Human haem oxygenase-1 induction by nitro-linoleic acid is mediated by cAMP, AP-1 and E-box response element interactions

Academic Article


  • Nitro-fatty acid products of oxidative inflammatory reactions mediate antiflammatory cell signalling responses. LNO2 (nitrolinoleic acid) induses expression of HO-1 (haem oxygenase-1), an enzyme that catabolizes haem into products exhibiting potent anti-inflammatory properties. In the present manuscript, the molecular mechanisms underlying HO-1 induction by LNO2 were examined in HAEC (human aortic endothelial cells), HEK-293 (human embryonic kidney 293) cells, and in transcription factor-deficient MEF (mouse embryonic fibroblasts). LN02 induced HO-1 expression in Nrf2 [NF-E2 (nuclear factor-erythroid 2)-related factor 2]-deficient MEF and in HEK-293 cells transfected with Nrf2-specific shRNA (small-hairpin RNA), supporting the fact that LNO2-mediated HO-1 induction can be regulated by Nrf2-independent mechanisms. LNO2 activated expression of a -4.5kb human HO-1 promoter construct, whereas a - 4.0 kb construct with deletion of 500 bp from the 5′ region was unresponsive. Site-directed mutagenesis of a CRE (cAMP-response element) or of a downstream NF-E2/AP-1 (activating protein-1) element, individually, within this 500 bp region modestly reduced activation of the HO-1 promoter by LNO2. Mutations of both the CRE and the NF-E2/AP-1 site also attenuated LNO2-mediated HO-1 promoter expression, whereas the addition of a third mutation in the proximal E-box sequence completely abolished LNO2-induced HO-1 expression. Chromatin immunoprecipitation assays confirmed CREB (CRE-binding protein)-1 binding to the CRE (located at - 4.0 kb) and E-box regions (located at - 44 bp) of the human HO-1 promoter. A 3C (Chromosome Conformation Capture) assay of intact cells showed LNO2-induced interactions between the CRE- and E-box-containing regions. These observations indicate that regulation of human HO-1 expression by LNO2 requires synergy between CRE, AP-1 and E-box sequences and involves the participation of CREB-1. © The Authors Journal compilation. © 2009 Biochemical Society.
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    Author List

  • Wright MM; Kim J; Hock TD; Leitinger N; Freeman BA; Agarwal A
  • Start Page

  • 353
  • End Page

  • 361
  • Volume

  • 422
  • Issue

  • 2