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

Chen-Lung Ho, Lan-Hui Li, Yueh-Chun Weng, Kuo-Feng Hua, Tz-Chuen Ju
2020 BMC Complementary Medicine and Therapies  
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. Lipopolysaccharide (LPS)-activated RAW264.7 macrophages were used to evaluate the anti-inflammatory activity of the leaf essential oils of Eucalyptus. The cell survival
more » ... s 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. 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. 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.
doi:10.1186/s12906-020-02999-0 pmid:32600338 fatcat:sjyamaojynfhhmboyq7gt6e33m