Faculty Collaboration Database

Autophagy, TERT, and mitochondrial dysfunction in hyperoxia. Am J Physiol Heart Circ Physiol 2021 Nov 01;321(5):H985-H1003

Date

09/25/2021

Pubmed ID

34559580

Pubmed Central ID

PMC8616608

DOI

10.1152/ajpheart.00166.2021

Scopus ID

2-s2.0-85120657950 (requires institutional sign-in at Scopus site)   17 Citations

Abstract

Ventilation with gases containing enhanced fractions of oxygen is the cornerstone of therapy for patients with hypoxia and acute respiratory distress syndrome. Yet, hyperoxia treatment increases free reactive oxygen species (ROS)-induced lung injury, which is reported to disrupt autophagy/mitophagy. Altered extranuclear activity of the catalytic subunit of telomerase, telomerase reverse transcriptase (TERT), plays a protective role in ROS injury and autophagy in the systemic and coronary endothelium. We investigated interactions between autophagy/mitophagy and TERT that contribute to mitochondrial dysfunction and pulmonary injury in cultured rat lung microvascular endothelial cells (RLMVECs) exposed in vitro, and rat lungs exposed in vivo to hyperoxia for 48 h. Hyperoxia-induced mitochondrial damage in rat lungs [TOMM20, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)], which was paralleled by increased markers of inflammation [myeloperoxidase (MPO), IL-1β, TLR9], impaired autophagy signaling (Beclin-1, LC3B-II/1, and p62), and decreased the expression of TERT. Mitochondrial-specific autophagy (mitophagy) was not altered, as hyperoxia increased expression of Pink1 but not Parkin. Hyperoxia-induced mitochondrial damage (TOMM20) was more pronounced in rats that lack the catalytic subunit of TERT and resulted in a reduction in cellular proliferation rather than cell death in RLMVECs. Activation of TERT or autophagy individually offset mitochondrial damage (MTT). Combined activation/inhibition failed to alleviate hyperoxic-induced mitochondrial damage in vitro, whereas activation of autophagy in vivo decreased mitochondrial damage (MTT) in both wild type (WT) and rats lacking TERT. Functionally, activation of either TERT or autophagy preserved transendothelial membrane resistance. Altogether, these observations show that activation of autophagy/mitophagy and/or TERT mitigate loss of mitochondrial function and barrier integrity in hyperoxia.NEW & NOTEWORTHY In cultured pulmonary artery endothelial cells and in lungs exposed in vivo to hyperoxia, autophagy is activated, but clearance of autophagosomes is impaired in a manner that suggests cross talk between TERT and autophagy. Stimulation of autophagy prevents hyperoxia-induced decreases in mitochondrial metabolism and sustains monolayer resistance. Hyperoxia increases mitochondrial outer membrane (TOMM20) protein, decreases mitochondrial function, and reduces cellular proliferation without increasing cell death.

Author List

Beyer AM, Norwood Toro LE, Hughes WE, Young M, Clough AV, Gao F, Medhora M, Audi SH, Jacobs ER

Authors

Said Audi PhD Professor in the Biomedical Engineering department at Marquette University
Andreas M. Beyer PhD Associate Professor in the Medicine department at Medical College of Wisconsin
William E. Hughes Postdoctoral Fellow in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Autophagy-Related Proteins
Capillary Permeability
Cells, Cultured
Disease Models, Animal
Endothelial Cells
Female
Gene Knockout Techniques
Hyperoxia
Inflammation Mediators
Lung
Lung Injury
Male
Membrane Transport Proteins
Microvessels
Mitochondria
Rats
Rats, Sprague-Dawley
Rats, Transgenic
Receptors, Cell Surface
Telomerase
Toll-Like Receptor 4
Toll-Like Receptor 9