Polyphenol amentoflavone affords neuroprotection against neonatal hypoxic‐ischemic brain damage via multiple mechanisms

Flavonoids are naturally occurring polyphenolic compounds that have many biological properties, including antioxidative, anti‐inflammatory and neuroprotective effects. Here, we report that amentoflavone significantly reduced cell death induced by staurosporine, etoposide and sodium nitroprusside in neuroblastoma SH‐SY5Y cells. In post‐natal day 7 rats, hypoxic‐ischemic (H‐I) brain damage induced by unilateral carotid ligation and hypoxia resulted in distinct features of neuronal cell death including apoptosis and necrosis. In this model, a systemic administration of amentoflavone (30 mg/kg) markedly reduced the H‐I‐induced brain tissue loss with a wide therapeutic time window up to 6 h after the onset of hypoxia. Amentoflavone blocked the activation of caspase 3, characteristic of apoptosis, and the proteolytic cleavage of its substrates following H‐I injury. Amentoflavone also reduced the excitotoxic/necrotic cell death after H‐I injury in vivo and after oxygen/glucose deprivation in mouse mixed cultures in vitro. Treatment of mouse microglial cells with amentoflavone resulted in a significant decrease in the lipopolysaccharide‐induced production of nitric oxide and induction of inducible nitric oxide synthase and cyclo‐oxygenase‐2. Furthermore, amentoflavone decreased the inflammatory activation of microglia after H‐I injury when assessed by the microglial‐specific marker OX‐42. These data demonstrate for the first time that amentoflavone strongly protects the neonatal brain from H‐I injury by blocking multiple cellular events leading to brain damage.