Nicotine decreases beta-amyloid through regulating BACE1 transcription in SH-EP1-α4ß2 nAChR-APP695 cells.

Alzheimer's disease (AD) is a neurodegenerative disorder that affects the elderly population. Deposition of beta-amyloid (Aß) in the brain is a hallmark of AD pathology. In our previous study, we have constructed a cell line expressing human APP695 (hAPP695) in SH-EP1 cells stably transfected with human nicotinic receptor (nAChR) α4 subunit and ß2 subunit gene. In present study, we found that activation of α4ß2 nAChR by nicotine and epibatidine decreased secreted Aß level in the cell line and hippocampal neurons, but had no effects on full-length APP695 and sAPP-α. Nicotine also decreases BACE1 and PSEN1 expression, as well as ERK1 and NFκB P65 subunit expression in the cell line. Furthermore, BACE1 promoter activity is, but PSEN1 not, decreased by nicotine in the cell line. All the results suggest that activation of α4ß2 nAChR decreases Aß through regulating BACE1 transcription by ERK1-NFκB pathway. Additionally, analysis of BACE1 promoter activity by dual-luciferase reporter assay may be useful for drug screening as a high throughput method.

Gelsemine, a principal alkaloid from Gelsemium sempervirens Ait., exhibits potent and specific antinociception in chronic pain by acting at spinal α3 glycine receptors.

The present study examined the antinociceptive effects of gelsemine, the principal alkaloid in Gelsemium sempervirens Ait. A single intrathecal injection of gelsemine produced potent and specific antinociception in formalin-induced tonic pain, bone cancer-induced mechanical allodynia, and spinal nerve ligation-induced painful neuropathy. The antinociception was dose-dependent, with maximal inhibition of 50% to 60% and ED50 values of 0.5 to 0.6 µg. Multiple daily intrathecal injections of gelsemine for 7 days induced no tolerance to antinociception in the rat model of bone cancer pain. Spinal gelsemine was not effective in altering contralateral paw withdrawal thresholds, and had only a slight inhibitory effect on formalin-induced acute nociception. The specific antinociception of gelsemine in chronic pain was blocked dose-dependently by the glycine receptor (GlyR) antagonist strychnine with an apparent ID50 value of 3.8 µg. Gelsemine concentration-dependently displaced H(3)-strychnine binding to the membrane fraction of rat spinal cord homogenates, with a 100% displacement and a Ki of 21.9µM. Gene ablation of the GlyR α3 subunit (α3 GlyR) but not α1 GlyR, by a 7-day intrathecal injection of small interfering RNA (siRNA) targeting α3 GlyR or α1 GlyR, nearly completely prevented gelsemine-induced antinociception in neuropathic pain. Our results demonstrate that gelsemine produces potent and specific antinociception in chronic pain states without induction of apparent tolerance. The results also suggest that gelsemine produces antinociception by activation of spinal α3 glycine receptors, and support the notion that spinal α3 glycine receptors are a potential therapeutic target molecule for the management of chronic pain.