Autophagy impairment with lysosomal and mitochondrial dysfunction is an important characteristic of oxidative stress-induced senescence

Abstract

Macroautophagy/autophagy has profound implications for aging. However, the true features of autophagy in the progression of aging remain to be clarified. In the present study, we explored the status of autophagic flux during the development of cell senescence induced by oxidative stress. In this system, although autophagic structures increased, the degradation of SQSTM1/p62 protein, the yellow puncta of mRFP-GFP-LC3 fluorescence and the activity of lysosomal proteolytic enzymes all decreased in senescent cells, indicating impaired autophagic flux with lysosomal dysfunction. The influence of autophagy activity on senescence development was confirmed by both positive and negative autophagy modulators; and MTOR-dependent autophagy activators, rapamycin and PP242, efficiently suppressed cellular senescence through a mechanism relevant to restoring autophagic flux. By time-phased treatment of cells with the antioxidant N-acetylcysteine (NAC), the mitochondria uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and ambroxol, a reagent with the effect of enhancing lysosomal enzyme maturation, we found that mitochondrial dysfunction plays an initiating role, while lysosomal dysfunction is more directly responsible for autophagy impairment and senescence. Interestingly, the effect of rapamycin on autophagy flux is linked to its role in functional revitalization of both mitochondrial and lysosomal functions. Together, this study demonstrates that autophagy impairment is crucial for oxidative stressinduced cell senescence, thus restoring autophagy activity could be a promising way to retard senescence.

Nutrient sensing, growth and senescence

“…The issue is further confused by the fact that autophagy is also suggested to prevent cellular senescence. Thus, it was shown that ROS can lead to perturbation of autophagic flux in senescent cells and restoration of flux can be achieved by AMPK activation . These conclusions seem to be consistent with the discussed above and well‐documented suppression of senescence by mTORC1 inhibitors which may, at least in part, act by autophagy upregulation .…”

“…Thus, it was shown that ROS can lead to perturbation of autophagic flux in senescent cells and restoration of flux can be achieved by AMPK activation . These conclusions seem to be consistent with the discussed above and well‐documented suppression of senescence by mTORC1 inhibitors which may, at least in part, act by autophagy upregulation . Similarly, recent reports suggest that autophagy can allow the bypass of RAS‐induced senescence and facilitate tumour growth .…”

The inhibitory effect in Fraxinellone on oxidative stress‐induced senescence correlates with AMP‐activated protein kinase‐dependent autophagy restoration

“…The relationship between aging and autophagy has been established. For example, the expression of the autophagic‐related genes is strongly associated with lifespan regulation in flies and worms (Lionaki & Tavernarakis, ; Simonsen et al, ) and the activation of autophagy evoked by mTOR inhibitor rapamaycin extends lifespan in Drosophila (Kapahi et al, ), in addition, our previous study demonstrated that autophagy impairment is positively correlated with senescence development (Tai et al, ). For this reason, the restoration of autophagic flux is a reasonable consideration for anti‐aging/senescence therapeutics.…”

Autophagy Is Pro-Senescence When Seen in Close-Up, but Anti-Senescence in Long-Shot

“…This is particularly prominent when cells are challenged with oxidative stress. Whereas oxidative stress normally activates autophagy, excessive oxidative stress has been shown to rather impair autophagic activity, eventually causing cellular senescence (Han et al, 2016; Tai et al, 2017). These observations are probably resulting from the balance act between the level of oxidative stress and the capacity of autophagy counteracting it.…”

“…These observations are probably resulting from the balance act between the level of oxidative stress and the capacity of autophagy counteracting it. Enhancing or restoring autophagic activity under excessive oxidative stress by either AMPK activation or mTOR inhibition efficiently suppresses cellular senescence (Dalle Pezze et al, 2014; Han et al, 2016; Nopparat et al, 2017; Tai et al, 2017). These results are also supported by recent findings that melatonin enhances autophagic activity via the SIRT1 signaling pathway to suppress oxidative stress-induced senescence (Nopparat et al, 2017).…”