Characthrization of cytokine induced microvascular leaks in the rat mesenteric window

Previous work by other investigators have shown changes in the morphology, cell junction organisation and barrier function of cultured endothelial cells (ECs) in response to inflammatory mediators. Interactions with other components of the vasculature (e.g. pericytes, smooth muscle cells), however, cannot be taken into account in those studies. Here, we examine the in vivo effects of Tumor Necrosis Factor alpha (TNF-α) and gamma Interferon (_γIFN) treatment on the endothelial barrier function of microvascular networks. These cytokines have been documented to play a role in many pathological settings involving the increase in macromolecule extravasation and cellular trafficking (e.g. septic shock, reperfusion injury and transplant rejection). The rat isolated mesenteric window is a well characterized system for examining the response of microvascular beds to edemagenic agents (Thurston G., et al. (1995) Am J. Physiol. 268(1 Pt 2), 316). In this preparation, we have documented changes in permeability and spatial reorganisation of the actin cytoskeleton. In contrast to comparable in vitro studies in which increased macromolecule flux across EC monolayers was measured >4 hours after cytokine treatment, this study demonstrates significantly increased discrete FITC-albumin leakages at 10 minutes. At the 30 minute time point, FITC albumin staining diffuses as the leaks worsen. The numbers of leaks at 5 and 10 minute time points are comparable to those seen at the peak of histamine induced leakage (3 minutes). Thus, cytokines can elicit an acute inflammatory response distinct from that generated in the chronic inflammatory response reflected in in vitro studies.