Role of tumor necrosis factor-α in the extraintestinal thrombosis associated with colonic inflammation.

BACKGROUND: Inflammatory bowel diseases (IBDs) are associated with a hypercoagulable state and an increased risk of thromboembolism, with accelerated thrombus formation occurring both within the inflamed bowel and in distant tissues. While the IBD-associated prothrombogenic state has been linked to the inflammatory response, the mediators that link inflammation and thrombosis remain poorly defined. The objective of this study was to assess the role of tumor necrosis factor alpha (TNF-α) in the enhanced extraintestinal microvascular thrombosis that accompanies colonic inflammation. METHODS: TNF-α concentration was measured in plasma, colon, and skeletal muscle of control mice and in mice with dextran sodium sulfate (DSS)-induced colitis. A light/dye injury method was used to induce microvascular thrombosis in cremaster microvessels. The effects of exogenous TNF-α on thrombus formation were determined in control mice. DSS-enhanced thrombus formation was evaluated in wildtype (WT) mice treated with an anti-TNF-α antibody (±an anti-IL-1ß antibody) and in TNF-α receptor-deficient (TNFr(-/-) ) mice. RESULTS: DSS colitis enhanced thrombus formation in cremaster arterioles. A similar response was produced by TNF-α administration in control mice. TNF-α concentration was elevated in plasma, colon, and skeletal muscle. Immunoblockade of TNF-α or genetic deficiency of the TNF-α receptor blunted the thrombotic response of arterioles to DSS colitis. Additional protection was noted in mice receiving antibodies to both TNF-α and IL-1ß. CONCLUSIONS: Our findings implicate TNF-α in the enhanced microvascular thrombosis that occurs in extraintestinal tissue during colonic inflammation, and suggests that the combined actions of TNF-α and IL-1ß accounts for most of the colitis-enhanced thrombotic response.

Selectin-mediated recruitment of bone marrow stromal cells in the postischemic cerebral microvasculature.

BACKGROUND AND PURPOSE: The therapeutic potential of bone marrow stromal cells (BMSCs) has been demonstrated in different models of stroke. Although it is well established that BMSCs selectively migrate to the site of brain injury, the mechanisms underlying this process are poorly understood. This study addresses the hypothesis that selectins mediate the recruitment of BMSCs into the postischemic cerebral microvasculature. METHODS: Focal ischemic stroke was induced by middle cerebral artery occlusion and reperfusion. Cell recruitment was monitored using either fluorescent- or radiolabeled BMSCs detected by intravital microscopy or tissue radioactivity. Mice were treated with either a blocking antibody against P- or E-selectin or with the nonselective selectin antagonist, fucoidin. The role of CD44 in cell recruitment was evaluated using BMSCs from CD44 knockout mice. RESULTS: Middle cerebral artery occlusion and reperfusion was associated with a significantly increased adhesion of BMSCs in cerebral venules compared with sham mice. Immunoneutralization of either E- or P-selectin blocked the middle cerebral artery occlusion and reperfusion-induced recruitment of adherent BMSCs. An attenuated recruitment response in the postischemic hemisphere was also noted after fucoidin treatment or administration of CD44-deficient BMSCs. CONCLUSIONS: Cerebral vascular endothelium assume a proadhesive phenotype after ischemic stroke that favors the recruitment of BMSCs, which use both P- and E-selectin to home into the infarct site. CD44 may serve as the critical ligand for selectin-mediated BMSC recruitment.

Role of coagulation factors in cerebral venous sinus and cerebral microvascular thrombosis.

OBJECTIVE: The objective of this study was to define the relative contributions of three major pro- and anti-coagulation pathways (heparin-antithrombin, protein C, and tissue factor (TF)) in the thrombogenic responses that occur in large and small vessels of the brain. METHODS: Cerebral venous sinus thrombosis was induced by topical application of FeCl3 on the superior sagittal sinus, while photoactivation of fluorescein was used to induce thrombus formation in cerebral microvessels. Heparin, activated protein C (APC), and antibodies to either APC or TF were used to assess thrombogenesis in wild-type mice. Mutant mice that overexpress the endothelial protein C receptor (EPCR-tg) or with TF deficiency in Tie2-expressing endothelial cells (LTFE) were also used. RESULTS: Thrombus formation in the superior sagittal sinus of wild-type mice was attenuated by heparin and in EPCR-tg mice, while treatment with the APC antibodies enhanced thrombogenesis. Arteriolar thrombosis was largely unresponsive to the interventions studied. However, in cerebral venules, thrombosis was inhibited by heparin and in EPCR-tg mice. TF antibody treatment also inhibited venular thrombosis, with a similar attenuation noted in LTFE mice. CONCLUSION: Thrombin promotes while the APC pathway blunts thrombus formation in an experimental model of cerebral venous sinus thrombosis. TF involvement is more evident in cerebral microvascular thrombogenesis, with endothelial cell-associated TF mediating this response in venules, but not arterioles.

Role of the protein C pathway in the extraintestinal thrombosis associated with murine colitis.

BACKGROUND & AIMS: Chronic inflammatory bowel diseases (IBD) are associated with an increased risk for thromboembolism. Although thrombosis is known to contribute to the morbidity and mortality of patients with IBD, the underlying mechanisms that contribute to the genesis of a hypercoagulable state during intestinal inflammation remain poorly defined. The objective of this study was to determine whether the protein C pathway contributes to the enhanced extraintestinal thrombosis that is associated with dextran sodium sulfate (DSS)-induced colitis in mice. METHODS: Microvascular thrombosis was induced in cremaster muscle microvessels of normal and colitic mice using a light/dye injury model. DSS colitis enhanced thrombus formation in cremaster arterioles of wild-type mice. RESULTS: The DSS-induced thrombosis response was greatly attenuated in transgenic mice over expressing the endothelial protein C receptor. Activated protein C (APC), administered to colitic WT mice immediately prior to photoactivation, also afforded protection against thrombosis, and an anti-APC antibody enhanced thrombus formation. CONCLUSIONS: These findings indicate that elevated APC levels, derived from either endogenous or exogenous sources, confer protection against the extraintestinal thrombosis that accompanies colonic inflammation.