Metrifonate, like acetylcholine, up-regulates neurotrophic activity of cultured rat astrocytes.

Metrifonate is an inhibitor of acetylcholinesterase (AChE). Several studies confirmed its positive effects on cognitive impairment in Alzheimer's disease but it was due to adverse events withdrawn from clinical trials. Based on the importance of astrocytes in physiological and pathological brain activities we investigated the impact of metrifonate and, for comparison, acetylcholine on intrinsic neurotrophic activity in these cells. Metabolic activity, intracellular adenosine 5'-triphosphate (ATP) levels and lactate dehydrogenase (LDH) release was measured to examine the impact of metrifonate on viability and integrity of cultured rat cortical astrocytes. The influence of metrifonate, acetylcholine and selective cholinergic ligands on nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) synthesis and secretion was determined by specific two-site enzyme immunoassays. Exposure of cultured astrocytes to metrifonate displayed no toxic effects on cell viability. Metrifonate and acetylcholine potently and transiently elevated NGF and BDNF, but not NT-3, protein levels and secretion with different intensity and time frame of their maximal response. Stimulatory effect on NGF was mimicked by selective nicotinic receptor agonist nicotine and completely blocked by nicotinic antagonist mecamylamine. The impact on BDNF synthesis was mimicked by muscarinic receptor agonist pilocarpine and abolished by selective muscarinic antagonist scopolamine. Metrifonate up-regulates astrocytic NGF and BDNF synthesis in the same manner as acetylcholine, their effect depends on different cholinergic pathways. These results suggest a trophic role of metrifonate, based on a well-known neurotrophic activity of NGF and BDNF in vivo.