Formononetin Inhibits Microglial Inflammatory Response and Contributes to Spinal Cord Injury Repair by Targeting the EGFR/MAPK Pathway

ABSTRACT

Zhenbao Pill contains many Chinese herbal medicinal ingredients and has been proven to have therapeutic effects on the repair of spinal cord injury (SCI). This study attempts to investigate the role of formononetin (FMN), an ingredient of Zhenbao Pill, in regulating neuroinflammation after SCI and the underlying mechanism. Primary microglia isolated from the spinal cord of newborn rats and human microglial clone 3 (HMC3) cells were stimulated with IL-1β followed by FMN incubation. The cell viability and inflammatory cytokine levels were detected. The target of FMN was predicted and screened using databases. By silencing or overexpression of epidermal growth factor receptor (EGFR), the anti-neuroinflammatory effect of FMN was assessed in vitro. In vivo, FMN was intraperitoneally injected into rats after SCI followed by the neurological function and histopathology examination. The isolated microglia were in high purity, and the different concentrations of FMN incubation had no toxic effects on primary microglia and HMC3 cells. FMN reduced the inflammatory cytokine levels (TNF-α and IL-6) in a concentration-dependent manner. EGFR silencing or FMN incubation decreased p-EGFR and p-p38 levels and down-regulated inflammatory cytokine levels in IL-1β-stimulated cells or supernatants. Nevertheless, the effects of FMN on microglial inflammation were reversed by EGFR overexpression. In vivo, FMN treatment improved the neuromotor function, repaired tissue injury, and inhibited EGFR/p38MAPK phosphorylation. Formononetin inhibits microglial inflammatory response and contributes to SCI repair via the EGFR/p38MAPK signaling pathway.

KEYWORDS:

• Epidermal growth factor receptor (EGFR)
• formononetin (FMN)
• microglia
• p38MAPK
• spinal cord injury (SCI)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Availability of data and material

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 82060398]