I was reading how "methylene blue is a strong anti-senescence agent" ncbi.nlm.nih.gov/pmc/articl... which made me wonder "is it a good thing that MB blue is a strong anti-senescence agent?", which led me to this: frontiersin.org/articles/10...
"Introduction to Cellular Senescence
Three fates ultimately await very aged or damaged cells: senescence, apoptosis, or autophagy (Vicencio et al., 2008). Autophagy (self-eating) is largely a homeostatic mechanism through lysosomal destruction of old or damaged cellular components, allowing for the recycling of cellular material. However, recent evidence also supports the view that autophagy plays an important role in mammalian cell death (Jung et al., 2020). Apoptosis (self-killing) is a morphologically unique, genetically programmed cell death. It has important roles in development, aging, and atrophy, to maintain an appropriate level of cells (Elmore, 2007). It also has many critical roles in immune system function (Nagata and Tanaka, 2017). Cells can also enter a state of senescence (stable cell cycle arrest) as a homeostatic response to various stressors in order to mitigate the proliferation of damaged cells and to prevent neoplastic transformation (Kritsilis et al., 2018). Senescent cells are metabolically active, stable, and viable, unlike cells destined for death and recycling. The classical understanding is that only mitotically active cells in the periphery can enter senescence by becoming arrested in the G1 phase, unlike quiescent cells that arrest in G0 (Di Leonardo et al., 1994; Vicencio et al., 2008). However, post-mitotic cells in the central nervous system are now recognized as being able to undergo senescence (Baker and Petersen, 2018). There is some evidence of crosstalk and shared regulated pathways between these three cell fate states, but there is much that is currently not understood about their relationships to one another (Abate et al., 2020). Also, there is some debate currently over the post-mitotic status of glia and CNS neurons.
Senescent cells accumulate during aging, both from an increased rate of production and a decreased clearance rate (Karin and Alon, 2021). Although the accumulation of senescent cells is associated with increasing age, it is not age-dependent. Senescence is a dynamic and context-specific state that involves many biochemical pathways, such as the p53/p21WAF1/CIP1 and p16INK4A/pRB tumor suppression pathways (McConnell et al., 1998; Kumari and Jat, 2021). Senescent cells that form in response to stress during earlier life stages, such as from oncogene activation, inflammation, or DNA damage, contribute to protective functions such as tumor suppression, wound healing, preventing the propagation of tissue damage, and embryogenesis (Storer and Keyes, 2014; Ovadya and Krizhanovsky, 2018). In non-pathological states, senescent cells attract the immune system and are cleared (Langhi Prata et al., 2018).
There is a physiological threshold where senescent cells interfere with their own clearance, described by the recently proposed “immune threshold theory of senescent cell burden” (Tchkonia et al., 2021). According to this theory, once the saturation of senescent cells passes the senescent cell abundance threshold, the spread of cellular senescence outpaces the immune system’s ability to clear them and cellular senescence becomes “self-amplifying” and contributes to age-associated diseases (Tchkonia et al., 2021)."
My conclusion from reading this is: Senescence is not good. Anti-senescence should be a good thing.