No abstract

Parkinson's disease is characterized by the mesencephalic dopaminergic neuronal loss, possibly by apoptosis, and the prevalence is higher in males than in females. The estrogen receptor (ER) subtype in the mesencephalon is exclusively ER beta, a recently cloned novel subtype. Bound with estradiol, it enhances gene transcription through the estrogen response element (ERE) or inhibits it through the activator protein-1 (AP-1) site. We demonstrated that 17beta-estradiol provided protection against nigral neuronal apoptosis caused by exposure to either bleomycin sulfate (BLM) or buthionine sulfoximine (BSO). BLM and BSO-induced nigral apoptosis was blocked by inhibitors for caspase-3 or c-Jun/AP-1. The antiapoptotic effect by estradiol was blocked by ICI 182,780, an antagonist for ER, but not by a synthesized peptide that inhibits binding of the ER to the ERE. Estradiol had no effects on caspase-3 activation and c-Jun NH(2)-terminal kinase (JNK), which were activated by BLM. It also suppressed apoptosis by serum deprivation, which was independent of caspase-3 activation. Therefore, the antiapoptotic neuroprotection by estradiol is mediated by transcription through AP-1 site downstream from JNK and caspase-3 activation. Furthermore, 17alpha-estradiol, a stereoisomer without female hormone activity, also provided an antiapoptotic effect. Therefore, the antiapoptotic effect is independent of female hormone activity.

No abstract

The conditions for obtaining the electrocapillary curves of the dilauroylphosphatidylcholine (DLPC) monolayer formed at the polarized nitrobenzene–water interface have been studied using the pendant drop method. To facilitate the measurement, the system for the interfacial tension measurement, including the computer software for the data handling, has been developed based on digital image processing of the video image of a pendant drop. The 95% confidence interval of the measured interfacial tension value was ±0.06 mN m−1. The time required to measure an electrocapillary curve with 30 points was 30 min, while the time necessary to convert the image data to the interfacial tension was 1 min. The potential drop across the monolayer has been demonstrated to influence the stability of the monolayer strongly. The DLPC markedly lowered the interfacial tension by forming a stable monolayer when the interface was polarized so that the aqueous phase has a negative potential with respect to the nitrobenzene phase. On the other hand, when the aqueous phase became positively polarized, the adsorbed DLPC molecules started to desorb from the interface, giving rise to the disruption of the monolayer. The electrocapillary curves only in the former potential range were found to be thermodynamically meaningful.

Glial cell line-derived neurotrophic factor (GDNF) provides neuroprotection, but its neuroprotective mechanism has not been resolved. We investigated the neuroprotective mechanism of GDNF using primary culture of the rat mesencephalon. Bleomycin sulfate (BLM) and L-buthionine-[S,R]-sulfoximine (BSO) caused apoptosis in both dopaminergic and nondopaminergic neurons, as revealed by the presence of chromatin condensation, and positive staining by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL). GDNF preincubation blocked the neurotoxicity and reduced the number of the TUNEL-positive cells caused by BLM and BSO exposure. In contrast, GDNF did not provide neuroprotection against glutamate toxicity, which was not accompanied by these apoptotic features. The neuroprotection was mediated by phosphatidylinositol 3-kinase, an effector downstream from c-Ret, because it was blocked by LY294002. GDNF pretreatment caused up-regulation of Bcl-2 and Bcl-x. Furthermore, GDNF suppressed oxygen radical accumulation caused by BLM. Apoptosis induced by BLM and BSO was blocked by a caspase-3 inhibitor. Caspase-3 activity was elevated by BLM and suppressed by GDNF pretreatment. These findings indicate that GDNF has no effect on necrosis but exerts protection against apoptosis by activation of phosphatidylinositol 3-kinase and the subsequent up-regulation of Bcl-2 and Bcl-x, which suppresses accumulation of oxygen radicals followed by caspase-3 activation.