BHLHE40 regulates microglia polarization after spinal cord injury via the NF-κB pathway

Spinal cord injury (SCI) is a devastating disease characterized by neuroinflammation and irreversible neuronal loss. The basic helix-loop-helix family member e40 (Bhlhe40) is a stress-responsive transcription factor involved in the pathological process of inflammation. However, Bhlhe40 expression and its role in SCI are largely unknown. SCI rat models were established with an aneurysm clip and then the rats were injected with lentiviral Bhlhe40 shRNA to knock down Bhlhe40 expression. In vitro, BV2 microglia cells were stimulated with LPS and IFN-γ to promote M1 microglia polarization. The results showed that Bhlhe40 expression was significantly elevated in the injured spinal cord tissue. Bhlhe40 deficiency reduced neuroinflammation and neuronal loss, and then promoted the recovery of neurological function. Additionally, Bhlhe40 knockdown alleviated neuronal apoptosis by regulating microglia polarization. In our study, Bhlhe40 knockdown inhibited M1 microglia polarization and the secretion of pro-inflammatory factors (TNF-α, IL-1β, and IL-6). Meanwhile, the NF-κB pathway was inhibited after the Bhlhe40 knockdown in SCI rats. To further explore the functional role of Bhlhe40, we performed in vitro experiments. Bhlhe40 knockdown decreased M1 microglia polarization by inhibiting the NF-κB pathway. In conclusion, our study indicates that Bhlhe40 knockdown can alleviate the progression of SCI and its underlying mechanism in regulating macrophage polarization through the NF-κB pathway.