RESUMEN
Objective:To evaluate the role of nuclear factor-erythroid 2-related factor 2 (Nrf2)/glutathione peroxidase-4 (GPX4) signaling pathway-mediated ferroptosis in midazolam-induced reduction of hypoxic-ischemic brain damage (HIBD) in neonatal rats.Methods:Ninety healthy 7-day-old neonatal rats, weighing 16-20 g, were divided into 6 groups ( n=15 each) using the random number table method: sham operation group (Sham group), HIBD group, low-dose midazolam (10 mg/kg) group (group L), medium-dose midazolam (20 mg/kg) group (group M), high-dose midazolam (40 mg/kg) group (group H), and Nrf2 inhibitor ML385 group (group I). The HIBD model was developed by ligating the left carotid artery and exposing to a hypoxic condition for 2 h in anesthetized animals. Starting from 2nd day after developing the model, the corresponding doses of midazolam were intraperitoneally injected in midazolam groups, the equal volume of normal saline was intraperitoneally injected in Sham and HIBD groups, midazolam 40 mg/kg and Nrf2 inhibitor ML385 30 mg/kg were intraperitoneally injected once a day for 8 consecutive days in group I. The rats were weighed and subjected to the Morris water maze test after the end of administration. Blood samples were taken from the abdominal aorta after the end of the Morris water maze test, and then the animals were sacrificed to remove the brain for determination of the concentrations of serum iron, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) (by enzyme-linked immunosorbent assay), contents of iron and GSH in hippocampal tissues (by ultraviolet spectrophotometry and micro method), the number of Nrf2/neuronal nuclear antigen (NeuN) and GPX4/NeuN positive cells (by immunofluorescent staining), and expression of Nrf2, GPX4, and 4-hydroxynonaenoic acid (4-HNE) in hippocampal tissues and for microscopic examination of the pathological changes of hippocampal neurons in brain tissues (after HE staining and Nissl staining). Results:Compared with Sham group, the first time to arrival at platform was significantly prolonged, the number of crossing the origional platform was reduced, and the time of staying at the target quadrant was shortened, the iron content in the hippocampal tissues was increased, the content of GSH and the number of Nrf2/NeuN and GPX4/NeuN positive cells were decreased, the expression of Nrf2 and GPX4 was down-regulated, the expression of 4-HNE was up-regulated, the concentrations of serum iron, IL-6 and TNF-α were increased, and the injury to hippocampal neurons was marked in HIBD group ( P<0.05). Compared with HIBD group, the first time to arrival at platform was significantly shortened, the number of crossing the origional platform was increased, and the time of staying at the target quadrant was prolonged, the iron content in the hippocampus tissues was decreased, the content of GSH and the number of Nrf2/NeuN and GPX4/NeuN positive cells were increased, the expression of Nrf2 and GPX4 was up-regulated, the expression of 4-HNE was down-regulated, the concentrations of serum iron, IL-6 and TNF-α were decreased ( P<0.05), and the injury to hippocampal neurons was significantly reduced in H, M and L groups. Compared with group H, the first time to arrival at platform was significantly prolonged, the number of crossing the origional platform was reduced, and the time of staying at the target quadrant was shortened, the iron content in the hippocampus tissue was increased, the content of GSH and the number of Nrf2/NeuN and GPX4/NeuN positive cells were decreased, the expression of Nrf2 and GPX4 was down-regulated, the expression of 4-HNE was up-regulated, the concentrations of serum iron, IL-6 and TNF-α were increased ( P<0.05), and the injury to hippocampal neurons was aggravated in group I. Conclusions:The mechanism by which midazolam reduces HIBD may be related to activation of the Nrf2/GPX4 signaling pathway and inhibition of hippocampal neuronal ferroptosis in neonatal rats.