Mitochondrial fission and fusion mediators, hFis1 and OPA1, modulate cellular senescence
ABSTRACT The number and morphology of mitochondria within a cell are precisely regulated by the mitochondrial fission and fusion machinery. The human protein, hFis1, participates in mitochondrial fission by recruiting the Drp1 into the mitochondria. Using short hairpin RNA, we reduced the expression levels of hFis1 in mammalian cells. Cells lacking hFis1 showed sustained elongation of mitochondria and underwent significant cellular morphological changes, including enlargement, flattening, and increased cellular granularity. In these cells, staining for acidic senescence-associated beta-galactosidase activity was elevated, and the rate of cell proliferation was greatly reduced, indicating that cells lacking hFis1 undergo senescence-associated phenotypic changes. Reintroduction of the hFis1 gene into hFis1-depleted cells restored mitochondrial fragmentation and suppressed senescence-associated beta-galactosidase activity. Moreover, depletion of both hFis1 and OPA1, a critical component of mitochondrial fusion, resulted in extensive mitochondrial fragmentation and markedly rescued cells from senescence-associated phenotypic changes. Intriguingly, sustained elongation of mitochondria was associated with decreased mitochondrial membrane potential, increased reactive oxygen species production, and DNA damage. The data indicate that sustained mitochondrial elongation induces senescence-associated phenotypic changes that can be neutralized by mitochondrial fragmentation. Thus, one of the key functions of mitochondrial fission might be prevention of the sustained extensive mitochondrial elongation that triggers cellular senescence.
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ABSTRACT: Cellular senescence is a process that results from a variety of stresses, leading to a state of irreversible growth arrest. Senescent cells accumulate during aging and have been implicated in promoting a variety of age-related diseases. Mitochondrial stress is an effective inducer of cellular senescence, but the mechanisms by which mitochondria regulate permanent cell growth arrest are largely unexplored. Here, we review some of the mitochondrial signaling pathways that participate in establishing cellular senescence. We discuss the role of mitochondrial reactive oxygen species (ROS), mitochondrial dynamics (fission and fusion), the electron transport chain (ETC), bioenergetic balance, redox state, metabolic signature, and calcium homeostasis in controlling cellular growth arrest. We emphasize that multiple mitochondrial signaling pathways, besides mitochondrial ROS, can induce cellular senescence. Together, these pathways provide a broader perspective for studying the contribution of mitochondrial stress to aging, linking mitochondrial dysfunction and aging through the process of cellular senescence.Aging cell 11/2014; 14(1). DOI:10.1111/acel.12287 · 5.94 Impact Factor
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ABSTRACT: A hallmark of ageing is dysfunction in nutrient signalling pathways that regulate glucose homeostasis, negatively affecting whole-body energy metabolism and ultimately increasing the organism's susceptibility to disease. Maintenance of insulin sensitivity depends on functional mitochondrial networks, but is compromised by alterations in mitochondrial energy metabolism during ageing. Here we discuss metabolic paradigms that influence mammalian longevity, and highlight recent advances in identifying fundamental signalling pathways that influence metabolic health and ageing through mitochondrial perturbations.
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ABSTRACT: Chronic microinflammation is a hallmark of many aging-related neurodegenerative diseases as well as metabolic syndrome-driven diseases. Recent research indicates that chronic caloric excess can lead to hypothalamic microinflammation, which in turn participates in the development and progression of metabolic syndrome disorders such as obesity, glucose intolerance, and hypertension. Additionally, it was recently shown that increasing age after young adulthood can cause hypothalamic microinflammation independently of nutritional status, mediating a central mechanism of systemic aging. Taken together, these findings suggest that the hypothalamus has a fundamental role, via hypothalamic microinflammation, in translating overnutrition and aging into complex outcomes. Here we summarize recent work and suggest a conceptual model in which hypothalamic microinflammation is a common mediator of metabolic syndrome and aging. Copyright © 2014 Elsevier Ltd. All rights reserved.Trends in Neurosciences 11/2014; 38(1). DOI:10.1016/j.tins.2014.10.002 · 12.90 Impact Factor