Transient Receptor Potential Ion Channels and Corneal Defense Against Bacterial Adhesion

University Of California Berkeley, Berkeley CA

Investigators

Linked publications, trials & patents

Abstract

Project summary/Abstract: Pseudomonas aeruginosa and Staphylococcus aureus are the two most frequent causes of sight- threatening bacterial keratitis in the USA. Infections caused by either pathogen can be difficult to treat, complicated by the ever-evolving problem of antibiotic resistance. Even successful treatment does not always prevent scarring and associated vision loss. Importantly, the healthy cornea is infection resistant, able of avoid adhesion by virtually all pathogens, including large inocula of P. aeruginosa or S. aureus. For over three decades, our lab has focused on understanding this intrinsic resistance to infection, and how its compromise by predisposing factors sets up conditions for infection initiation, focusing on both the cornea and the bacteria. The outcomes have contributed substantially to our knowledge about those topics. The cornea is endowed with a high density of sensory nerve endings, including some polymodal by virtue of their Transient Receptor Potential (TRP) cation channels. These are mostly TRPV1 (Vanilloid), with TRPA1 (Ankyrin) present only on a subset of TRPV1 expressing nerves. Recently, we reported that corneal nerves can modulate the healthy cornea’s susceptibility to bacterial adhesion involving TRPV1 and TRPA1. Our new data show that these two receptor types confer selectivity for pathogen type, with only TRPV1 countering S. aureus adhesion, and TRPA1 instead countering P. aeruginosa - only the latter requiring nerve firing. We further report that while inoculation with either pathogen elicits a TRPV1/A1 and nerve dependent immune cell response, the details differ. P. aeruginosa increases numbers of CD45+ and CD11c+ cells, the CD11c+ cell fraction shifting to being less spherical and closer to the corneal surface. Importantly, the CD11c+ cells contribute to countering bacterial adhesion. S. aureus causes a smaller CD45+ cell response, with no increase to CD11c+ cell numbers, and different changes to immune cell morphology and location - including a shift away from the corneal surface. Here, we aim to better understand how TRPV1 and TRPA1 differentially counter S. aureus and P. aeruginosa adhesion to the healthy murine cornea. Thus, we will compare them more thoroughly for contributions of immune cells (aim 1), direct-acting players at the ocular surface (aim 2), and roles of bacterial ligands (aim 3). The approach will include use of multiple state-of-the-art technologies including flow cytometry in aim 1, and high-resolution mass spectrometry and snRNAseq in aim 2. All three aims have potential to yield novel strategies for preventing infection before pathology and the associated risk of vision loss begins. Meanwhile, they will advance our general understanding of the healthy cornea’s response to microbial challenge, the relationship to neuroinflammation, roles of nerves, TRPA1 and TRPV1 in the cornea, and the biology of the ocular surface and tear fluid.