Selective inhibition of vagal afferent nerve pathways regulating cough using Na_v 1.7 shRNA silencing in guinea pig nodose ganglia

Abstract

Selective inhibition of vagal afferent nerve pathways regulating cough using Nav 1.7 shRNA silencing in guinea pig nodose ganglia. Am J Physiol Regul Integr Comp Physiol 304: R1017-R1023, 2013. First published April 10, 2013 doi:10.1152/ajpregu.00028.2013.-Adenoassociated virus delivery systems and short hairpin RNA (shRNA) were used to selectively silence the voltage-gated sodium channel NaV 1.7 in the nodose ganglia of guinea pigs. The cough reflex in these animals was subsequently assessed. NaV 1.7 shRNA was delivered to the majority of nodose ganglia neurons [50 -60% transfection rate determined by green fluorescent protein (GFP) gene cotransfection] and action potential conduction in the nodose vagal nerve fibers, as evaluated using an extracellular recording technique, was markedly and significantly reduced. By contrast, Ͻ5% of neurons in the jugular vagal ganglia neurons were transfected, and action potential conduction in the jugular vagal nerve fibers was unchanged. The control virus (with GFP expression) was without effect on action potential discharge and conduction in either ganglia. In vivo, NaV 1.7 silencing in the nodose ganglia nearly abolished cough evoked by mechanically probing the tracheal mucosa in anesthetized guinea pigs. Stimuli such as capsaicin and bradykinin that are known to stimulate both nodose and jugular C-fibers evoked coughing in conscious animals was unaffected by NaV 1.7 silencing in the nodose ganglia. Nodose C-fiber selective stimuli including adenosine, 2-methyl-5-HT, and ATP all failed to evoke coughing upon aerosol challenge. These results indicate that cough is independently regulated by two vagal afferent nerve subtypes in guinea pigs, with nodose A␦ fibers regulating cough evoked mechanically from the trachea and bradykinin-and capsaicinevoked cough regulated by C-fibers arising from the jugular ganglia. sodium channels; Nav 1.7; vagal reflex; C-fibers; capsaicin STUDIES IN GUINEA PIGS indicate that at least two vagal afferent nerve subtypes can induce coughing upon activation (7,9). In addition to C-fibers, which conduct action potentials at Ͻ2 m/s and are activated by bradykinin and agonists of transient receptor potential vanilloid-1 (TRPV1) and transient receptor potential ankyrin-1 (TRPA1) ion channels, cough is also regulated by neurons that conduct action potentials in the A␦ range (ϳ5 m/s). These small, myelinated afferent nerves are exquisitely sensitive to punctuate mechanical stimulation and rapid decreases in mucosal pH (15, 23) but are insensitive to activators of TRPV1 or TRPA1.The A␦ vagal afferents that regulate cough arise from the nodose ganglia and terminate in the subepithelial extracellular matrix of the extrapulmonary airways (21). C-fibers innervating the guinea pig respiratory tract project from both the nodose and jugular ganglia. The unmyelinated afferents derived from these embryologically distinct ganglia have unique activation profiles and sites of termination in the airways and lungs and thus represent physiologically distinct subtypes (...

Pharmacology of Bradykinin-Evoked Coughing in Guinea Pigs

“…The involvement of NKs also supports our previous assertions of jugular C-fiber involvement and against a role for either jugular Ad-fibers or nodose C-fibers (Ricco et al, 1996;Undem et al, 2004;Muroi et al, 2013).…”

“…Single, explosive coughing events evoked by mechanical stimulation of the airway mucosa in anesthetized guinea pigs-reflexes we attribute to activation of the bradykinin-insensitive nodose Ad fibers innervating the trachea, larynx, and main stem bronchi (Mazzone et al, 2009;Muroi et al, 2013)-were still present in all animals treated with a combination of the NK 1 , NK 2 , and NK 3 receptor antagonists (SR140333, SR48968, and SB223412, respectively; 3 mg·kg 21 each, i.p. ; n 5 3) or the vehicle for these antagonists (n 5 3).…”

Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine

“…Yet, indomethacin is also known to cause paradoxical cough as a side effect in a small subset (2.3%) of patients (www.ehealthme.com/ds/indomethacin/cough). In the guinea pig, Na v 1.7 knockdown by shRNA abolishes citric acid-induced cough (Muroi et al, 2013); this observation supports the feasibility of the third approach. This is in keeping with the antitussive action of nebulized lidocaine in patients with intractable cough (reviewed in Slaton et al, 2013).…”

Control of Neurotransmission by NaV1.7 in Human, Guinea Pig, and Mouse Airway Parasympathetic Nerves

“…Another speculative benefit therefore of topically applied (inhaled) NaV-blocking drugs over muscarinic receptor antagonists is that even central deposition of a NaV blocker my lead to bronchodilation of more peripheral bronchi and bronchioles. Finally, we have recently reported that blocking NaV1.7 can inhibit action potential conduction along sensory C-fibers in the respiratory tract, leading to inhibition of undesirable sensations such as dyspnea and urge to cough, an effect that antimuscarinic drugs would not share (Muroi et al, 2011(Muroi et al, , 2013. It should be kept in mind that the present study focused on airways from healthy laboratory animals and donors that did not have asthma or COPD; both the expression and function of NaV channels may potentially be altered in the diseased state (Chahine and O'Leary, 2014).…”