Positive allosteric modulation of alpha7 neuronal nicotinic acetylcholine receptors: lack of cytotoxicity in PC12 cells and rat primary cortical neurons.
OBJECTIVE
alpha7-Nicotinic acetylcholine receptors (alpha7 nAChRs) play an important role in cognitive function. Positive allosteric modulators (PAMs) amplify effects of alpha7 nAChR agonist and could provide an approach for treatment of cognitive deficits in neuropsychiatric diseases. PAMs can either predominantly affect the apparent peak current response (type I) or increase both the apparent peak current response and duration of channel opening, due to prolonged desensitization (type II). The delay of receptor desensitization by type II PAMs raises the possibility of Ca2+-induced toxicity through prolonged activation of alpha7 nAChRs. The present study addresses whether type I and II PAMs exhibit different cytotoxicity profiles.


METHODS
The present studies evaluated cytotoxic effects of type I PAM [N-(4-chlorophenyl)]-alpha-[(4-chlorophenyl)-aminomethylene]-3-methyl-5-isoxazoleacet-amide (CCMI) and type II PAM 1-[5-chloro-2,4-dimethoxy-phenyl]-3-[5-methyl-isoxazol-3-yl]-urea (PNU-120596), or 4-[5-(4chloro-phenyl)-2-methyl-3-propionyl-pyrrol-1-yl]-benzenesulphonamide (A-867744). The studies used cultures of PC12 cells and primary cultures of rat cortical neuronal cells.


RESULTS
Our results showed that neither type I nor type II PAMs had any detrimental effect on cell integrity or cell viability. In particular, type II PAMs did not affect neuron number and neurite outgrowth under conditions when alpha7 nAChR activity was measured by Ca2+ influx and extracellular signal-regulated kinases 1 and 2 phosphorylation, following exposure to alpha7 nAChR agonists.


CONCLUSIONS
This study demonstrated that both type I and type II alpha7 nAChR selective PAMs, although exhibiting differential electrophysiological profiles, did not exert cytotoxic effects in cells endogenously expressing alpha7 nAChRs.
Hu
Min
M
Neuroscience Research, Global Pharmaceutical Research & Development, Abbott Laboratories, Abbott Park, Illinois 60064-6125, USA.
Gopalakrishnan
Murali
M
Li
Jinhe
J
D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004594:Electrophysiology; D007555:Isoxazoles / Q000633:toxicity*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016501:Neurites / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018722:Nicotinic Agonists / Q000633:toxicity; D016716:PC12 Cells; D010671:Phenylurea Compounds / Q000633:toxicity*; D010766:Phosphorylation / Q000187:drug effects; D011758:Pyrroles / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000378:metabolism; D013449:Sulfonamides / Q000633:toxicity*; D064569:alpha7 Nicotinic Acetylcholine Receptor; D000096926:Benzenesulfonamides
D002118:Calcium; D007555:Isoxazoles; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D018722:Nicotinic Agonists; D010671:Phenylurea Compounds; D011758:Pyrroles; D011978:Receptors, Nicotinic; D013449:Sulfonamides; D064569:alpha7 Nicotinic Acetylcholine Receptor; C547642:(N-(4-chlorophenyl))-alpha-((4-chlorophenyl)-aminomethylene)-3-methyl-5-isoxazoleacet-amide; C508388:1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-methylisoxazol-3-yl)urea; C542089:4-(5-(4-chlorophenyl)-2-methyl-3-propionyl-1H-pyrrol-1-yl)benzenesulfonamide; D000096926:Benzenesulfonamides; C579165:Chrna7 protein, rat