Increased Sp1-dependent transactivation of the LAMgamma 1 promoter in hepatic stellate cells co-cultured with HepG2 cells overexpressing cytochrome P450 2E1

Circular RNA cVIM promotes hepatic stellate cell activation in liver fibrosis via miR-122-5p/miR-9-5p-mediated TGF-β signaling cascade

Hepatic stellate cell (HSC) activation is considered as a central driver of liver fibrosis and effective suppression of HSC activation contributes to the treatment of liver fibrosis. Circular RNAs (circRNAs) have been reported to be important in tumor progression. However, the contributions of circRNAs in liver fibrosis remain largely unclear. The liver fibrosis-specific circRNA was explored by a circRNA microarray and cVIM (a circRNA derived from exons 4 to 8 of the vimentin gene mmu_circ_32994) was selected as the research object. Further studies revealed that cVIM, mainly expressed in the cytoplasm, may act as a sponge for miR-122-5p and miR-9-5p to enhance expression of type I TGF-β receptor (TGFBR1) and TGFBR2 and promotes activation of the TGF-β/Smad pathway, thereby accelerating the progression of liver fibrosis. Our results demonstrate a vital role for cVIM in promoting liver fibrosis progression and provide a fresh perspective on circRNAs in liver fibrosis.

LAMC1 upregulation via TGFβ induces inflammatory cancer-associated fibroblasts in esophageal squamous cell carcinoma via NF-κB-CXCL1-STAT3

Cancer‐associated fibroblasts (CAF) are a heterogeneous cell population within the tumor microenvironment,and play an important role in tumor development. By regulating the heterogeneity of CAF, transforming growth factor β (TGFβ) influences tumor development. Here, we explored oncogenes regulated by TGFβ1 that are also involved in signaling pathways and interactions within the tumor microenvironment. We analyzed sequencing data of The Cancer Genome Atlas (TCGA) and our own previously established RNA microarray data (GSE53625), as well as esophageal squamous cell carcinoma (ESCC) cell lines with or without TGFβ1 stimulation. We then focused on laminin subunit gamma 1 (LAMC1), which was overexpressed in ESCC cells, affecting patient prognosis, which could be upregulated by TGFβ1 through the synergistic activation of SMAD family member 4 (SMAD4) and SP1. LAMC1 directly promoted the proliferation and migration of tumor cells, mainly via Akt–NFκB–MMP9/14 signaling. Additionally, LAMC1 promoted CXCL1 secretion, which stimulated the formation of inflammatory CAF (iCAF) through CXCR2–pSTAT3. Inflammatory CAF promoted tumor progression. In summary, we identified the dual mechanism by which the upregulation of LAMC1 by TGFβ in tumor cells not only promotes ESCC proliferation and migration, but also indirectly induces carcinogenesis by stimulating CXCL1 secretion to promote the formation of iCAF. This finding suggests that LAMC1 could be a potential therapeutic target and prognostic marker for ESCC.

Thymosin Beta 4 Is a Potential Regulator of Hepatic Stellate Cells

Liver fibrosis, a major characteristic of chronic liver disease, is inappropriate tissue remodeling caused by prolonged parenchymal cell injury and inflammation. During liver injury, hepatic stellate cells (HSCs) undergo transdifferentiation from quiescent HSCs into activated HSCs, which promote the deposition of extracellular matrix proteins, leading to liver fibrosis. Thymosin beta 4 (Tβ4), a major actin-sequestering protein, is the most abundant member of the highly conserved β-thymosin family and controls cell morphogenesis and motility by regulating the dynamics of the actin cytoskeleton. Tβ4 is known to be involved in various cellular responses, including antiinflammation, wound healing, angiogenesis, and cancer progression. Emerging evidence suggests that Tβ4 is expressed in the liver; however, its biological roles are poorly understood. Herein, we introduce liver fibrogenesis and recent findings regarding the function of Tβ4 in various tissues and discuss the potential role of Tβ4 in liver fibrosis with a special focus on the effects of exogenous and endogenous Tβ4. Recent studies have revealed that activated HSCs express Tβ4 in vivo and in vitro. Treatment with the exogenous Tβ4 peptide inhibits the proliferation and migration of activated HSCs and reduces liver fibrosis, indicating it has an antifibrotic action. Meanwhile, the endogenously expressed Tβ4 in activated HSCs is shown to promote HSCs activation. Although the role of Tβ4 has not been elucidated, it is apparent that Tβ4 is associated with HSC activation. Therefore, understanding the potential roles and regulatory mechanisms of Tβ4 in liver fibrosis may provide a novel treatment for patients.

Hepatitis C Virus NS5A Protein Triggers Oxidative Stress by Inducing NADPH Oxidases 1 and 4 and Cytochrome P450 2E1

Replication of hepatitis C virus (HCV) is associated with the induction of oxidative stress, which is thought to play a major role in various liver pathologies associated with chronic hepatitis C. NS5A protein of the virus is one of the two key viral proteins that are known to trigger production of reactive oxygen species (ROS). To date it has been considered that NS5A induces oxidative stress by altering calcium homeostasis. Herein we show that NS5A-induced oxidative stress was only moderately inhibited by the intracellular calcium chelator BAPTA-AM and not at all inhibited by the drug that blocks the Ca(2+) flux from ER to mitochondria. Furthermore, ROS production was not accompanied by induction of ER oxidoreductins (Ero1), H2O2-producing enzymes that are implicated in the regulation of calcium fluxes. Instead, we found that NS5A contributes to ROS production by activating expression of NADPH oxidases 1 and 4 as well as cytochrome P450 2E1. These effects were mediated by domain I of NS5A protein. NOX1 and NOX4 induction was mediated by enhanced production of transforming growth factor β1 (TGFβ1). Thus, our data show that NS5A protein induces oxidative stress by several multistep mechanisms.

The interplay between hepatic stellate cells and hepatocytes in an in vitro model of NASH

BACKGROUND & AIM

A complex interplay exists between hepatocytes and hepatic stellate cells (HSC) in hepatic fibrogenesis. The activation of HSCs after liver injury leads to production of extracellular matrix (ECM). Co-culture models could be useful to mimic the liver microenvironment. This study evaluates the effect of free fatty acids (FFA) on HSC cells and the interplay with hepatocytes via both soluble-mediator and cell-cell contact.

METHODS

The human hepatocyte cell line (HuH7) and HSC cells (LX2) were exposed to FFA for 24 h in 3 different experimental set-ups: (A) monoculture of HSC; (B) Transwell® system (effect of soluble mediators); and (C) Simultaneous Co-Culture (SCC) (cell-to-cell connections). Intracellular FFA accumulation was assessed qualitatively (microscopy) and quantitatively (flow cytometry); the activation of HSC (alpha smooth muscle actin, α-SMA) expression of ECM components were quantified by RT-PCR.

RESULTS

FFA exposure induces intracellular fat accumulation in all the experimental set-up but the expression of α-SMA was significantly increased only in SCC. On the contrary, the expression of ECM was substantially decreased in the transwell® system.

CONCLUSIONS

The HSC activation is independent of FFA accumulation but requires cell-to-cell interaction with hepatocyte. On the contrary, the gene regulation of ECM components seems to occur through paracrine mediators.

HCV core protein uses multiple mechanisms to induce oxidative stress in human hepatoma Huh7 cells

Hepatitis C virus (HCV) infection is accompanied by the induction of oxidative stress, mediated by several virus proteins, the most prominent being the nucleocapsid protein (HCV core). Here, using the truncated forms of HCV core, we have delineated several mechanisms by which it induces the oxidative stress. The N-terminal 36 amino acids of HCV core induced TGF\(\upbeta\)1-dependent expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases 1 and 4, both of which independently contributed to the production of reactive oxygen species (ROS). The same fragment also induced the expression of cyclo-oxygenase 2, which, however, made no input into ROS production. Amino acids 37-191 of HCV core up-regulated the transcription of a ROS generating enzyme cytochrome P450 2E1. Furthermore, the same fragment induced the expression of endoplasmic reticulum oxidoreductin 1\(\upalpha\). The latter triggered efflux of Ca2+ from ER to mitochondria via mitochondrial Ca2+ uniporter, leading to generation of superoxide anions, and possibly also H2O2. Suppression of any of these pathways in cells expressing the full-length core protein led to a partial inhibition of ROS production. Thus, HCV core causes oxidative stress via several independent pathways, each mediated by a distinct region of the protein.

Protective effects of hepatic stellate cells against cisplatin-induced apoptosis in human hepatoma G2 cells

The effects of hepatic stellate cells (HSCs) on tumorigenicity of HCC have been previously reported. However, the detailed mechanisms responsible for these effects remain unclear. In this study, we investigated the effects of HSCs on cisplatin-induced apoptosis in human hepatoma HepG2 cell lines. HepG2 cells were treated with cisplatin alone or co-cultured with LX-2 cells 3 days before incubation with cisplatin. Cisplatin causes apoptosis in HepG2 cells and LX-2 cells protect HepG2 cells from death. The protection of LX-2 cells against cisplatin-induced cytotoxicity in HepG2 cells appeared to be related to the inhibition of apoptosis, as determined by cytotoxicity assay and nuclear staining analysis. p53 and Bax mRNA levels were elevated, and cell cycle arrest was produced after cisplatin treatment. LX-2 cells suppressed this elevation of p53 and Bax as well as the cell cycle arrest induced by cisplatin, when compared with those of the treated cells with cisplatin alone. The LX-2 cells pretreatment inhibited the cisplatin-induced apoptosis, which was related with the incomplete blockage in p53 activation. In summary, the results of our present study demonstrate that HSCs protect HepG2 cells against cisplatin-induced apoptosis and its protective effects occur via inhibiting the activation of p53, which is of critical importance for enhanced understanding of fundamental cancer biology.

The importance of the interaction between hepatocyte and hepatic stellate cells in fibrogenesis induced by fatty accumulation

BACKGROUND & AIMS

Non-alcoholic fatty liver disease is characterized by an initial accumulation of triglycerides that can progress to non-alcoholic steatohepatitis, which can ultimately evolve to cirrhosis and hepatocellular carcinoma. Hepatic stellate cells play a key role in liver fibrogenesis by an increased activation and an altered profile of genes involved in the turnover of extracellular matrix components. To reproduce in-vitro the functional cell connections observed in vivo it is essential to consider cell-to-cell proximity and interaction. The aim of this study was to determine the response to free fatty acids in a simultaneous co-culture model of hepatocytes and hepatic stellate cells.

METHODS

Simultaneous co-culture model and monoculture of each cell type (control) were exposed to FFA for 24 up to 144 h. Quantification of steatosis; stellate cell activation; assessment of fibrogenic response; expression and activity of metalloproteinases as well as collagen biosynthesis were evaluated.

RESULTS

Free fatty acids induced comparable steatosis in simultaneous co-culture and monoculture. However, the activation of the stellate cells assessed by alpha-smooth muscle actin expression is greater when cells were in close contact. Furthermore, a time-dependent increment of tissue inhibitor metalloproteinase-2 protein was observed, which was inversely correlated with protein expression and activity of matrix-metalloproteinases, suggesting enhanced collagen biosynthesis. This behavior was absent in cell monoculture.

CONCLUSIONS

These data indicate that cell-to-cell proximity between hepatocytes and stellate cells is necessary for the initiation of the fibrotic process.

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.

Butein inhibits ethanol-induced activation of liver stellate cells through TGF-β, NFκB, p38, and JNK signaling pathways and inhibition of oxidative stress

BACKGROUND

Butein has been reported to prevent and partly reverse liver fibrosis in vivo; however, the mechanisms of its action are poorly understood. We, therefore, aimed to determine the antifibrotic potential of butein.

METHODS

We assessed the influence of the incubation of hepatic stellate cells (HSCs) and hepatoma cells (HepG2) with butein on sensitivity to ethanol- or acetaldehyde-induced toxicity; the production of reactive oxygen species (ROS); the expression of markers of HSC activation, including smooth muscle α-actin (α-SMA) and procollagen I; and the production of transforming growth factor-β1 (TGF-β1), metalloproteinases-2 and -13 (MMP-2and MMP-13), and tissue inhibitors of metalloproteinases (TIMPs). The influence of butein on intracellular signals in HSCs; i.e., nuclear factor-κB (NFκB), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (p38 MAPK) induced by ethanol was estimated.

RESULTS

Butein protected HSCs and HepG2 cells against ethanol toxicity by the inhibition of ethanol- or acetaldehyde-induced production of ROS when cells were incubated separately or in co-cultures; butein also inhibited HSC activation measured as the production of α-SMA and procollagen I. As well, butein downregulated ethanol- or acetaldehyde-induced HSC migration and the production of TGF-β, TIMP-1, and TIMP-2; decreased the activity of MMP-2; and increased the activity of MMP-13. In ethanol-induced HSCs, butein inhibited the activation of the p38 MAPK and JNK transduction pathways as well as significantly inhibiting the phosphorylation of NF κB inhibitor (IκB) and Smad3.

CONCLUSIONS

The results indicated that butein inhibited ethanol- and acetaldehyde-induced activation of HSCs at different levels, acting as an antioxidant and inhibitor of ethanol-induced MAPK, TGF-β, and NFκB/IκB transduction signaling; this result makes butein a promising agent for antifibrotic therapies.

Fibromodulin, an oxidative stress-sensitive proteoglycan, regulates the fibrogenic response to liver injury in mice

BACKGROUND & AIMS

Collagen I deposition contributes to liver fibrosis, yet little is known about other factors that mediate this process. Fibromodulin is a liver proteoglycan that regulates extracellular matrix organization and is induced by fibrogenic stimuli. We propose that fibromodulin contributes to the pathogenesis of fibrosis by regulating the fibrogenic phenotype of hepatic stellate cells (HSCs).

METHODS

We analyzed liver samples from patients with hepatitis C-associated cirrhosis and healthy individuals (controls). We used a coculture model to study interactions among rat HSCs, hepatocytes, and sinusoidal endothelial cells. We induced fibrosis in livers of wild-type and Fmod(-/-) mice by bile duct ligation, injection of CCl(4), or administration of thioacetamide.

RESULTS

Liver samples from patients with cirrhosis had higher levels of fibromodulin messenger RNA and protein than controls. Bile duct ligation, CCl(4), and thioacetamide each increased levels of fibromodulin protein in wild-type mice. HSCs, hepatocytes, and sinusoidal endothelial cells produced and secreted fibromodulin. Infection of HSCs with an adenovirus that expressed fibromodulin increased expression of collagen I and α-smooth muscle actin, indicating increased activation of HSCs and fibrogenic potential. Recombinant fibromodulin promoted proliferation, migration, and invasion of HSCs, contributing to their fibrogenic activity. Fibromodulin was sensitive to reactive oxygen species. HepG2 cells that express cytochrome P450 2E1 produced fibromodulin, and HSCs increased fibromodulin production in response to pro-oxidants. In mice, administration of an antioxidant prevented the increase in fibromodulin in response to CCl(4). Coculture of hepatocytes or sinusoidal endothelial cells with HSCs increased the levels of reactive oxygen species in the culture medium, along with collagen I and fibromodulin proteins; this increase was prevented by catalase. Fibromodulin bound to collagen I, but the binding did not prevent collagen I degradation by matrix metalloproteinase 13. Bile duct ligation caused liver fibrosis in wild-type but not Fmod(-/-) mice.

CONCLUSIONS

Fibromodulin levels are increased in livers of patients with cirrhosis. Hepatic fibromodulin activates HSCs and promotes collagen I deposition, which leads to liver fibrosis in mice.

Extracellular matrix bioengineering and systems biology approaches in liver disease

The extracellular matrix (ECM) in the liver as well as in many organs comprises a peripheral network linking numerous macromolecules typically classified into collagens, microfibrillar proteins, proteoglycans, chemokines, growth factors and glycoproteins. In addition to its role as an essential structural and physiological component, it plays a vital role in driving key cellular events such as cell adhesion, migration, proliferation, differentiation and survival. Any structural inherited or acquired defect and/or metabolic or pathologic alteration in the hepatic ECM may cause cellular and organ responses leading to the development or progression of liver disease. Therefore, the ECM molecules are key players in tissue engraftment and in the pathophysiology of liver disease. In this review we provide a snapshot on current efforts for understanding its role in physiological and non-physiological states, by describing how tissue engineering platforms can enhance in vitro and in vivo models of liver disease, by providing examples where bioengineered ECM can serve as systems biology approaches to study the ECM, and then by evaluating pathological protein regulatory networks in the liver using systems biology tools. These approaches hold great promise for future research.

Induction and progression of cholangiofibrosis in rat liver injured by oral administration of furan

Cholangiofibrosis is a structural anomaly that precedes the development of cholangiocarcinoma in some rodent models. In this article, the authors examine the contribution of the epithelial and mesenchymal cells in the pathogenesis of this complex lesion. Furan was administered to rats by gavage in corn oil at 30 mg/kg b.w. (five daily doses per week) and livers were sampled between eight hr to three months. Characteristically the administration of furan caused centrilobular injury, and restoration was accomplished by proliferation of hepatocytes. Some areas of the liver were, however, more severely affected, and here, injury extended into portal and capsular areas, which resulted in a rapid proliferation of ductular cells that extended into the parenchyma accompanied by a subtype of liver fibroblasts. These ductules either differentiated into hepatocytes, with loss of the associated fibroblasts, or progressed to form tortuous ductular structures that replaced much of the parenchyma, leading to cholangiofibrosis. Although it is unclear what determines the difference in the hepatic response, a loss of micro-environmental cues that instigate hepatocyte differentiation and termination of the hepatocyte stem cell repair response may be perturbed by continual furan administration that results in an irreversible expansile lesion that may mimic the features of cholangiocarcinoma.

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.

Ethanol and arachidonic acid synergize to activate Kupffer cells and modulate the fibrogenic response via tumor necrosis factor alpha, reduced glutathione, and transforming growth factor beta-dependent mechanisms

Because of the contribution of ethanol and polyunsaturated fatty acids (PUFAs) to alcoholic liver disease, we investigated whether chronic ethanol administration and arachidonic acid (AA) could synergistically mediate Kupffer cell (KC) activation and modulate the stellate cell (HSC) fibrogenic response.

RESULTS

(1) the effects of ethanol and AA on KC and HSC were as follows: Cell proliferation, lipid peroxidation, H(2)O(2), O(2).(-), nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase activity, and tumor necrosis factor alpha (TNF-alpha) were higher in KC(ethanol) than in KC(control), and were enhanced by AA; HSC(ethanol) proliferated faster, increased collagen, and showed higher GSH than HSC(control), with modest effects by AA. (2) AA effects on the control co-culture: We previously reported the ability of KC to induce a pro-fibrogenic response in HSC via reactive oxygen species (ROS)-dependent mechanisms; we now show that AA further increases cell proliferation and collagen in the control co-culture. The latter was prevented by vitamin E (an antioxidant) and by diphenyleneiodonium (a NADPH oxidase inhibitor). (3) Ethanol effects on the co-cultures: Co-culture with KC(control) or KC(ethanol) induced HSC(control) and HSC(ethanol) proliferation; however, the pro-fibrogenic response in HSC(ethanol) was suppressed because of up-regulation of TNF-alpha and GSH, which was prevented by a TNF-alpha neutralizing antibody (Ab) and by L-buthionine-sulfoximine, a GSH-depleting agent. (4) Ethanol plus AA effects on the co-cultures: AA lowered TNF-alpha in the HSC(control) co-cultures, allowing for enhanced collagen deposition; furthermore, AA restored the pro-fibrogenic response in the HSC(ethanol) co-cultures by counteracting the up-regulation of TNF-alpha and GSH with a significant increase in GSSG and in pro-fibrogenic transforming growth factor beta (TGF-beta).

CONCLUSION

These results unveil synergism between ethanol and AA to the mechanism whereby KC mediate ECM remodeling and suggest that even if chronic ethanol consumption sensitizes HSC to up-regulate anti-fibrogenic signals, their effects are blunted by a second "hit" such as AA.

Oxidative and nitrosative stress and fibrogenic response

Uncontrolled production of collagen I is the main feature of liver fibrosis. Following a fibrogenic stimulus such as alcohol, hepatic stellate cells (HSC) transform into an activated collagen-producing cell. In alcoholic liver disease, numerous changes in gene expression are associated with HSC activation, including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Detailed analyses for understanding the molecular basis of the collagen I gene regulation have revealed a complex process involving reactive oxygen species (ROS) as key mediators. Less is known, however, about the contribution of reactive nitrogen species (RNS). In addition, a series of cytokines, growth factors, and chemokines, which activate extracellular matrix (ECM)-producing cells through paracrine and autocrine loops, contribute to the fibrogenic response.

Redox mechanisms in hepatic chronic wound healing and fibrogenesis

Reactive oxygen species (ROS) generated within cells or, more generally, in a tissue environment, may easily turn into a source of cell and tissue injury. Aerobic organisms have developed evolutionarily conserved mechanisms and strategies to carefully control the generation of ROS and other oxidative stress-related radical or non-radical reactive intermediates (that is, to maintain redox homeostasis), as well as to 'make use' of these molecules under physiological conditions as tools to modulate signal transduction, gene expression and cellular functional responses (that is, redox signalling). However, a derangement in redox homeostasis, resulting in sustained levels of oxidative stress and related mediators, can play a significant role in the pathogenesis of major human diseases characterized by chronic inflammation, chronic activation of wound healing and tissue fibrogenesis. This review has been designed to first offer a critical introduction to current knowledge in the field of redox research in order to introduce readers to the complexity of redox signalling and redox homeostasis. This will include ready-to-use key information and concepts on ROS, free radicals and oxidative stress-related reactive intermediates and reactions, sources of ROS in mammalian cells and tissues, antioxidant defences, redox sensors and, more generally, the major principles of redox signalling and redox-dependent transcriptional regulation of mammalian cells. This information will serve as a basis of knowledge to introduce the role of ROS and other oxidative stress-related intermediates in contributing to essential events, such as the induction of cell death, the perpetuation of chronic inflammatory responses, fibrogenesis and much more, with a major focus on hepatic chronic wound healing and liver fibrogenesis.

Ethanol and fish oil induce NFkappaB transactivation of the collagen alpha2(I) promoter through lipid peroxidation-driven activation of the PKC-PI3K-Akt pathway

To analyze whether fish oil, as a source of polyunsaturated fatty acids from the n-3 series, could synergize with ethanol to promote collagen I upregulation in vivo, collagen alpha2(I) promoter-betaGal (COL1A2-betaGal) transgenic mice were fed a diet enriched in fish oil in the presence of ethanol (ethanol group) or dextrose (control group). Ethanol-fed mice showed mild steatosis, increased alanine aminotransferase (ALT), aspartate aminotransferase (AST), nonsterified fatty acids, and plasma alcohol levels along with elevated cytochrome P450 2E1 activity, lipid peroxidation end products, and low glutathione (GSH) levels, which suggested enhanced oxidant stress and liver injury. Increased transactivation of the COL1A2 promoter assessed by betaGal activity was shown in vivo and by transfection with deletion constructs for the collagen alpha1(I) promoter (COL1A1) and COL1A2 promoters in vitro. Transcriptional regulation of both COL1A1 and COL1A2 promoters was validated by nuclear in vitro transcription run-on, northern blot analysis, and quantitative polymerase chain reaction, which was followed by the subsequent upregulation of collagen I protein with no changes in matrix metalloproteinase 13 (MMP 13). To further analyze the potential mechanism for collagen I upregulation, an in vitro coculture model was designed with primary stellate cells seeded on the bottom plate of a Boyden chamber and the rest of the liver cells plated on a cell culture insert, and fish oil or fish oil plus ethanol were added. The combination of fish oil plus ethanol increased nuclear factor kappaB binding to the COL1A2 promoter both in vivo and in the cocultures and also resulted in increased phosphorylation of protein kinase C, activation of PI3 kinase, and phosphorylation of Akt. The in vitro addition of vitamin E prevented such activation and collagen I increase. Furthermore, inhibitors of all 3 kinases blocked the increase in collagen I and NFkappaB binding to the COL1A2 promoter; the latter was also prevented by vitamin E.

CONCLUSION

These results suggest that fish oil (mainly n-3 polyunsaturated fatty acids [PUFAs]) can synergize with ethanol to induce collagen I, transactivating the COL1A2 promoter through a lipid peroxidation-PKC-PI3K-Akt-NFkappaB-driven mechanism in the absence of overt steatosis and inflammation.

NOX in liver fibrosis

NADPH oxidase is a multi-protein complex producing reactive oxygen species (ROS) both in phagocytic cells, being essential in host defense, and in non-phagocytic cells, regulating intracellular signalling. In the liver, NADPH oxidase plays a central role in fibrogenesis. A functionally active form of the NADPH oxidase is expressed not only in Kupffer cells (phagocytic cell type) but also in hepatic stellate cells (HSCs) (non-phagocytic cell type), suggesting a role of the non-phagocytic NADPH oxidase in HSC activation. Consistent with this concept, profibrogenic agonists such as Angiotensin II (Ang II) and platelet derived growth factor (PDGF), or apoptotic bodies exert their activity through NADPH oxidase-activation in HSCs. Both pharmacological inhibition with DPI and genetic studies using p47(phox) knockout mice provided evidence for a central role of NADPH oxidase in the regulation of HSC-activity and liver fibrosis. In addition to the p47(phox) component, only Rac1 has been identified as a functional active component of the NADPH oxidase complex in HSCs.

Oxidative-stress and IL-6 mediate the fibrogenic effects of [corrected] Kupffer cells on stellate cells

The impact of Kupffer cells (KCs) on the hepatic stellate cell (HSC) fibrogenic response was examined in an in vitro coculture model of primary KCs and HSCs. Coculture with KCs induced a more activated phenotype and greater proliferation compared to HSC cultured alone. Similar results were obtained on Matrigel which maintains HSCs quiescent. The effect of KCs on HSC collagen I involved transcriptional regulation, as determined by nuclear in vitro transcription run-on assays, promoter studies, and Northern blot analysis, while stability of the COL1A1 and COL1A2 mRNA were similar. The minimal COL1A1 and COL1A2 promoter regions responsible for the KC effects were localized to the -515 and -378 base pair (bp) regions, respectively. Intracellular and extracellular collagen I protein, H2O2, and IL-6 increased in a time-dependent fashion, especially for HSCs in coculture. Catalase prevented these effects as well as the transactivation of both collagen promoters. The rate of collagen I protein synthesis and intracellular collagen I degradation remained similar but the t(1/2) of the secreted collagen I was lower for HSC in coculture. MMP13, a protease that degrades extracellular collagen I, decreased in the cocultures, while TIMP1, a MMP13 inhibitor, increased; and these effects were prevented by catalase, anti-IL-6, and siRNA-IL-6. Cocultured HSC showed elevated phosphorylation of p38 which when inhibited by catalase, anti-IL-6, and siRNA-IL-6 it blocked TIMP1 upregulation and collagen I accumulation. In conclusion, these results unveil a novel dual mechanism mediated by H2O2 and IL-6 by which KCs may modulate the fibrogenic response in HSCs.

Transfer of thesFLT-1Gene in Morris Hepatoma Results in Decreased Growth and Perfusion and Induction of Genes Associated with Stress Response

PURPOSE

Inhibition of tumor angiogenesis is emerging as a promising target in the treatment of malignancies. Therefore, monitoring of antiangiogenic approaches with functional imaging and histomorphometrical analyses are desirable to evaluate the biological effects caused by this treatment modality.

EXPERIMENTAL DESIGN

Using a bicistronic retroviral vector for transfer of the soluble receptor for the vascular endothelial growth factor (sFLT) hepatoma (MH3924A) cell lines with sFLT expression were generated. In human umbilical vein endothelial cells cultured with conditioned medium of sFLT-expressing hepatoma cells, the inhibitory action of secreted sFLT was determined using a Coulter counter and a thymidine incorporation assay. Furthermore, in vivo experiments were done to measure the effects on tumor growth and perfusion. Finally, the tumors were examined by immunohistochemistry (including computer-assisted morphometry) and DNA chip analysis.

RESULTS

Stable sFLT-expressing hepatoma cells inhibited endothelial cell proliferation in vitro. In vivo, growth and perfusion, as measured by H(2)(15)O positron emission tomography, were reduced in genetically modified tumors. However, the immunohistochemically quantified microvascularization and macrovascularization, as indicated by CD31- and alpha-actin-positive area, revealed no significant changes, whereas the number of apoptotic cells was increased in sFLT-expressing tumors, although not significantly. DNA chip analysis of tumors with gene transfer showed an increase of genes related to apoptosis, signal transduction, and oxidative stress.

CONCLUSION

Our results suggest that sFLT expression inhibits tumor growth and perfusion and enhances expression of apoptosis-related genes in this model. Enhanced expression of genes for signal transduction, stress, and metabolism indicates tumor defense reactions.

Kruppel-like factors regulate the Lama1 gene encoding the laminin alpha1 chain

Laminin-1 (alpha1beta1gamma1), a basement membrane (BM) constituent, has been associated with differentiation processes and also with malignant progression. In the intestinal tissue, the alpha1 chain is expressed and secreted in the subepithelial BM during the developmental period; in the adult rodent tissue, it is restricted to the BM of the dividing cells. To understand how laminin alpha1 chain expression is regulated, we cloned and characterized a 2-kb promoter region of the Lama1 mouse gene. Analysis of the promoter was conducted in the Caco2-TC7 intestinal epithelial cells by transient transfection of serially deleted and site-directed mutated promoter constructs, by electrophoretic mobility shift assays, and expression of selected transcription factors. We determined that a proximal region, which includes an Sp1-binding GC box and a Krüppel-like element, was important for the promoter activity. This region is conserved between the human and mouse genes. Interestingly, two Krüppel-like factors KLF4 and KLF5 exhibit opposing effects on the Lama1 promoter activity that are decreased and increased, respectively, in the intestinal epithelial cells. These data corroborate the complementary expression of KLF4 and KLF5 along the intestinal crypt-villus axis and the parallel expression of KLF5 and laminin alpha1 chain in the crypt region. Finally, we showed that glucocorticoids stimulate the promoter activity. This study is the first characterization of the Lama1 promoter; we identified regulatory elements that may account for the expression pattern of the endogenous protein in the mouse intestine.