Inhibited Monocyte Migration Research Articles

In vivo blood monocyte migration to acute inflammatory reactions, IL-1 alpha, TNF-alpha, IFN-gamma, and C5a utilizes LFA-1, Mac-1, and VLA-4. The relative importance of each integrin.

The role of the monocyte integrins, Mac-1, LFA-1, and VLA-4, on the adhesion of rat blood monocytes to rat microvascular endothelial cells in vitro and the importance of these receptors in monocyte migration to inflammation in vivo were evaluated. Monocyte adhesion to cytokine (IL-1, IFN-gamma, and TNF-alpha)-stimulated endothelial cells was mediated by Mac-1, LFA-1, and VLA-4, but Mac-1 appeared to be less important than LFA-1 or VLA-4. After i.v. injection, large numbers of 51Cr-labeled blood monocytes migrated within 2 h to dermal inflammatory sites induced by C5a, IL-1 alpha, IFN-gamma, TNF-alpha, LPS, and poly inosinic:cytidylic acid. Anti-Mac-1 mAb treatment had no effect, whereas anti-LFA-1 inhibited migration to C5a and the cytokines by 20 to 40%. Blocking both Mac-1 and LFA-1 decreased monocyte accumulation by 50 to 70% to all stimuli. Anti-VLA-4 inhibited monocyte migration to IL-1 alpha, IFN-gamma, TNF-alpha, and LPS, but not to C5a. Combining anti-Mac-1 with anti-VLA-4 did not increase this inhibition, whereas blocking VLA-4 and LFA-1 together further suppressed (60-85%) migration. Combined treatment with mAb to all three integrins inhibited > 98% of the monocyte migration to the inflammatory stimuli. 1) 51Cr blood monocytes can be used to quantify monocyte migration to inflammatory reactions in the rat. 2) Monocytes use Mac-1, LFA-1, and VLA-4 for in vitro adhesion and in vivo migration to cutaneous inflammation, and these integrins are essential for normal migration because blockade of all three virtually abolishes monocyte accumulation. 3) Mac-1 plays a less important role than LFA-1, as LFA-1 appears to substitute for Mac-1, and VLA-4 and LFA-1 can mediate much of the adhesion and migration. 4) The initiating inflammatory stimulus also modifies monocyte integrin usage, supporting the multistep combinatorial model of leukocyte extravasation.

A new antiinflammatory compound, leumedin, inhibits modification of low density lipoprotein and the resulting monocyte transmigration into the subendothelial space of cocultures of human aortic wall cells.

Addition of leumedin, N-[9H-(2,7-dimethylfluorenyl-9-methoxy) carbon]-L-leucine at 30-60 microM together with LDL almost completely prevented the induction of monocyte chemotactic protein mRNA, reduced monocyte chemotactic protein 1 levels by 84%, and inhibited monocyte migration into the subendothelial space of cocultures of human aortic wall cells by < or = 98%. LDL incubated with leumedin formed a stable complex that remained intact even after refloating in an ultracentrifuge. Leumedin at 50 microM did not change conjugated diene formation during coculture modification of LDL or Cu++ catalyzed oxidation of LDL. Unlike LDL from control rabbits, LDL isolated from rabbits that were injected with 20 mg/kg leumedin was remarkably resistant to modification by the coculture and did not induce monocyte migration to a significant degree. Moreover, HDL isolated from rabbits injected with leumedin was far more effective in protecting against LDL modification by the artery wall cocultures than HDL from control rabbits. We conclude that leumedins can associate with lipoproteins in vivo, rendering LDL resistant to biological modification and markedly amplifying the protective capacity of HDL against in vitro LDL oxidation by artery wall cells.

Minimally modified low density lipoprotein induces monocyte chemotactic protein 1 in human endothelial cells and smooth muscle cells.

After exposure to low density lipoprotein (LDL) that had been minimally modified by oxidation (MM-LDL), human endothelial cells (EC) and smooth muscle cells (SMC) cultured separately or together produced 2- to 3-fold more monocyte chemotactic activity than did control cells or cells exposed to freshly isolated LDL. This increase in monocyte chemotactic activity was paralleled by increases in mRNA levels for a monocyte chemotactic protein 1 (MCP-1) that is constitutively produced by the human glioma U-105MG cell line. Antibody that had been prepared against cultured baboon smooth muscle cell chemotactic factor (anti-SMCF) did not inhibit monocyte migration induced by the potent bacterial chemotactic factor f-Met-Leu-Phe. However, anti-SMCF completely inhibited the monocyte chemotactic activity found in the media of U-105MG cells, EC, and SMC before and after exposure to MM-LDL. Moreover, monocyte migration into the subendothelial space of a coculture of EC and SMC that had been exposed to MM-LDL was completely inhibited by anti-SMCF. Anti-SMCF specifically immunoprecipitated 10-kDa and 12.5-kDa proteins from EC. Incorporation of [35S]methionine into the immunoprecipitated proteins paralleled the monocyte chemotactic activity found in the medium of MM-LDL stimulated EC and the levels of MCP-1 mRNA found in the EC. We conclude that (i) SMCF is in fact MCP-1 and (ii) MCP-1 is induced by MM-LDL.

MIF-like activity of natural and recombinant human interferon-gamma and their neutralization by monoclonal antibody.

By utilizing elutriation-purified human monocytes, we found that human interferon (IFN) inhibits monocyte migration in a manner similar to migration inhibitory factor (MIF) and does it without demonstrable cytotoxicity. We observed that human IFN-gamma is 10 to 300 times more potent in its MIF activity than is IFN-alpha and that monoclonal antibodies (MoAb) can be used to distinguish between them. Studies with recombinant IFN-gamma indicate that the migration inhibition seen with natural IFN-gamma is due to IFN-gamma itself and is not due to co-purification of another lymphokine with the natural IFN-gamma. Although interferons exhibit MIF activities, there are apparently other cytokines, without antiviral activity, that also have MIF activities. MIF from the lymphoblastoid cell line RPMI 1788 was not neutralized by MoAb to IFN. However, MIF activity in supernatant fluid from human peripheral blood lymphocyte cultures stimulated with Con A-Sepharose was completely neutralized with MoAb anti-IFN-gamma. These data indicate that MIF is really a family of cytokines that inhibit macrophage/monocyte migration and that the major portion of MIF activity associated with crude supernatant of mitogen-stimulated lymphocytes is due to IFN-gamma.