Hepatocyte growth factor stimulates phosphoinositide hydrolysis and mitogenesis in cultured renal epithelial cells

A novel mechanism in maggot debridement therapy: protease in excretion/secretion promotes hepatocyte growth factor production

Maggot debridement therapy (MDT) is effective for treating intractable wounds, but its precise molecular mechanism, including the association between MDT and growth factors, remains unknown. We administered MDT to nine patients (66.3 ± 11.8 yr, 5 male and 4 female) with intractable wounds of lower extremities because they did not respond to conventional therapies. Significant increases of hepatocyte growth factor (HGF) levels were observed in femoral vein blood during 48 h of MDT (P < 0.05), but no significant change was found for vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), transforming growth factor-β1 (TGF-β1), or tumor necrosis factor-α (TNF-α). We conducted NIH-3T3 cell stimulation assay to evaluate the relation between HGF and protease activity in excretion/secretion (ES) derived from maggots. Compared with the control group, HGF was significantly higher in the 0.05 μg/ml ES group (P < 0.01). Furthermore, protease inhibitors suppressed the increase of HGF (P < 0.05). The HGF expression was increased in proportion to the ES protein concentration of 0.025 to 0.5 μg/ml. In fact, ES showed stronger capability of promoting HGF production and less cytotoxicity than chymotrypsin or bromelain. HGF is an important factor involved in cutaneous wound healing. Therefore, these results suggest that formation of healthy granulation tissue observed during MDT results from the increased HGF. Further investigation to identify molecules enhancing HGF expression by MDT will contribute greatly to drug target discovery for intractable wound healing therapy.

Hepatocyte growth factor gene therapy for hypertension

Hepatocyte growth factor (HGF) has mitogenic, motogenic, and morphogenic biological activities as well as helps in regenerating various tissues. In cardiovascular organs, HGF was reported to have anti-apoptotic, anti-fibrotic, and vasodilating effects. HGF has close relationships with hypertension, arteriosclerosis, and heart failure. HGF enhances renal regeneration and suppresses the progression of hypertension. Intramuscular electroporation of the therapeutic gene is a simple, economic, and low toxic method compared with systemic administration of the purified proteins or peptides. We outline the technique of intramuscular electroporation of HGF gene as a remedy for hypertension.

Vascular origin of a soluble truncated form of the hepatocyte growth factor receptor (c-met)

Hepatocyte growth factor (scatter factor) is an angiogenic growth factor that binds to its cellular transmembrane receptor, c-met. Both HGF and c-met are expressed by vascular smooth muscle and endothelial cells, where HGF may exert autocrine and paracrine effects. We have found that human aortic smooth muscle cells (HASMCs) and human umbilical vein endothelial cells (HUVECs) release a soluble, truncated form of c-met. Receptor shedding was induced by treatment of the cells with phorbol 12-myristate 13-acetate (PMA) and by the ligand, HGF. Shedding was inhibited by cycloheximide, a metalloproteinase inhibitor, and protein kinase C inhibitors. The soluble form of c-met was able to bind HGF, although with reduced affinity (K(d) approximately 10 nmol/L) compared with the membrane bound receptor. Conditioned medium containing soluble c-met inhibited the induction of Akt phosphorylation by HGF in HUVECs. The soluble truncated form of c-met was detectable in the plasma of 5 healthy volunteers. The shedding of c-met may represent a novel mechanism for regulating the mitogenic, motogenic, and morphogenic effects of hepatocyte growth factor.

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 induces MAPK-dependent formin IV translocation in renal epithelial cells

Renal epithelial tubule formation in cultured cells occurs after the addition of tubulogenic growth factors such as the hepatocyte growth factor (HGF). HGF activates the tyrosine kinase receptor c-met, initiating a series of complex events that regulate cell morphology, cell-cell interactions, and cell-matrix interactions and eventually result in the formation of branching tubular structures. The discovery that disruption of the formin gene locus in mice causes agenesis of the kidneys secondary to failure of ureteric bud outgrowth and branching tubule formation suggested that this family of proteins may be critical to the development of renal epithelial tubules. In this study, we investigated whether formin is involved in the HGF/c-met signaling pathway of in vitro tubulogenesis in renal epithelial cells. mIMCD-3 cells were analyzed by reverse transcription-PCR and found to express formin IV mRNA. With the use of an antibody that recognizes the carboxy terminus of all known formin isoforms, it was observed a formin isoform of approximately 165 kD markedly increased in the detergent soluble cell lysate after 10 min of stimulation with HGF. An antibody that is specific for formin IV was then generated and confirmed that the formin isoform regulated by HGF was formin IV. Cell fractionation and confocal localization of formin IV revealed that formin IV is primarily found in a submembranous band that co-localizes with the actin cytoskeleton and in a perinuclear location in quiescent epithelial cells but undergoes a rapid relocalization after HGF stimulation with translocation into the cell cytosol and into the nucleus. Formin IV was found to be a phosphorylation substrate for activated extracellular signal-regulated kinase in vitro, and pretreatment of cells with the mitogen-activated protein kinase inhibitor U0126 prevented the translocation of formin IV and inhibited HGF-dependent phosphorylation of formin IV in intact cells. In conclusion, activation of the c-met receptor results in cellular relocalization of formin IV in a mitogen-activated protein kinase-dependent manner.

Hepatocyte growth factor in renal regeneration, renal disease and potential therapeutics

Hepatocyte growth factor (HGF) has mitogenic, motogenic, morphogenic, and anti-apoptotic activities on renal cells and is a potential renotropin for renal protection and repair. In chronic renal failure/fibrosis, HGF in the kidney declines in a reciprocal manner to the increase in transforming growth factor-beta (TGF-beta). Neutralization of HGF by the antibody leads to acceleration of renal failure/fibrosis while HGF administration leads to remarkable attenuation, thus indicating the importance of HGF versus TGF-beta counterbalance in both pathogenesis and therapeutics in cases of chronic renal failure. HGF is being strongly considered for potential treatment of acute and chronic renal failure.

Hepatocyte growth factor/scatter factor-induced intracellular signalling

Hepatocyte growth factor (HGF) identical to scatter factor (SF) is a glycoprotein involved in the development of a number of cellular phenotypes, including proliferation, mitogenesis, formation of branching tubules and, in the case of tumour cells, invasion and metastasis. This fascinating cytokine transduces its activities via its receptor encoded by the c-met oncogene, coupled to a number of transducers integrating the HGF/SF signal to the cytosol and the nucleus. The downstream transducers coupled to HGF/MET, most of which participate in overlapping pathways, determine the development of the cell's phenotype, which in most cell types is dual.

Role of extracellular matrix and Ras in regulation of glomerular epithelial cell proliferation

Signals from extracellular matrix (ECM) to growth factor receptors regulate glomerular epithelial cell (GEC) proliferation. Epidermal growth factor (EGF), basic fibroblast growth factor, hepatocyte growth factor (HGF), or thrombin stimulated proliferation of GECs when the cells were adherent to collagen matrices, but not plastic substratum. Furthermore, EGF, HGF, or thrombin activated p42 mitogen-activated protein (MAP) kinase in collagen-adherent GECs, whereas activation was weak in GECs on plastic. To further examine the interaction of ECM with the Ras-MAP kinase cascade, GECs were stably transfected with a constitutively active Ras mutant (V12Ras). Low or moderate levels of V12Ras expression did not affect basal MAP kinase activity but, unlike parental GECs, in clones that express V12Ras, EGF was able to induce proliferation and activate MAP kinase when these cells were adherent to plastic. In parental and V12Ras-transfected GECs, MAP kinase activation was inhibited by cytochalasin D. Thus, adhesion of GECs to ECM facilitates proliferation and MAP kinase activation by mitogens acting via tyrosine kinase or non-tyrosine kinase receptors. Activation of pathway(s) downstream of V12Ras supplants signals from ECM that enable proliferation. These signals may involve the actin cytoskeleton.

Hepatocyte growth factor and the kidney: it is not just for the liver

Mesenchymal-epithelial interactions are important for many biological processes in epithelial organs such as the kidney. Hepatocyte growth factor (HGF) is a mesenchymally derived polypeptide cytokine that acts through its tyrosine kinase c-met receptor and is an important mediator of these interactions. This article reviews data showing the in vitro actions of HGF on renal epithelial cells that result in such diverse responses as mitogenesis, motogenesis, and morphogenesis. It also examines the in vivo evidence linking HGF and the c-met receptor to kidney development, regeneration following injury, and renal disease. Elucidating cellular mechanisms underlying the coordinated control of diverse HGF-induced phenotypic changes in renal epithelia in vitro should contribute to a clearer understanding of complex biological processes such as organogenesis, regeneration, and carcinogenesis in epithelial organs such as the kidney.

Evidence for a functional hepatocyte growth factor receptor in human mesangial cells

In this study we have investigated both the expression of c-met in cultured human mesangial cells and the proliferative effect of HGF on these cells. RNAse protection analysis using a c-met riboprobe showed c-met to be expressed and further that this expression was unaffected by the glucose concentration or osmolality of the media. Immunofluorescence studies performed using anti-HGF or anti-c-met antibodies clearly showed that both proteins are localised to human mesangial cells. Proliferation of human mesangial cells after 24-h treatment with HGF was also examined. HGF 10 ng/ml and 100 ng/ml stimulated 3-H-Thymidine incorporation 1.35-fold (P = 0.001) and 1.6-fold (P<0.00001) respectively in cells made quiescent for 24 h. A similar dose-dependent stimulation of proliferation was observed in cells made quiescent for 48 h. Finally, using RNAse protection analysis we have shown that HGF (10 ng/ml, 100 ng/ml) induces the expression of c-met in these cells in a dose-dependent manner. Together these results indicate for the first time a potential autocrine role for HGF in the human mesangium.

Hepatocyte growth factor-stimulated renal tubular mitogenesis: effects on expression of c-myc, c-fos, c-met, VEGF and the VHL tumour-suppressor and related genes

Hepatocyte growth factor (HGF/SF) is a potent renal proximal tubular cell (PTEC) mitogen involved in renal development. HGF/SF is the functional ligand for the c-met proto-oncogene, and germline c-met mutations are associated with familial papillary renal cell carcinoma. Somatic von Hippel-Lindau disease tumour-suppressor gene (VHL) mutations are frequently detected in sporadic clear cell renal cell carcinomas (RCC), and germline VHL mutations are the commonest cause of familial clear cell RCC. pVHL binds to the positive regulatory components of the trimeric elongin (SIII) complex (elongins B and C) and has been observed to deregulate expression of the vascular endothelial growth factor (VEGF) gene. HGF/SF has similarly been reported to up-regulate expression of the VEGF gene in non-renal experimental systems. To investigate the mechanism of HGF/SF action in PTECs and, specifically, to examine potential interactions between the HGF/c-met and the VHL-mediated pathways for renal tubular growth control, we have isolated untransformed PTECs from normal kidneys, developed conditions for their culture in vitro and used these cells to investigate changes in mRNA levels of the VHL, elongin A, B and C, VEGF, c-myc, c-fos and c-met genes after HGF/SF exposure. Significant elevations in the mRNA levels of VEGF, c-myc, c-fos, c-met and elongins A, B and C, but not VHL, were detected after HGF/SF stimulation of human PTECs (P < 0.02), with a consistent order of peak levels observed over successive replicates (c-fos at 1 h, VEGF at 2-4 h, c-myc, at 4 h, followed by c-met and all three elongin subunits at 8 h). This study highlights the spectrum of changes in gene expression observed in PTECs after HGF/SF stimulation and has identified possible candidate mediators of the HGF/SF-induced mitogenic response. Our evidence would suggest that the changes in PTEC VEGF expression induced by HGF/SF are mediated by a VHL-independent pathway.

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.

The tyrosine kinase receptors Ron and Sea control "scattering" and morphogenesis of liver progenitor cells in vitro

The mammalian RON and the avian sea genes encode tyrosine kinase receptors of poorly characterized biological functions. We recently identified macrophage-stimulating protein as the ligand for Ron; no ligand has yet been found for Sea. In this work we investigated the biological response to macrophage-stimulating protein in mouse liver progenitor cells expressing Ron. These cells were also transfected with a chimeric cDNA encoding the cytoplasmic domain of Sea, fused to the extracellular domain of Trk (nerve growth factor receptor). In the presence of nanomolar concentrations of the respective ligands, both receptors induced cell "scattering", extracellular matrix invasion, and DNA synthesis. When liver progenitor cells were grown in a tri-dimensional type-I collagen matrix, ligand-induced stimulation of either Ron or Sea induced sprouting of branched cell cords, evolving into ductular-like tubules. The motogenic, mitogenic, and morphogenic responses were also elicited by triggering the structurally related hepatocyte growth factor receptor (Met) but not epidermal growth factor or platelet-derived growth factor receptors. These data show that Ron, Sea, and Met belong to a receptor subfamily that elicits a distinctive biological response in epithelial cells.