Activated group 2 innate lymphoid cells (ILC2s) play a crucial role in respiratory syncytial virus (RSV)-induced airway
inflammation and
allergy-like symptoms because of their ability to secrete large quantities of type 2
cytokines.
Cytokines such as
IL-33, IL-25, and
thymic stromal lymphopoietin are activators of ILC2s. Besides, a regulatory effect of
neurotransmitters on ILC2 activation has been reported recently. However, whether and how
RSV infection induces
neurotransmitter production in the lungs and regulates pulmonary ILC2 activation remains unclear. In this study, using a murine model established by intranasal
infection with RSV, we found that acute
RSV infection induced the production of a
neurotransmitter,
neuromedin U (NMU), in the lungs of RSV-infected mice and upregulated the expression of NMUR1 (
neuromedin U receptor 1) on ILC2s. Moreover, in vivo administration of NMU exacerbated RSV-induced airway
inflammation by promoting the proliferation and activation of pulmonary ILC2s via the NMUR1 pathway, which involved PI3K,
mitogen-activated protein kinase kinase, and NFAT signaling
proteins. Furthermore, pulmonary neurons responded to the stimulation of
RSV infection and secreted NMU in a
Toll-like receptor 4- and
Toll-like receptor 7-dependent manner. Collectively, our data suggest that NMU is a powerful
neuropeptide to activate ILC2s, highlighting the critical regulatory effects of
neurotransmitters on
antiviral, inflammatory, and tissue homeostasis at the mucosal barrier during a viral respiratory
infection.