Synergistic activation of NF-{kappa}B by bacterial chemoattractant and TNF{alpha} is mediated by p38 MAPK-dependent RelA acetylation.

In the host immune system, leukocytes are often exposed to multiple inflammation inducers. NF-κB is of considerable importance in leukocyte function because of its ability to activate the transcription of many proinflammatory immediate-early genes. Tremendous efforts have been made toward understanding how NF-κB is activated by various inducers. However, most research on NF-κB regulation has been focused on understanding how NF-κB is activated by a single inducer. This is unlike the situation in the human immune system where multiple inflammation inducers, including both exogenous and endogenous mediators, are present concurrently. We now present evidence that the formylated peptide f-Met-Leu-Phe (fMLP), a bacterial chemoattractant, synergizes with TNFα to induce NF-κB activation and the resultant inflammatory response in vitro and in vivo. The mechanism of synergistic activation of NF-κB by bacterial fMLP and TNFα may be involved in the induction of RelA acetylation, which is regulated by p38 MAPK. Thus, this study provides direct evidence for the synergistic induction of NF-κB-dependent inflammatory responses by both exogenous and endogenous inducers. The ability of fMLP to synergize with TNFα and activate NF-κB represents a novel and potentially important mechanism through which bacterial fMLP not only attracts leukocytes but also directly contributes to inflammation by synergizing with the endogenous mediator TNFα.

Design of soymetide-4 derivatives to potentiate the anti-alopecia effect.

Previously, we found that soymetide-4 (MITL), an N-formyl-methionyl-leucyl-phenylalanine (fMLP) agonist peptide derived from soybean beta-conglycinin alpha' subunit, stimulated phagocytosis of human polymorphonuclear leukocytes, and inhibited alopecia induced by etoposide, an anticancer drug, in neonatal rats after oral administration. We found that the fMLP receptor affinity and phagocytosis-stimulating activity of soymetide-4 was potentiated by replacement of Thr(3) with hydrophobic residues. Among the derivatives synthesized, [Trp](3)-soymetide-4 (MIWL) was the most potent, stronger by 180 and 130 times than soymetide-4 in receptor affinity and phagocytosis-stimulating activity, respectively. The anti-alopecia effect of [Trp](3)-soymetide-4 was about 3 times larger than that of soymetide-4 after oral administration.

Soymetide, an immunostimulating peptide derived from soybean beta-conglycinin, is an fMLP agonist.

A tridecapeptide (MITLAIPVNKPGR) that stimulates phagocytosis of human neutrophils was isolated from a trypsin digest of soybean proteins. This peptide is derived from the soybean beta-conglycinin alpha' subunit and was named soymetide-13. The N-terminal methionine residue of soymetide-13 is essential for its activity, and removal of C-terminal residues revealed that soymetide-4 (MITL) is the minimal structure required for phagocytosis stimulation. Although they are not formylated at their N-termini, soymetides have a weak affinity for the N-formyl-methionyl-leucyl-phenylalanine (fMLP) receptor and their phagocytosis-stimulating activity is inhibited by the fMLP antagonist Boc-MLP. Interestingly, soymetide-4 promotes tumor necrosis factor alpha production at a higher level than soymetide-13 following oral administration in mice.

Actin polymerization in response to different chemoattractants is reduced in granulocytes from chronic myeloid leukemia patients.

Chronic myeloid leukemia (CML), a hematopoietic stem cell disorder, is characterized by the presence of Philadelphia chromosome (Ph1). Earlier studies have shown that various functions, such as chemotaxis, fluid phase pinocytosis, phagocytosis, and degranulation in response to chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP), were defective in polymorphonuclear leukocytes (PMNL) from CML patients. These functions depend on actin microfilaments (MF). Further studies showed that fMLP-induced actin polymerization was lower in CML PMNL. To see if this defect is specific to stimulation by fMLP alone or is a global phenomenon involving other chemoattractant receptors, chemotaxis and actin polymerization were studied in response to fMLP, an analog of fMLP, formyl-methionine-1 aminocyclooctane 1 carboxylic acid-phenyalanine-O-methionine (FACC8), platelet-activating factor (PAF), and leukotriene B4 (LTB4). These compounds bind to different chemoattractant receptors. Chemotaxis and actin polymerization in response to all four chemoattractants were significantly lower in CML PMNL compared with PMNL from normal subjects and were differentially affected for the different chemoattractants. These results suggest a global phenomenon involving all four chemoattractant-stimulated pathways. This lower amount of F-actin may be responsible for the defective chemotaxis seen in these cells.

Effects of interleukin (IL)-3 and IL-5 on human eosinophil degranulation induced by complement components C3a and C5a.

It is suggested that eosinophils (Eos) play an important role in the pathogenesis of bronchial asthma by releasing cytotoxic cationic eosinophil granule proteins and damaging bronchial epithelial cells. However, the exact nature of the actual inducer of eosinophil degranulation in vivo is unclear. We examined eosinophil cationic protein (ECP) release from human Eos in response to soluble agonists such as C5a, C3a, platelet-activating factor, and FMLP with or without interleukin (IL)-3 or IL-5 priming. Eosinophil degranulation induced by these soluble agonists required the pretreatment of Eos by cytochalasin B even in IL-3 priming. Among four agonists, C5a was the most effective stimulus of ECP release either with or without IL-5 priming. IL-3 and IL-5 remarkably enhanced ECP release in Eos triggered by C3a and C5a. The enhancement of ECP release by IL-3 and IL-5 occurred at 0.1-0.3 ng/ml and became maximal at 10-30 ng/ml, concentration-dependently. The enhancement of ECP release by cytokines became optimal at an interval of 10 min. Our data support the importance of complement components and cytokines in eosinophil degranulation in vivo.