Ozone treatment alleviates brain injury in cerebral ischemic rats by inhibiting the NF-κB signaling pathway and autophagy

Ozone-mediated cerebral protection: Unraveling the mechanism through ferroptosis and the NRF2/SLC7A11/GPX4 signaling pathway

BACKGROUND

The pathogenesis of brain ischemic/reperfusion (I/R) insult is characterized by neuronal loss due to excessive oxidative stress responses. Ferroptosis, a form of oxidative cell death, can be triggered when the balance between antioxidants and pro-oxidants in cells is disrupted. Ozone, a natural bioactive molecule with antioxidant/anti-apoptotic and pro-autophagic properties, has been shown to enhance the antioxidant system's capacity and ameliorate oxidative stress. However, its role in neuronal ferroptosis remains unclear. Therefore, we investigated the functions and possible mechanisms of ozone in cerebral I/R-induced ferroptotic neuronal death.

METHODS

A cerebral ischemia-reperfusion injury model was induced in Sprague-Dawley (SD) rats pre-treated with ozone. Intraperitoneal administration of the NRF2 inhibitor ML385, the SLC7A11 inhibitor Erastin, and the GPX4 inhibitor RSL3 was performed one hour prior to model establishment.

RESULTS

Our results showed that ozone preconditioning mitigated neuronal damage caused by cerebral I/R, reduced the severity of neurological deficits, lowered cerebral infarct volume in middle cerebral artery occlusion (MCAO) rats, and decreased the volume of cerebral infarcts. Transmission electron microscopy, immunofluorescence, and Western blotting indicated ferroptosis following MCAO-induced brain damage. MCAO resulted in morphological damage to neuronal mitochondria, increased lipid peroxidation accumulation, and elevated malondialdehyde (MDA) production. Furthermore, MCAO decreased levels of FTH1 and GPX4 (negative regulators of ferroptosis) and increased ACSL4 levels (a positive regulator of ferroptosis). Ozone preconditioning demonstrated a neuroprotective effect by increasing NRF2 nuclear translocation and the expression of SLC7A11 and GPX4. Treatment with ML385, Erastin, and RSL3 significantly reversed ozone preconditioning's protective effect on neuronal ferroptosis.

CONCLUSION

Our findings demonstrated that ozone treatment attenuates ferroptosis in a cerebral ischemia/reperfusion injury rat model via the NRF2/SLC7A11/GPX4 pathway, providing a theoretical basis for ozone's potential use as a therapy to prevent ischemic stroke.

Effects of dichloromethane extraction from Piper nigrum L. and P. longum L. on the expression of autophagy-related proteins in ischemic stroke

Piper nigrum L. and P. longum L. are widely used in various medicinal formulations. The dichloromethane fraction of Piper nigrum L. and P. longum L. (DF) can prevent cerebral ischemic injury although the underlying mechanisms are obscure. The aim of this study was to evaluate the potential neuroprotective effects of DF on a rat model of permanent middle cerebral artery occlusion (pMCAO) and assess the molecular mechanisms. Animals were administered with DF (50, 100, and 150 mg/kg) or nimodipine (12 mg/kg) 6 h after pMCAO for 14 consecutive days via intragastric gavage. In the vitro this study identified that DF reduced neurological severity scores and improved survival rate. Results showed that DF markedly inhibited the percentage of apoptotic cells as well as neuronal autophagy and mitigated the overall neuronal and vascular damage in the ischemic region. Western blot testing showed that at the molecular level, DF significantly suppressed ischemia-induced activated expression of LC3, Beclin1, Atg12, and Atg5. Overall, our study indicated that DF attenuated neuronal autophagy by suppressing the expression of autophagy-related proteins to generate neuroprotection effect for ischemic stroke.