Trypsin induces tumour necrosis factor-alpha secretion from a human leukemic mast cell line

Biomass-Derived Carbon Dots and Their Sensing Applications

Carbon dots (CDs) can be widely used in the field of sensing because of its good water solubility, low toxicity, high fluorescence stability and excellent biocompatibility. It has become a popular trend to prepare high-value, inexpensive, renewable and environmentally friendly CDs sensors from biomass resources. This article reviewed the research progress of biomass-derived CDs as chemical, physical and biological sensors in recent years and studied their preparation processes and sensing abilities. Furthermore, the prospects and challenges of biomass-CDs sensors were discussed. This article is expected to provide inspirations for the design, preparation and application of biomass-CDs sensors in the future.

Nitrogen-doped carbon quantum dots fabricated from cellulolytic enzyme lignin and its application to the determination of cytochrome c and trypsin

A sensitive and effective strategy for the detection of cytochrome c (Cyt c) and trypsin was developed using biomass nitrogen-doped carbon quantum dots (N-CQDs) as the fluorescence probe. N-CQDs were synthesized through a one-pot hydrothermal method by utilizing cellulolytic enzyme lignin as the carbon source and ammonia as the solvent and nitrogen source. The obtained N-CQDs had good water solubility and stable optical properties. The introduction of nitrogen increased fluorescence quantum yield (QY) to 8.23%, which was almost four times as high as that before nitrogen doping. The N-CQDs were fabricated as a label-free biosensor to detect Cyt c and trypsin. The fluorescence of N-CQDs was quenched with positively charged Cyt c due to electrostatic induction aggregation and static quenching. However, Cyt c tended to be hydrolyzed into small peptides in the presence of trypsin, which caused fluorescence recovery of the N-CQDs/Cyt c complex. A wide linear response range was achieved for Cyt c within 1-50 μM and the developed N-CQDs/Cyt c complex displayed a linear response for trypsin within 0.09-5.4 U/mL. The detection limits were 0.29 μM for Cyt c and 0.013 U/mL for trypsin, respectively. Furthermore, this assay had been applied to Cyt c and trypsin detection in serum samples with the recoveries in the range of 94.6-98.5% and 95.5-102.0%, respectively. The established method was sensitive, selective, easy to operate, and low cost, which proved its potential application in clinical diagnosis. The synthesis and fluorescence mechanism of N-CQDs and the strategy for Cyt c and trypsin detection.

Extracellular protease trypsin activates amiloride-insensitive sodium channels in human leukemia cells

Sodium influx is tightly regulated in the cells of blood origin. Amiloride-insensitive sodium channels were identified as one of the main sodium-transporting pathways in leukemia cells. To date, all known regulatory pathways of these channels are coupled with intracellular actin cytoskeleton dynamics. Here, to search for physiological mechanisms controlling epithelial Na⁺ channel (ENaC)-like channels, we utilized leukemia K562 cells as a unique model to examine single channel behavior in a whole-cell patch-clamp experiments. We have shown for the first time that extracellular serine protease trypsin directly activates sodium channels in plasma membrane of K562 cells. The whole-cell single current recordings clearly demonstrate no inhibition of trypsin-activated channels by amiloride or benzamil. Involvement of proteolytic cleavage in channel opening was confirmed in experiments with soybean trypsin inhibitor. More importantly, stabilization of F-actin with intracellular phalloidin did not prevent trypsin-induced channel activation indicating no implication of cytoskeleton rearrangements in stimulatory effect of extracellular protease. Our data reveals a novel mechanism modulating amiloride-insensitive ENaC-like channel activity and integral sodium permeability in leukemia cells.

Peptide self-assembly assisted signal labeling for an electrochemical assay of protease activity

Peptide self-assembly holds tremendous promise for a range of applications in chemistry and biology. In the work reported here, we explored the potential functions of peptide self-assembly in electrochemical bioanalysis by developing a peptide self-assembly assisted signal labeling strategy for assaying protease activity. The fundamental principle of this assay is that target-protease-catalyzed specific proteolytic cleavage blocks self-assembly between the probe peptide and signal peptide, thus preventing the signal labeling of electroactive silver nanoparticles on the electrode surface, which in turn causes the electrochemical signal to decrease. Using trypsin as an example protease target, the linear range of this assay was found to be 1 ng mL^-1 to 100 mg mL^-1, and its detection limit was 0.032 ng mL^-1, which are better than the corresponding parameters for previously reported assays. Further experiments also highlighted the good selectivity of the assay method and demonstrated its usability when applied to serum samples. Therefore, this report not only introduces a valuable tool for assaying protease activity, but it also promotes the utilization of peptide self-assembly in electrochemical bioanalysis, as this approach has great potential for practical use in the future.

Modulation of PAR expression and tryptic enzyme induced IL-4 production in mast cells by IL-29

Interleukin (IL)-29 is a relatively newly discovered cytokine, which has been shown to be actively involved in the pathogenesis of allergic inflammation. However, little is known of the effects of IL-29 on protease activated receptor (PAR) expression and potential mechanisms of cytokine production in mast cells. In the present study, we examined potential influence of IL-29 on PAR expression and cytokine production in P815 and bone marrow derived mast cells (BMMCs) by using flow cytometry analysis, quantitative real time PCR, and ELISA techniques. The results showed that IL-29 downregulated the expression of PAR-1 by up to 56.2%, but had little influence on the expression of PAR-2, PAR-3 and PAR-4. IL-29 also induced downregulation of expression of PAR-1 mRNA. However, when mast cells were pre-incubated with IL-29, thrombin-, trypsin- and tryptase-induced expression of PAR-2, PAR-3 and PAR-4 was upregulated, respectively. IL-29 provoked approximately up to 1.9-fold increase in IL-4 release when mast cells was challenged with IL-29. Administration of IL-29 blocking antibody, AG490 or LY294002 abolished IL-29-induced IL-4 release from P815 cells. It was found that IL-29 diminished trypsin- and tryptase-induced IL-4 release from P815 cells following 16 h incubation. In conclusion, IL-29 can regulate expression of PARs and tryptase- and trypsin-induced IL-4 production in mast cells, through which participates in the mast cell related inflammation.

An antagonist of human protease activated receptor-2 attenuates PAR2 signaling, macrophage activation, mast cell degranulation, and collagen-induced arthritis in rats

Multiple serine proteases exert proinflammatory actions by signaling through protease-activated receptor-2 (PAR2) on the cell surface. Although inhibitors of individual proteases are anti-inflammatory, we sought to discover whether the first potent antagonist of their common target PAR2 might be beneficial in treating chronic arthritis-like inflammatory disease. Using a fluorescence assay, a novel compound, GB88, was shown to antagonize PAR2-induced intracellular Ca(2+) release in human monocyte-derived macrophages, being 1000 times more potent than a control compound, ENMD-1068 (IC(50) 1.6 ± 0.5 μM vs. 1.2 ± 0.4 mM, respectively). In Wistar rats, GB88 was orally bioavailable (F=55%, T(max) 4 h, C(max) 1.7 μM, 10 mg/kg). GB88 inhibited the acute paw edema induced in Wistar rats by intraplantar λ-carrageenan or PAR2 agonists 2-furoyl-LIGRLO-NH(2) or mast cell β-tryptase, without inhibiting proteolytic activity of tryptase in vitro. In the chronic collagen-induced model of arthritis in rats, GB88 (10 mg/kg) was disease modifying and ameliorated pathological and histopathological changes (edema, pannus formation, synovial hyperplasia, collagen degradation, macrophage invasion, mast cell degranulation) compared to untreated arthritic controls. The results suggest that an orally active PAR2 antagonist is effective in treating chronic arthritis in rats through inhibiting macrophage infiltration, mast cell degranulation, and β-tryptase-PAR2 signaling in joint inflammation.

Structure, function and pathophysiology of protease activated receptors

Discovered in the 1990s, protease activated receptors(1) (PARs) are membrane-spanning cell surface proteins that belong to the G protein coupled receptor (GPCR) family. A defining feature of these receptors is their irreversible activation by proteases; mainly serine. Proteolytic agonists remove the PAR extracellular amino terminal pro-domain to expose a new amino terminus, or tethered ligand, that binds intramolecularly to induce intracellular signal transduction via a number of molecular pathways that regulate a variety of cellular responses. By these mechanisms PARs function as cell surface sensors of extracellular and cell surface associated proteases, contributing extensively to regulation of homeostasis, as well as to dysfunctional responses required for progression of a number of diseases. This review examines common and distinguishing structural features of PARs, mechanisms of receptor activation, trafficking and signal termination, and discusses the physiological and pathological roles of these receptors and emerging approaches for modulating PAR-mediated signaling in disease.

Expression of proteinase-activated receptor 1-4 (PAR 1-4) in human cancer

Proteinase activated receptors (PAR 1-4) are membrane receptors with a unique way of activation by proteinases like thrombin, trypsin and matrix metalloproteinases which lead to a specific cellular response. To evaluate the significance of expression and co-expression of PAR in cancer we performed a survey on published data. A Pubmed literature search on "PAR, thrombin, cancer" was performed and 46 publications were selected for systematic review based on the availability of information on tumor type, material type, detection method and specification of positive cases. PAR-1 was found in 77.3% of malignant samples (n = 678), PAR-2 in 79.5% (n = 592), PAR-3 in 12.6% (n = 87) and PAR-4 in 54.9% (n = 153). PAR-1 and -2 were present in adenocarcinomas, melanomas, osteosarcomas, glioblastomas, meningiomas, leukaemias and squamous cell carcinomas. Presence of PAR-3 was limited to kidney and liver cancer. The data on PAR-4 expression was inconclusive. Those studies analysing PAR-1 and PAR-2 reported coexpression of the two receptors. PAR-1 and -2 are widely expressed in human tumors suggesting an important role in tumorigenesis and providing potential targets for therapy. PAR-3 and PAR-4 are less frequently detectable, their expression and potential role in tumorigenesis require further investigation.

Increased expression of protease-activated receptor-2 in mucosal mast cells in Crohn's ileitis

BACKGROUND AND AIMS

Activation of protease-activated receptor-2 (PAR-2) may stimulate various events of importance in inflammatory processes, including release of inflammatory mast cell mediators. PAR-2 is frequently up-regulated during inflammatory conditions, but it is not known if the expression is altered in Crohn's disease. The aim of the present study was to investigate the ileal mucosal PAR-2 expression in Crohn's ileitis, with particular emphasis on the expression in ileal mucosal mast cells.

METHODS

Surgical specimens from the distal ileum were collected from patients with Crohn's ileitis and patients with colonic cancer as controls. The overall expression of PAR-2 was investigated by Western blot, and the presence of PAR-2 expressing mucosal mast cells by immunohistochemistry and cell counting. The effect of tumor necrosis factor-α (TNF-α) on the PAR-2 expression in a human mast cell line (HMC-1) was investigated by RT-PCR and immunocytochemistry.

RESULTS

In Crohn's specimens, the fraction of PAR-2-expressing mucosal mast cells was increased about 2.5 times (P<0.001; n=14) compared with specimens from control patients (n=6). No difference was found between inflamed (n=6) and uninflamed Crohn's specimens (P>0.05; n=8). Exposure to TNF-α for 48 h up-regulated PAR-2 mRNA and protein expression in the HMC-1 cell line.

CONCLUSION

PAR-2 is up-regulated on ileal mucosal mast cells in Crohn's ileitis, possibly due to the action of inflammatory cytokines, such as TNF-α. This may contribute to perpetuating the inflammatory process in the intestinal mucosa in Crohn's ileitis.

LIGR, a protease-activated receptor-2-derived peptide, enhances skin pigmentation without inducing inflammatory processes

The protease-activated receptor-2 (PAR-2) is a seven transmembrane G-protein-coupled receptor that could be activated by serine protease cleavage or by synthetic peptide agonists. We showed earlier that activation of PAR-2 with Ser-Leu-Ile-Gly-Arg-Leu-NH(2) (SLIGRL), a known PAR-2 activating peptide, induces keratinocyte phagocytosis and increases skin pigmentation, indicating that PAR-2 regulates pigmentation by controlling phagocytosis of melanosomes. Here, we show that Leu-Ile-Gly-Arg-NH(2) (LIGR) can also induce skin pigmentation. Both SLIGRL and LIGR increased melanin deposition in vitro and in vivo, and visibly darkened human skins grafted onto severe combined immuno-deficient (SCID) mice. Both SLIGRL and LIGR stimulated Rho-GTP activation resulting in keratinocyte phagocytosis. Interestingly, LIGR activates only a subset of the PAR-2 signaling pathways, and unlike SLIGRL, it does not induce inflammatory processes. LIGR did not affect many PAR-2 signaling pathways, including [Ca(2+)] mobilization, cAMP induction, the induction of cyclooxgenase-2 (COX-2) expression and the secretion of prostaglandin E2, interleukin-6 and -8. PAR-2 siRNA inhibited LIGR-induced phagocytosis, indicating that LIGR signals via PAR-2. Our data suggest that LIGR is a more specific regulator of PAR-2-induced pigmentation relative to SLIGRL. Therefore, enhancing skin pigmentation by topical applications of LIGR may result in a desired tanned-like skin color, without enhancing inflammatory processes, and without the need of UV exposure.

Induction of IL-6 release from human T cells by PAR-1 and PAR-2 agonists

Proteinase-activated receptors (PAR) have been recognized as playing an important role in inflammation and immune response. However, little is known of the expression and function of PAR on human T cells. In this study, the expression of PAR on highly purified human T cells was determined and the secretion of IL-6 from cultured T cells in response to serine proteinases and agonist peptides of PAR was examined. The results showed that T cells express PAR-1, PAR-2 and PAR-3 proteins and genes. Thrombin, trypsin and tryptase, but not elastase, were able to stimulate concentration-dependent secretion of IL-6 from T cells following a 16 h incubation period. The specific inhibitors of thrombin, trypsin and tryptase inhibited the actions of these proteinases on T cells, indicating that the enzymatic activity is essential for their actions. Agonist peptides of PAR SFLLR-NH2, TFLLRN-NH2 and SLIGKV-NH2, but not TFRGAP-NH2, GYPGQV-NH2 and AYPGKF-NH2, are also capable of inducing IL-6 release from T cells. In conclusion, induction of IL-6 secretion from T cells by thrombin, trypsin and tryptase is probably through the activation of PAR, suggesting that serine proteinases are involved in the regulation of immune response of the body.

Induction of interleukin-6 release from monocytes by serine proteinases and its potential mechanisms

Serine proteinases have been recognized playing an important role in inflammation via proteinase-activated receptors (PAR). However, little is known of the influence of serine proteinases and PAR on interleukin-6 (IL-6) secretion from highly purified monocytes. We challenged monocytes from human peripheral blood with serine proteinases and agonist peptides of PAR and measured the levels of IL-6, IL-1beta and IL-12 in culture supernatants by enzyme-linked immunosorbent assay. The results showed that thrombin, trypsin, tryptase and elastase stimulated approximately up to 2.9-, 2.0-, 1.8- and 2.1-fold increase in IL-6 release from monocytes following 16 h of incubation, respectively. Proteinase inhibitors inhibited the actions of proteinases on monocytes. Agonist peptides of PAR-1 (SFLLR-NH(3)) and PAR-4 (GYPGQV-NH(2)), but not PAR-3 (TFRGAP-NH(2)), also induced IL-6 release from monocytes. The proteinases and agonists of PAR failed to stimulate IL-1beta and IL-12 secretion. In conclusion, the induction of IL-6 secretion by serine proteinases may be through the activation of PAR.

Inhibition of trypsin-induced mast cell activation by acanthoic acid

Acanthoic acid (AA) is a pimaradiene diterpene isolated from the Korean medicinal plant, Acanthopanax koreanum (Araliaceae). In the present study, we examined whether AA has the inhibitory effect on the production of inflammatory mediators and activating signals induced in trypsin-treated human leukemic mast cell-1 (HMC-1). HMC-1 cells were stimulated with trypsin (100 nM) in the presence or absence of AA (1, 10, and 100 microg/ml). We assessed the production of TNF-alpha and tryptase by enzyme-linked immunosorbent assay (ELISA) or reverse transcription-PCR, ERK activation by Western blot, and NF-kappaB activation by gel shift assay. AA (10 and 100 microg/ml) significantly inhibited production of both TNF-alpha and tryptase in a dose-dependent manner in trypsin-stimulated HMC-1. Furthermore, AA inhibited ERK phosphorylation and NF-kappaB activation induced by trypsin treatment without blocking of trypsin activity even with 100 microg/ml. These results suggest that AA may inhibit the production of inflammatory mediators through inhibition of ERK phosphorylation and NF-kappaB activation pathway in human mast cells. It supports the evidence that AA may be used to blocks the development of inflammation caused from mast cells.

Inhibition of trypsin-induced mast cell activation by water fraction ofLonicera japonica

Lonicera japonica Thunb.(Caprifoliaceae) has long been known as an anti-inflammatory. In the present study, the effect of water fraction of Lonicera japonica (LJ) on trypsin-induced mast cell activation was examined. HMC-1 cells were stimulated with trypsin (100 nM) in the presence or absence of LJ (10, 100, and 1000 microg/mL). TNF-alpha and tryptase production were measured by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-PCR. Extracellular signal-regulated kinase (ERK) phosphorylation was assessed by Western blot. Trypsin activity was measured by using Bz-DL-Arg-p-nitroanilide (BAPNA) as substrate. LJ (10, 100, and 1000 microg/mL) inhibited TNF-alpha secretion in a dose-dependent manner. LJ (10, 100, and 1000 microg/mL) also inhibited TNF-alpha and tryptase mRNA expression in trypsin-stimulated HMC-1. Furthermore, LJ inhibited trypsin-induced ERK phosphorylation. However, LJ did not affect the trypsin activity even 1000 microg/mL. These results indicate that LJ may inhibit trypsin-induced mast cell activation through the inhibition of ERK phosphorylation than the inhibition of trypsin activity.

C3a enhances nerve growth factor-induced NFAT activation and chemokine production in a human mast cell line, HMC-1

Activation of cell surface G protein-coupled receptors leads to transphosphorylation and activation of a number of receptor tyrosine kinases. Human mast cells express G protein-coupled receptors for the complement component C3a (C3aR) and high affinity nerve growth factor (NGF) receptor tyrosine kinase, TrkA. To determine whether C3a cross-regulates TrkA signaling and biological responses, we used a human mast cell-line, HMC-1, that natively expresses both receptors. We found that NGF caused tyrosine phosphorylation of TrkA, resulting in a sustained Ca(2+) mobilization, NFAT activation, extracellular-signal regulated kinase (ERK) phosphorylation, and chemokine, macrophage inflammatory protein-1beta (MIP-1beta) production. In contrast, C3a induced a transient Ca(2+) mobilization and ERK phosphorylation but failed to stimulate TrkA phosphorylation, NFAT activation, or MIP-1beta production. Surprisingly, C3a significantly enhanced NGF-induced NFAT activation, ERK phosphorylation, and MIP-1beta production. Pertussis toxin, a G(i/o) inhibitor, selectively blocked priming by C3a but had no effect on NGF-induced responses. Mitogen-activated protein/ERK kinase inhibitor U0126 caused approximately 30% inhibition of NGF-induced MIP-1beta production but had no effect on priming by C3a. However, cyclosporin A, an inhibitor of calcineurin-mediated NFAT activation, caused substantial inhibition of NGF-induced MIP-1beta production both in the absence and presence of C3a. These data demonstrate that NGF caused tyrosine phosphorylation of TrkA to induce chemokine production in HMC-1 cells via a pathway that mainly depends on sustained Ca(2+) mobilization and NFAT activation. Furthermore, C3a enhances NGF-induced transcription factor activation and chemokine production via a G protein-mediated pathway that does not involve TrkA phosphorylation.

Curcumin inhibits protease-activated receptor-2 and -4-mediated mast cell activation

BACKGROUND

Curcumin, a major yellow pigment and active component of turmeric powder extracted from Curcuma longa L. (Gingiberaceae), has been shown to possess anti-inflammatory and anti-cancer activities. Protease-activated receptors (PARs) play a role in inflammation, and human leukemic mast cells (HMC-1) co-express PAR2 and PAR4. In the present study, the effect of curcumin on PAR2- and PAR4-mediated HMC-1 activation was examined.

METHODS

HMC-1 cells were stimulated with trypsin (100 nmol/l, PAR2 and PAR4 agonist), SLIGKV-NH(2) (100 microM, PAR2-activating peptide) or GYPGQV-NH(2) (100 micromol/l PAR4-activating peptide) in the presence or absence of curcumin (1, 10, and 100 micromol/l). TNF-alpha secretion was measured by enzyme-linked immunosorbent assay (ELISA). TNF-alpha and tryptase mRNA were measured by reverse-transcription PCR (RT-PCR). Mitogen-activated protein kinase (MAPK) activation was assessed by Western blot analysis. Trypsin activity was measured using the substrate Bz-DL-Arg-p-nitroanilide (BAPNA).

RESULTS

Curcumin (10 and 100 micromol/l) inhibited TNF-alpha secretion from trypsin or activating peptide-stimulated HMC-1. Curcumin (10 and 100 micromol/l) also inhibited TNF-alpha and tryptase mRNA expression in trypsin-stimulated HMC-1. Furthermore, curcumin inhibited trypsin-induced extracellular signal-regulated kinase (ERK) phosphorylation. However, curcumin did not affect the trypsin activity even at 100 micromol/l.

CONCLUSION

Curcumin inhibits PAR2- and PAR4-mediated human mast cell activation, not by inhibition of trypsin activity but by block of ERK pathway.

Inhibitory effect of kaurane type diterpenoids fromAcanthopanax koreanum on TNF-α secretion from trypsin-stimulated HMC-1 cells

Five known kaurane type diterpenoids, 16alphaH,17-isovaleryloxy-ent-kauran-19-oic acid (1), 16alpha-hydroxy-17-isovaleryloxy-ent-kauran-19-oic acid (2), paniculoside-IV (3), 16alpha-hydroxy-ent-kauran-19-oic acid (4), and ent-kaur-16-en-19-oic acid (5) were isolated from the root of Acanthopanax koreanum by repeated column chromatography and reversed phase preparative HPLC. The structures of these compounds were established from physicochemical and spectral data. Among the isolated compounds 16alphaH,17-isovaleryloxy-ent-kauran-19-oic acid (1) showed potent inhibitory activity (IC50 value, 16.2 uM) on TNF-alpha secretion from HMC-1, a trypsin-stimulated human leukemic mast cell line.

Expression of protease-activated receptor 2 in ulcerative colitis

Although tryptase released from mast cells might play a key role in the pathogenesis of ulcerative colitis (UC), the role of protease-activated receptor 2 (PAR2), tryptase receptor, remains unclear in the pathogenesis of this disease. The expressions of PAR2 and tumor necrosis factor (TNF) alpha in nine UC tissues and nine normal tissues were examined by immunohistochemistry. TNF-alpha levels secreted from human leukemic mast cell line (HMC-1) after the treatment of PAR2 agonists were also measured by enzyme-linked immunosorbent assay. The PAR2 and TNF-alpha proteins were more significantly detectable in UC tissues than in normal tissues. Furthermore, 65.2% of PAR2+ cells and 66.4% of TNF-alpha+ cells in UC tissues were tryptase-positive cells. In other words, 60.6% and 46.3% of tryptase-positive cells in UC tissues were PAR2+ cells and TNF-alpha+ cells, respectively. A chi2 analysis showed correlation (p < 0.007) between PAR2 and TNF-alpha in tryptase-positive mast cells. Moreover, PAR2 agonists significantly induced the TNF-alpha secretion from HMC-1. These results indicate that the activation of the mast cells through PAR2 may be involved in the pathogenesis of UC.

Anti-inflammatory effect of Lonicera japonica in proteinase-activated receptor 2-mediated paw edema

BACKGROUND

Lonicera japonica (Caprifoliaceae) has long been used for treatment of infectious diseases. In the present study, the anti-inflammatory effects of L. japonica water extract (AELJ) were investigated in proteinase-activated receptor 2 (PAR2)-mediated mouse paw edema.

METHODS

Paw edema was induced by injection of trypsin or trans-cinnamoyl-LIGRLO-NH(2) (tc-NH(2)) into hindpaw of mice. AELJ (10, 50, 100, and 200 mg/kg) was orally administered 1 h before induction of inflammation.

RESULTS

At doses of 50, 100 and 200 mg/kg, the AELJ showed significant inhibition of both change in paw thickness and vascular permeability. The AELJ (100 mg/kg) also significantly inhibited PAR2 agonists-induced myeloperoxidase (MPO) activity and tumor necrosis factor (TNF)-alpha expression in paw tissue.

CONCLUSION

The present study demonstrated that AELJ has an anti-inflammatory action for PAR2-mediated paw edema.