Changes in the fatty acid composition of rat lung lipids during development and following age-dependent lipid peroxidation

Early protein oxidation in the neonatal lung is related to development of chronic lung disease

Free radical-mediated oxidation of proteins may impair their function and cause cellular damage. We studied pulmonary protein oxidation and its association with the development of chronic lung disease in 61 newborn infants (mean gestational age 31.1 +/- 4.0, range 24-41 weeks) requiring intensive care with oxygen therapy. Protein oxidation was quantified as protein carbonylation in tracheal aspirates recovered daily during the first week of life. Mean carbonyl concentration was 3.5 +/- 1.6 mumol/mg protein. Negative correlations existed between protein carbonylation during days 2-4 and gestational age (day 2: r = -0.37, p = 0.01; day 3: r = -0.48, p = 0.001; and day 4: r = -0.33, p = 0.03). Patients who developed bronchopulmonary dysplasia showed significantly higher protein carbonylation on days 1-6 (all p < 0.05). In multiple regression analysis explaining bronchopulmonary dysplasia, using gestational age, inspired oxygen on days 1-3 and protein carbonylation on day 3 as independent variables, only protein carbonylation remained significant. We conclude that immaturity is the most important factor explaining free radical-mediated pulmonary protein oxidation in newborn infants and that oxidation of proteins is related to the development of chronic lung disease.

Oxidative influence on development and differentiation: an overview of a free radical theory of development

Metabolic gradients exist in developing organisms and are believed to influence development. It has been postulated that the effects of these gradients on development result from differential oxygen supplies to tissues. Oxygen has been found to influence the course of development. Cells and tissues in various stages of differentiation exhibit discrete changes in their antioxidant defenses and in parameters of oxidation. Metabolically generated oxidants have been implicated as one factor that directs the initiation of certain developmental events. Also implicated as factors that modulate developmental processes are the cellular distribution of ions and the cytoskeleton both of which can be influenced by oxidants. The interaction of oxidants with ion balance and cytoskeleton is discussed.

Polyunsaturated fatty acids and protection of newborn rats from oxygen toxicity

To test whether polyunsaturated fatty acids (PUFA) might be associated with protection against oxygen toxicity in newborn experimental animals, we performed two series of experiments. In the first series, adult female rats were fed one of three diets--regular Rat Chow, a high-PUFA (safflower oil-based) diet, or a low-PUFA (palm oil-based) diet--for several weeks before and throughout pregnancy and lactation. Newborn offspring of the three diet groups had similar antioxidant enzyme activities and surfactant development. Offspring of dams fed the high-PUFA diet had total lung lipid fatty acids characterized by increased linoleic acid (18:2 omega 6) and arachidonic acid (20:4 omega 6) and a significantly increased PUFA/saturated fatty acid ratio, compared with offspring of dams fed the regular diet or low-PUFA diet; associated with this increased PUFA pattern was markedly superior survival (80 of 84 (95%) vs 56 of 84 (67%) for regular-diet offspring, P less than 0.01) after 7 days in greater than 95% oxygen. Conversely, offspring born to dams fed the low-PUFA diet had decreased lung PUFA content and inferior tolerance to prolonged high O2 exposure (survival 38 of 84 (45%)). In the second experimental series, the postnatal provision of high PUFA rat milk to offspring born to dams fed the low-PUFA diet (via "cross-nurturing" by high-PUFA diet dams) rapidly increased their lung lipid PUFA and improved their hyperoxic survival (44 of 50 vs 25 of 50 for low-PUFA diet newborn animals kept with their low-PUFA mother rats, P less than 0.01). These studies suggest that increasing lung lipid PUFA can confer a protective effect against the toxic effects of hyperoxia on the newborn animal lung.

Unsaturated fatty acids in the postnatally developing rat lung

Fatty acid desaturase activity specific for the C-9 position is present in lung microsomes prepared from rats of all ages. This activity is significantly lower in neonatal rat lung compared with adult lung. A rapid increase in C-9 fatty acid desaturase activity seen at the approximate time of weaning may be related to a decrease in the polyunsaturated fatty acid (PUFA) content of the diet as the rat begins to consume laboratory chow instead of mother's milk. The 900 X g supernatant fraction of rat lung parenchymal cell homogenates is capable of incorporating linoleate, linolenate, and arachidonate into both triacylglycerols and phospholipids. Lung tissue from rats less than 20 days old incorporates these PUFA into phospholipids at a greater rate than lung tissue from adult rats. The incorporation of these PUFA into phospholipids in neonatal lung tissue occurred at a greater rate rate than their incorporation into triacylglycerols. In contrast, lung tissue from adult rats incorporated PUFA into triacylglycerols at a greater rate than into phospholipids. These data show that PUFA, known to be elevated in neonatal rat lungs, are used primarily for phospholipid biosynthesis in neonatal lung tissue whereas in adult lung tissue they are preferentially esterified to glycerol.

Age-related differences in GSH-shuttle enzymes in NO2- or O3-exposed rat lungs

The effect of age on changes in glutathione (GSH)-shuttle enzyme activities in rat lungs following a 72-hr exposure to NO2 (14 ppm) or O3 (approximately 0.9 ppm) was investigated. Exposed animals survived and were in the adaptive recovery phase at sacrifice. Glucose-6-phosphate dehydrogenase, glutathione reductase, and glutathione peroxidase levels were significantly elevated in young adult or older rats (maternal nursing or normal) and, to a lesser degree, in weanlings. Enzyme levels of neonates remained essentially unchanged and their lungs showed minimal morphological injury. At 50 ppm NO2, neonates also exhibited significant elevations in all three enzyme levels. The comparative unresponsiveness of neonates to short-term, low-level exposure to NO2 or O3, together with other observations, indicate that the relative importance of the GSH-shuttle in protecting lungs against injury requires further investigation.

Levels of lipid peroxidation in hepatocytes isolated from aging rats fed an antioxidant-free diet

Enzymatically isolated hepatocytes were utilized to evaluate levels of lipid peroxidation in young (3 months), adult (12 months) and aged (25 months) Fisher-344 female rats. Lipid peroxidation was measured by assaying levels of malonaldehyde, a by-product of the peroxidation reaction. Young, adult and aged animals were fed a liquid antioxidant-free diet for 21 days prior to the hepatocyte isolation. Cells isolated from young rats demonstrated the highest levels of lipid peroxidation (microgram of malonaldehyde/10(6) cells). This increase may be a result of the isolation procedure or of metabolic differences found in younger animals. When hepatocytes from aged animals on the antioxidant-free diet were incubated in the presence of lipid peroxidation inducers, such as cumene hydroperoxide or NADPH, significant elevations in lipid peroxidation over comparable adult values were observed. Aged hepatocytes appear to be more susceptible to the peroxidation process than adult hepatocytes, possibly due to defective peroxidation defenses.

Phospholipids of the lung in normal, toxic, and diseased states

The highly pulmonary concentration of 1,2-dipalmitoyl-sn-glycerol-3-phosphorylcholine (dipalmitoyllecithin) and its implication as an important component of lung surfactant have promoted investigation of phospholipid metabolism in the lung. This review will set the contents including recent informations for better understanding of phospholipid metabolism of the lung in normal state (physiological significances of lung phospholipids, characteristics of phospholipids in lung tissue and alveolar washing, biosynthetic pathways of dipalmitoyllecithin, etc.) as well as in toxic states (pulmonary oxygen toxicity, etc.) and in diseased states (idiopathic respiratory distress syndrome, pulmonary alveolar proteinosis, etc.) Since our main concern has been to clarify the most important route for supplying dipalmitoyllecithin, this review will be focused upon the various biosynthetic pathways leading to the formation of different molecular species of lecithin and their potential significance in the normal, toxic, and diseased lungs.

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--part III: free radical transfer from oxidizing lipids

Parallels and similarities in chemical and functional damage to proteins by ionizing and uv radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Free radicals play a key role in the transformation of energy to molecular and cellular damage. It is thus of critical importance to elucidate the general mechanisms of free radical formation and reactions in proteins in order to understand protein involvement in various pathological conditions and in food deterioration. Accordingly, this review is a detailed comparison of gamma-radiation, UV radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals.

Pulmonary fat accumulation after intralipid infusion in the preterm infant

Eight preterm infants who died after 'Intralipid' infusion had fat accumulation in the lungs. The rate of infusion in six of the infants was below the recommended maximum for preterm infants and in no case was the plasma lipaemic on regular visual inspection. Histological examination revealed varying degrees of lung involvement. The commonest finding was distension of empty pulmonary capillaries, but specific staining techniques for fat showed that the capillaries were engorged with large lipid globules. Removal of accumulated fat by histiocytes was seen in infants dying some time after cessation of intralipid infusion. Analysis of homogenised lung showed that those who died after intralipid infusion had a significantly greater (p < 0.001) concentration of lioleic acid, a marker for intralipid, than infants who died without receiving parenteral fat solution. Fat accumulation after intralipid infusion may be common but unrecognised and may seriously exacerbate ventilation/perfusion inequalities.