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Leukocytes play a critical role in both the initial steps of atherogenesis and the late events of plaque instability and thrombosis. Leukocyte-endothelial cell adhesion molecules (CAMs) modulate the interaction between circulating leukocytes and the vessel wall. Levels of soluble CAMs are increased in patients with dyslipidemia or other risk factors, and levels can be reduced by lipid-modifying therapy. Novel markers of inflammation and atherosclerosis may be useful to identify high-risk individuals and to assess the efficacy of antiatherosclerotic therapy.

Background: Increased expression of cell adhesion molecules (CAMs) on the vascular endothelium has been postulated to play an important role in atherogenesis. Both in vitro and in vivo studies have suggested that dyslipidemia may increase expression of CAMs., Methods and Results: To determine whether dyslipidemia is associated with increased expression of CAMs, we examined the levels of soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAM-1), and soluble E-selectin (sE-selectin) in individuals with either hypercholesterolemia or hypertriglyceridemia and in control subjects matched for age and sex. Patients with hypertriglyceridemia had significantly higher levels of sVCAM-1 (739 +/- 69 ng/mL) compared with patients with hypercholesterolemia (552 +/- 63 ng/mL) and control subjects (480 +/- 56 ng/mL). Levels of sICAM-1 were significantly increased in both the hypercholesterolemic and hypertriglyceridemic groups (298 +/- 29 and 342 +/- 31 ng/mL, respectively) compared with the control group (198 +/- 14 ng/mL). Levels of sE-selectin were significantly increased in hypercholesterolemic patients (74 +/- 9 ng/mL) compared with control subjects (48 +/- 5 ng/mL). Ten hypercholesterolemic patients were treated aggressively with atorvastatin alone or a combination of colestipol and either atorvastatin or simvastatin for a mean of 42 weeks and had an average LDL cholesterol reduction of 51%. Comparison of soluble CAMs before and after treatment showed a significant reduction only in sE-selectin (77 +/- 11 versus 56 +/- 6 ng/mL, P < or = .03) but not for sVCAM-1 or sICAM-1., Conclusions: Although severe hyperlipidemia is associated with increased levels of soluble CAMs, aggressive lipid-lowering treatment had only limited effects on the levels. Increased levels of soluble CAMs in patients with hyperlipidemia may be a marker for atherosclerosis.

Vascular cell adhesion molecule-1 (VCAM-1) is a member of the Ig superfamily that shows increased expression in a number of pathologic conditions. The role of VCAM-1 in human disease remains undefined and murine models are being extensively studied to help define the importance of VCAM-1 in inflammatory disorders. We have cloned and characterized the murine Vcam1 gene including 3 kb of 5'-flanking sequences and mapped the gene to chromosome 3 near Amy1. cDNA clones isolated from a stimulated hepatic library were found to encode a truncated form of VCAM-1 (T-VCAM-1) which contains Ig domains 1 through 3 and has a unique alternative carboxyl terminus. This form arises by alternative splicing. High level expression of T-VCAM-1 in transfected L cells was sufficient to support adhesion of lymphocytes, and this adhesion was blocked by Abs to VCAM-1. Treatment of transfected COS cells with phospholipase C led to reduced levels of T-VCAM-1 on the cell surface consistent with glycosylphosphatidylinositol linkage. Northern blot analysis showed that mRNA for T-VCAM-1 is inducible in multiple tissues after stimulation with endotoxin. Both forms of VCAM-1 were expressed in cultured endothelial, fibroblast, and aortic smooth muscle cells, whereas neither form was observed in monocyte- and lymphocyte-derived lines. Differential regulation of both forms of VCAM-1 was observed in the three different cell types that are present in the vessel wall. Thus, expression of VCAM-1 is restricted and controlled at the level of transcription and by alternative splicing.

Background: Acute inflammation may play a role in injury during reperfusion following myocardial ischemia. Studies in vitro suggest that intracellular adhesion molecule-1 (ICAM-1) mediates neutrophil adherence to cardiac myocytes and neutrophil-mediated injury. We have shown cytokine activity in postischemic cardiac lymph sufficient to maximally express ICAM-1 on myocytes and that ICAM-1 mRNA is found in the previously ischemic myocardium early in reperfusion., Methods and Results: In the present study, we used in situ hybridization techniques to detect ICAM-1 mRNA and examine the cells of origin, relation to cell injury, and relation to inflammatory infiltration after 1 hour of ischemia and varying times of reperfusion. By 1 hour of reperfusion, ICAM-1 mRNA was detected in much of the ischemic myocardium, except in areas of contraction band necrosis. At 2 and 3 hours, a clear demarcation of necrotic areas surrounding ischemic areas of viable myocardium with ICAM-1 mRNA staining was present, and ICAM-1 mRNA staining increased with time. Nonischemic areas had no visible ICAM-1 mRNA staining in the first 3 hours. By 24 hours of reperfusion, ICAM-1 mRNA was present in both control and ischemic segments (excluding the necrotic areas) compatible with a generalized circulation of cytokines persistent at 24 hours. In the absence of reperfusion, ICAM-1 mRNA staining was not seen in the first 3 hours and was markedly reduced at 24 hours. The interface of viable and necrotic cells also contained the most extensive inflammatory infiltration., Conclusions: Evidence is presented that induction of ICAM-1 mRNA has highly specific localization to ischemic but viable myocardium. Induction of ICAM-1 mRNA transcription in early reperfusion may render the viable "border zone" susceptible to neutrophil-induced injury.

Lung injury caused by breathing enriched oxygen continues to be a major problem in clinical medicine. Experimentally, hyperoxic lung injury is characterized by pulmonary edema and associated neutrophil accumulation. Although extensively investigated, the mechanisms for neutrophil accumulation and the role of this accumulation in hyperoxic lung injury remain controversial. Intercellular adhesion molecule-1 (ICAM-1) is an adhesion molecule that when increased on endothelium by inflammatory cytokines leads to increased adhesion of neutrophils to the inflamed endothelium and transendothelial migration. The purpose of this study was to examine the role of inflammation in hyperoxia-induced lung injury by investigating ICAM-1 expression in the lungs of mice exposed to > 95% oxygen continuously. Lung tissue from mice exposed to > 95% oxygen was analyzed for ICAM-1 mRNA by slot blot analysis and for ICAM-1 protein expression. We also examined lungs from mice exposed to hyperoxia for up to 96 h by light microscopy to correlate pulmonary inflammation with ICAM-1 expression. We found that mRNA for ICAM-1 increased 56% over baseline after 48 h of exposure to hyperoxia, that ICAM-1 protein increased by more than 5-fold over baseline after 96 h of exposure to hyperoxia, and that lung inflammation and injury were not evident until 96 h of exposure. Our data demonstrate that exposure to hyperoxia causes an increase in ICAM-1 gene transcription and/or mRNA stability in mouse lungs, and that this increase is followed by an increase in ICAM-1 protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene targeting was used to produce mice deficient in intercellular adhesion molecule 1 (ICAM-1) or CD54, an immunoglobulin-like cell adhesion molecule that binds beta 2 integrins. Homozygous deficient animals develop normally, are fertile, and have a moderate granulocytosis. The nature of the mutation, RNA analysis, and immunostaining are consistent with complete loss of surface expression of ICAM-1. Deficient mice exhibit prominent abnormalities of inflammatory responses including impaired neutrophil emigration in response to chemical peritonitis and decreased contact hypersensitivity to 2,4-dinitrofluorobenzene. Mutant cells provided negligible stimulation in the mixed lymphocyte reaction, although they proliferated normally as responder cells. These mutant animals will be extremely valuable for examining the role of ICAM-1 and its counterreceptors in inflammatory disease processes and atherosclerosis.

Acute inflammation has been suggested as a potential mechanism for some of the injury associated with reperfusion of the ischemic myocardium. This hypothesis implies that viable myocardial cells adjacent to the lethally injured cells are vulnerable to injury induced by the neutrophil influx observed to attend reperfusion. In our previous work, we demonstrated that the presence of ICAM-1 on the surface of cardiac myocytes is required for neutrophils to directly damage them; blocking monoclonal antibodies to either ICAM-1 on cardiac myocytes or Mac-1 on activated neutrophils completely precluded neutrophil-induced myocyte injury. We also demonstrated that postischemic cardiac lymph (cardiac extracellular fluid) contained leukotactic factors (primarily C5a) and cytokines present in concentrations sufficient to maximally induce Mac-1 on the surface of neutrophils and ICAM-1 on the surface of isolated dog cardiac myocytes. The present study sought to further these observations by examining the site of potential ICAM-1 induction as a function of time of reperfusion, degree of ischemia, and viability of myocardial cells. Our evidence suggests that ICAM-1 mRNA is induced very early after reperfusion only in the previously ischemic myocardium and is not seen in the nonischemic myocardium during the early hours of reperfusion. Moreover, ICAM-1 mRNA induction is seen most intensely in the ischemic area directly bordering the necrotic area (which, after 1-hr reperfusion, does not contain any ICAM-1 mRNA) and immediately abutting the site of maximal influx of neutrophils. Thus, the induction of ICAM-1 and the influx of neutrophils (presumably activated by the chemotactic factors that guided their migration) exists on the border between viable and necrotic cells. This provides the first direct molecular evidence for a jeopardized border zone on the edge of myocardial infarction during reperfusion. As previously demonstrated, this reaction is wholly dependent upon tissue injury of the ischemic myocardium and therefore represents an example of a mechanism of injury extension induced as a reaction to a primary injury. The degree of specificity of this reaction demonstrated by the subendocardial sparing directly adjacent to ischemic cells suggests finely modulated mechanisms by which this process is controlled.

Intercellular adhesion molecule-1 (ICAM-1, CD54) is a cell adhesion molecule that interacts with the leukocyte beta 2 integrins, LFA-1 and Mac-1. Murine inflammatory models are being utilized increasingly to define the role that ICAM-1 induction plays in the initiation of inflammation. We have isolated murine genomic clones that contain the Icam-1 gene including over 2 kb of 5' flanking sequence. The gene for murine Icam-1 spans over 13 kb and is composed of seven exons and six introns. Each of the extracellular immunoglobulin-like domains of ICAM-1 is encoded by a single exon that ends with the first base of the next codon. Examination of ICAM-1 expression in vivo shows that mRNA levels of ICAM-1 are low in all organs except for the lung but increase markedly in multiple organs at 3 h after administration of endotoxin. The 5' flanking region of the murine gene contains a putative TATA box and potential SP-1, AP-1, and AP-3 sites in positions nearly identical to those in the human gene.

Intercellular adhesion molecule-1 (ICAM-1) is an integral membrane protein, a member of the immunoglobulin superfamily, and a ligand for LFA-1, a beta 2 leukocyte integrin. ICAM-1 has a tissue distribution similar to that of the major histocompatibility complex class II antigens and is likely to play a role in inflammatory responses. We have mapped this gene to proximal mouse chromosome 9 by using mouse-hamster somatic cell hybrids and an interspecies backcross. Since human ICAM-1 maps to chromosome 19, it joins the LDL receptor to establish a new conserved syntenic segment between human chromosome 19 and proximal mouse chromosome 9. Murine Icam-1 maps between Cbl-2 and the centromere in the same region as one of the susceptibility genes for insulin-dependent diabetes mellitus (Idd-2) that is postulated to play a role in immune function and inflammation leading to insulitis. The mapping of Icam-1 to the region known to contain the Idd-2 gene raises the question of whether the phenotypic differences attributed to the Idd-2 locus might be due to genetic variation in Icam-1.