Reduced nicotinamide adenine dinucleotide fluorescence lifetime detected poly(adenosine-5′-diphosphate-ribose) polymerase-1-mediated cell death and therapeutic effect of pyruvate

摘要

Noninvasive detection of cell death has the potential for definitive diagnosis and monitoring treatmentnoutcomes in real time. Reduced nicotinamide adenine dinucleotide (NADH) fluorescence intensity has long beennused as a noninvasive optical probe of metabolic states. NADH fluorescence lifetime has recently been studied fornits potential as an alternative optical probe of cellular metabolic states and cell death. In this study, we investigatednthe potential using NADH fluorescence intensity and/or lifetime to detect poly(adenosine-5’-diphosphate-ribose)npolymerase-1 (PARP-1)-mediated cell death in HeLa cells.We also examined if NADH signals respond to treatmentnby pyruvate. Themechanismof PARP-1-mediated cell death has been well studied that extensive PARP-1 activationnleads to cytosolic nicotinamide adenine dinucleotide depletion resulting in glycolytic inhibition, mitochondrialnfailure, and death. Pyruvate could restore electron transport chain to prevent energy failure and death. Our resultsnshow that NADH fluorescence lifetime, not intensity, responded to PARP-1-mediated cell death and the rescueneffect of pyruvate. This lifetime change of NADH fluorescence happened before the collapse of mitochondrialnmembrane potential and mitochondrial uncoupling. Together with our previous findings in staurosporine-inducedncell death, we suggest that NADH fluorescence lifetime increase during cell death is mainly due to increasednprotein-protein interactions but not the intracellular NADH content.