Hypoxia induces autophagy in human vascular endothelial cells in a hypoxia-inducible factor 1‑dependent manner

Investigating the Association between the Autophagy Markers LC3B, SQSTM1/p62, and DRAM and Autophagy-Related Genes in Glioma

High-grade gliomas are extremely fatal tumors, marked by severe hypoxia and therapeutic resistance. Autophagy is a cellular degradative process that can be activated by hypoxia, ultimately resulting in tumor advancement and chemo-resistance. Our study aimed to examine the link between autophagy markers' expression in low-grade gliomas (LGGs) and high-grade gliomas (HGGs). In 39 glioma cases, we assessed the protein expression of autophagy markers LC3B, SQSTM1/p62, and DRAM by immunohistochemistry (IHC) and the mRNA expression of the autophagy genes PTEN, PI3K, AKT, mTOR, ULK1, ULK2, UVRAG, Beclin 1, and VPS34 using RT-qPCR. LC3B, SQSTM1/p62, and DRAM expression were positive in 64.1%, 51.3%, and 28.2% of glioma cases, respectively. The expression of LC3B and SQSTM1/p62 was notably higher in HGGs compared to LGGs. VPS34 exhibited a significant differential expression, displaying increased fold change in HGGs compared to LGGs. Additionally, it exhibited robust positive associations with Beclin1 (rs = 0.768), UVRAG (rs = 0.802), and ULK2 (rs = 0.786) in HGGs. This underscores a potential association between autophagy and the progression of gliomas. We provide preliminary data for the functional analysis of autophagy using a cell culture model and to identify potential targets for therapeutic interventions.

Molecular mechanism of autophagy and apoptosis in endometriosis: Current understanding and future research directions

Background

Endometriosis is a common gynecological condition, with symptoms including pain and infertility. Regurgitated endometrial cells into the peritoneal cavity encounter hypoxia and nutrient starvation. Endometriotic cells have evolved various adaptive mechanisms to survive in this inevitable condition. These adaptations include escape from apoptosis. Autophagy, a self-degradation system, controls apoptosis during stress conditions. However, to date, the mechanisms regulating the interplay between autophagy and apoptosis are still poorly understood. In this review, we summarize the current understanding of the molecular characteristics of autophagy in endometriosis and discuss future therapeutic challenges.

Methods

A search of PubMed and Google Scholar databases were used to identify relevant studies for this narrative literature review.

Results

Autophagy may be dynamically regulated through various intrinsic (e.g., PI3K/AKT/mTOR signal transduction network) and extrinsic (e.g., hypoxia and iron-mediated oxidative stress) pathways, contributing to the development and progression of endometriosis. Upregulation of mTOR expression suppresses apoptosis via inhibiting the autophagy pathway, whereas hypoxia or excess iron often inhibits apoptosis via promoting autophagy.

Conclusion

Endometriotic cells may have acquired antiapoptotic mechanisms through unique intrinsic and extrinsic autophagy pathways to survive in changing environments.

Pyroptosis, ferroptosis, and autophagy cross-talk in glioblastoma opens up new avenues for glioblastoma treatment

Glioma is a common primary tumor of the central nervous system (CNS), with glioblastoma multiforme (GBM) being the most malignant, aggressive, and drug resistant. Most drugs are designed to induce cancer cell death, either directly or indirectly, but malignant tumor cells can always evade death and continue to proliferate, resulting in a poor prognosis for patients. This reflects our limited understanding of the complex regulatory network that cancer cells utilize to avoid death. In addition to classical apoptosis, pyroptosis, ferroptosis, and autophagy are recognized as key cell death modalities that play significant roles in tumor progression. Various inducers or inhibitors have been discovered to target the related molecules in these pathways, and some of them have already been translated into clinical treatment. In this review, we summarized recent advances in the molecular mechanisms of inducing or inhibiting pyroptosis, ferroptosis, or autophagy in GBM, which are important for treatment or drug tolerance. We also discussed their links with apoptosis to better understand the mutual regulatory network among different cell death processes. Video Abstract.

Ablation of endothelial Atg7 inhibits ischemia-induced angiogenesis by upregulating Stat1 that suppresses Hif1a expression

Ischemia-induced angiogenesis is critical for blood flow restoration and tissue regeneration, but the underlying molecular mechanism is not fully understood. ATG7 (autophagy related 7) is essential for classical degradative macroautophagy/autophagy and cell cycle regulation. However, whether and how ATG7 influences endothelial cell (EC) function and regulates post-ischemic angiogenesis remain unknown. Here, we showed that in mice subjected to femoral artery ligation, EC-specific deletion of Atg7 significantly impaired angiogenesis, delayed the recovery of blood flow reperfusion, and displayed reduction in HIF1A (hypoxia inducible factor 1 subunit alpha) expression. In addition, in cultured human umbilical vein endothelial cells (HUVECs), overexpression of HIF1A prevented ATG7 deficiency-reduced tube formation. Mechanistically, we identified STAT1 (signal transducer and activator of transcription 1) as a transcription suppressor of HIF1A and demonstrated that ablation of Atg7 upregulated STAT1 in an autophagy independent pathway, increased STAT1 binding to HIF1A promoter, and suppressed HIF1A expression. Moreover, lack of ATG7 in the cytoplasm disrupted the association between ATG7 and the transcription factor ZNF148/ZFP148/ZBP-89 (zinc finger protein 148) that is required for STAT1 constitutive expression, increased the binding between ZNF148/ZFP148/ZBP-89 and KPNB1 (karyopherin subunit beta 1), which promoted ZNF148/ZFP148/ZBP-89 nuclear translocation, and increased STAT1 expression. Finally, inhibition of STAT1 by fludarabine prevented the inhibition of HIF1A expression, angiogenesis, and blood flow recovery in atg7 KO mice. Our work reveals that lack of ATG7 inhibits angiogenesis by suppression of HIF1A expression through upregulation of STAT1 independently of autophagy under ischemic conditions, and suggest new therapeutic strategies for cancer and cardiovascular diseases.Abbreviations: ATG5: autophagy related 5; ATG7: autophagy related 7; atg7 KO: endothelial cell-specific atg7 knockout; BECN1: beclin 1; ChIP: chromatin immunoprecipitation; CQ: chloroquine; ECs: endothelial cells; EP300: E1A binding protein p300; HEK293: human embryonic kidney 293 cells; HIF1A: hypoxia inducible factor 1 subunit alpha; HUVECs: human umbilical vein endothelial cells; IFNG/IFN-γ: Interferon gamma; IRF9: interferon regulatory factor 9; KPNB1: karyopherin subunit beta 1; MAP1LC3A: microtubule associated protein 1 light chain 3 alpha; MEFs: mouse embryonic fibroblasts; MLECs: mouse lung endothelial cells; NAC: N-acetyl-l-cysteine; NFKB1/NFκB: nuclear factor kappa B subunit 1; PECAM1/CD31: platelet and endothelial cell adhesion molecule 1; RELA/p65: RELA proto-oncogene, NF-kB subunit; ROS: reactive oxygen species; SP1: Sp1 transcription factor; SQSTM1/p62: sequestosome 1; STAT1: signal transducer and activator of transcription 1; ULK1: unc-51 like autophagy activating kinase 1; ulk1 KO: endothelial cell-specific ulk1 knockout; VSMCs: mouse aortic smooth muscle cells; WT: wild type; ZNF148/ZFP148/ZBP-89: zinc finger protein 148.

Regulation of autophagy fires up the cold tumor microenvironment to improve cancer immunotherapy

Immunotherapies, such as immune checkpoint inhibitors (ICIs) and chimeric antigen receptor (CAR) T cells, have revolutionized the treatment of patients with advanced and metastatic tumors resistant to traditional therapies. However, the immunosuppressed tumor microenvironment (TME) results in a weak response to immunotherapy. Therefore, to realize the full potential of immunotherapy and obstacle barriers, it is essential to explore how to convert cold TME to hot TME. Autophagy is a crucial cellular process that preserves cellular stability in the cellular components of the TME, contributing to the characterization of the immunosuppressive TME. Targeted autophagy ignites immunosuppressive TME by influencing antigen release, antigen presentation, antigen recognition, and immune cell trafficking, thereby enhancing the effectiveness of cancer immunotherapy and overcoming resistance to immunotherapy. In this review, we summarize the characteristics and components of TME, explore the mechanisms and functions of autophagy in the characterization and regulation of TME, and discuss autophagy-based therapies as adjuvant enhancers of immunotherapy to improve the effectiveness of immunotherapy.

Harnessing retinal phagocytes to combat pathological neovascularization in ischemic retinopathies?

Ischemic retinopathies (IR) are vision-threatening diseases that affect a substantial amount of people across all age groups worldwide. The current treatment options of photocoagulation and anti-VEGF therapy have side effects and are occasionally unable to prevent disease progression. It is therefore worthwhile to consider other molecular targets for the development of novel treatment strategies that could be safer and more efficient. During the manifestation of IR, the retina, normally an immune privileged tissue, encounters enhanced levels of cellular stress and inflammation that attract mononuclear phagocytes (MPs) from the blood stream and activate resident MPs (microglia). Activated MPs have a multitude of effects within the retinal tissue and have the potential to both counter and exacerbate the harmful tissue microenvironment. The present review discusses the current knowledge about the role of inflammation and activated retinal MPs in the major IRs: retinopathy of prematurity and diabetic retinopathy. We focus particularly on MPs and their secreted factors and cell–cell-based interactions between MPs and endothelial cells. We conclude that activated MPs play a major role in the manifestation and progression of IRs and could therefore become a promising new target for novel pharmacological intervention strategies in these diseases.

A Key Pathway to Cancer Resilience: The Role of Autophagy in Glioblastomas

There are no effective strategies for the successful treatment of glioblastomas (GBM). Current therapeutic modalities effectively target bulk tumor cells but leave behind marginal GBM cells that escape from the surgical margins and radiotherapy field, exhibiting high migratory phenotype and resistance to all available anti-glioma therapies. Drug resistance is mostly driven by tumor cell plasticity: a concept associated with reactivating transcriptional programs in response to adverse and dynamic conditions from the tumor microenvironment. Autophagy, or "self-eating", pathway is an emerging target for cancer therapy and has been regarded as one of the key drivers of cell plasticity in response to energy demanding stress conditions. Many studies shed light on the importance of autophagy as an adaptive mechanism, protecting GBM cells from unfavorable conditions, while others recognize that autophagy can kill those cells by triggering a non-apoptotic cell death program, called 'autophagy cell death' (ACD). In this review, we carefully analyzed literature data and conclude that there is no clear evidence indicating the presence of ACD under pathophysiological settings in GBM disease. It seems to be exclusively induced by excessive (supra-physiological) stress signals, mostly from in vitro cell culture studies. Instead, pre-clinical and clinical data indicate that autophagy is an emblematic example of the 'dark-side' of a rescue pathway that contributes profoundly to a pro-tumoral adaptive response. From a standpoint of treating the real human disease, only combinatorial therapy targeting autophagy with cytotoxic drugs in the adjuvant setting for GBM patients, associated with the development of less toxic and more specific autophagy inhibitors, may inhibit adaptive response and enhance the sensibility of glioma cells to conventional therapies.

Study 3D Endothelial Cell Network Formation under Various Oxygen Microenvironment and Hydrogel Composition Combinations Using Upside-Down Microfluidic Devices

Formation of 3D networks is a crucial process for endothelial cells during development of primary blood vessels under both normal and pathological conditions. In order to investigate effects of oxygen microenvironment and matrix composition on the 3D network formation, an upside-down microfluidic cell culture device capable of generating oxygen gradients is developed in this paper. In cell experiments, network formation of human umbilical vein endothelial cells (HUVECs) within fibrinogen-based hydrogels with different concentrations of hyaluronic acid (HA) is systematically studied. In addition, five different oxygen microenvironments (uniform normoxia, 5%, and 1% O₂ ; oxygen gradients under normoxia and 5% O₂ ) are also applied for the cell culture. The generated oxygen gradients are characterized based on fluorescence lifetime measurements. The experimental results show increased 3D cell network length when the cells are cultured under the oxygen gradients within the hydrogels with the HA addition suggesting their roles in promoting network formation. Furthermore, the formed networks tend to align along the direction of the oxygen gradients indicating the presence of gradient-driven cellular response. The results demonstrate that the developed upside-down microfluidic device can provide an advanced platform to investigate 3D cell culture under the controlled oxygen microenvironments for various biomedical studies in vitro.

Silicon Oxynitrophosphide Nanoscale Coating Enhances Antioxidant Marker-Induced Angiogenesis During in vivo Cranial Bone-Defect Healing

Critical-sized bone defects are challenging to heal because of the sudden and large volume of lost bone. Fixative plates are often used to stabilize defects, yet oxidative stress and delayed angiogenesis are contributing factors to poor biocompatibility and delayed bone healing. This study tests the angiogenic and antioxidant properties of amorphous silicon oxynitrophosphide (SiONPx) nanoscale-coating material on endothelial cells to regenerate vascular tissue in vitro and in bone defects. in vitro studies evaluate the effect of silicon oxynitride (SiONx) and two different SiONPx compositions on human endothelial cells exposed to ROS (eg, hydrogen peroxide) that simulates oxidative stress conditions. in vivo studies using adult male Sprague Dawley rats (approximately 450 g) were performed to compare a bare plate, a SiONPx-coated implant plate, and a sham control group using a rat standard-sized calvarial defect. Results from this study showed that plates coated with SiONPx significantly reduced cell death, and enhanced vascular tubule formation and matrix deposition by upregulating angiogenic and antioxidant expression (eg, vascular endothelial growth factor A, angiopoetin-1, superoxide dismutase 1, nuclear factor erythroid 2-related factor 2, and catalase 1). Moreover, endothelial cell markers (CD31) showed a significant tubular structure in the SiONPx coating group compared with an empty and uncoated plate group. This reveals that atomic doping of phosphate into the nanoscale coating of SiONx produced markedly elevated levels of antioxidant and angiogenic markers that enhance vascular tissue regeneration. This study found that SiONPx or SiONx nanoscale-coated materials enhance antioxidant expression, angiogenic marker expression, and reduce ROS levels needed for accelerating vascular tissue regeneration. These results further suggest that SiONPx nanoscale coating could be a promising candidate for titanium plate for rapid and enhanced cranial bone-defect healing. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Comparative transcriptomic analysis of vascular endothelial cells after hypoxia/re-oxygenation induction based on microarray technology

OBJECTIVE

To provide comprehensive data to understand mechanisms of vascular endothelial cell (VEC) response to hypoxia/re-oxygenation.

METHODS

Human umbilical vein endothelial cells (HUVECs) were employed to construct hypoxia/re-oxygenation-induced VEC transcriptome profiling. Cells incubated under 5% O₂, 5% CO₂, and 90% N₂ for 3 h followed by 95% air and 5% CO₂ for 1 h were used in the hypoxia/re-oxygenation group. Those incubated only under 95% air and 5% CO₂ were used in the normoxia control group.

RESULTS

By using a well-established microarray chip consisting of 58 339 probes, the study identified 372 differentially expressed genes. While part of the genes are known to be VEC hypoxia/re-oxygenation-related, serving as a good control, a large number of genes related to VEC hypoxia/re-oxygenation were identified for the first time. Through bioinformatic analysis of these genes, we identified that multiple pathways were involved in the reaction. Subsequently, we applied real-time polymerase chain reaction (PCR) and western blot techniques to validate the microarray data. It was found that the expression of apoptosis-related proteins, like pleckstrin homology-like domain family A member 1 (PHLDA1), was also consistently up-regulated in the hypoxia/re-oxygenation group. STRING analysis found that significantly differentially expressed genes SLC38A3, SLC5A5, Lnc-SLC36A4-1, and Lnc-PLEKHJ1-1 may have physical or/and functional protein-protein interactions with PHLDA1.

CONCLUSIONS

The data from this study have built a foundation to develop many hypotheses to further explore the hypoxia/re-oxygenation mechanisms, an area with great clinical significance for multiple diseases.

Identification of differentially expressed long non-coding RNAs in mice intestines after severe burns and a preliminary study into the key gene H19

BACKGROUND

The intestine is considered the key organ in stress response to severe burns and injury to intestine after severe burns can be fatal. However, the injury and subsequent repair of intestinal tissues after severe burns at the genetic level are poorly understood. Long non-coding RNAs (lncRNAs) have important functions in regulating many biological processes, including gene transcription and translation. Autophagy is a process of intracellular degradation and reutilization of cytoplasmic proteins and organelles.

METHODS

We herein analyzed the genome-wide expression profile of lncRNAs and mRNAs after severe burns in the intestines of mice by lncRNA microarray. qRT-PCR was performed to verify the reliability of microarray analysis results, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used for bioinformatics analysis of differentially expressed mRNAs. The common regulatory network between the top ten differentially expressed lncRNAs and trans-related mRNAs was visualized by Cytoscape (v3.7.2). Next, we hypothesized that H19 is the key gene for intestinal mucosal repair. After H19 was overexpressed, the changes in downstream autophagy protein expression levels were observed.

RESULTS

GO and KEGG analysis indicated that the differentially expressed mRNAs were mainly enriched in a cell cycle- and mitosis-related genes.Overexpression of lncRNA-H19 showed that the autophagy-related gene Trim21 was up-regulated, while HIF1α was down-regulated.

CONCLUSION

LncRNA-H19 played a key role in repairing the intestinal mucosa, and overexpression of lncRNA-H19 activated autophagy and migration of intestinal epithelial cells (IEC-6).

The Influence of Obesity and Associated Fatty Acids on Placental Inflammation

PURPOSE

Maternal obesity, affecting nearly 1 in 4 pregnancies, is associated with increased circulating saturated fatty acids, such as palmitate. These fatty acids are implicated in placental inflammation, which may in turn exacerbate both maternal-fetal tolerance and responses to pathogens, such as group B Streptococcus. In this review, we address the question, "How do obesity and associated fatty acids influence placental inflammation?"

METHODS

In this narrative review, we searched PubMed and Google Scholar using combinations of the key words placental inflammation or pregnancy and lipids, fatty acids, obesity, palmitate, or other closely related search terms. We also used references found within these articles that may have been absent from our original search queries. We analyzed methods and key results of these articles to compare and contrast their findings, which were occasionally at odds with each other.

FINDINGS

Although obesity can be studied as a whole, complex phenomena with in vivo mouse models and human samples from patients with obesity, in vitro modeling often relies on the treatment of cells or tissues with ≥1 fatty acids and occasionally other compounds (eg, glucose and insulin). We found that palmitate, most commonly used in vitro to recreate hallmarks of obesity, induces apoptosis, oxidative stress, mitochondrial dysfunction, autophagy defects, and inflammasome activation in many placental cell types. We compare this to in vivo models of obesity wherever possible. We found that obesity as a whole may have more complex regulation of these phenomena (apoptosis, oxidative stress, mitochondrial dysfunction, autophagy defects, and inflammasome activation) compared with in vitro models of fatty acid treatment (primarily palmitate) because of the presence of unsaturated fatty acids (ie, oleate), which may have anti-inflammatory effects.

IMPLICATIONS

The interaction of unsaturated fatty acids with saturated fatty acids may ameliorate many inflammatory effects of saturated fatty acids alone, which complicates interpretation of in vitro studies that focus on a particular fatty acid in isolation. This complication may explain why certain studies of obesity in vivo have differing outcomes from studies of specific fatty acids in vitro.

Upregulation of PSMD4 gene by hypoxia in prostate cancer cells

Ubiquitin-proteasome pathways have a crucial role in tumor progression. PSMD4 (Rpn10, 26S proteasome non-ATPase subunit 4), which is a subunit of the regulatory particle, is a major ubiquitin (Ub) receptor of 26S proteasome. PSMD4 overexpression has been observed in colon carcinoma, hepatocellular carcinoma, and breast cancer. In this work, we elucidated the effect of hypoxia on PSMD4 gene expression in prostate cancer cells (PC3). Chemically mimicked hypoxia drastically upregulated PSMD4 gene expression at both mRNA and protein levels. Transient transfection experiments indicated that all promoter fragments were active in PC3 cells. Hypoxia increased transcriptional activity of all PSMD4 promoter constructs. EMSA analysis shows that HIF-1a transcription factor binds to the hypoxia response element (HRE) present within the -98/+52 region of PSMD4 promoter. We also used human umbilical vein endothelial cell (HUVEC) as a different cell model, in which increased PSMD4 expression was seen only at 24 h. The increased expression of the PSMD4 level in the PC3 cell line was not parallel to the expression in hypoxic HUVEC.

Integrated On-Chip 3D Vascular Network Culture under Hypoxia

We developed a portable device made of poly(dimethylsiloxane) (PDMS)/polymethylmethacrylate (PMMA) for long-term 3D cell culture of vascular endothelial cells for the development of a vascular network and evaluated the device under different transitions between normoxia and hypoxia with good optical accessibility. The combination of a nested reservoir device and a bicarbonate/ascorbate buffer system accomplished on-chip incubation with 4.91 ± 0.86% pO₂ and 5.19 ± 1.70% pCO₂ for up to 10 days. Seventy-two hours of normoxic incubation preceding hypoxic culture increased the cell viability, network formation, and size and stability of the resulting lumens compared with those completely maintained in normoxia for the same total duration. We employed different parameters of the network (e.g., total mesh area, total length, number of branches, among others) for the comparison of different oxygen treatments in the device. The differential effect of hypoxic conditions based on the maturity of the vessels may be used as an external factor to improve vascular development in vitro.

The role of hypoxia-inducible factors in neovascular age-related macular degeneration: a gene therapy perspective

Understanding the mechanisms that underlie age-related macular degeneration (AMD) has led to the identification of key molecules. Hypoxia-inducible transcription factors (HIFs) have been associated with choroidal neovascularization and the progression of AMD into the neovascular clinical phenotype (nAMD). HIFs regulate the expression of multiple growth factors and cytokines involved in angiogenesis and inflammation, hallmarks of nAMD. This knowledge has propelled the development of a new group of therapeutic strategies focused on gene therapy. The present review provides an update on current gene therapies in ocular angiogenesis, particularly nAMD, from both basic and clinical perspectives.

ATG101 Single-Stranded Antisense RNA-Loaded Triangular DNA Nanoparticles Control Human Pulmonary Endothelial Growth via Regulation of Cell Macroautophagy

Autophagy plays a key role in pulmonary vascular remodeling via regulation of apoptosis and hyperproliferation of pulmonary arterial endothelial cells, which are the subject of increased attention. Autophagy-related 101 (ATG101) is an essential gene for the initiation of autophagy. Although the structure of ATG101 has been well-characterized, its exact biological function in autophagy is still unknown. In this study, an ATG101 single-stranded antisense RNA-loaded DNA triangular nanoparticle (ssATG101-TNP) is constructed to knock down the ATG101 gene expression. ssATG101-TNP can be effectively transfected into human pulmonary arterial endothelial cells (HPAECs) in time- and dose-dependent manners. Knockdown of ATG101 promotes cell apoptosis as well as inhibits cell autophagy and proliferation with hypoxic stimulation. Additionally, the hedgehog/Gli signal pathway is involved in ATG101-mediated macroautophagy and HPAEC proliferation. This study found that ATG101, an important member of the autophagy gene family, can regulate cell macroautophagy, apoptosis, and growth in HPAECs. ssATG101-TNP is demonstrated to be a nontoxic, highly efficient, gene-delivery vehicle for HPAECs. These findings also suggest that ATG101 might be a potential therapeutic target in diseases involving endothelial injury.

Effects of different hypoxia degrees on endothelial cell cultures-Time course study

INTRODUCTION

Exposure of the endothelial cells to hypoxia, the decrease in oxygen supply can trigger an endothelial response. This response is involved in inflammatory diseases, tumorigenesis, and also with the micro vascular damage associated with aging. The aim of our study was to determine the hypoxia/re-oxygenation induced response in vitro, using human umbilical vein endothelial cells (HUVEC) cultures, at different time points with focus on cell viability, apoptosis oxidative stress and angiogenesis stimulation.

MATERIALS AND METHODS

Cells were exposed to 10%, 5% or 0% O₂ for 6h, 12h, and 24h. Viability was measured through colorimetry, apoptosis - annexin V-FITC staining, DNA lesions (γH₂AX), endothelial activation (sICAM1), angiogenesis (HIF1α), oxidative stress (malondialdehyde, superoxidismutase and NFκB activation) were determined by ELISA, Western Blot and spectrophotometry.

RESULTS AND DISCUSSION

Hypoxia decreased viability, increased apoptosis, oxidative stress, endothelial activation and angiogenesis, depending on O₂ concentration and time exposure. Short exposures to 5% and 10% O₂, efficiently activated anti-apoptotic mechanisms through NFκB activation, HIF1α and γH₂AX related DNA damage repair pathways. However, severe hypoxia and longer exposures to mild hypoxia induced high oxidative stress related damage and eventually led to apoptosis, through strong increases of HIF1α and accumulating DNA lesions.

MicroRNA-17-5p mediates hypoxia-induced autophagy and inhibits apoptosis by targeting signal transducer and activator of transcription 3 in vascular smooth muscle cells

The aim of the present study was to investigate hypoxia-induced apoptosis and autophagy in vascular smooth muscle cells (VSMCs) and the underlying molecular mechanisms of microRNA (miR)-17-5p responses in an anaerobic environment. The results revealed that miR-17-5p expression was significantly upregulated in VSMCs subjected to hypoxic conditions (P<0.05) and lower miR-17-5p levels were observed in ethyl 3,4-dihydroxybenzoate-treated and hypoxia inducible factor-1 loss-of-function cells. Additionally, it was demonstrated that miR-17-5p is associated with hypoxia-induced autophagy, which was confirmed by upregulating the light chain 3-II/LC3-I ratio and downregulating nucleoporin p62. Cell apoptosis was inhibited in response to hypoxia, and levels of pro-apoptotic proteins B-cell lymphoma 2-associated X protein and p-caspase were markedly decreased when VSMCs were subjected to hypoxic conditions. Furthermore, expression of signal transducer and activator of transcription 3 (STAT3) decreased when cells were transfected with overexpressing miR-17-5p and subjected to hypoxic conditions, and the combination of miR-17-5p loss-of-function and hypoxia induced greater upregulation in the protein expression of STAT3 compared with a single treatment for hypoxia in VSMCs. In conclusion, miR-17-5p may be a novel hypoxia-responsive miR and hypoxia may induce protective autophagy and anti-apoptosis in VSMCs by targeting STAT3.

New Insights into the Role of Autophagy in Ovarian Cryopreservation by Vitrification

Ovarian cryopreservation by vitrification is a highly useful method for preserving female fertility during radiotherapy and chemotherapy. However, cryoinjury, osmotic stress during vitrification, and ischemia/reperfusion during transplantation lead to loss of ovarian follicles. Ovarian follicle loss may be partially reduced by several methods; however, studies regarding the mechanism of ovarian follicle loss have only investigated cell apoptosis, which consists of type I programmed cell death. Autophagy is type II programmed cell death, and cell homeostasis is maintained by autophagy during conditions of stress. The role of autophagy during cryopreservation by vitrification has rarely been reported. The potential role of autophagy during ovarian cryopreservation by vitrification is reviewed in this article.