Egr-1: new conductor for the tissue repair orchestra directs harmony (regeneration) or cacophony (fibrosis)

ADAMTS3 activity is mandatory for embryonic lymphangiogenesis and regulates placental angiogenesis

The only documented activity of a subclass of ADAMTS proteases comprising ADAMTS2, 3 and 14 is the cleavage of the aminopropeptide of fibrillar procollagens. A limited number of in vitro studies suggested that ADAMTS3 is mainly responsible for procollagen II processing in cartilage. Here, we created an ADAMTS3 knockout mouse (Adamts3^−/−) model to determine in vivo the actual functions of ADAMTS3. Heterozygous Adamts3^+/− mice were viable and fertile, but their intercrosses demonstrated lethality of Adamts3^−/− embryos after 15 days of gestation. Procollagens I, II and III processing was unaffected in these embryos. However, a massive lymphedema caused by the lack of lymphatics development, an abnormal blood vessel structure in the placenta and a progressive liver destruction were observed. These phenotypes are most probably linked to dysregulation of the VEGF-C pathways. This study is the first demonstration that an aminoprocollagen peptidase is crucial for developmental processes independently of its primary role in collagen biology and has physiological functions potentially involved in several human diseases related to angiogenesis and lymphangiogenesis.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

Key Fibrogenic Signaling

Fibrosis is defined as an excessive accumulation of extracellular matrix components that lead to the destruction of organ architecture and impairment of organ function. Moreover, fibrosis is an intricate process attributable to a variety of interlaced fibrogenic signals and intrinsic mechanisms of activation of myofibroblasts. Being the dominant matrix-producing cells in organ fibrosis, myofibroblasts may be differentiated from various types of precursor cells. Identification of the signal pathways that play a key role in the pathogenesis of fibrotic diseases may suggest potential therapeutic targets. Here, we emphasize several intracellular signaling pathways that control the activation of myofibroblasts and matrix production.

Extensive survey of STAT6 expression in a large series of mesenchymal tumors

OBJECTIVES

Expression of strong nuclear STAT6 is thought to be a specific marker for solitary fibrous tumors (SFTs). Little is known about subtle expression patterns in other mesenchymal lesions.

METHODS

We performed immunohistochemical studies against the C-terminus of STAT6 in tissue microarrays and whole sections, comprising 2366 mesenchymal lesions.

RESULTS

Strong nuclear STAT6 was expressed in 285 of 2,021 tumors, including 206 of 240 SFTs, 49 of 408 well-differentiated/dedifferentiated liposarcomas, eight of 65 unclassified sarcomas, and 14 of 184 desmoid tumors, among others. Expression in SFTs was predominately limited to the nucleus. Other positive tumors typically expressed both nuclear and cytoplasmic STAT6. Complete absence of STAT6 was most common in pleomorphic liposarcoma and alveolar soft part sarcoma (60% and 72% cases negative, respectively).

CONCLUSIONS

Strong nuclear STAT6 is largely specific for SFTs. Physiologic low-level cytoplasmic/nuclear expression is common in mesenchymal neoplasia and is of uncertain significance.

Systemic sclerosis

Systemic sclerosis is a complex autoimmune disease characterized by a chronic and frequently progressive course and by extensive patient-to-patient variability. Like other autoimmune diseases, systemic sclerosis occurs more frequently in women, with a peak of onset in the fifth decade of life. The exact cause of systemic sclerosis remains elusive but is likely to involve environmental factors in a genetically primed individual. Pathogenesis is dominated by vascular changes; evidence of autoimmunity with distinct autoantibodies and activation of both innate and adaptive immunity; and fibrosis of the skin and visceral organs that results in irreversible scarring and organ failure. Intractable progression of vascular and fibrotic organ damage accounts for the chronic morbidity and high mortality. Early and accurate diagnosis and classification might improve patient outcomes. Screening strategies facilitate timely recognition of life-threatening complications and initiation of targeted therapies to halt their progression. Effective treatments of organ-based complications are now within reach. Discovery of biomarkers - including autoantibodies that identify patient subsets at high risk for particular disease complications or rapid progression - is a research priority. Understanding the key pathogenetic pathways, cell types and mediators underlying disease manifestations opens the door for the development of targeted therapies with true disease-modifying potential. For an illustrated summary of this Primer, visit: http://go.nature.com/lchkcA.

NAB2-STAT6 fusion gene analysis in two cases of meningeal solitary fibrous tumor/hemangiopericytoma with late distant metastases

We present two cases of meningeal solitary fibrous tumor (SFT)/hemangiopericytoma (HPC) with immunohistochemistry of STAT6 and analysis of NAB2-STAT6 fusion genes. Case 1 was a 37-year-old male with a left middle fossa tumor; case 2 was a 68-year-old female with a cerebellar tumor. They showed late metastasis to the lung or bone 8 or 13 years, respectively, after the first surgery. Histology of both primary and metastatic tumors showed a cellular hemangiopericytomatous pattern with nuclear atypia. The primary tumors showed nuclear staining of STAT6, but both metastatic tumors showed nuclear and cytoplasmic STAT6. DNA sequencing revealed two kinds of NAB2-STAT6 fusion genes. One consisted of exon 6 of NAB2, intron 6 of NAB2, and the middle of exon 17 of STAT6 (observed in the primary and metastatic tumors of case 1); the other consisted of exon 6 of NAB2 and the beginning of exon 17 of STAT6 (observed in the metastatic tumor of case 2). The primary tumor of case 2 had both fusion genes. To the best of our knowledge, we are the first to report NAB2-STAT6 fusion gene analysis in primary and metastatic meningeal SFT/HPCs and a case showed different fusion gene status in the metastatic tumor.

Overexpression of Activation-Induced Cytidine Deaminase in MTX- and Age-Related Epstein-Barr Virus-Associated B-Cell Lymphoproliferative Disorders of the Head and Neck

Recent research has shown that activation-induced cytidine deaminase (AID) triggers somatic hypermutation and recombination, in turn contributing to lymphomagenesis. Such aberrant AID expression is seen in B-cell leukemia/lymphomas, including Burkitt lymphoma which is associated with c-myc translocation. Moreover, Epstein-Barr virus (EBV) latent membrane protein-1 (LMP-1) increases genomic instability through early growth transcription response-1 (Egr-1) mediated upregulation of AID in B-cell lymphoma. However, few clinicopathological studies have focused on AID expression in lymphoproliferative disorders (LPDs). Therefore, we conducted an immunohistochemical study to investigate the relationship between AID and LMP-1 expression in LPDs (MTX-/Age-related EBV-associated), including diffuse large B-cell lymphomas (DLBCLs). More intense AID expression was detected in LPDs (89.5%) than in DLBCLs (20.0%), and the expression of LMP-1 and EBER was more intense in LPDs (68.4% and 94.7%) than in DLBCLs (10.0% and 20.0%). Furthermore, stronger Egr-1 expression was found in MTX/Age-EBV-LPDs (83.3%) than in DLBCLs (30.0%). AID expression was significantly constitutively overexpressed in LPDs as compared with DLBCLs. These results suggest that increased AID expression in LPDs may be one of the processes involved in lymphomagenesis, thereby further increasing the survival of genetically destabilized B-cells. AID expression may be a useful indicator for differentiation between LPDs and DLBCLs.

MSCs seeded on bioengineered scaffolds improve skin wound healing in rats

Growing evidence has shown the promise of mesenchymal stromal cells (MSCs) for the treatment of cutaneous wound healing. We have previously demonstrated that MSCs seeded on an artificial dermal matrix, Integra (Integra Lifesciences Corp., Plainsboro, NJ) enriched with platelet-rich plasma (Ematrix) have enhanced proliferative potential in vitro as compared with those cultured on the scaffold alone. In this study, we extended the experimentation by evaluating the efficacy of the MSCs seeded scaffolds in the healing of skin wounds in an animal model in vivo. It was found that the presence of MSCs within the scaffolds greatly ameliorated the quality of regenerated skin, reduced collagen deposition, enhanced reepithelization, increased neo-angiogenesis, and promoted a greater return of hair follicles and sebaceous glands. The mechanisms involved in these beneficial effects were likely related to the ability of MSCs to release paracrine factors modulating the wound healing response. MSC-seeded scaffolds, in fact, up-regulated matrix metalloproteinase 9 expression in the extracellular matrix and enhanced the recruitment of endogenous progenitors during tissue repair. In conclusion, the results of this study provide evidence that the treatment with MSC-seeded scaffolds of cutaneous wounds contributes to the recreation of a suitable microenvironment for promoting tissue repair/regeneration at the implantation sites.

Promising new treatment targets in patients with fibrosing lung disorders

The processes of lung fibrogenesis and fibrotic healing are common to a number of conditions with different etiologies. The lungs are the only affected organ in some cases, whereas in others, several organ systems are involved. Therapeutic options can be discussed from various perspectives. In this review, we address the localization of therapeutic targets with regard to cell compartments, including secreted ligands, cell surface, plasma membrane-cytosol interplay, cytosol and nucleus. Complex approach using stem cell therapy is also discussed. As the prognosis of patients with these disorders remains grim, treatment combinations targeting different molecules within the cell should sometimes be considered. It is reasonable to assume that blocking specific pathways will more likely lead to disease stabilization, while stem cell-based treatments could potentially restore lung architecture. Gene therapy could be a candidate for preventive care in families with proven specific gene polymorphisms and documented familial lung fibrosis. Chronobiology, that takes into account effect of circadian rhythm on cell biology, has demonstrated that timed drug administration can improve treatment outcomes. However, the specific recommendations for optimal approaches are still under debate. A multifaceted approach to interstitial lung disorders, including cooperation between those doing basic research and clinical doctors as well as tailoring research and treatment strategies toward (until now) unmet medical needs, could improve our understanding of the diseases and, above all, provide benefits for our patients.

Proteomic analysis of plasma identifies the Toll-like receptor agonists S100A8/A9 as a novel possible marker for systemic sclerosis phenotype

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune disease characterised by fibrosis of the skin and the internal organs. Except for anticentromere, antitopoisomerase I and antipolymerase III antibodies, there are no reliable circulating markers predicting susceptibility and internal organ complications. This study has exploited a proteome-wide profiling method with the aim to identify new markers to identify SSc phenotype.

METHOD

40 SSc patients were included for proteomic identification. Patients were stratified as having diffuse cutaneous SSc (dcSSc) (n=19) or limited cutaneous SSc (lcSSc) (n=21) according to the extent of skin involvement. As controls 19 healthy donors were included. Blood was drawn and plasma was stored before analysing with the SELDI-TOF-MS. For replication in serum, the cohort was extended with 60 SSc patients.

RESULTS

Proteomic analysis revealed a list of 25 masspeaks that were differentially expressed between SSc patients and healthy controls. One of the peaks was suggestive for S100A8, a masspeak we previously found in supernatant of plasmacytoid dendritic cells from SSc patients. Increased expression of S100A8/A9 in SSc patients was confirmed in replication cohort compared with controls. Intriguingly, S100A8/A9 was highest in patients with limited cutaneous SSc having lung fibrosis.

CONCLUSIONS

S100A8/A9 was robustly found to be elevated in the circulation of SSc patients, suggesting its use as a biomarker for SSc lung disease and the need to further explore the role of TLR in SSc.

Egr1 protein acts downstream of estrogen-leukemia inhibitory factor (LIF)-STAT3 pathway and plays a role during implantation through targeting Wnt4

Embryo implantation is a highly synchronized process between an activated blastocyst and a receptive uterus. Successful implantation relies on the dynamic interplay of estrogen and progesterone, but the key mediators underlying embryo implantation are not fully understood. Here we show that transcription factor early growth response 1 (Egr1) is regulated by estrogen as a downstream target through leukemia inhibitory factor (LIF) signal transducer and activator of transcription 3 (STAT3) pathway in mouse uterus. Egr1 is localized in the subluminal stromal cells surrounding the implanting embryo on day 5 of pregnancy. Estrogen rapidly, markedly, and transiently enhances Egr1 expression in uterine stromal cells, which fails in estrogen receptor α knock-out mouse uteri. STAT3 is phosphorylated by LIF and subsequently recruited on Egr1 promoter to induce its expression. Our results of Egr1 expression under induced decidualization in vivo and in vitro show that Egr1 is rapidly induced after deciduogenic stimulus. Egr1 knockdown can inhibit in vitro decidualization of cultured uterine stromal cells. Chromatin immunoprecipitation data show that Egr1 is recruited to the promoter of wingless-related murine mammary tumor virus integration site 4 (Wnt4). Collectively, our study presents for the first time that estrogen regulates Egr1 expression through LIF-STAT3 signaling pathway in mouse uterus, and Egr1 functions as a critical mediator of stromal cell decidualization by regulating Wnt4.

Androgen deprivation therapy induces androgen receptor-dependent upregulation of Egr1 in prostate cancers

Early growth response gene-1 (Egr1) has a crucial function in the development and progression of prostate cancer. However, whether Egr1 contributes to the transition of advanced androgen-independent prostate cancer (AIPC) from androgen-dependent prostate cancer (ADPC) remains largely unknown. To the best of our knowledge, through immunohistochemical staining methods, we were the first to identify that Egr1 is more highly expressed in AIPC clinical specimens than in androgen-dependent prostate cancer (ADPC). An in vitro study with quantitative RT-PCR and Western blot demonstrated that Egr1 also has a higher expression in androgen-independent PC3 cells than in the androgen-dependent LNCaP cells. Egr1 expression in LNCaP cells was significantly upregulated during the androgen deprivation treatment (ADT) and was re-downregulated through the addition of dihydrotestosterone. Although no variation in PC3 cells was identified, Egr1 responded to dihydrotestosterone and flutamide in the androgen receptor (AR)-transfected PC3 cells. Further investigation with Egr1 agonist and specific siRNA-targeting Egr1 revealed that Egr1 upregulation or downregulation was accompanied by a change in inhibitors of differentiation and DNA binding-1 (Id1) in the same direction in both LNCaP and PC3 cells. The variation is shown to be negatively regulated by androgen through AR during ADT. Our data suggested that upregulated Egr1 might partially contribute to the emergence of AIPC after prolonged ADT. This study also elucidated the potential mechanism underlying Id1 participation in the progression of prostate cancer. Understanding the key molecular events in the transition from ADPC to AIPC may provide new therapeutic intervention strategies for patients with AIPC.

Computational identification of potential transcriptional regulators of TGF-ß1 in human atherosclerotic arteries

TGF-ß is protective in atherosclerosis but deleterious in metastatic cancers. Our aim was to determine whether TGF-ß transcriptional regulation is tissue-specific in early atherosclerosis. The computational methods included 5 steps: (i) from microarray data of human atherosclerotic carotid tissue, to identify the 10 best co-expressed genes with TGFB1 (TGFB1 gene cluster), (ii) to choose the 11 proximal promoters, (iii) to predict the TFBS shared by the promoters, (iv) to identify the common TFs co-expressed with the TGFB1 gene cluster, and (v) to compare the common TFs in the early lesions to those identified in advanced atherosclerotic lesions and in various cancers. Our results show that EGR1, SP1 and KLF6 could be responsible for TGFB1 basal expression, KLF6 appearing specific to atherosclerotic lesions. Among the TFs co-expressed with the gene cluster, transcriptional activators (SLC2A4RG, MAZ) and repressors (ZBTB7A, PATZ1, ZNF263) could be involved in the fine-tuning of TGFB1 expression in atherosclerosis.

Cellular mechanisms of tissue fibrosis. 8. Current and future drug targets in fibrosis: focus on Rho GTPase-regulated gene transcription

Tissue fibrosis occurs with excessive extracellular matrix deposition from myofibroblasts, resulting in tissue scarring and inflammation. It is driven by multiple mediators, such as the G protein-coupled receptor ligands lysophosphatidic acid and endothelin, as well as signaling by transforming growth factor-β, connective tissue growth factor, and integrins. Fibrosis contributes to 45% of deaths in the developed world. As current therapeutic options for tissue fibrosis are limited and organ transplantation is the only effective treatment for end-stage disease, there is an imminent need for efficacious antifibrotic therapies. This review discusses the various molecular pathways involved in fibrosis. It highlights the Rho GTPase signaling pathway and its downstream gene transcription output through myocardin-related transcription factor and serum response factor as a convergence point for targeting this complex set of diseases.

Arecoline stimulated early growth response-1 production in human buccal fibroblasts: suppression by epigallocatechin-3-gallate

BACKGROUND

Early growth response-1 (Egr-1) protein plays an important role in many human fibrotic diseases. Areca nut chewing is the most important risk factor of oral submucous fibrosis (OSF).

METHODS

Egr-1 protein expression in OSF was examined using antibody to Egr-1. Arecoline-induced Egr-1 expression and its signaling pathways were assessed by Western blot analyses in human buccal mucosal fibroblasts (BMFs).

RESULTS

Elevated Egr-1 staining was observed in epithelial cells, fibroblast, and inflammatory cells in 7 of 10 OSF cases. Arecoline, a main alkaloid found in the areca nut, stimulated Egr-1 synthesis in BMFs. Pretreatment with antioxidant N-acetyl-L-cysteine, c-Jun NH2-terminal kinase inhibitor SP600125, and extracellular signal-regulated kinase inhibitor PD98059 significantly reduced arecoline-induced Egr-1 synthesis. Epigallocatechin-3-gallate (EGCG) inhibited arecoline-induced Egr-1 synthesis and collagen gel contraction in a dose-responsive manner.

CONCLUSION

Constitutive Egr-1 expression during areca nut chewing may play a role in the pathogenesis of OSF. EGCG could be a good candidate for prevention or treatment of OSF.

Human gingival fibroblasts display a non-fibrotic phenotype distinct from skin fibroblasts in three-dimensional cultures

Scar formation following skin injury can be a major psychosocial and physiological problem. However, the mechanisms of scar formation are still not completely understood. Previous studies have shown that wound healing in oral mucosa is faster, associates with a reduced inflammatory response and results to significantly reduced scar formation compared with skin wounds. In the present study, we hypothesized that oral mucosal fibroblasts from human gingiva are inherently distinct from fibroblasts from breast and abdominal skin, two areas prone to excessive scar formation, which may contribute to the preferential wound healing outcome in gingiva. To this end, we compared the phenotype of human gingival and skin fibroblasts cultured in in vivo-like three-dimensional (3D) cultures that mimic the cells' natural extracellular matrix (ECM) niche. To establish 3D cultures, five parallel fibroblast lines from human gingiva (GFBLs) and breast skin (SFBLs) were seeded in high density, and cultured for up to 21 days in serum and ascorbic acid containing medium to induce expression of wound-healing transcriptome and ECM deposition. Cell proliferation, morphology, phenotype and expression of wound healing and scar related genes were analyzed by real-time RT-PCR, Western blotting and immunocytochemical methods. The expression of a set of genes was also studied in three parallel lines of human abdominal SFBLs. Findings showed that GFBLs displayed morphologically distinct organization of the 3D cultures and proliferated faster than SFBLs. GFBLs expressed elevated levels of molecules involved in regulation of inflammation and ECM remodeling (MMPs) while SFBLs showed significantly higher expression of TGF-β signaling, ECM and myofibroblast and cell contractility-related genes. Thus, GFBLs display an inherent phenotype conducive for fast resolution of inflammation and ECM remodeling, characteristic for scar-free wound healing, while SFBLs have a profibrotic, scar-prone phenotype.

Solitary fibrous tumors/hemangiopericytomas with different variants of the NAB2-STAT6 gene fusion are characterized by specific histomorphology and distinct clinicopathological features

Recurrent somatic fusions of the two genes, NGFI-A-binding protein 2 (NAB2) and STAT6, located at chromosomal region 12q13, have been recently identified to be presumable tumor-initiating events in solitary fibrous tumors (SFT). Herein, we evaluated a cohort of 52 SFTs/hemangiopericytomas (HPCs) by whole-exome sequencing (one case) and multiplex RT-PCR (all 52 cases), and identified 12 different NAB2-STAT6 fusion variants in 48 cases (92%). All 52 cases showed strong and diffuse nuclear positivity for STAT6 by IHC. We categorized the fusion variants according to their potential functional effects within the predicted fusion protein and found strong correlations with relevant clinicopathological features. Tumors with the most common fusion variant, NAB2ex4-STAT6ex2/3, corresponded to classic pleuropulmonary SFTs with diffuse fibrosis and mostly benign behavior and occurred in older patients (median age, 69 years). In contrast, tumors with the second most common fusion variant, NAB2ex6-STAT6ex16/17, were found in much younger patients (median age, 47 years) and represented typical HPCs from deep soft tissue with a more aggressive phenotype and clinical behavior. In summary, these molecular genetic findings support the concept that classic pleuropulmonary SFT and deep-seated HPC are separate entities that share common features but correlate to different clinical outcome.

Egr-1 upregulates Siva-1 expression and induces cardiac fibroblast apoptosis

The early growth response transcription factor Egr-1 controls cell specific responses to proliferation, differentiation and apoptosis. Expression of Egr-1 and downstream transcription is closely controlled and cell specific upregulation induced by processes such as hypoxia and ischemia has been previously linked to multiple aspects of cardiovascular injury. In this study, we showed constitutive expression of Egr-1 in cultured human ventricular cardiac fibroblasts, used adenoviral mediated gene transfer to study the effects of continuous Egr-1 overexpression and studied downstream transcription by Western blotting, immunohistochemistry and siRNA transfection. Apoptosis was assessed by fluorescence microscopy and flow cytometry in the presence of caspase inhibitors. Overexpression of Egr-1 directly induced apoptosis associated with caspase activation in human cardiac fibroblast cultures in vitro assessed by fluorescence microscopy and flow cytometry. Apoptotic induction was associated with a caspase activation associated loss of mitochondrial membrane potential and transient downstream transcriptional up-regulation of the pro-apoptotic gene product Siva-1. Suppression of Siva-1 induction by siRNA partially reversed Egr-1 mediated loss of cell viability. These findings suggest a previously unknown role for Egr-1 and transcriptional regulation of Siva-1 in the control of cardiac accessory cell death.

Extracellular acidosis stimulates NHE2 expression through activation of transcription factor Egr-1 in the intestinal epithelial cells

Na(+)/H(+) exchangers (NHEs) play important roles in regulating internal pH (pHi), cell volume and neutral Na(+) absorption in the human intestine. Earlier studies have shown that low extracellular pH (pHe) and metabolic acidosis increases the expression and function of NHE1-3 genes. However, transcriptional mechanisms involved remained unknown. Therefore, we investigated the molecular mechanisms underlying acid-induced NHE2 expression in C2BBe1 and SK-CO15 intestinal epithelial cells. Assessing total RNA and protein by RT-PCR and Western blot analysis, respectively, displayed significant increases in the NHE2 mRNA and protein levels in cells exposed to acidic media (pH 6.5 and 6.7) compared to normal medium. Acid treatment was also associated with a significant enhancement in NHE2 transport activity. Quantification of the heterogeneous nuclear RNA indicated that the rate of NHE2 transcription was increased in response to acid. Furthermore, acid caused a significant increase in NHE2 promoter activity confirming transcriptional upregulation. Through functional and mutational studies the acid-response element was mapped to a 15-nucleotide GC-rich sequence at bp -337 to -323 upstream from the transcription start site. We previously identified this element as an overlapping Egr-1/Sp1/Egr-1 motif that was essential for the NHE2 upregulation by mitogen-induced transcription factor Egr-1. Cells exposed to acid exhibited a temporal increase in Egr-1 mRNA and protein expression. These events were followed by Egr-1 nuclear accumulation, as detected by immunofluorescence microscopy, and potentiated its in vitro and in vivo interaction with the NHE2 promoter. Disruption of ESE motif and knockdown of Egr-1 expression by targeted small interfering RNA abrogated the acid-induced NHE2 transcriptional activity. These data indicate that the acid-dependent NHE2 stimulation is implemented by transcriptional upregulation of NHE2 via acid-induced Egr-1 in the intestinal epithelial cells.

Autotaxin and lysophosphatidic acid signalling in lung pathophysiology

Autotaxin (ATX or ENPP2) is a secreted glycoprotein widely present in biological fluids. ATX primarily functions as a plasma lysophospholipase D and is largely responsible for the bulk of lysophosphatidic acid (LPA) production in the plasma and at inflamed and/or malignant sites. LPA is a phospholipid mediator produced in various conditions both in cells and in biological fluids, and it evokes growth-factor-like responses, including cell growth, survival, differentiation and motility, in almost all cell types. The large variety of LPA effector functions is attributed to at least six G-protein coupled LPA receptors (LPARs) with overlapping specificities and widespread distribution. Increased ATX/LPA/LPAR levels have been detected in a large variety of cancers and transformed cell lines, as well as in non-malignant inflamed tissues, suggesting a possible involvement of ATX in chronic inflammatory disorders and cancer. In this review, we focus exclusively on the role of the ATX/LPA axis in pulmonary pathophysiology, analysing the effects of ATX/LPA on pulmonary cells and leukocytes in vitro and in the context of pulmonary pathophysiological situations in vivo and in human diseases.

Genome-wide approaches reveal EGR1-controlled regulatory networks associated with neurodegeneration

Early growth response gene 1 (Egr1) is a member of the immediate early gene (IEG) family of transcription factors and plays a role in memory formation. To identify EGR1 target genes in brain of Alzheimer's disease (AD) model mice - APP23, we applied chromatin immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq). Functional annotation of genes associated with EGR1 binding revealed a set of related networks including synaptic vesicle transport, clathrin-mediated endocytosis (CME), intracellular membrane fusion and transmission of signals elicited by Ca(2+) influx. EGR1 binding is associated with significant enrichment of activating chromatin marks and appears enriched near genes that are up-regulated in the brains of APP23 mice. Among the putative EGR1 targets identified and validated in this study are genes related to synaptic plasticity and transport of proteins, such as Arc, Grin1, Syn2, Vamp2 and Stx6, and genes implicated in AD such as Picalm, Psen2 and App. We also demonstrate a potential regulatory link between EGR1 and its newly identified targets in vivo, since conditions that up-regulate Egr1 levels in brain, such as a spatial memory test, also lead to increased expression of the targets. On the other hand, protein levels of EGR1 and ARC, SYN2, STX6 and PICALM are significantly lower in the brain of adult APP mice than in age-matched wild type animals. The results of this study suggest that EGR1 regulates the expression of genes involved in CME, vesicular transport and synaptic transmission that may be critical for AD pathogenesis.

Novel pathways and molecular targets for the treatment of sarcoma

Sarcomas collectively represent over 100 different subtypes of bone and soft tissue tumors of mesenchymal origin. The low response rate to cytotoxic chemotherapies has necessitated the need for development of either histologically driven or pathway-specific targeted therapies. As our understanding of the molecular mechanisms driving certain subtypes is rapidly advancing, the number of targeted therapies is also increasing. Recently identified novel druggable targets include the MDM2 amplifications in well-differentiated and dedifferentiated liposarcomas, the new translocation NAB2:STAT6 of solitary fibrous tumors, the angiopoeitin-TIE2 pathway in angiosarcoma, the suppression of Mcl1 in X:18/synovial sarcomas, the mTOR pathway in malignant peripheral nerve sheath tumors, CDK4 in alveolar rhabdomyosarcoma, cMET regulation in alveolar soft parts sarcoma, the metabolic abnormalities in wild-type/SHD GIST, and the lack of argininosuccinate synthetase 1 expression seen in most sarcomas. It is through a fundamental understanding of sarcoma biology that clinical trials based on molecular targets can be developed.

Early growth response 3 (Egr-3) is induced by transforming growth factor-β and regulates fibrogenic responses

Members of the early growth response (Egr) gene family of transcription factors have nonredundant biological functions. Although Egr-3 is implicated primarily in neuromuscular development and immunity, its regulation and role in tissue repair and fibrosis has not been studied. We now show that in normal skin fibroblasts, Egr-3 was potently induced by transforming growth factor-β via canonical Smad3. Moreover, transient Egr-3 overexpression was sufficient to stimulate fibrotic gene expression, whereas deletion of Egr-3 resulted in substantially attenuated transforming growth factor-β responses. Genome-wide expression profiling in fibroblasts showed that genes associated with tissue remodeling and wound healing were prominently up-regulated by Egr-3. Notably, <5% of fibroblast genes regulated by Egr-1 or Egr-2 were found to be coregulated by Egr-3, revealing substantial functional divergence among these Egr family members. In a mouse model of scleroderma, development of dermal fibrosis was accompanied by accumulation of Egr-3-positive myofibroblasts in the lesional tissue. Moreover, skin biopsy samples from patients with scleroderma showed elevated Egr-3 levels in the dermis, and Egr-3 mRNA levels correlated with the extent of skin involvement. These results provide the first evidence that Egr-3, a functionally distinct member of the Egr family with potent effects on inflammation and immunity, is up-regulated in scleroderma and is necessary and sufficient for profibrotic responses, suggesting important and distinct roles in the pathogenesis of fibrosis.

Social descent with territory loss causes rapid behavioral, endocrine and transcriptional changes in the brain

In social species that form hierarchies where only dominant males reproduce, lower-ranking individuals may challenge higher-ranking ones, often resulting in changes in relative social status. How does a losing animal respond to loss of status? Here, using the African cichlid fish Astatotilapia burtoni, we manipulated the social environment, causing males to descend in rank, and then examined changes in behavior, circulating steroids and immediate early gene (IEG) expression (cfos, egr-1) in micro-dissected brain regions as a proxy for neuronal activation. In particular, we examined changes in the conserved 'social behavior network' (SBN), a collection of brain nuclei known to regulate social behaviors across vertebrates. Astatotilapia burtoni has rapidly reversible dominant-subordinate male phenotypes, so that within minutes, descending males lost their bright body coloration, switched to submissive behaviors and expressed higher plasma cortisol levels compared with non-descending and control males. Descending males had higher IEG expression throughout the SBN, but each brain region showed a distinct IEG-specific response in either cfos or egr-1 levels, but not both. Overall, SBN IEG patterns in descending males were distinctly different from the pattern observed in males ascending (subordinate to dominant) in social status. These results reveal that the SBN rapidly coordinates the perception of social cues about status that are of opposite valence, and translates them into appropriate phenotypic changes. This shows for the first time in a non-mammalian vertebrate that dropping in social rank rapidly activates specific socially relevant brain nuclei in a pattern that differs from when males rise to a higher status position.

Inflammation, wound repair, and fibrosis: reassessing the spectrum of tissue injury and resolution

Estimates from various disease-specific registries suggest that chronic inflammatory and fibrotic disorders affect a large proportion of the world's population, yet therapies for these conditions are largely ineffective. Recent advances in our collective understanding of mechanisms underlying both physiological and pathological repair of tissue injury are informing new clinical approaches to deal with various human inflammatory and fibrotic diseases. This 2013 Annual Review Issue of The Journal of Pathology offers an up-to-date glimpse of ongoing research in the fields of inflammation, wound healing, and tissue fibrosis, and highlights novel pathways and mechanisms that may be exploited to provide newer, more effective treatments to patients worldwide suffering from these conditions.