Single–particle rotational microrheology enables pathological staging of macrophage foaming and antiatherosclerotic studies

The formation of macrophage–derived foam cells has been recognized as the pathological hallmark of atherosclerotic diseases. However, the pathological evolution dynamics and underlying regulatory mechanisms remain largely unknown. Herein, we introduce a single–particle rotational microrheology method for pathological staging of macrophage foaming and antiatherosclerotic explorations by probing the dynamic changes of lysosomal viscous feature over the pathological evolution progression. The principle of this method involves continuous monitoring of out–of–plane rotation–caused scattering brightness fluctuations of the gold nanorod (AuNR) probe–based microrheometer and subsequent determination of rotational relaxation time to analyze the viscous feature in macrophage lysosomes. With this method, we demonstrated the lysosomal viscous feature as a robust pathological reporter and uncovered three distinct pathological stages underlying the evolution dynamics, which are highly correlated with a pathological stage–dependent activation of the NLRP3 inflammasome–involved positive feedback loop. We also validated the potential of this positive feedback loop as a promising therapeutic target and revealed the time window–dependent efficacy of NLRP3 inflammasome–targeted drugs against atherosclerotic diseases. To our knowledge, the pathological staging of macrophage foaming and the pathological stage–dependent activation of the NLRP3 inflammasome–involved positive feedback mechanism have not yet been reported. These findings provide insights into in–depth understanding of evolutionary features and regulatory mechanisms of macrophage foaming, which can benefit the analysis of effective therapeutical drugs as well as the time window of drug treatment against atherosclerotic diseases in preclinical studies.