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Characterization of the acetylcholine-reducing effect of the amyloid-beta peptide in mouse SN56 cells
1Department of Pathology and Laboratory Medicine, Boston University School of Medicine, MA 02118, USA.
Abstract:
We previously reported that the amyloid-beta protein (Abeta) reduces the synthesis of acetylcholine (ACh) in a mouse septal cell line, SN56, without causing death of the cells. Here, we report that the ACh-reducing effect of either Abeta 1-28 or Abeta 1-42 (100 nM; 48 h) in SN56 cells can be prevented by a co-treatment with the tyrosine kinase inhibitors, genistein (75 microM) and tyrphostin A25 (50 microM). Treatment of the cells with either of these inhibitors alone increased ACh levels. An enhancement of the cellular ACh content was also obtained with aphidicolin, a compound which inhibits DNA synthesis. However, co-treatment of the cells for 48 h with aphidicolin (500 nM) and Abeta 1-42 (100 nM) did not prevent the reduction in ACh levels caused by the peptide. Furthermore, this effect could not prevented by a pre-treatment with vitamin E (50 microg/ml). These results suggest that the ACh-reducing effect of Abeta in SN56 cells is dependent on tyrosine phosphorylation, but is not dependent on DNA synthesis and may not be mediated by free radicals.
Insights
Amyloid-beta protein (Abeta) reduces acetylcholine (ACh) synthesis in mouse cells. This effect is blocked by tyrosine kinase inhibitors, suggesting a role for tyrosine phosphorylation, not DNA synthesis or free radicals.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Amyloid-beta protein (Abeta) is implicated in neurodegenerative diseases.
- Previous studies showed Abeta reduces acetylcholine (ACh) synthesis in SN56 cells without causing cell death.
Purpose of the Study:
- To investigate the mechanisms underlying Abeta-induced reduction of ACh synthesis in SN56 cells.
- To determine if tyrosine phosphorylation, DNA synthesis, or free radicals mediate this effect.
Main Methods:
- SN56 cells were treated with Abeta 1-28 or Abeta 1-42.
- Co-treatments included tyrosine kinase inhibitors (genistein, tyrphostin A25), aphidicolin (DNA synthesis inhibitor), and vitamin E.
- Acetylcholine (ACh) levels were measured.
Main Results:
- Abeta 1-28 and Abeta 1-42 reduced ACh synthesis in SN56 cells.
- Genistein and tyrphostin A25 prevented the Abeta-induced reduction in ACh levels.
- Aphidicolin and vitamin E did not prevent the Abeta-induced reduction in ACh levels.
- Tyrosine kinase inhibitors alone increased ACh levels.
Conclusions:
- The reduction of ACh synthesis by Abeta in SN56 cells is dependent on tyrosine phosphorylation.
- This effect is independent of DNA synthesis and likely not mediated by free radicals.