The corneal expression of antimicrobial peptides during experimental fungal keratitis.
PURPOSE/AIM OF STUDY: To investigate the expression of endogenous antimicrobial peptides within the murine cornea during the onset and progression of posttraumatic keratomycosis caused by Candida albicans.


METHODS
Scarified corneas of BALB/c mice were topically inoculated with C. albicans and monitored for one week. A murine gene microarray compared the relative expression of 36 antimicrobial peptide genes in infected corneas to controls. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) determined gene expression levels for murine cathelicidin and β-defensins in normal corneas, scarified corneas, and C. albicans-infected corneas. Immunofluorescent staining localized the expression of cathelicidin in corneal sections.


RESULTS
Traumatized eyes exposed to C. albicans developed progressive corneal inflammation, with a fungal inoculum of 10(6) colony-forming units (CFU) bringing about significantly (P < 0.05) more severe corneal inflammatory disease than a 10(5) CFU inoculum. Camp, encoding a murine cathelicidin-related antimicrobial peptide, was significantly upregulated 45-fold by microarray (P = 0.0007) and 36-fold by real-time RT-PCR (P = 0.0009). Camp increased significantly (P = 0.002) more in corneas receiving the higher than the lower fungal inoculum. Cathelicidin was preferentially expressed within the stroma on the first day after fungal inoculation, and Camp expression progressively declined over one week as the amount of recoverable fungi decreased. The genetic expression of β-defensin 1 and β-defensin 2 was initially downregulated (P ≤ 0.01) at the onset of fungal keratitis then returned toward normal levels.


CONCLUSIONS
The antimicrobial peptide cathelicidin rapidly increases within the inflamed murine corneal stroma after the initiation of fungal keratitis and may play a role in the host responses that follow corneal trauma and infection.
Yuan
Xiaoyong
X
Sid W. Richardson Ocular Microbiology Laboratory, Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, 6565 Fannin Street, Houston, TX 77030, USA.
Hua
Xia
X
Wilhelmus
Kirk R
KR
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism*; D002177:Candidiasis / Q000378:metabolism*; D054804:Cathelicidins / Q000378:metabolism; D003315:Cornea / Q000378:metabolism*; D015536:Down-Regulation; D015821:Eye Infections, Fungal / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D007634:Keratitis / Q000378:metabolism* / Q000382:microbiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014018:Tissue Distribution; D015854:Up-Regulation; D023083:beta-Defensins / Q000378:metabolism*
D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins; D023083:beta-Defensins