Biol. Pharm. Bull. 29(7) 1335—1338 (2006)

sis, protein folding, protein trafficking and intracellular Ca . The exposure of stress which interferes with the functions of the endoplasmic reticulum (ER) causes the accumulation of unfolded protein in the ER lumen. Under the these conditions, termed ER stress, a signal transduction pathway, which is called the unfolded protein response (UPR), is activated to increase the expression of ER stress genes such as chaperon protein genes. This pathway is activated by exposure to ER stressors such as tunicamycin (a glycosylation inhibitor) and thapsigargin, which perturb the calcium in the ER, and so on. The UPR systems such as over-expressions of Bip/GRP78, the inhibition of protein translation via phosphorylation of the a-subunit of translation initiation factor 2 (elF2a) and the activation of ubiquitin-proteasome system usually rescues the cells from any damage by ER-stress. However, prolonged ER stress may finally cause cell death by overcoming the threshold ability of UPR. Recently, ER stress has received growing attention because ER stress-mediated cell death has been linked to the pathogenesis of several neurodegenerative disorders such as Alzheimer’s disease and the obesity connection with type 2 diabetes. Such diseases have also been correlated with the overproduction of various reactive oxygen species (ROS) that are known to induce lipid peroxidation resulting in damage to membranes, proteins and DNA. Recently it has been demonstrated that accumulation of protein within the lumen of the ER causes accunulation of ROS and cell death. Thus anti-oxidative approach might rescue the cells from the disorder via ER stresses. We have previously synthesized several natural compounds and found that some of them had anti-oxidative or neurotrophic activities. Since it has been suggested that ER disorder is closely linked with neuronal dysfunction, these compounds are anticipated to have specific activities for overcoming ER stresses. Thus, in this manuscript, we screened these compounds on the basis of the neuroprotective effect of tunicamycin-mediated cell damage, which is used as an ER stress model, using IMR32 neuroblastoma cells.