Effect of a water-soluble benzoquinone derivative, 4-[4-N-(5-ethyl-1-thia-3, 4-diazol-2-yl)sulfophenylamino]-5-methoxy-1, 2-benzoquinone, on the injury to cultured aortic endothelial cells induced by linoleic acid hydroperoxide was examined. The benzoquinone derivative markedly inhibited the release of lactate dehydrogenase(LDH) from the cells into the medium in a concentration-dependent manner. The inhibitory effect of the benzoquinone derivative tended to be higher than that of butylated hydroxytoluene. Upon incubation of the endothelial cells with the hydroperoxide, the lipid peroxide level in the cells was increased prior to the release of LDH from the cells, and this increase was significantly inhibited by the novel antioxidant.
Whether or not the feeding of air-oxidized oil to rat dams during the period of gestation or lactation affects the lipid peroxide contents in their offspring was studied. Rat dams were given a diet containing 4g soybean oil or air-oxidized soybean oil/100g diet during gestation. Whole body lipid peroxides, thiobarbituric acid-reactive substances (TBARS) determined as malondialdehyde, in newborn pups from dams fed the air-oxidized oil diet were not different from those from dams fed the unoxidized oil diet. When dams were given the oxidized oil diet during lactation, whole body TBARS contents in suckling pups increased sharply in the 10-day-old neonate and decreased until 21 days old. However, these trends were not affected by the amounts of air-oxidized soybean oil nor the unoxidized oil diet. These findings indicate that a maternal diet containing air-oxidized oil during gestation or lactation does not affect the whole body lipid peroxides in neonatal rats.
We have found a circadian rhythm to serum triglyceride and phospholipid levels in the fasting rat. The diurnal rhythm of serum triglyceride levels could be regulated by changes in the feeding schedule. After one week of controlled feeding from 8:00 pm to 2:00 pm the next day, serum triglyceride levels peaked twice, at 10:00 am and at 9:00 pm; whereas when controlled feeding was from 5:00 pm to 9:00 am only one peak occurred, at 6:00 pm. The increase in serum triglyceride levels was correlated with the elevation of very low density lipoprotein. However, we found no diurnal variation in serum triglyceride levels in experimental diabetic rats.
Glutathione S-transferase (GST) isozymes purified from rat ovary and testis cytosols were grouped immunochemically into two classes, alpha and mu. The class-alpha isozymes of both tissue cytosols exhibited catalytic activities of Δ5-3-ketosteroid isomerase and glutathione (GSH)-peroxidase. The class-mu isozymes were characterized by showing potent GSH-conjugation activity toward a wide variety of electrophilic compounds. The most conspicuous difference in the isozymes between these gonadal tissue cytosols was shown to reside in the isozymes having Δ5-3-ketosteroid isomerase activity. Only GST 1-2 among the testicular GST isozymes showed the steroid isomerase activity, whereas two distinct ovarian class-alpha isozymes, GSTs 1-2 and 1′-1′, revealed the activity. Immunohistochemical analysis showed that the class-alpha isozymes were localized in the cells related to steroid hormone production such as testicular interstitial Leydig cells and the ovarian cells of theca folliculi and interstices, and the corpus lutheum. The class-mu isozymes were shown to be distributed throughout both gonadal tissues, but in the testis a remarkable localization of the isozymes was observed within Sertoli cells. These results suggest that each class of GST isozymes may be distributed in appropriate locations of the gonadal tissues to serve roles in generation of steroid hormones or in protection of ovum and sperm from various xenobiotics.
In this study, the effect of photosensitizers on lipid peroxidation in the retina was investigated. Porcine retinal homogenate was exposed to illumination from a fluorescent lamp with or without photosensitizers such as hematoporphyrin, rose bengal, and fluorescein for 60min. The control, which was exposed to illumination without photosensitizers, did not show a significant increase in lipid peroxidation. However, lipid peroxidation in the homogenates exposed to illumination with photosensitizers increased significantly and in a dose-dependent manner. For concentrations of more than 100μM of all three photosensitizers, lipid peroxidation in the retina homogenates increased to a level approximately 2-3 times higher than that in the sample before illumination, and to a level 10 times higher than that of the control. α-Tocopherol inhibited hematoporphyrin-induced lipid peroxidation in a dose-dependent manner, but superoxide dismutase did not show an inhibitory effect.
By the method using a methylene blue derivative, we investigated the hydroperoxide (LPO) level of erythrocyte membranes (EG) in patients suffering from diabetes mellitus, hypertension, cerebral stroke, hypercholesterolemia, and ischemic heart disease. In addition, the correlation between the EG-LPO level and the clinical parameters was analyzed. The EG-LPO level registered 1.6±0.9nmol/mg protein in the healthy controls, whereas higher EG-LPO levels were obtained in the diabetic and the hypertensive patients. However, the EG-LPO in the hypercholesterolemic patients showed lower value than that in the diabetic, from which we would suggest the inhibitory effect of high cholesterol on lipid peroxidation. There was no correlation between the EG-LPO level and the clinical parameters. The lipid peroxide in the erythrocyte membrane would be supposed to be one of the independent vascular risk factors, and especially the high values of the EG-LPO in the diabetic and hypertensive patients might be related to the high incidence of vascular accidents in these diseases.
In this study, the capability of superoxide production by LDL either without stimulation or under the stimulation of Fe-ADP and the manner of modification of low density lipoprotein (LDL) by copper (Cu++) in diabetic patients were examined and compared with those of healthy subjects. The amount of superoxide generated by diabetic LDL was similar to that of healthy subjects both at the basal level and following stimulation by Fe-ADP. LDL from healthy subjects and diabetic patients was modified in the presence of 10μM CuSO4. When the level of thiobarbituric acid-reactive substance was determined in the Cu++-modified LDL, no difference was found. On the other hand, when the incorporation of [14C]oleate into cholesteryl ester (CE) by mouse peritoneal macrophages was stimulated by the Cu++-modified LDL, we found that the modified diabetic LDL significantly enhanced the CE synthesis compared with the modified healthy LDL (p<0.01). To clarify the mechanism of the enhanced CE synthesis, the rate of degradation of [125I]Cu++-modified diabetic LDL was measured. We found that this rate was similar to that of healthy subjects. These data suggest that the degree of oxidation does not differ among patients although diabetic LDL is modified by Cu++ in a manner such that it preferentially promotes the activity of CE synthesis in macrophages by some unknown intracellular metabolic mechanism.
The overall composition of serum lipoproteins and the fatty acid composition of cholesterol esters and phospholipids in the VLDL, IDL, LDL, and HDL were studied in eleven patients with familial type IV primary hypertriglyceridemia. The patients were divided into two groups: HTG 1 (serum triglycerides below 350mg/dl: 200-294, n=5) and HTG2 (serum triglycerides above 350mg/dl: 368-820, n=6). The data were compared with those from 9 normolipidemic subjects. The proportion of the constituents of VLDL was normal in the HTG1 group, but cholesterol esters were increased and triglycerides decreased in this fraction in the HTG2 one. The increase in triglycerides and decrease in cholesterol esters in LDL and HDL modified the CE/TG and TG/total lipoprotein ratios in both groups of patients. The core lipid/surface ratio was increased in HDL in both groups, but not in the other three fractions. The saturated fatty acids of cholesterol esters were low (p<0.01) in the VLDL of the HTG2 group. The ω6 fatty acids of cholesterol esters and phospholipids were slightly increased (p<0.05) in the VLDL in the same group. However, there was a decrease in the ω6 fatty acids in cholesterol esters (p<0.05) and in the phospholipids (p<0.01) in the IDL of the HTG1 group. There was no significant difference in the LDL fatty acid composition between the hypertriglyceridemic patients and the controls. The phospholipids of the HDL in the HTG2 group contained less (p<0.05) saturated fatty acids and more (p<0.05) polyunsaturated fatty acids than did those in the HTG1 group. These observations suggest that the fatty acid composition of lipoproteins in hypertriglyceridemic subjects is not markedly altered and is not related to the major changes in the lipoprotein composition of their fractions.