449 Measuring activation of the NLRP inflammasomes in vitro via Active Caspase-1 Release: Implications in understanding epidermal inflammatory responses

Abstract

In 2002, a key component of cellular inflammatory response was discovered when the NLRP Inflammasomes were isolated and identified [1]. When skin cells are attacked by endogenous threats, the NLRP proteins oligomerize to form Inflammasomes. The Inflammasomes release Active Caspase-1 (ACase-1), which cleaves Pro-IL-1β and Pro-IL-18 present in the skin cells creating active interleukin cytokines. Activated IL-1β and IL-18 initiate a process of inflammation response that leads to accumulation of downstream curative moieties [2]. NLRP Inflammasomes have been linked to many skin abnormalities such as acne, dandruff, atopic dermatitis, and other skin problems. Inflammasomes are also linked to inflammation caused by external insults like UV radiation, chemical and allergenic agents, and bacterial and fungal attacks. The NLRP1 Inflammasome appears to be the key sensor for UV stress in human keratinocytes, while the NLRP3 Inflammasome has been implicated in wound healing in skin [3,4]. We describe in vitro studies examining the role of various NLRP activators on Normal Human Epidermal Keratinocytes (NHEKs) to elicit upregulation of ACase-1. Two key activators, UVB energy and ATP, cause significant upregulation of the NLRP Inflammasomes measured by release of ACase-1. The release of ACase-1 is delayed from the time of exposure to both NLRP activators. Various external topical treatments that include polysaccharide- and antioxidant-based ingredients were examined for their impact on the expression of ACase-1 in Inflammasome-activated NHEKs. [1] Martinon F et al., The inflammasomes: guardians of the body. Nature 2002. [2] Groslambert M et al., Spotlight on the NLRP3 inflammasome pathway. J Inflamm Res 2018. [3] Burian M et al., NLRP1 is the key inflammasome in primary human keratinocytes. J Invest Dermatol 2018. [4] Ito H. et al., activation of NLRP3 signaling accelerates skin wound healing. Ex Dermatol 2018.