Objectives Decreased lung function in chronic obstructive pulmonary disease (COPD) is correlated with abnormal excitability of the respiratory centre where orexin neuropeptides from the hypothalamus are responsible for regulating respiration. We hypothesised that improvements in pulmonary function with electroacupuncture (EA) may be related to orexins in a rat model of COPD.
Methods The COPD model was established by cigarette smoke exposure and lipopolysaccharide injection. Modelled rats received EA at BL13 and ST36 for two weeks, after which lung function was tested. Orexin levels in the hypothalamus and medulla were detected by ELISA, while mRNA/protein expression and localisation of orexins and their receptors were investigated using real time PCR, Western blotting and immunohistochemistry, respectively.
Results The decrease in lung function observed in COPD rats was improved after EA treatment. Orexin levels in the hypothalamus and medulla were significantly higher in COPD rats than in normal rats, but were significantly reduced in the EA-treated group. There was a negative correlation between orexin content and lung function. In the hypothalamus, mRNA and protein expression and immunoreactivity of orexins were significantly higher in the COPD group than in the normal group, but a significant decrease was observed after EA. In the medulla, the expression and immunoreactivity of orexin receptors were significantly higher in the COPD group than in the normal group, but a significant decrease was observed after EA.
Conclusions The positive effect of EA on pulmonary function in COPD rats may be related to downregulation of orexins and their receptors in the medulla.
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X-FZ, QQ and W-YG contributed equally.
Contributors X-FZ, QQ and W-YG contributed equally to this work, performed all the research and analysed the data. C-WJ, YL, X-LL and JL participated in data interpretation and discussion. Z-BL designed the research, drafted and revised the manuscript. All authors read and approved the final version of the manuscript accepted for publication.
Funding This work was supported by project grants from the National Natural Science Foundation of China (no.81072870, 81373743 and 81102660) and the Natural Science Foundation of Anhui Province (no. 1408085MH201).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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