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FSLLRY-NH2 is a selective PAR2 peptide antagonist. It reverses taxol-induced mechanical allodynia, heat hyperalgesia and PKC activation in ICR mice, also suppresses ERK activation and collagen production in isolated cardiac fibroblasts.

Peptide Inhibitors
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[Phe1,Ser2,Tyr6]-PAR-1 (1-6) amide (human)
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1.Aspergillus fumigatus Increased PAR-2 Expression and Elevated Proinflammatory Cytokines Expression Through the Pathway of PAR-2/ERK1/2 in Cornea.
Niu Y;Zhao G;Li C;Lin J;Jiang N;Che C;Zhang J;Xu Q Invest Ophthalmol Vis Sci. 2018 Jan 1;59(1):166-175. doi: 10.1167/iovs.17-21887.
Purpose: ;To determine the role of protease-activated receptor-2 (PAR-2) in cornea infected by Aspergillus fumigatus.;Methods: ;PAR-2 was tested in normal and infected corneas of C57BL/6 mice. Mice corneas were infected with A. fumigatus with or without pretreatment of PAR-2 antagonist (FSLLRY-NH2). Polymorphonuclear neutrophilic leukocytes (PMNs) were stimulated with 75% ethanol-killed A. fumigatus with or without pretreatment of FSLLRY-NH2. Disease severity was documented by clinical score and photographs with a slit lamp. PCR, Western blot, and ELISA tested expression of PAR-2, IL-1β, TNF-α, IFN-γ, MIP-2, and p-ERK1/2. PMN infiltration was assessed by myeloperoxidase assay and immunofluorescent staining.;Results: ;PAR-2 expression was significantly elevated by A. fumigatus, whereas the upregulation was significantly inhibited by FSLLRY-NH2 in mice corneas. FSLLRY-NH2 decreased disease response, PMN infiltration, and proinflammatory cytokine expression compared with infected control. In PMNs, PAR-2 expression was also significantly increased by A. fumigatus, which was significantly inhibited by FSLLRY-NH2. FSLLRY-NH2 significantly inhibited proinflammatory cytokine protein expression, as compared with that in infected control cells, which may be modified by p-ERK1/2.
2.Induction of IL-13 production and upregulation of gene expression of protease activated receptors in P815 cells by IL-6.
Zhang H;Lin L;Yang H;Zhang Z;Yang X;Zhang L;He S Cytokine. 2010 May;50(2):138-45. doi: 10.1016/j.cyto.2010.02.006. Epub 2010 Mar 1.
Interleukin (IL)-6 is a multifunctional cytokine which has been showed to induce up-regulated expression of Fc epsilon RI receptor and histamine production in mast cells. However, little is known of its effects on Th2 cytokine secretion and protease activated receptor (PAR) expression in mast cells. In the present study, we examined potential influence of IL-6 on IL-13, IL-4 and IL-10 release from P815 cells and PAR expression on P815 cells by using flow cytometry analysis, quantitative real-time PCR, ELISA and cellular activation of signaling ELISA (CASE) techniques. The results showed that IL-6 induced up to 1.8-fold increase in IL-13, but not IL-4 or IL-10 release from P815 cells, and FSLLRY-NH(2) did not affect IL-6 induced IL-13 release. Tryptase elicited 2.0-fold increase in IL-13 release from P815 cells, which can be inhibited by IL-6. IL-6 elicited the up-regulated expression of PAR-1, PAR-2, PAR-3 and PAR-4 mRNAs, but had little effects on expression of PAR proteins. U0126, PD98059 and LY204002 abolished IL-6 induced IL-13 release when they were preincubated with P815 cells, indicating ERK and Akt cell signaling pathways may be involved in the event. In conclusion, IL-6 can stimulate IL-13 release from mast cells through an ERK and Akt cell signaling pathway dependent, but PAR independent mechanism.
3.Inhibitory effect of FSLLRY-NH
Lee YJ;Kim SJ;Kwon KW;Lee WM;Im WJ;Sohn UD Arch Pharm Res. 2017 Jul;40(7):854-863. doi: 10.1007/s12272-017-0927-9. Epub 2017 Jun 22.
Proteinase activated receptor 2 (PAR2), which is localized in the GI tract, the respiratory system, and the kidney tubules is a G protein-coupled receptor associated with inflammation, metabolism, and disease. The aim of this study was to explore the role of PAR2 in hydrogen peroxide (H;2;O;2;)-induced HepG2 cells by using FSLLRY-NH;2; a PAR2 antagonist. H;2;O;2; treatment resulted in induction of PAR2 in esophageal, gastric, and liver cells, with the most robust response being in HepG2 cells. Furthermore, this effect was dose-dependent in HepG2 cells. Treatment with H;2;O;2; at concentrations above 400 μM for 24 h also reduced HepG2 cell viability. H;2;O;2; treatment increased both the protein and mRNA levels of IL-1β, IL-8, and TNF-α, as well as those of SAPK/JNK. The increased levels of these pro-inflammatory genes and SAPK/JNK induced by H;2;O;2; were attenuated in a dose-dependent manner when cells were co-treated with H;2;O;2; and FSLLRY-NH2. In summary, the PAR2 antagonist peptide, FSLLRY-NH2, reduces the level of the pro-inflammatory genes IL-8, IL-1β, and TNF-α induced by H;2;O;2;, through the SAPK/JNK pathways in HepG2 cells. These data suggest that a PAR2 antagonist could be an anti-inflammatory agent in HepG2 cells.

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