The Insect Peptide Coprisin Prevents Clostridium difficile-Mediated Acute Inflammation and Mucosal Damage through Selective Antimicrobial Activity

Abstract

ABSTRACTClostridium difficile-associated diarrhea and pseudomembranous colitis are typically treated with vancomycin or metronidazole, but recent increases in relapse incidence and the emergence of drug-resistant strains ofC. difficileindicate the need for new antibiotics. We previously isolated coprisin, an antibacterial peptide fromCopris tripartitus, a Korean dung beetle, and identified a nine-amino-acid peptide in the α-helical region of it (LLCIALRKK) that had antimicrobial activity (J.-S. Hwang et al., Int. J. Pept., 2009, doi:10.1155/2009/136284). Here, we examined whether treatment with a coprisin analogue (a disulfide dimer of the nine peptides) prevented inflammation and mucosal damage in a mouse model of acute gut inflammation established by administration of antibiotics followed byC. difficileinfection. In this model, coprisin treatment significantly ameliorated body weight decreases, improved the survival rate, and decreased mucosal damage and proinflammatory cytokine production. In contrast, the coprisin analogue had no apparent antibiotic activity against commensal bacteria, includingLactobacillusandBifidobacterium, which are known to inhibit the colonization ofC. difficile. The exposure ofC. difficileto the coprisin analogue caused a marked increase in nuclear propidium iodide (PI) staining, indicating membrane damage; the staining levels were similar to those seen with bacteria treated with a positive control for membrane disruption (EDTA). In contrast, coprisin analogue treatment did not trigger increases in the nuclear PI staining ofBifidobacterium thermophilum. This observation suggests that the antibiotic activity of the coprisin analogue may occur through specific membrane disruption ofC. difficile. Thus, these results indicate that the coprisin analogue may prove useful as a therapeutic agent forC. difficileinfection-associated inflammatory diarrhea and pseudomembranous colitis.