Neuroprotective effects of a novel non-receptor-binding estrogen analogue: in vitro and in vivo analysis.
OBJECTIVE
Although estrogens are neuroprotective, hormonal effects limit their clinical application. Estrogen analogues with neuroprotective function but lacking hormonal properties would be more attractive. The present study was undertaken to determine the neuroprotective effects of a novel 2-adamantyl estrogen analogue, ZYC3.


METHODS
Cytotoxicity was induced in HT-22 cells by 10 mmol/L glutamate. 17beta-Estradiol (E2) or ZYC3 was added immediately before the exposure to glutamate. Cell viability was determined by calcein assay. The binding of E2 and ZYC3 to human alpha (ERalpha) and beta (ERbeta) estrogen receptors was determined by ligand competition binding assay. Ischemia/reperfusion injury was induced by temporary middle cerebral artery occlusion (MCAO). E2 or ZYC3 (100 microg/kg) was administered 2 hours or immediately before MCAO, respectively. Infarct volume was determined by 2,3,5-triphenyltetrazolium chloride staining. Cerebral blood flow was recorded during and within 30 minutes after MCAO by a hydrogen clearance method.


RESULTS
ZYC3 significantly decreased toxicity of glutamate with a potency 10-fold that of E2. ZYC3 did not bind to either ERalpha or ERbeta. Infarct volume was significantly reduced to 122.4+/-17.6 and 83.1+/-19.3 mm(3) in E2 and ZYC3 groups, respectively, compared with 252.6+/-15.6 mm(3) in the ovariectomized group. During MCAO, both E2 and ZYC3 significantly increased cerebral blood flow in the nonischemic side, while no significant differences were found in the ischemic side. However, E2 and ZYC3 significantly increased cerebral blood flow in both sides within 30 minutes after reperfusion.


CONCLUSIONS
Our study shows that ZYC3, a non-receptor-binding estrogen analogue, possesses both neuroprotective and vasoactive effects, which offers the possibility of clinical application for stroke without the side effects of estrogens. It also suggests that both the neuroprotective and vasoactive effects of estrogen are receptor independent.
D000218:Adamantane / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001783:Blood Flow Velocity / Q000187:drug effects; D001921:Brain / Q000098:blood supply / Q000187:drug effects / Q000473:pathology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers; D004958:Estradiol / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D045166:Estradiol Congeners / Q000737:chemistry / Q000494:pharmacology*; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004970:Estrone / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D018698:Glutamic Acid / Q000633:toxicity; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000188:drug therapy / Q000473:pathology; D008024:Ligands; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000737:chemistry* / Q000378:metabolism
C468278:2-adamantylestra-1,3,5(10)-trien-3-ol-17-one; D004337:Drug Carriers; D045166:Estradiol Congeners; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D008024:Ligands; D018696:Neuroprotective Agents; D011960:Receptors, Estrogen; D004970:Estrone; D018698:Glutamic Acid; D004958:Estradiol; D000218:Adamantane