title: Rapamycin inhibits the secretory phenotype of senescent cells by a Nrf2-independent mechanism.
abstract: Senescent cells contribute to age-related pathology and loss of function, and their selective removal improves physiological function and extends longevity. Rapamycin, an inhibitor of mTOR, inhibits cell senescence in vitro and increases longevity in several species. Nrf2 levels have been shown to decrease with aging and silencing Nrf2 gene induces premature senescence. Therefore, we explored whether Nrf2 is involved in the mechanism by which rapamycin delays cell senescence. In wild-type (WT) mouse fibroblasts, rapamycin increased the levels of Nrf2, and this correlates with the activation of autophagy and a reduction in the induction of cell senescence, as measured by SA-β-galactosidase (β-gal) staining, senescence-associated secretory phenotype (SASP), and p16 and p21 molecular markers. In Nrf2KO fibroblasts, however, rapamycin still decreased β-gal staining and the SASP, but rapamycin did not activate the autophagy pathway or decrease p16 and p21 levels. These observations were further confirmed in vivo using Nrf2KO mice, where rapamycin treatment led to a decrease in β-gal staining and pro-inflammatory cytokines in serum and fat tissue; however, p16 levels were not significantly decreased in fat tissue. Consistent with literature demonstrating that the Stat3 pathway is linked to the production of SASP, we found that rapamycin decreased activation of the Stat3 pathway in cells or tissue samples from both WT and Nrf2KO mice. Our data thus suggest that cell senescence is a complex process that involves at least two arms, and rapamycin uses Nrf2 to regulate cell cycle arrest, but not the production of SASP.
authors.affiliation: Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.affiliation: Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.|Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Bharath
authors.initials: B
authors.lastname: Sunchu
authors.affiliation: Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: James
authors.initials: J
authors.lastname: Shoaf
authors.affiliation: Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Ivana
authors.initials: I
authors.lastname: Dang
authors.affiliation: Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Kelsey
authors.initials: K
authors.lastname: Caples
authors.affiliation: Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Lynda
authors.initials: L
authors.lastname: Bradley
authors.affiliation: Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.|School of Biological & Population Health Sciences, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Beaver
authors.affiliation: Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.|School of Biological & Population Health Sciences, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Ho
authors.affiliation: Department of Biomedical Sciences, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Christiane V
authors.initials: CV
authors.lastname: Löhr
authors.affiliation: Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.|Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Viviana I
authors.initials: VI
authors.lastname: Perez
mesh_terms: D000375:Aging / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001343:Autophagy / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D016922:Cellular Senescence / Q000187:drug effects*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D051267:NF-E2-Related Factor 2 / Q000172:deficiency / Q000235:genetics*; D010641:Phenotype; D061251:Primary Cell Culture; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016207:Cytokines; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D001616:beta-Galactosidase; D020123:Sirolimus
keywords: 
  SASP
  ; Nrf2; cell senescence; rapamycin; β-gal