Involvement of nicotinic acetylcholine receptors in amyloid β-fragment-induced intracellular Ca(2+) elevation in cultured rat cortical neurons.
The amyloid β-protein (Aβ)-induced disturbance of intracellular calcium homeostasis has been regarded as the final route whereby Aβ insults neurons. However, the mechanism of Aβ-induced Ca(2+) overloading is still unclear so far. Especially, it remains to be clarified whether nicotinic acetylcholine receptors (nAChRs) are involved in the Aβ-induced elevation of intracellular calcium concentration ([Ca(2+)](i)). In the present study, we observed the effects of Aβ fragments 25-35 (Aβ(25-35)) and 31-35 (Aβ(31-35)) on [Ca(2+)](i) in primary cultured rat cortical neurons using laser-scanning confocal calcium imaging technique, and investigated its probable cholinergic mechanism. The results showed that: (1) Both Aβ(25-35) and Aβ(31-35) induced similar and significant [Ca(2+)](i) elevation in a concentration-dependent manner, and no statistical difference was found between the effects of both peptides; (2) The reverse peptide of Aβ(31-35), i.e. Aβ(35-31), had no effect on [Ca(2+)](i) elevation; (3) Mecamylamine (MCA), a non-specific nAChRs antagonist, significantly and dose-dependently blocked the [Ca(2+)](i) elevation induced by Aβ(25-35) or Aβ(31-35) (4) Dihydro-β-erythroidine (D-β-E), a specific α4β2 subtype nAChRs antagonist, also significantly inhibited the [Ca(2+)](i) elevation induced by Aβ(25-35) and Aβ(31-35), but the effect was weaker than the effect of MCA at the same concentration. These results indicate that Aβ(31-35) may be a shorter active sequence in full length of Aβ molecule, and the overactivation of nAChRs, including α4β2 subtype, may be, at least partly, responsible for the Aβ-induced elevation of [Ca(2+)](i) in cultured rat cortical neurons. Thus, the present study suggests a new potential target of Aβ in the brain, and provides a new insight into the mechanisms by which Aβ impairs the cognitive function in Alzheimer's disease.
Wu
Mei-Na
MN
Department of Neurobiology, the First Hospital, Shanxi Medical University, Taiyuan 030001, China.
Li
Xin-Yi
XY
Guo
Fen
F
Qi
Jin-Shun
JS
D016229:Amyloid beta-Peptides / Q000737:chemistry*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D009474:Neurons / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry*; D051381:Rats; D011978:Receptors, Nicotinic / Q000378:metabolism*
D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D011978:Receptors, Nicotinic; C074636:amyloid beta-protein (25-35); D002118:Calcium