Abstract
Purpose :
Previously, we showed Transient Receptor Potential (TRP) ion channels help mediate corneal resistance to bacterial adhesion. TRPA1 counters adhesion of P. aeruginosa (Gram-negative) and TRPV1 counters that of S. aureus (Gram-positive). For P. aeruginosa, defense vs. adhesion was inhibited by bupivacaine, and correlated with CD45+ and CD11c+ cell responses that can counter adhesion. We hypothesized that TRPV1 defense vs. S. aureus adhesion also requires sensory nerve firing and elicits similar immune cell responses.
Methods :
Corneas of anesthetized C57BL/6J wild-type (WT), TRPA1 (-/-), and TRPV1 (-/-) mice were inoculated with S. aureus S33 (an ocular isolate), or P. aeruginosa PAO1 hourly for 4 h. Eyes were treated with Resiniferatoxin (RTX) to ablate TRPV1-expressing nerves, a TRPV1 antagonist JNJ-17203212, or bupivacaine and compared to controls. Mice were euthanized and fixed enucleated eyes examined by quantitative confocal imaging for adherent bacteria using a universal 16S rRNA FISH probe, or Lyz2+, CD11c+ or CD45+ cell responses. ANOVA was used for statistical analysis. P < 0.05 was considered significant.
Results :
As expected, TRPV1 (-/-) corneas showed increased S. aureus adhesion compared to WT (~2.7-fold, P < 0.01). RTX mimicked the effect of TRPV1 gene-knockout (~2.7-fold increase, P < 0.01). Local TRPV1 antagonism also increased S. aureus adhesion to healthy corneas vs. controls (~ 4-fold, P < 0.001). Ex vivo, TRPV1-dependent defense vs. S. aureus was abolished. In contrast to P. aeruginosa, defense vs. S. aureus remained after bupivacaine treatment (P > 0.05). For S. aureus and P. aeruginosa, inoculation did not increase Lyz2+ cell numbers despite increases in CD45+ immune cells. However, only P. aeruginosa increased CD11c+ cells and caused a greater increase in CD45+ cells. RTX inhibited the CD45+ response only for P. aeruginosa.
Conclusions :
Results showed differences in TRP-dependent defense between the Gram-negative pathogen P. aeruginosa and the Gram-positive pathogen S. aureus. Beyond different TRP ion channels utilized, only defense vs. P. aeruginosa required sensory nerve firing correlating with a different parainflammatory response. Other mechanisms involved in TRP-dependent countering of bacterial adhesion to the cornea, including the role of observed cellular responses, remain to be determined.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.