Evidence for Lysosomal Dysfunction within the Epidermis in Psoriasis and Atopic Dermatitis

Area of Science:

• Cell Biology
• Immunodermatology
• Molecular Medicine

Background:

• Atopic dermatitis and psoriasis are common chronic inflammatory skin conditions.
• Autophagy is a critical cellular process for maintaining homeostasis, and its dysfunction is linked to various diseases.
• The role of autophagy in atopic dermatitis and psoriasis remains to be fully elucidated.

Purpose of the Study:

• To investigate the role of autophagy in atopic dermatitis and psoriasis.
• To examine the levels of key autophagy-related proteins (ATGs) in human skin samples and keratinocytes.
• To understand the effect of tumor necrosis factor-alpha (TNF-α) on autophagy in epidermal keratinocytes.

Main Methods:

• Analysis of key ATG protein levels in human skin specimens from patients with atopic dermatitis and psoriasis.
• In vitro studies using primary human epidermal keratinocytes exposed to inflammatory stimuli, specifically TNF-α.
• Assessment of autophagy induction, lysosomal cathepsin activity, and protein levels following TNF-α exposure.

Main Results:

• TNF-α initially promoted autophagy but subsequently inhibited it in keratinocytes by reducing lysosomal cathepsin levels and activity.
• Protein levels of cathepsins D and L were found to be decreased in skin specimens from both psoriasis and atopic dermatitis patients.
• These findings suggest a dual role for TNF-α in regulating autophagy.

Conclusions:

• Long-term exposure to TNF-α inhibits autophagy in keratinocytes, potentially contributing to the chronicity of inflammatory skin diseases.
• Impaired autophagy due to TNF-α may be a shared mechanism in the pathogenesis of atopic dermatitis and psoriasis.
• This mechanism could also be relevant to chronic inflammatory conditions in other organs.