Aim: Aging in humans is associated with a 10–40-fold greater incidence of sudden cardiac death from malignant tachyarrhythmia. We have reported that thiol oxidation of ryanodine receptors (RyR2s) by mitochondria-derived reactive oxygen species (mito-ROS) contributes to defective Ca²⁺ homeostasis in cardiomyocytes (CMs) from aging rabbit hearts. However, mechanisms responsible for the increase in mito-ROS in the aging heart remain poorly understood. Here we test the hypothesis that age-associated decrease in autophagy is a major contributor to enhanced mito-ROS production and thereby pro-arrhythmic disturbances in Ca²⁺ homeostasis.

Methods and Results: Ventricular tissues from aged rabbits displayed significant downregulation of proteins involved in mitochondrial autophagy compared with tissues from young controls. Blocking autophagy with chloroquine increased total ROS production in primary rabbit CMs and mito-ROS production in HL-1 CMs. Furthermore, chloroquine treatment of HL-1 cells depolarized mitochondrial membrane potential (Δψm) to 50% that of controls. Blocking autophagy significantly increased oxidation of RyR2, resulting in enhanced propensity to pro-arrhythmic spontaneous Ca²⁺ release under β-adrenergic stimulation. Aberrant Ca²⁺ release was abolished by treatment with the mito-ROS scavenger mito-TEMPO. Importantly, the autophagy enhancer Torin1 and ATG7 overexpression reduced the rate of mito-ROS production and restored both Δψm and defective Ca²⁺ handling in CMs derived from aged rabbit hearts.

Conclusion: Decreased autophagy is a major cause of increased mito-ROS production in the aging heart. Our data suggest that promoting autophagy may reduce pathologic mito-ROS during normal aging and reduce pro-arrhythmic spontaneous Ca²⁺ release via oxidized RyR2s.

Back in January, we were joined by Dr. Aubrey de Grey, Dr. Amutha Boominathan, Dr. Matthew O’Conner, and Michael Rae from the SENS Research Foundation for a webinar discussion panel focused on MitoSENS, the mitochondrial repair program. During the webinar, a number of points were discussed, and the Lifespan Heroes in the audience got to ask the researchers questions about MitoSENS and about the work of the SENS Foundation in general.

In 2015, the MitoSENS team raised funding on Lifespan.io to launch a study testing if they could create mitochondrial DNA copies in the cell nucleus, and they were successful in doing so as a result of the funds they received. In October 2019, the MitoSENS team launched a new follow-up project called MitoMouse, which aims to bring its mitochondrial repair therapy to mammals as a proof of concept on the road to translation to human use.

GenSight Biologics has recently released data showing the effectiveness of GS010, the company’s gene therapy for Leber Hereditary Optic Neuropathy (LHON), a mitochondrial disease that can lead to blindness. Like in previous studies, this therapy had a bilateral effect.

Gene Therapy

In LHON, the mitochondrial protein ND4 is poorly expressed through mitochondrial DNA (mtDNA). GS010 is a gene therapy that causes this protein to be allotropically expressed in the nucleus, after which it is shuttled to the mitochondria through messenger RNA. This makes GS010 a partial treatment for mitochondrial dysfunction, which is one of the hallmarks of aging.

When it comes to regeneration, some animals are capable of amazing feats — if you cut the leg off a salamander, it will grow back. When threatened, some geckos drop their tails as a distraction, and regrow them later.

Other animals take the process even further. Planarian worms, jellyfish, and sea anemones can actually regenerate their entire bodies after being cut in half.

Led by Assistant Professor of Organismic and Evolutionary Biology Mansi Srivastava, a team of researchers is shedding new light on how animals pull off the feat, and uncovered a number of DNA switches that appear to control genes for whole-body regeneration. The study is described in a March 15 paper in Science.