Novel phospholipase A2 inhibitors from python serum are potent peptide antibiotics

• Eight different antimicrobial peptides (AMPs) design and synthesized from Python reticulatus serum protein.
• PIP-18[59–76], β-Asp65-PIP[59–67], D-Ala66-PNT.II, and D60,65E-PIP[59–67] displayed most potent bactericidal activity against S. aureus at 6.8 μg/disc dose within 6 h of incubation.
• Peptides were applied topically at a 150 mg/kg dose accelerates faster wound healing than the latter peptide at 14 days post-treatment.
• The topical application of peptides modulates NF-kB mediated wound repair in mice.
• Devoid of haemolytic (100–15.6 μg/ml) and cytotoxic (1000–31.25 μg/ml) effects were evidenced on human cells in vitro.

Antimicrobial peptides (AMPs) play a vital role in defense against resistant bacteria. In this study, eight different AMPs synthesized from Python reticulatus serum protein were tested for bactericidal activity against various Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Burkholderia pseudomallei (KHW and TES strains), and Proteus vulgaris) using a disc-diffusion method (20 μg/disc). Among the tested peptides, phospholipase A2 inhibitory peptide (PIP)-18[59–76], β-Asp65-PIP[59–67], D-Ala66-PNT.II, and D60,65E-PIP[59–67] displayed the most potent bactericidal activity against all tested pathogens in a dose-dependent manner (100–6.8 μg/ml), with a remarkable activity noted against S. aureus at 6.8 μg/ml dose within 6 h of incubation. Determination of minimum inhibitory concentrations (MICs) by a micro-broth dilution method at 100–3.125 μg/ml revealed that PIP-18[59–76], β-Asp65-PIP[59–67] and D-Ala66-PNT.II peptides exerted a potent inhibitory effect against S. aureus and B. pseudomallei (KHW) (MICs 3.125 μg/ml), while a much less inhibitory potency (MICs 12.5 μg/ml) was noted for β-Asp65-PIP[59–67] and D-Ala66-PNT.II peptides against B. pseudomallei (TES). Higher doses of peptides had no effect on the other two strains (i.e., Klebsiella pneumoniae and Streptococcus pneumoniae). Overall, PIP-18[59–76] possessed higher antimicrobial activity than that of chloramphenicol (CHL), ceftazidime (CF) and streptomycin (ST) (30 μg/disc). When the two most active peptides, PIP-18[59–76] and β-Asp65-PIP[59–67], were applied topically at a 150 mg/kg dose for testing wound healing activity in a mouse model of S. aureus infection, the former accelerates faster wound healing than the latter peptide at 14 days post-treatment. The western blot data suggest that the topical application of peptides (PIP-18[59–67] and β-Asp65-PIP[59–67]) modulates NF-kB mediated wound repair in mice with relatively little haemolytic (100–1.56 μg/ml) and cytotoxic (1000–3.125 μg/ml) effects evident on human cells in vitro.

Flow chart represent the in vitro and in vivo antibacterial effects of Python inhibitory peptides (PIP) derived from python serum (Symbol denotes: Interleukin-1 (IL-1), Interleukin-6 (IL-6), Interleukin-10 (IL-10), Tumor necrosis Factor-α (TNF-α), formation of type I collagen,. Sa-Staphylococcus aureus).Figure optionsDownload high-quality image (169 K)Download as PowerPoint slide