In vitro and in vivo relaxation and anti-inflammation of natural flavonoids from Elaeagnus pungens leaf via L-type calcium channel and targeting MAPK signal pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: In traditional Chinese medicine (TCM), the leaf of Elaeagnus pungens Thunb. (Family Elaeagnaceae) is a herb documented as an antiasthmatic remedy to treat the severe asthma, bronchitis and other respiratory diseases in the early material medica "Bencao Gangmu" (Ming dynasty, about 442 years ago).

AIM OF THE STUDY: This work is purposed to investigate the pharmacological effects and mechanism of total flavonoids from Elaeagnus pungens leaves (FLA) on asthma in vivo and vitro.

MATERIALS AND METHODS: Female BALB/c mice were sensitized by intraperitoneal injection of OVA with aluminum hydroxide and intranasal challenged with OVA. After treatment with FLA (10, 20 mg/kg p.o.), the behaviors of mice were observed by score evaluation. Enumeration of total cells and OVA-specific IgE assay in the blood were measured as well as enumeration of total cells and cytokines assay in the BALF. Furthermore, histopathological analysis was performed by HE staining. The in vitro relaxing action on muscle force of FLA (0.0316-10.0 mg/ml) was evaluated using isometric tension in tracheal rings, and VDLCC currents were recorded to explore the relaxation mechanism in the isolated tracheal rings and mouse ASM cells, respectively. In vitro anti-inflammatory actions were assessed with LPS-stimulated RAW 264.7 macrophages. The production of inflammatory mediators and MAPK signaling pathway was estimated using ELISA and Western blotting analysis, respectively.

RESULTS: The high dose of flavones from E. pungens leaf (20 mg/kg) can significantly improve the symptom of asthma breakout and relieve the lung swelling. FLA treatment decreased eosinophils and leukocytes numbers in blood and BLAF with a dosedependent manner. Furthermore, the inhibiting effect of FLA on the level of Ig E and inflammatory-related cytokines including TNF-α, IL-5 showed dose-independent. FLA relaxed high K + -induced contraction in a dose-dependent manner. The maximal relaxation produced by FLA was 99.7% (IC 50 = 0.46 mg/ml). The whole-cell VDLCC currents were abolished by FLA (3.16 mg/ml) and FLA significantly decreased the maximal amplitude of VDLCCs. No cytotoxic effect of FLA was observed in RAW264.7 cells under the tested concentrations (1-300 μg/mL). The increased IL-6 and NO by the stimulation of LPS in RAW264.7 cells were significantly inhibited by FLA in the dosedependent manner. Treatment with LPS in the presence of FLA, LPS-induced phosphorylation of ERK1/2 and JNK was inhibited in the macrophages.

CONCLUSION: FLA from Elaeagnus pungens leaf can alleviate the inflammation symptom via reducing the eosinophils and leukocytes numbers as well as the production of pro-inflammatory cytokines. This anti-inflammatory effect is related to the modulation of the MAPK signaling pathway. FLA can relax the precontracted TRs by blocking the VDLCCs, which interrupts extracellular Ca 2+ influx and inhibit the rise of [Ca 2+ ]i. It strongly suggests that these flavonoids components are the substances basis of Elaeagnus pungens leaves for allergic action, bronchospasm and inflammation in asthma.