PTX and MLT alone and in combination before onset of liver toxicity might prevent the oxidative damage by reducing oxidative stress and increasing antioxidant enzyme levels.

Selective targeting of pentoxifylline to hepatic stellate cells using a novel platinum-based linker technology

Targeting of antifibrotic drugs to hepatic stellate cells (HSC) is a promising strategy to block fibrotic processes leading to liver cirrhosis. For this purpose, we utilized the neo-glycoprotein mannose-6-phosphate-albumin (M6PHSA) that accumulates efficiently in HSC during liver fibrosis. Pentoxifylline (PTX), an antifibrotic compound that inhibits HSC proliferation and activation in vitro, was conjugated to M6PHSA. We employed a new type of platinum-based linker, which conjugates PTX via coordination chemistry rather than via covalent linkage. When incubated in plasma or in the presence of thiol compounds, free PTX was released from PTX-M6PHSA at a sustained slow rate. PTX-M6PHSA displayed pharmacological activity in cultured HSC as evidenced by changes in cell morphology and reduction of collagen I production. PTX-M6PHSA and platinum coupled PTX did not induce platinum-related toxicity (Alamar Blue viability assay) or apoptosis (caspase activation and TUNEL staining). In vivo distribution studies in fibrotic rats demonstrated specific accumulation of the conjugate in nonparenchymal cells in the fibrotic liver. In conclusion, we have developed PTX-M6PHSA employing a novel type of platinum linker, which allows sustained delivery of the drug to HSC in the fibrotic liver.

Pentoxifylline attenuates steatohepatitis induced by the methionine choline deficient diet

BACKGROUND/AIMS

Feeding mice a methionine choline deficient (MCD) diet serves as a nutritional model of non-alcoholic steatohepatitis (NASH). NASH and alcohol-induced steatohepatitis are histologically similar, suggesting a similar pathogenesis. Pentoxifylline (PTX) attenuates TNF-alpha production, acts as an antioxidant and decreases mortality in alcoholic steatohepatitis. The aim of our study is to determine if PTX attenuates MCD diet induced steatohepatitis and determine the mechanism of this effect.

METHODS

Mice were placed on an MCD or control diet for 2 weeks and were treated with or without PTX. Serum ALT, liver histology, and inflammatory mechanisms were evaluated.

RESULTS

PTX attenuates MCD diet induced steatohepatitis, decreasing both serum ALT levels and hepatic inflammation. Serum ALT levels were reduced approximately 50% in the MCD+PTX group compared to the MCD group. Hepatic glutathione levels were significantly higher in the MCD+PTX group compared to the MCD group. There was also a reduction in TNF-alpha mRNA in female mice treated with PTX. MCD+PTX mice had increased hepatic triglyceride content compared to the MCD mice, but less histologic evidence of inflammation despite the increased steatosis. Serum lipid and bile salt levels also were similar in PTX and vehicle control treated mice.

CONCLUSIONS

PTX decreases serum ALT levels and hepatic inflammation in the MCD model of steatohepatitis, likely via increasing glutathione levels or reducing TNF-alpha expression.

Effect of pentoxifylline on arachidonic acid metabolism, neutral lipid synthesis and accumulation during induction of the lipocyte phenotype by retinol in murine hepatic stellate cell

In liver fibrosis, the quiescent hepatic stellate cells (HSC) are activated to proliferate and express the activated myofibroblast phenotype, losing fat droplets and the stored vitamin A, and depositing more extracellular matrix. Therapeutic strategies for liver fibrosis are focused on HSC. Pentoxifylline (PTF), an analog of the methylxanthine, prevents the biochemical and histological changes associated with animal liver fibrosis. The aim of the present study was to investigate the phenotypic change of myofibroblasts into quiescent lipocytes by PTF and/or retinol, using a permanent cell line GRX that represents murine HSC. We studied the action of both drugs on the synthesis of neutral lipids, activity of phospholipase A2 (PLA2), release of arachidonic acid (AA) and prostaglandins synthesis. Accumulation and synthesis of neutral lipids was dependent upon association of retinol with PTF. PTF (0.5 mg/mL) alone did not induce lipid accumulation and synthesis, but in cells induced by physiologic concentration of retinol (1-2.5 microM), it increased the quantity of stored lipids. Retinol and PTF (5 microM and 0.1 mg/mL, respectively) had a synergistic effect on neutral lipid synthesis and accumulation. In higher PTF concentrations (0.5 and 0.7 mg/ml), the synthesis was stimulated but accumulation decreased. Membrane-associated PLA2 activity decreased after PTF treatment, which increased the AA release 8 fold, and significantly increased the production of PGE2, but not of PGF2. However, when in presence of retinol, we observed a slightly higher increase in PGE2 and PGF2a production. In conclusion, PTF treatment generated an excess of free AA. We propose that retinol counteracts the action of PTF on the AA release and PGs production, even though both drugs stimulated the lipocyte induction in the HSC.

Influence of serum collected from rat perfused with compound Biejiaruangan drug on hepatic stellate cells

AIM: To observe the effect of compound Biejiaruangan decoction (CBJRGC) (composite prescription of Carapax trionycis for softening the liver) on proliferation, activation, excretion of collagen and cytokine of hepatic stellate cells (HSCs) and to find the mechanism of prevention and treatment of hepatic fibrosis by CBJRGC.

METHODS: Using MTT, immunohistochemistry and image analysis technology, the related indexes for proliferation, activation, excretion of collagen and cytokine of hepatic stellate cells were detected in 24 h, 48 h, and 72 h after adminstration of different dosages of CBJRGC.

RESULTS: Statistical analysis showed that serum collected from rat perfused with CBJRGC could restrain the proliferation of HSC in 48 h and 72 h especially in high and medium dosage groups, markedly decrease the expression of desmin, synapsin and platelet derived growth factor (PDGF) in HSC in 24 h, 48 h and 72 h, as well as the expression of α-SMA, collagen III, TIMP and TGFβ1 in 48 h and 72 h, decrease the excretion of collagen I in 72 h. CBJRGC serum had no significant effect on collagens I, III and TIMP in 24 h.

CONCLUSION: CBJRGC serum has a good curative effect on hepatic fibrosis. Its main mechanism may be related to the following factors. The drug serum can restrain the proliferation and activation of HSC, decrease the number of activated HSC and the total number of HSC, the excretion of collagens I, III, enhance the degradation of collagen and restore the balance of synthesis and degradation of collagen, inhibit the expression of transforming growth factor β1 (TGFβ1) and platelet derived growth factor (PDGF) in HSC, block and delay the process of hepatic fibrosis. Synapsin is a new marker of activation of HSC, which provides a theoretical and testing basis for neural regulation in the developing process of hepatic fibrosis.

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Role of tissue stroma in cancer cell invasion

Maintenance of epithelial tissues needs the stroma. When the epithelium changes, the stroma inevitably follows. In cancer, changes in the stroma drive invasion and metastasis, the hallmarks of malignancy. Stromal changes at the invasion front include the appearance of myofibroblasts, cells sharing characteristics with fibroblasts and smooth muscle cells. The main precursors of myofibroblasts are fibroblasts. The transdifferentiation of fibroblasts into myofibroblasts is modulated by cancer cell-derived cytokines, such as transforming growth factor-beta (TGF-beta). TGF-beta causes cancer progression through paracrine and autocrine effects. Paracrine effects of TGF-beta implicate stimulation of angiogenesis, escape from immunosurveillance and recruitment of myofibroblasts. Autocrine effects of TGF-beta in cancer cells with a functional TGF-beta receptor complex may be caused by a convergence between TGF-beta signalling and beta-catenin or activating Ras mutations. Experimental and clinical observations indicate that myofibroblasts produce pro-invasive signals. Such signals may also be implicated in cancer pain. N-Cadherin and its soluble form act as invasion-promoters. N-Cadherin is expressed in invasive cancer cells and in host cells such as myofibroblasts, neurons, smooth muscle cells, and endothelial cells. N-Cadherin-dependent heterotypic contacts may promote matrix invasion, perineural invasion, muscular invasion, and transendothelial migration; the extracellular, the juxtamembrane and the beta-catenin binding domain of N-cadherin are implicated in positive invasion signalling pathways. A better understanding of stromal contributions to cancer progression will likely increase our awareness of the importance of the combinatorial signals that support and promote growth, dedifferentiation, invasion, and ectopic survival and eventually result in the identification of new therapeutics targeting the stroma.

Effects of pentoxifylline on the hepatic content of TGF-β1 and collagen in Schistosomiasis japonica mice with liver fibrosis

AIM: To study the effects of pentoxifylline (PTX) on the content of hepatic TGF-β1, type I and type III collagen in schistosomiasis japonica mice with liver fibrosis and its mechanism of anti-fibrosis.

METHODS: Forty mice with schistosomiasis were divided into four groups: one group as control without any treatment, other three were treated with Praziquantel 500 mg/(kg·d)for 2 d, high dose PTX 360 mg/(kg·d) for 8 wk, and low dose PTX 180 mg/(kg·d) for 8 wk respectively. Immunohistochemical technique and multimedia color pathographic analysis system were applied to observe the content change of hepatic TGF-β1, type I and type III collagen in schistosomiasis japonica mice with liver fibrosis before and after PTX treatment.

RESULTS: Effects of PTX on the content change of hepatic TGF-β1, type I and type III collagen in schistosomiasis japonica mice with liver fibrosis were related to the dosage of PTX, high dose PTX treated group could significantly reduce the content of TGF-β1 (0.709 ± 0.111), type I (0.644 ± 0.108) and type III (0.654 ± 0.152) collagen compared with those of control group (0.883 ± 0.140, 0.771 ± 0.156, 0.822 ± 0.129) with statistical significance (P < 0.05). Low dose PTX could also reduce the hepatic content of TGF-β1 (0.752 ± 0.152), type I (0.733 ± 0.117) and type III (0.788 ± 0.147) collagen, but without statistical significance (P > 0.05). Both high dose and low dose PTX groups have significant differences on the content of TGF-β1, type I and type III collagen (P < 0.05, P < 0.05, P < 0.01, respectively).

CONCLUSION: High dose of PTX treatment could reduce the content of hepatic TGF-β1, type I and type III collagen significantly in schistosomiasis japonica mice with liver fibrosis, and thus plays its role of antifibrosis.

Role of myofibroblasts at the invasion front

Tumor progression occurs within a microecosystem, where cancer cells and myofibroblasts exchange proteinases and cytokines that promote growth directly through stimulation of proliferation and survival, as well as invasion through local proteolysis of the extracellular matrix and stimulation of motility. Myofibroblasts maintain the capacity of fibroblasts to induce differentiation. Fibroblasts are the main source of tumor-associated myofibroblasts. The transition to myofibroblasts also occurs in noncancerous situations. This transition is modulated by mechanical stress and cytokines, amongst which transforming growth factor-beta. The cross-talk between cancer cells and myofibroblasts illustrates the microecosystem of tumor invasion. In order to consider myofibroblasts as a possibly new target for cancer therapy, further characterization of the molecular cross-talk between myofibroblasts and cancer cells is required.

Myofibroblast: a prognostic marker and target cell in progressive renal disease

Myofibroblasts play an important role in many tissue injuries, and particularly in renal disease. The myofibroblast differentiation is an early event in the development of fibrosis. Myofibroblast-like cells express smooth muscle (SM) cytoskeletal markers (alpha-SM actin in particular) and participate actively in the production of extracellular matrix. Identification of early risk factors, particularly histological criteria, could be useful to identify patients at risk of progressive renal failure and needing a treatment. The evaluation of myofibroblast differentiation in renal tissue may reflect the intensity of tissue injury, predict long term outcome of chronic renal disease and help physicians to select therapeutic choices. More than a disease activity indicator. myofibroblasts appear to be a pivotal target for future therapies in progressive renal disease.

Effects of pentoxifylline, pentifylline and gamma-interferon on proliferation, differentiation, and matrix synthesis of human renal fibroblasts

BACKGROUND

Kidneys that progress to end-stage renal failure are almost invariably characterized by the presence of tubulointerstitial fibrosis. Therapeutic interventions to halt the progressive deterioration of renal function are still limited. Pentoxifylline, pentifylline, and gamma-interferon have shown a potential benefit in the treatment of fibrotic processes in the skin and lung. Thus, the aim of the present study was the analysis of potential anti-fibrotic effects of these substances on human kidney fibroblasts in vitro.

METHODS

Primary renal fibroblasts were established from human kidney biopsies and were studied in addition to two renal fibroblast cell lines. Cells were first growth arrested by withdrawal of fetal calf serum (FCS) and subsequently stimulated with 10% FCS in the presence of different concentrations of pentoxifylline (PTX), pentifylline (PTF), or gamma-interferon (IFN-gamma). Fibroblast proliferation was determined by bromodeoxyuridine incorporation and cell counts. Northern and western blot hybridizations for basic fibroblast growth factor (FGF)-2 and transforming growth factor (TGF)-beta1 were performed to analyse inhibitory effects. The effects of all three substances on matrix synthesis were evaluated by immunoblot analyses and ELISA for collagen type I and fibronectin after stimulation with TGF-beta1. Finally, differentiation into myofibroblasts was examined by double immunofluorescence staining for alpha-smooth-muscle actin and Hoechst dye H33258.

RESULTS

PTX and PTF resulted in a dose- and time-dependent inhibition of proliferation in all fibroblast lines (maximum 78.9+/-6.2% at 500 microg/ml PTX). Conversely, IFN-gamma had only modest effects on fibroblast proliferation, resulting in a maximum of 36.0+/-6.1% inhibition at 500 U/ml. Northern blot hybridizations determined that FGF-2 mRNA levels in fibroblasts were decreased up to 73.7 and 91.5% by PTX (1000 microg/ml) and PTF (100 microg/ml), whereas IFN-gamma led to a reduction of 46.2% at 1000 U/ml, indicating that the inhibitory effects of all three substances may be mediated through inhibition of FGF-2 synthesis. These findings were corroborated by immunoblot analyses where again PTX and PTF had the strongest inhibitory effects. No change in TGF-beta1 mRNA levels was noted. Synthesis of cellular and secreted collagen type I was robustly inhibited by PTX and PTF, whereas IFN-gamma exerted the strongest inhibitory effect on fibronectin synthesis and secretion. In addition, IFN-gamma down-regulated the expression of alpha-smooth-muscle actin up to 73.3% (at 1000 U/ml) whereas PTX and PTF resulted in a down-regulation of up to 49.7+/-1.8 and 80.0+/-4.4% (at 1000 and 100 microg/ml) respectively. PTF was in all experiments about 10 times more potent than equimolar concentrations of PTX.

CONCLUSIONS

PTX and PTF exerted robust inhibitory effects on fibroblast proliferation, extracellular matrix synthesis, and myofibroblastic differentiation. Conversely, IFN-gamma caused strong inhibition of fibronectin synthesis and alpha-smooth-muscle cell actin expression but had only weak inhibitory influences on fibroblast proliferation and collagen type I synthesis. Inhibitory effects of all three substances on proliferation may be mediated through inhibition of FGF-2 synthesis.

The cell and molecular biology of hepatic fibrogenesis. Clinical and therapeutic implications

Much has been learned in the past 2 decades about the cellular and molecular mechanisms underlying hepatic fibrogenesis and about potential therapeutic approaches in patients with liver disease. The central event in fibrogenesis seems to be the activation of hepatic stellate cells. Stellate cell activation is characterized by several important features, including enhanced matrix synthesis and a prominent contractile phenotype, processes that probably contribute to the physical distortion and dysfunction of the liver in advanced disease. It is important to emphasize that the factors controlling activation are multifactorial and complex. The extracellular matrix is a dynamic, active constituent of the fibrogenic response and undergoes active remodeling, including synthesis and degradation. Effective therapy for hepatic fibrogenesis will probably also be multifactorial, based on the basic mechanisms underlying the fibrogenic process. The most effective therapies will probably be directed at the stellate cell. Approaches that address matrix remodeling (i.e., by enhancing matrix degradation or by inhibiting factors that prevent matrix breakdown) may be effective.

Hepatitis C: an update on the silent epidemic

Hepatitis C virus (HCV) currently infects an estimated 2-3 million people in the United States and 175 million people globally. Over 80% of infected patients go on to develop chronic disease. Most patients remain asymptomatic despite silent, insidious progression of the disease. The sequelae of HCV-induced chronic liver disease accounts for 8,000-10,000 deaths annually in the United States and is currently the leading indication for liver transplantation. The cost of this epidemic to the United States was estimated in 1991 at $600 million in terms of medical expenses (excluding costs related to liver transplantation) and work lost. Over the last decade, since the viral genome of HCV was first sequenced in 1989, there has been a great increase in understanding of this infection. This review summarizes current knowledge about the hepatitis C epidemic with particular reference to epidemiology of infection, viral characteristics, risk factors for disease, diagnostic testing, clinical manifestations, and current, as well as potential, therapeutic options.