Biomedical subjects

M Magazin

Publications and source records attributed to M Magazin.

22 records · Page 2Linked to original sources

PubMedDate not supplied

The biological activities of gro beta and IL-8 on human neutrophils are overlapping but not identical.

Gro beta and IL-8 are two members of the small induced secreted (SIS) cytokine family (C-X-C subgroup) with proinflammatory activities on neutrophils. In order to assess whether or not the interaction with their receptors results in similar biological actions, we compared the two cytokines in five different bioassays. Gro beta showed similar biological activities as IL-8 in tests of chemotaxis, induction of the respiratory burst, and induction of interleukin 6 (IL-6) production. However, for two other biological activities: augmentation of the expression of CD11b on the cell surface and rapid elevation of the intracellular calcium concentration, maximal effects required 100 times more gro beta than IL-8. Taken together, these results suggest that the stimulation of the IL-8 or gro beta receptor evokes three similar responses, but that only the activation of the IL-8 receptor and not that of gro beta results in elevated CD11b expression and calcium mobilization in human neutrophils.

Antimicrobial Cationic Peptides↗

PubMedDate not supplied

Interleukin-13 is a monocyte chemoattractant.

Recombinant human IL-13 is chemotactic for purified human peripheral blood monocytes Cell migration is stimulated with a typical bell-shaped concentration curve and is maximal at 10 ng/ml. Migration is the result of chemotaxis, and not chemokinesis, as shown by checkerboard experiments. The chemotactic activity of IL-13 on monocytes is not inhibited by preincubation of the cells with pertussis toxin but is diminished by preincubation with protein kinase inhibitors. The related cytokine, IL-4, also stimulates migration of monocytes in the Boyden chamber assays at concentrations similar to those effective for IL-13. Human IL-13 is capable of attracting rabbit peripheral blood monocytes at those concentrations active on human monocytes. On the other hand, no neutrophil migration was induced by IL-13, even at 1 microM concentrations.

Alkaloids↗

PubMedDate not supplied

Functional linkage of the Gro beta and IL-8 receptors on the surface of human neutrophils.

Gro beta and IL-8 are two pro-inflammatory cytokines with chemotactic activities on neutrophils. Binding studies were performed to ascertain whether their similar biological activities are mediated through the same receptor. Since Gro beta lacks tyrosine residues, recombinant Gro beta containing an additional carboxyterminal tyrosine residue (Gro beta-Tyr) was produced in transfected COS cells, purified to homogeneity and radiolabelled with 125INa. Saturation experiments using [125I]-Gro beta-Tyr allowed us to identify high affinity receptors on human neutrophils (Kd: 2 +/- 0.5 nM and Bmax: 4760 +/- 761 sites/cell). Experiments using [125I]-IL-8 as ligand, showed no significative differences in affinity (Kd: 4 +/- 0.9 nM) but about two times the number of sites (11316 +/- 1810 sites/cell). In competition experiments using [125I]-Gro beta-Tyr, unlabelled IL-8 and Gro beta-Tyr generated superposable displacement curves (IC50: 0.69 +/- 0.15 nM and 0.42 +/- 0.11 nM, respectively). Interesting, IL-8 binding sites could be down-regulated by Gro beta and IL-8, indicating that the two binding sites may be associated. Cross-linking experiments using [125I]-IL-8 revealed two major bands at 70 and 140 kDa, whereas experiments with [125I]-Gro beta-Tyr showed only the 70 kDa band. Taken together, these results suggest that the human neutrophil IL-8/Gro beta receptor is a dimeric complex with two high affinity binding sites for IL-8 and of those two, only one is shared by Gro beta.

Binding, Competitive↗

PubMedDate not supplied

Molecular cloning of the MCP-3 chemokine gene and regulation of its expression.

We have isolated a cDNA (NC28) transcribed from a mRNA which is transiently induced in U937 promonocytic cells by PMA and super-induced by cycloheximide. NC28 cDNA encodes a new member of the chemokine family, MCP-3, recently purified from MG-63 osteosarcoma cells by Van Damme et al. [1]. The MCP-3 protein sequence shows 74% identity with human monocyte chemoattractant protein 1 (MCP-1) and, like MCP-1, recombinant MCP-3 protein shows chemotactic activity for monocytes but not for neutrophils. However the secreted MCP-3 protein differs from MCP-1 in being N-glycosylated. The 3' noncoding regions of MCP-3 and MCP-1 mRNAs are more diverged (44%), allowing specific cDNA probes to be made, and indicating that the two genes are evolutionarily distant. Sequence comparisons of the 3' noncoding regions suggest that MCP-3 may be the human homologue of the mouse MARC gene [2], and that MCP-1 and MCP-3 genes arose by a gene duplication event before the mammalian radiation. Both MCP-1 and MCP-3 mRNAs are expressed by PBMC, principally by monocytes, with MCP-1 mRNA being expressed at levels 2-4 times that of MCP-3 mRNA. However, while MCP-1 mRNA is also expressed at high levels in fibroblast or astrocytoma cell lines after IL-1 and TNF stimulation, MCP-3 mRNA is expressed only at very low levels in these cells. The cellular origin of MCP-3 is thus more restricted than that of MCP-1. In our experiments on PBMC, LPS is not a consistent inducer of MCP-1 and MCP-3 mRNAs. In some experiments, it actually decreases levels of these two mRNAs, while concomitantly increasing IL-6 and TNF-alpha mRNA levels. Levels of MCP-1 and MCP-3 mRNAs in PBMC are both increased by IFN-gamma, although IL-6 mRNA is not induced. They are also increased by PHA-P and are decreased, in most cases, by IL-13 [3]. MCP-1 and MCP-3 mRNAs are thus co-ordinately regulated in monocytes in response to a number of inducing or inhibitory agents, in a manner differing in several respects from that of other monokines such as IL-6.

Amino Acid Sequence↗