Mechanism of Jizhi syrup’s prevention and treatment of acute bronchitis based on LPS-iNOS inflammatory mediators’ signalling pathway

Abstract

Ethnopharmacological relevanceJizhi syrup (JZTJ) is composed of eight medicinal herbs, including Houttuynia cordata, Fagopyrum dibotrys, Ilex chinensis, Ephedra sinica, Aster tataricus, Peucedanum praeruptorum, Citrus aurantium and Glycyrrhiza uralensis. It is mainly used for coughing caused by exogenous wind heat. Symptoms include fever, aversion to cold, chest and diaphragm tightness, cough and sore throat; and acute bronchitis and acute exacerbation of chronic bronchitis with the above symptoms. PurposeThis study aimed to preliminary analyse the chemical components in the liposoluble part of JZTJ, evaluate the anti-inflammatory effect of JZTJ by using six animal and cell models and predict the target and mechanism of acute bronchitis prevention and treatment with JZTJ. MethodsThe chemical components in the liposoluble fraction of JZTJ (extracted by cyclohexane) were quantitatively analysed using gas chromatography-mass spectrometry (GC-MS). Classic non-specific inflammation models and acute bronchitis models were established to systematically evaluate the anti-inflammatory effect of JZTJ. The anti-inflammatory intensity and characteristics of three doses of JZTJ were comprehensively compared on the basis of principal component analysis method at the cellular and overall animal levels. By using lipopolysaccharides (LPSs) as modelling factors, a RAW264.7 macrophage inflammatory response model and a rat acute bronchitis model were created to study the effect of JZTJ on the in-vitro and - vivo LPS-iNOS-inflammatory mediators’ inflammatory signalling pathway to reveal the mechanism of acute bronchitis prevention and treatment by JZTJ at the levels of genes, proteins, and inflammatory mediators. ResultsSeventeen alkane and ester compounds were preliminarily qualitatively identified from the lipid soluble fraction of JZTJ: dibutyl phthalate, tetradecane, ridecane, n-hexadecanoic acid, pentadecane, n-decanoic acid, 2,6,10,14,18,22-tetracosahexaene, 2,6,10,15,19,23-hexamethyl-(all-E)-; phenol, 2,2ʹ-methylenebis[6-(1,1-dimethylethyl)-4-methyl-; hexadecane. JZTJ has a significant inhibitory effect on acute non-specific inflammation, specifically inhibiting ‘xylene-induced ear swelling in mice’, ‘acetic acid-induced increased permeability of abdominal capillaries in mice’ and ‘egg white-induced foot swelling in rats’. The above effects are most evident in high doses, followed by medium doses, whereas low doses have poorer or no effects. JZTJ can prevent and treat acute bronchitis induced by LPS in mice and rats, significantly improve the pathological changes in patchy interstitial and alveolar bleeding with excessive neutrophil infiltration and inhibit the release of inflammatory mediators by LPS-induced RAW264.7 macrophages. Its mechanism of action may be by downregulating the phosphorylation level of p-ERK1/2 protein, thereby inhibiting inducible nitric oxide synthase (iNOS) mRNA, tumour necrosis factor (TNF)-α MRNA and IL-1β. The expression levels of genes, such as mRNA and IL-6 mRNA, thereby reducing iNOS, TNF-α and IL-1β. The expression of proteins in the cytoplasm of lung and bronchial tissue cells reduced the release of downstream inflammatory mediators NO and IL-6. ConclusionPreliminary analysis of the chemical components in the lipid soluble fraction of JZTJ can lay the foundation for subsequent research on its effective components. Evaluating the anti-inflammatory effect of JZTJ is helpful for further research on its mechanism of action. The anti-inflammatory effects are exerted by regulating the inflammatory signalling pathway of LPS-iNOS inflammatory mediators, providing a scientific basis for their clinical application.