Characterization and regulation of insulin-like growth factor binding proteins in human hepatic stellate cells

IGFBP-6: At the Crossroads of Immunity, Tissue Repair and Fibrosis

Insulin-like growth factors binding protein-6 (IGFBP-6) is involved in a relevant number of cellular activities and represents an important factor in the immune response, particularly in human dendritic cells (DCs). Over the past several years, significant insights into the IGF-independent effects of IGFBP-6 were discovered, such as the induction of chemotaxis, capacity to increase oxidative burst and neutrophils degranulation, ability to induce metabolic changes in DCs, and, more recently, the regulation of the Sonic Hedgehog (SHH) signaling pathway during fibrosis. IGFBP-6 has been implicated in different human diseases, and it plays a rather controversial role in the biology of tumors. Notably, well established relationships between immunity, stroma activity, and fibrosis are prognostic and predictive of response to cancer immunotherapy. This review aims at describing the current understanding of mechanisms that link IGFBP-6 and fibrosis development and at highlighting the multiple roles of IGFBP-6 to provide an insight into evolutionarily conserved mechanisms that can be relevant for inflammation, tumor immunity, and immunological diseases.

Postpartum nutrition affects the insulin-like growth factor system in dominant follicles and plasma of anestrous beef cows

Effects of nutrition on insulin-like growth factor-I (IGF-I), IGF binding proteins (IGFBP), and insulin in plasma and dominant follicles were evaluated at day 72 and 56 (Exp. 1, n = 12 and Exp. 2, n = 28, respectively) postpartum in anovulatory primiparous beef cows. Cows were stratified based on body condition score at calving and randomly assigned to nutritional treatments: maintain (M), 2.27 kg of a 40 % CP supplement per day and ad libitum hay; or gain (G), ad libitum access to a 50 % concentrate diet and ad libitum hay. Blood samples were collected twice weekly starting 30 days postpartum. Ovarian follicles were evaluated using ultrasonography commencing 42 (Exp. 1) or 30 (Exp. 2) days postpartum. Body weight and condition score were greater (P < 0.05) for cows of G than M groups and postpartum interval to luteal function was longer for cows of the M than G group. Insulin and IGF-I concentrations in follicular fluid (FF) and plasma were greater (P < 0.05) for cows of the G than M group at follicular aspiration. Plasma and FF IGFBP4 and IGFBP5 concentrations were greater (P <  0.05) in Exp. 2, and IGFBP5 was greater in Exp. 1 for cows of the G than M group. Treatment did not affect FF steroid concentrations or granulosal cell CYP19A1, PAPPA, IGFBP4, and IGFBP5 mRNA abundance. These results indicate concentrations of IGF-I, insulin, IGFBP4, and IGFBP5 in FF and plasma are affected by nutritional intake and may be related to follicular function.

The GH-IGF-SST system in hepatocellular carcinoma: biological and molecular pathogenetic mechanisms and therapeutic targets

Hepatocellular carcinoma (HCC) is the sixth most common malignancy worldwide. Different signalling pathways have been identified to be implicated in the pathogenesis of HCC; among these, GH, IGF and somatostatin (SST) pathways have emerged as some of the major pathways implicated in the development of HCC. Physiologically, GH-IGF-SST system plays a crucial role in liver growth and development since GH induces IGF1 and IGF2 secretion and the expression of their receptors, involved in hepatocytes cell proliferation, differentiation and metabolism. On the other hand, somatostatin receptors (SSTRs) are exclusively present on the biliary tract. Importantly, the GH-IGF-SST system components have been indicated as regulators of hepatocarcinogenesis. Reduction of GH binding affinity to GH receptor, decreased serum IGF1 and increased serum IGF2 production, overexpression of IGF1 receptor, loss of function of IGF2 receptor and appearance of SSTRs are frequently observed in human HCC. In particular, recently, many studies have evaluated the correlation between increased levels of IGF1 receptors and liver diseases and the oncogenic role of IGF2 and its involvement in angiogenesis, migration and, consequently, in tumour progression. SST directly or indirectly influences tumour growth and development through the inhibition of cell proliferation and secretion and induction of apoptosis, even though SST role in hepatocarcinogenesis is still opened to argument. This review addresses the present evidences suggesting a role of the GH-IGF-SST system in the development and progression of HCC, and describes the therapeutic perspectives, based on the targeting of GH-IGF-SST system, which have been hypothesised and experimented in HCC.

Gene expression profiling of early hepatic stellate cell activation reveals a role for Igfbp3 in cell migration

Background

Scarring of the liver is the result of prolonged exposure to exogenous or endogenous stimuli. At the onset of fibrosis, quiescent hepatic stellate cells (HSCs) activate and transdifferentiate into matrix producing, myofibroblast-like cells.

Aim and methods

To identify key players during early HSC activation, gene expression profiling was performed on primary mouse HSCs cultured for 4, 16 and 64 hours. Since valproic acid (VPA) can partly inhibit HSC activation, we included VPA-treated cells in the profiling experiments to facilitate this search.

Results

Gene expression profiling confirmed early changes for known genes related to HSC activation such as alphasmoothmuscleactin (Acta2), lysyloxidase (Lox) and collagen, type I, alpha 1 (Col1a1). In addition we noticed that, although genes which are related to fibrosis change between 4 and 16 hours in culture, most gene expression changes occur between 16 and 64 hours. Insulin-likegrowthfactorbinding protein 3 (Igfbp3) was identified as a gene strongly affected by VPA treatment. During normal HSC activation Igfbp3 is up regulated and this can thus be prevented by VPA treatment invitro and invivo. siRNA-mediated silencing of Igfbp3 in primary mouse HSCs induced matrix metalloproteinase (Mmp) 9 mRNA expression and strongly reduced cell migration. The reduced cell migration after Igfbp3 knock-down could be overcome by tissue inhibitor of metalloproteinase (TIMP) 1 treatment.

Conclusion

Igfbp3 is a marker for culture-activated HSCs and plays a role in HSC migration. VPA treatment prevents Igfbp3 transcription during activation of HSCs invitro and invivo.

Hepatoprotective effect of MMP-19 deficiency in a mouse model of chronic liver fibrosis

Liver fibrosis is characterized by the deposition and increased turnover of extracellular matrix. This process is controlled by matrix metalloproteinases (MMPs), whose expression and activity dynamically change during injury progression. MMP-19, one of the most widely expressed MMPs, is highly expressed in liver; however, its contribution to liver pathology is unknown. The aim of this study was to elucidate the role of MMP-19 during the development and resolution of fibrosis by comparing the response of MMP-19-deficient (MMP19KO) and wild-type mice upon chronic liver CCl(4)-intoxication. We show that loss of MMP-19 was beneficial during liver injury, as plasma ALT and AST levels, deposition of fibrillar collagen, and phosphorylation of SMAD3, a TGF-ß1 signaling molecule, were all significantly lower in MMP19KO mice. The ameliorated course of the disease in MMP19KO mice likely results from a slower rate of basement membrane destruction and ECM remodeling as the knockout mice maintained significantly higher levels of type IV collagen and lower expression and activation of MMP-2 after 4 weeks of CCl(4)-intoxication. Hastened liver regeneration in MMP19KO mice was associated with slightly higher IGF-1 mRNA expression, slightly increased phosphorylation of Akt kinase, decreased TGF-ß1 mRNA levels and significantly reduced SMAD3 phosphorylation. In addition, primary hepatocytes isolated from MMP19KO mice showed impaired responsiveness towards TGF-ß1 stimulation, resulting in lower expression of Snail1 and vimentin mRNA. Thus, MMP-19-deficiency improves the development of hepatic fibrosis through the diminished replacement of physiological extracellular matrix with fibrotic deposits in the beginning of the injury, leading to subsequent changes in TGF-ß and IGF-1 signaling pathways.

Insulin-like growth factor binding protein 5 enhances survival of LX2 human hepatic stellate cells

Background

Expression of insulin-like growth factor binding protein 5 (IGFBP5) is strongly induced upon activation of hepatic stellate cells and their transdifferentiation into myofibroblasts in vitro. This was confirmed in vivo in an animal model of liver fibrosis. Since IGFBP5 has been shown to promote fibrosis in other tissues, the aim of this study was to investigate its role in the progression of liver fibrosis.

Methods

The effect of IGFBP5 was studied in LX2 cells, a model for partially activated hepatic stellate cells, and in human primary liver myofibroblasts. IGFBP5 signalling was modulated by the addition of recombinant protein, by lentiviral overexpression, and by siRNA mediated silencing. Furthermore, the addition of IGF1 and silencing of the IGF1R was used to investigate the role of the IGF-axis in IGFBP5 mediated effects.

Results

IGFBP5 enhanced the survival of LX2 cells and myofibroblasts via a >50% suppression of apoptosis. This effect of IGFBP5 was not modulated by the addition of IGF1, nor by silencing of the IGF1R. Additionally, IGFBP5 was able to enhance the expression of established pro-fibrotic markers, such as collagen Iα1, TIMP1 and MMP1.

Conclusion

IGFBP5 enhances the survival of (partially) activated hepatic stellate cells and myofibroblasts by lowering apoptosis via an IGF1-independent mechanism, and enhances the expression of profibrotic genes. Its lowered expression may, therefore, reduce the progression of liver fibrosis.

REGULATION OF INSULIN-LIKE GROWTH FACTOR (IGF)-BINDING PROTEIN EXPRESSION BY GROWTH FACTORS AND CYTOKINES ALTERS IGF-MEDIATED PROLIFERATION OF POSTNATAL LUNG FIBROBLASTS

Postnatal day 5 is the beginning of septation and the peak of postnatal fibroblast proliferation. The author and colleagues studied fibroblasts from this developmental time period to determine factors that regulate cell proliferation. Exposure of cells to insulin-like growth factor (IGF)-I for 48 hours increased cell number whereas exposure to epithelial growth factor (EGF), platelet-derived growth factor (PDGF)-BB, fibroblast growth factor (FGF)-7, FGF-2, tumor necrosis factor-alpha (TNF-alpha), or interleukin (L)-1beta did not alter cell number. Long[R3]IGF-I (a synthetic IGF analog with reduced affinity for IGF-binding proteins [IGFBPs]) was more potent than IGF-I, with half-maximal stimulation at a dose of 0.6 nM for long[R3]IGF-I compared to 1.5 nM for IGF-I, suggesting that IGFBPs in the conditioned medium (CM) inhibit IGF activity. Addition of exogenous IGFBP-3 inhibited the IGF-stimulated increase in cell number. Addition of IGFBP-4 did not alter IGF activity because IGF-I stimulated proteolysis of IGFBP-4. The expression of mRNA for PAPP-A (a known IGFBP-4 protease) suggests that the clearance of IGFBP-4 is mediated by pregnancy-associated plasma protein (PAPP)-A. Exposure of cells to TNF-alpha or IL-1beta increased IGFBP-3 mRNA abundance and IGFBP-3 protein in CM. PDGF-BB and IL-1beta increased IGFBP-4 protein abundance and PDGF-BB and dibutyryl cAMP increased IGFBP-4 mRNA. The increase in CM IGFBP-3 following TNF-alpha exposure blocked IGF-mediated cell proliferation, suggesting that the growth factor- and cytokine-mediated changes in IGFBP abundance regulate postnatal fibroblast cell proliferation.

Cross-talk between MCP-3 and TGFbeta promotes fibroblast collagen biosynthesis

Recent studies have demonstrated upregulation of monocyte chemoattractant protein-3 (MCP-3/CCL7) in fibrosis and have suggested that in addition to a major role in regulating leucocyte recruitment this chemokine may also promote extracellular matrix (ECM) overproduction by fibroblasts. In the present study we explore interplay between MCP-3 and transforming growth factor beta (TGFbeta), a potent profibrotic cytokine. We demonstrate that MCP-3 promotes activation of TGFbeta signalling pathways leading to increased type I collagen secretion. In addition we show that MCP-3 gene expression is stimulated by recombinant TGFbeta1, raising the possibility for synergy between these two mediators in the fibrotic microenvironment. Comparison of downstream signalling pathways that regulate collagen gene activation by both cytokines confirms the central role of MAPK pathway activation in mediating the effects of both factors. An additive effect of these two agonists was demonstrated by comparative microarray analysis for key TGFbeta regulated transcripts including PAI-1, OSF2 and IGFBP6. Together, our results confirm cross-talk between MCP-3 and TGFbeta that may be critical in the development of fibrosis.

The insulin-like growth factor axis and risk of liver disease in hepatitis C virus/HIV-co-infected women

OBJECTIVE

Insulin-like growth factor (IGF) I stimulates the proliferation of hepatic stellate cells (HSC), the primary source of extracellular matrix accumulation in liver fibrosis. In contrast, insulin-like growth factor binding protein (IGFBP) 3, the most abundant IGFBP in circulation, negatively modulates HSC mitogenesis. To investigate the role of the IGF axis in hepatitis C virus (HCV)-related liver disease among high-risk patients, we prospectively evaluated HCV-viremic/HIV-positive women.

DESIGN

A cohort investigation.

METHODS

Total IGF-I and IGFBP-3 were measured in baseline serum specimens obtained from 472 HCV-viremic/HIV-positive subjects enrolled in the Women's Interagency HIV Study, a large multi-institutional cohort. The aspartate aminotransferase to platelet ratio index (APRI), a marker of liver fibrosis, was assessed annually.

RESULTS

Normal APRI levels (< 1.0) at baseline were detected in 374 of the 472 HCV-viremic/HIV-positive subjects tested, of whom 302 had complete liver function test data and were studied. IGF-I was positively associated [adjusted odds ratio comparing the highest and lowest quartiles (AORq4-q1), 5.83; 95% confidence interval (CI) 1.17-29.1; Ptrend = 0.03], and IGFBP-3 was inversely associated (AORq4-q1, 0.13; 95% CI 0.02-0.76; Ptrend = 0.04), with subsequent (incident) detection of an elevated APRI level (> 1.5), after adjustment for the CD4 T-cell count, alcohol consumption, and other risk factors.

CONCLUSION

High IGF-I may be associated with increased risk and high IGFBP-3 with reduced risk of liver disease among HCV-viremic/HIV-positive women.

Transcriptional profiling reveals novel markers of liver fibrogenesis: gremlin and insulin-like growth factor-binding proteins

Activated hepatic stellate cells (HSC) that transdifferentiate to myofibroblasts in the injured liver are responsible for scar formation that leads to fibrosis and eventually cirrhosis. To investigate the gene expression profile during different stages of this process, we performed serial analysis of gene expression, representing a quantitative and qualitative description of all expressed genes. Stellate cells were isolated from human livers and cultured. Serial analysis of gene expression was performed on RNA isolated from quiescent, activated, and transdifferentiated HSC. Comparison of the three resulting transcriptomes showed that less than 5% of all genes changed significantly in expression. Established markers of liver fibrosis showed enhanced expression in accordance with the transdifferentiation process. In addition, induction was seen for several genes not yet recognized to be involved in liver fibrosis, such as insulin-like growth factor-binding proteins (IGFBP) and antagonists of bone morphogenic proteins: follistatin and gremlin. The induction of these genes was validated in vivo in mice developing liver fibrosis. The expression of IGFBPs and gremlin was measurable in the livers of these mice, whereas it was low or undetectable in control mice without liver fibrosis. Since gremlin modulates the activity of bone morphogenic growth factors, it may represent a novel pathway and a target for therapeutic intervention and together with IGFBPs it could be a specific marker of liver fibrosis. In conclusion, the comparison of the three transcriptomes of (activated) stellate cells reveals novel genes involved in fibrogenesis and provides an appreciation of the sequence and timing of the fibrotic process in liver.

Expression of insulin-like growth factor binding proteins in healing tendon lesions

he treatment of overuse tendon injuries with exogenous growth factors such as insulin-like growth factor-I (IGF-I) may facilitate an improved return to sustained athletic function. The biological effects of IGF-I are exerted under the control of a complex of IGF receptors, binding proteins, and proteases. This IGF system includes a family of six structurally related high-affinity IGF binding proteins (IGFBPs) that protect IGF-I from local proteases and restrict access of IGF-I to its receptor. This study describes the expression of the IGFBPs in flexor tendon after acute injury and during healing over time. Collagenase-induced lesions were created in the tensile region of the flexor digitorum superficialis tendon of both forelimbs of 14 horses. Tendons were harvested from euthanatized horses 1, 2, 4, 8, or 24 weeks following injury. Gene expression was quantitated by fluorescent real-time PCR, and protein expression was evaluated by Western ligand blot (WLB). Message for IGFBPs 2 to 6 was expressed in both normal and healing tendon. No IGFBP-1 mRNA was detected in equine tendon. Message expression for IGFBP-2, -3, and -4 increased following injury, whereas message expression for IGFBP-5 and -6 decreased. Protein expression for IGFBP-2, -3, and -4 was detected by WLB in normal tendon and showed a marked increase following injury. Protein for IGFBP-5 and -6 was not detectable by WLB in normal or healing tendon. The results of this study document the IGFBP response of flexor tendons to injury and healing, which provides information necessary for the design of protocols that may enhance tendon healing through manipulation of IGF-I ligand and binding protein levels.

Cloning and expression of equine insulin-like growth factor binding proteins in normal equine tendon

OBJECTIVES

To define a portion of the nucleotide sequences of each of the 6 insulin-like growth factor (IGF) binding proteins (IGFBPs) in horses and describe patterns of messenger RNA (mRNA) and protein expression for IGFBPs in normal equine tendons.

ANIMALS

7 horses.

PROCEDURE

Total RNA was extracted from the tensile region of normal superficial digital flexor tendons and reverse transcribed into complimentary DNA (cDNA). The cDNA was amplified via PCR, and products representing portions of each IGFBP were cloned and sequenced. Nucleotide sequences were used to deduce the amino acid sequences, and both nucleotide and predicted amino acid sequences were compared with those published for bovine, human, mouse, and ovine IGFBPs. Gene expression was quantitated by real-time PCR assay, and protein expression was evaluated by western ligand blot (WLB).

RESULTS

Clones ranged in size from 262 to 522 bp and had high degrees of sequence homology with other mammalian species. Sequence homology was highest between bovine and equine IGFBPs (86% to 95%) and amongst the IGFBP-5 sequences from the various species (92% to 95%). Message for IGFBP-2 to -6, but not IGFBP-1, was expressed in normal tendon. Protein expression for IGFBP-2, -3, and -4 was detected byWLB in normal tendon and markedly increased in damaged tendons.

CONCLUSIONS AND CLINICAL RELEVANCE

Results provide basic information and tools needed for further characterization of the role of the IGF system in tendon healing and may lead to the ability to potentiate the response of healing tendon to exogenous IGF-I via concurrent manipulation of IGFBPs.

IGF-I induces DNA synthesis and apoptosis in rat liver hepatic stellate cells (HSC) but DNA synthesis and proliferation in rat liver myofibroblasts (rMF)

Several lines of evidence suggest a role of insulin-like growth factor I (IGF-I) in the regulation of apoptosis. Up to now its impact on many specific cells is unknown. We therefore studied the effect of IGF-I on two similar mesenchymal matrix-producing cell types of the liver, the hepatic stellate cells (HSC) and the myofibroblasts (rMF). The present study aimed to reveal the influence of IGF-I on cell cycle and apoptosis of HSC and rMF and to elucidate responsible signaling. While IGF-I significantly increased DNA synthesis in HSC, cell number decreased and apoptosis increased. In rMF IGF-I also increased DNA synthesis, which is, however, followed by proliferation. Blocking extracellular signal regulating kinase (ERK) revealed that in HSC, bcl-2 upregulation and bax downregulation are effected downstream of ERK, whereas downregulation of NFkappaB and consecutive of bcl-xL is mediated upstream. In the rMF upregulation of both, the antiapoptotic bcl-2 and bcl-xL is mediated upstream of ERK. The expression of the proapoptotic bax is not regulated by IGF-I in rMF. The studies demonstrate a completely different effect and signaling of IGF-I in two morphologically and functionally similar matrix-producing cells of the liver.

Insulin-like growth factor (IGF)-binding protein-1 is highly induced during acute carbon tetrachloride liver injury and potentiates the IGF-I-stimulated activation of rat hepatic stellate cells

Hepatic stellate cells (HSC) play a pivotal role in hepatic tissue repair and fibrogenesis. IGF-I has been considered a mitogenic signal for activation and proliferation of HSC in vitro. In the present study IGF-I and IGF-binding protein (IGFBP) gene expression was studied in a model of acute liver injury induced by a single intragastric dose of carbon tetrachloride (CCl(4)) in adult rats. Northern blot analysis revealed a marked increase in IGFBP-1 mRNA levels, with a maximum between 3 and 9 h after CCl(4) application, whereas steady state mRNA levels of IGF-I were only moderately altered. In situ hybridization experiments demonstrated that this increase in IGFBP-1 mRNA was due to a strong expression of IGFBP-1 in the perivenous region 6-12 h after CCl(4) application, extending to the midzonal region of the acinus within 24-48 h. Consequently, a prominent immunostaining for IGFBP-1 was observed in perivenous areas, with a maximum 24-48 h after intoxication. Preincubation of early cultured HSC with a nonphosphorylated IGFBP-1 from human amniotic fluid resulted in a 3.4-fold increase in IGF-I-induced DNA synthesis. The mitogenic effect of IGF-I was also potentiated when HSC were cocultivated with IGFBP-1-overexpressing BHK-21 cells compared with nontransfected cells. These data suggest that IGFBP-1 released during the early steps of liver tissue damage and repair may interact with HSC and potentiate the sensitivity of IGF-I to mitogenic signals.

Long term consequences of the 1944-1945 Dutch famine on the insulin-like growth factor axis

The insulin-like growth factor axis is highly responsive to nutritional status and may be involved as one of the underlying mechanisms through which caloric restriction could affect cancer risk. High levels of circulating insulin-like growth factor (IGF)-I, or IGF-I relative to IGF binding protein (IGFBP)-3 have been related to various human cancer types. In a group of 87 postmenopausal women, we found that childhood exposure to the 1944-1945 Dutch famine was associated with increased plasma levels of IGF-I and IGFBP-3, whereas IGFBP-1 and -2 levels were weakly decreased. These results are opposite to immediate responses seen under starvation and we hypothesize that this could indicate a permanent overshoot upon improvement of nutritional status after the famine.

Expression and regulation of the insulin-like growth factor axis components in rat liver myofibroblasts

Apart from hepatic stellate cells (HSC), liver myofibroblasts (MF) represent a second mesenchymal cell population involved in hepatic fibrogenesis. The IGF system including the insulin-like growth factors I and II (IGF-I, -II), their receptors (IGF-I receptor, IGF-IR; IGF-II/mannose 6-phosphate receptor, IGF-II/M6-PR), and six high affinity IGF binding proteins (IGFBPs) participate in the regulation of growth and differentiation of cells of the fibroblast lineage, possibly contributing to the fibrogenic process. The aim of this work was to study the expression and regulation of the IGF axis components in rat liver MF.

METHODS

Cultures of MF from passages 1 to 4 (P1-4) were studied. IGFBP secretion was analyzed by [(125)I]-IGF-I ligand and immunoblotting. IGF-I, IGF-IR, IGF-II/M6-PR, and IGFBP messenger RNA (mRNA) expression was assessed by Northern blot hybridization. DNA synthesis was evaluated by 5-bromo-2'-deoxyuridine (BrdU) incorporation assay.

RESULTS

MF from P1 to 4 constitutively expressed mRNA transcripts specific for IGF-I, IGF-IR, and IGF-II/M6-PR. In MF, biosynthesis of IGFBP-3 and -2 was observed that was stimulated by IGF-I, insulin, and transforming growth factor beta (TGF-beta), whereas platelet-derived growth factor (PDGF-BB) revealed inhibitory effects. IGF-I and to a lesser extent insulin increased DNA synthesis of MF. Simultaneous addition of recombinant human IGFBP-2 or -3 with IGF-I diminished the mitogenic effect of IGF-I on MF whereas preincubation of MF with IGFBP-2 or -3 further potentiated the IGF-I stimulated DNA synthesis. In conclusion, the present study demonstrates that the IGF axis may play a role in the regulation of MF proliferation in vitro which might be relevant in vivo for the process of fibrogenesis during acute and chronic liver injury.

Leptin receptor-deficient Zucker (fa/fa) rat retards the development of pig serum-induced liver fibrosis with Kupffer cell dysfunction

The aim of this study was to investigate the role of leptin in the development of liver fibrosis with Kupffer cell function using leptin receptor deficient rats. Male Zucker (fa/fa) and control (fa/-) rats received pig serum for 8 weeks. Animals were sacrificed to estimate the degree of liver fibrosis and stellate cell activation with the expression of alpha smooth muscle actin (alphaSMA). Microarray analysis was performed. Isolated Kuppfer cells of Zucker and control rats were treated with LPS. LPS uptake and TNF-alpha production were examined. Stellate cells were also isolated from Zucker and control rats. The expression of procollagen type I mRNAs was examined. Control rats developed liver fibrosis 8 weeks after injection of pig serum and showed an increased liver hydroxyproline content of 348 +/- 34 microg/g (n = 10) compared with Zucker rats (225 +/- 13, n = 10, P < 0.01). The procollagen type I mRNA level and alphaSMA expression of Zucker rats were also significantly reduced. Microarray analysis indicated significantly reduced expression of TNF-alpha, LPS-binding protein, urokinase-type plasminogen activator (uPA), IGF, IGF-binding protein (IGFBP)-3,5, and increased expression of apolipoprotein IV. Isolated Kupffer cells of Zucker rats showed significantly reduced LPS uptake as well as TNF-alpha production compared with control rats. However, no significant change was observed in procollagen type I mRNA levels of isolated stellate cells after 4 days of culture on plastic dishes. These results suggest that leptin receptor deficiency retards the development of liver fibrosis due to the dysfunction of Kuppfer cells.

ADAM12 in human liver cancers: TGF-beta-regulated expression in stellate cells is associated with matrix remodeling

"A disintegrin and metalloproteinases" (ADAMs) form a family of cell-surface glycoproteins with potential protease and cell-adhesion activities. We have investigated ADAM expression in human liver cancers and their regulation by several cytokines involved in liver injury. Using degenerative RT-PCR, cDNA encoding sequences for ADAM9 and ADAM12 were identified in human activated hepatic stellate cells (HSCs). Northern blot analyses showed that HSCs, but not hepatocytes, expressed transcripts for ADAM9 messenger RNA (mRNA) and both the long and short forms of ADAM12. This expression was associated with the transition from quiescent to activated state of rat HSCs and markedly increased in human livers with cirrhosis. ADAM12 but not ADAM9 expression was up-regulated by transforming growth factor beta (TGF-beta) in human activated HSCs. The PI3K inhibitor LY294002 and the mitogen-activated protein kinase kinase (MEK) inhibitor UO126 prevented ADAM12 induction by TGF-beta, suggesting the involvement of PI3K and MEK activities. In vivo, the steady-state of both ADAM9 and ADAM12 mRNA levels was nearly undetectable in both normal livers and benign tumors and increased in hepatocellular carcinomas (up to 3- and 6-fold, respectively) and liver metastases from colonic carcinomas (up to 40- and 60-fold, respectively). The up-regulation of both ADAM9 and ADAM12 was correlated with an increase in matrix metalloproteinase 2 expression and activity. In conclusion, in liver cancers ADAM9 and ADAM12 expression is associated with tumor aggressiveness and progression.

Effects of weaning and rearing environment on intestinal gene expression of IGF-I, IGFBP (1-6), and the IGF receptor and on specific binding of IGF-I to mucosal membranes in the pig

The objective of this study was to investigate changes in gene expression of intestinal IGF-I, IGFBPs, and IGF-I receptor in pigs in response to weaning and different rearing environment. Pigs were weaned early at 12 days of age and either remained on-site in a separate facility (CON) or were moved to a segregated site with reduced infection pressure (segregated early weaning; SEW). Small intestinal samples were collected from a total of 15 pigs killed at 11 (pre-weaning), 15 (3 days post-weaning), and 34 days of age. Intestinal IGF-I mRNA levels were higher (P < 0.01) in SEW than in CON pigs at 3 days post-weaning, but not at 34 days of age. Weaning reduced (P < 0.05) both IGF-IR mRNA levels and specific binding of IGF-1 in the jejunum in both groups at day 34, but only in SEW pigs (P < 0.05) at day 3 post-weaning. Weaning resulted in a major reduction (P < 0.05) in intestinal IGFBP-2 mRNA, with no difference between SEW and CON. Intestinal IGFBP-3 mRNA levels were unaffected by weaning or post-weaning environment. Weaning did not affect intestinal IGFBP-4 mRNA levels, except for an increase (P < 0.05) in CON pigs compared to pre-weaning, and to SEW pigs at 3 days post-weaning. The abundance of IGFBP-5 mRNA in the gut was highly variable with no apparent treatment effect. Intestinal IGFBP-6 mRNA levels were reduced (P < 0.05) after weaning, with lower (P < 0.05) levels in SEW pigs than in CON pigs at 34 days of age. This study documents the changes in IGF-1, IGF-IR, and IGFBP mRNA abundance, and in IGF-1 binding during post-weaning adaptation of the intestine in early-weaned pigs. In addition, the relative differences observed in intestinal expression of IGF-1, IGF-IR, and in IGF-1 binding between the post-weaning environments are consistent with previous observations in a companion study indicating that segregated early weaning enhances post-weaning intestinal maturation in pigs.

Gene expression profiles in the Peyronie's disease plaque

OBJECTIVES

To provide molecular insight into the pathophysiology of Peyronie's disease (PD), a preliminary profile of differential gene expression between the PD plaque and control tunica albuginea was obtained with DNA microarrays.

METHODS

Seven PD plaques and five control tunica albugineas were studied. cDNA specimens were prepared from RNA isolated from one calcified PD plaque and one control tissue and hybridized with the Clontech Atlas 1.2 Array. Another set of plaque and control RNA samples was hybridized with the Affymetrix GeneChip. Relative changes of greater than 2.0 defined up-regulation and down-regulation, respectively. RNA from the remaining tissues was used to determine, by reverse transcriptase-polymerase chain reaction and Western blot analysis, the expression of selected individual genes.

RESULTS

Some of up-regulated genes in the PD plaque detected by the Clontech assay were pleiotrophin, monocyte chemotactic protein 1, and early growth response protein, which are involved in osteoblast recruitment, inflammation, and fibroblast proliferation, respectively. Ubiquitin and Id-2, which are involved in tissue remodeling, were down-regulated. The Affymetrix DNA chips identified the up-regulation of elastase (involved in elastic fiber degradation) and the myofibroblast markers alpha and gamma-smooth muscle actin, desmin, and others, as well as the down-regulation of collagenase IV and transforming growth factor-beta modulators. Four of the five genes selected for reverse transcriptase-polymerase chain reaction and Western blotting confirmed the DNA microarray results.

CONCLUSIONS

In the PD tissue, the genes involved in collagen synthesis, myofibroblast differentiation, tissue remodeling, inflammation, ossification, and proteolysis are up-regulated, and the genes that inhibit some of these processes and collagenase are down-regulated.

Insights into the pathobiology of hepatitis C virus-associated cirrhosis: analysis of intrahepatic differential gene expression

The pathogenesis of hepatitis C virus (HCV)-associated liver injury involves many genes from multiple pathogenic pathways. cDNA array analysis, which examines the expression of many genes simultaneously, was used to achieve new insights into HCV liver injury. Membrane-based cDNA arrays of 874 genes compared HCV-associated cirrhosis with autoimmune hepatitis-associated cirrhosis as an inflammatory and cirrhotic control, and with nondiseased liver tissue. Array analysis identified many differentially expressed genes that are important in inflammation, fibrosis, proliferation, signaling, apoptosis, and oxidative stress. Genes up-regulated in HCV-associated cirrhosis were predominantly associated with a Th1 immune response, fibrosis, cellular proliferation, and apoptosis. Novel observations of differential gene expression included increased expression of secreted apoptosis-related protein 3, a Wnt pathway gene possibly involved in cellular apoptosis. EMMPRIN (CD147) and discoidin domain receptor 1 (CD167) were also shown to be increased and are likely to play a role in liver fibrosis. Real-time quantitative reverse transcriptase-polymerase chain reaction confirmed the increased expression of 15 genes. The comparison of HCV cirrhosis with autoimmune hepatitis cirrhosis showed a marked difference in the apoptosis-associated gene profile with HCV cirrhosis characterized by increased proapoptotic gene expression whereas autoimmune hepatitis was characterized by increased expression of both antiapoptotic and proapoptotic genes. Furthermore, expression of beta-catenin and the fibrosis-associated protein EMMPRIN were localized by immunohistochemistry to the plasma membranes of hepatocytes and biliary epithelium. In conclusion, HCV-associated cirrhosis was characterized by a proinflammatory, profibrotic, and proapoptotic gene expression profile.

Phosphatidylinositol-3 kinase and extracellular signal-regulated kinase mediate the chemotactic and mitogenic effects of insulin-like growth factor-I in human hepatic stellate cells

BACKGROUND/AIM

Several studies have shown that proliferation of hepatic stellate cells is stimulated by insulin-like growth factor-I. The aim of this study was to investigate the effect of insulin-like growth factor-I on human hepatic stellate cells chemotaxis and the intracellular pathways involved in both mitogenic and chemotactic effects.

METHODS/RESULTS

Insulin-like growth factor-I, at the concentration of 100 ng/ml, was able to induce a 2- to 3-fold increase in human hepatic stellate cells migration in a modified Boyden chamber system. This effect was associated with a marked activation of phosphatidylinositol 3-kinase by insulin-like growth factor-I, as evaluated by measurement of phosphatidylinositol 3-kinase activity in phosphotyrosine immunoprecipitates In order to establish a functional link between these observations, we then performed experiments employing two selective phosphatidylinositol 3-kinase inhibitors, namely wortmannin and LY294002. These compounds blocked activation of phosphatidylinositol 3-kinase and inhibited insulin-like growth factor-I-induced hepatic stellate cells migration. Since phosphatidylinositol 3-kinase activation has been shown to be necessary for platelet-derived growth factor-induced mitogenesis in hepatic stellate cells, we verified the effects of phosphatidylinositol 3-kinase inhibition on insulin-like growth factor-I-induced DNA synthesis. Incubation with either wortmannin or LY294002, dose-dependently reduced the mitogenic potential of insulin-like growth factor-I. Since phosphatidylinositol 3-kinase is involved, at least in part, in the activation of the Ras/extracellular signal-regulated kinase pathway in hepatic stellate cells, the role of extracellular signal-regulated kinase activation in mediating the biological effects of insulin-like growth factor-I was explored. Insulin-like growth factor-I induced mitogenesis and chemotaxis were markedly reduced by pre-incubation of hepatic stellate cells with PD-98059, a selective inhibitor of MEK.

CONCLUSIONS

Activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase is required for both insulin-like growth factor-I-dependent hepatic stellate cells proliferation and chemotaxis. Insulin-like growth factor-I, together with other soluble mediators, may contribute to the hepatic wound-healing response by modulating hepatic stellate cells migration and proliferation.

Hepatic regeneration in insulin-like growth factor binding protein-1 transgenic mice

BACKGROUND/AIMS

Partial hepatectomy results in activation of genes in the residual liver tissue which serve to restore glucose homeostasis and regenerate liver mass. Expression of insulin-like growth factor binding protein-1 (IGFBP-1) is up-regulated following partial hepatectomy and IGFBP-1 can modulate both the metabolic and mitogenic effects of insulin-like growth factor-1 (IGF-I). The aim of the study was to compare the effects of partial hepatectomy on blood glucose levels and hepatic regeneration in wild-type and transgenic mice which constitutively overexpress IGFBP-1.

METHODS

Hepatic IGFBP-1 mRNA, blood glucose concentrations, liver mass and hepatic DNA synthesis were compared in sham-operated and partially hepatectomized transgenic and wild-type mice.

RESULTS

Hepatic IGFBP-1 mRNA was higher in sham-operated transgenic than wild-type mice, but in both groups of mice, partial hepatectomy was associated with a significant rise in IGFBP-1 mRNA. The absolute decline in blood glucose levels following partial hepatectomy was greater in transgenic mice. Basal DNA synthesis and the response to IGF-I in isolated hepatocytes from both groups of mice were similar, and DNA synthesis in the regenerating liver in vivo was not significantly different in transgenic as compared to wild-type mice: 449.3 +/- 63.9 vs. 321.6 +/- 52.3 cpm/microgram DNA. Hepatic regeneration as measured by liver weight after hepatectomy was not different between transgenic and wild-type mice.

CONCLUSIONS

Constitutive overexpression of IGFBP-1 does not enhance hepatic regeneration and does not prevent the decline in blood glucose following partial hepatectomy.