1-Benzyl-1,2,3,4-tetrahydroisoquinoline binds with tubulin beta, a substrate of parkin, and reduces its polyubiquitination.

Substances that mimic the actions of causative gene products of familial Parkinson's disease (PD) are candidate as causative agents of idiopathic PD. 1-Benzyl-1,2,3,4-tetrahydroisoquinoline (1BnTIQ), an endogenous neurotoxin, is present at three times higher levels in CSF of PD patients than in CSF of control subjects. However, the mechanism of 1BnTIQ's neurotoxicity is unclear. In this study, we tried to identify 1BnTIQ-binding proteins by using a diazido-functionalized 1BnTIQ analog, 1-(3-azido-5-azidomethylbenzyl)-1,2,3,4-tetrahydroisoquinoline, designed and synthesized as a probe for radioisotope-free photoaffinity labeling. One major photolabeled protein identified using this probe was tubulin beta, which has been reported to be a substrate of parkin, a ubiquitin E3 ligase and a causative gene product of familial PD. Loss of function mutation of parkin is reported to result in loss of tubulin beta ubiquitination. Therefore, we examined the effect of 1BnTIQ on ubiquitination of tubulin beta. The polyubiquitinated tubulin beta level in human neuroblastoma SH-SY5Y cells was reduced in the presence of 1BnTIQ, even at concentrations as low as those detected in parkinsonian CSF. In vitro ubiquitination assay gave similar results. It is suggested that 1BnTIQ has the same effect on tubulin ubiquitination as does mutant parkin in familial PD. Taken together, substances which reduce polyubiquitination of tubulin such as 1BnTIQ are supposed to be candidates of etiological factors of PD.

Comparative study of the endocrine-disrupting activity of bisphenol A and 19 related compounds.

The endocrine-disrupting activities of bisphenol A (BPA) and 19 related compounds were comparatively examined by means of different in vitro and in vivo reporter assays. BPA and some related compounds exhibited estrogenic activity in human breast cancer cell line MCF-7, but there were remarkable differences in activity. Tetrachlorobisphenol A (TCBPA) showed the highest activity, followed by bisphenol B, BPA, and tetramethylbisphenol A (TMBPA); 2,2-bis(4-hydroxyphenyl)-1-propanol, 1,1-bis(4-hydroxyphenyl)propionic acid and 2,2-diphenylpropane showed little or no activity. Anti-estrogenic activity against 17beta-estradiol was observed with TMBPA and tetrabromobisphenol A (TBBPA). TCBPA, TBBPA, and BPA gave positive responses in the in vivo uterotrophic assay using ovariectomized mice. In contrast, BPA and some related compounds showed significant inhibitory effects on the androgenic activity of 5alpha-dihydrotestosterone in mouse fibroblast cell line NIH3T3. TMBPA showed the highest antagonistic activity, followed by bisphenol AF, bisphenol AD, bisphenol B, and BPA. However, TBBPA, TCBPA, and 2,2-diphenylpropane were inactive. TBBPA, TCBPA, TMBPA, and 3,3'-dimethylbisphenol A exhibited significant thyroid hormonal activity towards rat pituitary cell line GH3, which releases growth hormone in a thyroid hormone-dependent manner. However, BPA and other derivatives did not show such activity. The results suggest that the 4-hydroxyl group of the A-phenyl ring and the B-phenyl ring of BPA derivatives are required for these hormonal activities, and substituents at the 3,5-positions of the phenyl rings and the bridging alkyl moiety markedly influence the activities.

Estrogenic activity of an antioxidant, nordihydroguaiaretic acid (NDGA).

Nordihydroguaiaretic acid (NDGA), an antioxidant which has been used to preserve oils and foods, has recently become well known as a putative anticancer agent. Although NDGA is a member of the lignan family, its hormonal activities have not been well investigated. Here we show that NDGA has in vitro estrogenic activity in the ERE-luc reporter system using NIH3T3 cells, and in the estrogen-responsive cell growth assay in a pituitary cell line, MtT/E-2. Uterotropic assay in rats indicated that NDGA has estrogenic activity in vivo as well, albeit weak. Interestingly it preferentially induced ERalpha mediated ERE-luc activity, although it showed similar binding affinity to both ERalpha and ERbeta. With ERbeta, on the other hand, NDGA showed only weak agonistic action, and antagonized the estrogenic action of 17beta-estradiol when the two were coadministered. These data suggest that NDGA is an estrogenic agonist for ERalpha : ERE transcription and a mixed agonist/antagonist for ERbeta mediated ERE transactivation.