Cutting edge: a small molecule antagonist of LFA-1-mediated cell adhesion.

LFA-1 (CD18,CD11a) is a cell-adhesion molecule that mediates critical immunological processes. In this paper we report the discovery and characterization of (R)-5-(4-bromobenzyl)-3-(3, 5-dichlorophenyl)-1,5-dimethylimidazolidine-2,4-dione (BIRT 377), an orally bioavailable small molecule that interacts specifically with LFA-1 via noncovalent binding to the CD11a chain and prevents LFA-1 from binding to its ligand, ICAM-1. BIRT 377 inhibits lymphocyte activity both in vitro and in vivo, in functional assays that require LFA-1-mediated cell adhesion. These results demonstrate that LFA-1-mediated leukocyte adhesion can be antagonized with noncharged, low m.w. molecules and suggest that the potential therapeutic value of adhesion inhibitors can be attained with a small, orally bioavailable compound.

Alterations in circulating intercellular adhesion molecule-1 and L-selectin: further evidence for chronic inflammation in ischemic heart disease.

Atherosclerosis is increasingly thought to be a chronic inflammatory disease. Inflammation requires transmigration of leukocytes from the circulation to the tissues. Adhesion of leukocytes to endothelial calls is the initial event in an inflammatory response and is mediated by expression of several adhesion molecules. In this study we characterize the contribution of intercellular adhesion molecules (ICAM-1) and L-selectin in patients with different coronary artery disease syndromes. Serum concentrations of cICAM-1 and sL-selectin were measured by enzyme-linked immunosorbent assay in 31 patients with stable angina, 30 patients with unstable angina, 18 patients with acute myocardial infarction and 20 healthy subjects in a control group. All patients underwent coronary angiography. Mean (+/-SE) cICAM-1 levels were higher (p < 0.05) in patients with stable angina (249 +/- 6 ng/ml), unstable angina (260 +/- 16 ng/ml), or acute myocardial infarction (261 +/- 24 ng/ml) compared with those in subjects in the control group (171 +/- 11 ng/ml). In contrast, levels of sL-selectin were lower (p < 0.01) in patients with stable angina (1.2 +/- 0.1 microg/ml), unstable angina (1.1 +/- 0.6 microg/ml), or acute myocardial infarction (1.1 +/- 0.1 microg/ml) compared with those in subjects in the control group (1.8 +/- 0.1 microg/ml). No difference was found in cICAM-1 or sL-selectin levels among patients with stable angina, unstable angina, or acute myocardial infarction. No correlation was seen between cICAM-1 or sL-selectin levels and extent (or severity) of coronary artery disease or leukocyte count. L-selectin expression was observed to be depressed in patients with severe angina compared with that in members of the control group. To examine the mechanism of reduction in sL-selectin levels and L-selectin expression on leukocytes, leukocytes from the control group were stimulated in vitro. Stimulation of leukocytes resulted in a rapid downregulation of surface L-selectin expression, measured by flowcytometry, similar to the suppressed expression of L-selectin found on leukocytes from patients with coronary artery disease. In conclusion, altered cICAM-1 and sL-selectin levels in patients with coronary artery disease reflect the presence of a chronic inflammatory process. This inflammatory process results in downregulation of leukocyte expression of L-selectin and thus lower circulating sL-selectin levels.

Relationship of increased levels of circulating intercellular adhesion molecule 1 after heart transplantation to rejection: human leukocyte antigen mismatch and survival.

Noninvasive methods to assess immune activation would be helpful in optimizing therapy after heart transplantation to reduce rejection (acute and chronic) and complications caused by excessive immunosuppressive therapy. Intercellular adhesion molecule 1 has been shown to play an important role in T-cell activation and allograft rejection. A soluble form of intercellular adhesion molecule 1 has been discovered to be circulating in plasma. To test the hypothesis that increased levels of circulating intercellular adhesion molecule 1 may have prognostic value as a marker of immune activation, we examined whether levels of circulating intercellular adhesion molecule 1 during the early postoperative period correlated with endomyocardial biopsy scores, soluble interleukin-2 receptor levels, human leukocyte antigen mismatch, and survival. For the first 3 weeks after surgery, serum was obtained once weekly on the same day as endomyocardial biopsy samples from 52 patients who survived more than 30 days after heart transplantation. A sandwich enzyme-linked immunosorbent assay was used to measure circulating intercellular adhesion molecule 1 and soluble interleukin-2 receptor. Increased circulating intercellular adhesion molecule 1 levels did not correlate with endomyocardial biopsy scores but were associated with greater mismatch at the human leukocyte antigen-B and -DR loci (p = 0.02). A significant correlation was found (p = 0.002) between circulating intercellular adhesion molecule 1 levels and soluble interleukin-2 receptor, albeit with a low r value of 0.27. Survival was reduced in patients with high levels of circulating intercellular adhesion molecule 1 (p = 0.006) or soluble interleukin-2 receptor (p = 0.001) with the greatest reduction in survival when both were elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased levels of circulating intercellular adhesion molecule 1 in the sera of patients with rheumatoid arthritis.

OBJECTIVE: We sought to assess whether circulating levels of intercellular adhesion molecule 1 (ICAM-1) in patients with rheumatoid arthritis (RA) are elevated and correlate with clinical measures of disease activity and whether this ICAM-1 originates from the synovium. METHODS: Circulating ICAM-1 (cICAM-1) levels were determined by sandwich enzyme-linked immunosorbent assay of serum from 61 RA, 18 osteoarthritis (OA), and 11 inflammatory arthritis (IA) patients. In addition, paired serum and synovial fluid samples were collected from 17 RA, 9 OA, and 4 IA patients. The stability of cICAM-1 was assessed by overnight incubation at 37 degrees C. Finally, the potential degradative effects of synovial fluid proteases were assessed by incubation of recombinant soluble ICAM-1 with patient synovial fluid. RESULTS: RA sera contained significantly greater (P < 0.001) levels of cICAM-1 compared with RA synovial fluid and compared with sera or synovial fluid from the OA and IA patients. Circulating ICAM-1 levels were unaffected by overnight incubation at 37 degrees C and were unaffected by exposure to RA, OA, or IA synovial fluid. Serum levels of cICAM-1 demonstrated a weak, but significant (P < 0.05) correlation with the joint score and erythrocyte sedimentation rate in 25 RA patients treated with nonsteroidal antiinflammatory drugs. CONCLUSION: The greatest elevations of cICAM-1 were seen in RA patient sera. In both RA and OA, synovial fluid cICAM-1 levels were consistently lower than serum levels, suggesting that cICAM-1 did not originate in the synovium. Because the production of cICAM-1 can be increased by cytokines (e.g., interleukin-1, tumor necrosis factor alpha), elevated levels of circulating ICAM-1 in RA may be reflective of systemic exposure to elevated cytokine levels.

Elevated levels of circulating adhesion molecules in IDDM patients and in subjects at risk for IDDM.

Serum levels of recently discovered circulating forms of adhesion molecules, ICAM-1 and L-selectin, were found to be elevated in IDDM patients and in subjects at risk for developing IDDM compared with 100 normal, nondiabetic blood donors. Both adhesion molecules were determined by sandwich ELISA. Serum concentrations of either clCAM-1 or cL-selectin were > 2SD of normal mean in 10 of 14 recent-onset IDDM patients (P < 0.05). Serum levels of clCAM-1 and cL-selectin did not correlate. In first-degree relatives, elevated adhesion molecule levels were observed in the 6 ICA+ individuals and in the ICA- individuals all (n = 14) with a genetic risk of IDDM (sharing HLA-DR3 and/or-DR4 with the diabetic relative) but not in the HLA-DR3- and/or -DR4- relatives (n = 13). We conclude that elevated clCAM-1 and cL-selectin levels occur independently of ICA status and probably reflect ongoing immune processes in recent-onset IDDM patients and first-degree relatives at risk for IDDM.

A form of circulating ICAM-1 in human serum.

A circulating form of the usually membrane-bound intercellular adhesion molecule-1 (ICAM-1) was identified and characterized in normal human serum, and in sera from patients with leukocyte adhesion deficiency (LAD). The molecule, designated circulating ICAM-1 (cICAM-1) was detected and quantitated by sandwich ELISA. Levels of cICAM-1 in sera from normal individuals ranged from 100 to 200 ng/ml. Sera from LAD patients had elevated cICAM-1 levels ranging from 200 to 700 ng/ml. The elevated levels of cICAM-1 in LAD sera may be due to an inability to adsorb cICAM-1 to cell-bound LFA-1 or may be an indirect result of the pathology accompanying the syndrome. cICAM-1 bound to mAb specific for four distinct ICAM-1 epitopes localized in domains D1, D2, D4, and D5, and displayed similar molecular size properties as recombinant soluble ICAM-1 on FPLC size-exclusion chromatography. When immobilized via a domain D5-specific mAb, cICAM-1 mediated function (LFA-1)-dependent lymphocyte adhesion equivalent to sICAM-1. These data indicate that cICAM-1 contains most, if not all, of the five extracellular domains of membrane ICAM-1, as well as the ability to bind specifically to LFA-1. The cellular source of cICAM-1 appeared to be from mononuclear cells; only lymphoid cell lines or primary PBMC cultures had detectable levels of cICAM-1 in cell culture supernatants. Because cICAM-1 retains the ability to bind specifically to LFA-1, it may act to regulate cell adhesion by promoting de-adhesion. Alternatively, cICAM-1 may be the indirect consequence of inflammation or tissue damage. As such, the detection of cICAM-1 could be useful as a marker of inflammatory disease.