C57 mice

The use of mice in these experiments was in accordance with the guidelines established by the National Institutes of Health and the Animal Care and Use Committee of University of Southern California. Both male and female mice were used. C57 mice were purchased from The Jackson Laboratory. Generation of Arr1^−/− (Xu et al., 1997 (link)), Arr4^Arr1−/− (Chan et al., 2007 (link)), and Arr1-3A^Arr1−/− (Song et al., 2009 (link); Samaranayake et al., 2018 (link)) transgenic mice and their genotyping protocols were previously described. C57 mice and Arr1-3A transgenic mice were maintained at 12 h light/12 h dark cycle, whereas Arr1^−/− and Arr4^Arr1−/− transgenic mice were born and raised in darkness to avoid light-induced retinal degeneration (Chen et al., 1999 (link)). Mice were dark-adapted overnight, and retinae were dissected under infrared light for the dark condition. For light exposure, pupils of dark-adapted mice were dilated with 0.5% tropicamide and 2.5% phenylephrine hydrochloride ophthalmic solutions (Akorn) before they were placed in a clear cage and exposed to 5000 lux light for 15 min. Retinae were immediately dissected (T = 0), or mice were returned to darkness and their retinae were isolated under infrared light after the indicated times. Retinae were snap frozen in liquid N₂ and stored in −80°C until further use.

Tissue culture media was from Gibco (ThermoFisher), fetal bovine serum was from Hyclone (Logan, UT), and culture‐ware was from Falcon. Thirty percent H₂O₂ was from Mallinckrodt. Synthesis of the PrC‐210 HCl aminothiol is described separately.4, 9 PrC‐210 HCl crystals are stored under a nitrogen atmosphere at −20°C, and even with routine thawing, use, and re‐storage, crystalline PrC‐210 is completely stable for >4 years by mass spectrometry analysis. Other chemical reagents were obtained from Sigma Aldrich (St. Louis, MO). C57 mice were from Jackson Laboratory (Bar Harbor, ME). Mice were maintained on 12‐hour light/dark cycle and provided ad lib water and food. All animal procedures were conducted according to a protocol (#M05714) approved by the University of Wisconsin Institutional Animal Care and Use Committee.

All animal protocols and procedures were performed in compliance with the recommendations of the NIH “Guide for the Care and Use of Laboratory Animals” and were approved by the Research Ethics Committee (REC) on the Use of Live Animals in Teaching and Research of Hong Kong Baptist University (REC/19–20/0199). C57 mice were obtained from the Jackson Laboratory (Bar Harbor, ME, USA). Homozygous human P301S tau transgenic Thy1-hTau.P301S mice were a generous gift from Dr. Michael Goedert [23 (link)]. They were housed in a pathogen-free facility under a 12-h light, 12-h dark cycle, with food and water provided ad libitum from birth. The mice were randomly divided into four equal groups according to the tetrandrine dose (0 mg/kg, 2.5 mg/kg, 5 mg/kg, and 10 mg/kg). Tetrandrine or saline was delivered by intraperitoneal injection every two days starting when the mice were two months old. Treatment efficacy was assayed when the mice reached four months of age. Behavioural experiments, contextual fear conditioning (CFC), novel object recognition (NOR), hippocampal long-term potentiation (LTP) measurement, immunohistochemistry for tau NFTs and Western blot analyses for hyperphosphorylated tau aggregates were performed.