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5 pages, 3 figures. ; GRK2 is a member of the G protein-coupled receptor kinase family that phosphorylates the activated form of beta-adrenergic and other G protein-coupled receptors and plays an important role in their desensitization and modulation. Alterations in thyroid hormone levels have been reported to lead to important changes in adrenergic receptor responsiveness and signaling in a variety of tissues. In this context, we have explored the effects of experimental hypothyroidism on GRK2 protein levels in rat heart, lung, and liver using a specific antibody. Hypothyroid animals show significant up-regulation ( approximately 50% increase compared with controls) in GRK2 levels in heart and lung at 60 days after birth, whereas a 50% reduction is detected in the liver at this stage. These alterations are selective, as beta-adrenergic receptors or other G protein-coupled receptor regulatory proteins, such as G protein-coupled receptor kinase 5 or beta-arrestin-1, display a different pattern of expression changes in the hypothyroid animals. The reported changes in GRK2 levels and in the receptor/kinase ratio predict alterations in adrenergic receptor desensitization and signal transduction efficacy consistent with those observed in thyroid disorders, thus suggesting a relevant role for the modulation of GRK2 expression in this physiopathological condition. ; This work was supported by grants (to F.M.) from the Ministerio de Educación y Cultura (PM98-0020), the Comunidad de Madrid (8.4.6.98), and the European Union (BMH4-3596) and a grant (to A.M.) from Plan Nacional (SAF98-0060). The Centro de Biología Molecular Severo Ochoa holds and institutional grant from Fundación Ramón Areces. P.P. and M. A. D. recipients of a postdoctoral fellowship from Comunidad de Madrid. ; Peer reviewed

Aging and cancer are two interrelated processes, with aging being a major risk factor for the development of cancer. Parallel epigenetic alterations have been described for both, although differences, especially within the DNA hypomethylation scenario, have also been recently reported. Although many of these observations arise from the use of mouse models, there is a lack of systematic comparisons of human and mouse epigenetic patterns in the context of disease. However, such comparisons are significant as they allow to establish the extent to which some of the observed similarities or differences arise from pre-existing species-specific epigenetic traits. Here, we have used reduced representation bisulfite sequencing to profile the brain methylomes of young and old, tumoral and nontumoral brain samples from human and mouse. We first characterized the baseline epigenomic patterns of the species and subsequently focused on the DNA methylation alterations associated with cancer and aging. Next, we described the functional genomic and epigenomic context associated with the alterations, and finally, we integrated our data to study interspecies DNA methylation levels at orthologous CpG sites. Globally, we found considerable differences between the characteristics of DNA methylation alterations in cancer and aging in both species. Moreover, we describe robust evidence for the conservation of the specific cancer and aging epigenomic signatures in human and mouse. Our observations point toward the preservation of the functional consequences of these alterations at multiple levels of genomic regulation. Finally, our analyses reveal a role for the genomic context in explaining disease- and species-specific epigenetic traits. ; This work was supported by the Spanish Association Against Cancer (PROYE18061FERN to M.F.F.), the Asturias Government (PCTI) cofunding 2018-2022/FEDER (IDI/2018/146 to M.F.F.), Fundación General CSIC (0348_CIE_6_E to M.F.F.), and the Health Institute Carlos III (Plan Nacional de I + D+I) cofunding FEDER (PI15/00892 and PI18/01527 to M.F.F and A.F.F.). They also acknowledge support from the Ramón Areces Foundation (CIVP18A3891 to P.J.F.M.), the AECC (SIRTBIO to P.J.F.M.), the MICINN (SAF2017-85766-R to P.J.F.M.), a Ramón y Cajal fellowship (MICINN, RYC-2017-22335 to P.J.F.M.), and the European Commission ATTRACT project (777222 to A.P.C.). J.R.T. is supported by a Juan de la Cierva fellowship from the Spanish Ministry of Science and Innovation (FJCI-2015-26965). R.F.P. and P.S.O. are supported by the Severo Ochoa program (BP17-114 and BP17-165, respectively). R.G.U. is supported by the Centro de Investigación Biomédica en Red de Enfermedades Raras (Health Institute Carlos III). L.V. was supported by the UAB Predoctoral training programme (PIF predoctoral fellowships). They also acknowledge support from the IMDEA Food Institute and IUOPA-ISPA-FINBA (the IUOPA is supported by the Obra Social Cajastur-Liberbank, Spain). ; Peer reviewed

This work was supported by the Spanish Association Against Cancer (PROYE18061 FERN to M.F.F.), the Asturias Government (PCTI) cofunding 2018- 2022/FEDER (IDI/2018/146 to M.F.F.), Fundación General CSIC (0348_CIE_6_E to M.F.F.), and the Health Institute Carlos III (Plan Nacional de I þ DþI) cofunding FEDER (PI15/00892 and PI18/01527 to M.F.F and A.F.F.). They also acknowledge support from the Ramón Areces Foundation (CIVP18A3891 to P.J.F.M.), the AECC (SIRTBIO to P.J.F.M.), the MICINN (SAF2017-85766-R to P.J.F.M.), a Ramón y Cajal fellowship (MICINN, RYC-2017-22335 to P.J.F.M.), and the European Commission ATTRACT project (777222 to A.P.C.). J.R.T. is supported by a Juan de la Cierva fellowship from the Spanish Ministry of Science and Innovation (FJCI-2015-26965). R.F.P. and P.S.O. are supported by the Severo Ochoa program (BP17-114 and BP17-165, respectively). R.G.U. is supported by the Centro de Investigación Biomédica en Red de Enfermedades Raras (Health Institute Carlos III). L.V. was supported by the UAB Predoctoral training programme (PIF predoctoral fellowships). They also acknowledge support from the IMDEA Food Institute and IUOPA-ISPA-FINBA (the IUOPA is supported by the Obra Social Cajastur-Liberbank, Spain).

Compounds with specific cytotoxic activity in senescent cells, or senolytics, support the causal involvement of senescence in aging and offer therapeutic interventions. Here we report the identification of Cardiac Glycosides (CGs) as a family of compounds with senolytic activity. CGs, by targeting the Na+/K+ATPase pump, cause a disbalanced electrochemical gradient within the cell causing depolarization and acidification. Senescent cells present a slightly depolarized plasma membrane and higher concentrations of H+, making them more susceptible to the action of CGs. These vulnerabilities can be exploited for therapeutic purposes as evidenced by the in vivo eradication of tumors xenografted in mice after treatment with the combination of a senogenic and a senolytic drug. The senolytic effect of CGs is also effective in the elimination of senescence-induced lung fibrosis. This experimental approach allows the identification of compounds with senolytic activity that could potentially be used to develop effective treatments against age-related diseases. ; We thank Matthias Drosten, Alejo Efeyan and Sean Morrison for plasmids. F.T-M. is a postdoctoral fellow from CONACYT (cvu 268632); P.P. is a predoctoral fellow from Xunta de Galicia; M.C. is a "Miguel Servet II" investigator (CPII16/00015). P.P.-R. receives support from a program by the Deputacion de Coruna (BINV-CS/2019). Work in the laboratory of M.C. is funded by grant RTI2018-095818-B-100 (MCIU/AEI/FEDER, UE). P.J.F.-M. is funded by the IMDEA Food Institute, the Ramon Areces Foundation, (CIVP18A3891), and a Ramon y Cajal Award (MICINN) (RYC-2017-22335). M.P.I. is funded by Talento Modalidad-1 Program Grant, Madrid Regional Government (#2018-T1/BIO-11262). F.P. was funded by a Long Term EMBO Fellowship (ALTF-358-2017) and F.H-G. was funded by the PhD4MD Programme of the IRB, Hospital Clinic and IDIBAPS. Work in the laboratory of M.S. was funded by the IRB and by grants from the Spanish Ministry of Economy co-funded by the European Regional Development Fund (ERDF) (SAF2013-48256-R), the European Research Council (ERC-2014-AdG/669622), and "laCaixa" Foundation. ; Sí