NF-kappaB is a critical regulator of the survival of rodent and human hepatic myofibroblasts

Novel Compound HJC0416 Attenuates Hepatic Fibrosis via HSP90/NF-κB-Associated Mechanism

INTRODUCTION

Chronic liver disease is driven by a prolonged wound healing response leading to fibrogenesis, potentially progressing to cirrhosis. Hepatic stellate cells (HSCs) are the primary cells driving hepatic fibrosis because they are major producers of extracellular matrix. The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ΚB) pathway is a key regulator of inflammatory signaling, and survival of activated HSCs has been found to be NF-KB dependent. Our team previously synthesized HJC0416-a signal transducer and activator of transcription three inhibitor with potent anti-inflammatory effects. In HSCs, HJC0416 reduced cell viability, extracellular matrix production, and-notably-NF-KB activation. However, HJC0416's antifibrogenetic mechanism remains unknown. This study examined the effects of HJC0416 on NF-KB and its associate factor HSP-90 in HSCs.

METHODS

The activated human HSC line LX-2 was treated with either HJC0416 or 17-AAG, then exposed to TNFα as indicated. Nuclear and cytosolic proteins were isolated for Western blot or immunofluorescence assay.

RESULTS

HJC0416 significantly attenuated TNFα-induced IκBα phosphorylation, NF-KBp65 nuclear translocation, and DNA binding activity. Endogenous and TNFα-induced p65 phosphorylation of S536 was suppressed by HJC0416. Notably, HJC0416 dose-dependently attenuated the expression of FAK, IKKα, and signal transducer and activator of transcription three which are Heat Shock Protein 90 (HSP90) interacting proteins. The expression of other HSP90 interacting proteins-RIP1, AKT, FAK, and cyclin-dependent kinase nine-were decreased. HSP90-specific inhibitor 17-AAG significantly attenuated TNFα-induced IκBα phosphorylation and degradation, p65 nuclear translocation, DNA binding, and production of collagen type I and fibronectin.

CONCLUSIONS

The HSP90 chaperone protein may be a key intermediary linking HJC0416's ability to inhibit NF-κB activity. HJC0416 may be a promising drug candidate for liver fibrosis.

AMPK signaling inhibits the differentiation of myofibroblasts: impact on age-related tissue fibrosis and degeneration

Disruption of the extracellular matrix (ECM) and an accumulation of fibrotic lesions within tissues are two of the distinctive hallmarks of the aging process. Tissue fibroblasts are mesenchymal cells which display an impressive plasticity in the regulation of ECM integrity and thus on tissue homeostasis. Single-cell transcriptome studies have revealed that tissue fibroblasts exhibit a remarkable heterogeneity with aging and in age-related diseases. Excessive stress and inflammatory insults induce the differentiation of fibroblasts into myofibroblasts which are fusiform contractile cells and abundantly secrete the components of the ECM and proteolytic enzymes as well as many inflammatory mediators. Detrimental stresses can also induce the transdifferentiation of certain mesenchymal and myeloid cells into myofibroblasts. Interestingly, many age-related stresses, such as oxidative and endoplasmic reticulum stresses, ECM stiffness, inflammatory mediators, telomere shortening, and several alarmins from damaged cells are potent inducers of myofibroblast differentiation. Intriguingly, there is convincing evidence that the signaling pathways stimulated by the AMP-activated protein kinase (AMPK) are potent inhibitors of myofibroblast differentiation and accordingly AMPK signaling reduces fibrotic lesions within tissues, e.g., in age-related cardiac and pulmonary fibrosis. AMPK signaling is not only an important regulator of energy metabolism but it is also able to control cell fate determination and many functions of the immune system. It is known that AMPK signaling can delay the aging process via an integrated signaling network. AMPK signaling inhibits myofibroblast differentiation, e.g., by suppressing signaling through the TGF-β, NF-κB, STAT3, and YAP/TAZ pathways. It seems that AMPK signaling can alleviate age-related tissue fibrosis and degeneration by inhibiting the differentiation of myofibroblasts.

Promotion of myofibroblast differentiation through repeated treatment of fibroblasts to low concentrations of PM2.5

Exposure to particulate matter ≤ 2.5 µm (PM2.5) is a risk factor for many lung diseases. Although the toxicologic effects of PM2.5 on airway epithelium are well-described, the effects of PM2.5 on fibroblasts in the lung are less studied. Here, we sought to examine the effects of PM2.5 on the differentiation of fibroblasts into myofibroblasts. Although a single treatment of fibroblasts did not result in a change in collagen or the myofibroblast marker α-SMA, exposing fibroblasts to sequential treatments with PM2.5 at low concentrations caused a robust increase in these proteins. Treatment of fibroblasts with IMD0354, an inhibitor to nuclear factor κB, but not with an antagonist to aryl hydrocarbon receptor, abolished the ability of PM2.5 to induce myofibroblast differentiation. These data demonstrate that potential impact of PM2.5 to fibroblast activation and fibrosis and support the importance of utilizing low concentrations and varying exposure protocols to toxicologic studies.

p53 and Myofibroblast Apoptosis in Organ Fibrosis

Organ fibrosis represents a dysregulated, maladaptive wound repair response that results in progressive disruption of normal tissue architecture leading to detrimental deterioration in physiological function, and significant morbidity/mortality. Fibrosis is thought to contribute to nearly 50% of all deaths in the Western world with current treatment modalities effective in slowing disease progression but not effective in restoring organ function or reversing fibrotic changes. When physiological wound repair is complete, myofibroblasts are programmed to undergo cell death and self-clearance, however, in fibrosis there is a characteristic absence of myofibroblast apoptosis. It has been shown that in fibrosis, myofibroblasts adopt an apoptotic-resistant, highly proliferative phenotype leading to persistent myofibroblast activation and perpetuation of the fibrotic disease process. Recently, this pathological adaptation has been linked to dysregulated expression of tumour suppressor gene p53. In this review, we discuss p53 dysregulation and apoptotic failure in myofibroblasts and demonstrate its consistent link to fibrotic disease development in all types of organ fibrosis. An enhanced understanding of the role of p53 dysregulation and myofibroblast apoptosis may aid in future novel therapeutic and/or diagnostic strategies in organ fibrosis.

Endotoxemia and Gastrointestinal Cancers: Insight into the Mechanisms Underlying a Dangerous Relationship

Lipopolysaccharide (LPS), also known as endotoxin, is a component of the membrane of gram-negative bacteria and a well-recognized marker of sepsis. In case of disruption of the intestinal barrier, as occurs with unhealthy diets, alcohol consumption, or during chronic diseases, the microbiota residing in the gastrointestinal tract becomes a crucial factor in amplifying the systemic inflammatory response. Indeed, the translocation of LPS into the bloodstream and its interaction with toll-like receptors (TLRs) triggers molecular pathways involved in cytokine release and immune dysregulation. This is a critical step in the exacerbation of many diseases, including metabolic disorders and cancer. Indeed, the role of LPS in cancer development is widely recognized, and examples include gastric tumor related to Helicobacter pylori infection and hepatocellular carcinoma, both of which are preceded by a prolonged inflammatory injury; in addition, the risk of recurrence and development of metastasis appears to be associated with endotoxemia. Here, we review the mechanisms that link the promotion and progression of tumorigenesis with endotoxemia, and the possible therapeutic interventions that can be deployed to counteract these events.

Anti-fibrotic treatments for chronic liver diseases: The present and the future

Liver fibrosis reflects tissue scarring in the liver due to the accumulation of excessive extracellular matrix in response to chronically persistent liver injury. Hepatocyte cell death can trigger capillarization of liver sinusoidal endothelial cells, stimulation of immune cells including macrophages and Kupffer cells, and activation of hepatic stellate cells (HSCs), resulting in progression of liver fibrosis. Liver cirrhosis is the terminal state of liver fibrosis and is associated with severe complications, such as liver failure, portal hypertension, and liver cancer. Nevertheless, effective therapy for cirrhosis has not yet been established, and liver transplantation is the only radical treatment for severe cases. Studies investigating HSC activation and regulation of collagen production in the liver have made breakthroughs in recent decades that have advanced the knowledge regarding liver fibrosis pathophysiology. In this review, we summarize molecular mechanisms of liver fibrosis and discuss the development of novel anti-fibrotic therapies.

NF-κB activation persists into the remodeling phase of tendon healing and promotes myofibroblast survival

Although inflammation is necessary during the early phases of tissue repair, persistent inflammation contributes to fibrosis. Acute tendon injuries often heal through a fibrotic mechanism, which impedes regeneration and functional recovery. Because inflammation mediated by nuclear factor κB (NF-κB) signaling is implicated in this process, we examined the spatial, temporal, and cell type-specific activation profile of canonical NF-κB signaling during tendon healing. NF-κB signaling was maintained through all phases of tendon healing in mice, including the remodeling phase, and tenocytes and myofibroblasts from the Scleraxis (Scx) lineage were the predominant populations that retained NF-κB activation into the late stages of repair. We confirmed persistent NF-κB activation in myofibroblasts in human tendon scar tissue. Deleting the canonical NF-κB kinase, IKKβ, in Scx-lineage cells in mice increased apoptosis and the deposition of the matrix protein periostin during the late stages of tendon repair, suggesting that persistent NF-κB signaling may facilitate myofibroblast survival and fibrotic progression. Consistent with this, myofibroblasts in human tendon scar samples displayed enhanced prosurvival signaling compared to control tissue. Together, these data suggest that NF-κB may contribute to fibrotic tendon healing through both inflammation-dependent and inflammation-independent functions, such as NF-κB-mediated cell survival.

Hepatic Antifibrotic Pharmacotherapy: Are We Approaching Success?

The incidence rate and mortality of liver fibrosis caused by various etiologies are high throughout the world. Liver fibrosis, the subsequent cirrhosis and other serious related complications threaten the health of patients and represent a serious medical burden; yet, there is still a lack of approved methods to prevent or reverse liver fibrosis. Therefore, effective hepatic antifibrotic drugs are urgently needed. The activation and proliferation of hepatic stellate cells are still the mechanisms of fibrosis that remain the focus of therapeutic research. In recent years, significant progress has been made in the development and applicability of antifibrosis drugs. In this review, we summarize the effectiveness and safety of available antifibrosis drugs utilizing different targets. In addition, some characteristics of antifibrosis drugs in phase II and III trials are introduced in detail.

Hemistepsin A alleviates liver fibrosis by inducing apoptosis of activated hepatic stellate cells via inhibition of nuclear factor-κB and Akt

Hemistepsin A (HsA), isolated from Hemistepta lyrata (Bunge) Bunge, has the ability to ameliorate hepatitis in mice. However, the effects of H. lyrata and HsA on other types of liver disease have not been explored. In this report, we investigated the effects of H. lyrata and HsA on liver fibrosis and the underlying molecular mechanisms in activated hepatic stellate cells (HSCs). Based on cell viability-guided isolation, we found HsA was the major natural product responsible for H. lyrata-mediated cytotoxicity in LX-2 cells. HsA significantly decreased the viability of LX-2 cells and primary activated HSCs, increased the binding of Annexin V, and altered the expression of apoptosis-related proteins, suggesting that HsA induces apoptosis in activated HSCs. HsA reduced the phosphorylation of IKKε and the transactivation of nuclear factor-κB (NF-κB). Moreover, HsA decreased the phosphorylation of Akt and its downstream signaling molecules. Transfection experiments suggested that inhibition of NF-κB or Akt is essential for HsA-induced apoptosis of HSCs. In a CCl₄-induced liver fibrosis model, HsA administration significantly decreased ALT and AST activities. Furthermore, HsA attenuated CCl₄-mediated collagen deposits and profibrogenic genes expression in hepatic tissue. Thus, HsA may serve as a natural product for managing liver fibrosis through inhibition of NF-κB/Akt-dependent signaling.

TGF-β1/p65/MAT2A pathway regulates liver fibrogenesis via intracellular SAM

BACKGROUND

Hepatic stellate cell (HSC) activation induced by transforming growth factor β1 (TGF-β1) plays a pivotal role in fibrogenesis, while the complex downstream mediators of TGF-β1 in such process are largely unknown.

METHODS

We performed pharmacoproteomic profiling of the mice liver tissues from control, carbon tetrachloride (CCl4)-induced fibrosis and NPLC0393 administrated groups. The target gene MAT2A was overexpressed or knocked down in vivo by tail vein injection of AAV vectors. We examined NF-κB transcriptional activity on MAT2A promoter via luciferase assay. Intracellular SAM contents were analyzed by LC-MS method.

FINDINGS

We found that methionine adenosyltransferase 2A (MAT2A) is significantly upregulated in the CCl4-induced fibrosis mice, and application of NPLC0393, a known small molecule inhibitor of TGF-β1 signaling pathway, inhibits the upregulation of MAT2A. Mechanistically, TGF-β1 induces phosphorylation of p65, i.e., activation of NF-κB, thereby promoting mRNA transcription and protein expression of MAT2A and reduces S-adenosylmethionine (SAM) concentration in HSCs. Consistently, in vivo and in vitro knockdown of MAT2A alleviates CCl4- and TGF-β1-induced HSC activation, whereas in vivo overexpression of MAT2A facilitates hepatic fibrosis and abolishes therapeutic effect of NPLC0393.

INTERPRETATION

This study identifies TGF-β1/p65/MAT2A pathway that is involved in the regulation of intracellular SAM concentration and liver fibrogenesis, suggesting that this pathway is a potential therapeutic target for hepatic fibrosis. FUND: This work was supported by National Natural Science Foundation of China (No. 81500469, 81573873, 81774196 and 31800693), Zhejiang Provincial Natural Science Foundation of China (No. Y15H030004), the National Key Research and Development Program from the Ministry of Science and Technology of China (No. 2017YFC1700200) and the Key Program of National Natural Science Foundation of China (No. 8153000502).

New Concepts on Reversibility and Targeting of Liver Fibrosis; A Review Article

Currently, liver fibrosis and its complications are regarded as critical health problems. With the studies showing the reversible nature of liver fibrogenesis, scientists have focused on understanding the underlying mechanism of this condition in order to develop new therapeutic strategies. Although hepatic stellate cells are known as the primary cells responsible for liver fibrogenesis, studies have shown contributing roles for other cells, pathways, and molecules in the development of fibrosis depending on the etiology of liver fibrosis. Hence, interventions could be directed in the proper way for each type of liver diseases to better address this complication. There are two main approaches in clinical reversion of liver fibrosis; eliminating the underlying insult and targeting the fibrosis process, which have variable clinical importance in the treatment of this disease. In this review, we present recent concepts in molecular pathways of liver fibrosis reversibility and their clinical implications.

Liuweiwuling tablets attenuate BDL-induced hepatic fibrosis via modulation of TGF-β/Smad and NF-κB signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Liuweiwuling (LWWL) tablets contain a six-herb Chinese formula and are commonly prescribed to facilitate nourishment of the liver and kidneys, clear away toxic materials and activate blood circulation. Administration of LWWL is well known for its protective effects on the liver and its capacity to confer long-term stability in patients exhibiting reduced transaminase levels. Clinical studies have reported that LWWL can also be used for the treatment of liver fibrosis with associated treatment regimens resulting in a concomitant reduction in transforming growth factor β1 (TGF-β1) levels in the serum of patients with hepatic fibrosis. TGF-β1 plays a prominent role in stimulating liver fibrogenesis and this effect is mediated by myofibroblasts (MFB) derived from hepatic stellate cells (HSCs). It is likely that this phenomenon underpins the antifibrotic effects associated with LWWL.

AIM

The purpose of this study was to investigate the antifibrotic effects and mechanisms pertaining to LWWL.

METHODS

Hepatic fibrosis was induced in rats following bile duct ligation (BDL). Rats that underwent BDL received daily gavage administration of colchicine (0.2mg/kg per day), LWWL (0.4, 1.6, 6.4g/kg per day) or PBS (for the control group). Pathological changes in hepatic tissue were examined using hematoxylin and eosin (HE) and sirius red staining. Immunohistochemical analysis was performed to monitor α-SMA and type I collagen (Collagen I) protein expression. Real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot analyses were used to monitor the expression of genes and proteins in the TGF-β/Smad signaling pathway, including TGF-β1, bone morphogenic protein and activin membrane-bound inhibitor (Bambi), Smad3, phosphorylated Smad3 (p-Smad3) and Smad7. We also monitored the expression of genes and proteins in the nuclear factor-κB (NF-κB) signaling pathway, including NF-κB p65, IκBα and phosphorylation of IκBα (p-IκBα), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6) and interleukin 1β (IL-1β).

RESULTS

LWWL dose-dependently inhibited BDL-induced liver injury and hepatic fibrosis in rats. Furthermore, LWWL reduced liver tissue collagen deposition, hydroxyproline content, liver dysfunction and α-SMA expression in BDL-induced hepatic fibrosis rats. Moreover, LWWL markedly prevented activation of the TGF-β/Smad signaling pathway by inhibiting expression of Smad2/3 and phosphorylation of Smad3, and upregulating the expression of Bambi and Smad7. In addition, LWWL regulated the expression of the inflammatory cytokines IL-1β, TNF-α and IL-6 by inhibiting the activation of NF-κB p65 and the phosphorylation of IκBα, and increasing the expression of IκBα.

CONCLUSIONS

LWWL can attenuate BDL-induced hepatic fibrosis in rats, and this effect may be due to modulation of the NF-κB-dependent inflammatory response and activation of HSC and TGF-β/Smad-mediated synthesis and degradation of Collagen I.

Proanthocyanidin protects against cisplatin-induced oxidative liver damage through inhibition of inflammation and NF-κβ/TLR-4 pathway

Although cisplatin (CIS) is a highly effective anticancer drug, hepatotoxicity is one of the most common adverse effects associated with its use. Recently, reactive oxygen species (ROS) and inflammation are suggested to be key factors in the pathophysiology of CIS-induced acute liver damage. The aim of this study is to investigate the possible protective effect of proanthocyanidin (PRO) against CIS-induced acute hepatotoxicity. Rats were divided into four groups: 1, Control; 2, PRO; 3, CIS; and 4, PRO + CIS. Biochemical studies and histopathology were used to assess liver damage. ROS, inflammatory cytokines, nuclear factor kappa beta (NF-κβ), inducible cyclooxygenase enzyme (COX-2), inducible nitric oxide synthase (iNOS), toll-like receptor-4 (TLR-4) gene expression, and apoptotic markers were also assessed. PRO pretreatment protected the liver against CIS-induced toxicity as indicated by decreased plasma levels of liver function enzymes and the normal liver histopathology observed in the PRO + CIS group. PRO pretreatment also diminished indicators of oxidative stress in the liver, including nitric oxide (NO) and malondialdehyde (MDA). It also increased the antioxidants, reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) in the liver. Plasma interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor-alpha (TNF-α) were all reduced. Liver gene expression of NF-κβ, COX-2, iNOS, and TLR-4 were all downregulated. Furthermore, PRO administration downregulated the liver expression of the apoptotic marker, Bax, while upregulated the antiapoptotic marker, Bcl2. In conclusion, our results revealed that PRO may protect against CIS-induced acute liver damage mainly through inhibition of ROS, inflammation, and apoptosis.

A randomised controlled trial of losartan as an anti-fibrotic agent in non-alcoholic steatohepatitis

Introduction

Non-alcoholic fatty liver disease (NAFLD) is a common liver disease worldwide. Experimental and small clinical trials have demonstrated that angiotensin II blockers (ARB) may be anti-fibrotic in the liver. The aim of this randomised controlled trial was to assess whether treatment with Losartan for 96 weeks slowed, halted or reversed the progression of fibrosis in patients with non-alcoholic steatohepatitis (NASH).

Methods

Double-blind randomised-controlled trial of Losartan 50 mg once a day versus placebo for 96 weeks in patients with histological evidence of NASH. The primary outcome for the study was change in histological fibrosis stage from pre-treatment to end-of-treatment.

Results

The study planned to recruit 214 patients. However, recruitment was slower than expected, and after 45 patients were randomised (median age 55; 56% male; 60% diabetic; median fibrosis stage 2), enrolment was suspended. Thirty-two patients (15 losartan and 17 placebo) completed follow up period: one patient (6.7%) treated with losartan and 4 patients (23.5%) in the placebo group were “responders” (lower fibrosis stage at follow up compared with baseline). The major reason for slow recruitment was that 39% of potentially eligible patients were already taking an ARB or angiotensin converting enzyme inhibitor (ACEI), and 15% were taking other prohibited medications.

Conclusions

Due to the widespread use of ACEI and ARB in patients with NASH this trial failed to recruit sufficient patients to determine whether losartan has anti-fibrotic effects in the liver.

Trial registration

ISRCTN 57849521

FXR agonist obeticholic acid reduces hepatic inflammation and fibrosis in a rat model of toxic cirrhosis

Hepatic inflammation drives hepatic stellate cells (HSC), resulting in liver fibrosis. The Farnesoid-X receptor (FXR) antagonizes inflammation through NF-κB inhibition. We investigated preventive and therapeutic effects of FXR agonist obeticholic acid (OCA) on hepatic inflammation and fibrosis in toxic cirrhotic rats. Cirrhosis was induced by thioacetamide (TAA) intoxication. OCA was given during or after intoxication with vehicle-treated rats as controls. At sacrifice, fibrosis, hemodynamic and biochemical parameters were assessed. HSC activation, cell turn-over, hepatic NF-κB activation, pro-inflammatory and pro-fibrotic cytokines were determined. The effect of OCA was further evaluated in isolated HSC, Kupffer cells, hepatocytes and liver sinusoidal endothelial cells (LSEC). OCA decreased hepatic inflammation and fibrogenesis during TAA-administration and reversed fibrosis in established cirrhosis. Portal pressure decreased through reduced intrahepatic vascular resistance. This was paralleled by decreased expression of pro-fibrotic cytokines (transforming growth-factor β, connective tissue growth factor, platelet-derived growth factor β-receptor) as well as markers of hepatic cell turn-over, by blunting effects of pro-inflammatory cytokines (e.g. monocyte chemo-attractant protein-1). In vitro, OCA inhibited both LSEC and Kupffer cell activation; while HSC remained unaffected. This related to NF-κB inhibition via up-regulated IκBα. In conclusion, OCA inhibits hepatic inflammation in toxic cirrhotic rats resulting in decreased HSC activation and fibrosis.

Pomegranate protects liver against cecal ligation and puncture-induced oxidative stress and inflammation in rats through TLR4/NF-κB pathway inhibition

Acute liver injury secondary to sepsis is a major challenge in intensive care unit. This study was designed to investigate potential protective effects of pomegranate against sepsis-induced acute liver injury in rats and possible underlying mechanisms. Pomegranate was orally given (800mg/kg/day) for two weeks before sepsis induction by cecal ligation and puncture (CLP). Pomegranate improved survival and attenuated liver inflammatory response, likely related to downregulation of mRNA expression of toll like recptor-4, reduced nuclear translocation and DNA binding activity of proinflammatory transcription factor NF-κB subunit p65, decreased mRNA and protein expression of tumor necrosis factor-alpha and reduction in myeloperoxidase activity and mRNA expression. Pomegranate also decreased CLP-induced oxidative stress as reflected by decreased malondialdehyde content, and increased reduced glutathione level and superoxide dismutase activity. These results confirm the antiinflammatory and antioxidant effects of pomegranate in CLP-induced acute liver injury mediated through inhibiting TLR4/NF-κB pathway, lipid peroxidation and neutrophil infiltration.

Basic fibroblast growth factor-treated adipose tissue-derived mesenchymal stem cell infusion to ameliorate liver cirrhosis via paracrine hepatocyte growth factor

BACKGROUND AND AIM

Recent studies show that adipose tissue-derived mesenchymal stem cells have potential clinical applications. However, the mechanism has not been fully elucidated yet. Here, we investigated the effect of basic fibroblast growth factor-treated adipose tissue-derived mesenchymal stem cells infusion on a liver fibrosis rat model and elucidated the underlying mechanism.

METHODS

Adipose tissue-derived mesenchymal stem cells were infused into carbon tetrachloride-induced hepatic fibrosis rats through caudal vein. Liver functions and pathological changes were assessed. A co-culture model was used to clarify the potential mechanism.

RESULTS

Basic fibroblast growth factor treatment markedly improved the proliferation, differentiation, and hepatocyte growth factor expression ability of adipose tissue-derived mesenchymal stem cells. Although adipose tissue-derived mesenchymal stem cells infusion alone slightly ameliorated liver functions and suppressed fibrosis progression, basic fibroblast growth factor-treatment significantly enhanced the therapeutic effect in association with elevated hepatocyte growth factor expression. Moreover, double immunofluorescence staining confirmed that the infused cells located in fibrosis area. Furthermore, co-culture with adipose tissue-derived mesenchymal stem cell led to induction of hepatic stellate cell apoptosis and enhanced hepatocyte proliferation. However, these effects were significantly weakened by knockdown of hepatocyte growth factor. Mechanism investigation revealed that co-culture with adipose tissue-derived mesenchymal stem cells activated c-jun N-terminal kinase-p53 signaling in hepatic stellate cell and promoted apoptosis.

CONCLUSIONS

Basic fibroblast growth factor treatment enhanced the therapeutic effect of adipose tissue-derived mesenchymal stem cells, and secretion of hepatocyte growth factor from adipose tissue-derived mesenchymal stem cells plays a critical role in amelioration of liver injury and regression of fibrosis.

Serum amyloid A induces interleukin-6 in dermal fibroblasts via Toll-like receptor 2, interleukin-1 receptor-associated kinase 4 and nuclear factor-κB

Systemic sclerosis is an autoimmune idiopathic connective tissue disease, characterized by vasculopathy, inflammation and fibrosis. There appears to be a link between inflammation and fibrosis, although the exact nature of the relationship is unknown. Serum amyloid A (SAA) is an acute-phase protein that is elevated up to 1000-fold in times of infection or inflammation. This acute-phase reactant, as well as being a marker of inflammation, may initiate signals in a cytokine-like manner, possibly through toll-like receptors (TLRs) promoting inflammation. This study addressed the role of SAA in initiating interleukin-6 (IL-6) production in dermal fibroblasts and the role of TLR2 in this system. We show that SAA induces IL-6 secretion in healthy dermal fibroblasts and that blockade of TLR2 with a neutralizing antibody to TLR2 or specific small interfering RNA attenuated the SAA-induced IL-6 secretion and that this was also mediated through the TLR adaptor protein IL-1 receptor-associated kinase 4. The effect is nuclear factor-κB-mediated because blockade of nuclear factor-κB reduced the induction. We also demonstrate that dermal fibroblasts express TLR2; this is functional and over-expressed in the fibroblasts of patients with systemic sclerosis. Taken together these data suggest that SAA is a danger signal that initiates IL-6 signalling in systemic sclerosis via enhanced TLR2 signalling.

Extracellular matrix and liver disease

SIGNIFICANCE

The extracellular matrix (ECM) is a dynamic microenvironment that undergoes continuous remodeling, particularly during injury and wound healing. Chronic liver injury of many different etiologies such as viral hepatitis, alcohol abuse, drug-induced liver injury, obesity and insulin resistance, metabolic disorders, and autoimmune disease is characterized by excessive deposition of ECM proteins in response to persistent liver damage.

CRITICAL ISSUES

This review describes the main collagenous and noncollagenous components from the ECM that play a significant role in pathological matrix deposition during liver disease. We define how increased myofibroblasts (MF) from different origins are at the forefront of liver fibrosis and how liver cell-specific regulation of the complex scarring process occurs.

RECENT ADVANCES

Particular attention is paid to the role of cytokines, growth factors, reactive oxygen species, and newly identified matricellular proteins in the regulation of fibrillar type I collagen, a field to which our laboratory has significantly contributed over the years. We compile data from recent literature on the potential mechanisms driving fibrosis resolution such as MF' apoptosis, senescence, and reversal to quiescence.

FUTURE DIRECTIONS

We conclude with a brief description of how epigenetics, an evolving field, can regulate the behavior of MF and of how new "omics" tools may advance our understanding of the mechanisms by which the fibrogenic response to liver injury occurs.

Cellular and molecular mechanisms in liver fibrogenesis

Liver fibrogenesis is a dynamic and highly integrated molecular, tissue and cellular process, potentially reversible, that drives the progression of chronic liver diseases (CLD) towards liver cirrhosis and hepatic failure. Hepatic myofibroblasts (MFs), the pro-fibrogenic effector cells, originate mainly from activation of hepatic stellate cells and portal fibroblasts being characterized by a proliferative and survival attitude. MFs also contract in response to vasoactive agents, sustain angiogenesis and recruit and modulate activity of cells of innate or adaptive immunity. Chronic activation of wound healing and oxidative stress as well as derangement of epithelial-mesenchymal interactions are "major" pro-fibrogenic mechanisms, whatever the etiology. However, literature has outlined a complex network of pro-fibrogenic factors and mediators proposed to modulate CLD progression, with some of them being at present highly debated in the field, including the role of epithelial to mesenchymal transition and Hedgehog signaling pathways. Hypoxia and angiogenesis as well as inflammasomes are recently emerged as ubiquitous pro-inflammatory and pro-fibrogenic determinants whereas adipokines are mostly involved in CLD related to metabolic disturbances (metabolic syndrome and/or obesity and type 2 diabetes). Finally, autophagy as well as natural killer and natural killer-T cells have been recently proposed to significantly affect fibrogenic CLD progression.

Osteopontin delays resolution of liver fibrosis

To date, considerable progress has been made both in the mechanisms driving liver fibrosis and in the prevention of disease progression. Resolution of liver fibrosis is an emerging field in hepatology; yet, the mediators involved remain elusive. Earlier work from our laboratory demonstrated that the matricellular cytokine osteopontin (OPN) is pro-fibrogenic by promoting hepatic stellate cell (HSC) activation and extracellular matrix (ECM) deposition in vitro and in vivo and specifically by governing fibrillar collagen-I expression, the key pro-fibrogenic protein. Here we hypothesized that OPN could also delay the resolution of liver fibrosis by sustaining collagen-I synthesis or by preventing its degradation. To demonstrate this, wild-type (WT) and OPN-knockout (Opn(-/-)) mice were administered thioacetamide (TAA) in the drinking water for 4 months. Half of the mice were killed at 4 months to assess the extent of fibrosis at the peak of injury, and the rest of the mice were killed 2 months after TAA withdrawal to determine the rate of fibrosis resolution. Following TAA cessation, livers from Opn(-/-) mice showed no centrilobular and parenchymal necrosis along with faster ECM remodeling than WT mice. The latter was quantified by less fibrillar collagen-I immunostaining. Western blot analysis demonstrated a significant decrease in fibrillar collagen-I and in tissue inhibitor of metalloproteinase-1 (TIMP-1) in Opn(-/-) mice undergoing fibrosis resolution compared with WT mice. In conclusion, these results suggest that OPN delays liver fibrosis resolution due to sustained fibrillar collagen-I deposition; hence, inhibiting OPN could be an effective therapeutic strategy for resolving liver fibrosis.

Protective effect of the herbal medicine Gan‑fu‑kang against carbon tetrachloride‑induced liver fibrosis in rats

The aim of the present study was to investigate the effect of a herbal medicine formula, Gan-fu-kang (GFK), on the treatment of liver fibrosis in rats and the mechanisms via which it exerts its effect. Liver fibrosis was induced in rats by subcutaneous injection of carbon tetrachloride (CCl4) at 0.5 mg/kg body weight, twice a week for 8 weeks. The rats were randomly selected to receive saline or GFK at 31.25, 312.5 or 3,125 mg/kg body weight/day between weeks 9 and 20. An additional group of rats without CCl4 injection was used as the baseline. In the liver fibrosis model rats, an increase in plasma liver enzymes, fibrotic markers in serum and liver fibrosis, production of α-smooth muscle actin, matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-1, synthesis of collagen and activation of the Wnt/β-catenin signaling pathway were observed. GFK administration was found to significantly reduce these changes. Results of this study demonstrate that GFK has a protective and therapeutic effect on liver fibrosis induced by CCl4, which may be associated with its inhibitory activity on HSC proliferation and collagen synthesis, effectively downregulating Wnt/β-catenin signaling.

Mouse models for liver cancer

Hepatocellular carcinoma (HCC), the most common form of primary liver cancer is the third leading cause of cancer-related cell death in human and the fifth in women worldwide. The incidence of HCC is increasing despite progress in identifying risk factors, understanding disease etiology and developing anti-viral strategies. Therapeutic options are limited and survival after diagnosis is poor. Therefore, better preventive, diagnostic and therapeutic tools are urgently needed, in particular given the increased contribution from systemic metabolic disease to HCC incidence worldwide. In the last three decades, technological advances have facilitated the generation of genetically engineered mouse models (GEMMs) to mimic the alterations frequently observed in human cancers or to conduct intervention studies and assess the relevance of candidate gene networks in tumor establishment, progression and maintenance. Because these studies allow molecular and cellular manipulations impossible to perform in patients, GEMMs have improved our understanding of this complex disease and represent a source of great potential for mechanism-based therapy development. In this review, we provide an overview of the current state of HCC modeling in the mouse, highlighting successes, current challenges and future opportunities.

Inhibition of RelA-Ser536 phosphorylation by a competing peptide reduces mouse liver fibrosis without blocking the innate immune response

Phosphorylation of the RelA subunit at serine 536 (RelA-P-Ser536) is important for hepatic myofibroblast survival and is mechanistically implicated in liver fibrosis. Here, we show that a cell-permeable competing peptide (P6) functions as a specific targeted inhibitor of RelA-P-Ser536 in vivo and exerts an antifibrogenic effect in two progressive liver disease models, but does not impair hepatic inflammation or innate immune responses after lipopolysaccharide challenge. Using kinase assays and western blotting, we confirm that P6 is a substrate for the inhibitory kappa B kinases (IKKs), IKKα and IKKβ, and, in human hepatic myofibroblasts, P6 prevents RelA-P-Ser536, but does not affect IKK activation of IκBα. We demonstrate that RelA-P-Ser536 is a feature of human lung and skin fibroblasts, but not lung epithelial cells, in vitro and is present in sclerotic skin and diseased lungs of patients suffering from idiopathic pulmonary fibrosis.

CONCLUSION

RelA-P-Ser536 may be a core fibrogenic regulator of fibroblast phenotype.

Identification of a liver cirrhosis signature in plasma for predicting hepatocellular carcinoma risk in a population-based cohort of hepatitis B carriers

Liver cirrhosis is a critical state in the natural course of hepatocellular carcinoma (HCC). We sought to investigate the potential of in-depth proteomics to reveal plasma protein signatures that reflect common networks/pathways of liver cirrhosis, and to determine whether the cirrhosis-related signature in plasma is linked to the development of HCC among hepatitis B virus (HBV) carriers. We first compared plasma protein profiles using a 174-antibody microarray system between three groups of HBV carriers with different Child's grades of cirrhosis, which revealed a panel of 45 differentially expressed proteins with a high accuracy for discriminating Child's B/C. Ingenuity Pathway Analysis identified two main up-regulated networks connecting the 45 proteins that were most enriched for genes in the pathway of hepatic stellate cell activation. A parsimonious subset of 11 pathway-based proteins was then selected for quantification to correlate with HCC risk among 49 HCC cases and 50 controls in a nested case-control study within a 16-yr follow-up cohort of HBV carriers. A high risk score derived from a principal component analysis, which was used to extract the cluster structure of the 11 proteins, was associated with HCC (odds ratio = 4.83, 95% confidence interval: 1.26-18.56) even after adjustment for viral and clinical variables, implying the involvement of a pattern of coordinated proteins. Stepwise logistic regression on the 11 proteins revealed ICAM-2 as an independent predictor for HCC. These findings may give further insight into the pathobiology of hepatocarcinogenesis, allow testing of the cirrhosis-related plasma protein signature as a potential predictive biomarker for HCC.

Protective effect of ligustrazine on residual liver tissue in rats after hepatectomy

AIM: To investigate the effect of ligustrazine in alleviating inflammation and inhibiting the activation of NF-κB in rats after liver trauma.

METHODS: Sixty rats which underwent 2/3 hepatectomy were randomly and equally divided into three groups. Group A was intraperitoneally injected with normal saline, and groups B and C were injected with PDTC and ligustrazine, respectively. The general status of the rats was observed, and changes in serum levels of aminotransferases were measured. Hepatic pathological changes were examined, and the activation of NF-κB was investigated by Western blot.

RESULTS: Cellular swelling was milder in group C than in group A. Serum levels of ALT at 6 and 10 h after the operation were significantly lower in group C than in group A (6 h: 488.9 U/L ± 59.2 U/L vs 651.6 ± 65.3 U/L; 10 h: 670.0 U/L ± 73.4 U/L vs 930.0 U/L ± 62.9 U/L; both P < 0.05). Serum levels of AST at 6 and 10 h were also significantly lower in group C than in group A (6 h: 1113.1 U/L ± 138.7 U/L vs 1315.0 U/L ± 111.0 U/L; 10 h: 1388.2 U/L ± 209.6 U/L vs 1728.4 U/L ± 87.3 U/L; both P < 0.05). The levels of activated NF-κB in group C (0.78 ± 0.04, 0.75 ± 0.07) were lower than those in group A (both were 1), higher than those in group B (0.68 ± 0.09, 0.66 ± 0.04) at 2 and 10 h (all P < 0.05), but were comparable to that in group B at 6 h (0.71 ± 0.07 vs 0.64 ± 0.09, P > 0.05).

CONCLUSION: Ligustrazine protects the posttraumatic liver tissue possibly by inhibiting the activation of NF-κB.

Mesenchymal cell proliferation and programmed cell death: key players in fibrogenesis and new targets for therapeutic intervention

An exquisite equilibrium between cell proliferation and programmed cell death is required to maintain physiological homeostasis. In inflammatory bowel disease, and especially in Crohn's disease, enhanced proliferation along with defective apoptosis of immune cells are considered key elements of pathogenesis. Despite the relatively limited attention that has been given to research efforts devoted to intestinal fibrosis to date, there is evidence suggesting that enhanced proliferation along with defective programmed cell death of mesenchymal cells can significantly contribute to the development of excessive fibrogenesis in many different tissues. Moreover, some therapies have demonstrated potential antifibrogenic efficacy through the regulation of mesenchymal cell proliferation and programmed cell death. Further understanding of the pathways involved in the regulation of mesenchymal cell proliferation and apoptosis is, however, required.

Pathogenesis of liver fibrosis

Liver fibrosis is a major cause of morbidity and mortality worldwide due to chronic viral hepatitis and, more recently, from fatty liver disease associated with obesity. Hepatic stellate cell activation represents a critical event in fibrosis because these cells become the primary source of extracellular matrix in liver upon injury. Use of cell-culture and animal models has expanded our understanding of the mechanisms underlying stellate cell activation and has shed new light on genetic regulation, the contribution of immune signaling, and the potential reversibility of the disease. As pathways of fibrogenesis are increasingly clarified, the key challenge will be translating new advances into the development of antifibrotic therapies for patients with chronic liver disease.

Toll-like receptor 4 signaling in liver injury and hepatic fibrogenesis

Toll-like receptors (TLRs) are a family of transmembrane pattern recognition receptors (PRR) that play a key role in innate and adaptive immunity by recognizing structural components unique to bacteria, fungi and viruses. TLR4 is the most studied of the TLRs, and its primary exogenous ligand is lipopolysaccharide, a component of Gram-negative bacterial walls. In the absence of exogenous microbes, endogenous ligands including damage-associated molecular pattern molecules from damaged matrix and injured cells can also activate TLR4 signaling. In humans, single nucleotide polymorphisms of the TLR4 gene have an effect on its signal transduction and on associated risks of specific diseases, including cirrhosis. In liver, TLR4 is expressed by all parenchymal and non-parenchymal cell types, and contributes to tissue damage caused by a variety of etiologies. Intact TLR4 signaling was identified in hepatic stellate cells (HSCs), the major fibrogenic cell type in injured liver, and mediates key responses including an inflammatory phenotype, fibrogenesis and anti-apoptotic properties. Further clarification of the function and endogenous ligands of TLR4 signaling in HSCs and other liver cells could uncover novel mechanisms of fibrogenesis and facilitate the development of therapeutic strategies.

Bone marrow mesenchymal stem cells modulate cell proliferation and apoptosis and RohA expression in rat hepatic stellate cells

AIM: To observe the regulatory effects of bone marrow mesenchymal stem cells (BMSCs) on cell proliferation and apoptosis and RohA expression in rat hepatic stellate cells (HSCs) and to explore the possible mechanisms involved.

METHODS: BMSCs were isolated from Sprague-Dawley rats, cultured and purified in vitro. Activated HSCs were cultured on plastic plates. A co-culture system was established by culturing BMSCs in the Transwell insert and HSCs on the plastic plates (6 wells). Normal rat fibroblasts, BMSCs and HSCs were cultured alone as controls. A part of cells were pretreated with rabbit polyclonal anti-c-met antibody according to experimental needs. Cell proliferation and apoptosis were determined by MTT assay and flow cytometry, respectively. The expression of RohA mRNA and protein in HSCs was determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively. Cell supernatants were harvested to determine the concentration of hepatocyte growth factor (HGF) by enzyme-linked immunosorbent assay (ELISA).

RESULTS: BMSCs inhibited the proliferation of HSCs. After 24 h and 48 h of co-culture, the reduced rates of HSC proliferation were 12.21% and 35.43%, respectively. The reduced rates of HSC proliferation in the experimental group were significantly higher than those in the other three groups (all P < 0.01). The apoptosis rate of HSCs at 48 h was 25.80% in the experimental group, significantly higher than those in the other three groups (all P < 0.01). After 48 h of co-culture, BMSCs significantly inhibited the expression of RohA mRNA and protein in HSCs when compared with the other three groups (all P < 0.01). The concentrations of HGF in co-culture supernatants in the experimental group at 24 and 48 h were 250 ng/L and 570 ng/L, respectively, significantly higher than those in the supernatants of BMSCs and HSCs cultured alone (all P < 0.01).

CONCLUSION: BMSCs inhibit proliferation, promote apoptosis and reduce RohA expression in rat activated HSCs perhaps in an HGF paracrine-dependent manner.

Role of nuclear factor kappaB in liver health and disease

NF-kappaB (nuclear factor kappaB) is a heterodimeric transcription factor that is constitutively expressed in all cell types and has a central role as a transcriptional regulator in response to cellular stress. In the present review, we discuss the role of NF-kappaB signalling in the maintenance of liver homoeostasis as well as in the pathogenesis of a wide variety of conditions affecting the liver, including viral hepatitis, steatohepatitis, cirrhosis and hepatocellular carcinoma. Much of the current knowledge of NF-kappaB signalling in the liver relates to the canonical pathway, the IKK [IkappaB (inhibitor of kappaB) kinase] complex and the RelA subunit. We explore the weaknesses of the experimental approaches to date and suggest that further work is needed to investigate in detail the discreet functions of each of the Rel subunits in liver physiology and disease.

The c-Rel subunit of nuclear factor-kappaB regulates murine liver inflammation, wound-healing, and hepatocyte proliferation

In this study, we determined the role of the nuclear factor-kappaB (NF-kappaB) subunit c-Rel in liver injury and regeneration. In response to toxic injury of the liver, c-Rel null (c-rel(-/-)) mice displayed a defect in the neutrophilic inflammatory response, associated with impaired induction of RANTES (Regulated upon Activation, Normal T-cell Expressed, and Secreted; also known as CCL5). The subsequent fibrogenic/wound-healing response to both chronic carbon tetrachloride and bile duct ligation induced injury was also impaired and this was associated with deficiencies in the expression of fibrogenic genes, collagen I and alpha-smooth muscle actin, by hepatic stellate cells. We additionally report that c-Rel is required for the normal proliferative regeneration of hepatocytes in response to toxic injury and partial hepatectomy. Absence of c-Rel was associated with blunted and delayed induction of forkhead box M1 (FoxM1) and its downstream targets cyclin B1 and Cdc25C. Furthermore, isolated c-rel(-/-) hepatocytes expressed reduced levels of FoxM1 and a reduced rate of basal and epidermal growth factor-induced DNA synthesis. Chromatin immunoprecipitation revealed that c-Rel binding to the FoxM1 promoter is induced in the regenerating liver.

CONCLUSION

c-Rel has multiple functions in the control of liver homeostasis and regeneration and is a transcriptional regulator of FoxM1 and compensatory hepatocyte proliferation.

Biphasic dose response in low level light therapy

The use of low levels of visible or near infrared light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing cell death and tissue damage has been known for over forty years since the invention of lasers. Despite many reports of positive findings from experiments conducted in vitro, in animal models and in randomized controlled clinical trials, LLLT remains controversial in mainstream medicine. The biochemical mechanisms underlying the positive effects are incompletely understood, and the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence, power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones. A biphasic dose response has been frequently observed where low levels of light have a much better effect on stimulating and repairing tissues than higher levels of light. The so-called Arndt-Schulz curve is frequently used to describe this biphasic dose response. This review will cover the molecular and cellular mechanisms in LLLT, and describe some of our recent results in vitro and in vivo that provide scientific explanations for this biphasic dose response.

Transcriptional regulation of hepatic stellate cells

Hepatic stellate cell (HSC) activation is a process of cellular transdifferentiation in which, upon liver injury, the quiescent vitamin A storing perisinusoidal HSC is converted into a wound-healing myofibroblast and acquires potent pro-inflammatory and pro-fibrogenic activities. This remarkable phenotypic transformation is underpinned by changes in the expression of a vast number of genes. In this review we survey current knowledge of the transcription factors that either control HSC activation or which regulate specific fibrogenic functions of the activated HSC such as collagen expression, proliferation and resistance to apoptosis.

Heat shock protein 90 inhibitor induces apoptosis and attenuates activation of hepatic stellate cells

Activated hepatic stellate cells (HSCs) are major participants in hepatic fibrosis; thus, the induction of HSC apoptosis has been proposed as an antifibrotic treatment strategy. Heat shock protein (Hsp) 90 is a molecular chaperone that stabilizes major signal transduction proteins, and its inhibitors have antitumor activity. In this study, the susceptibility of HSCs to an Hsp90 inhibitor was evaluated. LX-2 cells, an immortalized human HSC line, 17-(allylamino)-17-demethoxygeldanamycin (17AAG), an Hsp90 inhibitor, and monensin, an acidic sphingomyelinase inhibitor, were used in this study. Cellular apoptosis was quantified by 4',6-diamidino-2-phenylindole dihydrochloride staining, and signaling cascades were explored using immunoblotting and immunoprecipitation techniques. Nuclear factor (NF) kappaB activities were evaluated by immunofluorescent microscopy and enzyme-linked immunosorbent assay. Collagen alpha1 and alpha-smooth muscle actin expressions were determined by real-time reverse transcription-polymerase chain reaction and immunoblotting, respectively. It was found that 17AAG induced HSC apoptosis and that caspase 8 cleavage preceded the downstream activation of apoptotic signaling cascades. Furthermore, this caspase 8 activation was dependent on ceramide generation by acidic sphingomyelinase. In addition, 17AAG prevented NFkappaB nuclear translocation and activation, specifically by inducing complex formation between NFkappaB and the glucocorticoid receptor. In accordance, NFkappaB-dependent cellular FLICE-like inhibitory protein expression level was found to be reduced by 17AAG. Finally, 17AAG down-regulated collagen alpha1 and alpha-smooth muscle actin expression levels in HSCs before inducing apoptosis. These results demonstrate that the Hsp90 inhibitor induces HSC apoptosis via a sphingomyelinase- and NFkappaB-dependent mechanism. Because this inhibitor also reduces HSC activation before apoptosis, Hsp90 inhibitor treatment might be therapeutically useful as an antifibrotic strategy in a variety of liver diseases.

Angiotensin II activates I kappaB kinase phosphorylation of RelA at Ser 536 to promote myofibroblast survival and liver fibrosis

BACKGROUND & AIMS

The transcription factor nuclear factor-kappaB (NF)-kappaB promotes survival of hepatic myofibroblasts and fibrogenesis through poorly defined mechanisms. We investigated the activities of angiotensin II and I kappaB kinase (IKK) in regulation of NF-kappaB activity and the role of these proteins in liver fibrosis in rodents and humans.

METHODS

Phosphorylation of the NF-kappaB subunit RelA at serine 536 (P-Ser(536)-RelA) was detected by immunoblot and immunohistochemical analyses. P-Ser(536)-RelA function was assessed using vectors that expressed mutant forms of RelA, cell-permeable blocking peptides, and assays for RelA nuclear transport and apoptosis. Levels of P-Ser(536)-RelA were compared with degree of fibrosis in liver sections from chronically injured rats and patients with hepatitis C virus-mediated fibrosis who had been treated with the AT1 antagonist losartan.

RESULTS

Constitutive P-Ser(536)-RelA is a feature of human hepatic myofibroblasts, both in vitro and in situ in diseased livers. Autocrine angiotensin II stimulated IKK-mediated phosphorylation of RelA at Ser(536), which was required for nuclear transport and transcriptional activity of NF-kappaB. Inhibition of angiotensin II, the angiotensin II receptor type 1 (AT1), or IKK blocked Ser(536) phosphorylation and stimulated myofibroblast apoptosis. Treatment of fibrotic rodent liver with the angiotensin converting enzyme (ACE) inhibitor captopril or the IKK inhibitor sulphasalazine resulted in loss of P-Ser(536)-RelA-positive myofibroblasts and fibrosis regression. In human liver samples, increased numbers of P-Ser(536)-RelA-positive cells were associated with fibrosis that regressed following exposure to losartan.

CONCLUSIONS

An autocrine pathway that includes angiotensin II, IKK, and P-Ser(536)-RelA regulates myofibroblast survival and can be targeted to stimulate therapeutic regression of liver fibrosis.

Toll-like receptors, wound healing, and carcinogenesis

Following acute injury, the concerted action of resident and nonresident cell populations evokes wound healing responses that entail a temporary increase in inflammation, extracellular matrix production, and proliferation to ultimately restore normal organ architecture. However, chronic injury evokes a perpetuating wound healing response promoting the development of fibrosis, organ failure, and cancer. Recent evidence points toward toll-like receptors (TLRs) as important regulators of inflammatory signals in wound healing. Here, we will review the activation of TLRs by different endogenous and bacterial TLR ligands during wound healing, and the contribution of TLR-induced signals to injury, fibrogenesis, regeneration, and carcinogenesis. We will discuss the hypothesis that TLRs act as sensors of danger signals in injured tissue to switch the wound healing response toward fibrogenesis and regeneration as a protective response to imminent danger at the cost of an increased long-term risk of developing scars and cancer.

Fibrosis and cirrhosis reversibility - molecular mechanisms

The concept that liver fibrosis is a dynamic process with potential for regression as well as progression has emerged in parallel with clinical evidence for remodeling of fibrotic extracellular matrix in patients who can be effectively treated for their underlying cause of liver disease. This article reviews recent discoveries relating to the cellular and molecular mechanisms that regulate fibrosis regression, with emphasis on studies that have used experimental in vivo models of liver disease. Apoptosis of hepatic myofibroblasts is discussed. The functions played by transcription factors, receptor-ligand interactions, and cell-matrix interactions as regulators of the lifespan of hepatic myofibroblasts are considered, as are the therapeutic opportunities for modulating these functions. Growth factors, proteolytic enzymes, and their inhibitors are discussed in detail.

Sphingosine 1-phosphate regulates regeneration and fibrosis after liver injury via sphingosine 1-phosphate receptor 2

Sphingosine 1-phosphate (S1P), a bioactive lipid mediator, stimulates proliferation and contractility in hepatic stellate cells, the principal matrix-producing cells in the liver, and inhibits proliferation via S1P receptor 2 (S1P(2)) in hepatocytes in rats in vitro. A potential role of S1P and S1P(2) in liver regeneration and fibrosis was examined in S1P(2)-deficient mice. Nuclear 5-bromo-2'-deoxy-uridine labeling, proliferating cell nuclear antigen (PCNA) staining in hepatocytes, and the ratio of liver weight to body weight were enhanced at 48 h in S1P(2)-deficient mice after a single carbon tetrachloride (CCl(4)) injection. After dimethylnitrosamine (DMN) administration with a lethal dose, PCNA staining in hepatocytes was enhanced at 48 h and survival rate was higher in S1P(2)-deficient mice. Serum aminotransferase level was unaltered in those mice compared with wild-type mice in both CCl(4)- and DMN-induced liver injury, suggesting that S1P(2) inactivation accelerated regeneration not as a response to enhanced liver damage. After chronic CCl(4) administration, fibrosis was less apparent, with reduced expression of smooth-muscle alpha-actin-positive cells in the livers of S1P(2)-deficient mice, suggesting that S1P(2) inactivation ameliorated CCl(4)-induced fibrosis due to the decreased accumulation of hepatic stellate cells. Thus, S1P plays a significant role in regeneration and fibrosis after liver injury via S1P(2).

Fish oil targets PTEN to regulate NFkappaB for downregulation of anti-apoptotic genes in breast tumor growth

The molecular mechanism for the beneficial effect of fish oil on breast tumor growth is largely undefined. Using the xenograft model in nude mice, we for the first time report that the fish oil diet significantly increased the level of PTEN protein in the breast tumors. In addition, the fish oil diet attenuated the PI 3 kinase and Akt kinase activity in the tumors leading to significant inhibition of NFkappaB activation. Fish oil diet also prevented the expression of anti-apoptotic proteins Bcl-2 and Bcl-XL in the breast tumors with concomitant increase in caspase 3 activity. To extend these findings we tested the functional effects of DHA and EPA, the two active omega-3 fatty acids of fish oil, on cultured MDA MB-231 cells. In agreement with our in vivo data, DHA and EPA treatment increased PTEN mRNA and protein expression and inhibited the phosphorylation of p65 subunit of NFkappaB in MDA MB-231 cells. Furthermore, DHA and EPA reduced expression of Bcl-2 and Bcl-XL. NFkappaB DNA binding activity and NFkappaB-dependent transcription of Bcl-2 and Bcl-XL genes were also prevented by DHA and EPA treatment. Finally, we showed that PTEN expression significantly inhibited NFkappaB-dependent transcription of Bcl-2 and Bcl-XL genes. Taken together, our data reveals a novel signaling pathway linking the fish oil diet to increased PTEN expression that attenuates the growth promoting signals and augments the apoptotic signals, resulting in breast tumor regression.

Stromal myofibroblasts are drivers of invasive cancer growth

Tissue integrity is maintained by the stroma in physiology. In cancer, however, tissue invasion is driven by the stroma. Myofibroblasts and cancer-associated fibroblasts are important components of the tumor stroma. The origin of myofibroblasts remains controversial, although fibroblasts and bone marrow-derived precursors are considered to be the main progenitor cells. Myofibroblast reactions also occur in fibrosis. Therefore, we wonder whether nontumorous myofibroblasts have different characteristics and different origins as compared to tumor-associated myofibroblasts. The mutual interaction between cancer cells and myofibroblasts is dependent on multiple invasive growth-promoting factors, through direct cell-cell contacts and paracrine signals. Since fibrosis is a major side effect of radiotherapy, we address the question how the main methods of cancer management, including chemotherapy, hormonotherapy and surgery affect myofibroblasts and by inference the surrogate endpoints invasion and metastasis.