Chemoptogenetic damage to mitochondria causes rapid telomere dysfunction

Abstract

Reactive oxygen species (ROS) play important roles in aging, inflammation, and cancer. Mitochondria are an important source of ROS; however, the spatiotemporal ROS events underlying oxidative cellular damage from dysfunctional mitochondria remain unresolved. To this end, we have developed and validated a chemoptogenetic approach that uses a mitochondrially targeted fluorogen-activating peptide (Mito-FAP) to deliver a photosensitizer MG-2I dye exclusively to this organelle. Light-mediated activation (660 nm) of the Mito-FAP–MG-2I complex led to a rapid loss of mitochondrial respiration, decreased electron transport chain complex activity, and mitochondrial fragmentation. Importantly, one round of singlet oxygen produced a persistent secondary wave of mitochondrial superoxide and hydrogen peroxide lasting for over 48 h after the initial insult. By following ROS intermediates, we were able to detect hydrogen peroxide in the nucleus through ratiometric analysis of the oxidation of nuclear cysteine residues. Despite mitochondrial DNA (mtDNA) damage and nuclear oxidative stress induced by dysfunctional mitochondria, there was a lack of gross nuclear DNA strand breaks and apoptosis. Targeted telomere analysis revealed fragile telomeres and telomere loss as well as 53BP1-positive telomere dysfunction-induced foci (TIFs), indicating that DNA double-strand breaks occurred exclusively in telomeres as a direct consequence of mitochondrial dysfunction. These telomere defects activated ataxia-telangiectasia mutated (ATM)-mediated DNA damage repair signaling. Furthermore, ATM inhibition exacerbated the Mito-FAP–induced mitochondrial dysfunction and sensitized cells to apoptotic cell death. This profound sensitivity of telomeres through hydrogen peroxide induced by dysregulated mitochondria reveals a crucial mechanism of telomere–mitochondria communication underlying the pathophysiological role of mitochondrial ROS in human diseases.

Mitochondrial Dysfunction in Aging and Cancer

“…A recent work has shown a direct connection between mitochondrial dysfunction and telomere attrition [121]. Qian et al have used a chemoptogenetic approach to produce short-lived singlet oxygen (a highly reactive ROS) in the mitochondrial matrix, whose destiny in the whole cells may be easily monitored.…”

“…DNA double-strand breaks were exclusively present in telomeres. In turn, telomere dysfunction promoted Ataxia-Telangiectasia Mutated (ATM)-dependent repair of DNA damage, preventing cells from undergoing apoptosis [121]. These findings highlight a novel mitochondria-telomere axis activated by mitochondrial ROS and associated with mitochondrial dysfunction that may be important both in aging and in cancer.…”

Cyclooctatetraene-conjugated cyanine mitochondrial probes minimize phototoxicity in fluorescence and nanoscopic imaging

“…However, because the membranous structures of mitochondria are prone to the attack by the reactive oxygen species (ROS) associated with uorescence excitation, focusing on improved photostability, alone, fails to maintain the health of mitochondria under prolonged light exposure. 7 Moreover, because apoptosis can be triggered by the damaged mitochondria through ROS-related pathways, 10,14 it is equally important to carefully evaluate the general toxicity of uorescent probes beyond phototoxicity, particularly in the sorting of sensitive cells based on their metabolic states.…”

GSK3 inhibition rescues growth and telomere dysfunction in dyskeratosis congenita iPSC-derived type II alveolar epithelial cells

“…This Wnt-telomere feedback loop might not be the only regulatory loop at play in AT2 cells. Given our evidence of upregulation of mitochondrial processes in DC iAT2 cells and how telomere dysfunction can drive mitochondrial dysfunction (Sahin et al, 2011) and how mitochondrial dysfunction can drive telomere dysfunction (Guha et al, 2018;Passos et al, 2007;Qian et al, 2019), we hypothesize that telomeres might be an integrator of multiple cellular stress responses. Furthermore, our finding of the upregulation of genes associated with the UPR argues that telomere dysfunction could drive the UPR.…”