Short senolytic or senostatic interventions rescue progression of radiation-induced frailty and premature ageing in mice

Article activity feed

1. 

   Version published to 10.7554/elife.75492 on eLife

   May 4, 2022
2. 

   eLife

   Apr 22, 2022

   Author Response

   Reviewer #1 (Public Review):

   Individuals who survive cancer treatment can experience health challenges that accelerate ageing and can lead to the development of frailty and early mortality when compared to others of the same age without a history of cancer. The authors propose that cancer therapy-induced cell senescence contributes to premature ageing in these individuals. The present study investigates whether a brief intervention with drugs that ablate senescent cells (senolytic drugs) or drugs that inhibit the damaging signalling molecules released by senescent cells (senostatic drugs) can block the progression of radiation-induced frailty and disability in a mouse model. The study shows that irradiation-induced frailty and disability can be reduced by a brief exposure to senolytic or senostatic drugs up to a year …

   Author Response

   Reviewer #1 (Public Review):

   Individuals who survive cancer treatment can experience health challenges that accelerate ageing and can lead to the development of frailty and early mortality when compared to others of the same age without a history of cancer. The authors propose that cancer therapy-induced cell senescence contributes to premature ageing in these individuals. The present study investigates whether a brief intervention with drugs that ablate senescent cells (senolytic drugs) or drugs that inhibit the damaging signalling molecules released by senescent cells (senostatic drugs) can block the progression of radiation-induced frailty and disability in a mouse model. The study shows that irradiation-induced frailty and disability can be reduced by a brief exposure to senolytic or senostatic drugs up to a year after the initial radiation exposure and that such therapies are at least partially beneficial even if administered after premature ageing is established.

   Strengths:

   Although several prior preclinical studies have explored adjuvant senolytic/senostatic drug therapy in the setting of chemotherapy, earlier work used short-term follow-up and focussed on adverse effects on specific body systems. Important advances made by Fielder and colleagues are: 1) the authors have followed mice for a long time after exposure to radiation plus senolytic drug treatment (up to one year); and 2) they have used a diverse array of system-wide and integrative measures (e.g. frailty assessment as well as tests of strength, coordination and cognition) to assess effects on health globally. These data provide strong preclinical evidence that short-term exposure to senolytic/senostatic drugs following radiation therapy can improve health over long time frames.

   Weaknesses:

   The authors have been careful in their conclusions, and most are well supported by their data. Still, there are some weaknesses to the data reported by Fielder et al.

   1. The introduction is lengthy, but it does not provide a rationale for all aspects of the work, and this makes it difficult to follow some of the proposed experiments. For example, the authors spend a lot of time discussing the selection of the senostatic, metformin but reasons for the other specific drugs used have not been provided in the introduction (e.g. navitoclax, dasatinib and quercetin are mentioned in the abstract but first appear in the methods section of the paper). Rapamycin is used in some studies but not discussed. Some relevant information is found in the results section, but this comes too late in the manuscript.

   We have now justified the selection of Navitoclax and D+Q in the introduction. We did use rapamycin only for some mechanistic analyses as control and have therefore not referred to it in the introduction.

   1. Dose selection is important in studies of senolytic drugs, but the authors did not introduce the rationale for the doses chosen in the introduction. Where they do mention this in the results section, they claim that the doses used are "...comparable to the lower range of therapeutically used doses..." with no references. This should be introduced - with supporting references - and discussed in the discussion.

   We have now given the rationales for dose selection (including references) in the results section.

   1. The selection of the tissues/cell lines chosen for investigation should be clarified/justified as well as listed in the methods. The authors mention effects of senolytics on liver toxicity and sarcopenia in the introduction. This could be used to justify studies on liver and quadriceps, although this should be made explicit and linked to functional assays where possible. No rationale for studies on the brain and cognition has been provided in the introduction and many other tissues could have been investigated (e.g. kidney, fat etc). Similarly, it would be helpful to know why the authors selected human lung MRC5 fibroblasts.

   We have now indicated in the introduction the major adverse outcomes in long-term cancer survivors as rationales for selection of our functional assays and the associated tissues. Specifically, we have cited the high risk for cognitive decline to explain why brain is one of the organs we concentrated our analyses on.

   1. The authors emphasize their work on metformin over the other drugs used throughout the manuscript. A more balanced manuscript with more emphasis on the senolytic interventions could address the issues raised here.

   The in-vivo intervention studies are actually balanced towards senolytics, as we have performed the late intervention only with these. However, the mechanism of action for Nav and DQ is essentially known based on a large number of published studies comparing these to pharmacogenetic senolytic interventions (which is why we chose these senolytics for our proof-of-principle study). Therefore, we feel that establishing their long-term senolytic capacity together with functional/physiological consequences was sufficient. On the other hand, it was not at all clear how metformin could act as a senostatic at the concentrations that are achievable in vivo, and we feel that our mechanistic work has added significantly to this.

   1. The authors have completed their studies using male mice only, so the generalizability of their findings to females is uncertain, as they note in their discussion. They also use only young adult mice subjected to radiation therapy. The authors justify the work in the introduction based, in part, on accelerated ageing seen in long-term survivors of childhood cancers but they do not test their interventions in juvenile mice. Older individuals also experience chemotherapy. The work should be extended, not only to female animals but also to younger and older mice.

   We completely agree. We have expanded the discussion on sexual dimorphism. We have also stated the absence of studies in very young and old mice as a limitation of the study in the discussion.

   Despite these shortcomings, in general the authors' claims and conclusions are justified by their data.

   Reviewer #2 (Public Review):

   Strengths of this study include the wide-ranging evaluation of frailty. Measurement of frailty and its effect on brain and liver function.

   Weaknesses The lack of head-to-head comparison of the senolytic and senostatic agents in the in--vivo and in-vitro. It would also be helpful to see the effects of specific agonists and antagonists for pathways the authors are targeting to comparatively evaluate the therapeutic activity of the drug treatment being tested.

   We do not claim in the paper that changes in functional indicators measured in the in-vivo experiments were mediated through the reduction of SASPs. What we claim and show is that both senolytic and senostatic interventions reduce senescent cell frequencies together with multiple functional outcomes over the lifecourse. We agree that the impact of senescent cell reduction onto these functional improvements could be mediated by different pathways that might be more or less tightly related to the SASP. These pathways are probably tissue- and cell-type specific. Assessing all these would in our opinion go far beyond what can be expected from a single paper.

   When assessing the senostatic activity of metformin in vivo, we claim and show that it reduces senescent ROS and the SASP, and we show the pathway that leads to it. We and others have shown previously that reducing ROS and SASP production from senescent cells reduces bystander senescence. Together, this identifies a pathway by which metformin at physiologically achievable concentrations reduces senescent cell frequencies. In order to link our data more closely to SASP, we have measured levels of 18 cytokines/chemokines that are part of the SASP at the end of the experiment in the serum of senolytic- and metformin-treated mice. These data are now integrated into results part 1 and 3. They show that at one year after senolytic intervention, there is no remaining difference in the measured SASP component levels. However, the longer-lasting metformin intervention still results in a persistent tendency for reduction of some SASP components, notably including IL17 and TNFa (albeit at only p=10%), which were also found reduced in vitro (Fig 4E), together with the prominent SASP component CCL2 (at p<0.05).

   We did discuss carefully the question of presenting our senolytics vs metformin data in a head-to-head format, e.g. combining the data in Figs 1 and 3 in the same graphs. The outcome is that we do not believe that this is the appropriate presentation for our results. We do show already the Navitoclax vs D+Q data head-to-head, because they were generated using a single common sham control group. However, metformin was given to the animals by a different route (in soaked food instead of gavage) in accordance with widespread practice. This required a separate control group also receiving soaked food, which resulted in higher food intake, greater body weight and somewhat different capabilities in the neuromuscular tests in the metformin control as compared to the senolytics control (most probably due to differences in body weight between the control groups). Therefore, a head-to-head comparison of all groups would distract from the essential information, e.g. the intervention effects. We have tried to make the comparison between the senolytic and senostatic interventions as easy as possible by presenting data in Figs 1 and 3 and their associated supplements as similarly as possible, but do think that a direct head-to-head comparison would not be correct for these two independently designed experiments.

   Read the original source
3. 

   eLife

   Mar 17, 2022

   Evaluation Summary:

   This study evaluates the use of senolytics and senostatic agents on post-irradiation-induced frailty. The authors studied the effect of navitoclax, dasatinib/quercitin and metformin on several frailty measures, cognitive function, neuroinflammation, liver function to evaluate the therapeutic efficacy of these treatments. This manuscript has strong translational implications and will be of interest to those working in the aging and cancer therapy fields. This study provides potential new therapeutic options for those developing frailty after radiation treatment.

   (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. The reviewers remained anonymous to the authors.)

   Read the original source
4. 

   eLife

   Mar 17, 2022

   Reviewer #1 (Public Review):

   Individuals who survive cancer treatment can experience health challenges that accelerate ageing and can lead to the development of frailty and early mortality when compared to others of the same age without a history of cancer. The authors propose that cancer therapy-induced cell senescence contributes to premature ageing in these individuals. The present study investigates whether a brief intervention with drugs that ablate senescent cells (senolytic drugs) or drugs that inhibit the damaging signalling molecules released by senescent cells (senostatic drugs) can block the progression of radiation-induced frailty and disability in a mouse model. The study shows that irradiation-induced frailty and disability can be reduced by a brief exposure to senolytic or senostatic drugs up to a year after the initial …

   Reviewer #1 (Public Review):

   Individuals who survive cancer treatment can experience health challenges that accelerate ageing and can lead to the development of frailty and early mortality when compared to others of the same age without a history of cancer. The authors propose that cancer therapy-induced cell senescence contributes to premature ageing in these individuals. The present study investigates whether a brief intervention with drugs that ablate senescent cells (senolytic drugs) or drugs that inhibit the damaging signalling molecules released by senescent cells (senostatic drugs) can block the progression of radiation-induced frailty and disability in a mouse model. The study shows that irradiation-induced frailty and disability can be reduced by a brief exposure to senolytic or senostatic drugs up to a year after the initial radiation exposure and that such therapies are at least partially beneficial even if administered after premature ageing is established.

   Strengths:

   Although several prior preclinical studies have explored adjuvant senolytic/senostatic drug therapy in the setting of chemotherapy, earlier work used short-term follow-up and focussed on adverse effects on specific body systems. Important advances made by Fielder and colleagues are: 1) the authors have followed mice for a long time after exposure to radiation plus senolytic drug treatment (up to one year); and 2) they have used a diverse array of system-wide and integrative measures (e.g. frailty assessment as well as tests of strength, coordination and cognition) to assess effects on health globally. These data provide strong preclinical evidence that short-term exposure to senolytic/senostatic drugs following radiation therapy can improve health over long time frames.

   Weaknesses:

   The authors have been careful in their conclusions, and most are well supported by their data. Still, there are some weaknesses to the data reported by Fielder et al.

   1. The introduction is lengthy, but it does not provide a rationale for all aspects of the work, and this makes it difficult to follow some of the proposed experiments. For example, the authors spend a lot of time discussing the selection of the senostatic, metformin but reasons for the other specific drugs used have not been provided in the introduction (e.g. navitoclax, dasatinib and quercetin are mentioned in the abstract but first appear in the methods section of the paper). Rapamycin is used in some studies but not discussed. Some relevant information is found in the results section, but this comes too late in the manuscript.

   2. Dose selection is important in studies of senolytic drugs, but the authors did not introduce the rationale for the doses chosen in the introduction. Where they do mention this in the results section, they claim that the doses used are "...comparable to the lower range of therapeutically used doses..." with no references. This should be introduced - with supporting references - and discussed in the discussion.

   3. The selection of the tissues/cell lines chosen for investigation should be clarified/justified as well as listed in the methods. The authors mention effects of senolytics on liver toxicity and sarcopenia in the introduction. This could be used to justify studies on liver and quadriceps, although this should be made explicit and linked to functional assays where possible. No rationale for studies on the brain and cognition has been provided in the introduction and many other tissues could have been investigated (e.g. kidney, fat etc). Similarly, it would be helpful to know why the authors selected human lung MRC5 fibroblasts.

   4. The authors emphasize their work on metformin over the other drugs used throughout the manuscript. A more balanced manuscript with more emphasis on the senolytic interventions could address the issues raised here.

   5. The authors have completed their studies using male mice only, so the generalizability of their findings to females is uncertain, as they note in their discussion. They also use only young adult mice subjected to radiation therapy. The authors justify the work in the introduction based, in part, on accelerated ageing seen in long-term survivors of childhood cancers but they do not test their interventions in juvenile mice. Older individuals also experience chemotherapy. The work should be extended, not only to female animals but also to younger and older mice.

   Despite these shortcomings, in general the authors' claims and conclusions are justified by their data.

   Read the original source
5. 

   eLife

   Mar 17, 2022

   Reviewer #2 (Public Review):

   Strengths of this study include the wide-ranging evaluation of frailty. Measurement of frailty and its effect on brain and liver function.

   A weakness is the lack of head-to-head comparison of the senolytic and senostatic agents in the in-vivo and in-vitro. It would also be helpful to see the effects of specific agonists and antagonists for pathways the authors are targeting to comparatively evaluate the therapeutic activity of the drug treatment being tested.

   Read the original source
6. 

   Version published to 10.1101/2021.12.15.472756v1 on bioRxiv

   Dec 16, 2021