Pentoxifylline blocks hepatic stellate cell activation independently of phosphodiesterase inhibitory activity

Lipopolysaccharide Reverses Hepatic Stellate Cell Activation Through Modulation of cMyb, Small Mothers Against Decapentaplegic, and CCAAT/Enhancer-Binding Protein C/EBP Transcription Factors

BACKGROUND AND AIMS

During liver injury, quiescent hepatic stellate cells (qHSCs) transdifferentiate into proliferative and fibrogenic activated myofibroblastic phenotype (activated hepatic stellate cell; aHSCs) expressing smooth muscle α-actin (αSMA) and platelet-derived growth factor beta receptor (PDGFβR). Their interactions with gut-derived bacterial lipopolysaccharide (LPS) are implicated in hepatic fibrogenesis. However, LPS can also attenuate fibrogenic characteristics of aHSCs.

APPROACH AND RESULTS

We examined molecular mechanisms of antifibrogenic effects of LPS on aHSCs in vitro and in vivo. Culture-activated rat HSCs were exposed to 0-100 ng/mL of LPS or its active component, diphosphoryl-lipid A (DPLA), and parameters of fibrosis and inflammatory cytokines/chemokines were determined by qRT-PCR, western, and immunohistochemical analyses. In vivo, HSCs were activated by repeated CCl4 administration to rats every 3 days for 3 or 8 weeks, then challenged with LPS (5 mg/kg; IP). HSCs were isolated 24 hours later, and fibrogenic/inflammatory parameters were analyzed. LPS induced phenotypic changes in aHSCs (rounding, size reduction) and loss of proliferation. LPS down-regulated expression of αSMA, PDGFβR, transforming growth factor beta receptor 1 (TGFβR1), collagen 1α1 (Col1α1), and fibronectin while up-regulating tumor necrosis factor alpha, interleukin-6, and C-X-C motif chemokine ligand 1 expression. LPS did not increase peroxisome proliferation-activated receptor gamma expression or lipid accumulation typical of qHSCs. DPLA elicited the same effects as LPS on aHSCs, indicating specificity, and monophosphoryl lipid A down-regulated fibrogenic markers, but elicited very weak inflammatory response. LPS down-regulated the expression of cMyb, a transcription factor for αSMA, and up-regulated small mother against decapentaplegic (SMAD)7 and CCAAT/enhancer-binding protein (C/EBP)δ, the transcriptional inhibitors of Col1α1 expression. In vivo LPS treatment of aHSCs inhibited their proliferation, down-regulated PDGFβR, αSMA, TGFβR1, Col1α1, and cMyb expression, and increased expression of SMAD7, C/EBPα, and C/EBPδ.

CONCLUSIONS

In conclusion, LPS induces a unique phenotype in aHSCs associated with down-regulation of key fibrogenic mechanisms and thus may have an important role in limiting fibrosis.

Comparative clinical study between the effect of fenofibrate alone and its combination with pentoxifylline on biochemical parameters and liver stiffness in patients with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease is a common health problem associated with increased liver and vascular specific complications.

AIM

The purpose of this study was to assess and compare the effect of fenofibrate alone or in combination with pentoxifylline on the measured biochemical parameters, inflammatory pathway and liver stiffness in patients with non-alcoholic fatty liver disease.

METHODS

The study design was randomized controlled trial. From July 2013 to June 2014, we recruited 90 non-alcoholic fatty liver patients from the Internal Medicine Department at Tanta University Hospital, Egypt. They were classified randomly into two groups to receive fenofibrate 300 mg daily or fenofibrate 300 mg daily plus pentoxifylline 1200 mg/day in three divided doses for 24 weeks. Fasting blood sample was obtained before and 24 weeks after treatment for biochemical analysis of liver and lipid panels, tumor necrosis factor-alpha, hyaluronic acid, transforming growth factor beta 1, fasting plasma insulin and fasting glucose. Liver stiffness measurement was carried out using fibro-scan. Data were statistically analyzed by paired and unpaired Student's t test.

RESULTS

The data obtained suggests that adding pentoxifylline to fenofibrate does not provide a beneficial effect on lipid panel, but has a beneficial effect on indirect biochemical markers of hepatic fibrosis, a direct marker linked to matrix deposition (hyaluronic acid), a cytokine/growth factor linked to liver fibrosis (transforming growth factor beta 1), the inflammatory pathway, insulin resistance and liver stiffness as compared to fenofibrate alone.

CONCLUSION

The combination pentoxifylline plus fenofibrate may represent a new therapeutic strategy for non-alcoholic fatty liver disease as it resulted in more beneficial effects on direct and indirect markers of liver fibrosis, liver stiffness, insulin resistance and inflammatory pathway implicated in NAFLD.

Pentoxifylline Plus Prednisolone versus Pentoxifylline Only for Severe Alcoholic Hepatitis: A Randomized Controlled Clinical Trial

Background:

Prednisolone and pentoxifylline (PTX) have been shown to be individually useful in severe alcoholic hepatitis with Maddrey discriminant function (MDF) score ≥32. Previous report suggests that PTX is probably superior to prednisolone alone. However the efficacy of PTX and prednisolone combination over PTX alone in the management of acute alcoholic hepatitis (MDF score ≥32) is yet unrevealed.

Aim:

The present study was initiated to find out the efficacy of combined pentoxifylline and prednisolone versus PTX alone in acute alcoholic hepatitis in respect of short and intermediate term outcomes.

Subjects and Methods:

A total of 124 patients with severe alcoholic hepatitis (MDF score ≥ 32) initially were evaluated. 62 patients who fulfilled the inclusion and exclusion criteria were randomized and divided into 2 groups. Group 1 received PTX only, whereas Group 2 received PTX plus Prednisolone. The total duration of follow-up was 12 months. Student's t-test, Chi-square test, the Kaplan-Meier methods were used for statistical analysis.

Results:

A total of 60 patients, 30 in each group were available for final analysis. In Group-1, 6 patients expired at the end of 1 year (5 within 3 months and another after 3 months). In Group 2, 10 patients expired at the end of 1 year (9 within 3 months and another after 3 months). Though survival probability is higher among Group 1 patients but the difference is not statistically significant.

Conclusion:

The combination of PTX plus Prednisolone yields no additional benefit in terms of mortality and morbidity from that of PTX monotherapy.

Pentoxifylline alleviates high-fat diet-induced non-alcoholic steatohepatitis and early atherosclerosis in rats by inhibiting AGE and RAGE expression

AIM

To investigate the expression of advanced glycation end products (AGEs) and their receptor RAGE in the livers and blood vessels of rats with non-alcoholic steatohepatitis (NASH) and the effect of pentoxifylline (PTX) on liver and artery function in rats with NASH.

METHODS

Sprague-Dawley rats were fed a high-fat diet for 12 weeks and given PTX by gavage for 4 weeks. The effects of PTX on hepatic liver and vessel function as well as the expression of AGE and RAGE in rats with NASH were assessed. The intima-media thickness (IMT) of the aorta and carotid artery was evaluated using ultrasonography.

RESULTS

Serum aspartic aminotransferase (AST) and blood levels of glucose (GLU) were reduced in the PTX group relative to the NASH group. The IMT of the aorta and carotid artery was increased in the NASH group compared with the control group. The IMT was reduced in NASH rats after treatment with PTX. Rats with NASH demonstrated higher AGE and RAGE protein levels in the liver and arteries compared with those of control rats. PTX treatment in NASH rats resulted in a decrease in AGE and RAGE protein levels in the liver and arteries compared with those in the NASH group.

CONCLUSION

Early atherosclerosis was observed in rats with NASH induced by a 16-week high-fat diet. High expression of AGE and RAGE in the livers and arteries of rats with NASH may contribute to the pathogenesis of NASH and early atherosclerosis. PTX showed protective effects on hepatic and arterial function, partially through inhibition of AGE and RAGE expression.

Effects of the administration of pentoxifylline and prednisolone on the evolution of portal fibrogenesis secondary to biliary obstruction-an experimental study in growing animals

BACKGROUND

Many chronic liver diseases lead to progressive hepatic fibrosis, a condition that can ultimately result in loss of organ function and severe portal hypertension necessitating hepatic transplantation. Within the last few decades, studies have been conducted to demonstrate the possibility of drug modulation of hepatic fibrogenesis. Regarding biliary obstruction, it has been suggested that administration of corticosteroids could promote better late outcomes for children with biliary atresia submitted to Kasai's portoenterostomy. Models used to test potential antifibrogenic drugs such as pentoxifylline (PTX) have not included growing animals.

METHODS

In this experimental study, 119 young rats (21st or 22nd days) were submitted to laparotomy and common bile duct ligation (CBDL) or to sham surgery (SHAM). Animals were allocated into 5 groups, according to surgical procedure, and administered the following solutions: (1) CBDL + distilled water, (2) SHAM + distilled water, (3) CBDL + PTX, (4) CBDL + prednisolone (PRED), and (5) CBDL + PTX + PRED (PTX + PRED). Each group was further divided into 2 subgroups according to the length of the experiment (15 or 30 days). At the end of the defined period, animals were weighed, and a hepatic fragment was collected from each one for analyses.

RESULTS

The PTX animals exhibited increased weight gain compared to animals in the PRED or PTX + PRED groups. Animals from the 3 therapeutic groups (PTX, PRED, and PTX + PRED) showed diminished collagen-filled area in portal spaces. Total portal space area was increased in the PTX group.

CONCLUSIONS

Hepatic fibrosis induced by bile duct ligation in young rats could be modulated by pharmacologic interventions. Administration of PTX or PRED, or the combination of both, resulted in diminished collagen-filled areas in portal spaces.

Pentoxifylline versus prednisolone for severe alcoholic hepatitis: A randomized controlled trial

AIM: To compare the efficacy of pentoxifylline and prednisolone in the treatment of severe alcoholic hepatitis, and to evaluate the role of different liver function scores in predicting prognosis.

METHODS: Sixty-eight patients with severe alcoholic hepatitis (Maddrey score ≥ 32) received pentoxifylline (n = 34, group I) or prednisolone (n = 34, group II) for 28 d in a randomized double-blind controlled study, and subsequently in an open study (with a tapering dose of prednisolone) for a total of 3 mo, and were followed up over a period of 12 mo.

RESULTS: Twelve patients in group II died at the end of 3 mo in contrast to five patients in group I. The probability of dying at the end of 3 mo was higher in group II as compared to group I (35.29% vs 14.71%, P = 0.04; log rank test). Six patients in group II developed hepatorenal syndrome as compared to none in group I. Pentoxifylline was associated with a significantly lower model for end-stage liver disease (MELD) score at the end of 28 d of therapy (15.53 ± 3.63 vs 17.78 ± 4.56, P = 0.04). Higher baseline Maddrey score was associated with increased mortality.

CONCLUSION: Reduced mortality, improved risk-benefit profile and renoprotective effects of pentoxifylline compared with prednisolone suggest that pentoxifylline is superior to prednisolone for treatment of severe alcoholic hepatitis.

The antioxidant activity of chondroitin-4-sulphate, in carbon tetrachloride-induced acute hepatitis in mice, involves NF-kappaB and caspase activation

BACKGROUND AND PURPOSE

Reactive oxygen species (ROC) are the main causes of carbon tetrachloride (CCl4)-induced acute liver injury. Chondroitin-4-sulphate (C4S) is known to inhibit lipid peroxidation through antioxidant mechanisms. Activation of nuclear factor (NF)-kappaB and caspases may strongly intensify inflammation and cell damage, in addition to that directly exerted by ROS. We investigated whether treatment with C4S, besides exerting antioxidant activity, was able to modulate NF-kappaB and apoptosis activation in CCl4-induced liver injury in mice.

EXPERIMENTAL APPROACH

Acute hepatitis was induced in mice by an i.p. injection of CCl(4). Varying doses of C4S were administered i.p. 1 h before, 6 and 12 h after CCl4 injection. 24 h after CCl4 injection, the mice were killed for biochemical and histological analysis.

KEY RESULTS

CCl4 injection produced: marked elevation of alanine aminotransferase and aspartate aminotransferase; hepatic membrane lipid peroxidation, assayed by 8-isoprostane levels; and depletion of reduced glutathione and superoxide dismutase. CCl4 also decreased NF-kappaB translocation and IkBalpha, and increased gene expression of mRNA and protein of metalloproteases (MMP)-2 and -9, and of pro- and cleaved forms of caspases-3 and -7. There was also increased liver polymorphonuclear infiltration, evaluated by elastase assay, and hepatic cell disruption.C4S treatment inhibited lipid peroxidation; blocked NF-kappaB activation and IkBalpha protein loss; decreased mRNA and proteins for MMPs and caspases; restored endogenous antioxidants; limited hepatic polymorphonuclear accumulation and tissue damage.

CONCLUSIONS AND IMPLICATIONS

As antioxidants may inhibit NF-kappaB and caspase activation, we hypothesize that treatment with C4S was able to inhibit NF-kappaB and apoptosis activation in hepatic injury.

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.

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.

Pentoxifylline attenuates cardiac dysfunction and reduces TNF-alpha level in ischemic-reperfused heart

Although pentoxifylline (PTXF), a phosphodiesterase inhibitor, has been reported to exert beneficial effects in cardiac bypass surgery, its effect and mechanisms against ischemia-reperfusion (I/R) injury in heart are poorly understood. Because I/R is known to increase the level of tumor necrosis factor (TNF)-alpha in myocardium and PTXF has been shown to depress the production of TNF-alpha in failing heart, this study examined the hypothesis that PTXF may attenuate cardiac dysfunction and reduce TNF-alpha content in I/R heart. For this purpose, isolated rat hearts were subjected to global ischemia for 30 min followed by reperfusion for 2-30 min. Although cardiac dysfunction due to ischemia was not affected, the recovery of heart function upon reperfusion was markedly improved by PTXF treatment. This cardioprotective effect of PTXF was dose dependent; maximal effect was seen at a concentration of 125 microM. TNF-alpha, nuclear factor-kappaB (NF-kappaB), and phosphorylated NF-kappaB contents were decreased in ischemic heart but were markedly increased within 2 min of starting reperfusion. The ratio of cytosolic-to-homogenate NF-kappaB was decreased, whereas the ratio of particulate-to-homogenate NF-kappaB was increased in I/R hearts. These changes in TNF-alpha and NF-kappaB protein contents as well as in NF-kappaB redistribution due to I/R were significantly attenuated by PTXF treatment. The results of this study indicate that the cardioprotective effects of PTXF against I/R injury may be due to reductions in the activation of NF-kappaB and the production of TNF-alpha content.

Inhibition by pentoxifylline of TNF-alpha-stimulated fractalkine production in vascular smooth muscle cells: evidence for mediation by NF-kappa B down-regulation

(1) Fractalkine is a CX(3)C chemokine for mononuclear leukocytes that is expressed mainly by vascular cells, and regulated by pro-inflammatory cytokines. This study investigated signal transduction mechanisms by which tumor necrosis factor (TNF)-alpha stimulated fractalkine expression in cultured rat vascular smooth muscle cells (VSMCs), and the modulatory effect of a haemorrheologic agent, pentoxifylline, on its production. (2) TNF-alpha (1-50 ng ml(-1)) stimulated fractalkine mRNA and protein expression in concentration- and time-dependent manners. Pretreatment with calphostin C (0.4 micro M, a selective inhibitor of protein kinase C (PKC), and PD98059 (40 micro M), a specific inhibitor of p42/44 mitogen-activated protein kinase (MAPK) kinase, attenuated TNF-alpha-stimulated fractalkine mRNA and protein expression. In contrast, H-89 (2 micro M), a selective inhibitor of cAMP-dependent protein kinase, wortmannin (0.5 micro M), a selective inhibitor of phosphatidylinositol 3-kinase, and SB203580 (40 micro M), a specific inhibitor of p38 MAPK, had no discernible effect. (3) The ubiquitin/proteosome inhibitors, MG132 (10 micro M) and pyrrolidine dithiocarbamate (200 micro M), suppressed activation of NF-kappaB as well as stimulation of fractalkine mRNA and protein expression by TNF-alpha. (4) TNF-alpha-activated phosphorylation of PKC was blocked by calphostin C, whereas TNF-alpha-augmented phospho-p42/44 MAPK and phospho-c-Jun levels were reduced by PD98059. Neither calphostin C nor PD98059 affected TNF-alpha-induced degradation of I-kappaBalpha or p65 nuclear translocation. (5) Pretreatment with pentoxifylline (0.1-1 mg ml(-1)) decreased TNF-alpha-stimulated fractalkine mRNA and protein expression, which was preceded by a reduction in TNF-alpha-activated phosphorylation of PKC, p42/44 MAPK and c-Jun as well as degradation of I-kappaBalpha and p65/NF-kappaB nuclear translocation. (6) These data indicate that activation of PKC, p42/44 MAPK kinase, and NF-kappaB are involved in TNF-alpha-stimulated fractalkine production in VSMCs. Down-regulation of the PKC, p42/44 MAPK, and p65/NF-kappaB signals by PTX may be therapeutically relevant and provide an explanation for the anti-fractalkine effect of this drug.

Immunopharmacological potential of selective phosphodiesterase inhibition. II. Evidence for the involvement of an inhibitory-kappaB/nuclear factor-kappaB-sensitive pathway in alveolar epithelial cells

In this report we investigated the immunopharmacological role of selective and nonselective phosphodiesterase (PDE) inhibition in regulating the inhibitory-kappaB (IkappaB-alpha)/nuclear factor-kappaB (NF-kappaB) signaling transduction pathway. In fetal alveolar type II epithelial cells, PDE blockade at the level of the diverging cAMP/cGMP pathways differentially regulated the phosphorylation and degradation of IkappaB-alpha, the major cytosolic inhibitor of NF-kappaB. Whereas selective inhibition of PDEs 1, 3, and 4, by the action of 8-methoxymethyl-3-isobutyl-1-methylxanthine, amrinone, and rolipram, respectively, exhibited a tendency to augment the translocation of NF-kappaB(1) (p50), RelA (p65), RelB (p68), and c-Rel (p75), selective blockade of PDE 5, 6, and 9, by the action of 4-[[3',4'-(methylenedioxy)benzyl]amino]-6-methoxyquinazoline and zaprinast, attenuated lipopolysaccharide-endotoxin (LPS)-mediated NF-kappaB translocation. Pentoxifylline, a nonspecific PDE inhibitor, reversed the excitatory effect of LPS on NF-kappaB subunit nuclear localization, in a dose-dependent manner. Furthermore, analysis of NF-kappaB activation under the same conditions revealed a biphasic effect mediated by LPS. PDEs 1, 3, and 4 inhibition was associated with up-regulating NF-kappaB transcriptional activity. In contrast, blockading the activity of PDEs 5, 6, and 9 negatively attenuated LPS-mediated NF-kappaB activation, similar to the effect of 3,7-dihydro-3,7-dimethyl-1-(5-oxohexyl)-1H-purine-2,6-dione (pentoxifylline). These results indicate that selective and nonselective interference with the control of the dynamic equilibrium of cyclic nucleotides via PDE isoenzyme regulation represents an immunoregulatory mechanism that requires the differential, biphasic targeting of the IkappaB-alpha/NF-kappaB pathway.

c-Myb modulates transcription of the alpha-smooth muscle actin gene in activated hepatic stellate cells

Expression of alpha-smooth muscle actin (alpha-SMA) defines the phenotype of activated (myofibroblastic) hepatic stellate cells. These cells, but not quiescent stellate cells, have a high level of alpha-SMA and c-Myb expression, as well as increased c-Myb-binding activities to the proximal alpha-SMA E box. Therefore, we analyzed the role of c-Myb in alpha-SMA transcription and stellate cell activation. Activated primary rat stellate cells displayed a high expression of the -724 and -271 alpha-SMA/luciferase (LUC) chimeric genes, which contain c-Myb binding sites (-223/-216 bp). Alpha-SMA/LUC minigenes with mutation (-219/-217 bp), truncation (-224 bp), or deletion (-191 bp) of the c-Myb binding site were not efficiently transcribed. Transfection of wild-type c-Myb into quiescent stellate cells, which do not express endogenous c-Myb, induced a approximately 10-fold stimulation of -724 alpha-SMA/LUC expression. Conversely, expression of either a dominant-negative c-Myb basic domain mutant (Cys(43) --> Asp) or a c-Myb antisense RNA blocked transcription from the -724 alpha-SMA/LUC or -271 alpha-SMA/LUC in activated cells. Moreover, transfection of c-myb antisense, but not sense, RNA inhibited both expression of the endogenous alpha-SMA gene and stellate cell activation, whereas transfection of c-myb stimulated alpha-SMA expression in quiescent stellate cells. These findings suggest that c-Myb modulates the activation of stellate cells and that integrity of the redox sensor Cys(43) in c-Myb is required for this effect.