Transgenic Mice Overexpressing PG1 Display Corneal Opacity and Severe Inflammation in the Eye

Abstract

Antimicrobial peptides (AMPs) are of interest as alternatives to antibiotics or immunomodulators. We generated and characterized the phenotypes of transgenic mice overexpressing protegrin 1 (PG1), a potent porcine cathelicidin. No obvious differences were observed between PG1 transgenic and wild-type mice in terms of growth, development, general behaviour, and the major immune cell population. However, PG1 transgenic mice intranasally infected with Staphylococcus aureus resulted in a reduction in microscopic pulmonary injury, improved clearance of bacteria, and lower proinflammatory cytokine secretion, compared to those of wild-type mice. On the other hand, approximately 25% of PG1 transgenic mice (n = 54/215) showed corneal opacity and developed inflammation in the eye, resulting ultimately in phthisis bulbi. Immunohistochemical analyses revealed that PG1 and its activator, neutrophil elastase, localized to the basal cells of the cornea and glands in eyelids, respectively. In addition, apoptosis indicated by a Terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive signal was detected from flat cells of the cornea. Our study suggests that the expression regulation or localization of AMPs such as PG1 is important to prevent their adverse effects. However, our results also showed that the cytotoxic effects of PG1 on cells could be tolerated in animals, except for the eyes.

Effective Healing of Staphylococcus aureus-Infected Wounds in Pig Cathelicidin Protegrin-1-Overexpressing Transgenic Mice

“…The immunomodulatory effects of PG1 may also contribute to bacterial clearance in wounds of PG1 Tg mice. Bacterial clearance and wound healing in the skin of PG1 Tg mice were consistent with the results of our previous study, in which PG1 Tg mice challenged with S. aureus showed bacterial clearance equivalent to that of conventional antibiotics as well as improved survival [37].…”

“…However, the results also suggest that PG1 expression in PG1 Tg KC primary cells was not sufficient to induce active migration of the cells. This is consistent with the fact that the expression of PG1 in the skin of PG1 Tg mice is lower than that in other tissues [37]. Furthermore, this suggests that circulating PG1 expressed in other tissues of PG1 Tg mice might be an additional source of PG1 for KCs in the infected wound.…”

“…Sterile wounds were generated on the backs of wild-type and PG1 Tg mice, i.e., which express low levels of PG1 in the skin [37]. In the bacterial infection group, wounds were infected with 10 6 colony-forming units (CFUs) of S. aureus ATCC 6538.…”

“…PG1 Tg mice were generated using preproPG1 under the control of the MUC1 promoter in a C57BL/6J background, as reported previously [37]. Hence, C57BL/6J mice were used as wild-type mice (Orient Bio Inc., Seongnam, Republic of Korea).…”

“…PG1 can eliminate biofilms and prevent biofilm formation and therefore plays a role in wound healing in methicillinresistant Staphylococcus aureus-infected tissues [36]. We recently reported that PG1 Tg mice infected with S. aureus exhibit bacterial clearance, reduced microscopic pulmonary injuries, and lower levels of pro-inflammatory cytokines than their wild-type counterparts [37]. Similarly, the ectopic expression of PG1 improved the survival of Tg mice following Actinobacillus suis infection [38].…”