Mitochondrial respiratory complex I probed by delayed luminescence spectroscopy.

Area of Science:

• Biochemistry
• Cell Biology
• Spectroscopy

Background:

• Mitochondrial complex I is crucial for cellular respiration and ATP production.
• Ultraweak photon emission, or delayed luminescence (DL), is a biophysical phenomenon linked to cellular metabolic states.
• The precise origin and mechanisms of DL within mitochondria remain incompletely understood.

Purpose of the Study:

• To investigate the role of mitochondrial complex I in the delayed luminescence (DL) of human leukemia Jurkat T cells.
• To explore the potential of DL spectroscopy as a tool for assessing mitochondrial function in situ.

Main Methods:

• Jurkat T cells were treated with complex I targeting agents: rotenone, menadione, and quercetin.
• Mitochondrial levels of reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavin mononucleotide (FMNox) were measured.
• Delayed luminescence (DL) was measured and correlated with cellular survival and apoptosis markers.

Main Results:

• Rotenone, a complex I inhibitor, increased NADH levels, reduced cell survival, induced apoptosis, and dose-dependently enhanced DL.
• Menadione and quercetin inhibited DL, NADH, and FMNox levels.
• A strong correlation was observed between mitochondrial NADH and FMNox levels across treatments.
• DL enhancement by rotenone provided insights into electron transfer times within complex I.

Conclusions:

• Delayed luminescence (DL) in Jurkat T cells primarily originates from mitochondrial complex I.
• Mitochondrial complex I likely functions as a dimer, with cooperative ligand binding in monomers.
• DL spectroscopy is a promising, sensitive technique for probing in situ electron flow within mitochondrial complex I.