Jean-Luc Wautier

EACH STEP DURING TRANSENDOTHELIAL MIGRATION OF FLOWING NEUTROPHILS IS REGULATED BY THE STIMULATORY CONCENTRATION OF TUMOUR NECROSIS FACTOR-ALPHA

Migration of circulating neutrophils occurs in several steps: capture and rolling adhesion are followed by activation of beta 2-integrins and immobilisation, and then neutrophils move over and through the endothelium. However, it is not clear how the underlying mechanisms and completion of each step depend on the concentration of stimulatory cytokines such as tumour necrosis factor-alpha (TNF). We therefore perfused neutrophils over human umbilical vein endothelial cells (HUVEC) which had been cultured with varying concentration of TNF (1-1000 U/ml) for 4 h, and recorded adhesion and migration by videomicroscopy. The number of adherent neutrophils increased with increasing TNF up to 5 U/ml, but changed little at higher concentrations. Interestingly, rolling adhesion at first predominated, but an increasing proportion of adherent cells became immobilised and migrated through the HUVEC monolayer over the complete TNF range. Immobilisation was inhibited by treating neutrophils with antibody against CD18, so that the major change in adhesive behaviour at higher levels of TNF occurred because the surface of the HUVEC presented agent(s) able to activate neutrophil beta 2-integrins. It was also evident that the selectins initiating capture of flowing neutrophils varied with concentration of TNF. At 100 U/ml TNF, both E-selectin and P-selectin supported capture and rolling adhesion, and antibody blockade of both receptors was required to inhibit adhesion. At lower dose (10 U/ml TNF), stable adhesion was blocked by antibody against E-selectin, although short-lived attachments could still be seen which were inhibited by antibody against P-selectin. Expression of sclectins increased with increasing concentration of TNF, judging from surface ELISA and reduction in the velocity of rolling adherent cells. Thus the efficiency of capture, the selectins mediating capture and the proportion of captured cells immobilised and migrating all depend on the concentration of TNF to which endothelial cells are exposed. These results suggest a model in which highly localised and efficient migration of neutrophils is achieved if a concentration gradient of TNF exists around an inflammatory locus.

Tumour necrosis factor-α, interleukin-1β and interleukin-6 in patients with renal cell carcinoma

Abstract Patients with renal cell carcinoma (RCC) can exhibit fever, weight loss and increases in acute phase proteins. Interleukin (IL)-1, tumour necrosis factor (TNF) and IL-6 are considered major mediators of local and systemic inflammation. We measured plasma IL-1β, TNF-α (immunoradiometric assay) and IL-6 (ELISA) in 78 consecutive patients with untreated RCC and in 56 normal subjects. IL-6 plasma levels were higher in patients with RCC (mean 24.2 pg/ml, 11.1–37.3, 95% confidence interval) than in normal subjects (11.6 pg/ml, 10.1–13.1, n = 39, P 40 pg/ml) had a positive predictive value of 91.0% for lymph node and/or metastatic spread of RCC. IL-6 was statistically correlated with C-reactive protein (nephelometric assay) blood values (r′ = 0.67, n = 78, P

Cytokines and thrombosis.

Cytokines are pleiotropic mediators of inflammation and immunity. Leukocytes and vascular cells are both sources of cytokines and targets for them. Several cytokines affect key functions of vascular wall cells. Several clinical acute or chronic inflammatory situations associate modifications of the cytokine network and a pro-thrombotic state. Many experimental data support the hypothesis that endothelial cells have an active role in these situations. Endothelial cells activated by cytokines such as tumor necrosis factor and interleukin-1 have decreased antithrombotic or prothrombotic properties and express leukocyte adhesion molecules to a greater extent. Cytokines, chemokines, and colony stimulating factors modulate the recruitment and activation of leukocytes. Activated platelets aggregate and bind to endothelial cells and to immobilized leukocytes, thus causing vascular occlusion accompanied by coagulation and leading to thrombosis. Cytokine activation may be limited by natural inhibitors or by therapeutic agents such as monoclonal antibodies, recombinant proteins, and drugs that alter cytokine synthesis, which may be of benefit in infection, inflammation, and possibly atherosclerosis.

Colchicine disposition in human leukocytes after single and multiple oral administration

Inasmuch as leukocytes were reported to be an active pharmacologic compartment, colchicine disposition was determined in plasma, granulocytes, and mononuclear cells in healthy volunteers after 1 mg oral single and multiple doses. After the single dose, maximal colchicine concentration was observed at 1 hour in plasma and 47 hours later in leukocytes. This delay was confirmed by the slow accumulation of colchicine by lymphocytes in culture. In the multiple‐dose study, mean granulocyte colchicine concentration (20 to 53 ng/109 cells) were twofold higher than in mononuclear cells (9 to 24 ng/109 cells). Mean predicted colchicine multiple‐dose granulocyte and mononuclear cell concentrations were 2.5‐fold and ninefold higher, respectively, than those measured. After the last dose, colchicine decreased, with half‐life values between 41 and 46 hours for leukocytes and 49 hours for plasma. This study validates leukocytes as a microcompartment whose kinetics correlates with colchicine biologic effects.

Prolonged E-selectin induction by monocytes potentiates the adhesion of flowing neutrophils to cultured endothelial cells

We investigated the hypothesis that the infiltration of monocytes into inflamed tissue or damaged vessels would induce a secondary accumulation of neutrophils. Confluent human umbilical vein endothelial cells (HUVEC) and blood monocytes (0.5 or 0.05 monocytes/endothelial cell) were co‐incubated for 4 or 24 h. The adhesion of neutrophils flowing over HUVEC was then analysed by video microscopy. Co‐incubation caused up to a 40‐fold increase in neutrophil adhesion, dependent upon monocyte/HUVEC ratio and duration of incubation. At the lower monocyte/HUVEC ratio, rolling adhesion alone was induced after 4 h co‐incubation; however, the full repertoire of rolling, immobilization and migration of neutrophils was observed at all other combinations of co‐culture ratio and exposure time. After maximal stimulation by monocytes, antibody blockade of the neutrophil integrin CD18 inhibited neutrophil arrest and migration and revealed underlying rolling adhesion. Rolling was supported by endothelial E‐selectin as demonstrated by the almost total abolition of adhesion by a blocking antibody. In a direct comparison, monocytes, tumour necrosis factor α (TNF‐α) and interleukin‐1β (IL‐1β) were assessed for their ability to induce endothelial expression of E‐selectin. E selectin was significantly increased by all agents at 4 h, but monocytes alone were able to maintain high levels of E‐selectin expression for 24 h. We conclude that monocytes can induce prolonged neutrophil adhesion and migration by activating endothelial cells and causing expression of E‐selectin.