bims-mitinf 2019-02-17 papers

Issue of 2019‒02‒17
three papers selected by
Prafull Kumar Singh
University of Freiburg Medical Center

Autophagy. 2019 Feb 11.

BNIP3L/NIX and FUNDC1-Mediated Mitophagy is Required for Mitochondrial Network Remodeling during Cardiac Progenitor Cell Differentiation.

Mark A Lampert, Amabel M Orogo, Rita H Najor, Babette C Hammerling, Leonardo J Leon, Bingyan J Wang, Taeyong Kim, Mark A Sussman, Åsa B Gustafsson.

Cell-based therapies represent a very promising strategy to repair and regenerate the injured heart to prevent progression to heart failure. To date, these therapies have had limited success due to a lack of survival and retention of the infused cells. Therefore, it is important to increase our understanding of the biology of these cells and utilize this information to enhance their survival and function in the injured heart. Mitochondria are critical for progenitor cell function and survival. Here, we demonstrate the importance of mitochondrial autophagy, or mitophagy, in the differentiation process in adult cardiac progenitor cells (CPCs). We found that mitophagy was rapidly induced upon initiation of differentiation in CPCs. We also found that mitophagy was mediated by mitophagy receptors, rather than the PINK1-PRKN/PARKIN pathway. Mitophagy mediated by BNIP3L/NIX and FUNDC1 was not involved in regulating progenitor cell fate determination, mitochondrial biogenesis, or reprogramming. Instead, mitophagy facilitated the CPCs to undergo proper mitochondrial network reorganization during differentiation. Abrogating BNIP3L- and FUNDC1-mediated mitophagy during differentiation led to sustained mitochondrial fission and formation of donut-shaped impaired mitochondria. It also resulted in increased susceptibility to cell death and failure to survive the infarcted heart. Finally, aging is associated with accumulation of mitochondrial DNA (mtDNA) damage in cells and we found that acquiring mtDNA mutations selectively disrupted the differentiation-activated mitophagy program in CPCs. These findings demonstrate the importance of BNIP3L- and FUNDC1-mediated mitophagy as a critical regulator of mitochondrial network formation during differentiation, as well as the consequences of accumulating mtDNA mutations.

Keywords: CPCs; autophagy; differentiation; heart; heart failure; mitochondria; mitophagy; stem cells

DOI: https://doi.org/10.1080/15548627.2019.1580095

Aging Cell. 2019 Feb 15. e12916

The exceptional longevity of the naked mole-rat may be explained by mitochondrial antioxidant defenses.

Daniel Munro, Cécile Baldy, Matthew E Pamenter, Jason R Treberg.

Naked mole-rats (NMRs) are mouse-sized mammals that exhibit an exceptionally long lifespan (>30 vs. <4 years for mice), and resist aging-related pathologies such as cardiovascular and pulmonary diseases, cancer, and neurodegeneration. However, the mechanisms underlying this exceptional longevity and disease resistance remain poorly understood. The oxidative stress theory of aging posits that (a) senescence results from the accumulation of oxidative damage inflicted by reactive oxygen species (ROS) of mitochondrial origin, and (b) mitochondria of long-lived species produce less ROS than do mitochondria of short-lived species. However, comparative studies over the past 28 years have produced equivocal results supporting this latter prediction. We hypothesized that, rather than differences in ROS generation, the capacity of mitochondria to consume ROS might distinguish long-lived species from short-lived species. To test this hypothesis, we compared mitochondrial production and consumption of hydrogen peroxide (H2 O2 ; as a proxy of overall ROS metabolism) between NMR and mouse skeletal muscle and heart. We found that the two species had comparable rates of mitochondrial H2 O2 generation in both tissues; however, the capacity of mitochondria to consume ROS was markedly greater in NMRs. Specifically, maximal observed consumption rates were approximately two and fivefold greater in NMRs than in mice, for skeletal muscle and heart, respectively. Our results indicate that differences in matrix ROS detoxification capacity between species may contribute to their divergence in lifespan.

Keywords: Heterocephalus glaber ; antioxidants; mitochondria; reactive oxygen species; skeletal muscle heart

DOI: https://doi.org/10.1111/acel.12916

Ann Am Thorac Soc. 2018 Dec;15(Supplement_4): S266-S272

Mitochondrial Dysfunction as a Pathogenic Mediator of Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis.

Stefan W Ryter, Ivan O Rosas, Caroline A Owen, Fernando J Martinez, Mary E Choi, Chun Geun Lee, Jack A Elias, Augustine M K Choi.

The mechanisms underlying the pathogenesis of chronic lung diseases, including chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis, remain incompletely understood. Mitochondria are vital cellular organelles crucial for energy generation, the maintenance of cellular metabolism, calcium homeostasis, intracellular signaling, and the regulation of cell death programs. Emerging evidence suggests that mitochondrial dysfunction plays a cardinal role in the initiation and progression of many human diseases, including chronic lung diseases. Upregulation of the autophagy program, a cellular adaptive mechanism for protein and organelle turnover, can occur in response to injury and may have a cell type-specific impact on the progression of disease. The selective autophagy subtype specific for mitochondria (mitophagy), regulated by PINK1 (phosphatase and tensin homolog-induced putative kinase 1), is a cellular response to accumulation of depolarized or injured mitochondria. Autophagy and mitophagy may be associated with either cellular protection or propagation of injury in a cell type-specific manner, and they may also be associated with modulation of cell death pathways. Genetic studies in mouse models have revealed opposing roles for PINK1 and/or mitophagy in the propagation of emphysema and fibrosis, whereas human studies have shown altered regulation of PINK1 in both idiopathic pulmonary fibrosis and COPD. We have also recently identified a role for mitophagy in regulating the cellular necroptosis program, with implications in COPD pathogenesis. Damage-associated molecular patterns released from injured mitochondria and/or necrotic cells may promote proinflammatory and profibrotic responses. In this review, we explore current experimental evidence for mitochondrial dysfunction as a key determinant in the pathogenesis of chronic lung diseases.

Keywords: autophagy; chronic obstructive pulmonary disease; idiopathic pulmonary fibrosis; mitochondrial dysfunction; mitophagy

DOI: https://doi.org/10.1513/AnnalsATS.201808-585MG