ABSTRACT
ObjectiveTo explore the mechanism of the combined therapy of lung and intestine （Mahuangtang + Da Chengqitang） in alleviating pulmonary edema in rats with acute lung injury （ALI） induced by lipopolysaccharide （LPS）. MethodWistar rats were randomly divided into blank group， model group， low-， medium-， and high-dose groups with combined therapy of lung and intestine， and positive control group. LPS （10 mg·kg-1） was given （ip） to induce ALI in rats. After modeling， the blank group was given normal saline （25 mL·kg-1）， the combined therapy of lung and intestine treatment groups were given （ig） low- （5 g·kg-1）， medium- （7.5 g·kg-1）， and high-dose （10 g·kg-1） Mahuangtang and Da Chengqitang， and the positive control group was given dexamethasone （5 mg·kg-1）. Medications were administered 0， 8， and 16 h after LPS injection for 3 times. Then lung tissue and serum were collected after administration. The lung tissues were stained with haematoxylin-eosin （HE）， and the pulmonary edema score was evaluated. The dry/wet （D/W） weight ratio of lung tissues in each group was measured， and the content of serum vasoactive intestinal peptide （VIP） in rats was detected by enzyme-linked immunosorbent assay （ELISA）. Western blot was used to detect the protein levels of aquaporin-1 （AQP1）， AQP5， VIP， cyclic adenosine monophosphate （cAMP）， phosphorylated protein kinase A （p-PKA）， and PKA in lung tissues of rats in each group. The level of VIP mRNA in lung tissues of rats was detected by real-time quantitative polymerase chain reaction （Real-time PCR）. ResultCompared with the blank group， the model group exhibited obvious lung injury， increased edema score， decreased D/W ratio （P<0.01）， declined AQP1， AQP5， cAMP， and p-PKA/PKA in lung tissues （P<0.05， P<0.01）， elevated VIP content （P<0.01）， and up-regulated levels of VIP protein and mRNA in lung tissues （P<0.05， P<0.01）. Compared with the model group， combined therapy of lung and intestine treatment groups showed alleviated lung injury， increased D/W ratio （P<0.01）， elevated AQP1， AQP5， VIP， cAMP， and p-PKA/PKA in lung tissues （P<0.05， P<0.01）， and up-regulated VIP levels in lung tissues （P<0.05， P<0.01）. ConclusionThe combined therapy of lung and intestine can alleviate ALI-induced lung tissue edema， and the mechanism may be related to the activation of the VIP/cAMP/PKA signaling pathway， which further promotes the expression of AQP1 and AQP5 and enhances the water metabolism of lung tissue.
ABSTRACT
Lung and intestine combination therapy(LICT) is effective in the treatment of acute lung injury(ALI). In this study, the combination of Mahuang Decoction and Dachengqi Decoction(hereinafter referred to as the combination), a manifestation of LICT, was employed to explore the effect of nuclear factor kappaB(NF-κB)/nucleotide binding oligomerization domain-like receptors-3(NLRP3) pathway and alveolar macrophage activation on the lung inflammation in rats with ALI, for the purpose of elucidating the mechanism of LICT in treating ALI. After the modeling of ALI with limpolysaccharide(LPS, ip), rats were respectively given(ig) the combination at 10, 7.5, and 5 g·kg~(-1)(high-dose, medium-dose, and low-dose LICT groups, separately), once every 8 h for 3 times. Haematoxylin-eosin(HE) staining was used to observe the histopathological changes of lung tissue, followed by the scoring of inflammation. Immunohistochemistry was applied to detect alveolar macrophage activation, enzyme-linked immunosorbent assay(ELISA) was applied to detect the serum content of tumor necrosis factor-α(TNF-α) and interleukin-18(IL-18), Western blot was applied to detect the protein expression of phosphorylated-nuclear factor kappaB p65(p-NF-κB p65), nuclear factor kappaB p65(NF-κB p65), phosphorylated-inhibitor kappaB alpha(p-IκBα), inhibitor kappaB alpha(IκBα), and NLRP3 in lung tissue, and quantitative reverse transcription-PCR(qRT-PCR) was applied to detect the mRNA expression of TNF-α, IL-18, NLRP3, and NF-κB p65 in lung tissue. The results showed that LICT groups demonstrated lung injury relief, decrease in inflammation score, alleviation of alveolar macrophage activation, significant decline in serum content of inflammatory factors TNF-α and IL-18, and decrease of the protein expression of p-NF-κB p65/NF-κB p65, p-IκBα/IκBα, and NLRP3, and mRNA expression of TNF-α, IL-18, NLRP3, and NF-κB p65 in lung tissue. In summary, LICT has definite therapeutic effect on ALI. The mechanism is that it inhibits alveolar macrophage activation by suppressing NF-κB/NLRP3 signaling pathway, thereby reducing the activation and release of inflammatory factors and finally inhibiting inflammation.