Optical redox imaging of ANT1-deficient muscles

Adenine nucleotide translocator (ANT) is a mitochondrial protein involved in the exchange of ADP and ATP across the mitochondrial inner membrane. It plays a crucial role in cellular energy metabolism by facilitating the transport of ATP synthesized within the mitochondria to the cytoplasm. The isoform ANT1 predominately expresses in cardiac and skeletal muscles. Mutations or dysregulation in ANT1 have been implicated in various mitochondrial disorders and neuromuscular diseases. We aimed to examine whether ANT1 deletion may affect mitochondrial redox state in our established ANT1-deficient mice. Hearts and quadriceps resected from age-matched wild type (WT) and ANT1-deficient mice were snap-frozen in liquid nitrogen. The Chance redox scanner was utilized to perform 3D optical redox imaging. Each sample underwent scanning across 3-5 sections. Global averaging analysis showed no significant differences in the redox indices (NADH, flavin adenine dinucleotide containing-flavoproteins Fp, and the redox ratio Fp/(NADH+Fp) between WT and ANT1-deficient groups. However, quadriceps had higher Fp than hearts in both groups (p = 0.0004 and 0.01, respectively). Furthermore, the quadriceps were also more oxidized (a higher redox ratio) than hearts in WT group (p = 0.004). NADH levels were similar in all cases. Our data suggest that under non-stressful physical condition, the ANT1-deficient muscle cells were in the same mitochondrial state as WT ones and that the significant difference in the mitochondrial redox state between quadriceps and hearts found in WT might be diminished in ANT1-deficient ones. Redox imaging of muscles under physical stress can be conducted in future.