Abstract Transcriptional factors of the NF-κB family and STAT3 are ubiquitously expressed and control numerous physiological processes including development, differentiation, immunity, metabolism and cancer. Both NF-κB and STAT3 are rapidly activated in response to various stimuli including stresses and cytokines, although they are regulated by entirely different signaling mechanisms. Once activated, NF-κB and STAT3 control the expression of anti-apoptotic, pro-proliferative and immune response genes. Some of these genes overlap and require transcriptional cooperation between the two factors. The activation of and interaction between STAT3 and NF-κB plays a key role in controlling the dialog between the malignant cell and its microenvironment, especially with inflammatory/immune cells that infiltrate tumors. Quite often, cytokines whose expression is induced in response to NF-κB in immune cells of the tumor microenvironment lead to STAT3 activation in both malignant and immune cells. While within malignant and pre-malignant cells STAT3 exerts important oncogenic functions, within inflammatory cells it may also suppress tumor promotion through its anti-inflammatory effects. Other interactions and forms of crosstalk between NF-κB and STAT3 include physical interaction between the two, cooperation of these factors at gene promoters/enhancers, the NF-κB dependent expression of inhibitors of STAT3 activation and the participation of STAT3 in inflammatory cells in the negative regulation NF-κB. Despite these versatile and occasionally antagonistic interactions, NF-κB and STAT3 cooperate to promote the development and progression of colon, gastric and liver cancers. In addition to explaining the molecular pathogenesis of cancer, these interactions also offer opportunities for the design of new therapeutic interventions.
Atherosclerosis, a chronic inflammatory disorder of the arteries, is responsible for most deaths in westernized societies with numbers increasing at a marked rate in developing countries. The disease is initiated by the activation of the endothelium by various risk factors leading to chemokine-mediated recruitment of immune cells. The uptake of modified lipoproteins by macrophages along with defective cholesterol efflux gives rise to foam cells associated with the fatty streak in the early phase of the disease. As the disease progresses, complex fibrotic plaques are produced as a result of lysis of foam cells, migration and proliferation of vascular smooth muscle cells and continued inflammatory response. Such plaques are stabilized by the extracellular matrix produced by smooth muscle cells and destabilized by matrix metalloproteinase from macrophages. Rupture of unstable plaques and subsequent thrombosis leads to clinical complications such as myocardial infarction. Cytokines are involved in all stages of atherosclerosis and have a profound influence on the pathogenesis of this disease. This review will describe our current understanding of the roles of different cytokines in atherosclerosis together with therapeutic approaches aimed at manipulating their actions. (C) 2015 The Authors. Published by Elsevier Ltd.
Abstract The molecular pathways involved in the cellular response to interferon (IFN)γ have been the focus of much research effort due to their importance in host defense against infection and disease, as well as its potential as a therapeutic agent. The discovery of the JAK–STAT signaling pathway greatly enhanced our understanding of the mechanism of IFNγ-mediated gene transcription. However, in recent years it has become apparent that other pathways, including MAP kinase, PI3-K, CaMKII and NF-κB, either co-operate with or act in parallel to JAK–STAT signaling to regulate the many facets of IFNγ biology in a gene- and cell type-specific manner. The complex interactions between JAK/STAT and alternate pathways and the impact of these signaling networks on the biological responses to IFNγ are beginning to be understood. This review summarizes and appraises current advances in our understanding of these complex interactions, their specificity and proposed biological outcomes.
Abstract Double-stranded RNA (dsRNA), the genetic material for many RNA viruses, induces robust host immune responses via pattern recognition receptors, which include Toll-like receptor 3 (TLR3), retinoic acid-inducible gene-I-like receptors (RLRs) and the multi-protein NLRP3 inflammasome complex. The engagement of dsRNA receptors or inflammasome activation by viral dsRNA initiates complex intracellular signaling cascades that play essential roles in inflammation and innate immune responses, as well as the resultant development of adaptive immunity. This review focuses on signaling pathways mediated by TLR3, RLRs and the NLRP3 inflammasome, as well as the potential use of agonists and antagonists that target these pathways to treat disease.
A high level of Interleukin-1 beta (IL1B), a key mediator of inflammation, is expressed in the brain, particularly in the hippocampus, which plays a pivotal role in memory and mood regulation. In the brain, IL1B exerts a myriad of effects such as neuronal proliferation, differentiation, apoptosis, and long-term potentiation. Considering its pleiotropic effects in the brain, IL1B has been implicated in the pathogenesis of various psychiatric disorders as well as cognitive function in normal individuals. Thus, IL1B has been considered a candidate gene for the study of psychiatric diseases as well as brain function in normal individuals. The polymorphisms of IL1B have been described in relation to various expression levels in response to stimulation. This review describes previous studies on the genetic effects of IL1B, which relate it to psychiatric diseases such as major depressive disorder, bipolar disorder, schizophrenia, and Alzheimer's disease, as well as cognitive function in normal individuals. Although many reports have indicated a possible role of the genetic effects of IL1B or its phenotypes in psychiatric diseases, some reports were unable to confirm these findings. IL1B release is mediated by an inflammatory response or psychological stress, leading to a cascade of immune reactions involving numerous immune components. To further explore the genetic effects of IL1B on mental diseases and brain function, gene-gene and gene-environment interactions should also be considered. (C) 2017 Elsevier Ltd. All rights reserved.
Abstract The type I interferon (IFN) α and β promoters have been a leading paradigm of virus-activated transcriptional regulation for more than two decades, and have contributed substantially to our understanding of virus-inducible gene regulation, the coordinated activities of NF-κB and IRF transcription factors, the temporal and spatial recruitment of co-activators to the enhanceosome, and signaling pathways that trigger the innate antiviral response. In 2003, the ISICR Milstein Award was presented to John Hiscott of McGill University and Tom Maniatis of Harvard University for their ongoing research describing the mechanisms of regulation of type 1 interferon genes and specifically for the identification of key signaling kinases involved in phosphorylation of the transcription factors IRF-3 and IRF-7. The specific roles played by IRFs and the IKK-related kinases TBK1 and IKKε are now recognized within the broader framework of TLR and RIG-I signaling pathways. This review summarizes the unique features of the IKK-related kinases and offers a summary of recent advances in the regulation of the early host response to virus infection.
Dermal fibroblasts, which make up the major cell type in the dermis, have, historically, been considered to be relatively ‘passive’ cells which are responsible for the synthesis and remodeling of extracellular matrix proteins. However, the dermal fibroblast population is composed of heterogeneous and distinct cell types, and it has been established that, under the stress conditions of healing wound environments, dermal fibroblasts participate in the regulation of ongoing inflammation and cell proliferation by secreting a variety of signaling molecules that modulate the functions of immune cells, keratinocyte, endothelial cells and mast cells via both direct cell to cell communication and autocrine and paracrine interactions. This review describes the capacity of dermal fibroblasts to sense and respond to signals from the micro-environment and to communicate with surrounding cells during cutaneous wound healing. The review further emphasizes the, to date, poorly understood roles of heterogeneous dermal fibroblast populations in the wound healing process.
Abstract IKKβ/IKBKB (IκB kinase beta), also designated as IKK2, was named after its function of phosphorylating IκB molecules, the inhibitors of NF-κB transcription factors. The kinase activity of IKKβ targets two adjacent serine residues of IκB leading to ubiquitination and proteasomal degradation of the inhibitor, followed by release and activation of NF-κB. Many signaling pathways that activate NF-κB converge at the level of IKKβ. Examples of stimuli leading to IKKβ and subsequent NF-κB activation include inflammatory cytokines (IL-1, TNFα), endotoxins (lipopolysaccharide), viral infection and double strand RNA as well as physical signals such as UV-irradiation. Transcription factors of the NF-κB protein family have a great variety of functions in regulating the immune system, cellular differentiation, survival and proliferation. NF-κB is an essential factor in acute as well as chronic inflammation, a pathological state which is either cause or co-factor in a great variety of diseases. Moreover, recent data suggest that many variants of cancer are characterized by elevated constitutive activity of NF-κB, which can act as a survival factor for malignant cells by its predominantly anti-apoptotic function. Given the tight regulation of NF-κB by IκB molecules and the central role of IKKβ in phosphorylation and degradation of the inhibitor, IKKβ is a very promising target for pharmaceutical substances aiming at interfering with NF-κB activation.
Tumor necrosis factor-α (TNF-α) signaling through TNF receptor 2 (TNFR2) plays a complex immune regulatory role in allogeneic hematopoietic cell transplantation (HCT). TNF-α is rapidly released in the circulation after the conditioning regimen with chemotherapy and/or radiotherapy. It activates the function of donor alloreactive T cells and donor Natural Killer cells and promotes graft versus tumor effects. However, donor alloreactive T cells also attack host tissues and cause graft versus host disease (GVHD), a life-threatening complication of HCT. Indeed, anti-TNF-α therapy has been used to treat steroid-refractory GVHD. Recent studies have highlighted another role for TNFR2 signaling, as it enhances the function of immune cells with suppressive properties, in particular CD4 Foxp3 regulatory T cells (Tregs). Various clinical trials are employing Treg-based treatments to prevent or treat GVHD. The present review will discuss the effects of TNFR2 signaling in the setting of allogeneic HCT, the implications for the use of anti-TNF-α therapy to treat GVHD and the clinical perspectives of strategies that specifically target this pathway.
Abstract Osteoclasts are responsible for bone resorption and play a pivotal role in the pathogenesis of osteolytic disorders. NF-κB is a set of nuclear factors that bind to consensus DNA sequences called κB sites, and is essential for osteoclast formation and survival. NF-κB signalling pathways are strictly regulated to maintain bone homeostasis by cytokines such as RANKL, TNF-α and IL-1, which differentially regulate classical and/or alternative NF-κB pathways in osteoclastic cells. These pathways are also modulated by NF-κB mediators, including TRAF6, aPKC, p62/SQSTM1 and deubiquitinating enzyme CYLD that are involved in the ubiquitin–proteasome system during RANK-mediated osteoclastogenesis. Abnormal activation of NF-κB signalling in osteoclasts has been associated with excessive osteoclastic activity, and frequently observed in osteolytic conditions, including periprosthetic osteolysis, arthritis, Paget's disease of bone, and periodontitis. NF-κB modulators such as parthenolide and NEMO-binding domain peptide demonstrate therapeutic effects on inflammation-induced bone destruction in mouse models. Unravelling the structure and function of NF-κB pathways in osteoclasts and other cell types will be important in developing new strategies for treatments of bone diseases.
Angiogenesis is a tightly regulated activity that is vital during embryonic development and for normal physiological repair processes and reproduction in healthy adults. Pathological angiogenesis is a driving force behind a variety of diseases including cancer and retinopathies, and inhibition of angiogenesis is a therapeutic option that has been the subject of much research, with several inhibitory agents now available for medical therapy. Conversely, therapeutic angiogenesis has been mooted as having significant potential in the treatment of ischemic conditions such as angina pectoris and peripheral arterial disease, but so far there has been less translation from lab to bedside. The insulin-like growth factor binding proteins (IGFBP) are a family of seven proteins essential for the binding and transport of the insulin-like growth factors (IGF). It is being increasingly recognised that IGFBPs have a significant role beyond simply modulating IGF activity, with evidence of both IGF dependent and independent actions through a variety of mechanisms. Moreover, the action of the IGFBPs can be stimulatory or inhibitory depending on the cell type and environment. Specifically the IGFBPs have been heavily implicated in angiogenesis, both pathological and physiological, and they have significant promise as targeted cell therapy agents for both pathological angiogenesis inhibition and therapeutic angiogenesis following ischemic injury. In this short review we will explore the current understanding of the individual impact of each IGFBP on angiogenesis, and the pathways through which these effects occur.
Mesenchymal Stem Cells (MSCs) have been shown to be a promising candidate for cell-based therapy. The therapeutic potential of MSCs, towards tissue repair and wound healing is essentially based on their paracrine effects. Numerous pre-clinical and clinical studies of MSCs have yielded encouraging results. Further, these cells have been shown to be relatively safe for clinical applications. MSCs harvested from numerous anatomical locations including the bone marrow, adipose tissue, Wharton’s jelly of the umbilical cord etc., display similar immunophenotypic profiles. However, there is a large body of evidence showing that MSCs secrete a variety of biologically active molecules such as growth factors, chemokines, and cytokines. Despite the similarity in their immunophenotype, the secretome of MSCs appears to vary significantly, depending on the age of the host and niches where the cells reside. Thus, by implication, proteomics-based profiling suggests that the therapeutic potential of the different MSC populations must also be different. Analysis of the secretome points to its influence on varied biological processes such as angiogenesis, neurogenesis, tissue repair, immunomodulation, wound healing, anti-fibrotic and anti-tumour for tissue maintenance and regeneration. Though MSC based therapy has been shown to be relatively safe, from a clinical standpoint, the use of cell-free infusions can altogether circumvent the administration of viable cells for therapy. Understanding the secretome of cultured MSC populations, by the analysis of the corresponding conditioned medium, will enable us to evaluate its utility as a new therapeutic option. This review will focus on the accumulating evidence that points to the therapeutic potential of the conditioned medium, both from pre-clinical and clinical studies. Finally, this review will emphasize the importance of profiling the conditioned medium for assessing its potential for cell-free therapy therapy.
Pregnancy is a dynamic and precisely organized process during which one or more baby develops. Embryonic development relies on the formation of the placenta, allowing nutrient and oxygen exchange between the mother and the fetus. Dysfunction of placental formation lead to pregnancy disorders such as preeclampsia (PE) with serious deleterious consequences for fetal and maternal health. Identifying factors involved in fetoplacental homeostasis could inform better diagnostic and therapeutic strategies for these pathological pregnancies. Here, we summarize actions of elabela, apelin and their common receptor APJ in the fetoplacental unit. Studies indicate that elabela is crucial for embryo cardiovascular system formation and early placental development, while apelin acts in mid/late gestation to modulate fetal angiogenesis and energy homeostasis. Most of these findings, drawn from animal models, indicate a key role of elabela/apelin-APJ system in the fetoplacental unit. This review also provides an overview of clinical studies investigating elabela/apelin-APJ system in pathological complicated pregnancies such as PE and gestational diabetes mellitus (GDM). While elabela-deficient mice display all the features of PE, current clinical studies show no difference in circulating elabela levels between PE and control patients which does not support a role in PE development. Conversely, apelin levels are increased during PE, but the use of apelin as an early PE marker remains to be fully investigated.
Activated phosphatidylinositol 3 kinase/Protein kinase B (PI3K/AKT) signalling with increased or reduced mTOR and GSK3β activity influences the wound repair process. Diabetic wounds, usually ulcerated, are characterised by reduced growth factors and cellular performance. The occurrence of diabetic ulcers is linked to peripheral arterial disease, neuropathy, and wound contamination. Lasers or light emitting diodes (LEDs) provide photon energy with therapeutic benefits (Photobiomodulation-PBM), and has been broadly commended to quicken diabetic wound healing. PBM is efficient in the visible red and near-infrared electromagnetic spectrum, and fluencies ranging from 2 to 6 J/cm . However, cellular and molecular mechanisms induced by PBM are not fully understood. In this review we discuss PBM and the PI3K/AKT pathway with specific focus on the mTOR and GSK3β downstream activity in diabetic wound healing.
Abstract The nuclear factor kappaB (NF-κB) family of transcription factors consists of 15 possible dimers whose activity is controlled by a family of inhibitor proteins, known as IκBs. A variety of cellular stimuli, many of them transduced by members of the tumor necrosis factor receptor (TNFR) superfamily, induce degradation of IκBs to activate an overlapping subset of NF-κB dimers. However, generation and stimulus-responsive activation of NF-κB dimers are intimately linked via various cross-regulatory mechanisms that allow crosstalk between different signaling pathways through the NF-κB signaling system. In this review, we summarize these mechanisms and discuss physiological and pathological consequences of crosstalk between apparently distinct inflammatory and developmental signals. We argue that a systems approach will be valuable for understanding questions of specificity and emergent properties of highly networked cellular signaling systems.