אפופטוזיס

Apoptosis is a programmed cell death process where specific signals lead to the death of unwanted or potentially harmful cells.

The intrinsic or mitochondrial-mediated apoptotic pathway is triggered by intracellular death signals produced due to DNA damage, hypoxia, and biochemical stress such as oxidative stress. In contrast, the extrinsic apoptotic pathway is initiated when extracellular death-inducing ligands, such as cytokines, bind to the death receptors present on the cell surface.

The key mediators of apoptosis are proteases called caspases. Initiator caspases are activated by both intrinsic and extrinsic apoptotic pathways through different mechanisms.

Each initiator caspase then activates multiple executioner caspases.

In both pathways, the activated executioner caspases cleave cellular proteins causing morphological changes, such as cell shrinkage, nuclear fragmentation, and plasma membrane blebbing.

Next, the cellular components are enclosed into membrane vesicles called apoptotic bodies, which are then engulfed by phagocytic cells.

Through these steps, apoptosis results in controlled and contained cell death without causing inflammation and damage to the neighboring cells.