Abstract
Purpose :
It is not known whether different pathogens induce distinct neuronal responses and how nociceptors affect infection outcomes.
Methods :
To monitor nociceptor responses during bacterial infection, C57BL6/N mice were either infected or sham treated, corneal whole mounts harvested at 24h and 48h post-infection, and stained for bIII tubulin and CGRP. To chemically ablate TRPV1+ nociceptors, C57BL6/N mice were treated with three consecutive doses of RTX: 30 ug/kg, 70 ug/kg, and 100 ug/kg subcutaneously. The capsaicin eye wipe test was performed to evaluate functional deficiency of nociceptors. To quantify blink reflexes, mice were monitored using Cochet-Bonnet aesthesiometer. To determine the impact of TRPV1- positive neurons on keratitis susceptibility, RTX-treated mice and vehicle-treated control mice were infected with P. aeruginosa strain 6294 at 5x105 CFU/ml and bacterial burdens were quantified. Myeloid cellular infiltrates were evaluated using CD45, CD11b, Ly6G, ICAM-1 markers using flow cytometry and ImageStream analysis.
Results :
Infection induced rapid loss of blink reflexes and collapse of subbasal plexus neuronal fibers. Resiniferatoxin (RTX)-treted mice showed significantly ablated corneal sensory neurons and a temporary mild decrease in blink reflexes, which was recovered. Infected RTX-treated mice exhibited decreased bacterial corneal burdens in the first 24h of infection, elevated myeloid trafficking of CD45+CD11b+Ly6G+ICAM-1- neutrophils and reduced CD45+CD11b+Ly6G+ICAM-1+neutrophils. Mechanistically, increased frequencies of CGRP-induced ICAM-1+ neutrophils in the infected vehicle-treated mice showed reduced neutrophil bactericidal activities.
Infected NaV1.8Cre DTA+ mice, lacking the NaV1.8 channel, showed decreased bacterial burdens at 24h and 48h post-infection, a phenotype which was stronger and more sustained when compared to the RTX-treated mice.
Conclusions :
These data showed that sensory neurons can regulate corneal neutrophil responses in a tissue-specific matter affecting disease progression during P. aeruginosa keratitis. Hence, therapeutic modalities that control nociceptor activation could impact anti-infective therapies.
This is a 2021 ARVO Annual Meeting abstract.