Salidroside engages HSPA5 and attenuates PERK-eIF2α-ATF4-CHOP signalling in ovariectomy-induced bone loss
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Estrogen-Like Effect of Bazi Bushen Capsule in Ovariectomized Rats
Published on: April 7, 2023
Bocheng Zhou1, Ruoyi Wang2, Tangliang Qian2
1School of Clinical Medicine, Beijing University of Chinese Medicine, Beijing 100029, China.
Ethnopharmacological Relevance:
Rhodiolae Crenulatae Radix et Rhizoma (Hong-jing-tian) is a well-documented traditional Chinese medicinal herb. Its pharmacopoeial marker salidroside exerts osteoprotective effects in ovariectomized models, yet its molecular targets remain elusive.
Aim Of The Study:
To investigate salidroside-HSPA5 engagement, restoration of ER-stress-disrupted BiP-PERK association, and HSPA5 requirement for salidroside responses in stressed osteoblasts.
Materials And Methods:
Ovariectomised rats received salidroside (30 or 100 mg·kg-1·d-1) or alendronate, followed by bone, serum and protein analyses. Plasma proteomics identified HSPA5. Salidroside-HSPA5 interaction was validated by docking, SPR, CETSA, DARTS and ATPase assays. Tunicamycin-stressed MC3T3-E1 osteoblasts were used to assess cellular rescue, HSPA5-PERK interaction (co-immunoprecipitation) and UPR signalling. Hspa5 siRNA verified HSPA5-dependent mechanisms.
Results:
HSPA5 and eIF2α were core network nodes. Molecular docking predicted that salidroside binds to the HSPA5 ATPase domain (-8.53 kcal mol-1). Direct target engagement was supported by SPR (KD = 30.3 μM), CETSA (ΔTm = 2.61 °C) and DARTS assays, which showed concentration-dependent HSPA5 stabilization (90.0% residual HSPA5 at 1 mM salidroside vs. 38.3% for vehicle). Salidroside mildly suppressed recombinant HSPA5 ATPase activity (<30% inhibition at 1 mM). In ovariectomized rats, high-dose salidroside increased bone volume fraction from 9.8% to 36.4%, restored bone-formation markers and reduced ER-stress signalling. In tunicamycin-challenged osteoblasts, salidroside recovered viability, osteogenic differentiation and nuclear RUNX2. It attenuated three UPR branches and partially restored stress-disrupted HSPA5-PERK interaction (normalized co-precipitated HSPA5: 0.74 vs. 0.15, P = 0.001). Hspa5 knockdown abrogated the cytoprotective and osteogenic responses to salidroside.
Conclusions:
Salidroside engages HSPA5 to restore stress-disrupted BiP-PERK complexes. It suppresses pathological PERK-driven UPR over-activation and rescues osteoblast function in osteoporosis models. Its osteoprotection is HSPA5-dependent.