Chelsea Tan

This research examined host metabolic processes associated with gingivitis and potential impacts of interventions. First, gingival brush samples from a previously reported clinical study in which participants used an intervention (stannous fluoride (SnF₂) toothpaste/cetylpyridinium chloride rinse/oscillating-rotating electric toothbrush) or control (standard fluoride toothpaste/manual toothbrush) were analyzed with Metabolon metabolomic assessment. Next, hypotheses were generated about mechanisms of metabolic observations and tested in two in vitro models. Human primary blood cells were treated with endotoxins and outer membrane vesicles (OMVs) in the presence of SnF₂. In clinical brush samples, 46 metabolites decreased with intervention at Week 3, including 9- and 13-hydroxyoctadecadienoic acid, citrulline, adenine, and hypoxanthine. Seven metabolites related to nitrogen metabolism and citrulline production were selected for targeted quantification. They were low in health and increased in gingivitis. Targeted quantification demonstrated reduced citrulline, succinate, ornithine and deoxycarnitine (p ≤ 0.001 for all) between baseline and Week 6 with intervention; reductions were greater for intervention vs. control for citrulline, succinate and deoxycarnitine at Week 6 (p ≤ 0.019). In vitro, endotoxin and OMVs increased citrulline and nitric oxide (NO). SnF₂ inhibited elevation of both. Citrulline, deoxycarnitine, succinate, and ornithine were identified as potential novel markers of gingivitis. Elevated NO production is a potential driver of oxidative stress, reduced with intervention.

Caffeoyl hexapeptide-9 (CH-9) is a novel cosmetic peptide designed by conjugating hexapeptide-9 (H-9), a known collagen-mimetic peptide with established skin anti-aging activity, with caffeic acid (CA) via an amide bond, leveraging peptide-drug conjugate (PDC) design principles. In ultraviolet (UV)-irradiated cellular and skin models, CH-9 outperformed H-9 in preserving cell viability, restoring collagen types I, III, and IV, and suppressing interleukin-6 and -8 secretion. Additionally, its direct antioxidant activity, absent in H-9, was demonstrated in vitro by scavenging of hydroxyl and peroxyl radicals. Molecular docking indicated CH-9 interacted with the catalytic domain of matrix metalloproteinase 2 (MMP2), a key enzyme in collagen degradation during photoaging, suggesting a potential inhibition of its activity. Molecular dynamics (MD) simulations revealed an improved insertion of CH-9 into a stratum corneum (SC) lipid bilayer compared to H-9, consistent with enhanced skin permeation in vivo. Moreover, CH-9 exhibited improved aqueous and cosmetic serum stability over CA. In a 28-day clinical study, topical application of CH-9 significantly improved skin elasticity and firmness compared to H-9. This work demonstrates that the PDC-based conjugate CH-9 combines enhanced anti-photoaging efficacy with improved transdermal permeation and stability, highlighting a promising strategy for the development of advanced cosmetic ingredients.