John N. Diana

Nutritional implications in vascular endothelial cell metabolism.

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.

Influence of nutrients and cytokines on endothelial cell metabolism

The vascular endothelium plays an active role in physiological processes such as hemostasis, regulation of vessel tone and vascular permeability. Cell injury, or any event which disrupts endothelial integrity and thus endothelial permeability properties, may be involved in the early events leading to atherosclerotic lesion formation. Because of its constant exposure to blood components, including prooxidants, diet-derived fats and their derivatives, the endothelium is susceptible to oxidative stress and to injury mediated by blood lipid components. It is likely that these events potentiate the overall inflammatory response to injury by increasing cytokine release in proximity to the endothelium, which then could further disrupt endothelial barrier function. Even though mechanisms associated with lipid/cytokine-mediated endothelial cell dysfunction are unclear, our data suggest that they may be both oxidative and non-oxidative in nature. We suggest that dietary fats, rich in certain unsaturated fatty acids are atherogenic by enhancing the formation of reactive oxygen intermediates. These intermediates can activate oxidative stress-responsive transcription factors, such as NF-kappa B, which in turn may promote cytokine production, adhesion molecule expression and ultimately endothelial barrier dysfunction. The resulting disturbances in endothelial integrity possibly allow increased penetration of cholesterol-rich lipoprotein remnants into the arterial wall, a critical event in the etiology of atherosclerosis. Data suggest that certain nutrients, which have antioxidant and/or membrane stabilizing properties, protect endothelial cells by interfering with the above proposed mechanisms of endothelial cell dysfunction.

Delta opioid extends hypothermic preservation time of the lung

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.

Eighteen to 37 hours' preservation of major organs using a new autoperfusion multiorgan preparation

A new autoperfusion preparation was used to preserve six major organs simultaneously. In 7 Yorkshire white swine, the heart and lungs were separated and removed with the liver, pancreas, duodenum, and both kidneys en bloc while they were self-perfused. Fresh blood, glucose, electrolytes, heparin sodium, methylprednisolone, and a fat emulsion (Soyacal) were infused through the portal vein. No inotropic drugs were necessary. The organs survived for 18 to 37 hours (average survival, 24.6 +/- 2.7 hours [+/- standard error of the mean]). Aortic systolic pressure ranged from 78.5 +/- 5.5 to 98.7 +/- 11.8 mm Hg. Arterial oxygen tension ranged from 206 +/- 23 to 266 +/- 15 mm Hg and arterial carbon dioxide tension, from 20.1 +/- 2.7 to 32.1 +/- 4.9 mm Hg. Blood lactic acid levels decreased from 8.75 +/- 2.06 to 5.50 +/- 2.45 mmol/L at 24 hours. Urine output ranged from 25 to 82 mL/h. Blood urea nitrogen levels decreased from 9.17 +/- 0.59 to 4.67 +/- 1.08 mg/dL. Blood creatinine levels decreased from 1.34 +/- 0.10 to 0.57 +/- 0.22 mg/dL. Serum glutamicoxaloacetic transaminase levels increased from 73.4 +/- 26.3 to 194 +/- 179.5 U/L and serum glutamic-pyruvic transaminase levels, from 44.8 +/- 5.7 to 91 +/- 66.4 U/L. Red blood cell count ranged from 6.94 +/- 0.58 to 13.23 +/- 2.30 x 10(6)/microliters. Lung wet/dry weight ratios changed from 5.79 +/- 0.17 at the beginning to 6.25 +/- 0.16 at 24 hours. The technique for simultaneous multiorgan preservation presented here is simple, effective, and highly reproducible. This study appears to have produced one of the longest average survival times for autoperfusion.

Effects of chronic smoke exposure on the cardiovascular responses to acute nicotine infusion in the rat

Rats were exposed daily to cigarette smoke for 17-22 weeks in order to characterize mean arterial pressure and regional hemodynamic effects of chronic smoke exposure and to determine if cardiovascular reactivity to acute nicotine infusions is altered by chronic smoke exposure. Urethane-anesthetized animals were instrumented with miniaturized pulsed-Doppler flow probes on the iliac and mesenteric vascular beds. Under resting conditions sham-smoked and smoke-exposed animals had similar levels of mean arterial pressure and mesenteric blood flow; however, resting heart rate was lower in the smoke-exposed group, while iliac blood flow was elevated in the smoke-exposed group. Acute nicotine infusion (6.25, 12.5 and 25 micrograms/kg per min) produced equivalent, dose-dependent pressor effects as well as increases in iliac and mesenteric resistance in sham and smoke-exposed groups. Thus, chronic cigarette smoke-exposure in rats may exert significant cardiovascular effects other than on arterial pressure such as lowered heart rate and elevated blood flow to skeletal muscle beds, while cardiovascular responses to nicotine are not altered by chronic smoke-exposure.

Tobacco Smoking and Atherosclerosis: Overview

Epidemiological studies from a variety of countries throughout the world have clearly established a relationship between smoking cigarettes and the development and/or progression of the atherosclerotic process (1). Although the epidemiologic evidence which correlates smoking and atherosclerosis is extensive, and thereby convincing, from a rigorous scientific point of view there are confounding variables in such studies which need further clarification. These confounding variables are life-style factors which predispose the individual to atherosclerotic disease in general (and coronary heart disease in particular), and are typified by sedentary living habits; obesity and/or unrestrained weight gain; a dietary intake which contains an excessive number of calories, fat, saturated fat, cholesterol, and salt; personal stress that is not modified; as well as cigarette smoking. It is not clear just how all of these risk factors interrelate among or between each other as variables in the pathogenesis of atherosclerosis. Analytical models which can unambiguously discriminate between such risk factors for a weighting of their contribution to the overall atherosclerotic process have yet to be developed.