p21 maintains senescent cell viability under persistent DNA damage response by restraining JNK and caspase signaling

Area of Science:

• Cell Biology
• Molecular Biology
• Aging Research

Background:

• Cellular senescence, a state of irreversible cell cycle arrest, plays a dual role in preventing cancer and maintaining tissue health.
• However, the accumulation of senescent cells with aging contributes to various age-related diseases.
• Understanding the regulation of senescent cell survival is crucial for developing interventions against aging pathologies.

Purpose of the Study:

• To investigate the role of the CDK inhibitor p21 (CDKN1A) in regulating the viability of DNA damage-induced senescent cells.
• To elucidate the molecular mechanisms by which p21 influences senescent cell survival and death pathways.
• To evaluate the therapeutic potential of targeting p21 in age-related fibrotic diseases.

Main Methods:

• Utilized cell culture models of DNA damage-induced senescence.
• Performed p21 knockdown experiments to assess its impact on senescent cell viability.
• Analyzed DNA damage markers, activation of ATM and NF-κB signaling pathways.
• Measured TNF-α secretion, JNK and caspase activation.
• Employed p21 knockout mouse models to study liver fibrosis and collagen production.

Main Results:

• The cyclin-dependent kinase (CDK) inhibitor p21 (CDKN1A) was found to be essential for maintaining the viability of senescent cells.
• Knockdown of p21 led to increased DNA lesions in senescent cells, activating ATM and NF-κB signaling.
• Activation of NF-κB induced TNF-α secretion and JNK activation, resulting in caspase- and JNK-dependent senescent cell death.
• In vivo, p21 knockout in mice resulted in the elimination of senescent stellate cells in the liver.
• This elimination correlated with alleviated liver fibrosis and reduced collagen production.

Conclusions:

• p21 plays a critical role in preserving the survival of DNA damage-induced senescent cells.
• A novel pathway involving p21, DNA damage, ATM, NF-κB, TNF-α, and JNK regulates senescent cell fate.
• Targeting p21 presents a potential therapeutic strategy for mitigating age-related fibrotic conditions like liver fibrosis.