Acacia catechu (L.f.) Willd and Scutellaria baicalensis Georgi extracts suppress LPS-induced pro-inflammatory responses through NF-кB, MAPK, and PI3K-Akt signaling pathways in alveolar epithelial type II cells.

Acacia catechu (L.f.) Willd (ACW) and Scutellaria baicalensis Georgi (SBG) are one of the most famous couplet Chinese medicines, widely used for treating infantile cough, phlegm, and fever caused by pulmonary infection. However, the underlying molecular mechanism of their anti-inflammatory activity has not been determined. The aim of this study was to evaluate the protective effect of this couplet Chinese medicines (ACW-SBG) on lipopolysaccharide (LPS)-induced inflammatory responses in acute lung injury (ALI) model of rats and the potential molecular mechanisms responsible for anti-inflammatory activities in alveolar epithelial type II cells (AEC-II). Standardization of the 70% ethanol extract of ACW and SBG was performed by using a validated reversed-phase high-pressure liquid chromatography method. Rats were pretreated with ACW-SBG for 7 days prior to LPS challenge. We assessed the effects of ACW-SBG on the LPS-induced production of tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) in the bronchoalveolar lavage fluid (BALF). The wet-to-dry weight ratio was calculated, and hematoxylin and eosin staining of lung tissue was performed. Cell viability of AEC-II was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Real-time quantitative reverse transcription polymerase chain reaction assay was carried out to quantify the relative gene expression of TNF-α and IL-1β in AEC-II. The western blotting analysis was executed to elucidate the expression of mediators linked to nuclear factor-kappa B (NF-κB), mitogen-activated protein kinase (MAPK), and phosphatidylinositol-3 kinase-protein kinase B (PI3K-Akt) signaling pathways. ACW-SBG significantly decreased lung wet-to-dry weight ratio, ameliorated LPS-induced lung histopathological changes, and reduced the release of inflammatory mediators such as TNF-α and IL-1β in BALF. In AEC-II, we found that the expression of TNF-α mRNA was also inhibited by ACW-SBG. ACW-SBG blocked NF-κB activation by preventing the phosphorylation of NF-κB (p65) as well as the phosphorylation and degradation of the inhibitor of kappa B kinase. ACW-SBG extracts also inhibited the phosphorylation of respective MAPKs (c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p38) as well as Akt. The present study demonstrated that ACW-SBG played a potent anti-inflammatory role in LPS-induced ALI in rats. The potential molecular mechanism was involved in attenuating the NF-κB, MAPKs, and PI3K-Akt signaling pathways in LPS-induced AEC-II.