Effects of colchicine on liver functions of cirrhotic rats: beneficial effects result from stellate cell inactivation and inhibition of TGF beta1 expression

Formononetin Induces Ferroptosis in Activated Hepatic Stellate Cells to Attenuate Liver Fibrosis by Targeting NADPH Oxidase 4

Ferroptosis is a newly discovered type of cell death that exerts a crucial role in hepatic fibrosis. Formononetin (FMN), a natural isoflavone compound mainly isolated from Spatholobus suberectus Dunn, shows multiple biological activities, including antioxidant, anti-inflammatory, and hepatoprotection. This research aims to explore the regulatory mechanism of FMN in liver fibrosis and the relationship between NADPH oxidase 4 (NOX4) and ferroptosis. The effects of FMN on HSC ferroptosis were evaluated in rat model of CCl4-induced hepatic fibrosis. In vitro, N-acetyl-L-cysteine (NAC) and deferoxamine (DFO) were used to block ferroptosis and then explored the anti-fibrotic effect of FMN. The target protein of FMN was identified by bio-orthogonal click chemistry reaction as well as drug affinity responsive target stability (DARTS), cellular thermal shift (CETSA), surface plasmon resonance (SPR) assays, and isothermal titration calorimetry (ITC) analysis. Here, we found that FMN exerted anti-fibrotic effects via inducing ferroptosis in activated HSCs. NAC and DFO prevented FMN-induced ferroptotic cell death and collagen reduction. Furthermore, FMN bound directly to NOX4 through possible active amino acid residues sites, and increased NOX4-based NADPH oxidase activity to enhance levels of NADP+/NADPH, thus promoting ferroptosis of activated HSCs and relieving liver fibrosis. These results demonstrate that the direct target and mechanism by which FMN improves liver fibrosis, suggesting that FMN may be a natural candidate for further development of liver fibrosis therapy.

Emerging insights into the role of IL-1 inhibitors and colchicine for inflammation control in type 2 diabetes

Type 2 diabetes mellitus (T2DM), a prevalent chronic metabolic disorder, is closely linked to persistent low-grade inflammation, significantly contributing to its development and progression. This review provides a comprehensive examination of the inflammatory mechanisms underlying T2DM, focusing on the role of the NLRP3 inflammasome and interleukin-1β (IL-1β) in mediating inflammatory responses. We discuss the therapeutic potential of IL-1 inhibitors and colchicine, highlighting their mechanisms in inhibiting the NLRP3 inflammasome and reducing IL-1β production. Recent studies indicate that these agents could effectively mitigate inflammation, offering promising avenues for the prevention and management of T2DM. By exploring the intricate connections between metabolic disturbances and chronic inflammation, this review underscores the need for novel anti-inflammatory strategies to address T2DM and its complications.

Transcriptional and Epigenetic Consequences of DMSO Treatment on HepaRG Cells

Dimethyl sulfoxide (DMSO) is used to sustain or favor hepatocyte differentiation in vitro. Thus, DMSO is used in the differentiation protocol of the HepaRG cells that present the closest drug-metabolizing enzyme activities to primary human hepatocytes in culture. The aim of our study is to clarify its influence on liver-specific gene expression. For that purpose, we performed a large-scale analysis (gene expression and histone modification) to determine the global role of DMSO exposure during the differentiation process of the HepaRG cells. The addition of DMSO drives the upregulation of genes mainly regulated by PXR and PPARα whereas genes not affected by this addition are regulated by HNF1α, HNF4α, and PPARα. DMSO-differentiated-HepaRG cells show a differential expression for genes regulated by histone acetylation, while differentiated-HepaRG cells without DMSO show gene signatures associated with histone deacetylases. In addition, we observed an interplay between cytoskeleton organization and EMC remodeling with hepatocyte maturation.

Mangiferin prevents hepatocyte epithelial-mesenchymal transition in liver fibrosis via targeting HSP27-mediated JAK2/STAT3 and TGF-β1/Smad pathway

Hepatocytes has been confirmed to undergo EMT and can be converted into myofibroblasts during hepatic fibrogenesis. However, the mechanism of hepatocyte EMT regulation in hepatic fibrosis, particularly through HSP27 (human homologue of rodent HSP25), remains unclear. Mangiferin (MAN), a compound extracted from Mangifera indica L, has been reported to attenuate liver injury. This study aimed to investigate the mechanisms underlying HSP27 inhibition and the anti-fibrotic effect of MAN in liver fibrosis. Our results revealed that the expression of HSP27 was remarkably increased in the liver tissues of patients with liver cirrhosis and CCl₄ -induced fibrotic rats. However, HSP27 shRNA treatment significantly alleviated fibrosis. Furthermore, MAN was found to inhibit CCl₄ - and TGF-β1-induced liver fibrosis and reduced hepatocyte EMT. More importantly, MAN decreased HSP27 expression to suppress the JAK2/STAT3 pathway, and subsequently blocked TGF-β1/Smad signaling, which were consistent with its protection against CCl₄ -induced EMT and liver fibrosis. Together, these results suggest that HSP27 may play a crucial role in hepatocyte EMT and liver fibrosis by activating JAK2/STAT3 signaling and TGF-β1/Smad pathway. The suppression of HSP27 expression by MAN may be a novel strategy for attenuating the hepatocyte EMT in liver fibrosis.

Colchicine attenuates renal ischemia-reperfusion-induced liver damage: implication of TLR4/NF-κB, TGF-β, and BAX and Bcl-2 gene expression

Ischemia-reperfusion injury (IRI) is typically associated with a vigorous inflammatory and oxidative stress response to hypoxia and reperfusion that disturbs the function of the organ. The remote effects of renal IRI on the liver, however, require further study. Renal damage associated with liver disease is a common clinical problem. Colchicine, a polymerization inhibitor of microtubules, has been used as an anti-inflammatory and anti-fibrotic drug for liver diseases. The goal of the current study was to investigate the possible protective mechanisms of colchicine on liver injury following renal IRI. Forty rats were divided randomly into four groups: sham group, colchicine-treated group, IRI group, and colchicine-treated + IRI group. Treatment with colchicine significantly reduced hepatic toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB) transcription factor, myeloid differentiation factor 88 (MyD88), and tumor necrosis factor-alpha (TNF-α) contents; downregulated BCL2 associated X apoptosis regulator (BAX) gene expression, transforming growth factor-β (TGF-β) content, and upregulated hepatic B cell lymphoma 2 (Bcl-2) gene expression as compared with the IRI group. Finally, hepatic histopathological examinations have confirmed the biochemical results. Renal IRI-induced liver damage in rats was alleviated by colchicine through its anti-inflammatory, anti-apoptotic, and anti-fibrotic actions.

Novel colchicine derivatives enhance graft survival after transplantation via suppression of T-cell differentiation and activity

Immunosuppressants are crucial in organ transplantation but their side effects are a trade-off for long-term use. Colchicine has been shown to be effective in various diseases, albeit with many side effects. To enhance the immunosuppressive effects of colchicine, in addition to minimizing its side effects, we attempted to synthesize new colchicine derivatives (KR compounds). In rat cardiac and pancreatic islet allograft, long-term graft survival was identified in KR compound-treated groups. The use of cyclosporine A (CsA) or colchicine inhibited the CD3⁺ and CD4⁺ T-cell proliferation, whereas KR compounds inhibited the CD8⁺ T cells as well as CD4⁺ T cells. KR compounds reduced the apoptosis, interleukin-2 receptor expression, and signal transducer and activator of transcription 3 phosphorylation more than CsA. These results indicate that KR compounds have a potential therapeutic value as novel agents for prevention of graft deterioration by allograft of rejection.

Anti-Fibrotic Effects of Neferine on Carbon Tetrachloride-Induced Hepatic Fibrosis in Mice

The effects of neferine, a bisbenzylisoquinline alkaloid extracted from the seed embryo of the Chinese traditional medicine Nelumbo nucifera Gaertn, on carbon tetrachloride ( CCl 4)-induced hepatic fibrosis in mice were evaluated. Adult male Kunming mice were administered with CCl 4 1 ml/kg via intraperitoneal injection twice a week for 8 weeks. At the beginning of the 9th week, mice were treated with normal saline, colchicine (0.1 mg/kg), and neferine (5, 10, 20 mg/kg) via intraperitoneal injection once a day for 2 weeks. The liver index and histological examination, plasma ALT/AST levels, hydroxyproline and TGF-β1 content of liver tissue were examined. In the model group, the liver index, the hydroxyproline content of liver tissue and plasma ALT/AST levels were increased, and a high expression of TGF-β1 was observed. The abnormal changes could be improved by neferine in a dose-dependent manner. Our data showed that neferine had an antifibrosis effect on CCl 4-induced hepatic fibrosis in mice, possibly partly due to the decreased expression of TGF-β1 in the liver.

The effect of antifibrotic drugs in rat precision-cut fibrotic liver slices

Two important signaling pathways in liver fibrosis are the PDGF- and TGFβ pathway and compounds inhibiting these pathways are currently developed as antifibrotic drugs. Testing antifibrotic drugs requires large numbers of animal experiments with high discomfort. Therefore, a method to study these drugs ex vivo was developed using precision-cut liver slices from fibrotic rat livers (fPCLS), representing an ex vivo model with a multicellular fibrotic environment. We characterized the fibrotic process in fPCLS from rat livers after 3 weeks of bile duct ligation (BDL) during incubation and tested compounds predominantly inhibiting the TGFβ pathway (perindopril, valproic acid, rosmarinic acid, tetrandrine and pirfenidone) and PDGF pathway (imatinib, sorafenib and sunitinib). Gene expression of heat shock protein 47 (Hsp47), α smooth muscle actin (αSma) and pro-collagen 1A1 (Pcol1A1) and protein expression of collagens were determined. During 48 hours of incubation, the fibrosis process continued in control fPCLS as judged by the increased gene expression of the three fibrosis markers, and the protein expression of collagen 1, mature fibrillar collagen and total collagen. Most PDGF-inhibitors and TGFβ-inhibitors significantly inhibited the increase in gene expression of Hsp47, αSma and Pcol1A1. Protein expression of collagen 1 was significantly reduced by all PDGF-inhibitors and TGFβ-inhibitors, while total collagen was decreased by rosmarinic acid and tetrandrine only. However, fibrillar collagen expression was not changed by any of the drugs. In conclusion, rat fPCLS can be used as a functional ex vivo model of established liver fibrosis to test antifibrotic compounds inhibiting the PDGF- and TGFβ signalling pathway.

Precision-cut liver slices as a model for the early onset of liver fibrosis to test antifibrotic drugs

Induction of fibrosis during prolonged culture of precision-cut liver slices (PCLS) was reported. In this study, the use of rat PCLS was investigated to further characterize the mechanism of early onset of fibrosis in this model and the effects of antifibrotic compounds. Rat PCLS were incubated for 48h, viability was assessed by ATP and gene expression of PDGF-B and TGF-β1 and the fibrosis markers Hsp47, αSma and Pcol1A1 and collagen1 protein expressions were determined. The effects of the antifibrotic drugs imatinib, sorafenib and sunitinib, PDGF-pathway inhibitors, and perindopril, valproic acid, rosmarinic acid, tetrandrine and pirfenidone, TGFβ-pathway inhibitors, were determined. After 48h of incubation, viability of the PCLS was maintained and gene expression of PDGF-B was increased while TGF-β1 was not changed. Hsp47, αSma and Pcol1A1 gene expressions were significantly elevated in PCLS after 48h, which was further increased by PDGF-BB and TGF-β1. The increased gene expression of fibrosis markers was inhibited by all three PDGF-inhibitors, while TGFβ-inhibitors showed marginal effects. The protein expression of collagen 1 was inhibited by imatinib, perindopril, tetrandrine and pirfenidone. In conclusion, the increased gene expression of PDGF-B and the down-regulation of fibrosis markers by PDGF-pathway inhibitors, together with the absence of elevated TGF-β1 gene expression and the limited effect of the TGFβ-pathway inhibitors, indicated the predominance of the PDGF pathway in the early onset of fibrosis in PCLS. PCLS appear a useful model for research of the early onset of fibrosis and for testing of antifibrotic drugs acting on the PDGF pathway.

Predicting in vivo anti-hepatofibrotic drug efficacy based on in vitro high-content analysis

Background/Aims

Many anti-fibrotic drugs with high in vitro efficacies fail to produce significant effects in vivo. The aim of this work is to use a statistical approach to design a numerical predictor that correlates better with in vivo outcomes.

Methods

High-content analysis (HCA) was performed with 49 drugs on hepatic stellate cells (HSCs) LX-2 stained with 10 fibrotic markers. ∼0.3 billion feature values from all cells in >150,000 images were quantified to reflect the drug effects. A systematic literature search on the in vivo effects of all 49 drugs on hepatofibrotic rats yields 28 papers with histological scores. The in vivo and in vitro datasets were used to compute a single efficacy predictor (E_predict).

Results

We used in vivo data from one context (CCl₄ rats with drug treatments) to optimize the computation of E_predict. This optimized relationship was independently validated using in vivo data from two different contexts (treatment of DMN rats and prevention of CCl₄ induction). A linear in vitro-in vivo correlation was consistently observed in all the three contexts. We used E_predict values to cluster drugs according to efficacy; and found that high-efficacy drugs tended to target proliferation, apoptosis and contractility of HSCs.

Conclusions

The E_predict statistic, based on a prioritized combination of in vitro features, provides a better correlation between in vitro and in vivo drug response than any of the traditional in vitro markers considered.

Decorin and colchicine as potential treatments for post-haemorrhagic ventricular dilatation in a neonatal rat model

BACKGROUND

Post-haemorrhagic ventricular dilatation (PHVD) after intraventricular haemorrhage (IVH) remains a significant problem in preterm infants. Due to serious disadvantages of ventriculoperitoneal shunt dependence, there is an urgent need for non-surgical interventions. Considerable experimental and clinical evidence implicates transforming growth factor β (TGFβ) in the pathogenesis of PHVD. Colchicine and decorin are both compounds with anti-TGFβ properties. The former downregulates TGFβ production and is in clinical use for another fibrotic disease, and the latter inactivates TGFβ.

OBJECTIVES

We hypothesized that administration of decorin or colchicine, which both have anti-TGFβ properties, would reduce ventricular dilatation in a model of PHVD.

METHODS

142 rat pups underwent intraventricular blood injection on postnatal days (PN) 7 and 8. Sixty-nine pups were randomized to colchicine 20 and 50 μg/kg/day or water by gavage for 13 days. Seventy were randomized to decorin 4 mg/kg or saline by intraventricular injection on PN8 and PN13. At PN21, the ventricular area was measured on coronal brain sections. Negative geotaxis was tested at PN14 in controls and in the decorin study group.

RESULTS

Ventricular size was not different between animals receiving either drug or water/saline. Intraventricular blood impaired neuromotor performance, but decorin had no effect.

CONCLUSION

Two drugs that block TGFβ by different mechanisms do not reduce ventricular dilatation in this model. Together with our previous work on losartan and pirfenidone, we conclude that blocking TGFβ alone does not prevent the development of PHVD.

Acute oral toxicity of colchicine in rats: effects of gender, vehicle matrix and pre-exposure to lipopolysaccharide

The oral toxicity of a single administration by gavage (10, 20 or 30 mg kg(-1) body weight) of colchicine (COL) was determined in young, mature male and female Sprague-Dawley rats. The effect of COL was evaluated in the presence or absence of additional treatment variables that included vehicle and lipopolysaccharide (LPS) pre-exposure. The vehicle for COL was either Half and Half cream (H & H) or saline, and each group included pretreatment with either saline or a low, minimally toxic dose (83 microg kg(-1) body weight) of LPS. Colchicine toxicity in both male and female age-matched rats was characterized by progressively more severe dose-related clinical signs of toxicity. These included mortality, decreased body weight and feed intake during the first several days after dosing, with recovery thereafter in surviving animals. There were differences in the severity of the toxic response to COL between male and female rats. The most notable sex-related difference was in COL lethality. Female rats were two times more susceptible to the lethal effects of COL than male rats. Saline or H & H delivery vehicles did not result in any apparent qualitative or quantitative differences in COL toxicity. LPS pretreatment significantly potentiated COL lethality in both males and females, although the potentiation in males was greater than in females. LPS pretreatment modestly increased the COL induced anorexic effect in surviving males, but not in surviving female animals. LPS did not appear to modulate either the body weights or clinical signs of COL induced toxicity in surviving males or females.

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Modern pathogenetic concepts of liver fibrosis suggest stellate cells and TGF-beta as major players and therapeutic targets

Hepatic fibrosis is a scarring process that is associated with an increased and altered deposition of extracellular matrix in liver. At the cellular and molecular level, this progressive process is mainly characterized by cellular activation of hepatic stellate cells and aberrant activity of transforming growth factor-beta1 and its downstream cellular mediators. Although the cellular responses to this cytokine are complex, the signalling pathways of this pivotal cytokine during the fibrogenic response and its connection to other signal cascades are now understood in some detail. Based on the current advances in understanding the pleiotropic reactions during fibrogenesis, various inhibitors of transforming growth factor-beta were developed and are now being investigated as potential drug candidates in experimental models of hepatic injury. Although it is too early to favour one of these antagonists for the treatment of hepatic fibrogenesis in human, the experimental results obtained yet provide stimulatory impulses for the development of an effective treatment of choice in the not too distant future. The present review summarises the actual knowledge on the pathogenesis of hepatic fibrogenesis, the role of transforming growth factor-beta and its signalling pathways in promoting the fibrogenic response, and the therapeutic modalities that are presently in the spotlight of many investigations and are already on the way to take the plunge into clinical studies.

Modern pathogenetic concepts of liver fibrosis suggest stellate cells and TGF-beta as major players and therapeutic targets

Hepatic fibrosis is a scarring process that is associated with an increased and altered deposition of extracellular matrix in liver. At the cellular and molecular level, this progressive process is mainly characterized by cellular activation of hepatic stellate cells and aberrant activity of transforming growth factor-beta1 and its downstream cellular mediators. Although the cellular responses to this cytokine are complex, the signalling pathways of this pivotal cytokine during the fibrogenic response and its connection to other signal cascades are now understood in some detail. Based on the current advances in understanding the pleiotropic reactions during fibrogenesis, various inhibitors of transforming growth factor-beta were developed and are now being investigated as potential drug candidates in experimental models of hepatic injury. Although it is too early to favour one of these antagonists for the treatment of hepatic fibrogenesis in human, the experimental results obtained yet provide stimulatory impulses for the development of an effective treatment of choice in the not too distant future. The present review summarises the actual knowledge on the pathogenesis of hepatic fibrogenesis, the role of transforming growth factor-beta and its signalling pathways in promoting the fibrogenic response, and the therapeutic modalities that are presently in the spotlight of many investigations and are already on the way to take the plunge into clinical studies.

Modern pathogenetic concepts of liver fibrosis suggest stellate cells and TGF-beta as major players and therapeutic targets

Hepatic fibrosis is a scarring process that is associated with an increased and altered deposition of extracellular matrix in liver. At the cellular and molecular level, this progressive process is mainly characterized by cellular activation of hepatic stellate cells and aberrant activity of transforming growth factor-beta1 and its downstream cellular mediators. Although the cellular responses to this cytokine are complex, the signalling pathways of this pivotal cytokine during the fibrogenic response and its connection to other signal cascades are now understood in some detail. Based on the current advances in understanding the pleiotropic reactions during fibrogenesis, various inhibitors of transforming growth factor-beta were developed and are now being investigated as potential drug candidates in experimental models of hepatic injury. Although it is too early to favour one of these antagonists for the treatment of hepatic fibrogenesis in human, the experimental results obtained yet provide stimulatory impulses for the development of an effective treatment of choice in the not too distant future. The present review summarises the actual knowledge on the pathogenesis of hepatic fibrogenesis, the role of transforming growth factor-beta and its signalling pathways in promoting the fibrogenic response, and the therapeutic modalities that are presently in the spotlight of many investigations and are already on the way to take the plunge into clinical studies.

Involvement of tumor necrosis factor-related apoptosis-inducing ligand and tumor necrosis factor-related apoptosis-inducing ligand receptors in viral hepatic diseases

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in tumor cells, but not in most normal cells. The role of TRAIL in hepatic cell death and hepatic diseases is not well understood. The present study investigated the expression of TRAIL and TRAIL receptors (TRAIL-Rs) in patients with hepatitis C virus infection using immunohistochemistry and examined physiological roles under viral infection in the HepG2 cell line. Staining of TRAIL or TRAIL-Rs was prominent in the cytoplasm and membrane of hepatocytes in the periportal area. Some liver-infiltrating lymphocytes also displayed positive staining for TRAIL. Staining intensity was significantly increased with disease progression, particularly in the periportal area. AdCMVLacZ (Q-BIOgene, Carisbad, Calif) infection was also found to induce apoptosis in HepG2 cells and significantly augment TRAIL-induced apoptosis. Anti-TRAIL antibody significantly inhibited apoptosis induced by AdCMVLacZ infection. Flow cytometry analysis revealed that both TRAIL-R2 and TRAIL were up-regulated on the cell surface of HepG2 cells with AdCMVLacZ infection. Transforming growth factor-beta1 also enhanced TRAIL expression in HepG2 cells. These results indicate that TRAIL/TRAIL-R apoptotic pathways play important roles in the hepatic cell death during viral infection.

Interaction of colchicine with human serum albumin investigated by spectroscopic methods

We investigated the interaction between colchicine and human serum albumin (HSA) by fluorescence and UV-vis absorption spectroscopy. In the mechanism discussion, it was proved that the fluorescence quenching of HSA by colchicine is a result of the formation of colchicines-HSA complex; van der Waals interactions and hydrogen bonds play a major role in stabilizing the complex. The modified Stern-Volmer quenching constant K(a) and corresponding thermodynamic parameters deltaH, deltaG, deltaS at different temperatures were calculated. The distance r between donor (Trp214) and acceptor (colchicine) was obtained according to fluorescence resonance energy transfer (FRET).

Effects of augmentation of liver regeneration recombinant plasmid on rat hepatic fibrosis

AIM

To investigate the effects of eukaryotic expression of plasmid on augmentation of liver regeneration (ALR) in rat hepatic fibrosis and to explore their mechanisms.

METHODS

Ten rats were randomly selected from 50 Wistar rats as normal control group. The rest were administered intraperitoneally with porcine serum twice weekly. After 8 wk, they were randomly divided into: model control group, colchicine group (Col), first ALR group (ALR1), second ALR group (ALR2). Then colchicine ALR recombinant plasmid were used to treat them respectively. At the end of the 4th wk, rats were killed. Serum indicators were detected and histopathological changes were graded. Expression of type I, III, collagen and TIMP-1 were detected by immunohistochemistry and expression of TIMP-1 mRNA was detected by semi-quantified RT-PCR.

RESULTS

The histologic examination showed that the degree of the rat hepatic fibrosis in two ALR groups was lower than those in model control group. Compared with model group, ALR significantly reduced the serum levels of ALT, AST, HA, LN, PCIII and IV (P<0.05). Immunohistochemical staining showed that expression of type I, III, collagen and TIMP-1 in two ALR groups was ameliorated dramatically compared with model group (I collagen: 6.94+/-1.42, 5.80+/-1.66 and 10.83+/-3.58 in ALR1, ALR2 and model groups, respectively; III collagen: 7.18+/-1.95, 4.50+/-1.67 and 10.25+/-2.61, respectively; TIMP-1: 0.39+/-0.05, 0.20+/-0.06 and 0.53+/-0.12, respectively, P<0.05 or P<0.01). The expression level of TIMP-1 mRNA in the liver tissues was markedly decreased in two ALR groups compared with model group (TIMP-1 mRNA/beta-actin: 0.89+/-0.08, 0.65+/-0.11 and 1.36+/-0.11 in ALR1, ALR2 and model groups respectively, P<0.01).

CONCLUSION

ALR recombinant plasmid has beneficial effects on rat hepatic fibrosis by enhancing regeneration of injured liver cells and inhibiting TIMP-1 expressions.

IL-13 activates a mechanism of tissue fibrosis that is completely TGF-beta independent

Fibrosis is a characteristic feature in the pathogenesis of a wide spectrum of diseases. Recently, it was suggested that IL-13-dependent fibrosis develops through a TGF-beta1 and matrix metalloproteinase-9-dependent (MMP-9) mechanism. However, the significance of this pathway in a natural disorder of fibrosis was not investigated. In this study, we examined the role of TGF-beta in IL-13-dependent liver fibrosis caused by Schistosoma mansoni infection. Infected IL-13-/- mice showed an almost complete abrogation of fibrosis despite continued and undiminished production of TGF-beta1. Although MMP-9 activity was implicated in the IL-13 pathway, MMP-9-/- mice displayed no reduction in fibrosis, even when chronically infected. To directly test the requirement for TGF-beta, studies were also performed with neutralizing anti-TGF-beta Abs, soluble antagonists (soluble TGF-betaR-Fc), and Tg mice (Smad3-/- and TGF-betaRII-Fc Tg) that have disruptions in all or part of the TGF-beta signaling cascade. In all cases, fibrosis developed normally and with kinetics similar to wild-type mice. Production of IL-13 was also unaffected. Finally, several genes, including interstitial collagens, several MMPs, and tissue inhibitors of metalloprotease-1 were up-regulated in TGF-beta1-/- mice by IL-13, demonstrating that IL-13 activates the fibrogenic machinery directly. Together, these studies provide unequivocal evidence of a pathway of fibrogenesis that is IL-13 dependent but TGF-beta1 independent, illustrating the importance of targeting IL-13 directly in the treatment of infection-induced fibrosis.