Inhibition of LDL oxidation by melatonin requires supraphysiologic concentrations.

Melatonin has been suggested as a potent antioxidant that may protect against development of atherosclerosis and cancer; however, these effects are unproven and controversial. The antioxidant capacity of melatonin was tested in comparison with alpha-tocopherol, ascorbic acid, and the melatonin precursors tryptophan and serotonin, by measuring inhibition of metal ion-mediated and human macrophage-mediated oxidation of LDL. Melatonin had weak antioxidant activity that was detectable only at concentrations 10000- to 100000-fold higher than physiologic concentrations. These results were comparable with published data showing that the radical scavenging activity of melatonin requires markedly supraphysiologic concentrations. In contrast, alpha-tocopherol was 50- to 100-fold more potent and was efficacious at physiologic concentrations. Ascorbic acid and tryptophan also were active at physiologic concentrations and were significantly more potent than melatonin. In summary, extremely supraphysiologic concentrations of melatonin had only weak antioxidant activity, which was surpassed by alpha-tocopherol, ascorbic acid, and tryptophan.

Differential effects of subcutaneous estrogen and progesterone on low-density lipoprotein size and susceptibility to oxidation in postmenopausal rhesus monkeys.

OBJECTIVE: To study the differential effects of subcutaneous E2 alone or in combination with P on the susceptibility of low-density lipoprotein (LDL) cholesterol to oxidation in naturally postmenopausal diet-controlled rhesus monkeys. DESIGN: Prospective, longitudinal controlled study. SETTING: Oregon Health Sciences University, Portland, Oregon, and Oregon Regional Primate Research Center, Beaverton, Oregon. PATIENT(S): Five naturally postmenopausal rhesus monkeys. INTERVENTION(S): Estradiol was administered subcutaneously for the first 4 weeks, followed by E2 plus P for 4 weeks, followed by a third 4-week washout period. MAIN OUTCOME MEASURE(S): Changes in plasma lipoprotein levels and oxidation of LDL and serum concentrations of E2 and P. RESULT(S): Levels of LDL cholesterol fell after 4 weeks of treatment with E2, compared with baseline. The lag time to half maximal light absorbancy after 4 weeks of E2 treatment was significantly increased compared with baseline. The maximal absorbance values and the slope of the propagation phase after 4 weeks of treatment with E2 were decreased compared with baseline. After 4 weeks of combined E2 and P treatment, all values were comparable to baseline. CONCLUSION(S): These results suggest that subcutaneous E2 therapy appears to enhance LDL resistance to oxidation and that this effect is attenuated by the addition of the P.

Airway secretory IgA concentrations in patients with lung cancer. Evaluation of the uninvolved lung.

To determine whether concentrations of the primary airway immunoglobulins (SIgA, IgG) are altered in the uninvolved lung of patients with lung cancer, we determined concentrations of SIgA and IgG in bronchial washings recovered from a proximal airway of the uninvolved lung in 24 patients with lung cancer and in ten patients with benign lung disease. When standardized for the amount of total protein recovered (SIgA/TP, IgG/TP), bronchial washings recovered from the uninvolved lung of lung cancer patients demonstrated a significantly decreased SIgA/TP ratio compared to control subjects (.14 +/- .02 vs .31 +/- .05, SEM, p less than 0.05). There were no differences in the IgG/TP ratios. Lung cancer patients with a decreased serum albumin (less than 3.2 g/dl) had a significantly decreased SIgA/TP ratio in bronchial washings compared to patients with a higher serum albumin (.08 +/- .03 vs .18 +/- .04, SEM, p less than 0.05). The decreased relative concentration of airway SIgA in lung cancer patients may adversely affect airway defenses against bacterial colonization.

Lymphocyte subsets in lung cancer.

Altered cellular immune function has been demonstrated in patients with lung cancer, including decreased numbers of circulating lymphocytes and changes in the percentage of lymphocytes in various functional subsets. We quantitated lymphocyte subsets in 54 patients with lung cancer including patients with limited (stages 1 and 2) nonsmall cell lung cancer (NSCLC, n = 23), advanced (stage 3) NSCLC (n = 16), and small cell cancer (SCLC, n = 15). Serum albumin was decreased in 15 lung cancer patients, and lymphocyte subsets were separately evaluated in these patients. Lymphocyte populations in cancer patients were compared to those of nonsmokers and a smoking patient population. No difference from smokers was noted in patients with limited NSCLC. Patients with SCLC and advanced NSCLC had significantly decreased numbers of T-helper and T-suppressor cells (p less than 0.05). Patients with lung cancer and hypoalbuminemia had the greatest decrease in number of circulating T-helper cells (p less than 0.001). B-lymphocytes were also decreased in patients with advanced NSCLC and patients with hypoalbuminemia (p less than 0.05). A decrease in population of T-lymphocytes subsets is frequent in patients with SCLC, advanced NSCLC, and lung cancer patients with hypoalbuminemia.