Calycosin alleviates hyperbilirubin nerve injury in Ugt1-/- mice by inhibiting oxidative stress, apoptosis, and mitochondrial function

Abstract

Background and purpose: Hyperbilirubinemia is a common condition in neonates that is associated with poor neurodevelopmental outcomes. Although studies have proposed that calycosin has a neuroprotective effect, the exact molecular mechanism underlying calycosin treatment of hyperbilirubinemia remains elusive. To fill this gap, we analyzed the mechanism of calycosin treatment in hyperbilirubinemia model mice.

Method: Thirty neonatal mice were randomly divided into wide type (WT), Ugt1^-/- and calycosin treatment group. Neuronal damage was observed with Nissl staining. Immunofluorescence staining were carried out to determine DNA damage repair and neurodegeneration. Oxidative stress was investigated by immunostaining with 4-hydroxynonenal (4-HNE). Western blot (WB) and Qpcr were used to detect relative protein and mRNA expression levels. Mitochondrial CI/CII activity of mitochondria was analyzed with a spectrophotometer.

Result: The total bilirubin concentration was significantly higher in Ugt1-/- group compared with WT, but calycosin treatment reduced concentration of bilirubin. The total bilirubin and bilirubin/albumin ratio were significantly higher at postnatal day 4 compared with day 2. Calycosin treatment reduced serum bilirubin concentration and bilirubin/albumin ratio. After calycosin treatment, Nissl body count increased, apoptosis-related protein was downregulated and 4-HNE level decreased. Compared with Ugt-/- group, calycosin treatment increased neurons (NeuN+) and calbindin positive cells and decreased fluorojade C(FJC)positive neurons in WT group. In mitochondria, calycosin alleviated mitochondrial electron transport chain dysfunction in Ugt1-/- mice.

Conclusion: We demonstrated that the mechanism of calycosin treatment on hyperbilirubinemia-induced Ugt1^-/- was associated mainly with antioxidant effects, antiapoptosis and inhibition of normal mitochondrial function.

Keywords: Calycosin; Hyperbilirubinemia; Mitochondrial function; Nerve injury; Ugt1(-/-) mice.