B

249

210

Lipoxins display selective activities on human leukocytes that are either stimulatory or inhibitory, depending on the target cell type involved. In human PMN, LXA 4 induces chemokinesis but inhibits chemotaxis toward leukotriene B 4 (LTB 4 ) and N-formylmethionylleucylphenylalanine (FMLP) (7). LXA 4 also inhibits FMLP-induced PMN transmigration across intestinal epithelium (8). In addition, LTB 4 -and LTC 4 -induced PMN adherence to human umbilical vein endothelial cells (HUVEC) is reduced by ϳ70% by LXA 4 and LXB 4 (9) and aspirin-triggered 15-epi-LXA 4 also inhibits LTB 4 -stimulated PMN adherence to HUVEC at nanomolar concentrations and is ϳtwo times more potent than LXA 4 in this setting (6). LXA 4 and LXB 4 also down-regulate peptidoleukotriene-induced Pselectin expression on HUVEC (9). LXA 4 displays in vivo activity, with inhibition of PMN migration into the kidney in rat glomerulonephritis models (3) and inhibition of PMN diapedesis from postcapillary venules (10). In contrast to the downregulation of PMN, LX exhibit selective stimulatory activities in the monocyte, as we recently described potent activation of human monocyte migration and adherence to laminin by both LXA 4 and LXB 4 (11).Human monocytes were also found to rapidly convert more than 80% of added LXA 4 to novel metabolites via dehydrogenation and reduction of double bonds and the products were identified as 15-oxo-LXA 4

Section: Resultsmentioning

confidence: 99%

Lipoxin A4 Stable Analogs Are Potent Mimetics That Stimulate Human Monocytes and THP-1 Cells via a G-protein-linked Lipoxin A4 Receptor

Maddox

Hachicha

Takano

et al. 1997

249

210

“…Purity of PMN was Ͼ95% as determined microscopically using Diff-Quick staining (Baxter). PMN, monocytes, or HMC-1 cells (1 ϫ 10 6 cells) were incubated with either anti-CD88 mAb 5S/1 (10 g/ml) (kindly provided by Dr. O. Götze, Göttingen, Germany) (27) or the protein A-purified polyclonal rabbitanti-C5L2 antibody (5 g/ml) described earlier (41) for 60 min at 4°C in 100 l of PBS-bovine serum albumin (1%). The purified polyclonal rabbit-anti-C5L2 antibody does not bind to untransfected RBL cells or RBL cells transfected with CD88, hC3aR, human formyl peptide receptor-like 1/lipoxin A4 receptor (FPRL1/LXA4R), or ChemR23 (42).…”

Section: C5a Mutants Are Antagonists For Cd88 and C5l2mentioning

confidence: 99%

“…Several antagonists for CD88 have been described, including peptides (20 -22), a nonpeptidic compound (23), C5a mutants (24 -26), and anti-C5aR antibodies (27,28). All of these compounds are potent CD88 antagonists in vitro; however, only the C5a mutants C5aRAM (24) and jun/fos-A8 (25), the cyclic peptide AcPhe[L-ornithinePro-D-cyclohexylalanine-Trp-Arg] (AcF-(OpdChaWR)) (29), and a nonpeptidic antagonist (23) have been proven useful in vivo.…”

mentioning

confidence: 99%

C5a Mutants Are Potent Antagonists of the C5a Receptor (CD88) and of C5L2

Otto

Hawlisch

Monk

et al. 2004

The anaphylatoxin C5a exerts a plethora of biologic activities critical in the pathogenesis of systemic inflammatory diseases. Recently, we reported on a C5a mutant, jun/fos-A8, as a potent antagonist for the human and mouse C5a receptor (CD88). Addressing the molecular mechanism accounting for CD88 receptor antagonism by site-directed mutagenesis, we found that a positively charged amino acid at position 69 is crucial. Replacements by either hydrophobic or negatively charged amino acids switched the CD88 antagonist jun/fos-A8 to a CD88 agonist. In addition to CD88, the seven-transmembrane receptor C5L2 has recently been found to provide high affinity binding sites for C5a and its desarginated form, C5adesArg 74 . A jun/fos-A8 mutant in which the jun/ fos moieties and amino acids at positions 71-73 were deleted, A8 ⌬71-73 , blocked C5a and C5adesArg 74 binding to CD88 and C5L2. In contrast, the cyclic C5a C-terminal analog peptide AcF-[OP-D-ChaWR] inhibited binding of the two anaphylatoxins to CD88 but not to C5L2, suggesting that the C5a core segment is important for high affinity binding to C5L2. Both receptors are coexpressed on human monocytes and the human mast cell line HMC-1; however, C5L2 expression on monocytes is weaker as compared with HMC-1 cells and highly variable. In contrast, no C5L2 expression was found on human neutrophils. A8 ⌬71-73 is the first antagonist that blocks C5a and C5adesArg 74 binding to both C5a receptors, CD88 and C5L2, making it a valuable tool for studying C5L2 functions and for blocking the biological activities of C5a and C5adesArg 74 in mice and humans.

“…Since the cloning of the C5a receptor (21,22), work has been focused on defining the structural features of the receptor molecule required for the C5a-receptor interaction (23)(24)(25)(26)(27)(28)(29)(30)(31). The cell-surface receptor for C5a is a member of the G-proteincoupled receptor superfamily, with an extracellular N-terminal region, an integral membrane helical domain, and a C-terminal tail extending into the cytoplasmic space (32).…”

mentioning

confidence: 99%

“…Several lines of investigation suggest that the recognition domain for the C5a-receptor interaction is localized in the extracellular N-terminal region of the C5a receptor (4). First, antibodies recognizing the receptor N-terminal fragments interfere with C5a binding (23,24). Second, truncation of the N terminus of the C5a receptor results in reduced binding of the receptor to intact C5a, but not to the agonist C5a tail peptides (27,28).…”

mentioning

confidence: 99%

Residues 21–30 within the Extracellular N-terminal Region of the C5a Receptor Represent a Binding Domain for the C5a Anaphylatoxin

Chen¹,

Zhang²,

Gonnella³

et al. 1998

The functions of the C5a anaphylatoxin are expressed through its interaction with a cell-surface receptor with seven transmembrane helices. The interaction of C5a with the receptor has been explained by a two-site model whereby recognition and effector sites on C5a bind, respectively, to recognition and effector domains on the receptor, leading to receptor activation (Chenoweth, D. E., and Hugli, T. E.