Psoralidin protects against cerebral hypoxia/reoxygenation injury: Role of GAS6/Axl signaling

Psoralidin (PSO) is a natural phenolic coumarin extracted from the seeds of Psoralea corylifolia L. Growing preclinical evidence indicates that PSO has anti-inflammatory, anti-vitiligo, anti-bacterial, and anti-viral effects. Growth arrest-specific gene 6 (GAS6) and its receptor, Axl, modulate cellular oxidative stress, apoptosis, survival, proliferation, migration, and mitogenesis. Notably, the neuroprotective role of the GAS6/Axl axis has been identified in previous studies. We hypothesize that PSO ameliorates cerebral hypoxia/reoxygenation (HR) injury via activating the GAS6/Axl signaling. We first confirmed that PSO was not toxic to the cells and upregulated GAS6 and Axl expression after HR injury. Moreover, PSO exerted a marked neuroprotective effect against HR injury, represented by restored cell viability and cell morphology, decreased lactate dehydrogenase (LDH) release, and reactive oxygen species (ROS) generation. Furthermore, PSO pretreatment also elevated the levels of nuclear factor-related factor 2 (Nrf-2), NAD(P)H dehydrogenase quinone-1 (NQO1), heme oxygenase-1 (HO-1), silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor coactivator 1α (PGC-1α), nuclear respiratory factor 1 (NRF1), uncoupling protein 2 (UCP2), and B-cell lymphoma 2 (BCl2) both in the condition of baseline and HR injury. However, GAS6 siRNA or Axl siRNA inhibited the neuroprotective effects of PSO. Our findings suggest that PSO pretreatment attenuated HR-induced oxidative stress, apoptosis, and mitochondrial dysfunction in neuroblastoma cells through the activation of GAS6/Axl signaling.