Caspase-8 deficiency in epidermal keratinocytes triggers an inflammatory skin disease

Area of Science:

• Immunology
• Dermatology
• Molecular Biology

Background:

• Caspase-8 is crucial for regulating cell death and inflammation.
• Its absence in epidermal keratinocytes leads to chronic skin inflammation in mice.
• This inflammation differs from pathways involving nuclear factor kappaB (NF-κB) or toll-like receptors (TLRs).

Purpose of the Study:

• To investigate the molecular mechanisms underlying caspase-8 deficiency-induced skin inflammation.
• To identify the key signaling pathways involved in this inflammatory process.
• To understand the role of caspase-8 in epidermal homeostasis and immune response.

Main Methods:

• Genetic deletion of caspase-8 in mouse basal epidermal keratinocytes.
• Analysis of inflammatory markers and signaling pathways (e.g., NF-κB, TNF, IL-1, MyD88, TRIF).
• Assessment of interferon regulatory factor 3 (IRF3) and TANK-binding kinase phosphorylation.
• Gene expression profiling and knockdown studies (IRF3).

Main Results:

• Caspase-8 deficiency triggers skin inflammation independent of TNF, IL-1, MyD88, or TRIF.
• Constitutive phosphorylation of IRF3 and TANK-binding kinase observed in caspase-8-deficient epidermis.
• Knockdown of IRF3 abrogated the expression of upregulated genes.
• Inflammatory gene expression changes initiated prenatally, primarily in suprabasal keratinocytes.
• Caspase-8-deficient keratinocytes showed enhanced responses to transfected DNA.

Conclusions:

• Caspase-8 deficiency-induced skin inflammation is mediated by IRF3 activation.
• An enhanced response to endogenous IRF3 activators, possibly linked to keratinocyte differentiation, contributes to the inflammation.
• These findings reveal a novel role for caspase-8 in regulating skin immunity and preventing inflammation.