Determining the Senotherapeutic Potential of SIRT2 Inhibition
The primary factor of multimorbidity is aging. As we age, our cells are exposed to various stressors that eventually result in the accumulation of macromolecular damage and persistent activation of stress signaling mechanisms which drive deleterious cell phenotypes, such as cellular senescence. Senomorphics are drugs that selectively target senescent cells and function to dampen senescent cell phenotypes, namely their deleterious Senescence-Associated Secretory Phenotype (SASP). The SASP of senescent cells has been shown to be driven by dysregulation in histone acetylation and their associated reader/writer/eraser proteins, allowing the formation and activation of senescence-associated super enhancer regions that upregulate many SASP genes. Our objective was to determine if modulating erasers of histone acetylation marks could be used to selectively target senescent cells and reduce their SASP expression. To do this, we screened over 70 histone-deacetylase inhibitors using our phenotypic senotherapeutic drug screening assay in etoposide-induced senescent IMR-90s. We identified a potent SIRT2 specific inhibitor that acts as a dual action, concentration dependent senotherapeutic able to kill and/or reduce the percentage of SA-ßgal+ cells using both IMR90’s and primary aged mouse adult fibroblast (2yrs). Gene expression analysis demonstrated that the SIRT2 inhibitor in IMR90 cells reduced the expression of a subset of SASP genes. Similar results were observed following siRNA-mediated knockdown of SIRT2 in senescent IMR90 cells. SIRT2 is a NAD+-dependent deacetylase with mono-ADP- ribosyltransferase activity, implicated in widespread deacetylation of H4K16 and deacetylates H3K56 in response to DNA damage. SIRT2 also has been shown to negatively regulate the activity of co-activator p300, a histone acetyltransferase implicated in the regulation of senescence. Ongoing experiments investigate senescence and SASP markers in primary mouse and human dermal fibroblasts along with DNA damage, fibrosis and mitochondrial health following SIRT2 inhibition in order to validate SIRT2 as a senotherapeutic target for extending healthspan.