Serum amyloid A inhibits dendritic cell differentiation by suppressing GM-CSF receptor expression and signaling

In this study, we report that an acute phase reactant, serum amyloid A (SAA), strongly inhibits dendritic cell differentiation induced by GM-CSF plus IL-4. SAA markedly decreased the expression of MHCII and CD11c. Moreover, SAA decreased cell surface GM-CSF receptor expression. SAA also decreased the expression of PU.1 and C/EBPα, which play roles in the expression of GM-CSF receptor. This inhibitory response by SAA is partly mediated by the well-known SAA receptors, Toll-like receptor 2 and formyl peptide receptor 2. Taken together, we suggest a novel insight into the inhibitory role of SAA in dendritic cell differentiation.

Serum amyloid A inhibits RANKL-induced osteoclast formation

When mouse bone marrow-derived macrophages were stimulated with serum amyloid A (SAA), which is a major acute-phase protein, there was strong inhibition of osteoclast formation induced by the receptor activator of nuclear factor kappaB ligand. SAA not only markedly blocked the expression of several osteoclast-associated genes (TNF receptor-associated factor 6 and osteoclast-associated receptor) but also strongly induced the expression of negative regulators (MafB and interferon regulatory factor 8). Moreover, SAA decreased c-fms expression on the cell surface via shedding of the c-fms extracellular domain. SAA also restrained the fusion of osteoclast precursors by blocking intracellular ATP release. This inhibitory response of SAA is not mediated by the well-known SAA receptors (formyl peptide receptor 2, Toll-like receptor 2 (TLR2) or TLR4). These findings provide insight into a novel inhibitory role of SAA in osteoclastogenesis and suggest that SAA is an important endogenous modulator that regulates bone homeostasis.

Scant Extracellular NAD Cleaving Activity of Human Neutrophils is Down-Regulated by fMLP via FPRL1

Extracellular nicotinamide adenine dinucleotide (NAD) cleaving activity of a particular cell type determines the rate of the degradation of extracellular NAD with formation of metabolites in the vicinity of the plasma membrane, which has important physiological consequences. It is yet to be elucidated whether intact human neutrophils have any extracellular NAD cleaving activity. In this study, with a simple fluorometric assay utilizing 1,N6-ethenoadenine dinucleotide (etheno-NAD) as the substrate, we have shown that intact peripheral human neutrophils have scant extracellular etheno-NAD cleaving activity, which is much less than that of mouse bone marrow neutrophils, mouse peripheral neutrophils, human monocytes and lymphocytes. With high performance liquid chromatography (HPLC), we have identified that ADP-ribose (ADPR) is the major extracellular metabolite of NAD degradation by intact human neutrophils. The scant extracellular etheno-NAD cleaving activity is decreased further by N-formyl-methionine-leucine-phenylalanine (fMLP), a chemoattractant for neutrophils. The fMLP-mediated decrease in the extracellular etheno-NAD cleaving activity is reversed by WRW4, a potent FPRL1 antagonist. These findings show that a much less extracellular etheno-NAD cleaving activity of intact human neutrophils compared to other immune cell types is down-regulated by fMLP via a low affinity fMLP receptor FPRL1.

The immune-stimulating peptide WKYMVm has therapeutic effects against ulcerative colitis

In this study, we examined the therapeutic effects of an immune-stimulating peptide, WKYMVm, in ulcerative colitis. The administration of WKYMVm to dextran sodium sulfate (DSS)-treated mice reversed decreases in body weight, bleeding score and stool score in addition to reversing DSS-induced mucosa destruction and shortened colon. The WKYMVm-induced therapeutic effect against ulcerative colitis was strongly inhibited by a formyl peptide receptor (FPR) 2 antagonist, WRWWWW, indicating the crucial role of FPR2 in this effect. Mechanistically, WKYMVm effectively decreases intestinal permeability by stimulating colon epithelial cell proliferation. WKYMVm also strongly decreases interleukin-23 and transforming growth factor-beta production in the colon of DSS-treated mice. We suggest that the potent immune-modulating peptide WKYMVm and its receptor FPR2 may be useful in the development of efficient therapeutic agents against chronic intestinal inflammatory diseases.

Identification of novel peptides that stimulate human neutrophils

Neutrophils play a key role in innate immunity, and the identification of new stimuli that stimulate neutrophil activity is a very important issue. In this study, we identified three novel peptides by screening a synthetic hexapeptide combinatorial library. The identified peptides GMMWAI, MMHWAM, and MMHWFM caused an increase in intracellular Ca2+ in a concentration-dependent manner via phospholipase C activity in human neutrophils. The three peptides acted specifically on neutrophils and monocytes and not on other non-leukocytic cells. As a physiological characteristic of the peptides, we observed that the three peptides induced chemotactic migration of neutrophils as well as stimulated superoxide anion production. Studying receptor specificity, we observed that two of the peptides (GMMWAI and MMHWFM) acted on formyl peptide receptor (FPR)1 while the other peptide (MMHWAM) acted on FPR2. Since the three novel peptides were specific agonists for FPR1 or FPR2, they might be useful tools to study FPR1- or FPR2-mediated immune response and signaling.

IL-27 regulates the expression of Mac-1, fMLP-R and IL-1beta in human neutrophils through p38 MAPK and PI3K signal pathways / 中国实验血液学杂志

The present study was aimed to investigate the pathways, by which IL-27 regulates the expression of adherent molecule Mac-1, chemotactic factor receptor fMLP-R and pro-inflammatory cytokine IL-1beta in human neutrophils. Highly purified human neutrophils were isolated from peripheral blood using Ficoll-Hypaque gradients centrifugation and erythrocyte lysis. The mRNA expression of IL-27 receptor components (WSX-1/TCCR and gp130) in human neutrophils was detected by reverse transcription polymerase chain reaction (RT-PCR). After incubation with IL-27 and specific inhibitors (p38 MAPK inhibitor SB203580, PI3K inhibitor LY294002 and ERK inhibitor U0126), the mRNA levels of fMLP-R and IL-1beta were determined by real time RT-PCR, and the adherent molecule Mac-1 expression in human neutrophils was determined by flow cytometry. The IL-1beta level in culture supernatant of human neutrophils was assayed by radioimmunoassay. The results showed that IL-27 receptor components (WSX-1/TCCR and gp130) were constitutively expressed in human neutrophils. IL-27 down-regulated Mac-1 expression in human neutrophils (p<0.05). After incubation with specific inhibitors, SB203580, not LY294002 and U0126, inhibited the down-regulation of Mac-1 expression by IL-27. However, IL-27 up-regulated the mRNA expression of fMLP-R and IL-1beta, and increased the release of IL-1beta (p<0.05). Interestingly, LY294002, not SB203580 and U0126, inhibited the up-regulation of fMLP-R and IL-1beta by IL-27. It is concluded that the IL-27 may regulate the expression of Mac-1, fMLP-R and IL-1beta in human neutrophils through p38 MAPK and PI3K signal pathways.

Lysophosphatidylglycerol inhibits formyl peptide receptor like-1-stimulated chemotactic migration and IL-1beta production from human phagocytes

In this study, we observed that lysophosphatidylglycerol (LPG) completely inhibited a formyl peptide receptor like-1 (FPRL1) agonist (MMK-1)-stimulated chemotactic migration in human phagocytes, such as neutrophils and monocytes. LPG also dramatically inhibited IL-1beta production by another FPRL1 agonist serum amyloid A (SAA) in human phagocytes. However, LPG itself induced intracellular calcium increase and superoxide anion production in human phagocytes. Keeping in mind that phagocytes migration and IL-1beta production by FPRL1 are important for the induction of inflammatory response, our data suggest that LPG can be regarded as a useful material for the modulation of inflammatory response induced by FPRL1 activation.

LL-37 inhibits serum amyloid A-induced IL-8 production in human neutrophils

Serum amyloid A (SAA) has been regarded as an important mediator of inflammatory responses. The effect of several formyl peptide receptor-like 1 (FPRL1) ligands on the production of IL-8 by SAA was investigated in human neutrophils. Among the ligands tested, LL-37 was found to specifically inhibit SAA-induced IL-8 production in transcriptional and post-transcriptional levels. Since SAA stimulated IL-8 production via ERK and p38 MAPK in human neutrophils, we tested the effect of LL-37 on SAA induction for these two MAPKs. LL-37 caused a dramatic inhibition of ERK and p38 MAPK activity, which is induced by SAA. LL-37 was also found to inhibit SAA-stimulated neutrophil chemotactic migration. Further, the LL-37-induced inhibitory effect was mediated by FPRL1. Our findings indicate that LL-37 is expected to be useful in the inhibition of SAA signaling and for the development of drugs against SAA-related inflammatory diseases.

LL-37 inhibits serum amyloid A-induced IL-8 production in human neutrophils

Serum amyloid A (SAA) has been regarded as an important mediator of inflammatory responses. The effect of several formyl peptide receptor-like 1 (FPRL1) ligands on the production of IL-8 by SAA was investigated in human neutrophils. Among the ligands tested, LL-37 was found to specifically inhibit SAA-induced IL-8 production in transcriptional and post-transcriptional levels. Since SAA stimulated IL-8 production via ERK and p38 MAPK in human neutrophils, we tested the effect of LL-37 on SAA induction for these two MAPKs. LL-37 caused a dramatic inhibition of ERK and p38 MAPK activity, which is induced by SAA. LL-37 was also found to inhibit SAA-stimulated neutrophil chemotactic migration. Further, the LL-37-induced inhibitory effect was mediated by FPRL1. Our findings indicate that LL-37 is expected to be useful in the inhibition of SAA signaling and for the development of drugs against SAA-related inflammatory diseases.

Effect of nordy on FPR function of malignant human glioma cell line U87 / 药学学报

Nordy is a synthesized chrial compound. To investigate the effects of nordy (25 - 100 micromol x L(-1)) on the function of formylpeptide receptor (FPR) of malignant human glioma cells, human glioblastoma cell line U87 was used to detect its proliferation, migration, calcium mobilization, vascular endothelial growth factor (VEGF) mRNA and protein levels after activation of FPR by its agonist N-formyl-methionyl-leucyl-phenylalanine (fMLF). Cell proliferation, migration ability, VEGF mRNA, VEGF protein and calcium mobilization were evaluated by cell counting, chemotaxis assay, RT-PCR, ELISA and spectrometry. Nordy (50 - 100 micromol x L(-1)) potently inhibited the proliferation, migration and calcium mobilization of U87 cells induced by fMLF (P < 0.05). Moreover, 100 micromol x L(-1) nordy showed a significantly impaired VEGF mRNA expression and protein secretion induced by fMLF (P < 0.05). Nordy could inhibit FPR functioning in glioma cell proliferation, migration and angiogenesis, which might be a possible mechanism of its anti-cancer effects.

Transfection of Lipoxin A4 receptor-like protein gene enhanced the inhibitory effect of Lipoxin A4 on human lung fibroblasts proliferation induced by connective tissue growth factor / 中华儿科杂志

<p><b>OBJECTIVE</b>Lipoxin A(4) is formed by the metabolism of arachidonic acid. Anti-inflammatory and anti-proliferative effect of lipoxin A(4) has been shown in many human diseases. Recently, as a novel high affinity receptor for ligand lipoxin A(4), Lipoxin A(4) receptor-like protein (LRLP) has been identified. Currently close attention is paid to the important contribution of connective tissue growth factor (CTGF) in lung fibrosis. The purpose of the study was to transfect LRLP gene into human lung fibroblasts and investigate the mechanism of its enhancing antagonistic effect of Lipoxin A(4) on human lung fibroblasts proliferation induced by connective tissue growth factor.</p><p><b>METHODS</b>Eukaryocytic expression vector pEGFP/LRLP which contained LRLP and green fluorescence protein fusion gene (GFP) was constructed and transfected into human lung fibroblasts (HLF). After selecting with G418, HLF/LRLP cell clone which stably expressed LRLP/GFP fusion protein was isolated and characterized by the laser scanning confocal microscope. Cultured HLF and HLF/LRLP were stimulated for 24 h with CTGF (1 microg/ml) in the presence and absence of pretreatment of Lipoxin A(4) (10.0 nmol/L) for 30 min. Inhibition of cell proliferation was determined by MTT assay. Cell cycle analysis was performed by flow cytometry. Western blot was used to detect the expression of cyclin D(1) protein. Electrophoretic mobility shift assay (EMSA) was employed to detect the DNA binding activity of STAT(3).</p><p><b>RESULTS</b>(1) HLF/LRLP cell clone which stably expressed LRLP and GFP fusion protein was successfully obtained. (2) Proliferation of HLF and HLF/LRLP was induced by 1 microg/ml CTGF. Pretreatment with 10 nm Lipoxin A(4) inhibited the proliferation of HLF and HLF/LRLP. And the inhibitory rate of HLF/LRLP was significantly higher than that of HLF [(54.1 +/- 4.2)%, (21.2 +/- 3.7)%, P < 0.05]. (3) The flow cytometry analysis showed that compared with HLF, more HLF/LRLP were arrested at G(0)/G(1) phase in the presence of pretreatment of Lipoxin A(4). [(76.3 +/- 3.5)%, (60.8 +/- 2.0)%, P < 0.05]. (4) Ten nmol/L Lipoxin A(4) antagonized CTGF induced increase of cyclin D(1) protein expression in HLF and HLF/LRLP. And its antagonistic effect on HLR/LRLP was stronger than that on HLF (P < 0.05). (5) Ten nmol/L Lipoxin A(4) antagonized CTGF induced increase of STAT(3) DNA binding activity, and its antagonistic effect on HLF/LRLP was more powerful than that on HLF (P < 0.05).</p><p><b>CONCLUSIONS</b>Transfection of Lipoxin A(4) receptor-like protein gene enhanced the inhibitory effect of Lipoxin A(4) on human lung fibroblasts proliferation induced by CTGF. Its mechanism might be related to regulation of cyclin D(1) protein expression and STAT(3) DNA binding activity.</p>

Trp-Lys-Tyr-Met-Val-Met stimulates phagocytosis via phospho-lipase D-dependent signaling in mouse dendritic cells

Dendritic cells (DCs) play a key role in activating the immune response against invading pathogens as well as dying cells or tumors. Although the immune response can be initiated by the phagocytic activity by DCs, the molecular mechanism involved in this process has not been fully investigated. Trp-Lys-Tyr-Met-Val-Met-NH2 (WKYMVM) stimulates the activation of phospholipase D (PLD) via Ca2+ increase and protein kinase C activation in mouse DC cell line, DC2.4. WKYMVM stimulates the phagocytic activity, which is inhibited in the presence of N-butanol but not t-butanol in DC2.4 cells. Furthermore, the addition of phosphatidic acid, an enzymatic product of PLD activity, enhanced the phagocytic activity in DC2.4 cells. Since at least two of formyl peptide receptor (FPR) family (FPR1 and FPR2) are expressed in DC2.4 as well as in mouse bone marrow-derived dendritic cells, this study suggests that the activation of FPR family by WKYMVM stimulates the PLD activity resulting in phagocytic activity in DC2.4 cells.

The primary study on a novel protein binding to the death domain of the death receptor 4 / 中国医学科学院学报

<p><b>OBJECTIVE</b>To clone and identify novel proteins binding to the death domain of the death receptor 4 (DR4).</p><p><b>METHODS</b>The yeast two-hybrid system was used for this study. Automatic sequencing was carried out for DNA sequencing. The sequence homology and the functional domains were analyzed by BLAST and the ScanProsite Tool softwares, respectively. Co-immunoprecipitate method was used to confirm human formyl peptide receptor-like 1 (FPRL1) binding specifically with DR4CD (the cytoplasmic domain of DR4) in HEK293T cells.</p><p><b>RESULTS</b>Two positive clones, named as pADB1 and pADB2, were obtained. BLAST searching showed that the homology of the insert sequence of pADB1 with the mRNA of FPRL1 was 97%. The insert of pADB2 shared no homology with any known peptides in GeneBank. Co-immunoprecipitate analysis further confirmed that FPRL1 could bind to DR4CD in vivo specifically.</p><p><b>CONCLUSIONS</b>FPRL1 may associate with DR4CD in vivo specifically. The functional studies of FPRL1 in signaling pathway mediated by TNF-related apoptosis inducing ligand (TRAIL) are in active progress in our laboratory.</p>