Can autophagy promote longevity? Nat Cell Biol. 2010;12:842-846. [PMID: 20811357 DOI: 10.1038/ncb0910-842]

Young plasma reverses age-dependent alterations in hepatic function through the restoration of autophagy

Recent studies showing the therapeutic effect of young blood on aging‐associated deterioration of organs point to young blood as the solution for clinical problems related to old age. Given that defective autophagy has been implicated in aging and aging‐associated organ injuries, this study was designed to determine the effect of young blood on aging‐induced alterations in hepatic function and underlying mechanisms, with a focus on autophagy. Aged rats (22 months) were treated with pooled plasma (1 ml, intravenously) collected from young (3 months) or aged rats three times per week for 4 weeks, and 3‐methyladenine or wortmannin was used to inhibit young blood‐induced autophagy. Aging was associated with elevated levels of alanine transaminase and aspartate aminotransferase, lipofuscin accumulation, steatosis, fibrosis, and defective liver regeneration after partial hepatectomy, which were significantly attenuated by young plasma injections. Young plasma could also restore aging‐impaired autophagy activity. Inhibition of the young plasma‐restored autophagic activity abrogated the beneficial effect of young plasma against hepatic injury with aging. In vitro, young serum could protect old hepatocytes from senescence, and the antisenescence effect of young serum was abrogated by 3‐methyladenine, wortmannin, or small interfering RNA to autophagy‐related protein 7. Collectively, our data indicate that young plasma could ameliorate age‐dependent alterations in hepatic function partially via the restoration of autophagy.

Oxidation of Atg3 and Atg7 mediates inhibition of autophagy

Macroautophagy (autophagy) is a crucial cellular stress response for degrading defective macromolecules and organelles, as well as providing bioenergetic intermediates during hypoxia and nutrient deprivation. Here we report a thiol-dependent process that may account for impaired autophagy during aging. This is through direct oxidation of key autophagy-related (Atg) proteins Atg3 and Atg7. When inactive Atg3 and Atg7 are protected from oxidation due to stable covalent interaction with their substrate LC3. This interaction becomes transient upon activation of Atg3 and Atg7 due to transfer of LC3 to phosphatidylethanolamine (lipidation), a process crucial for functional autophagy. However, loss in covalent-bound LC3 also sensitizes the catalytic thiols of Atg3 and Atg7 to inhibitory oxidation that prevents LC3 lipidation, observed in vitro and in mouse aorta. Here findings provide a thiol-dependent process for negatively regulating autophagy that may contribute to the process of aging, as well as therapeutic targets to regulate autophagosome maturation.

A dysfunction of autophagy can be detected in aged tissues, but how this is regulated is unclear. Here, the authors show in vitro and in aged mice aorta, that inhibition of LC3 lipidation under conditions of oxidative stress causes oxidation of Atg3 and Atg7, preventing autophagosome maturation.

Caloric Restriction and Rapamycin Differentially Alter Energy Metabolism in Yeast

Rapamycin (RM), a drug that inhibits the mechanistic target of rapamycin (mTOR) pathway and responds to nutrient availability, seemingly mimics the effects of caloric restriction (CR) on healthy life span. However, the extent of the mechanistic overlap between RM and CR remains incompletely understood. Here, we compared the impact of CR and RM on cellular metabolic status. Both regimens maintained intracellular ATP through the chronological aging process and showed enhanced mitochondrial capacity. Comparative transcriptome analysis showed that CR had a stronger impact on global gene expression than RM. We observed a like impact on the metabolome and identified distinct metabolites affected by CR and RM. CR severely reduced the level of energy storage molecules including glycogen and lipid droplets, whereas RM did not. RM boosted the production of enzymes responsible for the breakdown of glycogen and lipid droplets. Collectively, these results provide insights into the distinct energy metabolism mechanisms induced by CR and RM, suggesting that these two anti-aging regimens might extend life span through distinctive pathways.

Intercellular Transfer of Microvesicles from Young Mesenchymal Stromal Cells Rejuvenates Aged Murine Hematopoietic Stem Cells

Donor age is one of the major concerns in bone marrow transplantation, as the aged hematopoietic stem cells (HSCs) fail to engraft efficiently. Here, using murine system, we show that a brief interaction of aged HSCs with young mesenchymal stromal cells (MSCs) rejuvenates them and restores their functionality via inter-cellular transfer of microvesicles (MVs) containing autophagy-related mRNAs. Importantly, we show that MSCs gain activated AKT signaling as a function of aging. Activated AKT reduces the levels of autophagy-related mRNAs in their MVs, and partitions miR-17 and miR-34a into their exosomes, which upon transfer into HSCs downregulate their autophagy-inducing mRNAs. Our data identify previously unknown mechanisms operative in the niche-mediated aging of HSCs. Inhibition of AKT in aged MSCs increases the levels of autophagy-related mRNAs in their MVs and reduces the levels of miR-17 and miR-34a in their exosomes. Interestingly, transplantation experiments showed that the rejuvenating power of these "rescued" MVs is even better than that of the young MVs. We demonstrate that such ex vivo rejuvenation of aged HSCs could expand donor cohort and improve transplantation efficacy. Stem Cells 2018;36:420-433.

The Mitochondrial Basis of Aging and Age-Related Disorders

Aging is a natural phenomenon characterized by progressive decline in tissue and organ function leading to increased risk of disease and mortality. Among diverse factors that contribute to human aging, the mitochondrial dysfunction has emerged as one of the key hallmarks of aging process and is linked to the development of numerous age-related pathologies including metabolic syndrome, neurodegenerative disorders, cardiovascular diseases and cancer. Mitochondria are central in the regulation of energy and metabolic homeostasis, and harbor a complex quality control system that limits mitochondrial damage to ensure mitochondrial integrity and function. The intricate regulatory network that balances the generation of new and removal of damaged mitochondria forms the basis of aging and longevity. Here, I will review our current understanding on how mitochondrial functional decline contributes to aging, including the role of somatic mitochondrial DNA (mtDNA) mutations, reactive oxygen species (ROS), mitochondrial dynamics and quality control pathways. I will further discuss the emerging evidence on how dysregulated mitochondrial dynamics, mitochondrial biogenesis and turnover mechanisms contribute to the pathogenesis of age-related disorders. Strategies aimed to enhance mitochondrial function by targeting mitochondrial dynamics, quality control, and mitohormesis pathways might promote healthy aging, protect against age-related diseases, and mediate longevity.

To be or not to be cell autonomous? Autophagy says both

Although cells are a part of the whole organism, classical dogma emphasizes that individual cells function autonomously. Many physiological and pathological conditions, including cancer, and metabolic and neurodegenerative diseases, have been considered mechanistically as cell-autonomous pathologies, meaning those that damage or defect within a selective population of affected cells suffice to produce disease. It is becoming clear, however, that cells and cellular processes cannot be considered in isolation. Best known for shuttling cytoplasmic content to the lysosome for degradation and repurposing of recycled building blocks such as amino acids, nucleotides, and fatty acids, autophagy serves a housekeeping function in every cell and plays key roles in cell development, immunity, tissue remodeling, and homeostasis with the surrounding environment and the distant organs. In this review, we underscore the importance of taking interactions with the microenvironment into consideration while addressing the cell autonomous and non-autonomous functions of autophagy between cells of the same and different types and in physiological and pathophysiological situations.

Multifaceted Roles of GSK-3 in Cancer and Autophagy-Related Diseases

GSK-3 is a ubiquitously expressed serine/threonine kinase existing as GSK-3α and GSK-3β isoforms, both active under basal conditions and inactivated upon phosphorylation by different upstream kinases. Initially discovered as a regulator of glycogen synthesis, GSK-3 is also involved in several signaling pathways controlling many different key functions. Here, we discuss recent advances regarding (i) GSK-3 structure, function, regulation, and involvement in several cancers, including hepatocarcinoma, cholangiocarcinoma, breast cancer, prostate cancer, leukemia, and melanoma (active GSK-3 has been shown to induce apoptosis in some cases or inhibit apoptosis in other cases and to induce cancer progression or inhibit tumor cell proliferation, suggesting that different GSK-3 modulators may address different specific targets); (ii) GSK-3 involvement in autophagy modulation, reviewing signaling pathways involved in neurodegenerative and liver diseases; (iii) GSK-3 role in oxidative stress and autophagic cell death, focusing on liver injury; (iv) GSK-3 as a possible therapeutic target of natural substances and synthetic inhibitors in many diseases; and (v) GSK-3 role as modulator of mammalian aging, related to metabolic alterations characterizing senescent cells and age-related diseases. Studies summarized here underline the GSK-3 multifaceted role and indicate such kinase as a molecular target in different pathologies, including diseases associated with autophagy dysregulation.

Herpesvirus and Autophagy: "All Right, Everybody Be Cool, This Is a Robbery!"

Autophagy is an essential vacuolar process of the cell, leading to lysosomal degradation and recycling of proteins and organelles, which is extremely important in maintaining homeostasis. Multiple roles have been now associated with autophagy, in particular a pro-survival role in nutrient starvation or in stressful environments, a role in life span extension, in development, or in innate and adaptive immunity. This cellular process can also take over microorganisms or viral proteins inside autophagosomes and degrade them directly in autolysosomes and is then called xenophagy and virophagy, respectively. Several Herpesviruses have developed strategies to escape this degradation, by expression of specific anti-autophagic proteins. However, we are increasingly discovering that Herpesviruses hijack autophagy, rather than just fight it. This beneficial effect is obvious since inhibition of autophagy will lead to decreased viral titers for human cytomegalovirus (HCMV), Epstein-Barr virus (EBV) or Varicella-Zoster virus (VZV), for example. Conversely, autophagy stimulation will improve viral multiplication. The autophagic machinery can be used in whole or in part, and can optimize viral propagation or persistence. Some viruses block maturation of autophagosomes to avoid the degradation step, then autophagosomal membranes are used to contribute to the envelopment and/or the egress of viral particles. On the other hand, VZV stimulates the whole process of autophagy to subvert it in order to use vesicles containing ATG (autophagy-related) proteins and resembling amphisomes for their transport in the cytoplasm. During latency, autophagy can also be activated by latent proteins encoded by different oncogenic Herpesviruses to promote cell survival and achieve long term viral persistence in vivo. Finally, reactivation of gammaherpesvirus Murid Herpesvirus 68 (MHV68) in mice appears to be positively modulated by autophagy, in order to control the level of inflammation. Therefore, Herpesviruses appear to behave more like thieves than fugitives.

Slm35 links mitochondrial stress response and longevity through TOR signaling pathway

In most eukaryotic cells mitochondria are essential organelles involved in a great variety of cellular functions. One of the physiological processes linked to mitochondria is aging, a gradual process of damage accumulation that eventually promotes cell death. Aging depends on a balance between mitochondrial biogenesis, function and degradation. It has been previously shown that Tor1, Sch9 and Ras2 are activated in response to nutrient availability and regulate cell growth and division. A deficiency in any of these genes promotes lifespan extension and cell protection during oxidative and heat shock stress. In this work we report that in Saccharomyces cerevisiae, the uncharacterized mitochondrial protein Slm35 is functionally linked with the TOR signaling pathway. A Δtor1Δslm35 strain shows a severe decrease in lifespan and is unable to contend with oxidative and heat shock stresses. Specifically, this mutant shows decreased catalase activity indicating a misregulation of ROS scavenging mechanisms. In this study we show that Slm35 is also relevant for mitochondrial network dynamics and mitophagy. The results presented here suggest that Slm35 plays an important role connecting mitochondrial function with cytosolic responses and cell adaptation to stress and aging.

Omics Approaches for Identifying Physiological Adaptations to Genome Instability in Aging

DNA damage causally contributes to aging and age-related diseases. The declining functioning of tissues and organs during aging can lead to the increased risk of succumbing to aging-associated diseases. Congenital syndromes that are caused by heritable mutations in DNA repair pathways lead to cancer susceptibility and accelerated aging, thus underlining the importance of genome maintenance for withstanding aging. High-throughput mass-spectrometry-based approaches have recently contributed to identifying signalling response networks and gaining a more comprehensive understanding of the physiological adaptations occurring upon unrepaired DNA damage. The insulin-like signalling pathway has been implicated in a DNA damage response (DDR) network that includes epidermal growth factor (EGF)-, AMP-activated protein kinases (AMPK)- and the target of rapamycin (TOR)-like signalling pathways, which are known regulators of growth, metabolism, and stress responses. The same pathways, together with the autophagy-mediated proteostatic response and the decline in energy metabolism have also been found to be similarly regulated during natural aging, suggesting striking parallels in the physiological adaptation upon persistent DNA damage due to DNA repair defects and long-term low-level DNA damage accumulation occurring during natural aging. These insights will be an important starting point to study the interplay between signalling networks involved in progeroid syndromes that are caused by DNA repair deficiencies and to gain new understanding of the consequences of DNA damage in the aging process.

Cellular Senescence in Age-Related Macular Degeneration: Can Autophagy and DNA Damage Response Play a Role?

Age-related macular degeneration (AMD) is the main reason of blindness in developed countries. Aging is the main AMD risk factor. Oxidative stress, inflammation and some genetic factors play a role in AMD pathogenesis. AMD is associated with the degradation of retinal pigment epithelium (RPE) cells, photoreceptors, and choriocapillaris. Lost RPE cells in the central retina can be replaced by their peripheral counterparts. However, if they are senescent, degenerated regions in the macula cannot be regenerated. Oxidative stress, a main factor of AMD pathogenesis, can induce DNA damage response (DDR), autophagy, and cell senescence. Moreover, cell senescence is involved in the pathogenesis of many age-related diseases. Cell senescence is the state of permanent cellular division arrest and concerns only mitotic cells. RPE cells, although quiescent in the retina, can proliferate in vitro. They can also undergo oxidative stress-induced senescence. Therefore, cellular senescence can be considered as an important molecular pathway of AMD pathology, resulting in an inability of the macula to regenerate after degeneration of RPE cells caused by a factor inducing DDR and autophagy. It is too early to speculate about the role of the mutual interplay between cell senescence, autophagy, and DDR, but this subject is worth further studies.

Cancer and Aging - the Inflammatory Connection

Aging and cancer are highly correlated biological phenomena. Various cellular processes such as DNA damage responses and cellular senescence that serve as tumor suppressing mechanisms throughout life result in degenerative changes and contribute to the aging phenotype. In turn, aging is considered a pro-tumorigenic state, and constitutes the single most important risk factor for cancer development. However, the causative relations between aging and cancer is not straight forward, as these processes carry contradictory hallmarks; While aging is characterized by tissue degeneration and organ loss of function, cancer is a state of sustained cellular proliferation and gain of new functions. Here, we review the molecular and cellular pathways that stand in the base of aging related cancer. Specifically, we deal with the inflammatory perspective that link these two processes, and suggest possible molecular targets that may be exploited to modify their courses.

Mitophagy in neurodegeneration and aging

Mitochondrial dysfunction contributes to normal aging and a wide spectrum of age-related diseases, including neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. It is important to maintain a healthy mitochondrial population which is tightly regulated by proteolysis and mitophagy. Mitophagy is a specialized form of autophagy that regulates the turnover of damaged and dysfunctional mitochondria, organelles that function in producing energy for the cell in the form of ATP and regulating energy homeostasis. Mechanistic studies on mitophagy across species highlight a sophisticated and integrated cellular network that regulates the degradation of mitochondria. Strategies directed at maintaining a healthy mitophagy level in aged individuals might have beneficial effects. In this review, we provide an updated mechanistic overview of mitophagy pathways and discuss the role of reduced mitophagy in neurodegeneration. We also highlight potential translational applications of mitophagy-inducing compounds, such as NAD+ precursors and urolithins.

Autophagy in stem cell aging

Aging is responsible for changes in mammalian tissues that result in an imbalance to tissue homeostasis and a decline in the regeneration capacity of organs due to stem cell exhaustion. Autophagy is a constitutive pathway necessary to degrade damaged organelles and protein aggregates. Autophagy is one of the hallmarks of aging, which involves a decline in the number and functionality of stem cells. Recent studies show that stem cells require autophagy to get rid of cellular waste produced during the quiescent stage. In particular, two independent studies in muscle and hematopoietic stem cells demonstrate the relevance of the autophagy impairment for stem cell exhaustion and aging. In this review, we summarize the main results of these works, which helped to elucidate the impact of autophagy in stem cell activity as well as in age‐associated diseases.

Autophagy suppression potentiates the anti-glioblastoma effect of asparaginase in vitro and in vivo

Asparaginase has been reported to be effective in the treatment of various leukemia and several malignant solid cancers. However, the anti-tumor effect of asparaginase is always restricted due to complicated mechanisms. Herein, we investigated the mechanisms of how glioblastoma resisted asparaginase treatment and reported a novel approach to enhance the anti-glioblastoma effect of asparaginase. We found that asparaginase could induce growth inhibition and caspase-dependent apoptosis in U87MG/U251MG glioblastoma cells. Meanwhile, autophagy was activated as indicated by autophagosomes formation and upregulated expression of LC3-II. Importantly, abolishing autophagy using chloroquine (CQ) and LY294002 enhanced the cytotoxicity and apoptosis induced by asparaginase in U87MG/U251MG cells. Further study proved that Akt/mTOR and Erk signaling pathways participated in autophagy induction, while reactive oxygen species (ROS) served as an intracellular regulator for both cytotoxicity and autophagy in asparaginase-treated U87MG/U251MG cells. Moreover, combination treatment with autophagy inhibitor CQ significantly enhanced anti-glioblastoma efficacy of asparaginase in U87MG cell xenograft model. Taken together, our results demonstrated that inhibition of autophagy potentiated the anti-tumor effect of asparagine depletion on glioblastoma, indicating that targeting autophagy and asparagine could be a potential approach for glioblastoma treatment.

Autophagy negatively regulates pro-osteogenic activity in human aortic valve interstitial cells

BACKGROUND

Autophagy is a physiological process that plays an important role in maintaining cellular functions. When aortic valve interstitial cells (AVICs) are stimulated with inflammatory or mechanical stress, one response is elevated pro-osteogenic activity. We hypothesized that autophagy is important in the prevention or regulation of this pro-osteogenic activity in AVICs.

MATERIALS AND METHODS

AVICs were isolated. Autophagy activity was examined and its role in AVIC's pro-osteogenic activity was determined using chemical inhibitors and genetic techniques. The pro-osteogenic biomarker bone morphogenetic protein 2 (BMP-2) and alkaline phosphatase (ALP) were analyzed by immunoblotting and calcium deposition assay.

RESULTS

Human AVICs from normal aortic valve donors displayed significantly higher autophagic activity than those from calcified aortic valve donors as indicated by lower protein levels of light chain 3-II. Suppression of autophagy by 3-methyladenine, bafilomycin, or knockdown of Atg7 gene induced the expression of BMP-2 and ALP, increased ALP activity, and calcium deposit formation in normal AVICs. Conversely, upregulation of autophagy with rapamycin or overexpression of Atg7 gene decreased the levels of BMP-2 and ALP in diseased AVICs.

CONCLUSIONS

Our data showed that autophagy negatively regulates the pro-osteogenic activity in human AVICs, suggesting that upregulation of autophagy may prevent the progression of calcific aortic valve disease.

Sub-lethal oxidative stress induces lysosome biogenesis via a lysosomal membrane permeabilization-cathepsin-caspase 3-transcription factor EB-dependent pathway

Here we provide evidence to link sub-lethal oxidative stress to lysosome biogenesis. Exposure of cells to sub-lethal concentrations of exogenously added hydrogen peroxide resulted in cytosol to nuclear translocation of the Transcription Factor EB (TFEB), the master controller of lysosome biogenesis and function. Nuclear translocation of TFEB was dependent upon the activation of a cathepsin-caspase 3 signaling pathway, downstream of lysosomal membrane permeabilization and accompanied by a significant increase in lysosome numbers as well as induction of TFEB-dependent lysosome-associated genes expression such as Ctsl, Lamp2 and its spliced variant Lamp2a, Neu1and Ctsb and Sqstm1 and Atg9b. The effects of sub-lethal oxidative stress on lysosomal gene expression and biogenesis were rescued upon gene silencing of caspase 3 and TFEB. Notably, caspase 3 activation was not associated with phenotypic hallmarks of apoptosis, evidenced by the absence of caspase 3 substrate cleavage, such as PARP, Lamin A/C or gelsolin. Taken together, these data demonstrate for the first time an unexpected and non-canonical role of a cathepsin-caspase 3 axis in the nuclear translocation of TFEB leading to lysosome biogenesis under conditions of sub-lethal oxidative stress.

The alteration of autophagy and apoptosis in the hippocampus of rats with natural aging-dependent cognitive deficits

AIMS

The present study was aim to explore aging-dependent changes in hippocampal autophagy and apoptosis in a natural aging rat model from adult to old stages and to discover a suitable age for treating neurodegenerative diseases.

METHODS

Wistar rats at 5, 18 and 24months of age were used to mimic the adulthood, initial old, and old phases, respectively. The learning and cognitive ability of the rats was detected by the Morris water maze test. Morphological changes in the hippocampus were observed. Expressions of apoptosis and autophagy-related proteins were examined by Western blot.

RESULTS

The adult group (5months) exhibited high levels of autophagy related p-ULK p-ULK-1/ULK-1 ratio, Beclin-1, LC3II and cell survival, maintaining normal learning and cognitive function and integrated hippocampal morphology. The initial old group (18 months) presented a reduced number of neurons and cognitive deficits, and exhibited high levels of apoptosis related Bax/Bcl-2 ratio, Caspase-3 activation and autophagy related p-ULK p-ULK-1/ULK-1 ratio, Beclin-1, LC3II compared to the adult group. The old group (24 months) exhibited a high level of apoptosis related Bax/Bcl-2 ratio, Caspase-3 activation and a low level of autophagy related p-ULK p-ULK-1/ULK-1 ratio, Beclin-1, LC3II compared to its younger group, as well as significant neuronal death and cognitive deficits. The degree of autophagy was generally consistent with its negative regulator, the PI3K/Akt/mTOR axis, in all groups.

CONCLUSION

Our data suggest that cognitive deficits are first observed in the initial old stage. The levels of autophagy and apoptosis tend to be opposite in the adult and old phases. High levels of autophagy and apoptosis coexist in the initial old stage. Our study indicates that up-regulation of autophagy in the initial old phase to anti-cognitive deficits must be further evaluated.

Mitochondria in endothelial cells: Sensors and integrators of environmental cues

The involvement of angiogenesis in disease and its potential as a therapeutic target have been firmly established over recent decades. Endothelial cells (ECs) are central elements in vessel homeostasis and regulate the passage of material and cells into and out of the bloodstream. EC proliferation and migration are modified by alterations to mitochondrial biogenesis and dynamics resulting from several signals and environmental cues, such as oxygen, hemodynamics, and nutrients. As intermediary signals, mitochondrial ROS are released as important downstream modulators of the expression of angiogenesis-related genes. In this review, we discuss the physiological actions of these signals and aberrant responses during vascular disorders.

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Mitochondria in EC act as integrators of environmental cues.

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Circulating signals modify mitochondrial dynamics, altering EC phenotype.

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ROS release by EC mitochondria regulates expression of vascular genes.

Hormetic efficacy of rutin to promote longevity in Drosophila melanogaster

Hormetins are compounds that mediate hormesis by being beneficial at low doses but detrimental at high doses. Recent studies have highlighted that many compounds that extended lifespan in model organisms did so by mediating hormesis. Rutin is a glycosylate conjugate of quercetin and rutinose and is abundant in citrus fruits and buckwheat seeds. Rutin possess ROS scavenging, anti-cancer, cardio-protective, skin-regenerative and neuro-protective properties. Drosophila melanogaster is an attractive model organism for longevity studies owing to its homology of organ and cellular-pathways with mammals. In this study, we aimed to understand the effect of rutin on extending longevity in Drosophila melanogaster. Male and female flies were administered with a range of rutin doses (100-800 µM) to analyse whether rutin mediated lifespan-extension by hormesis. Effect of rutin on physiological parameters like food intake, fecundity, climbing activity, development and resistance to various stresses was also studied. Lifespan assays showed that rutin at 200 and 400 µM significantly extended median lifespan in both male and female flies beyond which flies exhibited drastically reduced longevity. Increase in survival at 400 µM was associated with reduced food intake and fecundity. Flies exhibited improved climbing capability with both 200 and 400 µM rutin. Flies fed with 100 and 200 µM rutin exhibited enhanced survival upon exposure to oxidative stress with 400 µM rutin exhibiting no improvement in median lifespan following oxidative stress. Analysis of endogenous peroxide upon treatment with rutin (100-400 µM) with or without 5% H₂O₂ showed elevated levels of endogenous peroxide with 400 µM rutin whereas no increase in hydrogen peroxide level was observed with rutin at 100 and 200 µM. Finally, gene expression studies in male flies revealed that rutin treatment at 200 and/or 400 µM elevated transcript levels of dFoxO, MnSod, Cat, dTsc1, dTsc2, Thor, dAtg1, dAtg5 and dAtg7 and reduced transcript levels of dTor. Collectively, rutin at 200 and 400 µM improved longevity in flies; 200 µM rutin acted as a mild stressor to prolong lifespan in flies by mediating hormesis whereas 400 µM, being a high dose for best positive effects.

Induction of autophagy by spermidine is neuroprotective via inhibition of caspase 3-mediated Beclin 1 cleavage

Spermidine, a natural polyamine presented widely in mammalian cells, has been implicated to extend the lifespan of several model organisms by inducing autophagy. However, the effect of spermidine against neuronal damage has not yet been fully determined. In this study, neuronal cell injury was induced by treating PC12 cells and cortical neurons with 1 μM staurosporine (STS). We found that STS-induced cell injury could be efficiently attenuated by pretreatment with 1 mM spermidine. Spermidine inhibited the caspase 3 activation induced by STS. Moreover, STS incubation resulted in autophagic degradation failure, which could be attenuated by the pretreatment of spermidine. Knocking down the expression of Beclin 1 efficiently suppressed autophagosome and autolysosome accumulation, and abolished the protective effects of spermidine against STS-induced neurotoxicity. Increased Beclin 1 cleavage and partial nuclear translocation of Beclin 1 fragment was detected in STS-treated cells, which could be blocked by spermidine, pan-caspase inhibitor or caspase 3-specific inhibitor. The nuclear translocation of Beclin 1 fragment universally occurs in damaged neurons. Beclin 1 mutation at the sites of 146 and 149 prevented the intracellular re-distribution of Beclin 1 induced by STS. In addition, intraperitoneal injection of spermidine ameliorated ischemia/reperfusion-induced neuronal injury in the hippocampus and cortex of rats, possibly via blocking caspase 3 activation and consequent Beclin 1 cleavage. Our findings suggest that caspase 3-mediated Beclin 1 cleavage occurs in acute neuronal cell injury both in vitro and in vivo. The neuroprotective effect of spermidine may be related to inhibition of the caspase 3-mediated Beclin 1 cleavage and restoration of the Beclin 1-dependent autophagy.

Mammalian Mitochondria and Aging: An Update

Mitochondria were first postulated to contribute to aging more than 40 years ago. During the following decades, multiple lines of evidence in model organisms and humans showed that impaired mitochondrial function can contribute to age-associated disease phenotypes and aging. However, in contrast to the original theory favoring oxidative damage as a cause for mtDNA mutations, there are now strong data arguing that most mammalian mtDNA mutations originate as replication errors made by the mtDNA polymerase. Currently, a substantial amount of mitochondrial research is focused on finding ways to either remove or counteract the effects of mtDNA mutations with the hope of extending the human health- and lifespan. This review summarizes the current knowledge regarding the formation of mtDNA mutations and their impact on mitochondrial function. We also critically discuss proposed pathways interlinked with mammalian mtDNA mutations and suggest future research strategies to elucidate the role of mtDNA mutations in aging.

The crucial impact of lysosomes in aging and longevity

Lysosomes are the main catabolic organelles of a cell and play a pivotal role in a plethora of cellular processes, including responses to nutrient availability and composition, stress resistance, programmed cell death, plasma membrane repair, development, and cell differentiation. In line with this pleiotropic importance for cellular and organismal life and death, lysosomal dysfunction is associated with many age-related pathologies like Parkinson's and Alzheimer's disease, as well as with a decline in lifespan. Conversely, targeting lysosomal functional capacity is emerging as a means to promote longevity. Here, we analyze the current knowledge on the prominent influence of lysosomes on aging-related processes, such as their executory and regulatory roles during general and selective macroautophagy, or their storage capacity for amino acids and ions. In addition, we review and discuss the roles of lysosomes as active players in the mechanisms underlying known lifespan-extending interventions like, for example, spermidine or rapamycin administration. In conclusion, this review aims at critically examining the nature and pliability of the different layers, in which lysosomes are involved as a control hub for aging and longevity.

Methods to Assess Autophagy and Chronological Aging in Yeast

Autophagy is a catabolic process that is crucial for cellular homeostasis and adaptive response to changing environments. Importantly, autophagy has been shown to be induced in many longevity-associated scenarios and to be required to maintain lifespan extension. Notably, autophagy is a highly conserved cellular process among eukaryotes, and the yeast Saccharomyces cerevisiae has become a universal model system for unraveling the molecular machinery underlying autophagic mechanisms. Here, we discuss different protocols to monitor survival and autophagy of yeast cells upon chronological aging. These include the use of propidium iodide to assess the loss of cell membrane integrity, as well as clonogenic assays to directly determine survival rates. Additionally, we describe methods to quantify autophagic flux, including the alkaline phosphatase activity or the GFP liberation assays, which measure the delivery of autophagosomal cargo to the vacuole. In sum, we have recapped established protocols used to evaluate a link between lifespan extension and autophagy in yeast.

Gradual downhill running improves age-related skeletal muscle and bone weakness: implication of autophagy and bone morphogenetic proteins

NEW FINDINGS

What is the central question of this study? Exercise training by running has an effect on age-related muscle and bone wasting that improves physical activity and quality of life in the elderly. However, the effect of downhill running on age-related muscle and bone wasting, and its mechanisms, are unclear. What is the main finding and its importance? Gradual downhill running can improve skeletal muscle growth and bone formation by enhancing autophagy and bone morphogenetic protein signalling in aged rats. Therefore, downhill running exercise might be a practical intervention to improve skeletal muscle and bone protection in the elderly. Recent evidence suggests that autophagy and the bone morphogenetic protein (BMP) signalling pathway regulate skeletal muscle growth and bone formation in aged rats. However, the effect of downhill running on muscle growth and bone formation is not well understood. Thus, we investigated the effect of downhill and uphill running on age-related muscle and bone weakness. Young and late middle-aged rats were randomly assigned to control groups (young, YC; and late middle-aged, LMC) and two types of running training groups (late middle-aged downhill, LMD; and late middle-aged uphill, LMU). Training was progressively carried out on a treadmill at a speed of 21 m min^-1 with a slope of +10 deg for uphill training versus 16 m min^-1 with a slope of -16 deg for downhill training, both for 60 min day^-1 , 5 days week^-1 for 8 weeks. Downhill and uphill training increased autophagy-related protein 5, microtubule-associated protein light chain, Beclin-1 and p62 proteins in aged rats. In addition, superoxide dismutase, haem oxygenase-1 and the BMP signalling pathway were elevated. Phosphorylation of mammalian target of rapamycin and myogenic differentiation were increased significantly in the LMD and LMU groups. Consequently, in the femur, BMP-2, BMP-7 and autophagy molecules were highly expressed in the LMD and LMU groups. These results suggest that both downhill and uphill training appear to have a positive effect on expression of autophagy molecules and BMPs. In particular, these physiological adaptations from gradual downhill exercise have an effect on bone morphological changes and muscle quality similar to gradual uphill training interventions in ageing.

Autophagy flux in CA1 neurons of Alzheimer hippocampus: Increased induction overburdens failing lysosomes to propel neuritic dystrophy

Defective autophagy contributes to Alzheimer disease (AD) pathogenesis although evidence is conflicting on whether multiple stages are impaired. Here, for the first time, we have comprehensively evaluated the entire autophagic process specifically in CA1 pyramidal neurons of hippocampus from early and late-stage AD subjects and nondemented controls. CA1 neurons aspirated by laser capture microdissection were analyzed using a custom-designed microarray comprising 578 neuropathology- and neuroscience-associated genes. Striking upregulation of autophagy-related genes, exceeding that of other gene ontology groups, reflected increases in autophagosome formation and lysosomal biogenesis beginning at early AD stages. Upregulated autophagosome formation was further indicated by elevated gene and protein expression levels for autophagosome components and increased LC3-positive puncta. Increased lysosomal biogenesis was evidenced by activation of MiTF/TFE family transcriptional regulators, particularly TFE3 (transcription factor binding to IGHM enhancer 3) and by elevated expression of their target genes and encoded proteins. Notably, TFEB (transcription factor EB) activation was associated more strongly with glia than neurons. These findings establish that autophagic sequestration is both competent and upregulated in AD. Autophagosome-lysosome fusion is not evidently altered. Despite this early disease response, however, autophagy flux is progressively impeded due to deficient substrate clearance, as reflected by autolysosomal accumulation of LC3-II and SQSTM1/p62 and expansion of autolysosomal size and total area. We propose that sustained induction of autophagy in the face of progressively declining lysosomal clearance of substrates explains the uncommonly robust autophagic pathology and neuritic dystrophy implicated in AD pathogenesis.

Exploring the power of yeast to model aging and age-related neurodegenerative disorders

Aging is a multifactorial process determined by molecular, cellular and systemic factors and it is well established that advancing age is a leading risk factor for several neurodegenerative diseases. In fact, the close association of aging and neurodegenerative disorders has placed aging as the greatest social and economic challenge of the 21st century, and age-related diseases have also become a key priority for countries worldwide. The growing need to better understand both aging and neurodegenerative processes has led to the development of simple eukaryotic models amenable for mechanistic studies. Saccharomyces cerevisiae has proven to be an unprecedented experimental model to study the fundamental aspects of aging and to decipher the intricacies of neurodegenerative disorders greatly because the molecular mechanisms underlying these processes are evolutionarily conserved from yeast to human. Moreover, yeast offers several methodological advantages allowing a rapid and relatively easy way of establishing gene-protein-function associations. Here we review different aging theories, common cellular pathways driving aging and neurodegenerative diseases and discuss the major contributions of yeast to the state-of-art knowledge in both research fields.

Autophagy mechanisms in sputum and peripheral blood cells of patients with severe asthma: a new therapeutic target

BACKGROUND

Autophagy and genetic predisposition have been suggested to potentially play roles in the development of asthma. However, little is known about the role of autophagy in the pathogenesis of severe asthma.

OBJECTIVE

We compared autophagy in the sputum granulocytes, peripheral blood cells (PBCs) and peripheral blood eosinophils (PBEs) between patients with severe asthma and those with non-severe asthma and investigated the functional effects of autophagy.

METHODS

We enrolled 36 patients with severe asthma, 14 with non-severe asthma and 23 normal healthy controls in this study. Sputum granulocytes, PBCs and PBEs were isolated from each subject. Autophagy was evaluated based on the expression of microtubule-associated protein light chain 3 (LC3) by Western blot, confocal microscopy, transmission electron microscopy and flow cytometry. IL-8 levels were measured by ELISA. To induce autophagy, HL-60 cells, human primary small airway epithelial cells (SAECs) and A549 cells were treated with IL-5, IL-1β and TNF-α. To inhibit autophagy, PI3K inhibitors (LY29400 and 3-methyladenine [3-MA]) and hydroxychloroquine (HCQ) were used. Knockdown of ATG5 and Beclin-1 was performed in A549 cells, and the therapeutic effects of dexamethasone were evaluated.

RESULTS

Higher autophagy levels were noted in sputum granulocytes, PBCs and PBEs from patients with severe asthma than from patients with non-severe asthma and healthy controls (P < 0.05 for all). IL-5 increased autophagy levels in both PBCs and PBEs (P < 0.05). 3-MA attenuated the increased expression of LC3-II and eosinophil cationic protein in HL-60 cells induced by IL-5 (P = 0.034 for both). Dexamethasone did not affect autophagy levels in PBEs. IL-1β increased LC3-II expression and IL-8 production (P < 0.01) in SAECs, and this was attenuated by LY294002, 3-MA, HCQ and knockdown of ATG5 and Beclin-1 (in A549 cells) (P < 0.01).

CONCLUSIONS AND CLINICAL RELEVANCE

Autophagy could play a role in the pathogenesis of severe asthma. Autophagy modulation may be a novel therapeutic target for conventional therapy-resistant severe asthma.

Plasma Biomarkers of Poor Muscle Quality in Older Men and Women from the Baltimore Longitudinal Study of Aging

Aging is characterized by progressive decline in muscle mass, strength, and quality all of which contribute to functional impairment, falls, mobility disability, and frailty. Circulating factors may provide clues on the mechanisms for decline in muscle quality with aging. Characterizing the metabolic profile associated with reduced muscle quality in older persons could have important translational implications for the early identification of subjects at high risk of developing sarcopenia and the identification of targets for new preventive strategies and treatments. In a pilot cross-sectional, case-control study nested in the Baltimore Longitudinal Study on Aging, we compared circulating metabolites between 79 participants with low muscle quality ratio and 79 controls with high muscle quality, matched by age, sex, and height. The concentrations of 180 metabolites were determined by LC MS/MS, using the Biocrates p180 system, a targeted metabolomics approach. Participants with low muscle quality had significantly higher levels of leucine, isoleucine, tryptophan, serotonin, and methionine, while those with high muscle quality had significantly lower levels of putrescine and the selected phophatidylcholine (PCs) and lysoPCs. The results of this study open a new road for future investigations aimed at identifying new metabolic pathways involved in the decline of muscle quality with aging.

Communications between Mitochondria, the Nucleus, Vacuoles, Peroxisomes, the Endoplasmic Reticulum, the Plasma Membrane, Lipid Droplets, and the Cytosol during Yeast Chronological Aging

Studies employing the budding yeast Saccharomyces cerevisiae as a model organism have provided deep insights into molecular mechanisms of cellular and organismal aging in multicellular eukaryotes and have demonstrated that the main features of biological aging are evolutionarily conserved. Aging in S. cerevisiae is studied by measuring replicative or chronological lifespan. Yeast replicative aging is likely to model aging of mitotically competent human cell types, while yeast chronological aging is believed to mimic aging of post-mitotic human cell types. Emergent evidence implies that various organelle-organelle and organelle-cytosol communications play essential roles in chronological aging of S. cerevisiae. The molecular mechanisms underlying the vital roles of intercompartmental communications in yeast chronological aging have begun to emerge. The scope of this review is to critically analyze recent progress in understanding such mechanisms. Our analysis suggests a model for how temporally and spatially coordinated movements of certain metabolites between various cellular compartments impact yeast chronological aging. In our model, diverse changes in these key metabolites are restricted to critical longevity-defining periods of chronological lifespan. In each of these periods, a limited set of proteins responds to such changes of the metabolites by altering the rate and efficiency of a certain cellular process essential for longevity regulation. Spatiotemporal dynamics of alterations in these longevity-defining cellular processes orchestrates the development and maintenance of a pro- or anti-aging cellular pattern.

Epigenetics and aging

Over the past decade, a growing number of studies have revealed that progressive changes to epigenetic information accompany aging in both dividing and nondividing cells. Functional studies in model organisms and humans indicate that epigenetic changes have a huge influence on the aging process. These epigenetic changes occur at various levels, including reduced bulk levels of the core histones, altered patterns of histone posttranslational modifications and DNA methylation, replacement of canonical histones with histone variants, and altered noncoding RNA expression, during both organismal aging and replicative senescence. The end result of epigenetic changes during aging is altered local accessibility to the genetic material, leading to aberrant gene expression, reactivation of transposable elements, and genomic instability. Strikingly, certain types of epigenetic information can function in a transgenerational manner to influence the life span of the offspring. Several important conclusions emerge from these studies: rather than being genetically predetermined, our life span is largely epigenetically determined; diet and other environmental influences can influence our life span by changing the epigenetic information; and inhibitors of epigenetic enzymes can influence life span of model organisms. These new findings provide better understanding of the mechanisms involved in aging. Given the reversible nature of epigenetic information, these studies highlight exciting avenues for therapeutic intervention in aging and age-associated diseases, including cancer.

The marine n-3 PUFA DHA evokes cytoprotection against oxidative stress and protein misfolding by inducing autophagy and NFE2L2 in human retinal pigment epithelial cells

Accumulation and aggregation of misfolded proteins is a hallmark of several diseases collectively known as proteinopathies. Autophagy has a cytoprotective role in diseases associated with protein aggregates. Age-related macular degeneration (AMD) is the most common neurodegenerative eye disease that evokes blindness in elderly. AMD is characterized by degeneration of retinal pigment epithelial (RPE) cells and leads to loss of photoreceptor cells and central vision. The initial phase associates with accumulation of intracellular lipofuscin and extracellular deposits called drusen. Epidemiological studies have suggested an inverse correlation between dietary intake of marine n-3 polyunsaturated fatty acids (PUFAs) and the risk of developing neurodegenerative diseases, including AMD. However, the disease-preventive mechanism(s) mobilized by n-3 PUFAs is not completely understood. In human retinal pigment epithelial cells we find that physiologically relevant doses of the n-3 PUFA docosahexaenoic acid (DHA) induce a transient increase in cellular reactive oxygen species (ROS) levels that activates the oxidative stress response regulator NFE2L2/NRF2 (nuclear factor, erythroid derived 2, like 2). Simultaneously, there is a transient increase in intracellular protein aggregates containing SQSTM1/p62 (sequestosome 1) and an increase in autophagy. Pretreatment with DHA rescues the cells from cell cycle arrest induced by misfolded proteins or oxidative stress. Cells with a downregulated oxidative stress response, or autophagy, respond with reduced cell growth and survival after DHA supplementation. These results suggest that DHA both induces endogenous antioxidants and mobilizes selective autophagy of misfolded proteins. Both mechanisms could be relevant to reduce the risk of developing aggregate-associate diseases such as AMD.

Ethanolamine: A novel anti-aging agent

Ethanolamine (Etn) is a naturally occurring aminoalcohol necessary for synthesis of the phospholipid phosphatidylethanolamine (PE), a major component of biological membranes. We recently reported that Etn treatment increases cellular PE levels, thereby inducing cytoprotective autophagy and protecting against aging across species.

Fasting, Circadian Rhythms, and Time-Restricted Feeding in Healthy Lifespan

Most animals alternate periods of feeding with periods of fasting often coinciding with sleep. Upon >24 hr of fasting, humans, rodents, and other mammals enter alternative metabolic phases, which rely less on glucose and more on ketone body-like carbon sources. Both intermittent and periodic fasting result in benefits ranging from the prevention to the enhanced treatment of diseases. Similarly, time-restricted feeding (TRF), in which food consumption is restricted to certain hours of the day, allows the daily fasting period to last >12 hr, thus imparting pleiotropic benefits. Understanding the mechanistic link between nutrients and the fasting benefits is leading to the identification of fasting-mimicking diets (FMDs) that achieve changes similar to those caused by fasting. Given the pleiotropic and sustained benefits of TRF and FMDs, both basic science and translational research are warranted to develop fasting-associated interventions into feasible, effective, and inexpensive treatments with the potential to improve healthspan.

Autophagy in acute brain injury

Autophagy is an evolutionarily ancient mechanism that ensures the lysosomal degradation of old, supernumerary or ectopic cytoplasmic entities. Most eukaryotic cells, including neurons, rely on proficient autophagic responses for the maintenance of homeostasis in response to stress. Accordingly, autophagy mediates neuroprotective effects following some forms of acute brain damage, including methamphetamine intoxication, spinal cord injury and subarachnoid haemorrhage. In some other circumstances, however, the autophagic machinery precipitates a peculiar form of cell death (known as autosis) that contributes to the aetiology of other types of acute brain damage, such as neonatal asphyxia. Here, we dissect the context-specific impact of autophagy on non-infectious acute brain injury, emphasizing the possible therapeutic application of pharmacological activators and inhibitors of this catabolic process for neuroprotection.

Cellular degradation activity is maintained during aging in long-living queen bees

Queen honeybees (Apis mellifera) have a much longer lifespan than worker bees. Whether cellular degradation activity is involved in the longevity of queen bees is unknown. In the present study, cellular degradation activity was evaluated in the trophocytes and oenocytes of young and old queen bees. The results indicated that (i) 20S proteasome activity and the size of autophagic vacuoles decreased with aging, and (ii) there were no significant differences between young and old queen bees with regard to 20S proteasome expression or efficiency, polyubiquitin aggregate expression, microtubule-associated protein 1 light chain 3-II (LC3-II) expression, 70 kDa heat shock cognate protein (Hsc70) expression, the density of autophagic vacuoles, p62/SQSTM1 expression, the activity or density of lysosomes, or molecular target of rapamycin expression. These results indicate that cellular degradation activity maintains a youthful status in the trophocytes and oenocytes of queen bees during aging and that cellular degradation activity is involved in maintaining the longevity of queen bees.

The interplay between apoptosis, mitophagy and mitochondrial biogenesis induced by resveratrol can determine activated hepatic stellate cells death or survival

Resveratrol has been the focus of numerous studies reporting opposite effects that depend on its concentration. The GRX is an activated hepatic stellate cells model used to study liver fibrosis development and resolution. We recently showed that GRX treatment with RSV (0.1-50 µM) for 24 h triggered dose-dependent pro-oxidant effects, resulting in cytotoxicity and cell damage only at the highest concentration. Here, we evaluated whether the pro-oxidant effect of resveratrol treatment is accompanied by alterations on the GRX mitochondrial metabolism, and whether the concomitantly autophagy/mitophagy induction can influence on cell death or survival. We demonstrated that all concentrations of resveratrol promoted an increase of GRX cell death signals, altering the mitochondrial dynamics and function. Cells treated with all resveratrol concentrations presented higher autophagy/mitophagy features, but only treatments with 1 and 10 µM of resveratrol-induced mitochondrial biogenesis. Since cell damage was higher and there was no mitochondrial biogenesis in GRX treated with 50 µM of resveratrol, we suggest that these cells failed to remove and replace all damaged mitochondria. In conclusion, the cytotoxic effect of resveratrol that effectively promotes cell death could be related to the interrelation between the concomitant induction of apoptosis, autophagy/mitophagy and mitochondrial biogenesis in GRX.

Tissue-specific autophagy responses to aging and stress in C. elegans

Cellular function relies on a balance between protein synthesis and breakdown. Macromolecular breakdown through autophagy is broadly required for cellular and tissue development, function, and recovery from stress. While Caenorhabditis elegans is frequently used to explore cellular responses to development and stress, the most common assays for autophagy in this system lack tissue-level resolution. Different tissues within an organism have unique functional characteristics and likely vary in their reliance on autophagy under different conditions. To generate a tissue-specific map of autophagy in C. elegans we used a dual fluorescent protein (dFP) tag that releases monomeric fluorescent protein (mFP) upon arrival at the lysosome. Tissue-specific expression of dFP::LGG-1 revealed autophagic flux in all tissues, but mFP accumulation was most dramatic in the intestine. We also observed variable responses to stress: starvation increased autophagic mFP release in all tissues, whereas anoxia primarily increased intestinal autophagic flux. We observed autophagic flux with tagged LGG-1, LGG-2, and two autophagic cargo reporters: a soluble cytoplasmic protein, and mitochondrial TOMM-7. Finally, an increase in mFP in older worms was consistent with an age-dependent shift in proteostasis. These novel measures of autophagic flux in C. elegans reveal heterogeneity in autophagic response across tissues during stress and aging.

Abrogation of Nrf2 impairs antioxidant signaling and promotes atrial hypertrophy in response to high-intensity exercise stress

BACKGROUND

Anomalies in myocardial structure involving myocyte growth, hypertrophy, differentiation, apoptosis, necrosis etc. affects its function and render cardiac tissue more vulnerable to the development of heart failure. Although oxidative stress has a well-established role in cardiac remodeling and dysfunction, the mechanisms linking redox state to atrial cardiomyocyte hypertrophic changes are poorly understood. Here, we investigated the role of nuclear erythroid-2 like factor-2 (Nrf2), a central transcriptional mediator, in redox signaling under high intensity exercise stress (HIES) in atria.

METHODS

Age and sex-matched wild-type (WT) and Nrf2(-/-) mice at >20 months of age were subjected to HIES for 6 weeks. Gene markers of hypertrophy and antioxidant enzymes were determined in the atria of WT and Nrf2(-/-) mice by real-time qPCR analyses. Detection and quantification of antioxidants, 4-hydroxy-nonenal (4-HNE), poly-ubiquitination and autophagy proteins in WT and Nrf2(-/-) mice were performed by immunofluorescence analysis. The level of oxidative stress was measured by microscopical examination of di-hydro-ethidium (DHE) fluorescence.

RESULTS

Under the sedentary state, Nrf2 abrogation resulted in a moderate down regulation of some of the atrial antioxidant gene expression (Gsr, Gclc, Gstα and Gstµ) despite having a normal redox state. In response to HIES, enlarged atrial myocytes along with significantly increased gene expression of cardiomyocyte hypertrophy markers (Anf, Bnf and β-Mhc) were observed in Nrf2(-/-) when compared to WT mice. Further, the transcript levels of Gclc, Gsr and Gstµ and protein levels of NQO1, catalase, GPX1 were profoundly downregulated along with GSH depletion and increased oxidative stress in Nrf2(-/-) mice when compared to its WT counterparts after HIES. Impaired antioxidant state and profound oxidative stress were associated with enhanced atrial expression of LC3 and ATG7 along with increased ubiquitination of ATG7 in Nrf2(-/-) mice subjected to HIES.

CONCLUSIONS

Loss of Nrf2 describes an altered biochemical phenotype associated with dysregulation in genes related to redox state, ubiquitination and autophagy in HIES that result in atrial hypertrophy. Therefore, our findings direct that preserving Nrf2-related antioxidant function would be one of the effective strategies to safeguard atrial health.

Molecular insights into the premature aging disease progeria

Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare premature aging disease presenting many features resembling the normal aging process. HGPS patients die before the age of 20 years due to cardiovascular problems and heart failure. HGPS is linked to mutations in the LMNA gene encoding the intermediate filament protein lamin A. Lamin A is a major component of the nuclear lamina, a scaffold structure at the nuclear envelope that defines mechanochemical properties of the nucleus and is involved in chromatin organization and epigenetic regulation. Lamin A is also present in the nuclear interior where it fulfills lamina-independent functions in cell signaling and gene regulation. The most common LMNA mutation linked to HGPS leads to mis-splicing of the LMNA mRNA and produces a mutant lamin A protein called progerin that tightly associates with the inner nuclear membrane and affects the dynamic properties of lamins. Progerin expression impairs many important cellular processes providing insight into potential disease mechanisms. These include changes in mechanosignaling, altered chromatin organization and impaired genome stability, and changes in signaling pathways, leading to impaired regulation of adult stem cells, defective extracellular matrix production and premature cell senescence. In this review, we discuss these pathways and their potential contribution to the disease pathologies as well as therapeutic approaches used in preclinical and clinical tests.

New Potential Pharmacological Functions of Chinese Herbal Medicines via Regulation of Autophagy

Autophagy is a universal catabolic cellular process for quality control of cytoplasm and maintenance of cellular homeostasis upon nutrient deprivation and environmental stimulus. It involves the lysosomal degradation of cellular components such as misfolded proteins or damaged organelles. Defects in autophagy are implicated in the pathogenesis of diseases including cancers, myopathy, neurodegenerations, infections and cardiovascular diseases. In the recent decade, traditional drugs with new clinical applications are not only commonly found in Western medicines, but also highlighted in Chinese herbal medicines (CHM). For instance, pharmacological studies have revealed that active components or fractions from Chaihu (Radix bupleuri), Hu Zhang (Rhizoma polygoni cuspidati), Donglingcao (Rabdosia rubesens), Hou po (Cortex magnoliae officinalis) and Chuan xiong (Rhizoma chuanxiong) modulate cancers, neurodegeneration and cardiovascular disease via autophagy. These findings shed light on the potential new applications and formulation of CHM decoctions via regulation of autophagy. This article reviews the roles of autophagy in the pharmacological actions of CHM and discusses their new potential clinical applications in various human diseases.

The Role of Autophagy, Mitophagy and Lysosomal Functions in Modulating Bioenergetics and Survival in the Context of Redox and Proteotoxic Damage: Implications for Neurodegenerative Diseases

Redox and proteotoxic stress contributes to age-dependent accumulation of dysfunctional mitochondria and protein aggregates, and is associated with neurodegeneration. The free radical theory of aging inspired many studies using reactive species scavengers such as alpha-tocopherol, ascorbate and coenzyme Q to suppress the initiation of oxidative stress. However, clinical trials have had limited success in the treatment of neurodegenerative diseases. We ascribe this to the emerging literature which suggests that the oxidative stress hypothesis does not encompass the role of reactive species in cell signaling and therefore the interception with reactive species with antioxidant supplementation may result in disruption of redox signaling. In addition, the accumulation of redox modified proteins or organelles cannot be reversed by oxidant intercepting antioxidants and must then be removed by alternative mechanisms. We have proposed that autophagy serves this essential function in removing damaged or dysfunctional proteins and organelles thus preserving neuronal function and survival. In this review, we will highlight observations regarding the impact of autophagy regulation on cellular bioenergetics and survival in response to reactive species or reactive species generating compounds, and in response to proteotoxic stress.

Autophagy and apoptosis in liver injury

Apoptosis is a primary characteristic in the pathogenesis of liver disease. Hepatic apoptosis is regulated by autophagic activity. However, mechanisms mediating their interaction remain to be determined. Basal level of autophagy ensures the physiological turnover of old and damaged organelles. Autophagy also is an adaptive response under stressful conditions. Autophagy can control cell fate through different cross-talk signals. A complex interplay between hepatic autophagy and apoptosis determines the degree of hepatic apoptosis and the progression of liver disease as demonstrated by pre-clinical models and clinical trials. This review summarizes recent advances on roles of autophagy that plays in pathophysiology of liver. The autophagic pathway can be a novel therapeutic target for liver disease.

Improved proteostasis in the secretory pathway rescues Alzheimer's disease in the mouse

The aberrant accumulation of toxic protein aggregates is a key feature of many neurodegenerative diseases, including Huntington's disease, amyotrophic lateral sclerosis and Alzheimer's disease. As such, improving normal proteostatic mechanisms is an active target for biomedical research. Although they share common pathological features, protein aggregates form in different subcellular locations. Nε-lysine acetylation in the lumen of the endoplasmic reticulum has recently emerged as a new mechanism to regulate the induction of autophagy. The endoplasmic reticulum acetylation machinery includes AT-1/SLC33A1, a membrane transporter that translocates acetyl-CoA from the cytosol into the endoplasmic reticulum lumen, and ATase1 and ATase2, two acetyltransferases that acetylate endoplasmic reticulum cargo proteins. Here, we used a mutant form of α-synuclein to show that inhibition of the endoplasmic reticulum acetylation machinery specifically improves autophagy-mediated disposal of toxic protein aggregates that form within the secretory pathway, but not those that form in the cytosol. Consequently, haploinsufficiency of AT-1/SLC33A1 in the mouse rescued Alzheimer's disease, but not Huntington's disease or amyotrophic lateral sclerosis. In fact, intracellular toxic protein aggregates in Alzheimer's disease form within the secretory pathway while in Huntington's disease and amyotrophic lateral sclerosis they form in different cellular compartments. Furthermore, biochemical inhibition of ATase1 and ATase2 was also able to rescue the Alzheimer's disease phenotype in a mouse model of the disease. Specifically, we observed reduced levels of soluble amyloid-β aggregates, reduced amyloid-β pathology, reduced phosphorylation of tau, improved synaptic plasticity, and increased lifespan of the animals. In conclusion, our results indicate that Nε-lysine acetylation in the endoplasmic reticulum lumen regulates normal proteostasis of the secretory pathway; they also support therapies targeting endoplasmic reticulum acetyltransferases, ATase1 and ATase2, for a subset of chronic degenerative diseases.