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

Regulation of the RhoA exchange factor GEF-H1 by profibrotic stimuli through a positive feedback loop involving RhoA, MRTF, and Sp1

RhoA and its effectors, the transcriptional coactivators myocardin-related transcription factor (MRTF) and serum response factor (SRF), control epithelial phenotype and are indispensable for profibrotic epithelial reprogramming during fibrogenesis. Context-dependent control of RhoA and fibrosis-associated changes in its regulators, however, remain incompletely characterized. We previously identified the guanine nucleotide exchange factor GEF-H1 as a central mediator of RhoA activation in renal tubular cells exposed to inflammatory or fibrotic stimuli. Here we found that GEF-H1 expression and phosphorylation were strongly elevated in two animal models of fibrosis. In the Unilateral Ureteral Obstruction mouse kidney fibrosis model, GEF-H1 was upregulated predominantly in the tubular compartment. GEF-H1 was also elevated and phosphorylated in a rat pulmonary artery banding (PAB) model of right ventricular fibrosis. Prolonged stimulation of LLC-PK1 tubular cells with tumor necrosis factor (TNF)-α or transforming growth factor (TGF)-β1 increased GEF-H1 expression and activated a luciferase-coupled GEF-H1 promoter. Knockdown and overexpression studies revealed that these effects were mediated by RhoA, cytoskeleton remodeling, and MRTF, indicative of a positive feedback cycle. Indeed, silencing endogenous GEF-H1 attenuated activation of the GEF-H1 promoter. Of importance, inhibition of MRTF using CCG-1423 prevented GEF-H1 upregulation in both animal models. MRTF-dependent increase in GEF-H1 was prevented by inhibition of the transcription factor Sp1, and mutating putative Sp1 binding sites in the GEF-H1 promoter eliminated its MRTF-dependent activation. As the GEF-H1/RhoA axis is key for fibrogenesis, this novel MRTF/Sp1-dependent regulation of GEF-H1 abundance represents a potential target for reducing renal and cardiac fibrosis.NEW & NOTEWORTHY We show that expression of the RhoA regulator GEF-H1 is upregulated in tubular cells exposed to fibrogenic cytokines and in animal models of kidney and heart fibrosis. We identify a pathway wherein GEF-H1/RhoA-dependent MRTF activation through its noncanonical partner Sp1 upregulates GEF-H1. Our data reveal the existence of a positive feedback cycle that enhances Rho signaling through control of both GEF-H1 activation and expression. This feedback loop may play an important role in organ fibrosis.

Bone resorption by osteoclasts involves fine tuning of RHOA activity by its microtubule-associated exchange factor GEF-H1

Bone health is controlled by the balance between bone formation by osteoblasts and degradation by osteoclasts. A disequilibrium in favor of bone resorption leads to osteolytic diseases characterized by decreased bone density. Osteoclastic resorption is dependent on the assembly of an adhesion structure: the actin ring, also called podosome belt or sealing zone, which is composed of a unique patterning of podosomes stabilized by microtubules. A better understanding of the molecular mechanisms regulating the crosstalk between actin cytoskeleton and microtubules network is key to find new treatments to inhibit bone resorption. Evidence points to the importance of the fine tuning of the activity of the small GTPase RHOA for the formation and maintenance of the actin ring, but the underlying mechanism is not known. We report here that actin ring disorganization upon microtubule depolymerization is mediated by the activation of the RHOA-ROCK signaling pathway. We next show the involvement of GEF-H1, one of RHOA guanine exchange factor highly expressed in osteoclasts, which has the particularity of being negatively regulated by sequestration on microtubules. Using a CRISPR/Cas9-mediated GEF-H1 knock-down osteoclast model, we demonstrate that RHOA activation upon microtubule depolymerization is mediated by GEF-H1 release. Interestingly, although lower levels of GEF-H1 did not impact sealing zone formation in the presence of an intact microtubule network, sealing zone was smaller leading to impaired resorption. Altogether, these results suggest that a fine tuning of GEF-H1 through its association with microtubules, and consequently of RHOA activity, is essential for osteoclast sealing zone stability and resorption function.

Preclinical Evidence that Arctigenin Effectively and Selectively Targets Clear Cell Renal Cell Carcinoma Via Suppressing EGFR and RhoA

Clear cell renal cell carcinoma (ccRCC) has poor clinical outcomes and necessitates new treatment options. Epidermal growth factor receptor (EGFR) is a potential therapeutic target, due to the associations with various carcinomas' progression. Arctigenin, a natural compound of Arctium lappa, has been shown to display anticancer abilities in various carcinomas. Cellular assays and combination studies were conducted using arctigenin and anti-ccRCC drugs. In vivo efficacy of arctigenin was determined using ccRCC xenograft mouse model. Immunoblotting and biochemistry analysis were applied to investigate the signaling affected by arctigenin. Arctigenin inhibits growth, migration, and survival of ccRCC cells while sparing normal kidney cells. Arctigenin acts synergistically with 5-FU and sorafenib but not temsirolimus in inhibiting ccRCC cells. Synergism of arctigenin with 5-FU and sorafenib was further shown in ccRCC xenograft mouse model. The combination of arctigenin with clinical anti-RCC drugs completely inhibits tumor growth without tumor progression even for an extended time period. Mechanistically, arctigenin inhibits migration in a RhoA-dependent manner while inhibits growth via suppressing EGFR-mediated signaling pathways. Our findings suggest that arctigenin performs well to add to current treatment in ccRCC and confirm the value to target EGFR to improve therapy in RCC.

EGFR-TNFR1 pathway in endothelial cell facilitates acute lung injury by NF-κB/MAPK-mediated inflammation and RIP3-dependent necroptosis

Tumor necrosis factor-α (TNFα) has emerged as a pivotal effector critically correlated with disease severity in acute lung injury (ALI). Because both the excessive activation of epidermal growth factor receptor (EGFR) and tumor necrosis factor receptor 1 (TNFR1) in sepsis-induced vasculitis are markedly diminished through EGFR tyrosine kinase inhibitor, a specific mechanism must exist to modulate TNFR1 cellular fates regulated by EGFR. Here, we demonstrated that EGFR, a specific binding partner of TNFR1, exhibited an increased NF-κB/MAPK-mediated inflammation that was governed by enhanced recruitment of TNFR-associated factor 2 (TRAF2) to TNFR1 complex I in endothelial cell (EC). Moreover, EGFR activation triggered a remarkable increase in the phosphorylation of receptor-interacting protein 1 (RIP1) and its binding with receptor-interacting protein 3 (RIP3) which led to enhanced frequency of necroptosis in complex IIb. Inhibiting the kinase of EGFR disrupted the formation of complex I and complex IIb and prevents EC from NF-κB/MAPK-mediated inflammation and RIP3-dependent necroptosis. Consistently, pharmacological inhibition of EGFR can limit the destructive effects of neutrophils activation and the hyperpermeability of lung vascular in hyperinflammation period. Collectively, we have identified EC-EGFR as a modulator of TNFR1-mediated inflammation and RIP3-dependent necroptosis, providing a possible explanation for the immunological basis of anti-EGFR therapy in sepsis-induced ALI.

Therapeutic Validation of GEF-H1 Using a De Novo Designed Inhibitor in Models of Retinal Disease

Inflammation and fibrosis are important components of diseases that contribute to the malfunction of epithelia and endothelia. The Rho guanine nucleotide exchange factor (GEF) GEF-H1/ARHGEF-2 is induced in disease and stimulates inflammatory and fibrotic processes, cell migration, and metastasis. Here, we have generated peptide inhibitors to block the function of GEF-H1. Inhibitors were designed using a structural in silico approach or by isolating an inhibitory sequence from the autoregulatory C-terminal domain. Candidate inhibitors were tested for their ability to block RhoA/GEF-H1 binding in vitro, and their potency and specificity in cell-based assays. Successful inhibitors were then evaluated in models of TGFβ-induced fibrosis, LPS-stimulated endothelial cell-cell junction disruption, and cell migration. Finally, the most potent inhibitor was successfully tested in an experimental retinal disease mouse model, in which it inhibited blood vessel leakage and ameliorated retinal inflammation when treatment was initiated after disease diagnosis. Thus, an antagonist that blocks GEF-H1 signaling effectively inhibits disease features in in vitro and in vivo disease models, demonstrating that GEF-H1 is an effective therapeutic target and establishing a new therapeutic approach.

Two Motors and One Spring: Hypothetic Roles of Non-Muscle Myosin II and Submembrane Actin-Based Cytoskeleton in Cell Volume Sensing

Changes in plasma membrane curvature and intracellular ionic strength are two key features of cell volume perturbations. In this hypothesis we present a model of the responsible molecular apparatus which is assembled of two molecular motors [non-muscle myosin II (NMMII) and protrusive actin polymerization], a spring [a complex between the plasma membrane (PM) and the submembrane actin-based cytoskeleton (smACSK) which behaves like a viscoelastic solid] and the associated signaling proteins. We hypothesize that this apparatus senses changes in both the plasma membrane curvature and the ionic strength and in turn activates signaling pathways responsible for regulatory volume increase (RVI) and regulatory volume decrease (RVD). During cell volume changes hydrostatic pressure (HP) changes drive alterations in the cell membrane curvature. HP difference has opposite directions in swelling versus shrinkage, thus allowing distinction between them. By analogy with actomyosin contractility that appears to sense stiffness of the extracellular matrix we propose that NMMII and actin polymerization can actively probe the transmembrane gradient in HP. Furthermore, NMMII and protein-protein interactions in the actin cortex are sensitive to ionic strength. Emerging data on direct binding to and regulating activities of transmembrane mechanosensors by NMMII and actin cortex provide routes for signal transduction from transmembrane mechanosensors to cell volume regulatory mechanisms.

The Crossroads between RAS and RHO Signaling Pathways in Cellular Transformation, Motility and Contraction

Ras and Rho proteins are GTP-regulated molecular switches that control multiple signaling pathways in eukaryotic cells. Ras was among the first identified oncogenes, and it appears mutated in many forms of human cancer. It mainly promotes proliferation and survival through the MAPK pathway and the PI3K/AKT pathways, respectively. However, the myriad proteins close to the plasma membrane that activate or inhibit Ras make it a major regulator of many apparently unrelated pathways. On the other hand, Rho is weakly oncogenic by itself, but it critically regulates microfilament dynamics; that is, actin polymerization, disassembly and contraction. Polymerization is driven mainly by the Arp2/3 complex and formins, whereas contraction depends on myosin mini-filament assembly and activity. These two pathways intersect at numerous points: from Ras-dependent triggering of Rho activators, some of which act through PI3K, to mechanical feedback driven by actomyosin action. Here, we describe the main points of connection between the Ras and Rho pathways as they coordinately drive oncogenic transformation. We emphasize the biochemical crosstalk that drives actomyosin contraction driven by Ras in a Rho-dependent manner. We also describe possible routes of mechanical feedback through which myosin II activation may control Ras/Rho activation.

Electric cell-substrate impedance sensing in kidney research

Electric cell-substrate impedance sensing (ECIS) is a quantitative, label-free, non-invasive analytical method allowing continuous monitoring of the behaviour of adherent cells by online recording of transcellular impedance. ECIS offers a wide range of practical applications to study cell proliferation, migration, differentiation, toxicity and monolayer barrier integrity. All of these applications are relevant for basic kidney research, e.g. on endothelial cells, tubular and glomerular epithelial cells. This review gives an overview on the fundamental principles of the ECIS technology. We name strengths and remaining hurdles for practical applications, present an ECIS array reuse protocol, and review its past, present and potential future contributions to preclinical kidney research.

Contribution of ADAM17 and related ADAMs in cardiovascular diseases

A disintegrin and metalloproteases (ADAMs) are key mediators of cell signaling by ectodomain shedding of various growth factors, cytokines, receptors and adhesion molecules at the cellular membrane. ADAMs regulate cell proliferation, cell growth, inflammation, and other regular cellular processes. ADAM17, the most extensively studied ADAM family member, is also known as tumor necrosis factor (TNF)-α converting enzyme (TACE). ADAMs-mediated shedding of cytokines such as TNF-α orchestrates immune system or inflammatory cascades and ADAMs-mediated shedding of growth factors causes cell growth or proliferation by transactivation of the growth factor receptors including epidermal growth factor receptor. Therefore, increased ADAMs-mediated shedding can induce inflammation, tissue remodeling and dysfunction associated with various cardiovascular diseases such as hypertension and atherosclerosis, and ADAMs can be a potential therapeutic target in these diseases. In this review, we focus on the role of ADAMs in cardiovascular pathophysiology and cardiovascular diseases. The main aim of this review is to stimulate new interest in this area by highlighting remarkable evidence.

TNF-α-induced sympathetic excitation requires EGFR and ERK1/2 signaling in cardiovascular regulatory regions of the forebrain

Peripherally or centrally administered TNF-α elicits a prolonged sympathetically mediated pressor response, but the underlying molecular mechanisms are unknown. Activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in cardiovascular regions of the brain has recently been recognized as a key mediator of sympathetic excitation, and ERK1/2 signaling is induced by activation of epidermal growth factor receptor (EGFR) tyrosine kinase activity. The present study examined the role of EGFR and ERK1/2 signaling in the sympathetic response to TNF-α. In urethane-anesthetized rats, intracarotid artery injection of TNF-α increased phosphorylation of EGFR and ERK1/2 in the subfornical organ (SFO) and the hypothalamic paraventricular nucleus (PVN); upregulated the gene expression of excitatory mediators in SFO and PVN; and increased blood pressure (BP), heart rate (HR), and renal sympathetic nerve activity (RSNA). A continuous intracerebroventricular infusion of the selective EGFR tyrosine kinase inhibitor AG1478 or the ERK1/2 inhibitor PD98059 significantly attenuated these responses. Bilateral PVN microinjections of TNF-α also increased phosphorylated ERK1/2 and the gene expression of excitatory mediators in PVN, along with increases in BP, HR, and RSNA, and these responses were substantially reduced by prior bilateral PVN microinjections of AG1478. These results identify activation of EGFR in cardiovascular regulatory regions of the forebrain as an important molecular mediator of TNF-α-driven sympatho-excitatory responses and suggest that EGFR activation of the ERK1/2 signaling pathway plays an essential role. These mechanisms likely contribute to sympathetic excitation in pathophysiological states like heart failure and hypertension, in which circulating and brain TNF-α levels are increased.NEW & NOTEWORTHY Proinflammatory cytokines contribute to the augmented sympathetic nerve activity in hypertension and heart failure, but the central mechanisms involved are largely unknown. The present study reveals that TNF-α transactivates EGFR in the subfornical organ and the hypothalamic paraventricular nucleus to initiate ERK1/2 signaling, upregulate the gene expression of excitatory mediators, and increase sympathetic nerve activity. These findings identify EGFR as a gateway to sympathetic excitation and a potential target for intervention in cardiovascular disease states.

Tumor necrosis factor-α induces claudin-3 upregulation in kidney tubular epithelial cells through NF-κB and CREB1

Claudins are essential for tight junction formation and paracellular transport, and they affect key cellular events including proliferation and migration. The properties of tight junctions are dynamically modulated by a variety of inputs. We previously showed that the inflammatory cytokine tumor necrosis factor-α (TNFα), a major pathogenic factor in kidney disease, alters epithelial permeability by affecting the expression of claudin-1, -2, and -4 in kidney tubular cells. Here, we explored the effect of TNFα on claudin-3 (Cldn-3), a ubiquitous barrier-forming protein. We found that TNFα elevated Cldn-3 protein expression in tubular epithelial cells (LLC-PK1 and IMCD3) as early as 3 h post treatment. Bafilomycin A and bortezomib, inhibitors of lysosomal and proteasomes, respectively, reduced Cldn-3 degradation. However, TNFα caused a strong upregulation of Cldn-3 in the presence of bafilomycin, suggesting an effect independent from lysosomes. Blocking protein synthesis using cycloheximide prevented Cldn-3 upregulation by TNFα, verifying the contribution of de novo Cldn-3 synthesis. Indeed, TNFα elevated Cldn-3 mRNA levels at early time points. Using pharmacological inhibitors and siRNA-mediated silencing, we determined that the effect of TNFα on Cldn-3 was mediated by extracellular signal regulated kinase (ERK)-dependent activation of NF-κB and PKA-induced activation of CREB1. These two pathways were turned on by TNFα in parallel and both were required for the upregulation of Cldn-3. Because Cldn-3 was suggested to modulate cell migration and epithelial-mesenchymal transition (EMT), and TNFα was shown to affect these processes, Cldn-3 upregulation may modulate regeneration of the tubules following injury.

Regulation and functions of the RhoA regulatory guanine nucleotide exchange factor GEF-H1

Since the discovery by Madaule and Axel in 1985 of the first Ras homologue (Rho) protein in Aplysia and its human orthologue RhoB, membership in the Rho GTPase family has grown to 20 proteins, with representatives in all eukaryotic species. These GTPases are molecular switches that cycle between active (GTP bound) and inactivate (GDP bound) states. The exchange of GDP for GTP on Rho GTPases is facilitated by guanine exchange factors (GEFs). Approximately 80 Rho GEFs have been identified to date, and only a few GEFs associate with microtubules. The guanine nucleotide exchange factor H1, GEF-H1, is a unique GEF that associates with microtubules and is regulated by the polymerization state of microtubule networks. This review summarizes the regulation and functions of GEF-H1 and discusses the roles of GEF-H1 in human diseases.

Measuring Cell Growth and Junction Development in Epithelial Cells Using Electric Cell-Substrate Impedance Sensing (ECIS)

Electric Cell-substrate Impedance Sensing (ECIS) is an automated method that can be used to quantify processes such as cell attachment, growth, migration and barrier functions (i.e., the properties of tight junctions). The method provides simultaneous information on cell number and tight junction function by detecting electric parameters of cells grown on electrodes. Samples are probed with small alternating current (AC) over a range of frequencies, and changes in capacitance and impedance are measured over time. Capacitance reflects the degree of electrode coverage by cells, that correlates with cell number, and can be used to assess cell proliferation or migration. Impedance values inform about barrier function. Obtaining real-time simultaneous information on these parameters is unique to this system and is of great value for addressing fundamental questions such as the role of tight junction proteins in cell growth and migration. This protocol describes the use of ECIS to follow cell growth and tight junction-dependent barrier generation in tubular epithelial cells. We used this method to explore how depleting claudin-2, a tight junction protein affects tubular cell growth and barrier function. During the process, cells are transfected with control or claudin-2-specific siRNA, and 24h later plated on electrodes. ECIS automatically collects information on cell growth and barrier as the monolayer develops. The data are initially analyzed using the ECIS software and exported into a graph software for further processing.

Receptor tyrosine kinase ligands and inflammatory cytokines cooperatively suppress the fibrogenic activity in temporomandibular-joint-derived fibroblast-like synoviocytes via mitogen-activated protein kinase kinase/extracellular signal-regulated kinase

Osteoarthritis (OA)-related fibrosis is a possible cause of temporomandibular joint (TMJ) stiffness. However, the molecular mechanisms underlying the fibrogenic activity in fibroblast-like synoviocytes (FLSs) remain to be clarified. The present study examined the effects of receptor tyrosine kinase (RTK) ligands, such as fibroblast growth factor (FGF)-1 and epidermal growth factor (EGF), on myofibroblastic differentiation of the FLS cell line FLS1, which is derived from the mouse TMJ. The present study revealed that both FGF-1 and EGF dose-dependently suppressed the expression of the myofibroblast (MF) markers, including α-smooth muscle actin (α-SMA) and type I collagen, in FLS1 cells. Additionally, both FGF-1 and EGF activated extracellular signal-regulated kinase (ERK) in FLS1 cells. In addition, the mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor U0126 abrogated the FGF-1- and EGF-mediated suppression of MF marker expression. On the other hand, inflammatory cytokines, such as interleukin-1β and tumor necrosis factor-α, also suppressed the expression of MF markers in FLS1 cells. Importantly, U0126 abrogated the inflammatory cytokine-mediated suppression of MF marker expression. Interestingly, RTK ligands and inflammatory cytokines additively suppressed the expression of type I collagen. These results suggested that RTK ligands and inflammatory cytokines cooperatively inhibited the fibrogenic activity in FLSs derived from the TMJ in a MEK/ERK-dependent manner. The present findings partially clarify the molecular mechanisms underlying the development of OA-related fibrosis in the TMJ and may aid in identifying therapeutic targets for this condition. Additionally, FGF-1 and EGF could be therapeutically utilized to prevent OA-related fibrosis around the inflammatory TMJ.

EGFR activation attenuates the mechanical threshold for integrin tension and focal adhesion formation

Mechanical forces, growth factors and the extracellular matrix all play crucial roles in cell adhesion. To understand how epidermal growth factor receptor (EGFR) impacts the mechanics of adhesion, we employed tension gauge tether (TGT) probes displaying the integrin ligand cRGDfK and quantified integrin tension. EGF exposure significantly increased spread area, cell circularity, integrated integrin tension, mechanical rupture density, radial organization and size of focal adhesions in Cos-7 cells on TGT surfaces. These findings suggest that EGFR regulates integrin tension and the spatial organization of focal adhesions. Additionally, we found that the mechanical tension threshold for outside-in integrin activation is tunable by EGFR. Parallel genetic and pharmacologic strategies demonstrated that these phenotypes are driven by ligand-dependent EGFR signaling. Our results establish a novel mechanism whereby EGFR regulates integrin activation and cell adhesion, providing control over cellular responses to the environment.This article has an associated First Person interview with the first author of the paper.

14-3-3β Is necessary in the regulation of polarization and directional migration of alveolar myofibroblasts by lipopolysaccharide

Aims:Bronchopulmonary dysplasia (BPD) is characterized by alveolarization arrest. During alveolarization, alveolar myofibroblasts are thought to migrate into the septal tips and elongate secondary septa. Lipopolysaccharide (LPS) exposure has been reported to disrupt directional migration and final location of alveolar myofibroblasts in a rat model of BPD induced by intra-amniotic injection of LPS. However, molecular mechanisms that control directional migration of alveolar myofibroblasts have not so far been investigated clearly. Materials and Methods: We assessed the polarization of myofibroblast using scrape wounding assays combined with Golgi tracking. Transwell migration assay was used to detect the directional migration of myofibroblasts. Pull-down assays were performed to isolate the active GTP-bound form using the RhoA activation assay kits. Western blotting analysis was performed to evaluate the changes in protein expression. Functional analysis was performed via siRNA interference. Results: Here, we showed that LPS might affect the directional migration of myofibroblasts by disturbing the polarization of myofibroblasts. In addition, as a main member of RhoGTPases family which plays a vital role in establishing and maintaining cell polarity, RhoA activity was significantly upregulated in myofibroblasts treated with LPS, while activity of epidermal growth factor receptor (EGFR) was upregulated and overexpression of its ligand, TGF-α, in myofibroblasts by LPS treatment. AG1478, an EGFR inhibitor, could abrogate the upregulated RhoA activity of myofibroblasts by LPS and rhTGF-α. Moreover, if we knock down 14-3-3β, LPS and rhTGF-α could not activate RhoA and disturb myofibroblasts polarization. Conclusions: Taken together, our findings suggest that LPS exposure may increase RhoA activity of myofibroblasts by TGF-α/EGFR/14-3-3β signaling pathway, and then disturb myofibroblasts polarization and directional migration.

Claudin-2 suppresses GEF-H1, RHOA, and MRTF, thereby impacting proliferation and profibrotic phenotype of tubular cells

The tight junctional pore-forming protein claudin-2 (CLDN-2) mediates paracellular Na⁺ and water transport in leaky epithelia and alters cancer cell proliferation. Previously, we reported that tumor necrosis factor-α time-dependently alters CLDN-2 expression in tubular epithelial cells. Here, we found a similar expression pattern in a mouse kidney injury model (unilateral ureteral obstruction), consisting of an initial increase followed by a drop in CLDN-2 protein expression. CLDN-2 silencing in LLC-PK¹ tubular cells induced activation and phosphorylation of guanine nucleotide exchange factor H1 (GEF-H1), leading to Ras homolog family member A (RHOA) activation. Silencing of other claudins had no such effects, and re-expression of an siRNA-resistant CLDN-2 prevented RHOA activation, indicating specific effects of CLDN-2 on RHOA. Moreover, kidneys from CLDN-2 knockout mice had elevated levels of active RHOA. Of note, CLDN-2 silencing reduced LLC-PK1 cell proliferation and elevated expression of cyclin-dependent kinase inhibitor P27 (P27KIP1) in a GEF-H1/RHOA-dependent manner. P27KIP1 silencing abrogated the effects of CLDN-2 depletion on proliferation. CLDN-2 loss also activated myocardin-related transcription factor (MRTF), a fibrogenic RHOA effector, and elevated expression of connective tissue growth factor and smooth muscle actin. Finally, CLDN-2 down-regulation contributed to RHOA activation and smooth muscle actin expression induced by prolonged tumor necrosis factor-α treatment, because they were mitigated by re-expression of CLDN-2. Our results indicate that CLDN-2 suppresses GEF-H1/RHOA. CLDN-2 down-regulation, for example, by inflammation, can reduce proliferation and promote MRTF activation through RHOA. These findings suggest that the initial CLDN-2 elevation might aid epithelial regeneration, and CLDN-2 loss could contribute to fibrotic reprogramming.

Death receptor 5 contributes to cardiomyocyte hypertrophy through epidermal growth factor receptor transactivation

Cardiomyocyte survival and death contributes to many cardiac diseases. A common mechanism of cardiomyocyte death is through apoptosis however, numerous death receptors (DR) have been virtually unstudied in the context of cardiovascular disease. Previous studies have identified TNF-related apoptosis inducing ligand (TRAIL) and its receptor, DR5, as being altered in a chronic catecholamine administration model of heart failure, and suggest a role of non-canonical signaling in cardiomyocytes. Furthermore, multiple clinical studies have identified TRAIL or DR5 as biomarkers in the prediction of severity and mortality following myocardial infarction and in heart failure development risk suggesting a role of DR5 signaling in the heart. While TRAIL/DR5 have been extensively studied as a potential cancer therapeutic due to their ability to selectively activate apoptosis in cancer cells, TRAIL and DR5 are highly expressed in the heart where their function is uncharacterized. However, many non-transformed cell types are resistant to TRAIL-induced apoptosis suggesting non-canonical functions in non-cancerous cell types. Our goal was to determine the role of DR5 in the heart with the hypothesis that DR5 does not induce cardiomyocyte apoptosis but initiates non-canonical signaling to promote cardiomyocyte growth and survival. Histological analysis of hearts from mice treated with a DR5 agonists showed increased hypertrophy with no differences in cardiomyocyte death, fibrosis or function. Mechanistic studies in the heart and isolated cardiomyocytes identified ERK1/2 activation with DR5 agonist treatment which contributed to hypertrophy. Furthermore, epidermal growth factor receptor (EGFR) was activated following DR5 agonist treatment through activation of MMP and HB-EGFR cleavage and specific inhibitors of MMP and EGFR prevented DR5-mediated ERK1/2 signaling and hypertrophy. Taken together, these studies identify a previously unidentified role for DR5 in the heart, which does not promote apoptosis but acts through non-canonical MMP-EGFR-ERK1/2 signaling mechanisms to contribute to cardiomyocyte hypertrophy.

Assessment of the nitrofen model of congenital diaphragmatic hernia and of the dysregulated factors involved in pulmonary hypoplasia

PURPOSE

To study pulmonary hypoplasia (PH) associated with congenital diaphragmatic hernia (CDH), investigators have been employing a fetal rat model based on nitrofen administration to dams. Herein, we aimed to: (1) investigate the validity of the model, and (2) synthesize the main biological pathways implicated in the development of PH associated with CDH.

METHODS

Using a defined strategy, we conducted a systematic review of the literature searching for studies reporting the incidence of CDH or factors involved in PH development. We also searched for PH factor interactions, relevance to lung development and to human PH.

RESULTS

Of 335 full-text articles, 116 reported the incidence of CDH after nitrofen exposure or dysregulated factors in the lungs of nitrofen-exposed rat fetuses. CDH incidence: 54% (27-85%) fetuses developed a diaphragmatic defect, whereas the whole litter had PH in varying degrees. Downregulated signaling pathways included FGF/FGFR, BMP/BMPR, Sonic Hedgehog and retinoid acid signaling pathway, resulting in a delay in early epithelial differentiation, immature distal epithelium and dysfunctional mesenchyme.

CONCLUSIONS

The nitrofen model effectively reproduces PH as it disrupts pathways that are critical for lung branching morphogenesis and alveolar differentiation. The low CDH rate confirms that PH is an associated phenomenon rather than the result of mechanical compression alone.

Exposure to 4100K fluorescent light elicits sex specific transcriptional responses in Xiphophorus maculatus skin

It has been reported that exposure to artificial light may affect oxygen intake, heart rate, absorption of vitamins and minerals, and behavioral responses in humans. We have reported specific gene expression responses in the skin of Xiphophorus fish after exposure to ultraviolet light (UV), as well as, both broad spectrum and narrow waveband visible light. In regard to fluorescent light (FL), we have shown that male X. maculatus exposed to 4100K FL (i.e. "cool white") rapidly suppress transcription of many genes involved with DNA replication and repair, chromosomal segregation, and cell cycle progression in skin. We have also detailed sex specific transcriptional responses of Xiphophorus skin after exposure to UVB. However, investigation of gender differences in global gene expression response after exposure to 4100K FL has not been reported, despite common use of this FL source for residential, commercial, and animal facility illumination. Here, we compare RNA-Seq results analyzed to assess changes in the global transcription profiles of female and male X. maculatus skin in response to 4100K FL exposure. Our results suggest 4100K FL exposure incites a sex-biased genetic response including up-modulation of inflammation in females and down modulation of DNA repair/replication in males. In addition, we identify clusters of genes that become oppositely modulated in males and females after FL exposure that are principally involved in cell death and cell proliferation.

The BH3-only protein BAD mediates TNFα cytotoxicity despite concurrent activation of IKK and NF-κB in septic shock

The inflammatory cytokine TNFα plays a crucial role in the pathology of many inflammatory and infectious diseases. However, the mechanism underlying TNFα cytotoxicity in these diseases is incompletely understood. Here we report that the pro-apoptotic BCL-2 family member BAD mediates TNFα cytotoxicity despite concurrent activation of IKK and NF-κB in vitro by inducing apoptosis in cultured cells and in vivo by eliciting tissue damage of multiple organs and contributing to mortality in septic shock. At high doses, TNFα significantly inactivates RhoA through activation of the Src-p190GAP pathway, resulting in massive actin stress fiber destabilization, followed by substantial BAD release from the cytoskeleton to the cytosol. Under this condition, activated IKK fails to phosphorylate all cytosolic BAD, allowing translocation of non-phosphorylated BAD to mitochondria to trigger apoptosis. Polymicrobial infection utilizes the same mechanism as high-dose TNFα to elicit apoptosis-associated tissue damage of multiple organs. Consequently, loss of Bad or elimination of BAD pro-apoptotic activity protects mice from tissue damage of multiple organs and reduces mortality rates. Our results support a model in which BAD mediates TNFα cytotoxicity despite concurrent activation of the IKK-NF-κB pathway in cultured mammalian cells and in septic shock.

Hair growth is promoted by BeauTop via expression of EGF and FGF‑7

Minoxidil and finasteride have been approved to treat hair loss by the Food and Drug Administration. However, the further elucidation of treatments for hair loss, including those using Chinese herbal medicine, remains important clinically. BeauTop (BT) is a health food supplement which contains Ginseng radix, Astragali radix, Radix Angelicae sinensis, Ligustri fructus, Rehmannia glutinosa and Eclipta prostrata (Linn). Susbsequent to oral administration of BT at 0.6 g/kg/day to wax/rosin-induced alopecia in C57BL/6 mice, BT significantly induced hair growth at day 8 compared with control treatment (P<0.05). The expression levels of epidermal growth factor (EGF), and fibroblast growth factor (FGF)-7 were increased compared with control animals on day 8. In contrast, levels of FGF-5 of the BT group were reduced compared with the control on day 12. There were no effects on the expression of insulin-like growth factor 1. The results demonstrated that the mechanism of BT improving alopecia is potentially associated with modulation of EGF and FGF-7 levels. Taken together, it is suggested that BT may have a potential effect of the promotion of hair growth.

iRhom2 promotes lupus nephritis through TNF-α and EGFR signaling

Lupus nephritis (LN) often results in progressive renal dysfunction. The inactive rhomboid 2 (iRhom2) is a newly identified key regulator of A disintegrin and metalloprotease 17 (ADAM17), whose substrates, such as TNF-α and heparin-binding EGF (HB-EGF), have been implicated in the pathogenesis of chronic kidney diseases. Here, we demonstrate that deficiency of iRhom2 protects the lupus-prone Fcgr2b-/- mice from developing severe kidney damage without altering anti-double-stranded DNA (anti-dsDNA) Ab production by simultaneously blocking HB-EGF/EGFR and TNF-α signaling in the kidney tissues. Unbiased transcriptome profiling of kidneys and kidney macrophages revealed that TNF-α and HB-EGF/EGFR signaling pathways are highly upregulated in Fcgr2b-/- mice, alterations that were diminished in the absence of iRhom2. Pharmacological blockade of either TNF-α or EGFR signaling protected Fcgr2b-/- mice from severe renal damage. Finally, kidneys from LN patients showed increased iRhom2 and HB-EGF expression, with interstitial HB-EGF expression significantly associated with chronicity indices. Our data suggest that activation of iRhom2/ADAM17-dependent TNF-α and EGFR signaling plays a crucial role in mediating irreversible kidney damage in LN, thereby uncovering a target for selective and simultaneous dual inhibition of 2 major pathological pathways in the effector arm of the disease.

Go with the flow: GEF-H1 mediated shear stress mechanotransduction in neutrophils

Neutrophils in circulation experience significant shear forces due to blood flow when they tether to the vascular endothelium. Biochemical and biophysical responses of neutrophils to the physical force of flowing blood modulate their behavior and promote tissue recruitment under pro-inflammatory conditions. Neutrophil mechanotransduction responses occur through mechanisms that are not yet fully understood. In our recent work, we showed that GEF-H1, a RhoA specific guanine nucleotide exchange factor (GEF), is required to maintain neutrophil motility and migration in response to shear stress. GEF-H1 re-localizes to flottilin-rich uropods in neutrophils in response to fluid shear stress and promotes spreading and crawling on activated endothelial cells. GEF-H1 drives cellular contractility through myosin light chain (MLC) phosphorylation downstream of the Rho-ROCK signaling axis. We propose that GEF-H1-dependent cell spreading and crawling in shear stress-dependent neutrophil recruitment from the vasculature are due to the specific localization of Rho-induced contractility in the uropod.

Cx32 inhibits TNFα-induced extrinsic apoptosis with and without EGFR suppression

Tumor necrosis factor α (TNFα) and TNF-related apoptosis-inducing ligand (TRAIL) can trigger the extrinsic apoptosis pathway. Our previous study indicated that connexin32 (Cx32) inhibited streptonigrin-induced intrinsic apoptosis via the epidermal growth factor receptor (EGFR) pathway. However, whether Cx32 can exert effects on the extrinsic apoptosis pathway through EGFR signaling remains unclear. In the present study, we investigated the role of Cx32 in extrinsic apoptosis induced by treatment with TNFα + cycloheximide (CHX) or afatinib in human cervical cancer (CaCx) cells. In stable inducible Cx32-transfected HeLa cells (HeLa-Cx32), Cx32 expression was induced by treatment with doxycycline (Dox). Furthermore, C-33A cells, which natively express high levels of Cx32, were used as a cell model for knockdown of Cx32 with siRNA. To determine the non-junctional function of Cx32 in apoptosis, 18α-glycyrrhetinic acid (18α-GA), a gap junction intracellular communication (GJIC) inhibitor, was used. Our results showed that Cx32 could inhibit apoptosis induced by TNFα + afatinib with or without the GJIC inhibitor. In clinical cervical tissue samples, we found that the expression of survivin was markedly higher in CaCx than in normal cervix tissue, which was in accordance with the expression of Cx32 in our previous study. In HeLa-Cx32 cells, we also found that Cx32 upregulated the expression of Cox-2. In addition, Cx32 upregulated EGFR expression in low-density culture (lacking GJ formation). Cx32 could also promote the expression of EGFR, phospho-STAT3 and phospho-ERK in HeLa-Cx32 cells following TNFα treatment. After knocking down Cx32 in C-33A cells, the expression levels of survivin and TNFα were downregulated. The present study verifies that Cx32 exerts an inhibitory effect on extrinsic apoptosis in CaCx cells, and suggests that Cx32 may regulate the progression and micro-environment of CaCx cells.

Cx32 suppresses extrinsic apoptosis in human cervical cancer cells via the NF‑κB signalling pathway

Tumour necrosis factor α (TNFα) and TNF‑related apoptosis inducing ligand (TRAIL) usually trigger either survival or apoptosis signals in various cell types, and nuclear factor κB (NF‑κB) is a key factor that regulates their biological effects. Connexin 32 (Cx32) is a gap junction (GJ) protein that plays vital roles in tumourigenesis and tumour progression. Our previous study explored abnormal Cx32 expression in para‑nuclear areas, exacerbated prognostic parameters and suppressed streptonigrin/cisplatin-induced apoptosis in human cervical cancer (CaCx) cells. In this study, we investigated the role of Cx32 in the extrinsic apoptosis pathway of CaCx cells. In transgenic HeLa cells and C-33A cells, Cx32 expression was manipulated using doxycycline or Cx32 siRNA. GJ inhibitors or low density culturing was used to change the status of gap junction intracellular communication (GJIC). We found that apoptosis induced by TNFα and TRAIL was suppressed by Cx32 expression despite the presence or absense of GJIC. We also found that Cx32 upregulated the expression of nuclear NF‑κB and its downstream targets c-IAP1, MMP‑2, and MMP‑9 in HeLa‑Cx32 and C-33A cells. Following our previous study design, our clinical data showed that NF‑κB and MMP‑2 levels increased in human CaCx specimens with high Cx32 expression compared to levels in para‑carcinoma of cervical specimens. SC75741 and JSH-23, NF‑кB signalling pathway inhibitors, inhibited the anti-apoptotic effects of Cx32. In conclusion, Cx32 suppressed TNFα /TRAIL-induced extrinsic apoptosis by upregulating the NF‑κB signalling pathway. This study demonstrates a novel mechanism for Cx32's anti-apoptotic effect and provides a reasonable explanation for the pro-tumour effect of Cx32 in human CaCx cells.

MMP inhibitor Ilomastat induced amoeboid-like motility via activation of the Rho signaling pathway in glioblastoma cells

Matrix metalloproteinases (MMPs) play the important role in the process of glioblastoma cell invasion through 3D matrices. However, the effects of MMP inhibitors used in the treatment of malignant gliomas are unsatisfactory. The aim of this study was to explore the reason and mechanism by which cells move through the dense extracellular matrix without proteolysis. The results showed that MMP inhibitor (MMPI), Ilomastat, induced glioma cells to have an amoeboid-like morphology with invasive ability. Moreover, the RhoA/Rho kinase (ROCK)/myosin light chain (MLC) signal is involved in the MMPI-induced movement mode switch, and RhoA activation is dependent on P115RhoGEF. Importantly, combined inhibition of MMPs and ROCK enhanced the inhibition invasion function of MMPI and increased survival time in vitro and in vivo. The results suggested that glioma cells with MMPI treatment were able to compensate for the loss of invasive proteolysis-dependent migration capacity by acquiring an amoeboid-like migration mode and indicated that the combined MMP inhibitor and ROCK inhibitor can be used as an attractive antitumor drug candidate for the treatment of GBM.

miR-194 is a negative regulator of GEF-H1 pathway in melanoma

The incidence and associated mortality of melanoma continues to increase worldwide. At present, there is no curative therapy for advanced stage of melanoma. It is necessary to find new indicators of prognosis and therapeutic targets. Increasing evidence shows that miRNA can provide potential candidate biomarkers for melanoma and therapeutic targets. GEF-H1, a regulator of RhoA, as oncogenic driver in melanoma, promotes the growth and invasion of melanoma. miR-194 is a tumor-suppressor gene in multiple tumors, such as bladder and non-small cell lung cancer, and clear cell renal cell carcinoma. In the present study, we demonstrated that GEF-H1 serves as target of miR-194. Overexpression of miR-194 downregulates the GEF-H1/RhoA pathway, inhibits melanoma cancer cell proliferation and metastasis. Furthermore, miR-194 expression is negatively associated with tumor-node-metastasis (TNM) stages. Briefly, our findings provided new theoretical basis for melanoma treatment.

Phosphorylation and Activation of RhoA by ERK in Response to Epidermal Growth Factor Stimulation

The small GTPase RhoA has been implicated in various cellular activities, including the formation of stress fibers, cell motility, and cytokinesis. In addition to the canonical GTPase cycle, recent findings have suggested that phosphorylation further contributes to the tight regulation of Rho GTPases. Indeed, RhoA is phosphorylated on serine 188 (188S) by a number of protein kinases. We have recently reported that Rac1 is phosphorylated on threonine 108 (108T) by extracellular signal-regulated kinases (ERK) in response to epidermal growth factor (EGF) stimulation. Here, we provide evidence that RhoA is phosphorylated by ERK on 88S and 100T in response to EGF stimulation. We show that ERK interacts with RhoA and that this interaction is dependent on the ERK docking site (D-site) at the C-terminus of RhoA. EGF stimulation enhanced the activation of the endogenous RhoA. The phosphomimetic mutant, GFP-RhoA S88E/T100E, when transiently expressed in COS-7 cells, displayed higher GTP-binding than wild type RhoA. Moreover, the expression of GFP-RhoA S88E/T100E increased actin stress fiber formation in COS-7 cells, which is consistent with its higher activity. In contrast to Rac1, phosphorylation of RhoA by ERK does not target RhoA to the nucleus. Finally, we show that regardless of the phosphorylation status of RhoA and Rac1, substitution of the RhoA PBR with the Rac1 PBR targets RhoA to the nucleus and substitution of Rac1 PBR with RhoA PBR significantly reduces the nuclear localization of Rac1. In conclusion, ERK phosphorylates RhoA on 88S and 100T in response to EGF, which upregulates RhoA activity.

Csk/Src/EGFR signaling regulates migration of myofibroblasts and alveolarization

Bronchopulmonary dysplasia (BPD) is characterized by premature alveolar developmental arrest. Antenatal exposure to inflammation inhibits lung morphogenesis, thus increasing the risk of developing BPD. Alveolar myofibroblasts are thought to migrate into the septal tips and elongate secondary septa during alveolarization. Here we found lipopolysaccharide (LPS) disrupted the directional migration of myofibroblasts and increased actin stress fiber expression and focal adhesion formation. In addition, COOH-terminal Src kinase (Csk) activity was downregulated in myofibroblasts treated with LPS, while activation of Src or epidermal growth factor receptor (EGFR) was upregulated by LPS treatment. Specifically, decreased Csk activity and increased activation of Src or EGFR was also observed in primary myofibroblasts isolated from newborn rat lungs with intra-amniotic LPS exposure, a model for BPD. Further investigation revealed that EGFR was involved in cell migration impairment induced by LPS, and Src inhibition blocked LPS-induced activation of EGFR or cell migration impairment. Csk silencing also resulted in EGFR activation and cell migration impairment. Besides, we found the effect of EGFR on myofibroblast migration was mediated through RhoA activation. EGFR inhibition alleviated the abnormal localization of myofibroblasts and improved alveolar development in antenatal LPS-treated rats. Taken together, our data suggest that the Csk/Src/EGFR signaling pathway is critically involved in regulating directional migration of myofibroblasts and may contribute to arrested alveolar development in BPD.

Effects of pyrrolidine dithiocarbamate on proliferation and nuclear factor-κB activity in autosomal dominant polycystic kidney disease cells

BACKGROUND

Pyrrolidine dithiocarbamate (PDTC) reduces renal cyst growth in a rodent model of polycystic kidney disease (PKD) but the mechanism of action is not clear. Here, we investigated the hypothesis that PDTC reduces the proliferation of cystic epithelial cells in vitro in a nuclear factor (NF)-κB-dependent manner.

METHODS

Immortalized autosomal dominant PKD (ADPKD) cells that are heterozygous (WT9-7) and homozygous (WT-9-12) for a truncating Pkd1 mutation, and immortalized normal human tubular cells (HK-2), were exposed to NF-κB-inducing agents with or without PDTC. Cell proliferation and apoptosis were assessed by bromodeoxyuridine assay and Annexin V flow cytometry, respectively. NF-κB activity was assessed by luciferase reporter assay and western blotting for nuclear p65, p50, and RelB subunits and cytoplasmic phosphorylated-IκBα.

RESULTS

Serum-induced proliferation was similar in all cell lines over 72 h. PDTC demonstrated anti-proliferative effects that were delayed in ADPKD cells compared to HK-2. Basal NF-κB-dependent luciferase reporter activity was lower in ADPKD cells compared to normal cells. Classical NF-κB stimulants, lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-α, increased NF-κB luciferase activity in HK-2, whereas in PKD cell lines, NF-κB activity was only induced by TNF-α. However, neither stimulant altered proliferation in any cell line. PDTC reduced TNF-α-stimulated NF-κB activity in HK-2 only.

CONCLUSIONS

PDTC reduced proliferation in ADPKD cells but did not consistently alter NF-κB activation, suggesting that other signalling pathways are likely to be involved in its ability to attenuate renal cyst growth in vivo.

Flavocoxid Protects Against Cadmium-Induced Disruption of the Blood–Testis Barrier and Improves Testicular Damage and Germ Cell Impairment in Mice [corrected]

Cadmium (Cd) causes male infertility. There is the need to identify safe treatments counteracting this toxicity. Flavocoxid is a flavonoid that induces a balanced inhibition of cyclooxygenase (COX)-1 and COX-2 peroxidase moieties and of 5-lipoxygenase (LOX) and has efficacy in the male genitourinary system. We investigated flavocoxid effects on Cd-induced testicular toxicity in mice. Swiss mice were divided into 4 groups: 2 control groups received 0.9% NaCl (vehicle; 1 ml/kg/day) or flavocoxid (20 mg/kg/day ip); 2 groups were challenged with cadmium chloride (CdCl2; 2 mg/kg/day ip) and administered with vehicle or flavocoxid. The treatment lasted for 1 or 2 weeks. The testes were processed for biochemical and morphological studies. CdCl2 increased phosphorylated extracellular signal-regulated kinase (p-ERK) 1/2, tumor necrosis factor (TNF)-α, COX-2, 5-LOX, malondialdehyde (MDA), B-cell-lymphoma (Bcl)-2-associated X protein (Bax), follicle-stimulating hormone (FSH), luteinizing hormone (LH), transforming growth factor (TGF) -β3, decreased Bcl-2, testosterone, inhibin-B, occludin, N-Cadherin, induced structural damages in the testis and disrupted the blood-testis barrier. Many TUNEL-positive germ cells and changes in claudin-11, occludin, and N-cadherin localization were present. Flavocoxid administration reduced, in a time-dependent way, p-ERK 1/2, TNF-α, COX-2, 5-LOX, MDA, Bax, FSH, LH, TGF-β3, augmented Bcl-2, testosterone, inhibin B, occludin, N-Cadherin, and improved the structural organization of the testis and the blood-testis barrier. Few TUNEL-positive germ cells were present and a morphological retrieval of the intercellular junctions was observed. In conclusion, flavocoxid has a protective anti-inflammatory, antioxidant, and antiapoptotic function against Cd-induced toxicity in mice testis. We suggest that flavocoxid may play a relevant positive role against environmental levels of Cd, otherwise deleterious to gametogenesis and tubular integrity.

Neutrophils Increase Oral Squamous Cell Carcinoma Invasion through an Invadopodia-Dependent Pathway

Neutrophils have recently been shown to promote invasion and correlate with a poor prognosis in different cancers, including head and neck squamous cell carcinomas. In this study, we analyze the effects of neutrophils in the invasion of oral squamous cell carcinoma (OSCC) using a combination of conditioned media, direct and indirect coculture of human peripheral blood neutrophils, and UMSCC47 cells (OSCC cell line). Invasion and matrix degradation were determined using a modified in vitro invasion assay and an invadopodia assay, respectively. UMSCC47 and neutrophil cocultures or conditioned media from cocultures increased UMSCC47 invasion, invadopodia formation, and matrix degradation. Further analysis revealed an increase in TNFα and IL8 in supernatants of cocultures compared with neutrophil or UMSCC47 cultures alone and that inhibition of TNFα and IL8 significantly decreased OSCC invasion. Our results show that neutrophils increase the invasiveness of OSCC through the activation of invadopodia and matrix degradation, suggesting a paracrine activation loop between the two cells. Importantly, the presence of neutrophils in the oral environment may modulate the clinical behavior of OSCC.

Differential Regulation of Gene Expression of Alveolar Epithelial Cell Markers in Human Lung Adenocarcinoma-Derived A549 Clones

Stem cell therapy appears to be promising for restoring damaged or irreparable lung tissue. However, establishing a simple and reproducible protocol for preparing lung progenitor populations is difficult because the molecular basis for alveolar epithelial cell differentiation is not fully understood. We investigated an in vitro system to analyze the regulatory mechanisms of alveolus-specific gene expression using a human alveolar epithelial type II (ATII) cell line, A549. After cloning A549 subpopulations, each clone was classified into five groups according to cell morphology and marker gene expression. Two clones (B7 and H12) were further analyzed. Under serum-free culture conditions, surfactant protein C (SPC), an ATII marker, was upregulated in both H12 and B7. Aquaporin 5 (AQP5), an ATI marker, was upregulated in H12 and significantly induced in B7. When the RAS/MAPK pathway was inhibited, SPC and thyroid transcription factor-1 (TTF-1) expression levels were enhanced. After treatment with dexamethasone (DEX), 8-bromoadenosine 3′5′-cyclic monophosphate (8-Br-cAMP), 3-isobutyl-1-methylxanthine (IBMX), and keratinocyte growth factor (KGF), surfactant protein B and TTF-1 expression levels were enhanced. We found that A549-derived clones have plasticity in gene expression of alveolar epithelial differentiation markers and could be useful in studying ATII maintenance and differentiation.

Tumor necrosis factor-α induces a biphasic change in claudin-2 expression in tubular epithelial cells: role in barrier functions

The inflammatory cytokine tumor necrosis factor-α (TNF-α) is a pathogenic factor in acute and chronic kidney disease. TNF-α is known to alter expression of epithelial tight junction (TJ) proteins; however, the underlying mechanisms and the impact of this effect on epithelial functions remain poorly defined. Here we describe a novel biphasic effect of TNF-α on TJ protein expression. In LLC-PK1 tubular cells, short-term (1-6 h) TNF-α treatment selectively elevated the expression of the channel-forming TJ protein claudin-2. In contrast, prolonged (>8 h) TNF-α treatment caused a marked downregulation in claudin-2 and an increase in claudin-1, -4, and -7. The early increase and the late decrease in claudin-2 expression involved distinct mechanisms. TNF-α slowed claudin-2 degradation through ERK, causing the early increase. This increase was also mediated by the EGF receptor and RhoA and Rho kinase. In contrast, prolonged TNF-α treatment reduced claudin-2 mRNA levels and promoter activity independent from these signaling pathways. Electric Cell-substrate Impedance Sensing measurements revealed that TNF-α also exerted a biphasic effect on transepithelial resistance (TER) with an initial decrease and a late increase. Thus there was a good temporal correlation between TNF-α-induced claudin-2 protein and TER changes. Indeed, silencing experiments showed that the late TER increase was at least in part caused by reduced claudin-2 expression. Surprisingly, however, claudin-2 silencing did not prevent the early TER drop. Taken together, the TNF-α-induced changes in claudin-2 levels might contribute to TER changes and could also play a role in newly described functions of claudin-2 such as proliferation regulation.

A mechanism of male germ cell apoptosis induced by bisphenol-A and nonylphenol involving ADAM17 and p38 MAPK activation

Germ cell apoptosis regulation is pivotal in order to maintain proper daily sperm production. Several reports have shown that endocrine disruptors such as Bisphenol-A (BPA) and Nonylphenol (NP) induce germ cell apoptosis along with a decrease in sperm production. Given their ubiquitous distribution in plastic products used by humans it is important to clarify their mechanism of action. TACE/ADAM17 is a widely distributed extracellular metalloprotease and participates in the physiological apoptosis of germ cells during spermatogenesis. The aims of this work were: 1) to determine whether BPA and NP induce ADAM17 activation; and 2) to study whether ADAM17 and/or ADAM10 are involved in germ cell apoptosis induced by BPA and NP in the pubertal rat testis. A single dose of BPA or NP (50 mg/kg) induces germ cell apoptosis in 21-day-old male rats, which was prevented by a pharmacological inhibitor of ADAM17, but not by an inhibitor of ADAM10. In vitro, we showed that BPA and NP, at similar concentrations to those found in human samples, induce the shedding of exogenous and endogenous (TNF-α) ADAM17 substrates in primary rat Sertoli cell cultures and TM4 cell line. In addition, pharmacological inhibitors of metalloproteases and genetic silencing of ADAM17 prevent the shedding induced in vitro by BPA and NP. Finally, we showed that in vivo BPA and NP induced early activation (phosphorylation) of p38 MAPK and translocation of ADAM17 to the cell surface. Interestingly, the inhibition of p38 MAPK prevents germ cell apoptosis and translocation of ADAM17 to the cell surface. These results show for the first time that xenoestrogens can induce activation of ADAM17 at concentrations similar to those found in human samples, suggesting a mechanism by which they could imbalance para/juxtacrine cell-to-cell-communication and induce germ cell apoptosis.

Decreased Mitogen Inducible Gene 6 (MIG-6) Associated with Symptom Severity in Children with Autism

BACKGROUND

Individuals with autism spectrum disorders (ASDs) demonstrate impairment in social interactions and problems in verbal and nonverbal communication. Autism spectrum disorders are thought to affect 1 in 88 children in the US. Recent research has shown that epidermal growth factor receptor (EGFR) activation is associated with nerve cell development and repair. Mitogen inducible gene 6 (MIG-6) is a 58-kDa non-kinase scaffolding adaptor protein consisting of 462 amino-acids, which has been shown to be a negative feedback regulator of EGFR and Met receptor tyrosine kinase (RTK) signaling.

SUBJECTS AND METHODS

In this study, we determined plasma levels of MIG-6, which suppresses the EGFR RTK pathway in autistic children, and compared MIG-6 levels with the EGFR ligand, epidermal growth factor (EGF), and the cMET ligand, hepatocyte growth factor (HGF). MIG-6 levels were also compared to the symptom severity of 19 different autistic behaviors.

Plasma MIG-6 concentration was measured in 40 autistic children and 39 neurotypical, age, and gender similar controls using an enzyme linked immunosorbent assay (ELISA). Plasma MIG-6 levels were compared to putative biomarkers known to be associated with EGFR and cMET and severity levels of 19 autism related symptoms [awareness, expressive language, receptive language, (conversational) pragmatic language, focus/attention, hyperactivity, impulsivity, perseveration, fine motor skills, gross motor skills, hypotonia (low muscle tone), tip toeing, rocking/pacing, stimming, obsessions/fixations, eye contact, sound sensitivity, light sensitivity, and tactile sensitivity].

RESULTS

In this study, we found that plasma MIG-6 levels in autistic children (182.41 ± 24.3 pg/ml) were significantly lower than neurotypical controls (1779.76 ± 352.5; P = 1.76E − 5). Decreased MIG-6 levels correlated with serotonin, dopamine, Tumor necrosis factor alpha (TNF-alpha), and urokinase receptor (uPAR) concentration, but not with other tested putative biomarkers. MIG-6 levels also correlated significantly with severity of expressive language, receptive language, tip toeing, rocking/pacing, and hand flapping/stimming.

CONCLUSIONS

These results suggest a relationship between decreased plasma MIG-6 levels, biomarkers associated with the EGFR pathway, and symptom severity in autism. A strong correlation between plasma MIG-6 and dopamine and serotonin levels suggest that decreased MIG-6 levels may be associated with abnormal neurotransmitter synthesis and/or action. A strong correlation between MIG-6 and uPAR and the inflammatory marker TNF-alpha suggests that low MIG-6 levels may be associated with the HGF/Met signaling pathway, as well as inflammation in autistic children.

Mechanistic insight into GPCR-mediated activation of the microtubule-associated RhoA exchange factor GEF-H1

The RhoGEF GEF-H1 can be sequestered in an inactive state on polymerized microtubules by the dynein motor light-chain Tctex-1. Phosphorylation of GEF-H1 Ser885 by PKA or PAK kinases creates an inhibitory 14-3-3-binding site. Here we show a new mode of GEF-H1 activation in response to the G-protein-coupled receptor (GPCR) ligands lysophosphatidic acid (LPA) or thrombin that is independent of microtubule depolymerization. LPA/thrombin stimulates disassembly of the GEF-H1:dynein multi-protein complex through the concerted action of Gα and Gβγ. Gα binds directly to GEF-H1 and displaces it from Tctex-1, while Gβγ binds to Tctex-1 and disrupts its interaction with the dynein intermediate chain, resulting in the release of GEF-H1. Full activation of GEF-H1 requires dephosphorylation of Ser885 by PP2A, which is induced by thrombin. The coordinated displacement of GEF-H1 from microtubules by G-proteins and its dephosphorylation by PP2A demonstrate a multistep GEF-H1 activation and present a unique mechanism coupling GPCR signalling to Rho activation.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and kidney disease

PURPOSE OF REVIEW

The tumor necrosis factor-like weak inducer of apoptosis (TWEAK) cytokine has been linked to kidney injury by functional studies in experimental animals, and has biomarker potential in kidney disease.

RECENT FINDINGS

TWEAK was known to promote tubular cell injury and kidney inflammation. Recent studies have expanded these observations, identifying additional targets of TWEAK relevant to kidney injury. Thus, TWEAK upregulates the chemokine and cholesterol scavenger receptor CXCL16 and downregulates the antiaging and antifibrotic molecule Klotho in tubular cells. Furthermore, fibrogenic TWEAK actions on renal fibroblasts were described. TWEAK or factor-inducible molecule 14 targeting decreased the kidney fibrosis resulting from immune and nonimmune kidney injury induced by transient tubular or glomerular insults or by persistent urinary tract obstruction. TWEAK might also contribute to the link between chronic kidney disease and kidney cancer, as suggested by its role in other genitourinary cancers. Progress has also been made in TWEAK targeting. A phase I clinical trial showed that TWEAK targeting is well tolerated in humans, and an ongoing trial is exploring efficacy in lupus nephritis. Nanomolecules and inhibitors of epidermal growth factor receptor pathway may also protect from the adverse effects of TWEAK in the kidney.

SUMMARY

These findings suggest that TWEAK targeting has clinical potential in kidney injury of immune and nonimmune origin.

Rho protein GTPases and their interactions with NFκB: crossroads of inflammation and matrix biology

The RhoGTPases, with RhoA, Cdc42 and Rac being major members, are a group of key ubiquitous proteins present in all eukaryotic organisms that subserve such important functions as cell migration, adhesion and differentiation. The NFκB (nuclear factor κB) is a family of constitutive and inducible transcription factors that through their diverse target genes, play a major role in processes such as cytokine expression, stress regulation, cell division and transformation. Research over the past decade has uncovered new molecular links between the RhoGTPases and the NFκB pathway, with the RhoGTPases playing a positive or negative regulatory role on NFκB activation depending on the context. The RhoA–NFκB interaction has been shown to be important in cytokine-activated NFκB processes, such as those induced by TNFα (tumour necrosis factor α). On the other hand, Rac is important for activating the NFκB response downstream of integrin activation, such as after phagocytosis. Specific residues of Rac1 are important for triggering NFκB activation, and mutations do obliterate this response. Other upstream triggers of the RhoGTPase–NFκB interactions include the suppressive p120 catenin, with implications for skin inflammation. The networks described here are not only important areas for further research, but are also significant for discovery of targets for translational medicine.

TWEAK transactivation of the epidermal growth factor receptor mediates renal inflammation

TWEAK, a member of the TNF superfamily, binds to the Fn14 receptor, eliciting biological responses. EGFR signalling is involved in experimental renal injury. Our aim was to investigate the relationship between TWEAK and EGFR in the kidney. Systemic TWEAK administration into C57BL/6 mice increased renal EGFR phosphorylation, mainly in tubular epithelial cells. In vitro, in these cells TWEAK phosphorylated EGFR via Fn14 binding, ADAM17 activation and subsequent release of the EGFR ligands HB-EGF and TGFα. In vivo the EGFR kinase inhibitor Erlotinib inhibited TWEAK-induced renal EGFR activation and downstream signalling, including ERK activation, up-regulation of proinflammatory factors and inflammatory cell infiltration. Moreover, the ADAM17 inhibitor WTACE-2 also prevented those TWEAK-induced renal effects. In vitro TWEAK induction of proinflammatory factors was prevented by EGFR, ERK or ADAM17 inhibition. In contrast, EGFR transactivation did not modify TWEAK-mediated NF-κB activation. Our data suggest that TWEAK transactivates EGFR in the kidney, leading to modulation of downstream effects, including ERK activation and inflammation, and suggest that inhibition of EGFR signalling could be a novel therapeutic tool for renal inflammation.

TRAF2 facilitates vaccinia virus replication by promoting rapid virus entry

Tumor necrosis factor receptor (TNFR)-associated factor 2 (TRAF2) is a pivotal intracellular mediator of signaling pathways downstream of TNFR1 and -2 with known pro- and antiviral effects. We investigated its role in the replication of the prototype poxvirus vaccinia virus (VACV). Loss of TRAF2 expression, either through small interfering RNA treatment of HeLa cells or through genetic knockout in murine embryonic fibroblasts (MEFs), led to significant reductions in VACV growth following low-multiplicity infection. In single-cycle infections, there was delayed production of both early and late VACV proteins as well as accelerated virus-induced alterations to cell morphology, indicating that TRAF2 influences early stages of virus replication. Consistent with an early role, uncoating assays showed normal virus attachment but delayed virus entry in the absence of TRAF2. Although alterations to c-Jun N-terminal kinase (JNK) signaling were apparent in VACV-infected TRAF2^−/− MEFs, treatment of wild-type cells with a JNK inhibitor did not affect virus entry. Instead, treatment with an inhibitor of endosomal acidification greatly reduced virus entry into TRAF2^−/− MEFs, suggesting that VACV is reliant on the endosomal route of entry in the absence of TRAF2. Thus, TRAF2 is a proviral factor for VACV that plays a role in promoting efficient viral entry, most likely via the plasma membrane.

IMPORTANCE Tumor necrosis factor receptor-associated factors (TRAFs) are key facilitators of intracellular signaling with roles in innate and adaptive immunity and stress responses. We have discovered that TRAF2 is a proviral factor in vaccinia virus replication in both HeLa cells and mouse embryonic fibroblasts and that its influence is exercised through promotion of efficient virus entry.

Role of guanine nucleotide exchange factor-H1 in complement-mediated RhoA activation in glomerular epithelial cells

Visceral glomerular epithelial cells (GEC), also known as podocytes, are vital for the structural and functional integrity of the glomerulus. The actin cytoskeleton plays a central role in maintaining GEC morphology. In a rat model of experimental membranous nephropathy (passive Heymann nephritis (PHN)), complement C5b-9-induced proteinuria was associated with the activation of the actin regulator small GTPase, RhoA. The mechanisms of RhoA activation, however, remained unknown. In this study, we explored the role of the epithelial guanine nucleotide exchange factor, GEF-H1, in complement-induced RhoA activation. Using affinity precipitation to monitor GEF activity, we found that GEF-H1 was activated in glomeruli isolated from rats with PHN. Complement C5b-9 also induced parallel activation of GEF-H1 and RhoA in cultured GEC. In GEC in which GEF-H1 was knocked down, both basal and complement-induced RhoA activity was reduced. On the other hand, GEF-H1 knockdown augmented complement-mediated cytolysis, suggesting a role for GEF-H1 and RhoA in protecting GEC from cell death. The MEK1/2 inhibitor, U0126, and mutation of the ERK-dependent phosphorylation site (T678A) prevented complement-induced GEF-H1 activation, indicating a role for the ERK pathway. Further, complement induced GEF-H1 and microtubule accumulation in the perinuclear region. However, both the perinuclear accumulation and the activation of GEF-H1 were independent of microtubules and myosin-mediated contractility, as shown using drugs that interfere with microtubule dynamics and myosin II activity. In summary, we have identified complement-induced ERK-dependent GEF-H1 activation as the upstream mechanism of RhoA stimulation, and this pathway has a protective role against cell death.

ERK pathway is activated in bare-FeNPs-induced autophagy

Iron oxide nanoparticles (FeNPs) are known to be one of the most biocompatible and safe nanoparticles. However, their long-term persistence remains a problem, and macrophages play as an important mediator in continuous stimulation of the immune system due to biopersistence of nanoparticles. In the present study, we identified the mechanisms underlying the uptake and toxicity of bare-FeNPs using RAW264.7 cells, a mouse peritoneal macrophage cell line. The bare-FeNPs penetrated the cell membrane through electrostatic interactions together with the general phagocytic pathway. At 24 h after exposure, they distributed freely in the cytosol or within autophagosome-like vacuoles. Bare-FeNPs induced decrease in the cell viability along with the cell cycle arrest in G1 phase. In addition, they increased the generation of ROS and the secretion of NO and TNF alpha as well as the expression of SOD-1 and SOD-2 proteins, which are an antioxidant. While the mitochondrial calcium level, the intensity of labeled mitochondria, and ATP production decreased, the levels of autophagy-related proteins such as p62, beclin 1, ATG5, and LC3B increased in a dose-dependent manner together with the levels of ATF 3, p-EGFR, and p-ERK proteins. However, the level of p-JNK protein clearly decreased. TEM images also showed that damaged organelle exist within autophagosome-like vacuoles with bare-FeNPs. On the basis of these results, we suggest that bare-FeNPs induce autophagy by initiating oxidative stress in RAW264.7 cells. Furthermore, ERK, but not JNK, pathway is activated in bare-FeNPs-induced autophagy.

EGFR-driven up-regulation of decoy receptor 3 in keratinocytes contributes to the pathogenesis of psoriasis

Decoy receptor 3 (DcR3) is a soluble receptor of Fas ligand (FasL), LIGHT (TNFSF14) and TNF-like molecule 1A (TL1A) and plays pleiotropic roles in many inflammatory and autoimmune disorders and malignant diseases. In cutaneous biology, DcR3 is expressed in primary human epidermal keratinocytes and is upregulated in skin lesions in psoriasis, which is characterized by chronic inflammation and angiogenesis. However, the regulatory mechanisms of DcR3 over-expression in skin lesions of psoriasis are unknown. Here, we demonstrate that DcR3 can be detected in both dermal blood vessels and epidermal layers of psoriatic skin lesions. Analysis of serum samples showed that DcR3 was elevated, but FasL was downregulated in psoriatic patients compared with normal individuals. Additional cell studies revealed a central role of epidermal growth factor receptor (EGFR) in controlling the basal expression of DcR3 in keratinocytes. Activation of EGFR by epidermal growth factor (EGF) and transforming growth factor (TGF)-α strikingly upregulated DcR3 production. TNF-αenhanced DcR3 expression in both keratinocytes and endothelial cells compared with various inflammatory cytokines involved in psoriasis. Additionally, TNF-α-enhanced DcR3 expression in keratinocytes was inhibited when EGFR was knocked down or EGFR inhibitor was used. The NF-κB pathway was critically involved in the molecular mechanisms underlying the action of EGFR and inflammatory cytokines. Collectively, the novel regulatory mechanisms of DcR3 expression in psoriasis, particularly in keratinocytes and endothelial cells, provides new insight into the pathogenesis of psoriasis and may also contribute to the understanding of other diseases that involve DcR3 overexpression.

Enhanced depolarization-induced pulmonary vasoconstriction following chronic hypoxia requires EGFR-dependent activation of NAD(P)H oxidase 2

AIMS

Chronic hypoxia (CH) enhances depolarization-induced myofilament Ca(2+) sensitization and resultant pulmonary arterial constriction through superoxide (O(2)(-))-dependent stimulation of RhoA. Because NAD(P)H oxidase (NOX) has been implicated in the development of pulmonary hypertension, we hypothesized that vascular smooth muscle (VSM) depolarization increases NOX-derived O(2)(-) production leading to myofilament Ca(2+) sensitization and augmented vasoconstrictor reactivity following CH. As epidermal growth factor receptor (EGFR) mediates Rac1-dependent NOX activation in renal mesangial cells, we further sought to examine the role EGFR plays in this response.

RESULTS

Vasoconstrictor responses to depolarizing concentrations of KCl were greater in lungs isolated from CH (4 wk, 0.5 atm) rats compared to normoxic controls, and this effect of CH was abolished by the general NOX inhibitor, apocynin. CH similarly augmented KCl-induced vasoconstriction and O(2)(-) generation (assessed using the fluorescent indicator, dihydroethidium) in Ca(2+)-permeabilized, pressurized small pulmonary arteries. These latter responses to CH were prevented by general inhibition of NOX isoforms (apocynin, diphenylene iodonium), and by selective inhibition of NOX 2 (gp91ds-tat), Rac1 (NSC 23766), and EGFR (AG 1478). Consistent with these observations, CH increased KCl-induced EGFR phosphorylation, and augmented depolarization-induced Rac1 activation in an EGFR-dependent manner.

INNOVATION

This study establishes a novel signaling axis in VSM linking membrane depolarization to contraction that is independent of Ca(2+) influx, and which mediates myofilament Ca(2+) sensitization in the hypertensive pulmonary circulation.

CONCLUSION

CH augments membrane depolarization-induced pulmonary VSM Ca(2+) sensitization and vasoconstriction through EGFR-dependent stimulation of Rac1 and NOX 2.

Tumor necrosis factor-α: regulation of renal function and blood pressure

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine that becomes elevated in chronic inflammatory states such as hypertension and diabetes and has been found to mediate both increases and decreases in blood pressure. High levels of TNF-α decrease blood pressure, whereas moderate increases in TNF-α have been associated with increased NaCl retention and hypertension. The explanation for these disparate effects is not clear but could simply be due to different concentrations of TNF-α within the kidney, the physiological status of the subject, or the type of stimulus initiating the inflammatory response. TNF-α alters renal hemodynamics and nephron transport, affecting both activity and expression of transporters. It also mediates organ damage by stimulating immune cell infiltration and cell death. Here we will summarize the available findings and attempt to provide plausible explanations for such discrepancies.