Sequential phases of Ca2+ alterations in pre-apoptotic cells.

Area of Science:

• Cell Biology
• Biochemistry

Background:

• The early events of intrinsic apoptosis, upstream of Bax activation, remain unclear, possibly involving physico-chemical changes like altered calcium (Ca2+) levels.
• Cellular apoptosis occurs asynchronously, complicating bulk analyses and obscuring early events.
• Understanding these initial physico-chemical alterations is crucial for elucidating the complete apoptotic cascade.

Purpose of the Study:

• To develop and apply a single-cell flow cytometry method for analyzing Ca2+ dynamics during apoptosis.
• To identify and characterize specific Ca2+ alterations that precede or coincide with the onset of apoptosis.
• To differentiate Ca2+ changes in viable cells, apoptotic cells, and cells undergoing secondary necrosis.

Main Methods:

• Utilized multiparametric flow cytometry for single-cell analysis of Ca2+.
• Discriminated distinct cell populations (viable, apoptotic, secondary necrosis).
• Analyzed both static and dynamic Ca2+ parameters within each sub-population.

Main Results:

• Identified a sequence of Ca2+ alterations during apoptosis.
• Discovered two distinct Ca2+ changes occurring very early, prior to other apoptotic markers.
• Observed a later Ca2+ change coinciding with the appearance of apoptosis, occurring over a variable timeframe.

Conclusions:

• Early, simultaneous Ca2+ changes precede other apoptotic events and occur at fixed times post-treatment.
• Later Ca2+ alterations are associated with the onset of apoptosis and occur asynchronously.
• Single-cell Ca2+ analysis provides a powerful tool to resolve early, asynchronous events in apoptosis.