A nonapoptotic endothelial barrier-protective role for caspase-3

Area of Science:

• Endothelial biology
• Cellular signaling
• Biochemistry

Background:

• Noncanonical roles for caspase-3 are increasingly recognized in cancer and developmental biology.
• However, its nonapoptotic functions in most cell types remain largely uncharacterized.
• Previous work indicated caspase-3 activation can occur independently of apoptosis, with cytoplasmic sequestration and preserved endothelial barrier function.

Purpose of the Study:

• To investigate the hypothesis that nonapoptotic caspase-3 activation promotes endothelial barrier integrity.
• To elucidate the role of cytoplasmic caspase-3 in maintaining the function of human lung microvascular endothelial cells.

Main Methods:

• Human lung microvascular endothelial cells were stimulated with thrombin, a nonapoptotic agent.
• Endothelial barrier function was measured using electric cell-substrate impedance sensing.
• Actin cytoskeleton, paracellular gaps, and cell stiffness were assessed; caspase-3 was inhibited pharmacologically and via RNA interference.

Main Results:

• Thrombin induced cytoplasmic caspase-3 activation with a transient, nonapoptotic decrease in endothelial barrier function.
• Inhibition of caspases exacerbated thrombin-induced barrier dysfunction, increasing cell stiffness and paracellular gaps.
• Specific inhibition or knockdown of caspase-3 led to more significant disruption of the endothelial barrier.

Conclusions:

• Cytoplasmic caspase-3 activation plays a nonapoptotic role in human endothelium.
• This nonapoptotic function of caspase-3 is crucial for promoting and maintaining endothelial barrier integrity.