X-Message-Number: 26132 Date: Wed, 4 May 2005 19:45:53 -0700 (PDT) From: Doug Skrecky <> Subject: Testing the "garbage" accumulation theory of ageing Biogerontology. 2005;6(1):39-47. Testing the "garbage" accumulation theory of ageing: mitotic activity protects cells from death induced by inhibition of autophagy. Stroikin Y, Dalen H, Brunk UT, Terman A. 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. Int J Biochem Cell Biol. 2004 Dec;36(12):2365-75. Aging as a catabolic malfunction. Terman A, Brunk UT. Cellular degradative processes, which include lysosomal (autophagic) and proteasomal degradation, as well as catabolism of proteins by cytosolic and mitochondrial proteases, provide for a continuous turnover of cellular components, such as damaged or obsolete biomolecules and organelles. Inherent insufficiency of these degradative processes results in progressive accumulation within long-lived postmitotic cells of biological 'garbage' (waste material), such as various oxidized proteins, functionally effete mitochondria, and lipofuscin (age pigment), an intralysosomal, polymeric, undegradable material. There is increasing evidence that lipofuscin hampers lysosomal degradative capacity, thus promoting the aggravation of accumulated damage at old age. Being rich in redox-active iron, lipofuscin granules also may exacerbate oxidative stress levels in senescent cells. Thus, increasing the efficiency of cellular degradative pathways and preventing involvement of iron in oxidant-induced lysosomal and cellular damage may be potential strategies for anti-aging interventions. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26132