Cytoprotective actions of 2,4‐dimethoxybenzylidene anabaseine in differentiated PC12 cells and septal cholinergic neurons

Abstract

The potential cytoprotective actions of a novel nicotinic agent 2,4-dimethoxybenzilidene anabaseine (DMXB) were investigated in differentiated PC12 cells and transected rat septal cholinergic neurons in vivo. In NGF-differentiated PC12 cells, removal of both NGF and serum led to cell loss, a reduced % of cells expressing neurites, the release of lactate dehydrogenase, and a decrease in total cellular protein. Cell loss was apparent within 24 h, and remained constant between 4-8 days post-NGF removal. NGF alone (100 ng/ml), DMXB (10 pM), but not nicotine (10 pM), prevented these cell and neurite losses. DMXB-induced cytoprotection was blocked'by 1 pM mecamylamine. DMXB (1 mg/kg, ip) injected twice but not once per day protected cholinesterasestaining septal neurons from retrograde degeneration following unilateral fimbrial transections. The twice per day DMXB injection-protocol also decreased cell roundness among cholinesterasestaining cells in the lesioned septal hemisphere compared to saline-injected animals. These studies suggest that DMXB may exert cytoprotective activity in NGF-sensitive neuronal populations.

Regulation of Neuronal Function by Choline and 4OH-GTS-21 Through α7 Nicotinic Receptors

“…Selective nicotinic ␣7 receptor activation has been shown to exert a neurotrophic function in several systems, including nerve growth factor (NGF)-differentiated PC12 cells that otherwise undergo significant degeneration when serum and NGF are removed (Martin et al 1994). Choline exerted a similar neuroprotective activity in these cells, as well as in sympathetic ganglion cultures that express pharmacologically defined ␣7 nicotinic receptors (Koike et al 1989).…”

Hydroxy Metabolites of the Alzheimer's Drug Candidate 3-[(2,4-Dimethoxy)Benzylidene]-Anabaseine Dihydrochloride (GTS-21): Their Molecular Properties, Interactions with Brain Nicotinic Receptors, and Brain Penetration

“…DMXBA enhances cognitive behavior in aging and nucleus basalis-lesioned mammals, including monkeys (Woodruff-Pak et al, 1994;Arendash et al, 1995;Briggs et al, 1997;Buccafusco and Terry, 2000). It also displays neuroprotective properties (Martin et al, 1994;Kihara et al, 1997;Shimohama et al, 1998). DMXBA did not display significant human toxicity in a phase I clinical trial (Kitagawa et al, 2003).…”

The Structural Basis for GTS-21 Selectivity between Human and Rat Nicotinic α7 Receptors

“…The neuronal ␣7-type nicotinic acetylcholine receptor (nAChR) has been identified as a potential target for the treatment of Alzheimer's disease (Lindstrom, 1997), and 3-(2,4-dimethoxybenzylidene) anabaseine (GTS-21; also called DMXBA), which selectively targets this receptor, has been shown to improve learning and memory in animal models of cholinergic hypofunction (Kem, 2000). This ␣7-selective partial agonist has also been shown to prevent the death of differentiated PC-12 cells that occurs after nerve growth factor removal and the death of cultured primary neurons that occurs after high levels of NMDA receptor activation (Martin et al, 1994;Shimohama et al, 1998). It is interesting that although GTS-21 was able to protect PC-12 cells from the cytotoxic effects of amyloid peptide exposure, it was not able to protect human-derived SK-N-SH cells from the same cytotoxic stress, although the GTS-21 4-hydroxy metabolite, 3-(4-hydroxy,2-methoxybenzylidene)anabaseine (4-OH-GTS-21), was cytoprotective in the same assay (Meyer et al, 1998a).…”