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Gems D, Kern CC, Nour J, Ezcurra M. Reproductive Suicide: Similar Mechanisms of Aging in C. elegans and Pacific Salmon. Front Cell Dev Biol 2021; 9:688788. [PMID: 34513830 PMCID: PMC8430333 DOI: 10.3389/fcell.2021.688788] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/21/2021] [Indexed: 12/17/2022] Open
Abstract
In some species of salmon, reproductive maturity triggers the development of massive pathology resulting from reproductive effort, leading to rapid post-reproductive death. Such reproductive death, which occurs in many semelparous organisms (with a single bout of reproduction), can be prevented by blocking reproductive maturation, and this can increase lifespan dramatically. Reproductive death is often viewed as distinct from senescence in iteroparous organisms (with multiple bouts of reproduction) such as humans. Here we review the evidence that reproductive death occurs in C. elegans and discuss what this means for its use as a model organism to study aging. Inhibiting insulin/IGF-1 signaling and germline removal suppresses reproductive death and greatly extends lifespan in C. elegans, but can also extend lifespan to a small extent in iteroparous organisms. We argue that mechanisms of senescence operative in reproductive death exist in a less catastrophic form in iteroparous organisms, particularly those that involve costly resource reallocation, and exhibit endocrine-regulated plasticity. Thus, mechanisms of senescence in semelparous organisms (including plants) and iteroparous ones form an etiological continuum. Therefore understanding mechanisms of reproductive death in C. elegans can teach us about some mechanisms of senescence that are operative in iteroparous organisms.
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Affiliation(s)
- David Gems
- Institute of Healthy Ageing, Research Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Carina C. Kern
- Institute of Healthy Ageing, Research Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Joseph Nour
- Institute of Healthy Ageing, Research Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Marina Ezcurra
- School of Biosciences, University of Kent, Canterbury, United Kingdom
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Ghosh MK, Chen KHE, Dill-Garlow R, Ma LJ, Yonezawa T, Itoh Y, Rivera L, Radecki KC, Wu QP, Arnold AP, Muller HK, Walker AM. Sex Differences in the Immune System Become Evident in the Perinatal Period in the Four Core Genotypes Mouse. Front Endocrinol (Lausanne) 2021; 12:582614. [PMID: 34122327 PMCID: PMC8191418 DOI: 10.3389/fendo.2021.582614] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 05/07/2021] [Indexed: 01/02/2023] Open
Abstract
We have used the four core genotypes (FCG) mouse model, which allows a distinction between effects of gonadal secretions and chromosomal complement, to determine when sex differences in the immune system first appear and what influences their development. Using splenic T cell number as a measure that could be applied to neonates with as yet immature immune responses, we found no differences among the four genotypes at postnatal day 1, but by day 7, clear sex differences were observed. These sex differences were unexpectedly independent of chromosomal complement and similar in degree to gonadectomized FCG adults: both neonatal and gonadectomized adult females (XX and XY) showed 2-fold the number of CD4+ and 7-fold the number of CD8+ T cells versus their male (XX and XY) counterparts. Appearance of this long-lived sex difference between days 1 and 7 suggested a role for the male-specific perinatal surge of testicular testosterone. Interference with the testosterone surge significantly de-masculinized the male CD4+, but not CD8+ splenic profile. Treatment of neonates demonstrated elevated testosterone limited mature cell egress from the thymus, whereas estradiol reduced splenic T cell seeding in females. Neonatal male splenic epithelium/stroma expressed aromatase mRNA, suggesting capacity for splenic conversion of perinatal testosterone into estradiol in males, which, similar to administration of estradiol in females, would result in reduced splenic T cell seeding. These sex steroid effects affected both CD4+ and CD8+ cells and yet interference with the testosterone surge only significantly de-masculinized the splenic content of CD4+ cells. For CD8+ cells, male cells in the thymus were also found to express one third the density of sphingosine-1-phosphate thymic egress receptors per cell compared to female, a male characteristic most likely an indirect result of Sry expression. Interestingly, the data also support a previously unrecognized role for non-gonadal estradiol in the promotion of intra-thymic cell proliferation in neonates of both sexes. Microarray analysis suggested the thymic epithelium/stroma as the source of this hormone. We conclude that some immune sex differences appear long before puberty and more than one mechanism contributes to differential numbers and distribution of T cells.
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Affiliation(s)
- Mrinal K. Ghosh
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Kuan-hui E. Chen
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Riva Dill-Garlow
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Lisa J. Ma
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Tomohiro Yonezawa
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Yuichiro Itoh
- Department of Integrative Biology & Physiology, University of California, Los Angeles, Los Angeles, CA, United States
| | - Lorena Rivera
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Kelly C. Radecki
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Quiming P. Wu
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Arthur P. Arnold
- Department of Integrative Biology & Physiology, University of California, Los Angeles, Los Angeles, CA, United States
| | - H. Konrad Muller
- School of Medicine, University of Tasmania, Hobart, TAS, Australia
| | - Ameae M. Walker
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
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