Context: Ajuga ovalifolia Bur. et Franch. var. calantha (Diels) C. Y. Wu et C. Chen (Labiatae), a traditional Chinese medicine, has been used to treat several inflammatory diseases.
Objective: To assess the anti-inflammatory activity of ajudecumin A isolated from Ajuga ovalifolia var. calantha, and its possible mechanisms.
Materials and methods: Lipopolysaccharide (LPS, 0.5 μg/mL)-stimulated RAW264.7 macrophages were used to assess the anti-inflammatory activity of ajudecumin A (1-40 μM) in vitro. Nitric oxide levels were evaluated by Griess reagent. The mRNA levels of iNOS, COX-2, TNF-α, IL-1β and IL-6 were determined using qRT-PCR. Phosphorylation of ERK, JNK, p38 MAPK and IκBα were detected by western Blot. To further assess the anti-inflammatory of ajudecumin A in vivo, mice were oral treated with ajudecumin A (10 mg/kg) or dexamethasone (0.25 mg/kg, positive control) for 5 days before administration of carrageenan or xylene. Paw and ear edema were then measured, respectively.
Results: Ajudecumin A (10-40 μM) decreased LPS-induced nitric oxide production with an IC50 value of 16.19 μM. Ajudecumin A (20 and 40 μM) also attenuated cell spreading and formation of pseudopodia-like structures, and decreased the mRNA levels of iNOS (55.23-67.04%, p < 0.001), COX-2 (57.58-70.25%, p < 0.001), TNF-α (53.75-58.94%, p < 0.01-0.001), IL-1β (79.41-87.85%, p < 0.001) and IL-6 (54.26-80.52%, p < 0.01-0.001) in LPS-activated RAW264.7 cells. Furthermore, ajudecumin A suppressed LPS-induced phosphorylation of ERK, p38 MAPK, and IκBα, as well as IκBα degradation (p < 0.05-0.001). Finally, ajudecumin A (10 mg/kg) attenuated carrageenan- and xylene-induced inflammation in mice by about 28 and 24%, respectively.
Discussion and conclusions: Ajudecumin A exhibited a potent anti-inflammatory activity in vitro and in vivo through inhibition on NF-κB and ERK/p38 MAPK pathways, suggesting that ajudecumin A may be potentially developed as a lead compound in anti-inflammatory drug discovery.
Keywords: ERK/p38 MAPK signalling; NF-κB pathway; Traditional Chinese medicine; natural products.