Oridonin Ameliorates Traumatic Brain Injury-Induced Neurological Damage by Improving Mitochondrial Function and Antioxidant Capacity and Suppressing Neuroinflammation through the Nrf2 Pathway

Traumatic brain injury (TBI) is a global public health concern, and few effective treatments for its delayed damages are available. Oridonin (Ori) recently has been reported to show a promising neuroprotective efficacy, but its potential therapeutic effect on TBI has not been thoroughly elucidated. The TBI mouse models were established and treated with Ori or vehicle 30 min post-operation and every 24 h since then. Impairments in cognitive and motor function and neuropathological changes were evaluated and compared. The therapeutic efficacy and mechanisms of action of Ori were further investigated using animal tissues and cell cultures. Ori restored motor function and cognition after TBI-induced impairment and exerted neuroprotective effects by reducing cerebral edema and cortical lesion volume. Ori increased neuronal survival, ameliorating gliosis and the accumulation of macrophages after injury. It suppressed the increased production of reactive oxygen species, lipid peroxide, and malondialdehyde and reversed the decrease of mitochondrial membrane potential and adenosine triphosphate content, which was also identified in oxidatively stressed neuronal cultures. Further, Ori inhibited the expression of nucleotide-binding domain leucine-rich repeats family protein 3 (NLRP3) inflammasome proteins and NLRP3-dependent cytokine interleukin-1 beta that can be induced by oxidative stress after TBI. Regarding underlying mechanisms, Ori significantly enhanced expression of key proteins of the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) pathway. Our results demonstrated that Ori effectively improved functional impairments and neuropathological changes in animals with TBI. By activating the Nrf2 pathway, it improved mitochondrial function and antioxidant capacity and suppressed the neuroinflammation induced by oxidative stress. The results therefore suggest Ori as a potent candidate for managing neurological damage after TBI.