Activation of the mitochondrial caspase pathway and subsequent calpain activation in monkey RPE cells cultured under...

Area of Science:

• Cell Biology
• Ophthalmology
• Biochemistry

Background:

• Age-related macular degeneration (AMD) is associated with decreased macular zinc levels.
• The zinc chelator N,N,N',N'-tetrakis (2- pyridylmethyl) ethylenediamine) (TPEN) induces retinal pigment epithelial (RPE) cell death.
• Understanding the molecular mechanisms of RPE cell death is crucial for AMD research.

Purpose of the Study:

• To investigate the signal transduction pathways involved in TPEN-induced RPE cell death.
• To elucidate the roles of calpain and caspase activation in this process.
• To determine if endoplasmic reticulum (ER) stress is involved in TPEN-induced RPE cell death.

Main Methods:

• Monkey RPE cells were cultured and treated with TPEN.
• Activation of calpains and caspases, and proteolysis of their substrates were assessed using immunoblotting.
• Specific protease inhibitors (SNJ-1945 for calpain, z-VAD-fmk for caspase) were used to confirm pathway activation.

Main Results:

• TPEN treatment led to a time-dependent decrease in RPE cell viability.
• Cell death was correlated with the activation of calpain-1, caspase-9, and caspase-3.
• Inhibitor studies confirmed the involvement of calpain and caspase pathways, while caspase-12 activation was not observed.

Conclusions:

• Relative zinc deficiency in RPE cells activates cytosolic calpain and mitochondrial caspase pathways.
• These pathways contribute to RPE cell death in a manner that does not involve ER stress.
• The findings provide insights into the cellular mechanisms underlying AMD pathogenesis.