LL-37-derived short antimicrobial peptide KR-12-a5 and its d-amino acid substituted analogs with cell selectivity, anti-biofilm activity, synergistic effect with conventional antibiotics, and anti-inflammatory activity.
Kim. Eun Young EY; Rajasekaran. Ganesan G; Shin. Song Yub SY
Key Findings
- Adding d‑amino acids to KR-12-a5 improved its safety for human cells by 2.6‑ to 13.6‑fold.
- The modified peptides were more effective than LL-37 against tough bugs like MRSA, MDR‑Pseudomonas, and VRE.
- They showed strong synergy with antibiotics (FICI 0.25‑0.5) and worked well in salty conditions and human serum.
Practical Outcomes
- For biohackers, the study suggests that specially engineered short peptides could become powerful, low‑toxicity tools to fight antibiotic‑resistant infections, especially when paired with existing drugs. However, the work is still at the laboratory stage, so there are no dosage guidelines or ready‑to‑use products yet.
Summary
Scientists tweaked a short piece of the human protein LL-37 (called KR-12-a5) by swapping some building blocks for their mirror‑image versions. These changes made the peptide kill resistant bacteria better, work well together with common antibiotics, break down bacterial films, and still calm down inflammation, all while being less harmful to human cells.
Abstract
KR-12-a5 is a 12-meric α-helical antimicrobial peptide (AMP) with dual antimicrobial and anti-inflammatory activities designed from human cathelicidin LL-37. We designed and synthesized a series of d-amino acid-substituted analogs of KR-12-a5 with the aim of developing novel α-helical AMPs that possess higher cell selectivity than KR-12-a5, while maintaining the anti-inflammatory activity. d-amino acid incorporation into KR-12-a5 induced a significant improvement in the cell selectivity by 2.6- to 13.6-fold as compared to KR-12-a5, while maintaining the anti-inflammatory activity. Among the three analogs, KR-12-a5 (6-<sup>D</sup>L) with d-amino acid in the polar-nonpolar interface (Leu<sup>6</sup>) showed the highest cell selectivity (therapeutic index: 61.2). Similar to LL-37, KR-12-a5 and its analogs significantly inhibited the expression and secretion of NO, TNF-α, IL-6 and MCP-1 from LPS-stimulated RAW264.7 cells. KR-12-a5 and its analogs showed a more potent antimicrobial activity against antibiotic-resistant bacteria, including clinically isolated MRSA, MDRPA, and VREF than LL-37 and melittin. Furthermore, compared to LL-37, KR-12-a5 and its analogs showed greater synergistic effects with conventional antibiotics, such as chloramphenicol, ciprofloxacin, and oxacillin against MDRPA; KR-12-a5 and its analogs had a FICI range between 0.25 and 0.5, and LL-37 had a range between 0.75 and 1.5. KR-12-a5 and its analogs were found to be more effective anti-biofilm agents against MDRPA than LL-37. In addition, KR-12-a5 and its analogs maintained antimicrobial activity in physiological salts and human serum. SYTOX Green uptake and membrane depolarization studies revealed that KR-12-a5 and its analogs kills microbial cells by permeabilizing the cell membrane and damaging membrane integrity. Taken together, our results suggest that KR-12-a5 and its analogs can be developed further as novel antimicrobial/anti-inflammatory agents to treat antibiotic-resistant infections.
Study Information
pubmed
2017
2017-05-11T00:00:00.000Z
10.1016/j.ejmech.2017.05.028
104
67