Infections in diabetes mellitus patients are more common and severe than in the general population. The susceptibility to infections in these patients has been associated with neutrophil dysfunction and more recently to an impaired leukocyte-endothelial interaction. Adhesion of leukocytes is an early and determinant event for an effective inflammatory or immune response. Leukocyte-endothelial interaction is enhanced by signals from blood borne activators, i.e. cytokines. Hyperglycemia is one of the most important risk factors leading to chronic complications in diabetes mellitus. Although suggested, the contribution of hyperglycemia to an impaired leukocyte-endothelial interaction in diabetic patients, has not been conclusively established. Since alterations in phosphoinositide metabolism is one of the proposed molecular mechanisms through which elevated glucose exerts its pathologic effect it seems relevant to explore this transduction process more closely. This project aims to study the effect of elevated glucose levels on the cytokine-induced signaling that permits the endothelial-leukocyte interaction necessary for the inflammatory response. A microvascular derived cell culture (i.e. bovine retina) will be used as the experimental model. Cytokine-induced signaling in endothelial cells will be followed through the determination of the generation of diacylglycerol in 3H-arachidonic acid labeled cultured cells; determination of production of inositol phosphates from 3H- myoinositol labeled cells and intracellular Ca2+ mobilization in FURA-AM loaded cells. Signaling will be correlated with endothelial-leukocyte interaction detected through the expression of cell adhesion molecules and leukocyte adherence tests. This study will expand our understanding of the biochemical mechanisms through which hyperglycemia alters the physiological response of target tissues such as the vascular endothelium, in particular its contribution to the increased susceptibility of diabetic patients to infections. The results obtained may eventually lead to therapeutic measures intended to prevent the appearance of chronic complications in diabetes mellitus patients.
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