Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human endothelial cells respond to extracellular proteases, endotoxin (lipopolysaccharide, LPS), and inflammatory cytokines. Endothelial cells express several protease-activated receptors (PAR), including the thrombin-activated receptors PAR-1 and PAR-3 and a thrombin-independent, protease-activated receptor, PAR-2. To examine the potential cooperation between PAR and inflammatory stimuli, we investigated the effects of the PAR-1 agonist peptide Ser-Phe-Leu-Leu-Arg-Asn (SFLLRN) and PAR-2 agonist peptide Ser-Leu-Ile-Gly-Lys-Val (SLIGKV) on endothelial cells. Human umbilical vein endothelial cells (HUVEC) were cultured in vitro with SFLLRN or SLIGKV in the presence and absence of LPS or tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) levels in the culture supernatants were assayed. Both SFLLRN and SLIGKV induced detectable levels of IL-6 production in a dose-dependent fashion, with the PAR-1 receptor agonist being more potent. In the presence of all stimulatory concentrations of LPS or TNF-alpha tested, both peptides were found to further enhance IL-6 production. The effects of SFLLRN and SLIGKV were specific, as related peptides with identical amino acid compositions, but lacking in consensus sequences, were biologically inactive either alone or in the presence of LPS. Both the direct and the amplifying effects of PAR agonist peptides on IL-6 production were pertussis toxin sensitive and caused an increase in the intracellular levels of calcium, implicating G-proteins and calcium mobilization in these pathways. Furthermore, the amplifying effect of LPS or TNF-alpha on PAR-mediated cytokine production was associated with corresponding increases in nuclear NF-kappaB proteins. The results demonstrate significant potentiation of PAR-induced signaling by LPS and TNF-alpha and indicate the potential cooperation of proteases and inflammatory stimuli in amplifying vascular inflammation.
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PMID:Interleukin-6 production by endothelial cells via stimulation of protease-activated receptors is amplified by endotoxin and tumor necrosis factor-alpha. 1135 54

Inhibition of the tissue factor-factor VIIa complex reduces coagulation and inflammation in animal models of endotoxemia and sepsis and in patients with severe sepsis. However, the mechanism by which tissue factor-dependent activation of the coagulation cascade enhances inflammation is not known. We tested the hypothesis that coagulation proteases enhance inflammation during endotoxemia by activating protease-activated receptors (PARs) within the vasculature. We found that genetically modified mice expressing low levels of tissue factor exhibited reduced interleukin-6 expression and increased survival in a mouse model of endotoxemia compared with control mice. In contrast, hirudin inhibition of thrombin or a deficiency in either PAR-1 or PAR-2 did not affect interleukin-6 expression or mortality. However, combining hirudin treatment to inhibit thrombin signaling through PAR-1 and PAR-4 with PAR-2 deficiency reduced lipopolysaccharide-induced interleukin-6 expression and increased survival. Taken together, our results suggest that activation of multiple PARs by coagulation proteases enhances inflammation during endotoxemia.
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PMID:Tissue factor, coagulation proteases, and protease-activated receptors in endotoxemia and sepsis. 1511 33

Recently a new concept has emerged implicating thrombin signaling as the "bridge" that connects tissue damage to hemostatic and inflammatory responses. In view of this concept, we hypothesized that induction of protease-activated receptor (PAR) expression may play a critical role in endotoxin-induced tissue injury through the cellular actions of thrombin. Thus, in this study, temporal changes in expression of key precoagulant molecules, including PARs, in lungs from rabbits rendered endotoxemic by 100 microg/kg lipopolysaccharide (LPS) were examined with measurements of variables reflecting acute lung injury (ALI). ALI induction by LPS was confirmed by blood gas derangement, lung vascular hyperpermeability, and histopathological changes, and was characterized by the deposition of fibrin in the alveolar spaces, bronchioles and vessels. Plasminogen activator inhibitor-1 (PAI-1) and tissue factor (TF) were highly expressed in lungs after LPS injection. While the peaks in levels of PAI-1 and TF were comparable (12 approximately 13-fold from control), their expression time-courses were different: PAI-1 exhibited a bell-shaped expression pattern and peak at 6 h, whereas TF level reached maximum at 10 h. Of note, LPS induced a rapid and significant increase in levels of PAR-1 compared to control, with a peak level at 1 h (3.3-fold). Although declining thereafter, it remained significantly higher than the control level throughout the study period. Expressions of PAR-2, -3, and -4 were also increased by LPS with different time courses from PAR-1 expression. Immunofluorescence staining for PAR-1 were localized in blood vessels, bronchial epithelium, and alveolar pneumocytes after LPS. These results suggest that the increased expression levels of PARs, in addition to PAI-1 and TF, may, in part, underlie the development of ALI occurring during endotoxemia.
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PMID:Temporal changes in pulmonary expression of key procoagulant molecules in rabbits with endotoxin-induced acute lung injury: elevated expression levels of protease-activated receptors. 1554 22

Human mononuclear phagocytes have recently been shown to express constitutively and even more so, upon stimulation with bacteria, fungi, lipopolysaccharide (LPS), zymosan, or thrombin platelet basic protein (PBP). This CXC chemokine as well as platelet factor 4 (PF4), which is located genomically at a short distance from the PBP, were previously considered to be specific markers for the megakaryocyte cell lineage. Both chemokines have signaling and antimicrobial activity. In the present studies, transcriptional and expressional regulation of PF4 and related chemokines was studied in human monocytes. As shown by quantitative mRNA analysis, Western blots, radioimmunoprecipitation of cell extracts, and immunofluorescence and quantitatively with enzyme-linked immunosorbent assay, human monocytes express PF4 in the same order of magnitude as the known, regulated CXC chemokine interleukin (IL)-8. Expression of PF4 is up-regulated at the mRNA and protein level by thrombin and mediated by proteinase-activated receptors (PARs), resulting in a 32- to 128-fold higher mRNA level and leading to an up-to-sixfold increase of the peptide concentration in monocyte culture supernatants. Thrombin and the synthetic ligand of PAR-1 and PAR-2, SFLLRN, also induced comparable increases in the levels of mRNA for PBP, IL-8, regulated on activation, normal T expressed and secreted (RANTES), monocyte chemoattractant protein-1, and macrophage-inflammatory protein-1alpha and increased synthesis of these chemokines as shown by immunofluorescence or a quantitative immunobead-based method. The induction of increased mRNA levels for all chemokines by SFLLRN was unsurpassed by LPS, zymosan, interferon-gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and IL-1. Activation of monocytes through PARs represents an alternate activation mechanism, independent from IFN-gamma, TNF-alpha, or other signaling pathways.
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PMID:Regulated expression of platelet factor 4 in human monocytes--role of PARs as a quantitatively important monocyte activation pathway. 1578 41

Activated neutrophils produce serine proteases, which activate cells through protease-activated receptor 2 (PAR2). As proteinase 3 (PR3) induces the secretion of interleukin (IL)-18 from epithelial cells in combination with lipopolysaccharide (LPS) in vitro, we examined whether neutrophils, serine proteases, and PAR2 are involved in the induction of serum IL-18 and IL-18-dependent liver injury in mice treated with heat-killed Propionibacterium acnes and LPS. LPS-induced serum IL-18 levels in P. acnes-primed mice were reduced significantly by anti-Gr-1 injection (depletion of neutrophils and macrophages) but not by a macrophage "suicide" technique, using liposomes encapsulating clodronate. The IL-18 induction was decreased significantly by coadministration of a serine protease inhibitor [Nafamostat mesilate (FUT-175)] with LPS. Serum levels of tumor necrosis factor alpha and liver enzymes induced by P. acnes and LPS were abolished by anti-Gr-1 treatment, and concomitantly, liver injury (necrotic change and granuloma formation) and Gr-1(+) cell infiltration into the liver were prevented by the treatment. A deficiency of PAR2 in mice significantly impaired IL-18 induction by treatment with P. acnes and LPS, and only slight pathological changes in hepatic tissues occurred in the PAR2-deficient mice treated with P. acnes and LPS. Furthermore, coadministration of exogenous murine PR3 or a synthetic PAR2 agonist (ASKH95) with LPS in the anti-Gr-1-treated mice restored the serum IL-18 levels to those in control mice treated with P. acnes and LPS. These results indicate that neutrophil recruitment and PAR2 activation by neutrophil serine proteases are critically involved in the induction of IL-18 and IL-18-dependent liver injury in vivo.
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PMID:Involvement of neutrophil recruitment and protease-activated receptor 2 activation in the induction of IL-18 in mice. 1626 May 85

The hypothesis that the expression of protease-activated receptors (PARs) protein is regulated at the level of transcription and that PAR isoforms, PAR-1, PAR-2, PAR-3, and PAR-4, in lung tissue show different patterns of expression in lipopolysaccharide (LPS)-induced acute lung injury (ALI) was tested. Male Wistar rats were rendered endotoxemic by intra-peritoneal injection of LPS (15 mg/kg body weight). We examined the expression of protein and mRNA and the immunohistochemical localization of PAR isoforms in lung tissues 1, 3, 6, and 10 h after LPS administration. Induction of ALI by LPS was confirmed based on histopathological changes. LPS administration induced significant increases in the expression of PAR isoforms (protein) at the level of transcription in ALI. While the time course of PAR-1 and -2 expressions were different, those of PAR-3 and -4 were almost similar. An immunohistochemical analysis showed localization of PAR isoforms in the vascular endothelium, alveolar epithelium, and alveolar macrophages. However, the cellular distribution patterns of PAR isoforms were different. We conclude that LPS induces increase in protein expression of PAR isoforms at the level of transcription in rats with ALI. The differential expression patterns (over a time course) and distribution of PAR isoforms suggests a distinct role for each isoform in the pathogenesis of LPS-induced ALI.
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PMID:Differential expression, time course and distribution of four PARs in rats with endotoxin-induced acute lung injury. 1713 98

Porphyromonas gingivalis activates protease-activated receptors (PARs) on oral keratinocytes, resulting in downstream signalling for an innate immune response. Activation depends on P. gingivalis gingipains, but could be confounded by lipopolysaccharide signalling through Toll-like receptors. We therefore hypothesized that P. gingivalis cleaves oral keratinocyte PARs in an Arg- (Rgp) or Lys- (Kgp) gingipain-specific manner to upregulate pro-inflammatory cytokines. Immortalized human oral keratinocytes (TERT-2) were incubated with wild-type P. gingivalis (ATCC 33277) or strains from a panel of isogenic gingipain deletion mutants: Kgp-deficient (KDP 129); Rgp-deficient (KDP 133); or Kgp- and Rgp-deficient (KDP 136). After incubation with P. gingivalis, keratinocytes were probed with specific antibodies against the N-terminus of PAR-1 and PAR-2. Using flow cytometry and immunofluorescence, receptor cleavage was marked by loss of specific antibody binding to the respective PARs. TERT-2 cells constitutively expressed high levels of PAR-1 and PAR-2, and lower levels of PAR-3. P. gingivalis ATCC 33277 cleaved PAR-1 and PAR-2 in a dose-dependent manner, while the receptors were unaffected by the protease-negative double mutant (KDP 136) at all m.o.i. tested. The single Kgp-negative mutant preferentially cleaved PAR-1, whereas the Rgp-negative mutant cleaved PAR-2. Wild-type or Kgp-negative mutant cleavage of PAR-1 upregulated expression of IL-1alpha, IL-1beta, IL-6 and TNF-alpha; the Rgp-negative mutant did not modulate these cytokines. Selective cleavage of PAR-1 on oral epithelial cells by P. gingivalis Rgp therefore upregulates expression of pro-inflammatory cytokines.
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PMID:Cleavage of protease-activated receptors on an immortalized oral epithelial cell line by Porphyromonas gingivalis gingipains. 1960 9

Protease-activated receptors (PARs) are cleaved and activated by thrombin and other extracellular proteases which are released during tissue trauma and inflammation. PAR-1 is the prototypic member of the PAR family and has been shown to be upregulated in several brain pathologies being expressed by neurons and glial cells. The present experiments show that the administration of the PAR-1 activating peptides (TRAP6 and TFLLR) inhibits the production of the pro-inflammatory cytokines TNF-alpha and IL-6 in microglial cells treated with lipopolysaccharide (LPS) while promoting the release of the anti-inflammatory cytokine IL-10. Conversely, the addition of the specific PAR-2 agonist SLIGRL had no effect on the amount of cytokines released following LPS treatment. Consistent with these data PAR-1, but not PAR-2, stimulation upregulates the expression of the suppressor of cytokine signaling-3 (SOCS-3). The present data support the hypothesis that in microglia PAR-1 may be involved in the regulation of inflammatory reactions modulating the balance between pro- and anti-inflammatory cytokines possibly through SOCS induction.
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PMID:Protease-activated receptor-1 regulates cytokine production and induces the suppressor of cytokine signaling-3 in microglia. 1963 29

Preterm delivery (PTD) has been associated with inflammation along with activation of the coagulation pathway. These studies sought to characterize the expression of several coagulation pathway genes including plasminogen activator inhibitor 1 (PAI-1), tissue factor (TF), protease-activated receptor 1 (Par1), protease-activated receptor 2 (Par2), fibrinogen-like protein 2 (Fgl2), and thrombomodulin (TM) during lipopolysaccharide (LPS)-induced PTD in day 15 pregnant CD-1 mice. Western blot studies confirmed protein expression for PAI-1, Par1, Par2, Fgl2, and TM in the mouse uterus. Quantitative reverse transcriptase polymerase chain reaction (RT-PCR) confirmed increased PAI-1 messenger RNA (mRNA) in the uteri, lung, kidney, and liver tissues at 2 to 6 hours after LPS injection. In contrast, TF expression significantly decreased by 12 hours in uterine tissue; whereas, its expression was unchanged in the other maternal tissues. The uterine mRNA for Par1, Par2, Fgl2, and TM remained stable. In summary, these studies have confirmed expression of coagulation pathway genes within the pregnant uterus; some of which are modulated during LPS-induced PTD.
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PMID:Expression of coagulation-related protein genes during LPS-induced preterm delivery in the pregnant mouse. 2169 78

The cytoprotective effects of activated protein C (aPC) are well established. In contrast, the receptors and signaling mechanism through which aPC conveys cytoprotection in various cell types remain incompletely defined. Thus, within the renal glomeruli, aPC preserves endothelial cells via a protease-activated receptor-1 (PAR-1) and endothelial protein C receptor-dependent mechanism. Conversely, the signaling mechanism through which aPC protects podocytes remains unknown. While exploring the latter, we identified a novel aPC/PAR-dependent cytoprotective signaling mechanism. In podocytes, aPC inhibits apoptosis through proteolytic activation of PAR-3 independent of endothelial protein C receptor. PAR-3 is not signaling competent itself as it requires aPC-induced heterodimerization with PAR-2 (human podocytes) or PAR-1 (mouse podocytes). This cytoprotective signaling mechanism depends on caveolin-1 dephosphorylation. In vivo aPC protects against lipopolysaccharide-induced podocyte injury and proteinuria. Genetic deletion of PAR-3 impairs the nephroprotective effect of aPC, demonstrating the crucial role of PAR-3 for aPC-dependent podocyte protection. This novel, aPC-mediated interaction of PARs demonstrates the plasticity and cell-specificity of cytoprotective aPC signaling. The evidence of specific, dynamic signaling complexes underlying aPC-mediated cytoprotection may allow the design of cell type specific targeted therapies.
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PMID:Cytoprotective signaling by activated protein C requires protease-activated receptor-3 in podocytes. 2211 49


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