formazans and Pheochromocytoma

Pheochromocytomas are catecholamine-producing tumors which are generally benign, but which can also present as or develop into malignancy. Molecular pathways of malignant transformation remain poorly understood. Pheochromocytomas express various trophic peptides which may influence tumoral cell behavior. Here, we investigated the expression of trophic amidated peptides, including pituitary adenylate cyclase-activating polypeptide (PACAP), neuropeptide Y (NPY), and adrenomedullin (AM), and their receptors in benign and malignant pheochromocytomas in order to assess their potential role in chromaffin cell tumorigenesis and malignant transformation. PACAP, NPY, and AM are expressed in the majority of pheochromocytomas studied; NPY exhibiting the highest mRNA levels relative to reference genes. Although median gene expression or peptide levels were systematically lower in malignant compared to benign tumors, no statistically significant difference was found. Among all the receptors of these peptides that were analyzed, only the AM receptor RDC1 displayed a differential expression between benign and malignant pheochromocytomas. This receptor exhibited a fourfold higher expression in malignant than in benign tumors. AM and stromal cell-derived factor 1, which has also been described as a ligand for RDC1, increased the number of human pheochromocytoma cells in primary culture and exerted anti-apoptotic activity on rat pheochromocytoma PC12 cells. In addition, RDC1 gene silencing decreased the number of viable PC12 cells. This study shows the expression of several trophic peptides and their receptors in benign and malignant pheochromocytomas, and suggests that AM and its RDC1 receptor could be involved in chromaffin cell tumorigenesis through pro-survival effects. Therefore, AM and RDC1 may represent valuable targets for the treatment of malignant pheochromocytomas.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Animals; Blotting, Western; Cell Survival; Formazans; Gene Expression Regulation, Neoplastic; Humans; Immunohistochemistry; Neuropeptide Y; PC12 Cells; Pheochromocytoma; Pituitary Adenylate Cyclase-Activating Polypeptide; Rats; Receptors, Adrenomedullin; Receptors, Neuropeptide Y; Receptors, Peptide; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Tetrazolium Salts

Amyloid beta protein (Abeta)-induced free radical-mediated neurotoxicity is a leading hypothesis as a cause of Alzheimer's disease (AD). Abeta increased free radical production and lipid peroxidation in PC12 nerve cells, leading to apoptosis and cell death. The effect of 4',5-dihydroxy-3',6,7-trimethoxyflavone from Artemisia asiatica on Abeta induced neurotoxicity was investigated using PC12 cells. Pretreatment with isolated 4',5-dihydroxy-3',6,7-trimethoxyflavone and vitamin E prevented the Abeta-induced reactive oxygen species (ROS). The 4',5-dihydroxy-3',6,7-trimethoxyflavone resulted in concentration-dependant decreased Abeta toxicity assessed by 3-(4, 5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. However, treatment with these antioxidants inhibited the Abeta-induced neurotoxic effect. Therefore, these results indicate that micromolecular Abeta-induced oxidative cell stress is reduced by 4,5-dihydroxy-3',6,7-trimethoxyflavone from Artemisia asiatica.

Topics: Adrenal Medulla; Amyloid beta-Peptides; Animals; Artemisia; Cell Survival; Drug Interactions; Exocytosis; Flavones; Flavonoids; Formazans; Lipid Peroxidation; Oxidative Stress; PC12 Cells; Pheochromocytoma; Rats; Reactive Oxygen Species; Tetrazolium Salts; Tumor Cells, Cultured; Vitamin E