Pkc Epsilon Stimulation Of Trpv1 Orchestrates Carotid Body Responses To Asthmakines

Key pointsWe have previously shown that carotid body stimulation by lysophosphatidic acid elicits a reflex stimulation of vagal efferent activity sufficient to cause bronchoconstriction in asthmatic rats.Here, we show that pathophysiological concentrations of asthma-associated prototypical Th2 cytokines also stimulate the carotid bodies.Stimulation of the carotid bodies by these asthmakines involves a PKC epsilon-transient receptor potential vanilloid 1 (TRPV1) signalling mechanism likely dependent on TRPV1 S502 and T704 phosphorylation sites.As the carotid bodies' oxygen sensitivity is independent of PKC epsilon-TRPV1 signalling, systemic blockade of PKC epsilon may provide a novel therapeutic target to reduce allergen-induced asthmatic bronchoconstriction.Consistent with the therapeutic potential of blocking the PKC epsilon-TRPV1 pathway, systemic delivery of a PKC epsilon-blocking peptide suppresses asthmatic respiratory distress in response to allergen and reduces airway hyperresponsiveness to bradykinin.The autonomic nervous system orchestrates organ-specific, systemic and behavioural responses to inflammation. Recently, we demonstrated a vital role for lysophosphatidic acid in stimulating the primary autonomic oxygen chemoreceptors, the carotid bodies, in parasympathetic-mediated asthmatic airway hyperresponsiveness. However, the cacophony of stimulatory factors and cellular mechanisms of carotid body activation are unknown. Therefore, we set out to determine the intracellular signalling involved in carotid body-mediated sensing of asthmatic blood-borne inflammatory mediators. We employed a range of in vitro and rat in situ preparations, site-directed mutagenesis, patch-clamp, nerve recordings and pharmacological inhibition to assess cellular signalling. We show that the carotid bodies are also sensitive to asthma-associated prototypical Th2 cytokines which elicit sensory nerve excitation. This provides additional asthmatic ligands contributing to the previously established reflex arc resulting in efferent vagal activity and asthmatic bronchoconstriction. This novel sensing role for the carotid body is mediated by a PKC epsilon-dependent stimulation of transient receptor potential vanilloid 1 (TRPV1), likely via TRPV1 phosphorylation at sites T704 and S502. Importantly, carotid body oxygen sensing was unaffected by blocking either PKC epsilon or TRPV1. Further, we demonstrate that systemic PKC epsilon blockade reduces asthmatic respiratory distress in response to allergen and airway hyperresponsiveness. These discoveries support an inflammation-dependent, oxygen-independent function for the carotid body and suggest that targeting PKC epsilon provides a novel therapeutic option to abate allergic airway disease without altering life-saving autonomic hypoxic reflexes.