beta-Amyloid-specific upregulation of stearoyl coenzyme A desaturase-1 in macrophages.

beta-Amyloid peptide (A beta), a major component of senile plaques, the formation of which is characteristic of Alzheimer's disease (AD), is believed to induce inflammation of the brain mediated by microglia, leading to neuronal cell loss. In this study, we performed an oligonucleotide microarray analysis to investigate the molecular events underlying the A beta-induced activation of macrophages and its specific suppression by the A beta-specific-macrophage-activation inhibitor, RS-1178. Of the approximately 36,000 genes and expressed sequence tags analyzed, eight genes were specifically and significantly upregulated by a treatment with interferon gamma (IFN gamma) and A beta compared to a treatment with IFN gamma alone (p<0.002). We found that the gene for a well-characterized lipogenetic enzyme, stearoyl coenzyme A desaturase-1 (SCD-1), was specifically upregulated by A beta treatment and was suppressed to basal levels by RS-1178. Although the underlying mechanisms remain unknown, our results suggest the presence of a link between AD and SCD-1.

A novel compound, RS-1178, specifically inhibits neuronal cell death mediated by beta-amyloid-induced macrophage activation in vitro.

beta-Amyloid peptide (Abeta), a major component of senile plaques, the formation of which is characteristic of Alzheimer's disease (AD), is believed to induce inflammation in the brain leading to cell loss and cognitive decline. Accumulating evidence shows Abeta activates microglia, which play the role of the brain's immune system, and mediates inflammatory responses in the brain. Thus, a compound inhibiting Abeta-induced activation of microglia may lead to a novel therapy for AD. However, the compound should not inhibit natural immune responses during events such as bacterial infections. We investigated the effect of a synthesized compound, 7,8-dihydro-5-methyl-8-(1-phenylethyl)-6H-pyrrolo [3,2-e] [1,2,4] triazolo [1,5-a] pyrimidine (RS-1178) on macrophage activation induced by various stimulants. The activation of macrophages was determined by nitric oxide or tumor necrosis factor alpha production. RS-1178 inhibited Abeta-induced macrophage activation but did not inhibit zymosan A- nor lipopolysaccharide (LPS)-induced macrophage activation. Moreover, RS-1178 attenuated neurotoxicity due to Abeta-induced macrophage activation in neuron-macrophage co-cultures but not neurotoxicity due to zymosan A- or LPS-induced macrophage activation. In conclusion, RS-1178 showed a specific inhibitory effect on Abeta-induced macrophage activation. Although the exact mechanisms of this effect remain unknown, RS-1178 may provide a novel therapy for AD.

Troglitazone inhibits both post-glutamate neurotoxicity and low-potassium-induced apoptosis in cerebellar granule neurons.

Both excitotoxicity and apoptosis contribute to neuronal loss in various neurodegenerative diseases such as Alzheimer's disease as well as stroke, and a drug inhibiting both types of cell death may lead to practical treatment for these diseases. Post-treatment with troglitazone, a potent and specific activator of peroxisome proliferator-activated receptor (PPAR)-gamma attenuated the cell death of cerebellar granule neurons, triggered by glutamate exposure. The inhibitory effect of troglitazone against glutamate excitotoxicity, in vitro, was observed even when added 2.5 h after the end of glutamate exposure, a time when glutamate antagonists are no longer neuroprotective. However, troglitazone did not block the glutamate-induced elevation of calcium influx, suggesting that troglitazone interfered with downstream consequences of excitotoxic glutamate receptor overactivation. In addition, troglitazone also suppressed low-potassium-induced apoptosis in cerebellar granule neurons in a phosphatidylinositol 3-kinase independent manner. In conclusion, although the mechanisms of troglitazone's neuroprotective effects are unknown, the post-treatment-neuroprotective effect and the dual-inhibitory-activity against both excitotoxicity and apoptosis may provide a novel therapy for various neurodegenerative diseases.