Vitamin E and other antioxidants inhibit human prostate cancer cells through apoptosis.

BACKGROUND: Many human prostate cancer cells have escaped the apoptotic effects of natural regulators of cell growth such as transforming growth factor betal (TGF beta-1) and tumor necrosis factor (TNF). METHODS: Prostate cancer cell growth was investigated by treating with antioxidants. DU-145 (androgen-unresponsive), LNCaP (androgen-responsive), and ALVA-101 (androgen moderately responsive) were grown in RPMI-1640 medium supplemented with bovine fetal calf serum and antibiotics, and were treated with various antioxidants for 1-7 days. Cell growth was then determined with the Cell Titer 96 AQ assay, and apoptosis was assessed by cell death detection ELISA, nuclear morphology, and TUNEL techniques. RESULTS: Cells treated with or without (+/-)-alpha-tocopherol (vitamin E) for 1-7 days at concentrations from 0.078-2.5 microg/ml modestly affected cell growth compared to other antioxidants tested. Tocopherol produced a significant (P < 0.01) inhibition of ALVA-101 and LNCaP (10-24% of control; 0.078-2.5 microg/ml; at 6 days; n = 6). DU-145 cells were not growth-inhibited significantly. However, pyrrolidinedithiocarbamate (PDTC) produced a significant (P < 0.01, n = 6; 17-80% of control; 2.5-20 microg/ml; 1-7 days) inhibition of DU-145 and ALVA-101 cells. A significant (P < 0.01) and maximum inhibition of LNCaP cells occurred at all concentration of PDTC (2. 5-20 microg/ml). A third compound, diethyldithiocarbamic acid (DETC), incubated for 1-7 days, produced a significant dose response suppression of cell growth of DU-145 and ALVA-101 cells (P < 0.01; 14-88% of control; 1.25-80 microg/ml; n = 6). LNCaP cells were inhibited by DETC (P < 0.01; 28% of control; 1.25-80 microg/ml; n = 6). All three antioxidants tested stimulated apoptosis in actively dividing ALVA-101, DU-145, and LNCaP cells (P < 0.01; n = 6), but confluent cells were affected less. Testosterone had additive inhibitory effects when combined with PDTC in ALVA-101 cells; however, the other cell lines were not influenced. CONCLUSIONS: These results demonstrate that antioxidants modulate human prostate cancer cell proliferation by altering apoptosis in dividing cells, and this necrosis or apoptosis in confluent cells is not as effective.

B-endorphin response to a low dosage of human corticotropin releasing hormone during metyrapone administration in depression.

This study defines the pituitary B-endorphin (BE) secretory response to a low dosage (0.3 ug/kg) of human corticotropin releasing hormone (CRH) in depressed patients and normal controls pretreated with metyrapone. We find no difference in the B-endorphin response to CRH in depressed subjects without evidence of HPA overactivity, compared with controls. This finding is contrasted with other data demonstrating a blunted B-endorphin response to CRH in depressives. The influence of metyrapone pretreatment on the pituitary B-endorphin response to CRH through a mechanism that minimizes the impact of cortisol negative feedback is discussed. Future studies which include low dose CRH infusion both in the presence and in the absence of metyrapone pretreatment will help investigate alterations in the regulation of pituitary B-endorphin secretion in depression including the possibility of increased pituitary sensitivity to the negative fast feedback of cortisol.

Reduction of testosterone synthesis after high dose interleukin-2 therapy of metastatic cancer.

We have investigated the effect of high dose iv bolus interleukin-2 (IL-2) therapy on sex hormone and adrenal steroid concentrations in six men treated for metastatic renal cell carcinoma or malignant melanoma. Blood concentrations of testosterone, 17 beta-estradiol, LH, FSH, cortisol, dehydroepiandrosterone (DHEA), and DHEA sulfate (DHEA-S) were measured before and after a 5-day course of IL-2 therapy. Cortisol levels rose and DHEA-S decreased insignificantly. DHEA declined, reaching a nadir (P less than 0.001) on day 6, and testosterone decreased significantly on day 2 and reached a nadir on day 6 (P less than 0.0001). Concentrations of both steroids then gradually rose. Estradiol rose on day 4 (P less than 0.001) and then declined. Neither LH nor FSH was affected significantly, although there was a rise in the mean level of LH after IL-2 therapy. Our results suggest that high dose IL-2 therapy in men affects both adrenal and testicular androgen production without inhibiting pituitary trophic hormone secretion. These effects of IL-2 on plasma sex steroids may be the result of cytokines stimulated by IL-2 therapy, rather than direct responses to IL-2.

Augmented pituitary corticotropin response to a threshold dosage of human corticotropin-releasing hormone in depressives pretreated with metyrapone.

We studied pituitary corticotropin response to exogenous corticotropin-releasing hormone infusion and attempted to control for the confounding effect of variable serum cortisol levels between depressed and control subjects. If metyrapone was given during the time of day when hypothalamic pituitary adrenal activity was otherwise low, the relative increase in the corticotropin concentration was small. Pituitary response to exogenous corticotropin-releasing hormone can be defined under conditions in which the amount of glucocorticoid-mediated negative feedback present at the level of the pituitary gland is equal in all subjects. When the ambient cortisol level was equalized (and suppressed) in all subjects at the time of study with a threshold dosage of corticotropin-releasing hormone, we found an augmented response to corticotropin-releasing hormone in depressives. This raises the possibility that either increased pituitary sensitivity to corticotropin-releasing hormone or an increased intracellular pool of corticotropin is available for release in subjects with major depressive illness.

Alterations of glucocorticoid actions by other drugs and disease states.

Glucocorticoids are used in physiological and pharmacological amounts in the management of a variety of clinical conditions. Concomitant utilisation of other drugs or the presence of some diseases may affect the physiological action of the steroid in the tissues. Phenytoin, phenobarbitone, ephedrine and rifampicin accelerate the metabolism of glucocorticoids thereby decreasing their biological activity. A similar phenomenon occurs in patients with hyperthyroidism. In contrast, glucocorticoid action is enhanced in hypothyroid patients and in those with hepatic damage as the result of a defect in the clearance of the hormone from blood. In turn, glucocorticoids antagonise the effects of cholinesterase inhibitors and ganglion blocking agents. The above mentioned effects should be kept in mind whenever glucocorticoids are utilised in the diagnosis and management of endocrine or non-endocrine conditions.