Palmitoyl KTTKS analogues inhibit plasmin and promote fibroblast growth without cytotoxicity

The matrikine KTTKS, derived from collagen hydrolysis, is known to stimulate extracellular matrix (ECM) production and collagen expression. Its more stable, palmitoylated form, pal-KTTKS (Matrixyl®), is a popular cosmeceutical ingredient. However, there's a continuous need for novel analogues with enhanced stability, bioavailability, and specific biological activities to improve skin regeneration and anti-aging treatments. This research addresses this gap by exploring modified KTTKS peptides for improved proteolytic modulation and cellular effects.

Researchers designed and synthesized a series of novel pentapeptides, analogues of KTTKS, with the general formula X-KTTKS-OH(NH2), where X represents acetyl, lipoyl, or palmitoyl residues. The team evaluated their effect on the amidolytic activity of various proteases, including urokinase, thrombin, trypsin, plasmin, t-PA, and kallikrein. Cytotoxicity tests were performed on fibroblasts, and selected peptides were further assessed for their impact on collagen and DNA biosynthesis to understand their regenerative potential.

The synthesized KTTKS analogues demonstrated varied effects on proteolytic activity, with specific modifications yielding significant results. The most active inhibitors of plasmin were consistently found to be the palmitoyl peptides, irrespective of whether they were in acid or amide form. Interestingly, modifying lysine to arginine within the peptide sequence did not yield any discernible biological effects. Importantly, none of the synthesized peptides exhibited cytotoxicity on fibroblasts, indicating a favorable safety profile. Furthermore, three of the novel compounds actively promoted fibroblast cell growth, suggesting potential regenerative properties. However, for these three cell-growth promoting compounds, no clear concentration-activity relationship was observed in the collagen and DNA biosynthesis assays.

Palmitoyl peptides, in both acid and amide forms, were identified as the most active plasmin inhibitors among the synthesized analogues.