Plasminogen activator inhibitor-1 regulates neutrophil influx during acute pyelonephritis

All tangled up: interactions of the fibrinolytic and innate immune systems

The hemostatic and innate immune system are intertwined processes. Inflammation within the vasculature promotes thrombus development, whilst fibrin forms part of the innate immune response to trap invading pathogens. The awareness of these interlinked process has resulted in the coining of the terms "thromboinflammation" and "immunothrombosis." Once a thrombus is formed it is up to the fibrinolytic system to resolve these clots and remove them from the vasculature. Immune cells contain an arsenal of fibrinolytic regulators and plasmin, the central fibrinolytic enzyme. The fibrinolytic proteins in turn have diverse roles in immunoregulation. Here, the intricate relationship between the fibrinolytic and innate immune system will be discussed.

BAP1-Related ceRNA (NEAT1/miR-10a-5p/SERPINE1) Promotes Proliferation and Migration of Kidney Cancer Cells

Background

BAP1 is an important tumor suppressor involved in various biological processes and is commonly lost or inactivated in clear-cell renal cell carcinoma (ccRCC). However, the role of the BAP1-deficient tumor competing endogenous RNA (ceRNA) network involved in ccRCC remains unclear. Thus, this study aims to investigate the prognostic BAP1-related ceRNA in ccRCC.

Methods

Raw data was obtained from the TCGA and the differentially expressed genes were screened to establish a BAP1-related ceRNA network. Subsequently, the role of the ceRNA axis was validated using phenotypic experiments. Dual-luciferase reporter assays and fluorescence in situ hybridization (FISH) assays were used to confirm the ceRNA network.

Results

Nuclear enriched abundant transcript 1 (NEAT1) expression was significantly increased in kidney cancer cell lines. NEAT1 knockdown significantly inhibited cell proliferation and migration, which could be reversed by miR-10a-5p inhibitor. Dual-luciferase reporter assay confirmed miR-10a-5p as a common target of NEAT1 and Serine protease inhibitor family E member 1 (SERPINE1). FISH assays revealed the co-localization of NEAT1 and miR-10a-5p in the cytoplasm. Additionally, the methylation level of SERPINE1 in ccRCC was significantly lower than that in normal tissues. Furthermore, SERPINE1 expression was positively correlated with multiple immune cell infiltration levels.

Conclusions

In BAP1-deficient ccRCC, NEAT1 competitively binds to miR-10a-5p, indirectly upregulating SERPINE1 expression to promote kidney cancer cell proliferation. Furthermore, NEAT1/miR-10a-5p/SERPINE1 were found to be independent prognostic factors of ccRCC.

SERPINE1 associated with remodeling of the tumor microenvironment in colon cancer progression: a novel therapeutic target

Background

The change of immune cell infiltration essentially influences the process of colorectal cancer development. The infiltration of immune cells can be regulated by a variety of genes. Thus, modeling the immune microenvironment of colorectal cancer by analyzing the genes involved can be more conducive to the in-depth understanding of carcinogenesis and the progression thereof.

Methods

In this study, the number of stromal and immune cells in malignant tumor tissues were first estimated by using expression data (ESTIMATE) and cell-type identification with relative subsets of known RNA transcripts (CIBERSORT) to calculate the proportion of infiltrating immune cell and stromal components of colon cancer samples from the Cancer Genome Atlas database. Then the relationship between the TMN Classification and prognosis of malignant tumors was evaluated.

Results

By investigating differentially expressed genes using COX regression and protein-protein interaction network (PPI), the candidate hub gene serine protease inhibitor family E member 1 (SERPINE1) was found to be associated with immune cell infiltration. Gene Set Enrichment Analysis (GSEA) further projected the potential pathways with elevated SERPINE1 expression to carcinogenesis and immunity. CIBERSORT was subsequently utilized to investigate the relationship between the expression differences of SERPINE1 and immune cell infiltration and to identify eight immune cells associated with SERPINE1 expression.

Conclusion

We found that SERPINE1 plays a role in the remodeling of the colon cancer microenvironment and the infiltration of immune cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08536-7.

Divergent Regulation of Alveolar Type 2 Cell and Fibroblast Apoptosis by Plasminogen Activator Inhibitor 1 in Lung Fibrosis

Increased apoptosis sensitivity of alveolar type 2 (ATII) cells and increased apoptosis resistance of (myo)fibroblasts, the apoptosis paradox, contributes to the pathogenesis of idiopathic pulmonary fibrosis (IPF). The mechanism underlying the apoptosis paradox in IPF lungs, however, is unclear. Aging is the greatest risk factor for IPF. In this study, we show, for the first time, that ATII cells from old mice are more sensitive, whereas fibroblasts from old mice are more resistant, to apoptotic challenges, compared with the corresponding cells from young mice. The expression of plasminogen activator inhibitor 1 (PAI-1), an important profibrogenic mediator, was significantly increased in both ATII cells and lung fibroblasts from aged mice. In vitro studies using PAI-1 siRNA and active PAI-1 protein indicated that PAI-1 promoted ATII cell apoptosis but protected fibroblasts from apoptosis, likely through dichotomous regulation of p53 expression. Deletion of PAI-1 in adult mice led to a reduction in p53, p21, and Bax protein expression, as well as apoptosis sensitivity in ATII cells, and their increase in the lung fibroblasts, as indicated by in vivo studies. This increase was associated with an attenuation of lung fibrosis after bleomycin challenge. Since PAI-1 is up-regulated in both ATII cells and fibroblasts in IPF, the results suggest that increased PAI-1 may underlie the apoptosis paradox of ATII cells and fibroblasts in IPF lungs.

A Serpin With a Finger in Many PAIs: PAI-1's Central Function in Thromboinflammation and Cardiovascular Disease

Plasminogen activator inhibitor 1 (PAI-1) is a member of the serine protease inhibitor (serpin) superfamily. PAI-1 is the principal inhibitor of the plasminogen activators, tissue plasminogen activator (tPA), and urokinase-type plasminogen activator (uPA). Turbulence in the levels of PAI-1 tilts the balance of the hemostatic system resulting in bleeding or thrombotic complications. Not surprisingly, there is strong evidence that documents the role of PAI-1 in cardiovascular disease. The more recent uncovering of the coalition between the hemostatic and inflammatory pathways has exposed a distinct role for PAI-1. The storm of proinflammatory cytokines liberated during inflammation, including IL-6 and TNF-α, directly influence PAI-1 synthesis and increase circulating levels of this serpin. Consequently, elevated levels of PAI-1 are commonplace during infection and are frequently associated with a hypofibrinolytic state and thrombotic complications. Elevated PAI-1 levels are also a feature of metabolic syndrome, which is defined by a cluster of abnormalities including obesity, type 2 diabetes, hypertension, and elevated triglyceride. Metabolic syndrome is in itself defined as a proinflammatory state associated with elevated levels of cytokines. In addition, insulin has a direct impact on PAI-1 synthesis bridging these pathways. This review describes the key physiological functions of PAI-1 and how these become perturbed during disease processes. We focus on the direct relationship between PAI-1 and inflammation and the repercussion in terms of an ensuing hypofibrinolytic state and thromboembolic complications. Collectively, these observations strengthen the utility of PAI-1 as a viable drug target for the treatment of various diseases.

Modulation of the inflammatory environment by spermatozoa through regulation of transforming growth factor beta in porcine uterine epithelial cells

This study investigated the changes in the mRNA expression of transforming growth factor beta (TGF-β), plasminogen activators (PAs), and interleukin (IL) caused by sperm, as well as the regulatory mechanism of PA activity through TGF-β, in porcine uterine epithelial cells. The cells were isolated from the uterine horn of pig and co-incubated with Percoll-separated boar sperm (45% or 90%), or TGF-β for 24 h. The mRNA expression of TGF-β isoforms (TGF-β1, 2 and 3) and their receptors (TGF-β R1 and R2), PAs (urokinase-type, uPA; tissue-type, tPA; uPA receptor, uPAR; type 1 PA inhibitor, PAI-1), IL-6 and IL-8 was analyzed using real-time PCR. Supernatant was used to measure PA activity. Co-incubation with sperm from the 90% Percoll layer increased TGF-β1 mRNA, whereas TGF-β2 and TGF-β3 were decreased (P < 0.05). However, both TGF-βRs were not changed by the presence of the spermatozoa. Expression of tPA, PAI-1, IL-6, and IL-8 mRNA was down-regulated by 90% Percoll-separated sperm (P < 0.05), and sperm from 45% Percoll increased uPA expression (P < 0.05). TGF-β decreased tPA and IL-8 mRNA expression, and increased uPAR and PAI-1 mRNA (P < 0.05). The suppressive effect of TGF-β on PA activity was blocked by Smad2/3 and JNK1/2 signaling inhibitors (P < 0.05). In conclusion, sperm separated in 90% in porcine uterus could suppressed inflammation via modulation of TGF-β and down-regulation of PAs and ILs. Therefore, the regulatory mechanism of inflammation by sperm in the porcine uterus could be associated with interactions between numerous cytokines including TGF-β.

Influence of Plasminogen Activator Inhibitor -1 Gene Polymorphism on Renal Scarring After First Febrile Urinary Tract Infection in Infants

Background

The pathogenesis of renal scarring (RS) after first febrile urinary tract infection (UTI) in children is multifactorial. In addition to well-known risk factors, a role for genetic predisposition has been suggested.

Aims

To determine whether deoxyribonucleic acid (DNA) polymorphisms at the plasminogen activator inhibitor -1 (PAI-1) gene were associated with evolution to RS following a febrile UTI in infants.

Materials and Methods

Our research included 100 infants, 84 girls and 16 boys, ages up to 1 year with a first febrile UTI, increased inflammatory parameters and positive urine culture treated at the Pediatric Clinic II of the University Clinical Center Sarajevo (UCCS). The diagnostic was based on the imaging studies: ultrasonography, voiding cystourethrography (VCUG) and initial and control static renal scintigraphy (DMSA renal scan), to assess the renal parenchymal damage (RPD). The polymorphisms of the PAI-1 were determined based on polymerase chain reaction technique. The distribution of PAI-1 genotypes and the allele frequencies were compared between different groups of patients with febrile UTI.

Results

Results presented that 66 infants had acute pyelonephritis (APN) and 22 had vesicoureteral reflux (VUR). On initial DMSA renal scan examination, we detected no RPD in any patient. After 6 months, the repeat DMSA renal scan revealed the presence of RPD in 18 (27%) out of 66 infants with APN. Distribution of PAI-1 genotypes was not different between various groups of patients with febrile UTI.

Conclusions

The results of our study have not shown that individual genetic variation in PAI-1 is an independent variable that predispose same of children for RS after first febrile UTI. Maybe that yet unknown gene polymorphisms together with geographical and /or socio-economic differences can influence on the development of RS.

PAI1 mediates fibroblast-mast cell interactions in skin fibrosis

Fibrosis is a prevalent pathological condition arising from the chronic activation of fibroblasts. This activation results from the extensive intercellular crosstalk mediated by both soluble factors and direct cell-cell connections. Prominent among these are the interactions of fibroblasts with immune cells, in which the fibroblast-mast cell connection, although acknowledged, is relatively unexplored. We have used a Tg mouse model of skin fibrosis, based on expression of the transcription factor Snail in the epidermis, to probe the mechanisms regulating mast cell activity and the contribution of these cells to this pathology. We have discovered that Snail-expressing keratinocytes secrete plasminogen activator inhibitor type 1 (PAI1), which functions as a chemotactic factor to increase mast cell infiltration into the skin. Moreover, we have determined that PAI1 upregulates intercellular adhesion molecule type 1 (ICAM1) expression on dermal fibroblasts, rendering them competent to bind to mast cells. This heterotypic cell-cell adhesion, also observed in the skin fibrotic disorder scleroderma, culminates in the reciprocal activation of both mast cells and fibroblasts, leading to the cascade of events that promote fibrogenesis. Thus, we have identified roles for PAI1 in the multifactorial program of fibrogenesis that expand its functional repertoire beyond its canonical role in plasmin-dependent processes.

Eosinophils Accelerate Pathogenesis of Psoriasis by Supporting an Inflammatory Milieu that Promotes Neutrophil Infiltration

Eosinophils are proinflammatory granulocytes that are involved in the pathogenesis of various inflammatory reactions. However, their roles in psoriasis remain largely unknown. In this study, by examining the inflammatory features of the eosinophilic cell line EoL-1 and an imiquimod-induced murine model of psoriasis, we show that eosinophils provide inflammatory signals that accelerate the pathogenesis of psoriasis. EoL-1 cells constitutively expressed TLR7, which mediates acute and rapidly developing psoriatic inflammation. The activation of TLR7 on EoL-1 cells using R837 resulted in the secretion of inflammatory mediators that support the migration, activation, and survival of neutrophils. The underlying pathologic role of eosinophils in psoriatic inflammation was further substantiated by markedly decreased psoriasiform inflammation in imiquimod-treated ΔdblGATA mice, which have a systemic eosinophil deficiency. While imiquimod-treated wild-type mice showed a significant increase in the eosinophils in their skin, neutrophils remarkably outnumbered the eosinophils in the skin, lymph nodes, and spleen in wild-type mice after imiquimod application. In addition, lesional skin samples from psoriasis patients also showed up-regulated eosinophil cytotoxic granules, accompanied by marked neutrophil infiltration. Based on these collective data, we propose that eosinophils accelerate psoriatic inflammation by supporting inflammatory microenvironments to favor the activation and infiltration of neutrophils.

Plasminogen activator inhibitor-1 stimulates macrophage activation through Toll-like Receptor-4

While inflammation is often associated with increased Plasminogen Activator Inhibitor-1 (PAI-1), the functional consequences of PAI-1 in inflammation have yet to be fully determined. The aim of this study was to establish the in vivo relevance of PAI-1 in inflammation. A mouse model of systemic inflammation was employed in wild-type (WT) and PAI-1 deficient (PAI-1(-/-)) mice. Mice survival, macrophage infiltration into the lungs, and plasma levels of pro-inflammatory cytokines were assessed after lipopolysaccharide (LPS) infusion. In vitro experiments were conducted to examine changes in LPS-induced inflammatory responses after PAI-1 exposure. PAI-1 was shown to regulate inflammation, in vivo, and affect macrophage infiltration into lungs. Further, PAI-1 activated macrophages, and increased pro-inflammatory cytokines at both the mRNA and protein levels in these cells. The effect of PAI-1 on macrophage activation was dose-dependent and LPS-independent. Proteolytic inhibitory activity and Lipoprotein Receptor-related Protein (LRP) and vitronectin (VN) binding functions, were not involved in PAI-1-mediated activation of macrophages. However, the effect of PAI-1 on macrophage activation was partially blocked by a TLR4 neutralizing antibody. Furthermore, PAI-1-induced Tumor Necrosis Factor-alpha (TNF-α) and Macrophage Inflammatory Protein-2 (MIP-2) expression was reduced in TLR4(-/-) macrophages compared to WT macrophages. These results demonstrate that PAI-1 is involved in the regulation of host inflammatory responses through Toll-like Receptor-4 (TLR4)-mediated macrophage activation.

Plasminogen activator inhibitor-1 regulates LPS-induced TLR4/MD-2 pathway activation and inflammation in alveolar macrophages

Toll-like receptor 4 (TLR4) and myeloid differentiation protein 2 (MD-2) are the main lipopolysaccharide (LPS) binding receptors that respond to inflammatory stimuli and mediate NF-kappa B (NF-κB) signaling pathway in macrophages. We have previously shown that plasminogen activator inhibitor-1 (PAI-1) deletion increased lung injury induced by intratracheal instillation of LPS through downregulation of TLR4 negative regulators. However, the mechanisms by which PAI-1 regulates lung inflammation are largely unknown. The aim of this study is to assess the relationship between PAI-1 and TLR4 signaling pathways in LPS-induced NR8383 cells inflammatory reaction. The results showed that the levels of PAI-1, TNF-α, and IL-1β protein were increased remarkably in NR8383 cell supernatants after LPS stimulation. PAI-1 gene knockdown reduced TNF-α and IL-1β levels in cell supernatants and inhibited the NF-κB p65 protein expression in NR8383 cells. The upregulated mRNA and protein expressions of TLR4, MD-2, and myeloid differentiation protein (MyD88) induced by LPS were attenuated after PAI-1 gene knockdown. Conversely, overexpression of PAI-1 in NR8383 cells not only resulted in additional mRNA and protein production of PAI-1, TLR4, MD-2, and MyD88, it also aggravated the inflammatory response induced by LPS. In conclusion, PAI-1 contributes to the regulation of LPS-induced inflammatory response in NR8383 cells, likely by affecting the TLR4-MD-2/NF-κB signaling transduction pathway.

The lectin like domain of thrombomodulin is involved in the defence against pyelonephritis

Pyelonephritis, a common complication of urinary tract infections, is frequently associated with kidney scarring and may lead to end-stage renal disease. During bacterial infections inflammatory and coagulation pathways and their mutual interaction are playing pivotal roles in the host response. Given that thrombomodulin (TM) is crucially involved in the interplay between coagulation and inflammation, we aimed to investigate the roles of its EGF and lectin-like domains in inflammation during acute pyelonephritis. Indeed, the EGF-like and the lectin-like domains of TM, are especially known to orchestrate inflammation and coagulation in different ways. Acute pyelonephritis was induced by intravesical inoculation of 1 × 10(8) CFU of uropathogenic Escherichia coli in two strains of TM transgenic mice. TM(pro/pro) mice carry a mutation in the EGF-like domain making them unable to activate protein C, an anticoagulant and anti-inflammatory protein. TM(LeD/LeD) mice lack the lectin-like domain of TM, which is critical for its anti-inflammatory and cytoprotective properties. Mice were sacrificed 24 and 48 h after inoculation. Bacterial loads, the immune response and the activation of coagulation were evaluated in the kidney and the bladder. TM(LeD/LeD) mice showed elevated bacterial load in bladder and kidneys compared to WT mice, whereas TM(pro/pro) had similar bacterial load as WT mice. TM(LeD/LeD) mice displayed a reduced local production of pro-inflammatory cytokines and neutrophil renal infiltration. Activation of coagulation was comparable in TM(LeD/LeD) and WT mice. From these data, we conclude that the lectin-like domain of thrombomodulin is critically involved in host defence against E. coli induced acute pyelonephritis.

In vivo evidence for an endothelium-dependent mechanism in radiation-induced normal tissue injury

The pathophysiological mechanism involved in side effects of radiation therapy, and especially the role of the endothelium remains unclear. Previous results showed that plasminogen activator inhibitor-type 1 (PAI-1) contributes to radiation-induced intestinal injury and suggested that this role could be driven by an endothelium-dependent mechanism. We investigated whether endothelial-specific PAI-1 deletion could affect radiation-induced intestinal injury. We created a mouse model with a specific deletion of PAI-1 in the endothelium (PAI-1KO^endo) by a Cre-LoxP system. In a model of radiation enteropathy, survival and intestinal radiation injury were followed as well as intestinal gene transcriptional profile and inflammatory cells intestinal infiltration. Irradiated PAI-1KO^endo mice exhibited increased survival, reduced acute enteritis severity and attenuated late fibrosis compared with irradiated PAI-1^flx/flx mice. Double E-cadherin/TUNEL labeling confirmed a reduced epithelial cell apoptosis in irradiated PAI-1KO^endo. High-throughput gene expression combined with bioinformatic analyses revealed a putative involvement of macrophages. We observed a decrease in CD68⁺cells in irradiated intestinal tissues from PAI-1KO^endo mice as well as modifications associated with M1/M2 polarization. This work shows that PAI-1 plays a role in radiation-induced intestinal injury by an endothelium-dependent mechanism and demonstrates in vivo that the endothelium is directly involved in the progression of radiation-induced enteritis.

Plasminogen activator inhibitor 1, fibroblast apoptosis resistance, and aging-related susceptibility to lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disorder with unknown cause and no effective treatment. The incidence of and mortality from IPF increase with age, suggesting that advanced age is a major risk factor for IPF. The mechanism underlying the increased susceptibility of the elderly to IPF, however, is unknown. In this study, we show for the first time that the protein level of plasminogen activator inhibitor 1 (PAI-1), a protease inhibitor which plays an essential role in the control of fibrinolysis, was significantly increased with age in mouse lung homogenate and lung fibroblasts. Upon bleomycin challenge, old mice experienced augmented PAI-1 induction and lung fibrosis as compared to young mice. Most interestingly, we show that fewer (myo)fibroblasts underwent apoptosis and more (myo)fibroblasts with increased level of PAI-1 accumulated in the lung of old than in young mice after bleomycin challenge. In vitro studies further demonstrate that fibroblasts isolated from lungs of old mice were resistant to H2O2 and tumor necrosis factor alpha-induced apoptosis and had augmented fibrotic responses to TGF-β1, compared to fibroblasts isolated from young mice. Inhibition of PAI-1 activity with a PAI-1 inhibitor, on the other hand, eliminated the aging-related apoptosis resistance and TGF-β1 sensitivity in isolated fibroblasts. Moreover, we show that knocking down PAI-1 in human lung fibroblasts with PAI-1 siRNA significantly increased their sensitivity to apoptosis and inhibited their responses to TGF-β1. Together, the results suggest that increased PAI-1 expression may underlie the aging-related sensitivity to lung fibrosis in part by protecting fibroblasts from apoptosis.

Deficiency of growth factor midkine exacerbates necrotizing glomerular injuries in progressive glomerulonephritis

Inflammatory cell infiltration and fibrin deposition play important roles in the development of crescentic glomerulonephritis (GN). In particular, activation of coagulation is an indispensable factor in crescent formation. However, the mechanisms underlying the pathogenesis of crescent formation have not been completely elucidated. We identified the growth factor midkine (MK) as a novel key molecule in the progression of crescentic GN induced by anti-glomerular basement membrane antibody. Despite the lack of significant differences in autologous and heterologous reactions, MK-deficient (Mdk(-/-)) mice unexpectedly showed a greater number of necrotizing glomerular injuries than wild-type (Mdk(+/+)) mice. Likewise, more tubulointerstitial damage was observed in Mdk(-/-) mice, and this damage positively correlated with glomerular injury. Plasminogen activator inhibitor (PAI)-1 was strongly induced in the injured glomerulus of Mdk(-/-) mice, particularly in crescents and endothelial cells. This enhanced PAI-1 production was associated with an increase in inflammatory cell infiltration and matrix deposition in the glomerulus and the interstitium of Mdk(-/-) mice. In line with these in vivo data, primary cultured endothelial cells derived from Mdk(-/-) mice exhibited higher PAI-1 mRNA expression on fibrin challenge and less fibrinolysis than Mdk(+/+) mice. In contrast, the expression of plasminogen activators was not affected. Our combined data suggest that MK leads to a blockade of PAI-1, which is closely associated with the suppression of crescentic GN.

Local and systemic expressions of MMP-9, TIMP-1 and PAI-1 in patients undergoing surgery for clinically suspected appendicitis

BACKGROUND/AIMS

To examine, compare and correlate the expressions of matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1) and plasminogen activator inhibitor type 1 (PAI-1) in appendiceal tissue and pre- and postoperative blood samples in patients undergoing surgery for clinically suspected appendicitis.

METHODS

Fifty-seven patients with complete tissue and blood samples were included and divided into groups of noninflamed appendix/lymphadenitis (n = 7), phlegmonous appendicitis (n = 30), gangrenous appendicitis (n = 11) and perforated appendicitis (n = 9). The protein expressions were assessed with ELISAs. The local expressions of MMP-9, TIMP-1 and PAI-1 were correlated with the systemic expressions at the time of surgery while the systemic individual differences between surgery and recovery were compared.

RESULTS

There was a positive correlation between tissue and plasma PAI-1 (p < 0.05). The individual differences for plasma MMP-9 and PAI-1 were statistically nonsignificant, while they were higher for TIMP-1 in patients with perforated appendicitis compared with phlegmonous (p < 0.0001) and gangrenous appendicitis (p < 0.01).

CONCLUSIONS

Plasma PAI-1 reflected the levels in appendiceal tissue at the time of surgery. Systemic TIMP-1 could have the potential of distinguishing perforated from nonperforated appendicitis.

Effects of pharmacological suppression of plasminogen activator inhibitor-1 in myocardial remodeling after ischemia reperfusion injury

Plasminogen activator inhibitor-1 (PAI-1) contributes to cardiac ventricular remodeling because migration of inflammatory cells and attenuation of extracellular matrix degradation are caused by plasmin and matrix metalloproteinase. However, the roles of PAI-1 in myocardial ischemia reperfusion (I/R) injury and the following inflammatory response have not yet been well elucidated. To clarify the role of PAI-1 in myocardial I/R injury, we used a specific PAI-1 inhibitor (IMD-1622) in a rat model. The left anterior descending coronary artery was ligated and reperfusion was performed by loosening the suture after 30 minutes of arterial occlusion. A single administration of IMD-1622 (20 mg/kg) or vehicle was given intraperitoneally and then the rats were sacrificed on day 1 or day 14 after I/R. Blood pressure, echocardiograms, histopathology, and molecular examination were performed. The examinations revealed that PAI-1 inhibitor showed limited effects on cardiac dysfunction and ventricular remodeling after I/R. We conclude that the pharmacological inhibition of PAI-1 may not affect ventricular remodeling after myocardial I/R injury.

Plasminogen activator inhibitor type-1 deficiency exaggerates LPS-induced acute lung injury through enhancing Toll-like receptor 4 signaling pathway

Mice lacking plasminogen activator inhibitor-1 (PAI-1) did not affect lung injury induced by gram-positive bacteria pneumococcal pneumonia but worsened lung injury induced by gram-negative bacteria Klebsiella. The exact mechanisms have not been completely elucidated. In this study, we examined the signaling pathway of Toll-like receptor 4 (TLR4) with/without PAI-1 in acute lung injury (ALI) induced by lipopolysaccharides (LPS) in mice. PAI-1 knockout mice (n=60) and wild-type mice (n=60) were exposed to LPS intratracheal instillation. Different groups of mice were then sacrificed at 0 and 8 h after LPS instillation. PAI-1-/- mice showed increased excess lung water and elevated cytokines production and release. In addition, expression of TLR4 was up-regulated and the phosphorylation activation of extracellular regulating kinase (ERK) and c-Jun N-terminal kinase (JNK) were also increased in PAI-1 knockout mice compared to wild-type mice. Inversely, interleukin (IL)-1 receptor-associated kinase-M (IRAK-M) and suppressor of cytokine signaling 1 (SOCS1) were both significantly reduced in PAI-1-/-mice after LPS challenge. PAI-1 deletion increased lung injury induced by LPS through up-regulation of TLR4, ERK and C-JNK and down-regulation of TLR4 negative regulators.

Neutrophil-cytokine interactions in a rat model of sulindac-induced idiosyncratic liver injury

Previous studies indicated that lipopolysaccharide (LPS) interacts with the nonsteroidal anti-inflammatory drug sulindac (SLD) to produce liver injury in rats. In the present study, the mechanism of SLD/LPS-induced liver injury was further investigated. Accumulation of polymorphonuclear neutrophils (PMNs) in the liver was greater in SLD/LPS-cotreated rats compared to those treated with SLD or LPS alone. In addition, PMN activation occurred specifically in livers of rats cotreated with SLD/LPS. The hypothesis that PMNs and proteases released from them play critical roles in the hepatotoxicity was tested. SLD/LPS-induced liver injury was attenuated by prior depletion of PMNs or by treatment with the PMN protease inhibitor, eglin C. Previous studies suggested that tumor necrosis factor-α (TNF) and the hemostatic system play critical roles in the pathogenesis of liver injury induced by SLD/LPS. TNF and plasminogen activator inhibitor-1 (PAI-1) can contribute to hepatotoxicity by affecting PMN activation and fibrin deposition. Therefore, the role of TNF and PAI-1 in PMN activation and fibrin deposition in the SLD/LPS-induced liver injury model was tested. Neutralization of TNF or inhibition of PAI-1 attenuated PMN activation. TNF had no effect on PAI-1 production or fibrin deposition. In contrast, PAI-1 contributed to fibrin deposition in livers of rats treated with SLD/LPS. In summary, PMNs, TNF and PAI-1 contribute to the liver injury induced by SLD/LPS cotreatment. TNF and PAI-1 independently contributed to PMN activation, which is critical to the pathogenesis of liver injury. Moreover, PAI-1 contributed to liver injury by promoting fibrin deposition.

PAI-1 is an essential component of the pulmonary host response during Pseudomonas aeruginosa pneumonia in mice

RATIONALE

Elevated plasma and bronchoalveolar lavage fluid plasminogen activator inhibitor 1 (PAI-1) levels are associated with adverse clinical outcome in patients with pneumonia caused by Pseudomonas aeruginosa. However, whether PAI-1 plays a pathogenic role in the breakdown of the alveolar-capillary barrier caused by P aeruginosa is unknown.

OBJECTIVES

The role of PAI-1 in pulmonary host defence and survival during P aeruginosa pneumonia in mice was tested. The in vitro mechanisms by which P aeruginosa causes PAI-1 gene and protein expression in lung endothelial and epithelial cells were also examined.

METHODS AND RESULTS

PAI-1 null and wild-type mice that were pretreated with the PAI-1 inhibitor Tiplaxtinin had a significantly lower increase in lung vascular permeability than wild-type littermates after the airspace instillation of 1×10(7) colony-forming units (CFU) of P aeruginosa bacteria. Furthermore, P aeruginosa in vitro induced the expression of the PAI-1 gene and protein in a TLR4/p38/RhoA/NF-κB (Toll-like receptor 4/p38/RhoA/nuclear factor-κB) manner in lung endothelial and alveolar epithelial cells. However, in vivo disruption of PAI-1 signalling was associated with higher mortality at 24 h (p<0.03) and higher bacterial burden in the lungs secondary to decreased neutrophil migration into the distal airspace in response to P aeruginosa.

CONCLUSIONS

The results indicate that PAI-1 is a critical mediator that controls the development of the early lung inflammation that is required for the activation of the later innate immune response necessary for the eradication of P aeruginosa from the distal airspaces of the lung.

Plasminogen activator inhibitor-type I gene deficient mice show reduced influx of neutrophils in ventilator-induced lung injury

Ventilator-induced lung injury (VILI) is associated with inhibition of the fibrinolytic system secondary to increased production of plasminogen activator inhibitor- (PAI-)1. To determine the role of PAI-1 on pulmonary coagulopathy and inflammation during mechanical ventilation, PAI-1 gene-deficient mice and their wild-type littermates were anesthetized (control), or anesthetized, tracheotomized and subsequently ventilated for 5 hours with either low tidal volumes (LV_T) or high tidal volumes (HV_T). VILI was assessed by pulmonary coagulopathy, lung wet-to-dry ratios, total protein level in bronchoalveolar lavage fluid, neutrophil influx, histopathology, and pulmonary and plasma cytokine levels. Ventilation resulted in pulmonary coagulopathy and inflammation, with more injury following ventilation with HV_T as compared to LV_T. In PAI-1 gene-deficient mice, the influx of neutrophils in the pulmonary compartment was attenuated, while increased levels of pulmonary cytokines were found. Other endpoints of VILI were not different between PAI-1 gene-deficient and wild-type mice. These data indicate that a defect fibrinolytic response attenuates recruitment of neutrophils in VILI.

Intracellular lifestyles and immune evasion strategies of uropathogenic Escherichia coli

Paradigms in the pathogenesis of urinary tract infections have shifted dramatically as a result of recent scientific revelations. Beyond extracellular colonization of the bladder luminal surface, as traditional clinical thinking would hold, uropathogenic bacteria direct a complex, intracellular cascade that shelters bacteria from host defenses and leads to persistent bacterial residence within the epithelium. After epithelial invasion, many organisms are promptly expelled by bladder epithelial cells; a minority establish a niche in the cytoplasm that results in the development of biofilm-like intracellular bacterial communities and serves as the primary location for bacterial expansion. Exfoliation of the superficial epithelial layer acts to reduce the bacterial load but facilitates chronic residence of small nests of bacteria that later reemerge to cause some episodes of recurrent cystitis, a familiar clinical scenario in otherwise healthy women. Advances in both in vitro and animal models of cystitis promise to provide insights into the bacterial and host transcriptional and biochemical pathways that define these pathogenic stages.