title: Fraxetin Induces Heme Oxygenase-1 Expression by Activation of Akt/Nrf2 or AMP-activated Protein Kinase α/Nrf2 Pathway in HaCaT Cells.
abstract: BACKGROUND
  Fraxetin (7,8-dihydroxy-6-methoxy coumarin), a coumarin derivative, has been reported to possess antioxidative, anti-inflammatory and neuroprotective effects. A number of recent observations suggest that the induction of heme oxygenase-1 (HO-1) inhibits inflammation and tumorigenesis. In the present study, we determined the effect of fraxetin on HO-1 expression in HaCaT human keratinocytes and investigated its underlying molecular mechanisms.
  
  
  METHODS
  Reverse transcriptase-PCR and Western blot analysis were performed to detect HO-1 mRNA and protein expression, respectively. Cell viability was measured by the MTS test. The induction of intracellular reactive oxygen species (ROS) by fraxetin was evaluated by 2',7'-dichlorofluorescin diacetate staining.
  
  
  RESULTS
  Fraxetin upregulated mRNA and protein expression of HO-1. Incubation with fraxetin induced the localization of nuclear factor-erythroid-2-related factor-2 (Nrf2) in the nucleus and increased the antioxidant response element-reporter gene activity. Fraxetin also induced the phosphorylation of Akt and AMP-activated protein kinase (AMPK)α and diminished the expression of phosphatase and tensin homolog, a negative regulator of Akt. Pharmacological inhibition of Akt and AMPKα abrogated fraxetin-induced expression of HO-1 and nuclear localization of Nrf2. Furthermore, fraxetin generated ROS in a concentration-dependent manner.
  
  
  CONCLUSIONS
  Fraxetin induces HO-1 expression through activation of Akt/Nrf2 or AMPKα/Nrf2 pathway in HaCaT cells.
authors.affiliation: College of Pharmacy, Keimyung University, Daegu, Korea.
authors.forename: Juthika
authors.initials: J
authors.lastname: Kundu
authors.affiliation: College of Pharmacy, Keimyung University, Daegu, Korea.
authors.forename: In Gyeong
authors.initials: IG
authors.lastname: Chae
authors.affiliation: College of Pharmacy, Keimyung University, Daegu, Korea.
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Chun
keywords: Fraxetin; Heme oxygenase-1; Keratinocytes; Nrf2