EGR2 affects mixed stroke repair through BNIP3L-mediated microglial mitophagy

Mixed stroke, also known as hemorrhagic infarction or infarction with hemorrhage, presents as a cerebral infarction combined with intracerebral hemorrhage (ICH) on computed tomography (CT) brain scans. ICH is a brain parenchymal hemorrhage caused by the loss of vascular integrity, which can lead to permanent disability or death. The early growth response 2 (EGR2) gene has been studied in a variety of brain diseases. However, effective treatments are still lacking.

In this study, a cell model was constructed using oxyhemoglobin (OxyHb), and cell viability was detected using CCK-8. The mitochondrial membrane potential was measured using a mitochondrial membrane potential detection kit. Protein stress was used to assess the expression of EGR2, BCL2/adenovirus E1B 19 kDa protein-interacting protein 3-like‌ (BNIP3L or BNIP3L/NIX), and autophagy-related proteins. RT-qPCR detected the expression of EGR2 and BNIP3L mRNA. Microtubule-associated protein 1 A/1B-light chain 3 (LC3) expression was detected by immunofluorescence.

This study found that OxyHb reduced microglial viability in a concentration-dependent manner, and 20 μM OxyHb produced the most robust effect and was selected for subsequent experiments. In the cell model, the membrane potential of microglia decreased, and the fluorescence intensities of autophagy-related proteins (ATG7, LC3 II/LC3 I, and P62) and LC3 were inhibited. Over-expression-EGR2 (oe-EGR2) can increase the membrane potential of microglia and promote the fluorescence intensity of autophagy-related proteins (ATG7, LC3 II/LC3 I, and P62) and LC3. Mitochondrial division inhibitor-1 (Mdivi-1) and sh-BNIP3L could reverse the effect of oe-EGR2.

EGR2 promotes microglial mitophagy by upregulating BNIP3L, thereby alleviating ICH.