BNIP3 is an RB/E2F target gene required for hypoxia-induced autophagy

HIF-dependent and reversible nucleosome disassembly in hypoxia-inducible gene promoters

Hypoxia causes dramatic changes in gene expression profiles, and the mechanism of hypoxia-inducible transcription has been analyzed for use as a model system of stress-inducible gene regulation. In this study, changes in chromatin organization in promoters of hypoxia-inducible genes were investigated during hypoxia-reoxygenation conditions. Most of the hypoxia-inducible gene promoters were hypersensitive to DNase I under both normal and hypoxic conditions, and our data indicate an immediate recruitment of transcription factors under hypoxic conditions. In some of the hypoxia-inducible promoters, nucleosome-free DNA regions (NFRs) were established in parallel with hypoxia-induced transcription. We also show that the hypoxia-inducible formation of NFRs requires that hypoxia-inducible transcription factors (HIFs) bind to the promoters together with the transcriptional coactivator CBP. Within 1 h after the hypoxia exposure was ended (reoxygenation), HIF complexes were dissociated from the promoter regions. Within 24 h of reoxygenation, the hypoxia-induced transcription returned to basal levels and the nucleosome structure was reassembled in the hypoxia-inducible NFRs. Nucleosome reassembly required the function of the transcriptional coregulator SIN3A. Thus, reversible changes in nucleosome organization mediated by transcription factors are notable features of stress-inducible gene regulation.

Mitochondrial Quality Control and Disease: Insights into Ischemia-Reperfusion Injury

Mitochondria are key regulators of cell fate during disease. They control cell survival via the production of ATP that fuels cellular processes and, conversely, cell death via the induction of apoptosis through release of pro-apoptotic factors such as cytochrome C. Therefore, it is essential to have stringent quality control mechanisms to ensure a healthy mitochondrial network. Quality control mechanisms are largely regulated by mitochondrial dynamics and mitophagy. The processes of mitochondrial fission (division) and fusion allow for damaged mitochondria to be segregated and facilitate the equilibration of mitochondrial components such as DNA, proteins, and metabolites. The process of mitophagy are responsible for the degradation and recycling of damaged mitochondria. These mitochondrial quality control mechanisms have been well studied in chronic and acute pathologies such as Parkinson's disease, Alzheimer's disease, stroke, and acute myocardial infarction, but less is known about how these two processes interact and contribute to specific pathophysiologic states. To date, evidence for the role of mitochondrial quality control in acute and chronic disease is divergent and suggests that mitochondrial quality control processes can serve both survival and death functions depending on the disease state. This review aims to provide a synopsis of the molecular mechanisms involved in mitochondrial quality control, to summarize our current understanding of the complex role that mitochondrial quality control plays in the progression of acute vs chronic diseases and, finally, to speculate on the possibility that targeted manipulation of mitochondrial quality control mechanisms may be exploited for the rationale design of novel therapeutic interventions.

Role of LncRNA MALAT-1 in hypoxia-induced PC12 cell injury via regulating p38MAPK signaling pathway

OBJECTIVE

To investigate the role of LncRNA MALAT-1 in hypoxia-induced cell injury.

METHODS

Pheochromocytoma-12 (PC12) cells were divided into seven groups: Control group, Hypoxia group (Cells treated with CoCl₂), MALAT-1 group (Hypoxic cells treated with MALAT-1), NC group (Hypoxic cells treated with empty plasmid), MALAT-1 siRNA group (Hypoxic cells treated with siRNA MALAT-1), SB203580 group (Hypoxic cells treated with p38MAPK inhibitor), and MALAT-1 + SB20358 group. The content of reactive oxygen species (ROS), malondialdehyde (MDA), super oxide dismutase (SOD) and lactate dehydrogenase (LDH) was determined. Cell viability was detected by MTT assay. Apoptotic cells were observed by Hoechst 33258 and TUNEL staining assay. Mitochondrial membrane potential (MMP) was measured using JC1 vital dye.

RESULTS

The decreased cell viability and increased expressions of MALAT-1 and p-p38 were observed in hypoxic PC12 cells time-dependently (P < 0.05). Besides, hypoxic PC12 cells had an elevation in p-p38, ROS, MDA and LDH with the increased apoptotic cells, but a reduction in SOD and MMP, and these similar changes were more obvious in those hypoxic cells treated with MALAT-1 when compared with Controls (all P < 0.05). However, the hypoxic PC12 cells treated with SB203580 and MALAT-1 siRNA led to opposite results compared with MALAT-1 group (all P < 0.05). Importantly, SB203580 could reverse the function of MALAT-1 in aggravating the hypoxia injury of PC12 cells.

CONCLUSION

MALAT-1 can promote the apoptosis and oxidative stress of PC12 cells by activating p38MAPK pathway, thus aggravating the damage of PC12 cells induced by chemical hypoxia.

In vitro study of FUZ as a novel potential therapeutic target in non-small-cell lung cancer

FUZ is regarded as a planar cell polarity effector that controls multiple cellular processes during vertebrate development. However, the role of FUZ in tumor biology remains poorly studied. Our purpose of this study is to discover the physiological effects and mechanism of FUZ in non-small-cell lung cancer (NSCLC) in vitro. With the help of bioinformatics analysis, we noticed that the expression level of FUZ negatively correlates with prognosis of NSCLC patients. Exogenous FUZ expression markedly promoted cell proliferation of NSCLC cells. The phosphorylation of Erk1/2, STAT3 and related signaling molecules were induced activated after FUZ over-expression. FUZ also plays an important role in cell motility by regulating cell signaling pathways and inducing epithelial to mesenchymal transition (EMT). FUZ promotes EMT along with the up-regulation of N-cadherin, vimentin, Zeb1, Twist1 and decreased level of E-cadherin. Furthermore, we also carried out FUZ directed siRNA treatments to prove the above observations. Knockdown of FUZ resulted in delayed cell growth as well as impaired cell migration and reversed EMT phonotype. Importantly, we reported for the first time that FUZ is a BNIP3-interacting protein. Loss of FUZ resulted in decreased BNIP3 protein level, but no influence on BNIP3 mRNA level, suggesting weakened stability of BNIP3 protein. Overall, our results in vitro show that FUZ is responsible for NSCLC progression and metastasis, suggesting that FUZ can be a potential therapeutic target for NSCLC.

Autophagy in diabetic kidney disease: regulation, pathological role and therapeutic potential

Diabetic kidney disease, a leading cause of end-stage renal disease, has become a serious public health problem worldwide and lacks effective therapies. Autophagy is a highly conserved lysosomal degradation pathway that removes protein aggregates and damaged organelles to maintain cellular homeostasis. As important stress-responsive machinery, autophagy is involved in the pathogenesis of various diseases. Emerging evidence has suggested that dysregulated autophagy may contribute to both glomerular and tubulointerstitial pathologies in kidneys under diabetic conditions. This review summarizes the recent findings regarding the role of autophagy in the pathogenesis of diabetic kidney disease and highlights the regulation of autophagy by the nutrient-sensing pathways and intracellular stress signaling in this disease. The advances in our understanding of autophagy in diabetic kidney disease will facilitate the discovery of a new therapeutic target for the prevention and treatment of this life-threatening diabetes complication.

Effect of Roux-en-Y gastric bypass on liver mitochondrial dynamics in a rat model of obesity

Bariatric surgery provides significant and durable improvements in glycemic control and hepatic steatosis, but the underlying mechanisms that drive improvements in these metabolic parameters remain to be fully elucidated. Recently, alterations in mitochondrial morphology have shown a direct link to nutrient adaptations in obesity. Here, we evaluate the effects of Roux-en-Y gastric bypass (RYGB) surgery on markers of liver mitochondrial dynamics in a diet-induced obesity Sprague-Dawley (SD) rat model. Livers were harvested from adult male SD rats 90-days after either Sham or RYGB surgery and continuous high-fat feeding. We assessed expression of mitochondrial proteins involved in fusion, fission, mitochondrial autophagy (mitophagy) and biogenesis, as well as differences in citrate synthase activity and markers of oxidative stress. Gene expression for mitochondrial fusion genes, mitofusin 1 (Mfn1; P < 0.05), mitofusin 2 (Mfn2; P < 0.01), and optic atrophy 1 (OPA1; P < 0.05) increased following RYGB surgery. Biogenesis regulators, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α; P < 0.01) and nuclear respiratory factor 1 (Nrf1; P < 0.05), also increased in the RYGB group, as well as mitophagy marker, BCL-2 interacting protein 3 (Bnip3; P < 0.01). Protein expression for Mfn1 (P < 0.001), PGC1α (P < 0.05), BNIP3 (P < 0.0001), and mitochondrial complexes I-V (P < 0.01) was also increased by RYGB, and Mfn1 expression negatively correlated with body weight, insulin resistance, and fasting plasma insulin. In the RYGB group, citrate synthase activity was increased (P < 0.02) and reactive oxygen species (ROS) was decreased compared to the Sham control group (P < 0.05), although total antioxidant capacity was unchanged between groups. These data are the first to show an association between RYGB surgery and improved markers of liver mitochondrial dynamics. These observed improvements may be related to weight loss and reduced energetic demand on the liver, which could facilitate normalization of glucose homeostasis and protect against hepatic steatosis.

EGFRvIII expression triggers a metabolic dependency and therapeutic vulnerability sensitive to autophagy inhibition

Expression of EGFRvIII is frequently observed in glioblastoma and is associated with increased cellular proliferation, enhanced tolerance to metabolic stresses, accelerated tumor growth, therapy resistance and poor prognosis. We observed that expression of EGFRvIII elevates the activation of macroautophagy/autophagy during starvation and hypoxia and explored the underlying mechanism and consequence. Autophagy was inhibited (genetically or pharmacologically) and its consequence for tolerance to metabolic stress and its therapeutic potential in (EGFRvIII+) glioblastoma was assessed in cellular systems, (patient derived) tumor xenopgrafts and glioblastoma patients. Autophagy inhibition abrogated the enhanced proliferation and survival advantage of EGFRvIII+ cells during stress conditions, decreased tumor hypoxia and delayed tumor growth in EGFRvIII+ tumors. These effects can be attributed to the supporting role of autophagy in meeting the high metabolic demand of EGFRvIII+ cells. As hypoxic tumor cells greatly contribute to therapy resistance, autophagy inhibition revokes the radioresistant phenotype of EGFRvIII+ tumors in (patient derived) xenograft tumors. In line with these findings, retrospective analysis of glioblastoma patients indicated that chloroquine treatment improves survival of all glioblastoma patients, but patients with EGFRvIII+ glioblastoma benefited most. Our findings disclose the unique autophagy dependency of EGFRvIII+ glioblastoma as a therapeutic opportunity. Chloroquine treatment may therefore be considered as an additional treatment strategy for glioblastoma patients and can reverse the worse prognosis of patients with EGFRvIII+ glioblastoma.

Expanding perspectives on the significance of mitophagy in cancer

Mitophagy is a selective mode of autophagy in which mitochondria are specifically targeted for degradation at the autophagolysosome. Mitophagy is activated by stresses such as hypoxia, nutrient deprivation, DNA damage, inflammation and mitochondrial membrane depolarization and plays a role in maintaining mitochondrial integrity and function. Defects in mitophagy lead to mitochondrial dysfunction that can affect metabolic reprogramming in response to stress, alter cell fate determination and differentiation, which in turn affects disease incidence and etiology, including cancer. Here, we discuss how different mitophagy adaptors and modulators, including Parkin, BNIP3, BNIP3L, p62/SQSTM1 and OPTN, are regulated in response to physiological stresses and deregulated in cancers. Additionally, we explore how these different mitophagy control pathways coordinate with each other. Finally, we review new developments in understanding how mitophagy affects stemness, cell fate determination, inflammation and DNA damage responses that are relevant to understanding the role of mitophagy in cancer.

Akebia saponin D alleviates hepatic steatosis through BNip3 induced mitophagy

Akebia Saponin D (ASD) is the most abundant constituent of the rhizome of Dipsacus asper Wall. The prior studies have shown that ASD alleviates hepatic steatosis targeted at the modulation of autophagy and exerts hepatoprotective effects through mitochondria. However, it is still unclear which signal transduction pathway that ASD increase autophagy and protect the mitochondria. The purpose of this paper was to explore the mechanisms through which ASD alleviates hepatic steatosis. ASD significantly reduced lipid accumulation in BRL cells. Furthermore, ASD significantly increased the mitophagy acting as increase the colocalization between mitochondria and punctate EGFP-LC3. ASD treatment increased the expression of BNip3, phospho-AMPK, prevented oleic acid (OA) induced LC3-II and phospho-mTOR expression. These effects were similar to the effects cotreatment with rapamycin. ASD treatment could not attenuate the expression of BNip3 blocked by chloroquine (CQ) or siRNA-mediated knockdown of BNip3. These results suggest that Akebia saponin D alleviates hepatic steatosis targeted at BNip3 mediated mitophagy. Activation of BNip3 via ASD may offer a new strategy for treating NAFLD.

The ultrastructural characteristics of porcine hepatocytes donated after cardiac death and preserved with warm machine perfusion preservation

The effects of warm machine perfusion preservation of liver grafts donated after cardiac death on the intracellular three-dimensional ultrastructure of the organelles in hepatocytes remain unclear. Here we analyzed comparatively the ultrastructure of the endomembrane systems in porcine hepatocytes under warm ischemia and successive hypothermic and midthermic machine perfusion preservation, a type of the warm machine perfusion. Porcine liver grafts which had a warm ischemia time of 60 minutes were perfused for 4 hours with modified University of Wisconsin gluconate solution. Group A grafts were preserved with hypothermic machine perfusion preservation at 8°C constantly for 4 hours. Group B grafts were preserved with rewarming up to 22°C by warm machine perfusion preservation for 4 hours. An analysis of hepatocytes after 60 minutes of warm ischemia by scanning electron microscope revealed the appearance of abnormal vacuoles and invagination of mitochondria. In the hepatocytes preserved by subsequent hypothermic machine perfusion preservation, strongly swollen mitochondria were observed. In contrast, the warm machine perfusion preservation could preserve the functional appearance of mitochondria in hepatocytes. Furthermore, abundant vacuoles and membranous structures sequestrating cellular organelles like autophagic vacuoles were frequently observed in hepatocytes after warm machine perfusion preservation. In conclusion, the ultrastructure of the endomembrane systems in the hepatocytes of liver grafts changed in accordance with the temperature conditions of machine perfusion preservation. In addition, temperature condition of the machine perfusion preservation may also affect the condition of the hepatic graft attributed to autophagy systems, and consequently alleviate the damage of the hepatocytes.

Autophagy protects auditory hair cells against neomycin-induced damage

Aminoglycosides are toxic to sensory hair cells (HCs). Macroautophagy/autophagy is an essential and highly conserved self-digestion pathway that plays important roles in the maintenance of cellular function and viability under stress. However, the role of autophagy in aminoglycoside-induced HC injury is unknown. Here, we first found that autophagy activity was significantly increased, including enhanced autophagosome-lysosome fusion, in both cochlear HCs and HEI-OC-1 cells after neomycin or gentamicin injury, suggesting that autophagy might be correlated with aminoglycoside-induced cell death. We then used rapamycin, an autophagy activator, to increase the autophagy activity and found that the ROS levels, apoptosis, and cell death were significantly decreased after neomycin or gentamicin injury. In contrast, treatment with the autophagy inhibitor 3-methyladenine (3-MA) or knockdown of autophagy-related (ATG) proteins resulted in reduced autophagy activity and significantly increased ROS levels, apoptosis, and cell death after neomycin or gentamicin injury. Finally, after neomycin injury, the antioxidant N-acetylcysteine could successfully prevent the increased apoptosis and HC loss induced by 3-MA treatment or ATG knockdown, suggesting that autophagy protects against neomycin-induced HC damage by inhibiting oxidative stress. We also found that the dysfunctional mitochondria were not eliminated by selective autophagy (mitophagy) in HEI-OC-1 cells after neomycin treatment, suggesting that autophagy might not directly target the damaged mitochondria for degradation. This study demonstrates that moderate ROS levels can promote autophagy to recycle damaged cellular constituents and maintain cellular homeostasis, while the induction of autophagy can inhibit apoptosis and protect the HCs by suppressing ROS accumulation after aminoglycoside injury.

Expression and Functional Characterization of the BNIP3 Protein in Renal Cell Carcinomas

BNIP3 (Bcl-2/adenovirus E1B 19-kDa interacting protein 3) is a BH3-only protein that regulates apoptosis and autophagy. BNIP3 plays also an important role in hypoxia-induced cell response and is regulated by HIF1. Here, we studied a possible association of BNIP3 expression and the prognosis of patients with renal cell carcinomas (RCCs) and examined the functional relevance of BNIP3 in the regulation of cell survival and apoptosis of renal carcinoma cells. BNIP3 expression was determined by immunohistochemistry in RCC tumor tissue samples of 569 patients using a tissue microarray. Functional characterization of BNIP3 in renal carcinoma cells indicates prosurvival effects. In human RCC tumor samples, high cytoplasmic BNIP3 expression was associated with high-grade RCCs and regional lymph node metastasis. BNIP3 expression correlated negatively with disease-specific survival. Multivariate Cox regression analysis retained BNIP3 expression as an independent prognostic factor in patients without distant metastasis. Together, our studies imply that BNIP3 regulates cell survival in RCCs and its expression is an independent prognostic marker in patients with localized RCCs.

Autophagy: The spotlight for cellular stress responses

Autophagy is an essential cellular mechanism which plays "housekeeping" role in normal physiological processes including removing of long lived, aggregated and misfolded proteins, clearing damaged organelles, growth regulation and aging. Autophagy is also involved in a variety of biological functions like development, cellular differentiation, defense against pathogens and nutritional starvation. The integration of autophagy into these biological functions and other stress responses is determined by the transcriptional factors that undertake the regulatory mechanism. This review discusses the machinery of autophagy, the molecular web that connects autophagy to various stress responses like inflammation, hypoxia, ER stress, and various other pathologic conditions. Defects in autophagy regulation play a central role in number of diseases, including neurodegenerative diseases, cancer, pathogen infection and metabolic diseases. Similarly, inhibiting autophagy would contribute in the treatment of cancer. However, understanding the biology of autophagy regulation requires pharmacologically active compounds which modulate the autophagy process. Inducers of autophagy are currently receiving considerable attention as autophagy upregulation may be a therapeutic benefit for certain neurodegenerative diseases (via removal of protein aggregates) while the inhibitors are being investigated for the treatment of cancers. Both induction and inhibition of autophagy have been proven to be beneficial in the treatment of cancer. This dual role of autophagy in cancers is now getting uncovered by the advancement in the research findings and development of effective autophagy modulators.

BNIP3 induces apoptosis and protective autophagy under hypoxia in esophageal squamous cell carcinoma cell lines: BNIP3 regulates cell death

Bcl-2/adenovirus E1B 19-kDa interacting protein (BNIP3), a pro-apoptosis protein regulated by the methylation status of its promoter, has been implicated in inducing autophagy. However, the roles of BNIP3 and BNIP3-induced autophagy under hypoxia remain uncertain in esophageal squamous cell carcinoma (ESCC). Two esophageal squamous cancer cell lines, CAES17 and KYSE140, were selected on the basis of the expression and methylation status of BNIP3 to investigate the features of BNIP3 under hypoxia. Hypoxia increased cell death and the expression of BNIP3, whose promoter status was lower methylation, in a time-dependent manner. BNIP3 knockdown by RNA interference downregulated cell death. These studies demonstrated that the exposure of ESCC cells to hypoxia increased the autophagic punctate distribution of MDC staining and GFP-LC3 and that autophagy rate could be inhibited by BNIP3-siRNA. In addition, under hypoxia, cells transfected with BNIP3-siRNA exhibited a lower apoptosis rate than the control, and the apoptosis induced by BNIP3 exhibited a caspase-independent manner. Furthermore, the administration of the autophagic inhibitor 3-methyladenine (3-MA) could augment BNIP3-induced cell apoptosis and death, suggesting that autophagy plays a protective role under hypoxia. Together, our studies indicated that BNIP3 exerts prodeath effects through the induction of caspase-independent apoptosis under hypoxia in ESCC, though BNIP3-induced autophagy acting as a survival mechanism.

ATF3 negatively regulates cellular antiviral signaling and autophagy in the absence of type I interferons

Stringent regulation of antiviral signaling and cellular autophagy is critical for the host response to virus infection. However, little is known how these cellular processes are regulated in the absence of type I interferon signaling. Here, we show that ATF3 is induced following Japanese encephalitis virus (JEV) infection, and regulates cellular antiviral and autophagy pathways in the absence of type I interferons in mouse neuronal cells. We have identified new targets of ATF3 and show that it binds to the promoter regions of Stat1, Irf9, Isg15 and Atg5 thereby inhibiting cellular antiviral signaling and autophagy. Consistent with these observations, ATF3-depleted cells showed enhanced antiviral responses and induction of robust autophagy. Furthermore, we show that JEV replication was significantly reduced in ATF3-depleted cells. Our findings identify ATF3 as a negative regulator of antiviral signaling and cellular autophagy in mammalian cells, and demonstrate its important role in JEV life cycle.

Transcriptional regulation of mammalian autophagy at a glance

Macroautophagy, hereafter referred to as autophagy, is a catabolic process that results in the lysosomal degradation of cytoplasmic contents ranging from abnormal proteins to damaged cell organelles. It is activated  under diverse conditions, including nutrient deprivation and hypoxia. During autophagy, members of the core autophagy-related (ATG) family of proteins mediate membrane rearrangements, which lead to the engulfment and degradation of cytoplasmic cargo. Recently, the nuclear regulation of autophagy, especially by transcription factors and histone modifiers, has gained increased attention. These factors are not only involved in rapid responses to autophagic stimuli, but also regulate the long-term outcome of autophagy. Now there are more than 20 transcription factors that have been shown to be linked to the autophagic process. However, their interplay and timing appear enigmatic as several have been individually shown to act as major regulators of autophagy. This Cell Science at a Glance article and the accompanying poster highlights the main cellular regulators of transcription involved in mammalian autophagy and their target genes.

Angiotensin II Type 1 Receptor-Associated Protein Regulates Kidney Aging and Lifespan Independent of Angiotensin

Background

The kidney is easily affected by aging‐associated changes, including glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Particularly, renal tubulointerstitial fibrosis is a final common pathway in most forms of progressive renal disease. Angiotensin II type 1 receptor (AT1R)‐associated protein (ATRAP), which was originally identified as a molecule that binds to AT1R, is highly expressed in the kidney. Previously, we have shown that ATRAP suppresses hyperactivation of AT1R signaling, but does not affect physiological AT1R signaling.

Methods and Results

We hypothesized that ATRAP has a novel functional role in the physiological age‐degenerative process, independent of modulation of AT1R signaling. ATRAP‐knockout mice were used to study the functional involvement of ATRAP in the aging. ATRAP‐knockout mice exhibit a normal age‐associated appearance without any evident alterations in physiological parameters, including blood pressure and cardiovascular and metabolic phenotypes. However, in ATRAP‐knockout mice compared with wild‐type mice, the following takes place: (1) age‐associated renal function decline and tubulointerstitial fibrosis are more enhanced; (2) renal tubular mitochondrial abnormalities and subsequent increases in the production of reactive oxygen species are more advanced; and (3) life span is 18.4% shorter (median life span, 100.4 versus 123.1 weeks). As a key mechanism, age‐related pathological changes in the kidney of ATRAP‐knockout mice correlated with decreased expression of the prosurvival gene, Sirtuin1. On the other hand, chronic angiotensin II infusion did not affect renal sirtuin1 expression in wild‐type mice.

Conclusions

These results indicate that ATRAP plays an important role in inhibiting kidney aging, possibly through sirtuin1‐mediated mechanism independent of blocking AT1R signaling, and further protecting normal life span.

MicroRNA-210 alleviates oxidative stress-associated cardiomyocyte apoptosis by regulating BNIP3

Oxidative stress-induced myocardial apoptosis and necrosis are involved in ischemia/reperfusion (I/R) injury. This study was performed to investigate microRNA (miR)-210's role in oxidative stress-related myocardial damage. The expression of miR-210 was upregulated in myocardial tissues of I/R rats, while that of Bcl-2 adenovirus E1B 19kDa-interacting protein 3 (BNIP3) was downregulated. To simulate in vivo oxidative stress, H9c2 cells were treated with H₂O₂ for 48 h. MiR-210 level was increased upon H₂O₂ stimulation, peaked at 8 h, and then decreased. An opposite expression pattern of BNIP3 was observed. BNIP3 was demonstrated as a direct target of miR-210 via luciferase reporter assay. H₂O₂-induced cell apoptosis was attenuated by miR-210 mimics, whereas aggravated by miR-210 inhibitor. MiR-210 knockdown-induced cell apoptosis in presence of H₂O₂ was attenuated by BNIP3 siRNA. Our work demonstrates that miR-210 plays a protective role in H₂O₂-induced cardiomyocyte apoptosis at least by regulating the pro-apoptotic BNIP3.

Dexmedetomidine preconditioning protects against lung injury induced by ischemia-reperfusion through inhibition of autophagy

The present study aimed to evaluate the role of autophagy in the protective effect of dexmedetomidine in lung injury caused by ischemia-reperfusion (IR) in rats. In total 48 adult male Sprague-Dawley rats were randomly divided into 6 groups (n=8) as follows: i) Sham group; ii) the IR group; iii) IR + 1 µg/kg dexmedetomidine preconditioning group (pre-LD); iv) IR + 10 µg/kg dexmedetomidine preconditioning group (pre-HD); v) IR + 1 µg/kg dexmedetomidine postconditioning group (post-LD); and vi) IR + 10 µg/kg dexmedetomidine postconditioning group (post-HD). After the rats were anesthetized, the hilum of the left lung was occluded with a non-invasive microvascular clip for 30 min to induce ischemia. The clip was then removed and the left lung was allowed to regain ventilation and blood for 2 h. The rats were then sacrificed, the left lung removed and the wet/dry (W/D) lung weight ratio was determined. Pathological changes to the lungs were evaluated by light and transmission electron microscopy. Furthermore, the rate of lung cell apoptosis was determined by the TUNEL assay. The expression of hypoxia-inducible factor 1α (HIF-1α), Bcl-2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3), BNIP3 like (BNIP3 L) and microtubule-associated protein 1A/1B light chain 3B (LC3II) was determined by western blotting. Compared with the sham group, a significant increase in the W/D lung weight ratio, and malondialdehyde (MDA), BNIP3, BNIP3 L and LC3II levels were observed in the IR group, and HIF-1α levels and superoxide dismutase (SOD) activity were decreased. Furthermore, the W/D ratio was lower in the pre-LD and pre-HD groups than in the IR group. Additionally, SOD activity was significantly higher and MDA expression was significantly lower in the pre-LD and pre-HD groups compared with the IR group. BNIP3, BNIP3 L and LC3II protein levels were significantly lower in the pre-LD and pre-HD groups compared with the IR group, while HIF-1α was notably upregulated in the pre-LD and pre-HD groups compared with the IR group. In conclusion, the results of the present study indicate that dexmedetomidine preconditioning protects against lung injury induced by IR through inhibition of autophagy and apoptosis.

RB1: a prototype tumor suppressor and an enigma

In this review, Dyson summarizes some recent developments in pRB research and focuses on progress toward answers for the three fundamental questions that sit at the heart of the pRB literature: What does pRB do? How does the inactivation of RB change the cell? How can our knowledge of RB function be exploited to provide better treatment for cancer patients?

The retinoblastoma susceptibility gene (RB1) was the first tumor suppressor gene to be molecularly defined. RB1 mutations occur in almost all familial and sporadic forms of retinoblastoma, and this gene is mutated at variable frequencies in a variety of other human cancers. Because of its early discovery, the recessive nature of RB1 mutations, and its frequency of inactivation, RB1 is often described as a prototype for the class of tumor suppressor genes. Its gene product (pRB) regulates transcription and is a negative regulator of cell proliferation. Although these general features are well established, a precise description of pRB's mechanism of action has remained elusive. Indeed, in many regards, pRB remains an enigma. This review summarizes some recent developments in pRB research and focuses on progress toward answers for the three fundamental questions that sit at the heart of the pRB literature: What does pRB do? How does the inactivation of RB change the cell? How can our knowledge of RB function be exploited to provide better treatment for cancer patients?

Bitter taste receptor agonists alter mitochondrial function and induce autophagy in airway smooth muscle cells

Airway remodeling, including increased airway smooth muscle (ASM) mass, is a hallmark feature of asthma and COPD. We previously identified the expression of bitter taste receptors (TAS2Rs) on human ASM cells and demonstrated that known TAS2R agonists could promote ASM relaxation and bronchodilation and inhibit mitogen-induced ASM growth. In this study, we explored cellular mechanisms mediating the antimitogenic effect of TAS2R agonists on human ASM cells. Pretreatment of ASM cells with TAS2R agonists chloroquine and quinine resulted in inhibition of cell survival, which was largely reversed by bafilomycin A1, an autophagy inhibitor. Transmission electron microscope studies demonstrated the presence of double-membrane autophagosomes and deformed mitochondria. In ASM cells, TAS2R agonists decreased mitochondrial membrane potential and increased mitochondrial ROS and mitochondrial fragmentation. Inhibiting dynamin-like protein 1 (DLP1) reversed TAS2R agonist-induced mitochondrial membrane potential change and attenuated mitochondrial fragmentation and cell death. Furthermore, the expression of mitochondrial protein BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 (Bnip3) and mitochondrial localization of DLP1 were significantly upregulated by TAS2R agonists. More importantly, inhibiting Bnip3 mitochondrial localization by dominant-negative Bnip3 significantly attenuated cell death induced by TAS2R agonist. Collectively the TAS2R agonists chloroquine and quinine modulate mitochondrial structure and function, resulting in ASM cell death. Furthermore, Bnip3 plays a central role in TAS2R agonist-induced ASM functional changes via a mitochondrial pathway. These findings further establish the cellular mechanisms of antimitogenic effects of TAS2R agonists and identify a novel class of receptors and pathways that can be targeted to mitigate airway remodeling as well as bronchoconstriction in obstructive airway diseases.

Autophagy and the Cell Cycle: A Complex Landscape

Autophagy is a self-degradation pathway, in which cytoplasmic material is sequestered in double-membrane vesicles and delivered to the lysosome for degradation. Under basal conditions, autophagy plays a homeostatic function. However, in response to various stresses, the pathway can be further induced to mediate cytoprotection. Defective autophagy has been linked to a number of human pathologies, including neoplastic transformation, even though autophagy can also sustain the growth of tumor cells in certain contexts. In recent years, a considerable correlation has emerged between autophagy induction and stress-related cell-cycle responses, as well as unexpected roles for autophagy factors and selective autophagic degradation in the process of cell division. These advances have obvious implications for our understanding of the intricate relationship between autophagy and cancer. In this review, we will discuss our current knowledge of the reciprocal regulation connecting the autophagy pathway and cell-cycle progression. Furthermore, key findings involving nonautophagic functions for autophagy-related factors in cell-cycle regulation will be addressed.

Albumin-Based Nitric Oxide Traffic System for the Treatment of Intractable Cancers

Biomacromolecules (>40 kDa) have been developed as drug delivery system (DDS) carriers of low-molecular weight drugs to promote these drugs' uptake by cancer tissues via enhanced permeability and retention (EPR) effects. Human serum albumin (HSA) has been found to accumulate in cancer tissues via this EPR effect. HSA is the most abundant protein in serum, which performs essential physiological functions such as the transportation of many endogenous and exogenous ligands. Nitric oxide (NO) is a very small ligand of HSA; it is a unique and diffusible molecular messenger that plays a central role in mammalian physiology. Although the in vivo half-life of NO is extremely short, HSA could prolong the half-life of NO via S-nitrosation at the position of Cys-34. S-Nitrosated HSA (mono-SNO-HSA) is called an 'Endogenous NO traffic protein,' due to the highly stable S-nitroso form in circulating blood, and to the efficiency of S-transnitrosation in cells that require NO. Mono-SNO-HSA possesses a very strong cytoprotective action via the induction of heme oxygenase-1. On the other hand, HSA reinforced with approximately seven NO molecules (poly-SNO-HSA), which we developed by means of chemical modification, possesses multiple anticancer activities. Our previous data clarified that the high expression of protein disulfide isomerase on the surface of cancer cells plays a very important role in the anticancer action of poly-SNO-HSA. In this review, we focus on the advantage of poly-SNO-HSA in treating intractable cancers from the viewpoint of drug delivery systems and drug resistance.

Activating Autophagy by Aerobic Exercise in Mice

Autophagy is a lysosomal degradation pathway essential for cell homeostasis, function and differentiation. Under stress conditions, autophagy is induced and targets various cargos, such as bulk cytosol, damaged organelles and misfolded proteins, for degradation in lysosomes. Resulting nutrient molecules are recycled back to the cytosol for new protein synthesis and ATP production. Upregulation of autophagy has beneficial effects against the pathogenesis of many diseases, and pharmacological and physiological strategies to activate autophagy have been reported. Aerobic exercise is recently identified as an efficient autophagy inducer in multiple organs in mice, including muscle, liver, heart and brain. Here we show procedures to induce autophagy in vivo by either forced treadmill exercise or voluntary wheel running. We also demonstrate microscopic and biochemical methods to quantitatively analyze autophagy levels in mouse tissues, using the marker proteins LC3 and p62 that are transported to and degraded in lysosomes along with autophagosomes.

Environmental factors in breast cancer invasion: a mathematical modelling review

This review presents a brief overview of breast cancer, focussing on its heterogeneity and the role of mathematical modelling and simulation in teasing apart the underlying biophysical processes. Following a brief overview of the main known pathophysiological features of ductal carcinoma, attention is paid to differential equation-based models (both deterministic and stochastic), agent-based modelling, multi-scale modelling, lattice-based models and image-driven modelling. A number of vignettes are presented where these modelling approaches have elucidated novel aspects of breast cancer dynamics, and we conclude by offering some perspectives on the role mathematical modelling can play in understanding breast cancer development, invasion and treatment therapies.

Mitochondrial Changes in Cancer

Mitochondrial structural and functional integrity defines the health of a cell by regulating cellular metabolism. Thus, mitochondria play an important role in both cell proliferation and cell death. Cancer cells are metabolically altered compared to normal cells for their ability to survive better and proliferate faster. Resistance to apoptosis is an important characteristic of cancer cells and given the contribution of mitochondria to apoptosis, it is imperative that mitochondria could behave differently in a tumor situation. The other feature associated with cancer cells is the Warburg effect, which engages a shift in metabolism. Although the Warburg effect often occurs in conjunction with dysfunctional mitochondria, the relationship between mitochondria, the Warburg effect, and cancer cell metabolism is not clearly decoded. Other than these changes, several mitochondrial gene mutations occur in cancer cells, mitochondrial biogenesis is affected and mitochondria see structural and functional variations. In cancer pharmacology, targeting mitochondria and mitochondria associated signaling pathways to reduce tumor proliferation is a growing field of interest. This chapter summarizes various changes in mitochondria in relevance to cancer, behavior of mitochondria during tumorigenesis, and the progress on using mitochondria as a therapeutic target for cancer.

Popdc1/Bves Functions in the Preservation of Cardiomyocyte Viability While Affecting Rac1 Activity and Bnip3 Expression

The Popeye domain containing1, also called Bves (Popdc1/Bves), is a transmembrane protein that functions in muscle regeneration, heart rate regulation, hypoxia tolerance, and ischemia preconditioning. The expression of Popdc1/Bves is elevated in cardiomyocytes maintained in serum free defined medium. We hypothesized that Popdc1/Bves is important for cardiomyocyte survival under the stress of serum deprivation and investigated the mechanisms involved. A deficit in Popdc1/Bves, achieved by siRNA-mediated gene silencing, results in cardiomyocyte injury and death, upregulation of the pro-apoptotic protein Bcl-2/adenovirus E1B 19-kDa interacting protein3 (Bnip3), as well as reduction in Rac1-GTPase activity and in Akt phosphorylation. Combined Popdc1/Bves and Bnip3 silencing attenuated cell injury and prevented Bnip3 upregulation induced by the silencing of Popdc1/Bves alone. Chromatin immunoprecipitation indicated an increased binding of the transcription factor FoxO3 to the Bnip3 promoter although augmentation of FoxO3 in the nuclei was not detected. By contrast, the transcription factor NFκB was excluded from the nuclei of Popdc1/Bves deficient cardiomyocytes and exhibited decreased binding to the Bnip3 promoter. The data indicates that Popdc1/Bves plays a role in the preservation of cardiomyocyte viability under serum deficiency through the alteration of Rac1 activity and the regulation of Bnip3 expression by FoxO3 and NFκB transcription factors pointing to Popdc1/Bves as a potential target to enhance heart protection. J. Cell. Biochem. 118: 1505-1517, 2017. © 2016 Wiley Periodicals, Inc.

Autophagy Induction Results in Enhanced Anoikis Resistance in Models of Peritoneal Disease

Peritoneal carcinomatosis and peritoneal sarcomatosis is a potential complication of nearly all solid tumors and results in profoundly increased morbidity and mortality. Despite the ubiquity of peritoneal carcinomatosis/peritoneal sarcomatosis, there are no clinically relevant targeted therapies for either its treatment or prevention. To identify potential therapies, we developed in vitro models of peritoneal carcinomatosis/peritoneal sarcomatosis using tumor cell lines and patient-derived spheroids (PDS) that recapitulate anoikis resistance and spheroid proliferation across multiple cancer types. Epithelial- and mesenchymal-derived cancer cell lines (YOU, PANC1, HEYA8, CHLA10, and TC71) were used to generate spheroids and establish growth characteristics. Differential gene expression analyses of these spheroids to matched adherent cells revealed a consensus spheroid signature. This spheroid signature discriminates primary tumor specimens from tumor cells found in ascites of ovarian cancer patients and in our PDS models. Key in this gene expression signature is BNIP3 and BNIP3L, known regulators of autophagy and apoptosis. Elevated BNIP3 mRNA expression is associated with poor survival in ovarian cancer patients and elevated BNIP3 protein, as measured by IHC, and is also associated with higher grade tumors and shorter survival. Pharmacologic induction of autophagy with rapamycin significantly increased spheroid formation and survival while decreasing the induction of apoptosis. In contrast, the autophagy inhibitor hydroxychloroquine abrogated spheroid formation with a clear increase in apoptosis. Modulation of BNIP3 and the critical autophagy gene Beclin-1 (BECN1) also caused a significant decrease in spheroid formation. Combined, these data demonstrate how modulation of BNIP3-related autophagy, in PDS and in vitro spheroid models, alters the survival and morphology of spheroids.

IMPLICATIONS

Development of BNIP3/BNIP3L-targeting agents or autophagy-targeting agents may reduce morbidity and mortality associated with peritoneal carcinomatosis and sarcomatosis. Mol Cancer Res; 15(1); 26-34. ©2016 AACR.

Global analysis of differential gene expression related to long-term sperm storage in oviduct of Chinese Soft-Shelled Turtle Pelodiscus sinensis

Important evolutionary and ecological consequences arise from the ability of female turtles to store viable spermatozoa for an extended period. Although previous morphological studies have observed the localization of spermatozoa in Pelodiscus sinensis oviduct, no systematic study on the identification of genes that are involved in long-term sperm storage has been performed. In this study, the oviduct of P. sinensis at different phases (reproductive and hibernation seasons) was prepared for RNA-Seq and gene expression profiling. In total, 2,662 differentially expressed genes (DEGs) including 1,224 up- and 1,438 down-regulated genes were identified from two cDNA libraries. Functional enrichment analysis indicated that many genes were predominantly involved in the immune response, apoptosis pathway and regulation of autophagy. RT-qPCR, ELISA, western blot and IHC analyses showed that the expression profiles of mRNA and protein in selected DEGs were in consistent with results from RNA-Seq analysis. Remarkably, TUNEL analysis revealed the reduced number of apoptotic cells during sperm storage. IHC and TEM analyses found that autophagy occurred in the oviduct epithelial cells, where the spermatozoa were closely attached. The outcomes of this study provide fundamental insights into the complex sperm storage regulatory process and facilitate elucidating the mechanism of sperm storage in P. sinensis.

Tyrosine kinase receptor EGFR regulates the switch in cancer cells between cell survival and cell death induced by autophagy in hypoxia

Autophagy is an intracellular lysosomal degradation pathway where its primary function is to allow cells to survive under stressful conditions. Autophagy is, however, a double-edge sword that can either promote cell survival or cell death. In cancer, hypoxic regions contribute to poor prognosis due to the ability of cancer cells to adapt to hypoxia in part through autophagy. In contrast, autophagy could contribute to hypoxia induced cell death in cancer cells. In this study, we showed that autophagy increased during hypoxia. At 4 h of hypoxia, autophagy promoted cell survival whereas, after 48 h of hypoxia, autophagy increased cell death. Furthermore, we found that the tyrosine phosphorylation of EGFR (epidermal growth factor receptor) decreased after 16 h in hypoxia. Furthermore, EGFR binding to BECN1 in hypoxia was significantly higher at 4 h compared to 72 h. Knocking down or inhibiting EGFR resulted in an increase in autophagy contributing to increased cell death under hypoxia. In contrast, when EGFR was reactivated by the addition of EGF, the level of autophagy was reduced which led to decreased cell death. Hypoxia led to autophagic degradation of the lipid raft protein CAV1 (caveolin 1) that is known to bind and activate EGFR in a ligand-independent manner during hypoxia. By knocking down CAV1, the amount of EGFR phosphorylation was decreased in hypoxia and amount of autophagy and cell death increased. This indicates that the activation of EGFR plays a critical role in the switch between cell survival and cell death induced by autophagy in hypoxia.

Receptor-mediated mitophagy

Mitochondria are essential organelles that supply ATP through oxidative phosphorylation to maintain cellular homeostasis. Extrinsic or intrinsic agents can impair mitochondria, and these impaired mitochondria can generate reactive oxygen species (ROS) as byproducts, inducing cellular damage and cell death. The quality control of mitochondria is essential for the maintenance of normal cellular functions, particularly in cardiomyocytes, because they are terminally differentiated. Accumulation of damaged mitochondria is characteristic of various diseases, including heart failure, neurodegenerative disease, and aging-related diseases. Mitochondria are generally degraded through autophagy, an intracellular degradation system that is conserved from yeast to mammals. Autophagy is thought to be a nonselective degradation process in which cytoplasmic proteins and organelles are engulfed by isolation membrane to form autophagosomes in eukaryotic cells. However, recent studies have described the process of selective autophagy, which targets specific proteins or organelles such as mitochondria. Mitochondria-specific autophagy is called mitophagy. Dysregulation of mitophagy is implicated in the development of chronic diseases including neurodegenerative diseases, metabolic diseases, and heart failure. In this review, we discuss recent progress in research on mitophagy receptors.

To live or let die: Unclear task of autophagy in the radiosensitization battle

Radiation-induced autophagy is believed to represent a radioprotective mechanism of cancer cells. Thus, its inhibition should support radiation treatment and increase its efficacy. On the other hand, there is evidence that radiation alone or in combination with various chemical agents can induce autophagy that results into increased cell death, especially within transformed apoptosis-resistant cells. In this paper, besides description of autophagic process and its relation to cancer and radiotherapy, we compared two contradictory radiosensitization approaches that employ inhibition and induction of autophagy. In spite of the classical concept based on cytoprotective model, there is a plethora of recently developed inducers of autophagy, which indicates the future trend in radiosensitization via modulation of autophagy. Because contemporary literature is conflicting and inconsistent in this respect, we reviewed the recent studies focused on enhancement of sensitivity of cancer cells toward radiation in regard to autophagy, revealing some striking discrepancies. The deeper the knowledge, the more complex this situation is. To interpret results of various studies correctly one has to take into account the methodology of autophagy assessment and also the fact that radiosensitization might be mediated by other than intrinsic mechanisms related to autophagy. Notwithstanding, targeting autophagy remains an attractive anti-tumor strategy.

Hypoxia-induced autophagy as an additional mechanism in human osteosarcoma radioresistance

Osteosarcoma (OS) responds poorly to radiotherapy, but the mechanism is unclear. We found OS tumor tissues expressed high level of protein HIF-1α, a common biological marker indicative of hypoxia. It is known that hypoxic cells are generally radioresistant because of reduced production of irradiation-induced DNA-damaging reactive oxygen species (ROS) in the anaerobic condition. Here we report another mechanism how hypoxia induces radioresistance. In MG-63 human osteosarcoma cells, hypoxic pretreatment increased the cellular survival in irradiation. These hypoxia-exposed cells displayed compartmental recruitment of GFP-tagged LC3 and expression of protein LC3-II, and restored the radiosensitivity upon autophagy inhibition. The following immunohistochemistry of OS tumor tissue sections revealed upregulated LC3 expression in a correlation with HIF-1α protein level, implying the possibly causative link between hypoxia and autophagy. Further studies in MG-63 cells demonstrated hypoxic pretreatment reduced cellular and mitochondrial ROS production during irradiation, while inhibition of autophagy re-elicited them. Taken together, our study suggests hypoxia can confer cells resistance to irradiation through activated autophagy to accelerate the clearance of cellular ROS products. This might exist in human osteosarcoma as an additional mechanism for radioresistance.

BRG1 and BRM SWI/SNF ATPases redundantly maintain cardiomyocyte homeostasis by regulating cardiomyocyte mitophagy and mitochondrial dynamics in vivo

There has been an increasing recognition that mitochondrial perturbations play a central role in human heart failure. Mitochondrial networks, whose function is to maintain the regulation of mitochondrial biogenesis, autophagy ('mitophagy') and mitochondrial fusion/fission, are new potential therapeutic targets. Yet our understanding of the molecular underpinning of these processes is just emerging. We recently identified a role of the SWI/SNF ATP-dependent chromatin remodeling complexes in the metabolic homeostasis of the adult cardiomyocyte using cardiomyocyte-specific and inducible deletion of the SWI/SNF ATPases BRG1 and BRM in adult mice (Brg1/Brm double mutant mice). To build upon these observations in early altered metabolism, the present study looks at the subsequent alterations in mitochondrial quality control mechanisms in the impaired adult cardiomyocyte. We identified that Brg1/Brm double-mutant mice exhibited increased mitochondrial biogenesis, increases in 'mitophagy', and alterations in mitochondrial fission and fusion that led to small, fragmented mitochondria. Mechanistically, increases in the autophagy and mitophagy-regulated proteins Beclin1 and Bnip3 were identified, paralleling changes seen in human heart failure. Evidence for perturbed cardiac mitochondrial dynamics included decreased mitochondria size, reduced numbers of mitochondria, and an altered expression of genes regulating fusion (Mfn1, Opa1) and fission (Drp1). We also identified cardiac protein amyloid accumulation (aggregated fibrils) during disease progression along with an increase in pre-amyloid oligomers and an upregulated unfolded protein response including increased GRP78, CHOP, and IRE-1 signaling. Together, these findings described a role for BRG1 and BRM in mitochondrial quality control, by regulating mitochondrial number, mitophagy, and mitochondrial dynamics not previously recognized in the adult cardiomyocyte. As critical to the pathogenesis of heart failure, epigenetic mechanisms like SWI/SNF chromatin remodeling seem more intimately linked to cardiac function and mitochondrial quality control mechanisms than previously realized.

Cardiac Kinetophagy Coincides with Activation of Anabolic Signaling

PURPOSE

Growing evidence has shown that endurance exercise is a strong inducer of autophagy in various tissues. Thus, we define here endurance exercise-induced autophagy as "kinetophagy" derived from the Greek terms "kineto" (movement), "auto" (self), and "phagy" (eating). Currently, the exact cellular mechanisms responsible for kinetophagy remain unclear; hence, we examined kinetophagy signaling transduction pathways occurring during acute endurance exercise (AEE).

METHODS

C57BL/6 mice were randomly assigned to either AEE (n = 7) or control sedentary group (CON, n = 7). After 5 d of treadmill running acclimation, mice performed 60 min of a single bout of treadmill running at 12 m · min(-1) on a 0% grade. Hearts were excised immediately 1 h after exercise and homogenized for Western blot analyses.

RESULTS

Our data showed that AEE promoted kinetophagy flux (an increase in LC3-II to LC3-I ratio and LC3-II levels and a reduction in p62 levels) with Beclin-1 levels suppressed but Atg7 levels elevated compared with those in the sedentary group. We also observed that AEE increased lysosome-associated membrane protein and cathepsin L, linked to the termination process of autophagy, and that AEE augmented potent autophagy inducers (i.e., adenosine monophosphate kinase phosphorylation, BNIP3, and HSP70). Moreover, we found that exercise-mediated BNIP3 upregulation is associated with hypoxia-inducing factor 1α rather than FoxO3a. Intriguingly, we found for the first time that kinetophagy parallels with anabolic signaling activation (Akt and mammalian target of rapamycin).

CONCLUSIONS

Our findings provide evidence that AEE results in kinetophagy without a time-associated elevation in Beclin-1 but with the presence of Akt-mTOR activation and that AEE-induced activation of anabolic signaling is not associated with kinetophagy promotion.

Autophagy, a double-edged sword in anti-angiogenesis therapy

Autophagy is a highly conservative cell behavior to keep the intracellular homeostasis and is frequently activated when cells encounter disgusting conditions, such as nutrition or growth factor deprive, hypoxia and cytotoxic agents. However, the precise role of autophagy under various conditions may be opposite, differ from protect cells survival to promote cells death, and the mechanism of this conditional-dependent role is still unclear. Anti-angiogenesis agents, such as bevacizumab, sorafenib and sunitinib, could reduce tumor microvascular density and increase tumor hypoxia, thus up-regulating autophagy activation of tumor cells, but the function of autophagy induced by anti-angiogenesis agents is still divergent and is considered to play a cytoprotective role in most cases. In this review, we mainly discuss the relationship between anti-angiogenesis therapy-induced hypoxia and autophagy, and pay special attention on the exact role of anti-angiogenesis agents induced autophagy in the process of anti-angiogenesis treatment.

Breast cancer cell line MDA-MB-231 miRNA profile expression after BIK interference: BIK involvement in autophagy

B-cell lymphoma 2 (BCL2)-interacting killer (apoptosis inducing) (BIK) has been proposed as a tumor suppressor in diverse types of cancers. However, BIK's overexpression in breast cancer (BC) and in non-small lung cancer cells (NSCLCs), associated with a poor prognosis, suggests its participation in tumor progression. In this study, we evaluated the global expression pattern of microRNAs (miRNAs), messenger RNA (mRNA) expression changes in autophagy, and autophagic flux after BIK interference. BIK gene expression was silenced by small interfering RNA (siRNA) in BC cell MDA-MB-231, and BIK interference efficiency was tested by real-time PCR and by Western blotting. BIK expression levels decreased by 75 ± 18 % in the presence of 600 nM siRNA, resulting in the abolishment of BIK expression by 94 ± 30 %. BIK interference resulted in the overexpression of 17 miRNAs that, according to the DIANA-miRPath v3.0 database, are mainly implied in the control of cell signaling, gene expression, and autophagy. The autophagy array revealed downregulation of transcripts which participate in autophagy, and their interactome revealed a complex network, where hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), α-synuclein (SNCA), unc-51-like autophagy activating kinase 1/2 (ULK1/2), and mitogen-activated protein kinase 3 (MAPK3) were shown to be signaling hubs. LC3-II expression-an autophagy marker-was increased by 169 ± 25 % after BIK interference, which indicates the involvement of BIK in autophagy. Altogether, our results indicate-for the first time-that BIK controls the expression of miRNAs, as well as the autophagic flux in MDA-MB-231 cells.

The Retinoblastoma Tumor Suppressor Protein (pRb)/E2 Promoter Binding Factor 1 (E2F1) Pathway as a Novel Mediator of TGFβ-induced Autophagy

TGFβ is a multifunctional cytokine that regulates cell proliferation, cell immortalization, and cell death, acting as a key homeostatic mediator in various cell types and tissues. Autophagy is a programmed mechanism that plays a pivotal role in controlling cell fate and, consequently, many physiological and pathological processes, including carcinogenesis. Although autophagy is often considered a pro-survival mechanism that renders cells viable in stressful conditions and thus might promote tumor growth, emerging evidence suggests that autophagy is also a tumor suppressor pathway. The relationship between TGFβ signaling and autophagy is context-dependent and remains unclear. TGFβ-mediated activation of autophagy has recently been suggested to contribute to the growth inhibitory effect of TGFβ in hepatocarcinoma cells. In the present study, we define a novel process of TGFβ-mediated autophagy in cancer cell lines of various origins. We found that autophagosome initiation and maturation by TGFβ is dependent on the retinoblastoma tumor suppressor protein/E2 promoter binding factor (pRb/E2F1) pathway, which we have previously established as a critical signaling axis leading to various TGFβ tumor suppressive effects. We further determined that TGFβ induces pRb/E2F1-dependent transcriptional activation of several autophagy-related genes. Together, our findings reveal that TGFβ induces autophagy through the pRb/E2F1 pathway and transcriptional activation of autophagy-related genes and further highlight the central relevance of the pRb/E2F1 pathway downstream of TGFβ signaling in tumor suppression.

Autophagy contributes to the chemo-resistance of non-small cell lung cancer in hypoxic conditions

BACKGROUND

The development of chemo-resistance in non-small lung cancer is a major obstacle in treating patients. Hypoxia is a commonly faced microenvironment in solid tumor and suggested to be related to both autophagy and chemo-resistance.

METHODS

In this study, we investigated the role of hypoxia-induced autophagy in acquiring chemo-resistance in both cancer cell (A549) and human cancer tissue

RESULTS

Hypoxic exposure (1 % O2) of A549 cell stimulated autophagic induction in cancer cells, shown by increase of LC3BI to LC3BII conversion and decrease of p62/sequestosome1 in Western blot, increased GFP-LC puncta in confocal microscopy, and increased number of double-membrane autophagic vacuoles in electron micrographs. Hypoxic exposure also induced resistance of cancer cells to cisplatin, and LC3B siRNA restored the sensitivity of cancer cells to chemotherapy. Furthermore, Human lung cancer tissues that experienced chemotherapy showed increase of LC3BI to LC3BII conversion and decrease of p62/sequestosome1 compared with chemo-naïve cancer tissue in Western blot.

CONCLUSION

Autophagy may play an important role in acquiring resistance to chemotherapy in lung cancer and hypoxia related pathway seems to be involved in autophagy induction.

Mitophagy defects arising from BNip3 loss promote mammary tumor progression to metastasis

BNip3 is a hypoxia-inducible protein that targets mitochondria for autophagosomal degradation. We report a novel tumor suppressor role for BNip3 in a clinically relevant mouse model of mammary tumorigenesis. BNip3 delays primary mammary tumor growth and progression by preventing the accumulation of dysfunctional mitochondria and resultant excess ROS production. In the absence of BNip3, mammary tumor cells are unable to reduce mitochondrial mass effectively and elevated mitochondrial ROS increases the expression of Hif-1α and Hif target genes, including those involved in glycolysis and angiogenesis—two processes that are also markedly increased in BNip3-null tumors. Glycolysis inhibition attenuates the growth of BNip3-null tumor cells, revealing an increased dependence on autophagy for survival. We also demonstrate that BNIP3 deletion can be used as a prognostic marker of tumor progression to metastasis in human triple-negative breast cancer (TNBC). These studies show that mitochondrial dysfunction—caused by defects in mitophagy—can promote the Warburg effect and tumor progression, and suggest better approaches to stratifying TNBC for treatment.

Physiological, pathological, and structural implications of non-enzymatic protein-protein interactions of the multifunctional human transglutaminase 2

Transglutaminase 2 (TG2) is a ubiquitously expressed member of an enzyme family catalyzing Ca(2+)-dependent transamidation of proteins. It is a multifunctional protein having several well-defined enzymatic (GTP binding and hydrolysis, protein disulfide isomerase, and protein kinase activities) and non-enzymatic (multiple interactions in protein scaffolds) functions. Unlike its enzymatic interactions, the significance of TG2's non-enzymatic regulation of its activities has recently gained importance. In this review, we summarize all the partners that directly interact with TG2 in a non-enzymatic manner and analyze how these interactions could modulate the crosslinking activity and cellular functions of TG2 in different cell compartments. We have found that TG2 mostly acts as a scaffold to bridge various proteins, leading to different functional outcomes. We have also studied how specific structural features, such as intrinsically disordered regions and embedded short linear motifs contribute to multifunctionality of TG2. Conformational diversity of intrinsically disordered regions enables them to interact with multiple partners, which can result in different biological outcomes. Indeed, ID regions in TG2 were identified in functionally relevant locations, indicating that they could facilitate conformational transitions towards the catalytically competent form. We reason that these structural features contribute to modulating the physiological and pathological functions of TG2 and could provide a new direction for detecting unique regulatory partners. Additionally, we have assembled all known anti-TG2 antibodies and have discussed their significance as a toolbox for identifying and confirming novel TG2 regulatory functions.

Hypoxia-induced autophagy mediates cisplatin resistance in lung cancer cells

Hypoxia which commonly exists in solid tumors, leads to cancer cells chemoresistance via provoking adaptive responses including autophagy. Therefore, we sought to evaluate the role of autophagy and hypoxia as well as the underlying mechanism in the cisplatin resistance of lung cancer cells. Our study demonstrated that hypoxia significantly protected A549 and SPC-A1 cells from cisplatin-induced cell death in a Hif-1α- and Hif-2α- dependent manner. Moreover, compared with normoxia, cisplatin-induced apoptosis under hypoxia was markedly reduced. However, when autophagy was inhibited by 3-MA or siRNA targeted ATG5, this reduction was effectively attenuated, which means autophagy mediates cisplatin resisitance under hypoxia. In parallel, we showed that hypoxia robustly augmented cisplatin-induced autophagy activation, accompanying by suppressing cisplatin-induced BNIP3 death pathways, which was due to the more efficient autophagic process under hypoxia. Consequently, we proposed that autophagy was a protective mechanism after cisplatin incubation under both normoxia and hypoxia. However, under normoxia, autophagy activation ‘was unable to counteract the stress induced by cisplatin, therefore resulting in cell death, whereas under hypoxia, autophagy induction was augmented that solved the cisplatin-induced stress, allowing the cells to survival. In conclusion, augmented induction of autophagy by hypoxia decreased lung cancer cells susceptibility to cisplatin-induced apoptosis.

Hypoxia signaling pathways: modulators of oxygen-related organelles

Oxygen (O2) is an essential substrate in cellular metabolism, bioenergetics, and signaling and as such linked to the survival and normal function of all metazoans. Low O2 tension (hypoxia) is a fundamental feature of physiological processes as well as pathophysiological conditions such as cancer and ischemic diseases. Central to the molecular mechanisms underlying O2 homeostasis are the hypoxia-inducible factors-1 and -2 alpha (HIF-1α and EPAS1/HIF-2α) that function as master regulators of the adaptive response to hypoxia. HIF-induced genes promote characteristic tumor behaviors, including angiogenesis and metabolic reprogramming. The aim of this review is to critically explore current knowledge of how HIF-α signaling regulates the abundance and function of major O2-consuming organelles. Abundant evidence suggests key roles for HIF-1α in the regulation of mitochondrial homeostasis. An essential adaptation to sustained hypoxia is repression of mitochondrial respiration and induction of glycolysis. HIF-1α activates several genes that trigger mitophagy and represses regulators of mitochondrial biogenesis. Several lines of evidence point to a strong relationship between hypoxia, the accumulation of misfolded proteins in the endoplasmic reticulum, and activation of the unfolded protein response. Surprisingly, although peroxisomes depend highly on molecular O2 for their function, there has been no evidence linking HIF signaling to peroxisomes. We discuss our recent findings that establish HIF-2α as a negative regulator of peroxisome abundance and suggest a mechanism by which cells attune peroxisomal function with O2 availability. HIF-2α activation augments peroxisome turnover by pexophagy and thereby changes lipid composition reminiscent of peroxisomal disorders. We discuss potential mechanisms by which HIF-2α might trigger pexophagy and place special emphasis on the potential pathological implications of HIF-2α-mediated pexophagy for human health.