Endothelial cells interact with blood components and the abluminal tissues, thus playing an active role in many aspects of vascular function. Numerous physiologic and pathophysiologic stimuli are often mediated by nutrients that can contribute to the overall functions of endothelial cells in the regulation of vascular tone, coagulation, cellular growth, immune and inflammatory responses. Therefore, nutrient-mediated functional changes of the endothelium and the underlying tissues may be significantly involved in disease processes such as atherosclerosis. There is evidence that individual nutrients or nutrient derivatives may either provoke or prevent metabolic and physiologic perturbations of the vascular endothelium. Diets high in fat and/or calories are considered a risk factor for the development of atherosclerosis. Our research has shown that certain diet-derived lipids and their derivatives can disrupt normal endothelial integrity, thus reducing the ability of the endothelium to act as a selectively permeable barrier to blood components. Mechanisms underlying fatty acid-mediated endothelial cell dysfunction may be related to changes in fatty acid composition as well as to an increase in cellular oxidative stress. Selective lipid accumulation and fatty acid changes in endothelial cells can modulate membrane fluidity, proteoglycan metabolism and signal transduction mechanisms. Most importantly, dietary fats rich in certain unsaturated fatty acids, may be atherogenic by enhancing the formation of reactive oxygen intermediates. A subsequent imbalance in cellular oxidative stress/antioxidant status can activate oxidative stress-responsive transcription factors, which in turn may promote cytokine production, expression of adhesion molecules on the surface of endothelial cells, and thus intensify an inflammatory response in atherosclerosis. Our data also suggest that certain nutrients, which have antioxidant and/or membrane stabilizing properties, can protect endothelial cells by interfering with lipid/cytokine-mediated endothelial cell dysfunction. These findings contribute to the understanding of the interactive role of dietary fats with inflammatory components, as well as with nutrients that exhibit antiatherogenic properties, in the development of atherosclerosis.
To test the hypothesis that a delta opioid, DADLE ([D-Ala2, D-Leu5]-enkephalin), could protect tissue from ischemic damage during hypothermic lung preservation, we studied three groups of rats. In group 1 (n = 8), lung function was studied immediately after harvesting. In group 2 (n = 8), the lung was flushed with 4 degrees C Euro-Collins solution and preserved for 24 hours. In group 3 (n = 8), the lung was flushed with 4 degrees C Euro-Collins solution plus DADLE (1 mg/kg) and preserved for 24 hours. Lung function was studied by using a living rat perfusion model. Venous blood from the host rat perfused the pulmonary artery of the isolated lung. Blood from the isolated lung was returned to the carotid artery of the host rat with a roller pump. Severe pulmonary edema, hemorrhage, and occlusive pulmonary artery resistance occurred in group 2 within 30 minutes of perfusion. Perfusion studies were carried out for more than 60 minutes in groups 1 and 3. Pulmonary blood flow was lower in group 2 than in either group 1 or group 3. Pulmonary vascular resistance was much higher in group 2 than in groups 1 and 3 (p < 0.05). Airway pressure and airway resistance were much higher in group 2 than in groups 1 and 3 (p < 0.05). Airway resistance was also higher in group 3 than in group 1 after 20 minutes of perfusion (p < 0.05). Oxygen tensions from the pulmonary vein of the isolated lung in group 2 were lower than those in groups 1 and 3 (p < 0.05). Alveolar-arterial oxygen difference was much higher in group 2 than in groups 1 and 3 (p < 0.05). Lung tissue wet/dry weight ratio after perfusion was much higher in group 2 than in groups 1 and 3. The results clearly show, for the first time, that DADLE can effectively enhance hypothermic lung preservation in rats.
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