mRNA-to-protein translation in hypoxia

FicD sensitizes cellular response to glucose fluctuations in mouse embryonic fibroblasts

During homeostasis, the endoplasmic reticulum (ER) maintains productive transmembrane and secretory protein folding that is vital for proper cellular function. The ER-resident HSP70 chaperone, binding immunoglobulin protein (BiP), plays a pivotal role in sensing ER stress to activate the unfolded protein response (UPR). BiP function is regulated by the bifunctional enzyme filamentation induced by cyclic-AMP domain protein (FicD) that mediates AMPylation and deAMPylation of BiP in response to changes in ER stress. AMPylated BiP acts as a molecular rheostat to regulate UPR signaling, yet little is known about the molecular consequences of FicD loss. In this study, we investigate the role of FicD in mouse embryonic fibroblast (MEF) response to pharmacologically and metabolically induced ER stress. We find differential BiP AMPylation signatures when comparing robust chemical ER stress inducers to physiological glucose starvation stress and recovery. Wildtype MEFs respond to pharmacological ER stress by down-regulating BiP AMPylation. Conversely, BiP AMPylation in wildtype MEFs increases upon metabolic stress induced by glucose starvation. Deletion of FicD results in widespread gene expression changes under baseline growth conditions. In addition, FicD null MEFs exhibit dampened UPR signaling, altered cell stress recovery response, and unconstrained protein secretion. Taken together, our findings indicate that FicD is important for tampering UPR signaling, stress recovery, and the maintenance of secretory protein homeostasis.

HIF-α signaling regulates the macrophage inflammatory response during Leishmania major infection

Cutaneous leishmaniasis (CL) contributes significantly to the global burden of neglected tropical diseases, with 12 million people currently infected with Leishmania parasites. CL encompasses a range of disease manifestations, from self-healing skin lesions to permanent disfigurations. Currently there is no vaccine available, and many patients are refractory to treatment, emphasizing the need for new therapeutic targets. Previous work demonstrated macrophage HIF-α-mediated lymphangiogenesis is necessary to achieve efficient wound resolution during murine L. major infection. Here, we investigate the role of macrophage HIF-α signaling independent of lymphangiogenesis. We sought to determine the relative contributions of the parasite and the host-mediated inflammation in the lesional microenvironment to myeloid HIF-α signaling. Because HIF-α activation can be detected in infected and bystander macrophages in leishmanial lesions, we hypothesize it is the host's inflammatory response and microenvironment, rather than the parasite, that triggers HIF-α activation. To address this, macrophages from mice with intact HIF-α signaling (LysM Cre ARNT f/+ ) or mice with deleted HIF-α signaling (LysM Cre ARNT f/f ) were subjected to RNASequencing after L. major infection and under pro-inflammatory stimulus. We report that L. major infection alone is enough to induce some minor HIF-α-dependent transcriptomic changes, while infection with L. major in combincation with pro-inflammatory stimuli induces numerous transcriptomic changes that are both dependent and independent of HIF-α signaling. Additionally, by coupling transcriptomic analysis with several pathway analyses, we found HIF-α suppresses pathways involved in protein translation during L. major infection in a pro-inflammatory environment. Together these findings show L. major induces a HIF-α-dependent transcriptomic program, but HIF-α only suppresses protein translation in a pro-inflammatory environment. Thus, this work indicates the host inflammatory response, rather than the parasite, largely contributes to myeloid HIF-α signaling during Leishmania infection.

Long-term severe hypoxia adaptation induces non-canonical EMT and a novel Wilms Tumor 1 (WT1) isoform

The majority of cancer deaths are caused by solid tumors, where the four most prevalent cancers (breast, lung, colorectal and prostate) account for more than 60% of all cases (1). Tumor cell heterogeneity driven by variable cancer microenvironments, such as hypoxia, is a key determinant of therapeutic outcome. We developed a novel culture protocol, termed the Long-Term Hypoxia (LTHY) time course, to recapitulate the gradual development of severe hypoxia seen in vivo to mimic conditions observed in primary tumors. Cells subjected to LTHY underwent a non-canonical epithelial to mesenchymal transition (EMT) based on miRNA and mRNA signatures as well as displayed EMT-like morphological changes. Concomitant to this, we report production of a novel truncated isoform of WT1 transcription factor (tWt1), a non-canonical EMT driver, with expression driven by a yet undescribed intronic promoter through hypoxia-responsive elements (HREs). We further demonstrated that tWt1 initiates translation from an intron-derived start codon, retains proper subcellular localization and DNA binding. A similar tWt1 is also expressed in LTHY-cultured human cancer cell lines as well as primary cancers and predicts long-term patient survival. Our study not only demonstrates the importance of culture conditions that better mimic those observed in primary cancers, especially with regards to hypoxia, but also identifies a novel isoform of WT1 which correlates with poor long-term survival in ovarian cancer.

A conjoint analysis of renal structure and omics characteristics reveal new insight to yak high-altitude hypoxia adaptation

BACKGROUND

Yaks have unique adaptive mechanisms to the hypoxic environment, in which the kidney plays an important role. The aim of this study was to explore the histological changes of yak kidney at different altitudes and the metabolites and genes associated with adaptation to the hypoxic environment.

METHODS

We analyzed the tissue structure and transcriptomic metabolomic data of yak kidney tissue at two altitudes, 2600 and 4400 m. We compared and identified the morphological adaptations of the kidney and the metabolites and genes associated with hypoxia adaptation in yaks. Changes in renal morphological adaptations, differential metabolites and genes were compared and identified, combining the two in a joint analysis.

RESULTS

High-altitude yak kidneys showed significant adaptive changes: increased mitochondria, increased glomerular thylakoid area, and decreased localized ribosomes. Transcriptomics and metabolomics identified 69 DAMs (Differential metabolites) and 594 DEGs (differential genes). Functional enrichment analysis showed that the DAMs were associated with protein digestion and absorption, ABC transporter, and MTOR signaling pathway; the DEGs were significantly enriched in Cholesterol metabolism and P53 signaling pathway. The joint analysis indicated that metabolites such as lysine and arginine, as well as key genes such as ABCB5 and COL1A2, were particularly affected under hypoxic conditions, whereas changes in mitochondria in the tissue structure may be related to the expression of MFN1 and OPA1, and changes in glomerular thylakoid membranes are related to VEGFA and TGFB3.

CONCLUSION

The kidney regulates metabolites and gene expression related to hormone synthesis, protein metabolism, and angiogenesis by adjusting the mitochondrial and glomerular thylakoid membrane structure to support the survival of yaks in high-altitude environments.

Aspartate-β-hydroxylase and hypoxia marker expression in head and neck carcinomas: implications for HPV-associated tumors

BACKGROUND

A proportion of head and neck carcinomas (HNSCCs) are induced by high-risk human papillomaviruses (HPVs) and are associated with better patient outcomes compared to patients with HNSCCs related to tobacco and alcohol abuse. In the microenvironment of solid tumors, including HNSCCs, oxygen levels are often reduced, and a hypoxic state is induced. This can lead to a poor treatment response and a worse patient prognosis. One of the hypoxia-responsive genes is aspartate-β-hydroxylase (ASPH), whose activity promotes the growth, invasiveness, and metastasis of many types of solid tumors.

METHODS

In our study, HNSCC samples were analyzed for the expression of ASPH and selected endogenous hypoxia markers by real-time PCR and/or multiplex fluorescence immunohistochemistry.

RESULTS

Except for the EPAS1 gene, which had higher mRNA expression in the HPV-negative group of HNSCC (p < 0.05), we found no other differences in the expression of the tested genes that were related to HPV status. On the contrary, a statistically significantly higher number of cells producing ASPH (p < 0.0001), HIF1A (p < 0.0001), GLUT1 (p < 0.0001), and MMP13 (p < 0.05) proteins were detected in the HPV-positive tumor group than in the HPV-negative sample group. All the evaluated markers, except for MMP9/13, were more abundant in the tumor parenchyma than in the tumor stroma. The Cox proportional hazard models showed that increased numbers of cells with GLUT1 and HIF1A protein expression were positive prognostic markers for overall and disease-specific survival in patients independent of HPV tumor status.

CONCLUSION

The study examined HNSCC samples and found that elevated ASPH and hypoxia marker proteins, typically associated with poor prognosis, may actually indicate active HPV infection, the strongest prognostic factor in HNSCC patients. In cases where HPV status is uncertain, increased expression of HIF1A and GLUT1 can serve as positive prognostic factors.

Efficacy of quercetin in ameliorating hypoxia-induced hematological and histopathological alterations in rohu Labeo rohita

Hypoxia, a major issue in aquatic ecosystems, in special reference to climate change, and exacerbated by anthropogenic activities. It is causing slow growth, disease outbreaks, and mortality in finfish and shellfish. Therefore, adaptation to lowering oxygen levels through supplementation of herbs or their extracts in diets is imperative. In this study, hypoxia was simulated in controlled conditions with quercetin-enriched diets. Quercetin is a plant pigment (flavonol) possessing anti-oxidant property and is present in vegetables, leaves, seeds, pulses, and fruits. The experiment was conducted on rohu Labeo rohita, which is most widely cultured in India. There were four treatments including T1 (Normoxia: > 5 ppm dissolved oxygen; DO2), T2 (hypoxia: 3-4 ppm DO2), T3 (hypoxia + 50 mg quercetin/kg diet), and T4 (hypoxia + 100 mg quercetin/kg diet). The study was conducted for 30 days, and water quality was measured regularly. The results revealed that the hematological parameters were negatively affected. The tissue micro-architecture illustrated the impairment through degeneration of neurons in the brain, increased pigmentation as melanosis in the kidney, increased thickness of primary lamellae in the gills, and dilatations of sinusoids in the liver in hypoxia groups, while quercetin-enriched diets improved the hematological and histomorphological parameters. The results confirm the utility of hematological and histopathological tools as biomarkers and reflect the possible threats of hypoxia on fish. In conclusion, quercetin in diets appeared to show resistance towards chronic hypoxia by restoring the structure and functions of the vital organs towards normalcy and could be recommended as a potential ameliorative agent.

Liquid foam improves potency and safety of gene therapy vectors

Interest in gene therapy medicines is intensifying as the first wave of gene-correcting drugs is now reaching patient populations. However, efficacy and safety concerns, laborious manufacturing protocols, and the high cost of the therapeutics are still significant barriers in gene therapy. Here we describe liquid foam as a vehicle for gene delivery. We demonstrate that embedding gene therapy vectors (nonviral or viral) in a methylcellulose/xanthan gum-based foam formulation substantially boosts gene transfection efficiencies in situ, compared to liquid-based gene delivery. We further establish that our gene therapy foam is nontoxic and retained at the intended target tissue, thus minimizing both systemic exposure and targeting of irrelevant cell types. The foam can be applied locally or injected to fill body cavities so the vector is uniformly dispersed over a large surface area. Our technology may provide a safe, facile and broadly applicable option in a variety of clinical settings.

HIF-1α Mediates Immunosuppression and Chemoresistance in Colorectal Cancer by Inhibiting CXCL9, -10 and -11

Uncertainty exists regarding the mechanisms by which hypoxia-inducible factors (HIFs) control CD8+T-cell migration into tumor microenvironments. Here, we found that HIF-1α knockdown or overexpression resulted in increased or decreased CXCL9, -10, and -11 expression in vitro, respectively. Gene Set Variation Analysis revealed that elevated HIF-1α levels correlated with a poor prognosis, severe pathological stage, and an absence of CD8+ T cells in the tumor microenvironment in colorectal cancer (CRC) patients. HIF-1α was inversely associated with pathways beneficial to anti-tumor immunotherapy and cytokine/chemokine function. In vivo, inhibiting HIF-1α or its upstream regulator BIRC2 significantly suppressed tumor growth and promoted CD8+ T-cell infiltration. CXCR3 neutralizing antibodies reversed these effects, implicating the involvement of CXCL9, -10, and -11/CXCR3 axis. The presence of HIF-1α weakened the upregulation of CXCL9, -10, and -11 by bleomycin and doxorubicin. Combining HIF-1α inhibition with bleomycin promoted CD8+ T-cell infiltration and tumor suppression in vivo. Moreover, doxorubicin could upregulate CXCL9, -10 and -11 by suppressing HIF-1α. Our findings highlight the potential of HIF-1α inhibition to improve CRC microenvironments and increase chemotherapy sensitivity.

Circadian Clock and Hypoxia

The timing of life on Earth is remarkable: between individuals of the same species, a highly similar temporal pattern is observed, with shared periods of activity and inactivity each day. At the individual level, this means that over the course of a single day, a person alternates between two states. They are either upright, active, and communicative or they lie down in a state of (un)consciousness called sleep where even the characteristic of neuronal signals in the brain shows distinctive properties. The circadian clock governs both of these time stamps-activity and (apparent) inactivity-making them come and go consistently at the same approximate time each day. This behavior thus represents the meeting of two pervasive systems: the circadian clock and metabolism. In this article, we will describe what is known about how the circadian clock anticipates daily changes in oxygen usage, how circadian clock regulation may relate to normal physiology, and to hypoxia and ischemia that can result from pathologies such as myocardial infarction and stroke.

Circular RNA-circLRP6 protects cardiomyocyte from hypoxia-induced apoptosis by facilitating hnRNPM-mediated expression of FGF-9

Coronary atherosclerosis-induced myocardial ischemia leads to cardiomyocyte apoptosis. The regulatory mechanisms for cardiomyocyte apoptosis have not been fully understood. Circular RNAs are non-coding RNAs which play important roles in heart function maintenance and progression of heart diseases by regulating gene transcription and protein translation. Here, we reported a conserved cardiac circular RNA, which is generated from the second exon of LRP6 and named circLRP62-2 . CircLRP62-2 can protect cardiomyocyte from hypoxia-induced apoptosis. The expression of circLRP62-2 in cardiomyocytes was down-regulated under hypoxia, while forced expression of circLRP62-2 inhibited cell apoptosis. Normally, circLRP62-2 was mainly localized in the nucleus. Under hypoxia, circLRP62-2 is associated with heterogeneous nuclear ribonucleoprotein M (hnRNPM) to be translocated into the cytoplasm. It recruited hnRNPM to fibroblast growth factor 9 (FGF9) mRNA to enhance the expression of FGF9 protein, promoting hypoxia-adaption and viability of cardiomyocytes. In summary, this study uncovers a new inhibitor of apoptosis and reveals a novel anti-apoptotic pathway composed of circLRP62-2 , hnRNPM, and FGF9, which may provide therapeutic targets for coronary heart disease and ischemic myocardial injury.

Hypoxia and its effect on the cellular system

Eukaryotic cells utilize oxygen for different functions of cell organelles owing to cellular survival. A balanced oxygen homeostasis is an essential requirement to maintain the regulation of normal cellular systems. Any changes in the oxygen level are stressful and can alter the expression of different homeostasis regulatory genes and proteins. Lack of oxygen or hypoxia results in oxidative stress and formation of hypoxia inducible factors (HIF) and reactive oxygen species (ROS). Substantial cellular damages due to hypoxia have been reported to play a major role in various pathological conditions. There are different studies which demonstrated that the functions of cellular system are disrupted by hypoxia. Currently, study on cellular effects following hypoxia is an important field of research as it not only helps to decipher different signaling pathway modulation, but also helps to explore novel therapeutic strategies. On the basis of the beneficial effect of hypoxia preconditioning of cellular organelles, many therapeutic investigations are ongoing as a promising disease management strategy in near future. Hence, the present review discusses about the effects of hypoxia on different cellular organelles, mechanisms and their involvement in the progression of different diseases.

Hypoxia, oxidative stress, and the interplay of HIFs and NRF2 signaling in cancer

Oxygen is crucial for life and acts as the final electron acceptor in mitochondrial energy production. Cells adapt to varying oxygen levels through intricate response systems. Hypoxia-inducible factors (HIFs), including HIF-1α and HIF-2α, orchestrate the cellular hypoxic response, activating genes to increase the oxygen supply and reduce expenditure. Under conditions of excess oxygen and resulting oxidative stress, nuclear factor erythroid 2-related factor 2 (NRF2) activates hundreds of genes for oxidant removal and adaptive cell survival. Hypoxia and oxidative stress are core hallmarks of solid tumors and activated HIFs and NRF2 play pivotal roles in tumor growth and progression. The complex interplay between hypoxia and oxidative stress within the tumor microenvironment adds another layer of intricacy to the HIF and NRF2 signaling systems. This review aimed to elucidate the dynamic changes and functions of the HIF and NRF2 signaling pathways in response to conditions of hypoxia and oxidative stress, emphasizing their implications within the tumor milieu. Additionally, this review explored the elaborate interplay between HIFs and NRF2, providing insights into the significance of these interactions for the development of novel cancer treatment strategies.

Does hypometabolism constrain innate immune defense?

Many animals routinely make energetic trade-offs to adjust to environmental demands and these trade-offs often have significant implications for survival. For example, environmental hypoxia is commonly experienced by many organisms and is an energetically challenging condition because reduced oxygen availability constrains aerobic energy production, which can be lethal. Many hypoxia-tolerant species downregulate metabolic demands when oxygen is limited; however, certain physiological functions are obligatory and must be maintained despite the need to conserve energy in hypoxia. Of particular interest is immunity (including both constitutive and induced immune functions) because mounting an immune response is among the most energetically expensive physiological processes but maintaining immune function is critical for survival in most environments. Intriguingly, physiological responses to hypoxia and pathogens share key molecular regulators such as hypoxia-inducible factor-1α, through which hypoxia can directly activate an immune response. This raises an interesting question: do hypoxia-tolerant species mount an immune response during periods of hypoxia-induced hypometabolism? Unfortunately, surprisingly few studies have examined interactions between immunity and hypometabolism in such species. Therefore, in this review, we consider mechanistic interactions between metabolism and immunity, as well as energetic trade-offs between these two systems, in hypoxia-tolerant animals but also in other models of hypometabolism, including neonates and hibernators. Specifically, we explore the hypothesis that such species have blunted immune responses in hypometabolic conditions and/or use alternative immune pathways when in a hypometabolic state. Evidence to date suggests that hypoxia-tolerant animals do maintain immunity in low oxygen conditions, but that the sensitivity of immune responses may be blunted.

Protein translation: biological processes and therapeutic strategies for human diseases

Protein translation is a tightly regulated cellular process that is essential for gene expression and protein synthesis. The deregulation of this process is increasingly recognized as a critical factor in the pathogenesis of various human diseases. In this review, we discuss how deregulated translation can lead to aberrant protein synthesis, altered cellular functions, and disease progression. We explore the key mechanisms contributing to the deregulation of protein translation, including functional alterations in translation factors, tRNA, mRNA, and ribosome function. Deregulated translation leads to abnormal protein expression, disrupted cellular signaling, and perturbed cellular functions- all of which contribute to disease pathogenesis. The development of ribosome profiling techniques along with mass spectrometry-based proteomics, mRNA sequencing and single-cell approaches have opened new avenues for detecting diseases related to translation errors. Importantly, we highlight recent advances in therapies targeting translation-related disorders and their potential applications in neurodegenerative diseases, cancer, infectious diseases, and cardiovascular diseases. Moreover, the growing interest lies in targeted therapies aimed at restoring precise control over translation in diseased cells is discussed. In conclusion, this comprehensive review underscores the critical role of protein translation in disease and its potential as a therapeutic target. Advancements in understanding the molecular mechanisms of protein translation deregulation, coupled with the development of targeted therapies, offer promising avenues for improving disease outcomes in various human diseases. Additionally, it will unlock doors to the possibility of precision medicine by offering personalized therapies and a deeper understanding of the molecular underpinnings of diseases in the future.

FicD Sensitizes Cellular Response to Glucose Fluctuations in Mouse Embryonic Fibroblasts

During homeostasis, the endoplasmic reticulum (ER) maintains productive transmembrane and secretory protein folding that is vital for proper cellular function. The ER-resident HSP70 chaperone, BiP, plays a pivotal role in sensing ER stress to activate the unfolded protein response (UPR). BiP function is regulated by the bifunctional enzyme FicD that mediates AMPylation and deAMPylation of BiP in response to changes in ER stress. AMPylated BiP acts as a molecular rheostat to regulate UPR signaling, yet little is known about the molecular consequences of FicD loss. In this study, we investigate the role of FicD in mouse embryonic fibroblast (MEF) response to pharmacologically and metabolically induced ER stress. We find differential BiP AMPylation signatures when comparing robust chemical ER stress inducers to physiological glucose starvation stress and recovery. Wildtype MEFs respond to pharmacological ER stress by downregulating BiP AMPylation. Conversely, BiP AMPylation in wildtype MEFs increases upon metabolic stress induced by glucose starvation. Deletion of FicD results in widespread gene expression changes under baseline growth conditions. In addition, FicD null MEFs exhibit dampened UPR signaling, altered cell stress recovery response, and unconstrained protein secretion. Taken together, our findings indicate that FicD is important for tampering UPR signaling, stress recovery, and the maintenance of secretory protein homeostasis.

Significance Statement

The chaperone BiP plays a key quality control role in the endoplasmic reticulum, the cellular location for the production, folding, and transport of secreted proteins. The enzyme FicD regulates BiP's activity through AMPylation and deAMPylation. Our study unveils the importance of FicD in regulating BiP and the unfolded protein response (UPR) during stress. We identify distinct BiP AMPylation signatures for different stressors, highlighting FicD's nuanced control. Deletion of FicD causes widespread gene expression changes, disrupts UPR signaling, alters stress recovery, and perturbs protein secretion in cells. These observations underscore the pivotal contribution of FicD for preserving secretory protein homeostasis. Our findings deepen the understanding of FicD's role in maintaining cellular resilience and open avenues for therapeutic strategies targeting UPR-associated diseases.

Chronic hypoxia stabilizes 3βHSD1 via autophagy suppression

Progression of prostate cancer depends on androgen receptor, which is usually activated by androgens. Therefore, a mainstay treatment is androgen deprivation therapy. Unfortunately, despite initial treatment response, resistance nearly always develops, and disease progresses to castration-resistant prostate cancer (CRPC), which remains driven by non-gonadal androgens synthesized in prostate cancer tissues. 3β-Hydroxysteroid dehydrogenase/Δ5-->4 isomerase 1 (3βHSD1) catalyzes the rate-limiting step in androgen synthesis. However, how 3βHSD1, especially the "adrenal-permissive" 3βHSD1(367T) that permits tumor synthesis of androgen from dehydroepiandrosterone (DHEA), is regulated at the protein level is not well understood. Here, we investigate how hypoxia regulates 3βHSD1(367T) protein levels. Our results show that, in vitro, hypoxia stabilizes 3βHSD1 protein by suppressing autophagy. Autophagy inhibition promotes 3βHSD1-dependent tumor progression. Hypoxia represses transcription of autophagy-related (ATG) genes by decreasing histone acetylation. Inhibiting deacetylase (HDAC) restores ATG gene transcription under hypoxia. Therefore, HDAC inhibition may be a therapeutic target for hypoxic tumor cells.

KSHV-encoded LANA bypasses transcriptional block through the stabilization of RNA Pol II in hypoxia

IMPORTANCE

Hypoxia can induce the reactivation of Kaposi sarcoma-associated virus (KSHV), which necessitates the synthesis of critical structural proteins. Despite the unfavorable energetic conditions of hypoxia, KSHV utilizes mechanisms to prevent the degradation of essential cellular machinery required for successful reactivation. Our study provides new insights on strategies employed by KSHV-infected cells to maintain steady-state transcription by overcoming hypoxia-mediated metabolic stress to enable successful reactivation. Our discovery that the interaction of latency-associated nuclear antigen with HIF1α and NEDD4 inhibits its polyubiquitination activity, which blocks the degradation of RNA Pol II during hypoxia, is a significant contribution to our understanding of KSHV biology. This newfound knowledge provides new leads in the development of novel therapies for KSHV-associated diseases.

Next-Cell Hypothesis: Mechanism of Obesity-Associated Carcinogenesis

Higher body fat content is related to a higher risk of mortality, and obesity-related cancer represents approximately 40% of all cancer patients diagnosed each year. Furthermore, epigenetic mechanisms are involved in cellular metabolic memory and can determine one's predisposition to being overweight. Low-grade chronic inflammation, a well-established characteristic of obesity, is a central component of tumor development and progression. Cancer-associated adipocytes (CAA), which enhance inflammation- and metastasis-related gene sets within the cancer microenvironment, have pro-tumoral effects. Adipose tissue is a major source of the exosomal micro ribonucleic acids (miRNAs), which modulate pathways involved in the development of obesity and obesity-related comorbidities. Owing to their composition of cargo, exosomes can activate receptors at the target cell or transfer molecules to the target cells and thereby change the phenotype of these cells. Exosomes that are released into the extracellular environment are internalized with their cargo by neighboring cells. The tumor-secreted exosomes promote organ-specific metastasis of tumor cells that normally lack the capacity to metastasize to a specific organ. Therefore, the communication between neighboring cells via exosomes is defined as the "next-cell hypothesis." The reciprocal interaction between the adipocyte and tumor cell is realized through the adipocyte-derived exosomal miRNAs and tumor cell-derived oncogenic miRNAs. The cargo molecules of adipocyte-derived exosomes are important messengers for intercellular communication involved in metabolic responses and have very specific signatures that direct the metabolic activity of target cells. RNA-induced silencing regulates gene expression through various mechanisms. Destabilization of DICER enzyme, which catalyzes the conversion of primary miRNA (pri-miRNA) to precursor miRNA (pre-miRNA), is an important checkpoint in cancer development and progression. Interestingly, adipose tissue in obesity and tumors share similar pathogenic features, and the local hypoxia progress in both. While hypoxia in obesity leads to the adipocyte dysfunction and metabolic abnormalities, in obesity-related cancer cases, it is associated with worsened prognosis, increased metastatic potential, and resistance to chemotherapy. Notch-interleukin-1 (IL-1)-Leptin crosstalk outcome is referred to as "NILCO effect." In this chapter, obesity-related cancer development is discussed in the context of "next-cell hypothesis," miRNA biogenesis, and "NILCO effect."

Targeting stroma and tumor, silencing galectin 1 treats orthotopic mouse hepatocellular carcinoma

This study examines inhibiting galectin 1 (Gal1) as a treatment option for hepatocellular carcinoma (HCC). Gal1 has immunosuppressive and cancer-promoting roles. Our data showed that Gal1 was highly expressed in human and mouse HCC. The levels of Gal1 positively correlated with the stages of human HCC and negatively with survival. The roles of Gal1 in HCC were studied using overexpression (OE) or silencing using Igals1 siRNA delivered by AAV9. Prior to HCC initiation induced by RAS and AKT mutations, lgals1-OE and silencing had opposite impacts on tumor load. The treatment effect of lgals1 siRNA was further demonstrated by intersecting HCC at different time points when the tumor load had already reached 9% or even 42% of the body weight. Comparing spatial transcriptomic profiles of Gal1 silenced and OE HCC, inhibiting matrix formation and recognition of foreign antigen in CD45+ cell-enriched areas located at tumor-margin likely contributed to the anti-HCC effects of Gal1 silencing. Within the tumors, silencing Gal1 inhibited translational initiation, elongation, and termination. Furthermore, Gal1 silencing increased immune cells as well as expanded cytotoxic T cells within the tumor, and the anti-HCC effect of lgals1 siRNA was CD8-dependent. Overall, Gal1 silencing has a promising potential for HCC treatment.

Distinct hypoxia-induced translational profiles of embryonic and adult-derived macrophages

Tissue resident macrophages are largely of embryonic (fetal liver) origin and long-lived, while bone marrow-derived macrophages (BMDM) are recruited following an acute perturbation, such as hypoxia in the setting of myocardial ischemia. Prior transcriptome analyses identified BMDM and fetal liver-derived macrophage (FLDM) differences at the RNA expression level. Posttranscriptional regulation determining mRNA stability and translation rate may override transcriptional signals in response to hypoxia. We profiled differentially regulated BMDM and FLDM transcripts in response to hypoxia at the level of mRNA translation. Using a translating ribosome affinity purification (TRAP) assay and RNA-seq, we identified non-overlapping transcripts with increased translation rate in BMDM (Ly6e, vimentin, PF4) and FLDM (Ccl7, Ccl2) after hypoxia. We further identified hypoxia-induced transcripts within these subsets that are regulated by the RNA-binding protein HuR. These findings define translational differences in macrophage subset gene expression programs, highlighting potential therapeutic targets in ischemic myocardium.

A Unified Strategy to Improve Lipid Nanoparticle Mediated mRNA Delivery Using Adenosine Triphosphate

A central goal of chemical and drug delivery sciences is to maximize the therapeutic efficacy of a given drug at the lowest possible dose. Here, we report a generalizable strategy that can be utilized to improve the delivery of mRNA drugs using lipid nanoparticles (LNPs), the clinically approved chemistry platforms utilized in the Moderna and Pfizer/BioNTech COVID-19 vaccines. In brief, our strategy updates the chemistry of LNPs to incorporate adenosine triphosphate (ATP) alongside mRNA, a modification that results in upward of a 79-fold increase in LNP-delivered mRNA-encoded protein expression in vitro and a 24-fold increase in vivo when compared to parent mRNA LNP formulations that do not contain ATP. Notably, we find that our ATP co-delivery strategy increases LNP-delivered mRNA-encoded protein expression across eight different LNP chemistries and three different cell lines, under normoxia and hypoxia, and in a well-tolerated fashion. Notably, our strategy also improves the expression of mRNA encoding for intracellular and secreted proteins both in vitro and in vivo, highlighting the utility of leveraging ATP co-delivery within mRNA LNPs as a means to increase protein expression. In developing this strategy, we hope that we have provided a simple yet powerful approach to improving mRNA LNPs that may one day be useful in developing therapies for human disease.

eIF4EHP promotes Ldh mRNA translation in and fruit fly adaptation to hypoxia

Hypoxia induces profound modifications in the gene expression program of eukaryotic cells due to lowered ATP supply resulting from the blockade of oxidative phosphorylation. One significant consequence of oxygen deprivation is the massive repression of protein synthesis, leaving a limited set of mRNAs to be translated. Drosophila melanogaster is strongly resistant to oxygen fluctuations; however, the mechanisms allowing specific mRNA to be translated into hypoxia are still unknown. Here, we show that Ldh mRNA encoding lactate dehydrogenase is highly translated into hypoxia by a mechanism involving a CA-rich motif present in its 3' untranslated region. Furthermore, we identified the cap-binding protein eIF4EHP as a main factor involved in 3'UTR-dependent translation under hypoxia. In accordance with this observation, we show that eIF4EHP is necessary for Drosophila development under low oxygen concentrations and contributes to Drosophila mobility after hypoxic challenge. Altogether, our data bring new insight into mechanisms contributing to LDH production and Drosophila adaptation to oxygen variations.

Hypoxia stress induces complicated miRNA responses in the gill of Chinese mitten crab (Eriocheir sinensis)

Hypoxia caused by global climate change and human activities has become a growing concern eliciting serious damages to aquatic animals. microRNAs (miRNAs) as non-coding regulatory RNAs exert vital effects on hypoxia responses. Chinese mitten crab (Eriocheir sinensis) with the habitat on the sediment surface or the pond bottom is susceptible to oxygen deficiency. However, whether miRNAs are involved in the response of the crabs to hypoxia stress remains enigmas. In this study, we conducted the whole transcriptome-based miRNA-mRNA integrated analysis of Chinese mitten crab gill under hypoxic condition for 3 h and 24 h We found that the acute hypoxia induces complex miRNA responses with the extensive influences on their target genes that engaged in various bio-processes, especially those associated with immunity, metabolism and endocrine. The impact of hypoxia on crab miRNAs is severer, as the exposure lasts longer. In response to the dissolved oxygen fluctuation, the HIF-1 signaling is activated by miRNAs to cope with the hypoxia stress through strategies including balancing inflammatory and autophagy involved in immunity, changing metabolism to reducing energy consumption, and enhancing oxygen-carrying and delivering capacities. The miRNAs and their corresponding target genes engaged in hypoxia response were intertwined into an intricate network. Moreover, the top hub molecular, miR-998-y and miR-275-z, discovered from the network might serve as biomarkers for hypoxia response in crabs. Our study provides the first systemic miRNA profile of Chinese mitten crab induced by hypoxia stress, and the identified miRNAs and the interactive network add new insights into the mechanism of hypoxia response in crabs.

An Efficacy and Mechanism Driven Study on the Impact of Hypoxia on Lipid Nanoparticle Mediated mRNA Delivery

Hypoxia is a common hallmark of human disease that is characterized by abnormally low oxygen levels in the body. While the effects of hypoxia on many small molecule-based drugs are known, its effects on several classes of next-generation medications including messenger RNA therapies warrant further study. Here, we provide an efficacy- and mechanism-driven study that details how hypoxia impacts the cellular response to mRNA therapies delivered using 4 different chemistries of lipid nanoparticles (LNPs, the frontrunner class of drug delivery vehicles for translational mRNA therapy utilized in the Moderna and Pfizer/BioNTech COVID-19 vaccines). Specifically, our work provides a comparative analysis as to how various states of oxygenation impact LNP-delivered mRNA expression, cellular association, endosomal escape, and intracellular ATP concentrations following treatment with 4 different LNPs across 3 different cell lines. In brief, we first identify that hypoxic cells express less LNP-delivered mRNA into protein than normoxic cells. Next, we identify generalizable cellular reoxygenation protocols that can reverse the negative effects that hypoxia imparts on LNP-delivered mRNA expression. Finally, mechanistic studies that utilize fluorescence-activated cell sorting, confocal microscopy, and enzyme inhibition reveal that decreases in mRNA expression correlate with decreases in intracellular ATP (rather than with differences in mRNA LNP uptake pathways). In presenting this data, we hope that our work provides a comprehensive efficacy and mechanism-driven study that explores the impact of differential oxygenation on LNP-delivered mRNA expression while simultaneously establishing fundamental criteria that may one day be useful for the development of mRNA drugs to treat hypoxia-associated disease.

EEF1A2 accelerates the protein translation of chemokine in rat myocardial cells induced by ischemia-reperfusion

How to reduce the damage caused by myocardial ischemia-reperfusion (IR) in a timely manner to save patients' lives is still a great clinical challenge. Although dexmedetomidine (DEX) has been reported to protect the myocardium, the regulatory mechanism of gene translation responding to IR injury and DEX protection is poorly understood. In this study, IR rat model with DEX and the antagonist yohimbine (YOH) pretreatment were established, and RNA sequencing was carried out to seek the important regulators in differential expressed genes. A series of cytokines and chemokine as well as eukaryotic translation elongation factor 1 alpha 2 (EEF1A2) were induced by IR compared to control and compromised by DEX pretreatment compared to IR, then reversed by YOH. Immunoprecipitation was conducted to identify that peroxiredoxin 1 (PRDX1) interacted with EEF1A2 and contributed to the recruitment of EEF1A2 on mRNA molecules of cytokines and chemokine. Knockdown of PRDX1 could weaken the enhancive effect of EEF1A2 for gene translation of IL6, CXCL2 and CXCL11 under the IR condition, and indeed reduce cell apoptosis of cardiomyocytes. We also determined that the RNA motif "USCAGDCU" at 5' UTR could be particularly recognized by PRDX1. Destruction of this motif at the 5' UTR of IL6, CXCL2 and CXCL11 by CRISPR-CAS9 could result in the loss occupancies of EEF1A2 and PRDX1 on the mRNA of these three genes. Our observations showed the importance of PRDX1 in the reasonable control of cytokine and chemokine expression to prevent excessive inflammatory response to cell damage.

Plant translational reprogramming for stress resilience

Organisms regulate gene expression to produce essential proteins for numerous biological processes, from growth and development to stress responses. Transcription and translation are the major processes of gene expression. Plants evolved various transcription factors and transcriptome reprogramming mechanisms to dramatically modulate transcription in response to environmental cues. However, even the genome-wide modulation of a gene's transcripts will not have a meaningful effect if the transcripts are not properly biosynthesized into proteins. Therefore, protein translation must also be carefully controlled. Biotic and abiotic stresses threaten global crop production, and these stresses are seriously deteriorating due to climate change. Several studies have demonstrated improved plant resistance to various stresses through modulation of protein translation regulation, which requires a deep understanding of translational control in response to environmental stresses. Here, we highlight the translation mechanisms modulated by biotic, hypoxia, heat, and drought stresses, which are becoming more serious due to climate change. This review provides a strategy to improve stress tolerance in crops by modulating translational regulation.

Epigenetic Reprogramming of Kaposi's Sarcoma-Associated Herpesvirus during Hypoxic Reactivation

The biphasic life cycle (latent and lytic) of Kaposi's sarcoma-associated Herpesvirus (KSHV) is regulated by epigenetic modification of its genome and its associated histone proteins. The temporal events driving epigenetic reprogramming of the KSHV genome on initial infection to establish latency has been well studied, but the reversal of these epigenetic changes during lytic replication, especially under physiological conditions such as hypoxia, has not been explored. In this study, we investigated epigenetic reprogramming of the KSHV genome during hypoxic reactivation. Hypoxia induced extensive enrichment of both transcriptional activators and repressors on the KSHV genome through H3K4Me3, H3K9Me3, and H3K27Me3, as well as histone acetylation (H3Ac) modifications. In contrast to uniform quantitative enrichment with modified histones, a distinct pattern of RTA and LANA enrichment was observed on the KSHV genome. The enrichment of modified histone proteins was due to their overall higher expression levels, which was exclusively seen in KSHV-positive cells. Multiple KSHV-encoded factors such as LANA, RTA, and vGPCR are involved in the upregulation of these modified histones. Analysis of ChIP-sequencing for the initiator DNA polymerase (DNAPol1α) combined with single molecule analysis of replicated DNA (SMARD) demonstrated the involvement of specific KSHV genomic regions that initiate replication in hypoxia.

The Role of the Hypoxia-Related Unfolded Protein Response (UPR) in the Tumor Microenvironment

Despite our understanding of the unfolded protein response (UPR) pathways, the crosstalk between the UPR and the complex signaling networks that different cancers utilize for cell survival remains to be, in most cases, a difficult research barrier. A major problem is the constant variability of different cancer types and the different stages of cancer as well as the complexity of the tumor microenvironments (TME). This complexity often leads to apparently contradictory results. Furthermore, the majority of the studies that have been conducted have utilized two-dimensional in vitro cultures of cancer cells that were exposed to continuous hypoxia, and this approach may not mimic the dynamic and cyclic conditions that are found in solid tumors. Here, we discuss the role of intermittent hypoxia, one of inducers of the UPR in the cellular component of TME, and the way in which intermittent hypoxia induces high levels of reactive oxygen species, the activation of the UPR, and the way in which cancer cells modulate the UPR to aid in their survival. Although the past decade has resulted in defining the complex, novel non-coding RNA-based regulatory networks that modulate the means by which hypoxia influences the UPR, we are now just to beginning to understand some of the connections between hypoxia, the UPR, and the TME.

Supraphysiological Oxygen Levels in Mammalian Cell Culture: Current State and Future Perspectives

Most conventional incubators used in cell culture do not regulate O2 levels, making the headspace O2 concentration ~18%. In contrast, most human tissues are exposed to 2-6% O2 (physioxia) in vivo. Accumulating evidence has shown that such hyperoxic conditions in standard cell culture practices affect a variety of biological processes. In this review, we discuss how supraphysiological O2 levels affect reactive oxygen species (ROS) metabolism and redox homeostasis, gene expression, replicative lifespan, cellular respiration, and mitochondrial dynamics. Furthermore, we present evidence demonstrating how hyperoxic cell culture conditions fail to recapitulate the physiological and pathological behavior of tissues in vivo, including cases of how O2 alters the cellular response to drugs, hormones, and toxicants. We conclude that maintaining physioxia in cell culture is imperative in order to better replicate in vivo-like tissue physiology and pathology, and to avoid artifacts in research involving cell culture.

Hypoxia: molecular pathophysiological mechanisms in human diseases

Hypoxia, a low O2 tension, is a fundamental feature that occurs in physiological events as well as pathophysiological conditions, especially mentioned for its role in the mechanism of angiogenesis, glucose metabolism, and cell proliferation/survival. The hypoxic state through the activation of specific mechanisms is an aggravating circumstance commonly noticed in multiple sclerosis, cancer, heart disease, kidney disease, liver disease, lung disease, and in inflammatory bowel disease. On the other hand, hypoxia could play a key role in tissue regeneration and repair of damaged tissues, especially by acting on specific tissue stem cells, but their features may result as a disadvantage when it is concerned for neoplastic stem cells. Furthermore, hypoxia could also have a potential role in tissue engineering and regenerative medicine due to its capacity to improve the performance of biomaterials. The current review aims to highlight the hypoxic molecular mechanisms reported in different pathological conditions to provide an overview of hypoxia as a therapeutic agent in regenerative and molecular therapy.

Graphical abstract

Generation of hyaline-like cartilage tissue from human mesenchymal stromal cells within the self-generated extracellular matrix

Chondrocytic hypertrophy, a phenotype not observed in healthy hyaline cartilage, is often concomitant with the chondrogenesis of human mesenchymal stromal cells (hMSCs). This undesired feature represents one of the major obstacles in applying hMSCs for hyaline cartilage repair. Previously, we developed a method to induce hMSC chondrogenesis within self-generated extracellular matrix (mECM), which formed a cartilage tissue with a lower hypertrophy level than conventional hMSC pellets. In this study, we aimed to test the utility of hypoxia and insulin-like growth factor-1 (IGF1) on further reducing hypertrophy. MSC-mECM constructs were first subjected to chondrogenic culture in normoxic or hypoxic (5%) conditions. The results indicated that hMSC-derived cartilage formed in hypoxic culture displayed a significantly reduced hypertrophy level than normoxic culture. However, hMSC chondrogenesis was also suppressed under hypoxic culture, partially due to the reduced activity of the IGF1 pathway. IGF1 was then supplemented in the chondrogenic medium, which promoted remarkable hMSC chondrogenesis under hypoxic culture. Interestingly, the IGF1-enhanced hMSC chondrogenesis, under hypoxic culture, was not at the expense of promoting significantly increased hypertrophy. Lastly, the cartilage tissues created by hMSCs with different conditions were implanted into osteochondral defect in rats. The results indicated that the tissue formed under hypoxic condition and induced with IGF1-supplemented chondrogenic medium displayed the best reparative results with minimal hypertrophy level. Our results demonstrate a new method to generate hyaline cartilage-like tissue from hMSCs without using exogenous scaffolds, which further pave the road for the clinical application of hMSC-based cartilage tissue engineering. STATEMENT OF SIGNIFICANCE: In this study, hyaline cartilage-like tissues were generated from human mesenchymal stromal cells (hMSCs), which displayed robust capacity in repairing the osteochondral defect in rats. In particular, the extracellular matrix created by hMSCs was used, so no exogenous scaffold was needed. Through a series of optimization, we defined that hypoxic culture and supplementation of insulin-like growth factor-1 (IGF-1) in chondrogenic medium resulted in robust cartilage formation with minimal hypertrophy. We also demonstrated that hypoxic culture suppressed chondrogenesis and hypertrophy through modulating the Wnt/β-catenin and IGF1 pathways, respectively. Our results demonstrate a new method to generate hyaline cartilage-like tissue from hMSCs without using exogenous scaffolds, which will further pave the road for the clinical application of hMSCs-based cartilage tissue engineering.

TRAP1 regulates the response of colorectal cancer cells to hypoxia and inhibits ribosome biogenesis under conditions of oxygen deprivation

Metabolic rewiring fuels rapid cancer cell proliferation by promoting adjustments in energetic resources, and increasing glucose uptake and its conversion into lactate, even in the presence of oxygen. Furthermore, solid tumors often contain hypoxic areas and can rapidly adapt to low oxygen conditions by activating hypoxia inducible factor (HIF)‑1α and several downstream pathways, thus sustaining cell survival and metabolic reprogramming. Since TNF receptor‑associated protein 1 (TRAP1) is a HSP90 molecular chaperone upregulated in several human malignancies and is involved in cancer cell adaptation to unfavorable environments and metabolic reprogramming, in the present study, its role was investigated in the adaptive response to hypoxia in human colorectal cancer (CRC) cells and organoids. In the present study, glucose uptake, lactate production and the expression of key metabolic genes were evaluated in TRAP1‑silenced CRC cell models under conditions of hypoxia/normoxia. Whole genome gene expression profiling was performed in TRAP1‑silenced HCT116 cells exposed to hypoxia to establish the role of TRAP1 in adaptive responses to oxygen deprivation. The results revealed that TRAP1 was involved in regulating hypoxia‑induced HIF‑1α stabilization and glycolytic metabolism and that glucose transporter 1 expression, glucose uptake and lactate production were partially impaired in TRAP1‑silenced CRC cells under hypoxic conditions. At the transcriptional level, the gene expression reprogramming of cancer cells driven by HIF‑1α was partially inhibited in TRAP1‑silenced CRC cells and organoids exposed to hypoxia. Moreover, Gene Set Enrichment Analysis of TRAP1‑silenced HCT116 cells exposed to hypoxia demonstrated that TRAP1 was involved in the regulation of ribosome biogenesis and this occurred with the inhibition of the mTOR pathway. Therefore, as demonstrated herein, TRAP1 is a key factor in maintaining HIF‑1α‑induced genetic/metabolic program under hypoxic conditions and may represent a promising target for novel metabolic therapies.

SNF1-Related Protein Kinase 1 Activity Represses the Canonical Translational Machinery

Protein biosynthesis is achieved through translation, which consumes enormous energy. Therefore, under conditions of limited energy supply, translation progress should be strictly coordinated. Sucrose non-fermenting kinase1 (SNF1)-related protein kinase 1 (SnRK1) is an evolutionarily conserved master regulator of cellular energy stress signaling in plants. Rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana) SnRK1 enhance hypoxia tolerance and induce the expression of stress-related genes. However, whether SnRK1 modulates protein synthesis in plants is unknown. In this study, using translational reporter constructs transfected in Arabidopsis protoplasts we showed that the expression of OsSnRK1A and AtSnRK1.1 decreases the abundance of canonical proteins without affecting their encoding transcript levels and protein stability. Moreover, the loading of total mRNAs and GFP mRNAs into the heavy polysome fraction which is normally translated was attenuated in transgenic Arabidopsis lines constitutively expressing OsSnRK1A or AtSnRK1.1. Taken together, these results suggest that OsSnRK1A and AtSnRK1.1 suppress protein translation to maintain energy homeostasis.

Mammalian eIF4E2-GSK3β maintains basal phosphorylation of p53 to resist senescence under hypoxia

Hypoxia modulates senescence, but their physiological link remains unclear. Here, we found that eIF4E2, a hypoxia-activated translation initiation factor, interacted with GSK3β to maintain phosphorylation of p53, thus resisting senescence under hypoxia. RNA-binding protein RBM38 interacted with eIF4E to inhibit the translation of p53, but GSK3β-mediated Ser195 phosphorylation disrupted the RBM38-eIF4E interaction. Through investigation of RBM38 phosphorylation, we found that the eIF4E2-GSK3β pathway specifically regulated proline-directed serine/threonine phosphorylation (S/T-P). Importantly, peptides e2-I or G3-I that blocking eIF4E2-GSK3β interaction can inhibit the basal S/T-P phosphorylation of p53 at multiple sites, therby inducing senescence through transcriptional inhibition. Additionally, a nanobody was screened via the domain where eIF4E2 bound to GSK3β, and this nanobody inhibited S/T-P phosphorylation to promote senescence. Furthermore, hypoxia inhibited eIF4E2-GSK3β pathway by mediating S-Nitrosylation of GSK3β. Blocking eIF4E2-GSK3β interaction promoted liver senescence under hypoxia, thus leading to liver fibrosis, eventually accelerating N, N-diethylnitrosamine (DEN)-induced tumorigenesis. Interestingly, eIF4E2 isoforms with GSK3β-binding motif exclusively exist in mammals, which protect zebrafish heart against hypoxia. Together, this study reveals a mammalian eIF4E2-GSK3β pathway that prevents senescence by maintaining basal S/T-P phosphorylation of p53, which underlies hypoxia adaptation of tissues.

Hypoxia-Induced Aquaporins and Regulation of Redox Homeostasis by a Trans-Plasma Membrane Electron Transport System in Maize Roots

In plants, flooding-induced oxygen deficiency causes severe stress, leading to growth reduction and yield loss. It is therefore important to understand the molecular mechanisms for adaptation to hypoxia. Aquaporins at the plasma membrane play a crucial role in water uptake. However, their role during hypoxia and membrane redox changes is still not fully understood. The influence of 24 h hypoxia induction on hydroponically grown maize (Zea mays L.) was investigated using an oil-based setup. Analyses of physiological parameters revealed typical flooding symptoms such as increased ethylene and H₂O₂ levels, an increased alcohol dehydrogenase activity, and an increased redox activity at the plasma membrane along with decreased oxygen of the medium. Transcriptomic analysis and shotgun proteomics of plasma membranes and soluble fractions were performed to determine alterations in maize roots. RNA-sequencing data confirmed the upregulation of genes involved in anaerobic metabolism, biosynthesis of the phytohormone ethylene, and its receptors. Transcripts of several antioxidative systems and other oxidoreductases were regulated. Mass spectrometry analysis of the plasma membrane proteome revealed alterations in redox systems and an increased abundance of aquaporins. Here, we discuss the importance of plasma membrane aquaporins and redox systems in hypoxia stress response, including the regulation of plant growth and redox homeostasis.

Epigenetic and post-transcriptional repression support metabolic suppression in chronically hypoxic goldfish

Goldfish enter a hypometabolic state to survive chronic hypoxia. We recently described tissue-specific contributions of membrane lipid composition remodeling and mitochondrial function to metabolic suppression across different goldfish tissues. However, the molecular and especially epigenetic foundations of hypoxia tolerance in goldfish under metabolic suppression are not well understood. Here we show that components of the molecular oxygen-sensing machinery are robustly activated across tissues irrespective of hypoxia duration. Induction of gene expression of enzymes involved in DNA methylation turnover and microRNA biogenesis suggest a role for epigenetic transcriptional and post-transcriptional suppression of gene expression in the hypoxia-acclimated brain. Conversely, mechanistic target of rapamycin-dependent translational machinery activity is not reduced in liver and white muscle, suggesting this pathway does not contribute to lowering cellular energy expenditure. Finally, molecular evidence supports previously reported chronic hypoxia-dependent changes in membrane cholesterol, lipid metabolism and mitochondrial function via changes in transcripts involved in cholesterol biosynthesis, β-oxidation, and mitochondrial fusion in multiple tissues. Overall, this study shows that chronic hypoxia robustly induces expression of oxygen-sensing machinery across tissues, induces repressive transcriptional and post-transcriptional epigenetic marks especially in the chronic hypoxia-acclimated brain and supports a role for membrane remodeling and mitochondrial function and dynamics in promoting metabolic suppression.

Targeting HIF-2α in the Tumor Microenvironment: Redefining the Role of HIF-2α for Solid Cancer Therapy

Inadequate oxygen supply, or hypoxia, is characteristic of the tumor microenvironment and correlates with poor prognosis and therapeutic resistance. Hypoxia leads to the activation of the hypoxia-inducible factor (HIF) signaling pathway and stabilization of the HIF-α subunit, driving tumor progression. The homologous alpha subunits, HIF-1α and HIF-2α, are responsible for mediating the transcription of a multitude of critical proteins that control proliferation, angiogenic signaling, metastasis, and other oncogenic factors, both differentially and sequentially regulating the hypoxic response. Post-translational modifications of HIF play a central role in its behavior as a mediator of transcription, as well as the temporal transition from HIF-1α to HIF-2α that occurs in response to chronic hypoxia. While it is evident that HIF-α is highly dynamic, HIF-2α remains vastly under-considered. HIF-2α can intensify the behaviors of the most aggressive tumors by adapting the cell to oxidative stress, thereby promoting metastasis, tissue remodeling, angiogenesis, and upregulating cancer stem cell factors. The structure, function, hypoxic response, spatiotemporal dynamics, and roles in the progression and persistence of cancer of this HIF-2α molecule and its EPAS1 gene are highlighted in this review, alongside a discussion of current therapeutics and future directions.

Dental mesenchymal stromal/stem cells in different microenvironments— implications in regenerative therapy

Current research data reveal microenvironment as a significant modifier of physical functions, pathologic changes, as well as the therapeutic effects of stem cells. When comparing regeneration potential of various stem cell types used for cytotherapy and tissue engineering, mesenchymal stem cells (MSCs) are currently the most attractive cell source for bone and tooth regeneration due to their differentiation and immunomodulatory potential and lack of ethical issues associated with their use. The microenvironment of donors and recipients selected in cytotherapy plays a crucial role in regenerative potential of transplanted MSCs, indicating interactions of cells with their microenvironment indispensable in MSC-mediated bone and dental regeneration. Since a variety of MSC populations have been procured from different parts of the tooth and tooth-supporting tissues, MSCs of dental origin and their achievements in capacity to reconstitute various dental tissues have gained attention of many research groups over the years. This review discusses recent advances in comparative analyses of dental MSC regeneration potential with regards to their tissue origin and specific microenvironmental conditions, giving additional insight into the current clinical application of these cells.

Oxygen nanocarrier broke the hypoxia trap of solid tumors and rescued transfection efficiency for gene therapy

BACKGROUND

Gene therapy shows great promise for a broad array of diseases. However, we found that hypoxic tumor microenvironment (TME) exerted significant inhibitory effects on transfection efficiency of a variety of gene vectors (such as Lipo 2000 and PEI) in an oxygen-dependent manner. Solid tumors inevitably resulted in acute hypoxic areas due to the rapid proliferation of tumor cells and the aberrant structure of blood vessels. Thus, the hypoxic TME severely limited the efficiency and application of gene therapy.

METHODS

In our previous study, we constructed endoplasmic reticulum-targeted cationic liposomes, PAR-Lipo, which could effectively deliver genes and ensure high transfection efficiency under normoxia. Unsatisfactorily, the transfection efficiency of PAR-Lipo was rather poor under hypoxia. We believed that reoxygenation was the most direct and effective means to rescue the low transfection under hypoxia. Hence, we fabricated liposomes modified with perfluorooctyl bromide (PFOB@Lipo) to load oxygen and deliver it to tumor sites, which effectively alleviated the hypoxic nature of tumor. Then PAR-Lipo were applied to mediate high-efficiency delivery of tumor suppressor gene pTP53 to inhibit tumor progression.

RESULTS

The results showed that such staged strategy augmented the expression of P53 protein in tumors and extremely suppressed tumor growth.

CONCLUSION

This work was the first attempt to utilize an oxygen nanocarrier to assist the therapeutic effect of gene therapy under hypoxia, providing a new reference for gene therapy in malignant tumors. GRAPHICAL ABSTARCT.

Mechanistic Insights Delineating the Role of Cholesterol in Epithelial Mesenchymal Transition and Drug Resistance in Cancer

Despite the significant advancements made in targeted anti-cancer therapy, drug resistance constitutes a multifaceted phenomenon leading to therapy failure and ultimately mortality. Emerging experimental evidence highlight a role of cholesterol metabolism in facilitating drug resistance in cancer. This review aims to describe the role of cholesterol in facilitating multi-drug resistance in cancer. We focus on specific signaling pathways that contribute to drug resistance and the link between these pathways and cholesterol. Additionally, we briefly discuss the molecular mechanisms related to the epithelial-mesenchymal transition (EMT), and the documented link between EMT, metastasis and drug resistance. We illustrate this by specifically focusing on hypoxia and the role it plays in influencing cellular cholesterol content following EMT induction. Finally, we provide a proposed model delineating the crucial role of cholesterol in EMT and discuss whether targeting cholesterol could serve as a novel means of combatting drug resistance in cancer progression and metastasis.

Cardiorespiratory and metabolic fitness indicators in novice volleyball trainees: effect of 1-week antioxidant supplementation with N-acetyl-cysteine/zinc/vitamin C

OBJECTIVES

This study aimed to determine the effect of 7-day dietary supplementation of N-acetylcysteine (NAC)/zinc/vitamin C on the time-to-exhaustion (TTE), the cardiorespiratory fitness (CRF) index, and metabolic indicators.

METHODS

This study enrolled volleyball student trainees (n = 18 men) who took NAC/zinc/vitamin C (750 mg/5 mg/100 mg) for 7 days at Jouf University, Saudi Arabia. The CRF index and TTE were determined. Serum concentrations of metabolic regulators (insulin, betatrophin, and hepatocyte growth factor), biomarkers of cellular damage/hypoxia, and indicators of lipid and glycemic control were measured.

RESULTS

Supplementation improved the TTE and CRF index, and lowered cytochrome c, C-reactive protein, hypoxia-inducible factor-1α (HIF-1α), total cholesterol, insulin, and glycated hemoglobin values. Before and after supplementation, the CRF index was negatively correlated with body mass index and positively correlated with the TTE. Before supplementation, the CRF index was positively correlated with betatrophin concentrations, and hepatocyte growth factor concentrations were positively correlated with betatrophin concentrations and negatively correlated with the homeostasis model assessment of insulin resistance index. After supplementation, the CRF index was negatively correlated with HIF-1α concentrations and metabolites. Additionally, the TTE was negatively correlated with HIF-1α, cytochrome c, and triacylglycerol concentrations.

CONCLUSION

Supplementation of NAC/zinc/vitamin C improves metabolic and CRF performance.

Quantitative Analyses Reveal How Hypoxia Reconfigures the Proteome of Primary Cytotoxic T Lymphocytes

Metabolic and nutrient-sensing pathways play an important role in controlling the efficacy of effector T cells. Oxygen is a critical regulator of cellular metabolism. However, during immune responses T cells must function in oxygen-deficient, or hypoxic, environments. Here, we used high resolution mass spectrometry to investigate how the proteome of primary murine CD8⁺ cytotoxic T lymphocytes (CTLs) is reconfigured in response to hypoxia in vitro. We identified and quantified over 7,600 proteins and discovered that hypoxia increased the abundance of a selected number of proteins in CTLs. This included glucose transporters, metabolic enzymes, transcription factors, cytolytic effector molecules, checkpoint receptors and adhesion molecules. While some of these proteins may augment the effector functions of CTLs, others may limit their cytotoxicity. Moreover, we determined that hypoxia could inhibit IL-2-induced proliferation cues and antigen-induced pro-inflammatory cytokine production in CTLs. These data provide a comprehensive resource for understanding the magnitude of the CTL response to hypoxia and emphasise the importance of oxygen-sensing pathways for controlling CD8⁺ T cells. Additionally, this study provides new understanding about how hypoxia may promote the effector function of CTLs, while contributing to their dysfunction in some contexts.

Proteomic-Based Analysis of Hypoxia- and Physioxia-Responsive Proteins and Pathways in Diffuse Large B-Cell Lymphoma

Hypoxia is a common feature in most tumors, including hematological malignancies. There is a lack of studies on hypoxia- and physioxia-induced global proteome changes in lymphoma. Here, we sought to explore how the proteome of diffuse large B-cell lymphoma (DLBCL) changes when cells are exposed to acute hypoxic stress (1% of O₂) and physioxia (5% of O₂) for a long-time. A total of 8239 proteins were identified by LC–MS/MS, of which 718, 513, and 486 had significant changes, in abundance, in the Ri-1, U2904, and U2932 cell lines, respectively. We observed that changes in B-NHL proteome profiles induced by hypoxia and physioxia were quantitatively similar in each cell line; however, differentially abundant proteins (DAPs) were specific to a certain cell line. A significant downregulation of several ribosome proteins indicated a translational inhibition of new ribosome protein synthesis in hypoxia, what was confirmed in a pathway enrichment analysis. In addition, downregulated proteins highlighted the altered cell cycle, metabolism, and interferon signaling. As expected, the enrichment of upregulated proteins revealed terms related to metabolism, HIF1 signaling, and response to oxidative stress. In accordance to our results, physioxia induced weaker changes in the protein abundance when compared to those induced by hypoxia. Our data provide new evidence for understanding mechanisms by which DLBCL cells respond to a variable oxygen level. Furthermore, this study reveals multiple hypoxia-responsive proteins showing an altered abundance in hypoxic and physioxic DLBCL. It remains to be investigated whether changes in the proteomes of DLBCL under normoxia and physioxia have functional consequences on lymphoma development and progression.

Hypoxia and the integrated stress response promote pulmonary hypertension and preeclampsia: Implications in drug development

Chronic hypoxia is a common cause of pulmonary hypertension, preeclampsia, and intrauterine growth restriction (IUGR). The molecular mechanisms underlying these diseases are not completely understood. Chronic hypoxia may induce the generation of reactive oxygen species (ROS) in mitochondria, promote endoplasmic reticulum (ER) stress, and result in the integrated stress response (ISR) in the pulmonary artery and uteroplacental tissues. Numerous studies have implicated hypoxia-inducible factors (HIFs), oxidative stress, and ER stress/unfolded protein response (UPR) in the development of pulmonary hypertension, preeclampsia and IUGR. This review highlights the roles of HIFs, mitochondria-derived ROS and UPR, as well as their interplay, in the pathogenesis of pulmonary hypertension and preeclampsia, and their implications in drug development.

Interplay within tumor microenvironment orchestrates neoplastic RNA metabolism and transcriptome diversity

The heterogeneous population of cancer cells within a tumor mass interacts intricately with the multifaceted aspects of the surrounding microenvironment. The reciprocal crosstalk between cancer cells and the tumor microenvironment (TME) shapes the cancer pathophysiome in a way that renders it uniquely suited for immune tolerance, angiogenesis, metastasis, and therapy resistance. This dynamic interaction involves a dramatic reconstruction of the transcriptomic landscape of tumors by altering the synthesis, modifications, stability, and processing of gene readouts. In this review, we categorically evaluate the influence of TME components, encompassing a myriad of resident and infiltrating cells, signaling molecules, extracellular vesicles, extracellular matrix, and blood vessels, in orchestrating the cancer-specific metabolism and diversity of both mRNA and noncoding RNA, including micro RNA, long noncoding RNA, circular RNA among others. We also highlight the transcriptomic adaptations in response to the physicochemical idiosyncrasies of TME, which include tumor hypoxia, extracellular acidosis, and osmotic stress. Finally, we provide a nuanced analysis of existing and prospective therapeutics targeting TME to ameliorate cancer-associated RNA metabolism, consequently thwarting the cancer progression. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing RNA Turnover and Surveillance > Regulation of RNA Stability RNA in Disease and Development > RNA in Disease.

Quantitative proteomics characterization of cancer biomarkers and treatment

Cancer accounted for 16% of all death worldwide in 2018. Significant progress has been made in understanding tumor occurrence, progression, diagnosis, treatment, and prognosis at the molecular level. However, genomics changes cannot truly reflect the state of protein activity in the body due to the poor correlation between genes and proteins. Quantitative proteomics, capable of quantifying the relatively different protein abundance in cancer patients, has been increasingly adopted in cancer research. Quantitative proteomics has great application potentials, including cancer diagnosis, personalized therapeutic drug selection, real-time therapeutic effects and toxicity evaluation, prognosis and drug resistance evaluation, and new therapeutic target discovery. In this review, the development, testing samples, and detection methods of quantitative proteomics are introduced. The biomarkers identified by quantitative proteomics for clinical diagnosis, prognosis, and drug resistance are reviewed. The challenges and prospects of quantitative proteomics for personalized medicine are also discussed.

HIF‑1α in myocardial ischemia‑reperfusion injury (Review)

Myocardial ischemia-reperfusion injury (MIRI) is a severe injury to the ischemic myocardium following the recovery of blood flow. Currently, there is no effective treatment for MIRI in clinical practice. Over the past two decades, biological studies of hypoxia and hypoxia-inducible factor-1α (HIF-1α) have notably improved understanding of oxygen homeostasis. HIF-1α is an oxygen-sensitive transcription factor that mediates adaptive metabolic responses to hypoxia and serves a pivotal role in MIRI. In particular, previous studies have demonstrated that HIF-1α improves mitochondrial function, decreases cellular oxidative stress, activates cardioprotective signaling pathways and downstream protective genes and interacts with non-coding RNAs. The present review summarizes the roles and associated mechanisms of action of HIF-1α in MIRI. In addition, HIF-1α-associated MIRI intervention, including natural compounds, exosomes, ischemic preconditioning and ischemic post-processing are presented. The present review provides evidence for the roles of HIF-1α activation in MIRI and supports its use as a therapeutic target.

Metabolomics analysis reveals a modified amino acid metabolism that correlates with altered oxygen homeostasis in COVID-19 patients

We identified the main changes in serum metabolites associated with severe (n = 46) and mild (n = 19) COVID-19 patients by gas chromatography coupled to mass spectrometry. The modified metabolic profiles were associated to an altered amino acid catabolism in hypoxic conditions. Noteworthy, three α-hydroxyl acids of amino acid origin increased with disease severity and correlated with altered oxygen saturation levels and clinical markers of lung damage. We hypothesize that the enzymatic conversion of α-keto-acids to α- hydroxyl-acids helps to maintain NAD recycling in patients with altered oxygen levels, highlighting the potential relevance of amino acid supplementation during SARS-CoV-2 infection.

Gene transcription and chromatin regulation in hypoxia

Oxygen sensing is an essential feature of metazoan biology and reductions in oxygen availability (hypoxia) have both physiological and pathophysiological implications. Co-ordinated mechanisms have evolved for sensing and responding to hypoxia, which involve diverse biological outputs, with the main aim of restoring oxygen homeostasis. This includes a dynamic gene transcriptional response, the central drivers of which are the hypoxia-inducible factor (HIF) family of transcription factors. HIFs are regulated in an oxygen-dependent manner and while their role in hypoxia is well established, it is apparent that other key players are required for gene expression control in hypoxia. In this review, we highlight the current understanding of the known and potential molecular mechanisms underpinning gene transcriptional responses to hypoxia in mammals, with a focus on oxygen-dependent effects on chromatin structure.