Control of NAD+ homeostasis by autophagic flux modulates mitochondrial and cardiac function
Ontology highlight
ABSTRACT:
SUBMITTER: Dr. quanjiang zhang
PROVIDER: S-SCDT-10_1038-S44318-023-00009-W | biostudies-other |
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Reperfusion injury after extended ischemia accounts for approximately 50% of myocardial infarct size, and there is no standard therapy. HDAC inhibition reduces infarct size and enhances cardiomyocyte autophagy and PGC1α-mediated mitochondrial biogenesis when administered at the time of reperfusion. Furthermore, a specific autophagy-inducing peptide, Tat-Beclin 1 (TB), reduces infarct size when administered at the time of reperfusion. However, since SAHA affects multiple pathways in addition to inducing autophagy, whether autophagic flux induced by TB maintains mitochondrial homeostasis during ischemia/reperfusion (I/R) injury is unknown. We tested whether the augmentation of autophagic flux by TB has cardioprotection by preserving mitochondrial homeostasis both in vitro and in vivo. Wild-type mice were randomized into two groups: Tat-Scrambled (TS) peptide as the control and TB as the experimental group. Mice were subjected to I/R surgery (45 min coronary ligation, 24 h reperfusion). Autophagic flux, mitochondrial DNA (mtDNA), mitochondrial morphology, and mitochondrial dynamic genes were assayed. Cultured neonatal rat ventricular myocytes (NRVMs) were treated with a simulated I/R injury to verify cardiomyocyte specificity. The essential autophagy gene, ATG7, conditional cardiomyocyte-specific knockout (ATG7 cKO) mice, and isolated adult mouse ventricular myocytes (AMVMs) were used to evaluate the dependency of autophagy in adult cardiomyocytes. In NRVMs subjected to I/R, TB increased autophagic flux, mtDNA content, mitochondrial function, reduced reactive oxygen species (ROS), and mtDNA damage. Similarly, in the infarct border zone of the mouse heart, TB induced autophagy, increased mitochondrial size and mtDNA content, and promoted the expression of PGC1α and mitochondrial dynamic genes. Conversely, loss of ATG7 in AMVMs and in the myocardium of ATG7 cKO mice abolished the beneficial effects of TB on mitochondrial homeostasis. Thus, autophagic flux is a sufficient and essential process to mitigate myocardial reperfusion injury by maintaining mitochondrial homeostasis and partly by inducing PGC1α-mediated mitochondrial biogenesis.
| S-EPMC9265292 | biostudies-literature
Project description:Nucleolar stress is a cellular response to inhibition of ribosome biogenesis or nucleolar disruption leading to cell cycle arrest and/or apoptosis. Emerging evidence points to a tight connection between nucleolar stress and autophagy as a mechanism underlying various diseases such as neurodegeneration and treatment of cancer. Peter Pan (PPAN) functions as a key regulator of ribosome biogenesis. We previously showed that human PPAN localizes to nucleoli and mitochondria and that PPAN knockdown triggers a p53-independent nucleolar stress response culminating in mitochondrial apoptosis. Here, we demonstrate a novel role of PPAN in the regulation of mitochondrial homeostasis and autophagy. Our present study characterizes PPAN as a factor required for maintaining mitochondrial integrity and respiration-coupled ATP production. PPAN interacts with cardiolipin, a lipid of the inner mitochondrial membrane. Down-regulation of PPAN enhances autophagic flux in cancer cells. PPAN knockdown promotes recruitment of the E3-ubiquitin ligase Parkin to damaged mitochondria. Moreover, we provide evidence that PPAN knockdown decreases mitochondrial mass in Parkin-expressing cells. In summary, our study uncovers that PPAN knockdown is linked to mitochondrial damage and stimulates autophagy.
| S-EPMC6721654 | biostudies-literature
Project description:AimTemporal and spatial variations in shear stress are intimately linked with vascular metabolic effects. Autophagy is tightly regulated in intracellular bulk degradation/recycling system for maintaining cellular homeostasis. We postulated that disturbed flow modulates autophagy with an implication in mitochondrial superoxide (mtO2(•-)) production.ResultsIn the disturbed flow or oscillatory shear stress (OSS)-exposed aortic arch, we observed prominent staining of p62, a reverse marker of autophagic flux, whereas in the pulsatile shear stress (PSS)-exposed descending aorta, p62 was attenuated. OSS significantly increased (i) microtubule-associated protein light chain 3 (LC3) II to I ratios in human aortic endothelial cells, (ii) autophagosome formation as quantified by green fluorescent protein (GFP)-LC3 dots per cell, and (iii) p62 protein levels, whereas manganese superoxide dismutase (MnSOD) overexpression by recombinant adenovirus, N-acetyl cysteine treatment, or c-Jun N-terminal kinase (JNK) inhibition reduced OSS-mediated LC3-II/LC3-I ratios and mitochondrial DNA damage. Introducing bafilomycin to Earle's balanced salt solution or to OSS condition incrementally increased both LC3-II/LC3-I ratios and p62 levels, implicating impaired autophagic flux. In the OSS-exposed aortic arch, both anti-phospho-JNK and anti-8-hydroxy-2'-deoxyguanosine (8-OHdG) staining for DNA damage were prominent, whereas in the PSS-exposed descending aorta, the staining was nearly absent. Knockdown of ATG5 with siRNA increased OSS-mediated mtO2(•-), whereas starvation or rapamycin-induced autophagy reduced OSS-mediated mtO2(•-), mitochondrial respiration, and complex II activity.InnovationDisturbed flow-mediated oxidative stress and JNK activation induce autophagy.ConclusionOSS impairs autophagic flux to interfere with mitochondrial homeostasis. Antioxid. Redox Signal. 23, 1207-1219.
| S-EPMC4657520 | biostudies-literature
Project description:We previously reported that facilitating the clearance of damaged mitochondria through macroautophagy/autophagy protects against acute myocardial infarction. Here we characterize the impact of exercise, a safe strategy against cardiovascular disease, on cardiac autophagy and its contribution to mitochondrial quality control, bioenergetics and oxidative damage in a post-myocardial infarction-induced heart failure animal model. We found that failing hearts displayed reduced autophagic flux depicted by accumulation of autophagy-related markers and loss of responsiveness to chloroquine treatment at 4 and 12 wk after myocardial infarction. These changes were accompanied by accumulation of fragmented mitochondria with reduced O2 consumption, elevated H2O2 release and increased Ca2+-induced mitochondrial permeability transition pore opening. Of interest, disruption of autophagic flux was sufficient to decrease cardiac mitochondrial function in sham-treated animals and increase cardiomyocyte toxicity upon mitochondrial stress. Importantly, 8 wk of exercise training, starting 4 wk after myocardial infarction at a time when autophagy and mitochondrial oxidative capacity were already impaired, improved cardiac autophagic flux. These changes were followed by reduced mitochondrial number:size ratio, increased mitochondrial bioenergetics and better cardiac function. Moreover, exercise training increased cardiac mitochondrial number, size and oxidative capacity without affecting autophagic flux in sham-treated animals. Further supporting an autophagy mechanism for exercise-induced improvements of mitochondrial bioenergetics in heart failure, acute in vivo inhibition of autophagic flux was sufficient to mitigate the increased mitochondrial oxidative capacity triggered by exercise in failing hearts. Collectively, our findings uncover the potential contribution of exercise in restoring cardiac autophagy flux in heart failure, which is associated with better mitochondrial quality control, bioenergetics and cardiac function.
| S-EPMC5584854 | biostudies-literature
Project description:Autophagy (macroautophagy) is a highly conserved eukaryotic degradation pathway in which cytosolic components and organelles are sequestered by specialized autophagic membranes and degraded through the lysosomal system. The autophagic pathway maintains basal cellular homeostasis and helps cells adapt during stress; thus, defects in autophagy can cause detrimental effects. It is therefore crucial that autophagy is properly regulated. In this study, we show that the cysteine protease Atg4B, a key enzyme in autophagy that cleaves LC3, is an interactor of the small GTPase Rab7b. Indeed, Atg4B interacts and co-localizes with Rab7b on vesicles. Depletion of Rab7b increases autophagic flux as indicated by the increased size of autophagic structures as well as the magnitude of macroautophagic sequestration and degradation. Importantly, we demonstrate that Rab7b regulates LC3 processing by modulating Atg4B activity. Taken together, our findings reveal Rab7b as a novel negative regulator of autophagy through its interaction with Atg4B.
| S-EPMC5623852 | biostudies-literature
Project description:Animal studies have demonstrated beneficial effects of therapeutic hypothermia on myocardial function, yet exact mechanisms remain unclear. Impaired autophagy leads to heart failure and mitophagy is important for mitigating ischemia/reperfusion injury. This study aims to investigate whether the beneficial effects of therapeutic hypothermia are due to preserved autophagy and mitophagy. Under general anesthesia, the left anterior descending coronary artery of 19 female farm pigs was occluded for 90 minutes with consecutive reperfusion. 30 minutes after reperfusion, we performed pericardial irrigation with warm or cold saline for 60 minutes. Myocardial tissue analysis was performed one and four weeks after infarction. Therapeutic hypothermia induced a significant increase in autophagic flux, mitophagy, mitochondrial mass and function in the myocardium after infarction. Cell stress, apoptosis, inflammation as well as fibrosis were reduced, with significant preservation of systolic and diastolic function four weeks post infarction. We found similar biochemical changes in human samples undergoing open chest surgery under hypothermic conditions when compared to the warm. These results suggest that autophagic flux and mitophagy are important mechanisms implicated in cardiomyocyte recovery after myocardial infarction under hypothermic conditions. New therapeutic strategies targeting these pathways directly could lead to improvements in prevention of heart failure.
| S-EPMC6620356 | biostudies-literature
Project description:Protein persulfidation is a significant post-translational modification that involves addition of a sulfur atom to the cysteine thiol group and is facilitated by sulfide species. Persulfidation targets reactive cysteine residues within proteins, influencing their structure and/or function across various biological systems. This modification is evolutionarily conserved and plays a crucial role in preventing irreversible cysteine overoxidation, a process that becomes prominent with aging. While, persulfidation decreases with age, its levels in the aged heart and the functional implications of such a reduction in cardiac metabolism remain unknown. Here we interrogated the cardiac persulfydome in wild-type adult mice and age-matched mice lacking the two sulfide generating enzymes, namely cystathionine gamma lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3MST). Our findings revealed that cardiac persulfidated proteins in wild type hearts are less abundant compared to those in other organs, with a primary involvement in mitochondrial metabolic processes. We further focused on one specific target, NDUFB7, which undergoes persulfidation by both CSE and 3MST derived sulfide species. In particular, persulfidation of cysteines C80 and C90 in NDUFB7 protects the protein from overoxidation and maintains the complex I activity in cardiomyocytes. As the heart ages, the levels of CSE and 3MST in cardiomyocytes decline, leading to reduced NDUFB7 persulfidation and increased cardiac NADH/NAD+ ratio. Collectively, our data provide compelling evidence for a direct link between cardiac persulfidation and mitochondrial complex I activity, which is compromised in aging.
| S-EPMC10792955 | biostudies-literature
Project description:Poly(ADP-ribose) polymerase (PARP) enzymes initiate (mt)DNA repair mechanisms and use nicotinamide adenine dinucleotide (NAD+) as energy source. Prolonged PARP activity can drain cellular NAD+ reserves, leading to de-regulation of important molecular processes. Here, we provide evidence of a pathophysiological mechanism that connects mtDNA damage to cardiac dysfunction via reduced NAD+ levels and loss of mitochondrial function and communication. Using a transgenic model, we demonstrate that high levels of mice cardiomyocyte mtDNA damage cause a reduction in NAD+ levels due to extreme DNA repair activity, causing impaired activation of NAD+-dependent SIRT3. In addition, we show that myocardial mtDNA damage in combination with high dosages of nicotinamideriboside (NR) causes an inhibition of sirtuin activity due to accumulation of nicotinamide (NAM), in addition to irregular cardiac mitochondrial morphology. Consequently, high doses of NR should be used with caution, especially when cardiomyopathic symptoms are caused by mitochondrial dysfunction and instability of mtDNA.
| S-EPMC8331182 | biostudies-literature
Project description:Insufficient lysosomal removal of autophagic cargoes in cardiomyocytes has been suggested as a main cause for the impairment of the autophagic-lysosomal pathway (ALP) in many forms of heart disease including cardiac proteinopathy and may play an important pathogenic role; however, the molecular basis and the correcting strategy for the cardiac ALP insufficiency require further investigation. The present study was sought to determine whether myocardial expression and activity of TFEB, the recently identified ALP master regulator, are impaired in a cardiac proteinopathy mouse model and to determine the effect of genetic manipulation of TFEB expression on autophagy and proteotoxicity in a cardiomyocyte model of proteinopathy. We found that increased myocardial TFEB mRNA levels and a TFEB protein isoform switch were associated with marked decreases in the mRNA levels of representative TFEB target genes and increased mTORC1 activation, in mice with cardiac transgenic expression of a missense (R120G) mutant αB-crystallin (CryABR120G), a well-established model of cardiac proteinopathy. Using neonatal rat ventricular cardiomyocyte cultures, we demonstrated that downregulation of TFEB decreased autophagic flux in cardiomyocytes both at baseline and during CryABR120G overexpression and increased CryABR120G protein aggregates. Conversely, forced TFEB overexpression increased autophagic flux and remarkably attenuated the CryABR120G overexpression-induced accumulation of ubiquitinated proteins, caspase 3 cleavage, LDH leakage, and decreases in cell viability. Moreover, these protective effects of TFEB were dramatically diminished by inhibiting autophagy. We conclude that myocardial TFEB signaling is impaired in cardiac proteinopathy and forced TFEB overexpression protects against proteotoxicity in cardiomyocytes through improving ALP activity.
| S-EPMC5656243 | biostudies-literature
Project description:Mitochondria constitute 30% of myocardial mass. Mitochondrial fusion and fission appear essential for health of most tissues. Mitochondrial fission occurs in neonatal cardiomycyte and is implicated in cardiomyocyte death. Mitochondrial fusion has not been observed in postmitotic myocytes of adult hearts, and its occurrence and function in this context are controversial.Determine the consequences on organelle and organ function of disrupting cardiomyocyte mitochondrial fusion in vivo.The murine mfn1 and mfn2 genes, encoding mitofusins (Mfn) 1 and 2 that mediate mitochondrial tethering and outer mitochondrial membrane fusion, were interrupted by Cre-mediated excision of essential exons in neonatal (Nkx2.5-Cre) and adult (MYH6 modified estrogen receptor-Cre-modified estrogen receptor plus tamoxifen or Raloxifene) hearts. Embryonic combined Mfn1/Mfn2 ablation was lethal after e9.5. Conditional combined Mfn1/Mfn2 ablation in adult hearts induced mitochondrial fragmentation, cardiomyocyte and mitochondrial respiratory dysfunction, and rapidly progressive and lethal dilated cardiomyopathy. Before heart failure developed, cardiomyocyte shortening and calcium cycling were unaffected by absence of Mfn1 and Mfn2. Based on the time course over which fusion-defective mitochondrial size decreases, a mitochondrial fusion/fission cycle in adult mouse hearts occurs approximately every 16 days.Mitochondrial fusion in adult cardiac myocytes is necessary to maintain normal mitochondrial morphology and is essential for normal cardiac respiratory and contractile function. Interruption of mitochondrial fusion causes lethal cardiac failure at a time corresponding to 3 or 4 cycles of unopposed mitochondrial fission.
| S-EPMC3237902 | biostudies-literature