Protease-activated Receptor-2 mRNA Levels Research Articles

Relative expression of protease-activated receptor 1 (PAR-1) mRNA in rat Schwann cells remains stable following PAR-1 activation

Protease-activated Receptor-1 (PAR-1) is a G protein-coupled receptor activated by the serine protease thrombin. Neurons and glial cells express PAR-1, and dysregulation of thrombin and/or PAR-1 is implicated in inflammatory disorders, neurodegenerative diseases, and spinal cord injury. We confirmed PAR-1 localization on rat Schwann cells using immunocytochemistry and confirmed gene expression with RT- qPCR (reverse transcription quantitative real-time PCR). We hypothesized that PAR-1 activation may involve a feedback mechanism, by which initial activation modulates PAR-1 mRNA levels, protein expression, and therefore future sensitivity of the cell to PAR-1 activation. Schwann cells were treated with 100 nM of the synthetic peptide SFLLRNP to activate PAR-1, and RT- qPCR was conducted for PAR-1 mRNA following incubations of 0, 4, 8, or 12 h. We demonstrate that PAR-1 mRNA levels are stable following PAR-1 activation in Schwann cells, indicating that other mechanisms may be responsible for the PAR-1 mRNA dysregulation observed in injury and disease. Our results also suggest that, in Schwann cells, there is no de novo synthesis of PAR-1 to replace internalized receptors in the period soon after (∼30 min after) extended periods of activation. Understanding the mechanisms underlying PAR-1 expression is essential since disruption of PAR-1 signaling in the nervous system can contribute to disease states.

Protease-activated-receptor 1 polymorphisms correlate with risk for unexplained recurrent pregnancy loss: a pilot study querying an association beyond coagulation

BackgroundRecurrent pregnancy loss (RPL) has been associated with impaired maternal–fetal communication. Protease-activated-receptor 1 (PAR1) is critical for trophoblast invasion and establishment unrelated to its role in vascular biology. ObjectivesTo analyze whether polymorphisms of PAR1 [-1426C/T], [-506I/D], and/or IVS[-14A/T] are associated with unexplained RPL. Patients/methodsA case-control pilot study conducted in 39 healthy women with history of unexplained RPL and 98 women with a full-term, uncomplicated deliveries and no history of RPL. ResultsWomen with RPL were significantly more likely to be heterozygous for [-1426C/T] (12.8% versus 3.2%; p=0.049); the heterozygous state for IVS[-14A/T] was also more common (15.4% versus 4.4%; p=0.064). There was no difference between groups for [-506I/D] genotypes. The functional consequence for [-1426C/T] and IVS[-14A/T] polymorphisms is underscored by the markedly low PAR1 mRNA levels in those women. Bioinformatics indicate generation of a new consensus motif for repressor Kruppel-like factor 3 (KLF3) in [-1426T]. Moreover, chromatin immunoprecipitation (ChIP) analysis confirmed a physical association between KLF3 protein and the hPar1 DNA obtained from women with the [-1426C/T] polymorphism. ConclusionsWe hypothesize that the significantly low PAR1 levels impact placenta establishment and consequently pregnancy outcome, thereby profiling a novel risk factor for unexplained RPL.

The Coagulation System Contributes to αVβ6 Integrin Expression and Liver Fibrosis Induced by Cholestasis

Chronic injury to intrahepatic bile duct epithelial cells (BDECs) elicits expression of various mediators, including the αVβ6 integrin, promoting liver fibrosis. We tested the hypothesis that tissue factor (TF)-dependent thrombin generation and protease activated receptor-1 (PAR-1) activation contribute to liver fibrosis induced by cholestasis via induction of αVβ6 expression. To test this hypothesis, mice deficient in either TF or PAR-1 were fed a diet containing 0.025% α-naphthylisothiocyanate (ANIT), a BDEC-selective toxicant. In genetically modified mice with a 50% reduction in liver TF activity fed an ANIT diet, coagulation cascade activation and liver fibrosis were reduced. Similarly, liver fibrosis was significantly reduced in PAR-1(-/-) mice fed an ANIT diet. Hepatic integrin β6 mRNA induction, expression of αVβ6 protein by intrahepatic BDECs, and SMAD2 phosphorylation were reduced by TF deficiency and PAR-1 deficiency in mice fed the ANIT diet. Treatment with either an anti-αVβ6 blocking antibody or soluble transforming growth factor-β receptor type II reduced liver fibrosis in mice fed the ANIT diet. PAR-1 activation enhanced transforming growth factor-β1-induced integrin β6 mRNA expression in both transformed human BDECs and primary rat BDECs. Interestingly, TF and PAR-1 mRNA levels were increased in livers from patients with cholestatic liver disease. These results indicate that a TF-PAR-1 pathway contributes to liver fibrosis induced by chronic cholestasis by increasing expression of the αVβ6 integrin, an important regulator of transforming growth factor-β1 activation.

Expression of protease activated receptor-2 related to angiogenesis in tumor advancement of uterine endometrial cancers

Protease activated receptor-2 (PAR-2) is the second member of a novel family of G-protein coupled seven-transmembrane domain receptors. PAR-2 has been reported to be expressed in various tumors and play a vital role in the regulation of cancer cell growth. The purpose of this study was to clarify the roles of PAR-2 in the angiogenic pathway in uterine endometrial cancers. PAR-2 expression was analyzed in 61 uterine endometrial cancer and 15 normal endometrium tissue specimens. PAR-2 histoscores and mRNA levels were determined by immunohistochemistry and real-time RT-PCR, respectively. Microvessel counts were determined by immunohistochemistry for CD31 and factor VIII-related antigen. The localization of PAR-2 was dominant in the cancer cells of endometrial cancer tissues of all cases studied. PAR-2 histoscores highly correlated with PAR-2 mRNA levels in the same tissues (r=0.87, p<0.001). PAR-2 histoscores and mRNA levels both significantly increased in uterine endometrial cancers with clinical stages (I<II<III, p<0.001), dedifferentiation (G1<G2<G3, p<0.001) and myometrial invasion (A<B, p<0.001; B<C, p<0.05) in comparison to normal endometria. There were significant correlations between PAR-2 histoscores and mRNA levels with microvessel counts in uterine endometrial cancers. PAR-2 was upregulated during uterine endometrial cancer progression with dedifferentiation and myometrial invasion. Therefore, PAR-2 might work on tumor advancement of uterine endometrial cancers via angiogenic activity.

Atorvastatin Downregulates Tissue Plasminogen Activator-Aggravated Genes Mediating Coagulation and Vascular Permeability in Single Cerebral Endothelial Cells Captured by Laser Microdissection

The effects of statins on gene expression of cerebral endothelial cells (ECs) in vivo have not been investigated after stroke. We developed a rapid double immunofluorescent staining protocol with antibodies against von Willebrand factor (a marker for endothelium) and glial fibrillary acidic protein (a marker for astrocytes) for laser capture microdissection to isolate single ECs in brain tissue of the rat. Using this protocol in combination with real-time PCR, we found that stroke significantly increased mRNA levels of protease-activated receptor 1 (PAR-1) and tissue factor (TF) in ECs isolated from ischemic cerebral microvessels compared with nonischemic vessels. Treatment of embolic stroke with recombinant human tissue plasminogen activator (rht-PA) 4 h after stroke further elevated PAR-1 mRNA levels nearly 1000-fold in the core and 500-fold in the boundary above the nonstroke group 30 h after stroke, while TF mRNA levels were elevated approximately 10 fold above the nonstroke group. Furthermore, stroke significantly increased matrix metalloproteinase (MMP) 2 and 9 mRNA levels in the ischemic core and boundary regions 6 and 30 h after stroke. Treatment with rht-PA-upregulated MMP2 expression in the ischemic boundary and core. Atorvastatin completely blocked rht-PA upregulation of the above genes, when atorvastatin in combination with rht-PA was administered 4 h after stroke. Monotherapy of atorvastatin 4 h after stroke did not significantly reduce expression of genes examined in the present study. These data provide evidence that atorvastatin reduces exogenous tPA-aggravated cerebral endothelial genes that mediate thrombosis and blood-brain barrier permeability, which could contribute to the beneficial effects of statins on thrombolytic treatment of acute stroke.

Deficiency of Microvascular Thrombomodulin and Up-Regulation of Protease-Activated Receptor-1 in Irradiated Rat Intestine: Possible Link Between Endothelial Dysfunction and Chronic Radiation Fibrosis

Microvascular injury is believed to be mechanistically involved in radiation fibrosis, but direct molecular links between endothelial dysfunction and radiation fibrosis have not been established in vivo. We examined radiation-induced changes in endothelial thrombomodulin (TM) and protease-activated receptor-1 (PAR-1) in irradiated intestine, and their relationship to structural, cellular, and molecular aspects of radiation injury. Rat small intestine was locally exposed to fractionated X-radiation. Structural injury was assessed 24 hours and 2, 6, and 26 weeks after the last radiation fraction using quantitative histology and morphometry. TM, neutrophils, transforming growth factor-beta, and collagens I and III were assessed by quantitative immunohistochemistry. PAR-1 protein was localized immunohistochemically, and cells expressing TM or PAR-1 transcript were identified by in situ hybridization. Steady-state PAR-1 mRNA levels in intestinal smooth muscle were determined using laser capture microdissection and competitive reverse transcriptase-polymerase chain reaction. Radiation caused a sustained, dose-dependent decrease in microvascular TM. The number of TM-positive vessels correlated with all parameters of radiation enteropathy and, after adjusting for radiation dose and observation time in a statistical model, remained independently associated with neutrophil infiltration, intestinal wall thickening, and collagen I accumulation. PAR-1 immunoreactivity and transcript increased in vascular and intestinal smooth muscle cells in irradiated intestine. PAR-1 mRNA increased twofold in irradiated intestinal smooth muscle. Intestinal irradiation up-regulates PAR-1 and causes a dose-dependent, sustained deficiency of microvascular TM that is independently associated with the severity of radiation toxicity. Interventions aimed at preserving or restoring endothelial TM or blocking PAR-1 should be explored as strategies to increase the therapeutic ratio in clinical radiation therapy.

Cyclic strain increases protease-activated receptor-1 expression in vascular smooth muscle cells.

Cyclic strain regulates many vascular smooth muscle cell (VSMC) functions through changing gene expression. This study investigated the effects of cyclic strain on protease-activated receptor-1 (PAR-1) expression in VSMCs and the possible signaling pathways involved, on the basis of the hypothesis that cyclic strain would enhance PAR-1 expression, reflecting increased thrombin activity. Uniaxial cyclic strain (1 Hz, 20%) of cells cultured on elastic membranes induced a 2-fold increase in both PAR-1 mRNA and protein levels. Functional activity of PAR-1, as assessed by cell proliferation in response to thrombin, was also increased by cyclic strain. In addition, treatment of cells with antioxidants or an NADPH oxidase inhibitor blocked strain-induced PAR-1 expression. Preincubation of cells with protein kinase inhibitors (staurosporine or Ro 31-8220) enhanced strain-increased PAR-1 expression, whereas inhibitors of NO synthase, tyrosine kinase, and mitogen-activated protein kinases had no effect. Cyclic strain in the presence of basic fibroblast growth factor induced PAR-1 mRNA levels beyond the effect of cyclic strain alone, whereas no additive effect was observed between cyclic strain and platelet-derived growth factor-AB. Our findings that cyclic strain upregulates PAR-1 mRNA expression but that shear stress downregulates this gene in VSMCs provide an opportunity to elucidate signaling differences by which VSMCs respond to different mechanical forces.

Lipopolysaccharide-induced subsensitivity of protease-activated receptor-2 in the mouse salivary glands in vivo.

Protease-activated receptor-2 (PAR-2) acts as a modulator of multiple physiological/pathophysiological functions including salivary exocrine secretion. Given the supersensitivity of endothelial PAR-2 under endotoxaemia, we investigated if endotoxin/lipopolysaccharide (LPS) could alter the sensitivity of PAR-2 in the salivary glands. The in vivo salivation in response to i.v. administration of the PAR-2-activating peptide SLIGRL-NH2, but not of carbachol, gradually decreased 6-20 h after LPS administration in the mice. The LPS-induced hyporeactivity to the PAR-2 agonist was partially reversed by repeated administration of aprotinin, a non-specific protease inhibitor. PAR-2 mRNA levels in the salivary glands, as assessed by the semi-quantitative RT-PCR analysis, remained unchanged following LPS challenge. Our findings indicate that in contrast to the supersensitivity of endothelial PAR-2 as described previously, subsensitivity of PAR-2 in the salivary glands develops during the LPS-induced systemic inflammation, which might involve desensitisation of PAR-2 by endogenous proteases.

Motor Neuron Cell Death in Wobbler Mutant Mice Follows Overexpression of the G-protein-coupled, Protease-activated Receptor for Thrombin

Mechanisms underlying neurodegeneration are actively sought for new therapeutic strategies. Transgenic, knockout and genetic mouse models greatly aid our understanding of the mechanisms for neuronal cell death. A naturally occurring, autosomal recessive mutant, known as wobbler, and mice transgenic for familial amyotrophic lateral sclerosis (FALS) superoxide dismutase (SOD)1 mutations are available, but the molecular mechanisms remain equally unknown. Both phenotypes are detectable after birth. Wobbler is detectable in the third week of life, when homozygotes (wr/wr) exhibit prominent gliosis and significant motor neuron loss in the cervical, but not in lumbar, spinal cord segments. To address molecular mechanisms, we evaluated "death signals" associated with the multifunctional serine protease, thrombin, which leads to apoptotic motor neuronal cell death in culture by cleavage of a G-protein coupled, protease-activated receptor 1 (PAR-1). Thrombin activities were determined with chromogenic substrate assays, Western immunoblots and immunohistochemistry were performed with anti-PAR-1 to observe localizations of the receptor and anti-GFAP staining was used to monitor astrocytosis. PAR-1 mRNA levels and locations were determined by reverse transcription polymerase chain reaction (qRT-PCR) and in situ hybridizations. Cell death was monitored with in situ DNA fragmentation assays. In preliminary studies we found a 5-fold increase in PAR-1 mRNA in cervical spinal cords from wr/wr, compared with wild-type (wt) littermates. Our current studies suggested that reactive astrocytosis and motor neuron cell death were causally linked with alterations in thrombin signaling. PAR-1 protein expression was increased, as demonstrated by immunocytochemistry and confirmed with in situ hybridization, in phenotypic wr/wr motor neurons, compared with wt, but not in astrocytes. This increase was much greater in cervical, compared with lumbar, segments, paralleling motor neuron degeneration. We also found, using reverse transcription polymerase chain reaction (qRT-PCR) with RNA from genotyped embryos, that PAR-1 was already increased in wr/wr cords at E12, the earliest time examined. Thus, motor neuron degeneration and death follows PAR-1 expression both temporally and topographically in wobbler mice. Since our culture studies show that thrombin mobilized [Ca2+]i by activating PAR-1, eventually leading to motor neuron apoptosis, up-regulation of PAR-1 during development may contribute both to "appropriate" as well as "inappropriate" neuronal death in wobbler.

Differential regulation of protease activated receptor-1 and tissue plasminogen activator expression by shear stress in vascular smooth muscle cells.

Recent studies have demonstrated that vascular smooth muscle cells are responsive to changes in their local hemodynamic environment. The effects of shear stress on the expression of human protease activated receptor-1 (PAR-1) and tissue plasminogen activator (tPA) mRNA and protein were investigated in human aortic smooth muscle cells (HASMCs). Under conditions of low shear stress (5 dyn/cm2), PAR-1 mRNA expression was increased transiently at 2 hours compared with stationary control values, whereas at high shear stress (25 dyn/cm2), mRNA expression was decreased (to 29% of stationary control; P<0.05) at all examined time points (2 to 24 hours). mRNA half-life studies showed that this response was not due to increased mRNA instability. tPA mRNA expression was decreased (to 10% of stationary control; P<0.05) by low shear stress after 12 hours of exposure and was increased (to 250% of stationary control; P<0.05) after 24 hours at high shear stress. The same trends in PAR-1 mRNA levels were observed in rat smooth muscle cells, indicating that the effects of shear stress on human PAR-1 were not species-specific. Flow cytometry and ELISA techniques using rat smooth muscle cells and HASMCs, respectively, provided evidence that shear stress exerted similar effects on cell surface-associated PAR-1 and tPA protein released into the conditioned media. The decrease in PAR-1 mRNA and protein had functional consequences for HASMCs, such as inhibition of [Ca2+] mobilization in response to thrombin stimulation. These data indicate that human PAR-1 and tPA gene expression are regulated differentially by shear stress, in a pattern consistent with their putative roles in several arterial vascular pathologies.