Salidroside directly activates HSC70, revealing a new role for HSC70 in BDNF signalling and neurogenesis after cerebral ischemia

Abstract

Salidroside, a principal bioactive component of Rhodiola crenulata, is neuroprotective across a wide time window in stroke models. We investigated whether salidroside induced neurogenesis after cerebral ischemia and aimed to identify its primary molecular targets. Rats, subjected to transient 2 h of middle cerebral artery occlusion (MCAO), received intraperitoneal vehicle or salidroside ± intracerebroventricular HSC70 inhibitor VER155008 or TrkB inhibitor ANA‐12 for up to 7 days. MRI, behavioural tests, immunofluorescent staining and western blotting measured effects of salidroside. Reverse virtual docking and enzymatic assays assessed interaction of salidroside with purified recombinant HSC70. Salidroside dose‐dependently decreased cerebral infarct volumes and neurological deficits, with maximal effects by 50 mg/kg/day. This dose also improved performance in beam balance and Morris water maze tests. Salidroside significantly increased BrdU+/nestin+, BrdU+/DCX+, BrdU+/NeuN+, BrdU−/NeuN+ and BDNF+ cells in the peri‐infarct cortex, with less effect in striatum and no significant effect in the subventricular zone. Salidroside was predicted to bind with HSC70. Salidroside dose‐dependently increased HSC70 ATPase and HSC70‐dependent luciferase activities, but it did not activate HSP70. HSC70 immunoreactivity concentrated in the peri‐infarct cortex and was unchanged by salidroside. However, VER155008 prevented salidroside‐dependent increases of neurogenesis, BrdU−/NeuN+ cells and BDNF+ cells in peri‐infarct cortex. Salidroside also increased BDNF protein and p‐TrkB/TrkB ratio in ischemic brain, changes prevented by VER155008 and ANA‐12, respectively. Additionally, ANA‐12 blocked salidroside‐dependent neurogenesis and increased BrdU−/NeuN+ cells in the peri‐infarct cortex. Salidroside directly activates HSC70, thereby stimulating neurogenesis and neuroprotection via BDNF/TrkB signalling after MCAO. Salidroside and similar activators of HSC70 might provide clinical therapies for ischemic stroke.