I’m sure many of you are probably reading this while wearing some kind of corrective lenses. Some of you might be wearing some cool hipster glasses, but many of you are probably wearing contacts. And as you might know, wearing contacts can be a dangerous sport. Putting them in incorrectly can cause you to damage your eye. In fact, there are 42,000 injuries to the cornea (the transparent part of the eye that covers the iris) per year. And what’s worse than getting a small scratch in your eye? Getting it infected. The big bug for this is a bacteria called Pseudomonas aeruginosa, and half of the cases of infection will result in poor vision.
So how do we prevent these scratches to our delicate corneas and the infections that can go with them? Well, for starters, take good care of your contacts! But if worst comes to worst, it’s possible that there may be a little protein that you ALREADY HAVE, that can help you out.
Griffith, Russell, Pereira. “Cationic antimicrobial protein, 37kDa, mediates corneal wound healing in vitro” Department of Pharmaceutical Science, University of Oklahoma Health Sciences Center, presented at Experimental Biology, 2011.
This protein is called Cationic Antimicrobial protein, and it weighs 37 kiloDaltons, and thus for short they call it CAP37. It was actually a surprise to me that we produced antimicrobial proteins in the first place, but this one is quite useful. It’s expressed in neutrophils which circulate in the blood, and it is especially effective against gram-negative bacteria, including the Pseudomonas bacteria I mentioned above. But it’s also found in the EYE, in the corneal epithelium, the layer below it known as the stroma, and in the lacrimal glands, where it gets released in tears.
While CAP37 is usually known as an antimicrobial peptide, some of the previous findings from the laboratory have indicated that it could play a role in inflammation, and possibly wound healing.
To examine this, Griffith took human corneal cells and made little cell monolayers on plates. She then scratched the monolayers, creating a “wound” in the layer. She applied various doses of CAP37 and tracked how quickly the wounds healed. While the normal cells had only recovered by about 50{9f43b4361d9a125bc126dd2a2d1949be02545ec69880430bc4fed2272fd72da3} after 48 hours, cells treated with a 250ng/mL dose of CAP37 showed closer to 75{9f43b4361d9a125bc126dd2a2d1949be02545ec69880430bc4fed2272fd72da3} recovery, indicating that the protein might be speeding up the recovery from the wound.
But of course, we have to know HOW this might be taking place. Right now, CAP37 is relatively understudied, and no one knows what receptor it might bind to. But they hypothesized that CAP37 might be binding to a specific TYPE of receptor, the type known as G protein coupled. This receptor type recruits other proteins within a cell when it is stimulated, which can then produce downstream effects. One of the proteins that is recruited by G protein coupled receptors is a protein called Protein Kinase C delta (PKC delta). When Griffith looked at her healing corneal cells, she found that PKC delta was expressed near the wounded area, and hypothesized that CAP37 might be acting via recruitment of PKC delta.
To test this, she treated scratched monolayers with CAP37 and stained them for PKC delta, and found that the monolayers treated with more CAP37 showed more PKC delta, suggesting that this may be the mechanism, though this won’t be known for certain without more experiments.
So what are the implications? Well, WAY down the road (this is in cells in a dish after all, we’d have to do studies in animals and in humans before this became a reality), if CAP37 can help with wound healing in the cornea, we may be able to administer it to help with corneal injury, where it can also help prevent infection. It is also possible that we could use it in people getting eye surgery, to speed up wound healing and prevent infections there. And finally, since CAP37 is expressed in other tissues in the body (like the vasculature), it may have influences on wound healing in other areas as well.
References:
Lee TD, Gonzalez ML, Kumar P, Chary-Reddy S, Grammas P, & Pereira HA (2002). CAP37, a novel inflammatory mediator: its expression in endothelial cells and localization to atherosclerotic lesions. The American journal of pathology, 160 (3), 841-8 PMID: 11891183
Pereira HA (2006). Novel therapies based on cationic antimicrobial peptides. Current pharmaceutical biotechnology, 7 (4), 229-34 PMID: 16918399
