SIRT6 knockout cells resist apoptosis initiation but not progression: a computational method to evaluate the progression of apoptosis

Abstract

Apoptosis is essential for numerous processes, such as development, resistance to infections, and suppression of tumorigenesis. Here, we investigate the influence of the nutrient sensing and longevity-assuring enzyme SIRT6 on the dynamics of apoptosis triggered by serum starvation. Specifically, we characterize the progression of apoptosis in wild type and SIRT6 deficient mouse embryonic fibroblasts using time-lapse flow cytometry and computational modelling based on rate-equations and cell distribution analysis.We find that SIRT6 deficient cells resist apoptosis by delaying its initiation. Interestingly, once apoptosis is initiated, the rate of its progression is higher in SIRT6 null cells compared to identically cultured wild type cells. However, SIRT6 null cells succumb to apoptosis more slowly, not only in response to nutrient deprivation but also in response to other stresses. Our data suggest that SIRT6 plays a role in several distinct steps of apoptosis. Overall, we demonstrate the utility of our computational model to describe stages of apoptosis progression and the integrity of the cellular membrane. Such measurements will be useful in a broad range of biological applications. Significance StatementWe describe a computational method to evaluate the progression of apoptosis through different stages. Using this method, we describe how cells devoid of SIRT6 longevity gene respond to apoptosis stimuli, specifically, how they respond to starvation. We find that SIRT6 cells resist apoptosis initiation; however, once initiated, they progress through the apoptosis at a faster rate. These data are first of the kind and suggest that SIRT6 activities might play different roles at different stages of apoptosis. The model that we propose can be used to quantitatively evaluate progression of apoptosis induced by numerous treatments and genetic manipulations and will be useful in studies of cancer treatments, development, degenerative disorders, and other areas, where apoptosis is involved.

Nicotine promotes neuron survival and partially protects from Parkinson’s disease by suppressing SIRT6

“…Recent studies have reported that SIRT6 protects from DNA-damage associated with Alzheimer’s disease (AD) [ 28 , 29 ]; more specifically, Kaluski et al showed that cells without SIRT6 succumbed to apoptosis faster, following DNA-damage induced by ionizing radiation. We find SIRT6 KO cells (fibroblast lines and primary neurons) are more resistant to apoptosis induced by oxidative damage, proteotoxicity, and nutrient shortage, which is supported by other independent studies [ 51 , 63 , 67 ] and our previous work [ 14 ]. It is possible that the effect of SIRT6 on stress-induced survival depends on the nature of the stress.…”

“…However, SIRT6 activity can also promote apoptosis in non-cancer cells, including neurons [ 9 , 43 ]. In fact, SIRT6 inhibition was recently demonstrated to suppress stress-induced apoptosis [ 14 , 51 ] and protect from retinal neurodegeneration [ 67 ]. SIRT6 promotes production and secretion of inflammatory cytokines [ 4 , 26 , 27 , 62 ], and chronic inflammation is thought to underlie neuronal death in PD and other neurodegenerative diseases.…”

Cellular energetics and mitochondrial uncoupling in canine aging

“…To test this, we stressed cells with nutrient deprivation or rotenone exposure. Survival of cells was measured by staining with the apoptosis markers annexin-V and propidium iodide followed by flow cytometry, as described previously (Domanskyi et al 2017). Fibroblasts from longlived breeds survived on average 8% more after rotenone challenge (*p = 0.01) (Fig.…”

SIRT6 overexpression induces apoptosis of nasopharyngeal carcinoma by inhibiting NF-κB signaling

“…In accordance with our study, SIRT6 overexpression-induced apoptosis, activated caspase-9 and caspase-3 in human gastric cancer cells, resulting in cell cycle arrest, induced cellular apoptosis through inactivation of JAK2/STAT3 signaling, and by downregulation of cyclin D1 and Bcl2. 28 Apoptosis was also observed in A549 non-small-cell lung cancer cells, 29 mouse embryonic fibroblasts, 30 and hepatocellular carcinoma, 10 with downregulation of cell survival proteins (JAK2/STAT3 and Bcl-2), and upregulation of pro-apoptotic proteins (p53 and E2F-1, Bid and bax). However, several reports implicate a suppressive role of SIRT6 in cellular apoptosis, which is inconsistent with the results of our study.…”