Thrombin and leukocyte recruitment in endotoxemia

Abstract

Because thrombin has been implicated in sepsis, it has been proposed that antithrombin III (AT III) is beneficial due to its anticoagulatory and antiadhesive effects. Using intravital microscopy, we visualized leukocyte-endothelium interactions in postcapillary venules of the feline mesentery exposed to lipopolysaccharide (LPS). At a concentration of AT III that blocks leukocyte adhesion in postischemic mesentery, we found no role for thrombin in LPS-induced rolling, adhesion and emigration, or microvascular dysfunction. Furthermore, AT III did not attenuate leukocyte-endothelial interactions after tumor necrosis factor-alpha superfusion of the mesentery. In contrast, fucoidan, a selectin inhibitor, prevented almost all LPS-induced rolling and reduced adhesion, emigration, and microvascular dysfunction. In a model of endotoxemia, leukocyte recruitment into mesentery or lungs was unaffected by AT III. Finally, in a human cell system that mimics the flow conditions in vivo, human neutrophils rolled, adhered, and emigrated similar to the feline postcapillary microvessels, and AT III had no effect on leukocyte recruitment induced by LPS. If AT III has beneficial effects in endotoxemia, it is not due to a direct effect upon leukocyte rolling, adhesion, or emigration in postcapillary venules in vivo.

In Vivo Impairment of Neutrophil Recruitment during Lentivirus Infection

“…The microvasculature was videotaped for the last 10 min of every hour. In previous work we established that the LPS-induced neutrophil rolling was indeed endothelial selectin dependent, and the adhesion was dependent upon neutrophil integrins (19,20).…”

Plasma from stored packed red blood cells and MHC class I antibodies causes acute lung injury in a 2-event in vivo rat model

“…[76][77][78] The presented model is superior to other in vivo modeling because it better approximates clinical TRALI: (1) the first event, LPS, approximates acute active infection, a proposed risk factor for TRALI, and causes proinflammatory activation of the pulmonary capillary bed without causing death or other organ injury. 13,19,[79][80][81][82][83] LPS has been used in many animal models and even injected into human volunteers and mimics infection. 13,19,[79][80][81][82][83][84][85] (2) ALI was induced by 2 separate second events, like clinical TRALI, and the second events demonstrated a concentration:response relationship in ALI using multiple parameters, unlike other in vivo models.…”

An Animal Model of Sepsis in Appendicitis: Assessment of the Microcirculation

“…In addition, intravital microscopy has also been used to test novel prophylactic and therapeutic approaches that aim to prevent or attenuate manifestations of sepsis-associated microvascular disorders and cellular dysfunctions. In the mesentery, microcirculatory observations have focused on capillary obstruction, capillary or arteriolar density, microvessel reactivity and leukocyte-endothelial interactions in post-capillary venules (Harris, 2006;Kim & Harris, 2006;Nakagawa et al, 2006Nakagawa et al, , 2007Schimidt et al, 1997;Smalley et al, 2000;Walther et al, 2004;Woodman et al, 2000). A representative photomicrograph of rat mesenteric microcirculation is shown in Figure 3.…”

“…Microcirculatory dysfunctions, as seen in humans (De Backer & Dubois, 2001;De Backer et al, 2002;Groner et al, 1999;Trzeciak et al, 2007), have been shown to occur in most experimental models of sepsis (Baveja et al, 2002;Kamoun et al, 2005;Kim & Harris, 2006;Kubo et al, 1999;Nakagawa et al, 2006Nakagawa et al, , 2007Nakajima et al, 2001;Schimidt et al, 1997;Smalley et al, 2000;Waisman et al, 2006;Walther et al, 2004;Woodman et al, 2000). Endotoxin infusion is a widely used experimental model (Kim & Harris, 2006;Schimidt et al, 1997;Smalley et al, 2000;Nakajima et al, 2001).…”

“…Endotoxin infusion is a widely used experimental model (Kim & Harris, 2006;Schimidt et al, 1997;Smalley et al, 2000;Nakajima et al, 2001). Increased leukocyte-endothelial interactions and protein leakage in mesenteric microvessels have been shown to occur after acute endotoxemia in rats (Schimidt et al, 1997;Woodman et al, 2000) and cats (Walther et al, 2004). However, there are two major concerns regarding this experimental model: 1) clinical sepsis typically evolves over many days, in contrast to studies on the early effects (1 to 6 hours) of endotoxin administration, and 2) rats are generally more resistant to the effects of endotoxin.…”