A heparin-binding growth factor secreted by macrophage-like cells that is related to EGF

Kinetics of bromhexine-mediated down-regulation of focal adhesive molecules of uterus and trophectoderm affecting conception in the rat

PURPOSE

Quantitative evaluation of properties of bromhexine (B) for expression of uterine proteins in ovariectomized (OVX) and pregnant rats.

MATERIALS AND METHODS

Expression of proteins through SDS-PAGE, along with incorporation of glycosidic moieties, was conducted in pregnant and OVX rats under B influence. These findings were corroborated with other tests such as implantation sites, fetal and litter sizes in pregnant rats.

RESULTS

In OVX animals, even under the influence of estradiol dipropionate and progesterone, the B recreated a condition akin to OVX animals. It also induced 50-80% inhibition in the incorporation of glycosidic moieties to polypeptide chain. Distinct reduction in implantation sites, fetal sizes and interference in the conception (16/46) in pregnant rats substantiated the results of the action of B as an antiimplantation agent.

CONCLUSION

Bromhexine has shown interference in blastocyst attachment, conception, reduction in number of implantation sites and dwarfing of fetuses; hence, it is a potential candidate for antiimplantation.

Control of ErbB signaling through metalloprotease mediated ectodomain shedding of EGF-like factors

Epidermal growth factor (EGF)-like proteins comprise a group of structurally similar growth factors, which contain a conserved six-cysteine residue motif called the EGF-domain. EGF-like factors are synthesized as transmembrane precursors, which can undergo proteolytic cleavage at the cell surface to release a mature soluble ectodomain; a process often referred to as "ectodomain shedding". Ectodomain shedding of EGF-like factors has been linked to multiple zinc-binding metalloproteases of the matrix metalloprotease (MMP) and a disintegrin and metalloprotease (ADAM) families. Shedding can be activated by a variety of pharmacological and physiological stimuli and these activation events have been linked to the enhancement of metalloprotease activity, possibly via the action of intracellular signaling modules. Once shed from the cell surface, EGF-like factors bind to a family of four cell surface receptors named ErbB-1, -2, -3 and -4. Heterodimerization or homodimerization of these receptors following ligand binding drives intracellular signal transduction cascades, which eventuate in diverse cell fates including proliferation, differentiation, migration and inhibition of apoptosis. In addition to its role in driving normal developmental processes, a wealth of evidence now exists showing that de-regulated ErbB signaling is associated with the formation of tumors in a variety of tissues and that ectodomain shedding of EGF-like factors plays a critical event in this process. Thus, knowledge of the molecular mechanisms by which EGF-like factors are shed from the cell surface and the nature of the proteases and cellular signals that govern this process is crucial to understanding ErbB receptor signaling and potentially also in the development of novel cancer therapeutics targeting the ErbB pathway. This review focuses on the structure and function of EGF-like factors, and the mechanisms that govern the shedding of these transmembrane molecules from the cell surface.

Heparin-binding epidermal growth factor-like growth factor as a novel targeting molecule for cancer therapy

HB-EGF, a member of the EGF family of growth factors, exerts its biological activity through activation of the EGFR and other ErbB receptors. HB-EGF participates in diverse biological processes, including heart development and maintenance, skin wound healing, eyelid formation, blastocyst implantation, progression of atherosclerosis and tumor formation, through the activation of signaling molecules downstream of ErbB receptors and interactions with molecules associated with HB-EGF. Recent studies have indicated that HB-EGF gene expression is significantly elevated in many human cancers and its expression level in a number of cancer-derived cell lines is much higher than those of other EGFR ligands. Several lines of evidence have indicated that HB-EGF plays a key role in the acquisition of malignant phenotypes, such as tumorigenicity, invasion, metastasis and resistance to chemotherapy. Studies in vitro and in vivo have indicated that HB-EGF expression is essential for tumor formation of cancer-derived cell lines. CRM197, a specific inhibitor of HB-EGF, and an antibody against HB-EGF are both able to inhibit tumor growth in nude mice. These results indicate that HB-EGF is a promising target for cancer therapy, and that the development of targeting tools against HB-EGF could represent a novel type of therapeutic strategy, as an alternative to targeting ErbB receptors.

Metalloprotease-dependent amphiregulin release mediates tumor necrosis factor-α-induced IL-8 secretion in the human airway epithelial cell line NCI-H292

Tumor necrosis factor-alpha (TNF-alpha) is a potent multifunctional cytokine that plays a central role in the pathogenesis of many inflammatory diseases. Interleukin-8 (IL-8) is a principle neutrophil chemoattractant and activator in humans. The alveolar macrophage-derived TNF-alpha initiates lung inflammation through its ability to stimulate IL-8 synthesis in airway epithelial cells. Since recent studies demonstrated that the stimulation of epidermal growth factor receptor (EGFR) could induce IL-8 secretion, the involvement of EGFR in TNF-alpha-induced IL-8 secretion in airway epithelium-like NCI-H292 cells was investigated in this study. TNF-alpha and epidermal growth factor (EGF) stimulated IL-8 secretion in a time- and concentration-dependent manner. Inhibition of the EGFR by either an anti-EGFR neutralizing antibody or by its specific inhibitor AG1478 (1 microM) blocked TNF-alpha-induced IL-8 secretion. In addition, TNF-alpha stimulated tyrosine phosphorylation of the EGFR within 5 min after stimulation. Further, TNF-alpha-induced IL-8 secretion was completely inhibited by the neutralizing antibody against amphiregulin (AR), an EGFR ligand, suggesting that TNF-alpha-induced IL-8 secretion was mediated by the AR-EGFR pathway. Furthermore, TNF-alpha stimulated the release of AR in a concentration-dependent manner. Finally, both AR and IL-8 release-induced by TNF-alpha were eliminated by pretreatment with either GM6001, a broad-spectrum inhibitor for metalloprotease, or TAPI-1, relatively selective inhibitor for TNF-alpha converting enzyme (TACE). These findings indicate that metalloprotease-mediated AR shedding and subsequent activation of EGFR play a critical role in TNF-alpha-induced IL-8 secretion from the human airway epithelium-like NCI-H292 cells, and that TACE is one of the most possible candidates for metalloprotease responsible for TNF-alpha-induced AR shedding.

Cytoplasmic domain phosphorylation of heparin-binding EGF-like growth factor

Heparin-binding EGF-like growth factor (HB-EGF) is synthesized as a transmembrane precursor protein that is anchored to the plasma membrane. The extracellular EGF-like domain acts as a mitogen and motogen upon ectodomain shedding, but the functional roles of the transmembrane and cytoplasmic domains are largely unknown. We demonstrate here that cytoplasmic domain of HB-EGF is phosphorylated by external stimuli, and that the phosphorylation site is involved in HB-EGF-dependent tumorigenesis. Treatment of Vero cells overexpressing human HB-EGF with 12-O-tetradecanoylphorbol-13-acetate (TPA) caused ectodomain shedding of HB-EGF and generated two carboxyl (C)-terminal fragments with distinct electrophoretic mobilities. Mutation analysis showed that Ser207 in the cytoplasmic domain of HB-EGF is phosphorylated upon TPA stimulation, generating two C-terminal fragments with distinct phosphorylation states. Treatment of cells with lysophosphatidic acid, anisomycin, and calcium ionophore, all of which are known to induce ectodomain shedding, also caused phosphorylation of HB-EGF. Although ectodomain shedding and phosphorylation of HB-EGF occurred coordinately, Ala substitution of Ser207 had no effect on TPA-induced or constitutive ectodomain shedding. Injection of cells overexpressing HB-EGF into nude mice showed that Ala substitution of Ser207 reduced the tumorigenic activity of HB-EGF, even though the cell surface level and ectodomain shedding of HB-EGF were not affected by the mutation. Moreover, we found that the cytoplasmic domain of another EGFR ligand, transforming growth factor-alpha, is phosphorylated upon TPA stimulation. Thus, the present results suggest a novel role for the cytoplasmic domain of HB-EGF and other EGF family growth factors that is regulated by phosphorylation.

Heparin-binding epidermal growth factor (HB-EGF) may improve embryonic development and implantation by increasing vitronectin receptor (integrin alphanubeta3) expression in peri-implantation mouse embryos

PURPOSE

This study investigated the effects of HB-EGF on expression of integrin alphanubeta3 and implantation of embryos.

METHODS

Two-cell embryos were recovered and cultured with or without 10 ng/mL HB-EGF for 96h. Expression of integrin alphanubeta3 in cultured embryos was examined by real time-RT-PCR and immunofluorescence analysis; embryos were cultured with or without HB-EGF, then transferred into the uteri of pseudo-pregnant female mice in order to analyze their implantation rate.

RESULTS

HB-EGF improved embryonic hatching and outgrowth during extended culture, and up-regulated expression of integrin alphanubeta3 in both the preimplantation embryo and outgrowing blastocyst. Also, integrin alphanubeta3 subunits were localized at the pericellular borders and cell-cell contact areas. The number of successful implantation sites of transferred HB-EGF-treated embryos in the uterus was increased when compared to number of implantation sites with non-treated controls.

CONCLUSIONS

HB-EGF may improve implantation by accelerating expression of integrin alphanubeta3 in peri-implantation mouse embryos.

Epidermal growth factor receptor overexpression results in increased tumor cell motility in vivo coordinately with enhanced intravasation and metastasis

Although overexpression of the epidermal growth factor receptor (EGFR; ErbB1) has been correlated with poor prognosis in breast and other cancers, clinical trials of ErbB1 inhibitors have shown limited efficacy in inhibiting tumor proliferation. To evaluate other possible roles of ErbB1 in tumor malignancy besides proliferation, we have developed a series of tools for analysis of intravasation. Overexpression of ErbB1 in MTLn3 mammary adenocarcinoma cells results in increased intravasation and lung metastasis from tumors formed by injection of cells in the mammary fat pad. However, increased ErbB1 expression has no effect on primary tumor growth and lung seeding efficiency of cells injected i.v. Chemotactic responses to low concentrations of EGF in vitro and cell motility in vivo in the primary tumor measured using intravital imaging are significantly increased by ErbB1 overexpression. The increased cell motility is restricted to ErbB1-overexpressing cells in tumors containing mixtures of cells expressing different ErbB1 levels, arguing for a cell-autonomous effect of increased ErbB1 expression rather than alteration of the tumor microenvironment. In summary, we propose that ErbB1 overexpression makes more significant contributions to intravasation than growth in some tumors and present a novel model for studying ErbB1 contributions to tumor metastasis via chemotaxis and intravasation.

Human airway trypsin-like protease induces amphiregulin release through a mechanism involving protease-activated receptor-2-mediated ERK activation and TNF alpha-converting enzyme activity in airway epithelial cells

Human airway trypsin-like protease (HAT), a serine protease found in the sputum of patients with chronic airway diseases, is an agonist of protease-activated receptor-2 (PAR-2). Previous results have shown that HAT enhances the release of amphiregulin (AR); further, it causes MUC5AC gene expression through the AR-epidermal growth factor receptor pathway in the airway epithelial cell line NCI-H292. In this study, the mechanisms by which HAT-induced AR release can occur were investigated. HAT-induced AR gene expression was mediated by extracellular signal-regulated kinase (ERK) pathway, as pretreatment of cells with ERK pathway inhibitor eliminated the effect of HAT on AR mRNA. Both HAT and PAR-2 agonist peptide (PAR-2 AP) induced ERK phosphorylation; further, desensitization of PAR-2 with a brief exposure of cells to PAR-2 AP resulted in inhibition of HAT-induced ERK phosphorylation, suggesting that HAT activates ERK through PAR-2. Moreover, PAR-2 AP induced AR gene expression subsequent to protein production in the cellular fraction through the ERK pathway indicating that PAR-2-mediated activation of ERK is essential for HAT-induced AR production. However, in contrast to HAT, PAR-2 AP could not cause AR release into extracellular space; it appears that activation of PAR-2 is not sufficient for HAT-induced AR release. Finally, HAT-induced AR release was eliminated by blockade of tumour necrosis factor alpha-converting enzyme (TACE) by the TAPI-1 and RNA interference, suggesting that TACE activity is necessary for HAT-induced AR release. These observations show that HAT induces AR production through the PAR-2 mediated ERK pathway, and then causes AR release by a TACE-dependent mechanism.

Epidermal growth factor receptor in adult retinal neurons of rat, mouse, and human

During development, the epidermal growth factor receptor (EGFR) regulates proliferation and differentiation of many types of cells, including precursors of neurons and glia. In the adult, EGFR continues to drive the growth and differentiation of epithelial cells but is absent from glia in the CNS. However, the localization and functions of EGFR in adult neurons are not well defined. By using immunohistochemistry and Western blotting, we have identified EGFR and its ligands in adult retinal ganglion cells in the normal rat, mouse, and human retina. EGFR and its ligands were also present in certain other adult retinal neurons, for example, horizontal cells and amacrine cells, and had different distribution patterns among these species. In addition, we found that EGFR was expressed in the rat retinal ganglion cell line RGC-5. One of the EGFR ligands, EGF, caused a cell shape change and increased neurofilament phosphorylation in RGC-5 cells. The expression of EGFR in postmitotic, terminally differentiated adult retinal neurons suggests that EGFR has pleiotropic functions. In addition to the conventional mitogenic role in adult epithelial cells, EGFR must serve a different, nonmitogenic function in adult neurons. Our work localizes EGFR and its ligands in the adult retinas of several species as a step toward investigating the nonmitogenic functions of EGFR in adult neurons.

ErbB and HB-EGF Signaling in Heart Development and Function

The epidermal growth factor (EGF)-ErbB signaling network is composed of multiple ligands of the EGF family and four tyrosine kinase receptors of the ErbB family. In higher vertebrates, these four receptors bind a multitude of ligands. Ligand binding induces the formation of various homo- and heterodimers of ErbB, potentially providing for a high degree of signal diversity. ErbB receptors and their ligands are expressed in a variety of tissues throughout development. Recent advances in gene targeting strategies in mice have revealed that the EGF-ErbB signaling network has fundamental roles in development, proliferation, differentiation, and homeostasis in mammals. The heparin-binding EGF-like growth factor (HB-EGF) is a member of the EGF family of growth factors that binds to and activates the EGF receptor (EGFR/ErbB1) and ErbB4. Recent studies using several mutant mice lacking HB-EGF expression have revealed that HB-EGF has a critical role in normal heart function and in normal cardiac valve formation in conjunction with ErbB receptors. HB-EGF signaling through ErbB2 is essential for the maintenance of homeostasis in the adult heart, whereas HB-EGF signaling through EGFR is required during cardiac valve development. In this review, we introduce and discuss the role of ErbB receptors in heart function and development, focusing on the physiological function of HB-EGF in these processes.

Expression of heparin-binding epidermal growth factor–like growth factor and its receptors in the human fallopian tube and endometrium after treatment with mifepristone

OBJECTIVE

To study the effect of mifepristone on heparin-binding epidermal growth factor (HB-EGF) and its receptors HER1 and HER4 in the fallopian tube and in the endometrium.

DESIGN

Prospective clinical study.

SETTING

Hospital-based unit for obstetrics and gynecology and research laboratories.

PATIENT(S)

Healthy women divided into two groups: controls and patients treated with a single dose of 200 mg mifepristone on day LH+2.

INTERVENTION(S)

Endometrial biopsies from 30 women were obtained during one control cycle or one treatment cycle. Fallopian tubes from 14 women were collected during laparoscopic sterilizations.

MAIN OUTCOME MEASURE(S)

Immunohistochemistry and reverse transcriptase-polymerase chain reaction.

RESULT(S)

The staining intensity of HB-EGF was not affected by mifepristone treatment. Treatment with mifepristone increased the immunostaining on HER1 in the epithelium and the stroma of the endometrium, which was not seen in the fallopian tube. The immunostaining of HER4 decreased in the stroma of the fallopian tube, while an increase was seen in the epithelial cells of the endometrium.

CONCLUSION(S)

Treatment with mifepristone has a limited effect on HB-EGF and its receptors in the fallopian tube, while the increase in HER1 and HER4 in the endometrium probably reflects defective endometrial maturation.

Timing, route, and dose of administration of heparin-binding epidermal growth factor-like growth factor in protection against intestinal ischemia-reperfusion injury

PURPOSE

We have previously demonstrated that heparin-binding epidermal growth factor-like growth factor (HB-EGF) is an intestinal cytoprotective agent. The current study examined whether HB-EGF is effective as salvage therapy as well as prophylactic therapy for intestinal ischemia-reperfusion (I/R) injury, whether intravenous administration is as effective as intraluminal administration, and whether increased benefits are seen with increasing dose.

METHODS

Total midgut I/R injury in rats was achieved by occlusion of a first-order branch of the superior mesenteric artery for 60 minutes, followed by reperfusion for 6 hours. Rats were treated with HB-EGF 5 minutes before ischemia, halfway through the ischemic event, or 5 minutes after ischemia. Route of administration was tested by administering HB-EGF either intraluminally or intravenously. Seven different doses of HB-EGF were tested.

RESULTS

Heparin-binding, EGF-like growth factor protected the intestine from injury when administered before injury and was also effective when administered during ischemia or even after injury. Intraluminal administration of HB-EGF was superior to intravenous administration. Increasing doses of HB-EGF resulted in a greater cytoprotective effect.

CONCLUSION

These data demonstrate that HB-EGF acts as an effective intestinal cytoprotective agent when administered intraluminally not only before injury, but also during injury and, most importantly, even after intestinal injury has already occurred. These findings support a basis for the prophylactic use of intraluminal HB-EGF in high-risk patients, as well as for the administration of HB-EGF to salvage patients in whom an intestinal insult has already occurred.

Helicobacter pylori-stimulated interleukin-8 (IL-8) promotes cell proliferation through transactivation of epidermal growth factor receptor (EGFR) by disintegrin and metalloproteinase (ADAM) activation

Helicobacter pylori infection increases the risk of hyperplastic polyps and gastric cancer, but the mechanisms remain to be elucidated. H. pylori was recently shown to transactivate epidermal growth factor receptor (EGFR) through metalloprotease stimulation. The present study was designed to investigate the effect of interleukin-8 (IL-8) induced by H. pylori infection on EGFR transactivation and epithelial cell growth. H. pylori Sydney strain 1 (SS1) having wild-type cag(+)A was used. Phospho-EGFR assay was performed by immunoprecipitation using anti-human EGFR and anti-phosphotyrosine antibodies. DNA synthesis was evaluated by [3H]thymidine uptake using the human gastric cancer cell line, KATO III. H. pylori induced EGFR phosphorylation, and a disintegrin and metalloproteinase (ADAM) inhibitor, KB-R7785, completely suppressed EGFR phosphorylation. IL-8 also induced EGFR phosphorylation, while anti-IL-8 and anti-IL-8 receptor (CXCR1) neutralizing antibodies suppressed EGFR phosphorylation. [(3)H]Thymidine uptake analysis demonstrated that H. pylori increased DNA synthesis in gastric epithelial cells, and tyrosine kinase inhibitor, MEK inhibitor, and ADAM inhibitor suppressed the DNA synthesis induced by H. pylori. H. pylori-stimulated IL-8 accelerates processing of EGFR ligands through ADAM activation, and cleaved EGFR ligands bind and stimulate EGFR in paracrine and autocrine manners to induce cell proliferation. This may be one of the mechanisms of hyperplastic polyp and gastric cancer development in H. pylori-infected gastric mucosa.

HB-EGF promotes epithelial cell migration in eyelid development

Heparin-binding EGF-like growth factor (HB-EGF) is a member of the EGF family of growth factors that binds to and activates the EGF receptor (EGFR)and ERBB4. Here, we show that HB-EGF-EGFR signaling is involved in eyelid development. HB-EGF expression is restricted to the tip of the leading edge of the migrating epithelium during eyelid closure in late gestation mouse embryos. Both HB-EGF null (HBdel/del) and secretion-deficient(HBuc/uc) mutant embryos exhibited delayed eyelid closure, owing to slower leading edge extension and reduced actin bundle formation in migrating epithelial cells. No changes in cell proliferation were observed in these embryos. In addition, activation of EGFR and ERK was decreased in HBdel/del eyelids. Crosses between HBdel/del mice and waved 2 mice, a hypomorphic EGFR mutant strain, indicate that HB-EGF and EGFR interact genetically in eyelid closure. Together with our data showing that embryos treated with an EGFR-specific kinase inhibitor phenocopy HBdel/del embryos, these data indicate that EGFR mediates HB-EGF-dependent eyelid closure. Finally, analysis of eyelid closure in TGFα-null mice and in HB-EGF and TGFα double null mice revealed that HB-EGF and TGFα contribute equally to and function synergistically in this process. These results indicate that soluble HB-EGF secreted from the tip of the leading edge activates the EGFR and ERK pathway, and that synergy with TGFα is required for leading edge extension in epithelial sheet migration during eyelid closure.

Heparin-binding epidermal growth factor-like growth factor stimulates cell proliferation in cerebral cortical cultures through phosphatidylinositol 3′-kinase and mitogen-activated protein kinase

Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) stimulates cell proliferation in the adult mammalian brain, but the mechanism involved is unknown. To address this issue we treated mouse brain cerebral cortical cultures enriched in neuronal precursors with full-length HB-EGF, its HB or EGF-like domain alone, or both domains in combination. Labeling of cultures with bromodeoxyuridine (BrdU), a marker of cell proliferation, was increased approximately 10% by the HB domain and approximately 20% by the EGF-like domain, and the effects of the two domains were additive. Full-length HB-EGF was most effective (approximately 50% increase) in stimulating BrdU incorporation. Preincubation with heparinase III or with Na-chlorate abolished cell proliferation induced by HB-EGF, consistent with dependence on cell-surface heparan sulfate proteoglycans. The effect of HB-EGF was also blocked by the EGF receptor (EGFR/ErbB1) inhibitors PD153035 and PD158780, implicating EGFR in HB-EGF-induced cell proliferation. The phosphatidylinositol 3'-kinase (PI3K) inhibitors LY294002 and wortmannin, and the MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitors U0126 and PD98059, reduced HB-EGF-induced BrdU incorporation into cultures, and HB-EGF enhanced phosphorylation of Akt and ERK, implying a role for PI3K/Akt and MEK/ERK signaling in HB-EGF-stimulated cell proliferation. These findings help to clarify the molecular mechanisms through which HB-EGF operates.

Heparin-binding EGF-like growth factor (HB-EGF) and necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal disease that occurs predominantly in premature infants. Despite various advances in management, the mortality of this disease remains high. During the last decade, studies from our laboratory have shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the epidermal growth factor (EGF) family, can protect intestinal epithelial cells (IEC) from various forms of injury in vitro. Furthermore, we have used both an intestinal I/R injury model in adult rats, and a neonatal rat pup model of NEC, to show that HB-EGF can protect the intestines from injury. On administration of HB-EGF in the neonatal rat model, the incidence of NEC is reduced from 65% to 27.3% (P < 0.05), and the histological injury score is decreased from 2 to 1.1 (P < 0.05). In addition, the survival rate is increased from 25% to 63.6% and the survival time extended from 59 hours to 73 hours (P < 0.05). In addition, using human specimens from newborns undergoing bowel resection for NEC, we found that the expression of endogenous HB-EGF mRNA in normal areas of the intestine at the resection margins was higher than that of the intestine afflicted with acute NEC. Endogenous HB-EGF may be involved in epithelial cell repair, proliferation, and regeneration during recovery from injury. Exogenous administration of HB-EGF potentiates recovery from intestinal injury in vitro and in vivo. Taken together, these results support a potential therapeutic role for HB-EGF in the treatment of NEC in the future.

The epidermal growth factor receptors and their family of ligands: their putative role in atherogenesis

The epidermal growth factor receptor is a member of type-I growth factor receptor family with tyrosine kinase activity that is activated following the binding of multiple cognate ligands. Several members of the EGF family of ligands are expressed by cells involved in atherogenesis. EGF receptor mediated processes have been well characterised within epithelial, smooth muscle and tumour cell lines in vitro, and the EGF receptor has been identified immunocytochemically on intimal smooth muscle cells within atherosclerotic plaques. There is also limited evidence for the expression of the EGF receptor family on leukocytes, although their function has yet to be clarified. In this review, we will discuss the biological functions of this receptor and its ligands and their potential to modulate the function of cells involved in the atherosclerotic process.

Local overexpression of HB-EGF exacerbates remodeling following myocardial infarction by activating noncardiomyocytes

Insulin-like growth factor (IGF), hepatocyte growth factor (HGF), and heparin-binding epidermal growth factor-like growth factor (HB-EGF) are cardiogenic and cardiohypertrophic growth factors. Although the therapeutic effects of IGF and HGF have been well demonstrated in injured hearts, it is uncertain whether natural upregulation of HB-EGF after myocardial infarction (MI) plays a beneficial or pathological role in the process of remodeling. To answer this question, we conducted adenoviral HB-EGF gene transduction in in vitro and in vivo injured heart models, allowing us to highlight and explore the HB-EGF-induced phenotypes. Overexpressed HB-EGF had no cytoprotective or additive death-inducible effect on Fas-induced apoptosis or oxidative stress injury in primary cultured mouse cardiomyocytes, although it significantly induced hypertrophy of cardiomyocytes and proliferation of cardiac fibroblasts. Locally overexpressed HB-EGF in the MI border area in rabbit hearts did not improve cardiac function or exhibit an angiogenic effect, and instead exacerbated remodeling at the subacute and chronic stages post-MI. Namely, it elevated the levels of apoptosis, fibrosis, and the accumulation of myofibroblasts and macrophages in the MI area, in addition to inducing left ventricular hypertrophy. Thus, upregulated HB-EGF plays a pathophysiological role in injured hearts in contrast to the therapeutic roles of IGF and HGF. These results imply that regulation of HB-EGF may be a therapeutic target for treating cardiac hypertrophy and fibrosis.

Regenerative and therapeutic effects of heparin-binding epidermal growth factor-like growth factor on diabetes by gene transduction through retrograde pancreatic duct injection of adenovirus vector

OBJECTIVES

In the adult pancreas, pre-existing beta cells, stem cells, and endocrine progenitor cells residing in the duct lining are considered important sources for beta-cell regeneration. A member of the epidermal growth factor (EGF) family, heparin binding (HB)-EGF, may promote this process. We examined whether HB-EGF gene transduction into duct cells could promote beta-cell regeneration.

METHODS

We administered an HB-EGF adenovirus vector construct to male Institute of Cancer Research mice by retrograde injection through the pancreatic duct. We also performed HB-EGF gene transduction into cultured duct cells.

RESULTS

On immunohistochemical and histomorphometric analysis of the experimental group, insulin-positive cells differentiated from duct cells, and the 5-bromo-2-deoxyuridine labeling index of beta cells was significantly increased. beta-cell mass was also increased, and the glucose tolerance of diabetic mice was improved at 12 weeks after injection. Using cultured pancreatic duct cells, we confirmed that HB-EGF gene transduction induced both insulin gene expression and insulin production by these cells.

CONCLUSIONS

These results indicate that HB-EGF gene transduction into adult pancreatic duct cells not only promotes the proliferation of pre-existing beta cells but also leads to beta-cell differentiation from duct cells, and the resulting increase in beta-cell mass improves glucose tolerance.

Heparin-binding epidermal growth factor-like growth factor, collateral vessel development, and angiogenesis in skeletal muscle ischemia

OBJECTIVE

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a potent mitogen for smooth muscle cells and has been implicated in atherosclerosis, tissue regeneration after ischemia, vascular development, and tumor angiogenesis. We examined the hypothesis that HB-EGF participates in angiogenesis and collateral growth in ischemia.

METHODS AND RESULTS

During 3 weeks after femoral artery ligation, no attenuation occurred in recovery of hindlimb perfusion or distal saphenous artery flow in HB-EGF-null (HB-EGF(-/-)) versus wild-type mice. Lumen diameters of remodeled collaterals in gracilis muscle were similar by morphometry (87+/-8 versus 94+/-6 microm) and angiography, although medial thickening was reduced. Gastrocnemius muscle underwent comparable angiogenesis (41% and 33% increase in capillary-to-muscle fiber ratio). Renal renin mRNA, arterial pressure, and heart rate during anesthesia or conscious unrestrained conditions were similar between groups. These latter findings validate comparisons of perfusion data and also suggest that differences in arterial pressure and/or renin-angiotensin activity are not masking an otherwise inhibitory effect of HB-EGF absence. Four days after ligation, EGF receptor phosphorylation increased in muscle by 104% in wild-type but by only 30% in HB-EGF(-/-) mice. This argues against compensation by other EGF receptor ligands.

CONCLUSIONS

Our results suggest that HB-EGF is not required for arteriogenesis or angiogenesis in hindlimb ischemia.

Gene expression and immunolocalization of heparin-binding epidermal growth factor-like growth factor and human epidermal growth factor receptors in human corpus luteum

BACKGROUND

The objective of this study was to elucidate gene expression and immunolocalization of heparin-binding epidermal growth factor-like growth factor (HB-EGF) and human epidermal growth factor receptor (HER) family in the human ovary during luteal growth and regression.

METHODS

Ovaries obtained from pre-menopausal women were used for immunohistochemistry and semiquantitative RT-PCR analysis.

RESULTS

Immunoreactive HB-EGF was not detected in follicles or oocyte, while HB-EGF became apparent in granulosa luteal cells in the early luteal phase, and most abundant in the mid-luteal phase, but less abundant in the late luteal phase. Immunostaining for HER1 was very weak in granulosa luteal cells in the early and mid-luteal phases, and was not detected in the late luteal phase. Immunoreactive HER4 was abundant in the early luteal phase and became less abundant in the mid-luteal phase, whereas it was negative in the late luteal phase. Semiquantitative RT-PCR analysis revealed that HB-EGF and HER1 mRNA levels were high in the mid-luteal phase, whereas HER4 mRNA expression was high in the early luteal phase.

CONCLUSIONS

HB-EGF may play a vital role in regulating luteal growth in a juxtacrine manner and through activating HER4 signalling.

Intestinal adaptation after massive intestinal resection

Patients with short bowel syndrome require long term parenteral nutrition support. However, after massive intestinal resection the intestine undergoes adaptation and nutritional autonomy may be obtained. Given that the complications of parenteral nutrition may be life threatening or result in treatment failure and the need for intestinal transplantation, a more attractive option is to wean patients off nutrition support by optimising the adaptive process. The article examines the evidence that after extensive small bowel resection adaptation occurs in humans and focuses on the factors that influence adaptation and the strategies that have been used to optimise this process. The review is based on an English language Medline search with secondary references obtained from key articles. There is evidence that adaptation occurs in humans. Adaptation is a complex process that results in response to nutrient and non-nutrient stimuli. Successful and reproducible strategies to improve adaptation remain elusive despite an abundance of experimental data. Nevertheless given the low patient survival and quality of life associated with other treatments for irreversible intestinal failure it is imperative that clinical research continues into the optimisation of the adaptation.

Intestinal adaptation after massive intestinal resection

Patients with short bowel syndrome require long term parenteral nutrition support. However, after massive intestinal resection the intestine undergoes adaptation and nutritional autonomy may be obtained. Given that the complications of parenteral nutrition may be life threatening or result in treatment failure and the need for intestinal transplantation, a more attractive option is to wean patients off nutrition support by optimising the adaptive process. The article examines the evidence that after extensive small bowel resection adaptation occurs in humans and focuses on the factors that influence adaptation and the strategies that have been used to optimise this process. The review is based on an English language Medline search with secondary references obtained from key articles. There is evidence that adaptation occurs in humans. Adaptation is a complex process that results in response to nutrient and non-nutrient stimuli. Successful and reproducible strategies to improve adaptation remain elusive despite an abundance of experimental data. Nevertheless given the low patient survival and quality of life associated with other treatments for irreversible intestinal failure it is imperative that clinical research continues into the optimisation of the adaptation.

The membrane-anchoring domain of epidermal growth factor receptor ligands dictates their ability to operate in juxtacrine mode

All ligands of the epidermal growth factor (EGF) receptor (EGFR) are synthesized as membrane-anchored precursors. Previous work has suggested that some ligands, such as EGF, must be proteolytically released to be active, whereas others, such as heparin-binding EGF-like growth factor (HB-EGF) can function while still anchored to the membrane (i.e., juxtacrine signaling). To explore the structural basis for these differences in ligand activity, we engineered a series of membrane-anchored ligands in which the core, receptor-binding domain of EGF was combined with different domains of both EGF and HB-EGF. We found that ligands having the N-terminal extension of EGF could not bind to the EGFR, even when released from the membrane. Ligands lacking an N-terminal extension, but possessing the membrane-anchoring domain of EGF, still required proteolytic release for activity, whereas ligands with the membrane-anchoring domain of HB-EGF could elicit full biological activity while still membrane anchored. Ligands containing the HB-EGF membrane anchor, but lacking an N-terminal extension, activated EGFR during their transit through the Golgi apparatus. However, cell-mixing experiments and fluorescence resonance energy transfer studies showed that juxtacrine signaling typically occurred in trans at the cell surface, at points of cell-cell contact. Our data suggest that the membrane-anchoring domain of ligands selectively controls their ability to participate in juxtacrine signaling and thus, only a subclass of EGFR ligands can act in a juxtacrine mode.

Ectodomain shedding of membrane-anchored heparin-binding EGF like growth factor and subcellular localization of the C-terminal fragment in the cell cycle

Heparin-binding EGF-like growth factor (HB-EGF) is initially synthesized as a type I transmembrane protein (proHB-EGF). The proHB-EGF is shed by specific metalloproteases, releasing the N-terminal fragment into the extracellular space as a soluble growth factor (HB-EGF) and the C-terminal fragment (HB-EGF-C) into the intracellular space, where it prevents transcriptional repression by the promyelocytic leukemia zinc finger protein (PLZF). The goal of the present study was to characterize regulation of proHB-EGF shedding and study its temporal variations in HB-EGF-C localization throughout the cell cycle. Quantitative combination analyses of cell surface proHB-EGF and HB-EGF in conditioned medium showed that proHB-EGF shedding occurred during the G(1) cell cycle phase. Laser scanning cytometry (LSC) revealed that HB-EGF-C was internalized into the cytoplasm during the late G1 phase and accumulated in the nucleus beginning in the S phase. Subsequent nuclear export of PLZF occurred during the late S phase. Further, HB-EGF-C was localized around the centrosome following breakdown of the nuclear envelope and was localized to the interzonal space with chromosome segregation in the late M phase. Temporal variations in HB-EGF localization throughout the cell cycle were also characterized by time-lapse imaging of cells expressing YFP-tagged proHB-EGF, and these results were consistent with those obtained in cytometry studies. These results indicate that proHB-EGF shedding and subsequent HB-EGF-C signaling are related with progression of the cell cycle and may provide a clue to understand the unique biological significance of non-receptor-mediated signaling of proHB-EGF in cell growth.

Comparative effects of heparin-binding epidermal growth factor-like growth factor on the growth of cultured human uterine leiomyoma cells and myometrial cells

BACKGROUND

The objective of this study was to investigate the comparative effects of heparin-binding epidermal growth factor-like growth factor (HB-EGF) on the growth of cultured human leiomyoma cells and myometrial cells.

METHODS

Isolated cells were subcultured in Phenol Red-free Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum for 120 h and then stepped down to serum-free conditions for an additional 24 and 48 h in the presence or absence of graded concentrations of HB-EGF (0.1, 1, 10 and 100 ng/ml). These cells were used for immunocytochemical analysis for Ki67, western blot analysis for proliferating cell nuclear antigen (PCNA) and human EGF receptor (HER1), and TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labelling (TUNEL) assay.

RESULTS

Treatment with HB-EGF at concentrations >1 ng/ml significantly increased the Ki67-positive rate of cultured leiomyoma cells and myometrial cells. Treatment with HB-EGF also resulted in a dose-dependent increase in PCNA expression in both cells compared with untreated control cultures. A significant increase in PCNA expression in cultured myometrial cells was noted following treatment with HB-EGF at concentrations >1 ng/ml, whereas an increase in PCNA expression in cultured leiomyoma cells was noted following treatment with HB-EGF at concentrations >10 ng/ml. HER1 expression was significantly higher in untreated myometrial cells than in untreated leiomyoma cells. A significant increase in HER1 expression in myometrial cells was observed when treated with HB-EGF at concentrations >10 ng/ml, whereas a significant increase in HER1 expression in leiomyoma cells was noted only by the treatment with HB-EGF at concentrations >100 ng/ml. Treatment with HB-EGF decreased the TUNEL-positive rate of those cells with no significant differences between the two cell types.

CONCLUSIONS

The results obtained suggest that HB-EGF plays a role in stimulating the proliferation of leiomyoma cells and myometrial cells and in inhibiting apoptosis of those cells through augmentation of HER1 expression. Since the proliferative potential of myometrial cells responded better to HB-EGF than that of leiomyoma cells, HB-EGF may play a more vital role in myometrial growth than leiomyoma growth.

HB-EGF/HER-1 signaling in bone marrow mesenchymal stem cells: inducing cell expansion and reversibly preventing multilineage differentiation

Epidermal growth factor receptor-1 (EGFR-1/HER-1/ErbB-1) regulates proliferation and cell fate during epidermal development. HER-1 is activated by several EGF-family ligands including heparin-binding epidermal growth factor-like growth factor (HB-EGF), a mitogenic and chemotactic molecule that participates in tissue repair, tumor growth, and other tissue-modeling phenomena, such as angiogenesis and fibrogenesis. We found that mesenchymal stem cells (MSCs), the precursors of different mesenchymal tissues with a role in processes in which HB-EGF is often involved, normally express HER-1, but not HB-EGF itself. Under the effect of HB-EGF, MSCs proliferate more rapidly and persistently, without undergoing spontaneous differentiation. This effect occurs in a dose-dependent fashion, and is specific, direct, and HER-1 mediated, as it is inhibited by anti-HER-1 and anti-HB-EGF blocking antibodies. Moreover, HB-EGF reversibly prevents adipogenic, osteogenic, and chondrogenic differentiation induced with specific media. These data show that HB-EGF/HER-1 signaling is relevant to MSC biology, by regulating both proliferation and differentiation.

Phenotypic variation resulting from a deficiency of epidermal growth factor receptor in mice is caused by extensive genetic heterogeneity that can be genetically and molecularly partitioned

The timing of lethality caused by homozygosity for a null allele of the epidermal growth factor receptor (Egfrtm1Mag) in mice is strongly dependent on genetic background. Initial attempts to genetically map background modifiers using Swiss-derived, outbred CD-1 mice were unsuccessful. To investigate the genetic architecture contributing to survival of Egfrtm1Mag homozygous embryos, the genetic variability segregating within the outbred population was partitioned by surveying viability of Egfrtm1Mag mutants using intercrosses between 129S6/SvEvTAC-Egfrtm1Mag and nine Swiss-derived, inbred strains: ALR/LtJ, ALS/LtJ, APN, APS, ICR/HaRos, NOD/LtJ, NON/LtJ, SJL/J, and SWR/J. The observations showed that these strains support varying levels of survival of Egfrtm1Mag homozygous embryos, suggesting that genetic heterogeneity within the CD-1 stock contributed to the original lack of Egfrtm1Mag modifier detection. Similar to the Swiss-derived intercrosses, nine congenic strains, derived from 129S6/SvEvTAC, AKR/J, APN, BALB/cJ, BTBR-T+ tf/tf, C3H/HeJ, C57BL/6J, DBA/2J, and FVB/NJ inbred backgrounds, also supported varying levels of survival of Egfrtm1Mag mutants. By intercrossing the congenic lines to create hybrid F1 embryos, different genetic backgrounds were found to have complementary modifiers. Analysis of the congenic lines argues against heterosis of outbred backgrounds contributing to Egfrtm1Mag phenotypic variability. A detailed analysis of the crosses suggests that modifiers function at three distinct stages of development. One class of modifiers supports survival of Egfrtm1Mag homozygous embryos to mid-gestation, another class supports development through the mid-gestation transition from yolk-sac to placental-derived nutrient sources, and a third class supports survival through later stages of gestation. Data from microarray analysis using RNA from wild-type and Egfrtm1Mag mutant placentas support the existence of extensive genetic heterogeneity and suggest that it can be molecularly partitioned. This method should be generally useful to partition heterogeneity contributing to other complex traits.

Expression profiling of cardiovascular disease

Cardiovascular disease is the most important cause of morbidity and mortality in developed countries, causing twice as many deaths as cancer in the USA. The major cardiovascular diseases, including coronary artery disease (CAD), myocardial infarction (MI), congestive heart failure (CHF) and common congenital heart disease (CHD), are caused by multiple genetic and environmental factors, as well as the interactions between them. The underlying molecular pathogenic mechanisms for these disorders are still largely unknown, but gene expression may play a central role in the development and progression of cardiovascular disease. Microarrays are high-throughput genomic tools that allow the comparison of global expression changes in thousands of genes between normal and diseased cells/tissues. Microarrays have recently been applied to CAD/MI, CHF and CHD to profile changes in gene expression patterns in diseased and non-diseased patients. This same technology has also been used to characterise endothelial cells, vascular smooth muscle cells and inflammatory cells, with or without various treatments that mimic disease processes involved in CAD/MI. These studies have led to the identification of unique subsets of genes associated with specific diseases and disease processes. Ongoing microarray studies in the field will provide insights into the molecular mechanism of cardiovascular disease and may generate new diagnostic and therapeutic markers.

Soluble Form of Heparin-binding EGF-like Growth Factor Contributes to Retinoic Acid-induced Epidermal Hyperplasia

Heparin-binding EGF-like growth factor (HB-EGF), a member of the EGF-family, is thought to be important for keratinocyte functions. HB-EGF is first synthesized as a membrane-anchored form, and its soluble form is released by ectodomain shedding. Here we investigate the role of HB-EGF in epidermal hyperplasia induced by all-trans retinoic acid (tRA) treatment. HB-EGF is normally expressed in epidermis of normal adult mice at very low levels, but topical tRA treatment results in epidermal hyperplasia, concomitant with the strong induction of HB-EGF expression in the suprabasal layer. tRA-induced epidermal hyperplasia was reduced both in the keratinocyte-specific HB-EGF null mice (K5-HB(del/del)) and knock-in mice expressing the uncleavable mutant form of HB-EGF (HB(uc/uc)), as compared with wild-type HB-EGF knock-in mice (HB(lox/lox)). Among ErbB tyrosine kinase receptors, EGF receptor (EGFR) and ErbB2 were selectively activated by tRA treatment in skin from wild-type mice, while the activation of these ErbB receptors was significantly reduced in the skin of HB-EGF null mice. These results indicate that expression of HB-EGF and generation of its soluble form, followed by activation of EGFR and ErbB2, are pivotal processes in tRA-induced epidermal hyperplasia.

Growth factor and cytokine regulation of chondroitin sulfate proteoglycans by astrocytes

After injury to the adult central nervous system (CNS), numerous cytokines and growth factors are released that contribute to reactive gliosis and extracellular matrix production. In vitro examination of these cytokines revealed that the presence of transforming growth factor-beta1 (TGF-beta1) and epidermal growth factor (EGF) greatly increased the production of several chondroitin sulfate proteoglycans (CSPG) by astrocytes. Treatment of astrocytes with other EGF-receptor (ErbB1) ligands, such as TGF-alpha and HB-EGF, produced increases in CSPG production similar to those observed with EGF. Treatment of astrocytes, however, with heregulin, which signals through other members of the EGF-receptor family (ErbB2, ErbB3, ErbB4), did not induce CSPG upregulation. The specificity of activation through the ErbB1 receptor was further verified by using a selective antagonist (AG1478) to this tyrosine kinase receptor. Western blot analysis of astrocyte supernatant pre-digested with chondroitinase ABC indicated the presence of multiple core proteins containing 4-sulfated or 6-sulfated chondroitin. To identify some of these CSPGs, Western blots were screened using antibodies to several known CSPG core proteins. These analyses showed that treatment of astrocytes with EGF increased phosphacan expression, whereas treatment with TGF-beta1 increased neurocan expression. Reverse transcription-polymerase chain reaction (RT-PCR) was used to examine the expression of these molecules in vivo, which result in increased expression of TGF-beta1, EGF-receptor, neurocan, and phosphacan after injury to the brain. These data begin to elucidate some of the injury-induced growth factors that regulate the expression of CSPGs which could be targeted in the future to modulate CSPG production after injury to the central nervous system.

Suprabasal expression of human amphiregulin in the epidermis of transgenic mice induces a severe, early-onset, psoriasis-like skin pathology: expression of amphiregulin in the basal epidermis is also associated with synovitis

The expression of amphiregulin (AR) in the basal epidermis of transgenic mice [keratin 14 promoter AR gene (K14-ARGE)] has been previously shown to induce an early-onset and severe skin pathology, with many similarities to psoriasis. In this study, it is demonstrated that involucrin enhancer/promoter-dependent expression of human AR (INV-AR) in the suprabasal epidermis of transgenic mice also produces a cutaneous psoriasis-like phenotype. INV-AR mice possess a limited lifespan and scaling, papillomatous, erythematous skin with partial alopecia. INV-AR mouse histopathology also revealed epidermal hyperkeratosis, parakeratosis, acanthosis, and an exaggerated dermal vasculature. A dermal and epidermal infiltrate was also evident and consisted of both neutrophils and CD3(+) T lymphocytes. The histology of synovial joints in both the INV-AR mice and the K14-ARGE mice of our previous investigation was examined. The histologic examination revealed that 3-week-old INV-AR transgenic mice displayed normal knee joint histology, while 2- to 3-week-old K14-ARGE transgenic mice frequently displayed synovitis, as exemplified by the presence of a mixed leukocytic infiltration, increased vascularization, and enhanced deposition of fibrous matrix in the knee synovium. These results demonstrate that AR overexpression in both the basal and suprabasal epidermis of transgenic mice induces a phenotype that mimics cutaneous psoriasis, while basal AR expression is also associated with synovial inflammation, a precursor to the psoriasis-associated arthropathy, psoriatic arthritis. Collectively, the results implicate epidermal AR expression as a possible mediator of innate cutaneous immunity and epidermal proliferation and also as a potential trigger of both cutaneous psoriasis and psoriatic arthritis.

ADAM-mediated ectodomain shedding of HB-EGF in receptor cross-talk

All ligands of the epidermal growth factor receptor (EGFR) which has important roles in development and disease, are shed from the plasma membrane by metalloproteases. The ectodomain shedding of EGFR ligands has emerged as a critical component in the functional activation of EGFR in the interreceptor cross-talk. Identification of the sheddases for EGFR ligands using mouse embryonic cells lacking candidate sheddases (a disintegrin and metalloprotease; ADAM) has revealed that ADAM10, -12 and -17 are the sheddases of the EGFR ligands in response to various shedding stimulants such as GPCR agonists, growth factors, cytokines, osmotic stress, wounding and phorbol ester. Among the EGFR ligands, heparin-binding EGF-like growth factor (HB-EGF) is a representative ligand to understand the pathophysiological roles of the ectodomain shedding in wound healing, cardiac diseases, etc. Here we focus on the ectodomain shedding of HB-EGF by ADAMs, which is not only a key event of receptor cross-talk but also a novel intercellular signaling by the carboxy-terminal fragment (CTF signal).

Collagenous matrices as release carriers of exogenous growth factors

We have investigated the use of natural and synthetic collagenous matrices as carriers of exogenous growth factors. A bladder acellular matrix (BAM) was processed from rat bladder and compared with sponge matrix of porcine type 1 collagen. The lyophilized matrices were rehydrated by the aqueous solutions of basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), platelet derived growth factor-BB (PDGF-BB), vascular endothelial growth factor (VEGF), insulin like growth factor-1 (IGF-1) and heparin binding epidermal growth factor-like growth factor (HB-EGF), to obtain the matrix incorporating each growth factor. The rehydration method enabled the growth factor protein to distribute into the matrix homogeneously. In vivo release test in the mouse subcutis revealed that, the property of BAM for growth factor release was similar to that of collagen sponge. Among the growth factors examined, bFGF release was the most sustained, followed by HGF and PDGF-BB. bFGF released from the two matrices showed similar in vivo angiogenic activity at the mouse subcutis in a dose-dependent manner. These findings demonstrate that the collagenous matrices function as release carriers of growth factors. This feature is promising to create a scaffold, which has a nature to control the tissue regeneration actively.

CEACAM1 modulates epidermal growth factor receptor--mediated cell proliferation

Phosphorylation of the cell adhesion protein CEACAM1 increases insulin sensitivity and decreases insulin-dependent mitogenesis in vivo. Here we show that CEACAM1 is a substrate of the EGFR and that upon being phosphorylated, CEACAM1 reduces EGFR-mediated growth of transfected Cos-7 and MCF-7 cells in response to EGF. Using transgenic mice overexpressing a phosphorylation-defective CEACAM1 mutant in liver (L-SACC1), we show that the effect of CEACAM1 on EGF-dependent cell proliferation is mediated by its ability to bind to and sequester Shc, thus uncoupling EGFR signaling from the ras/MAPK pathway. In L-SACC1 mice, we also show that impaired CEACAM1 phosphorylation leads to ligand-independent increase of EGFR-mediated cell proliferation. This appears to be secondary to visceral obesity and the metabolic syndrome, with increased levels of output of free fatty acids and heparin-binding EGF-like growth factor from the adipose tissue of the mice. Thus, L-SACC1 mice provide a model for the mechanistic link between increased cell proliferation in states of impaired metabolism and visceral obesity.

Heparin-binding EGF-like growth factor shows transient left–right asymmetrical expression in mouse myotome pairs

Heparin-binding EGF-like growth factor (HB-EGF) is a potent mitogen and chemoattractant for diverse cell types including, keratinocytes, fibroblasts and vascular smooth muscle cells. In adult mice, skeletal muscle and endothelial cells prominently express HB-EGF, although analysis of embryonic expression has been limited to studies of heart and kidney development. Here we survey HB-EGF mRNA expression in E7.5-E15 mouse embryos and show that HB-EGF is expressed in branchial arches, limb buds and, transiently, in mature somites between E9.25 and E11. This somitic expression is restricted to the myotomal compartment. Intriguingly, within myotome pairs, the expression of HB-EGF is stronger on the left side of the body, whilst cognate receptors, ErbB1 and ErbB4, are symmetrically expressed in left and right somite pairs. In iv/iv mutant embryos, with inverted left-right body axis, the expression of HB-EGF was also inverted, now being stronger in myotomes on the right side of the body. Thus, the expression of HB-EGF in myotome pairs is regulated by global cues that define the left-right body axis.

Suppression of the Biological Activities of the Epidermal Growth Factor (EGF)-like Domain by the Heparin-binding Domain of Heparin-binding EGF-like Growth Factor

Heparin-binding EGF-like growth factor (HB-EGF) is a member of the EGF family of growth factors that has a high affinity for heparin and heparan sulfate. While interactions with heparin are thought to modulate the biological activity of HB-EGF, the precise role of the heparin-binding domain has remained unclear. We analyzed the activity of wild-type HB-EGF and a mutant form lacking the heparin-binding domain (DeltaHB) in the presence or absence of heparin. The activity of the EGF-like domain of HB-EGF was determined by measuring binding to diphtheria toxin (DT) as well as the growth factor activity in EGF receptor-expressing cells. The binding affinity of DeltaHB for DT was much higher than that of wild-type HB-EGF in the absence of heparin. The binding affinity of HB-EGF for DT was increased by addition of exogenous heparin and reached the level close to the affinity of DeltaHB, whereas that of DeltaHB was not affected. Moreover, the growth factor activity of DeltaHB was much higher than that of wild-type HB-EGF in the absence of heparin but was not affected by addition of exogenous heparin, whereas HB-EGF had increased growth factor activity with added heparin. These results indicate that the heparin-binding domain suppresses the activity of the EGF-like domain of HB-EGF and that association of heparin with HB-EGF via this domain removes the suppressive effect. Thus, we conclude that the heparin-binding domain serves as a negative regulator of this growth factor.

Transactivation of epidermal growth factor receptor mediates catecholamine-induced growth of vascular smooth muscle

Stimulation of alpha1-adrenoceptors induces proliferation of vascular smooth muscle cells (SMCs) and contributes to arterial remodeling. Although activation of NAD(P)H oxidase and generation of reactive oxygen species (ROS) are required, little is known about this pathway. In this study, we examined the hypothesis that epidermal growth factor receptor (EGFR) transactivation and extracellular regulated kinases (ERK) are involved in alpha1-adrenoceptor-mediated SMC growth. Phenylephrine increased protein synthesis in association with a rapid (< or =5 minutes) and sustained (> or =60 minutes) doubling of phosphorylation of EGFR and ERK1/2, but not p38 or JNK in the media of rat aorta maintained in organ culture. Antagonists of EGFR phosphotyrosine activity (AG-1478) and ERK phosphorylation (PD-98059, U-0126) abolished phenylephrine-induced protein synthesis, whereas antagonists of p38 or JNK phosphorylation had no specific effect. A competitive antagonist (P22) for heparin binding EGF-like growth factor (HB-EGF) blocked phenylephrine-induced protein synthesis, as did downregulation of pro-HB-EGF (CRM197). Phenylephrine-induced protein synthesis was inhibited by neutralizing antibody to HB-EGF and absent in HB-EGF-/- SMCs. Inhibitors of metalloproteinases (BiPS, KB-R7785) also blocked adrenergic growth. The neutralizing antibody against HB-EGF had no effect on the two-fold increase in ROS generation induced by phenylephrine (DCF fluorescence), suggesting that stimulation of NAD(P)H oxidase by alpha1-adrenoceptor occupation precedes HB-EGF release. Cell culture studies confirmed and extended these findings. These data suggest that alpha1-adrenoceptor-mediated SMC growth requires ROS-dependent shedding of HB-EGF, transactivation of EGFR, and activation of the MEK1/2-dependent MAP kinase pathway. This trophic pathway may link sympathetic activity to arterial wall growth in adaptive remodeling and hypertrophic disease.

Neuroglycan C, a novel member of the neuregulin family

Neuroglycan C (NGC) is a transmembrane chondroitin sulfate proteoglycan expressed predominantly in the brain that possesses an EGF-like extracellular domain. The goal of the present study was to determine whether NGC may activate ErbB tyrosine kinases. A recombinant human NGC extracellular domain induced tyrosine phosphorylation of ErbB2 and ErbB3 as well as cell growth of the human breast tumor cell lines, T47D and MDA-MB-453. In vitro pull-down assay revealed that NGC could directly bind to a recombinant ErbB3-immunoglobulin Fc fusion protein (ErbB3-Fc) but not to ErbB1-Fc, ErbB2-Fc or ErbB4-Fc. A newly established anti-ErbB3 neutralizing monoclonal antibody (#5C3) almost completely blocked NGC-induced ErbB activation in MDA-MB-453 cells. Taken together, these data indicate that NGC is an active growth factor and a direct ligand for ErbB3 and that NGC transactivates ErbB2. Thus, NGC should be classified as the sixth member (neuregulin-6) of the neuregulin family.

Heparin-binding EGF-like growth factor induces expression of lectin-like oxidized LDL receptor-1 in vascular smooth muscle cells

Receptor-mediated endocytosis of oxidized LDL (Ox-LDL) has been implicated in lipid accumulation and vascular cell dysfunction. Lectin-like Ox-LDL receptor-1 (LOX-1) is highly inducible by proinflammatory cytokines, as well as angiotensin II and Ox-LDL in vitro. LOX-1 is expressed in macrophages and smooth muscle cells accumulated in the intima of advanced atherosclerotic plaques in vivo. Here we show that heparin-binding epidermal growth factor-like growth factor (HB-EGF), a potent mitogen for vascular smooth muscle cells, induces LOX-1 expression in cultured bovine aortic smooth muscle cells. HB-EGF (1-100 ng/ml) induced LOX-1 expression, which was peaked between 8 and 16 h after HB-EGF stimulation. HB-EGF-induced expression of LOX-1 was suppressed by ZD1839, an inhibitor of EGF receptor phosphorylation. Both MEK and p38 mitogen-activated protein kinase (MAPK) inhibitors significantly blocked LOX-1 upregulation induced by HB-EGF. Phosphatidylinositol 3-kinase (PI3K) inhibitors also blocked HB-EGF-induced LOX-1 expression. HB-EGF induced phosphorylation of ERK, p38 MAPK and Akt, which were suppressed by ZD1839. Upregulated expression of LOX-1 was associated with enhanced uptake of DiI-labeled Ox-LDL in smooth muscle cells. Taken together, HB-EGF can also act as an inducer of LOX-1 expression and play an integral role in foam cell transformation, cellular dysfunction, and proliferation of smooth muscle cells in atherogenesis.

Heparin-binding EGF-like growth factor is a promising target for ovarian cancer therapy

Ovarian cancer is the most frequent cause of cancer death among all gynecologic cancers. We demonstrate here that lysophosphatidic acid (LPA)-induced ectodomain shedding of heparin-binding EGF-like growth factor (HB-EGF) is a critical to tumor formation in ovarian cancer. We found that among the epidermal growth factor receptor (EGFR) family of growth factors, HB-EGF gene expression in cancerous tissues and HB-EGF protein levels in patients' ascites fluid were significantly elevated. The human ovarian cancer cell lines SKOV3 and RMG-1 form tumors in nude mice. Tumor formation of these cells was enhanced by exogenous expression of pro-HB-EGF and completely blocked by pro-HB-EGF gene RNA interference or by CRM197, a specific HB-EGF inhibitor. Transfection with mutant forms of HB-EGF indicated that the release of soluble HB-EGF is essential for tumor formation. LPA, which is constitutively produced by ovarian cancer cells, induced HB-EGF ectodomain shedding in SKOV3 and RMG-1 cells, resulting in the transactivation of EGFR and the downstream kinase extracellular signal-regulated kinase/mitogen-activated protein kinase. LPA-induced transactivation was abrogated by HB-EGF gene RNA interference or by CRM197. Introduction of lipid phosphate phosphohydrolase, which hydrolyzes LPA, decreased the constitutive shedding of HB-EGF, EGFR transactivation, and the tumorigenic potential of SKOV3 and RMG-1 cells. These results indicate that HB-EGF is the primary member of the EGFR family of growth factors expressed in ovarian cancer and that LPA-induced ectodomain shedding of this growth factor is a critical step in tumor formation, making HB-EGF a novel therapeutic target for ovarian cancer.

Distinct roles for ADAM10 and ADAM17 in ectodomain shedding of six EGFR ligands

All ligands of the epidermal growth factor receptor (EGFR), which has important roles in development and disease, are released from the membrane by proteases. In several instances, ectodomain release is critical for activation of EGFR ligands, highlighting the importance of identifying EGFR ligand sheddases. Here, we uncovered the sheddases for six EGFR ligands using mouse embryonic cells lacking candidate-releasing enzymes (a disintegrin and metalloprotease [ADAM] 9, 10, 12, 15, 17, and 19). ADAM10 emerged as the main sheddase of EGF and betacellulin, and ADAM17 as the major convertase of epiregulin, transforming growth factor α, amphiregulin, and heparin-binding EGF-like growth factor in these cells. Analysis of adam9/12/15/17^−/− knockout mice corroborated the essential role of adam17^−/− in activating the EGFR in vivo. This comprehensive evaluation of EGFR ligand shedding in a defined experimental system demonstrates that ADAMs have critical roles in releasing all EGFR ligands tested here. Identification of EGFR ligand sheddases is a crucial step toward understanding the mechanism underlying ectodomain release, and has implications for designing novel inhibitors of EGFR-dependent tumors.

HB-EGF is a potent inducer of tumor growth and angiogenesis

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been shown to stimulate the growth of a variety of cells in an autocrine or paracrine manner. Although HB-EGF is widely expressed in tumors compared with normal tissue, its contribution to tumorigenicity is unknown. HB-EGF can be produced as a membrane-anchored form (pro-HB-EGF) and later processed to a soluble form (s-HB-EGF), although a significant amount of pro-HB-EGF remains uncleaved on the cell surface. To understand the roles of two forms of HB-EGF in promoting tumor growth, we have studied the effects of HB-EGF expression in the process of tumorigenesis using in vitro and in vivo systems. We demonstrate here that in EJ human bladder cancer cells containing a tetracycline-regulatable s-HB-EGF or pro-HB-EGF expression system, s-HB-EGF expression increased their transformed phenotypes, including growth rate, colony-forming ability, and activation of cyclin D1 promoter, as well as induction of vascular endothelial growth factor in vitro. Moreover, s-HB-EGF or wild-type HB-EGF induced the expression and activities of the metalloproteases, MMP-9 and MMP-3, leading to enhanced cell migration. In vivo studies also demonstrated that tumor cells expressing s-HB-EGF or wild-type HB-EGF significantly enhanced tumorigenic potential in athymic nude mice and exerted an angiogenic effect, increasing the density and size of tumor blood vessels. However, cells expressing solely pro-HB-EGF did not exhibit any significant tumorigenic potential. These findings establish s-HB-EGF as a potent inducer of tumor growth and angiogenesis and suggest that therapeutic intervention aimed at the inhibition of s-HB-EGF functions may be useful in cancer treatment.

Role of EGFR transactivation in preventing apoptosis in Pseudomonas aeruginosa-infected human corneal epithelial cells

PURPOSE

To determine the role of epidermal growth factor (EGF) receptor (EGFR)-mediated signaling pathways in preventing infection-induced apoptosis in human corneal epithelial cells (HCECs).

METHODS

Epithelial monolayers of a telomerase-immortalized HCEC line, HUCL, and primary culture of HCECs were infected with Pseudomonas aeruginosa in the presence of the EGFR inhibitor tyrphostin AG1478, the extracellular signal-regulated kinase (ERK) inhibitor U0126, the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, the heparin-binding EGF-like growth factor (HB-EGF) antagonist CRM197, the HB-EGF neutralizing antibody, or the matrix metalloproteinase inhibitor GM6001. The activation of EGFR was analyzed by immunoprecipitation using EGFR antibodies, followed by Western blot analysis with phosphotyrosine antibody. Phosphorylation of ERK and Akt, a major substrate of PI3K, and generation of cleaved caspase-3 and poly (ADP-ribose) polymerase (PARP) were determined by Western blot analysis. Apoptotic cells were characterized by positive staining of active caspase-3, loss of mitochondrial cytochrome c, and condensation of chromosomes. Apoptosis was also confirmed by measuring caspase-3 activity and assessing the generation of cleaved caspase-3 and PARP.

RESULTS

P. aeruginosa infection of HUCL cells resulted in EGFR activation and EGFR-dependent ERK1/2 and PI3K phosphorylation. Inhibition of EGFR, ERK1/2, and PI3K activities with kinase-specific inhibitors (AG1478, U0126, and LY294002, respectively) resulted in an increase in the number of apoptotic cells, in elevated cellular caspase-3 activity, and/or in increased cleaved PARP in P. aeruginosa-infected HUCL cells or primary culture of HCECs. Blocking HB-EGF ectodomain shedding by inhibition of matrix metalloproteinase-mediated proteolysis, downregulation of HB-EGF, or neutralization of its activity retarded infection-induced EGFR transactivation and, as a consequence, increased infection-induced HUCL apoptosis.

CONCLUSIONS

Bacterial infection of HCECs induces EGFR transactivation through HB-EGF ectodomain shedding. EGFR and its downstream ERK and PI3K signaling pathways play a role in preventing epithelial apoptosis in the early stage of bacterial infection.

The mechanism of cleavage of EGFR ligands induced by inflammatory cytokines in gastric cancer cells

BACKGROUND & AIMS

The epidermal growth factor (EGF) receptor (EGFR) can be transactivated by many factors including G-protein-coupled receptor agonists and cytokines. Although this EGFR transactivation reportedly requires a disintegrin and metalloproteinase (ADAM) that sheds the ectodomain of EGFR ligands, the detailed mechanisms are still unknown. This study evaluated the mechanism of interleukin (IL)-8- and IL-1beta-dependent shedding of the EGFR ligand in KATO III cells.

METHODS

We established transfectants stably expressing alkaline phosphatase-tagged heparin-binding EGF-like growth factor (HB-EGF), transforming growth factor alpha, or amphiregulin precursors, and depleted ADAM proteins, using short interfering RNA against ADAM10, 12, or 17. We assessed shedding of EGFR ligands by measuring AP activities in the conditioned media after IL-1beta or IL-8 stimulation. EGFR activation was examined by immunoprecipitation and Western blotting using antiphosphotyrosine antibody. KB-R7785 and anti-IL-8 neutralizing antibody were used to inhibit activities of ADAMs and IL-8 action, respectively.

RESULTS

IL-8 dose dependently released the EGFR ligands and transiently phosphorylated EGFR, with a peak at 15 minutes. KB-R7785 completely blocked IL-8-induced shedding and EGFR transactivation. Depletion of ADAM10 also dramatically reduced IL-8-induced shedding and EGFR transactivation, but depletion of ADAM12 and 17 did not. IL-1beta dose dependently enhanced shedding of HB-EGF, which was not blocked by KB-R7785 in the early phase. In the late phase, however, the EGFR transactivation was blocked by KB-R7785 and abrogated by anti-IL-8 neutralizing antibody.

CONCLUSIONS

IL-8 induces shedding of EGFR ligands because of an ADAM10-dependent pathway in gastric cancer cells, whereas IL-1beta acts principally by an ADAM-independent pathway. IL-1beta-dependent prolonged EGFR transactivation involves multiple pathways, including an IL-8-dependent pathway.

ADAM binding protein Eve-1 is required for ectodomain shedding of epidermal growth factor receptor ligands

A disintegrin and metalloproteases (ADAMs) are implicated in the ectodomain shedding of epidermal growth factor receptor (EGFR) ligands in EGFR transactivation. However, the activation mechanisms of ADAMs remain elusive. To analyze the regulatory mechanisms of ADAM activation, we performed yeast two-hybrid screening using the cytoplasmic domain of ADAM12 as bait, and identified a protein that we designated Eve-1. Two cDNAs were cloned and characterized. They encode alternatively spliced isoforms of Eve-1, called Eve-1a and Eve-1b, that have four and five tandem Src homology 3 (SH3) domains in the carboxyl-terminal region, respectively, and seven proline-rich SH3 domain binding motifs in the amino-terminal region. The short forms of Eve-1, Eve-1c and Eve-1d, translated at Met-371 are human counterparts of mouse Sh3d19. Northern blot analysis demonstrated that Eve-1 is abundantly expressed in skeletal muscle and heart. Western blot analysis revealed the dominant production of Eve-1c in human cancer cell lines. Knockdown of Eve-1 by small interfering RNA in HT1080 cells reduced the shedding of proHB-EGF induced by angiotensin II and 12-O-tetradecanoylphorbol-13-acetate, as well as the shedding of pro-transforming growth factor-alpha, promphiregulin, and proepiregulin by 12-O-tetradecanoylphorbol-13-acetate, suggesting that Eve-1 plays a role in positively regulating the activity of ADAMs in the signaling of EGFR-ligand shedding.

Diphtheria toxin-induced autophagic cardiomyocyte death plays a pathogenic role in mouse model of heart failure

It is still not clear whether loss of cardiomyocytes through programmed cell death causes heart failure. To clarify the role of cell death in heart failure, we generated transgenic mice (TG) that express human diphtheria toxin receptor in the hearts. A mosaic expression pattern of the transgene was observed, and the transgene-expressing cardiomyocytes (17.3% of the total cardiomyocytes) were diffusely scattered throughout the ventricles. Intramuscular injection of diphtheria toxin induced complete elimination of the transgene-expressing cardiomyocytes within 7 days, and approximately 80% of TG showed pathophysiological features characteristic of heart failure and were dead within 14 days. Degenerated cardiomyocytes of the TG heart showed characteristic features indicative of autophagic cell death such as up-regulated lysosomal markers and abundant autophagosomes containing cytosolic organelles like cardiomyocytes of human dilated cardiomyopathy. The heart failure-inducible TG are a useful model for dilated cardiomyopathy, and provided evidence indicating that myocardial cell loss through autophagic cell death plays of a causal role in the pathogenesis heart failure.

Raf promotes human herpesvirus-8 (HHV-8/KSHV) infection

Human herpesvirus-8 (HHV-8/KSHV) is etiologically associated with Kaposi's sarcoma (KS) and other tumors. Constitutive activation of the mitogen-activated protein kinase (MAPK) signaling pathway has been associated with a variety of tumors, including AIDS-related KS. The oncoprotein Raf is situated at a pivotal position in regulating the MAPK pathway. Hence, we analysed the effect of oncoprotein Raf on HHV-8 infectious entry into target cells. Here we report Raf expression to significantly enhance HHV-8 infection of target cells. These findings implicate a role for Raf not only in the infectious entry of HHV-8 but also in modulating KS pathogenesis.