Epithelial monolayer wounding stimulates binding of USF-1 to an E-box motif in the plasminogen activator inhibitor type 1 gene

SERPINE1: Role in Cholangiocarcinoma Progression and a Therapeutic Target in the Desmoplastic Microenvironment

A heterogenous population of inflammatory elements, other immune and nonimmune cells and cancer-associated fibroblasts (CAFs) are evident in solid malignancies where they coexist with the growing tumor mass. In highly desmoplastic malignancies, CAFs are the prominent mesenchymal cell type in the tumor microenvironment (TME), where their presence and abundance signal a poor prognosis. CAFs play a major role in the progression of various cancers by remodeling the supporting stroma into a dense, fibrotic matrix while secreting factors that promote the maintenance of cancer stem-like characteristics, tumor cell survival, aggressive growth and metastasis and reduced sensitivity to chemotherapeutics. Tumors with high stromal fibrotic signatures are more likely to be associated with drug resistance and eventual relapse. Identifying the molecular underpinnings for such multidirectional crosstalk among the various normal and neoplastic cell types in the TME may provide new targets and novel opportunities for therapeutic intervention. This review highlights recent concepts regarding the complexity of CAF biology in cholangiocarcinoma, a highly desmoplastic cancer. The discussion focuses on CAF heterogeneity, functionality in drug resistance, contributions to a progressively fibrotic tumor stroma, the involved signaling pathways and the participating genes.

A novel risk score model for stomach adenocarcinoma based on the expression levels of 10 genes

Stomach adenocarcinoma (STAD) accounts for 95% of cases of malignant gastric cancer, which is the third leading cause of cancer-associated mortality worldwide. The pathogenesis and effective diagnosis of STAD have become popular topics for research in the previous decade. In the present study, high-throughput RNA sequencing expression profiles and clinical data from patients with STAD were obtained from The Cancer Genome Atlas database and were used as a training dataset to screen differentially expressed genes (DEGs). Prognostic DEGs were identified using univariate Cox regression analysis and were further screened by the least absolute shrinkage and selection operator regularization regression algorithm. The resulting genes were used to construct a risk score model, the validation and effectiveness evaluation of which were performed on an independent dataset downloaded from the Gene Expression Omnibus database. Stratified and functional pathway (gene set enrichment) analyses were performed on groups with different estimated prognosis. A total of 92 genes significantly associated with STAD prognosis were obtained by univariate Cox regression analysis, and 10 prognosis-associated DEGs; hemoglobin b, chromosome 4 open reading frame 48, Dickkopf WNT signaling pathway inhibitor 1, coagulation factor V, serpin family E member 1, transmembrane protein 200A, NADPH oxidase organizer 1, C-X-C motif chemokine ligand 3, mannosidase endo-α-like and tripartite motif-containing 31; were selected for the development of the risk score model. The reliability of this prognostic method was verified using a validation set, and the results of multivariate Cox analysis indicated that the risk score may serve as an independent prognostic factor. In functional DEG analysis, eight Kyoto Encyclopedia of Genes and Genomes pathways were identified to be significantly associated with STAD risk factors. Thus, the 10-gene risk score model established in the present study was regarded as credible. This risk assessment tool may help identify patients with a high risk of STAD, and the proposed prognostic mRNAs may be useful in elucidating STAD pathogenesis.

Identification of SERPINE1 as a Regulator of Glioblastoma Cell Dispersal with Transcriptome Profiling

High mortality rates of glioblastoma (GBM) patients are partly attributed to the invasive behavior of tumor cells that exhibit extensive infiltration into adjacent brain tissue, leading to rapid, inevitable, and therapy-resistant recurrence. In this study, we analyzed transcriptome of motile (dispersive) and non-motile (core) GBM cells using an in vitro spheroid dispersal model and identified SERPINE1 as a modulator of GBM cell dispersal. Genetic or pharmacological inhibition of SERPINE1 reduced spheroid dispersal and cell adhesion by regulating cell-substrate adhesion. We examined TGFβ as a potential upstream regulator of SERPINE1 expression. We also assessed the significance of SERPINE1 in GBM growth and invasion using TCGA glioma datasets and a patient-derived orthotopic GBM model. SERPINE1 expression was associated with poor prognosis and mesenchymal GBM in patients. SERPINE1 knock-down in primary GBM cells suppressed tumor growth and invasiveness in the brain. Together, our results indicate that SERPINE1 is a key player in GBM dispersal and provide insights for future anti-invasive therapy design.

Targeted Inhibition of PAI-1 Activity Impairs Epithelial Migration and Wound Closure Following Cutaneous Injury

Objective: Aberrant plasminogen activator inhibitor-1 (PAI-1) expression and activity have been implicated in bleeding disorders, multiorgan fibrosis, and wound healing anomalies. This study details the physiological consequences of targeted PAI-1 functional inhibition on cutaneous injury repair. Approach: Dorsal skin wounds from FVB/NJ mice, created with a 4 mm biopsy punch, were treated topically with the small-molecule PAI-1 antagonist tiplaxtinin (or vehicle control) for 5 days and then analyzed for markers of wound repair. Results: Compared to controls, tiplaxtinin-treated wounds displayed dramatic decreases in wound closure and re-epithelialization. PAI-1 immunoreactivity was evident at the migratory front in all injury sites indicating these effects were due to PAI-1 functional blockade and not PAI-1 expression changes. Stimulated HaCaT keratinocyte migration in response to recombinant PAI-1 in vitro was similarly attenuated by tiplaxtinin. While tiplaxtinin had no effect on keratinocyte proliferation, cell cycle progression, or apoptosis, it effectively reduced collagen deposition, the number of Ki-67⁺ fibroblasts, and incidence of differentiated myofibroblasts (i.e., smooth muscle α-actin immunoreactive cells), but not fibroblast apoptosis. Innovation: The role for PAI-1 in hemostasis and fibrinolysis is established; involvement of PAI-1 in cutaneous wound healing, however, remains unclear. This study tests the effect of a small-molecule PAI-1 inhibitor in a murine model of skin wound repair. Conclusion: Loss of PAI-1 activity significantly impaired wound closure. Re-epithelialization and fibroblast recruitment/differentiation were both reduced in tiplaxtinin-treated mice. Therapies directed at manipulation of PAI-1 expression and/or activity may have applicability as a treatment option for chronic wounds and scarring disorders.

The mRNA expressions and immunohistochemistry of factors involved in angiogenesis and lymphangiogenesis in the early stage of rat skin incision wounds

Wound healing evaluation is important in forensic pathology, in which angiogenesis plays an important role. We have already shown that vascular endothelial growth factor A (VEGF) is produced in the rat skin incision wounds by neutrophils, endothelial cells, and fibroblasts. In this study, we assessed the changes in the mRNA expressions of various factors possibly involved in angiogenesis including angiopoietin (ANGPT) 1 and 2, cadherin 5 (CDH5), granulocyte-macrophage colony stimulating factor (CSF2/GM-CSF), granulocyte colony stimulating factor (CSF3/G-CSF), chemokine (C-X-C motif) ligand 2 (CXCL2), chemokine (C-X-C motif) ligand12 (CXCL12/SDF1), endothelin 1 (ET1), fibroblast growth factor 1 (FGF 1), hepatocyte growth factor (HGF), hypoxia inducible factor 1 alpha (HIF1a), leptin, matrix metallopepitidase 9 (MMP9), serpine/plasminogen activator inhibitor1 (PAI1), platelet-derived growth factor-A (PDGF-A), transforming growth factor alpha and beta 1 (TGFa and b1), tenomodulin (TNMD), and troponin I type 2 (TNNI2) in the early stage of the rat skin incision wounds by real time RT-PCR. Factors reported to be involved in lymphangiogenesis such as fibroblast growth factor 2 (FGF 2), c-fos induced growth factor (FIGF/VEGF-D), forkhead box C2 (FOXC2), and prospero homeobox 1 (PROX1) were also studied. One and 3 days after the dorsal skin incisions, wounds on male Sprague-Dawley rats showed the statistically significant increases in the mRNA expressions for CXCL2, CSF3, MMP9, PAI1, and CSF2, whereas TGFa, TNNI2, FGF1, TNMD, leptin, and CXCL12 showed the statistically significant decreases. Interestingly, lymphgangiogenic factors FOXC2, PROX1, and FGF2 also showed the statistically significant decreases. In situ hybridization and immunohistochemistry showed the mRNA and protein positivity in endothelial cells, fibroblasts, and some leukocytes at the bottom of the wound tissue for PAI1, CSF3, and MMP9, 1 day after the skin incisions. Our novel findings show the possible involvement of several factors involved in angiogenesis and lymphangiogenesis in the early stage of wound healing process, which may be useful for forensic wound evaluations.

Protein kinases as switches for the function of upstream stimulatory factors: implications for tissue injury and cancer

The upstream stimulatory factors (USFs) are regulators of important cellular processes. Both USF1 and USF2 are supposed to have major roles in metabolism, tissue protection and tumor development. However, the knowledge about the mechanisms that control the function of USFs, in particular in tissue protection and cancer, is limited. Phosphorylation is a versatile tool to regulate protein functions. Thereby, phosphorylation can positively or negatively affect different aspects of transcription factor function including protein stability, protein-protein interaction, cellular localization, or DNA binding. The present review aims to summarize the current knowledge about the regulation of USFs by direct phosphorylation and the consequences for USF functions in tissue protection and cancer.

SERPINE1: A Molecular Switch in the Proliferation-Migration Dichotomy in Wound-"Activated" Keratinocytes

Significance: A highly interactive serine protease/plasmin/matrix metalloproteinase axis regulates stromal remodeling in the wound microenvironment. Current findings highlight the importance of stringent controls on protease expression and their topographic activities in cell proliferation, migration, and tissue homeostasis. Targeting elements in this cascading network may lead to novel therapeutic approaches for fibrotic diseases and chronic wounds. Recent Advances: Matrix-active proteases and their inhibitors orchestrate wound site tissue remodeling, cell migration, and proliferation. Indeed, the serine proteases urokinase plasminogen activator and tissue-type plasminogen activator (uPA/tPA) and their major phsyiological inhibitor, plasminogen activator inhibitor-1 (PAI-1; serine protease inhibitor clade E member 1 [SERPINE1]), are upregulated in several cell types during injury repair. Coordinate expression of proteolytic enzymes and their inhibitors in the wound bed provides a mechanism for fine control of focal proteolysis to facilitate matrix restructuring and cell motility in complex environments. Critical Issues: Cosmetic and tissue functional consequences of wound repair anomalies affect the quality of life of millions of patients in the United States alone. The development of novel therapeutics to manage individuals most affected by healing anomalies will likely derive from the identification of critical, translationally accessible, control elements in the wound site microenvironment. Future Directions: Activation of the PAI-1 gene early after wounding, its prominence in the repair transcriptome and varied functions suggest a key role in the global cutaneous injury response program. Targeting PAI-1 gene expression and/or PAI-1 function with molecular genetic constructs, neutralizing antibodies or small molecule inhibitors may provide a novel, therapeutically relevant approach, to manage the pathophysiology of wound healing disorders associated with deficient or excessive PAI-1 levels.

Urokinase receptor orchestrates the plasminogen system in airway epithelial cell function

PURPOSE

The plasminogen system plays many roles in normal epithelial cell function, and components are elevated in diseases, such as cancer and asthma. The relative contribution of each component to epithelial function is unclear. We characterized normal cell function in airway epithelial cells with increased expression of selected pathway components.

METHODS

BEAS-2B R1 bronchial epithelial cells stably overexpressing membrane urokinase plasminogen activator receptor (muPAR), soluble spliced uPAR (ssuPAR), the ligand (uPA) or inhibitors (PAI1 or PAI2), were characterized for pathway expression. Cell function was examined using proliferation, apoptosis, and scratch wound assays. A549 alveolar epithelial cells overexpressing muPAR were similarly characterized and downstream plasmin activity, MMP-1, and MMP-9 measured.

RESULTS

Elevated expression of individual components led to changes in the plasminogen system expression profile, indicating coordinated regulation of the pathway. Increased muPAR expression augmented wound healing rate in BEAS-2B R1 and attenuated repair in A549 cells. Elevated expression of other system components had no effect on cell function in BEAS-2B R1 cells. This is the first study to investigate activity of the splice variant ssuPAR, with results suggesting that this variant plays a limited role in epithelial cell function in this model.

CONCLUSIONS

Our data highlight muPAR as the critical molecule orchestrating effects of the plasminogen system on airway epithelial cell function. These data have implications for diseases, such as cancer and asthma, and suggest uPAR as the key therapeutic target for the pathway in approaches to alter epithelial cell function.

Endogenous retrovirus-K promoter: a landing strip for inflammatory transcription factors?

Humans are symbiotic organisms; our genome is populated with a substantial number of endogenous retroviruses (ERVs), some remarkably intact, while others are remnants of their former selves. Current research indicates that not all ERVs remain silent passengers within our genomes; re-activation of ERVs is often associated with inflammatory diseases. ERVK is the most recently endogenized and transcriptionally active ERV in humans, and as such may potentially contribute to the pathology of inflammatory disease. Here, we showcase the transcriptional regulation of ERVK. Expression of ERVs is regulated in part by epigenetic mechanisms, but also depends on transcriptional regulatory elements present within retroviral long terminal repeats (LTRs). These LTRs are responsive to both viral and cellular transcription factors; and we are just beginning to appreciate the full complexity of transcription factor interaction with the viral promoter. In this review, an exploration into the inflammatory transcription factor sites within the ERVK LTR will highlight the possible mechanisms by which ERVK is induced in inflammatory diseases.

Association analysis of USF1 gene polymorphisms and total unstable carotid plaque area in atherosclerotic stroke patients

Polymorphisms of the upstream stimulatory factor 1 (USF1) have been associated with carotid artery intima-media thickness and coronary atherosclerotic lesions. Unstable carotid plaque is an atherosclerotic change of vascular morphology that has been correlated with cerebrovascular ischemic symptoms. Associations of three single nucleotide polymorphisms of the USF1 gene with total unstable carotid plaque area (CPA) were investigated in Chinese atherosclerotic stroke patients. We recruited 668 atherosclerotic stroke patients and 602 controls. Total unstable CPA values were measured by ultrasound. Genotypes were analyzed using polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) or mismatched PCR-RFLP. A significant difference in total unstable CPA was found for rs2516838 and rs2516839 genotypes (P = 0.039 and 0.046, respectively) in atherosclerotic stroke patients with unstable carotid plaque. Furthermore, in multiple logistic regression analysis adjusted by age, sex, BMI, hypertension, smoking status, glucose, total cholesterol, triglycerides, high-density lipoprotein-cholesterols, low-density lipoprotein-cholesterols and high-sensitivity C-reactive protein, significant associations were seen between the total unstable CPA values and genotypes of the rs2516838 or the rs2516839 in these patients. The rare allele C of rs2516838 or rare allele A of rs2516839 could predict relative low total unstable CPA values. The rs2516838 and rs2516839 polymorphisms of USF1 influence total unstable CPA in atherosclerotic stroke patients, which might be new markers to predict the risk of recurrence for this disease.

Ascochlorin suppresses TGF-β1-induced PAI-1 expression through the inhibition of phospho-EGFR in rat kidney fibroblast cells

Fibrosis is induced by the excessive and abnormal deposition of extracellular matrix (ECM) with various growth factors in tissues. Transforming growth factor-β1 (TGF-β1), the growth factor involved in fibrosis, modulates ECM synthesis and accumulation. TGF-β1 enhances the production of stimulators of ECM synthesis such as plasminogen activator inhibitor type 1 (PAI-1). As such, PAI-1 expression directly influences the proteolysis, invasion, and accumulation of ECM. It was shown in this study that ascochlorin, a prenylpenl antiobiotic, prevents the expression of profibrotic factors, such as PAI-1 and collagen type I, and that the TGF-β1-induced PAI-1 promoter activity is inhibited by ascochlorin. Ascochlorin abolishes the phosphorylation of the EGFR-MEK-ERK signaling pathway to regulate the TGF-β1-induced expression of PAI-1 without the inhibition of TβRII phosphorylation. Furthermore, the MEK inhibitor and EGFR siRNA block PAI-1 expression, and the Raf-1, MEK, and ERK signaling pathways for the regulation of PAI-1 expression. Ascochlorin suppresses the matrix metalloproteinases (MMPs) activity to activate the heparin-binding EGF-like growth factor (HB-EGF), to induce the phosphorylation of EGFR, and the MMPs inhibitor suppresses EGFR phosphorylation and the PAI-1 mRNA levels. These results suggest that ascochlorin prevents the expression of PAI-1 via the inhibition of an EGFR-dependent signal transduction pathway activated by MMPs.

PAI-1: An Integrator of Cell Signaling and Migration

Cellular migration, over simple surfaces or through complex stromal barriers, requires coordination between detachment/re-adhesion cycles, involving structural components of the extracellular matrix and their surface-binding elements (integrins), and the precise regulation of the pericellular proteolytic microenvironment. It is now apparent that several proteases and protease inhibitors, most notably urokinase plasminogen activator (uPA) and plasminogen activator inhibitor type-1 (PAI-1), also interact with several cell surface receptors transducing intracellular signals that significantly affect both motile and proliferative programs. These events appear distinct from the original function of uPA/PAI-1 as modulators of the plasmin-based proteolytic cascade. The multifaceted interactions of PAI-1 with specific matrix components (i.e., vitronectin), the low-density lipoprotein receptor-related protein-1 (LRP1), and the uPA/uPA receptor complex have dramatic consequences on the migratory phenotype and may underlie the pathophysiologic sequalae of PAI-1 deficiency and overexpression. This paper focuses on the increasingly intricate role of PAI-1 as a major mechanistic determinant of the cellular migratory phenotype.

Upstream stimulatory factor-2 mediates quercetin-induced suppression of PAI-1 gene expression in human endothelial cells

The polyphenol quercetin (Quer) represses expression of the cardiovascular disease risk factor plasminogen activator inhibitor-1 (PAI-1) in cultured endothelial cells (ECs). Transfection of PAI-1 promoter-luciferase reporter deletion constructs identified a 251-bp fragment (nucleotides -800 to -549) responsive to Quer. Two E-box motifs (CACGTG), at map positions -691 (E-box1) and -575 (E-box2), are platforms for occupancy by several members of the c-MYC family of basic helix-loop-helix leucine zipper (bHLH-LZ) proteins. Promoter truncation and electrophoretic mobility shift/supershift analyses identified upstream stimulatory factor (USF)-1 and USF-2 as E-box1/E-box2 binding factors. ECs co-transfected with a 251 bp PAI-1 promoter fragment containing the two E-box motifs (p251/luc) and a USF-2 expression vector (pUSF-2/pcDNA) exhibited reduced luciferase activity versus p251/luc alone. Overexpression of USF-2 decreased, while transfection of a dominant-negative USF construct increased, EC growth consistent with the known anti-proliferative properties of USF proteins. Quer-induced decreases in PAI-1 expression and reduced cell proliferation may contribute, at least in part, to the cardioprotective benefit associated with daily intake of polyphenols.

The TGF-beta1/upstream stimulatory factor-regulated PAI-1 gene: potential involvement and a therapeutic target in Alzheimer's disease

Amyloid peptide (Aβ) aggregates, derived from initial β-site proteolytic processing of the amyloid precursor protein (APP), accumulate in the brains of Alzheimer's disease patients. The plasmin-generating cascade appears to serve a protective role in the central nervous system since plasmin-mediated proteolysis of APP utilizes the α site, eventually generating nontoxic peptides, and plasmin also degrades Aβ. The conversion of plasminogen to plasmin by tissue-type plasminogen activator in the brain is negatively regulated by plasminogen activator inhibitor type-1 (PAI-1) resulting in attenuation of plasmin-dependent substrate degradation with resultant accumulation of Aβ. PAI-1 and its major physiological inducer TGF-β1, moreover, are increased in models of Alzheimer's disease and have been implicated in the etiology and progression of human neurodegenerative disorders. This review highlights the potential role of PAI-1 and TGF-β1 in this process. Current molecular events associated with TGF-β1-induced PAI-1 transcription are presented with particular relevance to potential targeting of PAI-1 gene expression as a molecular approach to the therapy of neurodegenerative diseases associated with increased PAI-1 expression such as Alzheimer's disease.

Molecular basis for hair loss in mice carrying a novel nonsense mutation (Hrrh-R ) in the hairless gene (Hr)

Animal models carrying mutations in the hairless (Hr) gene provide a rich resource for study of hair follicle biology. A spontaneous mouse mutant with a phenotype strikingly similar to rhino mutants of Hr arose spontaneously in the mouse facility at Oak Ridge National Laboratory. Sequence analysis of Hr in these mutants uncovered a nonsense mutation in exon 12, designated as Hr(rh-R) (rhino, Oak Ridge). The mutation led to significant reduction in Hr mRNA levels, predicted to be due to nonsense-mediated decay. Histological analysis indicated dilated hair follicle infundibula at 14 days of age that rapidly became filled with cornified material. Microarray analyses revealed that expression levels of many genes involved in keratinocyte differentiation, epidermal regeneration, and wound healing were significantly upregulated before morphological detection of the phenotype, suggesting their role in onset of the Hr(rh-R) phenotype. Identification of this new Hr allele and the underlying molecular alterations allows further understanding of the role of Hr in hair follicle biology.

Id3 is a novel atheroprotective factor containing a functionally significant single-nucleotide polymorphism associated with intima-media thickness in humans

RATIONALE

The gene encoding the helix-loop-helix transcription factor Id3 (inhibitor of differentiation-3) is located within atherosclerosis susceptibility loci of both mice and humans, yet its influence on atherosclerosis is not known.

OBJECTIVE

The present study sought to determine whether polymorphisms in the ID3 gene were associated with indices of atherosclerosis in humans and if loss of Id3 function modulated atherogenesis in mice.

METHODS AND RESULTS

Six tagging single-nucleotide polymorphisms (SNPs) (tagSNPs) in the human ID3 gene were assessed in participants of the Diabetes Heart Study. One tagSNP, rs11574, was independently associated with carotid intima-media thickness (IMT). The human ID3 variant at rs11574 results in an alanine to threonine substitution in the C terminus. To determine the effect of this polymorphism on the basic function of Id3, site-directed mutagenesis of the human ID3 gene at rs11574 was performed. Results demonstrated a significant reduction in coimmunoprecipitation of the known E-protein partner, E12, with Id3 when it contains the sequence encoded by the risk allele (Id3105T). Further, Id3105T had an attenuated ability to modulate E12-mediated transcriptional activation compared to Id3 containing the ancestral allele (Id3105A). Microarray analysis of vascular smooth muscle cells from WT and Id3(-/-) mice revealed significant modulation of multiple gene pathways implicated in atherogenesis. Moreover, Id3(-/-)ApoE(-/-) mice developed significantly more atherosclerosis in response to 32 weeks of Chow or Western diet feeding than Id3(+/+)ApoE(-/-) mice.

CONCLUSIONS

Taken together, results provide novel evidence that Id3 is an atheroprotective factor and link a common SNP in the human ID3 gene to loss of Id3 function and increased IMT.

Supraphysiologic extracellular pressure inhibits intestinal epithelial wound healing independently of luminal nutrient flow

BACKGROUND

Luminal pressure may injure the gut mucosa in obstruction, ileus, or inflammatory bowel disease.

METHODS

We formed Roux-en-Y anastomoses in 19 mice, creating proximal and defunctionalized partially obstructed limbs and a distal limb to vary luminal pressure and flow. We induced mucosal ulcers by serosal acetic acid, and assessed proliferation (proliferating cell nuclear antigen) and ERK (immunoblotting). Parallel studies compared Caco-2 enterocyte migration and proliferation after pressure and/or ERK blockade.

RESULTS

At 3 days, anastomoses were probe-patent, proximal and distal limbs contained chyme, and defunctionalized limbs were empty. The proximal and defunctionalized limbs showed increased pressure and slower healing despite increased proliferation, ERK protein, and ERK activation. In vitro, pressure decreased Caco-2 migration across collagen or fibronectin, stimulated proliferation, and activated ERK. However, ERK blockade did not prevent pressure effects.

CONCLUSIONS

Luminal pressure during obstruction or ileus may impair mucosal healing independently of luminal flow despite increased mitosis and ERK activation.

PAI-1 and functional blockade of SNAI1 in breast cancer cell migration

Introduction

Snail, a family of transcriptional repressors implicated in cell movement, has been correlated with tumour invasion. The Plasminogen Activation (PA) system, including urokinase plasminogen activator (uPA), its receptor and its inhibitor, plasminogen activator inhibitor type 1(PAI-1), also plays a key role in cancer invasion and metastasis, either through proteolytic degradation or by non-proteolytic modulation of cell adhesion and migration. Thus, Snail and the PA system are both over-expressed in cancer and influence this process. In this study we aimed to determine if the activity of SNAI1 (a member of the Snail family) is correlated with expression of the PA system components and how this correlation can influence tumoural cell migration.

Methods

We compared the invasive breast cancer cell-line MDA-MB-231 expressing SNAI1 (MDA-mock) with its derived clone expressing a dominant-negative form of SNAI1 (SNAI1-DN). Expression of PA system mRNAs was analysed by cDNA microarrays and real-time quantitative RT-PCR. Wound healing assays were used to determine cell migration. PAI-1 distribution was assessed by immunostaining.

Results

We demonstrated by both cDNA microarrays and real-time quantitative RT-PCR that the functional blockade of SNAI1 induces a significant decrease of PAI-1 and uPA transcripts. After performing an in vitro wound-healing assay, we observed that SNAI1-DN cells migrate more slowly than MDA-mock cells and in a more collective manner. The blockade of SNAI1 activity resulted in the redistribution of PAI-1 in SNAI1-DN cells decorating large lamellipodia, which are commonly found structures in these cells.

Conclusions

In the absence of functional SNAI1, the expression of PAI-1 transcripts is decreased, although the protein is redistributed at the leading edge of migrating cells in a manner comparable with that seen in normal epithelial cells.

Allelic variants of upstream transcription factor 1 associate with carotid artery intima-media thickness: the Cardiovascular Risk in Young Finns study

BACKGROUND

Polymorphisms of the upstream transcription factor 1 (USF1) have been associated with familial combined hyperlipidemia and coronary heart disease. The impact of this gene on subclinical atherosclerosis is unknown. Associations of 3 allelic variants of the USF1 gene and their haplotypes with carotid artery intima - media thickness (IMT), carotid artery compliance (CAC) and brachial artery flow mediated dilatation (FMD) were studied in a population of Finnish healthy young adults.

METHODS AND RESULTS

The study population comprised 2,281 individuals participating in the Cardiovascular Risk in Young Finns study. IMT, CAC and FMD values were measured by ultrasound examination. Genotypes were analysed using the 5' nuclease assay. A significant difference in IMT was found for usf1s1 (rs3737787) and usf1s8 (rs2516838) genotypes (p-values 0.046 and 0.021, respectively). Moreover, there was a significant difference between groups in haplotype 1 and haplotype 2 for IMT (p-values 0.011 and 0.028 respectively). In multivariate stepwise linear regression models adjusted by age, sex, body mass index, systolic and diastolic blood pressures, smoking, C-reactive protein, glucose, high- and low-density lipoprotein-cholesterols and triglycerides there were significant associations for the usf1s1 minor genotype AA to predict low IMT (p=0.038) and usf1s8 minor genotype GG to predict high IMT (p=0.003). There was also a significant association for haplotype 2 to predict low IMT in the otherwise similar multivariate model (p=0.006). No associations were found for polymorphisms and CAC, FMD or serum lipids.

CONCLUSIONS

The rs2516838 and rs3737787 polymorphisms of USF1 influence the carotid artery IMT, which is a new finding.

Enhancement of prostaglandin D(2) production through cyclooxygenase-2 and lipocalin-type prostaglandin D synthase by upstream stimulatory factor 1 in human brain-derived TE671 cells under serum starvation

We found that prostaglandin (PG) D(2) production was induced through transcriptional activation of cyclooxygenase (COX)-2 and lipocalin-type PGD synthase (L-PGDS) genes under serum-starved conditions in human brain-derived TE671 cells. Analysis of promoter and intron regions of the human L-PGDS gene demonstrated that an atypical E-box within intron 4 mediated serum starvation-induced up-regulation of L-PGDS gene expression. The results of electrophoretic mobility shift assay and chromatin immunoprecipitation assay showed that upstream stimulatory factor (USF) 1 bound to this atypical E-box. USF1 gene expression was also enhanced during serum starvation in TE671 cells through activation of p38 mitogen activated protein kinase, and the efficiency of the binding of USF1 to the atypical E-box was clearly increased by serum starvation. Administration of USF1 siRNA suppressed both L-PGDS and COX-2 gene expression and PGD(2) production. Moreover, NS-398, a COX-2 inhibitor and AT-56, an L-PGDS inhibitor, suppressed PGD(2) production in TE671 cells cultured under the serum-starved condition. These results indicate that PGD(2) production stimulated by serum starvation is mediated by both COX-2 and L-PGDS through enhancement of USF1 in TE671 cells.

SERPINE1 (PAI-1) is deposited into keratinocyte migration "trails" and required for optimal monolayer wound repair

Cutaneous tissue injury, both in vivo and in vitro, initiates activation of a "wound repair" transcriptional program. One such highly induced gene encodes plasminogen activator inhibitor type-1 (PAI-1, SERPINE1). PAI-1-GFP, expressed as a fusion protein under inducible control of +800 bp of the wound-activated PAI-1 promoter, prominently "marked" keratinocyte migration trails during the real-time of monolayer scrape-injury repair. Addition of active recombinant PAI-1 to wounded wild-type keratinocyte monolayers as well as to PAI-1(-/-) MEFs and PAI-1(-/-) keratinocytes significantly stimulated directional motility above basal levels in all cell types. PAI-1 expression knockdown or antibody-mediated functional inhibition, in contrast, effectively attenuated injury repair. The defect in wound-associated migratory activity as a consequence of antisense-mediated PAI-1 down-regulation was effectively reversed by addition of recombinant PAI-1 immediately after scrape injury. One possible mechanism underlying the PAI-1-dependent motile response may involve fine control of the keratinocyte substrate detachment/re-attachment process. Exogenous PAI-1 significantly enhanced keratinocyte spread cell "footprint" area while PAI-1 neutralizing antibodies, but not control non-immune IgG, effectively inhibited spreading with apoptotic hallmarks evident within 24 h. Importantly, PAI-1 not only stimulated keratinocyte adhesion and wound-initiated planar migration but also rescued keratinocytes from plasminogen-induced substrate detachment/anoikis. The early transcriptional response of the PAI-1 gene to monolayer trauma and its prominence in the injury repair genetic signature are consistent with its function as both a survival factor and regulator of the time course of epithelial migration as part of the cutaneous injury response program.

Association analysis of allelic variants of USF1 in coronary atherosclerosis

OBJECTIVE

USF1 regulates the transcription of more than 40 cardiovascular related genes and is well established as a gene associated with familial combined hyperlipidemia, a condition increasing the risk for coronary heart disease. No detailed data, however, exists on the impact of this gene to the critical outcome at the tissue level: different types of atherosclerotic lesions.

METHODS AND RESULTS

We analyzed the USF1 in 2 autopsy series of altogether 700 middle-aged men (the Helsinki Sudden Death Study) with quantitative morphometric measurements of coronary atherosclerosis. SNP rs2516839, tagging common USF1 haplotypes, associated with the presence of several types of atherosclerotic lesions, particularly with the proportion of advanced atherosclerotic plaques (P=0.02) and area of calcified lesions (P<0.001) of the coronary arteries. Importantly, carriers of risk alleles of rs2516839 also showed a 2-fold risk for sudden cardiac death (genotype TT versus CC; OR 2.10, 95% CI 1.17 to 3.75, P=0.04). The risk effect of rs2516839 was present also in aorta samples of the men.

CONCLUSIONS

Our findings in this unique study sample suggest that USF1 contributes to atherosclerosis, the pathological arterial wall phenotype resulting in coronary heart disease and in its most dramatic consequence-sudden cardiac death.

Migration of the epidermal over the dermal component (epiboly) in a bilayered bioengineered skin construct

A bilayered bioengineered living skin construct (LSC) consisting of viable human neonatal keratinocytes over a collagenous dermis seeded with dermal fibroblasts has been used extensively in difficult-to heal human wounds. Its biological properties include production of several mediators, cytokines, and growth factors and the ability to heal itself upon injury. In this study, we investigated the process of keratinocyte migration in LSC. At baseline, 6-mm punch biopsies of the construct were placed in serum-free medium (AIM-V) or Dulbecco's modified Eagle medium. At varying time points, the LSC samples were processed and analyzed using histology and immunohistochemistry. By 72 h, in a time-dependent manner, the overlying epidermis had migrated over and enveloped the entire underlying dermis, a process known as epiboly. Increasing concentrations of neutralizing antibodies to epidermal growth factor or interleukin-1 alpha down-regulated the extent of epiboly, as measured using computerized planimetry, but antibodies to transforming growth factor-beta 1 did not affect it. The consistent expression of laminin V, alpha3beta1 integrin, and vitronectin (epibolin) and its integrin receptor (alphavbeta5) characterized the tongue of migrating epidermis. Increasing concentrations of antibodies to vitronectin blocked the process of epiboly, as did antibodies to the alphavbeta5 integrin receptor, which mediates vitronectin-driven keratinocyte locomotion. This process of epiboly provides novel mechanisms of action for bioengineered skin constructs.

Dual role for plasminogen activator inhibitor type 1 as soluble and as matricellular regulator of epithelial alveolar cell wound healing

Epithelium repair, crucial for restoration of alveolo-capillary barrier integrity, is orchestrated by various cytokines and growth factors. Among them keratinocyte growth factor plays a pivotal role in both cell proliferation and migration. The urokinase plasminogen activator (uPA) system also influences cell migration through proteolysis during epithelial repair. In addition, the complex formed by uPAR-uPA and matrix-bound plasminogen activator inhibitor type-1 (PAI-1) exerts nonproteolytic roles in various cell types. Here we present new evidence about the dual role of PAI-1 under keratinocyte growth factor stimulation using an in vitro repair model of rat alveolar epithelial cells. Besides proteolytic involvement of the uPA system, the availability of matrix-bound-PAI-1 is also required for an efficient healing. An unexpected decrease of healing was shown when PAI-1 activity was blocked. However, the proteolytic action of uPA and plasmin were still required. Moreover, immediately after wounding, PAI-1 was dramatically increased in the newly deposited matrix at the leading edge of wounds. We thus propose a dual role for PAI-1 in epithelial cell wound healing, both as a soluble inhibitor of proteolysis and also as a matrix-bound regulator of cell migration. Matrix-bound PAI-1 could thus be considered as a new member of the matricellular protein family.

PAI-1 transcriptional regulation during the G0 --> G1 transition in human epidermal keratinocytes

Plasminogen activator inhibitor type-1 (PAI-1) is the major negative regulator of the plasmin-dependent pericellular proteolytic cascade. PAI-1 gene expression is normally growth state regulated but frequently elevated in chronic fibroproliferative and neoplastic diseases affecting both stromal restructuring and cellular migratory activities. Kinetic modeling of cell cycle transit in synchronized human keratinocytes (HaCaT cells) indicated that PAI-1 transcription occurred early after serum stimulation of quiescent (G0) cells and prior to entry into a cycling G1 condition. PAI-1 repression (in G0) was associated with upstream stimulatory factor-1 (USF-1) occupancy of two consensus E box motifs (5'-CACGTG-3') at the PE1 and PE2 domains in the PF1 region (nucleotides -794 to -532) of the PAI-1 promoter. Chromatin immunoprecipitation (ChIP) analysis established that the PE1 and PE2 site E boxes were occupied by USF-1 in quiescent cells and by USF-2 in serum-activated, PAI-1-expressing keratinocytes. This reciprocal and growth state-dependent residence of USF family members (USF-1 vs. USF-2) at PE1/PE2 region chromatin characterized the G0 --> G1 transition period and the transcriptional status of the PAI-1 gene. A consensus E box motif was required for USF/E box interactions, as a CG --> AT substitution at the two central nucleotides inhibited formation of USF/probe complexes. The 5' flanking sites (AAT or AGAC) in the PE2 segment were not necessary for USF binding. USF recognition of the PE1/PE2 region E box sites required phosphorylation with several potential involved residues, including T153, maping to the USF-specific region (USR). A T153A substitution in USF-1 did not repress serum-induced PAI-1 expression whereas the T153D mutant was an effective suppressor. As anticipated from the ChIP results, transfection of wild-type USF-2 failed to inhibit PAI-1 induction. Collectively, these data suggest that USF family members are important regulators of PAI-1 gene control during serum-stimulated recruitment of quiescent human epithelial cells into the growth cycle.

The motogenic effects of cyclic mechanical strain on intestinal epithelial monolayer wound closure are matrix dependent

BACKGROUND & AIMS

Complex deformation during normal digestion due to peristalsis or villous motility may be trophic for the intestinal mucosa. Because tissue fibronectin is increased in inflammatory states that may accompany mucosal injury, we evaluated the effects of cyclic mechanical strain and fibronectin on intestinal epithelial monolayer wound closure in Caco-2 and IEC-6 intestinal epithelial cells.

METHODS

Wounds created in intestinal epithelial monolayers were subjected to cyclic deformation. Wound closure was assessed by morphometry using microscopic imaging. Cell signals were assessed by Western blot and confocal microscopy.

RESULTS

Mechanical strain stimulated wound closure on fibronectin but inhibited closure on collagen in Caco-2 and IEC-6 cells. The effect was independent of proliferation or cell spreading. Myosin light chain (MLC) and extracellular signal-regulated kinase (ERK) were phosphorylated in response to strain in confluent monolayers on both collagen and fibronectin. Blocking MLC or ERK phosphorylation inhibited the motogenic effect of strain on fibronectin. Although phosphorylated MLC was redistributed to the leading edge of migrating cells following 6 hours of strain on collagen and fibronectin, phosphorylated ERK was redistributed to the lamellipodial edge only on fibronectin.

CONCLUSIONS

Strain promotes intestinal epithelial wound closure by a pathway requiring ERK and MLC kinase. Fibronectin-dependent ERK redistribution in response to strain in confluent migrating cells may explain the matrix dependence of the motogenic effect. Repetitive deformation stimulates intestinal epithelial proliferation on a collagen substrate, but not fibronectin. Deformation may exert matrix-dependent effects on intestinal epithelial cells, promoting epithelial restitution in fibronectin-rich tissue and proliferation in fibronectin-poor mucosa.

TGF-beta 1-induced PAI-1 expression is E box/USF-dependent and requires EGFR signaling

Transforming growth factor-beta1 (TGF-beta1) transcriptionally regulates the expression of genes that encode specific proteins (e.g., plasminogen activator inhibitor-1; PAI-1) important in stromal remodeling and cellular invasion. Definition of molecular events underlying TGF-beta1-initiated PAI-1 transcription, therefore, may lead to the identification of new therapeutic targets for diseases associated with elevated PAI-1 synthesis (e.g., tissue fibrosis, vascular disorders, tumor progression). An intact upstream stimulatory factor (USF)-binding E box motif (5'-(-165)CACGTG(-160)-3') at the HRE-2 site in the rat PAI-1 gene was required for PAI-1 transcription in TGF-beta1-treated cells. Mutation of the CA dinucleotide to TC at position -165/-164 in a reporter construct driven by 764 bp of PAI-1 promoter sequence decreased TGF-beta1-dependent CAT activity by >80% indicating the necessity for a consensus hexanucleotide E box motif in induced expression. The same CA --> TC substitution eliminated USF binding to an 18-bp HRE-2 DNA target highlighting the importance of site occupancy to transcriptional activation. Transfection of a dominant-negative USF construct, moreover, completely inhibited formation of USF/HRE-2 probe complexes, attenuated PAI-1 promoter-driven luciferase activity and reduced the response of the endogenous PAI-1 gene to TGF-beta1 (to that approximating quiescent controls). Maximal immediate-early PAI-1 induction upon exposure to TGF-beta1 required EGFR, p21ras, MEK and pp60(c-src) signaling as pharmacologic or dominant-negative inhibition of any of the four intermediates (EGFR, p21ras, MEK, pp60(c-src)) virtually eliminated TGF-beta1-augmented PAI-1 levels. U0126 titering experiments, furthermore, revealed that the same MEK inhibitor concentration that blocked the TGF-beta1 increase in ERK1/2 phosphorylation (20 microM) also effectively attenuated the PAI-1 inductive response suggesting a requirement for stimulated ERK signaling in TGF-beta1-mediated PAI-1 expression. These data suggest a model whereby TGF-beta1 activates a complex signaling cascade to affect PAI-1 gene control and involves USF occupancy of a critical E box motif at the HRE-2 site in the PAI-1 gene.

Involvement of urokinase-type plasminogen activator in sphingosylphosphorylcholine-induced angiogenesis

Sphingosylphosphorylcholine (SPC) has been shown to accelerate wound healing. As angiogenesis is fundamental to proper wound healing, we examined the effect of SPC on angiogenesis using a well-established rat aortic ring assay. SPC significantly stimulated the sprouting of endothelial cells from rat aortic ring. Recognizing its potential effect on angiogenesis, we further investigated the action of SPC using human umbilical vein endothelial cells (HUVECs) cultured in vitro. SPC significantly accelerated the closure of in vitro wound. In addition, SPC markedly enhanced the chemotactic migration and capillary-like tube formation. Subsequently, we examined whether SPC affected the production of urokinase-type plasminogen activator (uPA), an important regulator of angiogenesis, and found that SPC stimulated the expression of uPA at both the transcriptional and translational levels. Consistent with these results, SPC increased the activity of cell-surface-associated plasminogen activator. Pretreatment with antiuPA antibody significantly diminished both the chemotactic migration and capillary-like tube formation, indicating the potential importance of uPA in SPC-induced angiogenesis. Together, these results suggest that SPC may affect angiogenesis in the wound-healing process via regulation of uPA production.

Upstream stimulatory factor regulates E box-dependent PAI-1 transcription in human epidermal keratinocytes

Certain growth factors (e.g., TGF-beta1) initiate a "plastic" response in human keratinocytes (HaCaT cells) characterized by changes in gene expression and increased cell motility. While microarray analyses identified a number of involved genes, plasminogen activator inhibitor type 1 (PAI-1) is among the subset most highly responsive to TGF-beta1. Previous antisense attenuation of PAI-1 synthesis confirmed an essential role for this protease inhibitor in cell motility (Providence et al., 2002, J Cell Sci 115:3767-3777; Providence and Higgins, 2004, J Cell Physiol 200:297-308). It was important, therefore, to clarify molecular mechanisms underlying PAI-1 expression control in human keratinocytes. A consensus E box motif (5'-CACGTG-3') at nucleotides -566 to -561 in the PE2 region of the PAI-1 gene was required for TGF-beta1-induced transcription of a PAI-1 promoter-driven luceriferase reporter. Truncation of the PE2 E box or mutation of the CACGTG hexanucleotide to CAATTG inhibited growth factor-stimulated promoter function confirming the importance of this site in inducible expression. A similar mutation at the PE1 E box (nucleotides -682 to -677), in contrast, did not result in reduced luciferase activity. Competing CACGTG-containing DNAs, regardless of the presence or absence of PAI-1-specific flanking sequences or lacking accessory sequences (i.e., Smad-binding sites, AAT trinucleotide spacer), inhibited complex formation between HaCaT cell nuclear factors and a 45-mer PE2 region probe. A deoxyoligonucleotide that differed from the consensus E box by a CG --> AT substitution (the same base change incorporated into the PAI-1p806-lucerifase reporter by site-directed mutagenesis) but with random (i.e., non-PAI-1) flanking sequences also failed to compete with the PE2 region probe for protein binding whereas the same construct with an intact CACGTG motif was an effective competitor. The major protein/DNA interactions in the PE2 segment, therefore, are E box-dependent. USF-1, a member of the upstream stimulatory factor family, bound the PE2 construct suggesting a role for USF proteins in E box residence and PAI-1 gene expression. Chromatin immunoprecipitation, using primers designed to amplify a 300-bp PE2-associated promoter fragment and containing no other E box motifs except the target CACGTG at nucleotides -566 to -561, confirmed that this site was occupied by USF-1 or a USF-1-containing complex in both quiescent and TGF-beta1-stimulated cells. Transfection of a dominant-negative USF construct effectively attenuated serum- and TGF-beta1-induced PAI-1 synthesis as well as TGF-beta1-stimulated Matrigel barrier invasion. Dominant-negative USF-expressing keratinocytes, moreover, specifically had a reduced capacity for Matrigel barrier invasion. USF elements, therefore, are important regulators of growth factor-initiated PAI-1 transcription (as predicted from the identification of PAI-1 as a direct USF target gene) and the associated epithelial migratory response.

Plasminogen activator inhibitor-1 (PAI-1) stimulates human corneal epithelial cell adhesion and migration in vitro

In addition to its role as an inhibitor of urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) is hypothesized to regulate epithelial cell adhesion and migration. We have previously reported that PAI-1 may be an important regulatory factor of the uPA system in cornea. The purpose of this study was to extend those observations by determining the effect of exogenous PAI-1 on the migration and adhesion of human corneal epithelial cells (HCEC) in vitro. The expression of PAI-1 in non-transformed early passage HCEC was confirmed by immunofluorescence microscopy and Western blot analysis. Colorimetric assays coupled with function-inhibiting antibody studies using the matrix assembled in situ by cultured cells demonstrate that immobilized PAI-1 serves as an efficient substrate for HCEC adhesion. HCEC attachment to PAI-1 is comparable to that of laminin-10, a known strong adhesion protein for epithelial cells. In addition to serving as an adhesion substrate, PAI-1 also functions as a chemotactic agent for corneal epithelium. Additionally it promotes the random migration of HCEC, from an initial cell cluster, along a culture substrate. Our results in corneal epithelium are consistent with reports from other investigators showing that PAI-1 facilitates both epithelial adhesion and migration. From our studies we conclude that PAI-1 may play a dual role in corneal wound healing. Initially PAI-1 may function to stimulate migration and facilitate the reepithelialization of the wound bed. Post-reepithelization, PAI-1 may ensure corneal epithelial cell adhesion to matrix to promote successful wound healing.

Plasminogen activator inhibitor type-1 gene expression and induced migration in TGF-β1-stimulated smooth muscle cells is pp60c-src/MEK-dependent

Transforming growth factor-beta1 (TGF-beta1) stimulates expression of plasminogen activator inhibitor type-1 (PAI-1), a serine protease inhibitor (SERPIN) important in the control of stromal barrier proteolysis and cell-to-matrix adhesion. Pharmacologic agents that target MEK (PD98059, U0126) or src family (PP1) kinases attenuated TGF-beta1-dependent PAI-1 transcription in R22 aortic smooth muscle cells. Pretreatment with PP1 at concentrations that inhibited TGF-beta1-dependent PAI-1 expression also blocked ERK1/2 activation/nuclear accumulation suggesting that the required src kinase activity is upstream of ERK1/2 in the TGF-beta1-initiated signaling cascade. The IC(50) of the PP1-sensitive kinase, furthermore, specifically implied involvement of pp60(c-src) in PAI-1 induction. Indeed, addition of TGF-beta1 to quiescent R22 cells resulted in a 3-fold increase in pp60(c-src) autophosphorylation and kinase activity. Transfection of a dominant-negative pp60(c-src) construct, moreover, reduced TGF-beta1-induced PAI-1 expression levels to that of unstimulated controls or PP1-pretreated cells. A >/=170 kDa protein that co-immunoprecipitated with TGF-beta1-activated pp60(c-src) was also phosphorylated transiently in response to TGF-beta1. TGF-beta1 is known to transactivate the 170 kDa EGF receptor (EGFR) by autocrine HB-EGF or TGF-alpha mechanisms suggesting involvement of EGFR activation in certain TGF-beta1-initiated responses. Incubation of quiescent R22 cells with the EGFR-specific inhibitor AG1478 prior to growth factor (EGF or TGF-beta1) addition effectively blocked EGFR activation as determined by direct visualization of receptor internalization. AG1478 suppressed (in a dose-dependent fashion) EGF-induced PAI-1 protein levels and, at a final concentration of 2.5 muM, virtually eliminated EGF-dependent PAI-1 synthesis. More importantly, AG1478 similarly repressed inducible PAI-1 levels in TGF-beta1-stimulated R22 cultures. PP1, PD98059, and U0126 also inhibited TGF-beta1-dependent cell motility at concentrations that significantly attenuated PAI-1 expression. Consistent with the AG1478-associated reductions in EGF- and TGF-beta1-stimulated PAI-1 expression, pretreatment of R22 cell cultures with AG1478 effectively suppressed growth factor-stimulated cell motility. These data indicate that two major phenotypic characteristics of TGF-beta1-exposure (i.e., transcription of specific target genes [e.g., PAI-1], increased cell motility) are linked in the R22 vascular smooth muscle cell system, require pp60(c-src) kinase activity and MEK signaling and involve activation of an AG1478-sensitive (likely EGFR-dependent) pathway.

Oxidised-HDL3 induces the expression of PAI-1 in human endothelial cells. Role of p38MAPK activation and mRNA stabilization

Modified lipoproteins have been suggested to modulate endothelial expression of plasminogen activator inhibitor-1 (PAI-1). As oxidized high-density lipoprotein (Ox-HDL) has been found in atheromatous plaques and receptors for modified HDL are present on endothelial cells, we investigated the role of Ox-HDL3 on the expression of PAI-1. Ox-HDL3 but not native HDL3, increased PAI-1 mRNA expression in endothelial cells. Furthermore, PAI-1 antigen expression and activity increased in the supernatant of cells incubated with Ox-HDL3. The intracellular pathways involved in this effect were investigated. Ox-HDL3 activated both extracellular signal-regulated kinases (ERK) 1/2 and p38 mitogen-activated protein kinase (MAPK). Moreover, incubation with specific inhibitors of these kinases showed that p38MAPK was mainly involved in the Ox-HDL3-dependent PAI-1 induction. Transient transfection experiments suggested that none of the response elements in the proximal promoter (-804 to 17) were involved in Ox-HDL3-mediated PAI-1 expression. mRNA stability experiments showed that Ox-HDL3 increased the PAI-1 mRNA half-life. In summary, Ox-HDL3 induced PAI-1 mRNA expression and antigen release through a molecular mechanism involving MAPK activation and mRNA stabilization. Thus, oxidative modification converts HDL to a prothrombotic lipoprotein species.

PAI-1 expression is required for epithelial cell migration in two distinct phases of in vitro wound repair

Several proteases and their specific inhibitors modulate the interdependent processes of cell migration and matrix proteolysis as part of the global program of trauma repair. Expression of plasminogen activator inhibitor type-1 (PAI-1), a serine protease inhibitor (SERPIN) important in the control of barrier proteolysis and cell-to-matrix adhesion, for example, is spatially-temporally regulated following epithelial denudation injury in vitro as well as in vivo. PAI-1 mRNA/protein synthesis was induced early after epidermal monolayer scraping and restricted to keratinocytes comprising the motile cohort closely recapitulating, thereby, similar events during cutaneous healing. The time course of PAI-1 promoter-driven PAI-1-GFP fusion "reporter" expression in wound-juxtaposed cells approximated that of the endogenous PAI-1 gene confirming the location-specificity of gene regulation in this model. ERK activation was evident within 5 min after injury and particularly prominent in cells residing at the scrape-edge (suggesting a possible role in PAI-1 induction and/or the motile response) as was myosin light chain (MLC) phosphorylation. Indeed, MEK blockade with PD98059 or U0126 attenuated keratinocyte migration (by > or =60%), as did transient transfection of a dominant-negative ERK1 construct (40% decrease in monolayer repair), and completely inhibited PAI-1 transcript expression. Anti-sense down-regulation of PAI-1 synthesis (by 80-85%), or addition of PAI-1 neutralizing antibodies also inhibited injury site closure over a 24 h period establishing that PAI-1 was required for efficient long-term planar motility in this system. PAI-1 anti-sense transfection or actinomycin D transcriptional blockade, in contrast, did not affect the initial migratory response suggesting that residual PAI-1 protein levels (at least in transfectant cells and actinomycin D-treated cultures) may be sufficient to support early cell movement. Pharmacologic inhibition of keratinocyte MEK signaling effectively ablated scrape-induced PAI-1 mRNA expression but failed to attenuate wound-associated increases in cellular PAI-1 protein levels soon after monolayer injury. Collectively, these data suggest that basal PAI-1 transcripts may be mobilized for initial PAI-1 synthesis and, perhaps, the early motile response while maintenance of the normal rate of migration requires the prolonged PAI-1 expression that typically accompanies the repair response. To assess this possibility, scrape site closure studies were designed using keratinocytes isolated from PAI-1-/- mice. PAI-1-/- keratinocytes, in fact, had a significant wound healing defect evident even within the first 6 h following monolayer denudation injury. Addition of active PAI-1 protein to PAI-/- keratinocytes rescued the migratory phenotype that that approximating wild-type cells. These findings validate use of the present keratinocyte model to investigate injury-related controls on PAI-1 gene regulation and, collectively, implicate participation of PAI-1 in two distinct phases of epidermal wound repair.

Allelic frequency of the PAI-1 4G/5G promoter polymorphism in patients with type 2 diabetes mellitus and lack of association with PAI-1 plasma levels

Plasminogen activator inhibitor-1 (PAI-1) levels were found to be associated with obesity, indicating that adipocytes might influence PAI-1 plasma levels. In addition, the 4G/5G promoter polymorphism of the PAI-1 gene possibly modulates PAI-1 gene transcription and, as a consequence, PAI-1 plasma levels. Metabolic parameters, diabetes complications, PAI-1 plasma levels, and PAI-1 promoter genotypes were determined and were tested for correlation in 547 Caucasian patients with type 2 diabetes. Genotyping was performed by using allele-specific PCR, and PAI-1 plasma levels were measured in 547 well-characterized subjects with type 2 diabetes. The allelic frequencies of the polymorphism (0.56 for the 4G-genotype, 0.44 for the 5G-genotype) were not different from those observed in nondiabetic controls. The PAI-1 concentration was positively associated with MI, but not with the 4G/5G polymorphism. Statistical analysis of metabolic parameters, diabetic complications, and the 4G/5G polymorphism revealed that serum fibrinogen levels were significantly higher in the 4G/4G subgroup compared with the 4G/5G and 5G/5G subgroups. The correlation between serum fibrinogen and 4G allele remained significant, even when additional variables, such as gender, age, BMI, duration of diabetes, and HbA1c, were controlled. In patients with type 2 diabetes mellitus, the PAI-1 4G/5G promoter polymorphism does not predict PAI-1 plasma levels and is not associated with common metabolic parameters besides fibrinogen levels.

An in vitro outgrowth culture system for normal human keratinocytes

BACKGROUND

Normal human epidermal keratinocytes usually proliferate in low-calcium and differentiate in high-calcium without a feeder layer, but they stop proliferating and differentiate at confluency even in low-calcium, serum-free medium.

OBJECTIVE

We speculated that this contact inhibition would be mediated in part by mechanical tension. To prove this, we created a new assay system.

METHODS

A 10 mm diameter cloning ring was put on the center of a 60 mm dish coated with type I collagen. Keratinocytes were plated in the ring and incubated for 4h, then we had a circular epidermal monolayer sheet. We changed the mechanical tension by removing the ring and measured the diameter of the sheet under various conditions.

RESULTS

When we used keratinocyte-serum free medium (SFM) whose calcium concentration is below 0.1 mM as a medium, the keratinocytes in the perimeter migrated individually, and the keratinocytes in the center portion started differentiation. However, when we added calcium chloride to SFM (final concentration more than 0.5 mM), keratinocytes at the periphery showed marked lamellipodia without losing contact with the surrounding cells. These keratinocytes showed coordinate sheet-like outgrowth as a whole even in high concentrations of calcium.

CONCLUSION

These results suggest that other than calcium concentration, change of the mechanical tension would be one of the factors that mediate proliferation or differentiation of keratinocytes and that this new assay can be useful in analyzing proliferation, differentiation, and migration of keratinocytes.

Pp60c-src mediates ERK activation/nuclear localization and PAI-1 gene expression in response to cellular deformation

Release of transcellular tension upon disruption of actin stress fibers with cytochalasin D (CD) and associated changes in cell morphology are reflected in the rapid transcription of "deformation-responsive" genes. For certain genes (e.g., urokinase plasminogen activator and its type-1 inhibitor PAI-1), de novo mRNA synthesis appears to require cell shape-dependent activation of the MAP kinases ERK1/2. ERK activation in response to microfilament disruption was inhibited completely by the broad-spectrum tyrosine kinase inhibitor genistein and the relatively src-kinase selective compound PP1. Such inhibitor sensitivity profiles suggested that src-family members, likely pp60(c-src), were important upstream elements in deformation-related ERK activation. pp60(c-src) kinase activity was elevated fourfold within 15 min after CD addition to quiescent R22 smooth muscle cells and declined quickly thereafter. CD-induced increases in the phosphorylation levels of both pp60(c-src) and IgG heavy chain (a substrate target in the coupled immunoprecipitation/in vitro pp60(c-src) kinase assay) were ablated completely by pretreatment with the src-type kinase inhibitor PP1. Prior PP1 exposure similarly repressed CD-stimulated PAI-1 transcript accumulation. Consistent with the pharmacologic findings, transfection of a dominant-negative pp60(c-src) expression construct (DN-Src) effectively suppressed (in a concentration-dependent manner) CD-induced PAI-1 synthesis in R22 cells. To more specifically address the potential involvement of src kinases in CD-initiated ERK mobilization, R22 cells were transiently co-transfected with DN-Src and Myc-tagged ERK2 expression constructs, serum-deprived then stimulated with CD. The effect of DN-Src expression on endogenous ERK1/2 activation and nuclear translocation was assessed in separate experiments. The phosphorylation levels of both exogenous (Myc-ERK2) and endogenous ERK1/2 targets was significantly reduced by DN-Src; nuclear accumulation of pERK1/2 was completely inhibited. These data indicate that pp60(c-src) is a critical upstream activator of the ERK cascade leading to PAI-1 transcription in response to cellular deformation stimuli.