Protective effect of Schisandra chinensis lignans on hypoxia-induced PC12 cells and signal transduction.

It is well-known that hypoxia induces neuronal injury; however, the mechanisms underlying this observed effect remain to be determined. Schisandra chinensis lignans (SCL). The aim of this study was thus to examine the ability of Schisandra chinensis lignans (SCL) to prevent hypoxia-induced neuronal injury using a human adrenal pheochromocytoma cell line (PC12). Exposure to hypoxia significantly reduced cell survival rate in cultured PC12 cells. However, pretreatment with SCL at 10, 20 or 40 µmol/L followed by hypoxia prevented loss of cellular viability. Flow cytometry demonstrated that the apoptotic rate in PC12 cells following hypoxia was significantly increased. Pretreatment with SCL 20 or 40 µmol/L in hypoxia-exposed cells resulted in significantly reduced apoptotic rates compared to hypoxia. Immunocytochemical staining showed that protein expression of p-Akt was significantly diminished by hypoxia. Following pre-treatment with different concentrations of SCL, PC12 cells were markedly stimulated as evidenced by elevated protein expression of p-Akt in a concentration-dependent manner. The expression of p-Akt protein in the presence of PI3K/Akt signaling pathway inhibitor LY294002 and SCL was not markedly changed indicating that signal transduction was affected by this Chinese herb. There were no significant differences in total Akt protein expression following hypoxia or pretreatment with SCL. Western blot demonstrated that expression levels of caspase-3 protein were significantly increased while expression levels of Bcl-2 protein were decreased in hypoxic cells. Pretreatment with SCL followed by hypoxia significantly lowered expression levels of caspase-3 protein accompanied by elevated expression levels of Bcl-2 protein in a concentration-dependent manner. After co-incubation with LY29004 and SCL, down-regulation of expression of caspase-3 protein and up-regulation of the expression of Bcl-2 protein noted with SCL alone were suppressed. Data suggest that the protective effect exerted by SCL in hypoxia-induced PC12 cell injury involves enhanced cell proliferation and inhibition of apoptosis mediated by activation of PI3K/Akt signaling pathway. The increased protein Akt phosphorylation expression levels resulted in consequent reduced downstream caspase-3 expression and enhanced Bcl-2 expression.

Thiazolidinediones inhibit the growth of PC12 cells both in vitro and in vivo.

Thiazolidinediones (TZDs) have recently been proposed as a therapy for PPARgamma-expressing tumors. Pheochromocytoma (PHEO) is associated with high morbidity and mortality due to excess catecholamine production, and few effective drug therapies currently exist. We investigated the effects of TZDs on PHEO both in vitro and in vivo. PPARgamma protein was expressed in human adrenal PHEO tissues as well as in rat PHEO cells, PC12. TZDs, including rosiglitazone (RGZ) and pioglitazone (PGZ), inhibited proliferation of PC12 cells in a dose-dependent manner and increased casapse-3 expression of PC12 cells. TZDs also reduced expression of cyclin E and cyclin-dependent kinase2. RGZ inhibited nerve growth factor-induced neurite outgrowth and reduced expression of catecholamine-synthesizing enzymes. Finally, rat PHEO growth generated by subcutaneous injection of PC12 cells was slowed in an RGZ-treated mouse. These data suggest that TZDs may be a promising therapeutic approach for medical treatment for PHEO.

Lack of carcinogenicity and increased survival in F344 rats treated with 5-fluorouracil for two years.

The carcinogenicity of 5-fluorouracil (5-FU), a compound employed as an antineoplastic drug, was investigated in F344 rats of both sexes. 5-FU was administered to groups of 50 male and 50 female rats ad lib. for 104 weeks, added to drinking water at concentrations of 0 (control), 62 and 125 ppm, these dose levels being selected on the basis of results of a 13-week subchronic toxicity study. Body weight gains were slightly depressed in the 125 ppm group of both sexes. While not statistically significant in females, final survival rates at week 111 in the 125 ppm group of both sexes were higher than those in the control group, suggesting an ability of 5-FU to prolong the lifespan. Histopathologically, a decreased incidence of islet cell adenomas in males and increased incidences of pituitary gland adenomas and pheochromocytomas in females were observed in the 62 ppm group without dose dependence. There was no significant induction of any other neoplastic or non-neoplastic lesions. These results indicate a lack of carcinogenicity of 5-FU under the present experimental conditions using rats.

Results of a screening program for multiple endocrine neoplasia type II.

After the diagnosis of MEN IIa syndrome in five members of a British family, a further 180 members were identified, 167 of whom were still alive. From death certificates, a further three were found to have been affected. Of these eight patients, only two were diagnosed and survived. Over the next four years, these two survivors and 90 others (those over the age of ten years) attended a screening program using alcohol or pentagastrin stimulated plasma calcitonin for MCT or urinary catecholamines for pheochromocytoma. The two surviving patients and 12 others were thought to have abnormal screening tests. One patient with an abnormal catecholamine excretion level had bilateral pheochromocytomas removed. Of the 13 patients with abnormal stimulated plasma calcitonin levels, five underwent total thyroidectomy, but MCT was found in only two. One of these patients and two of those in whom no tumor was found had persistently elevated stimulated plasma calcitonin levels postoperatively, suggesting the presence of C cells and, thus, persisting risk of MCT. In all patients, plasma calcitonin concentrations were variable, and an established normal range of values is essential if unnecessary surgical treatment is to be avoided. Pheochromocytoma proved difficult to diagnose, and pentagastrin stimulated plasma catecholamines deserves evaluation as a screening test. Despite the large effort involved, permanent screening of all family members is recommended as the only means of reducing mortality. Following any treatment, screening should continue because new disease or recurrence is possible.