Release of mitochondrial dsRNA into the cytosol is a key driver of the inflammatory phenotype of senescent cells

Abstract

Mitochondrial dsRNA; Cytosol; Inflammatory phenotype

dsRNA mitocondrial; Citosol; Fenotipo inflamatorio

dsRNA mitocondrial; Citosol; Fenotip inflamatori

The escape of mitochondrial double-stranded dsRNA (mt-dsRNA) into the cytosol has been recently linked to a number of inflammatory diseases. Here, we report that the release of mt-dsRNA into the cytosol is a general feature of senescent cells and a critical driver of their inflammatory secretome, known as senescence-associated secretory phenotype (SASP). Inhibition of the mitochondrial RNA polymerase, the dsRNA sensors RIGI and MDA5, or the master inflammatory signaling protein MAVS, all result in reduced expression of the SASP, while broadly preserving other hallmarks of senescence. Moreover, senescent cells are hypersensitized to mt-dsRNA-driven inflammation due to their reduced levels of PNPT1 and ADAR1, two proteins critical for mitigating the accumulation of mt-dsRNA and the inflammatory potency of dsRNA, respectively. We find that mitofusin MFN1, but not MFN2, is important for the activation of the mt-dsRNA/MAVS/SASP axis and, accordingly, genetic or pharmacologic MFN1 inhibition attenuates the SASP. Finally, we report that senescent cells within fibrotic and aged tissues present dsRNA foci, and inhibition of mitochondrial RNA polymerase reduces systemic inflammation associated to senescence. In conclusion, we uncover the mt-dsRNA/MAVS/MFN1 axis as a key driver of the SASP and we identify novel therapeutic strategies for senescence-associated diseases.

We are grateful to the IRB Functional Genomics Unit and CRG/CNAG for library preparation and genomic sequencing, to the IRB microscopy unit, and to the CCiUB flow cytometry facility for the technical support. We thank Ms. Tanya Liesel de Silva from the Gavathiotis lab for her technical assistance. V.L.P. was the recipient of a predoctoral contract from the Spanish Ministry of Education (FPU-18/05917). M.M. received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement (No 794744), and from the Spanish Ministry of Science and Innovation (MCIN) (RYC2020-030652-I /AEI /10.13039/501100011033 and PID2022-142205OB-I00). E.Z., F.D.M.M. and E.G. were funded by the National Institutes of Health grants P01AG031782, P30AG038072, R01CA223243, and a Hevolution Foundation partnership grant. M.K. was funded by the Barcelona Institute of Science and Technology (BIST) and Asociación Española Contra el Cáncer (AECC; POSTD18020SERR), and supported by the European Molecular Biology Organization (EMBO). Work in the laboratory of M.S. was funded by the IRB and “laCaixa” Foundation, and by grants from the Spanish Ministry of Science co-funded by the European Regional Development Fund (ERDF) (SAF2017-82613-R), European Research Council (ERC-2014-AdG/669622), and Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement of Catalonia (Grup de Recerca consolidat 2017 SGR 282).