How to live long and prosper: autophagy, mitochondria, and aging

Autophagy in aging-related diseases and cancer: Principles, regulatory mechanisms and therapeutic potential

Macroautophagy/autophagy is primarily accountable for the degradation of damaged organelles and toxic macromolecules in the cells. Regarding the essential function of autophagy for preserving cellular homeostasis, changes in, or dysfunction of, autophagy flux can lead to disease development. In the current paper, the complicated function of autophagy in aging-associated pathologies and cancer is evaluated, highlighting the underlying molecular mechanisms that can affect longevity and disease pathogenesis. As a natural biological process, a reduction in autophagy is observed with aging, resulting in an accumulation of cell damage and the development of different diseases, including neurological disorders, cardiovascular diseases, and cancer. The MTOR, AMPK, and ATG proteins demonstrate changes during aging, and they are promising therapeutic targets. Insulin/IGF1, TOR, PKA, AKT/PKB, caloric restriction and mitochondrial respiration are vital for lifespan regulation and can modulate or have an interaction with autophagy. The specific types of autophagy, such as mitophagy that degrades mitochondria, can regulate aging by affecting these organelles and eliminating those mitochondria with genomic mutations. Autophagy and its specific types contribute to the regulation of carcinogenesis and they are able to dually enhance or decrease cancer progression. Cancer hallmarks, including proliferation, metastasis, therapy resistance and immune reactions, are tightly regulated by autophagy, supporting the conclusion that autophagy is a promising target in cancer therapy.

Melatonin suppresses TLR4-mediated RSV infection in the central nervous cells by inhibiting NLRP3 inflammasome formation and autophagy

Respiratory syncytial virus (RSV) infects neuronal cells in the central nervous system (CNS), resulting in neurological symptoms. In the present study, we intended to explore the mechanism of RSV infection-induced neuroinflammatory injury from the perspective of the immune response and sought to identify effective protective measures against the injury. The findings showed that toll-like receptor 4 (TLR4) was activated after RSV infection in human neuronal SY5Y cells. Furthermore, TLR4 activation induced autophagy and apoptosis in neuronal cells, promoted the formation of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, and increased the secretion of downstream inflammatory cytokines such as interleukin-1β (IL-1β), interleukin-18 (IL-18) and tumour necrosis factor-α (TNF-α). Interestingly, blockade of TLR4 or treatment with exogenous melatonin significantly suppressed TLR4 activation as well as TLR4-mediated apoptosis, autophagy and immune responses. Therefore, we infer that melatonin may act on the TLR4 to ameliorate RSV-induced neuronal injury, which provides a new therapeutic target for RSV infection.

Deletion of a Putative GPI-Anchored Protein-Encoding Gene Aog185 Impedes the Growth and Nematode-Trapping Efficiency of Arthrobotrys oligospora by Disrupting Transmembrane Transport Homeostasis

Nematode-trapping fungus (NTF) is a crucial predator of nematodes, which can capture nematodes by developing specific trapping devices. However, there is limited understanding of the role and mechanism of cell surface proteins attached to the surface of mycelia or trapping cells. Here, the effects of a putative GPI-anchored protein-encoding gene Aog185 on the growth and nematode-trapping efficiency of A. oligospora were investigated. Compared to the wild-type (WT) strain, the ΔAog185 mutant grew more slowly, exhibited a 20% decrease in conidiation, delayed conidial germination, generated fewer traps, attenuated nematode trapping efficiency, and was more sensitive to chemical stressors. Transcriptomic analysis indicated that a large number of transmembrane transport-related genes were differentially expressed between the WT and ΔAog185 mutant strains. Aog185 deletion could damage the intrinsic components of the membrane and cytoskeleton. Specifically, knockout of Aog185 disrupted transmembrane transport homeostasis during the phagocytosis, cell autophagy, and oxidative phosphorylation processes, which were associated with the fusion of cells and organelle membranes, transport of ions and substrates, and energy metabolism. Hence, the putative GPI-anchored protein-encoding gene Aog185 may contribute to the lifestyle switch of NTF and nematode capture, and the effect of Aog185 gene on cell transmembrane transport is considered key to this process. Our findings provide new insights into the mechanism of Aog185 gene during the process of nematode trapping by NTF.

TIPE2 protects cardiomyocytes from ischemia‑reperfusion‑induced apoptosis by decreasing cell autophagy via the mTORC1 signaling pathway

In cardiac ischemia-reperfusion (I/R), autophagy of hyperactivated cardiomyocytes degrades normal proteins and organelles, destroys cells and causes irreversible cell death. The present study aimed to determine the molecular mechanism through which TNF-α-induced protein 8-like protein 2 (TIPE2) regulates cardiomyocyte apoptosis via autophagy in I/R. The results revealed that the number of apoptotic cells and the protein expression levels of TIPE2 in the heart tissue of I/R model mice were significantly increased. In vitro, the overexpression of TIPE2 decreased oxygen glucose deprivation (OGD)-induced autophagy, apoptosis and activation of the mTOR complex 1 (mTORC1) signaling pathway in H9c2 cells. Treatment with the mTORC1 inhibitor not only inhibited the TIPE2-activated mTORC1 signaling pathway, but also increased OGD-induced autophagy and apoptosis of H9c2 cells. In conclusion, the results of the present study revealed that TIPE2 may protect cardiomyocytes from I/R-induced apoptosis by decreasing cell autophagy via the mTORC1 signaling pathway.

The Underexplored Dimensions of Nutritional Hormesis

PURPOSE OF REVIEW

Hormesis is biphasic response wherein low and high doses of chemical and nutrient confer beneficial and toxic effects respectively, typically in a U-shaped manner. Hormesis is intricately related to bioenergetic state of a cell, and therefore, nutrition impacts it. Excessive nutrition can halt the endogenous antioxidant synthesis leading to cytotoxic effects. While low and optimum doses of the same bring about hormetic stimulation that can exalt the antioxidant response and reduce susceptibility towards degenerative diseases. The sirtuin family of proteins is triggered by mild stress of calorie restriction and exerts hormesis. Similarly, several phytochemicals and micronutrients are known to bring about health benefits at optimum dose and deleterious effects at high doses. Despite this attribute, nutritional hormesis is not very well researched upon because the magnitude of hormetic effect observed is generally quite modest. There is no precise regulation of optimal intake of certain foods to witness hormesis and no characterization of any biomarker that reports stress responses at various doses above or below optimal intakes. There is a major gap in research between nutrition and hormesis being affected by sirtuin family of proteins, phytochemicals, and micronutrients.

RECENT FINDINGS

Mild stress of calorie restriction elevates sirtuin protein and effect of sirtuin protein on hormesis has been recently reported. More foods that enhance sirtuin protein, phytochemicals, and micronutrients need to be explored in relation to hormesis and associated health benefits.

Polystyrene microplastics induce mitochondrial damage in mouse GC-2 cells

Microplastics are widely distributed, such as oceans, rivers and the atmosphere, with many opportunities for human exposure and potential health risks. Polystyrene microplastic (PS-MPS) exposure has been found to cause sperm damage to mice; however, the mechanism by which this happens remains unclear. Here, GC-2 cells, a mouse spermatocyte line, were exposed to 5 µm PS-MPS to investigate mitochondrial damage. The results showed that 5 µm PS-MPS decreased ATP content, reduced the mitochondrial membrane potential, damaged the integrity of the mitochondrial genome, and caused an imbalance of homoeostasis between mitochondrial division and fusion. The mitochondrial PINK1/Parkin autophagy pathway was activated. Time-series analysis revealed that PS-MPS damaged the mitochondrial structure through cellular oxidative stress, and mitochondrial function was maintained to some extent after PS-MPS damage. This study revealed the mitochondrial toxicity of polystyrene microplastics, thus providing a basis for understanding the causes of sperm damage by polystyrene microplastics.

Coenzyme Q0 Inhibits NLRP3 Inflammasome Activation through Mitophagy Induction in LPS/ATP-Stimulated Macrophages

Coenzyme Q (CoQ) analogs with a variable number of isoprenoid units have exhibited as anti-inflammatory as well as antioxidant molecules. Using novel quinone derivative CoQ₀ (2,3-dimethoxy-5-methyl-1,4-benzoquinone, zero side chain isoprenoid), we studied its molecular activities against LPS/ATP-induced inflammation and redox imbalance in murine RAW264.7 macrophages. CoQ₀'s non- or subcytotoxic concentration suppressed the NLRP3 inflammasome and procaspase-1 activation, followed by downregulation of IL1β expression in LPS/ATP-stimulated RAW264.7 macrophages. Similarly, treatment of CoQ₀ led to LC3-I/II accumulation and p62/SQSTM1 activation. An increase in the Beclin-1/Bcl-2 ratio and a decrease in the expression of phosphorylated PI3K/AKT, p70 S6 kinase, and mTOR showed that autophagy was activated. Besides, CoQ₀ increased Parkin protein to recruit damaged mitochondria and induced mitophagy in LPS/ATP-stimulated RAW264.7 macrophages. CoQ₀ inhibited LPS/ATP-stimulated ROS generation in RAW264.7 macrophages. Notably, when LPS/ATP-stimulated RAW264.7 macrophages were treated with CoQ₀, Mito-TEMPO (a mitochondrial ROS inhibitor), or N-acetylcysteine (NAC, a ROS inhibitor), there was a significant reduction of LPS/ATP-stimulated NLRP3 inflammasome activation and IL1β expression. Interestingly, treatment with CoQ₀ or Mito-TEMPO, but not NAC, significantly increased LPS/ATP-induced LC3-II accumulation indicating that mitophagy plays a key role in the regulation of CoQ₀-inhibited NLRP3 inflammasome activation. Nrf2 knockdown significantly decreased IL1β expression in LPS/ATP-stimulated RAW264.7 macrophages suggesting that CoQ₀ inhibited ROS-mediated NLRP3 inflammasome activation and IL1β expression was suppressed due to the Nrf2 activation. Hence, this study showed that CoQ₀ might be a promising candidate for the therapeutics of inflammatory disorders due to its effective anti-inflammatory as well as antioxidant properties.

The Association Between Regular Physical Exercise, Sleep Patterns, Fasting, and Autophagy for Healthy Longevity and Well-Being: A Narrative Review

This narrative review of the literature assessed whether regular physical exercise and sleep patterns, fasting and autophagy, altogether can be an adequate strategy for achieving healthy longevity and well-being within different stage of life. There are a large number of studies dealing with well-being and healthy longevity; however, few of them have given us a specific formula for how to live long and healthy. Despite all the advances that have been made to create adequate physical exercise programs, sleep patterns or nutritional protocols, the relation between different types of fasting, nutritional supplementation as well as regular physical exercise and sleep patterns have not yet been satisfactorily resolved to cause the best effects of autophagy and, therefore, well-being and healthy longevity. In this way, future studies should clarify more efficiently the relationship between these variables to understand the association between regular physical exercise, sleep patterns, fasting and autophagy for healthy longevity and well-being.

Ketone body β-hydroxybutyrate is an autophagy-dependent vasodilator

Autophagy has long been associated with longevity, and it is well established that autophagy reverts and prevents vascular deterioration associated with aging and cardiovascular diseases. Currently, our understanding of how autophagy benefits the vasculature is centered on the premise that reduced autophagy leads to the accumulation of cellular debris, resulting in inflammation and oxidative stress, which are then reversed by reconstitution or upregulation of autophagic activity. Evolutionarily, autophagy also functions to mobilize endogenous nutrients in response to starvation. Therefore, we hypothesized that the biosynthesis of the most physiologically abundant ketone body, β-hydroxybutyrate (βHB), would be autophagy dependent and exert vasodilatory effects via its canonical receptor, Gpr109a. To the best of our knowledge, we have revealed for the first time that the biosynthesis of βHB can be impaired by preventing autophagy. Subsequently, βHB caused potent vasodilation via potassium channels but not Gpr109a. Finally, we observed that chronic consumption of a high-salt diet negatively regulates both βHB biosynthesis and hepatic autophagy and that reconstitution of βHB bioavailability prevents high-salt diet–induced endothelial dysfunction. In summary, this work offers an alternative mechanism to the antiinflammatory and antioxidative stress hypothesis of autophagy-dependent vasculoprotection. Furthermore, it reveals a direct mechanism by which ketogenic interventions (e.g., intermittent fasting) improve vascular health.

Caloric Restriction Mimetics in Nutrition and Clinical Trials

The human diet and dietary patterns are closely linked to the health status. High-calorie Western-style diets have increasingly come under scrutiny as their caloric load and composition contribute to the development of non-communicable diseases, such as diabetes, cancer, obesity, and cardiovascular disorders. On the other hand, calorie-reduced and health-promoting diets have shown promising results in maintaining health and reducing disease burden throughout aging. More recently, pharmacological Caloric Restriction Mimetics (CRMs) have gained interest of the public and scientific community as promising candidates that mimic some of the myriad of effects induced by caloric restriction. Importantly, many of the CRM candidates activate autophagy, prolong life- and healthspan in model organisms and ameliorate diverse disease symptoms without the need to cut calories. Among others, glycolytic inhibitors (e.g., D-allulose, D-glucosamine), hydroxycitric acid, NAD+ precursors, polyamines (e.g., spermidine), polyphenols (e.g., resveratrol, dimethoxychalcones, curcumin, EGCG, quercetin) and salicylic acid qualify as CRM candidates, which are naturally available via foods and beverages. However, it is yet unclear how these bioactive substances contribute to the benefits of healthy diets. In this review, we thus discuss dietary sources, availability and intake levels of dietary CRMs. Finally, since translational research on CRMs has entered the clinical stage, we provide a summary of their effects in clinical trials.

Chlorogenic Acid Ameliorates Damage Induced by Fluorene-9-Bisphenol in Porcine Sertoli Cells

4,4′-(9-Fluorenylidene) diphenol (BPFL, also known as BHPF and fluorene-9-bisphenol) is a novel bisphenol A substitute that is used in the plastics industry as an organic synthesis intermediate and is a potential endocrine disruptor. However, the deleterious effects of BPFL on porcine Sertoli cells (SCs) and the possible underlying mechanisms are still unclear. Chlorogenic acid (CA) is a free radical scavenger in the cellular antioxidant system that prevents oxidative damage and apoptosis. In the present research, we found that BPFL induced impairments in porcine SCs in a dose-dependent manner and that CA protected porcine SCs against BPFL exposure-induced impairments. Cell viability, proliferation and apoptosis assay results revealed that BPFL exposure could inhibit porcine SC proliferation and induce apoptosis, while CA supplementation ameliorated the effects of BPFL. Further analysis revealed that BPFL exposure induced oxidative stress, mitochondrial membrane potential dysfunction and DNA damage accumulation. Transcriptome analysis and further real-time quantitative PCR and Western blot results showed that BPFL exposure induced endoplasmic reticulum stress and apoptosis. Supplementation with CA dramatically ameliorated these phenotypes in BPFL-exposed porcine SCs. Overall, the present research reveals the possible underlying mechanisms by which BPFL exposure induced impairments and CA supplementation protected against these impairments in porcine SCs.

Aging-Related Changes in the Ultrastructure of Hepatocytes and Cardiomyocytes of Elderly Mice Are Enhanced in ApoE-Deficient Animals

Biological aging is associated with various morphological and functional changes, yet the mechanisms of these phenomena remain unclear in many tissues and organs. Hyperlipidemia is among the factors putatively involved in the aging of the liver and heart. Here, we analyzed morphological, ultrastructural, and biochemical features in adult (7-month-old) and elderly (17-month-old) mice, and then compared age-related features between wild type (C57Bl/6 strain) and ApoE-deficient (transgenic ApoE^−/−) animals. Increased numbers of damaged mitochondria, lysosomes, and lipid depositions were observed in the hepatocytes of elderly animals. Importantly, these aging-related changes were significantly stronger in hepatocytes from ApoE-deficient animals. An increased number of damaged mitochondria was observed in the cardiomyocytes of elderly animals. However, the difference between wild type and ApoE-deficient mice was expressed in the larger size of mitochondria detected in the transgenic animals. Moreover, a few aging-related differences were noted between wild type and ApoE-deficient mice at the level of plasma biochemical markers. Levels of cholesterol and HDL increased in the plasma of elderly ApoE^−/− mice and were markedly higher than in the plasma of elderly wild type animals. On the other hand, the activity of alanine transaminase (ALT) decreased in the plasma of elderly ApoE^−/− mice and was markedly lower than in the plasma of elderly wild type animals.

Phycocyanin Improves Reproductive Ability in Obese Female Mice by Restoring Ovary and Oocyte Quality

Reproductive dysfunction associated with obesity is increasing among women of childbearing age. Emerging evidence indicates that maternal obesity impairs embryo development and offspring health, and these defects are linked to oxidative stress in the ovary and in oocytes. Phycocyanin (PC) is a biliprotein from Spirulina platensis that possesses antioxidant, anti-inflammatory, and radical-scavenging properties. Our previous studies have shown that PC can reduce reactive oxygen species (ROS) accumulation in oocytes in D-gal-induced aging mice. Here, at the Institute of Cancer Research (ICR) mice fed a high-fat diet (HFD) to model obesity were used to test the effect of PC on reversing the fertility decline caused by obesity. We observed a significant increase in litter size and offspring survival rates after PC administration to obese mice. Further, we found that PC not only ameliorated the level of ovarian antioxidant enzymes, but also reduced the occurrence of follicular atresia in obese female mice. In addition, the abnormal morphology of the spindle-chromosome complex (SCC), and the abnormal mitochondrial distribution pattern in oocytes both recovered. The obesity-related accumulation of ROS, increased number of early apoptotic cells, and the abnormal expression of H3K9me3 in oocytes were all partially reversed after PC administration. In summary, this is the first demonstration that PC can improve fertility by partially increasing ovarian and oocyte quality in obese female mice and provides a new strategy for clinically treating obesity-related infertility in females.

Impacts of Green Tea on Joint and Skeletal Muscle Health: Prospects of Translational Nutrition

Osteoarthritis and sarcopenia are two major joint and skeletal muscle diseases prevalent during aging. Osteoarthritis is a multifactorial progressive degenerative and inflammatory disorder of articular cartilage. Cartilage protection and pain management are the two most important strategies in the management of osteoarthritis. Sarcopenia, a condition of loss of muscle mass and strength, is associated with impaired neuromuscular innervation, the transition of skeletal muscle fiber type, and reduced muscle regenerative capacity. Management of sarcopenia requires addressing both skeletal muscle quantity and quality. Emerging evidence suggests that green tea catechins play an important role in maintaining healthy joints and skeletal muscle. This review covers (i) the prevalence and etiology of osteoarthritis and sarcopenia, such as excessive inflammation and oxidative stress, mitochondrial dysfunction, and reduced autophagy; (ii) the effects of green tea catechins on joint health by downregulating inflammatory signaling mediators, upregulating anabolic mediators, and modulating miRNAs expression, resulting in reduced chondrocyte death, collagen degradation, and cartilage protection; (iii) the effects of green tea catechins on skeletal muscle health via maintaining a dynamic balance between protein synthesis and degradation and boosting the synthesis of mitochondrial energy metabolism, resulting in favorable muscle homeostasis and mitigation of muscle atrophy with aging; and (iv) the current study limitations and future research directions.

Platycodon grandifloras polysaccharides inhibit mitophagy injury induced by Cr (VI) in DF-1 cells

This study aimed to investigate the role of Platycodon grandiflorus polysaccharide (PGPS) in chromium (VI)-induced autophagy in a chicken embryo fibroblast cell lines (DF-1 cells). DF-1 cells were exposed to Cr (VI), PGPS_t, and Cr (VI) + PGPS_t, and their effects on cell viability, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and autophagy-related proteins were examined. The results showed that the cell viability was reduced after Cr (VI) treatment, and 3-MA, CsA or PGPS_t suppressed this decrease. Cr (VI) treatment increased the ROS levels and decreased the MMP, thereby enhancing the expression of mitochondrial autophagy marker proteins (PINK1, Parkin, and LC3-II), inhibiting mitophagy autophagy protein TOMM20 expression, and promoting the degradation of autophagy-related marker p62. These changes led to exceeding mitochondrial autophagy and cell trauma and could be mitigated by PGPS_t. Overall, our research showed that Cr (VI) can induce exceeding mitochondrial autophagy in DF-1 cells, whereas PGPS_t can improve Cr (VI)-induced mitochondrial autophagy by inhibiting ROS and restoring MMP.

Mitophagy in Hypertension-Associated Premature Vascular Aging

Hypertension has been described as a condition of premature vascular aging, relative to actual chronological age. In fact, many factors that contribute to the deterioration of vascular function as we age are accelerated and exacerbated in hypertension. Nonetheless, the precise mechanisms that underlie the aged phenotype of arteries from hypertensive patients and animals remain elusive. Classically, the aged phenotype is the buildup of cellular debris and dysfunctional organelles. One means by which this can occur is insufficient degradation and cellular recycling. Mitophagy is the selective catabolism of damaged mitochondria. Mitochondria are organelles that contribute importantly to the determination of cellular age via their production of reactive oxygen species (ROS; Harman's free radical theory of aging). Therefore, the accumulation of dysfunctional and ROS-producing mitochondria could contribute to the acceleration of vascular age in hypertension. This review will address and critically evaluate the current literature on mitophagy in vascular physiology and hypertension.

Lysosomes, Autophagy, and Hormesis in Cell Physiology, Pathology, and Age-Related Disease

Autophagy has been strongly linked with hormesis, however, it is only relatively recently that the mechanistic basis underlying this association has begun to emerge. Lysosomal autophagy is a group of processes that degrade proteins, protein aggregates, membranes, organelles, segregated regions of cytoplasm, and even parts of the nucleus in eukaryotic cells. These degradative processes are evolutionarily very ancient and provide a survival capability for cells that are stressed or injured. Autophagy and autophagic dysfunction have been linked with many aspects of cell physiology and pathology in disease processes; and there is now intense interest in identifying various therapeutic strategies involving its regulation. The main regulatory pathway for augmented autophagy is the mechanistic target of rapamycin (mTOR) cell signaling, although other pathways can be involved, such as 5'-adenosine monophosphate-activated protein kinase. Mechanistic target of rapamycin is a key player in the many highly interconnected intracellular signaling pathways and is responsible for the control of cell growth among other processes. Inhibition of mTOR (specifically dephosphorylation of mTOR complex 1) triggers augmented autophagy and the search is on the find inhibitors that can induce hormetic responses that may be suitable for treating many diseases, including many cancers, type 2 diabetes, and age-related neurodegenerative conditions.

Cold Atmospheric Plasma and Silymarin Nanoemulsion Activate Autophagy in Human Melanoma Cells

Background: Autophagy is reported as a survival or death-promoting pathway that is highly debatable in different kinds of cancer. Here, we examined the co-effect of cold atmospheric plasma (CAP) and silymarin nanoemulsion (SN) treatment on G-361 human melanoma cells via autophagy induction. Methods: The temperature and pH of the media, along with the cell number, were evaluated. The intracellular glucose level and PI3K/mTOR and EGFR downstream pathways were assessed. Autophagy-related genes, related transcriptional factors, and autophagy induction were estimated using confocal microscopy, flow cytometry, and ELISA. Results: CAP treatment increased the temperature and pH of the media, while its combination with SN resulted in a decrease in intracellular ATP with the downregulation of PI3K/AKT/mTOR survival and RAS/MEK transcriptional pathways. Co-treatment blocked downstream paths of survival pathways and reduced PI3K (2 times), mTOR (10 times), EGFR (5 times), HRAS (5 times), and MEK (10 times). CAP and SN co-treated treatment modulates transcriptional factor expressions (ZKSCAN3, TFEB, FOXO1, CRTC2, and CREBBP) and specific genes (BECN-1, AMBRA-1, MAP1LC3A, and SQSTM) related to autophagy induction. Conclusion: CAP and SN together activate autophagy in G-361 cells by activating PI3K/mTOR and EGFR pathways, expressing autophagy-related transcription factors and genes.

Heparan Sulfate Structure Affects Autophagy, Lifespan, Responses to Oxidative Stress, and Cell Degeneration in Drosophila parkin Mutants

Autophagy is a catabolic process that provides cells with energy and molecular building blocks during nutritional stress. Autophagy also removes misfolded proteins and damaged organelles, a critical mechanism for cellular repair. Earlier work demonstrated that heparan sulfate proteoglycans, an abundant class of carbohydrate-modified proteins found on cell surfaces and in the extracellular matrix, suppress basal levels of autophagy in several cell types during development in Drosophila melanogaster. In studies reported here, we examined the capacity of heparan sulfate synthesis to influence events affected by autophagy, including lifespan, resistance to reactive oxygen species (ROS) stress, and accumulation of ubiquitin-modified proteins in the brain. Compromising heparan sulfate synthesis increased autophagy-dependent processes, evident by extended lifespan, increased resistance to ROS, and reduced accumulation of ubiquitin-modified proteins in the brains of ROS exposed adults. The capacity of altering heparan sulfate biosynthesis to protect cells from injury was also evaluated in two different models of neurodegeneration, overexpression of Presenilin and parkin mutants. Presenilin overexpression in the retina produces cell loss, and compromising heparan sulfate biosynthesis rescued retinal patterning and size abnormalities in these animals. parkin is the fly homolog of human PARK2, one of the genes responsible for juvenile onset Parkinson’s Disease. Parkin is involved in mitochondrial surveillance and compromising parkin function results in degeneration of both flight muscle and dopaminergic neurons in Drosophila. Altering heparan sulfate biosynthesis suppressed flight muscle degeneration and mitochondrial dysmorphology, indicating that activation of autophagy-mediated removal of mitochondria (mitophagy) is potentiated in these animals. These findings provide in vivo evidence that altering the levels of heparan sulfate synthesis activates autophagy and can provide protection from a variety of cellular stressors.

Autophagy-regulating N-heterocycles derivatives as potential anticancer agents

As a double-edged sword, autophagy in cancer cells could either suppress or promote tumorigenesis. Nowadays, more and more natural compounds with autophagy-regulating activities exhibit therapeutic effects against various cancers. N-Heterocycle derivatives plays an important role for discovery new drugs. In this review, we summarize and classify 116 N-heterocycle derivatives with autophagy-regulating activities in the past decade into 12 classes according to structure characteristics. The structural features, bioactivities, mechanism and problems faced in this field are discussed and reported for the first time. Some of these even exhibited outstanding in vivo antitumor activities, including bisaminoquinoline (3), pancratistatin (8), 10-hydroxyevodiamine (18), lycorine (28), piperine (31) and iridium (III) complex (57), which are potential drug candidates for antitumor therapy.

Reconstitution of autophagy ameliorates vascular function and arterial stiffening in spontaneously hypertensive rats

Insufficient autophagy has been proposed as a mechanism of cellular aging, as this leads to the accumulation of dysfunctional macromolecules and organelles. Premature vascular aging occurs in hypertension. In fact, many factors that contribute to the deterioration of vascular function as we age are accelerated in clinical and experimental hypertension. Previously, we have reported decreased autophagy in arteries from spontaneously hypertensive rats (SHRs); however, the effects of restoring autophagic activity on blood pressure and vascular function are currently unknown. We hypothesized that reconstitution of arterial autophagy in SHRs would decrease blood pressure and improve endothelium-dependent relaxation. We treated 14- to 18-wk-old Wistar rats (n = 7 vehicle and n = 8 trehalose) and SHRs (n = 7/group) with autophagy activator trehalose (2% in drinking water) for 28 days. Blood pressure was measured by radiotelemetry, and vascular function and structure were measured in isolated mesenteric resistance arteries (MRAs) using wire and pressure myographs, respectively. Treatment with trehalose had no effect on blood pressure in SHRs; however, isolated MRAs presented enhanced relaxation to acetylcholine, in a cyclooxygenase- and reactive oxygen species-dependent manner. Similarly, trehalose treatment shifted the relaxation to the Rho kinase (ROCK) inhibitor Y-27632 to the right, indicating reduced ROCK activity. Finally, trehalose treatment decreased arterial stiffness as indicated by the slope of the stress-strain curve. Overall these data indicate that reconstitution of arterial autophagy in SHRs improves endothelial and vascular smooth muscle function, which could synergize to prevent stiffening. As a result, restoration of autophagic activity could be a novel therapeutic for premature vascular aging in hypertension.NEW & NOTEWORTHY This work supports the concept that diminished arterial autophagy contributes to premature vascular aging in hypertension and that therapeutic reconstitution of autophagic activity can ameliorate this phenotype. As vascular age is a new clinically used index for cardiovascular risk, understanding this mechanism may assist in the development of new drugs to prevent premature vascular aging in hypertension.

Sodium nitrite negatively affects reproductive ability and offspring survival in female mice

Sodium nitrite (NaNO₂) is an industrial chemical that is frequently used as a food additive to prevent botulism and enhance glossiness, such as curing meat. In addition, in some regions, water source NaNO₂ concentrations exceed standard regulatory levels. Whether the excessive intake of NaNO₂ has toxic effects on female fertility and fetal development remain unknown. In this study, we administered ICR mice control saline, low-dose NaNO₂ (60 mg/kg/day), or high-dose NaNO₂ (120 mg/kg/day) by intragastric gavage for 21 days. We then assessed oocyte morphology, spindle-chromosome dynamics, mitochondrial distribution, ATP content, apoptotic cell numbers, DNA damage levels, histone modifications, reactive oxygen species (ROS) levels, and offspring survival. Results showed that NaNO₂ treatment decreased oocyte number, impaired polar body extrusion, and increased zona pellucida thickness in oocytes. Furthermore, NaNO₂ disrupted MII spindle integrity, caused abnormal mitochondrial distribution, decreased ATP content, and increased levels of ROS and H3K4me2. Moreover, the number of oocytes in early stages of apoptosis and with levels of DNA damage increased in NaNO₂-treated mice along with decreased offspring numbers and survival rates. We demonstrated the negative effects of NaNO₂ on female reproductive abilities in mice.

Mitochondrial quality control mechanisms as molecular targets in cardiac ageing

Cardiovascular disease is the leading cause of morbidity and mortality worldwide. Advancing age is a major risk factor for developing cardiovascular disease because of the lifelong exposure to cardiovascular risk factors and specific alterations affecting the heart and the vasculature during ageing. Indeed, the ageing heart is characterized by structural and functional changes that are caused by alterations in fundamental cardiomyocyte functions. In particular, the myocardium is heavily dependent on mitochondrial oxidative metabolism and is especially susceptible to mitochondrial dysfunction. Indeed, primary alterations in mitochondrial function, which are subsequently amplified by defective quality control mechanisms, are considered to be major contributing factors to cardiac senescence. In this Review, we discuss the mechanisms linking defective mitochondrial quality control mechanisms (that is, proteostasis, biogenesis, dynamics, and autophagy) to organelle dysfunction in the context of cardiac ageing. We also illustrate relevant molecular pathways that might be exploited for the prevention and treatment of age-related heart dysfunction.

Novel Contributors and Mechanisms of Cellular Senescence in Hypertension-Associated Premature Vascular Aging

Hypertension has been described as a condition of premature vascular aging, relative to actual chronological age. In fact, many factors that contribute to the deterioration of vascular function as we age are accelerated in hypertension. Nonetheless, the precise mechanisms that underlie the aged phenotype of arteries from hypertensive patients and animals remain elusive. Cellular senescence is an age-related physiologic process in which cells undergo irreversible growth arrest. Although controlled senescence negatively regulates cell proliferation and promotes tissue regeneration, uncontrolled senescence can contribute to disease pathogenesis by presenting the senescence-associated secretory phenotype, in which molecules such as proinflammatory cytokines, matrix metalloproteases, and reactive oxygen species are released into tissue microenvironments. This review will address and critically evaluate the current literature on the role of cellular senescence in hypertension, with particular emphasis on cells types that mediate and modulate vascular function and structure.

Autophagy in Skin Diseases

Autophagy, or self-eating, is an evolutionarily conserved process in which cytosol and organelles are sequestered within double-membrane vesicles that deliver the contents to the lysosome/vacuole for the degradation and recycling of cytoplasmic components in eukaryotes. It is well recognized that autophagy plays an important role in maintaining cellular homeostasis under physiological and pathophysiological con-ditions and the upregulation of autophagy may serve as an adaptive process to provide nutrients and energy when under stresses. Recently, studies have illustrated that autophagy is intricately related to skin diseases. This review provides a brief synopsis of the process of autophagy and aims to elucidate the roles of autophagy in different skin diseases and to highlight the need for increased research in the field.

Extensive mechanical tension promotes annulus fibrosus cell senescence through suppressing cellular autophagy

Background: Mechanical load contributes a lot to the initiation and progression of disc degeneration. Annulus fibrosus (AF) cell biology under mechanical tension remains largely unclear.Objective: The present study was aimed to investigate AF cell senescence under mechanical tension and the potential role of autophagy.Methods: Rat AF cells were cultured and experienced different magnitudes (5% elongation and 20% elongation) of mechanical tension for 12 days. Control AF cells were kept static. Cell proliferation, telomerase activity, cell cycle fraction, and expression of senescence-related molecules (p16 and p53) and matrix macromolecules (aggrecan and collagen I) were analyzed to evaluate cell senescence. In addition, expression of Beclin-1 and LC3, and the ratio of LC3-II to LC3-I were analyzed to investigate cell autophagy.Results: Compared with the control group and 5% tension group, 20% tension group significantly decreased cell proliferation potency and telomerase activity, increased G1/G0 phase fraction, and up-regulated gene/protein expression of p16 and p53, whereas down-regulated gene/protein expression of aggrecan and collagen I. In addition, autophagy-related parameters such as gene/protein expression of Beclin-1 and LC3, and the ratio of LC3-II to LC3-I, were obviously suppressed in the 20% tension group.Conclusion: High mechanical tension promotes AF cell senescence though suppressing cellular autophagy. The present study will help us to better understand AF cell biology under mechanical tension and mechanical load-related disc degeneration.

HMGB1/autophagy pathway mediates the atrophic effect of TGF-β1 in denervated skeletal muscle

Background

Transforming growth factor beta 1 (TGF-β1) is a classical modulator of skeletal muscle and regulates several processes, such as myogenesis, regeneration and muscle function in skeletal muscle diseases. Skeletal muscle atrophy, characterized by the loss of muscle strength and mass, is one of the pathological conditions regulated by TGF-β1, but the underlying mechanism involved in the atrophic effects of TGF-β1 is not fully understood.

Methods

Mice sciatic nerve transection model was created and gastrocnemius were analysed by western blot, immunofluorescence staining and fibre diameter quantification after 2 weeks. Exogenous TGF-β1 was administrated and high-mobility group box-1 (HMGB1), autophagy were blocked by siRNA and chloroquine (CQ) respectively to explore the mechanism of the atrophic effect of TGF-β1 in denervated muscle. Similar methods were performed in C2C12 cells.

Results

We found that TGF-β1 was induced in denervated muscle and it could promote atrophy of skeletal muscle both in vivo and in vitro, up-regulated HMGB1 and increased autophagy activity were also detected in denervated muscle and were further promoted by exogenous TGF-β1. The atrophic effect of TGF-β1 could be inhibited when HMGB1/autophagy pathway was blocked.

Conclusions

Thus, our data revealed that TGF-β1 is a vital regulatory factor in denervated skeletal muscle in which HMGB1/ autophagy pathway mediates the atrophic effect of TGF-β1. Our findings confirmed a new pathway in denervation-induced skeletal muscle atrophy and it may be a novel therapeutic target for patients with muscle atrophy after peripheral nerve injury.

Electronic supplementary material

The online version of this article (10.1186/s12964-018-0310-6) contains supplementary material, which is available to authorized users.

Nonselective autophagy reduces mitochondrial content during starvation in Caenorhabditis elegans

Starvation significantly alters cellular physiology, and signs of aging have been reported to occur during starvation. Mitochondria are essential to the regulation of cellular energetics and aging. We sought to determine whether mitochondria exhibit signs of aging during starvation and whether quality control mechanisms regulate mitochondrial physiology during starvation. We describe effects of starvation on mitochondria in the first and third larval stages of the nematode Caenorhabditis elegans. When starved, C. elegans larvae enter developmental arrest. We observed fragmentation of the mitochondrial network, a reduction in mitochondrial DNA (mtDNA) copy number, and accumulation of DNA damage during starvation-induced developmental arrest. Mitochondrial function was also compromised by starvation. Starved worms had lower basal, maximal, and ATP-linked respiration. These observations are consistent with reduced mitochondrial quality, similar to mitochondrial phenotypes during aging. Using pharmacological and genetic approaches, we found that worms deficient for autophagy were short-lived during starvation and recovered poorly from extended starvation, indicating sensitivity to nutrient stress. Autophagy mutants unc-51/Atg1 and atg-18/Atg18 maintained greater mtDNA content than wild-type worms during starvation, suggesting that autophagy promotes mitochondrial degradation during starvation. unc-51 mutants also had a proportionally smaller reduction in oxygen consumption rate during starvation, suggesting that autophagy also contributes to reduced mitochondrial function. Surprisingly, mutations in genes involved in mitochondrial fission and fusion as well as selective mitophagy of damaged mitochondria did not affect mitochondrial content during starvation. Our results demonstrate the profound influence of starvation on mitochondrial physiology with organismal consequences, and they show that these physiological effects are influenced by autophagy.

Wild-type p53-modulated autophagy and autophagic fibroblast apoptosis inhibit hypertrophic scar formation

Hypertrophic scarring is a serious fibrotic skin disease, and the abnormal activation of hypertrophic scar fibroblasts (HSFs) intensifies its pathogenesis. Our previous studies have demonstrated that the dysregulation of autophagy in HSFs is associated with fibrosis. However, knowledge regarding the regulation of HS fibrosis by p53-modulated autophagy is limited. Here, we investigated the effect of p53-modulated autophagy on HS fibrosis. The overexpression of wtp53 (Adp53) promoted autophagic capacity and inhibited collagen and α-SMA expression in HSFs. In contrast, LC3 (AdLC3) overexpression did not suppress Col 1, Col 3, or α-SMA expression, but LC3 (shLC3) knockdown downregulated collagen expression. Adp53-modulated autophagy altered Bcl-2 and Bcl-xL expression, but AdLC3 affected only Bcl-xL expression. Silencing Bcl-xL suppressed collagen expression, but autophagy was also inhibited. Flow cytometry showed that the silencing of Bcl-2 (sibcl-2), Bcl-xL (sibcl-xL), and Adp53 significantly increased apoptosis in the HSFs. Therefore, wtp53 inhibited fibrosis in the HSFs by modulating autophagic HSF apoptosis; moreover, the inhibition of autophagy by sibcl-xL had antifibrotic effects. In addition, treatment with Adp53, AdLC3, shLC3, sibcl-2, and sibcl-xL reduced scar formation in a rabbit ear scar model. These data confirm that wtp53-modulated autophagy and autophagic HSF apoptosis can serve as potential molecular targets for HS therapy.

Neurodegenerative Diseases: Regenerative Mechanisms and Novel Therapeutic Approaches

Regeneration refers to regrowth of tissue in the central nervous system. It includes generation of new neurons, glia, myelin, and synapses, as well as the regaining of essential functions: sensory, motor, emotional and cognitive abilities. Unfortunately, regeneration within the nervous system is very slow compared to other body systems. This relative slowness is attributed to increased vulnerability to irreversible cellular insults and the loss of function due to the very long lifespan of neurons, the stretch of cells and cytoplasm over several dozens of inches throughout the body, insufficiency of the tissue-level waste removal system, and minimal neural cell proliferation/self-renewal capacity. In this context, the current review summarized the most common features of major neurodegenerative disorders; their causes and consequences and proposed novel therapeutic approaches.

Detecting senescent fate in mesenchymal stem cells: a combined cytofluorimetric and ultrastructural approach

Senescence can impair the therapeutic potential of stem cells. In this study, senescence-associated morphofunctional changes in periosteum-derived progenitor cells (PDPCs) from old and young individuals were investigated by combining cytofluorimetry, immunohistochemistry, and transmission electron microscopy. Cell cycle analysis demonstrated a large number of G0/G1 phase cells in PDPCs from old subjects and a progressive accumulation of G0/G1 cells during passaging in cultures from young subjects. Cytofluorimetry documented significant changes in light scattering parameters and closely correlated with the ultrastructural features, especially changes in mitochondrial shape and autophagy, which are consistent with the mitochondrial-lysosomal axis theory of ageing. The combined morphological, biofunctional, and ultrastructural approach enhanced the flow cytometric study of PDPC ageing. We speculate that impaired autophagy, documented in replicative senescent and old PDPCs, reflect a switch from quiescence to senescence. Its demonstration in a tissue with limited turnover-like the cambium layer of the periosteum, where reversible quiescence is the normal stem cell state throughout life-adds a new piece to the regenerative medicine jigsaw in an ageing society.

Environmental hormesis and its fundamental biological basis: Rewriting the history of toxicology

It has long been debated whether a little stress may be "good" for you. Extensive evidence has now sufficiently accumulated demonstrating that low doses of a vast range of chemical and physical agents induce protective/beneficial effects while the opposite occurs at higher doses, a phenomenon known as hormesis. Low doses of environmental agents have recently induced autophagy, a critical adaptive response that protects essentially all cell types, as well as being transgenerational via epigenetic mechanisms. These collective findings highlight a generalized and substantial ongoing dose-response transformation with significant implications for disease biology and clinical applications, challenging the history and practice of toxicology and pharmacology along with an appeal to stake holders to reexamine the process of risk assessment, with the goal of optimizing public health rather than simply avoiding harm.

Stem cell rejuvenation and the role of autophagy in age retardation by caloric restriction: An update

Stem cells being pluripotent in nature can differentiate into a wide array of specific cells and asymmetrically divide to produce new ones but may undergo aging by themselves. Aging has both quantitative and qualitative effects on stem cells, and could eventually restrain them from replenishing into progenitor cells. Reactive oxygen species (ROS) accumulated in the aging cells could not only block the cell cycle but also affect autophagy by damaging the mitochondria. Autophagy could eliminate redundant production of ROS in aging stem cells and helps to maintain the proliferation capacity by restraining the expression of p16^INK4a. Current studies showed that improving autophagy could restore the regenerative ability of aging stem cells. Therefore, it is important for an organism to maintain the appropriate autophagy. Caloric restriction (CR) was shown to retard the stem cell aging by a certain basic level of autophagy, suggesting that CR was an effective way to extend longevity in mammals. However, little is known about the underlying mechanisms. In this review, we tried to explore the molecular mechanisms on how CR induces appropriate autophagy to restore aging stem cell regenerative ability.

Long-term effects of low-dose mouse liver irradiation involve ultrastructural and biochemical changes in hepatocytes that depend on lipid metabolism

The aim of the study was to investigate long-term effects of radiation on the (ultra)structure and function of the liver in mice. The experiments were conducted on wild-type C57BL/6J and apolipoprotein E knock-out (ApoE^-/-) male mice which received a single dose (2 or 8 Gy) of X-rays to the heart with simultaneous exposure of liver to low doses (no more than 30 and 120 mGy, respectively). Livers were collected for analysis 60 weeks after irradiation and used for morphological, ultrastructural, and biochemical studies. The results show increased damage to mitochondrial ultrastructure and lipid deposition in hepatocytes of irradiated animals as compared to non-irradiated controls. Stronger radiation-related effects were noted in ApoE^-/- mice than wild-type animals. In contrast, radiation-related changes in the activity of lysosomal hydrolases, including acid phosphatase, β-glucuronidase, N-acetyl-β-D-hexosaminidase, β-galactosidase, and α-glucosidase, were observed in wild type but not in ApoE-deficient mice, which together with ultrastructural picture suggests a higher activity of autophagy in ApoE-proficient animals. Irradiation caused a reduction of plasma markers of liver damage in wild-type mice, while an increased level of hepatic lipase was observed in plasma of ApoE-deficient mice, which collectively indicates a higher resistance of hepatocytes from ApoE-proficient animals to radiation-mediated damage. In conclusion, liver dysfunctions were observed as late effects of irradiation with an apparent association with malfunction of lipid metabolism.

Estrogen and/or Estrogen Receptor α Inhibits BNIP3-Induced Apoptosis and Autophagy in H9c2 Cardiomyoblast Cells

The process of autophagy in heart cells maintains homeostasis during cellular stress such as hypoxia by removing aggregated proteins and damaged organelles and thereby protects the heart during the times of starvation and ischemia. However, autophagy can lead to substantial cell death under certain circumstances. BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3), a hypoxia-induced marker, has been shown to induce both autophagy and apoptosis. A BNIP3-docked organelle, e.g., mitochondria, also determines whether autophagy or apoptosis will take place. Estrogen (E2) and estrogen receptor (ER) alpha (ERα) have been shown to protect the heart against mitochondria-dependent apoptosis. The aim of the present study is to investigate the mechanisms by which ERα regulates BNIP3-induced apoptosis and autophagy, which is associated with hypoxic injury, in cardiomyoblast cells. An in vitro model to mimic hypoxic injury in the heart by engineering H9c2 cardiomyoblast cells to overexpress BNIP3 was established. Further, the effects of E2 and ERα in BNIP3-induced apoptosis and autophagy were determined in BNIP3 expressing H9c2 cells. Results from TUNEL assay and Immunoflourecense assay for LC3 puncta formation, respectively, revealed that ERα/E2 suppresses BNIP3-induced apoptosis and autophagy. The Western blot analysis showed ERα/E2 decreases the protein levels of caspase 3 (apoptotic marker), Atg5, and LC3-II (autophagic markers). Co-immunoprecipitation of BNIP3 and immunoblotting of Bcl-2 and Rheb showed that ERα reduced the interaction between BNIP3 and Bcl-2 or Rheb. The results confirm that ERα binds to BNIP3 causing a reduction in the levels of functional BNIP3 and thereby inhibits cellular apoptosis and autophagy. In addition, ERα attenuated the activity of the BNIP3 promoter by binding to SP-1 or NFκB sites.

Nutraceutical or Pharmacological Potential of Moringa oleifera Lam

Moringa oleifera Lam. (M. oleifera), which belongs to the Moringaceae family, is a perennial deciduous tropical tree, and native to the south of the Himalayan Mountains in northern India. M. oleifera is rich in proteins, vitamin A, minerals, essential amino acids, antioxidants, and flavonoids, as well as isothiocyanates. The extracts from M. oleifera exhibit multiple nutraceutical or pharmacological functions including anti-inflammatory, antioxidant, anti-cancer, hepatoprotective, neuroprotective, hypoglycemic, and blood lipid-reducing functions. The beneficial functions of M. oleifera are strongly associated with its phytochemicals such as flavonoids or isothiocyanates with bioactivity. In this review, we summarize the research progress related to the bioactivity and pharmacological mechanisms of M. oleifera in the prevention and treatment of a series of chronic diseases-including inflammatory diseases, neuro-dysfunctional diseases, diabetes, and cancers-which will provide a reference for its potential application in the prevention and treatment of chronic diseases or health promotion.

A novel modelling mechanism of PAEL receptor and GABARAPL2 interaction involved in Parkinson's disease

Parkin associated endothelin like receptor (PAELR) is G-protein coupled and ubiquitinated by parkin, promoting its degradation. In autosomal recessive Parkinson's disease, mutations in parkin lead to PAELR aggregation in the endoplasmic reticulum (ER), ER stress, neurotoxicity and cell death. We have identified previously that the protein kinase C interacting protein (PICK1) interacts with and regulates the expression and cell toxicity of PAELR. Here, we experimentally identify and provide in-silico modelling of a novel interaction between PAELR and GABARAPL2 (γ-aminobutyrate type A receptor associated protein like 2), which is an autophagosome-specific Ub-like protein implicated in vesicle trafficking and autophagy. We show that the family of GABARAPs interact with the carboxy terminal (ct) of PAELR and find the cysteine rich region (-CCCCCC-EEC) of ct-PAELR interacts with the GABA_A binding site of GABARAPL2. This interaction is modelled by in-slico analysis and confirmed using affinity chromatography, showing Myc-tagged GABARAPL2 is retained by a GST fusion of the ct-PAELR. We also demonstrate that transient transfection of GABARAPL2 in HEK293 cells reduces PAELR expression. This study supports the idea that protein levels of PAELR are likely regulated by a multitude of proteins including parkin, PICK1 and GABARAPL2 via mechanisms that include ubiquitination, proteasomal degradagtion and autophagy.

Crosstalk of clock gene expression and autophagy in aging

Autophagy and the circadian clock counteract tissue degeneration and support longevity in many organisms. Accumulating evidence indicates that aging compromises both the circadian clock and autophagy but the mechanisms involved are unknown. Here we show that the expression levels of transcriptional repressor components of the circadian oscillator, most prominently the human Period homologue PER2, are strongly reduced in primary dermal fibroblasts from aged humans, while raising the expression of PER2 in the same cells partially restores diminished autophagy levels. The link between clock gene expression and autophagy is corroborated by the finding that the circadian clock drives cell-autonomous, rhythmic autophagy levels in immortalized murine fibroblasts, and that siRNA-mediated downregulation of PER2 decreases autophagy levels while leaving core clock oscillations intact. Moreover, the Period homologue lin-42 regulates autophagy and life span in the nematode Caenorhabditis elegans, suggesting an evolutionarily conserved role for Period proteins in autophagy control and aging. Taken together, this study identifies circadian clock proteins as set-point regulators of autophagy and puts forward a model, in which age-related changes of clock gene expression promote declining autophagy levels.

The crosstalk between autophagic and endo-/exosomal pathways in antigen processing for MHC presentation in anticancer T cell immune responses

T cells recognize antigen fragments from proteolytic products that are presented to them in the form of peptides on major histocompatibility complex (MHC) molecules, which is crucial for the T cell to identify infected or transformed cells. Autophagy, a process that delivers cytoplasmic constituents for lysosomal degradation, has been observed to provide a substantial source of intra- and extracellular antigens for MHC presentation to T cells, which will impact the tumor-specific immune response. Meanwhile, extracellular components are transported to cytoplasm for the degradation/secretion process by the endo-/exosomal pathway and are thus involved in multiple physiological and pathological processes, including immune responses. Autophagy and endo-/exosomal pathways are intertwined in a highly intricate manner and both are closely involved in antigen processing for MHC presentation; thus, we propose that they may coordinate in antigen processing and presentation in anticancer T cell immune responses. In this article, we discuss the molecular and functional crosstalk between autophagy and endo-/exosomal pathways and their contributions to antigen processing for MHC presentation in anticancer T cell immune responses.

Autophagy protein LC3 regulates the fibrosis of hypertrophic scar by controlling Bcl-xL in dermal fibroblasts

Hypertrophic scar (HS) is a serious skin fibrotic disease characterized by excessive hypercellularity and extracellular matrix (ECM) component deposition. Autophagy is a tightly regulated physiological process essential for cellular maintenance, differentiation, development and homeostasis. However, during the formation of HS, whether and how autophagy is regulated in dermal fibroblasts are still far from elucidated. Here we detected the autophagic capacity in HS and normal skin (NS) counterparts, explored and verified the key regulatory molecules of autophagy in HS-derived fibroblasts (HSFs), and validated the data using rabbit ear scar model. Transmission electron microscopy (TEM) and immunostaining data showed that LC3-positive cells and autophagosomes in HS/HSFs were more intensive relative to those in NS/NSFs groups. Knockdown of LC3 (shLC3) could significantly block the expressionof type I collagen (Col 1, p < 0.01) and type III collagen (Col 3, p < 0.01) and thus inhibit the fibrosis of HSFs. shLC3 resistant to autophagy was shown to be Bcl-xL-, not Bcl-2-dependent, and silencing of Bcl-xL (sibcl-xL) significantly increased apoptosis of HSFs (p < 0.01). Immunofluorescence results showed that instead of inhibiting α-SMA protein expression, shLC3 could change its architecture arrangement in HSFs. sibcl-xL showed that Bcl-xL was a key signaling molecule involved in HSFs autophagy. More importantly, both shLC3 and sibcl-xL obviously improved the appearance and architecture of the rabbit ear scar, and reduced scar formation on the rabbit ear. Therefore, the aberration of LC3 protein processing compromised autophagy in HS might associate with its pathogenesis in wound repair. LC3 regulated HS fibrosis by controlling the expression of Bcl-xL in HSFs. Thus, Bcl-xL might serve as a potential molecular target, providing a novel strategy for HS therapy.

Autophagy and Human Neurodegenerative Diseases-A Fly's Perspective

Neurodegenerative diseases in humans are frequently associated with prominent accumulation of toxic protein inclusions and defective organelles. Autophagy is a process of bulk lysosomal degradation that eliminates these harmful substances and maintains the subcellular environmental quality. In support of autophagy's importance in neuronal homeostasis, several genetic mutations that interfere with autophagic processes were found to be associated with familial neurodegenerative disorders. In addition, genetic mutations in autophagy-regulating genes provoked neurodegenerative phenotypes in animal models. The Drosophila model significantly contributed to these recent developments, which led to the theory that autophagy dysregulation is one of the major underlying causes of human neurodegenerative disorders. In the current review, we discuss how studies using Drosophila enhanced our understanding of the relationship between autophagy and neurodegenerative processes.

Chemical screening identifies ROCK as a target for recovering mitochondrial function in Hutchinson-Gilford progeria syndrome

Hutchinson-Gilford progeria syndrome (HGPS) constitutes a genetic disease wherein an aging phenotype manifests in childhood. Recent studies indicate that reactive oxygen species (ROS) play important roles in HGPS phenotype progression. Thus, pharmacological reduction in ROS levels has been proposed as a potentially effective treatment for patient with this disorder. In this study, we performed high-throughput screening to find compounds that could reduce ROS levels in HGPS fibroblasts and identified rho-associated protein kinase (ROCK) inhibitor (Y-27632) as an effective agent. To elucidate the underlying mechanism of ROCK in regulating ROS levels, we performed a yeast two-hybrid screen and discovered that ROCK1 interacts with Rac1b. ROCK activation phosphorylated Rac1b at Ser71 and increased ROS levels by facilitating the interaction between Rac1b and cytochrome c. Conversely, ROCK inactivation with Y-27632 abolished their interaction, concomitant with ROS reduction. Additionally, ROCK activation resulted in mitochondrial dysfunction, whereas ROCK inactivation with Y-27632 induced the recovery of mitochondrial function. Furthermore, a reduction in the frequency of abnormal nuclear morphology and DNA double-strand breaks was observed along with decreased ROS levels. Thus, our study reveals a novel mechanism through which alleviation of the HGPS phenotype is mediated by the recovery of mitochondrial function upon ROCK inactivation.

Integrin αvβ5 inhibition protects against ischemia-reperfusion-induced lung injury in an autophagy-dependent manner

Integrin αvβ5 mediates pulmonary endothelial barrier function and acute lung injury (LI), but its roles in cell apoptosis and autophagy are unclear. Thus, the aims of this study were to investigate the significance of αvβ5 in ischemia-reperfusion (I/R)-induced apoptosis and LI and to explore the relationship between αvβ5 and autophagy. Human pulmonary microvascular endothelial cells (HPMVECs) were pretreated with an αvβ5-blocking antibody (ALULA) and challenged with oxygen-glucose deprivation/oxygen-glucose restoration, which mimics I/R; then, cellular autophagy and apoptosis were detected, and cell permeability was assessed. In vivo, mice were pretreated with the autophagy inhibitor chloroquine (CLQ), followed by treatment with ALULA. The mice then underwent operative lung I/R. LI was assessed by performing a pathological examination, calculating the wet/dry lung weight ratio and detecting the bronchial alveolar lavage fluid (BALF) protein concentration. αvβ5 inhibition promoted HPMVEC autophagy under I/R in vitro, alleviated cell permeability, decreased the apoptosis ratio, and activated caspase-3 expression. These outcomes were significantly diminished when autophagy was inhibited with a small-interfering RNA construct targeting autophagy-related gene 7 (siATG7). Moreover, ALULA pretreatment alleviated I/R-induced LI (I/R-LI), which manifested as a decreased wet/dry lung weight ratio, an altered BALF protein concentration, and lung edema. Preinhibiting autophagy with CLQ, however, eliminated the protective effects of ALULA on I/R-LI. Therefore, inhibiting αvβ5 effectively ameliorated I/R-induced endothelial cell apoptosis and I/R-LI. This process was dependent on improved autophagy and its inhibitory effects on activated caspase-3.

AMPK and vacuole-associated Atg14p orchestrate μ-lipophagy for energy production and long-term survival under glucose starvation

Dietary restriction increases the longevity of many organisms, but the cell signaling and organellar mechanisms underlying this capability are unclear. We demonstrate that to permit long-term survival in response to sudden glucose depletion, yeast cells activate lipid-droplet (LD) consumption through micro-lipophagy (µ-lipophagy), in which fat is metabolized as an alternative energy source. AMP-activated protein kinase (AMPK) activation triggered this pathway, which required Atg14p. More gradual glucose starvation, amino acid deprivation or rapamycin did not trigger µ-lipophagy and failed to provide the needed substitute energy source for long-term survival. During acute glucose restriction, activated AMPK was stabilized from degradation and interacted with Atg14p. This prompted Atg14p redistribution from ER exit sites onto liquid-ordered vacuole membrane domains, initiating µ-lipophagy. Our findings that activated AMPK and Atg14p are required to orchestrate µ-lipophagy for energy production in starved cells is relevant for studies on aging and evolutionary survival strategies of different organisms.

DOI:http://dx.doi.org/10.7554/eLife.21690.001

Inhibition of Beclin-1-Mediated Autophagy by MicroRNA-17-5p Enhanced the Radiosensitivity of Glioma Cells

The role of miRNAs in the radiosensitivity of glioma cells and the underlying mechanism is still far from clear. In the present study, we detected six downregulated and seven upregulated miRNAs in the serum after radiotherapy compared with paired serum samples before radiotherapy via miRNA panel PCR. Among these, miR-17-5p was highly reduced (fold change = −4.21). Further, we validated the levels of miR-17-5p in all serum samples with qRT-PCR. In addition, statistical analysis suggested that a reduced miR-17-5P level was positively associated with advanced clinical stage of glioma, incidence of relapse, and tumor differentiation. Moreover, we provided evidence that irradiation markedly activated autophagy and decreased miR-17-5p in the glioma cell line. Further, we demonstrated that irradiation-induced autophagy activation was mediated by beclin-1, and downregulation of beclin-1 via siRNA significantly abolished the irradiation-activated autophagy. Interestingly, we demonstrated that miR-17-5p could directly target beclin-1 via luciferase gene reporter assay. Exotic expression of miRNA-17-5p decreased autophagy activity in vitro. In nude mice, miRNA-17-5p upregulation sensitized the xenograft tumor to irradiation and suppressed irradiation-induced autophagy. Finally, pharmacal inhibition of autophagy markedly enhanced the cytotoxicity of irradiation in RR-U87 cells.

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.