Melaleuca alternifolia Induces Heme Oxygenase-1 Expression in Murine RAW264.7 Cells through Activation of the Nrf2-ARE Pathway

Am J Chin Med. 2017;45(8):1631-1648. doi: 10.1142/S0192415X17500884. Epub 2017 Nov 9.


Melaleuca alternifolia concentrate (MAC) is the refined essential oil of the Australian native plant Melaleuca alternifolia. MAC has been reported to suppress the production of pro-inflammatory cytokines in both murine RAW264.7 macrophages and human monocytes stimulated with lipopolysaccharide (LPS). However, the mechanisms involved in this effect remain unclear. This study aims to delineate the molecular mechanisms that drive the anti-inflammatory activity of MAC and its active component, terpinen-4-ol, in macrophages. The effects of MAC on RAW264.7 cells were studied using western blotting, real-time PCR, an electrophoretic mobility shift assay (EMSA), and NF-[Formula: see text]B luciferase reporter assays. Our results showed that MAC significantly increased both the mRNA and protein levels of heme oxygenase-1 (HO-1) via p38 and JNK MAPK activation. In addition, we showed that MAC significantly increased the activation and nuclear translocation of NF-E2-related factor 2 (Nrf2), a key transcription factor regulating HO-1 induction. MAC was also associated with significant inhibition of iNOS expression, NO production, and NF-[Formula: see text]B activation. HO-1 was required for these anti-inflammatory effects as tin protoporphyrin IX (SnPPIX), an HO-1 inhibitor, abolished the effects of MAC on LPS-induced iNOS, NO, and NF-[Formula: see text]B activation. Our results indicate that MAC induces HO-1 expression in murine macrophages via the p38 MAPK and JNK pathways and that this induction is required for its anti-inflammatory activity.

Keywords: HO-1; Macrophage; Melaleuca alternifolia; Nrf2.

MeSH terms

  • Animals
  • Anti-Inflammatory Agents*
  • Gene Expression / drug effects*
  • Heme Oxygenase-1 / genetics*
  • Heme Oxygenase-1 / metabolism*
  • Humans
  • Inflammation Mediators / metabolism*
  • Melaleuca / chemistry*
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism*
  • Mice
  • Monocytes / metabolism
  • NF-E2-Related Factor 2 / metabolism*
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type II / genetics
  • Nitric Oxide Synthase Type II / metabolism
  • RAW 264.7 Cells
  • RNA, Messenger / metabolism
  • Signal Transduction / drug effects*
  • Tea Tree Oil / isolation & purification
  • Tea Tree Oil / pharmacology*
  • Terpenes / isolation & purification
  • Terpenes / pharmacology


  • Anti-Inflammatory Agents
  • Inflammation Mediators
  • Membrane Proteins
  • NF-E2-Related Factor 2
  • Nfe2l2 protein, mouse
  • RNA, Messenger
  • Terpenes
  • Nitric Oxide
  • terpinenol-4
  • Tea Tree Oil
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse
  • Heme Oxygenase-1
  • Hmox1 protein, mouse