TRPV1 Defends the Healthy Murine Cornea Against Staphylococcus aureus Adhesion Independently of Sensory Nerve Firing.

PURPOSE: Previously, we showed that transient receptor potential ion channels TRPA1 and TRPV1 selectively protect the cornea against bacterial adhesion, with TRPA1 countering the Gram-negative pathogen Pseudomonas aeruginosa (P. aeruginosa) and TRPV1 countering environmental bacteria. Here, we explored parameters of this specificity using a Gram-positive pathogen Staphylococcus aureus (S. aureus). METHODS: Healthy corneas of C57BL/6J wild-type (WT), TRPA1 (-/-), or TRPV1 (-/-) mice were challenged with S. aureus for 4 or 6 hours. Some experiments instead/also used resiniferatoxin (RTX) to deplete TRPV1-expressing nerves, JNJ-17203212 to selectively antagonize TRPV1, or the anesthetic bupivacaine to inhibit nerve firing. Adherent bacteria were quantified using fluorescence in situ hybridization (FISH) labeling (16S rRNA-targeted probe). Lyz2+, CD11c+, and CD45+ cells were visualized/quantified using hybrid mT/mG + LysMcre mice (red cell membranes; Lyz2+-GFP), CD11c+-YFP mice, and anti-CD45-antibody, respectively. RESULTS: Corneas of TRPV1 (-/-) not TRPA1 (-/-) mice were found more susceptible to S. aureus adhesion compared to WT. Accordingly, either ablation of TRPV1-expressing nerves or TRPV1 antagonism increased adhesion. Defense against S. aureus adhesion did not depend on nerve firing. Despite having no significant impact on CD11c+ or Lyz2+ cell numbers, the S. aureus challenge increased CD45+ cell counts, also dependent on TRPV1-expressing nerves, and it increased Lyz2+ cell sphericity and volume. CONCLUSIONS: Healthy corneas utilize TRPV1 to protect against S. aureus adhesion independently of sensory nerve firing. This contrasts with defense against P. aeruginosa adhesion which requires TRPA1 and nerve firing. How the differential immune cell responses to these two pathogens relate to TRP-dependent defense against adhesion remains to be determined.