Hypoxic Stress Response Research Articles

Long non-coding RNA PANDA promotes endothelial senescence and oxidative damage through the interaction with NRF2

Abstract Background Accumulation of reactive oxygen species and inflammation are major features of diabetic vasculopathy, yet the underlying mechanisms remain elusive. LncRNAs are emerging as important players in the pathogenesis of cardiovascular disease. PANDA, a newly identified lncRNA, is a key regulator of cellular senescence, apoptosis and oxidative stress. Purpose To investigate the role and molecular mechanism of PANDA in diabetic vascular disease. Methods RNAseq was performed to aorta specimen from diabetic and no diabetic patients as well to HAECs exposed to 5 mM and 25 mM concentrations (Normal -NG- and High -HG-, respectively). PANDA depletion in HG-treated HAECs was obtained by siRNA transfection while a scrambled siRNA wass used as a negative control. RNAseq and network perturbation analysis (NPA) of treated HAECs unveiled transcriptional changes upon PANDA depletion. Expression of PANDA was assessed by real time PCR. PANDA RNA-IP was performed to check its binding to relevant transcriptional factor (such as NRF2) as well Ch-IP was performed to check the NRF2 binding on oxidative gene promoters. Cellular localization of NRF2 was investigated by Immunofluorescence. Beta-galactosidase and superoxide staining was used to detect endothelial senescence and ROS formation; while, migration and tube formation were employed to evaluate angiogenic properties of HAECs. Results PANDA expression was significantly increased in diabetic human aorta as well in HG-treated HAECs (Figure1 A-B). Transcriptomic analysis revealed dysregulation of several genes upon PANDA silencing with the antioxidant gene heme oxygenase-1 (HMOX1) as the top-ranking transcript in HG cells (Figure1 C-D). Western blot analysis reveals the restored level of HMOX1 and TFRC1 upon PANDA depletion (Figure1 E-G). NPA analysis showed a strong involvement of PANDA in senescence, DNA damage, NRF2 signaling, hypoxic stress response and proliferation. In HG, NFR2 is downregulated while PANDA silencing restores its level (Figure1 I-J). We found that in HG condition PANDA binds the transcription factor NRF2 and blocks its nuclear translocation thus impeding its binding on HMOX1 and TFRC promoters (Figure1 K-M). Silencing of PANDA in HG-treated HAECs reduced genes and cellular features of senescence (Figure2 A-B), restored the expression of anti-apoptotic genes and decreases caspase 3 activity (Figure2 C-D), improved endothelial migration and tube formation (Figure2 E and G), and reduced ROS formation (Figure2 F). Conclusions In hyperglycemia PANDA upregulation drives endothelial senescence while impairing angiogenic properties. On the other hand, PANDA depletion in HG-treated HAECs rescues maladaptive transcriptional changes through the release of NRF2 that in turn translocate into the nucleus enhancing the expression of the antioxidant gene HMOX1. The results indicate PANDA as a putative novel molecular target in the setting of diabetic vascular disease (Figure2 H).

Acquired sensorineural hearing loss, oxidative stress, and microRNAs.

Hearing loss is the third leading cause of human disability. Age-related hearing loss, one type of acquired sensorineural hearing loss, is largely responsible for this escalating global health burden. Noise-induced, ototoxic, and idiopathic sudden sensorineural are other less common types of acquired hearing loss. The etiology of these conditions is complex and multi-factorial involving an interplay of genetic and environmental factors. Oxidative stress has recently been proposed as a likely linking cause in most types of acquired sensorineural hearing loss. Short non-coding RNA sequences known as microRNAs (miRNAs) have increasingly been shown to play a role in cellular hypoxia and oxidative stress responses including promoting an apoptotic response. Sensory hair cell death is a central histopathological finding in sensorineural hearing loss. As these cells do not regenerate in humans, it underlies the irreversibility of human age-related hearing loss. Ovid EMBASE, Ovid MEDLINE, Web of Science Core Collection, and ClinicalTrials. gov databases over the period August 1, 2018 to July 31, 2023 were searched with "hearing loss," "hypoxamiRs," "hypoxia," "microRNAs," "ischemia," and "oxidative stress" text words for English language primary study publications or registered clinical trials. Registered clinical trials known to the senior author were also assessed. A total of 222 studies were thus identified. After excluding duplicates, editorials, retractions, secondary research studies, and non-English language articles, 39 primary studies and clinical trials underwent full-text screening. This resulted in 11 animal, in vitro, and/or human subject journal articles and 8 registered clinical trial database entries which form the basis of this narrative review. MiRNAs miR-34a and miR-29b levels increase with age in mice. These miRNAs were demonstrated in human neuroblastoma and murine cochlear cell lines to target Sirtuin 1/peroxisome proliferator-activated receptor gamma coactivator-1-alpha (SIRT1/PGC-1α), SIRT1/p53, and SIRT1/hypoxia-inducible factor 1-alpha signaling pathways resulting in increased apoptosis. Furthermore, hypoxia and oxidative stress had a similar adverse apoptotic effect, which was inhibited by resveratrol and a myocardial inhibitor-associated transcript, a miR-29b competing endogenous mRNA. Gentamicin reduced miR-182-5p levels and increased cochlear oxidative stress and cell death in mice - an effect that was corrected by inner ear stem cell-derived exosomes. There is ongoing work seeking to determine if these findings can be effectively translated to humans.

Controlled atmosphere as cold chain support for extending postharvest life in cabbage

Postharvest management of cabbage relies on high-intensity cooling to control postharvest physiology, minimising quality loss despite incurring significant energy and environmental costs. As an alternative, we hypothesised that controlled atmosphere (CA) could allow increased storage temperature by supporting physiological regulation, while maintaining quality and reducing energy demand. This study examined the effect CA (1.5 kPa CO2 and 6 kPa O2) at 5 or 10 °C on cabbage quality, with the aim of proposing a more sustainable and resilient supply chain. CA treatment was effective at reducing head respiration at higher temperature, with CA/10 °C treatment achieving lower respiration rates than Control/5 °C. Improved head colour retention and maintenance of stump quality were observed in cabbage under CA conditions. CA effects were seen also at a regulatory level; CA promoted an average of 25.4% reduction in abscisic acid accumulation potentially as part of a wider hypoxia stress response and was successful in decreasing expression of the senescence-coordinating transcription factor BoORE15. This finding was linked with a lower in downstream expression of pheophytinase and subtilisin protease. These results demonstrated that CA treatment fundamentally modified postharvest physiology in cabbage, which can be exploited to enable storage at warmer temperatures, contributing to supply chains with lower energy demand and its associated environmental benefits.

Cartilage Homeostasis under Physioxia.

Articular cartilage receives nutrients and oxygen from the synovial fluid to maintain homeostasis. However, compared to tissues with abundant blood flow, articular cartilage is exposed to a hypoxic environment (i.e., physioxia) and has an enhanced hypoxic stress response. Hypoxia-inducible factors (HIFs) play a pivotal role in this physioxic environment. In normoxic conditions, HIFs are downregulated, whereas in physioxic conditions, they are upregulated. The HIF-α family comprises three members: HIF-1α, HIF-2α, and HIF-3α. Each member has a distinct function in articular cartilage. In osteoarthritis, which is primarily caused by degeneration of articular cartilage, HIF-1α is upregulated in chondrocytes and is believed to protect articular cartilage by acting anabolically on it. Conversely, in contrast to HIF-1α, HIF-2α exerts a catabolic influence on articular cartilage. It may therefore be possible to develop a new treatment for OA by controlling the expression of HIF-1α and HIF-2α with drugs or by altering the oxygen environment in the joints.

Transcriptomic changes reveal hypoxic stress response in submerged seeds of maize (Zea mays L.)

Maize is highly sensitive to waterlogging stress, and seeds fail to germinate under hypoxic conditions induced by submergence, leading to severe yield losses. We conducted a comparative transcriptome analysis during the initial stages of seed germination, exploring aerobic and hypoxic conditions in two inbred lines, B73 and Okcheon Chal-1. Notably, significant differences emerged between aerobic and hypoxic conditions on the first day of germination, particularly in genes associated with fermentation and phytohormone regulation. However, consistent transcriptomic changes were observed in primary metabolic pathways such as glycolysis, the TCA cycle, and the pentose phosphate pathway. These differences strongly correlate with each other, illustrating the efficacy of the hypoxic response for survival in water. Furthermore, this suggests that germinating seeds serve as a promising model for studying plant hypoxia responses with controlled environmental conditions. Insights from this study contribute to understanding the fundamental mechanisms of hypoxia response and hold promise for developing strategies to cultivate waterlogging-tolerant maize cultivars.

Long non-coding RNA PANDA drives diabetic vascular dysfunction by promoting endothelial senescence and oxidative damage

Abstract Funding Acknowledgements None. Background ROS and inflammation are major features of diabetic vasculopathy, yet the underlying mechanisms remain elusive. Long non-coding RNAs (lncRNAs) are emerging as important players in the pathogenesis of cardiovascular disease. Recent work has shown that PANDA, a newly identified lncRNA, is a key regulator of cellular senescence and apoptosis. Purpose To elucidate the role and molecular mechanism of lncRNA PANDA in diabetic vascular disease. Methods Human aortic endothelial cells (HAECs) were exposed to normal (NG, 5 mmol/L) and high glucose concentrations (HG, 25 mmol/L). PANDA depletion in HG-treated HAECs was obtained by siRNA transfection. Expression of PANDA was assessed by real time PCR. RNAs sequencing (RNA-seq) and bioinformatic analysis (network perturbation amplitude, NPA) were leveraged to unveil transcriptional changes upon PANDA depletion. PANDA RNA immuno-precipitation (RIP) was performed to check its binding to relevant transcriptional factor. Western Blots was used to investigate on NRF2 protein and its products. Beta-galactosidase staining was used to detect endothelial senescence while, migration and tube formation were employed to evaluate angiogenic properties of HAECs. ROS production and NRF2 localization were investigated by fluorescence staining. The ex vivo effect of PANDA siRNA on endothelial function was assessed in aortic rings from diabetic mice. Results PANDA expression was significantly increased in HAECs exposed to HG as compared to NG. Transcriptomic analysis revealed dysregulation of several genes upon PANDA silencing with the antioxidant gene heme oxygenase-1 as the top-ranking transcript in HG-treated cells (Fig). NPA analysis showed a strong involvement of PANDA in senescence, DNA damage, NRF2 signaling, hypoxic stress response and proliferation. Under HG conditions PANDA perturbed the pathway of the transcription factor NRF2, thus inhibiting the expression of NRF2-dependent pro-survival and anti-aging gene. Indeed, silencing of PANDA in HG-treated HAECs reduced the apotosis and senescence (Figure 1). PANDA depletion in HG improved endothelial migration and tube formation, while ROS production was reduced. In HG, there was an increasing of PANDA-NRF2 binding (Fig). Interesting, in HG NRF2 was more present in the cytosol, while PANDA siRNA allowed its translocation into the where it can promote the transcription of HMOX1. Of interest, PANDA levels were increased in aortas from diabetic mice while depletion of PANDA rescued endothelial dysfunction (Figure 2). Conclusions The hyperglycemia induced the upregulation of PANDA driving endothelial senescence and impairing angiogenic properties. PANDA depletion in HG-treated HAECs rescued maladaptive transcriptional changes enhancing NRF2 pathway. Of note, targeting PANDA in the diabetic vasculature was able to rescue endothelial dysfunction. These results indicate PANDA as a novel molecular target in the setting of diabetic vascular disease.

Potency-Enhanced Peptidomimetic VHL Ligands with Improved Oral Bioavailability.

The von Hippel-Lindau (VHL) protein plays a pivotal role in regulating the hypoxic stress response and has been extensively studied and utilized in the targeted protein degradation field, particularly in the context of bivalent degraders. In this study, we present a comprehensive peptidomimetic structure-activity relationship (SAR) approach, combined with cellular NanoBRET target engagement assays to enhance the existing VHL ligands. Through systematic modifications of the molecule, we identified the 1,2,3-triazole group as an optimal substitute of the left-hand side amide bond that yields 10-fold higher binding activity. Moreover, incorporating conformationally constrained alterations on the methylthiazole benzylamine moiety led to the development of highly potent VHL ligands with picomolar binding affinity and significantly improved oral bioavailability. We anticipate that our optimized VHL ligand, GNE7599, will serve as a valuable tool compound for investigating the VHL pathway and advancing the field of targeted protein degradation.

Hypoxia stress alters gene expression in the gills and spleen of greater amberjack (Serioladumerili)

Greater amberjack (Seriola dumerili) is a fish species that has significant economic and cultural value. It has a large size and grows rapidly. However, the intolerance to hypoxia poses a major obstacle to the growth of its aquaculture industry. This study focuses on the gills and spleen, two organs closely associated with the response to acute hypoxic stress. By simulating the acute hypoxic environment and using Illumina RNA-Seq technology, we explored the gills and spleen transcriptome changes in the acute hypoxia intolerant and tolerant groups of greater amberjack. It was discovered that gill tissues in the tolerant group may maintain a stable intracellular energy supply by promoting glycolysis and β-oxidation compared to the intolerant group. Additionally, it promotes angiogenesis, enhances the ability to absorb dissolved oxygen, and accelerates oxygen transport to the mitochondria, adapting to the hypoxic environment. Anti-apoptotic genes were up-regulated in gill tissues in the tolerant group compared to the intolerant group, thereby minimizing the damage of acute hypoxia. On the other hand, the spleen inhibited the TCA and energy-consuming lipid synthesis pathways to supply energy under acute hypoxic stress. Pro-angiogenic genes were down-regulated in the spleen of individuals in the tolerant group compared to the intolerant group, which may be related to organ function. The suppressed reactive oxygen species (ROS) production and the impaired immune response function of the spleen were also found. The study explored the acute hypoxic stress response in greater amberjack and the molecular mechanisms underlying its tolerance to acute hypoxia.

Transcriptional elongation control of hypoxic response

The release of paused RNA polymerase II (RNAPII) from promoter-proximal regions is tightly controlled to ensure proper regulation of gene expression. The elongation factor PTEF-b is known to release paused RNAPII via phosphorylation of the RNAPII C-terminal domain by its cyclin-dependent kinase component, CDK9. However, the signal and stress-specific roles of the various RNAPII-associated macromolecular complexes containing PTEF-b/CDK9 are not yet clear. Here, we identify and characterize the CDK9 complex required for transcriptional response to hypoxia. Contrary to previous reports, our data indicate that a CDK9 complex containing BRD4 but not AFF1/4 is essential for this hypoxic stress response. We demonstrate that BRD4 bromodomains (BET) are dispensable for the release of paused RNAPII at hypoxia-activated genes and that BET inhibition by JQ1 is insufficient to impair hypoxic gene response. Mechanistically, we demonstrate that the C-terminal region of BRD4 is required for Polymerase-Associated Factor-1 Complex (PAF1C) recruitment to establish an elongation-competent RNAPII complex at hypoxia-responsive genes. PAF1C disruption using a small-molecule inhibitor (iPAF1C) impairs hypoxia-induced, BRD4-mediated RNAPII release. Together, our results provide insight into potentially targetable mechanisms that control the hypoxia-responsive transcriptional elongation.

Retracted: Neuroglobin Is Involved in the Hypoxic Stress Response in the Brain.

[This retracts the article DOI: 10.1155/2022/8263373.].

Cascade-driven nanomotors promote diabetic wound healing by eradicating MRSA biofilm infection

Bacterial infection, hypoxia, and inflammatory stress responses are the key obstacles that delay the healing of diabetic ulcers. Herein, DMSNs-Pt-LOX@Nisin (DPLN) nanomotors that exhibits cascade propulsion and can specifically target methicillin-resistant Staphylococcus aureus (MRSA) is developed. The DPLN can facilitate the conversion of the abundant lactic acid existed in diabetic wounds, resulting in the generation of hydrogen peroxide (H2O2). Meanwhile, the unilateral Pt nanodendrites (Pt DNs) catalyze H2O2 to produce O2, driving the nanomotors to rapidly penetrate into the biofilm. Moreover, by loading Nisin, which can bind to lipid II of Gram-positive bacteria, the nanomotors can target MRSA through a self-driven process. Both in vitro and in vivo experiments demonstrate that the nanomotors can eradicate MRSA biofilms. Furthermore, animal studies show that DPLN are able to expedite the process of wound healing in diabetic mice through the eradication of biofilms, facilitation of angiogenesis, and mitigation of inflammation. These novel nanomotors combining cascade propulsion and MRSA targeting represent an encouraging and potentially effective approach in diabetic ulcer treatment.

Molecular Cloning, Tissue Distribution, and Hypoxia and Ammonia Stress Response of the p38 MAPK of Black Seabream (Acanthopagrus schlegelii)

Molecular Cloning, Tissue Distribution, and Hypoxia and Ammonia Stress Response of the p38 MAPK of Black Seabream (Acanthopagrus schlegelii)

Integrated transcriptomic and proteomic analysis reveals Guizhi-Fuling Wan inhibiting STAT3-EMT in ovarian cancer progression

BackgroundOvarian cancer (OC) is the most lethal gynecological malignancy. Frequent peritoneal dissemination is the main cause of low survival rate. Guizhi-Fuling Wan (GZFL) is a classical traditional Chinese herbal formula that has been clinically used for treating ovarian cancer with good outcome. However, its therapeutic mechanism for treating OC has not been clearly elucidated. PurposeWe aim to elucidate the potential mechanisms of GZFL in treating OC with a focus on STAT3 signaling pathway. MethodsIn vivo efficacy of GZFL was assessed using an OC xenograft mouse model. Proteomics analysis in OC cells and RNA-seq analysis in mice tumors were performed to fully capture the translational and transcriptional signature of GZFL. Effects of GZFL on proliferation, spheroid formation and reactive oxygen species (ROS) were assessed using wildtype and STAT3 knockout OC cells in vitro. STAT3 activation and transcription activity, hypoxia and EMT-related protein expression were assessed to validate the biological activity of GZFL. ResultsGZFL suppresses tumor growth with a safety profile in mice, while prevents cell growth, spheroid formation and accumulates ROS in a STAT3-dependent manner in vitro. GZFL transcriptionally and translationally affects genes involved in inflammatory signaling, EMT, cell migration, and cellular hypoxic stress response. In depth molecular study confirmed that GZFL-induced cytotoxicity and EMT suppression in OC cells are directly corelated to inhibition of STAT3 activation and transcription activity. ConclusionOur study provides the first evidence that GZFL inhibits OC progression through suppressing STAT3-EMT signaling. These results will further support its potential clinical use in OC.

Linking HIF oxygen-sensing system diversity to hypoxia fitness in Eleutheronema: Molecular characterization and transcriptional response to hypoxia exposure

Hypoxia is a mounting environmental problem affecting coastal waters globally, posing severe consequences for biodiversity and marine life. Metazoans respond to hypoxia stress via the hypoxia-inducible factor (HIF) pathway, but few studies have addressed the gene diversity of the functionally important HIF-pathway. Understanding whether functional diversity exists in the HIF-pathway is a key first step in identifying genes that may impact hypoxia fitness. Here, we leveraged whole-genome resequencing data and bioinformatics tools to identify the key members of the HIF-pathway (HIFα/β, EGLN, and VHL) and genetic diversity in the threatened Eleutheronema. Phylogenetic analysis revealed that teleost-specific duplicates of epas1 (epas1a/b) were followed by the loss of one of each hif1α and hif1αl in Eleutheronema species. Strong collinearity and similarity of gene characteristics suggested the functional conservation of the HIF-pathway during Eleutheronema evolution. Purifying selection was the major theme in HIF-pathway evolution, leading to a reduction in genetic diversity. Substantially low nucleotide diversity of the HIF-pathway was observed among populations, which might indicate the loss of hypoxia fitness in Eleutheronema. Additionally, the normoxic presence of the HIF-pathway differed among tissues and was species-dependent, indicating their diverse roles during development. Significant regulation of HIF-pathway expression levels was observed across tissues under hypoxic conditions, suggesting critical roles in the hypoxia stress response. Moreover, variant molecular characters suggested different roles in response to hypoxia of the HIF-pathway, which were reflected in the different expression patterns across tissues. Our present study provides novel insights into the interplay between gene diversity within the HIF-pathway and hypoxia fitness in threatened Eleutheronema. We highlighted the importance of HIF-pathway-mediated transcriptional regulation in response to hypoxia stress, which provided valuable information for the genetic mechanisms underlying hypoxia adaptation in fish. The bioinformatic methods developed here have broad applications for other species.

Long non-coding RNA PANDA drives diabetic vascular dysfunction by promoting endothelial senescence and oxidative damage

Abstract Background Accumulation of reactive oxygen species and inflammation are major features of diabetic vasculopathy, yet the underlying mechanisms remain elusive. Long non-coding RNAs (lncRNAs) are emerging as important players in the pathogenesis of cardiovascular disease. Recent work has shown that PANDA, a newly identified lncRNA, is a key regulator of cellular senescence and apoptosis. Purpose To investigate the role of lncRNA PANDA in diabetic vascular disease. Methods Human aortic endothelial cells (HAECs) were exposed to normal (NG, 5 mmol/L) and high glucose concentrations (HG, 25 mmol/L). PANDA depletion in HG-treated HAECs was obtained by siRNA transfection while a scrambled RNA was used as a negative control. Expression of PANDA was assessed by real time PCR. PANDA RNA immuno-precipitation (RIP) was performed to check its binding to relevant transcriptional factors (NF-YA). Beta-galactosidase staining was used to detect endothelial senescence while, migration and tube formation were employed to evaluate angiogenic properties of HAECs. Finally, RNAs sequencing (RNA-seq) and bioinformatic analysis (network perturbation amplitude, NPA) were leveraged to unveil transcriptional changes upon PANDA depletion. Finally, the ex vivo effect of PANDA siRNA on endothelial function was assessed in aortic rings from diabetic mice. Results PANDA expression was significantly increased in HAECs exposed to HG as compared to NG (Fig. 1A). We found that under HG conditions PANDA sequesters the transcription factor NF-YA, thus inhibiting the expression of NF-YA-dependent pro-survival and anti-aging genes (Fig. 1B). Indeed, silencing of PANDA in HG-treated HAECs restored the expression of anti-apoptotic genes Bcl-X(L) and Bcl-2 while blunting senescence-related genes such as p53 and p16INK (Fig. 1C). PANDA depletion also abolished HG-induced cellular apoptosis and senescence, as assessed by caspase-3 activity assay and b-gal staining (Fig. 1D-E), while improving endothelial migration and tube formation (Fig.1F-G). Transcriptomic analysis revealed dysregulation of several genes upon PANDA silencing with the antioxidant gene heme oxygenase-1 (HMOX1) as the top-ranking transcript in HG-treated cells (Fig.1H). NPA analysis showed a strong involvement of PANDA in senescence, DNA damage, NRF2 signaling, hypoxic stress response and proliferation (Fig. 1I). Of interest, PANDA levels were increased in aortas from diabetic mice (Fig. 2A) while depletion of PANDA rescued endothelial dysfunction (Fig. 2B). Conclusions Hyperglycemia-induced upregulation of PANDA drives endothelial senescence while impairing angiogenic properties. PANDA depletion in HG-treated HAECs rescues maladaptive transcriptional changes by restoring expression of the antioxidant gene HMOX1. Of note, targeting PANDA in the diabetic vasculature was able to rescue endothelial dysfunction. Our results indicate PANDA as a novel molecular target in the setting of diabetic vascular disease.

Inhibiting neddylation with MLN4924 potentiates hypoxia-induced apoptosis of mouse type B spermatogonia GC-2 cells

Hypoxia, an inadequate supply of tissue oxygen tension, has been reported to induce apoptosis of spermatogenic cells and is associated with male infertility. Neddylation, a post-translational modification similar to ubiquitination, has been shown to be involved in the hypoxia stress response. However, the functions of neddylation in hypoxia-induced apoptosis of spermatogenic cells and its association with male infertility remain largely unexplored. In this study, aiming to explore the role of neddylation in male infertility, we used the specific neddylation inhibitor MLN4924 for treatment in mouse type B spermatogonia GC-2 cells. Our results showed that MLN4924 had no apparent effect on GC-2 cell apoptosis under normoxia, but significantly increased apoptotic cells under hypoxia. Transcriptomic analysis and qPCR assay confirmed that MLN4924 could suppress the expression of hypoxia target genes in GC-2 cells under hypoxia. In addition, MLN4924 could enhance the induction of intracellular and mitochondrial reactive oxygen species (ROS) under hypoxia. These results indicate that the neddylation inhibitor MLN4924 potentiates hypoxia-induced apoptosis of mouse type B spermatogonia GC-2 cells, and neddylation may play an important role in promoting spermatogenic cells to adapt to hypoxia stress.

Dysregulation of microRNAs may contribute to neurosensory impairment in Arctic cod (Boreogadus saida) following CO2 exposure

MicroRNAs (miRNAs) are epigenetic markers with a key role in post-transcriptional gene regulation. Several studies have described the dysregulation of miRNAs in temperature and hypoxic stress responses of marine organisms, but their role in the response to acidification conditions has remained relatively underexplored. We investigated the differential expression of miRNAs in whole brain tissue of Arctic cod (Boregogadus saida) exposed to elevated aqueous CO2 levels representative of future climate change predictions. We detected the expression of 17 miRNAs of interest that are either directly or indirectly associated with reduced auditory performance; 12 of the 17 miRNAs showed significant differential expression in high treatment vs. low (control) aqueous CO2 conditions. Target gene predictions indicated that these miRNAs are likely involved with inner ear maintenance, hair cell degradation, age-related hearing loss, neural inflammation, and injury. The highest differential expression was observed in mir-135b, which is linked with increased neural inflammation and injury that may be associated with neurosensory dysfunction. Collectively, these results elucidate the contributions of miRNA mechanisms underlying CO2-induced sensory deficits in fishes facing abiotic environmental change and suggest strong potential for this approach to yield novel insights into the mechanistic effects of climate change on marine organisms.

An emerging research: the role of hepatocellular carcinoma-derived exosomal circRNAs in the immune microenvironment.

Hepatocellular carcinoma (HCC), the most common primary malignancy of the liver, is one of the leading causes of cancer-related death and is associated with a poor prognosis. The tumor microenvironment (TME) of HCC comprises immune, immunosuppressive, and interstitial cells with hypoxic, angiogenic, metabolic reprogramming, inflammatory, and immunosuppressive features. Exosomes are nanoscale extracellular vesicles that secrete biologically active signaling molecules such as deoxyribonucleic acid (DNA), messenger ribonucleic acid (mRNA), microribonucleic acid (miRNA), proteins, and lipids. These signaling molecules act as messengers in the tumor microenvironment, especially the tumor immunosuppressive microenvironment. Exosomal circRNAs reshape the tumor microenvironment by prompting hypoxic stress response, stimulating angiogenesis, contributing to metabolic reprogramming, facilitating inflammatory changes in the HCC cells and inducing tumor immunosuppression. The exosomes secreted by HCC cells carry circRNA into immune cells, which intervene in the activation of immune cells and promote the overexpression of immune checkpoints to regulate immune response, leading tumor cells to acquire immunosuppressive properties. Furthermore, immunosuppression is the final result of a combination of TME-related factors, including hypoxia, angiogenesis, metabolic reprogramming, and inflammation changes. In conclusion, exosomal circRNA accelerates the tumor progression by adjusting the phenotype of the tumor microenvironment and ultimately forming an immunosuppressive microenvironment. HCC-derived exosomal circRNA can affect HCC cell proliferation, invasion, metastasis, and induction of chemoresistance. Therefore, this review aimed to summarize the composition and function of these exosomes, the role that HCC-derived exosomal circRNAs play in microenvironment formation, and the interactions between exosomes and immune cells. This review outlines the role of exosomal circRNAs in the malignant phenotype of HCC and provides a preliminary exploration of the clinical utility of exosomal circRNAs.

Molecular Characterization and Response of Silver Carp (Hypophthalmichthys molitrix) GLUT1 under Hypoxia Stress

As an important freshwater species with economic and ecological benefits, silver carp (Hypophthalmichthys molitrix) exhibits poor tolerance to hypoxia. Glucose transporters (GLUTs) are core membrane proteins that transport glucose to tissues and regulate essential life activities. Its expression is regulated by HIF-1α and cells in hypoxic conditions to maintain energy demand through GLUTs inducing enhanced glucose transport. We cloned H. molitrix glut1 (SLC2A1) and analyzed its sequence using bioinformatics tools. The glut1 cDNA was 2104 base pairs long and encoded a 490 amino acid protein. Phylogenetic analysis revealed that sliver carp glut1 is evolutionarily conserved and exhibited the highest sequence similarity with Ctenopharyngodon idella glut1. Glut1 expression was the highest and lowest in the gills and liver, respectively. Hypoxic stress significantly increased glut1 expression in the brain (p < 0.05); in the gills, it was the highest and lowest in the semi-asphyxia and asphyxia groups, respectively; in the liver, it was significantly higher under hypoxia than that of the normoxia group; and in the heart, it was significantly higher in the floating head, semi-asphyxia, and asphyxia groups than in the normoxia group (p < 0.05). The proposed mechanism may thus provide the basis for elucidating the molecular basis of silver carp’s hypoxia stress response mediated by glut1.

Change to the transcriptomic profile, oxidative stress, apoptotic and immunity in the liver of small yellow croaker (Larimichthys polyactis) under hypoxic stress

The small yellow croaker (Larimichthys polyactis) is one of the most highly cultured fish in China, contributing considerably to the country's economy. However, conditions experienced under high-density culture make the fish susceptible to hypoxia, which impacts growth and consequently product quality. To understand the effects of hypoxia stress on physiological and biochemical responses of L. polyactis, we subjected the fish to hypoxic (2.5 mg/L) stress for 96 h. We observed histological changes in the liver pre- and post-hypoxia and measured the changes in liver injury parameters. The results showed injury to the liver of L. polyactis following hypoxic stress, indicating that the liver is an important organ in the hypoxic stress response. To explore the genes and biological processes involved in hypoxic adaptation of L. polyactis at the overall transcription level, liver tissues were obtained pre- (0 h) and post- (6, 24, 48, and 96 h) hypoxia for transcriptomic analysis. GO and KEGG enrichment analysis of differentially expressed genes (DEGs) showed that DEGs were mainly enriched in redox equilibrium, metabolism, immunity, and apoptosis pathways under hypoxic stress. In addition, we examined the changes in molecular indices related to oxidative stress, cell apoptosis, and non-specific immunity in L. polyactis under hypoxic stress. The results showed that hypoxia induced reactive oxygen species overproduction, altered the activity of oxidase (MDA, PCO, 8-OhdG) and antioxidant enzymes (T-AOC, SOD, CAT, GPx, GR), and reduced the mRNA expression of key antioxidant genes (sod1, sod2, cat) in the liver, thus confirming that hypoxic stress induced oxidative stress. Additionally, we confirmed that hypoxic stress induced apoptosis in the liver by inducing the enzyme activity of Caspase-3/8/9 and the mRNA expression of key apoptotic genes (bcl2, bax, fas, and bnip3). Furthermore, hypoxic stress inhibited the activity of non-specific enzymes (AKP, ACP, and LZM) and mRNA expression of immune-related genes (tnf-α, il-1β, and il-17c); hence, hypoxic stress inhibited the non-specific immune function of L. polyactis. In conclusion, our study provides new insights into the molecular mechanisms underlying hypoxia adaptation in marine fish, which will aid in selective breeding of hypoxia-tolerant L. polyactis.