No abstract

Trials over two years were conducted using 1389 sweetpotato (Ipomoea batatas L.) genotypes collected from all over the world to characterize the polyphenolic composition in sweetpotato leaves. Wide variation was observed in relation to their total and individual leaf polyphenolic constituents. In all genotypes studied, the total polyphenol contents of sweetpotato leaf ranged from 1.42 to 17.1 g/100 g dry weight. The six different polyphenolic compounds were identified and quantified by NMR, FABMS, and RPHPLC analysis procedures. This is the first report of polyphenolic compositions in sweetpotato leaves. The relative levels of polyphenolic acids in sweetpotato leaves were as follows: 3,5-di-O-caffeoylquinic acid > 4,5-di-O-caffeoylquinic acid > chlorogenic acid (3-O-caffeoylquinic acid) > 3,4-di-O-caffeoylquinic acid > 3,4,5-tri-O-caffeoylquinic acid > caffeic acid. The highest 3,4,5-tri-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid occurred at 221 and 1183.30 mg/100 g dry weight, respectively.

The c-Jun N-terminal protein kinase (JNK) signaling pathway is implicated in neuronal apoptosis. The mechanism by which activated JNK induces neuronal apoptosis is strongly linked to mitochondrial apoptogenic proteins, although the molecular machinery downstream of JNK has not been precisely elucidated. Our study examined the relevance of proapoptotic Bcl-2 family members in JNKmediated apoptosis after transient focal cerebral ischemia (tFCI), which, when induced by 60 min of middle cerebral artery (

A cDNA encoding the homolog of the human pre-Bcell colony-enhancing factor (PBEF), a cytokine-like secreted protein, was isolated from a rat cDNA library. This protein existed in both the cytoplasm and nucleus of the cells, and the amount was higher in the cytoplasm than in the nucleus of proliferating PC-12 and Swiss 3T3 cells but higher in the nucleus than in the cytoplasm of the PC-12 cells treated with nerve growth factor and the 3T3 cells grown to a con£uent state. Thus, the so-called PBEF is not a cytokine-like secreted protein but an intracellular protein associated with the cell cycle.

No abstract

The endoplasmic reticulum (ER), which plays a role in apoptosis, is susceptible to oxidative stress. Because superoxide is produced in the brain after ischemia/reperfusion, oxidative injury to this organelle may be implicated in ischemic neuronal cell death. Activating transcription factor-4 (ATF-4) and C/EBP-homologous protein (CHOP), both of which are involved in apoptosis, are induced by severe ER stress. Using wild-type and human copper/zinc superoxide dismutase transgenic rats, we observed induction of these molecules in the brain after global cerebral ischemia and compared them with neuronal degeneration. In ischemic, wild-type brains, expression of ATF-4 and CHOP was increased in the hippocampal CA1 neurons that would later undergo apoptosis. Transgenic rats had a mild increase in ATF-4 and CHOP and minimal neuronal degeneration, indicating that superoxide was involved in ER stress-induced cell death. We further confirmed attenuation on induction of these molecules in transgenic mouse brains after focal ischemia. When superoxide was visualized with ethidium, signals for ATF-4 and superoxide overlapped in the same cells. Moreover, lipids in the ER were robustly peroxidized by ischemia but were attenuated in transgenic animals. This indicates that superoxide attacked and damaged the ER, and that oxidative ER damage is implicated in ischemic neuronal cell death.

The Akt signaling pathway contributes to regulation of apoptosis after a variety of cell death stimuli. A novel proline-rich Akt substrate (PRAS) was recently detected and found to be involved in apoptosis. In our study, Akt activation was modulated by growth factors, and treatment with nerve growth factor (NGF) reduced apoptotic cell death after ischemic injury. However, the role of the PRAS pathway in apoptotic neuronal cell death after ischemia remains unknown. Phosphorylated PRAS (pPRAS) and the binding of pPRAS/phosphorylated Akt (pPRAS/pAkt) to 14-3-3 (pPRAS/14-3-3) were detected, and their expression transiently decreased in mouse brains after transient focal cerebral ischemia (tFCI). Liposome-mediated pPRAS cDNA transfection induced overexpression of pPRAS, promoted pPRAS/14-3-3, and inhibited apoptotic neuronal cell death after tFCI. The expression of pPRAS, pPRAS/pAkt, and pPRAS/14-3-3 increased in NGF-treated mice but decreased with inhibition of phosphatidylinositol-3 kinase and the NGF receptor after tFCI. These results suggest that PRAS phosphorylation and its interaction with pAkt and 14-3-3 might play an important role in neuroprotection mediated by NGF in apoptotic neuronal cell death after tFCI.

Although the endoplasmic reticulum (ER) is implicated in neuronal degeneration in some situations, its role in delayed neuronal cell death (DND) after ischemia remains uncertain. The authors speculated that ER stress is involved in DND, that it is reduced by ischemic preconditioning, and that ER stress reduction by preconditioning is due to ER molecular chaperone induction. The phosphorylation status of eukaryotic initiation factor 2alpha (eIF2alpha) and RNA-dependent protein kinase-like ER eIF2alpha kinase (PERK) was investigated in the rat hippocampus after ischemia with and without preconditioning. PERK is phosphorylated by ER stress, which phosphorylates eIF2alpha. To investigate the role of ER molecular chaperones in preconditioning, the authors examined GRP78 and GRP94 expression, both of which are ER chaperones that inhibit PERK phosphorylation, and compared their induction and ischemic tolerance time windows. Phosphorylation of eIF2alpha and PERK was confirmed after severe ischemia but was inhibited by preconditioning. After preconditioning, GRP78 was increased in the brain with a peak at 2 days, which corresponded with the ischemic tolerance time window. Immunoprecipitation and double staining demonstrated involvement of GRP78 in prevention of PERK phosphorylation. These results suggest that GRP78 induced by preconditioning may reduce ER stress and eventual DND after ischemia.