Direct vagus nerve stimulation: A new tool to control allergic airway
inflammation through α7 nicotinic acetylcholine receptor
Abstract
Background and Purpose Asthma is characterized by airway inflammation,
mucus hypersecretion and airway hyperresponsiveness (AHR). The
activation of cholinergic anti‐inflammatory pathway (CAP) through
nicotinic agents has been shown to control experimental asthma. Yet, the
effects of vagus nerve stimulation (VNS)-induced CAP on allergic
inflammation remain unknown. Experimental Approach BALB/c mice were
sensitized and challenged with house dust mite (HDM) extract, and
treated with active VNS (5Hz, 0.5 ms, 0.1 mA). Bronchoalveolar lavage
(BAL) fluid was assessed for total and differential cell counts and
cytokine levels. Lungs were examined by histopathology and electron
microscopy. AHR in response to methacholine was also measured. Key
Results In the HDM mouse asthma model, active but not sham VNS reduced
BAL fluid total and differential cell counts, blocked mucus
hypersecretion and suppressed choline acetyltransferase (ChAT)
expression in bronchial epithelial cells. Besides, active VNS also
abated HDM-induced elevation of type 2 cytokines IL-4 and IL-5.
Furthermore, goblet cell hyperplasia and collagen deposition were
diminished in VNS-treated mice. Mechanistically, VNS was found to block
the phosphorylation of transcription factor STAT6 and the level of IRF4
in total lung lysates. Finally, VNS abrogated methacholine-induced AHR
in asthma mice. Therapeutic effects of VNS were abolished by prior
administration with α-bungarotoxin, a specific inhibitor of α7 nicotinic
receptors (α7nAChR). Conclusion Our data revealed the protective effects
of VNS on various clinical features in allergic airway inflammation
model. VNS, a clinically approved therapy for depression and epilepsy,
appears to be a promising new strategy for controlling allergic asthma
through α7nAChR.