1
|
Santos CS, Macedo F, Kowaltowski AJ, Bertotti M, Unwin PR, Marques da Cunha F, Meloni GN. Unveiling the contribution of the reproductive system of individual Caenorhabditis elegans on oxygen consumption by single-point scanning electrochemical microscopy measurements. Anal Chim Acta 2021; 1146:88-97. [PMID: 33461723 PMCID: PMC7836392 DOI: 10.1016/j.aca.2020.12.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/11/2020] [Accepted: 12/17/2020] [Indexed: 01/03/2023]
Abstract
Metabolic analysis in animals is usually either evaluated as whole-body measurements or in isolated tissue samples. To reveal tissue specificities in vivo, this study uses scanning electrochemical microscopy (SECM) to provide localized oxygen consumption rates (OCRs) in different regions of single adult Caenorhabditis elegans individuals. This is achieved by measuring the oxygen reduction current at the SECM tip electrode and using a finite element method model of the experiment that defines oxygen concentration and flux at the surface of the organism. SECM mapping measurements uncover a marked heterogeneity of OCR along the worm, with high respiration rates at the reproductive system region. To enable sensitive and quantitative measurements, a self-referencing approach is adopted, whereby the oxygen reduction current at the SECM tip is measured at a selected point on the worm and in bulk solution (calibration). Using genetic and pharmacological approaches, our SECM measurements indicate that viable eggs in the reproductive system are the main contributors in the total oxygen consumption of adult Caenorhabditis elegans. The finding that large regional differences in OCR exist within the animal provides a new understanding of oxygen consumption and metabolic measurements, paving the way for tissue-specific metabolic analyses and toxicity evaluation within single organisms.
Collapse
Affiliation(s)
- Carla S Santos
- Departamento de Química Fundamental, Av. Professor Lineu Prestes, 748, 05508-000, São Paulo, SP, Brazil.
| | - Felipe Macedo
- Departamento de Bioquímica, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua três de Maio, 100, 04044-020, São Paulo, Brazil
| | - Alicia J Kowaltowski
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Professor Lineu Prestes, 748, 05508-000, São Paulo, SP, Brazil
| | - Mauro Bertotti
- Departamento de Química Fundamental, Av. Professor Lineu Prestes, 748, 05508-000, São Paulo, SP, Brazil
| | - Patrick R Unwin
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, United Kingdom; Bio-Electrical Engineering Innovation Hub, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | - Fernanda Marques da Cunha
- Departamento de Bioquímica, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua três de Maio, 100, 04044-020, São Paulo, Brazil
| | - Gabriel N Meloni
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, United Kingdom; Bio-Electrical Engineering Innovation Hub, University of Warwick, Coventry, CV4 7AL, United Kingdom.
| |
Collapse
|
2
|
Dhondt I, Petyuk VA, Bauer S, Brewer HM, Smith RD, Depuydt G, Braeckman BP. Changes of Protein Turnover in Aging Caenorhabditis elegans. Mol Cell Proteomics 2017; 16:1621-1633. [PMID: 28679685 DOI: 10.1074/mcp.ra117.000049] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Indexed: 11/06/2022] Open
Abstract
Protein turnover rates severely decline in aging organisms, including C. elegans However, limited information is available on turnover dynamics at the individual protein level during aging. We followed changes in protein turnover at one-day resolution using a multiple-pulse 15N-labeling and accurate mass spectrometry approach. Forty percent of the proteome shows gradual slowdown in turnover with age, whereas only few proteins show increased turnover. Decrease in protein turnover was consistent for only a minority of functionally related protein subsets, including tubulins and vitellogenins, whereas randomly diverging turnover patterns with age were the norm. Our data suggests increased heterogeneity of protein turnover of the translation machinery, whereas protein turnover of ubiquitin-proteasome and antioxidant systems are well-preserved over time. Hence, we presume that maintenance of quality control mechanisms is a protective strategy in aging worms, although the ultimate proteome collapse is inescapable.
Collapse
Affiliation(s)
- Ineke Dhondt
- From the ‡Laboratory for Aging Physiology and Molecular Evolution, Biology Department, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent Belgium
| | - Vladislav A Petyuk
- §Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Sophie Bauer
- From the ‡Laboratory for Aging Physiology and Molecular Evolution, Biology Department, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent Belgium
| | - Heather M Brewer
- §Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Richard D Smith
- §Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Geert Depuydt
- From the ‡Laboratory for Aging Physiology and Molecular Evolution, Biology Department, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent Belgium.,¶Laboratory for Functional Genomics and Proteomics, Department of Biology, KU Leuven, Naamsestraat 59, 3000 Leuven, Belgium
| | - Bart P Braeckman
- From the ‡Laboratory for Aging Physiology and Molecular Evolution, Biology Department, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent Belgium;
| |
Collapse
|
3
|
Knowlton WM, Hubert T, Wu Z, Chisholm AD, Jin Y. A Select Subset of Electron Transport Chain Genes Associated with Optic Atrophy Link Mitochondria to Axon Regeneration in Caenorhabditis elegans. Front Neurosci 2017; 11:263. [PMID: 28539870 PMCID: PMC5423972 DOI: 10.3389/fnins.2017.00263] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 04/24/2017] [Indexed: 12/13/2022] Open
Abstract
The role of mitochondria within injured neurons is an area of active interest since these organelles are vital for the production of cellular energy in the form of ATP. Using mechanosensory neurons of the nematode Caenorhabditis elegans to test regeneration after neuronal injury in vivo, we surveyed genes related to mitochondrial function for effects on axon regrowth after laser axotomy. Genes involved in mitochondrial transport, calcium uptake, mitophagy, or fission and fusion were largely dispensable for axon regrowth, with the exception of eat-3/Opa1. Surprisingly, many genes encoding components of the electron transport chain were dispensable for regrowth, except for the iron-sulfur proteins gas-1, nduf-2.2, nduf-7, and isp-1, and the putative oxidoreductase rad-8. In these mutants, axonal development was essentially normal and axons responded normally to injury by forming regenerative growth cones, but were impaired in subsequent axon extension. Overexpression of nduf-2.2 or isp-1 was sufficient to enhance regrowth, suggesting that mitochondrial function is rate-limiting in axon regeneration. Moreover, loss of function in isp-1 reduced the enhanced regeneration caused by either a gain-of-function mutation in the calcium channel EGL-19 or overexpression of the MAP kinase DLK-1. While the cellular function of RAD-8 remains unclear, our genetic analyses place rad-8 in the same pathway as other electron transport genes in axon regeneration. Unexpectedly, rad-8 regrowth defects were suppressed by altered function in the ubiquinone biosynthesis gene clk-1. Furthermore, we found that inhibition of the mitochondrial unfolded protein response via deletion of atfs-1 suppressed the defective regrowth in nduf-2.2 mutants. Together, our data indicate that while axon regeneration is not significantly affected by general dysfunction of cellular respiration, it is sensitive to the proper functioning of a select subset of electron transport chain genes, or to the cellular adaptations used by neurons under conditions of injury.
Collapse
Affiliation(s)
- Wendy M Knowlton
- Section of Neurobiology, Division of Biological Sciences, University of CaliforniaSan Diego, CA, USA
| | - Thomas Hubert
- Section of Neurobiology, Division of Biological Sciences, University of CaliforniaSan Diego, CA, USA
| | - Zilu Wu
- Howard Hughes Medical Institute, University of CaliforniaSan Diego, CA, USA
| | - Andrew D Chisholm
- Section of Neurobiology, Division of Biological Sciences, University of CaliforniaSan Diego, CA, USA
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of CaliforniaSan Diego, CA, USA.,Howard Hughes Medical Institute, University of CaliforniaSan Diego, CA, USA.,Department of Cellular and Molecular Medicine, School of Medicine, University of CaliforniaSan Diego, CA, USA
| |
Collapse
|
4
|
Davies SK, Bundy JG, Leroi AM. Metabolic Youth in Middle Age: Predicting Aging in Caenorhabditis elegans Using Metabolomics. J Proteome Res 2015; 14:4603-9. [PMID: 26381038 DOI: 10.1021/acs.jproteome.5b00442] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Many mutations and allelic variants are known that influence the rate at which animals age, but when in life do such variants diverge from normal patterns of aging? Is this divergence visible in their physiologies? To investigate these questions, we have used (1)H NMR spectroscopy to study how the metabolome of the nematode Caenorhabditis elegans changes as it grows older. We identify a series of metabolic changes that, collectively, predict the age of wild-type worms. We then show that long-lived mutant daf-2(m41) worms are metabolically youthful compared to wild-type worms, but that this relative youth only appears in middle age. Finally, we show that metabolic age predicts the timing and magnitude of differences in age-specific mortality between these strains. Thus, the future mortality of these two genotypes can be predicted long before most of the worms die.
Collapse
Affiliation(s)
- Sarah K Davies
- Department of Life Sciences and ‡Department of Surgery and Cancer, Imperial College London , Sir Alexander Fleming Building, London SW7 2AZ, U.K
| | - Jacob G Bundy
- Department of Life Sciences and ‡Department of Surgery and Cancer, Imperial College London , Sir Alexander Fleming Building, London SW7 2AZ, U.K
| | - Armand M Leroi
- Department of Life Sciences and ‡Department of Surgery and Cancer, Imperial College London , Sir Alexander Fleming Building, London SW7 2AZ, U.K
| |
Collapse
|
5
|
Cañuelo A, Peragón J. Proteomics analysis in Caenorhabditis elegans to elucidate the response induced by tyrosol, an olive phenol that stimulates longevity and stress resistance. Proteomics 2013; 13:3064-75. [PMID: 23929540 DOI: 10.1002/pmic.201200579] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 06/13/2013] [Accepted: 07/01/2013] [Indexed: 02/03/2023]
Abstract
Tyrosol (TYR, 2-(4-hydroxyphenyl)ethanol), one of the main phenols in olive oil and olive fruit, significantly strengthens resistance to thermal and oxidative stress in the nematode Caenorhabditis elegans and extends its lifespan. To elucidate the cellular functions regulated by TYR, we have used a proteomic procedure based on 2DE coupled with MS with the aim to identify the proteins differentially expressed in nematodes grown in a medium containing 250 μM TYR. After the comparison of the protein profiles from 250 μM TYR and from control, 28 protein spots were found to be altered in abundance (≥twofold). Analysis by MALDI-TOF/TOF and PMF allowed the unambiguous identification of 17 spots, corresponding to 13 different proteins. These proteins were as follows: vitellogenin-5, vitellogenin-2, bifunctional glyoxylate cycle protein, acyl CoA dehydrogenase-3, alcohol dehydrogenase 1, adenosylhomocysteinase, elongation factor 2, GTP-binding nuclear protein ran-1, HSP-4, protein ENPL-1 isoform b, vacuolar H ATPase 12, vacuolar H ATPase 13, GST 4. Western-blot analysis of yolk protein 170, ras-related nuclear protein, elongation factor 2, and vacuolar H ATPase H subunit supported the proteome evidence.
Collapse
Affiliation(s)
- Ana Cañuelo
- Biochemistry and Molecular Biology Section, Department of Experimental Biology, University of Jaén, Jaén, Spain
| | | |
Collapse
|
6
|
Austin MU, Liau WS, Balamurugan K, Ashokkumar B, Said HM, LaMunyon CW. Knockout of the folate transporter folt-1 causes germline and somatic defects in C. elegans. BMC DEVELOPMENTAL BIOLOGY 2010; 10:46. [PMID: 20441590 PMCID: PMC2874772 DOI: 10.1186/1471-213x-10-46] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 05/04/2010] [Indexed: 12/02/2022]
Abstract
BACKGROUND The C. elegans gene folt-1 is an ortholog of the human reduced folate carrier gene. The FOLT-1 protein has been shown to transport folate and to be involved in uptake of exogenous folate by worms. A knockout mutation of the gene, folt-1(ok1460), was shown to cause sterility, and here we investigate the source of the sterility and the effect of the folt-1 knockout on somatic function. RESULTS Our results show that folt-1(ok1460) knockout hermaphrodites have a substantially reduced germline, generate a small number of functional sperm, and only rarely produce a functional oocyte. We found no evidence of increased apoptosis in the germline of folt-1 knockout mutants, suggesting that germline proliferation is defective. While folt-1 knockout males are fertile, their rate of spermatogenesis was severely diminished, and the males were very poor maters. The mating defect is likely due to compromised metabolism and/or other somatic functions, as folt-1 knockout hermaphrodites displayed a shortened lifespan and elongated defecation intervals. CONCLUSIONS The FOLT-1 protein function affects both the soma and the germline. folt-1(ok1460) hermaphrodites suffer severely diminished lifespan and germline defects that result in sterility. Germline defects associated with folate deficiency appear widespread in animals, being found in humans, mice, fruit flies, and here, nematodes.
Collapse
Affiliation(s)
- Misa U Austin
- Department of Biological Sciences, California State University Pomona, CA 91768, USA
| | - Wei-Siang Liau
- Department of Biological Sciences, California State University Pomona, CA 91768, USA
- Current Address: Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Krishnaswamy Balamurugan
- Veterans Affairs Medical Center, Long Beach, CA 90822, USA
- Departments of Medicine and Physiology/Biophysics, University of California, Irvine, CA 92697, USA
- Current Address: Department of Biotechnology, Alagappa University, Karaikudi 630 003, India
| | - Balasubramaniem Ashokkumar
- Veterans Affairs Medical Center, Long Beach, CA 90822, USA
- Departments of Medicine and Physiology/Biophysics, University of California, Irvine, CA 92697, USA
| | - Hamid M Said
- Veterans Affairs Medical Center, Long Beach, CA 90822, USA
- Departments of Medicine and Physiology/Biophysics, University of California, Irvine, CA 92697, USA
| | - Craig W LaMunyon
- Department of Biological Sciences, California State University Pomona, CA 91768, USA
| |
Collapse
|
7
|
Yen K, Mobbs CV. Evidence for only two independent pathways for decreasing senescence in Caenorhabditis elegans. AGE (DORDRECHT, NETHERLANDS) 2010; 32:39-49. [PMID: 19662517 PMCID: PMC2829647 DOI: 10.1007/s11357-009-9110-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Accepted: 07/22/2009] [Indexed: 05/22/2023]
Abstract
Cold temperature, dietary restriction, reduced insulin/insulin-like growth factor signaling, and mutations in mitochondrial genes have all been shown to extend the lifespan of Caenorhabditis elegans (Kenyon et al., Nature 366:461-464, 1993; Klass, Mech Ageing Dev 6:413-429, 1977; Lakowski and Hekimi, Science 272:1010-1013, 1996). Additionally, all of them extend the lifespan of mice (Bluher et al., Science 299:572-574, 2003; Conti et al., Science 314:825-828, 2006; Holzenberger et al., Nature 421:182-187, 2003; Liu et al., Genes Dev 19:2424-2434, 2005; Weindruch and Walford, Science 215:1415-1418, 1982). The mechanism by which these treatments extend lifespan is currently unknown, but our study uses an epistatic approach to show that these four manipulations are mainly additive in terms of lifespan. Classical interpretation of this data suggests that these manipulations are independent of each other. However, using a Gompertz mortality rate analysis, the maximum mortality rate doubling time can be achieved through the use of only dietary restriction and cold temperature, suggesting that the mechanisms by which cold temperature and caloric restriction extend lifespan are the only independent mechanisms.
Collapse
Affiliation(s)
- Kelvin Yen
- University of Massachusetts Medical School, Worcester, MA 01606, USA.
| | | |
Collapse
|
8
|
Abstract
The processes that determine an organism's lifespan are complex and poorly understood. Yet single gene manipulations and environmental interventions can substantially delay age-related morbidity. In this review, we focus on the two most potent modulators of longevity: insulin/insulin-like growth factor 1 (IGF-1) signaling and dietary restriction. The remarkable molecular conservation of the components associated with insulin/IGF-1 signaling and dietary restriction allow us to understand longevity from a multi-species perspective. We summarize the most recent findings on insulin/IGF-1 signaling and examine the proteins and pathways that reveal a more genetic basis for dietary restriction. Although insulin/IGF-1 signaling and dietary restriction pathways are currently viewed as being independent, we suggest that these two pathways are more intricately connected than previously appreciated. We highlight that numerous interactions between these two pathways can occur at multiple levels. Ultimately, both the insulin/IGF-1 pathway and the pathway that mediates the effects of dietary restriction have evolved to respond to the nutritional status of an organism, which in turn affects its lifespan.
Collapse
Affiliation(s)
- Sri Devi Narasimhan
- Program in Gene Function and Expression, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Kelvin Yen
- Program in Gene Function and Expression, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Heidi A. Tissenbaum
- Program in Gene Function and Expression, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
- Program in Molecular Medicine, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| |
Collapse
|
9
|
Liau WS, Gonzalez-Serricchio AS, Deshommes C, Chin K, LaMunyon CW. A persistent mitochondrial deletion reduces fitness and sperm performance in heteroplasmic populations of C. elegans. BMC Genet 2007; 8:8. [PMID: 17394659 PMCID: PMC1852114 DOI: 10.1186/1471-2156-8-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Accepted: 03/29/2007] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Mitochondrial DNA (mtDNA) mutations are of increasing interest due to their involvement in aging, disease, fertility, and their role in the evolution of the mitochondrial genome. The presence of reactive oxygen species and the near lack of repair mechanisms cause mtDNA to mutate at a faster rate than nuclear DNA, and mtDNA deletions are not uncommon in the tissues of individuals, although germ-line mtDNA is largely lesion-free. Large-scale deletions in mtDNA may disrupt multiple genes, and curiously, some large-scale deletions persist over many generations in a heteroplasmic state. Here we examine the phenotypic effects of one such deletion, uaDf5, in Caenorhabditis elegans (C. elegans). Our study investigates the phenotypic effects of this 3 kbp deletion. RESULTS The proportion of uaDf5 chromosomes in worms was highly heritable, although uaDf5 content varied from worm to worm and within tissues of individual worms. We also found an impact of the uaDf5 deletion on metabolism. The deletion significantly reduced egg laying rate, defecation rate, and lifespan. Examination of sperm bearing the uaDf5 deletion revealed that sperm crawled more slowly, both in vitro and in vivo. CONCLUSION Worms harboring uaDf5 are at a selective disadvantage compared to worms with wild-type mtDNA. These effects should lead to the rapid extinction of the deleted chromosome, but it persists indefinitely. We discuss both the implications of this phenomenon and the possible causes of a shortened lifespan for uaDf5 mutant worms.
Collapse
Affiliation(s)
- Wei-Siang Liau
- Department of Biological Science, California State Polytechnic University, Pomona, CA, USA
| | | | - Cleonique Deshommes
- School of Graduate Medical Sciences, Barry University, Miami Shores, FL, USA
| | - Kara Chin
- Department of Biological Science, California State Polytechnic University, Pomona, CA, USA
| | - Craig W LaMunyon
- Department of Biological Science, California State Polytechnic University, Pomona, CA, USA
| |
Collapse
|
10
|
Walker G, Houthoofd K, Vanfleteren JR, Gems D. Dietary restriction in C. elegans: from rate-of-living effects to nutrient sensing pathways. Mech Ageing Dev 2005; 126:929-37. [PMID: 15896824 DOI: 10.1016/j.mad.2005.03.014] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2004] [Revised: 01/28/2005] [Accepted: 03/15/2005] [Indexed: 11/30/2022]
Abstract
The nematode Caenorhabditis elegans has been subjected to dietary restriction (DR) by a number of means, with varying results in terms of fecundity and lifespan. Two possible mechanisms by which DR increases lifespan are reduction of metabolic rate and reduction of insulin/IGF-1 signalling. Experimental tests have not supported either possibility. However, interaction studies suggest that DR and insulin/IGF-1 signalling may act in parallel on common regulated processes. In this review, we discuss recent developments in C. elegans DR research, including new discoveries about the biology of nutrient uptake in the gut, and the importance of invasion by the bacterial food source as a determinant of lifespan. The evidence that the effect of DR on lifespan in C. elegans is mediated by the TOR pathway is discussed. We conclude that the effect of DR on lifespan is likely to involve multiple mechanisms, which may differ according to the DR regimen used and the organism under study.
Collapse
Affiliation(s)
- Glenda Walker
- Department of Biology, University College London, Gower Street, WC1E 6BT, UK
| | | | | | | |
Collapse
|
11
|
Massie MR, Lapoczka EM, Boggs KD, Stine KE, White GE. Exposure to the metabolic inhibitor sodium azide induces stress protein expression and thermotolerance in the nematode Caenorhabditis elegans. Cell Stress Chaperones 2003; 8:1-7. [PMID: 12820649 PMCID: PMC514849 DOI: 10.1379/1466-1268(2003)8<1:ettmis>2.0.co;2] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Historically, sodium azide has been used to anesthetize the nematode Caenorhabditis elegans; however, the mechanism by which it survives this exposure is not understood. In this study, we report that exposure of wild-type C elegans to 10 mM sodium azide for up to 90 minutes confers thermotolerance (defined as significantly increased survival probability [SP] at 37 degrees C) on the animal. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed enhanced Hsp70 expression, whereas Western blot analysis revealed the induction of Hsp16. We also tested the only known C elegans Hsp mutant def-21 (codes for Hsp90), which constitutively enters the stress-resistant state known as the dauer larvae. Daf-21 mutants also acquire sodium azide-induced thermotolerance, whereas 3 non-Hsp, constitutive dauer-forming mutants exhibited a variable response to azide exposure. We conclude that the ability of C elegans to survive exposure to azide is associated with the induction of at least 2 stress proteins.
Collapse
Affiliation(s)
- Michelle R Massie
- Department of Biology/Toxicology, Ashland University, Ashland, OH 44805, USA
| | | | | | | | | |
Collapse
|
12
|
Abstract
Much of the recent interest in aging research is due to the discovery of genes in a variety of model organisms that appear to modulate aging. A large amount of research has focused on the use of such long-lived mutants to examine the fundamental causes of aging. While model organisms do offer many advantages for studying aging, it also critical to consider the limitations of these systems. In particular, ectothermic (poikilothermic) organisms can tolerate a much larger metabolic depression than humans. Thus, considering only chronological longevity when assaying for long-lived mutants provides a limited perspective on the mechanisms by which longevity is increased. In order to provide true insight into the aging process additional physiological processes, such as metabolic rate, must also be assayed. This is especially true in the nematode Caenorhabditis elegans, which can naturally enter into a metabolically reduced state in which it survives many times longer than its usual lifetime. Currently it is seen as controversial if long-lived C. elegans mutants retain normal metabolic function. Resolving this issue requires accurately measuring the metabolic rate of C. elegans under conditions that minimize environmental stress. Additionally, the relatively small size of C. elegans requires the use of sensitive methodologies when determining metabolic rates. Several studies indicating that long-lived C. elegans mutants have normal metabolic rates may be flawed due to the use of inappropriate measurement conditions and techniques. Comparisons of metabolic rate between long-lived and wild-type C. elegans under more optimized conditions indicate that the extended longevity of at least some long-lived C. elegans mutants may be due to a reduction in metabolic rate, rather than an alteration of a metabolically independent genetic mechanism specific to aging.
Collapse
Affiliation(s)
- Wayne A Van Voorhies
- Molecular Biology Program, MSC 3MLS, New Mexico State University, Las Cruces, NM 88003-8001, USA.
| |
Collapse
|
13
|
Abstract
A major challenge in current research into aging using model organisms is to establish whether different treatments resulting in slowed aging involve common or distinct mechanisms. Such treatments include gene mutation, dietary restriction (DR), and manipulation of reproduction, gonadal signals and temperature. The principal method used to determine whether these treatments act through common mechanisms is to compare the magnitude of the effect on aging of each treatment separately with that when two are applied simultaneously. In this discussion we identify five types of methodological shortcomings that have marred such studies. These are (1) submaximal lifespan-extension by individual treatments, e.g. as a result of the use of hypomorphic rather than null alleles; (2) effects of a single treatment on survival through more than one mechanism, e.g. pleiotropic effects of lifespan mutants; (3) the difficulty of interpreting the magnitude of increases in lifespan in double treatments, and failure to measure and model age-specific mortality rates; (4) the non-specific effects of life extension suppressors; and (5) the possible occurrence of artefactual mutant interactions. When considered in the light of these problems, the conclusions of a number of recent lifespan interaction studies appear questionable. We suggest six rules for avoiding the pitfalls that can beset interaction studies.
Collapse
Affiliation(s)
- David Gems
- Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.
| | | | | |
Collapse
|
14
|
Abstract
Research into the causes of aging has greatly increased in recent years. Much of this interest is due to the discovery of genes in a variety of model organisms that appear to modulate aging. Studies of long-lived mutants can potentially provide valuable insights into the fundamental mechanisms of aging. While there are many advantages to the use of model organisms to study aging it is also important to consider the limitations of these systems, particularly because ectothermic (poikilothermic) organisms can survive a far greater metabolic depression than humans. As such, the consideration of only chronological longevity when assaying for long-lived mutants provides a limited perspective on the mechanisms by which longevity is increased. Additional physiological processes, such as metabolic rate, must also be assayed to provide true insight into the aging process. This is especially true in the nematode Caenorhabditis elegans, which has the natural ability to enter into a metabolically reduced state in which it can survive many times longer than its normal lifetime. The extended longevity of at least some long-lived C. elegans mutants may be due to a reduction in metabolic rate, rather than an alteration of a metabolically independent genetic mechanism specific for aging.
Collapse
Affiliation(s)
- Wayne A Van Voorhies
- Molecular Biology Program, New Mexico State University, Las Cruces, NM 88003-8001, USA.
| |
Collapse
|
15
|
Gershon H, Gershon D. Caenorhabditis elegans--a paradigm for aging research: advantages and limitations. Mech Ageing Dev 2002; 123:261-74. [PMID: 11744039 DOI: 10.1016/s0047-6374(01)00401-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In 1967, as we became interested in the biology of aging, we were faced with the following basic biological paradox: organisms are endowed with the capacity to detect and repair damage encountered at the molecular and cellular levels and yet functional capacity declines with time. In accordance with Strehler's suggestion (Time, Cells, and Aging, 2nd ed., Academic Press, New York, 1962), we adopted the basic premise that the underlying mechanisms of aging are common to all multi-cellular organisms. A search for a suitable experimental organism that fulfills the basic criteria for an appropriate model for aging research (Exp. Gerontol. 5 (1970) 7; Mech. Ageing Dev. 117 (2000) 21) led us to the selection of nematodes as a model for our initial series of experiments. Nematodes have thus been used in aging research for three decades. This review critically examines the major merits and shortcomings of this model organism for aging research and argues for greater appreciation of the need to understand the biology of the nematode life cycle not only as it is maintained in the laboratory, but also as it evolved and lives in nature.
Collapse
Affiliation(s)
- Harriet Gershon
- Department of Immunology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | | |
Collapse
|
16
|
Affiliation(s)
- H Gershon
- Department of Immunology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | | |
Collapse
|
17
|
Toussaint O, Baret PV, Brion JP, Cras P, Collette F, De Deyn PP, Geenen V, Kienlen-Campard P, Labeur C, Legros JJ, Nève J, Octave JN, Piérard GE, Salmon E, van den Bosch de Aguilar P P, Van der Linden M, Leuven FV, Vanfleteren J. Experimental gerontology in Belgium: from model organisms to age-related pathologies. Exp Gerontol 2000; 35:901-16. [PMID: 11121679 DOI: 10.1016/s0531-5565(00)00177-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- O Toussaint
- Unit of Cellular Biochemistry, University of Namur, Rue de Bruxelles, 61, B-5000 Namur, Belgium.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|