Cell communication networks: epidermal growth factor receptor transactivation as the paradigm for interreceptor signal transmission

CX3CL1 (Fractalkine)-CX3CR1 Axis in Inflammation-Induced Angiogenesis and Tumorigenesis

The chemotactic cytokine fractalkine (FKN, chemokine CX3CL1) has unique properties resulting from the combination of chemoattractants and adhesion molecules. The soluble form (sFKN) has chemotactic properties and strongly attracts T cells and monocytes. The membrane-bound form (mFKN) facilitates diapedesis and is responsible for cell-to-cell adhesion, especially by promoting the strong adhesion of leukocytes (monocytes) to activated endothelial cells with the subsequent formation of an extracellular matrix and angiogenesis. FKN signaling occurs via CX3CR1, which is the only known member of the CX3C chemokine receptor subfamily. Signaling within the FKN-CX3CR1 axis plays an important role in many processes related to inflammation and the immune response, which often occur simultaneously and overlap. FKN is strongly upregulated by hypoxia and/or inflammation-induced inflammatory cytokine release, and it may act locally as a key angiogenic factor in the highly hypoxic tumor microenvironment. The importance of the FKN/CX3CR1 signaling pathway in tumorigenesis and cancer metastasis results from its influence on cell adhesion, apoptosis, and cell migration. This review presents the role of the FKN signaling pathway in the context of angiogenesis in inflammation and cancer. The mechanisms determining the pro- or anti-tumor effects are presented, which are the cause of the seemingly contradictory results that create confusion regarding the therapeutic goals.

Transactivation of receptor tyrosine kinases by purinergic P2Y and adenosine receptors

Transactivation of receptor tyrosine kinases (RTK) is a crosstalk mechanism exhibited by G-protein-coupled receptors (GPCR) to activate signaling pathways classically associated with growth factors. The discovery of RTK transactivation was a breakthrough in signal transduction that contributed to developing current concepts in intracellular signaling. RTK transactivation links GPCR signaling to important cellular processes, such as cell proliferation and differentiation, and explains the functional diversity of these receptors. Purinergic (P2Y and adenosine) receptors belong to class A of GPCR; in the present work, we systematically review the experimental evidence showing that purinergic receptors have the ability to transactivate RTK in multiple tissues and physiopathological conditions resulting in the modulation of cellular physiology. Of particular relevance, the crosstalk between purinergic receptors and epidermal growth factor receptor is a redundant pathway that participates in multiple pathophysiological processes. Specific and detailed knowledge of purinergic receptor-regulated pathways advances our understanding of the complexity of GPCR signal transduction and opens the way for pharmacologic intervention in the pathological context.

The role of EGFR in vascular AT1R signaling: From cellular mechanisms to systemic relevance

The epidermal growth factor receptor (EGFR) belongs to the ErbB-family of receptor tyrosine kinases that are of importance in oncology. During the last years, substantial evidence accumulated for a crucial role of EGFR concerning the action of the angiotensin II type 1 receptor (AT1R) in blood vessels, resulting form AT1R-induced EGFR transactivation. This transactivation occurs through the release of membrane-anchored EGFR-ligands, cytosolic tyrosine kinases, heterocomplex formation or enhanced ligand expression. AT1R-EGFR crosstalk amplifies the signaling response and enhances the biological effects of angiotensin II. Downstream signaling cascades include ERK1/2 and p38 MAPK, PLCγ and STAT. AT1R-induced EGFR activation contributes to vascular remodeling and hypertrophy via e.g. smooth muscle cell proliferation, migration and extracellular matrix production. EGFR transactivation results in increased vessel wall thickness and reduced vascular compliance. AT1R and EGFR signaling pathways are also implicated the induction of vascular inflammation. Again, EGFR transactivation exacerbates the effects, leading to endothelial dysfunction that contributes to vascular inflammation, dysfunction and remodeling. Dysregulation of the AT1R-EGFR axis has been implicated in the pathogenesis of various cardiovascular diseases and inhibition or prevention of EGFR signaling can attenuate part of the detrimental impact of enhanced renin-angiotensin-system (RAAS) activity, highlighting the importance of EGFR for the adverse consequences of AT1R activation. In summary, EGFR plays a critical role in vascular AT1R action, enhancing signaling, promoting remodeling, contributing to inflammation, and participating in the pathogenesis of cardiovascular diseases. Understanding the interplay between AT1R and EGFR will foster the development of effective therapeutic strategies of RAAS-induced disorders.

Ontogeny of collective behaviour

During their lifetime, superorganisms, like unitary organisms, undergo transformations that change the machinery of their collective behaviour. Here, we suggest that these transformations are largely understudied and propose that more systematic research into the ontogeny of collective behaviours is needed if we hope to better understand the link between proximate behavioural mechanisms and the development of collective adaptive functions. In particular, certain social insects engage in self-assemblage, forming dynamic and physically connected architectures with striking similarities to developing multicellular organisms, making them good model systems for ontogenetic studies of collective behaviour. However, exhaustive time series and three-dimensional data are required to thoroughly characterize the different life stages of the collective structures and the transitions between these stages. The well-established fields of embryology and developmental biology offer practical tools and theoretical frameworks that could speed up the acquisition of new knowledge about the formation, development, maturity and dissolution of social insect self-assemblages and, by extension, other superorganismal behaviours. We hope that this review will encourage an expansion of the ontogenetic perspective in the field of collective behaviour and, in particular, in self-assemblage research, which has far-reaching applications in robotics, computer science and regenerative medicine. This article is part of a discussion meeting issue 'Collective behaviour through time'.

Chemical and Pharmacological Profiling of Wrightia coccinea (Roxb. Ex Hornem.) Sims Focusing Antioxidant, Cytotoxic, Antidiarrheal, Hypoglycemic, and Analgesic Properties

The aim of the study was to conduct phytochemical and pharmacological investigations of Wrightia coccinea (Roxb. ex Hornem.) Sims via several in vitro, in vivo, and in silico models. A total of four compounds were identified and isolated from the methanol extract of the bark and the methanol extract of the seed pulp of W. coccinea through successive chromatographic techniques and were characterized as 3β-acetyloxy-olean-12-en-28-ol (1), wrightiadione (2), 22β-hydroxylupeol (3), and β-sitosterol (4) by spectroscopic analysis. The aqueous fraction of the bark and chloroform fraction of the fruits provided the most potent antioxidant capacity (IC50 = 7.22 and 4.5 µg/mL, respectively) in DPPH free radical scavenging assay compared with the standard ascorbic acid (IC50 = 17.45 µg/mL). The methanol bark extract and the methanol fruit coat extract exerted anti-diarrheal activity by inhibiting 74.55 ± 0.67% and 77.78 ± 1.5% (mean ± SEM) of the diarrheal episode in mice, respectively, after four hours of loading the samples. In the hypoglycemic test, the methanol bark extract and the methanol fruit coat extract (400 mg/kg) produced a significant (p < 0.05) reduction in the blood glucose level in mice. Both doses of the plant extracts (200 mg/kg and 400 mg/kg) used in the study induced a significant (p < 0.05) increase in pain reaction time. The in vitro and in vivo findings were supported by the computational studies. The isolated compounds exhibited higher binding affinity compared with the standard drugs towards the active binding sites of glutathione reductase, epidermal growth factor receptor (EGFR), kappa opioid receptor, glucose transporter 3 (GLUT 3), Mu opioid receptor, and cyclooxygenase 2 (COX-2) proteins due to their potent antioxidant, cytotoxic, anti-diarrheal, hypoglycemic, and central and peripheral analgesic properties, respectively. The current findings concluded that W. coccinea might be a potential natural source for managing oxidative stress, diarrhea, hyperglycemia, and pain. Further studies are warranted for extensively phytochemical screening and establishing exact mechanisms of action.

Biomaterials to enhance stem cell transplantation

The successful transplantation of stem cells has the potential to transform regenerative medicine approaches and open promising avenues to repair, replace, and regenerate diseased, damaged, or aged tissues. However, pre-/post-transplantation issues of poor cell survival, retention, cell fate regulation, and insufficient integration with host tissues constitute significant challenges. The success of stem cell transplantation depends upon the coordinated sequence of stem cell renewal, specific lineage differentiation, assembly, and maintenance of long-term function. Advances in biomaterials can improve pre-/post-transplantation outcomes by integrating biophysiochemical cues and emulating tissue microenvironments. This review highlights leading biomaterials-based approaches for enhancing stem cell transplantation.

Lactobacillus rhamnosus GG colonization in early life regulates gut-brain axis and relieves anxiety-like behavior in adulthood

Evidence reveals that gut dysbiosis is involved in bidirectional interactions in gut-brain axis and participates in the progress of multiple disorders like anxiety. Gut microbes in early life are crucial for establishment of host health. We aimed to investigate whether early life probiotics Lactobacillus rhamnosus GG (LGG) colonization could relieve anxiety in adulthood through regulation of gut-brain axis. Live or fixed LGG was gavaged to C57BL/6 female mice from day 18 of pregnancy until natural birth, and newborn mice from day 1 to day 5 respectively. In this study, we found that live LGG could be effectively colonized in the intestine of offspring. LGG colonization increased intestinal villus length and colonic crypt depth, accompanied with barrier function protection before weaning. Microbiota composition by 16S rRNA sequencing showed that some beneficial bacteria, such as Akkermansia and Bifidobacteria, were abundant in LGG colonization group. The protective effect of LGG on gut microbiota persisted from weaning to adulthood. Intriguingly, behavioral results assessed by elevated plus mazed test and open field test demonstrated relief of anxiety-like behavior in adult LGG-colonized offspring. Mechanically, LGG colonization activated epithelial growth factor receptor (EGFR) and enhanced serotonin transporter (SERT) expression and modulated serotonergic system in the intestine, and increased brain-derived neurotrophic factor and γ-aminobutyric acid receptor levels in the hippocampus and amygdala. Blocking EGFR blunted LGG-induced the increased SERT and zonula occludens-1 expression. Collectively, early life LGG colonization could protect intestinal barrier of offspring and modulate gut-brain axis in association with relief of anxiety-like behavior in adulthood.

Multiplexed Single-Cell Plasmonic Immunoassay of Intracellular Signaling Proteins Enables Non-Destructive Monitoring of Cell Fate

It is of significant importance in cancer biology to identify signaling pathways that play key roles in cell fate determination. Dissecting cellular signaling pathways requires the measurement of a large number of signaling proteins. However, tools for simultaneously monitoring multiple signaling pathway components in single living cells remain limited at present. Herein, we describe an approach, termed multiplexed single-cell plasmonic immunosandwich assay (mxscPISA), for simultaneous detection of multiple signaling proteins in individual living cells. This approach enabled simultaneous non-destructive monitoring of multiple (up to five, currently the highest multiplexing capacity in living cells) cytoplasmic and nucleus signaling proteins in individual cells with ultrahigh detection sensitivity. As a proof of principle, the epidermal growth factor receptor (EGFR) pathway, which plays a central role in cell fate determination, was investigated using this approach in this study. We found that there were differential attenuation rate of pro-survival and accumulation rate of pro-death signaling protein of the EGFR pathway in response to EGFR inactivation. These findings implicate that, after EGFR inactivation, a transient imbalance between survival and apoptotic signaling outputs contributed to the final cell fate of death. The mxscPISA approach can be a promising tool to reveal a signaling dynamic pattern at the single-cell level and to identify key components of signaling pathways that contribute to the final cell fate using only a limited number of cells.

Interleukin-1β Induces Tissue Factor Expression in A549 Cells via EGFR-Dependent and -Independent Mechanisms

Tissue factor (TF) plays an important role in the progression and angiogenesis of tumor cells. The present study investigated the mechanism of interleukin-1β (IL-1β)-induced TF expression in A549 lung cancer cells. Based on mRNA and protein analyses, including appropriate inhibitor experiments, IL-1β was shown to induce TF expression in a time-dependent manner, mediated by IL-1 receptor-dependent phosphorylation of the mitogen-activated protein kinases (MAPK) p38, p42/44 and c-jun N-terminal kinase (JNK), as well as the Src kinase and the epidermal growth factor receptor (EGFR). Thereby, inhibition of EGFR transactivation by the Src inhibitor PP1 or direct EGFR inhibition by the EGFR tyrosine kinase inhibitor (TKI) erlotinib led to a reduction of IL-1β-induced TF expression and to a suppression of p42/44 MAPK and EGFR activation, while IL-1β-induced p38 MAPK and JNK activation remained unchanged. A knockdown of EGFR by siRNA was associated with decreased IL-1β-mediated p42/44 MAPK activation, which was no longer inhibitable by erlotinib. Concentration-dependent inhibition of IL-1β-induced TF expression was also observed in the presence of gefitinib and afatinib, two other EGFR TKIs. In summary, our results suggest that IL-1β leads to increased TF formation in lung cancer cells via both Src/EGFR/p42/44 MAPK-dependent and EGFR-independent signaling pathways, with the latter mediated via p38 MAPK and JNK.

G Protein-Coupled Estrogen Receptor in Cancer and Stromal Cells: Functions and Novel Therapeutic Perspectives

Estrogen is involved in numerous physiological and pathophysiological systems. Its role in driving estrogen receptor-expressing breast cancers is well established, but it also has important roles in a number of other cancers, acting both on tumor cells directly as well as in the function of multiple cells of the tumor microenvironment, including fibroblasts, immune cells, and adipocytes, which can greatly impact carcinogenesis. One of its receptors, the G protein-coupled estrogen receptor (GPER), has gained much interest over the last decade in both health and disease. Increasing evidence shows that GPER contributes to clinically observed endocrine therapy resistance in breast cancer while also playing a complex role in a number of other cancers. Recent discoveries regarding the targeting of GPER in combination with immune checkpoint inhibition, particularly in melanoma, have led to the initiation of the first Phase I clinical trial for the GPER-selective agonist G-1. Furthermore, its functions in metabolism and corresponding pathophysiological states, such as obesity and diabetes, are becoming more evident and suggest additional therapeutic value in targeting GPER for both cancer and other diseases. Here, we highlight the roles of GPER in several cancers, as well as in metabolism and immune regulation, and discuss the therapeutic value of targeting this estrogen receptor as a potential treatment for cancer as well as contributing metabolic and inflammatory diseases and conditions.

New 1,2,3-Triazole-Containing Hybrids as Antitumor Candidates: Design, Click Reaction Synthesis, DFT Calculations, and Molecular Docking Study

In an effort to improve and achieve biologically active anticancer agents, a novel series of 1,2,3-triazole-containing hybrids were designed and efficiently synthesized via the Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction of substituted-arylazides with alkyne-functionalized pyrazole-[1,2,4]-triazole hybrids. The structure geometry of these new clicked 1,2,3-triazoles was explored by density functional theory (DFT) using the B3LYP/6-311++G(d,p) level; also, the potential activity of the compounds for light absorption was simulated by time-dependent DFT calculations (TD-DFT). The antitumor impacts of the newly synthesized compounds were in vitro estimated to be towards the human liver cancer cell line (HepG-2), the human colon cancer cell line (HCT-116), and human breast adenocarcinoma (MCF-7). Among the tested compounds, conjugate 7 was the most potent cytotoxic candidate towards HepG-2, HCT-116, and MCF-7, with IC₅₀ = 12.22, 14.16, and 14.64 µM, respectively, in comparison to that exhibited by the standard drug doxorubicin (IC₅₀ = 11.21, 12.46, and 13.45 µM). Finally, a molecular docking study was conducted within the epidermal growth factor receptor (EGFR) active site to suggest possible binding modes. Hence, it could conceivably be hypothesized that analogies 7, 6, and 5 could be considered as decent lead candidate compounds for anticancer agents.

B-cell clonogenic activity of HIV-1 p17 variants is driven by PAR1-mediated EGF transactivation

Combined antiretroviral therapy (cART) for HIV-1 dramatically slows disease progression among HIV⁺ individuals. Currently, lymphoma represents the main cause of death among HIV-1-infected patients. Detection of p17 variants (vp17s) endowed with B-cell clonogenic activity in HIV-1-seropositive patients with lymphoma suggests their possible role in lymphomagenesis. Here, we demonstrate that the clonogenic activity of vp17s is mediated by their binding to PAR1 and to PAR1-mediated EGFR transactivation through Gq protein. The entire vp17s-triggered clonogenic process is MMPs dependent. Moreover, phosphoproteomic and bioinformatic analysis highlighted the crucial role of EGFR/PI3K/Akt pathway in modulating several molecules promoting cancer progression, including RAC1, ABL1, p53, CDK1, NPM, Rb, PTP-1B, and STAT1. Finally, we show that a peptide (F1) corresponding to the vp17s functional epitope is sufficient to trigger the PAR1/EGFR/PI3K/Akt pathway and bind PAR1. Our findings suggest novel potential therapeutic targets to counteract vp17-driven lymphomagenesis in HIV⁺ patients.

Neurotransmitters and Endothelins Acting on Radial Glial G-Protein-Coupled Receptors Are, Through Proteolytic NRG/ErbB4 Activation, Able to Modify the Migratory Behavior of Neocortical Cells and Mediate Bipolar-to-Multipolar Transition

Cell-cell communication plays a central role in the guidance of migrating neurons during the development of the cerebral cortex. Neuregulins (NRGs) are essential mediators for migration and maintenance of the radial glial scaffold. We show, in this study that soluble NRG reduces neuronal motility, causes transition of bipolar cells to multipolar ones, and induces neuronal mitosis. Blocking the NRG receptor, ErbB4, results in reduction of neuron-neuron and neuron-radial glial contacts and causes an increase in neuronal motility. Blocking the radial glial metabotropic glutamate receptor 5 (mGluR5), the nonselective cation channel transient receptor potential 3 (TRPC3), or matrix metalloproteinases (MMPs) results in similar effects as ErbB4 blockade. Soluble NRG counteract the changes in motility pattern. Stimulation of other radial glial G-protein-coupled receptors (GPCRs), such as muscarinic acetylcholine receptors or endothelin receptors counteract all the effect of mGluR5 blockade, but not that of ErbB4, TRPC3, and MMP blockade. The results indicate that neurotransmitters and endothelins acting on radial glial GPCRs are, through proteolytic NRG/ErbB4 activation, able to modify the migratory behavior of neurons.

Role of Heparin-Binding Epidermal Growth Factor-Like Growth Factor in Oxidative Stress-Associated Metabolic Diseases

Heparin-binding EGF-like growth factor (HB-EGF) is an EGF family member that interacts with epidermal growth factor receptor (EGFR) and ERBB4. Since HB-EGF was first identified as a novel growth factor secreted from a human macrophage cell line, numerous pathological and physiological functions related to cell proliferation, migration, and inflammation have been reported. Notably, the expression of HB-EGF is sensitively upregulated by oxidative stress in the endothelial cells and functions for auto- and paracrine-EGFR signaling. Overnutrition and obesity cause elevation of HB-EGF expression and EGFR signaling in the hepatic and vascular systems. Modulations of HB-EGF signaling showed a series of protections against phenotypes related to metabolic syndrome and advanced metabolic diseases, suggesting HB-EGF as a potential target against metabolic diseases.

RTK signaling requires C3ar1/C5ar1 and IL-6R joint signaling to repress dominant PTEN, SOCS1/3 and PHLPP restraint

How receptor tyrosine kinase (RTK) growth signaling is controlled physiologically is incompletely understood. We have previously provided evidence that the survival and mitotic activities of vascular endothelial cell growth factor receptor-2 (VEGFR2) signaling are dependent on C3a/C5a receptor (C3ar1/C5ar1) and IL-6 receptor (IL-6R)-gp130 joint signaling in a physically interactive platform. Herein, we document that the platelet derived and epidermal growth factor receptors (PDGFR and EGFR) are regulated by the same interconnection and clarify the mechanism underlying the dependence. We show that the joint signaling is required to overcome dominant restraint on RTK function by the combined repression of tonically activated PHLPP, SOCS1/SOCS3, and CK2/Fyn dependent PTEN. Signaling studies showed that augmented PI-3Kɣ activation is the process that overcomes the multilevel growth restraint. Live-cell flow cytometry and single-particle tracking indicated that blockade of C3ar1/C5ar1 or IL-6R signaling suppresses RTK growth factor binding and RTK complex formation. C3ar1/C5ar1 blockade abrogated growth signaling of four additional RTKs. Active relief of dominant growth repression via joint C3ar1/C5ar1 and IL-6R joint signaling thus enables RTK mitotic/survival signaling.

Involvement of Oxidative Stress and the Epidermal Growth Factor Receptor in Diesel Exhaust Particle-Induced Expression of Inflammatory Mediators in Human Mononuclear Cells

Exposure to diesel exhaust particles (DEPs) has been associated with increased incidence of cardiopulmonary diseases. This study is aimed at examining the proinflammatory effects of DEP on primary human peripheral blood mononuclear cells (PBMC) and the underlying mechanisms using a human mononuclear cell line, THP-1. DEPs were incubated with the PBMC and THP-1 cells for 24 h, respectively. The supernatants were collected and subjected to measurement of proinflammatory mediators including interleukin 8 (IL-8) or tumor necrosis factor α (TNFα) by ELISA. Levels of reactive oxygen species (ROS) were determined using flow cytometry. Phosphorylation of the epidermal growth factor receptor (EGFR) was examined with immunoblotting. Exposure to DEP induced a concentration-dependent increase in the expression of IL-8 and TNFα in the PBMC and THP-1 cells. Further mechanistic studies with THP-1 cells indicated that DEP stimulation increased intracellular levels of ROS, an indicator of oxidative stress, and phosphorylation of the EGFR, indicative of EGFR activation. Pretreatment of THP-1 cells with the antioxidant N-acetyl-L-cysteine (NAC) markedly blunted DEP-induced EGFR phosphorylation, indicating that oxidative stress was involved in DEP-induced EGFR activation. Furthermore, the pretreatment of THP-1 cells with either NAC or a selective EGFR inhibitor significantly blocked DEP-induced IL-8 expression, implying that oxidative stress and subsequent EGFR activation mediated DEP-induced inflammatory response. In summary, DEP stimulation increases the expression of proinflammatory mediators in human mononuclear cells, which is regulated by oxidative stress-EGFR signaling pathway.

Rebalancing metal dyshomeostasis for Alzheimer's disease therapy

Alzheimer's disease (AD) is a type of neurodegenerative malady that is associated with the accumulation of amyloid plaques. Metal ions are critical for the development and upkeep of brain activity, but metal dyshomeostasis can contribute to the development of neurodegenerative diseases, including AD. This review highlights the association between metal dyshomeostasis and AD pathology, the feasibility of rebalancing metal homeostasis as a therapeutic strategy for AD, and a survey of current drugs that action via rebalancing metal homeostasis. Finally, we discuss the challenges that should be overcome by researchers in the future to enable the practical use of metal homeostasis rebalancing agents for clinical application.

Receptor tyrosine kinase activation induces free fatty acid 4 receptor phosphorylation, β-arrestin interaction, and internalization

FFA4 (Free Fatty Acid receptor 4, previously known as GPR120) is a G protein-coupled receptor that acts as a sensor of long-chain fatty acids, modulates metabolism, and whose dysfunction participates in endocrine disturbances. FFA4 is known to be phosphorylated and internalized in response to agonists and protein kinase C activation. In this paper report the modulation of this fatty acid receptor by activation of receptor tyrosine kinases. Cell-activation with growth factors (insulin, epidermal growth factor, insulin-like growth factor-I, and platelet-derived growth factor) increases FFA4 phosphorylation in a time- and concentration-dependent fashion. This effect was blocked by inhibitors of protein kinase C and phosphoinositide 3-kinase, suggesting the involvement of these kinases in it. FFA4 phosphorylation did not alter agonist-induced FFA4 calcium signaling, but was associated with decreased ERK 1/2 phosphorylation. In addition, insulin, insulin-like growth factor-I, epidermal growth factor, and to a lesser extent, platelet-derived growth factor, induce receptor internalization. This action of insulin, insulin-like growth factor I, and epidermal growth factor was blocked by inhibitors of protein kinase C and phosphoinositide 3-kinase. Additionally, cell treatment with these growth factors induced FFA4-β-arrestin coimmunoprecipitation. Our results evidenced cross-talk between receptor tyrosine kinases and FFA4 and suggest roles of protein kinase C and phosphoinositide 3-kinase in such a functional interaction.

Role of GPCR (mu-opioid)-receptor tyrosine kinase (epidermal growth factor) crosstalk in opioid-induced hyperalgesic priming (type II)

Repeated stimulation of mu-opioid receptors (MORs), by an MOR-selective agonist DAMGO induces type II priming, a form of nociceptor neuroplasticity, which has 2 components: opioid-induced hyperalgesia (OIH) and prolongation of prostaglandin-E2 (PGE2)-induced hyperalgesia. We report that intrathecal antisense knockdown of the MOR in nociceptors, prevented the induction of both components of type II priming. Type II priming was also eliminated by SSP-saporin, which destroys the peptidergic class of nociceptors. Because the epidermal growth factor receptor (EGFR) participates in MOR signaling, we tested its role in type II priming. The EGFR inhibitor, tyrphostin AG 1478, prevented the induction of prolonged PGE2-induced hyperalgesia, but not OIH, when tested out to 30 days after DAMGO. However, even when repeatedly injected, an EGFR agonist did not induce hyperalgesia or priming. A phosphopeptide, which blocks the interaction of Src, focal adhesion kinase (FAK), and EGFR, also prevented DAMGO-induced prolongation of PGE2 hyperalgesia, but only partially attenuated the induction of OIH. Inhibitors of Src and mitogen-activated protein kinase (MAPK) also only attenuated OIH. Inhibitors of matrix metalloproteinase, which cleaves EGF from membrane protein, markedly attenuated the expression, but did not prevent the induction, of prolongation of PGE2 hyperalgesia. Thus, although the induction of prolongation of PGE2-induced hyperalgesia at the peripheral terminal of peptidergic nociceptor is dependent on Src, FAK, EGFR, and MAPK signaling, Src, FAK, and MAPK signaling is only partially involved in the induction of OIH.

Analysis of Cancer Cell Invasion and Anti-metastatic Drug Screening Using Hydrogel Micro-chamber Array (HMCA)-based Plates

Cancer metastasis is known to cause 90% of cancer lethality. Metastasis is a multistage process which initiates with the penetration/invasion of tumor cells into neighboring tissue. Thus, invasion is a crucial step in metastasis, making the invasion process research and development of anti-metastatic drugs, highly significant. To address this demand, there is a need to develop 3D in vitro models which imitate the architecture of solid tumors and their microenvironment most closely to in vivo state on one hand, but at the same time be reproducible, robust and suitable for high yield and high content measurements. Currently, most invasion assays lean on sophisticated microfluidic technologies which are adequate for research but not for high volume drug screening. Other assays using plate-based devices with isolated individual spheroids in each well are material consuming and have low sample size per condition. The goal of the current protocol is to provide a simple and reproducible biomimetic 3D cell-based system for the analysis of invasion capacity in large populations of tumor spheroids. We developed a 3D model for invasion assay based on HMCA imaging plate for the research of tumor invasion and anti-metastatic drug discovery. This device enables the production of numerous uniform spheroids per well (high sample size per condition) surrounded by ECM components, while continuously and simultaneously observing and measuring the spheroids at single-element resolution for medium throughput screening of anti-metastatic drugs. This platform is presented here by the production of HeLa and MCF7 spheroids for exemplifying single cell and collective invasion. We compare the influence of the ECM component hyaluronic acid (HA) on the invasive capacity of collagen surrounding HeLa spheroids. Finally, we introduce Fisetin (invasion inhibitor) to HeLa spheroids and nitric oxide (NO) (invasion activator) to MCF7 spheroids. The results are analyzed by in-house software which enables semi-automatic, simple and fast analysis which facilitates multi-parameter examination.

Cell proliferation and apoptosis inhibition: essential processes for recruitment of the full thermogenic capacity of brown adipose tissue

In mice living under normal animal house conditions, the brown adipocytes in classical brown adipose tissue depots are already essentially fully differentiated: UCP1 mRNA and UCP1 protein levels are practically saturated. This means that any further recruitment - in response to cold exposure or any other browning agent - does not result in significant augmentation of these parameters. This may easily be construed to indicate that classical brown adipose tissue cannot be further recruited. However, this is far from the case: the capacity for further recruitment instead lies in the ability of the tissue to increase the number of brown-fat cells, a remarkable and highly controlled physiological recruitment process. We have compiled here the available data concerning the unique ability of norepinephrine to increase cell proliferation and inhibit apoptosis in brown adipocytes. Adrenergically stimulated cell proliferation is fully mediated via β₁-adrenoceptors and occurs through activation of stem cells in the tissue; intracellular mediation of the signal involves cAMP and protein kinase A activation, but activation of Erk1/2 is not part of the pathway. Apoptosis inhibition in brown adipocytes is induced by both β- and α₁-adrenergic receptors and here the intracellular pathway includes Erk1/2 activation. This unique ability of norepinephrine to increase cell number in an apparently mitogenically dormant tissue provides possibilities to augment the metabolic capacity of brown adipose tissue, also for therapeutic purposes.

G Protein Coupled Receptor-mediated Transactivation of Extracellular Proteases

G protein-coupled receptors (GPCRs) comprise the largest family of receptors in humans. Traditional activation of GPCRs involves binding of a ligand to the receptor, activation of heterotrimeric G proteins and induction of subsequent signaling molecules. It is now known that GPCR signaling occurs through G protein-independent pathways including signaling through β-arrestin and transactivation of other receptor types. Generally, transactivation occurs when activation of one receptor leads to the activation of another receptor(s). GPCR-mediated transactivation is an essential component of GPCR signaling, as activation of other receptor types, such as receptor tyrosine kinases, allows GPCRs to expand their signal transduction and affect various cellular responses. Several mechanisms have been identified for receptor transactivation downstream of GPCRs, one of which involves activation of extracellular proteases, such as a disintegrin and metalloprotease, and matrix metalloproteases . These proteases cleave and release ligands that are then able to activate their respective receptors. A disintegrin and metalloprotease, and matrix metalloproteases can be activated via various mechanisms downstream of GPCR activation, including activation via second messenger, direct phosphorylation, or direct G protein interaction. Additional understanding of the mechanisms involved in GPCR-mediated protease activation and subsequent receptor transactivation could lead to identification of new therapeutic targets.

ERK Activation Pathways Downstream of GPCRs

GPCRs, the 7-TM receptors, represent a class of cell surface receptors which modulate a variety of physiological responses. The serpentine structure in addition to contributing the diversity of stimuli these receptors can sense also provides flexibility to the extracellular and intracellular regions where other proteins can interact with and can form functionally active multimeric entities. The range in signaling and physiological responses generated by these receptors can be attributed to a large repertoire of the receptor subtypes as well as their differential coupling to various classes of G-protein subunits and other proteins which facilitate multistate activation. A multistate GPCR can engage diverse signaling molecules, thereby modulating not only the canonical cellular responses but also noncanonical responses typically associated with activation of other cascades such as RTK and MAPK/ERK signaling. Given the crucial involvement of MAP kinase/ERK signaling in cell fate determination specially with respect to regulating cell proliferation, cellular apoptosis, and survival, GPCR-mediated cross-activation of MAPK has been explored in various systems and shown to involve functional integration of multiple pathways. This review describes the present knowledge of the different mechanisms of ERK activation downstream of GPCRs and our present understanding of receptor-dependent and -independent MAPK activation cascades.

Epidermal growth factor receptor inhibitors trigger a type I interferon response in human skin

The Epidermal Growth Factor Receptor (EGFR) is centrally involved in the regulation of key processes of the epithelia, including cell proliferation, survival, differentiation, and also tumorigenesis. Humanized antibodies and small-molecule inhibitors targeting EGFR were developed to disrupt these functions in cancer cells and are currently used in the treatment of diverse metastatic epithelial cancers. By contrast, these drugs possess significant skin-specific toxic effects, comprising the establishment of a persistent inflammatory milieu. So far, the molecular mechanisms underlying these epiphenomena have been investigated rather poorly. Here we showed that keratinocytes respond to anti-EGFR drugs with the development of a type I interferon molecular signature. Upregulation of the transcription factor IRF1 is early implicated in the enhanced expression of interferon-kappa, leading to persistent activation of STAT1 and further amplification of downstream interferon-induced genes, including anti-viral effectors and chemokines. When anti-EGFR drugs are associated to TNF-α, whose expression is enhanced by the drugs themselves, all these molecular events undergo a dramatic enhancement by synergy mechanisms. Finally, high levels of interferon-kappa can be observed in epidermal keratinocytes and also in leukocytes infiltrating the upper dermis of cetuximab-driven skin lesions. Our data suggest that dysregulated activation of type I interferon innate immunity is implicated in the molecular processes triggered by anti-EGFR drugs and leading to persistent skin inflammation.

GPCRs: Emerging anti-cancer drug targets

G protein-coupled receptors (GPCRs) constitute the largest and most diverse protein family in the human genome with over 800 members identified to date. They play critical roles in numerous cellular and physiological processes, including cell proliferation, differentiation, neurotransmission, development and apoptosis. Consequently, aberrant receptor activity has been demonstrated in numerous disorders/diseases, and as a result GPCRs have become the most successful drug target class in pharmaceuticals treating a wide variety of indications such as pain, inflammation, neurobiological and metabolic disorders. Many independent studies have also demonstrated a key role for GPCRs in tumourigenesis, establishing their involvement in cancer initiation, progression, and metastasis. Given the growing appreciation of the role(s) that GPCRs play in cancer pathogenesis, it is surprising to note that very few GPCRs have been effectively exploited in pursuit of anti-cancer therapies. The present review provides a broad overview of the roles that various GPCRs play in cancer growth and development, highlighting the potential of pharmacologically modulating these receptors for the development of novel anti-cancer therapeutics.

Biocompatibility of Titania Nanotube Coatings Enriched with Silver Nanograins by Chemical Vapor Deposition

Bioactivity investigations of titania nanotube (TNT) coatings enriched with silver nanograins (TNT/Ag) have been carried out. TNT/Ag nanocomposite materials were produced by combining the electrochemical anodization and chemical vapor deposition methods. Fabricated coatings were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The release effect of silver ions from TNT/Ag composites immersed in bodily fluids, has been studied using inductively coupled plasma mass spectrometry (ICP-MS). The metabolic activity assay (MTT) was applied to determine the L929 murine fibroblasts adhesion and proliferation on the surface of TNT/Ag coatings. Moreover, the results of immunoassays (using peripheral blood mononuclear cells-PBMCs isolated from rats) allowed the estimation of the immunological activity of TNT/Ag surface materials. Antibacterial activity of TNT/Ag coatings with different morphological and structural features was estimated against two Staphylococcus aureus strains (ATCC 29213 and H9). The TNT/Ag nanocomposite layers produced revealed a good biocompatibility promoting the fibroblast adhesion and proliferation. A desirable anti-biofilm activity against the S. aureus reference strain was mainly noticed for these TiO₂ nanotube coatings, which contain dispersed Ag nanograins deposited on their surface.

Regulation of radial glial process growth by glutamate via mGluR5/TRPC3 and neuregulin/ErbB4

Radial glial cells play an essential role through their function as guides for neuronal migration during development. Disruption of metabotropic glutamate receptor 5 (mGluR5) function retards the growth of radial glial processes in vitro. Neuregulins (NRG) are activated by proteolytic cleavage and regulate (radial) glial maintenance via ErbB3/ErbB4 receptors. We show here that blocking ErbB4 disrupts radial process extension. Soluble NRG acting on ErbB4 receptors is able to promote radial process extension in particular where process elongation has been impeded by blockade of mGluR5, the nonselective cation channel canonical transient receptor potential 3 (TRPC3), or matrix metalloproteases (MMP). NRG does not restore retarded process growth caused by ErbB4 blockade. Stimulation of muscarinic receptors restores process elongation due to mGluR5 blockade but not that caused by TRPC3, MMP or ErbB4 blockade suggesting that muscarinic receptors can replace mGluR5 with respect to radial process extension. Additionally, NRG/ErbB4 causes Ca²⁺ mobilization in a population of cells through cooperation with ErbB1 receptors. Our results indicate that mGluR5 promotes radial process growth via NRG activation by a mechanism involving TRPC3 channels and MMPs. Thus neurotransmitters acting on G-protein coupled receptors could play a central role in the maintenance of the radial glial scaffold through activation of NRG/ErbB4 signaling.

Agonist-induced activation of human FFA1 receptor signals to extracellular signal-regulated kinase 1 and 2 through Gq- and Gi-coupled signaling cascades

Background

FFA1 is abundantly expressed in the liver, skeletal muscle, monocytes and nervous system, but is particularly abundant in pancreatic β cells. It is widely believed that FFA1 exerts its regulatory roles in a variety of physiological and pathological functions. In response to oleic acid, FFA1 has been shown to induce the activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) through a mechanism involving EGFR transactivation in a breast cancer cell line. However, the underlying molecular mechanism for ERK1/2 activation mediated by n-6 free fatty acid (LA) in HEK293 cells remains to be further elucidated.

Methods

A FLAG-FFA1 vector was stably expressed in HEK293 cells. Western blot analysis was applied to investigate the change in LA-induced ERK1/2 phosphorylation change in response to kinase inhibitors. Arrestin-2/3-specific siRNA was used to analyze the effect of arrestin-2/3 knockdown on FFA1-mediated ERK1/2 activation.

Results

We proved that activation of ERK1/2 by LA was rapid, peaking at 5 min. Further experiments proved that FFA1 couples to a Gq protein and activates PI-PLC, which induces the IP3/Ca²⁺ and DAG/PKC signal pathways, both of which are involved in ERK1/2 activation. We also showed that there is no EGFR transactivation, arrestin-2/3 or Gβγ pathway participation in ERK1/2 phosphorylation. Treating cells with PTX abolished ERK1/2 activation at a late time point (≥20 min), indicating a critical role for Gi subunits in FFA1-mediated ERK1/2 activation.

Conclusions

Our study provides a detailed delineation of the LA-mediated activation of ERK1/2 in HEK293 cells that are stably transfected with human FFA1. We also present evidence of Gi/Gq-induced synergism in the regulation of ERK1/2 phosphorylation. These observations may provide new insights into the pharmacological effects of FFA1 and the physiological functions modulated by FFA1-mediated activation of ERK1/2.

Electronic supplementary material

The online version of this article (doi:10.1186/s11658-017-0043-3) contains supplementary material, which is available to authorized users.

Polychlorinated biphenyls disrupt hepatic epidermal growth factor receptor signaling

1. Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that disrupt hepatic xenobiotic and intermediary metabolism, leading to metabolic syndrome and nonalcoholic steatohepatitis (NASH). 2. Since phenobarbital indirectly activates Constitutive Androstane Receptor (CAR) by antagonizing growth factor binding to the epidermal growth factor receptor (EGFR), we hypothesized that PCBs may also diminish EGFR signaling. 3. The effects of the PCB mixture Aroclor 1260 on the protein phosphorylation cascade triggered by EGFR activation were determined in murine (in vitro and in vivo) and human models (in vitro). EGFR tyrosine residue phosphorylation was decreased by PCBs in all models tested. 4. The IC₅₀ values for Aroclor 1260 concentrations that decreased Y1173 phosphorylation of EGFR were similar in murine AML-12 and human HepG2 cells (∼2-4 μg/mL). Both dioxin and non-dioxin-like PCB congeners decreased EGFR phosphorylation in cell culture. 5. PCB treatment reduced phosphorylation of downstream EGFR effectors including Akt and mTOR, as well as other phosphoprotein targets including STAT3 and c-RAF in vivo. 6. PCBs diminish EGFR signaling in human and murine hepatocyte models and may dysregulate critical phosphoprotein regulators of energy metabolism and nutrition, providing a new mechanism of action in environmental diseases.

IGF1R Protein Expression Is Not Associated with Differential Benefit to Concurrent Trastuzumab in Early-Stage HER2+ Breast Cancer from the North Central Cancer Treatment Group (Alliance) Adjuvant Trastuzumab Trial N9831

Background: Preclinical evidence indicates that increased insulin-like growth factor receptor-1 (IGF1R) signaling interferes with the action of trastuzumab suggesting a possible mechanism of trastuzumab resistance. Thus, we evaluated IGF1R prevalence, relationship with demographic data, and association with disease-free survival (DFS) of patients randomized to chemotherapy alone (Arm A) or chemotherapy with sequential (Arm B) or concurrent trastuzumab (Arm C) in the prospective phase III HER2⁺ adjuvant N9831 trial.Experimental Design: IGF1R protein expression was determined in tissue microarray sections (three cores per block; N = 1,197) or in whole tissue sections (WS; N = 537) using IHC (rabbit polyclonal antibody against IGF1R β-subunit). A tumor was considered positive (IGF1R⁺) if any core or WS had ≥1+ membrane staining in >0% invasive cells. Median follow-up was 8.5 years.Results: Of 1,734 patients, 708 (41%) had IGF1R⁺ breast tumors. IGF1R⁺ was associated with younger age (median 48 vs. 51, P = 0.007), estrogen receptor/progesterone receptor positivity (78% vs. 35%, P < 0.001), nodal positivity (89% vs. 83%, P < 0.001), well/intermediate grade (34% vs. 24%, P < 0.001), tumors ≥2 cm (72% vs. 67%, P = 0.02) but not associated with race or tumor histology. IGF1R did not affect DFS within arms. Between Arms A and C, patients with IGF1R⁺ and IGF1R^- tumors had DFS HRs of 0.48 (P ≤ 0.001) and 0.68 (P = 0.009), respectively (P_interaction = 0.17). Between Arms A and B, patients with IGF1R⁺ and IGF1R^- tumors had DFS HRs of 0.83 (P = 0.25) and 0.69 (P = 0.01), respectively (P_interaction = 0.42).Conclusions: In contrast to preclinical studies that suggest a decrease in trastuzumab sensitivity in IGF1R⁺ tumors, our adjuvant data show benefit of adding trastuzumab for patients with either IGF1R⁺ and IGF1R^- breast tumors. Clin Cancer Res; 23(15); 4203-11. ©2016 AACR.

Involvement of EGF receptor signaling and NLRP12 inflammasome in fine particulate matter-induced lung inflammation in mice

Epidemiological studies have shown that exposure to ambient fine particulate matter (PM_2.5 ) is associated with respiratory diseases. Lung inflammation is a central feature of many pulmonary diseases, which can be induced by PM_2.5 exposure. However, the mechanisms underlying PM_2.5 -induced lung inflammation remain unclear. To characterize the role of epidermal growth factor receptor (EGFR) and inflammasome in PM_2.5 -induced lung inflammation in mice, 30 BALB/c mice were intrabroncheally instilled with saline and PM_2.5 suspension (4.0 mg/kg b.w.) for 5 consecutive days, respectively. Bronchoalveolar lavage (BAL) was conducted and BAL fluid (BALF) was collected. The levels of reactive oxygen species (ROS), inducible nitric oxide synthase (iNOS), epidermal growth factor (EGF), CXCL1, interleukin (IL)-1β, and IL-18 in BALF were determined using ELISA. mRNA levels of IL-6, IL-1β, IL-18, CXCL1, IL-10, NLRP3, Caspase-1, and NLRP12 in lung tissues were determined by RT-PCR. Phospho-EGFR (Tyr1068) and phospho-Akt (Thr308) in lung tissues were examined using immunohistochemical staining and Western blotting, respectively. Protein levels of Caspase-1, NLRP3, NF-κB-p52/p100, and NF-κB-p65 in bronchial epithelium were examined using immunohistochemical staining. It was shown that PM_2.5 exposure induced lung inflammation. Levels of total protein, ROS, iNOS, EGF, and CXCL1 and cell number in the BALF of mice exposed to PM_2.5 were markedly elevated relative to the control. mRNA levels of CXCL1, IL-1β, and IL-18 in lung tissues of PM_2.5 -exposed mice were increased in comparison with the control. However, level of NLRP12 mRNA in lung tissues of PM_2.5 -exposed mice was reduced. Phospho-EGFR (Tyr1068) and phospho-Akt (Thr308) levels in the lungs of PM_2.5 -instilled mice were higher than those in the lungs of the control. The protein levels of NF-κB-p52/p100 and NF-κB-p65 in bronchial epithelium of PM_2.5 -exposed mice were also increased compared with the control. This study suggests that EGF-EGFR-Akt-NF-κB signaling and NLRP12 inflammasome may be associated with PM_2.5 -induced lung inflammation in mice. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1121-1134, 2017.

Triggering Mechanisms and Inflammatory Effects of Combustion Exhaust Particles with Implication for Carcinogenesis

A number of biological responses may contribute to the carcinogenic effects of combustion-derived particulate matter (CPM). Here, we focus on mechanisms that trigger CPM-induced pro-inflammatory responses. Inflammation has both genotoxic and non-genotoxic implications and is considered to play a central role in development of various health outcome associated with CPM exposure, including cancer. Chronic, low-grade inflammation may cause DNA damage through a persistent increased level of reactive oxygen species (ROS) produced and released by activated immune cells. Moreover, a number of pro-inflammatory cytokines and chemokines display mitogenic, motogenic, morphogenic and/or angiogenic properties and may therefore contribute to tumour growth and metastasis. The key triggering events involved in activation of pro-inflammatory responses by CPM and soluble CPM components can be categorized into (i) formation of ROS and oxidative stress, (ii) interaction with the lipid layer of cellular membranes, (iii) activation of receptors, ion channels and transporters on the cell surface and (iv) interactions with intracellular molecular targets including receptors such as the aryl hydrocarbon receptor (AhR). In particular, we will elucidate the effects of diesel exhaust particles (DEP) using human lung epithelial cells as a model system.

Purinergic Receptor Transactivation by the β2-Adrenergic Receptor Increases Intracellular Ca2+ in Nonexcitable Cells

The β₂ adrenergic receptor (β₂AR) increases intracellular Ca²⁺ in a variety of cell types. By combining pharmacological and genetic manipulations, we reveal a novel mechanism through which the β₂AR promotes Ca²⁺ mobilization (pEC₅₀ = 7.32 ± 0.10) in nonexcitable human embryonic kidney (HEK)293S cells. Downregulation of Gs with sustained cholera toxin pretreatment and the use of Gs-null HEK293 (∆Gs-HEK293) cells generated using the clustered regularly interspaced short palindromic repeat-associated protein-9 nuclease (CRISPR/Cas9) system, combined with pharmacological modulation of cAMP formation, revealed a Gs-dependent but cAMP-independent increase in intracellular Ca²⁺ following β₂AR stimulation. The increase in cytoplasmic Ca²⁺ was inhibited by P2Y purinergic receptor antagonists as well as a dominant-negative mutant form of Gq, a Gq-selective inhibitor, and an inositol 1,4,5-trisphosphate (IP₃) receptor antagonist, suggesting a role for this Gq-coupled receptor family downstream of the β₂AR activation. Consistent with this mechanism, β₂AR stimulation promoted the extracellular release of ATP, and pretreatment with apyrase inhibited the β₂AR-promoted Ca²⁺ mobilization. Together, these data support a model whereby the β₂AR stimulates a Gs-dependent release of ATP, which transactivates Gq-coupled P2Y receptors through an inside-out mechanism, leading to a Gq- and IP₃-dependent Ca²⁺ mobilization from intracellular stores. Given that β₂AR and P2Y receptors are coexpressed in various tissues, this novel signaling paradigm could be physiologically important and have therapeutic implications. In addition, this study reports the generation and validation of HEK293 cells deleted of Gs using the CRISPR/Cas9 genome editing technology that will undoubtedly be powerful tools to study Gs-dependent signaling.

Protease-Activated Receptor 2 Promotes Pro-Atherogenic Effects through Transactivation of the VEGF Receptor 2 in Human Vascular Smooth Muscle Cells

Background: Obesity is associated with impaired vascular function. In the cardiovascular system, protease-activated receptor 2 (PAR2) exerts multiple functions such as the control of the vascular tone. In pathological conditions, PAR2 is related to vascular inflammation. However, little is known about the impact of obesity on PAR2 in the vasculature. Therefore, we explored the role of PAR2 as a potential link between obesity and cardiovascular diseases.

Methods: C57BL/6 mice were fed with either a chow or a 60% high fat diet for 24 weeks prior to isolation of aortas. Furthermore, human coronary artery endothelial cells (HCAEC) and human coronary smooth muscle cells (HCSMC) were treated with conditioned medium obtained from in vitro differentiated primary human adipocytes. To investigate receptor interaction vascular endothelial growth factor receptor 2 (VEGFR2) was blocked by exposure to calcium dobesilate and a VEGFR2 neutralization antibody, before treatment with PAR2 activating peptide. Student's t-test or one-way were used to determine statistical significance.

Results: Both, high fat diet and exposure to conditioned medium increased PAR2 expression in aortas and human vascular cells, respectively. In HCSMC, conditioned medium elicited proliferation as well as cyclooxygenase 2 induction, which was suppressed by the PAR2 antagonist GB83. Specific activation of PAR2 by the PAR2 activating peptide induced proliferation and cyclooxygenase 2 expression which were abolished by blocking the VEGFR2. Additionally, treatment of HCSMC with the PAR2 activating peptide triggered VEGFR2 phosphorylation.

Conclusion: Under obesogenic conditions, where circulating levels of pro-inflammatory adipokines are elevated, PAR2 arises as an important player linking obesity-related adipose tissue inflammation to atherogenesis. We show for the first time that the underlying mechanisms of these pro-atherogenic effects involve a potential transactivation of the VEGFR2 by PAR2.

Regulation of ozone-induced lung inflammation by the epidermal growth factor receptor in mice

Human exposure to the highly reactive oxidant gas Ozone (O₃ ) is associated with inflammatory responses in the airway epithelium. The mechanisms responsible have not been fully elucidated. Epidermal growth factor receptor (EGFR) has previously been shown to play a critical role in the pathogenesis of lung inflammation. To define the role of EGFR in O₃ -induced lung inflammation in mice. 40 BALB/c mice were exposed to filtered air (FA) or (0.25, 0.5, 1.00 ppm) O₃ for 3 h per day for 7 consecutive days. Levels of reactive oxygen species (ROS), EGF, and transforming growth factor α (TGF-α) in the bronchoalveolar lavage fluid (BALF) of mice were measured using ELISA. BALB/c mice were intratracheally instilled with the EGFR kinase inhibitor PD153035 2 h prior to O₃ exposure and every other day thereafter. Phosphorylation of EGFR (Y1068) in lung sections was determined using immunohistochemical staining and western blot 24 h after exposure. Inhalation of O₃ induced pronounced lung inflammation in a dose-dependent manner. Levels of ROS, TGF-α, and total proteins and cells in the BALF of mice exposed to 0.5 ppm or 1.0 ppm of O₃ were markedly elevated relative to those in the BALF of the mice exposed to FA. In addition, exposure to O₃ induced EGFR(Y1068) phosphorylation in the airway epithelium. Administration of PD153035 resulted in a significantly reduced lung inflammation as well as EGFR phosphorylation induced by O₃ exposure. Inhalation of O₃ leads to inflammatory responses that are dependent on the activation the EGFR in the airway epithelium. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2016-2027, 2016.

Molecular mechanisms of LL-37-induced receptor activation: An overview

The human cathelicidin peptide LL-37 plays a crucial role in the immune system on many levels, from the first line of defense in epithelial cells to restoring the tissue after infection. On host cells, the majority of the LL-37-induced effects are mediated via the direct or indirect activation of several structurally unrelated cell surface receptors or intracellular targets. How LL-37 is able to affect multiple receptors is currently not well understood. So far, the mechanistic details underlying receptor activation are poorly investigated and evidence for a conventional ligand/receptor interaction is scarce. Over the past few decades, a large number of studies have reported on the activation of a receptor and/or components of the downstream signal transduction pathway induced by LL-37. This review summarizes the current knowledge on molecular mechanisms underlying LL-37-induced receptor activation.

Protective Role of Postbiotic Mediators Secreted by Lactobacillus rhamnosus GG Versus Lipopolysaccharide-induced Damage in Human Colonic Smooth Muscle Cells

BACKGROUND

Some beneficial effects of probiotics may be due to secreted probiotic-derived factors, identified as "postbiotic" mediators. The aim of this study was to evaluate whether supernatants harvested from Lactobacillus rhamnosus GG (LGG) cultures (ATCC53103 strain) protect colonic human smooth muscle cells (HSMCs) from lipopolysaccharide (LPS)-induced myogenic damage.

MATERIALS AND METHODS

LGG was grown in de Man, Rogosa, Share medium at 37°C and samples were collected in middle and late exponential, stationary, and overnight phases. Supernatants were recovered by centrifugation, filtered, and stored at -20°C. The primary HSMCs culture was exposed for 24 hours to purified LPS of a pathogen strain of Escherichia coli (O111:B4) (1 μg/mL) with and without supernatants. Postbiotic effects were evaluated on the basis of HSMCs morphofunctional alterations and interleukin-6 (IL-6) production. Data are expressed as mean±SE (P<0.05 significant).

RESULTS

LPS induced persistent, significant, 20.5%±0.7% cell shortening and 34.5%±2.2% decrease in acetylcholine-induced contraction of human HSMCs. These morphofunctional alterations were paralleled to a 365.65%±203.13% increase in IL-6 production. All these effects were dose-dependently reduced by LGG supernatants. Supernatants of the middle exponential phase already partially restored LPS-induced cell shortening by 57.34%±12.7% and IL-6 increase by 145.8%±4.3% but had no effect on LPS-induced inhibition of contraction. Maximal protective effects were obtained with supernatants of the late stationary phase with LPS-induced cell shortening restored by 84.1%±4.7%, inhibition of contraction by 85.5%±6.4%, and IL-6 basal production by 92.7%±1.2%.

CONCLUSIONS

LGG-derived products are able to protect human SMCs from LPS-induced myogenic damage. Novel insights have been provided for the possibility that LGG-derived products could reduce the risk of progression to postinfective motor disorders.

Sphingosine 1-Phosphate Activation of EGFR As a Novel Target for Meningitic Escherichia coli Penetration of the Blood-Brain Barrier

Central nervous system (CNS) infection continues to be an important cause of mortality and morbidity, necessitating new approaches for investigating its pathogenesis, prevention and therapy. Escherichia coli is the most common Gram-negative bacillary organism causing meningitis, which develops following penetration of the blood-brain barrier (BBB). By chemical library screening, we identified epidermal growth factor receptor (EGFR) as a contributor to E. coli invasion of the BBB in vitro. Here, we obtained the direct evidence that CNS-infecting E. coli exploited sphingosine 1-phosphate (S1P) for EGFR activation in penetration of the BBB in vitro and in vivo. We found that S1P was upstream of EGFR and participated in EGFR activation through S1P receptor as well as through S1P-mediated up-regulation of EGFR-related ligand HB-EGF, and blockade of S1P function through targeting sphingosine kinase and S1P receptor inhibited EGFR activation, and also E. coli invasion of the BBB. We further found that both S1P and EGFR activations occurred in response to the same E. coli proteins (OmpA, FimH, NlpI), and that S1P and EGFR promoted E. coli invasion of the BBB by activating the downstream c-Src. These findings indicate that S1P and EGFR represent the novel host targets for meningitic E. coli penetration of the BBB, and counteracting such targets provide a novel approach for controlling E. coli meningitis in the era of increasing resistance to conventional antibiotics.

Concomitant Statin Use Has a Favorable Effect on Gemcitabine-Erlotinib Combination Chemotherapy for Advanced Pancreatic Cancer

PURPOSE

Erlotinib-gemcitabine combined chemotherapy is considered as the standard treatment for unresectable pancreatic cancer. This study aimed to determine the clinical factors associated with response to this treatment.

MATERIALS AND METHODS

This retrospective study included 180 patients with unresectable pancreatic cancer who received ≥2 cycles of gemcitabine-erlotinib combination therapy as first-line palliative chemotherapy between 2006 and 2014. "Long-term response" was defined as tumor stabilization after >6 chemotherapy cycles.

RESULTS

The median progression-free survival (PFS) and overall survival (OS) were 3.9 and 8.1 months, respectively. On univariate analysis, liver metastasis (p=0.023) was negatively correlated with long-term response. Locally advanced stage (p=0.017), a history of statin treatment (p=0.01), and carcinoembryonic antigen levels <4.5 (p=0.029) had a favorable effect on long-term response. On multivariate analysis, a history of statin treatment was the only independent favorable factor for long-term response (p=0.017). Prognostic factors for OS and PFS were significantly correlated with liver metastasis (p=0.031 and 0.013, respectively). A history of statin treatment was also significantly associated with OS after adjusting for all potential confounders (hazard ratio, 0.48; 95% confidence interval, 0.26-0.92; p=0.026).

CONCLUSION

These results suggest that statins have a favorable effect on "long-term response" to gemcitabine-erlotinib chemotherapy in unresectable pancreatic cancer patients. Statins may have a chemoadjuvant role in stabilizing long-term tumor growth.

Nucleolin inhibitor GroA triggers reduction in epidermal growth factor receptor activation: Pharmacological implication for glial scarring after spinal cord injury

Glial scarring, formed by reactive astrocytes, is one of the major impediments for regeneration after spinal cord injury (SCI). Reactive astrocytes become hypertrophic, proliferate and secrete chondroitin sulphate proteoglycans into the extracellular matrix (ECM). Many studies have demonstrated that epidermal growth factor receptors (EGFR) can mediate astrocyte reactivity after neurotrauma. Previously we showed that there is crosstalk between nucleolin and EGFR that leads to increased EGFR activation followed by increased cell proliferation. Treatment with the nucleolin inhibitor GroA (AS1411) prevented these effects in vitro and in vivo. In this study, we hypothesized that similar interactions may mediate astrogliosis after SCI. Our results demonstrate that nucleolin and EGFR interaction may play a pivotal role in mediating astrocyte proliferation and reactivity after SCI. Moreover, we demonstrate that treatment with GroA reduces EGFR activation, astrocyte proliferation and chondroitin sulphate proteoglycans secretion, therefore promoting axonal regeneration and sprouting into the lesion site. Our results identify, for the first time, a role for the interaction between nucleolin and EGFR in astrocytes after SCI, indicating that nucleolin inhibitor GroA may be used as a novel treatment after neurotrauma. A major barrier for axonal regeneration after spinal cord injury is glial scar created by reactive and proliferating astrocytes. EGFR mediate astrocyte reactivity. We showed that inhibition of nucleolin by GroA, reduces EGFR activation, which results in attenuation of astrocyte reactivity and proliferation in vivo and in vitro. EGFR, epidermal growth factor receptor.

p85α promotes nucleolin transcription and subsequently enhances EGFR mRNA stability and EGF-induced malignant cellular transformation

p85α is a regulatory subunit of phosphatidylinositol 3-kinase (PI3K) that is a key lipid enzyme for generating phosphatidylinositol 3, 4, 5-trisphosphate, and subsequently activates signaling that ultimately regulates cell cycle progression, cell growth, cytoskeletal changes, and cell migration. In addition to form a complex with the p110 catalytic subunit, p85α also exists as a monomeric form due to that there is a greater abundance of p85α than p110 in many cell types. Our previous studies have demonstrated that monomeric p85α exerts a pro-apoptotic role in UV response through induction of TNF-α gene expression in PI3K-independent manner. In current studies, we identified a novel biological function of p85α as a positive regulator of epidermal growth factor receptor (EGFR) expression and cell malignant transformation via nucleolin-dependent mechanism. Our results showed that p85α was crucial for EGFR and nucleolin expression and subsequently resulted in an increase of malignant cellular transformation by using both specific knockdown and deletion of p85α in its normal expressed cells. Mechanistic studies revealed that p85α upregulated EGFR protein expression mainly through stabilizing its mRNA, whereas nucleolin (NCL) was able to bind to egfr mRNA and increase its mRNA stability. Consistently, overexpression of NCL in p85α-/- cells restored EGFR mRNA stabilization, protein expression and cell malignant transformation. Moreover, we discovered that p85α upregulated NCL gene transcription via enhancing C-Jun activation. Collectively, our studies demonstrate a novel function of p85α as a positive regulator of EGFR mRNA stability and cell malignant transformation, providing a significant insight into the understanding of biomedical nature of p85α protein in mammalian cells and further supporting that p85α might be a potential target for cancer prevention and therapy.

Inflammatory cell signaling following exposures to particulate matter and ozone

BACKGROUND

Particulate matter (PM) and ozone (O3) are two major ambient air pollutants. Epidemiological and toxicological studies have demonstrated exposure to these pollutants is associated with a variety of adverse health effects, including cardiovascular and respiratory disease, in which inflammation is believed to be a common and essential factor.

SCOPE OF REVIEW

This review mainly focuses on major inflammatory cell signaling pathways triggered by exposure to PM and O3. The receptors covered in this review include the EGF receptor, toll like receptor, and NOD-like receptor. Intracellular signaling protein kinases depicted in this review are phosphatidylinositol 3-kinase and mitogen-activated protein kinases. Activation of antioxidant and inflammatory transcription factors such as NrF2 and NFκB induced by PM and O3 is also discussed.

MAJOR CONCLUSIONS

Exposure to PM or O3 can activate cellular signaling networks including membrane receptors, intracellular kinases and phosphatases, and transcription factors that regulate inflammatory responses. While PM-induced cell signaling is associated with resultant ROS, O3-induced cell signaling implicates phosphates. Notably, the cellular signaling induced by PM and O3 exposure varies with cell type and physiochemical properties of these pollutants.

GENERAL SIGNIFICANCE

Cellular signaling plays a critical role in the regulation of inflammatory pathogenesis. Elucidation of cellular signaling pathways initiated by PM or O3 cannot only help to uncover the mechanisms of air pollutant toxicity but also provide clues for development of interventional measures against air pollution-induced disorders. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.