In Vivo Efficacy of Anuran Trypsin Inhibitory Peptides against Staphylococcal Skin Infection and the Impact of Peptide Cyclization

Abstract

Staphylococcus aureus is a virulent pathogen that is responsible for a wide range of superficial and invasive infections. Its resistance to existing antimicrobial drugs is a global problem, and the development of novel antimicrobial agents is crucial. Antimicrobial peptides from natural resources offer potential as new treatments against staphylococcal infections. In the current study, we have examined the antimicrobial properties of peptides isolated from anuran skin secretions and cyclized synthetic analogues of these peptides. The structures of the peptides were elucidated by nuclear magnetic resonance (NMR) spectroscopy, revealing high structural and sequence similarity with each other and with sunflower trypsin inhibitor 1 (SFTI-1). SFTI-1 is an ultrastable cyclic peptide isolated from sunflower seeds that has subnanomolar trypsin inhibitory activity, and this scaffold offers pharmaceutically relevant characteristics. The five anuran peptides were nonhemolytic and noncytotoxic and had trypsin inhibitory activities similar to that of SFTI-1. They demonstrated weak in vitro inhibitory activities against S. aureus, but several had strong antibacterial activities against S. aureus in an in vivo murine wound infection model. pYR, an immunomodulatory peptide from Rana sevosa, was the most potent, with complete bacterial clearance at 3 mg · kg ؊1 . Cyclization of the peptides improved their stability but was associated with a concomitant decrease in antimicrobial activity. In summary, these anuran peptides are promising as novel therapeutic agents for treating infections from a clinically resistant pathogen. Staphylococcus aureus is one of the most virulent and opportunistic pathogens, causing increasing numbers of nosocomial and community-acquired infections, and is a leading cause of skin and soft tissue infections (1-3). These Gram-positive cocci produce a myriad of virulence factors that allow the bacteria to attach to host cells, to invade tissues, to evade the host immune system, and to release an array of exoproteins and toxins (4, 5). Contagious S. aureus skin infections can lead to severe muscle or bone infections that ultimately can spread to the lungs or heart (6). The primary treatment involves prescription of ␤-lactam antibiotics such as penicillins and cephalosporins, along with clinical woundcleaning procedures (6, 7). Strains resistant to antibiotics have been emerging since the 1960s, however, especially methicillinresistant S. aureus (MRSA), which is most common in nosocomial skin infections (8). Alarmingly, there have been reports of S. aureus strains that are resistant to the drug of last resort, vancomycin (9).Antimicrobial peptides are now recognized as novel alternative therapeutic agents for infection control (10). Several hypotheses have been examined regarding the mode of action of antimicrobial peptides, including autolysin activation, lipopolysaccharide (LPS) permeabilization, fatal depolarization of the energized bacterial membrane, formation of barrel-stave pores that cause leakage of...

An anti-infective synthetic peptide with dual antimicrobial and immunomodulatory activities

“…injection of each peptide to groups of 10 C57BL/6 mice as described42. Each mouse was injected with a 0.5-ml solution of freshly prepared peptide in PBS.…”

“…Doses of peptide administered per mouse were 0, 10, 30, 50, 70 and 90 mg.kg −1 of body weight. Animals were directly inspected for adverse effects after 6 hours, and mortality was monitored for 7 days thereafter1242.…”

Prospects for the design of new therapeutically significant protease inhibitors based on knottins and sunflower seed trypsin inhibitor (SFTI 1)

“…Для недавно открытых структурных аналогов SFTI 1, коротких пептидов ануранов из кожи амфибий, в экспериментах in vivo показано, что их антимикробная активность в отношении Staphylococcus aureus прямо коррелирует с их ингибиторной активностью в отношении триптического гидролиза [145].…”

Linking inhibitor motions to proteolytic stability of sunflower trypsin inhibitor-1

“…[15][16][17][18][19][20] Sequences with completely novel function can be graed into the SFTI-1 framework, for engineering of radiopharmaceuticals, antimicrobials, proangiogenic compounds, and rheumatoid arthritis and autoimmune disease peptides. [21][22][23][24][25][26][27][28] SFTI-1 binds to trypsin in a substrate manner but can resist proteolysis for a quite long time. The hydrolysis rates of SFTI-1 and its analogs have been studied extensively.…”