Ethanol extract of Alismatis Rhizoma reduces acute lung inflammation by suppressing NF-κB and activating Nrf2

Abstract

Ethnopharmacological relevance: The tuber of Alisma orientale Juzepzuk, a medicinal herb that has been used for the treatment of various disorders in Korea, has an anti-inflammatory effect. Here, we investigated a possible underlying mechanism and a protective effect on acute lung injury (ALI).

Materials and methods: Alisma orientale tuber was extracted in 80% ethanol and dried. The powder of the ethanol extract of Alisma orientale tuber (EEAO) was dissolved in PBS. The effect of EEAO on NF-κB and Nrf2 activities was analyzed with RAW 264.7 cells. The effect of EEAO on lung inflammation was determined by histologic and molecular biological analyses of the lung tissue of C57BL/6 mice that were gavaged once a day with 0.3 or 1.2 g/kg of EEAO for 14 days, prior to an intranasal administration of LPS (0.01 g/kg) for inducing ALI.

Results: EEAO pre-treatment of RAW 264.7 cells suppressed NF-κB activity and the expression of its dependent genes including COX-2, IL-1β and iNOS. Similar treatment enhanced Nrf2 activity and the expression of Nrf2-regulated genes including NQO-1, HO-1 and GCLC. LPS instillation induced acute neutrophilic lung inflammation, which was significantly suppressed by pre-treatment with EEAO. Analysis of the lungs revealed that EEAO pre-treatment induced the expression of Nrf2-regulated genes, with concomitant down-regulation of inflammatory gene expression.

Conclusions: EEAO attenuated lung inflammation in LPS-induced ALI mice, which was associated with differential regulation of NF-κB and Nrf2 activities. We suggest that EEAO can be developed as a potential therapeutics for the treatment of ALI.