Monocytes may amplify their recruitment into inflammatory lesions by inducing monocyte chemotactic protein.

Abstract

By Northern analysis, freshly isolated monocytes contained no detectable mRNA for monocyte chemotactic protein-1 (MCP-1). However, after 4 hours of incubation at 37°C, MCP-1 mRNA was clearly induced in the monocytes and was found to be highly dependent and directly proportional to the monocyte density. The level of MCP-1 mRNA continued to increase, reaching a peak after 22 hours of incubation. After 3 days in culture, MCP-1 mRNA levels had declined substantially and after 8 days were undetectable in the monocytes/macrophages. The amount of MCP-1 protein secreted correlated with the density-dependent increase in MCP-1 message. We hypothesize that the migration of monocytes into inflammatory lesions may be amplified by the density and time-dependent induction of MCP-1. (Arteriosclerosis and Thrombosis 1992;12:78-82) T he infiltration of circulating blood monocytes across vascular endothelium is an important early event in the inflammatory response that is common to a variety of injurious conditions, including infection, cancer, atherogenesis, and trauma. -8 This monocyte infiltration and the subsequent events that lead to the acute and chronic presence of inflammatory macrophages within infected or diseased tissue are probably regulated by a series of rapid environmental changes.9 These changes most likely begin with a local elaboration of a chemoattractant to mediate accumulation of monocytes at the site of inflammation. Previous studies have demonstrated that endothelial cells 10 ' 11 and smooth muscle cells 12 -13 in culture constitutively express monocyte chemotactic protein-1 (MCP-1). 1415 Recently, we have shown that MCP-1 accounts for virtually all of the monocyte chemotactic activity produced by endothelial cells and smooth muscle cells, alone and in coculture. 16 The results of this study suggest that after the initial recruitment by cells of the vessel wall, monocytes may be involved in the amplification of their own recruitment into inflammatory lesions by inducing MCP-1. Methods Cell CultureHuman monocytes and lymphocytes were obtained by a modification of the Recalde method. 17The monocytes were suspended in Iscove's modified Dulbecco's medium containing 30% autologous serum, 1% glutamine, 1% penicillin/streptomycin/ fungizone, and 0.0022% insulin (supplemented media) and then plated at varying densities in plastic culture dishes or treated lipopolysaccharide-free Teflon pots. The cells were incubated at 37°C from 4 hours to 8 days. The media were endotoxin free 18 ' 19 and were changed every 3-4 days. Northern Blot AnalysisTotal RNA was isolated from the monocytes/macrophages by the guanidinium isothiocyanate method of Chomczynski and Sacchi. 20 The alcohol-precipitated RNA was electrophoresed on formaldehyde/1% agarose gels and transblotted to Biotrans nylon membranes (Bio-Rad, Richmond, Calif.). The blots were hybridized with a 32 P-end-labeled 35-mer oligonucleotide probe. The probe was complementary to nucleotides 257-291 of the published cDNA sequence for MCP-1. 21 The sequence of the p...

Thematic review series: The Pathogenesis of Atherosclerosis The oxidation hypothesis of atherogenesis: the role of oxidized phospholipids and HDL

“…Studying the arteries of human fetuses, they found that LDL was present and was oxidized before the entry of monocytes and that monocyte entry occurred at sites of oxidized LDL accumulation, strongly suggesting that LDL oxidation is a cause of monocyte entry and not just a by-product of monocyte metabolism (19). Berliner and colleagues (20)(21)(22)(23)(24)(25)(26) reported that mildly oxidized LDL, which was still recognized by the LDL receptor, stimulated human aortic endothelial cells to bind monocytes but not neutrophils and caused artery wall cells to produce the potent monocyte chemoattractant monocyte chemoattractant protein-1 and the differentiation factor monocyte colony stimulating factory. Subsequently, it was found that the biological activity of this minimally modified LDL (MM-LDL) was attributable to the oxidation of LDL phospholipids, which contain arachidonic acid in the sn -2 position (27)(28)(29)(30)(31)(32)(33)(34).…”

Human innate immune responses to hexamethylene diisocyanate (HDI) and HDI–albumin conjugates

“…[17][18][19][20] Monocytes possess the capacity to modulate immune responses by secreting chemokines and processing/presenting exogenous and "self" antigens. [21][22][23] Functional responses of monocytes (and other cells of the innate immune system) are also governed, in part, via germline-encoded pattern-recognition receptors, evolved to detect specific molecular motifs. 24 The present study investigates human monocyte responses to a major commercial isocyanate, hexamethylene diisocyanate (HDI), primarily used in protective spray coatings (e.g.…”

Dietary ω-3, ω-6, and ω-9 Unsaturated Fatty Acids and Growth Factor and Cytokine Gene Expression in Unstimulated and Stimulated Monocytes

“…8,17 MCP-1 is an attractor and activator of monocytes. 12 Both MCP-1 and PDGF are currently thought to be intimately involved in the pathogenesis of atherosclerosis. 8,9,18 It is currently unknown whether human gene expression for PDGF-A and PDGF-B can be reduced by other dietary unsaturated fatty acids, such as -6 or -9 fatty acids, or is reduced solely and specifically by -3 fatty acids.…”