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T. D. Petkova, L. C. Huang, R. Y. Reins, A. M. McDermott; Antimicrobial Peptide Expression in Experimentally Induced Pseudomonas Aeruginosa Keratitis in Mice. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2656.
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Antimicrobial peptides such as defensins and cathelicidin are suggested to protect against infection and participate in regulation of immune responses and wound healing. Here we investigated the corneal expression of beta-defensins (mBD) and CRAMP (cathelin- related antimicrobial protein) in response to Pseudomonas aeruginosa (PA) keratitis in wild type 129/svJ (Cnlp+/+, WT) and genetically modified mice deficient in CRAMP (heterozygous (Cnlp +/-, HZ) and knockout (Cnlp -/-, KO)).
Experimental PA (ATCC 19660) keratitis was induced in the right eye of the mice, while the left eye was left uninfected. Both corneas, from each animal, were collected at days 1, 3, 7, 14 or 21 post infection. Comparative quantitative real-time RT-PCR was used to determine the log fold change for the genes of interest, using RNA from Cnlp +/- corneal tissue as calibrator. For each time point five mice per strain were used and a total of two independent experiments were conducted.
Expression of mBD-1, -2 and -6 and CRAMP was detected in the uninfected corneas whereas expression of mBD-3, -4 and -5 was not observed.In the infected corneas of WT mice there was upregulation of mBD-3, -4, -5, -6 and CRAMP expression at all time points post infection. mBD-3 showed the greatest change (5-7 log fold), CRAMP was increased by 1.7-5.4 log fold and the smallest change was with mBD-6 at 1-2.5 log fold. A downregulation of mBD-1 and -2 was found, with that of mBD-2 being the greater at 3.8 log fold.Similar changes for mBD-1, -2, -3, -4, -5, -6 and CRAMP expression were seen in the infected eyes of HZ mice, although the magnitude of the changes were decreased in comparison to the WT mice. Infected corneas of KO mice also showed upregulation of mBD-3,-4,-5 and -6 (range 1.4 to 11 log fold), while mBD-1 and -2 remained unchaged or slightly upregulated depending upon the time post infection.
While mBD-1 and -2 expression remains almost invariable, the expression of mBD-3,-4,-5,-6 and CRAMP is significantly increased in response to Pseudomonas aeruginosa infection. Induction of these antimicrobial peptides may serve to boost innate and adaptive defenses in response to infection.
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