Caspase 8-activated bioluminescence probe for in vivo imaging of programmable cell death

Area of Science:

• Biochemistry
• Molecular Biology
• Medical Imaging

Background:

• Programmable cell death, including apoptosis and pyroptosis, is crucial for homeostasis.
• Caspase-8 is a key molecular switch in these cell death pathways.
• A specific bioluminescence probe for in vivo Caspase-8 imaging was lacking.

Purpose of the Study:

• To develop and validate a Caspase-8-activated bioluminescence probe for in vivo imaging.
• To assess the probe's specificity and sensitivity in detecting apoptosis and pyroptosis.
• To evaluate the probe's utility in real-time monitoring of cell death in a preclinical model.

Main Methods:

• Synthesis of a Caspase-8-activated bioluminescence probe, Ac-Ile-Glu-Thr-Asp-D-Aminoluciferin (Ac-IETD-Amluc).
• In vitro validation of probe cleavage by Caspase-8 and assessment of bioluminescence output.
• In vivo imaging of apoptosis and pyroptosis in firefly luciferase-transfected 4T1 cells and tumor-bearing mice.

Main Results:

• Ac-IETD-Amluc was efficiently and specifically cleaved by Caspase-8, releasing bioluminescent Amluc with a low limit of detection (0.082 g/L).
• In vitro, the probe generated significant bioluminescence signals upon induction of apoptosis and pyroptosis.
• In vivo studies in tumor-bearing mice showed rapid and enhanced tumor bioluminescence signals following probe injection, with 4.2-fold and 6.8-fold increases for apoptosis and pyroptosis, respectively.

Conclusions:

• Ac-IETD-Amluc is a novel, highly sensitive, and specific bioluminescence probe for real-time in vivo imaging of Caspase-8 activity.
• The probe enables effective monitoring of apoptosis and pyroptosis in preclinical models.
• This probe holds potential for diagnosing diseases characterized by dysregulated cell death, including cancers and inflammatory disorders.