Quantum sensing of free radicals in macrophages reveals early autophagy-lysosome regulation in an atherosclerosis cell model

Atherosclerosis is the predominant cause of death in industrialized countries and is on track to become the foremost cause of death worldwide. Free radicals play a crucial role in regulating the degradation system in macrophages within plaques which lead to complications in atherosclerosis. They are linked to the decline of autophagy-lysosomes and plaque progression. However, their specific production sites and timing remain unclear. To investigate free radical production in the macrophage autophagy-lysosome system's response to stress, we employed nanodiamond-based quantum sensing. By incubating RAW 264.7 macrophages with nanodiamonds and oxidized low-density lipoprotein, we observed colocalization of nanodiamonds with oxLDL in the autophagy-lysosomal system. Quantum sensing was then applied to sense free radical production in the surrounding area. Our findings revealed a decrease in spin lattice relaxation (T1) times (more free radicals), with a 36.7 % and 31.8 % rise at 0.5 and 4 h of oxLDL incubation compared to controls. Additionally, we observed the nuclear translocation of transcriptional factor EB (TFEB), the master transcriptional regulator of autophagy-lysosomal biogenesis. This suggests the initiation of an autophagy-lysosomal program, which enhanced the cell's degradative capacity. Consequently, T1 values firstly increased after 1h. At 4h, a significant TFEB nuclear translocation was observed, leading to the increase of T1 values by 8.2 % and 20.3 % at 6 and 8 h, respectively, compared to the 4-h mark.