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Mitochondria are required for pro-ageing features of the senescent phenotype.

ABSTRACT: Cell senescence is an important tumour suppressor mechanism and driver of ageing. Both functions are dependent on the development of the senescent phenotype, which involves an overproduction of pro-inflammatory and pro-oxidant signals. However, the exact mechanisms regulating these phenotypes remain poorly understood. Here, we show the critical role of mitochondria in cellular senescence. In multiple models of senescence, absence of mitochondria reduced a spectrum of senescence effectors and phenotypes while preserving ATP production via enhanced glycolysis. Global transcriptomic analysis by RNA sequencing revealed that a vast number of senescent-associated changes are dependent on mitochondria, particularly the pro-inflammatory phenotype. Mechanistically, we show that the ATM, Akt and mTORC1 phosphorylation cascade integrates signals from the DNA damage response (DDR) towards PGC-1?-dependent mitochondrial biogenesis, contributing to aROS-mediated activation of the DDR and cell cycle arrest. Finally, we demonstrate that the reduction in mitochondrial content in vivo, by either mTORC1 inhibition or PGC-1? deletion, prevents senescence in the ageing mouse liver. Our results suggest that mitochondria are a candidate target for interventions to reduce the deleterious impact of senescence in ageing tissues.

SUBMITTER: Correia-Melo C

PROVIDER: S-EPMC4818766 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Mitochondria are required for pro-ageing features of the senescent phenotype.

Correia-Melo Clara C Marques Francisco D M FD Anderson Rhys R Hewitt Graeme G Hewitt Rachael R Cole John J Carroll Bernadette M BM Miwa Satomi S Birch Jodie J Merz Alina A Rushton Michael D MD Charles Michelle M Jurk Diana D Tait Stephen W G SW Czapiewski Rafal R Greaves Laura L Nelson Glyn G Bohlooly-Y Mohammad M Rodriguez-Cuenca Sergio S Vidal-Puig Antonio A Mann Derek D Saretzki Gabriele G Quarato Giovanni G Green Douglas R DR Adams Peter D PD von Zglinicki Thomas T Korolchuk Viktor I VI Passos João F JF

The EMBO journal 20160204 7

Cell senescence is an important tumour suppressor mechanism and driver of ageing. Both functions are dependent on the development of the senescent phenotype, which involves an overproduction of pro-inflammatory and pro-oxidant signals. However, the exact mechanisms regulating these phenotypes remain poorly understood. Here, we show the critical role of mitochondria in cellular senescence. In multiple models of senescence, absence of mitochondria reduced a spectrum of senescence effectors and phe ...[more]

PMID: 26848154

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Project description:The incidence of cardiovascular disease (CVD) is higher in cancer survivors than in the general population. Several cancer treatments are recognized as risk factors for CVD, but specific therapies are unavailable. Many cancer treatments activate shared signaling events, which reprogram myeloid cells (MCs) towards persistent senescence-associated secretory phenotype (SASP) and consequently CVD, but the exact mechanisms remain unclear. This study aimed to provide mechanistic insights and potential treatments by investigating how chemo-radiation can induce persistent SASP. We generated ERK5 S496A knock-in mice and determined SASP in myeloid cells (MCs) by evaluating their efferocytotic ability, antioxidation-related molecule expression, telomere length, and inflammatory gene expression. Candidate SASP inducers were identified by high-throughput screening, using the ERK5 transcriptional activity reporter cell system. Various chemotherapy agents and ionizing radiation (IR) up-regulated p90RSK-mediated ERK5 S496 phosphorylation. Doxorubicin and IR caused metabolic changes with nicotinamide adenine dinucleotide depletion and ensuing mitochondrial stunning (reversible mitochondria dysfunction without showing any cell death under ATP depletion) via p90RSK-ERK5 modulation and poly (ADP-ribose) polymerase (PARP) activation, which formed a nucleus-mitochondria positive feedback loop. This feedback loop reprogramed MCs to induce a sustained SASP state, and ultimately primed MCs to be more sensitive to reactive oxygen species. This priming was also detected in circulating monocytes from cancer patients after IR. When PARP activity was transiently inhibited at the time of IR, mitochondrial stunning, priming, macrophage infiltration, and coronary atherosclerosis were all eradicated. The p90RSK-ERK5 module plays a crucial role in SASP-mediated mitochondrial stunning via regulating PARP activation. Our data show for the first time that the nucleus-mitochondria positive feedback loop formed by p90RSK-ERK5 S496 phosphorylation-mediated PARP activation plays a crucial role of persistent SASP state, and also provide preclinical evidence supporting that transient inhibition of PARP activation only at the time of radiation therapy can prevent future CVD in cancer survivors.

Project description:Colorectal cancer (CRC) is the second leading cause of death among cancer patients in the Northern countries. CRC can reappear a long time after treatment. Recent clinical studies demonstrated that, in response to chemotherapy, cancer cells may undergo stress-induced premature senescence (SIPS), which typically results in growth arrest. Nonetheless, these senescent cells were reported to divide in an atypical manner and thus contribute to cancer re-growth. Therefore, we examined if SIPS escape may follow treatment with chemotherapeutics used clinically: 5-fluorouracil (5-FU), oxaliplatin (OXA) and irinotecan (IRINO). To mimic the therapeutic regimes we exposed human colon cancer HCT116 and SW480 cells to repeated cycles of drug treatment. The cells treated with 5-FU or IRINO exhibited several hallmarks of SIPS: growth arrest, increased size and granularity, polyploidization, augmented activity of the SA-β-galactosidase, accumulation of P21 and CYCLIN D1 proteins, and the senescence-associated secretory phenotype. Moreover, re-population of the cancer cell cultures was delayed upon treatment with the senescence-inducing agents. At the same time, we detected a subpopulation of senescent colon cancer cells with features of stemness: elevated NANOG expression, exclusion of Hoechst 33342 (typical for side population) and increased CD24 expression. Additionally, rare, polyploid cells exhibited blastocyst-like morphology and produced progeny. In parallel, majority of chemotherapeutics-treated cells underwent mesenchymal to epithelial transition, as the percentage of CD44-positve cells was reduced, and levels of E-cadherin (epithelial marker) were elevated. Our study demonstrates that a subpopulation of chemotherapeutics-treated colon cancer cells display a specific phenotype being a combination of stem-like and senescent cell features. This may contribute to their resistance to chemotherapy and their ability to re-grow cancer after completion of therapeutic intervention.

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Mitochondria are required for pro-ageing features of the senescent phenotype.

Publications

Mitochondria are required for pro-ageing features of the senescent phenotype.

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