B2RP-ERa

The emergence of Acinetobacter sp. strains resistant to all antibacterial agents including colistin necessitates the development of new types of antimicrobial agents. Six cationic α-helical frog skin-derived peptides (CPF-AM1, PGLa-AM1, B2RP-ERa, [E4K]alyteserin-1c, [D4K]B2RP and [G4K]XT-7) were selected for this study on the basis of potent growth-inhibitory activity against Gram-negative bacteria and low haemolytic activity against human erythrocytes. All peptides were active against a range of colistin-susceptible [minimum inhibitory concentration (MIC)≤2 μg/mL] and colistin-resistant (MIC≥64 μg/mL) clinical isolates of multidrug-resistant strains of Acinetobacter baumannii and Acinetobacter nosocomialis. The most potent peptides against the colistin-resistant strains were [D4K]B2RP and [E4K]alyteserin-1c (MIC=4-16 μg/mL for both). The MIC values of these peptides against the colistin-susceptible strains were in the same range. The frog peptides show potential for development into drugs to treat infections caused by pandrug-resistant Gram-negative pathogens.

The pathogenesis of acne vulgaris is multifactorial involving infection of the pilosebaceous unit with Propionibacterium acnes and a cytokine-mediated inflammatory response. Five frog skin-derived antimicrobial peptides ([D4k]ascaphin-8, [G4K]XT-7, [T5k]temporin-DRa, brevinin-2GU, and B2RP-ERa), chosen for their low hemolytic activity against human erythrocytes, were assessed for their effects on the growth of clinical isolates of P. acnes and on the release of pro-inflammatory and anti-inflammatory cytokines from peripheral blood mononuclear (PBM) cells. All peptides inhibited the growth of P. acnes with the highest potency exhibited by [D4k]ascaphin-8 (minimum inhibitory concentration, MIC=3-12.5 μM). Release of TNF-α from concanavalin A (ConA)-stimulated PBM cells was significantly reduced by [D4k]ascaphin-8, [G4K]XT-7, brevinin-2GU, and B2RP-ERa (1 and 20 μg/ml) and by [T5k]temporin-DRa (20 μg/ml). Release of IFN-γ from unstimulated PBM cells was significantly reduced by [D4k]ascaphin-8 and brevinin-2GU (1 and 20 μg/ml). No peptide showed significant effects on Il-17 release. Release of the anti-inflammatory cytokines TGF-β, IL-4, and IL-10 from both unstimulated and ConA-treated PBM cells was significantly increased by [T5k]temporin-DRa and B2RP-ERa (1 and 20μg/ml). The potent activities of [D4k]ascaphin-8 and [T5k]temporin-DRa in inhibiting the growth of P. acnes and the release of pro-inflammatory cytokines, and in stimulating the release of anti-inflammatory cytokines suggest a possible therapeutic role in the treatment of acne vulgaris.