Hyperbaric oxygenation improves redox control and reduces mortality in the acute phase of myocardial infarction in a rat model.

Among the mechanisms of action of hyperbaric oxygenation (HBO), the chance of reducing injury by interfering with the mechanisms of redox homeostasis in the heart leads to the possibility of extending the period of viability of the myocardium at risk. This would benefit late interventions for reperfusion to the ischemic area. The objective of the present study was to investigate the changes in the redox system associated with HBO therapy maintained during the first hour after coronary occlusion in an acute myocardial infarction (MI) rat model. Surviving male rats (n=105) were randomly assigned to one of three groups: Sham (SH=26), myocardial infarction (MI=45) and infarction+hyperbaric therapy (HBO=34, 1 h at 2.5 atm). After 90 min of coronary occlusion, a sample of the heart was collected for western blot analysis of total protein levels of superoxide dismutase, catalase, peroxiredoxin and 3­nitrotyrosine. Glutathione was measured by enzyme­linked immunosorbent assay (ELISA). The detection of the superoxide radical anion was carried out by oxidation of dihydroethidium analyzed with confocal microscopy. The mortality rate of the MI group was significantly higher than that of the HBO group. No difference was noted in the myocardial infarction size. The oxidized/reduced glutathione ratio and peroxiredoxin were significantly higher in the SH and MI when compared to the HBO group. Superoxide dismutase enzymes and catalase were significantly higher in the HBO group compared to the MI and SH groups. 3­Nitrotyrosine and the superoxide radical were significantly lower in the HBO group compared to these in the MI and SH groups. These data demonstrated that hyperbaric oxygenation therapy decreased mortality by improving redox control in the hearts of rats in the acute phase of myocardial infarction.

Serum from calorie-restricted rats activates vascular cell eNOS through enhanced insulin signaling mediated by adiponectin.

eNOS activation resulting in mitochondrial biogenesis is believed to play a central role in life span extension promoted by calorie restriction (CR). We investigated the mechanism of this activation by treating vascular cells with serum from CR rats and found increased Akt and eNOS phosphorylation, in addition to enhanced nitrite release. Inhibiting Akt phosphorylation or immunoprecipitating adiponectin (found in high quantities in CR serum) completely prevented the increment in nitrite release and eNOS activation. Overall, we demonstrate that adiponectin in the serum from CR animals increases NO• signaling by activating the insulin pathway. These results suggest this hormone may be a determinant regulator of the beneficial effects of CR.

Accumulation of chylomicron remnants and impaired vascular reactivity occur in subjects with isolated low HDL cholesterol: effects of niacin treatment.

Fasting hypertriglyceridemia relates with high-density lipoprotein (HDL) cholesterol, but it is not known whether low HDL cholesterol is associated with disturbances of chylomicron metabolism. To clarify this issue this metabolism was studied in subjects with low HDL cholesterol together with vascular reactivity and evaluation of no-flush niacin treatment. Thirty men with HDL < 1.04 mmol/L and no other risk factors for coronary artery disease (CAD) and 11 normal controls with HDL > 1.04 mmol/L were studied. The plasma kinetics of a chylomicron-like emulsion labeled with 14C-cholesterol oleate (CO) and 3H-triolein (TG) was determined and the fractional clearance rate (FCR, min(-1)) was calculated. Vascular reactivity was evaluated using high-resolution ultrasonography. CO FCR was markedly reduced in the low HDL group compared to controls (3.6 x 10(-3) +/- 5.1 x 10(-3) min(-1) versus 12.2 x 10(-3) +/- 8.4 x 10(-3) min(-1), p < 0.001) but TG FCR was similar. Flow-mediated dilation (FMD) was diminished in low HDL (7.4 +/- 4.1 versus 12.8 +/- 4.6%, p < 0.001), whereas nitrate-mediated dilation was similar. Twenty-two low HDL subjects with reduced FMD were randomized into two groups, one given 1.5 g/day niacin and a placebo group. After 3-month treatment, plasma lipids and chylomicron kinetics were not changed by niacin treatment but FMD improved to normal values (5.44 +/- 1.89 to 11.13 +/- 3.4%, p < 0.01). In conclusion, isolated low HDL cholesterol subjects may also bear chylomicron remnant accumulation and endothelial dysfunction, which highlight the importance of their preventive treatment.

Uptake of a cholesterol-rich emulsion by breast cancer.

OBJECTIVE: Overexpression of low-density lipoprotein (LDL) receptors occurs in several cancer cell lines and offers a unique strategy for drug targeting by using LDL as vehicle. However, the native lipoprotein is difficult to obtain and handle. Previously, we showed that a lipidic emulsion (LDE) similar to the lipid structure of native LDL may bind to LDL receptors and be taken up by acute myelocytic leukemia cells. We also showed that LDE can also concentrate in ovarian cancer tissue. In this study, we tested whether LDE is taken up by breast carcinoma. METHODS: LDE labeled with (99m)Tc was injected into 18 breast cancer patients, and nuclear medicine images of the tumor and metastatic sites were acquired. Subsequently, LDE labeled with [3H]cholesteryl oleate was intravenously injected into 14 breast cancer patients 24-30 h before total mastectomy procedure. Fragments of normal and of breast cancer tissue excised during surgery were lipid extracted with chloroform/methanol and their radioactivity was measured in a scintillation solution. RESULTS: (99m)Tc-LDE images of the primary tumor and of metastasis sites were obtained in all 18 breast cancer patients. As directly measured in the tumor and in the normal mammary tissue, the amount of the emulsion radioactive label in the tumor was 4.5 times greater than in the normal tissue (range 1.2- to 8.8-fold). CONCLUSION: LDE concentrates much more in malignant breast tumor tissue than in the normal tissue. Thus it has potential to carry drugs or radionuclides directed against mammary carcinoma cells for diagnostic or therapeutic purposes.