NLRP inflammasomes and induced skin inflammation, barrier recovery and extended skin hydration.

Abstract

In vitro assays were designed to examine the release of active Caspase-1 (ACasp-1) from NLRP inflammasome-activated Normal Human Epidermal Keratinocytes (NHEK) employing a bioluminescent assay specific for measuring inflammasome-induced ACasp-1 expression. Four anticipated exogenous activators of the NLRP inflammasome including: UVB, ATP, Nigericin and Urban Dust were examined. Follow-up studies examined the influence of extracellular application of three different natural blends of known anti-inflammatories, one a polysaccharide blend and the other two antioxidant blends, one oil-soluble the other water-soluble, to examine ACasp-1 inhibition. Clinical work using the same blend of polysaccharides employed at 3% in a moisturizing formulation was examined for skin barrier recovery, measured with TEWL over a 60-h time frame after tape stripping on 10 individuals, and extended moisturization, measured using corneometer conductance after a single product application out through a 48-h regression on 10 individuals. In vitro results indicated that two exogenous activators, 60mJcm-2 UVB and 5mM ATP, worked to upregulate expression of ACasp-1 within a 20-h timeframe. Additional studies were conducted to examine the influence of three extracellularly applied active ingredient blends. A blend of polysaccharides demonstrated potential to inhibit ACasp-1 expression in both UVB- and ATP-activated skin cells. Oil-soluble and water-soluble antioxidant blends inhibited ACasp-1 expression in UVB-activated keratinocytes but not ATP-activated keratinocytes. Barrier disruption studies indicated that 3% of the polysaccharide blend accelerated barrier recovery in a 60-h time frame as measured by TEWL. Skin hydration studies showed an ability for the polysaccharide blend to show significant improvements in skin hydration out to 48h after a single application vs. a moisturizing placebo. The role of the skin's innate immune response, controlled by NLRP inflammasomes, is beginning to be linked to numerous skin conditions including inflammaging. In this work, it was found that: (i) an in vitro assay could activate NHEKs to express NLRP inflammasome-induced ACasp-1 expression, (ii) Ingredient blends inhibited UVB and ATP-induced NLRP inflammasome-induced ACasp-1 expression, and (iii) skin barrier disruption improvements and extended skin hydration could be achieved with 3% of the polysaccharide blend.