Hypoxia-inducible Factor Signaling Research Articles

Sustained Morphine Delivery Suppresses Bone Formation and Alters Metabolic and Circulating miRNA Profiles in Male C57BL/6J Mice.

Opioid use is detrimental to bone health, causing both indirect and direct effects on bone turnover. Although the mechanisms of these effects are not entirely clear, recent studies have linked chronic opioid use to alterations in circulating miRNAs. Here, we developed a model of opioid-induced bone loss to understand bone turnover and identify candidate miRNA-mediated regulatory mechanisms. We evaluated the effects of sustained morphine treatment on male and female C57BL/6J mice by treating with vehicle (0.9% saline) or morphine (17 mg/kg) using subcutaneous osmotic minipumps for 25 days. Morphine-treated mice had higher energy expenditure and respiratory quotient, indicating a shift toward carbohydrate metabolism. Micro-computed tomography (μCT) analysis indicated a sex difference in the bone outcome, where male mice treated with morphine had reduced trabecular bone volume fraction (Tb.BV/TV) (15%) and trabecular bone mineral density (BMD) (14%) in the distal femur compared with vehicle. Conversely, bone microarchitecture was not changed in females after morphine treatment. Histomorphometric analysis demonstrated that in males, morphine reduced bone formation rate compared with vehicle, but osteoclast parameters were not different. Furthermore, morphine reduced bone formation marker gene expression in the tibia of males (Bglap and Dmp1). Circulating miRNA profile changes were evident in males, with 14 differentially expressed miRNAs associated with morphine treatment compared with two differentially expressed miRNAs in females. In males, target analysis indicated hypoxia-inducible factor (HIF) signaling pathway was targeted by miR-223-3p and fatty acid metabolism by miR-484, -223-3p, and -328-3p. Consequently, expression of miR-223-3p targets, including Igf1r and Stat3, was lower in morphine-treated bone. In summary, we have established a model where morphine leads to a lower trabecular bone formation in males and identified potential mediating miRNAs. Understanding the sex-specific mechanisms of bone loss from opioids will be important for improving management of the adverse effects of opioids on the skeleton. © 2022 American Society for Bone and Mineral Research (ASBMR).

Yak milk–derived exosomal microRNAs regulate intestinal epithelial cells on proliferation in hypoxic environment

Intestinal epithelial cells (IEC) act as an important intestinal barrier whose function can be impaired upon induction by hypoxia. Although intestinal barrier injuries are preventable by milk-derived exosomal microRNAs (miRNAs), the underlying mechanism remains poorly understood. This study aimed to characterize the effect of yak and cow milk-derived exosomal miRNA on the barrier function of IEC-6 under hypoxic conditions, and explore the mechanism of yak milk exosomal miRNA to relieve the hypoxia stress. First, by Illumina HiSeq 2500 (Illumina Inc., San Diego, CA) sequencing, the miRNA expression was systematically screened, and differential expression of 130 miRNAs was identified with 51 being upregulated and 79 downregulated in yak and cow milk-derived exosomes. Furthermore, the top 20 miRNAs that had a relatively consistent high expression in yak milk exosome were identified, and bta-miR-34a was found to be an effective regulator for alleviating hypoxic injury of IEC-6. In vitro assay of the role of bta-miR-34a on survival of IEC-6 in hypoxia by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) confirmed its effectiveness to significantly increase IEC-6 survival up to 13% for 12 h, and up to 9.5% for 24 h. Investigation on the regulatory relationship between bta-miRNA-34a and the hypoxia-inducible factor/apoptosis signaling pathway provided insights into the possible mechanisms by which bta-miR-34a activated the hypoxia-inducible factor and apoptosis signaling pathway, thus promoting IEC-6 survival. The results of this study suggest an important relationship between miRNA expression and intestine barrier integrity, which facilitated further understanding of the physiological function of yak and cow milk exosomal miRNAs, as well as mechanisms of hypoxia-driven epithelial homeostasis.

Computational Prediction of Antiangiogenesis Synergistic Mechanisms of Total Saponins of Panax japonicus Against Rheumatoid Arthritis.

Objective: To investigate the anti-angiogenesis mechanisms and key targets of total saponins of Panax japonicus (TSPJ) in the treatment of rheumatoid arthritis (RA). Methods: RStudio3.6.1 software was used to obtain differentially expressed genes (DEGs) by analyzing the differences in gene expression in the synovial tissue of RA and to predict the potential targets of active compounds from TSPJ by the PharmMapper and SwissTargetPrediction databases. We evaluated the overlapping genes by intersectional analysis of DEGs and drug targets. Based on the overlapping genes, we used Cytoscape 3.7.2 software to construct a protein–protein interactions (PPI) network and applied Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis to determine the mechanisms of the treatment. Finally, the correlations with angiogenesis-related genes were explored. Collagen-induced arthritis (CIA) model was established and treated with different doses of TSPJ. The manifestations of CIA were determined by evaluation of arthritis index and histology score. Serum levels of vascular endothelial growth factor (VEGF) and the hypoxia-inducible factor 1 (HIF-1) were tested by ELISA. The mRNA levels of IL-1β and IL-17A were detected by real time-quantitative PCR. Results: Altogether, 2670 DEGs were obtained by differential analysis, and 371 drug targets were predicted for four active components (Araloside A, Chikusetsusaponin IVa, Ginsenoside Rg2, and Ginsenoside Ro). A total of 52 overlapping genes were included in the PPI network and the KEGG analysis. However, only 41 genes in the PPI network had protein interactions. The results of the KEGG enrichment analysis were all related to angiogenesis, including VEGF and HIF-1 signaling pathways. Seven genes with negative correlations and 16 genes with positive correlations were obtained by correlational analysis of DEGs in the VEGF and HIF-1 signaling pathways. SRC proto-oncogene, nonreceptor tyrosine kinase (SRC), and the signal transducer and activator of transcription 3 (STAT 3) had a higher value of degree and showed a significant correlation in the pathways; they were regarded as key targets. Compared with the model group, TSPJ significantly relieved the symptoms and decreased the expression of VEGFA, HIF-1α, IL-1β, and IL-17A in serum or spleens of CIA mice. Conclusion: In the current study, we found that antiangiogenesis is one of the effective strategies of TSPJ against RA; SRC and STAT 3 may be the key targets of TSPJ acting on the VEGF and HIF-1 signaling pathways, which will provide new insight into the treatment of RA by inhibiting inflammation and angiogenesis.

Oxygen Sensing and Viral Replication: Implications for Tropism and Pathogenesis.

The ability to detect and respond to varying oxygen tension is an essential prerequisite to life. Several mechanisms regulate the cellular response to oxygen including the prolyl hydroxylase domain (PHD)/factor inhibiting HIF (FIH)-hypoxia inducible factor (HIF) pathway, cysteamine (2-aminoethanethiol) dioxygenase (ADO) system, and the lysine-specific demethylases (KDM) 5A and KDM6A. Using a systems-based approach we discuss the literature on oxygen sensing pathways in the context of virus replication in different tissues that experience variable oxygen tension. Current information supports a model where the PHD-HIF pathway enhances the replication of viruses infecting tissues under low oxygen, however, the reverse is true for viruses with a selective tropism for higher oxygen environments. Differences in oxygen tension and associated HIF signaling may play an important role in viral tropism and pathogenesis. Thus, pharmaceutical agents that modulate HIF activity could provide novel treatment options for viral infections and associated pathological conditions.

Integrating Pharmacology and Gut Microbiota Analysis to Explore the Mechanism of Citri Reticulatae Pericarpium Against Reserpine-Induced Spleen Deficiency in Rats.

Citri Reticulatae Pericarpium (CRP), dried peels of Citrus reticulata Blanco and its cultivars, is an important traditional Chinese medicine for the treatment of spleen deficiency-related diseases. To date, the mechanism of CRP alleviating spleen deficiency has not been well investigated. This study aimed to explore corresponding mechanisms with integrating pharmacology and gut microbiota analysis. Firstly, the therapeutic effects of CRP against spleen deficiency were evaluated in reserpine-treated rats. CRP was found to effectively relieve the typical symptoms of spleen deficiency, including poor digestion and absorption capacity, and disorder in gastrointestinal hormones, immune cytokines and oxidative stress. Secondly, high throughput 16S rRNA gene sequencing revealed that CRP could not only up-regulate some short-chain fatty acids producing and anti-inflammatory bacteria but also down-regulate certain spleen deficiency aggravated related bacteria, eventually led to the rebalance of gut microbiota in spleen deficiency rats. In addition, a total of 49 compounds derived from CRP were identified in rat urine using ultra-high performance liquid chromatography-quadrupole- time of flight tandem mass spectrometry. Network pharmacology analysis showed that apigenin, luteolin, naringenin, hesperidin, hesperetin, homoeriodictyol, dihydroxy-tetramethoxyflavone, and monohydroxy-tetramethoxyflavone were the core bioactive components for CRP against spleen deficiency. Further Gene Ontology analysis and pathway enrichment suggested that therapeutic effects of CRP against spleen deficiency involved multiple pathways such as tumor necrosis factor signaling, hypoxia-inducible factor-1 signaling and Toll-like receptor signaling pathway. These results would help to understand the mechanism of CRP alleviating spleen deficiency and provide a reference for further studies.

A New Therapeutic Strategy Targeting Protein Deacetylation for Spinal Cord Injury

Lysine acetylation is a post-translational modification that regulates a diversity of biological processes. However, its implication in spinal cord injury (SCI) remains unclear. Here we investigated the acetylation events in injured spinal cords on a proteomic scale for the first time. Additionally, whether promoting acetylation could mitigate SCI was evaluated. A total of 268 differentially acetylated peptides were identified. Among them, 2 peptides were up-acetylated and 141 peptides were down-acetylated in the injured spinal cord tissues (Fold change >2 and P < 0.05). There were also 116 unique acetylated peptides in the sham group and 9 unique acetylated peptides in the SCI group. Functional enrichment analysis revealed that differently acetylated proteins were involved in multiple cellular processes and metabolic processes. Kyoto Encyclopaedia of Genes and Genomes analysis showed that several pathways, including cGMP-PKG signaling pathway and hypoxia-inducible factor-1 (HIF-1) signaling pathway, were predominantly presented. Moreover, promoting acetylation using glycerol triacetate (GTA) showed a therapeutic effect on SCI, with improved Basso–Beattie–Bresnahan scores and histologic morphology, and decreased neuronal apoptosis and inflammation. In conclusion, our data indicated that protein deacetylation might play crucial roles in the development of secondary injury of SCI, and promoting acetylation by GTA effectively mitigated SCI. Our data not only enhance our understanding on acetylproteome dataset in the spinal cord tissues, but also provide novel insights for the treatment of SCI.

THERAPEUTIC TARGETING OF HYPOXIA-INDUCIBLE FACTOR SIGNALING PATHWAYS- A PROMISING APPROACH IN CANCER TREATMENT

Oxygen and nutrients are delivered to the cells with the help of the vascular networking system, which makes availability of oxygen as primary regulator for many processes. Low oxygen availability condition activates the Hypoxia Inducible Factors (HIF), which are transcription regulators helping in the expression of genes related to cell cycle regulation and angiogenesis. HIF is hence regarded as the master regulator of angiogenesis. The oxygen deprival is due to the increased consumption of oxygen in the tumor microenvironment and in turn leads to hypoxia. A thorough understanding of how hypoxia influences angiogenesis mediated by several pathways has become essential for identifying novel strategies targeting HIF thereby blocking angiogenesis. In this review we would discuss about the HIF signaling pathways and altered functions of immune cells due to hypoxia by considering that reducing or targeting hypoxia may in turn prevent the suppression of anti-tumor immune response.

Hypoxia-inducible factor signaling in pulmonary hypertension.

Pulmonary hypertension (PH) is characterized by pulmonary artery remodeling that can subsequently culminate in right heart failure and premature death. Emerging evidence suggests that hypoxia-inducible factor (HIF) signaling plays a fundamental and pivotal role in the pathogenesis of PH. This Review summarizes the regulation of HIF isoforms and their impact in various PH subtypes, as well as the elaborate conditional and cell-specific knockout mouse studies that brought the role of this pathway to light. We also discuss the current preclinical status of pan- and isoform-selective HIF inhibitors, and propose new research areas that may facilitate HIF isoform-specific inhibition as a novel therapeutic strategy for PH and right heart failure.

Histone demethylase JMJD2D activates HIF1 signaling pathway via multiple mechanisms to promote colorectal cancer glycolysis and progression.

Hypoxia-inducible factor 1 (HIF1) signaling pathway plays a key role in cancer progression by enhancing glycolysis through activating the transcription of glycolytic genes. JMJD2D, a histone demethylase that specifically demethylates H3K9me2/3, can promote colorectal cancer (CRC) progression. However, it is unknown whether JMJD2D could promote CRC progression by enhancing glycolysis through activating HIF1 signaling pathway. In this study, we found that downregulation of JMJD2D inhibited the glycolysis in CRC cells through suppressing HIF1 signaling pathway to downregulate glycolytic gene expression. Restoring HIF1 signaling by enforced expression of HIF1α in JMJD2D-knockdown CRC cells partially recovered CRC cell glycolysis, proliferation, migration, invasion, xenograft growth, and metastasis, suggesting that JMJD2D promotes CRC progression by enhancing glycolysis through activating HIF1 signaling pathway. JMJD2D activated HIF1 signaling pathway through three different mechanisms: JMJD2D cooperated with the transcription factor SOX9 to enhance mTOR expression and then to promote HIF1α translation; JMJD2D cooperated with the transcription factor c-Fos to enhance HIF1β transcription; JMJD2D interacted and cooperated with HIF1α to enhance the expression of glycolytic gene. The demethylase-defective mutant of JMJD2D could not induce the expression of mTOR, HIF1α, HIF1β, and glycolytic genes, suggesting that the demethylase activity of JMJD2D is important for glycolysis through activating HIF1 signaling. Clinically, a highly positive correlation between the expression of JMJD2D and mTOR, HIF1β, and several glycolytic genes in human CRC specimens was identified. Collectively, our study reveals an important role of JMJD2D in CRC progression by enhancing glycolysis through activating HIF1 signaling pathway.

Attenuating hypoxia driven malignant behavior in glioblastoma with a novel hypoxia-inducible factor 2 alpha inhibitor

Hypoxia inducible factor (HIFs) signaling contributes to malignant cell behavior in glioblastoma (GBM). We investigated a novel HIF2α inhibitor, PT2385, both in vitro, with low-passage patient-derived cell lines, and in vivo, using orthotopic models of glioblastoma. We focused on analysis of HIF2α expression in situ, cell survival/proliferation, and survival in brain tumor-bearing mice treated with PT2385 alone and in combination with standard of care chemoradiotherapy. HIF2α expression increased with glioma grade, with over half of GBM specimens HIF2α positive. Staining clustered in perivascular and perinecrotic tumor regions. Cellular phenotype including proliferation, viability, migration/invasion, and also gene expression were not altered after PT2385 treatment. In the animal model, PT2385 single-agent treatment did improve median overall survival compared to placebo (p = 0.04, n = 21) without a bioluminescence correlate (t = 0.67, p = 0.52). No difference in animal survival was seen in combination treatment with radiation (RT)/temozolomide (TMZ)/PT2385 (p = 0.44, n = 10) or mean tumor bioluminescence (t 1.13, p = 0.32). We conclude that HIF2α is a reasonable novel therapeutic target as expressed in the majority of glioblastomas in our cohort. PT2385 as a single-agent was efficacious in vivo, however, an increase in animal survival was not seen with PT2385 in combination with RT/TMZ. Further study for targeting HIF2α as a therapeutic approach in GBM is warranted.

Hypoxia-inducible factors and innate immunity in liver cancer.

The liver has strong innate immunity to counteract pathogens from the gastrointestinal tract. During the development of liver cancer, which is typically driven by chronic inflammation, the composition and biological roles of the innate immune cells are extensively altered. Hypoxia is a common finding in all stages of liver cancer development. Hypoxia drives the stabilization of hypoxia-inducible factors (HIFs), which act as central regulators to dampen the innate immunity of liver cancer. HIF signaling in innate immune cells and liver cancer cells together favors the recruitment and maintenance of pro-tumorigenic immune cells and the inhibition of anti-tumorigenic immune cells, promoting immune evasion. HIFs represent attractive therapeutic targets to inhibit the formation of an immunosuppressive microenvironment and growth of liver cancer.

Neuroprotection of hypoxic/ischemic preconditioning in neonatal brain with hypoxic-ischemic injury.

The neonatal brain is susceptible to hypoxic-ischemic injury due to its developmental characteristics. Hypoxia-ischemia means a decreased perfusion of oxygen and glucose, which can lead to severe encephalopathy. Although early initiation of therapeutic hypothermia was reported to provide neuroprotection for infants after HI, hypothermia administered alone after the acute insult cannot reverse the severe damage that already has occurred or improve the prognosis of severe hypoxic-ischemic encephalopathy. Therefore, exploring new protective mechanisms for treating hypoxic-ischemic brain damage are imperative. Until now, many studies reported the neuroprotective mechanisms of hypoxic/ischemic preconditioning in protecting the hypoxic-ischemic newborn brains. After hypoxia and ischemia, hypoxia-inducible factor signaling pathway is involved in the transcriptional regulation of many genes and is also play a number of different roles in protecting brains during hypoxic/ischemic preconditioning. Hypoxic/ischemic preconditioning could protect neonatal brain by several mechanisms, including vascular regulation, anti-apoptosis, anti-oxidation, suppression of excitotoxicity, immune regulation, hormone levels regulation, and promote cell proliferation. This review focused on the protective mechanisms underlying hypoxic/ischemic preconditioning for neonatal brain after hypoxia-ischemia and emphasized on the important roles of hypoxia inducible factor 1 signaling pathway.

Identification of Prostate Cancer-Related Circular RNA Through Bioinformatics Analysis.

BackgroundProstate cancer (PCa) is one of the most common malignant tumors worldwide. Accumulating evidence has suggested that circular RNAs (circRNAs) are involved in the development and progression of various cancers, and they show great potential as novel biomarkers. However, the underlying mechanisms and specific functions of most circRNAs in PCa remain unknown. Here, we aimed to identify circRNAs with potential roles in PCa from the PCa expression profile.MethodsWe used data downloaded from the Gene Expression Omnibus to identify circRNAs that were differentially expressed between PCa samples and adjacent non-tumor samples. Relative expression levels of identified circRNAs were validated by quantitative real-time PCR. Micro (mi)RNA response elements were predicted by the CircInteractome database, and miRNA target genes were predicted by miRDB, miRTarBase, and TargetScan databases. Gene ontology (GO) enrichment analysis and pathway analysis revealed the potential biological and functional roles of these target genes. A circRNA–miRNA–mRNA interaction network was constructed by Cytoscape. The interaction between circRNAs and miRNAs in PCa was thoroughly reviewed in the PubMed. Finally, the mRNA expression of these genes was validated by the Cancer Genome Atlas (TCGA) and Gene Expression Profiling Interactive Analysis (GEPIA) databases. The expression of proteins encoded by these genes was further validated by the Human protein Atlas (HPA) database.ResultsA total of 60 circRNAs that were differentially expressed between PCa and healthy samples were screened, of which 15 were annotated. Three circRNAs (hsa_circ_0024353, hsa_circ_0085494, hsa_circ_0031408) certified the criteria were studied. The results of quantitative real-time PCR demonstrated that the expression of hsa_circ_0024353 was significantly downregulated in PC-3 cells when compared with RWPE-1 cells, while the expression of hsa_circ_0031408 and hsa_circ_0085494 was significantly upregulated in PC-3 cells when compared with RWPE-1 cells. GO and Kyoto Encyclopedia of Genes and Genomes analyses found that target genes were mainly enriched in metabolic processes and pathways involving phosphoinositide 3-kinase-Akt signaling, hypoxia-inducible factor-1 signaling, p53 signaling, and the cell cycle. A total of 11 miRNA target genes showing differential expression between PCa and healthy samples were selected, and their mRNA and protein expression were validated by GEPIA and HPA databases, respectively. Of these, PDE7B, DMRT2, and TGFBR3 were identified as potentially playing a role in PCa progression. Finally, three circRNA–miRNA–mRNA interaction axes were predicted by bioinformatics: hsa_circ_0024353–hsa-miR-940–PDE7B, hsa_circ_0024353–hsa-miR-1253–DMRT2, and hsa_circ_0085494–hsa-miR-330-3p–TGFBR3.ConclusionThis study identified three circRNA–miRNA–mRNA interaction axes that might provide novel insights into the potential mechanisms underlying PCa development.

Abstract 115: Hedgehog signaling pathway promotes breast cancer adaptation to hypoxia

Abstract Breast cancer is the most commonly diagnosed cancer in women in the US. Metastasis accounts for the majority of breast cancer-related deaths. Rapidly proliferating primary tumors experience oxygen levels that are lower in comparison to the normal tissue. The proportions of these hypoxic tumor cells in breast cancer strongly correlate to the incidence of metastasis. Around 70% of breast cancers present with bone metastasis. Tumor cells that metastasize to the bone can lead to an imbalance in bone homeostasis, often leading to osteolysis. Our lab has previously reported that the activation of Hedgehog (Hh) signaling, one of the embryonic developmental pathways found to be abnormally activated in breast cancer, leads to increased osteolysis in vivo. The incidence of osteolytic metastasis at the tibio-femoral junction was significantly reduced in the Hh signaling-deficient mice. Since a hypoxic microenvironment is prevalent in bone, it is imperative to understand how Hh signaling drives tumor cell adaptation to hypoxia. The hypoxic tumor microenvironment in the primary tumor might select for metastatic cells that are better able to metastasize to the bone. We hypothesize that Hh signaling enables the adaptation of breast cancer cells to hypoxia and consequently their metastatic potential. Hh signaling can be canonically activated through smoothened (SMO)-dependent activation of the transcriptional regulator GLI. Cellular response to hypoxia is mediated by the hypoxia-inducible factors (HIFs). To understand the importance of Hh signaling activation in hypoxic condition, we inhibited the Hh signaling pathway using GLI and SMO inhibitors. Additionally, we knocked-down GLI1 in breast cancer cell lines. We have identified a feed-forward mechanism between Hh signaling and HIF signaling in hypoxic conditions leading to sustained hypoxia response by stabilization of HIF-1α. Future investigations will address the significance of Hh signaling inhibition in a murine model of TNBC. This study will help determine the therapeutic benefit of hedgehog inhibitors in controlling hypoxia-mediated metastasis and tumorigenesis. Citation Format: Tshering D. Lama-Sherpa, Sarah C. Kammerud, Lalita A. Shevde. Hedgehog signaling pathway promotes breast cancer adaptation to hypoxia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 115.

Abstract 6395: VHL deficiency sensitizes CC-RCC to inhibition of small GTPases by statins

Abstract Clear cell renal cell carcinoma (CC-RCC) type of kidney cancer has limited therapeutic options available for advanced stages. The objective of this study was to investigate statins as potential therapeutics for CC-RCC. Importantly, treatment with statins was found to be synthetically lethal with the loss of the von Hippel-Lindau (VHL) tumor suppressor gene, which occurs in 90% of CC-RCC driving the disease. Treatment with statins causes a profound cytostatic effect at nanomolar concentrations and becomes cytotoxic at low micromolar concentrations in VHL-deficient CC-RCC. The synthetic lethal effect can be fully rescued by both mevalonate and geranylgeranylpyrophosphate, but not by squalene, indicating that the effect is due to disruption of small GTPase isoprenylation and not the inhibition of cholesterol synthesis. Rho and Rho kinase (ROCK) inhibition by siRNAs, as well as C3-toxin (for Rho) and Y27637 (for ROCK) mimic the statin-mediated synthetic lethality effect, suggesting the involvement of Rho/ROCK pathway in the mechanism. Overactivation of hypoxia-inducible factor signaling resulting from VHL loss is required for statin-mediated toxicity. Since both VHL and ROCK were previously reported to control mitosis fidelity, we show that mitotic catastrophe is one of the mechanisms of action of compounds targeting the Rho/ROCK pathway in VHL-deficient CC-RCC. Finally, statin treatment is able to inhibit both tumor initiation and progression of subcutaneous 786-OT1-based CC-RCC tumors in mice. Thus, statins represent potential therapeutics for the treatment of VHL-deficient CC-RCC. Citation Format: Olga V. Razorenova, Jordan M. Thompson, Alejandro Alvarez, Monika K. Singha, Matthew W. Pavesic MW, Quy H. Nguyen, Luke J. Nelson, David A. Fruman. VHL deficiency sensitizes CC-RCC to inhibition of small GTPases by statins [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6395.

Hypoxia and HIF Signaling: One Axis with Divergent Effects.

The correct concentration of oxygen in all tissues is a hallmark of cellular wellness, and the negative regulation of oxygen homeostasis is able to affect the cells and tissues of the whole organism. The cellular response to hypoxia is characterized by the activation of multiple genes involved in many biological processes. Among them, hypoxia-inducible factor (HIF) represents the master regulator of the hypoxia response. The active heterodimeric complex HIF α/β, binding to hypoxia-responsive elements (HREs), determines the induction of at least 100 target genes to restore tissue homeostasis. A growing body of evidence demonstrates that hypoxia signaling can act by generating contrasting responses in cells and tissues. Here, this dual and controversial role of hypoxia and the HIF signaling pathway is discussed, with particular reference to the effects induced on the complex activities of the immune system and on mechanisms determining cell and tissue responses after an injury in both acute and chronic human diseases related to the heart, lung, liver, and kidney.

Mechanisms Leading to Differential Hypoxia-Inducible Factor Signaling in the Diabetic Kidney: Modulation by SGLT2 Inhibitors and Hypoxia Mimetics

Sodium/glucose cotransporter 2 (SGLT2) inhibitors exert important renoprotective effects in the diabetic kidney, which cannot be readily explained by their actions to lower blood glucose, blood pressure, or glomerular filtration pressures. Their effects to promote erythrocytosis suggest that these drugs act on hypoxia-inducible factors (HIFs; specifically, HIF-1α and HIF-2α), which may underlie their ability to reduce the progression of nephropathy. Type 2 diabetes is characterized by renal hypoxia, oxidative and endoplasmic reticulum stress, and defective nutrient deprivation signaling, which (acting in concert) are poised to cause both activation of HIF-1α and suppression of HIF-2α. This shift in the balance of HIF-1α/HIF-2α activities promotes proinflammatory and profibrotic pathways in glomerular and renal tubular cells. SGLT2 inhibitors alleviate renal hypoxia and cellular stress and enhance nutrient deprivation signaling, which collectively may explain their actions to suppress HIF-1α and activate HIF-2α and thereby augment erythropoiesis, while muting organellar dysfunction, inflammation, and fibrosis. Cobalt chloride, a drug conventionally classified as a hypoxia mimetic, has a profile of molecular and cellular actions in the kidney that is similar to those of SGLT2 inhibitors. Therefore, many renoprotective benefits of SGLT2 inhibitors may be related to their effect to promote oxygen deprivation signaling in the diabetic kidney.

Platelet Lysate Induces in Human Osteoblasts Resumption of Cell Proliferation and Activation of Pathways Relevant for Revascularization and Regeneration of Damaged Bone.

To understand the regenerative effect of platelet-released molecules in bone repair one should investigate the cascade of events involving the resident osteoblast population during the reconstructive process. Here the in vitro response of human osteoblasts to a platelet lysate (PL) stimulus is reported. Quiescent or very slow dividing osteoblasts showed a burst of proliferation after PL stimulation and returned to a none or very slow dividing condition when the PL was removed. PL stimulated osteoblasts maintained a differentiation capability in vitro and in vivo when tested in absence of PL. Since angiogenesis plays a crucial role in the bone healing process, we investigated in PL stimulated osteoblasts the activation of hypoxia-inducible factor 1-alpha (HIF-1α) and signal transducer and activator of transcription 3 (STAT3) pathways, involved in both angiogenesis and bone regeneration. We observed phosphorylation of STAT3 and a strong induction, nuclear translocation and DNA binding of HIF-1α. In agreement with the induction of HIF-1α an enhanced secretion of vascular endothelial growth factor (VEGF) occurred. The double effect of the PL on quiescent osteoblasts, i.e., resumption of proliferation and activation of pathways promoting both angiogenesis and bone formation, provides a rationale to the application of PL as therapeutic agent in post-traumatic bone repair.

If it's not one thing, HIF's another: immunoregulation by hypoxia inducible factors in disease.

Hypoxia‐inducible factors (HIFs) have emerged in recent years as critical regulators of immunity. Localised, low oxygen tension is a hallmark of inflamed and infected tissues. Subsequent myeloid cell HIF stabilisation plays key roles in the innate immune response, alongside emerging oxygen‐independent roles. Manipulation of regulatory proteins of the HIF transcription factor family can profoundly influence inflammatory profiles, innate immune cell function and pathogen clearance and, as such, has been proposed as a therapeutic strategy against inflammatory diseases. The direction and mode of HIF manipulation as a therapy are dictated by the inflammatory properties of the disease in question, with innate immune cell HIF reduction being, in general, advantageous during chronic inflammatory conditions, while upregulation of HIF is beneficial during infections. The therapeutic potential of targeting myeloid HIFs, both genetically and pharmacologically, has been recently illuminated in vitro and in vivo, with an emerging range of inhibitory and activating strategies becoming available. This review focuses on cutting edge findings that uncover the roles of myeloid cell HIF signalling on immunoregulation in the contexts of inflammation and infection and explores future directions of potential therapeutic strategies.

MRNA overexpression of prolyl hydroxylase PHD3 is inversely related to nuclear grade in renal cell carcinoma.

The aim of the present study was to evaluate the relative mRNA expression levels of genes involved in the hypoxia inducible factor (HIF) signalling pathway in renal cell carcinoma (RCC) and to analyse their associations with clinicopathological parameters and survival outcomes. Reverse transcription-quantitative PCR was used to quantify the mRNA expression levels of HIF-1α, HIF-2α, prolyl hydroxylase (PHD)1, PHD2 and PHD3 in formalin-fixed paraffin-embedded (FFPE) tumour tissue samples from 41 patients with RCC, including 33 cases of clear cell RCC (ccRCC). FFPE samples of corresponding adjacent normal kidney tissues were used as a comparison. mRNA expression levels were analysed in regard to clinical parameters, histological type, stage, nuclear grade, cancer specific survival and overall survival. Compared with adjacent normal kidney tissue, HIF-1α levels were lower in 16/33 ccRCC samples (48.48%), while HIF-2α, PHD1 and PHD2 levels did not exhibit a specific expression pattern. By contrast, the PHD3 mRNA level was higher in 29/33 (87.87%) of the tumour samples. HIF-1α was positively associated with HIF-2α, PHD1 and PHD2. HIF-2α levels were associated with PHD1, PHD2 and PHD3, while PHD3 was strongly associated with PHD2. PHD3 mRNA levels were inversely associated with nuclear grade (P=0.015). However, in univariate analysis, PHD3 was not associated with cancer-specific or overall survival rates. The present findings suggest an important involvement of PHD3 in ccRCC, since PHD3 mRNA expression was inversely associated with nuclear grade. However, PHD3 mRNA levels did not have an independent prognostic value. Further studies are required to investigate whether PHD3 could be used as either a therapeutic target or prognostic marker.