AUTHOR=Yin Shuomiao , Ding Meizhu , Fan Long , Yu Xuhua , Liang Ziyao , Wu Lei , Gao Zhiling , Lin Lin , Chen Yuanbin 

TITLE=Inhibition of Inflammation and Regulation of AQPs/ENaCs/Na+-K+-ATPase Mediated Alveolar Fluid Transport by Total Flavonoids Extracted From Nervilia fordii in Lipopolysaccharide-induced Acute Lung Injury

JOURNAL=Frontiers in Pharmacology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2021.603863

DOI=10.3389/fphar.2021.603863

ISSN=1663-9812

ABSTRACT=<p><bold>Aims:</bold> The occurrence of vascular permeability pulmonary edema in acute lung injury (ALI) is related to the imbalance of alveolar fluid transport. Regulating the active transport of alveolar fluid by aquaporins (AQPs), epithelial sodium channels (ENaCs), and Na<sup>+</sup>-K<sup>+</sup>-ATPase can effectively reduce the edema fluid in the alveolar cavity and protect against ALI. We evaluated the therapeutic effects of total flavonoids, extracted from <italic>Nervilia fordii</italic> (TFENF), and investigated its potential mechanisms of alveolar fluid transport in a rat ALI model.</p><p><bold>Materials and methods:</bold> A model of lipopolysaccharide (LPS, 5 mg/kg)-induced ALI was established in Sprague-Dawley (SD) rats through the arteriae dorsalis penis. SD rats were divided into six groups, including the vehicle, LPS model, TFENF (6 mg/kg, 12 mg/kg, 24 mg/kg), and dexamethasone group (DEX group, 5 mg/kg). The wet-to-dry (W/D) lung weight ratio, oxygenation index, and histopathological observation were used to evaluate the therapeutic effect of TFENF. The mRNA expression of <italic>AQPs, ENaCs</italic>, and pro-inflammatory cytokines was determined using real-time polymerase chain reaction, whereas protein expression was determined using immunohistochemistry. The <italic>Na</italic><sup><italic>+</italic></sup><italic>-K</italic><sup><italic>+</italic></sup><italic>-ATPase</italic> activity was assessed using enzyme-linked immunosorbent assay.</p><p><bold>Results:</bold> LPS significantly stimulated the production of inflammatory mediators including tumor necrosis factor (TNF)-α and interleukin (IL)-1β, and disrupted the water transport balance in the alveolar cavity by inhibiting <italic>AQPs/ENaCs/Na</italic><sup><italic>+</italic></sup><italic>-K</italic><sup><italic>+</italic></sup><italic>-ATPase</italic>. Pretreatment with TFENF reduced the pathological damage and W/D ratio of the lungs and ameliorated the arterial blood oxygen partial pressure (PaO<sub>2</sub>) and oxygenation index. TFENF further decreased the mRNA level of <italic>TNF-α</italic> and <italic>IL-1β</italic>; increased the expression of <italic>AQP-1, AQP-5, αENaC, and βENaC</italic>; and increased <italic>Na</italic><sup><italic>+</italic></sup><italic>-K</italic><sup><italic>+</italic></sup><italic>-ATPase</italic> activity. Moreover, the regulation of <italic>AQPs, βENaC,</italic> and <italic>Na</italic><sup><italic>+</italic></sup><italic>-K</italic><sup><italic>+</italic></sup><italic>-ATPase</italic> and the inhibition of <italic>TNF-α</italic> and <italic>IL-1β</italic> by TFENF were found to be dose dependent.</p><p><bold>Conclusion:</bold> TFENF protects against LPS-induced ALI, at least in part, through the suppression of inflammatory cytokines and regulation of the active transport capacity of <italic>AQPs/ENaCs/Na</italic><sup><italic>+</italic></sup><italic>-K</italic><sup><italic>+</italic></sup><italic>-ATPase</italic>. These findings suggest the therapeutic potential of TFENF as phytomedicine to treat inflammation and pulmonary edema in ALI.</p>