Marked induction of hepatocyte growth factor mRNA in intact kidney and spleen in response to injury of distant organs

Exhaled breath condensate and serum levels of hepatocyte growth factor in pneumonia

Hepatocyte growth factor (HGF) is a protein produced by mesenchymal cells in many organs, which can stimulate epithelial growth. An enhanced production and concentration of HGF is observed after injuries. The lung is one of the major sources of HGF. By cooling exhaled air, a condensate is formed containing molecules from bronchi and alveoli. In order to investigate HGF-concentration and time course in pneumonia, paired serum and exhaled breath condensate was collected from 10 patients with pneumonia, 10 patients with non-respiratory infections and 11 healthy controls. The concentration of HGF was measured by an immunoassay kit. In the acute phase HGF-levels in breath condensate and serum were significantly higher in the patients with pneumonia compared to the control groups. Similar concentrations in breath condensate were seen in healthy controls and in patients with non-respiratory infections. In the patients with pneumonia a decrease in serum HGF was seen already after 4-7 days while HGF values in breath condensate remained elevated even after 4-6 weeks. These results might imply local product on of HGF in the lungs and a long repair and healing process after pneumonia.

Hepatocyte growth factor as a potential predictor of the presence of atherosclerotic aorto-iliac artery disease

BACKGROUND

Hepatocyte growth factor (HGF), a member of the endothelial-specific growth factors with the greatest mitogenic activity, may play a role in the protection and/or repair of vascular endothelial cells injured by atherosclerosis. As a result, plasma HGF concentration may increase in response to endothelial cell damage. To test this hypothesis, we measured plasma concentrations of HGF in patients with or without aorto-iliac artery atherosclerotic disease.

METHODS

One hundred ten consecutive patients who underwent coronary angiography were enrolled in this study. Abdominal aortography was performed after coronary arteriography to determine whether aorto-iliac artery atherosclerotic disease was present. Peripheral venous blood samples were obtained to measure the plasma HGF concentration.

RESULTS

Aortography revealed aorto-iliac atherosclerotic disease in 35 patients (32%). The plasma HGF concentration was significantly higher in patients with arteriosclerotic lesions (0.35 +/- 0.11 ng/mL) than in patients without atherosclerotic lesions (0.27 +/- 0.09 ng/mL, P =.0002). On the basis of multiple logistic regression analysis of the relationships between coronary risk factors, age, sex, severity of coronary artery disease, plasma HGF concentration, and the presence of arteriosclerotic lesions, plasma HGF concentration (P =.0005) and age (P =.035) were found to predict independently the presence of aorto-iliac arteriosclerosis.

CONCLUSION

Plasma HGF concentration can be used to predict the presence of arteriosclerotic lesions in the region from the abdominal aorta to the femoral arteries.

Peroxisome proliferator-activated receptor gamma-mediated transcriptional up-regulation of the hepatocyte growth factor gene promoter via a novel composite cis-acting element

Hepatocyte growth factor (HGF) is a pleotropic polypeptide that can function as a morphogen, motogen, mitogen, angiogen, carcinogen, and tumor suppressor, depending on the target cell and tissue. Previous studies from our laboratory using transgenic mice have shown that HGF gene expression is tightly regulated at the transcriptional level and that the upstream regulatory elements are crucial for the control of HGF gene transcription. In the present study, we have identified and characterized one of these elements as a peroxisome proliferator-activated receptor gamma (PPARgamma)-responsive element. This regulatory element was localized at -246 to -233 base pairs upstream from the transcription start site of the HGF gene promoter having the sequence GGGCCAGGTGACCT. Gel mobility shift and supershift assays demonstrated that this cis-acting element strongly binds to the PPARgamma isoforms as well as to chicken ovalbumin upstream promoter-transcription factor, a member of the orphan nuclear receptor subfamily. Mutational analysis and gel mobility band shift assays indicated that the binding site is an inverted repeat of the AGGTCA motif with two spacers (inverted repeat 2 configuration) and that the two spacers are important for PPARgamma binding. This binding site overlaps with functional binding sites for activating protein-2, nuclear factor 1, and upstream stimulatory factor, and together, they constitute a multifunctional composite binding site through which these different transcription factors exert their regulatory effects on HGF promoter activity. Functional assays revealed that PPARgamma, with its ligand, 15-deoxy-prostaglandin J2, strongly stimulates HGF promoter activity. On the other hand, nuclear factor 1, activating protein-2, and chicken ovalbumin upstream promoter-transcription factor transcription factors repress the stimulatory action of PPARgamma by competing with PPARgamma for their overlapping binding sites. Furthermore, for the first time, our studies demonstrate that the PPARgamma ligand, 15-deoxy-prostaglandin J2, induces endogenous HGF mRNA and protein expression in fibroblasts in culture.

Hepatocyte growth factor: renotropic role and potential therapeutics for renal diseases

Hepatocyte growth factor (HGF), a ligand for the c-Met receptor tyrosine kinase, has mitogenic, motogenic, anti-apoptotic, and morphogenic (for example, induction of branching tubulogenesis) activities for renal tubular cells, while it has angiogenic and angioprotective actions for endothelial cells. Stromal cells such as mesangial cells, endothelial cells, and macrophages are sources of renal HGF; thus, HGF mediates epithelial-stromal and endothelial-mesangial interactions in the kidney. In response to acute renal injury, the expression of HGF increases in the injured kidney and in distant intact organs such as the lung and spleen. Locally and systemically increased HGF supports renal regeneration, possibly not only by enhancing cell growth but also by promoting morphogenesis of renal tissue. During progression of chronic renal failure/renal fibrosis, the expression of HGF decreases in a manner reciprocal to the increase in expression of transforming growth factor-beta (TGF-beta), a key player in tissue fibrosis. A decrease in endogenous HGF, as well as increase in TGF-beta, augments susceptibility to the onset of chronic renal failure/renal fibrosis. On the other hand, supplements of exogenous HGF have preventive and therapeutic effects in cases of acute and chronic renal failure/renal fibrosis in laboratory animals. HGF prevents epithelial cell death and enhances regeneration and remodeling of renal tissue with injury or fibrosis. A renotropic system underlies the vital potential of the kidney to regenerate, while an impaired renotropic system may confer susceptibility to the onset of renal diseases. Thus, HGF supplementation may be one therapeutic strategy to treat subjects with renal diseases, as it enhances the intrinsic ability of the kidney to regenerate.

Hepatocyte growth factor receptor in acute tubular necrosis

In acute tubular necrosis, there are early transient increases in circulating and local bioactive hepatocyte growth factor (HGF) levels and renal HGF receptor (c-MET) gene expression. It has therefore been suggested that endogenous HGF may play a role in initiating renal repair. To test this hypothesis, changes in the levels, activity, and anatomic distribution of c-MET protein were characterized in relation to the onset and localization of DNA synthesis in kidneys of rats with ischemia-induced acute tubular necrosis. Whole-kidney c-MET protein levels were significantly increased in the injured kidneys 12 h after injury and rose to a maximum after 1 d, exceeding the control values by sevenfold. Eight days after injury, c-MET levels, although decreasing, were still elevated above control values. An increase in the levels of activated c-MET, i.e., tyrosine-phosphorylated c-MET, was also evident as early as 12 h after injury. Histologic analyses demonstrated that the increase in c-MET immunoreactivity was most marked in the most severely damaged nephron segments in the outer medulla. In injured proximal tubules, the receptor was redistributed from an apical location to an intracellular location. DNA synthesis was increased in the injured kidneys, especially in the outer medulla, where the increase in c-MET protein levels was most prominent. The increase in DNA synthesis was first detected 12 h after the initial increase in activated c-MET levels. It is concluded that the early increases in the levels of c-MET protein and activated receptor support the hypothesis that HGF participates in the initiation of renal regeneration. In addition, the persistent elevation of c-Met protein levels suggests that prolonged and even late treatment with HGF may be of therapeutic value

Changes in the expression of lipid-mediated signal-transducing enzymes in the rat liver after partial hepatectomy

Prostaglandins (PGs), metabolites of arachidonic acid, and other lipid mediators produced by phospholipases C (PLC) and D (PLD) are thought to play important roles in hepatocyte proliferation. The present study examined lipid-mediated signaling in the rat liver after partial hepatectomy (PH). Rats were killed 1-48 h after 70% PH and the remaining liver tissue was removed. The mRNA and protein levels of some signaling molecules were measured by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting, respectively. The levels of hepatocyte growth factor (HGF) mRNA showed a biphasic change, peaking 3 h and 9 h after PH. The expression of PLCdelta4 peaked at 12 h, but no significant changes in the expression of PLCbeta1 and PLCgamma1 were seen after PH. T he enzymes involved in PG production, namely, the expression of cytosolic PLA2 and cyclooxygenase 1 (COX1), remained constant after PH. However, the mRNA of COX2 increased transiently at 3 h, and Western blot analysis showed an increase in COX2 protein at 12 h. The expression of PLD1b peaked at 9 h and PLD1a at 12 h, whereas the expression of PLD2 remained consistent for 24 h. These results suggest that transcriptional controls may act for PLCdelta4, PLD1a/b, and COX2 during hepatocyte regeneration after PH.

Myocardial protection from ischemia/reperfusion injury by endogenous and exogenous HGF

Using a rat model of ischemia/reperfusion injury, we demonstrate here that HGF is cardioprotective due to its antiapoptotic effect on cardiomyocytes. Following transient myocardial ischemia and reperfusion, c-Met/HGF receptor expression rapidly increased in the ischemic myocardium, an event accompanied by a dramatic increase in plasma HGF levels in the infarcted rats. When endogenous HGF was neutralized with a specific antibody, the number of myocyte cell deaths increased markedly, the infarct area expanded, and the mortality increased to 50%, as compared with a control group in which there was no mortality. Plasma from the myocardial infarcted rats had cardioprotective effects on primary cultured cardiomyocytes, but these effects were significantly diminished by neutralizing HGF. In contrast, recombinant HGF administration reduced the size of infarct area and improved cardiac function by suppressing apoptosis in cardiomyocytes. HGF rapidly augmented Bcl-xL expression in injured cardiomyocytes both in vitro and in vivo. As apoptosis of cardiomyocytes is one of the major contributors to the pathogenesis in subjects with ischemia/reperfusion injury, prevention of apoptosis may prove to be a reasonable therapeutic strategy. Supplements of HGF, an endogenous cardioprotective factor, may be found clinically suitable in treating subjects with myocardial infarction.

Development of highly sensitive enzyme-linked immunosorbent assays for hepatocyte growth factor/scatter factor (HGF/SF): determination of HGF/SF in serum and urine from normal human subjects

A sandwich enzyme-linked immunosorbent assay (ELISA) using rabbit anti-hepatocyte growth factor (HGF) IgG for human HGF, also known as the scatter factor, has previously been developed for determining increases in serum HGF levels in various liver diseases. The sensitivity limit of the ELISA is, however, approximately 0.2 ng/ml sample, and HGF concentrations in about 50% of normal subjects are not accurately measurable by this method, because the mean level of HGF in normal serum is close to the sensitivity limit. In the present study, chicken Fab' from egg yolk anti-HGF immunoglobulin Y and rabbit Fab' from rabbit anti-HGF IgG were conjugated with beta-D-galactosidase. With these conjugates as the second antibodies, we developed two sandwich ELISAs for human HGF and found that the sensitivities were about 20 pg/ml with the former conjugate and 2 pg/ml with the latter. The HGF concentration in sera from 138 normal subjects determined by the ELISA with the rabbit conjugate was 244+/-65 (SD) pg/ml serum, and it correlated very well with the number of leukocytes. Moreover, the ELISA with the rabbit conjugate permitted the determination of HGF levels in urine from normal subjects without first concentrating the sample. The determination of HGF in various biological fluids other than blood and urine by these ELISAs may aid the diagnosis and prognosis of various diseases.

Differential expression of hepatocyte growth factor in liver, kidney, lung, and spleen following burn in rats

Hepatocyte growth factor (HGF) plays a role as an organotropic factor for regeneration of injured organs. HGF is synthesized as an inactive single-chain precursor which is then converted to a biologically active heterodimeric form by proteolytic processing. Burn is the insult that results in hypovolemia which causes systemic organ injury. In this study, we investigated the induction and activation of HGF in various rat organs following burn trauma. Tissue HGF content determined as the total amount of the single-chain and heterodimeric form increased significantly in liver, lung, spleen, and kidney 12 h after burn. Molecular analysis revealed that HGF in these four organs of control rats was the single-chain precursor. In the burned rats, HGF was the single-chain form in the liver and lung, whereas heterodimeric HGF was detected in the spleen and kidney. Tissue protein content, an index of tissue injury, decreased significantly in the spleen and kidney, indicating that tissue damage was severe in these two organs. These results suggest that burn induces the production of HGF in various organs, and that the induced HGF is activated according to the severity of tissue damage caused by burn.

The repressive function of AP2 transcription factor on the hepatocyte growth factor gene promoter

Hepatocyte growth factor is an important multifunctional growth factor whose gene expression is tightly regulated at the transcriptional level. Previous studies from our laboratory have shown that several cis-acting elements are present in the promoter and proximal promoter region of the HGF gene. In this study, we have uncovered that AP2 transcription factor specifically binds to a regulatory site located at -230 to -260 in the upstream region of the HGF gene promoter. Gelshift and supershift assays confirmed that AP2 has high binding affinity to this region. Functional studies which introduced a mutation in the AP2 core binding region as well as cotransfection experiments using an AP2 expression vector revealed that AP2 exerts a repressive role on the HGF gene promoter activity. The AP2 binding site overlaps with those of NF1 and USF/E-box binding sites which we have recently shown to constitute a composite multifunctional docking site for the members of the NF1 and USF transcription factor families. An inverse correlation was noted between AP2 binding activity to this composite site and HGF gene expression in different cell lines. Therefore, AP2-mediated repression of the HGF gene promoter may be part of the molecular mechanism responsible for regulating HGF expression.

The concerted regulatory functions of the transcription factors nuclear factor-1 and upstream stimulatory factor on a composite element in the promoter of the hepatocyte growth factor gene

Hepatocyte growth factor (HGF) is an important multifunctional cytokine whose gene expression is regulated mainly at the transcriptional level. Previous studies using transgenic mice as well as in vitro analyses showed that a potential regulatory element(s) exists between -260 to -230 bp in the upstream region of the HGF gene promoter. In the present study, we have discovered that this region is a composite site through which members of the nuclear factor 1 (NF1) and upstream stimulatory factor (USF) families bind to and regulate HGF gene transcription. Gel mobility shift and supershift assays revealed that USF and NF1 have high binding affinity for this region and that the binding sites of the two different transcription factor families overlap. Functional studies showed that NF1 suppresses HGF gene promoter activity and that USF has an activating function. We found that the NF1/X and NF1/Red1 isoforms strongly suppressed HGF promoter activity while the NF1/L variant had no obvious effects. USF1, but not USF2, of the USF family stimulated HGF gene promoter activity. More interestingly, during liver regeneration after partial hepatectomy, a process which activates the HGF gene, we noted that the binding activity of USF to the HGF promoter element increased while that of NF1 decreased. These data provide insight into the molecular mechanisms that govern HGF gene transcription. Oncogene (2000).

Hepatocyte growth factor in renal failure: promise and reality

Can science discover some secrets of Greek mythology? In the case of Prometheus, we can now suppose that his amazing hepatic regeneration was caused by a peptide growth factor called hepatocyte growth factor (HGF). Increasing evidence indicates that HGF acts as a multifunctional cytokine on different cell types. This review addresses the molecular mechanisms that are responsible for the pleiotropic effects of HGF. HGF binds with high affinity to its specific tyrosine kinase receptor c-met, thereby stimulating not only cell proliferation and differentiation, but also cell migration and tumorigenesis. The three fundamental principles of medicine-prevention, diagnosis, and therapy-may be benefited by the rational use of HGF. In renal tubular cells, HGF induces mitogenic and morphogenetic responses. In animal models of toxic or ischemic acute renal failure, HGF acts in a renotropic and nephroprotective manner. HGF expression is rapidly up-regulated in the remnant kidney of nephrectomized rats, inducing compensatory growth. In a mouse model of chronic renal disease, HGF inhibits the progression of tubulointerstitial fibrosis and kidney dysfunction. Increased HGF mRNA transcripts were detected in mesenchymal and tubular epithelial cells of rejecting kidney. In transplanted patients, elevated HGF levels may indicate renal rejection. When HGF is considered as a therapeutic agent in human medicine, for example, to stimulate kidney regeneration after acute injury, strategies need to be developed to stimulate cell regeneration and differentiation without an induction of tumorigenesis.

Neu differentiation factor/heregulin induction by hepatocyte and keratinocyte growth factors

Hepatocyte growth-factor (HGF) is a potent, widely produced, pleiotropic mediator of mesenchymal-epithelial interaction. In a study of changes in gene expression initiated by HGF in Balb/MK keratinocytes, we observed the induction of Neu-differentiation factor (NDF) mRNA (also known as heregulin, or HRG). Further characterization of the regulation of NDF expression in Balb/MK keratinocytes revealed potent induction by keratinocyte growth factor (KGF) and epidermal growth factor (EGF), but not by HGF/NK2, an alternative HGF isoform with motogenic but not mitogenic or morphogenic activities. Sustained treatment (8 h) of Balb/MK cells with KGF stimulated secretion of mature NDF protein into the culture medium, and Balb/ MK cells treated with purified recombinant NDF protein showed increased DNA synthesis. We also found evidence of NDF induction in two models of tissue repair in mice: in full-thickness skin wounds, following locally increased KGF production, and in kidney after partial hepatectomy, following elevation of circulating HGF levels. These results reveal that mesenchymally-derived HGF and KGF can activate autocrine NDF signaling in their epithelial targets, and suggest that this mechanism contributes to the coordination of stages of wound repair, and possibly development, where these growth factors act in concert to direct epithelial proliferation, morphogenesis and differentiation.

Prostaglandin E2 predominantly induces production of hepatocyte growth factor/scatter factor in human dental pulp in acute inflammation

Hepatocyte growth factor (HGF), which is also known as the scatter factor, is a broad-spectrum and multifunctional cytokine, mediates epithelial-mesenchyme interaction, and is shown to be involved in the development and regeneration of various tissues, including tooth. Here, we report that HGF was present in adult human dental pulps, and its levels increased during acute inflammation of the tissue. Levels of HGF mRNA in dental pulps also increased with inflammation, as determined by reverse-transcription/polymerase chain-reaction. The production of HGF in fibroblasts from dental pulps in culture was dose-dependently stimulated by inflammatory cytokines such as interleukin (IL)-1alpha and tumor necrosis factor (TNF)-alpha, and by prostaglandin (PG) E2, as determined by an enzyme-linked immunosorbent assay. We also showed that indomethacin did not affect the increase in HGF production by the cells with IL-1alpha, TNF-alpha, and PGE2. The levels of HGF mRNA in the cells were simultaneously increased by these stimulants, as determined by Northern blotting. Since the production of PGs is known to increase at the beginning of inflammation, PGE2 may be involved in the regeneration of dental pulps by the induction of HGF expression after inflammation.

Comparison of the levels of hepatocyte growth factor and vascular endothelial growth factor in aqueous fluid and serum with grades of retinopathy in patients with diabetes mellitus

AIMS

To determine the relation between the stages of diabetic retinopathy (DR) and the levels of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) in aqueous fluid and serum.

METHODS

Levels of HGF and VEGF in serum and aqueous humour obtained during ocular surgery were measured by enzyme linked immunosorbent assay in 58 diabetic patients with 32 non-diabetic patients (NDM) as controls. The patients with diabetes were classified into three groups according to the stage of DR: no DR (NDR; 15 cases), non-proliferative DR (NPDR; six cases), and proliferative DR (PDR; 37 cases).

RESULTS

No significant differences were found between any of the groups in serum concentrations of HGF or VEGF. The aqueous HGF levels increased with the stage of DR: NDM, median 397 pg/ml, range 133-930 pg/ml; NDR, 371 pg/ml, 142-1536 pg/ml; NPDR, 455 pg/ml, 162-1007 pg/ml; and PDR, 638 pg/ml, 187-2222 pg/ml. The aqueous VEGF levels in PDR (median 212 pg/ml, range 14-1216 pg/ml) were significantly higher than in NDM (105 pg/ml, 9-203 pg/ml), but aqueous HGF concentrations were unrelated to those of VEGF.

CONCLUSION

The results of the present study suggest that both HGF and VEGF present in the ocular tissues may play important roles in the progression of DR.

Up-regulation of hepatocyte growth factor receptor: an amplification and targeting mechanism for hepatocyte growth factor action in acute renal failure

BACKGROUND

Hepatocyte growth factor (HGF) and its c-met receptor comprise a signaling system that has been implicated in tissue repair and regeneration. HGF action is specifically targeted to the damaged organ following injury; however, the mechanism underlying this important targeting process remains to be elucidated. We reasoned that induction of c-met expression might be a critical factor in determining the site specificity of this receptor-ligand system. To test this hypothesis, we examined changes in activity of the HGF/c-met system in the folic acid model of acute tubular injury and repair.

METHODS

Tissue HGF and c-met mRNA levels were detected by RNase protection assay and Northern blot analysis following acute renal injury induced by a single injection of folic acid. HGF and c-met proteins were examined by a specific enzyme immunoassay and Western blotting, respectively. C-met expression and trans-activation were investigated by exposing renal epithelial mIMCD-3 cells to various cytokines in vitro.

RESULTS

Extremely rapid induction of renal HGF and c-met mRNA was observed beginning one hour following injection of folic acid. Circulating plasma HGF protein level rose dramatically (approximately 16-fold), peaking first at two hours and again at 24 hours following injection. Despite elevated HGF mRNA in the kidney, total kidney HGF protein actually decreased significantly at 24 hours following injury. On the other hand, both c-met mRNA and c-met protein were markedly increased in the kidney, where active renal tubule repair and regeneration take place. In vitro studies suggested that increased levels of HGF, as well as other cytokines, might account for enhanced c-met expression in renal tubular epithelial cells. Pretreatment of the cells with actinomycin D totally blocked c-met induction, suggesting that induced c-met expression occurs primarily at the transcriptional level. Using a cloned region of the c-met promoter coupled to a reporter gene, we demonstrated that HGF directly stimulated c-met promoter transactivation in renal epithelial cells.

CONCLUSION

These results suggest that local up-regulation of c-met transcription in the kidney is crucial to renal tubule repair and regeneration, not only because it increases overall activity of this receptor-ligand system, but also as a mechanism targeting HGF action specifically to renal epithelia.

Enhanced hepatocyte growth factor expression associated with prolonged rat hepatic allograft survival in recipients pretreated with donor-specific blood

BACKGROUND

Pretransplantation injection of freshly heparinized donor blood (donor-specific blood transfusion, or DST) significantly prolongs the survival of hepatic allografts from ACI(RT1a) to LEW(RT1l) rats. We investigated hepatocyte growth factor (HGF) expression in rat hepatic allografts of recipients pretreated with or without DST.

METHODS

The levels of HGF mRNA and protein in hepatic allografts were determined after transplantation. The localization of HGF+ cells was identified with a rat anti-HGF monoclonal antibody.

RESULTS

Plasma HGF concentrations in transplanted rats treated with DST were significantly and persistently increased compared to untreated rats with hepatic allografts. The number of HGF+ cells in hepatic allografts of recipients pretreated with DST on day 14 was significantly greater than that in allografts of untreated recipients on day 7. HGF+ cells were also found in the marginal zone and red pulp of recipient spleens. Northern blot analysis revealed the presence of three HGF+ cell phenotypes: HGF+ED1+, HGF+ED2+, and HGF+ED1-ED2-. Most HGF+ cells were ED1-ED2-. In situ hybridization demonstrated HGF mRNA in the mononuclear cells in the portal and sinusoidal areas as well as the marginal zone and red pulp in both DST-treated and untreated recipient spleens.

CONCLUSIONS

Enhanced HGF expression in rat hepatic allografts is associated with immunologic unresponsiveness induced by DST.

Hepatocyte growth factor (HGF) in patients with pneumonia: a comparison between survivors and non-survivors

Hepatocyte growth factor (HGF) is a multifunctional growth factor. After lung injury HGF is secreted in the lung and promotes reconstruction of the damaged organ. We measured, retrospectively, the serum HGF concentrations collected on admission in 55 patients with bacterial pneumonia, using an enzyme-linked immunosorbent assay (ELISA). The patients were divided into 3 groups: Group 1 was survivors with normal liver function (n = 14), Group 2 was survivors with abnormal liver function (n = 31) and Group 3 was non-survivors (n = 10). Median concentrations of HGF were elevated in Groups 1 and 2; and no statistically significant difference between these 2 groups was found. Group 3 had a median HGF concentration within the reference range, significantly lower than both Group 1 and Group 2. In addition LDH was significantly higher in non-survivors as compared with survivors. The combination of LDH and HGF concentrations discriminated between survivors and non-survivors (sensitivity 0.90 and specificity 0.96). The results support the hypothesis that increased levels of HGF might be a natural part of the healing process of lung injury, irrespective of liver involvement, and that patients without increased HGF levels, especially those with concomitant liver function impairment, may have a poor prognosis.

The upstream regulatory regions of the hepatocyte growth factor gene promoter are essential for its expression in transgenic mice

To understand the molecular mechanisms of hepatocyte growth factor (HGF) gene transcription in vivo, we report the generation and characterization of transgenic mice harboring various lengths of the mouse HGF promoter linked to the chloramphenicol acetyltransferase reporter gene. Analysis of different tissues of the transgenic mouse lines having the 2.7-kilobase (kb) promoter construct revealed a pattern of reporter gene expression in embryonic and adult tissues that paralleled that of endogenous HGF gene expression. A similar expression pattern was observed in the 0.7-kb transgenic lines. However, in contrast to in vitro data, no promoter activity was detected in four independent transgenic lines harboring the 0.1-kb construct. Akin to the activity of the endogenous HGF gene, which is induced in the liver, lung, and spleen in response to 70% partial hepatectomy, the reporter gene driven by the 2.7-kb promoter construct was strongly induced, whereas that driven by the 0.7-kb promoter construct was modestly induced in these organs after partial hepatectomy. Together, these data suggest that the region between -0.1 and -0.7 kb of the HGF gene promoter is essential to drive its expression in vivo and that additional upstream sequences located between -0.7 and -2.7 kb are also necessary for its maximum inducibility in response to cues that stimulate tissue growth and regeneration.

Increased serum concentrations of human hepatocyte growth factor in proliferative diabetic retinopathy

Human hepatocyte growth factor (hHGF) is a powerful inducer of angiogenesis. We investigated the relationship between serum hHGF concentrations and proliferative diabetic retinopathy, the major characteristic of which is retinal neovascularization. Serum hHGF concentrations were measured in diabetic (n = 135) and nondiabetic subjects (n = 80). The mean serum hHGF concentration in diabetic subjects without retinopathy was lower than that in nondiabetic subjects [0.041 +/- 0.003 ng/mL (n = 62) vs. 0.080 +/- 0.010 ng/mL (n = 80); P < 0.05], but was not different from that in diabetic subjects with background retinopathy (0.058 +/- 0.007 ng/mL; n = 26) or preproliferative retinopathy (0.048 +/- 0.010 ng/mL; n = 10). The mean serum hHGF concentration was increased in subjects with proliferative retinopathy who had not undergone photocoagulation (0.213 +/- 0.025 ng/mL; n = 24), but not in those who had undergone photocoagulation (0.040 +/- 0.008 ng/mL; n = 13). Circulating hHGF may be involved in the mechanism of neovascularization in the proliferative diabetic retinopathy, and measurement of serum hHGF may be helpful in predicting the presence of proliferative retinopathy in diabetic subjects.

A novel transcriptional regulatory region within the core promoter of the hepatocyte growth factor gene is responsible for its inducibility by cytokines via the C/EBP family of transcription factors

Hepatocyte growth factor (HGF) is an inducible cytokine that is essential for the normal growth and development of various tissues, such as the liver. To decipher the molecular mechanisms that regulate HGF gene induction at the transcriptional level, we carried out in vitro and in vivo studies on the mouse HGF gene promoter. We have identified a novel regulatory element, located between -6 and +7 bp (from the transcription start site) in the HGF basal promoter region, which binds to inducible transcription factors and dictates responsiveness to extracellular stimuli that activate this gene. The core binding sequence for the inducible cis-acting factors was determined to be TTTGCAA (-4 to +3 bp) within the HGF promoter. Competition and gel mobility supershift assays showed that these binding complexes are composed of C/EBPbeta (CCAAT/enhancer-binding protein beta) and C/EBPdelta. DNA binding analysis also revealed that the binding site for the C/EBP family of transcription factors in the HGF promoter region overlaps that of another binding protein (complex C1), which binds specifically to a novel sequence with a core binding site of ACCGGT located adjacent to the C/EBP site (-9 to -4 bp). C1 binds to this region of the promoter and represses the inducible upregulation by C/EBP through direct competition for their individual binding sites. Partial hepatectomy, which is known to activate HGF gene expression in the liver, increased C/EBP (especially C/EBPbeta) binding activity to this region of the HGF promoter. Thus, our present results provide a mechanistic explanation for the transcriptional induction of the HGF gene by extracellular signals (i.e., cytokines) that induce tissue growth and regeneration.

C-met proto-oncogene expression in benign and malignant human renal tissues

PURPOSE

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent mitogen to renal epithelial cells in vitro and in vivo. HGF/SF signals through its receptor which is coded by the c-met proto-oncogene. We hypothesized that altered expression of the HGF/SF receptor, c-met, may be involved in the pathogenesis of certain renal cell carcinomas. Our objectives were to 1) assess the presence and localization of c-met protein in benign and malignant human renal tissues, and 2) correlate the presence of c-met protein with renal carcinoma histological subtype, tumor stage and tumor grade.

MATERIALS AND METHODS

Immunohistochemical analysis of c-met protein was performed in 41 normal and malignant human renal samples.

RESULTS

c-met Immunostaining was detected in the normal kidney tissue in all 41 samples. In the normal kidney c-met immunostaining was limited to the cell membrane and/or cytoplasm of epithelial cells in specific tubular segments, including the proximal convoluted tubule, thin and thick limbs of the loop of Henle, and the collecting duct. The glomeruli, distal convoluted tubule and stroma were consistently negative for c-met staining. c-met Immunostaining was detected in 68% of renal cell carcinomas and was more common in higher nuclear grade cancers (p < 0.034).

CONCLUSIONS

The c-met receptor is present in specific tubular segments in the normal kidney and is frequently expressed in higher nuclear grade renal cancers, suggesting a role in renal carcinoma progression. Future studies should evaluate the biological significance of the HGF/ SF-c-met pathway in normal renal physiology, and renal cancer growth and progression.

Enhanced expression of hepatocyte growth factor/c-Met by myocardial ischemia and reperfusion in a rat model

BACKGROUND

Hepatocyte growth factor (HGF) is a multifunctional factor implicated in tissue regeneration, wound healing, and angiogenesis. Circulating HGF is reportedly elevated during the early stage of myocardial infarction. However, its precise effect on the heart is unknown. To evaluate the regulation of HGF in ischemically damaged myocardium, the production of HGF and its high-affinity receptor, c-Met, was studied in a rat model of myocardial ischemia and reperfusion.

METHODS AND RESULTS

The plasma concentration of HGF began to increase within 1 hour of reperfusion after 1 hour of ischemia. The peak level was reached at 3 hours after reperfusion. Northern blotting revealed that HGF mRNA expression in the heart was augmented threefold at 24 and 48 hours and remained elevated by twofold at 120 hours after the myocardium was reperfused. The signal for c-met, high-affinity HGF receptor mRNA, was also upregulated parallel to upregulation for HGF. In the kidney, liver, lung, and spleen, HGF mRNA was also maximally increased at 12 hours after reperfusion. However, c-met was not upregulated in these organs. Immunohistochemical studies disclosed that capillary endothelial and interstitial cells, including infiltrating macrophages, were intensely stained for HGF, whereas capillary endothelial cells in the reperfused myocardium were positive for c-Met.

CONCLUSIONS

This study is the first to show that myocardial ischemia and reperfusion induced HGF expression in various organs in vivo. These results indicate that HGF/c-Met plays a role in capillary endothelial cell regeneration in the ischemically injured heart.

Transcriptional regulation of the hepatocyte growth factor gene by the nuclear receptors chicken ovalbumin upstream promoter transcription factor and estrogen receptor

Hepatocyte growth factor (HGF) is a multifunctional cytokine that controls the growth and differentiation of various tissues. Previously, we described the existence of a negative cis-acting regulatory element(s) within the -1- to -0.7-kilobase pair (kb) portion of the 5'-flanking region of the mouse HGF promoter. In the present study, we show that the repressor element is located at position -872 to -860 base pairs and comprises an imperfect estrogen-responsive element 5'-AGGTCAGAAAGACCA-3'. We demonstrate that chicken ovalbumin upstream promoter transcription factor (COUP-TF), a nuclear orphan receptor belonging to the steroid/thyroid hormone receptor superfamily, through binding to this site effectively silences the transcriptional activity of the HGF promoter. We show that estrogen receptor, on the other hand, relieves the repressive action of COUP-TF, resulting in the induction of the HGF promoter. Using mice transgenic for either 2.7 or 0.7 kb of the HGF promoter region linked to the chloramphenicol acetyltransferase reporter gene, we found that injection of estradiol stimulates HGF promoter activity in tissues such as the mammary gland and ovary of mice harboring 2.7 but not 0.7 kb of the mouse HGF promoter region. Potential involvement of the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors in the regulation of HGF gene expression is also discussed.

Measurement of replicative DNA synthesis (RDS) by a 5-bromo-2'-deoxyuridine (BrdU) labeling technique for detection of hepatocyte proliferation

The hypothesis has been proposed that cell proliferation, or replicative DNA synthesis (RDS) in S-phase cells, is a nongenotoxic (Ames-negative) mechanism involved in tumorigenesis, providing a very useful conceptual basis for carcinogen testing. In this present study, hepatocyte RDS experiments were conducted using 5-bromo-2'-deoxyuridine (BrdU) labeling in combination with histopathological observation, comparing our results with earlier findings for in situ [3H]thymidine (TdR) labeling. The present BrdU data proved to be consistent with the previous TdR data in all but one case. Hepatocyte RDS induction was observed for some chemicals without hepatotoxicity. BrdU labeling in combination with histopathological observation is therefore a reliable approach to assessment of test compound effects in vivo.

Increase in histamine synthesis by liver macrophages in CCl4-injured mast cell-deficient W/Wv mice

This study set out to examine the possible role of liver macrophages in histamine synthesis in the injured liver. The effects of the hepatotoxins Escherichia coli lipopolysaccharide (LPS) and CCl4 on histamine synthesis in the liver of mice were evaluated. C3H/HeJ mice were resistant to LPS in including histidine decarboxylase (HDC) in the liver compared with C3H/HeN mice and mast cell-deficient W/Wv mice. However, C3H/HeJ mice did respond strongly to another hepatotoxin, CCl4, leading to a significant increase in HDC activity. CCl4 also caused a marked increase in HDC activity and histamine levels in the liver of W/Wv mice. In addition, injection of CCl4 produced a large increase in the activity of HDC in the spleen and lung of W/Wv mice. HDC activity was confined to the nonparenchymal cells, with parenchymal cells expressing essentially no HDC activity. The CCl4-induced increase in HDC activity was confined, at least in part, to the liver macrophages. These results indicate that the macrophages are responsible for the increase in HDC-dependent histamine production in the liver caused by the injection of hepatotoxins. The possible role of histamine in liver regeneration after injury is discussed.

Mediators, cytokines, and growth factors in liver-lung interactions

Multiple mediators have been implicated in the interactions between the liver and the lungs in various disease states. The best characterized mediator of liver-lung interaction is alpha 1-antitrypsin. Several cytokines and mediators may be involved in the pathogenesis of the hepatopulmonary syndrome and in the cytokine cascades that are activated in systemic inflammatory states such as acute respiratory distress syndrome. Hepatocyte growth factor or scatter factor is a recently described peptide with a broad range of biologic effects that may mediate lung-liver interactions.

Expression of HGF mRNA in human rejecting kidney as evidenced by in situ hybridization

In situ hybridization was performed to demonstrate hepatocyte growth factor (HGF) mRNA in two patients with normal kidney and in 23 patients with allograft nephrectomy. In situ hybridization was combined with immunohistochemistry to identify HGF-producing cells. In the two patients with normal kidney, no HGF mRNA was obtainable. In 15 of the 23 allograft patients, signals of HGF mRNA were detectable. In six of these 15 patients, the signals were present mainly at the medullocortex junction, and in the other nine patients at the cortex and/or medulla. Strong and frequent signals were present in gland-like structures in 15 cases. Some scattered signals were also present in the fibrosed glomeruli in five cases, in the thickened intimas of large arteries in three cases, and in the arterial muscle coats of two cases. Combined immunohistochemistry and in situ hybridization showed that HGF mRNA-positive cells in gland-like arrangements were also positive for cytokeratin and negative for factor VIII. Cells with HGF mRNA signal and located in the arterial media were also positive for actin. These findings suggest that HGF mRNA is transcribed both in the urinary tubular epithelium and in the mesenchymal cells (fibroblasts, and smooth muscle cells in chronic vascular rejection and endothelial cells and/or mesangial cells in transplant glomerulopathy) in human rejecting kidney.

Hepatic nitric oxide production following acute endotoxemia in rats is mediated by increased inducible nitric oxide synthase gene expression

In the present studies, we analyzed the effects of acute endotoxemia on hepatocyte nitric oxide production and functional activity. Treatment of rats with 5 mg/kg of lipopolysaccharide (LPS), which induces acute endotoxemia, caused an increase in nitric oxide production in the liver, as measured by electron paramagnetic spin trapping, which was evident within 6 hours. This was associated with expression of inducible nitric oxide synthase (iNOS) messenger (m) RNA in hepatocytes and in sinusoidal cells throughout the liver lobule. Acute endotoxemia also caused alterations in hepatic structure, including hypertrophy, vacuolization, and chromosomal emargination, however these changes were not apparent for 24 to 48 hours. Hepatocytes isolated from endotoxemic rats released increased amounts of nitric oxide, measured by nitrite production, in response to interferon gamma (gamma-IFN) alone or in combination with LPS, tumor necrosis factor alpha, macrophage-colony stimulating factor, granulocyte/macrophage-colony stimulating factor, or hepatocyte growth factor. These results show that hepatocytes are sensitized by acute endotoxemia to respond to inflammatory mediators and growth factors. Increased nitrite production by hepatocytes was due to increased expression of iNOS mRNA and protein and was correlated with the time following induction of acute endotoxemia. Thus, cells isolated 48 hours after induction of acute endotoxemia released significantly more nitrite than cells recovered after 6 hours, a response that was not due to alterations in hepatocyte viability. Hepatocytes isolated from endotoxemic rats also exhibited a marked increase in proliferative capacity when compared with cells from control rats. Nitric oxide production by hepatocytes in vitro was associated with inhibition of cell growth and protein synthesis, which was reversed by the nitric oxide synthase inhibitor, NG-monomethyl-l-arginine (L-NMMA). Agarose gel electrophoresis showed extensive cytoplasmic DNA fragmentation in hepatocytes treated with LPS and gamma-IFN, a characteristic of apoptosis, which was also reversed by L-NMMA. These results, together with our findings that treatment of rats with an inhibitor of nitric oxide synthase partially reversed the structural alterations in the liver associated with acute endotoxemia suggest that nitric oxide may contribute to the pathophysiologic response to this bacterially derived toxin.

Hepatocyte growth factor is involved in formation of osteoclast-like cells mediated by clonal stromal cells (MC3T3-G2/PA6)

Osteoclast formation from hemopoietic precursors has been shown to require the support of stromal cells in bone tissue. In this study, we demonstrated that hepatocyte growth factor (HGF) is one of the stromal cell-derived molecules responsible for osteoclast-like cell formation. For our experiments, we used a coculture system for osteoclastic cell formation and activation in which hemopoietic blast cells are cocultured with calvaria-derived stromal MC3T3-G2/PA6 (PA6) cells on dentine slices in the presence of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. Addition of anti-HGF neutralizing IgG to the cocultures inhibited the formation of osteoclastic cells and their dentine-resorbing activity. We detected a single 6.0-kb transcript for HGF in PA6 cells, and also recognized immunoreactive M(r) 81,000 and 88,000 forms of HGF in conditioned medium (CM) from PA6 cell cultures, the level of which reached 6 ng/ml. Both the CM and HGF stimulated the proliferation of blast cells synergistically with granulocyte-macrophage colony-stimulating factor, resulting in an increased number of osteoclast precursors that respond to 1,25(OH)2D3 that are tartrate-resistant acid phosphatase-positive multinucleate cells in stromal cell-free blast cell cultures in plastic wells. The effect of the CM was diminished by the addition of anti-HGF IgG. However, neither the CM nor HGF stimulated the formation of osteoclastic cells and pits on dentine slices in the absence of PA6 cells. These results suggest that although HGF cannot completely replace stromal cells, it is one of the paracrine mediators produced by stromal cells that act on proliferation of osteoclastic cell precursors.

Hepatocyte growth factor remains as an inactive single chain after partial hepatectomy or unilateral nephrectomy

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes and renal tubular epithelial cells. HGF is proteolytically activated in the tissue injured by hepatotoxin or nephrotoxin, suggesting that HGF functions as a crucial growth factor for tissue regeneration following hepatotoxin- or nephrotoxin-induced injury. In this study, we analyzed the molecular form of HGF after partial hepatectomy or after unilateral nephrectomy. The active form of HGF was not detected under our experimental conditions after these operations. Thus, HGF may play little role in liver regeneration after partial hepatectomy and in compensatory renal enlargement after unilateral nephrectomy.

Expression of hepatocyte growth factor and transforming growth factor beta 1 mRNA in P. acnes and lipopolysaccharide-treated rats

Hepatocyte growth factor (HGF), a potent hepatocyte mitogen in vitro, triggers hepatocyte regeneration after partial hepatectomy and acute liver cell necrosis induced by chemicals. In contrast, transforming growth factor beta 1 inhibits hepatocyte proliferation in vitro and suppresses liver regeneration in vivo. We assessed the expression of HGF and TGF beta 1 mRNA in an endotoxin-related hepatic cell necrosis model. Intravenous injection of Gram-negative lipopolysaccharide (LPS) into rats previously given heat-killed Propionibacterium acnes induced endotoxin-related hepatic cell necrosis. In this model, serum ALT began to rise to more than 100IU as early as 3 h after LPS injection, reaching 300IU 12h after injection. HGF mRNA levels in the liver did not increase significantly until 5h after LPS injection; at 12h, they had increased about threefold compared with controls. TGF beta 1 mRNA expression increased threefold after P. acnes treatment alone and increased further after LPS injection. In the spleen, HGF mRNA levels increased within 3h, but in the lung no increase in HGF mRNA was observed. Early elevation of liver TGF beta 1 mRNA levels and delayed elevation of HGF mRNA levels, with low expression of HGF in the lung, may play a role in the pathogenesis of endotoxin-related hepatic necrosis.

Serum hepatocyte growth factor levels in liver diseases: clinical implications

Although recent studies have shown that hepatocyte growth factor (HGF) is a potent mitogen in vivo, the significance of serum HGF in liver diseases remains unclear. To clarify clinical significance of serum HGF in liver diseases, serum HGF was measured in 127 patients with liver diseases and in 200 healthy individuals, using a highly sensitive immunoradiometric assay (IRMA). This assay is specific for HGF and is sensitive enough to detect 0.1 ng/mL of HGF. Mean values for serum HGF in acute hepatitis (AH), chronic hepatitis (CH), liver cirrhosis (LC), hepatocellular carcinoma (HCC), primary biliary cirrhosis (PBC), fulminant hepatic failure (FHF), and normal controls were 0.45, 0.40, 1.05, 1.06, 0.44, 16.40, and 0.27 ng/mL, respectively. Serum HGF levels in these diseases were significantly increased compared with those in the controls (P < .001), and exhibited a positive correlation with total bilirubin, indocyanine green (ICG) test (R15), asparate aminotransferase (AST), and a negative correlation with albumin and prothrombin time (P < .001). Cirrhotic patients with modified Child class C had higher levels of serum HGF than those graded as modified Child class A or B (P < .001). In CH, serum HGF levels were significantly related to the histological activity index (HAI) score (P < .002). Seven patients with HCC who underwent transcatheter arterial embolization (TAE) exhibited a gradual increase in serum HGF levels up to day 4 after treatment; these higher levels were maintained until day 7, although AST reached a peak on day 2 and then decreased gradually.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of HGF and HGFR gene expression

Hepatocyte growth factor and its receptor (the product of the c-met protooncogene) are believed to be necessary for the normal growth and development of many tissues and organs. This ligand/receptor system controls essential cellular responses such as cell proliferation and motility as well as morphogenesis and differentiation. HGF mRNA is expressed primarily in mesenchymal but not in epithelial cells while its receptor is predominately expressed in epithelial cells. This pattern of HGF and HGFR gene expression in combination with the unique biological effects of HGF on its target cells has led to the postulate that HGF is one of the long-sought mediators conveying cross-talk between the epithelial and stromal compartments of a given tissue. The expression of HGF and HGFR genes are unregulated in several types of human cancer; therefore, understanding the control mechanisms governing HGF and HGFR gene expression is of great clinical interest. Toward this goal, we have analyzed the effects of various physiological agents such as cytokines and hormones on the expression of HGF and the HGFR in a multitude of cell types in vitro. Moreover, we have cloned and analyzed the HGF promoter and its 5'-flanking region to uncover the basis for its inducible and cell-type specific expression at the transcriptional level. Our results indicate that HGF and HGFR gene expression is inducible and their expression is orchestrated in stromal and epithelial cells, respectively, by extracellular signals derived from steroid hormones as well as cytokines such as IL-1, IL-6, and TNF alpha.

Identification of a cell-type-specific transcriptional repressor in the promoter region of the mouse hepatocyte growth factor gene

Hepatocyte growth factor (HGF), a cytokine with multiple functions, exhibits cell-type-specific as well as cytokine- and steroid hormone-regulated expression. The HGF gene is known to be expressed predominately in mesenchymal but not in epithelial cells. In this study, we report the identification of a cell-type-specific transcriptional repressor in the promoter region of the mouse HGF gene, which is evidently responsible for the suppression of HGF expression in epithelial cells. Gel mobility shift assays and DNase I footprinting studies revealed that a 27-bp element (-16 to +11) around the transcription initiation site is responsible for the binding of a nuclear protein which is present in epithelial but not in mesenchymally derived cells. Further analysis of the binding activity of the DNA region with nuclear protein revealed that an approximately 19-bp sequence containing a unique palindromic structure (5'-AACCGACCGGTT-3') overlapped by a CAP box is essential for binding. Substitution of a single base (the contact site) within this region by site-directed mutagenesis resulted in total abrogation of the binding of the nuclear protein and a concomitant increase in the transcriptional activity of various lengths of HGF-chloramphenicol acetyltransferase fused genes when transfected into the epithelial cell line RL95-2 but not the mesenchymal cell line NIH 3T3. Southwestern (DNA-protein) analyses revealed that the nuclear protein which binds to this repressor element is a single polypeptide of approximately 70 kDa. Analysis of the nuclear extract prepared from regenerating mouse liver at various times after two-thirds partial hepatectomy by gel mobility shift assay revealed a substantial reduction (more than 75% within 3 h) in the binding of the repressor to its cognate binding site. Our results suggest that a cis-acting transcriptional repressor in the promoter region of the mouse HGF gene is involved in cell-type-specific regulation through binding to its cognate trans-acting protein which exists in epithelial cells but is absent in fibroblast cells.

Identification of a cell-type-specific transcriptional repressor in the promoter region of the mouse hepatocyte growth factor gene

Hepatocyte growth factor (HGF), a cytokine with multiple functions, exhibits cell-type-specific as well as cytokine- and steroid hormone-regulated expression. The HGF gene is known to be expressed predominately in mesenchymal but not in epithelial cells. In this study, we report the identification of a cell-type-specific transcriptional repressor in the promoter region of the mouse HGF gene, which is evidently responsible for the suppression of HGF expression in epithelial cells. Gel mobility shift assays and DNase I footprinting studies revealed that a 27-bp element (-16 to +11) around the transcription initiation site is responsible for the binding of a nuclear protein which is present in epithelial but not in mesenchymally derived cells. Further analysis of the binding activity of the DNA region with nuclear protein revealed that an approximately 19-bp sequence containing a unique palindromic structure (5'-AACCGACCGGTT-3') overlapped by a CAP box is essential for binding. Substitution of a single base (the contact site) within this region by site-directed mutagenesis resulted in total abrogation of the binding of the nuclear protein and a concomitant increase in the transcriptional activity of various lengths of HGF-chloramphenicol acetyltransferase fused genes when transfected into the epithelial cell line RL95-2 but not the mesenchymal cell line NIH 3T3. Southwestern (DNA-protein) analyses revealed that the nuclear protein which binds to this repressor element is a single polypeptide of approximately 70 kDa. Analysis of the nuclear extract prepared from regenerating mouse liver at various times after two-thirds partial hepatectomy by gel mobility shift assay revealed a substantial reduction (more than 75% within 3 h) in the binding of the repressor to its cognate binding site. Our results suggest that a cis-acting transcriptional repressor in the promoter region of the mouse HGF gene is involved in cell-type-specific regulation through binding to its cognate trans-acting protein which exists in epithelial cells but is absent in fibroblast cells.

Rapid induction of mRNAs for liver regeneration factor and insulin-like growth factor binding protein-1 in primary cultures of rat hepatocytes by hepatocyte growth factor and epidermal growth factor

Liver regeneration factor belongs to the leucine-zipper family of transcription factors. It was originally cloned and characterized through differential screening of a regenerating rat liver cDNA library. The mRNA for liver regeneration factor-1 is barely detectable in normal rat liver but is dramatically induced after two-thirds hepatectomy, with a peak 1 to 3 hr after surgery. The nature of the signaling molecule(s) for this rapid induction is not known. It has been suggested that the liver regeneration factor-1 protein product, through complex interactions with other transcription factors such as c-Jun and Jun-B, controls expression of genes that are required during the G1 phase of hepatic growth. Hepatocyte growth factor has been shown to be the most potent mitogen for hepatocytes in vitro and in vivo. Plasma levels of hepatocyte growth factor rapidly (within 30 min) increase after loss of hepatic parenchyma induced by partial hepatectomy or carbon tetrachloride treatment. It has been postulated that hepatocyte growth factor plays a crucial role in stimulating the hepatocyte to enter the cell cycle. In this communication, we report that addition of pure hepatocyte growth factor to primary cultures of rat hepatocytes in the absence of serum and insulin results in rapid and transient induction of liver regeneration factor-1 mRNA (more than 20-fold) with a peak of expression 1 hr after treatment. The levels of jun-B and c-fos mRNAs, which are also known to be induced during the early hours of liver regeneration, were also increased after treatment of isolated hepatocytes with hepatocyte growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of hepatocyte growth factor gene expression by estrogen in mouse ovary

Hepatocyte growth factor (HGF) is expressed in a variety of tissues and cell types under normal conditions and in response to various stimuli such as tissue injury. In the present study, we demonstrate that the transcription of the HGF gene is stimulated by estrogen in mouse ovary. A single injection of 17 beta-estradiol results in a dramatic and transient elevation of the levels of mouse HGF mRNA. Sequence analysis has found that two putative estrogen responsive elements (ERE) reside at -872 in the 5'-flanking region and at +511 in the first intron, respectively, of the mouse HGF gene. To test whether these ERE elements are responsible for estrogen induction of HGF gene expression, chimeric plasmids containing variable regions of the 5'-flanking sequence of HGF gene and the coding region for chloramphenicol acetyltransferase (CAT) gene were transiently transfected into both human endometrial carcinoma RL 95-2 cells and mouse fibroblast NIH 3T3 cells to assess hormone responsiveness. Transfection results indicate that the ERE elements of the mouse HGF gene can confer estrogen action to either homologous or heterologous promoters. Nuclear protein extracts either from RL95-2 cells transfected with the estrogen receptor expression vector or from mouse liver bound in vitro to ERE elements specifically, as shown by band shift assay. Therefore, our results demonstrate that the HGF gene is transcriptionally regulated by estrogen in mouse ovary; and such regulation is mediated via a direct interaction of the estrogen receptor complex with cis-acting ERE elements identified in the mouse HGF gene.

Hepatocyte growth factor/scatter factor stimulates hair growth of mouse vibrissae in organ culture

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional polypeptide that acts as a mitogen, motogen, or morphogen, depending on the biologic context. In this study, we examined the effect of HGF/SF on hair growth using a serum-free organ culture system. Vibrissal hair follicles isolated from newborn mice were cultured at 31 degrees C in 95% O2/5% CO2 for 72 h in the presence of various cytokines or growth factors, and elongation of hair shaft, DNA, and protein synthesis in hair follicles were measured. Among the agents tested, only HGF/SF significantly increased hair follicle length (p < 0.001), 3H-thymidine (p < 0.001), and 35S-cysteine (p < 0.05) incorporation. The effect of HGF/SF was dose dependent, with maximal stimulation obtained at 10 ng/ml. The increase in hair follicle length and thymidine incorporation were specifically inhibited by a neutralizing antibody against HGF/SF. These results indicate that HGF/SF can promote hair growth and may have clinical utility in this regard.

The effect of various cytokines on hair growth of mouse vibrissae in organ culture

Hepatocyte growth factor/scatter factor (HGF) is a multifunctional polypeptide which acts as a mitogen, motogen or morphogen depending on the biological context. In this study, we examined the effect of HGF on hair growth using a serum-free organ culture system. Vibrissal hair follicles isolated from newborn mice were cultured at 31 degrees C in 95% O2-5%CO2 for 72 h in the presence of various cytokines or growth factors. DNA, protein synthesis and elongation of the hair shaft in the hair follicles were measured. Among the agents tested, only HGF significantly increased hair follicle length (P < 0.001) and 3H-thymidine (P < 0.001) incorporation. The effect of HGF was dose-dependent, with maximal stimulation obtained at 10 ng/ml. The increase in hair follicle length and thymidine incorporation were specifically inhibited by a neutralizing antibody against HGF. These results indicate that HGF is able to promote hair growth and may have clinical utility in this regard.

In vivo response of hepatocytes to growth factors requires an initial priming stimulus

Although growth factor effects have been studied in cultured hepatocytes, little information exists as to whether these factors can trigger hepatocyte replication in vivo. In this study we infused epidermal growth factor, transforming growth factor-alpha and hepatocyte growth factor directly into the portal vein of rats for 24 hr to see whether they could induce DNA synthesis in normal livers or in livers subjected to one-third hepatectomy. Infusion of transforming growth factor-alpha or epidermal growth factor at doses up to 80 micrograms/24 hr had little effect on hepatic DNA synthesis in normal liver, whereas the monomeric and heterodimeric forms of hepatocyte growth factor generally produced increases of less than threefold in hepatic DNA synthesis. In contrast, after one-third hepatectomy infusion of epidermal growth factor, transforming growth factor-alpha or hepatocyte growth factor produced dose-dependent increases in hepatic DNA synthesis. At a dose of 40 micrograms/24 hr, epidermal growth factor increased DNA synthesis threefold, whereas transforming growth factor-alpha or hepatocyte growth factor increased DNA synthesis to greater than six times that in rats that had undergone hepatectomy alone. Furthermore, infusion of these growth factors, with or without one third-hepatectomy, induced the expression of transforming growth factor-alpha mRNA in the liver. The pattern of protooncogene expression induced by one-third hepatectomy was studied to determine the effect of this procedure in sensitizing the liver to the growth factors. Compared with the well-characterized two-thirds hepatectomy system, there was a similar but smaller increase in c-myc expression but no induction of c-jun expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocyte growth factor elevates the activity levels of glycolipid sulfotransferases in renal cell carcinoma cells

Accumulation of sulfoglycolipids associated with markedly elevated activity levels of glycolipid sulfotransferases has previously been demonstrated in the human renal cell carcinoma cell line, SMKT-R3. To elucidate the regulatory mechanisms of sulfoglycolipid synthesis in SMKT-R3 cells, the effects of various growth factors on the metabolic enzymes of sulfoglycolipids were investigated. Hepatocyte growth factor (HGF) significantly increased the activity levels of the sulfotransferases in a dose-dependent manner, but did not change that of arylsulfatase A, which hydrolyzes sulfoglycolipids. Scatchard analysis of 125I-HGF binding to SMKT-R3 cells indicated that the cells expressed high-affinity receptors for HGF with a Kd of 36 pM and 750 sites/cell. Furthermore, metabolic labeling with [35S]sulfate revealed that the addition of HGF to the culture medium of the cells resulted in an increment of sulfoglycolipid synthesis. Therefore, these observations suggest that HGF can function as a regulatory factor in sulfoglycolipid synthesis through the modulation of the sulfotransferase activity levels in renal cell carcinoma cells. In addition, HGF stimulated the proliferation and motility of SMKT-R3 cells, suggesting that HGF has multiple biological activities in renal cell carcinoma cells.

Expression of hepatocyte growth factor mRNA during oval cell activation in the rat liver

The customary wave of hepatocyte regeneration which occurs in the rat liver after two-thirds partial hepatectomy can be abolished by oral administration of the carcinogen 2-acetylaminofluorene. Instead, regeneration is achieved through the proliferation and differentiation of potential stem cells (oval cells) which appear to emanate from the portal space. Ultrastructural studies have illustrated the undifferentiated nature of these cells in the first 3 days after resection, but very rapidly they acquire features of small hepatocytes or biliary epithelia. Oval cell progeny can form either cohesive columns of cells within sinusoids which may later differentiate into new hepatic plates, or single cells that can insinuate within existing plates. Using a 35S antisense riboprobe to hepatocyte growth factor (HGF) mRNA, the synthesis of HGF mRNA was observed in sinusoid-lining cells. There were few HGF mRNA-expressing cells in the liver removed at resection, but numbers steadily increased in the remnant over the next 7 days. In particular, an almost nine-fold increase in the density of HGF mRNA-producing cells occurred in the periportal areas, resulting in approximately double the density present within the centrilobular parenchyma. The superabundance of HGF-producing cells in the immediate vicinity of oval cell proliferation and differentiation strongly suggests that this growth factor is involved in all aspects of stem cell behaviour--proliferation, migration, and differentiation, through a paracrine mechanism.

Properties and functions of scatter factor/hepatocyte growth factor and its receptor c-Met

Scatter factor (SF), a cell motility factor with a multimodular structure, is identical to hepatocyte growth factor (HGF), a potent mitogen of various cell types. The receptor for SF/HGF has recently been identified as the c-Met proto-oncogene product, a transmembrane receptor tyrosine kinase. Depending on the target cells and culture conditions, SF/HGF has several distinct activities in vitro, i.e., it induces cell motility, proliferation, invasiveness, tubular morphogenesis, angiogenesis, or cytotoxicity. In vivo, SF/HGF might be involved in tissue regeneration, tumor progression, and embryological processes.

Up-regulation of hepatocyte growth factor gene expression by interleukin-1 in human skin fibroblasts

Hepatocyte growth factor (HGF) functions as a hepatotrophic and renotrophic factor for regeneration of the liver and kidney. When 1 ng/ml of interleukin-1 alpha (IL-1 alpha) or interleukin-1 beta (IL-1 beta) was added to cultures of human skin fibroblasts, the production of HGF was 5-6 fold higher than levels in the controls. HGF mRNA level in the cells was increased to 4-fold higher levels at 6 h after exposure to IL-1 alpha. Tumor necrosis factor-alpha and interferon-gamma but no other cytokine tested had slightly stimulatory effects on HGF production. The tumor promoter, tetradecanoylphorbol 13-acetate (TPA) markedly enhanced the stimulatory effect of IL-1 alpha and IL-1 beta on the production of HGF. The stimulatory effect of both IL-1 alpha and IL-1 beta and the synergistical stimulation with TPA were completely abrogated by 10 ng/ml TGF-beta 1 or 1 microM dexamethasone. These results suggest that IL-1 alpha and IL-1 beta are positive regulators for expression of the HGF gene and are likely have a role in regeneration of tissues following the occurrence of inflammatory diseases.