Melatonin regulates the MST1/Nrf2 pathway to alleviate oxidative stress injury after hypoxic-ischemic brain damage in neonatal rats

Oxidative stress is a key factor in neonatal hypoxic-ischemic encephalopathy (HIE). Despite the widespread attention on melatonin (Mel) as a potential therapeutic agent, its antioxidative mechanisms in HIE remain incompletely understood. This study seeks to determine the neuroprotective action of Mel on HIE and elucidate the underlying molecular mechanisms.

The rat hypoxic-ischemic brain damage (HIBD) model and the neuronal cell oxygen-glucose deprivation (OGD) model were constructed. The extent of brain damage was assessed 24 hours after modeling using hematoxylin-eosin staining and Nissl staining. Immunofluorescence staining and Western blotting were used to analyze the expression levels of mammalian STE20-like kinase1 (MST1), nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) proteins. SOD activity, MDA content and ROS levels were measured using colorimetric methods and fluorescent probe DCFH-DA.

In vivo, Mel treatment not only significantly reduced HIBD-induced cortical injury in rats but also inhibited the activation of MST1 while simultaneously promoting the activation of Nrf2. Further in vitro, Mel could alleviate oxidative stress-induced neuronal damage, which was blocked by the Nrf2 inhibitor ML385, indicating its action is dependent on the Nrf2 pathway. Additionally, the specific MST1 inhibitor XMU-MP-1 demonstrated neuroprotective effects similar to those of Mel in both in vivo and in vitro models, with mechanisms related to enhanced activation of Nrf2.

Melatonin protects against HIBD by reducing oxidative stress via MST1 inhibition and subsequent Nrf2/HO-1 pathway activation. The MST1-Nrf2 axis is a key mechanism, offering new insights and a potential therapeutic target for neonatal HIE.