4-Hydroxytamoxifen (Synonyms: Afimoxifene, 4-OHT)

4-hydroxytamoxifen is a major metabolite of tamoxifen and selective estrogen receptor antagonist. It potentiated the protective effects of estradiol against the MA-induced nigrostriatal DA depletion.^[1] 4-Hydroxytamoxifen has the superoxide anion radical-scavenging activity, the antioxidative characteristics of 4-Hydroxytamoxifen can attenuate the MA-induced dopaminergic toxicity.^[4]

In vitro, 4-Hydroxytamoxifen decreased the transcriptional activity of ERRγ by more than 75%, with an EC50 value of 2 μM.^[5] In MPNST cells were treated with 8-12 μM 4-Hydroxytamoxifen after 48 hours, there has a concentration-dependent increase in caspase 3-like enzymatic activity. 4-Hydroxytamoxifen also triggers autophagic death in MPNST cells.^[2] In vitro study it indicated that 10 or 2 µM 4-hydroxytamoxifen abolished the generation of action potentials and repolarized the membrane potential in rat pancreatic beta-cells stimulated by 16 mM glucose. 4-hydroxytamoxifen impairs beta-cell electrical and secretory activity by inhibiting calcium and anion channel currents.^[6]

In vivo experiment it shown that αMHC-MerCreMer mice were treated 20 mg/kg 4-hydroxytamoxifen intraperitoneally for 5 consecutive days, neither cardiac function nor cardiac energetic status in αMHC-MerCreMer mice was disturbed. In addition, the injection of 40 mg/kg 4-hydroxytamoxifen also did not impair cardiac function.^[3] In vivo efficacy test it demonstrated that treatment with 6 µg/0.1 mL/day subcutaneously of 4-Hydroxytamoxifen significantly mitigated MA-induced nigrostriatal DA and DOPAC depletions in both male and female mice.^[4]

References:
[1].Yu L., et al. (2002a) Ovarian hormones do not attenuate methamphetamine-induced dopaminergic neurotoxicity in mice gonadectomized at 4 weeks postpartum. Neuroendocrinology 75, 282–287.
[2].Kohli L, et al. 4-Hydroxytamoxifen induces autophagic death through K-Ras degradation. Cancer Res. 2013 Jul 15;73(14):4395-405.
[3].Heinen A, et al. 4-hydroxytamoxifen does not deteriorate cardiac function in cardiomyocyte-specific MerCreMer transgenic mice. Basic Res Cardiol. 2021 Feb 5;116(1):8.
[4].Kuo YM, et al. 4-Hydroxytamoxifen attenuates methamphetamine-induced nigrostriatal dopaminergic toxicity in intact and gonadetomized mice. J Neurochem. 2003 Dec;87(6):1436-43.
[5].Coward P, et al. 4-Hydroxytamoxifen binds to and deactivates the estrogen-related receptor gamma. Proc Natl Acad Sci U S A. 2001 Jul 17;98(15):8880-4.
[6].Best L. Inhibition of glucose-induced electrical activity by 4-hydroxytamoxifen in rat pancreatic beta-cells. Cell Signal. 2002 Jan;14(1):69-73.