Domestic pig skin peptides: targeted starvation therapy for gram-positive bacteria MRSA through ABC transporters

Antimicrobial peptides (AMPs), which were conserved constituents of the innate immune system, exhibit antimicrobial properties similar to those of traditional antibiotics and have a low potential for the development of resistance. Thus, they were showing a great capacity for application. This study performed screening of twelve candidate antimicrobial peptides by means of pig skin enzymatic hydrolysis and activity prediction. The synthesis of these peptides was undertaken using Fmoc solid phase synthesis and purified via HPLC than 95%. The Methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus aureus (SA) and Escherichia coli (E. coli) were selected to evaluate antibacterial activity in vitro. The results indicated that peptide P5 exhibited the most significant inhibitory effect on MRSA and SA, with an inhibition rate of 91.83%. Furthermore, its antibacterial activity against MRSA and SA was found to be stronger than that against E. coli, demonstrating a dose-dependent relationship. Growth curve analysis revealed that P5 completely inhibited the growth of MRSA within 16 h at 3 mg/mL. Cytotoxicity was assessed using the CCK-8 assay and live/dead cell staining. The survival rates of both L929 and MDCK cells exceeded 87%, indicating good biocompatibility. Transcriptome sequencing (RNA-seq) and quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses demonstrated that treatment with the P5 was associated with significant transcriptional changes in MRSA. The differentially expressed genes were enriched in the ABC transporter pathway, as well as pathways related to arginine biosynthesis and metabolism, histidine metabolism, and quorum sensing. These findings suggest a potential link between P5 and these pathways, thereby providing a foundation for future mechanistic studies. In conclusion, the porcine skin-derived antimicrobial peptide P5 exhibited significant antimicrobial activity, low cytotoxicity, and a mechanism of action that was distinct from traditional antibiotics, thereby demonstrating promising potential for clinical translation in the fight against drug-resistant bacterial infections.