Reduced levels of Aβ 40 and Aβ 42 in brains of smoking controls and Alzheimer's patients

Abstract

The effects of nicotine on levels of Aβ 40 and Aβ 42 and nicotinic receptor binding sites were studied in brains from nonsmoking and smoking patients with Alzheimer's disease (AD) and aged-matched controls. The levels of soluble and insoluble Aβ 40 and Aβ 42 in frontal cortex and Aβ 40 in temporal cortex and hippocampus were significantly decreased in smoking AD patients compared to nonsmokers with AD. In smoking controls the levels of soluble and insoluble Aβ 40 and Aβ 42 in the frontal and temporal cortex were significantly lower than in nonsmoking controls. The binding of [ 3H]cytisine in temporal cortex was significantly increased in smokers with AD compared to nonsmokers with AD. In smoking controls [ 3H]cytisine and [ 3H]epibatidine binding were significantly increased from 1.5- to 2-fold compared to nonsmoking controls whereas binding sites for [ 125I]α-bungarotoxin was less up-regulated. These results indicate that selective nicotinic receptor agonists may be a novel protective therapy in AD by reducing Aβ levels as well as the loss of nicotinic receptors in AD brain.