Eucalyptus essential oils inhibit the lipopolysaccharide-induced inflammatory response in RAW264.7 macrophages through reducing MAPK and NF-κB pathways

  • BMC Complement Med Ther. 2020 Jun 29;20(1):200. doi: 10.1186/s12906-020-02999-0.
Chen-Lung Ho  1 ,  Lan-Hui Li  2  3 ,  Yueh-Chun Weng  4 ,  Kuo-Feng Hua  3  5  6 ,  Tz-Chuen Ju  7
Affiliations
  • 1. Division of Wood Cellulose, Taiwan Forestry Research Institute, Taipei, Taiwan.
  • 2. Department of Laboratory Medicine, Linsen, Chinese Medicine and Kunming Branch, Taipei City Hospital, Taipei, Taiwan.
  • 3. Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
  • 4. EMA program in College of Bioresources, National Ilan University, Ilan, Taiwan.
  • 5. Department of Biotechnology and Animal Science, National Ilan University, Ilan, Taiwan.
  • 6. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan.
  • 7. Department of Animal Science and Biotechnology, Tunghai University, No. 1727, Sec. 4, Taiwan Blvd., Xitun Dist, Taichung City, 40704, Taiwan. [email protected].
PMID: 32600338 DOI: 10.1186/s12906-020-02999-0
Abstract

Background: Eucalyptus essential oils have been used in traditional medicine for centuries. It was reported that Eucalyptus leaves possess antioxidant and antimicrobial effects. Here, we investigated the anti-inflammatory activity of the essential oils extracted from the leaves of four different Eucalyptus species in RAW264.7 macrophages.

Methods: Lipopolysaccharide (LPS)-activated RAW264.7 macrophages were used to evaluate the anti-inflammatory activity of the leaf essential oils of Eucalyptus. The cell survival was quantified by an Alamar Blue assay. Nitric oxide (NO) production was assessed by Griess reaction. TNF-α and IL-6 production were measured by enzyme-linked immunosorbent assay (ELISA). Nuclear factor-κB (NF-κB) transcriptional activity was measured by NF-κB reporter assay. Intracellular protein expression levels were determined by Western blot. The expression levels of inducible NO Synthase (iNOS), cyclooxygenase-2 (COX-2), mitogen-activated protein kinase (MAPK), protein kinase C (PKC) and NF-κB pathway were measured by western blot in LPS-activated RAW 264.7 macrophage.

Results: The essential oils extracted from Eucalyptus citriodora leaf exert the best NO inhibitory activity in LPS-activated RAW264.7 macrophages. The essential oils were fractionated into fractions A-H, and fraction F has been demonstrated to inhibit the expression levels of TNF-α, IL-6, NO, iNOS and COX-2 in LPS-activated RAW264.7 macrophages. Mechanistic analysis revealed that fraction F reduced the phosphorylation levels of ERK1/2, p38, PKC-α, PKC-ε and PKC-δ, and inhibited the NF-κB transcriptional activity. The chemical composition of Fraction F was determined by GC-MS.

Conclusions: The discoveries made herein could help develop innovative nonsteroidal anti-inflammatory drugs with minimal side effects and strong efficacy. Clinical trials on these Eucalyptus leaf essential oils will help customize and optimize their therapeutic administration.

Keywords
Anti-inflammation; Cytokine; Eucalyptus essential oils; Lipopolysaccharide; Macrophages.
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