Aberrant serine protease activities in atopic dermatitis

Area of Science:

• Dermatology
• Biochemistry
• Genetics

Background:

• Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by epidermal barrier dysfunction, allergic inflammation, and itching.
• Excessive serine protease activity is a key abnormality in AD skin, disrupting the epidermal barrier.
• Kallikrein-related peptidases (KLKs) and their inhibitors, like lympho-epithelial Kazal-type-related inhibitor (LEKTI), normally regulate protease activity.

Purpose of the Study:

• To investigate the role of excessive KLK activity in atopic dermatitis pathogenesis.
• To explore the mechanisms by which KLKs contribute to inflammation and itching in AD.
• To understand the impact of genetic variations in LEKTI on AD development.

Main Methods:

• Analysis of epidermal serine protease activity in AD lesions.
• Investigation of KLK expression patterns in AD.
• Examination of KLK-mediated activation of protease-activated receptor 2 (PAR2).
• Evaluation of the functional consequences of SPINK5 gene polymorphisms (encoding LEKTI) in AD patients.

Main Results:

• KLKs are overexpressed in AD lesions, leading to increased protease activity and enhanced allergen/microorganism invasion.
• Certain KLKs activate PAR2 in keratinocytes and nerves, inducing inflammation and itching.
• SPINK5 gene polymorphisms (e.g., E420K, D386N) impair LEKTI function, further promoting KLK activity and susceptibility to allergens.

Conclusions:

• Dysregulated serine protease activity by KLKs is a central mechanism in atopic dermatitis.
• KLK-PAR2 signaling contributes significantly to AD-associated inflammation and pruritus.
• Genetic defects in LEKTI underscore the importance of protease regulation in maintaining skin barrier integrity and preventing AD.