Caspase-8 is the molecular switch for apoptosis, necroptosis and pyroptosis

Area of Science:

• Cellular Biology
• Immunology
• Developmental Biology

Background:

• Caspase-8 initiates extrinsic apoptosis and suppresses necroptosis.
• Caspase-8 deficiency in mice leads to embryonic lethality, which can be rescued by inhibiting necroptosis pathways.
• The precise roles of caspase-8's enzymatic activity in regulating cell death and tissue homeostasis remain incompletely understood.

Purpose of the Study:

• To investigate the in vivo consequences of enzymatically inactive caspase-8 (CASP8(C362S)) expression.
• To elucidate the distinct roles of necroptosis and inflammasome activation in CASP8(C362S)-induced pathologies.
• To define caspase-8's function as a molecular switch controlling apoptosis, necroptosis, and pyroptosis.

Main Methods:

• Generation of Casp8(C362S) mutant mice and compound mutant lines (e.g., Casp8(C362S)Mlkl-/-).
• Analysis of embryonic lethality, cardiovascular defects, and intestinal inflammation phenotypes.
• Assessment of inflammasome activation, including ASC speck formation, caspase-1 activation, and IL-1β secretion.

Main Results:

• Expression of CASP8(C362S) caused embryonic lethality due to endothelial cell necroptosis and cardiovascular defects.
• MLKL deficiency rescued cardiovascular defects but caused perinatal lethality, indicating necroptosis-independent death.
• Blocking necroptosis exacerbated intestinal inflammation and led to premature lethality, with inflammasome activation (ASC, caspase-1, IL-1β) promoting pathology.

Conclusions:

• Caspase-8 acts as a critical molecular switch regulating apoptosis, necroptosis, and pyroptosis.
• CASP8(C362S)-induced pathology highlights the interplay between necroptosis and inflammasome activation in tissue damage.
• Caspase-8 is essential for preventing tissue damage during embryonic development and in adulthood.