Induction of hepatocyte growth factor/scatter factor by interferon-gamma in human leukemia cells

Comparative effects of hepatocyte growth factor and tacrolimus on acute liver allograft early tolerance

Allostimulated CD8+ T cells (aCD8+ T cells), as the main mediators of acute liver rejection (ARJ), are hyposensitive to apoptosis due to the inactivation of death receptor FAS-mediated pathways and fail to allow tolerance induction, eventually leading to acute graft rejection. Although tacrolimus (FK506), the most commonly used immunosuppressant (IS) in the clinic, allows tolerance induction, its use is limited because its target immune cells are unknown and it is associated with increased incidences of malignancy, infection, and nephrotoxicity, which substantially impact long-term liver transplantation (LTx) outcomes. The dark agouti (DA)-to-Lewis rat LTx model is a well-known ARJ model and was hence chosen for the present study. We show that both hepatocyte growth factor (HGF) (cHGF, containing the main form of promoting HGF production) and recombinant HGF (h-rHGF) exert immunoregulatory effects mainly on allogeneic aCD8+ T cell suppression through FAS-mediated apoptotic pathways by inhibiting cMet to FAS antagonism and Fas trimerization, leading to acute tolerance induction. We also showed that such inhibition can be abrogated by treatment with neutralizing antibodies against cMet (HGF-only receptor). In contrast, we did not observe these effects in rats treated with FK506. However, we observed that the effect of anti-rejection by FK506 was mainly on allostimulated CD4+ T cell (aCD4+ T cell) suppression and regulatory T cell (Treg) promotion, in contrast to the mechanism of HGF. In addition, the protective mechanism of HGF in FK506-mediated nephrotoxicity was addressed. Therefore, HGF as a tolerance inducer, whether used in combination with FK506 or as monotherapy, may have good clinical value. Additional roles of these T-cell subpopulations in other biological systems and studies in these fields will also be meaningful.

Hepatocyte growth factor-mediated apoptosis mechanisms of cytotoxic CD8(+) T cells in normal and cirrhotic livers

Intrahepatic stem/progenitor cells and cytotoxic CD8⁺ T cells (CD8⁺ T cells) in the cirrhotic liver undergo apoptosis, which potentially facilitates progression to cancer. Here, we report that hepatocyte growth factor (HGF) signaling plays an important role in promoting normal and damaged liver CD8⁺ T cell Fas-mediated apoptosis through its only receptor, c-Met. In addition to binding with HGF, c-Met also binds to Fas to form a complex. Using a diethylnitrosamine (DEN)-induced liver fibrosis/cirrhosis mouse model, immunostaining, and terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining, we found that HGF secretion was significantly higher at 10 weeks post-DEN, the liver cirrhotic phase (LCP), than at 3 weeks post-DEN, the liver fibrotic phase (LFP). Correspondingly, differences in CD8⁺ T cell proliferation and apoptosis were noted between the two phases. Interestingly, staining and TUNEL assays revealed lower smooth muscle actin (α-SMA)⁺ cell apoptosis, a marker for hepatic stellate cells (HSCs), in the LFP group than in the LCP group, which suggested a beneficial correlation among HGF, CD8⁺ T cells and HSCs in improving the fibrotic load during damaged liver repair. In cultures, when met different concentrations of recombinant HGF (rHGF), phytohemagglutinin (PHA)-stimulated naive mouse splenic CD8⁺ T cells (pn-msCD8⁺ T cells) responded differently; as increases in rHGF increased were associated with decreases in the clonal numbers of pn-msCD8⁺ T cells, and when the rHGF dose was greater than 200 ng/mL, the clonal numbers significantly decreased. In the presence of 400 ng/mL rHGF, the death-inducing signaling complex (DISC) can be directly activated in both nsCD8⁺ T cells and healthy human peripheral blood CD8⁺ T cells (hp-CD8⁺ T cells), as indicated by recruitment of FADD and caspase-8 because DISC forms via the recruitment of FADD and caspase-8, among others. These findings suggest that Fas-mediated apoptosis, may also indicate a regulatory role of HGF signaling in hepatic homeostasis.

Ad-IRF-1 induces apoptosis in esophageal adenocarcinoma

The nuclear transcription factor interferon regulatory factor-1 (IRF-1) is a putative tumor suppressor, but the expression and function of IRF-1 in esophageal adenocarcinoma (EA) remain unknown. We hypothesized that IRF-1 expression was reduced or lost in EA and that restoration of IRF-1 would result in the apoptosis of EA cells in vitro and the inhibition of tumor growth in vivo. Three EA cell lines were used to examine IRF-1 expression, IFN-gamma responsiveness, and the effects of IRF-1 overexpression using a recombinant adenoviral vector (Ad-IRF-1). All three EA cell lines produced IRF-1 protein following IFN-gamma stimulation, although IFN-gamma did not induce cell death. In contrast, Ad-IRF-1 infection resulted in high levels of IRF-1 protein and triggered apoptosis in all three EA cell lines. Potential mechanisms for the differential response to IFN-gamma versus Ad-IRF-1--such as modulation of c-Met or extracellular regulated kinase signaling, or altered expression of IRF-2, Fas, or survivin--were investigated, but none of these mechanisms can account for this observation. In vivo administration of IRF-1 in a murine model of EA modestly inhibited tumor growth, but did not lead to tumor regression. Strategies aimed at increasing or restoring IRF-1 expression may have therapeutic benefits in EA.

Modulation of hepatocyte growth factor induction in human skin fibroblasts by retinoic acid

Topical treatment of skin with all-trans-retinoic acid (ATRA), the major biologically active form of vitamin A, results in hyperproliferation of basal keratinocytes, leading to an accelerated turnover of epidermis cells and thickening of the epidermis, probably via induction of production of paracrine growth factors for keratinocytes in epidermal suprabasal keratinocytes and/or dermal fibroblasts. Since hepatocyte growth factor (HGF) is a factor mitogenic to epidermal keratinocytes secreted from dermal fibroblasts, the effect of ATRA on basal and induced HGF production in human dermal fibroblasts in culture was examined. ATRA alone did not induce HGF production, but it significantly enhanced HGF production induced by the cAMP-elevating agent cholera toxin or the membrane-permeable cAMP analog 8-bromo-cAMP. Cholera toxin-induced activation of cAMP responsive element (CRE)-binding protein (CREB) was enhanced by pretreating cells with ATRA for 24 h. In contrast, HGF production induced by epidermal growth factor (EGF) or phorbol 12-myristate 13-acetate (PMA) was potently inhibited by ATRA. These modulatory effects of ATRA were different from the effects of transforming growth factor-beta1 (TGF-beta) and dexamethasone, both of which inhibited HGF production induced by all of the four inducers. Up-regulation of HGF gene expression by cholera toxin and EGF was also enhanced and inhibited, respectively, by ATRA. Both 9-cis-retinoic acid (9-cis-RA) and 13-cis-retinoic acid (13-cis-RA), which are stereo-isomers of ATRA, showed a modulatory effect on HGF induction similar to that of ATRA. These results suggest that ATRA augments the induction of HGF production caused by increased intracellular cAMP.

Synergistic induction of hepatocyte growth factor in human skin fibroblasts by the inflammatory cytokines interleukin-1 and interferon-γ

Hepatocyte growth factor (HGF) is one of the vital factors for wound healing. HGF expression markedly increases in wounded skin and is mainly localized in dermal fibroblasts. HGF expression level in human dermal fibroblasts in vitro, however, is low and thus may be stimulated by some factors in the process of wound healing. Candidates of the factors are inflammatory cytokines released by polymorphonuclear and mononuclear cells infiltrating the wounded area, but HGF production in human dermal fibroblasts is only slightly induced by interleukin (IL)-1, tumor necrosis factor (TNF)-alpha or interferon (IFN)-gamma. We here report that a combination of IL-1beta and IFN-gamma or a combination of TNF-alpha and IFN-gamma very markedly induced HGF production. The synergistic effect of the former was more marked than that of the latter. Synergistic effects of IL-1beta and IFN-gamma were observed at more than 10 pg/ml and 10 IU/ml, respectively, and were detectable as early as 12 h after addition. Neither IFN-alpha nor IFN-beta was able to replace IFN-gamma. HGF mRNA expression was also synergistically upregulated by IL-1beta and IFN-gamma. IL-1beta plus IFN-gamma-induced synergistic production of HGF was potently inhibited by treatment of cells with the extracellular signal-regulated kinase (ERK) kinase inhibitor PD98059 and the p38 inhibitor SB203580 but not by the c-Jun N-terminal kinase (JNK) inhibitor SP600125. Taken together, our results indicate that a combination of IL-1beta and IFN-gamma synergistically induced HGF production in human dermal fibroblasts and suggest that activation of ERK and p38 but not of JNK is involved in the synergistic effect.

Inhibition of Hepatocyte Growth Factor Induction in Human Dermal Fibroblasts by Tryptanthrin

In addition to regulation of normal cell functions, hepatocyte growth factor (HGF) has also been shown to be involved in malignant cell transformation and in growth, invasion and metastasis in cancer cells. Inhibitors of HGF production have a potential for interfering with malignant cell transformation and progression of tumors. We found that tryptanthrin, one of the major compounds extracted from the medicinal plant Polygonum tinctorium, which is known for its antitumor activity, strongly inhibited HGF production stimulated by various HGF inducers in human dermal fibroblasts. HGF production induced by phorbol 12-myristate 13-acetate (PMA) was potently inhibited by tryptanthrin without any appreciable cytotoxic effect. Tryptanthrin also inhibited HGF production induced by epidermal growth factor (EGF) and platelet-derived growth factor. Moreover, proliferation of the fibroblasts induced by the two growth factors was potently suppressed by tryptanthrin to the level of proliferation of unstimulated fibroblasts. However, tryptanthrin did not inhibit HGF production induced by the protein kinase A-activating agents cholera toxin and 8-bromo-cAMP. These effects of tryptanthrin were different from the effects of transforming growth factor beta1 and dexamethasone, both of which inhibit HGF production induced by all the above inducers. Upregulations of HGF gene expression by PMA and EGF were also inhibited by tryptanthrin. Activation of the mitogen-activated protein kinase (MAPK) signaling pathway is crucial for PMA-induced HGF production, but tryptanthrin did not attenuate phosphorylation of MAPK induced by PMA. These results indicate that tryptanthrin potently inhibited induction of HGF production probably through events downstream of MAPK activation.

Inhibition of Hepatocyte Growth Factor Production in Human Fibroblasts by Ursodeoxycholic Acid

Hepatocyte growth factor (HGF) stimulates the proliferation of hepatocytes and biliary epithelial cells and protects hepatocytes from apoptosis induced by various stimuli. In view of HGF induction by interferons, substances used for the treatment of chronic hepatitis C, this study was conducted to determine whether ursodeoxycholic acid (UDCA), which is widely used for the treatment of cholestatic liver diseases, modulates HGF production. UDCA did not induce HGF production in human dermal fibroblasts, but it potently inhibited phorbol-12-myristate-13-acetate (PMA)- and cholera-toxin-induced HGF production without affecting cell viability. The inhibitory effects of UDCA were as potent as those of transforming growth factor-beta1 and dexamethasone. Up-regulations of HGF gene expression induced by PMA and cholera toxin were also inhibited by UDCA. Moreover, UDCA dose-dependently inhibited high constitutive HGF production by MRC-5 cells without decreasing cell viability. Deoxycholate, chenodeoxycholate, taurochenodeoxycholate and glycochenodeoxycholate also inhibited cholera-toxin-induced HGF production at non-cytotoxic doses. UDCA, however, had no apparent effect on PMA-induced phosphorylation of mitogen-activated protein kinase, which is crucial for HGF induction by PMA. These results indicate that non-cytotoxic doses of UDCA inhibited constitutive and induced HGF production and suggest that UDCA supplemented with HGF or HGF inducers could have a more potential therapeutic effect.

Inhibition of hepatocyte growth factor induction in human dermal fibroblasts by interleukin-1 and its prevention by interferon-γ

Hepatocyte growth factor (HGF) is one of the vital factors for liver regeneration. HGF production is induced by the activation of protein kinase A and protein kinase C-mediated pathways, interleukin (IL)-1, tumor necrosis factor (TNF)-alpha, and epidermal growth factor (EGF) in mesenchymal cells. We here report that IL-1 and TNF-alpha, hitherto regarded as HGF inducers, potently inhibited HGF production stimulated by other HGF inducers. IL-1alpha, IL-1beta, and TNF-alpha alone had minimal stimulating effects on HGF production in human dermal fibroblasts, but they strongly inhibited production of HGF induced by cholera toxin, 8-bromo-cAMP, EGF, and phorbol 12-myristate 13-acetate (PMA). Moreover, although the high level of HGF production in MRC-5 cells was enhanced by PMA and less markedly by IL-1beta, HGF production in MRC-5 cells treated with PMA plus IL-1beta was less than that in the cells treated with PMA alone. In the presence of interferon (IFN)-gamma, however, cholera toxin- and 8-bromo-cAMP-induced HGF production was not inhibited by IL-1beta. Pretreatment of cells with IL-1beta suppressed the phosphorylation of cAMP-responsive element-binding protein induced by cholera toxin but not that induced by 8-bromo-cAMP. Taken together, our results indicate that IL-1 inhibited HGF production stimulated by various inducers, including protein kinase A-activating agents, and that IFN-gamma overcame this inhibition of induction of HGF production.

Hepatocyte growth factor/scatter factor in development, inflammation and carcinogenesis: its expression and role in oral tissues

Hepatocyte growth factor (HGF) was discovered as a potent mitogen for adult hepatocytes from the plasma of patients with fulminant hepatic failure. It is now known to be a broad-spectrum, multi-functional mitogen, motogen and morphogen. The activities of HGF are mediated through the signalling pathway of its receptor, c-Met. During tooth development, HGF is expressed in the dental papilla and c-Met is expressed in the inner enamel epithelium. The expression of HGF and c-Met indicates that HGF is involved in morphogenesis of the tooth by mediating epithelial-mesenchymal interactions. In the mature tooth, HGF expression by fibroblasts is enhanced in pulpitis and mediated through the induction of prostaglandin (PG) E(2); it is induced not only by inflammatory cytokines, but also by components of oral bacteria. Consequently, concentrations of HGF in gingival crevicular fluid (GCF) increase in periodontitis. The mitogenic and other biological activities, such as angiogenesis, of HGF contribute towards wound healing. Both HGF and c-Met are expressed in the developing tongue, and the signalling pathway of the latter is shown to be essential for myogenesis. Dysregulation of c-Met signalling is observed in carcinogenesis, but HGF also has cytotoxic activity to certain tumour cells. The reason for the discrepancy between these observations is not clear at present.

Induction by staurosporine of hepatocyte growth factor production in human skin fibroblasts independent of protein kinase inhibition

Staurosporine is one of the most potent and well known inhibitors of protein kinases, and it is often used to study the involvement of protein kinases in signal transduction pathways. We now report that staurosporine can induce the production of hepatocyte growth factor (HGF) independently of protein kinase inhibition. Staurosporine markedly stimulated the production of HGF in various cell types, including human skin fibroblasts. Its effect was accompanied by up-regulation of HGF gene expression. The inhibition of protein kinases appears not to be involved in staurosporine-induced HGF production, because other protein kinase inhibitors, K-252a, H-7, GF 109203X and genistein, had no HGF-inducing activity. UCN-01, 7-hydroxystaurosporine, which differs from staurosporine only in its aglycone moiety, also showed HGF-inducing activity, and inactive K-252a differs from staurosporine only in its sugar moiety. These results indicate that the sugar moiety, a six-atom ring structure, is important in the HGF-inducing activity of staurosporine. Experiments were then carried out to determine whether the characteristics of staurosporine-induced HGF production have similarities to those of HGF production stimulated by other HGF inducers. The effect of staurosporine like that of 8-bromo-cAMP and that of cholera toxin was marked in human skin fibroblasts from all four different sources, whereas the effects of epidermal growth factor and phorbol 12-myristate 13-acetate were variable depending on cells. The net increase in HGF production induced by staurosporine was not reduced in protein kinase C-depleted human skin fibroblasts. Moreover, synergistic induction of HGF was detected between staurosporine and interferon-gamma as well as between 8-bromo-cAMP and interferon-gamma. Staurosporine, however, did not increase intracellular cAMP levels in human skin fibroblasts. These results indicate that staurosporine induced HGF in different cell types via a signaling pathway similar to the cAMP-mediated pathway without increasing cAMP levels.

The mitogenic activity of the liver growth factor is mediated by tumor necrosis factor alpha in rat liver

BACKGROUND/AIMS

Liver growth factor (LGF) is a hepatic mitogen, however, the hepatic stimulation pathway remains to be characterized. The aim of this study was to determine whether tumor necrosis factor alpha (TNF-alpha) stimulation constitutes a step in the mitogenic pathway of LGF.

METHODS

Rats were injected with 4.5 microg LGF/rat, and LGF activity was measured both by liver DNA synthesis stimulation and "proliferating cell nuclear antigen (PCNA)-positive" hepatocytes in rats injected with LGF or +anti-TNF-alpha. TNF-alpha expression was evaluated by reverse-transcription polymerase chain reaction. TNF-alpha-producing cells were immunodetected. Human endothelial cells (HUVEC) were stimulated by LGF. TNF-alpha was detected in the supernatant, and the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular endothelial adhesion molecule-1 (VCAM-1) by flow cytometry analysis.

RESULTS

LGF-injected rats showed higher intrahepatic TNF-alpha expression. DNA synthesis and PCNA-positive hepatocytes induced by LGF were inhibited by anti-TNF-alpha, PCNA-positive hepatocytes being especially abundant around the central vein when LGF was injected alone, but TNF-alpha exhibited increased signal intensity in endothelial cells of the portal vein. LGF stimulated TNF-alpha secretion in HUVEC, but did not stimulate ICAM-1 or VCAM-1 up-regulation.

CONCLUSIONS

The mitogenic cascade initiated by LGF in rat liver in vivo depends, at least in part, on TNF-alpha stimulation. Portal vein endothelial cells seem to be a source of TNF-alpha.

A critical function of USF in HGF gene regulation mediated by a multiconsensus region

Hepatocyte growth factor (HGF) is a multifunctional growth factor implicated in a variety of tissue restructuring processes. Since HGF acts as a highly potent mitogen, HGF expression is suggested to be under a well-defined transcriptional control. The 5' sequence of the HGF gene clusters a set of several binding sites for transcription factors in a so-called multiconsensus region (MCR) located between -230 and 260. Our studies demonstrate that a NF1-like element and the E(1)-box of the MCR form the main complexes with nuclear proteins and that both are involved in transcriptional silencing of the HGF gene in non-HGF expressing cell types. The E(1)-box of two tandemly arranged E-boxes was shown to be a binding site of high affinity interacting with the upstream stimulatory factor (USF). While recombinant expression of a wild-type USF did not affect gene expression, a USF variant lacking the DNA binding domain restored the MCR mediated transcriptional repression. In conclusion, our data provide evidence that USF is a central factor of cell-type specific HGF regulation, acting in cooperation with additional regulatory proteins as a bivalent mediator of transcriptional activation or repression.

Novel growth factors involved in the pathogenesis of proliferative vitreoretinopathy

AIMS

To determine whether hepatocyte growth factor (HGF) and connective tissue growth factor (CTGF) are expressed in human specimens of proliferative vitreoretinopathy (PVR) and to propose a model of PVR pathogenesis based upon the known activities of these growth factors. Methods Immunohistochemical methods (ABC Elite) were used to demonstrate the presence of HGF and CTGF in cryostat sections of five human PVR membranes.

RESULTS

In each of the five PVR membranes, stromal cells were immunohistochemically positive for both HGF and CTGF. Based upon this information and the known actions of these growth factors, a model of PVR pathogenesis was developed. In this model, injury of the retina induces an inflammatory response that upregulates HGF expression inducing the formation of multilayered groups of migratory retinal pigment epithelial cells (RPE). These RPE, present in a provisional extracellular matrix, come in contact with vitreous containing TGF-beta. The TGF-beta is activated, upregulating expression of CTGF. Under the influence of TGF-beta and CTGF, RPE become myofibroblastic and fibrosis ensues. Retinal traction induces further detachment continuing the cycle of retinal injury.

CONCLUSIONS

HGF and CTGF are expressed in PVR membranes and may play important roles in the pathogenesis of PVR. The expression and function of these growth factors should be critically examined in human PVR specimens, in in vitro cultures of RPE, and in animal models of PVR.

[Function and regulation of production of hepatocyte growth factor (HGF)]

Hepatocyte growth factor (HGF) was purified as a potent mitogen for rat hepatocytes in primary culture and is believed to be the most physiological hepatotrophic factor that triggers liver regeneration. HGF is one of the largest disulfide-linked cytokines, consisting of a 60-kDa heavy chain and a 35-kDa light chain. Human HGF is synthesized as a single polypeptide chain precursor of 728 amino acid residues that has an appreciable homology with plasminogen, and it is processed proteolytically to release an N-terminal signal peptide of 31 amino acids and to generate an active heterodimer after secretion. The novel serine protease HGF activator and urokinase-type plasminogen activator (u-PA) are responsible for the latter extracellular processing. HGF stimulates the proliferation of rat hepatocytes in primary culture at concentrations as low as 10 pM. It also stimulates the growth of various epithelial cells, endothelial cells, and some kinds of mesenchymal cells. HGF inhibits the proliferation of several tumor cell lines and induces apoptosis of some of them. It also has motogenic, morphogenic, anti-apoptotic, angiogenic, and immunoregulatory activities. The receptor of HGF is the product of c-met proto-oncogene with tyrosine kinase activity that mediates the transduction of multiple biological signals of HGF. During liver regeneration, HGF gene expression in the liver, spleen, and lung and HGF levels in the blood and liver increase prior to the induction of liver DNA synthesis. Liver regeneration is markedly inhibited by continuous administration of a neutralizing anti-HGF antibody. HGF production in cultured cells is induced by PKC-activating agents, cAMP-elevating agents, PKA-activating agents, growth factors, and inflammatory cytokines; and it is inhibited by TGF-beta, glucocorticoids, 1,25-dihydroxyvitamin D3, and retinoic acid. There are many reports on potential application of HGF as a therapeutic agent for organ diseases that are difficult to cure such as liver cirrhosis, chronic renal failure, pulmonary fibrosis, myocardial infarction, and arteriosclerosis obliterans utilizing its potent growth-stimulating activity for a wide variety of cells. ELISA kits for assays of serum and plasma HGF levels are clinically used to prognosticate the development of fulminant hepatic failure.

Social isolation stress augments angiogenesis induced by colon 26-L5 carcinoma cells in mice

We have previously shown that tumor necrosis factor-alpha (TNF-alpha), which is an important angiogenesis-related factor, was over-secreted in male BALB/c mice under social isolation stress as compared with the control, and closely associated with a remarkable elevation of tumor invasion and metastasis of colon 26-L5 carcinoma cells. In the present study, we explored the effect of isolation stress on the angiogenesis caused by colon 26-L5 carcinoma cells in vivo and in vitro. Social isolation lead to the enhancement of tumor growth after intrahepatic implantation with a fragment of colon 26-L5 tumor. Angiogenic response (number of vessels oriented towards tumor mass) and tumor growth (size) were significantly increased in the socially isolated mouse relative to that in the group-housed mice. Furthermore, higher protein level of hepatic TNF-alpha was found in the stressed mice than that in the control. Expression of mRNA for vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) were also elevated in the tumor regions and liver tissues of the stressed mice in comparison with that in group-housed mice. On the other hand, hepatic sinusoidal endothelial (HSE) cells treated with TNF-alpha exhibited a marked promotion of the migration, invasion, expression of mRNA for matrix metalloproteinase (MMP)-9, and tube-like formation, but no cytotoxicity against the cells in vitro. The above data suggest that the social isolation stress augmented the tumor-induced angiogenesis probably by up-regulating the angiogenesis-related factors, including TNF-alpha, VEGF and HGF, and consequently mediating the functions of endothelial cells such as migration, invasion, and tube-like formation.

Stimulation of hepatocyte growth factor production in human fibroblasts by the protein phosphatase inhibitor okadaic acid

In this study, we examined whether the production of hepatocyte growth factor (HGF) in fibroblasts is regulated by protein phosphatase(s). Inhibitors of the enzymes okadaic acid and calyculin A were used for this purpose. Both inhibitors markedly stimulated HGF production in human skin fibroblasts in a dose-dependent manner. The effects of okadaic acid and calyculin A were maximal at 25-37.5 and 1.25 nM, respectively. Highly active HGF production in MRC-5 human embryonic lung fibroblasts was also promoted by both inhibitors. The effect of okadaic acid was accompanied by an up-regulation of HGF gene expression. The stimulating effect of okadaic acid on HGF production was synergistic with that of phorbol 12-myristate 13-acetate (PMA) and epidermal growth factor (EGF), whereas it was additive to the effect of cholera toxin. The protein kinase C (PKC) inhibitor GF 109203X inhibited the effect of PMA, but not of okadaic acid and EGF. The effect of okadaic acid as well as EGF was not inhibited, but rather enhanced in human skin fibroblasts pretreated for 24 hr with a high dose of PMA to deplete PKC, as compared with its effect in untreated cells. PD 98059, an inhibitor of mitogen-activated protein (MAP) kinase kinase, suppressed the effects of okadaic acid and EGF, but not those of cholera toxin and 8-bromo-adenosine 3',5'-cyclic monophosphate (cAMP). These results suggest that HGF production in human skin fibroblasts is down-regulated by protein phosphatase(s) and that HGF production stimulated by okadaic acid is, at least in part, dependent on the activation of the MAP kinase cascade.

Synergism between interferon-gamma and cAMP in induction of hepatocyte growth factor in human skin fibroblasts

Interferon (IFN)-gamma stimulates hepatocyte growth factor (HGF) production markedly in various human leukemia cell lines, but its positive effect in human skin fibroblasts is slight. We examined the combined effect of IFN-gamma and various HGF inducers on HGF production in human skin fibroblasts. IFN-gamma synergistically enhanced HGF production stimulated by 8-bromo-cAMP, one of the most effective inducers of HGF: HGF secreted from cells incubated with 1 mM of 8-bromo-cAMP, 1000 U/ml of IFN-gamma and both of these was approximately 8, 1.5 and 24 times, respectively, that secreted from untreated cells. The effect of IFN-gamma was dose-dependent and was nullified by an anti-IFN-gamma antibody. Neither IFN-alpha nor IFN-beta had such an enhancing effect, but both these IFNs inhibited the synergistic effect of IFN-gamma and 8-bromo-cAMP. IFN-gamma also synergistically augmented HGF production induced by interleukin-1beta and cAMP-increasing agents cholera toxin, forskolin and prostaglandin E(2). HGF gene expression upregulated by cholera toxin, forskolin and 8-bromo-cAMP was markedly enhanced by IFN-gamma, which was detected as early as 3 h after its addition. The synergy between HGF inducers and IFN-gamma is not common to all HGF inducers, because HGF production stimulated by epidermal growth factor and protein-kinase-C-activating phorbol esters was significantly inhibited by IFN-gamma. These results indicate that IFN-gamma synergistically stimulates cAMP-induced HGF production and inhibits HGF production induced by growth factors and protein kinase C activators in human skin fibroblasts.

Hepatocyte growth factor/scatter factor enhances the thrombopoietin mRNA expression in rat hepatocytes and cirrhotic rat livers

BACKGROUND

Although thrombopoietin (TPO) is mainly produced in the liver, the regulatory mechanism of TPO gene expression in hepatocytes remains unclear. The role of TPO in thrombocytopenia associated with liver cirrhosis has not been identified.

METHODS

We examined the effects of various growth factors and cytokines on TPO mRNA expression in adult rat hepatocytes in primary cultures using a semiquantitative reverse transcription-polymerase chain reaction assay.

RESULTS

Among them, only hepatocyte growth factor/scatter factor (HGF/SF) enhanced TPO mRNA expression; other growth factors (epidermal growth factor and transforming growth factor-beta) and cytokines (erythropoietin, granulocyte-colony stimulating factor, granulocyte-macrophage-colony stimulating factor, interleukin (IL)-3, IL-6 and interferon-gamma) did not. Next, we examined TPO mRNA expression in the livers of rats with CCl4-induced cirrhosis, the effects of HGF/SF on hepatic TPO mRNA expression and peripheral platelet and bone marrow megakaryocyte counts in the cirrhotic rats. In the cirrhotic rats, both the peripheral platelet count and TPO mRNA expression in the livers were markedly decreased compared with those of the normal rats. The administration of HGF/SF to the cirrhotic rats stimulated TPO mRNA expression in the livers and resulted in significant increases of peripheral platelets and bone marrow megakaryocytes.

CONCLUSIONS

These results suggest that HGF/SF is a possible regulatory factor for TPO gene expression and that HGF/SF increases platelet production through an enhancement of TPO mRNA expression in the livers of cirrhotic rats.

Hepatocyte growth factor in human milk and reproductive tract fluids

PROBLEM

Despite evidence indicating a role for hepatocyte growth factor (HGF) in gastrointestinal and reproductive physiology, the concentration and distribution of HGF in human breast milk (BM) and reproductive tract fluids remain unknown.

METHOD OF STUDY

Using enzyme-linked immunosorbent assay (ELISA), the HGF concentrations were determined in human oviductal fluid (hOF), follicular fluid (FF), amniotic fluid (AF), seminal plasma (SP), and colostrum/milk samples, and expression of HGF mRNA by milk cells and AF cells were examined by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

HGF is present at nearly 70-fold normal serum (0.85+/-0.15 ng/mL) concentration in FF (n = 3; x = 57+/-16 ng/mL) and AF (n = 17; x = 57+/-26 ng/mL), and is also present in hOF (n = 3; x = 4.8+/-2.3 ng/mL) and CVL (n = 8; x = 0.7+/-1.1 ng/mL) varying throughout the menstrual cycle. HGF is found at 3-times serum concentration in BM (n = 24; x = 2.3+/-1.3 ng/mL) with no significant difference between premature and full term or stage of lactation (colostrum, transitional, mature milk). HGF mRNA was detected in BM cells but not in AF cells.

CONCLUSIONS

HGF is present in sufficient amounts to profoundly affect gastrointestinal maturation in the fetus via swallowed AF and neonate via BM, and helps to explain the increased rate of necrotizing enterocolitis (NEC) in infants of premature rupture of membrane (PROM)-complicated pregnancies, and the decreased rate in breast fed neonates. HGF in FF may be necessary for the development and maturation of the oocyte. HGF in hOF, SP, and cervicovaginal lavage (CVL) is likely to enhances epithelial cell integrity and the mucosal barrier. Thus, HGF is widely available in the reproductive tract with functions that remain to be fully elucidated.