Protease activated receptor-1 regulates mixed lineage kinase-3 to drive triple-negative breast cancer tumorigenesis.

Triple-negative breast cancer (TNBC) is difficult to treat breast cancer subtype due to lack or insignificant expressions of targetable estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2). Therefore, finding a targetable protein or signaling pathway in TNBC would impact patient care. Here, we report that a member of the Mixed Lineage Kinase (MLK) family, MLK3, is an effector of G-protein-coupled protease-activated receptors 1 (PAR1) and targeting MLK3 by a small-molecule inhibitor prevented PAR1-mediated TNBC tumorigenesis. In silico and immunohistochemistry analysis of human breast tumors showed overexpression of PAR1 and MLK3 in TNBC tumors. Treating α-thrombin and PAR1 agonist increased MLK3 and JNK activities and induced cell migration in TNBC cells. The PAR1 positive/high (PAR1+/hi) population of TNBC cells showed aggressive tumor phenotype with increased MLK3 signaling. Moreover, combined inhibition of the PAR1 and MLK3 mitigated the TNBC tumor burden in preclinical TNBC models. Our data suggests that activation of the PAR1-MLK3 axis promotes TNBC tumorigenesis. Therefore, combinatorial therapy targeting MLK3 and PAR1 could effectively reduce TNBC tumor burden.

Recombinant hirudin and PAR-1 regulate macrophage polarisation status in diffuse large B-cell lymphoma.

BACKGROUND: Diffuse large B-cell lymphoma (DLBCL) is a malignant tumour. Although some standard therapies have been established to improve the cure rate, they remain ineffective for specific individuals. Therefore, it is meaningful to find more novel therapeutic approaches. Macrophage polarisation is extensively involved in the process of tumour development. Recombinant hirudin (rH) affects macrophages and has been researched frequently in clinical trials lately. Our article validated the regulatory role of rH in macrophage polarisation and the mechanism of PAR-1 by collecting clinical samples and subsequently establishing a cellular model to provide a scientifically supported perspective for discovering new therapeutic approaches. METHOD: We assessed the expression of macrophage polarisation markers, cytokines and PAR-1 in clinical samples. We established a cell model by co-culture with THP-1 and OCI-Ly10 cell. We determined the degree of cell polarisation and expression of validation cytokines by flow cytometry, ELISA, and RT-qPCR to confirm the success of the cell model. Subsequently, different doses of rH were added to discover the function of rH on cell polarisation. We confirmed the mechanism of PAR-1 in macrophage polarisation by transfecting si-PAR-1 and pcDNA3.1-PAR-1. RESULTS: We found higher expression of M2 macrophage markers (CD163 + CMAF+) and PAR-1 in 32 DLBCL samples. After inducing monocyte differentiation into M0 macrophages and co-culturing with OCI-Ly10 lymphoma cells, we found a trend of these expressions in the cell model consistent with the clinical samples. Subsequently, we discovered that rH promotes the polarisation of M1 macrophages but inhibits the polarisation of M2 macrophages. We also found that PAR-1 regulates macrophage polarisation, inhibiting cell proliferation, migration, invasion and angiogenic capacity. CONCLUSION: rH inhibits macrophage polarisation towards the M2 type and PAR-1 regulates polarisation, proliferation, migration, invasion, and angiogenesis of DLBCL-associated macrophages.

PAR1 Activation, via LMBR1/BMP Axis, Promotes the Osteogenesis of Periodontal Ligament Stem Cells (PDLSCs) and Alleviates the Inhibitory Effect of Sodium Butyrate on PDLSCs Osteogenesis.

BACKGROUND: Periodontitis is the leading cause of tooth loss and can exacerbate various systemic inflammatory conditions. Periodontal ligament stem cells (PDLSCs) stand out as prominent and favorable candidates for promoting periodontal tissue regeneration. This study aimed to investigate whether the protease-activated receptor type 1 (PAR1) can mitigate the sodium butyrate (NaB)-induced PDLSCs osteogenesis inhibition and unravel the underlying mechanism. METHODS: Public datasets from the Gene Expression Omnibus (GEO) were utilized to analyze differentially expressed genes (DEGs) in periodontitis and subsequent Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. PDLSCs were cultured normally in control medium (CM) as the negative control or in osteogenic medium (OM) to induce osteogenesis. PAR1 was either activated or suppressed using a selective agonist or antagonist (OM+agonist and OM+antagonist). The evaluation of PDLSCs osteogenesis was based on the levels of osteogenesis-related markers, including runt-related transcription factor 2 (RUNX2), osterix (OSX), osteocalcin (OCN), and osteopontin (OPN), alkaline phosphatase (ALP) activity, and calcium concentration. Additionally, cell proliferation and osteogenic differentiation were measured through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Alizarin Red Staining. To determine the PAR1 targeting the limb development membrane protein 1 (LMBR1)/bone morphogenetic protein (BMP) pathway, LMBR1 was upregulated through cell transfection and BMP2 was inhibited using the selective inhibitor Noggin protein. Finally, NaB was introduced into PDLSCs to investigate the effect on NaB-induced inhibition of PDLSCs osteogenesis. RESULTS: PAR1, RUNX2, OSX, OCN, OPN, proliferation, ALP activity, calcium concentration, osteogenic differentiation, BMP2, and BMP4 exhibited significant increases in PDLSCs cultured in OM (p < 0.01). These parameters were further elevated by PAR1 agonist and conversely reduced by PAR1 antagonist (p < 0.01). Conversely, LMBR1 was decreased in PDLSCs cultured in OM (p < 0.001), with further reduction induced by PAR1 agonist and a reverse increase observed with PAR1 antagonist (p < 0.001). OE-LMBR1 transfection successfully elevated LMBR1 levels, subsequently inhibiting BMP2 and BMP4 (p < 0.001). Meanwhile, the Noggin protein effectively suppressed BMP2 and BMP4 (p < 0.001). All observed osteogenesis-related changes were reversed by the increased LMBR1 or inhibition of the BMP pathway (p < 0.001). Furthermore, NaB suppressed osteogenesis-related changes in OM-cultured PDLSCs (p < 0.001), and these effects were entirely reversed by PAR1 agonist (p < 0.001). Conversely, the increased LMBR1 or inhibited BMP pathway disrupted the osteogenesis reversion induced by PAR1 agonist (p < 0.001). CONCLUSION: The activation of PAR1, through suppressing LMBR1 signaling and activating BMP pathway, demonstrates the ability to enhance the osteogenesis of PDLSCs and mitigate the inhibitory effects on PDLSCs osteogenesis caused by NaB.

Baicalein promotes KDM4E to induce BICD1 and inhibit triple-negative breast cancer progression by blocking PAR1 signaling.

Baicalein has been implicated in the chemotherapy overcoming triple-negative breast cancer (TNBC). However, many unanswered questions remain regarding its role in treating TNBC. Here, we sought to demonstrate the molecular pathway mediated by baicalein in TNBC. Lysine-specific demethylase 4E (KDM4E), reduced in TNBC cells, was identified as a target protein of baicalein, and baicalein enhanced the protein expression and stability of KDM4E in TNBC cells. Knockdown of KDM4E attenuated the inhibitory effect of baicalein on TNBC cell activity, as demonstrated by intensified mobility, viability, and apoptosis resistance in TNBC cells. KDM4E activated protein bicaudal D homolog 1 (BICD1) expression by reducing the deposition of histone H3 lysine 9 trimethylation (H3K9me3) in its promoter, whereas BICD1 promoted protease-activated receptor-1 (PAR1) endocytosis and blocked PAR1 signaling through physical interaction with PAR1. Knockdown of KDM4E strengthened the PAR1-dependent activity of TNBC cells in response to thrombin activation, whereas TNBC progression activated by PAR1 signaling was blocked by combined overexpression of BICD1. Taken together, our data indicate that baicalein-promoted KDM4E enhanced the expression of BICD1 and activated the inhibitory effect of BICD1 on PAR1 signaling, thereby inhibiting TNBC progression.

Mechanism of Hirudin-Mediated Inhibition of Proliferation in Ovarian Cancer Cells.

To investigate the inhibitory effect of hirudin on the cell proliferation of human ovarian cancer A2780 cells by preventing thrombin and its underlying molecular mechanism. Cell Counting Kit-8 (CCK-8) method was used to detect the effect of different concentrations of hirudin and thrombin on the cell proliferation of A2780 cells. PAR-1 wild-type overexpression plasmid was constructed utilizing enzyme digestion identification, and it was transferred to A2780 cells. Sequencing and Western blot were used to detect the changes in PAR-1 protein expression. Western blot detection of PKCα protein phosphorylation in A2780 cells was performed. We also implemented quantitative PCR to detect the mRNA expression levels of epithelial-mesenchymal transition (EMT)-related genes, CDH2, Snail, and Vimentin, in A2780 cells. 1 µg/ml hirudin treatment maximally inhibited the promotion of A2780 cell proliferation by thrombin. Hirudin inhibited the binding of thrombin to the N-terminus of PAR-1, hindered PKCα protein phosphorylation in A2780 cells, and downregulated the mRNA expression levels of CDH2, Snail, and Vimentin. In conclusion, hirudin inhibits the cell proliferation of ovarian cancer A2780 cells, and the underlying mechanism may be through downregulating the transcription level of EMT genes, CDH2, Snail, and Vimentin. This study indicates that hirudin may have a therapeutic potential as an anti-cancer agent for ovarian cancer.

Combination of minimal residual disease on day 15 and copy number alterations results in BCR-ABL1-negative pediatric B-ALL: A powerful tool for prediction of induction failure.

The current genomic abnormalities provide prognostic value in pediatric Acute Lymphoblastic Leukemia (ALL). Furthermore, Copy Number Alteration (CNA) has recently been used to improve the genetic risk stratification of patients. This study aimed to evaluate CNA profiles in BCR-ABL1-negative pediatric B-ALL patients and correlate the data with Minimal Residual Disease (MRD) results after induction therapy. We examined 82 bone marrow samples from pediatric BCR-ABL1-negative B-ALL using the MLPA method for the most common CNAs, including IKZF1, CDKN2A/B, PAX5, RB1, BTG1, ETV6, EBF1, JAK2, and PAR1 region. Subsequently, patients were followed-up by multiparameter Flow Cytometry for MRD (MFC-MRD) assessment on days 15 and 33 after induction. Data showed that 58.5 % of patients carried at least one gene deletion, whereas 41.7 % of them carried more than one gene deletion simultaneously. The most frequent gene deletions were CDKN2A/B, ETV6, and IKZF1 (30.5 %, 14.6 %, and 14.6 %, respectively), while the PAR1 region showed predominantly duplication (30.5 %). CDKN2A/B and IKZF1 were related to positive MRD results on day 15 (p = 0.003 and p = 0.007, respectively). The simultaneous presence of more than one deletion was significantly associated with high induction failure (p = 0.001). Also, according to the CNA profile criteria, the CNA with poor risk (CNA-PR) profile was statistically associated with older age and positive MRD results on day 15 (p = 0.014 and p = 0.013, respectively). According to our results, the combined use of CNAs with MRD results on day 15 can predict induction failure and be helpful in ameliorating B-ALL risk stratification and treatment approaches.

Thrombomodulin Switches Signaling and Protease-Activated Receptor 1 Cleavage Specificity of Thrombin.

BACKGROUND: Cleavage of the extracellular domain of PAR1 (protease-activated receptor 1) by thrombin at Arg41 and by APC (activated protein C) at Arg46 initiates paradoxical cytopathic and cytoprotective signaling in endothelial cells. In the latter case, the ligand-dependent coreceptor signaling by EPCR (endothelial protein C receptor) is required for the protective PAR1 signaling by APC. Here, we investigated the role of thrombomodulin in determining the specificity of PAR1 signaling by thrombin. METHODS: We prepared a PAR1 knockout (PAR1-/-) EA.hy926 endothelial cell line by CRISPR/Cas9 and transduced PAR1-/- cells with lentivirus vectors expressing PAR1 mutants in which either Arg41 or Arg46 was replaced with an Ala. Furthermore, human embryonic kidney 293 cells were transfected with wild-type or mutant PAR1 cleavage reporter constructs carrying N-terminal Nluc (NanoLuc luciferase) and C-terminal enhanced yellow fluorescent protein tags. RESULTS: Characterization of transfected cells in signaling and receptor cleavage assays revealed that, upon interaction with thrombomodulin, thrombin cleaves Arg46 to elicit cytoprotective effects by a ß-arrestin-2 biased signaling mechanism. Analysis of functional data and cleavage rates indicated that thrombin-thrombomodulin cleaves Arg46>10-fold faster than APC. Upon interaction with thrombin, the cytoplasmic domain of thrombomodulin recruited both ß-arrestin-1 and -2 to the plasma membrane. Thus, the thrombin cleavage of Arg41 was also cytoprotective in thrombomodulin-expressing cells by ß-arrestin-1-biased signaling. APC in the absence of EPCR cleaved Arg41 to initiate disruptive signaling responses like thrombin. CONCLUSIONS: These results suggest that coreceptor signaling by thrombomodulin and EPCR determines the PAR1 cleavage and signaling specificity of thrombin and APC, respectively.

KLK10 promotes the progression of KRAS mutant colorectal cancer via PAR1-PDK1-AKT signaling pathway.

Kirsten rat sarcoma virus (KRAS) gene mutation is common in colorectal cancer (CRC) and is often predictive of treatment failure and poor prognosis. To understand the mechanism, we compared the transcriptome of CRC patients with wild-type and mutant KRAS and found that KRAS mutation is associated with the overexpression of a secreted serine protease, kallikrein-related peptidase 10 (KLK10). Moreover, using in vitro and in vivo models, we found that KLK10 overexpression favors the rapid growth and liver metastasis of KRAS mutant CRC and can also impair the efficacy of KRAS inhibitors, leading to drug resistance and poor survival. Further functional assays revealed that the oncogenic role of KLK10 is mediated by protease-activated receptor 1 (PAR1). KLK10 cleaves and activates PAR1, which further activates 3-phosphoinositide-dependent kinase 1 (PDK1)-AKT oncogenic pathway. Notably, suppressing PAR1-PDK1-AKT cascade via KLK10 knockdown can effectively inhibit CRC progression and improve the sensitivity to KRAS inhibitor, providing a promising therapeutic strategy. Taken together, our study showed that KLK10 promotes the progression of KRAS mutant CRC via activating PAR1-PDK1-AKT signaling pathway. These findings expanded our knowledge of CRC development, especially in the setting of KRAS mutation, and also provided novel targets for clinical intervention.

Effect of chimeric antigen receptor T cells against protease-activated receptor 1 for treating pancreatic cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with a 5-year survival rate of 6% following a diagnosis, and novel therapeutic modalities are needed. Protease-activated receptor 1 (PAR1) is abundantly overexpressed by both tumor cells and multiple stroma cell subsets in the tumor microenvironment (TME), thereby offering a suitable immunotherapy target. METHODS: A chimeric antigen receptor (CAR) strategy was applied to target PAR1 using a human anti-PAR1 scFv antibody fused to the transmembrane region with two co-stimulatory intracellular signaling domains of cluster of differentiation 28 (CD28) and CD137 (4-1BB), added to CD3ζ in tandem. RESULTS: The engineered PAR1CAR-T cells eliminated PAR1 overexpression and transforming growth factor (TGF)-ß-mediated PAR1-upregulated cancer cells by approximately 80% in vitro. The adoptive transfer of PAR1CAR-T cells was persistently enhanced and induced the specific regression of established MIA PaCa-2 cancer cells by > 80% in xenograft models. Accordingly, proinflammatory cytokines/chemokines increased in CAR-T-cell-treated mouse sera, whereas Ki67 expression in tumors decreased. Furthermore, the targeted elimination of PAR1-expressing tumors reduced matrix metalloproteinase 1 (MMP1) levels, suggesting that the blocking of the PAR1/MMP1 pathway constitutes a new therapeutic option for PDAC treatment. CONCLUSIONS: Third-generation PAR1CAR-T cells have antitumor activity in the TME, providing innovative CAR-T-cell immunotherapy against PDAC.

Thrombin receptor PAR1 silencing in endothelial colony-forming cells modifies stemness and vasculogenic properties.

BACKGROUND: The involvement of thrombin receptor PAR1 in blood vessel development has been largely demonstrated in knockout mice; however, its implication in adult mouse angiogenesis seems very moderate. OBJECTIVES: We aimed to explore the potential relationships between PAR1, stemness, and angiogenic properties of human endothelial colony-forming cells (ECFCs). METHODS AND RESULTS: PAR1 activation on ECFCs using the selective PAR1-activating peptide induced a significant decrease in CD133 expression (RTQ-PCR analysis). In line, silencing of PAR1 gene expression with siRNA increased CD133 mRNA as well as intracellular CD133 protein expression. To confirm the link between CD133 and PAR1, we explored the association between PAR1 and CD133 levels in fast and slow fibroblasts prone to reprogramming. An imbalance between PAR1 and CD133 levels was evidenced, with a decreased expression of PAR1 in fast reprogramming fibroblasts expressing a high CD133 level. Regarding in vitro ECFC angiogenic properties, PAR1 silencing with specific siRNA induced cell proliferation evidenced by the overexpression of Ki67. However, it did not impact migration properties nor ECFC adhesion on smooth muscle cells or human arterial endothelial cells. In a mouse model of hind-limb ischemia, PAR1 silencing in ECFCs significantly increased postischemic revascularization compared to siCtrl-ECFCs along with a significant increase in cutaneous blood flows (P < .0001), microvessel density (P = .02), myofiber regeneration (P < .0001), and human endothelial cell incorporation in muscle (P < .0001). CONCLUSION: In conclusion, our work describes for the first time a link between PAR1, stemness, and vasculogenesis in human ECFCs.

Protease-Activated Receptor 1-Mediated Damage of Podocytes in Diabetic Nephropathy.

There is clinical evidence that increased urinary serine proteases are associated with the disease severity in the setting of diabetic nephropathy (DN). Elevation of serine proteases may mediate [Ca2+]i dynamics in podocytes through the protease-activated receptors (PARs) pathway, including associated activation of nonspecific cation channels. Cultured human podocytes and freshly isolated glomeruli were used for fluorescence and immunohistochemistry stainings, calcium imaging, Western blot analysis, scanning ion conductance microscopy, and patch clamp analysis. Goto-Kakizaki, Wistar, type 2 DN (T2DN), and a novel PAR1 knockout on T2DN rat background rats were used to test the importance of PAR1-mediated signaling in DN settings. We found that PAR1 activation increases [Ca2+]i via TRPC6 channels. Both human cultured podocytes exposed to high glucose and podocytes from freshly isolated glomeruli of T2DN rats had increased PAR1-mediated [Ca2+]i compared with controls. Imaging experiments revealed that PAR1 activation plays a role in podocyte morphological changes. T2DN rats exhibited a significantly higher response to thrombin and urokinase. Moreover, the plasma concentration of thrombin in T2DN rats was significantly elevated compared with Wistar rats. T2DNPar1-/- rats were embryonically lethal. T2DNPar1+/- rats had a significant decrease in glomerular damage associated with DN lesions. Overall, these data provide evidence that, during the development of DN, elevated levels of serine proteases promote an excessive [Ca2+]i influx in podocytes through PAR1-TRPC6 signaling, ultimately leading to podocyte apoptosis, the development of albuminuria, and glomeruli damage. ARTICLE HIGHLIGHTS: Increased urinary serine proteases are associated with diabetic nephropathy. During the development of diabetic nephropathy in type 2 diabetes, the elevation of serine proteases could overstimulate protease-activated receptor 1 (PAR1). PAR1 signaling is involved in the development of DN via TRPC6-mediated intracellular calcium signaling. This study provides fundamental knowledge that can be used to develop efficient therapeutic approaches targeting serine proteases or corresponding PAR pathways to prevent or slow the progression of diabetes-associated kidney diseases.

Protease-Activated Receptor 1 (PAR1) Expression Contributes to HPV-Associated Oropharyngeal Cancer Prognosis.

BACKGROUND: Human papillomavirus (HPV)-associated oropharyngeal cancer occasionally has a poor prognosis, making prognostic risk stratification crucial. Protease-activated receptor-1 (PAR1) is involved in carcinogenesis, and its expression is regulated by alpha-arrestin domain-containing protein 3 (ARRDC3). It is also involved in the tumor microenvironment. We sought to evaluate the predictive ability of PAR1, ARRDC3, and tumor-infiltrating lymphocyte (TIL) scores in patients with oropharyngeal, hypopharyngeal, and uterine cervical cancers, serving as comparators for HPV-associated oropharyngeal cancer. METHODS: Immunohistochemical analysis of p16, ARRDC3, and PAR1 expression was performed on 79 oropharyngeal, 44 hypopharyngeal, and 42 uterine cervical cancer samples. The TIL scores were assessed and classified into the following groups based on invasion: low: 0-10%, medium: 20-40%, and high: > 50%. For prognostic analysis, the three groups were evaluated by dividing them into low, medium, and high categories, or alternatively into two groups using the median value as the cutoff. RESULTS: p16 was expressed in 44 (56%) oropharyngeal, 8 (18%) hypopharyngeal, and all uterine cervical cancer samples. ARRDC3 was detected in 39 (49%) oropharyngeal, 25 (57%) hypopharyngeal, and 23 (55%) uterine cervical cancer samples. PAR1 was expressed in 45 (57%) oropharyngeal, 22 (50%) hypopharyngeal, and 22 (50%) uterine cervical cancer samples. Patients diagnosed with p16-positive oropharyngeal cancer had a substantially improved prognosis compared to those diagnosed with p16-negative cancer. The PAR1-negative cases had a considerably improved prognosis compared to the positive cases (disease-specific survival [DSS] and -negative cases (disease-free survival [DFS]). Multivariate analysis revealed that ARRDC3-positive cases had an appreciably better DSS prognosis than patients with p16-negative oropharyngeal cancers. PAR1-positive patients among patients with p16-positive oropharyngeal cancer had a poor prognosis. With respect to DFS, patients with PAR1-positive and p16-negative oropharyngeal cancer had a 35-fold higher recurrence rate than those with PAR1-negative and p16-negative oropharyngeal cancer. CONCLUSION: Our results suggest that PAR1 expression affects the prognosis and recurrence rate of HPV-associated oropharyngeal cancer.

CLIC4 Regulates Endothelial Barrier Control by Mediating PAR1 Signaling via RhoA.

BACKGROUND: Endothelial CLICs (chloride intracellular channel proteins) CLIC1 and CLIC4 are required for the GPCRs (G-protein-coupled receptors) S1PR1 (sphingosine-1-phosphate receptor 1) and S1PR3 to activate the small GTPases Rac1 (Ras-related C3 botulinum toxin substrate 1) and RhoA (Ras homolog family member A). To determine whether CLIC1 and CLIC4 function in additional endothelial GPCR pathways, we evaluated CLIC function in thrombin signaling via the thrombin-regulated PAR1 (protease-activated receptor 1) and downstream effector RhoA. METHODS: We assessed the ability of CLIC1 and CLIC4 to relocalize to cell membranes in response to thrombin in human umbilical vein endothelial cells (HUVEC). We examined CLIC1 and CLIC4 function in HUVEC by knocking down expression of each CLIC protein and compared thrombin-mediated RhoA or Rac1 activation, ERM (ezrin/radixin/moesin) phosphorylation, and endothelial barrier modulation in control and CLIC knockdown HUVEC. We generated a conditional murine allele of Clic4 and examined PAR1-mediated lung microvascular permeability and retinal angiogenesis in mice with endothelial-specific loss of Clic4. RESULTS: Thrombin promoted relocalization of CLIC4, but not CLIC1, to HUVEC membranes. Knockdown of CLIC4 in HUVEC reduced thrombin-mediated RhoA activation, ERM phosphorylation, and endothelial barrier disruption. Knockdown of CLIC1 did not reduce thrombin-mediated RhoA activity but prolonged the RhoA and endothelial barrier response to thrombin. Endothelial-specific deletion of Clic4 in mice reduced lung edema and microvascular permeability induced by PAR1 activating peptide. CONCLUSIONS: CLIC4 is a critical effector of endothelial PAR1 signaling and is required to regulate RhoA-mediated endothelial barrier disruption in cultured endothelial cells and murine lung endothelium. CLIC1 was not critical for thrombin-mediated barrier disruption but contributed to the barrier recovery phase after thrombin treatment.

Autocrine proteinase-activated receptor signaling in PC3 prostate cancer cells.

Proteinase-activated receptors (PARs) are G protein-coupled receptors (GPCRs) activated by limited n-terminal proteolysis. PARs are highly expressed in many cancer cells, including prostate cancer (PCa), and regulate various aspects of tumor growth and metastasis. Specific activators of PARs in different physiological and pathophysiological contexts remain poorly defined. In this study, we examined the androgen-independent human prostatic cancer cell line PC3 and find the functional expression of PAR1 and PAR2, but not PAR4. Using genetically encoded PAR cleavage biosensors, we showed that PC3 cells secrete proteolytic enzymes that cleave PARs and trigger autocrine signaling. CRISPR/Cas9 targeting of PAR1 and PAR2 combined with microarray analysis revealed genes that are regulated through this autocrine signaling mechanism. We found several genes that are known PCa prognostic factors or biomarker to be differentially expressed in the PAR1-knockout (KO) and PAR2-KO PC3 cells. We further examined PAR1 and PAR2 regulation of PCa cell proliferation and migration and found that absence of PAR1 promotes PC3 cell migration and suppresses cell proliferation, whereas PAR2 deficiency showed opposite effects. Overall, these results demonstrate that autocrine signaling through PARs is an important regulator of PCa cell function.

Early growth response factor 1 upregulates pro-fibrotic genes through activation of TGF-ß1/Smad pathway via transcriptional regulation of PAR1 in high-glucose treated HK-2 cells.

Tubulointerstitial fibrosis (TIF) makes a key role in diabetic kidney disease (DKD). In this study, we revealed that the expressions of Egr1 and protease-activated receptor 1 (PAR1) were increased in renal tissues of DKD rats. In vitro experiments demonstrated that both Egr1 overexpression and high glucose (HG) condition could promote the expressions of PAR1, fibronectin (FN) and collagen I (COL I). Furthermore, HG stimulation enhanced the binding capacity of Egr1 to PAR1 promoter. Both HG condition and Egr1 upregulation could increase, and thrombin inhibitor did not affect activity of TGF-ß1/Smad pathway via PAR1. Collectively, Egr1 is involved in TIF of DKD partly through activating TGF-ß1/Smad pathway via transcriptional regulation of PAR1 in HG treated HK-2 cells.

Prognostic impact of kallikrein-related peptidase transcript levels in prostate cancer.

We aimed to study mRNA levels and prognostic impact of all 15 human kallikrein-related peptidases (KLKs) and their targets, proteinase-activated receptors (PARs), in surgically treated prostate cancer (PCa). Seventy-nine patients with localized grade group 2-4 PCas represented aggressive cases, based on metastatic progression during median follow-up of 11 years. Eighty-six patients with similar baseline characteristics, but no metastasis during follow-up, were assigned as controls. Transcript counts were detected with nCounter technology. KLK12 protein expression was investigated with immunohistochemistry. The effects of KLK12 and KLK15 were studied in LNCaP cells using RNA interference. KLK3, -2, -4, -11, -15, -10 and -12 mRNA, in decreasing order, were expressed over limit of detection (LOD). The expression of KLK2, -3, -4 and -15 was decreased and KLK12 increased in aggressive cancers, compared to controls (P < .05). Low KLK2, -3 and -15 expression was associated with short metastasis-free survival (P < .05) in Kaplan-Meier analysis. PAR1 and -2 were expressed over LOD, and PAR1 expression was higher, and PAR2 lower, in aggressive cases than controls. Together, KLKs and PARs improved classification of metastatic and lethal disease over grade, pathological stage and prostate-specific antigen combined, in random forest analyses. Strong KLK12 immunohistochemical staining was associated with short metastasis-free and PCa-specific survival in Kaplan-Meier analysis (P < .05). Knock-down of KLK15 reduced colony formation of LNCaP cells grown on Matrigel basement membrane preparation. These results support the involvement of several KLKs in PCa progression, highlighting, that they may serve as prognostic PCa biomarkers.

Amplification of protease-activated receptors signaling in sporadic cerebral cavernous malformation endothelial cells.

In the central nervous system, thrombin-mediated activation of protease-activated receptors (PARs) results in neuroinflammation and increased vascular permeability. These events have been linked to cancer and neurodegeneration. Endothelial cells (ECs) isolated from sporadic cerebral cavernous malformation (CCM) specimens showed dysregulation of genes involved in "thrombin-mediated PAR-1 activation" signaling. CCM is a vascular disease involving brain capillaries. In CCM, ECs show defective cell junctions. Oxidative stress and neuroinflammation play a key role in disease onset and progression. In order to confirm the possible role of thrombin pathway in sporadic CCM pathogenesis, we evaluated PARs expression in CCM-ECs. We found that sporadic CCM-ECs overexpress PAR1, PAR3 and PAR4, together with other coagulation factor encoding genes. Moreover, we investigated about expression of the three familial CCM genes (KRIT1, CCM2 and PDCD10) in human cerebral microvascular ECs, following thrombin exposure, as well as protein level. Thrombin exposure affects EC viability and results in dysregulation of CCM gene expression and, then, in decreased protein level. Our results confirm amplification of PAR pathway in CCM suggesting, for the first time, the possible role of PAR1-mediated thrombin signaling in sporadic CCM. Thrombin-mediated PARs over activation results in increased blood-brain barrier permeability due to loss of cell junction integrity and, in this context, also the three familial CCM genes may be involved.

Podocyte protease activated receptor 1 stimulation in mice produces focal segmental glomerulosclerosis mirroring human disease signaling events.

About 30% of patients who have a kidney transplant with underlying nephrotic syndrome (NS) experience rapid relapse of disease in their new graft. This is speculated to be due to a host-derived circulating factor acting on podocytes, the target cells in the kidney, leading to focal segmental glomerulosclerosis (FSGS). Our previous work suggests that podocyte membrane protease receptor 1 (PAR-1) is activated by a circulating factor in relapsing FSGS. Here, the role of PAR-1 was studied in human podocytes in vitro, and using a mouse model with developmental or inducible expression of podocyte-specific constitutively active PAR-1, and using biopsies from patients with nephrotic syndrome. In vitro podocyte PAR-1 activation caused a pro-migratory phenotype with phosphorylation of the kinase JNK, VASP protein and docking protein Paxillin. This signaling was mirrored in podocytes exposed to patient relapse-derived NS plasma and in patient disease biopsies. Both developmental and inducible activation of transgenic PAR-1 (NPHS2 Cre PAR-1Active+/-) caused early severe nephrotic syndrome, FSGS, kidney failure and, in the developmental model, premature death. We found that the non-selective cation channel protein TRPC6 could be a key modulator of PAR-1 signaling and TRPC6 knockout in our mouse model significantly improved proteinuria and extended lifespan. Thus, our work implicates podocyte PAR-1 activation as a key initiator of human NS circulating factor and that the PAR-1 signaling effects were partly modulated through TRPC6.

Tubulovascular protection from protease-activated receptor-1 depletion during AKI-to-CKD transition.

BACKGROUND: Thromboembolic events are prevalent in chronic kidney disease (CKD) patients due to increased thrombin generation leading to a hypercoagulable state. We previously demonstrated that inhibition of protease-activated receptor-1 (PAR-1) by vorapaxar reduces kidney fibrosis. METHODS: We used an animal model of unilateral ischemia-reperfusion injury-induced CKD to explore the tubulovascular crosstalk mechanisms of PAR-1 in acute kidney injury (AKI)-to-CKD transition. RESULTS: During the early phase of AKI, PAR-1-deficient mice exhibited reduced kidney inflammation, vascular injury, and preserved endothelial integrity and capillary permeability. During the transition phase to CKD, PAR-1 deficiency preserved kidney function and diminished tubulointerstitial fibrosis via downregulated transforming growth factor-ß/Smad signaling. Maladaptive repair in the microvasculature after AKI further exacerbated focal hypoxia with capillary rarefaction, which was rescued by stabilization of hypoxia-inducible factor and increased tubular vascular endothelial growth factor A in PAR-1-deficient mice. Chronic inflammation was also prevented with reduced kidney infiltration by both M1- and M2-polarized macrophages. In thrombin-induced human dermal microvascular endothelial cells (HDMECs), PAR-1 mediated vascular injury through activation of NF-κB and ERK MAPK pathways. Gene silencing of PAR-1 exerted microvascular protection via a tubulovascular crosstalk mechanism during hypoxia in HDMECs. Finally, pharmacologic blockade of PAR-1 with vorapaxar improved kidney morphology, promoted vascular regenerative capacity, and reduced inflammation and fibrosis depending on the time of initiation. CONCLUSIONS: Our findings elucidate a detrimental role of PAR-1 in vascular dysfunction and profibrotic responses upon tissue injury during AKI-to-CKD transition and provide an attractive therapeutic strategy for post-injury repair in AKI.