Caspase activation occurs through two principal pathways: the intrinsic (or mitochondrial) pathway and the extrinsic (or death receptor) pathway. The intrinsic pathway is triggered by internal cellular stress such as oxidative stress or DNA damage, leading to the release of cytochrome c from mitochondria. This event forms the apoptosome, which activates initiator caspase-9. In contrast, the extrinsic pathway is initiated by the binding of extracellular ligands to death receptors, activating initiator caspase-8. Both pathways converge on the activation of effector caspases, such as caspase-3, which execute the apoptotic process.
