Young Su Jung

Wnt5a stimulates chemotactic migration and chemokine production in human neutrophils

Wnt5a is a ligand that activates the noncanonical Wnt signaling pathways (β-catenin-independent pathways). Human neutrophils expressed several Wnt5a receptors, such as Frizzled 2, 5 and 8. Stimulation of human neutrophils with Wnt5a caused chemotactic migration and the production of two important chemokines, CXCL8 and CCL2. CCL2 production by Wnt5a was mediated by a pertussis toxin-sensitive G-protein-dependent pathway. Wnt5a also stimulated the phosphorylation of three mitogen-activated protein kinases (MAPKs: ERK, p38 MAPK and JNK) and Akt. Inhibition of ERK, p38 MAPK or JNK by specific inhibitors induced a dramatic reduction in Wnt5a-induced CCL2 production. Supernatant collected from lipopolysaccharide-stimulated macrophages induced neutrophil chemotaxis, which was significantly inhibited by anti-Wnt5a antibody. Our results suggested that Wnt5a may contribute to neutrophil recruitment, mediating the inflammation response.

Sphingosylphosphorylcholine stimulates CCL2 production from human umbilical vein endothelial cells.

Sphingosylphosphorylcholine (SPC) is a component of high-density lipoprotein particles. We investigated the functional role of SPC in HUVECs. SPC stimulation induced production of the CCL2 chemokine in a PTX-sensitive G-protein–dependent manner. SPC treatment caused the activation of NF-κB and AP-1, which are essential for SPC-induced CCL2 production, and induced the activation of three MAPKs, ERK, p38 MAPK, and JNK. Inhibition of p38 MAPK or JNK by specific inhibitors caused a dramatic decrease in SPC-induced CCL2 production. The Jak/STAT3 pathway was also activated upon SPC stimulation of HUVECs. Pretreatment with a Jak inhibitor blocked not only SPC-induced p38 MAPK and JNK activation, but also NF-κB and AP-1 activation. Our results suggest that SPC stimulates HUVECs, resulting in Jak/STAT3–, NF-κB–, and AP-1–mediated CCL2 production. We also observed that SPC stimulated expression of the adhesion molecule ICAM-1 in HUVECs. Our results suggest that SPC may contribute to atherosclerosis; therefore, SPC and its unidentified target receptor offer a starting point for the development of a treatment for atherosclerosis.

Mouse neutrophils express functional umami taste receptor T1R1/T1R3

Neutrophils play an important role in the initiation of innate immunity against infection and injury. Although many different types of G-protein coupled receptors are functionally expressed in neutrophils, no reports have demonstrated functional expression of umami taste receptor in these cells. We observed that mouse neutrophils express the umami taste receptor T1R1/T1R3 through RNA sequencing and quantitative RT-PCR analysis. Stimulation of mouse neutrophils with L-alanine or L-serine, which are ligands for the umami taste receptor, elicited not only ERK or p38 MAPK phosphorylation but also chemotactic migration. Moreover, addition of L-alanine or L-serine markedly reduced the production of several cytokines including TNF-α induced by lipopolysaccharide (LPS) through inhibition of NF-κB activity or STAT3 phosphorylation in neutrophils. Our findings demonstrate that neutrophils express the umami taste receptor, through which tastants stimulate neutrophils, resulting in chemotactic migration, and attenuation of LPS-induced inflammatory response. [BMB Reports 2014; 47(11): 649-654]

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.

Antimicrobial peptide scolopendrasin VII, derived from the centipede Scolopendra subspinipes mutilans, stimulates macrophage chemotaxis via formyl peptide receptor 1

In this study, we report that one of the antimicrobial peptides scolopendrasin VII, derived from Scolopendra subspinipes mutilans, stimulates actin polymerization and the subsequent chemotactic migration of macrophages through the activation of ERK and protein kinase B (Akt) activity. The scolopendrasin VII-induced chemotactic migration of macrophages is inhibited by the formyl peptide receptor 1 (FPR1) antagonist cyclosporine H. We also found that scolopendrasin VII stimulate the chemotactic migration of FPR1-transfected RBL-2H3 cells, but not that of vector-transfected cells; moreover, scolopendrasin VII directly binds to FPR1. Our findings therefore suggest that the antimicrobial peptide scolopendrasin VII, derived from Scolopendra subspinipes mutilans, stimulates macrophages, resulting in chemotactic migration via FPR1 signaling, and the peptide can be useful in the study of FPR1-related biological responses. [BMB Reports 2015; 48(8): 479-484]

Phospholipase C activator m-3M3FBS protects against morbidity and mortality associated with sepsis.

Although phospholipase C (PLC) is a crucial enzyme required for effective signal transduction and leukocyte activation, the role of PLC in polymicrobial sepsis remains unclear. In this study, we show that the direct PLC activator m-3M3FBS treatment significantly attenuates vital organ inflammation, widespread immune cell apoptosis, and mortality in a mouse sepsis model induced by lethal cecal ligation and puncture challenge. Mechanistically, m-3M3FBS–dependent protection was largely abolished by pretreatment of mice with the PLC-selective inhibitor U-73122, thus confirming PLC agonism by m-3M3FBS in vivo. PLC activation enhanced the bactericidal activity and hydrogen peroxide production of mouse neutrophils, and it also enhanced the production of IFN-γ and IL-12 while inhibiting proseptic TNF-α and IL-1β production in cecal ligation and puncture mice. In a second model of sepsis, PLC activation also inhibited the production of TNF-α and IL-1β following systemic LPS challenge. In conclusion, we show that agonizing the central signal transducing enzyme PLC by m-3M3FBS can reverse the progression of toxic shock by triggering multiple protective downstream signaling pathways to maintain organ function, leukocyte survival, and to enhance microbial killing.

Phospholipase Cγ in Toll-like receptor-mediated inflammation and innate immunity

Among the phospholipase C (PLC) isoforms, PLCγ not only has unique structural characteristics in terms of harboring SH2 and SH3 domains but also mediates growth factor-induced signaling pathways. PLCγ isoforms are expressed in several innate immune cell types, including macrophages, natural killer cells, mast cells, and neutrophils. Stimulation of Fc receptor or integrin in innate immune cells induces PLCγ activation, which leads to phosphoinositide hydrolysis and calcium increase. The products of PLCγ activity mediate the innate immune response by regulating respiratory burst, phagocytosis, cell adhesion, and cell migration. PLCγ also regulates the inflammatory response by affecting Toll-like receptor-mediated signaling. Here, we briefly review the current understanding of the functional role of PLCγ in inflammation and innate immunity in some innate immune cell types.

Promotion of formyl peptide receptor 1-mediated neutrophil chemotactic migration by antimicrobial peptides isolated from the centipede Scolopendra subspinipes mutilans.

We investigated the effects of two antimicrobial peptides (AMPs) isolated from Scolopendra subspinipes mutilans on neutrophil activity. Stimulation of mouse neutrophils with the two AMPs elicited chemotactic migration of the cells in a pertussis toxin-sensitive manner. The two AMPs also stimulated activation of ERK and Akt, which contribute to chemotactic migration of neutrophils. We found that AMP-stimulated neutrophil chemotaxis was blocked by a formyl peptide receptor (FPR) 1 antagonist (cyclosporin H); moreover the two AMPs stimulated the chemotactic migration of FPR1-expressing RBL-2H3 cells but not of vector-expressing RBL-2H3 cells. We also found that the two AMPs stimulate neutrophil migration in vivo, and that this effect is blocked in FPR1-deficient mice. Taken together, our results suggest that the two AMPs stimulate neutrophils, leading to chemotactic migration through FPR1, and the two AMPs will be useful for the study of FPR1 signaling and neutrophil activation. [BMB Reports 2016; 49(9): 520-525]

Role of CXCR2 on the immune modulating activity of α-iso-cubebenol a natural compound isolated from the Schisandra chinensis fruit.

Previously, we demonstrated that α-iso-cubebenol, a natural compound isolated from the fruits of Schisandra chinensis, strongly enhances therapeutic efficacy against cecal ligation and puncture challenge-induced sepsis. In this study, we found that α-iso-cubebenol stimulated calcium increase and degranulation in human neutrophils. α-Iso-cubebenol also strongly induced neutrophil chemotaxis, which was completely blocked by a CXCR2 antagonist, SB225002. The increased survival rate by α-iso-cubebenol was also significantly attenuated by SB225002. Taken together, the results indicate that α-iso-cubebenol-induced anti-septic activity was mediated by CXCR2, suggesting CXCR2 as an important target for the regulation of sepsis and inflammation.

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.