Autophagy and Mitophagy in Cellular Damage Control

Mitochondrial dysfunction associated with autophagy and mitophagy in cerebrospinal fluid cells of patients with delayed cerebral ischemia following subarachnoid hemorrhage

Decreased mitochondrial membrane potential in cerebrospinal fluid (CSF) was observed in patients with subarachnoid hemorrhage (SAH) accompanied by delayed cerebral ischemia (DCI). However, whether abnormal mechanisms of mitochondria are associated with the development of DCI has not been reported yet. Under cerebral ischemia, mitochondria can transfer into the extracellular space. Mitochondrial dysfunction can aggravate neurologic complications. The objective of this study was to evaluate whether mitochondrial dysfunction might be associated with autophagy and mitophagy in CSF cells to provide possible insight into DCI pathogenesis. CSF samples were collected from 56 SAH patients (DCI, n = 21; and non-DCI, n = 35). We analyzed CSF cells using autophagy and mitophagy markers (DAPK1, BNIP3L, BAX, PINK1, ULK1, and NDP52) via qRT-PCR and western blotting of proteins (BECN1, LC3, and p62). Confocal microscopy and immunogold staining were performed to demonstrate the differentially expression of markers within dysfunctional mitochondria. Significant induction of autophagic flux with accumulation of autophagic vacuoles, increased expression of BECN1, LC3-II, and p62 degradation were observed during DCI. Compared to non-DCI patients, DCI patients showed significantly increased mRNA expression levels (2^-ΔCt) of DAPK1, BNIP3L, and PINK1, but not BAX, ULK1, or NDP52. Multivariable logistic regression analysis revealed that Hunt and Hess grade ≥ IV (p = 0.023), DAPK1 (p = 0.003), and BNIP3L (p = 0.039) were related to DCI. Increased mitochondrial dysfunction associated with autophagy and mitophagy could play an important role in DCI pathogenesis.

Copper impair autophagy on zebrafish (Danio rerio) gill epithelium

Copper (Cu) is an essential element for organism's metabolism, being controversially listed as a priority pollutant. Importantly, the toxicity of Cu has been linked to several cell death pathways. Thus, this study aimed to assess if macroautophagic pathways are triggered by Cu in zebrafish gill, the main target of waterborne pollutants. The electron microscopy findings indicated that Cu induced profound impacts on zebrafish gill structure and functions, being this tissue a biomarker sensitive enough to indicate early toxic effects. The findings also support a clear impairment of autophagy, througth the absence of phagossomes and the significant down-regulation mRNA transcript levels of microtubule-associated protein light chain 3 (LC3). The reduction of LC3 levels was often associated to an increase of apoptotic activation, indicating that the inhibition of macroautophagy triggers apoptosis in zebrafish gills. This study highlighted that the autophagic down-regulation might be affected through the activation of other cell death signaling pathway.

University of Alabama at Birmingham Nathan Shock Center: comparative energetics of aging

The UAB Nathan Shock Center focuses on comparative energetics and aging. Energetics, as defined for this purpose, encompasses the causes, mechanisms, and consequences of the acquisition, storage, and use of metabolizable energy. Comparative energetics is the study of metabolic processes at multiple scales and across multiple species as it relates to health and aging. The link between energetics and aging is increasingly understood in terms of dysregulated mitochondrial function, altered metabolic signaling, and aberrant nutrient responsiveness with increasing age. The center offers world-class expertise in comprehensive, integrated energetic assessment and analysis from the level of the organelle to the organism and across species from the size of worms to rats as well as state-of-the-art data analytics. The range of services offered by our three research cores, (1) The Organismal Energetics Core, (2) Mitometabolism Core, and (3) Data Analytics Core, is described herein.

Curcumin Attenuates Cerebral Ischemia-reperfusion Injury Through Regulating Mitophagy and Preserving Mitochondrial Function

BACKGROUND

Curcumin, the complex extracted from the traditional edible herb, has a wide range of pharmacological effects. A great deal of studies has demonstrated that curcumin could protect against cerebral ischemia-reperfusion (I/R) injury. In the present study, we aimed to test the hypothesis that curcumin reduces brain damage via regulating mitophagy and preserving mitochondrial function. To clarify the potential effect and mechanism of curcumin on cerebral I/R, we utilize MCAO followed by reperfusion rats and OGD/R neurons as cerebral I/R in vivo and in vitro, respectively.

METHODS

We determined the cellular ROS levels and mitochondrial function, including mitochondrial membrane potential (MMP), ATP levels, state 3 respiration and state 4 respiration. We also detected the levels of mitophagy by immunofluorescent staining and western blotting.

RESULTS

Results found that curcumin decreased neurological deficit scores, infarct volume and morphological changes of neurons in rats after brain I/R injury. Curcumin also reduced the levels of ROS while increased MMP, ATP levels and state 3 respiration to prevent the impairment of mitochondrial function from cerebral I/R. Furthermore, curcumin enhanced the co-localization of LC3B and mitochondrial marker VDAC1, the ratio of LC3-II to LC3-I, improving cerebral I/Rinduced mitophagy.

CONCLUSION

In conclusion, our results suggest that curcumin protects against cerebral I/R injury by improving mitophagy and preserving mitochondrial function.

Melatonin Represses Mitophagy to Protect Mouse Granulosa Cells from Oxidative Damage

Various environmental stimuli, including oxidative stress, could lead to granulosa cell (GC) death through mitophagy. Recently, it was reported that melatonin (MEL) has a significant effect on GC survival during oxidative damage. Here, we found that MEL inhibited oxidative stress-induced mitophagy to promote GC survival. The loss of cell viability upon H₂O₂ exposure was significantly restored after MEL treatment. Concomitantly, MEL inhibited the activation of mitophagy during oxidative stress. Notably, blocking mitophagy repressed GC death caused by oxidative stress. However, MEL cannot further restore viability of cells treated with mitophagy inhibitor. Moreover, PTEN-induced putative kinase 1 (PINK1), a mitochondrial serine/threonine-protein kinase, was inhibited by MEL during oxidative stress. As a result, the E3 ligase Parkin failed to translocate to mitochondria, leading to impaired mitochondria clearance. Using RNAi to knock down PINK1 expression, we further verified the role of the MEL-PINK1-Parkin (MPP) pathway in maintaining GC survival by suppressing mitophagy. Our findings not only clarify the protective mechanisms of MEL against oxidative damage in GCs, but also extend the understanding about how circadian rhythms might influence follicles development in the ovary. These findings reveal a new mechanism of melatonin in defense against oxidative damage to GCs by repressing mitophagy, which may be a potential therapeutic target for anovulatory disorders.

The crosstalk between mitochondrial dysfunction and endoplasmic reticulum stress promoted ATF4-mediated mitophagy induced by hexavalent chromium

Chromium (Cr) compounds are markedly toxic and carcinogenic. Previously, we found that Cr (VI) induced autophagy in A549 cells. Here, the effect of mitochondrial dysfunction and endoplasmic reticulum (ER) stress on inducing mitophagy was investigated in both A549 and H1299 cells. Exposure to Cr (VI) for 6 h significantly enhanced reactive oxygen species (ROS) production and reduced mitochondrial membrane potential (MMP). Transmission electron microscopy showed that Cr (VI) induced mitochondrial morphological changes, such as, mitochondrial swelling and vacuolization. The elevated expression of GRP78 and p-PERK suggested that Cr (VI) resulted in ER stress. Both mitochondrial dysfunction and ER stress played an important role in Cr (VI)-induced mitophagy, as the mitochondrial function inhibitor, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) induced PINK1 and PARK2 and increased the expression of GRP78 and p-PERK while the levels of Cr (VI)-induced PINK1, PARK2, LC3-II were reduced after ER stress inhibitor, phenylbutyric acid (4PBA) pretreatment. When A549 cells were treated with CCCP and 4-PBA simultaneously, CCCP-induced expressions of PINK1, PARK2 and LC3-II decreased significantly compared with that of only CCCP-treated cells, indicating that there was a crosstalk between mitochondria and ER in inducing mitophagy. Additionally, the crosstalk between mitochondrial dysfunction and ER stress modulated the expression of Cr (VI)-induced ATF4, which resulted in mitophagy. Collectively, our data demonstrated that Cr (VI)-induced mitophagy mediated by ATF4 via the crosstalk between ER stress and mitochondrial dysfunction.

DHA Protects Hepatocytes from Oxidative Injury through GPR120/ERK-Mediated Mitophagy

Oxidative stress occurs in a variety of clinical liver diseases and causes cellular damage and mitochondrial dysfunction. The clearance of damaged mitochondria by mitophagy may facilitate mitochondrial biogenesis and enhance cell survival. Although the supplementation of docosahexaenoic acid (DHA) has been recognized to relieve the symptoms of various liver diseases, the antioxidant effect of DHA in liver disease is still unclear. The purpose of our research was to investigate the antioxidant effect of DHA in the liver and the possible role of mitophagy in this. In vitro, H₂O₂-induced injury was caused in AML12 cells. The results showed that DHA repressed the level of reactive oxygen species (ROS) induced by H₂O₂ and stimulated the cellular antioxidation response. Most notably, DHA restored oxidative stress-impaired autophagic flux and promoted protective autophagy. In addition, PINK/Parkin-mediated mitophagy was activated by DHA in AML12 cells and alleviated mitochondrial dysfunction. The ERK1/2 signaling pathway was inhibited during oxidative stress but reactivated by DHA treatment. It was proven that the expression of ERK1/2 was involved in the regulation of mitophagy by the ERK1/2 inhibitor. We further proved these results in vivo. DHA effectively alleviated the liver oxidative damage caused by CCl₄ and enhanced antioxidation capacity; intriguingly, autophagy was also activated. In summary, our data demonstrated that DHA protected hepatocytes from oxidative damage through GPR120/ERK-mediated mitophagy.

Metabolic and Amino Acid Alterations of the Tumor Microenvironment

Metabolic changes driven by the hostile tumor microenvironment surrounding cancer cells and the effect of these changes on tumorigenesis and metastatic potential have been known for a long time. The usual point of interest is glucose and changes in its utilization by cancer cells, mainly in the form of the Warburg effect. However, amino acids, both intra- and extracellular, also represent an important aspect of tumour microenvironment, which can have a significant effect on cancer cell metabolism and overall development of the tumor. Namely, alterations in the metabolism of amino acids glutamine, sarcosine, aspartate, methionine and cysteine have been previously connected to the tumor progression and aggressivity of cancer. The aim of this review is to pinpoint current gaps in our knowledge of the role of amino acids as a part of the tumor microenvironment and to show the effect of various amino acids on cancer cell metabolism and metastatic potential. This review shows limitations and exceptions from the traditionally accepted model of Warburg effect in some cancer tissues, with the emphasis on prostate cancer, because the traditional definition of Warburg effect as a metabolic switch to aerobic glycolysis does not always apply. Prostatic tissue both in a healthy and transformed state significantly differs in many metabolic aspects, including the metabolisms of glucose and amino acids, from the metabolism of other tissues. Findings from different tissues are, therefore, not always interchangeable and have to be taken into account during experimentation modifying the environment of tumor tissue by amino acid supplementation or depletion, which could potentially serve as a new therapeutic approach.

DUSP1 overexpression attenuates renal tubular mitochondrial dysfunction by restoring Parkin-mediated mitophagy in diabetic nephropathy

Diabetic nephropathy (DN) is the primary cause of end-stage renal disease, and renal tubular cell dysfunction contributes to the pathogenesis of many kidney diseases. Our previous study demonstrated that dual-specificity protein phosphatase 1 (DUSP1) reduced hyperglycemia-mediated mitochondrial damage; however, its role in hyperglycemia-driven dysfunction of tubular cells is still not fully understood. In this study, we found that DUSP1 is reduced in human proximal tubular epithelial (HK-2) cells under high-glucose conditions. DUSP1 overexpression in HK-2 cells partially restored autophagic flux, improved mitochondrial function, and reduced reactive oxygen species generation and cell apoptosis under high-glucose conditions. Surprisingly, overexpressing DUSP1 abolished the decrease in mitochondrial parkin expression caused by high-glucose stimulation. In addition, knockdown of parkin in HK-2 cells reversed the effects of DUSP1 overexpression on mitophagy and apoptosis under high-glucose conditions. Overall, these data indicate that DUSP1 plays a defensive role in the pathogenesis of DN by restoring parkin-mediated mitophagy, suggesting that it may be considered a prospective therapeutic strategy for the amelioration of DN.

LC3B/p62-mediated mitophagy protects A549 cells from resveratrol-induced apoptosis

AIMS

Complicated mechanisms in cancer cells have been restricting the medicinal value of resveratrol (Res). The mechanisms by which Res exerts its anti-tumor activity in lung cancer cells have diverged among reports in recent years, whether cells choose to undergo autophagic cell death or apoptosis remains controversial. Yet, whether Res-induced autophagic cell death transforms into apoptosis is still unknown, and by which autophagy regulates programmed cell death is still undefined.

MAIN METHODS

Here, A549 cells were treated with Res to investigate the mechanisms of autophagy and apoptosis using western blot, immunofluorescence staining for LC3B.

KEY FINDINGS

Non-canonical autophagy was induced by Res-treatment in a Beclin-1- and ATG5-independent manner, with apoptosis being activated simultaneously. Autophagy induced by Res was activated by rapamycin with decreased apoptosis, suggesting that autophagy may serve as a protective pathway in cells. Mitophagy was found to be induced by Res using fluorescence co-localization of mitochondria with lysosomes. Subsequently, it was identified that mitophagy was mediated by LC3B/p62 interaction and could be inhibited by LC3B knockout and p62 knockdown following increased apoptosis.

SIGNIFICANCE

In conclusion, the current results demonstrate that Res-induced non-canonical autophagy in A549 lung cancer cells with apoptosis activation simultaneously, while LC3B/p62-mediated mitophagy protects tumor cells against apoptosis, providing novel mechanisms about the critical role of mitophagy in regulating cell fate.

Sepsis-induced myocardial dysfunction: the role of mitochondrial dysfunction

INTRODUCTION

Sepsis-induced myocardial dysfunction (SIMD) is a condition manifested by an intrinsic myocardial systolic and diastolic dysfunction during sepsis, which is associated with worse clinical outcomes and a higher mortality.

MATERIALS AND METHODS

Several pathophysiological mechanisms including mitochondrial dysfunction, abnormal body immune reaction, metabolic reprogramming, excessive production of reactive oxygen species (ROS), and disorder of calcium regulation have been involved in SIMD. Mitophagy has potential role in protecting myocardial cells in sepsis, especially in survivors.

CONCLUSION

In the current review, we focus on the role of mitochondrial dysfunction and other mitochondria-related mechanisms including immunologic imbalance, energetic reprogramming, mitophagy, and pyroptosis in the mechanisms of SIMD.

Dynamic properties of mitochondria during human corticogenesis

Mitochondria are signaling hubs responsible for the generation of energy through oxidative phosphorylation, the production of key metabolites that serve the bioenergetic and biosynthetic needs of the cell, calcium (Ca2+) buffering and the initiation/execution of apoptosis. The ability of mitochondria to coordinate this myriad of functions is achieved through the exquisite regulation of fundamental dynamic properties, including remodeling of the mitochondrial network via fission and fusion, motility and mitophagy. In this Review, we summarize the current understanding of the mechanisms by which these dynamic properties of the mitochondria support mitochondrial function, review their impact on human cortical development and highlight areas in need of further research.

Modulation of Autophagy: A Novel "Rejuvenation" Strategy for the Aging Liver

Aging is a natural life process which leads to a gradual decline of essential physiological processes. For the liver, it leads to alterations in histomorphology (steatosis and fibrosis) and function (protein synthesis and energy generation) and affects central hepatocellular processes (autophagy, mitochondrial respiration, and hepatocyte proliferation). These alterations do not only impair the metabolic capacity of the liver but also represent important factors in the pathogenesis of malignant liver disease. Autophagy is a recycling process for eukaryotic cells to degrade dysfunctional intracellular components and to reuse the basic substances. It plays a crucial role in maintaining cell homeostasis and in resisting environmental stress. Emerging evidence shows that modulating autophagy seems to be effective in improving the age-related alterations of the liver. However, autophagy is a double-edged sword for the aged liver. Upregulating autophagy alleviates hepatic steatosis and ROS-induced cellular stress and promotes hepatocyte proliferation but may aggravate hepatic fibrosis. Therefore, a well-balanced autophagy modulation strategy might be suitable to alleviate age-related liver dysfunction. Conclusion. Modulation of autophagy is a promising strategy for "rejuvenation" of the aged liver. Detailed knowledge regarding the most devastating processes in the individual patient is needed to effectively counteract aging of the liver without causing obvious harm.

Effects of sulforaphane on brain mitochondria: mechanistic view and future directions

The organosulfur compound sulforaphane (SFN; C₆H₁₁NOS₂) is a potent cytoprotective agent promoting antioxidant, anti-inflammatory, antiglycative, and antimicrobial effects in in vitro and in vivo experimental models. Mitochondria are the major site of adenosine triphosphate (ATP) production due to the work of the oxidative phosphorylation (OXPHOS) system. They are also the main site of reactive oxygen species (ROS) production in nucleated human cells. Mitochondrial impairment is central in several human diseases, including neurodegeneration and metabolic disorders. In this paper, we describe and discuss the effects and mechanisms of action by which SFN modulates mitochondrial function and dynamics in mammalian cells. Mitochondria-related pro-apoptotic effects promoted by SFN in tumor cells are also discussed. SFN may be considered a cytoprotective agent, at least in part, because of the effects this organosulfur agent induces in mitochondria. Nonetheless, there are certain points that should be addressed in further experiments, indicated here as future directions, which may help researchers in this field of research.

Perfluorooctanoic acid-induced cellular and subcellular alterations in fish hepatocytes

Liver perfluorooctanoic acid (PFOA) pathophysiology and related morphofunction disturbances were studied in common carp at the cellular and subcellular level and with box-counting fractal analysis of ultrathin sections to assess the effect of PFOA exposure on hepatocyte structure complexity and heterogeneity. Three experimental groups were investigated: unexposed; low exposure (200 ng L^-1 PFOA); high exposure (2 mg L^-1 PFOA). PFOA-exposed cells showed differences from controls at both tested concentrations, manifested mainly as cloudy swelling and reversible vacuolar degeneration. Subcellular modifications primarily involved mitochondria and secondarily endoplasmic reticulum, with evidence of increased subcellular turnover. The alterations were consistent with oxidative stress related pathophysiology. Fractal analysis discriminated exposed from unexposed fish and low from high PFOA exposure based on lacunarity and fractal dimension, respectively. The absence of irreversible organelle alterations and apoptosis/necrosis, along with the increase of cellular complexity, led to the conclusion that the patterns observed represented an adaptive recovery response.

The inhibition of eIF5A hypusination by GC7, a preconditioning protocol to prevent brain death-induced renal injuries in a preclinical porcine kidney transplantation model

The eIF5A hypusination inhibitor GC7 (N1-guanyl-1,7-diaminoheptane) was shown to protect from ischemic injuries. We hypothesized that GC7 could be useful for preconditioning kidneys from donors before transplantation. Using a preclinical porcine brain death (BD) donation model, we carried out in vivo evaluation of GC7 pretreatment (3 mg/kg iv, 5 minutes after BD) at the beginning of the 4h-donor management, after which kidneys were collected and cold-stored (18h in University of Wisconsin solution) and 1 was allotransplanted. Groups were defined as following (n = 6 per group): healthy (CTL), untreated BD (Vehicle), and GC7-treated BD (Vehicle + GC7). At the end of 4h-management, GC7 treatment decreased BD-induced markers, as radical oxygen species markers. In addition, GC7 increased expression of mitochondrial protective peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC1α) and antioxidant proteins (superoxyde-dismutase-2, heme oxygenase-1, nuclear factor [erythroid-derived 2]-like 2 [NRF2], and sirtuins). At the end of cold storage, GC7 treatment induced an increase of NRF2 and PGC1α mRNA and a better mitochondrial integrity/homeostasis with a decrease of dynamin- related protein-1 activation and increase of mitofusin-2. Moreover, GC7 treatment significantly improved kidney outcome during 90 days follow-up after transplantation (fewer creatininemia and fibrosis). Overall, GC7 treatment was shown to be protective for kidneys against BD-induced injuries during donor management and subsequently appeared to preserve antioxidant defenses and mitochondria homeostasis; these protective effects being accompanied by a better transplantation outcome.

The Role of iPSC Modeling Toward Projection of Autophagy Pathway in Disease Pathogenesis: Leader or Follower

Autophagy is responsible for degradation of non-essential or damaged cellular constituents and damaged organelles. The autophagy pathway maintains efficient cellular metabolism and reduces cellular stress by removing additional and pathogenic components. Dysfunctional autophagy underlies several diseases. Thus, several research groups have worked toward elucidating key steps in this pathway. Autophagy can be studied by animal modeling, chemical modulators, and in vitro disease modeling with induced pluripotent stem cells (iPSC) as a loss-of-function platform. The introduction of iPSC technology, which has the capability to maintain the genetic background, has facilitated in vitro modeling of some diseases. Furthermore, iPSC technology can be used as a platform to study defective cellular and molecular pathways during development and unravel novel steps in signaling pathways of health and disease. Different studies have used iPSC technology to explore the role of autophagy in disease pathogenesis which could not have been addressed by animal modeling or chemical inducers/inhibitors. In this review, we discuss iPSC models of autophagy-associated disorders where the disease is caused due to mutations in autophagy-related genes. We classified this group as "primary autophagy induced defects (PAID)". There are iPSC models of diseases in which the primary cause is not dysfunctional autophagy, but autophagy is impaired secondary to disease phenotypes. We call this group "secondary autophagy induced defects (SAID)" and discuss them. Graphical abstract.

Paricalcitol Attenuates Contrast-Induced Acute Kidney Injury by Regulating Mitophagy and Senescence

Contrast-induced acute kidney injury (CI-AKI) is the third most common cause of hospital-acquired renal failure, with an incidence of 11%. However, the disease mechanism remains unclear, and no effective treatment is available. Paricalcitol has been reported to be effective in animal models of kidney injury. We hypothesized that paricalcitol could play a renoprotective role against CI-AKI. Rats were divided into control, paricalcitol, contrast, and paricalcitol-plus-contrast groups. We used a previously published protocol to produce CI-AKI. Paricalcitol (0.3 μg/kg) was administered intraperitoneally before 24 h and 30 min before indomethacin. We used HK-2 cells to evaluate the effects of paricalcitol on mitophagy and senescence. Ioversol triggered renal dysfunction, increasing blood urea nitrogen and serum creatinine. Significant tubular damage, increased 8-OHdG expression, and apoptosis were apparent. Ioversol injection induced high expression levels of the mitophagy markers Pink1, Parkin, and LC3 and the senescence markers β-galactosidase and p16INK4A. Paricalcitol pretreatment prevented renal dysfunction and reduced tissue damage by reducing both mitophagy and senescence. Cellular morphological changes were found, and expression of LC3B and HMGB1 was increased by ioversol in HK-2 cells. Paricalcitol countered these effects. This study showed that mitochondria might drive injury phenotypes in CI-AKI, and that paricalcitol protects against CI-AKI by decreasing mitochondrial damage.

Effect of mitophagy in oocytes and granulosa cells on oocyte quality†

Mitophagy is the process by which cells selectively remove supernumerary or damaged mitochondria through autophagy, and is crucial for mitochondrial homeostasis and cell survival. Mitochondria play vital roles in determining the developmental competence of oocytes. During the early stages of oogenesis, aberrant mitochondria can be removed by mitophagy. After oocyte formation, mitophagy is not actively initiated to clear damaged mitochondria despite the presence of mitophagy regulators in oocytes, which leads to the transmission of dysfunctional mitochondria from the oocyte to the embryo. However, granulosa cells around oocytes can improve mitochondrial function through mitophagy, thereby improving oocyte developmental capacity. Furthermore, this review discusses recent work on the substances and environmental conditions that affect mitophagy in oocytes and granulosa cells, thus providing new directions for improving oocyte quality during assisted reproductive technology treatment.

Net protein balance correlates with expression of autophagy, mitochondrial biogenesis, and fat metabolism-related genes in skeletal muscle from older adults

The mechanisms leading to sarcopenia, the main cause for frailty in older adults, are still unclear. Autophagy and the ubiquitin-proteasome system (UPS) may play a role in mediating muscle protein breakdown related to sarcopenia. In addition to loss of muscle mass, compromised muscle performance observed in sarcopenic patients has been linked to muscle mitochondria dysfunction. Increased fat deposition and fat cell infiltration in muscle frequently seen in skeletal muscle of older adults may play an additional role for the pathogenesis of sarcopenia. Therefore, the first objective of this study was to understand differences in expression of genes related to autophagy, UPS, mitochondrial biogenesis, and fat metabolism in skeletal muscle of older adults compared with young adults. Our second objective was to determine the correlation between whole body protein kinetics (WBPK) and gene expression with age. Real-time quantitative PCR was used to determine the relative expression of targeted genes, and hierarchical regression analysis was used to determine if age had a moderating effect on the correlation between expression of targeted genes and WBPK. Increases in the expression of autophagy-related genes and fat metabolism-related genes were observed in muscle of older adults compared with young adults. In addition, age enhanced the negative correlations between mitochondrial biogenesis genes and net protein balance. These results suggest that dysregulated gene expression of mitochondrial biogenesis could play a role in muscle loss in older adults.

Dietary Mitophagy Enhancer: A Strategy for Healthy Brain Aging?

Recently, nutritional interventions have received attention as promising approaches to promote human health during a lifespan. The Mediterranean and Okinawan diets have been associated with longevity and decreasing risk for age-related diseases in contrast to the Western diet. The effect might be due to several antioxidative bioactive compounds highly consumed in both diets, namely, resveratrol, hydroxytyrosol, oleuropein, curcumin, and spermidine. This review aims to address the underlying mechanisms of these compounds to enhance mental fitness throughout life with a focus on brain mitophagy. Mitophagy is the autophagic clearance of dysfunctional, redundant, and aged mitochondria. In aging and neurodegenerative disorders, mitophagy is crucial to preserve the autophagy mechanism of the whole cell, especially during oxidative stress. Growing evidence indicates that curcumin, astaxanthin, resveratrol, hydroxytyrosol, oleuropein, and spermidine might exert protective functions via antioxidative properties and as well the enhanced induction of mitophagy mediators. The compounds seem to upregulate mitophagy and thereby alleviate the clearance of dysfunctional and aged mitochondria as well as mitogenesis. Thus, the Mediterranean or Okinawan diet could represent a feasible nutritional approach to reduce the risk of developing age-related cognitive impairment and corresponding disorders via the stimulation of mitophagy and thereby ensure a balanced redox state of brain cells.

KLF2 regulates dental pulp-derived stem cell differentiation through the induction of mitophagy and altering mitochondrial metabolism

To define the regulatory role of Kruppel-like factor 2 (KLF2) during osteoblast (OB) differentiation of dental pulp-derived stem cell (DPSC)s, herein, we show that the levels of KLF2 and autophagy-related molecules were significantly increased in differentiated cells. Gain-of-function and loss-of-function approaches of KLF2 confirmed that KLF2 modulated autophagic and OB differentiation-related molecules. In addition, knockdown of the autophagic molecule (ATG7 or BECN1) in DPSCs resulted in reduced levels of KLF2 and OB differentiation-related molecules. Conversely, the induction of autophagy increased levels of KLF2 and OB differentiation-related molecules. Moreover, OB differentiation induced mitophagy and mitochondrial membrane potential-related molecules. In addition, OB differentiation reduced the generation of total and mitochondrial ROS productions and induced intracellular Ca²⁺ production. Measurements of glycolysis and oxidative phosphorylation simultaneously in live cells revealed that OB differentiation decreased the oxygen consumption rate, which is an indicator of mitochondrial respiration and reduced the level of ATP production. Furthermore, flux analysis also revealed that OB differentiation increased the extracellular acidification rate (ECAR) in the non-glycolytic acidification, and the glycolytic capacity conditions, increasing the lactate production and reducing the metabolic activity of the cells. Thus, a metabolic shift from mitochondrial respiration to the glycolytic pathway was observed during OB differentiation. Finally, chromatin immunoprecipitation (ChIP) analysis confirmed that the KLF2 and active epigenetic marks (H3K27Ac and H3K4me3) were upregulated in the promoter region of ATG7 during OB differentiation. These results provide evidence that the mitophagy process is important during OB differentiation, and KLF2 critically regulates it.

Mitochondrial Quality Control in the Heart: New Drug Targets for Cardiovascular Disease

Despite considerable efforts to prevent and treat cardiovascular disease (CVD), it has become the leading cause of death worldwide. Cardiac mitochondria are crucial cell organelles responsible for creating energy-rich ATP and mitochondrial dysfunction is the root cause for developing heart failure. Therefore, maintenance of mitochondrial quality control (MQC) is an essential process for cardiovascular homeostasis and cardiac health. In this review, we describe the major mechanisms of MQC system, such as mitochondrial unfolded protein response and mitophagy. Moreover, we describe the results of MQC failure in cardiac mitochondria. Furthermore, we discuss the prospects of 2 drug candidates, urolithin A and spermidine, for restoring mitochondrial homeostasis to treat CVD.

A connection in life and death: The BCL-2 family coordinates mitochondrial network dynamics and stem cell fate

The B cell CLL/lymphoma-2 (BCL-2) family of proteins control the mitochondrial pathway of apoptosis, also known as intrinsic apoptosis. Direct binding between members of the BCL-2 family regulates mitochondrial outer membrane permeabilization (MOMP) after an apoptotic insult. The ability of the cell to sense stress and translate it into a death signal has been a major theme of research for nearly three decades; however, other mechanisms by which the BCL-2 family coordinates cellular homeostasis beyond its role in initiating apoptosis are emerging. One developing area of research is understanding how the BCL-2 family of proteins regulate development using pluripotent stem cells as a model system. Understanding BCL-2 family-mediated regulation of mitochondrial homeostasis in cell death and beyond would uncover new facets of stem cell maintenance and differentiation potential.

Impairment of mitochondrial dynamics involved in iron oxide nanoparticle-induced dysfunction of dendritic cells was alleviated by autophagy inhibitor 3-methyladenine

Iron oxide nanoparticles are nanomaterials that are used extensively in the biomedical field, but they are associated with adverse effects, including mitochondrial toxicity. Mitochondrial homeostasis is achieved through dynamic stability based on two sets of antagonistic balanced processes: mitochondrial biogenesis and degradation as well as mitochondrial fission and fusion. In this study, we showed that PEG-COOH-coated Fe₃ O₄ (PEG-Fe₃ O₄ ) nanoparticles induced mitochondrial instability in dendritic cells (DCs) by impairing mitochondrial dynamics due to promotion of mitochondrial biogenesis through activation of the peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) pathway, inhibiting mitochondrial degradation via decreased autophagy, and facilitating mitochondrial fragmentation involving increased levels of DRP1 and MFN2. The resulting reduced levels of dextran uptake, CD80, CD86 and chemokine receptor 7 (CCR7) suggested that PEG-Fe₃ O₄ nanoparticles impaired the functionally immature state of DCs. Autophagy inhibitor 3-methyladenine (3-MA) alleviated PEG-Fe₃ O₄ nanoparticle-induced mitochondrial instability and impairment of the functionally immature state of DCs due to unexpected enhancement of PGC1α/MFN2-mediated coordination of mitochondrial biogenesis and fusion.

Uremic toxins promote accumulation of oxidized protein and increased sensitivity to hydrogen peroxide in endothelial cells by impairing the autophagic flux

Chronic kidney disease (CKD) is associated with high mortality rates, mainly due to cardiovascular diseases (CVD). Uremia has been considered a relevant risk factor for CVD in CKD patients, since uremic toxins (UTs) promote systemic and vascular inflammation, oxidative stress and senescence. Here, we demonstrate that uremic toxins indoxyl sulfate (IxS), p-cresyl sulfate (pCS) and indole acetic acid (IAA) are incorporated by human endothelial cells and inhibit the autophagic flux, demonstrated by cellular p62 accumulation. Moreover, isolated and mixed UTs impair the lysosomal stage of autophagy, as determined by cell imaging of the mRFP-GFP-LC3 protein. Endothelial cells exposed to UTs display accumulation of carbonylated proteins and increased sensitivity to hydrogen peroxide. Rapamycin, an autophagy activator which induces both autophagosome formation and clearance, prevented these effects. Collectively, our findings demonstrate that accumulation of oxidized proteins and enhanced cell sensitivity to hydrogen peroxide are consequences of impaired autophagic flux. These data provide evidence that UTs-induced impaired autophagy may be a novel contributor to endothelial dysfunction.

Activation of autophagy inhibits cadmium-triggered apoptosis in human placental trophoblasts and mouse placenta

Cadmium (Cd), a ubiquitous environmental pollutant, is known to impair placental development. However, the underlying mechanisms remain unclear. The present study used in vivo and in vitro models to investigate the effects of Cd on apoptosis and autophagy in placental trophoblasts and its mechanism. Pregnant mice were exposed to CdCl₂ (4.5 mg/kg) on gestational day (GD) 9. Human JEG-3 cells were exposed to CdCl₂ (0-40 μM) for different time points. Gestational Cd exposure obviously lowered the weight and diameter of mouse placentas. Number of TUNEL-positive cells was markedly elevated in Cd-administered mouse placentas and JEG-3 cells. Correspondingly, Cd significantly up-regulated cleaved caspase-3 protein level, a key indicator of apoptosis, in murine placentas and JEG-3 cells. Simultaneously, Cd also triggered autophagy, as determined by an elevation of LC3B-II and p62 protein, and accumulation of LC3-positive puncta, in placental trophoblasts. Chloroquine an autophagy inhibitor, obviously aggravated Cd-induced apoptosis in JEG-3 cells. By contrast, rapamycin, a specific autophagy inducer, significantly alleviated Cd-triggered apoptosis in JEG-3 cells. Mechanistically, autophagy inhibited Cd-induced apoptosis mainly via degrading caspase-9. Co-localizations of p62, a classical autophagic receptor, and caspase-9 were observed in Cd-stimulated human JEG-3 cells. Moreover, p62 siRNAs pretreatment markedly blocked the degradation of caspase 9 proteins via Cd-activated autophagy in JEG-3 cells. Collectively, our data suggest that activation of autophagy inhibits Cd-induced apoptosis via p62-mediated caspase-9 degradation in placental trophoblasts. These findings provide a new mechanistic insight into Cd-induced impairments of placental and fetal development.

Mitochondrial Dysfunction: Metabolic Drivers of Pulmonary Hypertension

Significance: Pulmonary hypertension (PH) is a progressive disease characterized by pulmonary vascular remodeling and lung vasculopathy. The disease displays progressive dyspnea, pulmonary artery uncoupling and right ventricular (RV) dysfunction. The overall survival rate is ranging from 28-72%. Recent Advances: The molecular events that promote the development of PH are complex and incompletely understood. Metabolic impairment has been proposed to contribute to the pathophysiology of PH with evidence for mitochondrial dysfunction involving the electron transport chain proteins, antioxidant enzymes, apoptosis regulators, and mitochondrial quality control. Critical Issues: It is vital to characterize the mechanisms by which mitochondrial dysfunction contribute to PH pathogenesis. This review focuses on the currently available publications that supports mitochondrial mechanisms in PH pathophysiology. Future Directions: Further studies of these metabolic mitochondrial alterations in PH could be viable targets of diagnostic and therapeutic intervention.

Functional consequences of mitochondrial mismatch in reconstituted embryos and offspring

Animal cloning technology has been developed to produce progenies genetically identical to a given donor cell. However, in nuclear transfer protocols, the recipient oocytes contribute a heritable mitochondrial genomic (mtDNA) background to the progeny. Additionally, a small amount of donor cell-derived mitochondria accompanies the transferred nucleus in the process; hence, the mtDNAs of two origins are mixed in the cytoplasm (heteroplasmy) of the reconstituted oocyte. Herein, I would like to introduce some of our previous results concerning five key considerations associated with animal cloning, including: mtDNA heteroplasmy in somatic cell nuclear transferred (SCNT) animals, the variation in the transmission of mtDNA heteroplasmy to subsequent generations SCNT cows and pigs, the influence of mtDNA sequence differences on mitochondrial proteins in SCNT cows and pigs, the effects of the introduction of mitochondria derived from somatic cells into recipient oocytes on embryonic development, and alterations of mtDNA heteroplasmy in inter/intraspecies nuclear transfer embryos.

Acute increases in O-GlcNAc indirectly impair mitochondrial bioenergetics through dysregulation of LonP1-mediated mitochondrial protein complex turnover

The attachment of O-linked β-N-acetylglucosamine (O-GlcNAc) to the serine and threonine residues of proteins in distinct cellular compartments is increasingly recognized as an important mechanism regulating cellular function. Importantly, the O-GlcNAc modification of mitochondrial proteins has been identified as a potential mechanism to modulate metabolism under stress with both potentially beneficial and detrimental effects. This suggests that temporal and dose-dependent changes in O-GlcNAcylation may have different effects on mitochondrial function. In the current study, we found that acutely augmenting O-GlcNAc levels by inhibiting O-GlcNAcase with Thiamet-G for up to 6 h resulted in a time-dependent decrease in cellular bioenergetics and decreased mitochondrial complex I, II, and IV activities. Under these conditions, mitochondrial number was unchanged, whereas an increase in the protein levels of the subunits of several electron transport complex proteins was observed. However, the observed bioenergetic changes appeared not to be due to direct increased O-GlcNAc modification of complex subunit proteins. Increases in O-GlcNAc were also associated with an accumulation of mitochondrial ubiquitinated proteins; phosphatase and tensin homolog induced kinase 1 (PINK1) and p62 protein levels were also significantly increased. Interestingly, the increase in O-GlcNAc levels was associated with a decrease in the protein levels of the mitochondrial Lon protease homolog 1 (LonP1), which is known to target complex IV subunits and PINK1, in addition to other mitochondrial proteins. These data suggest that impaired bioenergetics associated with short-term increases in O-GlcNAc levels could be due to impaired, LonP1-dependent, mitochondrial complex protein turnover.

Proteomic Analysis and Biochemical Correlates of Mitochondrial Dysfunction after Low-Intensity Primary Blast Exposure

Service members during military actions or combat training are frequently exposed to primary blasts by weaponry. Most studies have investigated moderate or severe brain injuries from blasts generating overpressures >100 kPa, whereas understanding the pathophysiology of low-intensity blast (LIB)-induced mild traumatic brain injury (mTBI) leading to neurological deficits remains elusive. Our recent studies, using an open-field LIB-induced mTBI mouse model with a peak overpressure at 46.6 kPa, demonstrated behavioral impairments and brain nanoscale damages, notably mitochondrial and axonal ultrastructural changes. In this study, we used tandem mass tagged (TMT) quantitative proteomics and bioinformatics analysis to seek insights into the molecular mechanisms underlying ultrastructural pathology. Changes in global- and phospho-proteomes were determined at 3 and 24 h and at 7 and 30 days post injury (DPI), in order to investigate the biochemical and molecular correlates of mitochondrial dysfunction. Results showed striking dynamic changes in a total of 2216 proteins and 459 phosphorylated proteins at vary time points after blast. Disruption of key canonical pathways included evidence of mitochondrial dysfunction, oxidative stress, axonal/cytoskeletal/synaptic dysregulation, and neurodegeneration. Bioinformatic analysis identified blast-induced trends in networks related to cellular growth/development/movement/assembly and cell-to-cell signaling interactions. With observations of proteomic changes, we found LIB-induced oxidative stress associated with mitochondrial dysfunction mainly at 7 and 30 DPI. These dysfunctions included impaired fission-fusion dynamics, diminished mitophagy, decreased oxidative phosphorylation, and compensated respiration-relevant enzyme activities. Insights on the early pathogenesis of primary LIB-induced brain damage provide a template for further characterization of its chronic effects, identification of potential biomarkers, and targets for intervention.

Mitophagy links oxidative stress conditions and neurodegenerative diseases

Mitophagy is activated by a number of stimuli, including hypoxia, energy stress, and increased oxidative phosphorylation activity. Mitophagy is associated with oxidative stress conditions and central neurodegenerative diseases. Proper regulation of mitophagy is crucial for maintaining homeostasis; conversely, inadequate removal of mitochondria through mitophagy leads to the generation of oxidative species, including reactive oxygen species and reactive nitrogen species, resulting in various neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. These diseases are most prevalent in older adults whose bodies fail to maintain proper mitophagic functions to combat oxidative species. As mitophagy is essential for normal body function, by targeting mitophagic pathways we can improve these disease conditions. The search for effective remedies to treat these disease conditions is an ongoing process, which is why more studies are needed. Additionally, more relevant studies could help establish therapeutic conditions, which are currently in high demand. In this review, we discuss how mitophagy plays a significant role in homeostasis and how its dysregulation causes neurodegeneration. We also discuss how combating oxidative species and targeting mitophagy can help treat these neurodegenerative diseases.

Toxicant-mediated redox control of proteostasis in neurodegeneration

Disruption in redox signaling and control of cellular processes has emerged as a key player in many pathologies including neurodegeneration. As protein aggregations are a common hallmark of several neuronal pathologies, a firm understanding of the interplay between redox signaling, oxidative and free radical stress, and proteinopathies is required to sort out the complex mechanisms in these diseases. Fortunately, models of toxicant-induced neurodegeneration can be utilized to evaluate and report mechanistic alterations in the proteostasis network (PN). The epidemiological links between environmental toxicants and neurological disease gives further credence into characterizing the toxicant-mediated PN disruptions observed in these conditions. Reviewed here are examples of mechanistic interaction between oxidative or free radical stress and PN alterations. Additionally, investigations into toxicant-mediated PN disruptions, specifically focusing on environmental metals and pesticides, are discussed. Finally, we emphasize the need to distinguish whether the presence of protein aggregations are contributory to phenotypes related to neurodegeneration, or if they are a byproduct of PN deficiencies.

Curcumin: A naturally occurring autophagy modulator

Autophagy is a self-degradative process that plays a pivotal role in several medical conditions associated with infection, cancer, neurodegeneration, aging, and metabolic disorders. Its interplay with cancer development and treatment resistance is complicated and paramount for drug design since an autophagic response can lead to tumor suppression by enhancing cellular integrity and tumorigenesis by improving tumor cell survival. In addition, autophagy denotes the cellular ability of adapting to stress though it may end up in apoptosis activation when cells are exposed to a very powerful stress. Induction of autophagy is a therapeutic option in cancer and many anticancer drugs have been developed to this aim. Curcumin as a hydrophobic polyphenol compound extracted from the known spice turmeric has different pharmacological effects in both in vitro and in vivo models. Many reports exist reporting that curcumin is capable of triggering autophagy in several cancer cells. In this review, we will focus on how curcumin can target autophagy in different cellular settings that may extend our understanding of new pharmacological agents to overcome relevant diseases.

Geraniol Protects Against the Protein and Oxidative Stress Induced by Rotenone in an In Vitro Model of Parkinson's Disease

Dysfunction of autophagy, mitochondrial dynamics and endoplasmic reticulum (ER) stress are currently considered as major contributing factors in the pathogenesis of Parkinson's disease (PD). Accumulation of oxidatively damaged cytoplasmic organelles and unfolded proteins in the lumen of the ER causes ER stress and it is associated with dopaminergic cell death in PD. Rotenone is a pesticide that selectively kills dopaminergic neurons by a variety of mechanism, has been implicated in PD. Geraniol (GE; 3,7-dimethylocta-trans-2,6-dien-1-ol) is an acyclic monoterpene alcohol occurring in the essential oils of several aromatic plants. In this study, we investigated the protective effect of GE on rotenone-induced mitochondrial dysfunction dependent oxidative stress leads to cell death in SK-N-SH cells. In addition, we assessed the involvement of GE on rotenone-induced dysfunction in autophagy machinery via α-synuclein accumulation induced ER stress. We found that pre-treatment of GE enhanced cell viability, ameliorated intracellular redox, preserved mitochondrial membrane potential and improves the level of mitochondrial complex-1 in rotenone treated SK-N-SH cells. Furthermore, GE diminishes autophagy flux by reduced autophagy markers, and decreases ER stress by reducing α-synuclein expression in SK-N-SH cells. Our results demonstrate that GE possess its neuroprotective effect via reduced rotenone-induced oxidative stress by enhanced antioxidant status and maintain mitochondrial function. Furthermore, GE reduced ER stress and improved autophagy flux in the neuroblastomal SK-N-SH cells. The present study could suggest that GE a novel therapeutic avenue for clinical intervention in neurodegenerative diseases especially for PD.

Lipin-1 regulates Bnip3-mediated mitophagy in glycolytic muscle

Autophagy of mitochondria (mitophagy) is essential for maintaining muscle mass and healthy skeletal muscle. Patients with heritable phosphatidic acid phosphatase lipin-1-null mutations present with severe rhabdomyolysis and muscle atrophy in glycolytic muscle fibers, which are accompanied with mitochondrial aggregates and reduced mitochondrial cytochrome c oxidase activity. However, the underlying mechanisms leading to muscle atrophy as a result of lipin-1 deficiency are still not clear. In this study, we found that lipin-1 deficiency in mice is associated with a marked accumulation of abnormal mitochondria and autophagic vacuoles in glycolytic muscle fibers. Our studies using lipin-1-deficient myoblasts suggest that lipin-1 participates in B-cell leukemia (BCL)-2 adenovirus E1B 19 kDa protein-interacting protein 3 (Bnip3)-regulated mitophagy by interacting with microtubule-associated protein 1A/1B-light chain (LC)3, which is an important step in the recruitment of mitochondria to nascent autophagosomes. The requirement of lipin-1 for Bnip3-mediated mitophagy was further verified in vivo in lipin-1-deficient green fluorescent protein-LC3 transgenic mice (lipin-1^-/--GFP-LC3). Finally, we showed that lipin-1 deficiency in mice resulted in defective mitochondrial adaptation to starvation-induced metabolic stress and impaired contractile muscle force in glycolytic muscle fibers. In summary, our study suggests that deregulated mitophagy arising from lipin-1 deficiency is associated with impaired muscle function and may contribute to muscle rhabdomyolysis in humans.-Alshudukhi, A. A., Zhu, J., Huang, D., Jama, A., Smith, J. D., Wang, Q. J., Esser, K. A., Ren, H. Lipin-1 regulates Bnip3-mediated mitophagy in glycolytic muscle.

AKT signalling selectively regulates PINK1 mitophagy in SHSY5Y cells and human iPSC-derived neurons

The discovery of mutations within genes associated with autosomal recessive Parkinson's disease allowed for the identification of PINK1/Parkin regulated mitophagy as an important pathway for the removal of damaged mitochondria. While recent studies suggest that AKT-dependent signalling regulates Parkin recruitment to depolarised mitochondria, little is known as to whether this can also regulate PINK1 mitochondrial accumulation and downstream mitophagy. Here, we demonstrate that inhibition of AKT signalling decreases endogenous PINK1 accumulation in response to mitochondria depolarisation, subsequent Parkin recruitment, phosphorylation of ubiquitin, and ultimately mitophagy. Conversely, we show that upon stimulation of AKT signalling via insulin, the mitophagy pathway is increased in SHSY5Y cells. These data suggest that AKT signalling is an upstream regulator of PINK1 accumulation on damaged mitochondria. Importantly, we show that the AKT pathway also regulates endogenous PINK1-dependent mitophagy in human iPSC-derived neurons.

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.

The kinetics of autophagy in the lung following acute spinal cord injury in rats

BACKGROUND CONTEXT

Lung injury is a major cause of respiratory complications following an acute spinal cord injury (ASCI), which are associated with a high mortality rate. Autophagy has been shown to be involved in a variety of lung diseases; however, whether autophagy is activated in the lung following ASCI remains unknown.

PURPOSE

The objective of this study was to investigate the induction of autophagy in the lung after ASCI.

STUDY DESIGN

This is an experimental animal study of ASCI investigating kinetics of autophagy in the lung following ASCI.

METHODS

One hundred and forty-four rats (N=144) were divided into two groups: (1) a sham (n=72) and (2) an injury group (n=72). Allen's method was used to induce an injury at the level of the 10th thoracic vertebra. Rats were sacrificed at 6, 12, 24, 48, and 72 hours, 1 week, and 2 weeks after surgery. Lung pathology and apoptosis were assessed to determine the level of damage in the lung. LC3, RAB7, P62, and Beclin 1 were used to detect the induction of autophagy. The study was funded by the Natural Science Foundation of China (NSFC,81272172); National Key Specialty Construction of Clinical Projects of China (#2013-544). The funder of the present study had no capacity to influence the scholarly conduct of the research, interpretation of results, or dissemination of study outcomes.

RESULTS

In the injury group, pathologic changes (i.e., pulmonary congestion, hemorrhage, inflammatory exudation, and alveolar collapse) occurred within the lung tissue within 72 hours after ASCI. Apoptosis of the lung cells gradually increased and peaked 72 hours after ASCI. Within 24 hours of ASCI, LC3 expression decreased, recovered, and gradually increased from 24 hours to 72 hours. As RAB7 decreased, P62 increased, and the ratio of RAB7/LC3 significantly decreased.

CONCLUSIONS

After ASCI, autophagy in the injured lung underwent dynamic changes, as early autophagosome formation decreased and late autophagosomes accumulated; thus, autophagy is in a state of inhibition.

Therapeutic Potential of a Prolyl Hydroxylase Inhibitor FG-4592 for Parkinson's Diseases in Vitro and in Vivo: Regulation of Redox Biology and Mitochondrial Function

As the main transcription factor that regulates the cellular responses to hypoxia, Hypoxia-inducible factor-1α (HIF-1α) plays an important role in the pathogenesis of Parkinson’s disease (PD). HIF-1α is normally degraded through ubiquitination after hydroxylation by prolyl hydroxylases (PHD). Emerging evidence has suggested that HIF PHD inhibitors (HIF-PHI) may have neuroprotective effects on PD through increasing HIF-1α levels. However, the therapeutic benefit of HIF-PHI for PD remains poorly explored due to the lack of proper clinical compounds and understanding of the underlying molecular mechanisms. In this study, we examined the therapeutic benefit of a new HIF-PHI, FG-4592, which is currently in phase 3 clinical trials to treat anemia in patients with chronic kidney diseases (CKD) in PD models. FG-4592 attenuates MPP⁺ -induced apoptosis and loss of tyrosine hydroxylase (TH) in SH-SY5Y cells. Pretreatment with FG-4592 mitigates MPP⁺-induced loss of mitochondrial membrane potential (MMP), mitochondrial oxygen consumption rate (OCR), production of reactive oxygen species (ROS) and ATP. Furthermore, FG-4592 counterbalances the oxidative stress through up-regulating nuclear factor erythroid 2 p45-related factor 2 (Nrf-2), heme oxygenase-1 (HO-1) and superoxide dismutase 2 (SOD2). FG-4592 treatment also induces the expression of Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) through increasing the phosphorylation of AMP-activated protein kinase (AMPK). In MPTP-treated mice, FG-4592 protects against MPTP-induced loss of TH-positive neurons of substantia nigra and attenuates behavioral impairments. Collectively, our study demonstrates that FG-4592 is a promising therapeutic strategy for PD through improving the mitochondrial function under oxidative stress.

Quercetogetin protects against cigarette smoke extract-induced apoptosis in epithelial cells by inhibiting mitophagy

Recent studies demonstrate that the autophagy-dependent turnover of mitochondria (mitophagy) mediates pulmonary epithelial cell death in response to cigarette smoke extract (CSE) exposure, and contributes to emphysema development in vivo during chronic cigarette smoke (CS)-exposure, although the underlying mechanisms remain unclear. Here, we investigated the role of mitophagy in regulating apoptosis in CSE-exposed human lung bronchial epithelial cells. Furthermore, we investigated the potential of the polymethoxylated flavone antioxidant quercetogetin (QUE) to inhibit CSE-induced mitophagy-dependent apoptosis. Our results demonstrate that CSE induces mitophagy in epithelial cells via mitochondrial dysfunction, and causes increased expression levels of the mitophagy-regulator protein PTEN-induced putative kinase-1 (PINK1) and the mitochondrial fission protein dynamin-1-like protein (DRP-1). CSE induced epithelial cell death and increased the expression of the apoptosis-related proteins cleaved caspase-3, -8 and -9. Caspase-3 activity was significantly increased in Beas-2B cells exposed to CSE, and decreased by siRNA-dependent knockdown of DRP-1. Treatment of epithelial cells with QUE inhibited CSE-induced mitochondrial dysfunction and mitophagy by inhibiting phospho (p)-DRP-1 and PINK1 expression. QUE suppressed mitophagy-dependent apoptosis by inhibiting the expression of cleaved caspase-3, -8 and -9 and downregulating caspase activity in human bronchial epithelial cells. These findings suggest that QUE may serve as a potential therapeutic in CS-induced pulmonary diseases.

Mitochondrial function and autophagy: integrating proteotoxic, redox, and metabolic stress in Parkinson's disease

Parkinson's disease (PD) is a movement disorder with widespread neurodegeneration in the brain. Significant oxidative, reductive, metabolic, and proteotoxic alterations have been observed in PD postmortem brains. The alterations of mitochondrial function resulting in decreased bioenergetic health is important and needs to be further examined to help develop biomarkers for PD severity and prognosis. It is now becoming clear that multiple hits on metabolic and signaling pathways are likely to exacerbate PD pathogenesis. Indeed, data obtained from genetic and genome association studies have implicated interactive contributions of genes controlling protein quality control and metabolism. For example, loss of key proteins that are responsible for clearance of dysfunctional mitochondria through a process called mitophagy has been found to cause PD, and a significant proportion of genes associated with PD encode proteins involved in the autophagy-lysosomal pathway. In this review, we highlight the evidence for the targeting of mitochondria by proteotoxic, redox and metabolic stress, and the role autophagic surveillance in maintenance of mitochondrial quality. Furthermore, we summarize the role of α-synuclein, leucine-rich repeat kinase 2, and tau in modulating mitochondrial function and autophagy. Among the stressors that can overwhelm the mitochondrial quality control mechanisms, we will discuss 4-hydroxynonenal and nitric oxide. The impact of autophagy is context depend and as such can have both beneficial and detrimental effects. Furthermore, we highlight the potential of targeting mitochondria and autophagic function as an integrated therapeutic strategy and the emerging contribution of the microbiome to PD susceptibility.

Activation of Ca2+-sensing receptor as a protective pathway to reduce Cadmium-induced cytotoxicity in renal proximal tubular cells

Cadmium (Cd), as an extremely toxic metal could accumulate in kidney and induce renal injury. Previous studies have proved that Cd impact on renal cell proliferation, autophagy and apoptosis, but the detoxification drugs and the functional mechanism are still in study. In this study, we used mouse renal tubular epithelial cells (mRTECs) to clarify Cd-induced toxicity and signaling pathways. Moreover, we proposed to elucidate the prevent effect of activation of Ca²⁺ sensing receptor (CaSR) by Calcimimetic (R-467) on Cd-induced cytotoxicity and underlying mechanisms. Cd induced intracellular Ca²⁺ elevation through phospholipase C-inositol 1, 4, 5-trisphosphate (PLC) followed stimulating p38 mitogen-activated protein kinases (MAPK) activation and suppressing extracellular signal-regulated kinase (ERK) activation, which leaded to increase apoptotic cell death and inhibit cell proliferation. Cd induced p38 activation also contribute to autophagic flux inhibition that aggravated Cd induced apoptosis. R-467 reinstated Cd-induced elevation of intracellular Ca²⁺ and apoptosis, and it also increased cell proliferation and restored autophagic flux by switching p38 to ERK pathway. The identification of the activation of CaSR-mediated protective pathway in renal cells sheds light on a possible cellular protective mechanism against Cd-induced kidney injury.

Mitochondrial dysfunction and pulmonary hypertension: cause, effect, or both

Pulmonary hypertension describes a heterogeneous disease defined by increased pulmonary artery pressures, and progressive increase in pulmonary vascular resistance due to pathologic remodeling of the pulmonary vasculature involving pulmonary endothelial cells, pericytes, and smooth muscle cells. This process occurs under various conditions, and although these populations vary, the clinical manifestations are the same: progressive dyspnea, increases in right ventricular (RV) afterload and dysfunction, RV-pulmonary artery uncoupling, and right-sided heart failure with systemic circulatory collapse. The overall estimated 5-yr survival rate is 72% in highly functioning patients, and as low as 28% for those presenting with advanced symptoms. Metabolic theories have been suggested as underlying the pathogenesis of pulmonary hypertension with growing evidence of the role of mitochondrial dysfunction involving the major proteins of the electron transport chain, redox-related enzymes, regulators of the proton gradient and calcium homeostasis, regulators of apoptosis, and mitophagy. There remain more studies needed to characterize mitochondrial dysfunction leading to impaired vascular relaxation, increase proliferation, and failure of regulatory mechanisms. The effects on endothelial cells and resulting interactions with their microenvironment remain uncharted territory for future discovery. Additionally, on the basis of observations that the "plexigenic lesions" of pulmonary hypertension resemble the unregulated proliferation of tumor cells, similarities between cancer pathobiology and pulmonary hypertension have been drawn, suggesting interactions between mitochondria and angiogenesis. Recently, mitochondria targeting has become feasible, which may yield new therapeutic strategies. We present a state-of-the-art review of the role of mitochondria in both the pathobiology of pulmonary hypertension and potential therapeutic targets in pulmonary vascular processes.