Protective effects of Hinokitiol on neuronal ferroptosis by activating the KEAP1/NRF-2/HO-1 pathway in traumatic brain injury

Hinokitiol (β-thujaplicin, HIK) is a natural monoterpene small molecule compound showing various biological effects including antibacterial, anti- inflammatory and anti-tumor. Ferroptosis, a new form of iron-dependent cell death, has been demonstrated as one of the pathophysiological mechanisms of traumatic brain injury (TBI). However, the effect of hinokitiol on neuronal ferroptosis after traumatic brain injury has not been reported. Here, we show that hinokitiol alleviated excessive glutamate-induced intracellular reactive oxygen species (ROS), lipid peroxidation, and Fe2+ accumulation in HT-22. Moreover, hinokitiol upregulated heme oxygenase-1 (HO-1) expression, promoted nuclear factor-erythroid factor 2-related factor 2 (Nrf2) nuclear translocation, and inhibited the activation of microglia and astrocyte after TBI. Furthermore, hinokitiol remarkably reduced brain tissue lesions, mitigated neuron loss, iron deposition and attenuated neurologic impairment in the CCI-constructed TBI model in vivo. These results suggest that hinokitiol has neuroprotective effects on rescuing cells from TBI-induced neuronal ferroptosis. In summary, we reveal a novel role of hinokitiol in TBI, which has neuroprotective effects on rescuing cells from TBI-induced neuronal ferroptosis. Moreover, hinokitiol through activating the Nrf2/Keap1/HO-1 signaling pathway significantly reduces the neuronal damage, suggesting that it is a potential therapeutic candidate for TBI.