The Volatile Oil of Zanthoxylum bungeanum Pericarp Improved the Hypothalamic-Pituitary-Adrenal Axis and Gut Microbiota to Attenuate Chronic Unpredictable Stress-Induced Anxiety Behavior in Rats

Abstract

Background

Anxiety disorders (ADs) are the most prevalent mental disorders worldwide. Stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis and dysbiosis of gut microbiota seem to contribute to the onset of ADs. This study was designed to investigate the ameliorative effect of volatile oil of Zanthoxylum bungeanum (VOZB) on chronic unpredictable stress (CUS) induced anxiety behavior, as well as the altered HPA axis and gut microbiota.

Methods

Experimental rats were exposed to the CUS for 14 consecutive days. Meanwhile, VOZB was administered at doses of 50, 100 and 200 mg/kg/day for 14 days. The anxiety behavior was evaluated by elevated plus-maze (EPM) and open field (OF). The protein expressions and mRNA levels of corticotropin-releasing hormone (CRH) and glucocorticoid receptor (GR) in hypothalamus was determined, as well the hormone levels of HPA axis in serum. Furthermore, gut microbiota was detected by16S rRNA gene sequencing. The chemical constituents of VOZB were identified by GC-MS analysis.

Results

VOZB treatment (100 and 200 mg/kg/day) increased the ratio of open-arm entries and time in EPM test, as well as the central zone entries and time in OF test. Moreover, VOZB treatment reduced the protein expressions and mRNA levels of CRH, but elevated those of GR in hypothalamus. Similarly, the hormone levels of the HPA axis in serum were decreased by VOZB treatment. Besides, VOZB treatment restored the CUS-induced dysbiosis of gut microbiota, raising the Sobs and Chao indexes, inhibiting Lachnospiraceae, but facilitating Bacteroidales_S24-7_group, Lactobacillaceae, and Prevotellaceae. Additionally, Sobs and Chao indexes were negatively correlated to the serum corticosterone and CRH levels.

Conclusion

VOZB showed an ameliorative effect on CUS-induced anxiety behavior, potentially via inhibiting activation of the HPA axis and restoring the dysbiosis of gut microbiota, thus improving the stress-induced abnormality of the microbiota-gut-brain axis.

Keywords:

• Zanthoxylum bungeanum
• anxiety disorders
• stress
• neuroendocrine
• hypothalamic-pituitary-adrenal axis
• gut microbiota

Acknowledgments

This work was supported by the “Xinglin Scholars” Scientific Research Promotion Program of Chengdu University of Traditional Chinese Medicine (No. 030041167).

Abbreviations

ADs, anxiety disorders; VOZB, volatile oil of Zanthoxylum bungeanum; HPA axis, hypothalamic-pituitary-adrenal axis; CUS, chronic unpredictable stress; EPM, elevated plus-maze; OF, open field; CRH, corticotropin-releasing hormone; GR, glucocorticoid receptor; ACTH, adrenocorticotropic hormone; CORT, corticosterone; GC-MS, Gas Chromatography-Mass Spectrometry; GF, Germ-free; SPF, specific pathogen-free; CMC-Na, sodium carboxymethyl cellulose; AOD, average optical density; ANOVA, analysis of variance; ROE, ratio of open-arm entries; ROT, ratio of open-arm time; OTUs, operational taxonomic units; PCoA, principal coordinates analysis; NMDS, nonmetric multidimensional scaling.

Data Sharing Statement

The data used to support the findings of this study are available from Chunjie Wu upon request.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no conflicts of interest in this work.