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

Pathophysiology of Lung Disease and Wound Repair in Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive, life-threatening condition affecting many organs and tissues, the lung disease being the chief cause of morbidity and mortality. Mutations affecting the CF Transmembrane Conductance Regulator (CFTR) gene determine the expression of a dysfunctional protein that, in turn, triggers a pathophysiological cascade, leading to airway epithelium injury and remodeling. In vitro and in vivo studies point to a dysregulated regeneration and wound repair in CF airways, to be traced back to epithelial CFTR lack/dysfunction. Subsequent altered ion/fluid fluxes and/or signaling result in reduced cell migration and proliferation. Furthermore, the epithelial-mesenchymal transition appears to be partially triggered in CF, contributing to wound closure alteration. Finally, we pose our attention to diverse approaches to tackle this defect, discussing the therapeutic role of protease inhibitors, CFTR modulators and mesenchymal stem cells. Although the pathophysiology of wound repair in CF has been disclosed in some mechanisms, further studies are warranted to understand the cellular and molecular events in more details and to better address therapeutic interventions.

Alpha-1-antitrypsin: A possible host protective factor against Covid-19

Understanding Covid-19 pathophysiology is crucial for a better understanding of the disease and development of more effective treatments. Alpha-1-antitrypsin (A1AT) is a constitutive tissue protector with antiviral and anti-inflammatory properties. A1AT inhibits SARS-CoV-2 infection and two of the most important proteases in the pathophysiology of Covid-19: the transmembrane serine protease 2 (TMPRSS2) and the disintegrin and metalloproteinase 17 (ADAM17). It also inhibits the activity of inflammatory molecules, such as IL-8, TNF-α, and neutrophil elastase (NE). TMPRSS2 is essential for SARS-CoV-2-S protein priming and viral infection. ADAM17 mediates ACE2, IL-6R, and TNF-α shedding. ACE2 is the SARS-CoV-2 entry receptor and a key component for the balance of the renin-angiotensin system, inflammation, vascular permeability, and pulmonary homeostasis. In addition, clinical findings indicate that A1AT levels might be important in defining Covid-19 outcomes, potentially partially explaining associations with air pollution and with diabetes. In this review, we focused on the interplay between A1AT with TMPRSS2, ADAM17 and immune molecules, and the role of A1AT in the pathophysiology of Covid-19, opening new avenues for investigating effective treatments.

Amphiregulin potentiates airway inflammation and mucus hypersecretion induced by urban particulate matter via the EGFR-PI3Kα-AKT/ERK pathway

Ambient particulate matter (PM) promotes the development and exacerbation of chronic respiratory diseases, including chronic obstructive pulmonary disease (COPD) and asthma, by increasing inflammation and mucus hypersecretion. However, the biological mechanisms underlying PM-induced airway inflammation and mucus hypersecretion remain unclear. Amphiregulin (AREG) is an important ligand for epidermal growth factor receptor (EGFR) and participates in the regulation of several biological functions. Here, the PM-exposed human bronchial epithelial cell (HBEC) model was used to define the role of AREG in PM-induced inflammation and mucus hypersecretion and its related signaling pathways. The expression of AREG was significantly increased in a dose-dependent manner in HBECs subjected to PM exposure. Moreover, PM could induce inflammation and mucus hypersecretion by upregulating the expression of IL-1α, IL-1β, and Muc-5ac in HBECs. The EGFR, AKT, and ERK signaling pathways were also activated in a time- and dose-dependent manner. The AREG siRNA markedly attenuated PM-induced inflammation and mucus hypersecretion, and activation of the EGFR-AKT/ERK pathway. Exogenous AREG significantly increased the expression of IL-1α, IL-1β, and Muc-5ac, and induced activation of the EGFR-AKT/ERK pathway in HBECs. Further, under PM exposure, exogenous AREG significantly potentiated PM-induced inflammation and mucus hypersecretion, and activation of the EGFR-AKT/ERK pathway. Tumor-necrosis factor-alpha converting enzyme (TACE) and EGFR specific inhibitor pretreatment showed that AREG was secreted by TACE-mediated cleavage to regulate PM-induced inflammation and mucus hypersecretion by binding to the EGFR. Moreover, according to the inhibitory effect of specific inhibitors of the class I PI3K isoforms, AKT and ERK, PM-induced inflammation and mucus hypersecretion was regulated by PI3Kα activation and its downstream AKT and ERK pathways. This study strongly suggests the adverse effect of AREG in PM-induced inflammation and mucus hypersecretion via the EGFR-PI3Kα-AKT/ERK pathway. These findings contribute to a better understanding of the biological mechanisms underlying exacerbation of chronic respiratory diseases induced by PM exposure.

Extracellular oxidation in cystic fibrosis airway epithelium causes enhanced EGFR/ADAM17 activity

The EGF receptor (EGFR)/a disintegrin and metalloproteinase 17 (ADAM17) signaling pathway mediates the shedding of growth factors and secretion of cytokines and is involved in chronic inflammation and tissue remodeling. Since these are hallmarks of cystic fibrosis (CF) lung disease, we hypothesized that CF transmembrane conductance regulator (CFTR) deficiency enhances EGFR/ADAM17 activity in human bronchial epithelial cells. In CF bronchial epithelial CFBE41o^- cells lacking functional CFTR (iCFTR^-) cultured at air-liquid interface (ALI) we found enhanced ADAM17-mediated shedding of the EGFR ligand amphiregulin (AREG) compared with genetically identical cells with induced CFTR expression (iCFTR⁺). Expression of the inactive G551D-CFTR did not have this effect, suggesting that active CFTR reduces EGFR/ADAM17 activity. This was confirmed in CF compared with normal differentiated primary human bronchial epithelial cells (HBEC-ALI). ADAM17-mediated AREG shedding was tightly regulated by the EGFR/MAPK pathway. Compared with iCFTR⁺ cells, iCFTR^- cells displayed enhanced apical presentation and phosphorylation of EGFR, in accordance with enhanced EGFR/ADAM17 activity in CFTR-deficient cells. The nonpermeant natural antioxidant glutathione (GSH) strongly inhibited AREG release in iCFTR and in primary HBEC-ALI, suggesting that ADAM17 activity is directly controlled by extracellular redox potentials in differentiated airway epithelium. Furthermore, the fluorescent redox probe glutaredoxin 1-redox-sensitive green fluorescent protein-glycosylphosphatidylinositol (Grx1-roGFP-GPI) indicated more oxidized conditions in the extracellular space of iCFTR^- cells, consistent with the role of CFTR in GSH transport. Our data suggest that in CFTR-deficient airway epithelial cells a more oxidized state of the extracellular membrane, likely caused by defective GSH secretion, leads to enhanced activity of the EGFR/ADAM17 signaling axis. In CF lungs this could contribute to tissue remodeling and hyperinflammation.

Cytosolic Phospholipase A2α Promotes Pulmonary Inflammation and Systemic Disease during Streptococcus pneumoniae Infection

Pulmonary infection by Streptococcus pneumoniae is characterized by a robust alveolar infiltration of neutrophils (polymorphonuclear cells [PMNs]) that can promote systemic spread of the infection if not resolved. We previously showed that 12-lipoxygenase (12-LOX), which is required to generate the PMN chemoattractant hepoxilin A₃ (HXA₃) from arachidonic acid (AA), promotes acute pulmonary inflammation and systemic infection after lung challenge with S. pneumoniae As phospholipase A₂ (PLA₂) promotes the release of AA, we investigated the role of PLA₂ in local and systemic disease during S. pneumoniae infection. The group IVA cytosolic isoform of PLA₂ (cPLA₂α) was activated upon S. pneumoniae infection of cultured lung epithelial cells and was critical for AA release from membrane phospholipids. Pharmacological inhibition of this enzyme blocked S. pneumoniae-induced PMN transepithelial migration in vitro Genetic ablation of the cPLA₂ isoform cPLA₂α dramatically reduced lung inflammation in mice upon high-dose pulmonary challenge with S. pneumoniae The cPLA₂α-deficient mice also suffered no bacteremia and survived a pulmonary challenge that was lethal to wild-type mice. Our data suggest that cPLA₂α plays a crucial role in eliciting pulmonary inflammation during pneumococcal infection and is required for lethal systemic infection following S. pneumoniae lung challenge.

A Monoclonal Antibody to ADAM17 Inhibits Tumor Growth by Inhibiting EGFR and Non-EGFR-Mediated Pathways

ADAM17 is the primary sheddase for HER pathway ligands. We report the discovery of a potent and specific ADAM17 inhibitory antibody, MEDI3622, which induces tumor regression or stasis in many EGFR-dependent tumor models. The inhibitory activity of MEDI3622 correlated with EGFR activity both in a series of tumor models across several indications as well in as a focused set of head and neck patient-derived xenograft models. The antitumor activity of MEDI3622 was superior to that of EGFR/HER pathway inhibitors in the OE21 esophageal model and the COLO205 colorectal model suggesting additional activity outside of the EGFR pathway. Combination of MEDI3622 and cetuximab in the OE21 model was additive and eradicated tumors. Proteomics analysis revealed novel ADAM17 substrates that function outside of the HER pathways and may contribute toward the antitumor activity of the monoclonal antibody.

ADAM17 at the interface between inflammation and autoimmunity

The discovery of the disintegrin and metalloproteinase 17 (ADAM17), originally identified as tumor necrosis factor-a converting enzyme (TACE) for its ability as sheddase of TNF-α inspired scientists to attempt to elucidate the molecular mechanisms underlying ADAM17 implication in diseased conditions. In recent years, it has become evident that this protease can modify many non matrix substrates, such as cytokines (e.g. TNF-α), cytokine receptors (e.g. IL-6R and TNF-R), ligands of ErbB (e.g. TGF-α and amphiregulin) and adhesion proteins (e.g. Lselectin and ICAM-1). Several recent studies have described experimental model system to better understand the role of specific signaling molecules, the interplay of different signals and tissue interactions in regulating ADAM17-dependent cleavage of most relevant substrates in inflammatory diseases. The central question is whether ADAM17 can influence the outcome of inflammation and if so, how it performs this regulation in autoimmunity, since inflammatory autoimmune diseases are often characterized by deregulated metalloproteinase activities. This review will explore the latest research on the influence of ADAM17 on the progression of inflammatory processes linked to autoimmunity and its role as modulator of inflammation.

TACE-dependent amphiregulin release is induced by IL-1β and promotes cell invasion in fibroblast-like synoviocytes in rheumatoid arthritis

OBJECTIVES

The aims of this study were to investigate the expression of amphiregulin (AREG) and TNF-α-converting enzyme (TACE) in fibroblast-like synoviocytes from humans with RA (FLS-RA) when stimulated with proinflammatory cytokines and to explore whether AREG plays a role in RA.

METHODS

The effects of cytokines on the expression of AREG and TACE in FLS-RA were measured by quantitative RT-PCR and western blotting. Blockade of IL-1β-mediated pathways was used to verify the involvement of intracellular signal pathways in the induction of AREG and TACE. TAPI-1 and TACE short hairpin RNA (shRNA) infection were used to identify the role of TACE in IL-1β-induced AREG secretion and shedding. AREG-induced production of MMP-1 and cadherin-11 in FLS-RA were measured by ELISA or western blotting. The effect of AREG on FLS-RA invasion was examined using a Transwell invasion assay.

RESULTS

IL-1β, but not other tested cytokines, increased the expressions of AREG mRNA and protein in a dose-responsive and time-dependent manner in FLS-RA. IL-1β induced AREG expression via p38 MAPK, NF-κB, JNK and ERK1/2 signalling pathways and induced TACE expression via PI3K, p38MAPK and NF-κB signalling pathways in FLS-RA. TACE mediated AREG secretion and shedding. EGFR (ErbB1) and Her-2 (ErbB2) were expressed in FLS-RA, and AREG increased MMP-1 and cadherin-11 expression in FLS-RA. AREG promoted the FLS-RA invasion ability.

CONCLUSION

AREG and TACE expression were up-regulated by IL-1β and their activations on FLS-RA lead to the matrix degradation by inducing MMP-1 and cadherin-11 production. TACE activity is necessary for IL-1β-induced AREG release. Our results demonstrate that IL-1β-induced AREG release may be involved in the pathogenesis of RA.

Central role of the EGF receptor in neurometabolic aging

A strong connection between neuronal and metabolic health has been revealed in recent years. It appears that both normal and pathophysiological aging, as well as neurodegenerative disorders, are all profoundly influenced by this "neurometabolic" interface, that is, communication between the brain and metabolic organs. An important aspect of this "neurometabolic" axis that needs to be investigated involves an elucidation of molecular factors that knit these two functional signaling domains, neuronal and metabolic, together. This paper attempts to identify and discuss a potential keystone signaling factor in this "neurometabolic" axis, that is, the epidermal growth factor receptor (EGFR). The EGFR has been previously demonstrated to act as a signaling nexus for many ligand signaling modalities and cellular stressors, for example, radiation and oxidative radicals, linked to aging and degeneration. The EGFR is expressed in a wide variety of cells/tissues that pertain to the coordinated regulation of neurometabolic activity. EGFR signaling has been highlighted directly or indirectly in a spectrum of neurometabolic conditions, for example, metabolic syndrome, diabetes, Alzheimer's disease, cancer, and cardiorespiratory function. Understanding the positioning of the EGFR within the neurometabolic domain will enhance our appreciation of the ability of this receptor system to underpin highly complex physiological paradigms such as aging and neurodegeneration.

Suppression of amphiregulin/epidermal growth factor receptor signals contributes to the protective effects of quercetin in cirrhotic rats

The hepatic wound-healing response to chronic noxious stimuli may lead to liver fibrosis, a key feature of the preneoplastic cirrhotic liver. Fibrogenic cells activate in response to a variety of cytokines, growth factors, and inflammatory mediators. The involvement of members of the epidermal growth factor family in this process has been suggested. Amphiregulin is an epidermal growth factor receptor (EGFR) ligand specifically induced upon liver injury. We investigated the effects of quercetin on the amphiregulin/EGFR signal and on the activation of downstream pathways leading to cell growth. Rats were divided into 4 groups (8 rats/group): rats subjected to common bile duct ligation (CBDL), Sham (rats subjected to simulated CBDL), quercetin-treated sham, and quercetin-treated CBDL (CBDL-Q). Quercetin (50 mg/kg i.p. injection) was administered daily for 2 wk starting on d 14 after surgery. Overexpression of amphiregulin, EGFR, TNFα, IL-6, TGFβ, platelet-derived growth factor (PDGF), extracellular regulated kinase, protein kinase B (Akt), cycloxygenase (COX)-2, and glioma-associated oncogenes (GLI)-1 and-2 were observed in liver of CBDL rats after 4 wk of bile duct ligation. CBDL-Q rats had a significantly diminished expression of amphiregulin and EGFR compared with untreated CBDL rats. Furthermore, mRNA levels of TNFα, IL-6, TGFβ, and PDGF and the protein content of COX-2, GLI-1, and GLI-2 were significantly lower in CBDL-Q rats than in untreated CBDL rats. The findings indicate that quercetin ameliorated activation of survival pathways and downregulated the expression of genes related to inflammation and precancerous conditions. Suppression of amphiregulin/EGFR signals may contribute to this effect.

The epidermal growth factor receptor mediates tumor necrosis factor-alpha-induced activation of the ERK/GEF-H1/RhoA pathway in tubular epithelium

Tumor necrosis factor (TNF)-α induces cytoskeleton and intercellular junction remodeling in tubular epithelial cells; the underlying mechanisms, however, are incompletely explored. We have previously shown that ERK-mediated stimulation of the RhoA GDP/GTP exchange factor GEF-H1/Lfc is critical for TNF-α-induced RhoA stimulation. Here we investigated the upstream mechanisms of ERK/GEF-H1 activation. Surprisingly, TNF-α-induced ERK and RhoA stimulation in tubular cells were prevented by epidermal growth factor receptor (EGFR) inhibition or silencing. TNF-α also enhanced phosphorylation of the EGFR. EGF treatment mimicked the effects of TNF-α, as it elicited potent, ERK-dependent GEF-H1 and RhoA activation. Moreover, EGF-induced RhoA activation was prevented by GEF-H1 silencing, indicating that GEF-H1 is a key downstream effector of the EGFR. The TNF-α-elicited EGFR, ERK, and RhoA stimulation were mediated by the TNF-α convertase enzyme (TACE) that can release EGFR ligands. Further, EGFR transactivation also required the tyrosine kinase Src, as Src inhibition prevented TNF-α-induced activation of the EGFR/ERK/GEF-H1/RhoA pathway. Importantly, a bromodeoxyuridine (BrdU) incorporation assay and electric cell substrate impedance-sensing (ECIS) measurements revealed that TNF-α stimulated cell growth in an EGFR-dependent manner. In contrast, TNF-α-induced NFκB activation was not prevented by EGFR or Src inhibition, suggesting that TNF-α exerts both EGFR-dependent and -independent effects. In summary, in the present study we show that the TNF-α-induced activation of the ERK/GEF-H1/RhoA pathway in tubular cells is mediated through Src- and TACE-dependent EGFR activation. Such a mechanism could couple inflammatory and proliferative stimuli and, thus, may play a key role in the regulation of wound healing and fibrogenesis.

Correlation of polymorphism of IL-8 and MMP-7 with occurrence and lymph node metastasis of early stage cervical cancer

The IL-8 and MMP-7 genes participate in the carcinogenesis of many malignancies, but the role of both genes in cervical cancer is not fully elucidated. The aim of this study was to determine the frequency of IL-8 and MMP-7 gene mutations and to assess their effects on the risk of early stage cervical cancer and lymph node metastasis. The clinical stage and histological grade of cervical cancer were also studied. The peripheral blood from the patients with early stage cervical cancers and normal controls was collected and the DNA was extracted. The incidence of IL-8 and MMP-7 gene mutations was assessed by using tetra-primer amplification refractory mutation system polymerase chain reaction (ARMS PCR) and restriction fragment length polymorphism (RFLP). The data were statistically analyzed by x2 test. The results showed that: (1) The genotype frequency of IL-8 -251AT and TT was significantly higher in the cervical cancer group than in the normal control group (OR=2.290 and 2.619 respectively, P=0.001), and it was also higher in the lymphatic metastasis group than that without metastasis (OR=2.917, P=0.035); (2) The frequency of MMP-7 -181G/G genotype was significantly higher in the cervical cancer group and in the lymphatic metastasis group (P<0.05); (3) The incidence of IL-8 mutation was two times higher in IIa cervical cancer group than in Ib1 and Ib2 cervical cancer group (P=0.006). For the MMP-7 gene, there was statistically significant difference in the incidence of mutation between the Ib1, Ib2 and the IIa (P=0.000); (4) Different histological types and different grades of cervical cancer had different incidence of mutations, statistically. It was suggested that there was significant difference in the genotype of IL-8 -251TT and MMP-7 -181GG polymorphism between the cervical cancer group and the lymph node metastasis group. Moreover, individuals with IL-8 T allele or MMP-7 G allele carriers were at significantly higher risk of cervical cancer, particularly the early (IIa) and medium, poorly differentiated cervical cancer (G2+G3).

LTD₄ induces HB-EGF-dependent CXCL8 release through EGFR activation in human bronchial epithelial cells

Airway epithelial cells release proinflammatory mediators that may contribute to airway remodeling and leukocyte recruitment. We explored the hypothesis that leukotriene D₄ (LTD₄) may trigger the release of proremodeling factors through activation of the EGF receptor (EGFR). We particularly focused on the effects of LTD₄ on release of heparin-binding EGF-like factor (HB-EGF) and IL-8 (CXCL8), a potent neutrophil chemoattractant that may be released downstream of EGFR activation. To address this hypothesis, both primary (NHBE) and transformed bronchial human epithelial cells (BEAS-2B) were grown on an air-liquid interface and stimulated with LTD₄. HB-EGF and CXCL8 were evaluated by ELISA in cell culture supernatants. To explore the EGFR signaling pathway, we used a broad-spectrum matrix metalloproteinase (MMP) inhibitor, GM-6001, two selective EGFR tyrosine kinase inhibitors, AG-1478 and PD-153035, an HB-EGF neutralizing antibody, and a specific small interfering RNA (siRNA) against the EGFR. Expression of the CysLT₁ cysteinyl leukotriene receptor was demonstrated by RT-PCR and immunocytochemistry in both BEAS-2B and NHBE cells. Four hours after stimulation with LTD₄, HB-EGF and CXCL8 were significantly increased in cell culture supernatant. GM-6001 and montelukast, a specific CysLT₁ receptor antagonist, blocked the LTD₄-induced increase in HB-EGF. All inhibitors/antagonists decreased LTD₄-induced CXCL8 release. siRNA against EGFR abrogated CXCL8 release following stimulation with LTD₄ and exogenous HB-EGF. These findings suggest LTD₄ induced EGFR transactivation through the release of HB-EGF in human bronchial epithelial cells with downstream release of CXCL8. These effects may contribute to epithelial-mediated airway remodeling in asthma and other conditions associated with cysteinyl leukotriene release.

RETRACTED: Blockade of TNF-α signaling suppresses the AREG-mediated IL-6 and IL-8 cytokines secretion induced by anti-Ro/SSA autoantibodies

The aim of this study was to analyze the Furin-TNF-α-converting enzyme (TACE)-amphiregulin (AREG)-IL-6/IL-8 secretion pathway in non-neoplastic human salivary gland epithelial cells (SGECs) stimulated with anti-Ro/SSA autoantibodies (Abs). We examined whether anti-Ro/SSA Abs-mediated TACE activation is responsible for AREG activation. As recent studies have demonstrated that AREG could induce proinflammatory cytokines secretion in epithelial cells, we discuss how TACE-mediated AREG shedding, caused by anti-Ro/SSA Abs treatment, could have a critical role in TNF-α-induced IL-6 and IL-8 secretion by SGEC. Furthermore, the effects of TNF-α blockade on AREG expression and TNF-α-AREG-mediated IL-6 and IL-8 secretion were evaluated. We have discovered that the upregulation of AREG occurs through TNF-α produced after anti-Ro/SSA Abs uptake via Fcγ receptors. Biological drug adalimumab and the gene silencing technique were used to study the AREG-IL-6/IL-8 secretion pathway, demonstrating that (i) adalimumab-mediated TNF-α blocking and TNF-α gene silencing provoke a significant decrease of proinflammatory cytokines production and AREG expression in anti-Ro/SSA Abs-treated SGEC; (ii) AREG gene silencing has a potent inhibitory effect on TNF-α-induced IL-6 and IL-8 secretion in SGEC treated with anti-Ro/SSA Abs; (iii) an inspection of the kinetics of cytokine production after exogeni TNF-α and AREG addition, and the use of cycloheximide in the presence of exogenous TNF-α as stimulant, clarified that TNF-α induces IL-6 and IL-8 secretion through AREG.Laboratory Investigation advance online publication, 20 September 2010; doi:10.1038/labinvest.2010.168.

Prolyl-4-hydroxylase PHD2- and hypoxia-inducible factor 2-dependent regulation of amphiregulin contributes to breast tumorigenesis

Hypoxia-elicited adaptations of tumor cells are essential for tumor growth and cancer progression. Although ample evidence exists for a positive correlation between hypoxia-inducible factors (HIFs) and tumor formation, metastasis and bad prognosis, the function of the HIF-α protein stability regulating prolyl-4-hydroxylase domain enzyme PHD2 in carcinogenesis is less well understood. In this study, we demonstrate that downregulation of PHD2 leads to increased tumor growth in a hormone-dependent mammary carcinoma mouse model. Tissue microarray analysis of PHD2 protein expression in 281 clinical samples of human breast cancer showed significantly shorter survival times of patients with low-level PHD2 tumors over a period of 10 years. An angiogenesis-related antibody array identified, amongst others, amphiregulin to be increased in the absence of PHD2 and normalized after PHD2 reconstitution. Cultivation of endothelial cells in conditioned media derived from PHD2-downregulated cells resulted in enhanced tube formation that was blocked by the addition of neutralizing anti-amphiregulin antibodies. Functionally, amphiregulin was regulated on the transcriptional level specifically by HIF-2 but not HIF-1. Our data suggest that PHD2/HIF-2/amphiregulin signaling has a critical role in the regulation of breast tumor progression and propose PHD2 as a potential tumor suppressor in breast cancer.

Expression of pro-inflammatory TACE-TNF-α-amphiregulin axis in Sjögren's syndrome salivary glands

The tumor-necrosis-factor-converting-enzyme (TACE)-TNF-α-Amphiregulin (AREG) axis plays an important pathogenic role in inflammatory and autoimmune disorders. However, the pathological roles of these proteins in the chronic autoimmune disease Sjögren's syndrome (SS) remain to be elucidated. It is known that the TACE-AREG axis is clearly part of a larger cascade of signals that starts with the activation of Furin, responsible for maturation of TACE that, in turn, determines the production of active TNF-α, directly involved in the up-regulation of AREG expression. This study showed that Furin, TACE, TNF-α, and AREG proteins, detected in acinar and ductal cells of human salivary glands from SS patients, increased remarkably in comparison with biopsies of labial salivary glands from healthy controls. The changes in Furin, TACE, TNF- α, and AREG proteins' level detected in salivary glands biopsies of SS patients could be responsible for pro-inflammatory cytokines overexpression characterizing Sjögren's syndrome.

ADAM-17: the enzyme that does it all

This review focuses on the role of ADAM-17 in disease. Since its debut as the tumor necrosis factor converting enzyme (TACE), ADAM-17 has been reported to be an indispensible regulator of almost every cellular event from proliferation to migration. The central role of ADAM-17 in cell regulation is rooted in its diverse array of substrates: cytokines, growth factors, and their receptors as well as adhesion molecules are activated or inactivated by their cleavage with ADAM-17. It is therefore not surprising that ADAM-17 is implicated in numerous human diseases including cancer, heart disease, diabetes, rheumatoid arthritis, kidney fibrosis, Alzheimer's disease, and is a promising target for future treatments. The specific role of ADAM-17 in the pathophysiology of these diseases is very complex and depends on the cellular context. To exploit the therapeutic potential of ADAM-17, it is important to understand how its activity is regulated and how specific organs and cells can be targeted to inactivate or activate the enzyme.

Potential for functional redundancy in EGF and TGFalpha signaling in desmoid cells: a cDNA microarray analysis

Genes that replace or duplicate the function of other genes are considered functionally redundant. In this cDNA microarray study, using an Agilent microarray platform and GeneSifter analysis software, we evaluated (1) the degree of downstream transcriptional redundancy and (2) the level of genetic uniqueness apparent in desmoid tumor cells stimulated in vitro for 3 h or for 24 h with 100 ng/ml of exogenous recombinant human EGF (rhEGF) or with recombinant human transforming growth factor alpha (rhTGFalpha). Our intent was to identify genes costimulated, or genes unique to, desmoid cells stimulated in vitro with rhEGF and rhTGFalpha. This experimental approach demonstrated a 55% transcriptional redundancy in the number of desmoid genes significantly upregulated or downregulated following 3 h of stimulation with rhEGF or with rhTGFalpha, and a 65% transcriptional redundancy following 24 h of growth factor stimulation. Approximately 150 genes costimulated by rhEGF and rhTGFalpha were identified. This study suggests that EGF and TGFalpha retain some level of functional redundancy, possibly resulting from their divergence from a common ancestral gene.

Transactivation of ErbB-2 induced by tumor necrosis factor alpha promotes NF-kappaB activation and breast cancer cell proliferation

Tumor necrosis factor alpha (TNFalpha) is a pleiotropic cytokine which, acting locally, induces tumor growth. Accumulating evidence, including our findings, showed that TNFalpha is mitogenic in breast cancer cells in vitro and in vivo. In the present study, we explored TNFalpha involvement on highly aggressive ErbB-2-overexpressing breast cancer cells. We found that TNFalpha induces ErbB-2 phosphorylation in mouse breast cancer C4HD cells and in the human breast cancer cell lines SK-BR-3 and BT-474. ErbB-2 phosphorylation at Tyr877 residue was mediated by TNFalpha-induced c-Src activation. Moreover, TNFalpha promoted ErbB-2/ErbB-3 heterocomplex formation, Akt activation and NF-kappaB transcriptional activation. Inhibition of ErbB-2 by addition of AG825, an epidermal growth factor receptor/ErbB-2-tyrosine kinase inhibitor, or knockdown of ErbB-2 by RNA interference strategy, blocked TNFalpha-induced NF-kappaB activation and proliferation. However, the humanized monoclonal antibody anti-ErbB-2 Herceptin could not inhibit TNFalpha ability to promote breast cancer growth. Interestingly, our work disclosed that TNFalpha is able to transactivate ErbB-2 and use it as an obligatory downstream signaling molecule in the generation of mitogenic signals. As TNFalpha has been shown to be present in the tumor microenvironment of a significant proportion of human infiltrating breast cancers, our findings would have clinical implication in ErbB-2-positive breast cancer treatment.

Inflammation and liver cancer: new molecular links

A connection between inflammation and cancer has been long suspected. Epidemiological studies have established that many tumors occur in association with chronic infectious diseases, and it is also known that persistent inflammation in the absence of infections increases the risk and accelerates the development of cancer. One clear example of inflammation-related cancer is hepatocellular carcinoma (HCC). HCC is a type tumor that slowly unfolds on a background of chronic inflammation mainly triggered by exposure to infectious agents (hepatotropic viruses) or to toxic compounds (ethanol). The molecular links that connect inflammation and cancer are not completely known, but evidences gathered over the past few years are beginning to define the precise mechanisms. In this article we review the most compelling evidences on the role of transcription factors such as NF-kappaB and STAT3, cytokines like IL-6 and IL-1alpha, ligands of the EGF receptor and other inflammatory mediators in cancer development, with special emphasis in HCC. The molecular dissection of the pathways connecting the inflammatory reaction and neoplasia will pave the way for better therapies to treat cancers.

Comparisons of affinities, avidities, and complement activation of adalimumab, infliximab, and etanercept in binding to soluble and membrane tumor necrosis factor

The TNF antagonists adalimumab, infliximab, and etanercept are effective treatments for rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, and psoriasis, but only adalimumab and infliximab have been found to be efficacious in Crohn's disease. The present studies evaluated the TNF-binding and complement-activating properties of adalimumab, infliximab, and etanercept to determine whether these properties may explain differences in their clinical efficacy profiles. Association and dissociation rates of binding to soluble TNF were measured by surface plasmon resonance, and were found to be similar for adalimumab, infliximab, and etanercept, as were their calculated binding affinities. Avidity of binding to soluble TNF, measured by KinExA technology, was 10- to 20-fold greater for soluble etanercept (K(D)=0.4 picomolars [pM]) than for soluble adalimumab or infliximab (K(D)=8.6 and 4.2 pM, respectively). (125)I-adalimumab, -infliximab, and -etanercept bound to membrane TNF (mTNF) on mTNF-transfected cells with similar affinities (K(D)=483, 468, and 445 pM, respectively) that were each lower than for soluble TNF. Complement-dependent cytotoxicity (CDC) was induced in mTNF-transfected cells by adalimumab and infliximab, but was not induced in activated normal human PBMC by any of the 3 agents. In conclusion, the binding properties of adalimumab, infliximab, and etanercept were similar for soluble TNF, and very similar for mTNF, yet none of the 3 was able to induce CDC in activated PBMC. These results suggest that the different clinical efficacy profiles of these agents are not explained by differences in either TNF-intrinsic binding properties or complement lysis.

Structural aspects of airway remodeling in asthma

Airway remodeling in asthma is a complex process that involves structural changes in virtually all tissues of the airway wall. The histologic changes to the airways consist of epithelial proliferation and goblet cell differentiation, subepithelial fibrosis, airway smooth muscle (ASM) growth, angiogenesis, matrix protein deposition, gland hyperplasia and hypertrophy, and nerve proliferation. Cytokines, chemokines, and growth factors from inflammatory cells and structural cells contribute to remodeling. There are complex interactions among the various signaling pathways involving matrix metalloproteinases that are required for growth factor release. The physiologic consequences of remodeling are airway hyperresponsiveness from ASM growth and mucus hypersecretion from gland and goblet cell hyperplasia. Airway stiffening is a probable contributor to airway hyperresponsiveness through attenuation of the transmission of potently bronchodilating cyclical stress to the ASM during breathing. The epidermal growth factor receptor's role in remodeling and its interaction with other potential causes of remodeling are discussed.

Amphiregulin as a novel target for breast cancer therapy

Amphiregulin, an EGF family growth factor, binds and activates the epidermal growth factor receptor (EGFR or ErbB1). Activation of the EGFR by amphiregulin can occur through autocrine, paracrine and juxtacrine mechanisms. Amphiregulin plays a role in several biological processes including nerve regeneration, blastocyst implantation, and bone formation. Amphiregulin also plays an important role in mammary duct formation as well as the outgrowth and branching of several other human tissues such as the lung, kidney and prostate. This effect is most likely due to the induction of genes involved in invasion and migration such as cytokines and matrix metalloproteases. Clinical studies have suggested that amphiregulin also plays a role in human breast cancer progression and its expression has been associated with aggressive disease. Therefore, amphiregulin may be a novel and effective target for the treatment of breast cancer and could represent an alternative to targeting the EGFR.

The epidermal growth factor receptor system in skin repair and inflammation

The epidermal growth factor (EGF) family comprises multiple mediators such as transforming growth factor-alpha, amphiregulin, heparin binding-EGF, and epiregulin, which are crucially involved in the tissue-specific proliferation/differentiation homeostasis. Typically, they act in an autocrine and paracrine manner on their specific cell membrane receptor and mount an effective reparative response to any attack to biophysical integrity. In addition, the EGFR can be activated by transactivation from a variety of G-protein-coupled receptors, integrins, and cytokine receptors, so that it acts as the major transducer of disparate cell functions, including changes in proliferation rate, cellular shape, attachment and motility, and regulation of proinflammatory activation. However, numerous experimental observations indicate that the different EGFR ligands are not redundant, but may rather provide distinct and specific contributions to keratinocyte functions. Importantly, increasing evidence now suggests that the EGFR pathway has a major impact on the inflammatory/immune reactions of the skin, in the apparent effort of enhancing innate immune defense while opposing overactivation of keratinocyte pro-inflammatory functions. This review covers the molecular mechanisms and functions activated by this major growth factor system in the regulation of keratinocyte biology and focuses on the complex contribution of EGFR signaling to the inflammatory processes in the skin.

Cancer cell-derived IL-1alpha induces IL-8 release in endothelial cells

PURPOSE

Cancer cells release a multitude of cytokines and growth factors that influence neighboring cells and help establish a favorable environment for tumor development. As part of our studies designed to elucidate the complex cellular interactions within the tumor microenvironment that facilitate tumor development, we investigated cancer cell-induced changes in gene expression in endothelial cells.

METHODS

After treatment of human umbilical vein endothelial cells (HUVEC) with conditioned medium (CM) of SNUC5 colon cancer cells, gene expression profile in HUVEC was analyzed using cDNA microarray. Neutralizing antibodies against pro-inflammatory cytokines were used to identify the major effecter in SNUC5 CM.

RESULTS

IL-8 was one of the four genes up-regulated over fourfold, and IL-1alpha in SNUC5 CM was revealed as a major effecter of IL-8 over-expression and release, which was nearly completely neutralized by anti-IL-1alpha antibody. Constitutive secretion of IL-1alpha was confirmed in many other human cancer cells.

CONCLUSIONS

IL-1alpha is constitutively expressed in many human cancer cells and directly induces IL-8 secretion in neighboring endothelial cells.

Screening of differentially expressed transcripts in infectious bursal disease virus-induced apoptotic chicken embryonic fibroblasts by using cDNA microarrays

Infectious bursal disease virus (IBDV) induces apoptosis and immunosuppression. To understand the molecular mechanisms involved in the pathogenesis of infectious bursal disease (IBD) and the host-directed antiviral responses, cDNA microarrays were used to identify the differentially expressed transcripts in IBDV-infected chicken embryonic fibroblasts. The results suggest a general suppression of surface receptors, including CD40 ligand and SEMA4D. These are related to T- and B-cell activation and differentiation, which may contribute to the immunosuppression of IBD. In addition, activation of genes involved in Toll-like receptor- and interferon (IFN)-mediated antiviral responses was detected. In particular, upregulation of Toll-like receptor 3, a double-stranded (ds) RNA receptor, and MX1, an IFN-inducible antiviral GTPase, may represent the possible host-directed defence responses against the virus and its dsRNA genome. Interestingly, several lines of evidence suggest the modulation of G protein-coupled receptors and receptor tyrosine kinase signalling pathways, especially the possible transactivation of epidermal growth factor receptor by lysophosphatidic acid. Alteration of these may contribute to the previously reported activation of mitogen-activated protein kinases upon IBDV infection, resulting in macrophage activation and inflammatory responses. Additionally, numerous target genes and inducers of nuclear factor kappa B (NF-κB) were upregulated profoundly, implying that IBDV may modulate host-cell survival and apoptosis to support its replication and facilitate viral spread through NF-κB activation. In summary, this investigation of host-gene expression unravelled the candidate physiological pathways involved in host–virus interaction on a molecular level, providing a foundation for researchers to design experiments based on testable hypotheses targeting individual genes.

New molecular targets for hepatocellular carcinoma: the ErbB1 signaling system

Hepatocellular carcinoma (HCC) is a major cause of cancer-related deaths. This malignancy is often diagnosed at an advanced state, when most potentially curative therapies are of limited efficacy. In addition, HCC is a type of tumor highly resistant to available chemotherapeutic agents, which leaves HCC patients with no effective therapeutic options and a poor prognosis. From a molecular perspective, HCC is a heterogeneous type of tumor. However, in most cases, HCC emerges on a background of persistent liver injury, inflammation and hepatocellular proliferation, which is characteristic of chronic hepatitis and cirrhosis. Recent studies have revealed that dysregulation of a limited number of growth and survival-related pathways can play a key role in HCC development. The epidermal growth factor receptor (ErbB1) can be bound and activated by a broad family of ligands, and can also engage in extensive cross talk with other signaling pathways. This system is considered as an important defense mechanism for the liver during acute tissue injury; however, accumulating evidences suggest that its chronic stimulation can participate in the neoplastic conversion of the liver. Agents that target the ErbB1 receptor have shown antineoplastic activity in other types of tumors, but their efficacy either alone or in combination with other compounds has just started to be tested in experimental and human HCC. Here, we review the evidences that support the involvement of the ErbB1 in HCC development and that provide a rationale for ErbB1 targeting in HCC prevention and treatment.