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Testing the “garbage” accumulation theory of ageing: mitotic activity protects cells from death induced by inhibition of autophagy
Linköping University, Department of Clinical and Experimental Medicine, Experimental Pathology . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Experimental Pathology . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Health Sciences, Pharmacology . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Experimental Pathology . Linköping University, Faculty of Health Sciences.
2005 (English)In: Biogerontology, ISSN 1389-5729 (Print) 1573-6768 (Online), Vol. 6, no 1, 39-47 p.Article in journal (Refereed) Published
Abstract [en]

Imperfect autophagic degradation of oxidatively damaged macromolecules and organelles (so-called biological garbage) is considered an important contributor to ageing and consequent death of postmitotic (non-dividing) cells, such as neurons and cardiac myocytes. In contrast, proliferating cells apparently escape senescence by a continuous dilution and repair of damaged structures during division. Postmitotic ageing can be mimicked and studied in cultures of potentially dividing cells if their mitotic activity is inhibited. To test the garbage accumulation theory of ageing, we compared survival of density-dependent growth-arrested (confluent) and proliferating human fibroblasts and astrocytes following inhibition of autophagic sequestration with 3-methyladenine (3MA). Exposure of confluent fibroblast cultures to 3MA for two weeks resulted in a significantly increased proportion of dying cells compared to both untreated confluent cultures and dividing cells with 3MA-inhibited autophagy. Similar results were obtained when autophagic degradation was suppressed by the protease inhibitor leupeptin. In 3MA- or leupeptin-exposed cultures, dying cells were overloaded with undegraded autofluorescent material. The results support a key role of biological lysosomal garbage accumulation in the triggering of ageing and death of postmitotic cells, as well as the anti-ageing role of cell division.

Place, publisher, year, edition, pages
2005. Vol. 6, no 1, 39-47 p.
Keyword [en]
ageing, apoptosis, astrocytes, autophagocytosis, fibroblasts, 3-methyladenine, leupeptin, mitosis
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-14212DOI: 10.1007/s10522-004-7382-yOAI: diva2:22910
Available from: 2007-01-09 Created: 2007-01-09 Last updated: 2009-06-04
In thesis
1. Ageing-associated changes of lysosomal compartment: implications on cellular functions
Open this publication in new window or tab >>Ageing-associated changes of lysosomal compartment: implications on cellular functions
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The lysosomal compartment is a major site for intracellular degradation. Lysosomal degradation of the cell’s own constituents, so-called autophagy, not only provides a cell with nutrients, but also removes damaged and potentially dangerous endogenous structures, thus securing intracellular homeostasis. On the other hand, lysosomes have been shown to be involved in the initial stages of apoptosis, and the protective effect of autophagy has been suggested to switch to cell death when excessive.

Ageing-related changes of cellular structures result from damage caused by eactive oxygen species (ROS), which are an inevitable by-product of aerobic life. Intracellular turnover of compromised organelles and macromolecules, to which lysosomal degradation is a major contributor, does not function perfectly, even under favourable conditions. This inherent incompleteness of lysosomal degradation is responsible for the accumulation of a variety of nondegraded and functionally inefficient structures, which can be considered biological “garbage”. Biological “garbage” includes damaged non-degraded macromolecules and organelles, as well as intralysosomal non-degradable polymer-like structure called lipofuscin, or age pigment. Although accumulation of biological “garbage” has been suggested harmful, little is known about the mechanisms of its deleterious effects.

To gain a better understanding of ageing-related changes of the lysosomal compartment and their influence on cell functions, we focused on studying: (1) the role of macroautophagy in the turnover of organelles and lipofuscin formation; (2) the role of biological “garbage” accumulation in the development of ageing-related changes and eventual death of growth-arrested, postmitotic-like cells; (3) the possible cell-protective effect of mitosis; (4) the influence of lipofuscin on cell survival during complete starvation; and (5) the effects of lipofuscin on lysosomal stability.

As a model of induced biological “garbage” accumulation we used confluent human fibroblasts treated with the autophagy inhibitor 3-methyladenine (3MA). Alternatively, lysosomal degradation was suppressed by using the cysteine protease inhibitor leupeptin, or the cathepsin D inhibitor pepstatin A. As a cellular model of aged cells, we used lipofucsin-loaded human fibroblasts. Lipofuscin-loading was achieved by culturing confluent fibroblasts under hyperoxic conditions for 2-4 months. Using these in vitro models, the present study shows that: (1) inhibition of autophagy results in accumulation of lysosome-associated autofluorescent material and mitochondria with low membrane potential; (2) detrimental effect of biological “garbage” accumulation following inhibition of autophagy is prevented by continuous cell division; (3) lipofuscin-loaded cells are more resistant to starvation-induced cell death than control cells; (4) lysosomes of lipofuscinloaded fibroblasts are more resistant to the organelle-targeted stress then lysosomes of control cells.

Based on the results of the present study we conclude that properly operating autophagic machinery plays a crucial role in preventing age-related changes associated with accumulation of biological “garbage”. We also suggest that continual proliferation is the natural mechanism by which cells cope with the accumulation of non-degradable material, employing mechanical dilution during the cell division. Finally, we introduce an idea of lipofuscin being a hormetic agent, and possibly possessing some lysosome-stabilising properties. Better understanding of the influence of the age-related accumulation of biological “garbage” on cellular functions may be helpful for future development of anti-ageing therapy and management of age-associated pathologies.

Place, publisher, year, edition, pages
Institutionen för nervsystem och rörelseorgan, 2007. 68 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 978
Ageing, Apoptosis, Biological gabarge, Hormesis, Lipofuscin, Lysosome
National Category
urn:nbn:se:liu:diva-8012 (URN)91-85643-13-0 (ISBN)
Public defence
2007-02-02, Berzeliussalen, Campus US, Linköpings Universitet, Linköping, 09:00 (English)
Available from: 2007-01-09 Created: 2007-01-09 Last updated: 2009-08-22

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