Autophagy in the eukaryotic cell

A mathematical model of cell population dynamics with autophagy response to starvation

In this paper, we study the role of autophagy in yeast cell population dynamics in response to starvation by a mathematical model based on the logistic growth model. We analytically study the boundedness of solutions, and the existence and stability of equilibrium states under general biologically acceptable assumptions. Finally, we perform numerical studies for Saccharomyces cerevisiae response to starvation with autophagy. The results show that autophagy is valuable in maintaining cell population in starvation, and attenuating population fluctuations in response to perturbations in environmental nutrients. Furthermore, we show that proper level autophagy promotes cell survival through the inhibition of cell death by autophagy as well as the secretion of nutrients from autophagic cells, however excessive autophagy can decrease cell population due to autophagic cell death.

Autophagy activation aggravates neuronal injury in the hippocampus of vascular dementia rats

It remains unclear whether autophagy affects hippocampal neuronal injury in vascular dementia. In the present study, we investigated the effects of autophagy blockade on hippocampal neuronal injury in a rat model of vascular dementia. In model rats, hippocampal CA1 neurons were severely damaged, and expression of the autophagy-related proteins beclin-1, cathepsin B and microtubule-associated protein 1 light chain 3 was elevated compared with that in sham-operated animals. These responses were suppressed in animals that received a single intraperitoneal injection of wortmannin, an autophagy inhibitor, prior to model establishment. The present results confirm that autophagy and autophagy-related proteins are involved in the pathological changes of vascular dementia, and that inhibition of autophagy has neuroprotective effects.

The role of autophagic and lysosomal pathways in ischemic brain injury

Autophagy is involved in neural cell death after cerebral ischemia. Our previous studies showed that rapamycin-induced autophagy decreased the rate of apoptosis, but the rate of apoptosis was creased after the autophagy inhibitor, 3-methyladenine, was used. In this study, a suture-occluded method was performed to generate a rat model of brain ischemia. Under a transmission electron microscope, autophagic bodies and autophagy lysosomes were markedly accumulated in neurons at 4 hours post brain ischemic injury, with their numbers gradually reducing over time. Western blotting demonstrated that protein levels of light chain 3-II and cathepsin B were significantly increased within 4 hours of ischemic injury, but these levels were not persistently upregulated over time. Confocal microscopy showed that autophagy was mainly found in neurons with positive light chain 3 signal. Injection of rapamycin via tail vein promoted the occurrence of autophagy in rat brain tissue after cerebral ischemia and elevated light chain 3 and cathepsin B expression. However, injection of 3-methyladenine significantly diminished light chain 3-II and cathepsin B expression. Results verified that autophagic and lysosomal activity is increased in ischemic neurons. Abnormal components in cells can be eliminated through upregulating cell autophagy or inhibiting autophagy after ischemic brain injury, resulting in a dynamic balance of substances in cells. Moreover, drugs that interfere with autophagy may be potential therapies for the treatment of brain injury.

Functional analysis of a novel glioma antigen, EFTUD1

BACKGROUND

A cDNA library made from 2 glioma cell lines, U87MG and T98G, was screened by serological identification of antigens by recombinant cDNA expression (SEREX) using serum from a glioblastoma patient. Elongation factor Tu GTP binding domain containing protein 1 (EFTUD1), which is required for ribosome biogenesis, was identified. A cancer microarray database showed overexpression of EFTUD1 in gliomas, suggesting that EFTUD1 is a candidate molecular target for gliomas.

METHODS

EFTUD1 expression in glioma cell lines and glioma tissue was assessed by Western blot, quantitative PCR, and immunohistochemistry. The effect on ribosome biogenesis, cell growth, cell cycle, and induction of apoptosis and autophagy in glioma cells during the downregulation of EFTUD1 was investigated. To reveal the role of autophagy, the autophagy-blocker, chloroquine (CQ), was used in glioma cells downregulating EFTUD1. The effect of combining CQ with EFTUD1 inhibition in glioma cells was analyzed.

RESULTS

EFTUD1 expression in glioma cell lines and tissue was higher than in normal brain tissue. Downregulating EFTUD1 induced G1 cell-cycle arrest and apoptosis, leading to reduced glioma cell proliferation. The mechanism underlying this antitumor effect was impaired ribosome biogenesis via EFTUD1 inhibition. Additionally, protective autophagy was induced by glioma cells as an adaptive response to EFTUD1 inhibition. The antitumor effect induced by the combined treatment was significantly higher than that of either EFTUD1 inhibition or CQ alone.

CONCLUSION

These results suggest that EFTUD1 represents a novel therapeutic target and that the combination of EFTUD1 inhibition with autophagy blockade may be effective in the treatment of gliomas.

Enhancement of dynein-mediated autophagosome trafficking and autophagy maturation by ROS in mouse coronary arterial myocytes

Dynein-mediated autophagosome (AP) trafficking was recently demonstrated to contribute to the formation of autophagolysosomes (APLs) and autophagic flux process in coronary arterial myocytes (CAMs). However, it remains unknown how the function of dynein as a motor protein for AP trafficking is regulated under physiological and pathological conditions. The present study tested whether the dynein-mediated autophagy maturation is regulated by a redox signalling associated with lysosomal Ca²⁺ release machinery. In primary cultures of CAMs, reactive oxygen species (ROS) including H₂O₂ and O₂^−. (generated by xanthine/xanthine oxidase) significantly increased dynein ATPase activity and AP movement, which were accompanied by increased lysosomal fusion with AP and APL formation. Inhibition of dynein activity by (erythro-9-(2-hydroxy-3-nonyl)adenine) (EHNA) or disruption of the dynein complex by dynamitin (DCTN2) overexpression blocked ROS-induced dynein activation, AP movement and APL formation, and resulted in an accumulation of AP along with a failed breakdown of AP. Antagonism of nicotinic acid adenine dinucleotide phosphate (NAADP)-mediated Ca²⁺ signalling with NED-19 and PPADS abolished ROS-enhanced lysosomal Ca²⁺ release and dynein activation in CAMs. In parallel, all these changes were also enhanced by overexpression of NADPH oxidase-1 (Nox1) gene in CAMs. Incubation with high glucose led to a marked O₂^−. production compared with normoglycaemic CAMs, while Nox1 inhibitor ML117 abrogated this effect. Moreover, ML117 and NED-19 and PPADS significantly suppressed dynein activity and APL formation caused by high glucose. Taken together, these data suggest that ROS function as important players to regulate dynein-dependent AP trafficking leading to efficient autophagic maturation in CAMs.

Region-specific changes in the immunoreactivity of Atg9A in the central nervous system of SOD1(G93A) transgenic mice

Autophagy is a eukaryotic self-degradation system that plays a pivotal role in the maintenance of cellular homeostasis. Atg9 is the only transmembrane Atg protein required for autophagosome formation. Although the subcellular localization of the Atg9A has been examined, little is known about its precise cell and tissue distribution. In the present study, we used G93A mutation in superoxide dismutase 1 [SOD1(G93A)] mutant transgenic mice as an in vivo model of amyotrophic lateral sclerosis (ALS) and performed immunohistochemical studies to investigate the changes of Atg9A immunoreactivity in the central nervous system of these mice. Atg9A-immunoreactivity was detected in the spinal cord, cerebral cortex, hippocampal formation, thalamus and cerebellum of symptomatic SOD1(G93A) transgenic mice. By contrast, no Atg9A-immunoreactivity were observed in any brain and spinal cord region of wtSOD1, pre-symptomatic and early symptomatic mice, and the number and staining intensity of Atg9A-positive cells did not differ in SOD1(G93A) mice between 8 and 13 weeks of age. These results provide evidence that Atg9A-immunoreactivity were found in the central nervous system of SOD1(G93A) transgenic mice after clinical symptoms, suggesting a possible role in the pathologic process of ALS. However, the mechanisms underlying the increased immunoreactivity for Atg9A and the functional implications require elucidation.

Molecular processes that drive cigarette smoke-induced epithelial cell fate of the lung

Cigarette smoke contains numerous chemical compounds, including abundant reactive oxygen/nitrogen species and aldehydes, and many other carcinogens. Long-term cigarette smoking significantly increases the risk of various lung diseases, including chronic obstructive pulmonary disease and lung cancer, and contributes to premature death. Many in vitro and in vivo studies have elucidated mechanisms involved in cigarette smoke-induced inflammation, DNA damage, and autophagy, and the subsequent cell fates, including cell death, cellular senescence, and transformation. In this Translational Review, we summarize the known pathways underlying these processes in airway epithelial cells to help reveal future challenges and describe possible directions of research that could lead to better management and treatment of these diseases.

Role of autophagy and its significance in cellular homeostasis

Autophagy is a catabolic pathway that regulates homeostasis in cells. It is an exceptional pathway of membrane trafficking. Autophagy is characterized by the formation of double-membrane vesicles; autophagosomes that are responsible for delivering damaged organelle and extra proteins to lysosome for recycling. A series of actions including environmental and genetic factors are responsible for induction of autophagy. In the past few decades, the research on autophagy has been immensely expanded because it is a vital process in maintaining cellular balance as well as deeply connected with pathogenesis of a number of diseases. The aim of this review is to present an overview of modern work on autophagy and highlight some essential genetic role in the induction of autophagy. There is an emerging need to identify, quantify, and manipulate the pathway of autophagy, due to its close relationship with a variety of developmental pathways and functions especially in cancer, diabetes, neurodegenerative disorders, and infectious diseases.

Autophagy in Trypanosoma brucei: amino acid requirement and regulation during different growth phases

Autophagy in the protozoan parasite, Trypanosoma brucei, may be involved in differentiation between different life cycle forms and during growth in culture. We have generated multiple parasite cell lines stably expressing green fluorescent protein- or hemagglutinin-tagged forms of the autophagy marker proteins, TbAtg8.1 and TbAtg8.2, in T. brucei procyclic forms to establish a trypanosome system for quick and reliable determination of autophagy under different culture conditions using flow cytometry. We found that starvation-induced autophagy in T. brucei can be inhibited by addition of a single amino acid, histidine, to the incubation buffer. In addition, we show that autophagy is induced when parasites enter stationary growth phase in culture and that their capacity to undergo starvation-induced autophagy decreases with increasing cell density.

Role of autophagy and apoptosis in wound tissue of deep second-degree burn in rats

OBJECTIVES

The pathogenesis of burn wound progression is poorly understood. Contributing factors include continuous loss of blood perfusion, excessive inflammation, and elevated apoptosis levels in wound tissue. Macroautophagy (here referred to simply as "autophagy") is associated with many chronic diseases. The authors hypothesized that autophagy is involved in burn wound progression in a rat model of deep second-degree burn.

METHODS

Deep second-degree burns were modeled using a brass rod heated to 100°C applied for 6 seconds to the back skin of Wistar rats. Full-thickness biopsies were obtained from burned and nonburned controls at several times postburn. Western blotting and immunohistochemical (IHC) staining determined expression of the autophagy markers Light Chain 3 (LC3) and beclin-1. Apoptosis was determined by terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) assay and laser Doppler flowmetry (LDF)-measured tissue perfusion. Myeloperoxidase (MPO) activity assay measured inflammation. Hematoxylin and eosin (H&E) and Masson's trichrome staining-determined pathology and wound depth.

RESULTS

The LC3 and beclin-1 protein level in burn wounds decreased to one-fourth of normal levels (p<0.01) over 24 hours and then began to increase but still did not reach their normal level. TUNEL-positive cells in burn wounds were 3.7-fold (p<0.01) elevated over 48 hours and then decreased slightly, yet still remained higher than in normal skin. The burn wound progressed in depth over 72 hours. In addition, significant decrease in LDF values and upregulation of MPO activity were observed. Enhanced LC3-positive cells were observed in the deep dermal layer of burn wounds as shown by IHC staining.

CONCLUSIONS

A reduction in autophagy and blood flow and an increase in apoptosis and inflammation were observed in burn wounds early during the course of burn injury progression. This suggests that autophagy, complemented by apoptosis, play important roles in burn progression. Enhanced autophagy in the deep dermis may be a prosurvival mechanism against ischemia and inflammation after burn injury.

Ghrelin induces apoptosis in colon adenocarcinoma cells via proteasome inhibition and autophagy induction

Ghrelin is a metabolism-regulating hormone recently investigated for its role in cancer survival and progression. Controversially, ghrelin may act as either anti-apoptotic or pro-apoptotic factor in different cancer cells, suggesting that the effects are cell type dependent. Limited data are currently available on the effects exerted by ghrelin on intracellular proteolytic pathways in cancer. Both the lysosomal and the proteasomal systems are fundamental in cellular proliferation and apoptosis regulation. With the aim of exploring if the proteasome and autophagy may be possible targets of ghrelin in cancer, we exposed human colorectal adenocarcinoma cells to ghrelin. Preliminary in vitro fluorimetric assays evidenced for the first time a direct inhibition of 20S proteasomes by ghrelin, particularly evident for the trypsin-like activity. Moreover, 1 μM ghrelin induced apoptosis in colorectal adenocarcinoma cells by inhibiting the ubiquitin-proteasome system and by activating autophagy, with p53 having an "interactive" role.

Sirtuins' modulation of autophagy

The sirtuin family of class III histone deacetylases has been extensively implicated in modulating a myriad of cellular processes, including energy metabolism, stress response, cell/tissue survival and malignancy. Recent studies have also identified multifaceted roles for Sirt1 and Sirt2 in the regulation of autophagy. Sirt1 could influence autophagy directly via its deacetylation of key components of the autophagy induction network, such as the products of autophagy genes (Atg) 5, 7, and 8. Nucleus-localized Sirt1 is also known to induce the expression of autophagy pathway components through the activation of FoxO transcription factor family members. The perception of a linear Sirt1-FoxO axis in autophagy induction is complicated by recent findings that acetylated FoxO1 could bind to Atg7 in the cytoplasm and affect autophagy directly. This occurs with prolonged stress signaling, with FoxO1's continuous dissociation from cytoplasmic Sirt2 and its consequential hyperacetylation. FoxO-mediated nuclear transcription may induce/enhance autophagy in ways that are different compared to cytoplasmic FoxO, thereby leading to contrasting (cell survival versus cell death) outcomes. FoxO and Sirt1 are both subjected to regulation by stress signaling (e.g., through the c-Jun N-terminal kinases (JNK)) in the context of autophagy induction, which are also critical in determining between cell survival and death in a context-dependent manner. We discussed here the emerging molecular intricacies of sirtuins' connections with autophagy. A good understanding of these connections would serve to consolidate a framework of mechanisms underlying Sirt1's protective effects in multiple physiological systems.

The interplay between mitochondria and autophagy and its role in the aging process

Mitochondria are highly dynamic organelles which play a central role in cellular homeostasis. Mitochondrial dysfunction leads to life-threatening disorders and accelerates the aging process. Surprisingly, on the other hand, a mild reduction of mitochondria functionality can have pro-longevity effects in organisms spanning from yeast to mammals. Autophagy is a fundamental cellular housekeeping process that needs to be finely regulated for proper cell and organism survival, as underlined by the fact that both its over- and its defective activation have been associated with diseases and accelerated aging. A reciprocal interplay exists between mitochondria and autophagy, which is needed to constantly adjust cellular energy metabolism in different pathophysiological conditions. Here we review general features of mitochondrial function and autophagy with particular focus on their crosstalk and its possible implication in the aging process.

Rapamycin induces apoptosis when autophagy is inhibited in T-47D mammary cells and both processes are regulated by Phlda1

Autophagy is an evolutionarily conserved lysosomal degradation pathway and plays a critical role in the homeostatic process of recycling proteins and organelles. Functional relationships have been described between apoptosis and autophagy. Perturbations in the apoptotic machinery have been reported to induce autophagic cell deaths. Inhibition of autophagy in cancer cells has resulted in cell deaths that manifested hallmarks of apoptosis. However, the molecular relationships and the circumstances of which molecular pathways dictate the choice between apoptosis and autophagy are currently unknown. This study aims to identify specific gene expression of rapamycin-induced autophagy and the effects of rapamycin when the autophagy process is inhibited. In this study, we have demonstrated that rapamycin is capable of inducing autophagy in T-47D breast carcinoma cells. However, when the autophagy process was inhibited by 3-MA, the effects of rapamycin became apoptotic. The Phlda1 gene was found to be up-regulated in both autophagy and apoptosis and silencing this gene was found to reduce both activities, strongly suggests that Phlda1 mediates and positively regulates both autophagy and apoptosis pathways.

The proteolytic landscape of the yeast vacuole

The vacuole in the yeast Saccharomyces cerevisiae plays a number of essential roles, and to provide some of these required functions the vacuole harbors at least seven distinct proteases. These proteases exhibit a range of activities and different classifications, and they follow unique paths to arrive at their ultimate, common destination in the cell. This review will first summarize the major functions of the yeast vacuole and delineate how proteins are targeted to this organelle. We will then describe the specific trafficking itineraries and activities of the characterized vacuolar proteases, and outline select features of a new member of this protease ensemble. Finally, we will entertain the question of why so many proteases evolved and reside in the vacuole, and what future research challenges exist in the field.

Defective autophagosome trafficking contributes to impaired autophagic flux in coronary arterial myocytes lacking CD38 gene

AIM

Autophagic flux is an important process during autophagy maturation in smooth muscle cells. However, the molecular mechanisms underlying autophagic flux in these cells are largely unknown. Here, we revealed a previously undefined role of CD38, an enzyme that metabolizes NADP(+) into NAADP, in the regulation of autophagic flux in coronary arterial myocytes (CAMs).

METHODS AND RESULTS

In vivo CD38 gene knockout mice (CD38(-/-)) fed the high-fat Western diet showed increased accumulation of autophagosomes in coronary arterial media compared with that in wild-type (CD38(+/+)) mice, suggesting that CD38 gene deletion results in a defective autophagic process in CAMs of coronary arteries. In primary cultured CAMs, CD38 gene deletion markedly enhanced 7-ketocholesterol (7-Ket, an atherogenic stimulus and autophagy inducer)-induced accumulation of autophagosomes and increased expression of an autophagic marker, LC3B. However, no difference in autophagosome formation was observed between CD38(+/+) and CD38(-/-) CAMs when autophagic flux was blocked, which indicates that CD38 regulates autophagic flux rather than induction of autophagosome formation. Further, 7-Ket-induced formation of autophagolysosomes was markedly attenuated in CD38(-/-) CAMs compared with CD38(+/+) CAMs. Mechanistically, CD38 gene deletion markedly inhibited 7-Ket-induced dynein activation and autophagosome trafficking, which were associated with attenuated lysosomal Ca(2+) release. Importantly, coronary arterial smooth muscle from CD38(-/-) mice fed the Western diet exhibited phenotypic changes towards a more dedifferentiated state with abnormal extracellular matrix metabolism.

CONCLUSION

Taken together, these results suggest that CD38 plays a critical role in autophagosome trafficking and fusion with lysosomes, thus controlling autophagic flux in CAMs under atherogenic stimulation.

Interactions between endosomal maturation and autophagy: analysis of ESCRT machinery during Caenorhabditis elegans development

Endocytosis and autophagy are key vesicular pathways involved in degradation and recycling of cellular material. Both degradative pathways finally fuse with lysosome but are indeed interconnected at several levels. In particular, the fusion between endosomes and autophagosomes can generate intermediate vesicles named amphisomes. We analyzed the physiological and developmental roles of the ESCRT machinery in a model organism, the nematode Caenorhabditis elegans and showed that the blockage of the endosomal maturation triggers the induction of autophagic activity. This chapter describes several methods for studying endocytosis, autophagy, and their interconnection in C. elegans. A series of genetic, biochemical, and microscopy analyses has been used to study at the cellular and developmental levels, the cross talks between autophagy and endocytosis.

The evidence and the possible significance of autophagy in degeneration model of human cervical end-plate cartilage

The aim of this study was to observe autophagy in chondrocytes from degenerative human cervical vertebral end-plates and to investigate the significance of variations in autophagy in the degeneration of cervical vertebral end-plate chondrocytes. Cartilage end-plates were obtained from 48 inpatients admitted to hospital between February 2011 and August 2012. The patients were divided into the control group (n=17) with cervical vertebral fracture or dislocation and the cervical spondylosis group (n=31) with cervical spondylotic myelopathy. End-plate chondrocytes were isolated via enzyme digestion and then cultured in vitro. The cells were stained with toluidine blue and hematoxylin-eosin (H&E). A laser scanning confocal microscope and monodansylcadaverine (MDC) were used to reveal autophagy in the end-plate chondrocytes. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect mRNA expression of type II collagen and aggrecan. Western blotting was conducted to detect LC3 proteins. The chondrocytes isolated from the degenerative human cervical end-plates were cultured successfully in vitro. The morphology of the cells from the cervical spondylosis group tended to exhibit changes in spindle morphology compared with the control group. Autophagic bodies were stained with MDC. LC3 proteins were visible in the intracellular and perinuclear regions under the laser scanning confocal microscope. The mRNA expression levels (relative to those of β-actin) of aggrecan (0.715±0.194) and type II collagen (0.628±0.254) in the cervical spondylosis group were markedly decreased compared with those in the control group (0.913±0.254 and 0.845±0.186, respectively; both P<0.05). The LC3-II/LC3-I ratio was observed to be significantly reduced in the cervical spondylosis group by Western blot analysis. Autophagy has an important role in human cervical disc degeneration. The regulation of autophagy may prevent disc degeneration in cartilage end-plate cells.

The C. elegans LC3 acts downstream of GABARAP to degrade autophagosomes by interacting with the HOPS subunit VPS39

The formation of the autophagic vesicles requires the recruitment of ubiquitin-like Atg8 proteins to the membrane of nascent autophagosomes. Seven Atg8 homologs are present in mammals, split into the LC3 and the GABARAP/GATE-16 families, whose respective functions are unknown. Using Caenorhabditis elegans, we investigated the functions of the GABARAP and the LC3 homologs, LGG-1 and LGG-2, in autophagosome biogenesis. Both LGG-1 and LGG-2 localize to the autophagosomes but display partially overlapping patterns. During allophagy, a developmentally stereotyped autophagic flux, LGG-1 acts upstream of LGG-2 to allow its localization to autophagosomes. LGG-2 controls the maturation of LGG-1-positive autophagosomes and facilitates the tethering with the lysosomes through a direct interaction with the VPS-39 HOPS complex subunit. Genetic analyses sustain a sequential implication of LGG-1, LGG-2, RAB-7, and HOPS complex to generate autolysosomes. The duplications of Atg8 in metazoans thus allowed the acquisition of specialized functions for autophagosome maturation.

Silencing of Barkor/ATG14 sensitizes osteosarcoma cells to cisplatin‑induced apoptosis

Although surgical excision following neoadjuvant chemotherapy has contributed to the long-term survival of osteosarcoma patients, patients that do not respond to commonly used drugs including cisplatin, have a poor prognosis. Autophagy is important in the inhibition of chemotherapeutic apoptosis. Therefore, we investigated whether knockdown of Beclin1-associated autophagy-related key regulator (Barkor/ATG14) promoted cisplatin-induced apoptosis in a drug-resistant osteosarcoma cell line in vitro. Saos-2 cells were transfected with Barkor siRNA. Sensitivity of the Barkor siRNA-transfected cell line to cisplatin was evaluated. Silencing of Barkor did not directly inhibit the growth rate of the transfected cells, but it significantly increased their sensitivity to cisplatin. The results of flow cytometry and 4′,6-diamidino-2-phenylindole (DAPI) staining revealed that Barkor siRNA-transfected Saos-2 cells treated with cisplatin exhibited much higher rates of apoptosis than the control and control siRNA-transfected cells. Additionally, the combination of silencing of Barkor with cisplatin treatment promoted the expression of caspase-12 and calpain. The increase of cisplatin cytotoxicity may therefore be involved in endoplasmic reticulum (ER) stress-associated apoptosis. Bcl-2 was markedly downregulated in dose-dependent cisplatin-treated Barkor-transfected-Saos-2 cells. Findings of the present study suggest that the combination of silencing of Barkor and cisplatin enhanced the antitumor efficacy through the Barkor-related ER- and mitochondrial-mediated apoptotic pathway.

Autophagy maturation associated with CD38-mediated regulation of lysosome function in mouse glomerular podocytes

Podocytes are highly differentiated glomerular epithelial cells that contribute to the glomerular barrier function of kidney. A role for autophagy has been proposed in maintenance of their cellular integrity, but the mechanisms controlling autophagy in podocytes are not clear. The present study tested whether CD38-mediated regulation of lysosome function contributes to autophagic flux or autophagy maturation in podocytes. Podocytes were found to exhibit a high constitutive level of LC3-II, a robust marker of autophagosomes (APs), suggesting a high basal level of autophagic activity. Treatment with the mTOR inhibitor, rapamycin, increased LC3-II and the content of both APs detected by Cyto-ID Green staining and autophagolysosomes (APLs) measured by acridine orange staining and colocalization of LC3 and Lamp1. Lysosome function inhibitor bafilomycin A1 increased APs, but decreased APLs content under both basal and rapamycin-induced conditions. Inhibition of CD38 activity by nicotinamide or silencing of CD38 gene produced the similar effects to that bafilomycin A1 did in podocytes. To explore the possibility that CD38 may control podocyte autophagy through its regulation of lysosome function, the fusion of APs with lysosomes in living podocytes was observed by co-transfection of GFP-LC3B and RFP-Lamp1 expression vectors. A colocalization of GFP-LC3B and RFP-Lamp1 upon stimulation of rapamycin became obvious in transfected podocytes, which could be substantially blocked by nicotinamide, CD38 shRNA, and bafilomycin. Moreover, blockade of the CD38-mediated regulation by PPADS completely abolished rapamycin-induced fusion of APs with lysosomes. These results indicate that CD38 importantly control lysosomal function and influence autophagy at the maturation step in podocytes.

Burkholderia cenocepacia J2315 escapes to the cytosol and actively subverts autophagy in human macrophages

Selective autophagy functions to specifically degrade cellular cargo tagged by ubiquitination, including bacteria. Strains of the Burkholderia cepacia complex (Bcc) are opportunistic pathogens that cause life-threatening infections in patients with cystic fibrosis (CF) and chronic granulomatous disease (CGD). While there is evidence that defective macrophage autophagy in a mouse model of CF can influence B. cenocepacia susceptibility, there have been no comprehensive studies on how this bacterium is sensed and targeted by the host autophagy response in human macrophages. Here, we describe the intracellular life cycle of B. cenocepacia J2315 and its interaction with the autophagy pathway in human cells. Electron and confocal microscopy analyses demonstrate that the invading bacteria interact transiently with the endocytic pathway before escaping to the cytosol. This escape triggers theselective autophagy pathway, and the recruitment of ubiquitin, the ubiquitin-binding adaptors p62 and NDP52 and the autophagosome membrane-associated protein LC3B, to the bacterial vicinity. However, despite recruitment of these key autophagy pathway effectors, B. cenocepacia blocks autophagosome completion and replicates in the host cytosol. We find that a pre-infection increase in cellular autophagy flux can significantly inhibit B. cenocepacia replication and that lower autophagy flux in macrophages from immunocompromised CGD patients could contribute to increased B. cenocepacia susceptibility, identifying autophagy manipulation as a potential therapeutic approach to reduce bacterial burden in B. cenocepacia infections.

Bioenergetic and autophagic control by Sirt3 in response to nutrient deprivation in mouse embryonic fibroblasts

Sirt3 (sirtuin 3) is an NAD-dependent deacetylase localized to mitochondria. Sirt3 expression is increased in mouse muscle and liver by starvation, which could protect against the starvation-dependent increase in oxidative stress and protein damage. Damaged proteins and organelles depend on autophagy for removal and this is critical for cell survival, but the role of Sirt3 is unclear. To examine this, we used Sirt3-KO (knockout) mouse embryonic fibroblast cells, and found that, under basal conditions, Sirt3-KO cells exhibited increased autophagy flux compared with WT (wild-type) cells. In response to nutrient deprivation, both WT and KO cells exhibited increased basal and ATP-linked mitochondrial respiration, indicating an increased energy demand. Both cells exhibited lower levels of phosphorylated mTOR (mammalian target of rapamycin) and higher autophagy flux, with KO cells exhibiting lower maximal mitochondrial respiration and reserve capacity, and higher levels of autophagy than WT cells. KO cells exhibit higher phospho-JNK (c-Jun N-terminal kinase) and phospho-c-Jun than WT cells under starvation conditions. However, inhibition of JNK activity in Sirt3-KO cells did not affect LC3-I (light chain 3-I) and LC3-II levels, indicating that Sirt3-regulated autophagy is independent of the JNK pathway. Caspase 3 activation and cell death are significantly higher in Sirt3-KO cells compared with WT cells in response to nutrient deprivation. Inhibition of autophagy by chloroquine exacerbated cell death in both WT and Sirt3-KO cells, and by 3-methyadenine exacerbated cell death in Sirt3-KO cells. These data suggest that nutrient deprivation-induced autophagy plays a protective role in cell survival, and Sirt3 decreases the requirement for enhanced autophagy and improves cellular bioenergetics.

The scavenger protein apoptosis inhibitor of macrophages (AIM) potentiates the antimicrobial response against Mycobacterium tuberculosis by enhancing autophagy

Apoptosis inhibitor of macrophages (AIM), a scavenger protein secreted by tissue macrophages, is transcriptionally regulated by the nuclear receptor Liver X Receptor (LXR) and Retinoid X Receptor (RXR) heterodimer. Given that LXR exerts a protective immune response against M. tuberculosis, here we analyzed whether AIM is involved in this response. In an experimental murine model of tuberculosis, AIM serum levels peaked dramatically early after infection with M. tuberculosis, providing an in vivo biological link to the disease. We therefore studied the participation of AIM in macrophage response to M. tuberculosis in vitro. For this purpose, we used the H37Rv strain to infect THP-1 macrophages transfected to stably express AIM, thereby increasing infected macrophage survival. Furthermore, the expression of this protein enlarged foam cell formation by enhancing intracellular lipid content. Phagocytosis assays with FITC-labeled M. tuberculosis bacilli indicated that this protein was not involved in bacterial uptake; however, AIM expression decreased the number of intracellular cfus by up to 70% in bacterial killing assays, suggesting that AIM enhances macrophage mycobactericidal activity. Accordingly, M. tuberculosis-infected AIM-expressing cells upregulated the production of reactive oxygen species. Moreover, real-time PCR analysis showed increased mRNA levels of the antimicrobial peptides cathelicidin and defensin 4B. These increases were concomitant with greater cellular concentrations of the autophagy-related molecules Beclin 1 and LC3II, as well as enhanced acidification of mycobacterial phagosomes and LC3 co-localization. In summary, our data support the notion that AIM contributes to key macrophage responses to M. tuberculosis.

WetA is required for conidiogenesis and conidium maturation in the ascomycete fungus Fusarium graminearum

Fusarium graminearum, a prominent fungal pathogen that infects major cereal crops, primarily utilizes asexual spores to spread disease. To understand the molecular mechanisms underlying conidiogenesis in F. graminearum, we functionally characterized the F. graminearum ortholog of Aspergillus nidulans wetA, which has been shown to be involved in conidiogenesis and conidium maturation. Deletion of F. graminearum wetA did not alter mycelial growth, sexual development, or virulence, but the wetA deletion mutants produced longer conidia with fewer septa, and the conidia were sensitive to acute stresses, such as oxidative stress and heat stress. Furthermore, the survival rate of aged conidia from the F. graminearum wetA deletion mutants was reduced. The wetA deletion resulted in vigorous generation of single-celled conidia through autophagy-dependent microcycle conidiation, indicating that WetA functions to maintain conidial dormancy by suppressing microcycle conidiation in F. graminearum. Transcriptome analyses demonstrated that most of the putative conidiation-related genes are expressed constitutively and that only a few genes are specifically involved in F. graminearum conidiogenesis. The conserved and distinct roles identified for WetA in F. graminearum provide new insights into the genetics of conidiation in filamentous fungi.

Location and membrane sources for autophagosome formation - from ER-mitochondria contact sites to Golgi-endosome-derived carriers

Recent advances have revealed much about the signaling events and molecular components associated with autophagy. Although it is clear that there are multiple points of intersection and connection between autophagy and known vesicular membrane transport processes between membrane compartments, autophagy is modulated by a distinct set of molecular components, and the autophagosome has a unique membrane composition. A key question that has yet to be resolved with regards to autophagosome formation is its membrane source. Various evidences have indicated that membranes from the endoplasmic reticulum (ER), mitochondria, Golgi, endosomes and the plasma membrane could all potentially act as a source of autophagosomal membrane in non-specialized macroautophagy. Recent investigations have generated advances in terms of the mitochondria's involvement in starvation-induced autophagy, and refined localization of autophagosome formation to ER-mitochondria contact sites. On the other hand, data accumulates on the delivery of membrane sources to the pre-autophagosome structure by Atg9-containing mobile carriers, which likely originated from the Golgi-endosome system. The answer to the question on the origin of membrane materials for autophagosome biogenesis awaits further reconciliation of these different findings.

PSF knockdown enhances apoptosis via downregulation of LC3B in human colon cancer cells

Our previous study demonstrated that PTB-associated splicing factor (PSF) is an important regulator of cell death and plays critical roles in the survival and growth of colon cancer cells. However, the molecular mechanism that activates these downstream signaling events remains unknown. To address this issue, we investigated the effects of PSF knockdown in two different colon cancer cell lines, DLD-1 and HT-29. We found that knockdown of PSF markedly decreased the autophagic molecule LC3B in DLD-1 cells but not in HT-29 cells. Furthermore, DLD-1 cells were more susceptible to PSF knockdown-induced cell growth inhibition and apoptosis than HT-29 cells. This susceptibility is probably a result of LC3B inhibition, given the known relationship between autophagy and apoptosis. C3B is associated with a number of physiological processes, including cell growth and apoptotic cell death. Our results suggest that autophagy is inhibited by PSF knockdown and that apoptosis and cell growth inhibition may act together to mediate the PSF-LC3B signaling pathway. Furthermore, we found that the peroxisome proliferator-activated receptor gamma (PPARγ)-PSF complex induced LC3B downregulation in DLD-1 cells. The results of this study identify a new physiological role for the PSF-LC3B axis as a potential endogenous modulator of colon cancer treatment.

Bovine herpesvirus type 4 infection modulates autophagy in a permissive cell line

Bovine herpesvirus type 4 (BoHV-4), like other herpesviruses, induces a series of alterations in the host cell that modify the intracellular environment in favor of viral replication, survival and spread. This research examined the impact of BoHV-4 infection on autophagy in BoHV-4 infected Madin Darby bovine kidney (MDBK) cells. Protein extracts of BoHV-4 infected and control MDBK cells were subjected to Western blot. The concentrations of the autophagy and apoptosis-related proteins Beclin 1, p21, PI3 kinase, Akt1/2, mTOR, phospho mTOR, p62 and the light chain three (LC3) were normalized to the actin level and expressed as the densitometric ratio. Western blot analysis of virus-infected cells revealed that autophagic degradation pathway was induced in the late phase of BoHV-4 infection. After 48 h post-infection the protein LC3II, which is essential for autophagy was found to be markedly increased, while infection of MDBK cells with BoHV-4 resulted in a depletion of p62 levels. Becline 1, PI3 kinase, Akt1/2 and p21 expression increased between 24 and 48 h post-infection. Surprisingly, mTOR and its phosphorylated form, which are negative regulators of autophagy, also increased after 24 h post-infection. In conclusion, our findings suggest that BoHV-4 has developed mechanisms for modulation of autophagy that are probably part of a strategy designed to enhance viral replication and to evade the immune system. Additional studies on the relationship between autophagy and BoHV-4 replication and survival, in both lytic and latent replication phases, are needed to understand the role of autophagy in BoHV-4 pathogenesis.

bZIP transcription factor SmJLB1 regulates autophagy-related genes Smatg8 and Smatg4 and is required for fruiting-body development and vegetative growth in Sordaria macrospora

Autophagy is a precisely controlled degradation process in eukaryotic cells, during which the bulk of the cytoplasm is engulfed by a double membrane vesicle, the autophagosome. Fusion of the autophagosome with the vacuole leads to breakdown of its contents, such as proteins and organelles, and the recycling of nutrients. Earlier studies of autophagic genes of the core autophagic machinery in the filamentous ascomycete Sordaria macrospora elucidated the impact of autophagy on fungal viability, vegetative growth and fruiting-body development. To gain further knowledge about the regulation of autophagy in S. macrospora, we analyzed the function of the bZIP transcription factor SmJLB1, a homolog of the Podospora anserina basic zipper-type transcription factor induced during incompatibility 4 (IDI-4) and the Aspergillus nidulans transcription factor jun-like bZIP A (JlbA). Generation of the homokaryotic deletion mutant demonstrated S. macrospora Smjlb1 is associated with autophagy-dependent processes. Deletion of Smjlb1 abolished fruiting-body formation and impaired vegetative growth. SmJLB1 is localized to the cytoplasm and to nuclei. Quantitative real-time PCR experiments revealed an upregulated expression of autophagy-related genes Smatg8 and Smatg4 in the Smjlb1 deletion mutant, suggesting a transcriptional repression function of SmJLB1.

Effects of a marine serine protease inhibitor on viability and morphology of Trypanosoma cruzi, the agent of Chagas disease

It has been reported that serine peptidase activities of Trypanosoma cruzi play crucial roles in parasite dissemination and host cell invasion and therefore their inhibition could affect the progress of Chagas disease. The present study investigates the interference of the Stichodactyla helianthus Kunitz-type serine protease inhibitor (ShPI-I), a 55-amino acid peptide, in T. cruzi serine peptidase activities, parasite viability, and parasite morphology. The effect of this peptide was also studied in Leishmania amazonensis promastigotes and it was proved to be a powerful inhibitor of serine proteases activities and the parasite viability. The ultrastructural alterations caused by ShPI-I included vesiculation of the flagellar pocket membrane and the appearance of a cytoplasmic vesicle that resembles an autophagic vacuole. ShPI-I, which showed itself to be an important T. cruzi serine peptidase inhibitor, reduced the parasite viability, in a dose and time dependent manner. The maximum effect of peptide on T. cruzi viability was observed when ShPI-I at 1×10(-5)M was incubated for 24 and 48h which killed completely both metacyclic trypomastigote and epimastigote forms. At 1×10(-6)M ShPI-I, in the same periods of time, reduced parasite viability about 91-95% respectively. Ultrastructural analysis demonstrated the formation of concentric membranar structures especially in the cytosol, involving organelles and small vesicles. Profiles of endoplasmic reticulum were also detected, surrounding cytosolic vesicles that resembled autophagic vacuoles. These results suggest that serine peptidases are important in T. cruzi physiology since the inhibition of their activity killed parasites in vitro as well as inducing important morphological alterations. Protease inhibitors thus appear to have a potential role as anti-trypanosomatidal agents.

Pathological ventricular remodeling: mechanisms: part 1 of 2

Despite declines in heart failure morbidity and mortality with current therapies, rehospitalization rates remain distressingly high, substantially affecting individuals, society, and the economy. As a result, the need for new therapeutic advances and novel medical devices is urgent. Disease-related left ventricular remodeling is a complex process involving cardiac myocyte growth and death, vascular rarefaction, fibrosis, inflammation, and electrophysiological remodeling. Because these events are highly interrelated, targeting a single molecule or process may not be sufficient. Here, we review molecular and cellular mechanisms governing pathological ventricular remodeling.

Roles of autophagy-related genes Beclin-1 and LC3 in the development and progression of prostate cancer and benign prostatic hyperplasia

Prostate cancer (PCa) is common in Western populations and the second leading cause of cancer-related mortality among males in North America, with an increasing morbidity in China and other Asian countries. The aim of this study was to evaluate the protein expression of autophagy-related genes Beclin-1 and LC3 in patients with prostate cancer (PCa) and benign prostatic hyperplasia (BPH) and elucidate their association with p53 and Bcl-2. The total protein of 34 PCa and 50 BPH samples was extracted and the expression of Beclin-1 and LC3 was analyzed by western blotting assay. Subsequently, a total of 96 paraffin-embedded BPH tissue samples was subdivided into 2 groups, one group in which patients had received 5α-reductase inhibitor, due to its effect of androgen ablation, and the control group, in which patients had not received the 5α-reductase inhibitor. The samples were randomly collected and examined using immunohistochemical (IHC) analysis. The western blot analysis demonstrated that Beclin-l and LC3 expression was higher in BPH tissues compared to PCa tissues (P<0.001). There was no statistically significant difference between PCas of different Gleason scores (P>0.05). The result of IHC revealed that Beclin-l and LC3 expression in the group of patients who had received the 5α-reductase inhibitor was significantly higher compared to that in the control group; however, the expression of Bcl-2 and p53 was lower (P<0.05). Beclin-1 expression exhibited a negative correlation with Bcl-2 (r=-0.402, P<0.001), whereas LC3 expression exhibited a positive correlation with Beclin-1 (r=0.345, P=0.001) and a negative correlation with Bcl-2 (r=-0.216, P=0.035). It was suggested that autophagy-related genes Beclin-l and LC3 may be involved in the development and progression of PCa. In addition, the expression of these genes was higher in patients with BPH who had received a 5α-reductase inhibitor, due to androgen reduction. As a result, the induced autophagy may reduce the risk of PCa.

Highly purified, multi-wall carbon nanotubes induce light-chain 3B expression in human lung cells

Bronchial epithelial cells are targets of inhalation and play a critical role in the maintenance of mucosal integrity as mechanical barriers against various particles. Our previous result suggest that vapor-grown carbon fiber, HTT2800, which is one of the most highly purified multi-wall carbon nanotubes (MWCNT) showed cellular uptake of the carbon nanotube, increased cell death, enhanced DNA damage, and induced cytokine release. Increasing evidence suggests that autophagy may critically influence vital cellular processes such as apoptosis, cell proliferation and inflammation and thereby may play a critical role in pulmonary diseases. Autophagy was recently recognized as a critical cell death pathway, and autophagosome accumulation has been found to be associated with the exposure of various nanoparticles. In this study, the authors focus on the autophagic responses of HTT2800 exposure. The HTT2800-exposed cells induced LC3B expression and induced cell growth inhibition.

Oxidative stress, neurodegeneration, and the balance of protein degradation and protein synthesis

Oxidative stress occurs in a variety of disease settings and is strongly linked to the development of neuron death and neuronal dysfunction. Cells are equipped with numerous pathways to prevent the genesis, as well as the consequences, of oxidative stress in the brain. In this review we discuss the various forms and sources of oxidative stress in the brain and briefly discuss some of the complexities in detecting the presence of oxidative stress. We then focus the review on the interplay between the diverse cellular proteolytic pathways and their roles in regulating oxidative stress in the brain. Additionally, we discuss the involvement of protein synthesis in regulating the downstream effects of oxidative stress. Together, these components of the review demonstrate that the removal of damaged proteins by effective proteolysis and the synthesis of new and protective proteins are vital in the preservation of brain homeostasis during periods of increased levels of reactive oxygen species. Last, studies from our laboratory and others have demonstrated that protein synthesis is intricately linked to the rates of protein degradation, with impairment of protein degradation sufficient to decrease the rates of protein synthesis, which has important implications for successfully responding to periods of oxidative stress. Specific neurodegenerative diseases, including Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, and stroke, are discussed in this context. Taken together, these findings add to our understanding of how oxidative stress is effectively managed in the healthy brain and help elucidate how impairments in proteolysis and/or protein synthesis contribute to the development of neurodegeneration and neuronal dysfunction in a variety of clinical settings.

Ras inhibition enhances autophagy, which partially protects cells from death

Autophagy, a process of regulated turnover of cellular constituents, is essential for normal growth control but may be defective under pathological conditions. The Ras/PI3K/mTOR signaling pathway negatively regulates autophagy. Ras signaling has been documented in a large number of human cancers. In this in-vitro study we examined the effect of the Ras inhibitor Salirasib (S-trans, trans-farnesylthiosalicylic acid; FTS) on autophagy induction and cell viability. We show that Ras inhibition by FTS induced autophagy in several cell lines, including mouse embryonic fibroblasts and the human cancer cell lines HeLa, HCT-116 and DLD-1. The autophagy induced by FTS seems to inhibit the cell death induced by FTS, since in the absence of autophagy the death of FTS-treated cells was enhanced. Therefore, inhibition of autophagy may promote the inhibition of tumor cell growth and the cell death mediated by FTS.

Autophagic kinases SmVPS34 and SmVPS15 are required for viability in the filamentous ascomycete Sordaria macrospora

Autophagy is a tightly controlled degradation process of all eukaryotes. It includes the sequestration of cytoplasmic contents and organelles within a double-membraned autophagosome. Autophagy involves core autophagy related (atg) genes as well as genes regulating vesicle trafficking. Previously, we analyzed the impact of proteins of the core autophagic machinery SmATG7, SmATG8 and SmATG4 on the sexual and vegetative development of the filamentous ascomycete Sordaria macrospora. While deletion of Smatg8 and Smatg4 abolished fruiting-body formation and impaired vegetative growth, Smatg7 is required for viability. In yeast, the phosphatidylinositol 3-kinase vacuolar protein sorting 34 (Vps34) and its myristoylated membrane targeting unit, the protein kinase Vps15 have been shown to be important regulators of autophagy and vacuolar protein sorting. However, their exact role in filamentous ascomycetes remains elusive. To determine the function of Smvps34 and Smvps15 we isolated genes with high sequence similarity to Saccharomyces cerevisiae VPS34 and VPS15. For both genes we were not able to generate a homokaryotic knockout mutant in S. macrospora, suggesting that Smvps34 and Smvps15 are required for viability. Furthermore, we analyzed the repertoire of vps genes encoded by S. macrospora and could identify putative homologs of nearly all of the 61 VPS genes of S. cerevisiae.

Autophagy is a key feature in the pathogenesis of systemic sclerosis

Autophagosomes are formed during autophagy, which is activated by hypoxia and starvation. Autophagy is important for mast cell degranulation. We hypothesized that autophagy is a key feature in the pathogenesis of systemic sclerosis (SSc). We examined SSc clinical features and mast cell density across the presence and severity of autophagy. Skin punch biopsy was performed on 33 SSc patients and 6 healthy controls (HC). Autophagy was evaluated by immunofluorescence on paraffin sections using LC3-FITC staining on these patients. The intensity of staining and mast cell density was examined across clinical features in 19 of the SSc patients. Presence of autophagosome formation was assessed by EM in 17 of the SSc patients and 4 HC. In our SSc study population, 29 of subjects were female and 23 were limited cutaneous. Twenty-nine of 33 SSc patients had autophagy by LC3-FITC staining. Intensity of staining decreased with longer duration of SSc (p = 0.09) and RP (p = 0.10). Bloating and distention differed across level of intensity staining (Wilcoxon signed-rank test, p = 0.05), with the greatest levels among those with moderate intensity. On EM, autophagosome formation was present in 16 of 17 SSc patients and no HC. All SSc patients had perivascular mast cells. Autophagy was present in 29 of 33 SSc patients, and none of our HC suggesting importance in pathogenesis. Autophagy staining was greater among those with shorter duration of SSc. Bloating and distention were higher in patients with moderate autophagy staining. Perivascular mast cells were present in all SSc patients. The role of autophagy in vasculopathy and mast cell activation in SSc warrants further studies.

Probiotic Lactobacillus rhamnosus GG mono-association suppresses human rotavirus-induced autophagy in the gnotobiotic piglet intestine

BACKGROUND

Human rotavirus (HRV) is the most important cause of severe diarrhea in infants and young children. Probiotic Lactobacillus rhamnosus GG (LGG) reduces rotavirus infection and diarrhea. However, the molecular mechanisms of LGG-mediated protection from rotavirus infection are poorly understood. Autophagy plays an essential role in responses to microbial pathogens. However, the role of autophagy in HRV infection and LGG treatment is unknown. We hypothesize that rotavirus gastroenteritis activates autophagy and that LGG suppresses virus-induced autophagy and prevents intestinal damage in infected piglets.

METHODS

We used LGG feeding to combat viral gastroenteritis in the gnotobiotic pig model of virulent HRV infection.

RESULTS

We found that LGG feeding did not increase autophagy, whereas virus infection induced autophagy in the piglet intestine. Virus infection increased the protein levels of the autophagy markers ATG16L1 and Beclin-1 and the autophagy regulator mTOR. LGG treatment during viral gastroenteritis reduced autophagy marker expression to normal levels, induced apoptosis and partially prevented virus-induced tissue damage.

CONCLUSION

Our study provides new insights into virus-induced autophagy and LGG suppression of uncontrolled autophagy and intestinal injury. A better understanding of the antiviral activity of LGG will lead to novel therapeutic strategies for infant infectious diseases.

Rosiglitazone protects against palmitate-induced pancreatic beta-cell death by activation of autophagy via 5'-AMP-activated protein kinase modulation

Promoting beta-cell survival is crucial for the prevention of beta-cell failure in diabetes. Thiazolidinediones, a widely used drug to improve insulin sensitivity in clinical practice, is found to have a protective effect on islet beta-cell. To date, the mechanism underlying the protective role of thiazolidinedione on beta-cell survival remain largely unknown. Activation of autophagy was detected by transmission electron microscopy, western blot, and GFP-LC3 transfection. Cell viability was examined by WST-8. Cell apoptosis was demonstrated by DAPI and Annexin V/PI staining. Colony formation assay was used to detect long-term cell viability. We demonstrated that rosiglitazone-treated beta-cells were more resistant to palmitate-induced apoptosis. The conversion of LC3-I to LC3-II and accumulated autophagosomes were found to be upregulated in rosiglitazone-treated cells. Inhibition of autophagy augmented palmitate-induced apoptosis with rosiglitazone treatment, suggesting that autophagy plays an important role in the survival function of rosiglitazone on beta-cells. Furthermore, we showed that rosiglitazone could induce AMP-activated protein kinase (AMPK) phosphorylation and reduce p70S6 kinase phosphorylation. Inhibition of AMPK impaired autophagy activation and enhanced palmitate-induced apoptosis during rosiglitazone treatment. These findings reveal that rosiglitazone-induced autophagy contributes to its protective function on beta-cells during palmitate treatment.

Maintenance of mitochondrial morphology by autophagy and its role in high glucose effects on chronological lifespan of Saccharomyces cerevisiae

In Saccharomyces cerevisiae, mitochondrial morphology changes when cells are shifted between nonfermentative and fermentative carbon sources. Here, we show that cells of S. cerevisiae grown in different glucose concentrations display different mitochondrial morphologies. The morphology of mitochondria in the cells growing in 0.5% glucose was similar to that of mitochondria in respiring cells. However, the mitochondria of cells growing in higher glucose concentrations (2% and 4%) became fragmented after growth in these media, due to the production of acetic acid; however, the fragmentation was not due to intracellular acidification. From a screen of mutants involved in sensing and utilizing nutrients, cells lacking TOR1 had reduced mitochondrial fragmentation, and autophagy was found to be essential for this reduction. Mitochondrial fragmentation in cells grown in high glucose was reversible by transferring them into conditioned medium from a culture grown on 0.5% glucose. Similarly, the chronological lifespan of cells grown in high glucose medium was reduced, and this phenotype could be reversed when cells were transferred to low glucose conditioned medium. These data indicate that chronological lifespan seems correlated with mitochondrial morphology of yeast cells and that both phenotypes can be influenced by factors from conditioned medium of cultures grown in low glucose medium.

Visualization and quantitation of abundant macroautophagy in virus-infected cells by confocal three-dimensional fluorescence imaging

Varicella-zoster virus (VZV) is a human herpesvirus. Primary infection causes varicella (chickenpox), a viremic illness typified by an exanthem consisting of several hundred vesicles. When VZV reactivates from latency in the spinal ganglia during late adulthood, the emerging virus causes a vesicular dermatomal rash (herpes zoster or shingles). To expand investigations of autophagy during varicella and zoster, newer 3D imaging technology was combined with laser scanning confocal microscopy to provide animations of autophagosomes in the vesicular rash. First, the cells were immunolabeled with antibodies against VZV proteins and the LC3 protein, an integral autophagosomal protein. Antibody reagents lacking activity against the human blood group A1 antigen were selected. After laser excitation of the samples, optimized emission detection bandwidths were configured by Zeiss Zen control software. Confocal Z-stacks comprising up to 40 optical slices were reconstructed into 3D animations with the aid of Imaris software. With this imaging technology, individual autophagosomes were clearly detectable as spheres within each vesicular cell. To enumerate the number of autophagosomes, data sets from 50 cells were reconstructed as 3D fluorescence images and analyzed with MeasurementPro software. The mean number of autophagosomes per infected vesicular cell was >100, although over 200 autophagosomes were seen in a few cells. In summary, macroautophagy was easily quantitated within VZV-infected cells after immunolabeling and imaging by 3D confocal animation technology. These same 3D imaging techniques will be applicable for investigations of autophagy in other virus-infected cells.

Role of autophagy in prion protein-induced neurodegenerative diseases

Prion diseases, characterized by spongiform degeneration and the accumulation of misfolded and aggregated PrP(Sc) in the central nervous system, are one of fatal neurodegenerative and infectious disorders of humans and animals. In earlier studies, autophagy vacuoles in neurons were frequently observed in neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's diseases as well as prion diseases. Autophagy is a highly conserved homeostatic process by which several cytoplasmic components (proteins or organelles) are sequestered in a double-membrane-bound vesicle termed 'autophagosome' and degraded upon their fusion with lysosome. The pathway of intercellular self-digestion at basal physiological levels is indispensable for maintaining the healthy status of tissues and organs. In case of prion infection, increasing evidence indicates that autophagy has a crucial ability of eliminating pathological PrP(Sc) accumulated within neurons. In contrast, autophagy dysfunction in affected neurons may contribute to the formation of spongiform changes. In this review, we summarized recent findings about the effect of mammalian autophagy in neurodegenerative disorders, particularly in prion diseases. We also summarized the therapeutic potential of some small molecules (such as lithium, rapamycin, Sirtuin 1 and resveratrol) targets to mitigate such diseases on brain function. Furthermore, we discussed the controversial role of autophagy, whether it mediates neuronal toxicity or serves a protective function in neurodegenerative disorders.

Blood-brain barrier alterations provide evidence of subacute diaschisis in an ischemic stroke rat model

BACKGROUND

Comprehensive stroke studies reveal diaschisis, a loss of function due to pathological deficits in brain areas remote from initial ischemic lesion. However, blood-brain barrier (BBB) competence in subacute diaschisis is uncertain. The present study investigated subacute diaschisis in a focal ischemic stroke rat model. Specific focuses were BBB integrity and related pathogenic processes in contralateral brain areas.

METHODOLOGY/PRINCIPAL FINDINGS

In ipsilateral hemisphere 7 days after transient middle cerebral artery occlusion (tMCAO), significant BBB alterations characterized by large Evans Blue (EB) parenchymal extravasation, autophagosome accumulation, increased reactive astrocytes and activated microglia, demyelinization, and neuronal damage were detected in the striatum, motor and somatosensory cortices. Vascular damage identified by ultrastuctural and immunohistochemical analyses also occurred in the contralateral hemisphere. In contralateral striatum and motor cortex, major ultrastructural BBB changes included: swollen and vacuolated endothelial cells containing numerous autophagosomes, pericyte degeneration, and perivascular edema. Additionally, prominent EB extravasation, increased endothelial autophagosome formation, rampant astrogliosis, activated microglia, widespread neuronal pyknosis and decreased myelin were observed in contralateral striatum, and motor and somatosensory cortices.

CONCLUSIONS/SIGNIFICANCE

These results demonstrate focal ischemic stroke-induced pathological disturbances in ipsilateral, as well as in contralateral brain areas, which were shown to be closely associated with BBB breakdown in remote brain microvessels and endothelial autophagosome accumulation. This microvascular damage in subacute phase likely revealed ischemic diaschisis and should be considered in development of treatment strategies for stroke.