Effects of Hesperetin Early Intervention on Brain Neurons and Microglia in APPswe/PS1dE9 Mice.

INTRODUCTION

Neuroinflammation and microglial dysfunction play central roles in the pathogenesis of Alzheimer's disease (AD). This study investigated whether early intervention with hesperetin, a citrus flavonoid, could attenuate neuroinflammation and modulate microglial polarization in both wild-type (WT) and APPswe/PS1dE9 transgenic (TG) mice.

METHODS

Three-month-old male C57BL/6J WT and APPswe/PS1dE9 TG mice were administered hesperetin (10 or 20 mg/kg/day for WT; 20, 40, or 80 mg/kg/day for TG) or vehicle for six months. Neuronal morphology was assessed using thionine staining. Microglial polarization was evaluated via CD11b/iNOS and CD11b/Arginase-1 immunofluorescence. Protein expression of CD11b, iNOS, Arginase-1, and TREM2 was measured by Western blot, and cytokine levels (TNF-α, IL-10) were quantified by ELISA.

RESULTS

In WT mice, hesperetin improved neuronal integrity, reduced M1 markers (CD11b⁺/ iNOS⁺ cells, iNOS, TNF-α), and enhanced M2 markers (CD11b⁺/Arginase-1⁺ cells, Arginase-1, TREM2). TG mice exhibited exacerbated neuroinflammation and neuronal loss compared to WT controls, which was significantly mitigated by hesperetin treatment. All hesperetin doses in TG groups reduced pro-inflammatory markers and increased anti-inflammatory and repair-associated factors.

DISCUSSION: These results indicate that hesperetin shifts microglial polarization toward the protective M2 phenotype, potentially via TREM2 upregulation, thereby reducing neuroinflammation and neuronal damage. This effect was observed in both age-related and Aβ-driven pathology, suggesting a dual role for hesperetin in immunomodulation and neuroprotection.

CONCLUSION

Early hesperetin intervention exerts neuroprotective effects by rebalancing microglial polarization and enhancing TREM2 expression, highlighting its potential as a preventive strategy against AD-related neuroinflammation.