Reduced leukocyte–endothelial cell interactions in the inflamed microcirculation of macrophage migration inhibitory factor–deficient mice

Abstract

Objective. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with established roles in a range of inflammatory conditions. However, it is not known whether MIF influences inflammation via the direct promotion of leukocyteendothelial cell interactions. Therefore, the aim of these experiments was to investigate the ability of MIF to regulate leukocyte-endothelial cell interactions in the inflamed microvasculature.Methods. Intravital microscopy was used to examine postcapillary venules in the cremaster muscle and synovium of wild-type and MIF ؊/؊ mice. Leukocyte-endothelial cell interactions (rolling, adhesion, emigration) were compared under a range of inflammatory conditions.Results. In cremasteric postcapillary venules of MIF ؊/؊ mice, lipopolysaccharide (LPS)-induced leukocyte rolling, adhesion, and emigration were significantly reduced relative to that in wild-type mice. Similar responses were observed in response to tumor necrosis factor ␣ and histamine. Examination of the synovial microvasculature following exposure to carrageenan revealed that leukocyte rolling and adhesion in synovial postcapillary venules and leukocyte entry into the joint space were also reduced significantly in MIF ؊/؊ mice. In each of these models, the level of P-selectindependent rolling was reduced in MIF ؊/؊ mice. Despite this, no difference in P-selectin expression was observed following LPS treatment. However, microvascular shear forces were elevated in MIF ؊/؊ mice, raising a possible mechanism to explain the reduced interactions in these animals.Conclusion. MIF ؊/؊ mice consistently displayed a reduction in P-selectin-dependent rolling, suggesting that MIF exerts proinflammatory effects, in part, via the promotion of P-selectin-mediated rolling. Together, these data indicate that MIF promotes interactions between leukocytes and endothelial cells, thereby enhancing the entry of leukocytes into sites of inflammation.

Macrophage Migration Inhibitory Factor Increases Leukocyte–Endothelial Interactions in Human Endothelial Cells via Promotion of Expression of Adhesion Molecules

“…These experiments revealed that deficiency of MIF in HUVECs was associated with reductions in TNFinduced expression of adhesion molecules and chemokines, with concomitant reductions in TNF-induced leukocyte-endothelial cell interactions. These data are in agreement with our earlier observation of reduced TNF-induced rolling and adhesive interactions in postcapillary venules of MIF 2/2 mice following TNF treatment (14). In the current study, MIF deficiency also reduced basal endothelial cell expression of VCAM-1, ICAM-1, IL-6, IL-8, and MCP-1, suggesting that the presence of MIF contributes to constitutive expression of these molecules.…”

“…This indicated that exogenous MIF can facilitate the proinflammatory effects of TNF and LPS on leukocyte recruitment. Given the presence of extracellular MIF in normal plasma, this finding is likely to be relevant to the observation that MIF facilitates in vivo leukocyte-endothelial cell interactions induced by TNF or LPS (13,14). However, the finding that this effect was not associated with increased HUVEC expression of E-selectin, ICAM-1, VCAM-1, or various chemokines indicated the involvement of an alternative pathway for this effect, which we found to be induction of P selectin expression.…”

“…We have observed that MIF deficiency results in decreased leukocyte-endothelial cell interactions under inflammatory conditions, as demonstrated using intravital microscopy, and that this is associated with reduced endothelial expression of VCAM-1 (13,14). The mechanisms whereby MIF facilitates endothelial adhesion molecule expression are not known.…”

Macrophage Migration Inhibitory Factor Deficiency Attenuates Macrophage Recruitment, Glomerulonephritis, and Lethality in MRL/lpr Mice

“…Abundant urine MCP-1 expression in MIF ϩ/ϩ MRL/lpr mice was associated with macrophage recruitment, both of which were significantly reduced in the absence of MIF. MIF has been shown to regulate leukocyte recruitment to the inflamed microvasculature in other tissues (44), and we have recently found that rMIF up-regulates endothelial cell MCP-1 expression and macrophage recruitment (62). It has been previously shown that the up-regulation of MCP-1 in the inflamed kidney interstitium in MRL/lpr mice is most striking in the tubular epithelial cells (26), in a similar distribution to that of MIF.…”

A key role for G-CSF–induced neutrophil production and trafficking during inflammatory arthritis

“…The synovial microcirculation was exposed for intravital microscopy as previously described. 30,31 Neutrophils were stained using PE-conjugated anti-Gr-1 mAb (2 g, intravenous injection), and 500 kDa FITC-dextran (17 g, intravenous injection; Molecular Probes) was used to delineate the microvasculature. Neutrophil rolling and adhesion were assessed in synovial postcapillary venules using a Leica SP5 multiphoton microscope (Leica-Microsystems) equipped with a 20ϫ, 1.0 NA objective and twin nondescanned detectors.…”