Elsevier

Journal of Ethnopharmacology

Volume 235, 10 May 2019, Pages 424-434
Journal of Ethnopharmacology

Srolo Bzhtang, a traditional Tibetan medicine formula, inhibits cigarette smoke induced airway inflammation and muc5ac hypersecretion via suppressing IL-13/STAT6 signaling pathway in rats

https://doi.org/10.1016/j.jep.2019.02.006Get rights and content

Abstract

Ethnopharmacological relevance

Srolo Bzhtang (SBT), a traditional Tibetan medicine formula, was composed of three herbs, Solms-Laubachia eurycarpa, Bergenia purpurascens, Glycyrrhiza uralensis, and one lac, and was first documented in the ancient Tibetan medical work Four Medical Tantras (rGyud-bzhi) in the eighth century AD. It has been widely used to treat lung “phlegm-heat” syndromes such as chronic bronchitis and chronic obstructive pulmonary disease (COPD).

Objective

The aim of this study was to evaluate the potential influences of aqueous extract of SBT on airway inflammation and mucus secretion and to reveal the underlying mechanism in a rat model of cigarette smoke (CS)-induced chronic bronchitis (CB).

Materials and methods

Sixty male Sprague-Dawley rats were randomly divided to six groups: control (room air exposure), model (CS exposure), DEX (CS exposure and 0.2 mg/kg/day dexamethasone), and three SBT (CS exposure and 1.67, 2.50, and 3.34 g/kg/day SBT) groups. DEX and the three doses of SBT were administered by oral gavage every day for eight weeks. Pathological changes and mucus expression in the lung tissue were determined by hematoxylin and eosin (H&E), Alcian blue-periodic acid-Schiff (AB-PAS) and immunohistochemical staining. The levels of cytokines in bronchoalveolar lavage fluid (BALF) were assessed by ELISA. Western blot analysis and qRT-PCR were performed to explore the effects of SBT on the expression of IL-13, STAT6 and MUC5AC.

Results

Pretreatment with SBT attenuated the TNF-α, IL-8, IL-13 expression levels in BALF and the inflammatory cell infiltration in bronchial walls and peribronchial lung tissue. SBT exhibited a dose-dependent downregulation of MUC5AC expression as assessed by AB-PAS and immunohistochemical staining. The protein and mRNA levels of IL-13, STAT6/p-STAT6 and MUC5AC were also downregulated by SBT preconditioning.

Conclusion

These results for the first time demonstrated that SBT exhibited protective effects on CS-induced airway inflammation and MUC5AC hypersecretion, which might be related to the downregulation of the IL-13/STAT6 signaling pathway.

Introduction

Chronic bronchitis (CB) and chronic obstructive pulmonary disease (COPD) are two of the most common diseases characterized by chronic airway inflammation and mucin hypersecretion (Fahy and Dickey, 2010). CB is closely associated with COPD because of its chronic potential facilitation of lung function deterioration and airway obstruction (Pelkonen et al., 2006). Furthermore, CB has been considered an important factor that induces respiratory infection and mortality (Guerra et al., 2009, Pelkonen et al., 2017).

Mucus hypersecretion is closely associated with the rate of decline in lung function and mortality of patients with CB and COPD (Hogg et al., 2004, Stewart and Criner, 2013). MUC5AC and MUC5B are the principal gel-forming mucins found in airway mucus (Ma et al., 2018). MUC5AC is highly expressed in superficial airway goblet cells, and goblet cell metaplasia (GCM) result in mucus hypersecretion in the inflammatory lung diseases (Curran and Cohn, 2010). Furthermore, the level of MUC5AC and mucociliary-beating frequency are closely related in inflammatory airway (Nabissi et al., 2018, Oliviero et al., 2016).

Srolo Bzhtang (SBT), a Tibetan traditional medicine formula, is composed of three medicinal herbs, Solms-laubachia eurycarpa (Maxim.) Botsch. (Brassicaceae), Bergenia purpurascens (Hook. f. et Thoms.) Engl. (Saxifragaceae), Glycyrrhiza uralensis Fisch. (Leguminosae) and one lac secreted by Laccifer lacca Kerr (Lacciferidae Cockerell). According to the records of the Tibetan medical work Four Medical Tantras, SBT has been traditionally used to treat lung “phlegm-heat” syndrome, by clearing “lung heat”, eliminating phlegm, and relieving cough, for over 1200 years in the Qinghai-Tibetan Plateau. In clinic, SBT had significant antitussive effects and was able to reduce airway inflammation induced phlegm-overproduction in patients with CB and lung “phlegm-heat” syndrome (Cuo and CaiRang, 1999, SuoNan and DaJie, 2015, Yang, 2013).

In traditional Chinese medicine, the rhizome of S.-L. eurycarpa and B. purpurascens, dried roots of G. uralensis are applied for treatment of various disease by clearing “lung heat” and resolving toxin (Luo, 1997). Lac (紫草茸), the dry gum (secreted by Laccifer lacca Kerr) surround the branch of some plant, is used as a remedy to “clear heat”, “cool blood” and detoxify the body (Editorial Committee, 1999). Previously published studies indicated that α-linolenic acid (isolated from S.-L. eurycarpa) (Kaplan et al., 2018), bergenin (main active compounds from B. purpurascens) (Ren et al., 2016, Yang et al., 2017b), G. uralensis (Wu et al., 2017, Yang et al., 2013), laccaic acid (isolated from lac) (Sekido et al., 2010), exerted an inhibition effect on inflammation in vitro and in vivo. However, to this formula, the data about its pharmacological activities of anti-inflammation and anti-mucus hypersecretion have not been reported up to present.

The aim of this study was to explore the effects of aqueous extract of SBT on CS-induced airway inflammation and MUC5AC hypersecretion and to explore the underlying mechanism in a rat model of CB.

Section snippets

Chemicals and reagents

The SBT formula components, including S.-L. eurycarpa, B. purpurascens, G. uralensis and lac, were purchased from the Xining Traditional Chinese and Tibetan Medicine Market (Qinghai, China) and were identified by Prof. Dejun Zhang, Qinghai University. The specimens of S.-L. eurycarpa, B. purpurascens, G. uralensis and lac were deposited at the Research Center for High Altitude Medicine under the accession numbers 2016–051, 2016–052, 2016–053, 2016–054, respectively. Dexamethasone was purchased

Effect of SBT on rat body weight and blood leukocyte

At the end of the eighth CS-exposure week, the body weights of rats in the control group were 473.5 ± 23.1 g, whereas the body weights of the CS-exposed rats in the model, DEX, SBT-L, SBT-M and SBT-H groups were decreased to 369.9 ± 19.2 g, 231.7 ± 25.5 g, 386.3 ± 28.1 g, 388.7 ± 24.6 g, 389.0 ± 23.2 g, respectively. There were no significant differences in the weekly body weight gain of the rats in the SBT-L, SBT-M and SBT-H groups (data not shown). Furthermore, pretreatment with a high dose

Discussion

Noxious environmental stimuli, usually air pollutants and cigarette smoke (CS), increase inflammation in the airways and the lung tissue (Bhat et al., 2015, Stampfli and Anderson, 2009). Chronic bronchitis (CB) is common in people who smoke or are ex-smokers with a long productive cough and sputum production history. Smoking is the first risk factor for developing CB (Kim and Criner, 2013), which induces airway inflammation and mucus overproduction and contributes to airway obstruction,

Conclusion

These findings for the first time suggested that SBT exhibited a significant protective effect against CS-induced CB by ameliorating airway inflammation and MUC5AC hypersecretion, which might be related to the downregulation of the IL-13/STAT6 signaling pathway. Furthermore, research examining the specific compound responsible for the effect of SBT against CS-induced CB is ongoing.

Acknowledgement

This work was supported by grants from the Natural Science Foundation of China (81460663) and Natural Science Foundation for Young Scientists of Science and Technology Department in Qinghai province, China (2017-ZJ-937Q). The authors wish to thank Zhancui Dang, Qilian He for their help in taking care of animals and harvesting animal specimens in this study.

Authors contributions

Linde Jing performed the experiments, collected data of various activities and wrote the manuscript. Shanshan Su performed the UHPLC-Q-Exactive hybrid quadrupole-orbitrap mass analysis. Dejun Zhang authenticated the Tibetan herb medicines. Zhanqiang Li, Dianxiang Lu and Rili Ge designed this study, provided necessary facilities for experiments and revised the manuscript. All authors read and approved the final manuscript.

Conflict of interest

The authors declare that they have no conflict of interest.

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