Mitochondrial dysfunction increases bronchopulmonary C‐fiber excitability via PKC alpha signaling

Abstract

Airway sensory nerve excitability is a key determinant of respiratory disease‐associated reflexes and sensations such as cough and dyspnea. One notable feature of peripheral terminals of sensory nerves is that they are packed with mitochondria. Mitochondrial dysfunction and subsequent oxidative stress has been reported for a variety of cell types in inflammatory diseases. We have previously shown that reactive oxygen species (ROS) produced by Antimycin A (a mitochondrial complex III Qi site inhibitor) increase excitability in bronchopulmonary nociceptive C‐fibers. This increased excitability decreases the mechanical threshold for activation and increases action potential firing in response to a P2X2/3 agonist. This Antimycin A–induced hyperexcitability is dependent on mitochondrial ROS and is blocked by intracellular antioxidants.Given that ROS are known to activate protein kinase C (PKC), we hypothesized that this increased excitability was due to PKC activation. We used dissociated vagal ganglion neurons to study activation of the PKC isoforms: alpha, beta1, beta2, delta and epsilon in response to Antimycin‐A. Cells were stained with antibodies against the specific isoforms to determine their cellular location. Of these isoforms, only PKC alpha translocated to the region of the cell membrane in response to Antimycin A treatment.We also examined the effects of Antimycin A induced ROS production on sensory nerve terminals. We recorded action potential firing from the terminals of individual bronchopulmonary C‐fibers using a mouse ex vivo lung‐vagal ganglia preparation. C‐fibers were characterized as nociceptors or non‐nociceptors based upon conduction velocity and response to transient receptor potential (TRP) channel agonists. Antimycin A–induced hyperexcitability was inhibited by the PKC inhibitor bisindolylmaleimide (BIM) I, but not by its inactive analog BIM V. Further, this BIM I inhibition occurred at a concentration that specifically blocks activity of PKC alpha over other isoforms. In conclusion, ROS evoked by mitochondrial dysfunction caused nociceptor hyperexcitability via the translocation and activation of PKC alpha.Support or Funding InformationThis work was supported by the National Heart Lung and Blood Institute in Bethesda, USA (R01‐HL119802)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.