ERK activation upon hypoxia: involvement in HIF-1 activation

The Warburg effect: The hacked mitochondrial-nuclear communication in cancer

Mitochondrial-nuclear communication is vital for maintaining cellular homeostasis. This communication begins with mitochondria sensing environmental cues and transmitting signals to the nucleus through the retrograde cascade, involving metabolic signals such as substrates for epigenetic modifications, ATP and AMP levels, calcium flux, etc. These signals inform the nucleus about the cell's metabolic state, remodel epigenome and regulate gene expression, and modulate mitochondrial function and dynamics through the anterograde feedback cascade to control cell fate and physiology. Disruption of this communication can lead to cellular dysfunction and disease progression, particularly in cancer. The Warburg effect is the metabolic hallmark of cancer, characterized by disruption of mitochondrial respiration and increased lactate generation from glycolysis. This metabolic reprogramming rewires retrograde signaling, leading to epigenetic changes and dedifferentiation, further reprogramming mitochondrial function and promoting carcinogenesis. Understanding these processes and their link to tumorigenesis is crucial for uncovering tumorigenesis mechanisms. Therapeutic strategies targeting these disrupted pathways, including metabolic and epigenetic components, provide promising avenues for cancer treatment.

Antitumor effects of dauricine on sorafenib-treated human lung cancer cell lines via modulation of HIF-1α signaling pathways

The majority of lung cancer cases are non-small cell lung cancer (NSCLC) which continues to be a serious global health concern. Hypoxia-inducible factor (HIF-α) pathway is a promising therapeutic target because it has a vital function in advanced non-small cell lung carcinoma. Antiangiogenic multi-kinase inhibitor, sorafenib may have a part in regulating HIF signaling in cancer. As a result, there is now more interest in employing it to target hypoxia-driven pathways in non-small cell lung cancer, especially when paired with natural bioactive products such as dauricine which is a naturally occurring alkaloid molecule targets multiple cellular pathways to provide strong anticancer effects. To examine molecular impacts of combining dauricine with sorafenib on HIF-mediated signaling pathways in human lung cancer cell lines. Cell viability was assessed using MTT assay in A549 and H1975 lung tumor cell lines. Levels of key proteins (AKT, mTORC1, HIF-1 α, ERK, VEGF, Cyclin-D1, BCL2, and E-Cadherin) were measured by ELISA.A colorimetric test was utilized to assess the activity of caspase-3, as a marker of apoptosis. qRT-PCR was employed to identify PI3K and VEGFR2 genes expression. Combination of sorafenib and dauricine significantly enhanced cytotoxicity compared to either agent alone. This combination also led to a marked reduction in VEGFR2, PI3K expression and VEGF, AKT, mTOR, HIF-1α, BCL2, ERK and E-Cadherin, and Cyclin-D1 levels. In addition, there was a significant increase in caspase-3 activity. Dauricine potentiates antitumor effects of sorafenib in human NSCLC by modulating HIF-1α-mediated pathways that are involved in several cancer hallmarks. This combination shows promise as a potential lung cancer treatment approach.

Hypoxia-induced histone methylation and NF-κB activation in pancreas cancer fibroblasts promote EMT-supportive growth factor secretion

The pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment contains hypoxic tissue subdomains and cancer-associated fibroblasts (CAFs) of multiple subtypes that play tumor-promoting and -restraining roles. Here, we demonstrate that hypoxia promotes an inflammatory-like CAF phenotype and that hypoxic CAFs selectively promote epithelial-mesenchymal transition (EMT) in PDAC cancer cells through growth factor-mediated cell crosstalk. By analyzing patient tumor single-cell transcriptomics and conducting an inhibitor screen, we identified IGF-2 and HGF as specific EMT-inducing growth factors produced by hypoxic CAFs. We further found that reactive oxygen species-activated NF-κB cooperates with hypoxia-dependent histone methylation to promote IGF-2 and HGF expression in hypoxic CAFs. In lineage-traced autochthonous PDAC mouse tumors, hypoxic CAFs resided preferentially near hypoxic, mesenchymal cancer cells. However, in subcutaneous tumors engineered with hypoxia fate-mapped CAFs, once-hypoxic re-oxygenated CAFs lacked a spatial correlation with mesenchymal cancer cells. Thus, hypoxia promotes reversible CAF-malignant cell interactions that drive EMT through druggable signaling pathways.

One-sentence summary

We show that hypoxic fibroblasts in pancreas cancer leverage histone methylation and ROS-mediated NF-κB activation to produce growth factors that drive epithelial-mesenchymal transition in malignant cells, demonstrating how tumor stromal features cooperate to initiate a signaling process for disease progression.

Genome-Wide Selection Signals Reveal Candidate Genes Associated with Plateau Adaptation in Tibetan Sheep

Tibetan sheep have developed unique adaptations for survival in the Qinghai-Tibet Plateau environment. However, the functional genes and molecular mechanisms that regulate hypoxia adaptation have not been fully characterized. In this study, based on the whole-genome resequencing data for Tibetan sheep at different altitudes, the population differentiation index (FST) and nucleotide diversity ratio (θπ ratio) were evaluated in populations of 20 Oula sheep (3501 m altitude, OL), 20 Zashijia sheep (4369 m altitude, ZSJ), and 20 Awang sheep (4643 m altitude, AW) to reveal candidate loci related to high-altitude hypoxia. We screened 728 and 524 candidate genes in the AW vs. OL and ZSJ vs. OL groups, respectively, of which 134 genes were jointly screened. Candidate genes were mainly enriched in the Ras, melanoma, melanogenesis, VEGF, and PPAR signaling pathways. HIF1AN, PDGFA, PDGFD, ANXA2, SOCS2, NOXA1, WNT7B, MMP14, GNG2, ATF6, PGAM2, PPP3R1, GSTCD, and PPARA may play important roles in the high-altitude adaptation of Tibetan sheep. In conclusion, this study provides valuable insights into the genes and molecular mechanisms that underlie high-altitude hypoxia adaptation in Tibetan sheep.

Dynamics simulations of hypoxia inducible factor-1 regulatory network in cancer using formal verification techniques

Hypoxia-inducible factor-1 (HIF-1) regulates cell growth, protein translation, metabolic pathways and therefore, has been advocated as a promising biological target for the therapeutic interventions against cancer. In general, hyperactivation of HIF-1 in cancer has been associated with increases in the expression of glucose transporter type-1 (GLUT-1) thus, enhancing glucose consumption and hyperactivating metabolic pathways. The collective behavior of GLUT-1 along with previously known key players AKT, OGT, and VEGF is not fully characterized and lacks clarity of how glucose uptake through this pathway (HIF-1) probes the cancer progression. This study uses a Rene Thomas qualitative modeling framework to comprehend the signaling dynamics of HIF-1 and its interlinked proteins, including VEGF, ERK, AKT, GLUT-1, β-catenin, C-MYC, OGT, and p53 to elucidate the regulatory mechanistic of HIF-1 in cancer. Our dynamic model reveals that continuous activation of p53, β-catenin, and AKT in cyclic conditions, leads to oscillations representing homeostasis or a stable recovery state. Any deviation from this cycle results in a cancerous or pathogenic state. The model shows that overexpression of VEGF activates ERK and GLUT-1, leads to more aggressive tumor growth in a cancerous state. Moreover, it is observed that collective modulation of VEGF, ERK, and β-catenin is required for therapeutic intervention because these genes enhance the expression of GLUT-1 and play a significant role in cancer progression and angiogenesis. Additionally, SimBiology simulation unveils dynamic molecular interactions, emphasizing the need for targeted therapeutics to effectively regulate VEGF and ERK concentrations to modulate cancer cell proliferation.

LAT1 expression in colorectal cancer cells is unresponsive to HIF-1/2α accumulation under experimental hypoxia

L-type amino acid transporter 1 (LAT1) is upregulated in various cancer types and contributes to disease progression. Previous studies have demonstrated or suggested that hypoxia-inducible factors (HIFs), the key transcription factors in hypoxic responses, control the expression of LAT1 gene in several types of cancer cells. However, this regulatory relationship has not been investigated yet in colorectal cancer (CRC), one of the cancer types in which the increased LAT1 expression holds prognostic significance. In this study, we found that neither LAT1 mRNA nor protein is induced under hypoxic condition (1% O2) in CRC HT-29 cells in vitro, regardless of the prominent HIF-1/2α accumulation and HIFs-dependent upregulation of glucose transporter 1. The hypoxic treatment generally did not increase either the mRNA or protein expression of LAT1 in eight CRC cell lines tested, in contrast to the pronounced upregulation by amino acid restriction. Interestingly, knockdown of von Hippel-Lindau ubiquitin ligase to inhibit the proteasomal degradation of HIFs caused an accumulation of HIF-2α and increased the LAT1 expression in certain CRC cell lines. This study contributes to delineating the molecular mechanisms responsible for the pathological expression of LAT1 in CRC cells, emphasizing the ambiguity of HIFs-dependent transcriptional upregulation of LAT1 across cancer cells.

Pathophysiology in Brain Arteriovenous Malformations: Focus on Endothelial Dysfunctions and Endothelial-to-Mesenchymal Transition

Brain arteriovenous malformations (bAVMs) substantially increase the risk for intracerebral hemorrhage (ICH), which is associated with significant morbidity and mortality. However, the treatment options for bAVMs are severely limited, primarily relying on invasive methods that carry their own risks for intraoperative hemorrhage or even death. Currently, there are no pharmaceutical agents shown to treat this condition, primarily due to a poor understanding of bAVM pathophysiology. For the last decade, bAVM research has made significant advances, including the identification of novel genetic mutations and relevant signaling in bAVM development. However, bAVM pathophysiology is still largely unclear. Further investigation is required to understand the detailed cellular and molecular mechanisms involved, which will enable the development of safer and more effective treatment options. Endothelial cells (ECs), the cells that line the vascular lumen, are integral to the pathogenesis of bAVMs. Understanding the fundamental role of ECs in pathological conditions is crucial to unraveling bAVM pathophysiology. This review focuses on the current knowledge of bAVM-relevant signaling pathways and dysfunctions in ECs, particularly the endothelial-to-mesenchymal transition (EndMT).

PICK1 modulates glycolysis and angiogenesis of hypoxic endothelial cells by regulating iron homeostasis

Iron accumulation, which is controlled by transferrin receptor 1 (TfR1), modulates hypoxia-inducible factor-1α (HIF-1α) activation and angiogenesis of hypoxic endothelial cells. The study examined the role of protein interacting with C-kinase 1 (PICK1), a scaffold protein containing PDZ domain, in regulating glycolysis and angiogenesis of hypoxic vascular endothelial cells through its potential effect on TfR1, which features a supersecondary structure that interacts with the PDZ domain. Iron chelator deferoxamine and TfR1 siRNA were employed to assess the impact of iron accumulation on angiogenesis, while the effects of PICK1 siRNA and overexpressing lentivirus on TfR1-mediated iron accumulation were also investigated in hypoxic human umbilical vein vascular endothelial cells (HUVECs). The study found that 72-h hypoxia impaired the proliferation, migration, and tube formation of HUVECs, and reduced the upregulation of vascular endothelial growth factor, HIF-1α, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3, and PICK1, while increasing the expression of TfR1 as compared to 24-h hypoxia. Administration of deferoxamine or TfR1 siRNA reversed these effects and led to increased glycolysis, ATP content, and phosphofructokinase activity, along with increased PICK1 expression. PICK1 overexpression improved glycolysis, enhanced angiogenic capacity, and attenuated TfR1 protein upregulation in hypoxic HUVECs, with higher expression of angiogenic markers, which could be significantly reversed by the PDZ domain inhibitor. PICK1 knockdown exerted opposite effects. The study concluded that PICK1 modulated intracellular iron homeostasis, thereby promoting glycolysis and angiogenesis of HUVECs in response to prolonged hypoxia, at least in part, by regulating TfR1 expression.

CX3CL1 (Fractalkine)-CX3CR1 Axis in Inflammation-Induced Angiogenesis and Tumorigenesis

The chemotactic cytokine fractalkine (FKN, chemokine CX3CL1) has unique properties resulting from the combination of chemoattractants and adhesion molecules. The soluble form (sFKN) has chemotactic properties and strongly attracts T cells and monocytes. The membrane-bound form (mFKN) facilitates diapedesis and is responsible for cell-to-cell adhesion, especially by promoting the strong adhesion of leukocytes (monocytes) to activated endothelial cells with the subsequent formation of an extracellular matrix and angiogenesis. FKN signaling occurs via CX3CR1, which is the only known member of the CX3C chemokine receptor subfamily. Signaling within the FKN-CX3CR1 axis plays an important role in many processes related to inflammation and the immune response, which often occur simultaneously and overlap. FKN is strongly upregulated by hypoxia and/or inflammation-induced inflammatory cytokine release, and it may act locally as a key angiogenic factor in the highly hypoxic tumor microenvironment. The importance of the FKN/CX3CR1 signaling pathway in tumorigenesis and cancer metastasis results from its influence on cell adhesion, apoptosis, and cell migration. This review presents the role of the FKN signaling pathway in the context of angiogenesis in inflammation and cancer. The mechanisms determining the pro- or anti-tumor effects are presented, which are the cause of the seemingly contradictory results that create confusion regarding the therapeutic goals.

Identification of mapk genes, and their expression profiles in response to low salinity stress, in cobia (Rachycentron canadum)

Mitogen-activated protein kinases (MAPKs) are a class of protein kinases that regulate various physiological processes, and play a crucial role in maintaining the osmotic equilibrium of fish. The objective of this study was to identify and characterize the mapk family genes in cobia (Rachycentron canadum) and examine their expression profiles under different low salinity stress regimes (acute: from 30‰ to 10‰ in 1 h, sub-chronic: from 30‰ to 10‰ over 4 d). A total of 12 cobia mapk genes (Rcmapks) were identified and cloned, including six erk subfamily genes (Rcmapk1/3/4/6/7/15), three jnk subfamily genes (Rcmapk8/9/10) and three p38 mapk subfamily genes (Rcmapk 11/13/14). Domain analysis indicated that the RcMAPKs possessed the typical domains including S_TKc and PKc_like domain. Phylogenetic analysis revealed that the Rcmapks were most closely related to those of the turbot (Scophthalmus maximus). The tissue distribution of mapk genes in adult cobia and the expression patterns of Rcmapks under different low salinity stress regimes were investigated using quantitative real-time PCR (qRT-PCR). The results revealed that Rcmapk3/9/10/11/13/14 exhibited a relatively broad expression distribution across 14 different tissues. For all these genes the highest expression level was in the brain, except for Rcmapk14 (highly expressed in the stomach, gill, and skin). The genes Rcmapk1/6/15 showed significantly higher expression in the testis. Under acute low salinity stress, expression of Rcmapk1/3/6/7/9/11/13/14 was significantly altered in the gill, intestine, and trunk kidney, however, the aforementioned genes exhibited very different expression patterns among the three tissues. In the gill, most of the genes from the erk (Rcmapk3/6/7) and p38 mapk subfamily (Rcmapk11/13/14) were significantly up-regulated at almost all the time points (P < 0.05); Similarly, the expression of Rcmapk3/9/11/13/14 genes were significantly increased in the trunk kidney; while in the intestine, most of the altered genes (Rcmapk6/7/9/11/13/14) were significantly down-regulated at 1 h. Following the sub-chronic low salinity stress, expression of Rcmapk1/3/6/7/9/11/13/14 genes were significantly altered in all three tissues. These findings provide important reference data for elucidating the roles of cobia mapk family genes in response to low salinity stress.

SQSTM1/p62 inhibition impairs pro-survival signaling in hypoxic human dendritic cells

The sequestosome 1 (SQSTM1)/p62 is an adaptor protein which plays multiple roles in several cell functions, including cell survival and autophagy. Dendritic cells (DCs) are the most prominent antigen presenting cells and during their lifespan they are exposed to different oxygen tensions, including hypoxia. By using a siRNA approach we found out that p62 was implicated in the maintenance of Erk1/2 phosphorylation and preservation of hypoxic DC survival, as well as in the reduction of AMPK activation. Thus, p62 expression in DCs in hypoxic microenvironments, such as in the lymphoid organs, may extend their lifespan to ensure their functions.

Hyperthermia Influences the Secretion Signature of Tumor Cells and Affects Endothelial Cell Sprouting

Tumors are a highly heterogeneous mass of tissue showing distinct therapy responses. In particular, the therapeutic outcome of tumor hyperthermia treatments has been inconsistent, presumably due to tumor versus endothelial cell cross-talks related to the treatment temperature and the tumor tissue environment. Here, we investigated the impact of the average or strong hyperthermic treatment (43 °C or 47 °C for 1 h) of the human pancreatic adenocarcinoma cell line (PANC-1 and BxPC-3) on endothelial cells (HUVECs) under post-treatment normoxic or hypoxic conditions. Immediately after the hyperthermia treatment, the distinct repression of secreted pro-angiogenic factors (e.g., VEGF, PDGF-AA, PDGF-BB, M-CSF), intracellular HIF-1α and the enhanced phosphorylation of ERK1/2 in tumor cells were detectable (particularly for strong hyperthermia, 2D cell monolayers). Notably, there was a significant increase in endothelial sprouting when 3D self-organized pancreatic cancer cells were treated with strong hyperthermia and the post-treatment conditions were hypoxic. Interestingly, for the used treatment temperatures, the intracellular HIF-1α accumulation in tumor cells seems to play a role in MAPK/ERK activation and mediator secretion (e.g., VEGF, PDGF-AA, Angiopoietin-2), as shown by inhibition experiments. Taken together, the hyperthermia of pancreatic adenocarcinoma cells in vitro impacts endothelial cells under defined environmental conditions (cell-to-cell contact, oxygen status, treatment temperature), whereby HIF-1α and VEGF secretion play a role in a complex context. Our observations could be exploited for the hyperthermic treatment of pancreatic cancer in the future.

Hypobaric Hypoxia Aggravates Renal Injury by Inducing the Formation of Neutrophil Extracellular Traps through the NF-κB Signaling Pathway

OBJECTIVE

The hypersensitivity of the kidney makes it susceptible to hypoxia injury. The involvement of neutrophil extracellular traps (NETs) in renal injury resulting from hypobaric hypoxia (HH) has not been reported. In this study, we aimed to investigate the expression of NETs in renal injury induced by HH and the possible underlying mechanism.

METHODS

A total of 24 SD male rats were divided into three groups (n=8 each): normal control group, hypoxia group and hypoxia+pyrrolidine dithiocarbamate (PDTC) group. Rats in hypoxia group and hypoxia+PDTC group were placed in animal chambers with HH which was caused by simulating the altitude at 7000 meters (oxygen partial pressure about 6.9 kPa) for 7 days. PDTC was administered at a dose of 100 mg/kg intraperitoneally once daily for 7 days. Pathological changes of the rat renal tissues were observed under a light microscope; the levels of serum creatinine (SCr), blood urea nitrogen (BUN), cell-free DNA (cf-DNA) and reactive oxygen species (ROS) were measured; the expression levels of myeloperoxidase (MPO), citrullinated histone H3 (cit-H3), B-cell lymphoma 2 (Bcl-2), Bax, nuclear factor kappa B (NF-κB) p65 and phospho-NF-κB p65 (p-NF-κB p65) in rat renal tissues were detected by qRT-qPCR and Western blotting; the localization of NF-κB p65 expression in rat renal tissues was observed by immunofluorescence staining and the expression changes of NETs in rat renal tissues were detected by multiplex fluorescence immunohistochemical staining.

RESULTS

After hypoxia, the expression of NF-κB protein in renal tissues was significantly increased, the levels of SCr, BUN, cf-DNA and ROS in serum were significantly increased, the formation of NETs in renal tissues was significantly increased, and a large number of tubular dilatation and lymphocyte infiltration were observed in renal tissues. When PDTC was used to inhibit NF-κB activation, NETs formation in renal tissue was significantly decreased, the expression level of Bcl-2 in renal tissues was significantly increased, the expression level of Bax was significantly decreased, and renal injury was significantly alleviated.

CONCLUSION

HH induces the formation of NETs through the NF-κB signaling pathway, and it promotes apoptosis and aggravates renal injury by decreasing Bcl-2 and increasing Bax expression.

Targeting a thrombopoietin-independent strategy in the discovery of a novel inducer of megakaryocytopoiesis, DMAG, for the treatment of thrombocytopenia

Thrombocytopenia is a thrombopoietin (TPO)-related disorder with very limited treatment options, and can be lifethreatening. There are major problems with typical thrombopoietic agents targeting TPO signaling, so it is urgent to discover a novel TPO-independent mechanism involving thrombopoiesis and potential druggable targets. We developed a drug screening model by the multi-grained cascade forest (gcForest) algorithm and found that 3,8-di-O-methylellagic acid 2- O-glucoside (DMAG) (10, 20 and 40 μM) promoted megakaryocyte differentiation in vitro. Subsequent investigations revealed that DMAG (40 mM) activated ERK1/2, HIF-1b and NF-E2. Inhibition of ERK1/2 blocked megakaryocyte differentiation and attenuated the upregulation of HIF-1b and NF-E2 induced by DMAG. Megakaryocyte differentiation induced by DMAG was inhibited via knockdown of NF-E2. In vivo studies showed that DMAG (5 mg/kg) accelerated platelet recovery and megakaryocyte differentiation in mice with thrombocytopenia. The platelet count of the DMAG-treated group recovered to almost 72% and 96% of the count in the control group at day 10 and 14, respectively. The platelet counts in the DMAG-treated group were almost 1.5- and 1.3-fold higher compared with those of the irradiated group at day 10 and 14, respectively. Moreover, DMAG (10, 25 and 50 mM) stimulated thrombopoiesis in zebrafish. DMAG (5 mg/kg) could also increase platelet levels in c-MPL knockout (c-MPL-/-) mice. In summary, we established a drug screening model through gcForest and demonstrated that DMAG promotes megakaryocyte differentiation via the ERK/HIF1/NF-E2 pathway which, importantly, is independent of the classical TPO/c-MPL pathway. The present study may provide new insights into drug discovery for thrombopoiesis and TPO-independent regulation of thrombopoiesis, as well as a promising avenue for thrombocytopenia treatment.

Submersion and hypoxia inhibit alveolar epithelial Na+ transport through ERK/NF-κB signaling pathway

BACKGROUND

Hypoxia is associated with many respiratory diseases, partly due to the accumulation of edema fluid and mucus on the surface of alveolar epithelial cell (AEC), which forms oxygen delivery barriers and is responsible for the disruption of ion transport. Epithelial sodium channel (ENaC) on the apical side of AEC plays a crucial role to maintain the electrochemical gradient of Na⁺ and water reabsorption, thus becomes the key point for edema fluid removal under hypoxia. Here we sought to explore the effects of hypoxia on ENaC expression and the further mechanism related, which may provide a possible treatment strategy in edema related pulmonary diseases.

METHODS

Excess volume of culture medium was added on the surface of AEC to simulate the hypoxic environment of alveoli in the state of pulmonary edema, supported by the evidence of increased hypoxia-inducible factor-1 expression. The protein/mRNA expressions of ENaC were detected, and extracellular signal-regulated kinase (ERK)/nuclear factor κB (NF-κB) inhibitor was applied to explore the detailed mechanism about the effects of hypoxia on epithelial ion transport in AEC. Meanwhile, mice were placed in chambers with normoxic or hypoxic (8%) condition for 24 h, respectively. The effects of hypoxia and NF-κB were assessed through alveolar fluid clearance and ENaC function by Ussing chamber assay.

RESULTS

Hypoxia (submersion culture mode) induced the reduction of protein/mRNA expression of ENaC, whereas increased the activation of ERK/NF-κB signaling pathway in parallel experiments using human A549 and mouse alveolar type 2 cells, respectively. Moreover, the inhibition of ERK (PD98059, 10 µM) alleviated the phosphorylation of IκB and p65, implying NF-κB as a downstream pathway involved with ERK regulation. Intriguingly, the expression of α-ENaC could be reversed by either ERK or NF-κB inhibitor (QNZ, 100 nM) under hypoxia. The alleviation of pulmonary edema was evidenced by the administration of NF-κB inhibitor, and enhancement of ENaC function was supported by recording amiloride-sensitive short-circuit currents.

CONCLUSIONS

The expression of ENaC was downregulated under hypoxia induced by submersion culture, which may be mediated by ERK/NF-κB signaling pathway.

Regulation of Hypoxic-Adenosinergic Signaling by Estrogen: Implications for Microvascular Injury

Loss of estrogen, as occurs with normal aging, leads to increased inflammation, pathologic angiogenesis, impaired mitochondrial function, and microvascular disease. While the influence of estrogens on purinergic pathways is largely unknown, extracellular adenosine, generated at high levels by CD39 and CD73, is known to be anti-inflammatory in the vasculature. To further define the cellular mechanisms necessary for vascular protection, we investigated how estrogen modulates hypoxic-adenosinergic vascular signaling responses and angiogenesis. Expression of estrogen receptors, purinergic mediators inclusive of adenosine, adenosine deaminase (ADA), and ATP were measured in human endothelial cells. Standard tube formation and wound healing assays were performed to assess angiogenesis in vitro. The impacts on purinergic responses in vivo were modeled using cardiac tissue from ovariectomized mice. CD39 and estrogen receptor alpha (ERα) levels were markedly increased in presence of estradiol (E2). Suppression of ERα resulted in decreased CD39 expression. Expression of ENT1 was decreased in an ER-dependent manner. Extracellular ATP and ADA activity levels decreased following E2 exposure while levels of adenosine increased. Phosphorylation of ERK1/2 increased following E2 treatment and was attenuated by blocking adenosine receptor (AR) and ER activity. Estradiol boosted angiogenesis, while inhibition of estrogen decreased tube formation in vitro. Expression of CD39 and phospho-ERK1/2 decreased in cardiac tissues from ovariectomized mice, whereas ENT1 expression increased with expected decreases in blood adenosine levels. Estradiol-induced upregulation of CD39 substantially increases adenosine availability, while augmenting vascular protective signaling responses. Control of CD39 by ERα follows on transcriptional regulation. These data suggest novel therapeutic avenues to explore in the amelioration of post-menopausal cardiovascular disease, by modulation of adenosinergic mechanisms.

ROS elevate HIF-1α phosphorylation for insect lifespan through the CK2-MKP3-p38 pathway

Diapause in insects is akin to dauer in Caenorhabditis elegans and hibernation in vertebrates, characterized by metabolic depression and lifespan extension. Previous studies have shown that reactive oxygen species (ROS) and hypoxia-inducible factor-1α (HIF-1α) in brains of diapause-destined pupae are more abundant than those in nondiapause-destined pupae in Helicoverpa armigera, but the ROS regulating HIF-1α activity remain unknown. Here, we showed that high ROS levels in brains of diapause-destined pupae resulted in low casein kinase 2 (CK2) activity and that downregulation of CK2 caused low expression of mitogen-activated protein kinase phosphatase 3 (MKP3), which is an inhibitor of p-p38. Thus, high p-p38 levels accumulate to improve HIF-1α activity via activating HIF-1α phosphorylation at the S732 residue to regulate insect diapause. This is the first report showing that a new pathway, ROS-CK2-MKP3-p38, regulates HIF-1α activity for lifespan in insects.

Targeting de novo lipid synthesis induces lipotoxicity and impairs DNA damage repair in glioblastoma mouse models

Deregulated de novo lipid synthesis (DNLS) is a potential druggable vulnerability in glioblastoma (GBM), a highly lethal and incurable cancer. Yet the molecular mechanisms that determine susceptibility to DNLS-targeted therapies remain unknown, and the lack of brain-penetrant inhibitors of DNLS has prevented their clinical evaluation as GBM therapeutics. Here, we report that YTX-7739, a clinical-stage inhibitor of stearoyl CoA desaturase (SCD), triggers lipotoxicity in patient-derived GBM stem-like cells (GSCs) and inhibits fatty acid desaturation in GSCs orthotopically implanted in mice. When administered as a single agent, or in combination with temozolomide (TMZ), YTX-7739 showed therapeutic efficacy in orthotopic GSC mouse models owing to its lipotoxicity and ability to impair DNA damage repair. Leveraging genetic, pharmacological, and physiological manipulation of key signaling nodes in gliomagenesis complemented with shotgun lipidomics, we show that aberrant MEK/ERK signaling and its repression of the energy sensor AMP-activated protein kinase (AMPK) primarily drive therapeutic vulnerability to SCD and other DNLS inhibitors. Conversely, AMPK activation mitigates lipotoxicity and renders GSCs resistant to the loss of DNLS, both in culture and in vivo, by decreasing the saturation state of phospholipids and diverting toxic lipids into lipid droplets. Together, our findings reveal mechanisms of metabolic plasticity in GSCs and provide a framework for the rational integration of DNLS-targeted GBM therapies.

Marine-Inspired Drugs and Biomaterials in the Perspective of Pancreatic Cancer Therapies

Despite its low prevalence, pancreatic cancer (PC) is one of the deadliest, typically characterised as silent in early stages and with a dramatically poor prognosis when in its advanced stages, commonly associated with a high degree of metastasis. Many efforts have been made in pursuing innovative therapeutical approaches, from the search for new cytotoxic drugs and other bioactive compounds, to the development of more targeted approaches, including improved drug delivery devices. Marine biotechnology has been contributing to this quest by providing new chemical leads and materials originating from different organisms. In this review, marine biodiscovery for PC is addressed, particularly regarding marine invertebrates (namely sponges, molluscs, and bryozoans), seaweeds, fungi, and bacteria. In addition, the development of biomaterials based on marine-originating compounds, particularly chitosan, fucoidan, and alginate, for the production of advanced cancer therapies, is also discussed. The key role that drug delivery can play in new cancer treatments is highlighted, as therapeutical outcomes need to be improved to give further hope to patients.

Impact of the redox environment on propagation of radiation bystander effects: The modulating effect of oxidative metabolism and oxygen partial pressure

Redox modulated pathways play important roles in out-of-field effects of ionizing radiation. We investigated how the redox environment impacts the magnitude of propagation of stressful effects from irradiated to bystander cells. Normal human fibroblasts that have incorporated [³H]-thymidine were intimately co-cultured with bystander cells in a strategy that allowed isolation of bystander cells with high purity. The antioxidant glutathione peroxidase (GPX) was maintained either at wild-type conditions or overexpressed in the bystanders. Following 24 h of coculture, levels of stress-responsive p21^Waf1, p-Hdm2, and connexin43 proteins were increased in bystander cells expressing wild-type GPX relative to respective controls. These levels were significantly attenuated when GPX was ectopically overexpressed, demonstrating by direct approach the involvement of a regulator of intracellular redox homeostasis. Evidence of participation of pro-oxidant compounds was generated by exposing confluent cell cultures to low fluences of 3.7 MeV α particles in presence or absence of t-butyl hydroperoxide. By 3 h post-exposure to fluences wherein only ∼2% of cells are traversed through the nucleus by a particle track, increases in chromosomal damage were greater than expected in absence of the drug (p < 0.001) and further enhanced in its presence (p < 0.05). While maintenance and irradiation of cell cultures at low oxygen pressure (pO₂ 3.8 mm Hg) to mimic in vivo still supported the participation of bystander cells in responses assessed by chromosomal damage and stress-responsive protein levels (p < 0.001), the effects were attenuated compared to ambient pO₂ (155 mm Hg) (p < 0.05). Together, the results show that bystander effects are attenuated at below ambient pO₂ and when metabolic oxidative stress is reduced but increased when the basal redox environment tilts towards oxidizing conditions. They are consistent with bystander effects being independent of radiation dose rate.

Spatiotemporal correlation between HIF-1α and bone regeneration

Hypoxia-inducible factors (HIFs) are core regulators of the hypoxia response. HIF signaling is activated in the local physiological and pathological hypoxic environment, acting on downstream target genes to synthesize the corresponding proteins and regulate the hypoxic stress response. HIFs belong to the hypoxia-activated transcription family and contain two heterodimeric transcription factors, HIF-α and HIF-β. Under hypoxia, the dimer formed by HIF-α binding to HIF-β translocates into the nucleus and binds to the hypoxia response element (HRE) to induce transcription of a series of genes. HIF-1α plays an important role in innate bone development and acquired bone regeneration. HIF-1α promotes bone regeneration mainly through the following two pathways: (1) By regulating angiogenesis-osteoblast coupling to promote bone regeneration; and (2) by inducing metabolic reprogramming in osteoblasts, promoting cellular anaerobic glycolysis, ensuring the energy supply of osteoblasts under hypoxic conditions, and further promoting bone regeneration and repair. This article reviews recent basic research on HIF-1α and its role in promoting osteogenesis, discusses the possible molecular mechanisms, introduces the hypoxia-independent role of HIF-1α and reviews the application prospects of HIF-1α in tissue engineering.

Natural adaptation and human selection of northeast African sheep genomes

African sheep manifest diverse but distinct physio-anatomical traits, which are the outcomes of natural- and human-driven selection. Here, we generated 34.8 million variants from 150 indigenous northeast African sheep genomes sequenced at an average depth of ∼54× for 130 samples (Ethiopia, Libya) and ∼20× for 20 samples (Sudan). These represented sheep from diverse environments, tail morphology and post-Neolithic introductions to Africa. Phylogenetic and model-based admixture analysis provided evidence of four genetic groups corresponding to altitudinal geographic origins, tail morphotypes and possible historical introduction and dispersal of the species into and across the continent. Running admixture at higher levels of K (6 ≤ K ≤ 25), revealed cryptic levels of genome intermixing as well as distinct genetic backgrounds in some populations. Comparative genomic analysis identified targets of selection that spanned conserved haplotype structures overlapping clusters of genes and gene families. These were related to hypoxia responses, ear morphology, caudal vertebrae and tail skeleton length, and tail fat-depot structures. Our findings provide novel insights underpinning morphological variation and response to human-driven selection and environmental adaptation in African indigenous sheep.

Overexpression of Annexin A1 is associated with the formation of capillaries in infantile hemangioma

Infantile hemangioma is a common benign tumor in infants. However, the molecular mechanism that controls the proliferation and differentiation of hemangioma is not well understood. Annexin A1 (ANX A1) is a phospholipid-binding protein involved in a variety of biological processes, including inflammation, cell proliferation and apoptosis. To explore the significance of ANX A1 in the process of proliferation or differentiation of hemangioma, proliferating and involuting hemangioma tissues were collected to detect the expression of ANX A1 using immunohistochemistry and western blotting. Normal skin tissues were used as the negative control. The results revealed that ANX A1 was upregulated in the proliferative phase of hemangioma, and its expression was decreased when the hemangioma entered the involuting phase. Additionally, in the proliferative phase, the strongest staining of ANX A1 was observed in newly born capillaries, and the staining of ANX A1 became weaker in enlarged vessels, indicating that ANX A1 plays an important role in promoting the formation of capillaries. The expression of hypoxia-inducible factor (HIF)-1α was positively associated with the expression trend of ANX A1, suggesting that the overexpression of ANX A1 may be associated with the increase of HIF-1α. In summary, the results of the present study revealed that the expression of ANX A1 was increased in proliferating hemangioma tissue, and that high expression of ANX A1 may be closely associated with the formation of capillaries in infantile hemangioma.

Hypoxia Induces Autophagy in Human Dendritic Cells: Involvement of Class III PI3K/Vps34

Hypoxia is a component of both physiological and pathological conditions, including inflammation, solid tumors, and lymphoid tissues, where O2 demand is not balanced by O2 supply. During their lifespan, dendritic cells (DCs) are exposed to different pO2 and activate different adaptive responses, including autophagy, to preserve their viability and functions. Autophagy plays multiple roles in DC physiology. Very recently, we demonstrated that hypoxia shapes autophagy in DCs upon their differentiation state. Here, we proposed a role for PI3Ks, and especially class III PI3K/Vps34, that could be relevant in hypoxia-induced autophagy, in either immature or mature DCs. Hypoxia inhibited mTOR phosphorylation and activated a pro-autophagic program. By using different pharmacological inhibitors, we demonstrated that hypoxia-induced autophagy was mediated by PI3Ks, especially by Vps34. Furthermore, Vps34 expression was enhanced by LPS, a TLR4 ligand, along with the promotion of autophagy under hypoxia. The Vps34 inhibitor, SAR405, abolished hypoxia-induced autophagy, inhibited pro-survival signaling and viability, and increased the expression of proinflammatory cytokines. Our results underlined the impact of autophagy in the maintenance of DC homeostasis at both cell survival and inflammatory response levels, therefore, contributing to a better understanding of the significance of autophagy in DC physiology and pathology.

Galectin 1-A Key Player between Tissue Repair and Fibrosis

Galectins are ten family members of carbohydrate-binding proteins with a high affinity for β galactose-containing oligosaccharides. Galectin-1 (Gal-1) is the first protein discovered in the family, expressed in many sites under normal and pathological conditions. In the first part of the review article, we described recent advances in the Gal-1 modulatory role on wound healing, by focusing on the different phases triggered by Gal-1, such as inflammation, proliferation, tissue repair and re-epithelialization. On the contrary, Gal-1 persistent over-expression enhances angiogenesis and extracellular matrix (ECM) production via PI3K/Akt pathway activation and leads to keloid tissue. Therefore, the targeted Gal-1 modulation should be considered a method of choice to treat wound healing and avoid keloid formation. In the second part of the review article, we discuss studies clarifying the role of Gal-1 in the pathogenesis of proliferative diabetic retinopathy, liver, renal, pancreatic and pulmonary fibrosis. This evidence suggests that Gal-1 may become a biomarker for the diagnosis and prognosis of tissue fibrosis and a promising molecular target for the development of new and original therapeutic tools to treat fibrosis in different chronic diseases.

Matrix Hyaluronic Acid and Hypoxia Influence a CD133+ Subset of Patient-Derived Glioblastoma Cells

Glioblastoma (GBM) displays diffusive invasion throughout the brain microenvironment, which is partially responsible for its short median survival rate (<15 months). Stem-like subpopulations (GBM stem-like cells, GSCs) are believed to play a central role in therapeutic resistance and poor patient prognosis. Given the extensive tissue remodeling and processes such as vessel co-option and regression that occur in the tumor microenvironment, it is essential to understand the role of metabolic constraint such as hypoxia on GBM cell populations. This work describes the use of a multidimensional gelatin hydrogel to culture patient-derived GBM cells, to evaluate the influence of hypoxia and the inclusion brain-mimetic hyaluronic acid on the relative activity of GSCs versus overall GBM cells. Notably, CD133+ GBM cell fraction is crucial for robust formation of tumor spheroids in multidimensional cultures. In addition, while the relative size of the CD133+ GBM subpopulation increased in response to both hypoxia and matrix-bound hyaluronan, we did not observe cell subtype-specific changes in invasion signaling pathway activation. Taken together, this study highlights the potential of biomimetic culture systems for resolving changes in the population dynamics and behavior of subsets of GBM specimens for the future development of precision medicine applications. Impact Statement This study describes a gelatin hydrogel platform to investigate the role of extracellular hyaluronic acid and hypoxia on the behavior of a CD133+ subset of cells within patient-derived glioblastoma (GBM) specimens. We report that the relative expansion of the CD133+ GBM stem cell-like population is strongly responsive to extracellular cues, highlighting the significance of biomimetic hydrogel models of the tumor microenvironment to investigate invasion and therapeutic response.

Vitamin D and Hypoxia: Points of Interplay in Cancer

Vitamin D is a hormone that, through its action, elicits a broad spectrum of physiological responses ranging from classic to nonclassical actions such as bone morphogenesis and immune function. In parallel, many studies describe the antiproliferative, proapoptotic, antiangiogenic effects of calcitriol (the active hormonal form) that contribute to its anticancer activity. Additionally, epidemiological data signify the inverse correlation between vitamin D levels and cancer risk. On the contrary, tumors possess several adaptive mechanisms that enable them to evade the anticancer effects of calcitriol. Such maladaptive processes are often a characteristic of the cancer microenvironment, which in solid tumors is frequently hypoxic and elicits the overexpression of Hypoxia-Inducible Factors (HIFs). HIF-mediated signaling not only contributes to cancer cell survival and proliferation but also confers resistance to anticancer agents. Taking into consideration that calcitriol intertwines with signaling events elicited by the hypoxic status cells, this review examines their interplay in cellular signaling to give the opportunity to better understand their relationship in cancer development and their prospect for the treatment of cancer.

Role and regulation of autophagy in cancer

Autophagy is an intracellular self-degradative mechanism which responds to cellular conditions like stress or starvation and plays a key role in regulating cell metabolism, energy homeostasis, starvation adaptation, development and cell death. Numerous studies have stipulated the participation of autophagy in cancer, but the role of autophagy either as tumor suppressor or tumor promoter is not clearly understood. However, mechanisms by which autophagy promotes cancer involves a diverse range of modifications of autophagy associated proteins such as ATGs, Beclin-1, mTOR, p53, KRAS etc. and autophagy pathways like mTOR, PI3K, MAPK, EGFR, HIF and NFκB. Furthermore, several researches have highlighted a context-dependent, cell type and stage-dependent regulation of autophagy in cancer. Alongside this, the interaction between tumor cells and their microenvironment including hypoxia has a great potential in modulating autophagy response in favour to substantiate cancer cell metabolism, self-proliferation and metastasis. In this review article, we highlight the mechanism of autophagy and their contribution to cancer cell proliferation and development. In addition, we discuss about tumor microenvironment interaction and their consequence on selective autophagy pathways and the involvement of autophagy in various tumor types and their therapeutic interventions concentrated on exploiting autophagy as a potential target to improve cancer therapy.

Endothelial Transient Receptor Potential Canonical Channel Regulates Angiogenesis and Promotes Recovery After Myocardial Infarction

Background

Transient receptor potential canonical (TRPC) channels play a role in angiogenesis. However, the involvement of TRPC1 in myocardial infarction (MI) remains unclear. The present study was aimed at investigating whether TRPC1 can improve the recovery of cardiac function via prompting angiogenesis following MI.

Methods and Results

In vitro, coronary artery endothelial cells from floxed TRPC1 mice and endothelial cell‐specific TRPC1 channel knockout mice were cultured to access EC angiogenesis. Both EC tube formation and migration were significantly suppressed in mouse coronary artery endothelial cells from endothelial cell‐specific TRPC1 channel knockout mice. In vivo, coronary artery endothelial cells from floxed TRPC1 and endothelial cell‐specific TRPC1 channel knockout mice were subjected to MI, then echocardiography, triphenyltetrazolium chloride staining and immunofluorescence were performed to assess cardiac repair on day 28. Endothelial cell‐specific TRPC1 channel knockout mice had higher ejection fraction change, larger myocardial infarct size, and reduced capillary density in the infarct area compared with coronary artery endothelial cells from floxed TRPC1 mice. Furthermore, we found underlying regulation by HIF‐1α (hypoxic inducible factor‐1α) and MEK‐ERK (mitogen‐activated protein kinase/extracellular signal‐regulated kinase) that could be the mechanism for the angiogenetic action of TRPC1. Significantly, treatment with dimethyloxaloylglycine, an activator of HIF‐1α, induced cardiac improvement via the HIF‐1α‐TRPC1‐MEK/ERK pathway in MI mice.

Conclusions

Our study demonstrated TRPC1 improves cardiac function after MI by increasing angiogenesis via the upstream regulator HIF‐1α and downstream MEK/ERK, and dimethyloxaloylglycine treatment has protective effect on MI through the HIF‐1α‐TRPC1‐MEK/ERK pathway.

USP33 deubiquitinates and stabilizes HIF-2alpha to promote hypoxia response in glioma stem cells

Hypoxia regulates tumor angiogenesis, metabolism, and therapeutic response in malignant cancers including glioblastoma, the most lethal primary brain tumor. The regulation of HIF transcriptional factors by the ubiquitin-proteasome system is critical in the hypoxia response, but hypoxia-inducible deubiquitinases that counteract the ubiquitination remain poorly defined. While the activation of ERK1/2 also plays an important role in hypoxia response, the relationship between ERK1/2 activation and HIF regulation remains elusive. Here, we identified USP33 as essential deubiquitinase that stabilizes HIF-2alpha protein in an ERK1/2-dependent manner to promote hypoxia response in cancer cells. USP33 is preferentially induced in glioma stem cells by hypoxia and interacts with HIF-2alpha, leading to its stabilization through deubiquitination. The activation of ERK1/2 upon hypoxia promoted HIF-2alpha phosphorylation, enhancing its interaction with USP33. Silencing of USP33 disrupted glioma stem cells maintenance, reduced tumor vascularization, and inhibited glioblastoma growth. Our findings highlight USP33 as an essential regulator of hypoxia response in cancer stem cells, indicating a novel potential therapeutic target for brain tumor treatment.

An ApoA-I Mimic Peptide of 4F Promotes SDF-1α Expression in Endothelial Cells Through PI3K/Akt/ERK/HIF-1α Signaling Pathway

Atherosclerosis (AS) seriously impairs the health of human beings and is manifested initially as endothelial cells (ECs) impairment and dysfunction in vascular intima, which can be alleviated through mobilization of endothelial progenitor cells (EPCs) induced by stromal-cell-derived factor-1α (SDF-1α). A strong inverse correlation between HDL and AS has been proposed. The aim of the present work is to investigate whether 4F, an apolipoprotein A-I (apoA-I, major component protein of HDL) mimic peptide, can upregulate SDF-1α in mice and human umbilical vein endothelial cells (HUVECs) and the underlying mechanism. The protein levels of SDF-1α were measured by ELISA assay. Protein levels of HIF-1α, phosphorylated Akt (p-Akt), and phosphorylated ERK (p-ERK) were evaluated by Western blotting analysis. The results show that L-4F significantly upregulates protein levels of HIF-1α, Akt, and ERK, which can be inhibited by the PI3K inhibitor, LY294002, or ERK inhibitor, PD98059, respectively. Particularly, LY294002 can downregulate the levels of p-ERK, while PD98059 cannot suppress that of p-Akt. D-4F can upregulate the levels of HIF, p-Akt, and p-ERK in the abdominal aorta and inferior vena cava from mice. These results suggest that 4F promotes SDF-1α expression in ECs through PI3K/Akt/ERK/HIF-1α signaling pathway.

Hypoxia signaling pathway: A central mediator in endocrine tumors

Adequate oxygen levels are essential for the functioning and maintenance of biological processes in virtually every cell, albeit based on specific need. Thus, any change in oxygen pressure leads to modulated activation of the hypoxia pathway, which affects numerous physiological and pathological processes, including hematopoiesis, inflammation, and tumor development. The Hypoxia Inducible Factors (HIFs) are essential transcription factors and the driving force of the hypoxia pathway; whereas, their inhibitors, HIF prolyl hydroxylase domain (PHDs) proteins are the true oxygen sensors that critically regulate this response. Recently, we and others have described the central role of the PHD/HIF axis in various compartments of the adrenal gland and its potential influence in associated tumors, including pheochromocytomas and paragangliomas. Here, we provide an overview of the most recent findings on the hypoxia signaling pathway in vivo, including its role in the endocrine system, especially in adrenal tumors.

Canagliflozin Modulates Hypoxia-Induced Metastasis, Angiogenesis and Glycolysis by Decreasing HIF-1α Protein Synthesis via AKT/mTOR Pathway

The microenvironment plays a vital role in tumor progression, and hypoxia is a typical microenvironment feature in nearly all solid tumors. In this study, we focused on elucidating the effect of canagliflozin (CANA), a new class of antidiabetic agents, on hepatocarcinoma (HCC) tumorigenesis under hypoxia, and demonstrated that CANA could significantly inhibit hypoxia-induced metastasis, angiogenesis, and metabolic reprogramming in HCC. At the molecular level, this was accompanied by a reduction in VEGF expression level, as well as a reduction in the epithelial-to-mesenchymal transition (EMT)-related proteins and glycolysis-related proteins. Next, we focused our study particularly on the modulation of HIF-1α by CANA, which revealed that CANA decreased HIF-1α protein level by inhibiting its synthesis without affecting its proteasomal degradation. Furthermore, the AKT/mTOR pathway, which plays an important role in HIF-1α transcription and translation, was also inhibited by CANA. Thus, it can be concluded that CANA decreased metastasis, angiogenesis, and metabolic reprogramming in HCC by inhibiting HIF-1α protein accumulation, probably by targeting the AKT/mTOR pathway. Based on our results, we propose that CANA should be evaluated as a new treatment modality for liver cancer.

Dual Lactate Clearance in the Viability Assessment of Livers Donated After Circulatory Death With Ex Situ Normothermic Machine Perfusion

Supplemental Digital Content is available in the text.

Perfusate lactate clearance (LC) is considered one of the useful indicators of liver viability assessment during normothermic machine perfusion (NMP); however, the applicable scope and potential mechanisms of LC remain poorly defined in the setting of liver donation after circulatory death.

Tumour Microenvironment Stress Promotes the Development of Drug Resistance

Multi-drug resistance (MDR) is a leading cause of cancer-related death, and it continues to be a major barrier to cancer treatment. The tumour microenvironment (TME) has proven to play an essential role in not only cancer progression and metastasis, but also the development of resistance to chemotherapy. Despite the significant advances in the efficacy of anti-cancer therapies, the development of drug resistance remains a major impediment to therapeutic success. This review highlights the interplay between various factors within the TME that collectively initiate or propagate MDR. The key TME-mediated mechanisms of MDR regulation that will be discussed herein include (1) altered metabolic processing and the reactive oxygen species (ROS)-hypoxia inducible factor (HIF) axis; (2) changes in stromal cells; (3) increased cancer cell survival via autophagy and failure of apoptosis; (4) altered drug delivery, uptake, or efflux and (5) the induction of a cancer stem cell (CSC) phenotype. The review also discusses thought-provoking ideas that may assist in overcoming the TME-induced MDR. We conclude that stressors from the TME and exposure to chemotherapeutic agents are strongly linked to the development of MDR in cancer cells. Therefore, there remains a vast area for potential research to further elicit the interplay between factors existing both within and outside the TME. Elucidating the mechanisms within this network is essential for developing new therapeutic strategies that are less prone to failure due to the development of resistance in cancer cells.

Phototoxicity-free blue light for enhancing therapeutic angiogenic efficacy of stem cells

Low-level light therapy (LLLT) is a safe and noninvasive technique that has drawn attention as a new therapeutic method to treat various diseases. However, little is known so far about the effect of blue light for LLLT due to the generation of reactive oxygen species (ROS) that can cause cell damage. We introduced a blue organic light-emitting diode (bOLED) as a safe and effective light source that could generate a low amount of heat and luminance compared to conventional light sources (e.g., light-emitting diodes). We compared phototoxicity of bOLED light with different light fluences to human adipose-derived stem cells (hADSC). We further explored molecular mechanisms involved in the therapeutic efficacy of bOLED for enhancing angiogenic properties of hADSC, including intracellular ROS control in hADSCs. Using optimum conditions of bOLED light proposed in this study, photobiomodulation and angiogenic properties of hADSCs were enhanced. These findings might open new methods for using blue light in LLLT. Such methods can be implemented in future treatments for ischemic disease.

Hypoxia-inducible factor 1-alpha acts as a bridge factor for crosstalk between ERK1/2 and caspases in hypoxia-induced apoptosis of cementoblasts

Hypoxia‐induced apoptosis of cementoblasts (OCCM‐30) may be harmful to orthodontic treatment. Hypoxia‐inducible factor 1‐alpha (HIF‐1α) mediates the biological effects during hypoxia. Little is known about the survival mechanism capable to counteract cementoblast apoptosis. We aimed to investigate the potential roles of HIF‐1α, as well as the protein‐protein interactions with ERK1/2, using an in‐vitro model of chemical‐mimicked hypoxia and adipokines. Here, OCCM‐30 were co‐stimulated with resistin, visfatin or ghrelin under CoCl₂‐mimicked hypoxia. In‐vitro investigations revealed that CoCl₂‐induced hypoxia triggered activation of caspases, resulting in apoptosis dysfunction in cementoblasts. Resistin, visfatin and ghrelin promoted the phosphorylated ERK1/2 expression in OCCM‐30 cells. Furthermore, these adipokines inhibited hypoxia‐induced apoptosis at different degrees. These effects were reversed by pre‐treatment with ERK inhibitor (FR180204). In cells treated with FR180204, HIF‐1α expression was inhibited despite the presence of three adipokines. Using dominant‐negative mutants of HIF‐1α, we found that siHIF‐1α negatively regulated the caspase‐8, caspase‐9 and caspase‐3 gene expression. We concluded that HIF‐1α acts as a bridge factor in lengthy hypoxia‐induced apoptosis in an ERK1/2‐dependent pathway. Gene expressions of the caspases‐3, caspase‐8 and caspase‐9 were shown to be differentially regulated by adipokines (resistin, visfatin and ghrelin). Our study, therefore, provides evidence for the role of ERK1/2 and HIF‐1α in the apoptotic response of OCCM‐30 cells exposed to CoCl₂‐mimicked hypoxia, providing potential new possibilities for molecular intervention in obese patients undergoing orthodontic treatment.

TAT for Enzyme/Protein Delivery to Restore or Destroy Cell Activity in Human Diseases

Much effort has been dedicated in the recent decades to find novel protein/enzyme-based therapies for human diseases, the major challenge of such therapies being the intracellular delivery and reaching sub-cellular organelles. One promising approach is the use of cell-penetrating peptides (CPPs) for delivering enzymes/proteins into cells. In this review, we describe the potential therapeutic usages of CPPs (mainly trans-activator of transcription protein, TAT) in enabling the uptake of biologically active proteins/enzymes needed in cases of protein/enzyme deficiency, concentrating on mitochondrial diseases and on the import of enzymes or peptides in order to destroy pathogenic cells, focusing on cancer cells.

The prognostic outcome of 'type 2 diabetes mellitus and breast cancer' association pivots on hypoxia-hyperglycemia axis

Type 2 diabetes mellitus and breast cancer are complex, chronic, heterogeneous, and multi-factorial diseases; with common risk factors including but not limited to diet, obesity, and age. They also share mutually inclusive phenotypic features such as the metabolic deregulations resulting from hyperglycemia, hypoxic conditions and hormonal imbalances. Although, the association between diabetes and cancer has long been speculated; however, the exact molecular nature of this link remains to be fully elucidated. Both the diseases are leading causes of death worldwide and a causal relationship between the two if not addressed, may translate into a major global health concern. Previous studies have hypothesized hyperglycemia, hyperinsulinemia, hormonal imbalances and chronic inflammation, as some of the possible grounds for explaining how diabetes may lead to cancer initiation, yet further research still needs to be done to validate these proposed mechanisms. At the crux of this dilemma, hyperglycemia and hypoxia are two intimately related states involving an intricate level of crosstalk and hypoxia inducible factor 1, at the center of this, plays a key role in mediating an aggressive disease state, particularly in solid tumors such as breast cancer. Subsequently, elucidating the role of HIF1 in establishing the diabetes-breast cancer link on hypoxia-hyperglycemia axis may not only provide an insight into the molecular mechanisms underlying the association but also, illuminate on the prognostic outcome of the therapeutic targeting of HIF1 signaling in diabetic patients with breast cancer or vice versa. Hence, this review highlights the critical role of HIF1 signaling in patients with both T2DM and breast cancer, potentiates its significance as a prognostic marker in comorbid patients, and further discusses the potential prognostic outcome of targeting HIF1, subsequently establishing the pressing need for HIF1 molecular profiling-based patient selection leading to more effective therapeutic strategies emerging from personalized medicine.

HIF-1: structure, biology and natural modulators

Hypoxia-inducible factor 1 (HIF-1), as a main transcriptional regulator of metabolic adaptation to changes in the oxygen environment, participates in many physiological and pathological processes in the body, and is closely related to the pathogenesis of many diseases. This review outlines the mechanisms of HIF-1 activation, its signaling pathways, natural inhibitors, and its roles in diseases. This article can provide new insights in the diagnosis and treatment of human diseases, and recent progress on the development of HIF-1 inhibitors.

Photobiomodulation Therapy to Promote Angiogenesis in Diabetic Mice with Hindlimb Ischemia

Objective: To assess whether photobiomodulation therapy (PBMT) induces angiogenesis in diabetic mice with hindlimb ischemia (HLI). Background: Patients with diabetes mellitus (DM) are at high risk of developing peripheral arterial disease (PAD) in the lower extremities. PBMT has been shown to promote angiogenesis both in vitro and in vivo and could be a treatment for DM patients with PAD. Methods: Femoral artery ligation/excision in mice was performed to induce HLI as an animal model of PAD. PBMT at a dose of 660 nm and 1.91 J/cm² was delivered for 10 min on 5 consecutive days after the HLI surgery. Control mice received HLI only. Mice in the DM group were injected with streptozocin to induce diabetes before HLI surgery. Mice in the laser and DM+ laser groups received both HLI and PBMT, and the latter group had induced DM. After the laser treatment, lower limb blood flow was evaluated by laser Doppler. The capillary density and CD31 were analyzed by immunofluorescence staining, and protein levels of vascular endothelial growth factor (VEGF)-A, hypoxia-inducible factor-1α (HIF-1α), inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), and extracellular signal-regulated kinases (ERK) were measured by Western blotting of tissue samples. Results: Compared with the control and DM mice, the laser and DM+ laser groups had more than double the capillary density and blood perfusion rate. Levels of CD31 and VEGF-A proteins in groups that received laser were increased by 1.9- to 3.2-fold compared with groups that did not undergo laser treatment. Animals treated with PBMT exhibited significantly increased HIF-1α expression and ERK phosphorylation compared with animals that did not receive this treatment, and the amount of phospho-eNOS and iNOS increased and decreased, respectively. Conclusions: PBMT can induce therapeutic angiogenesis, indicating that low intensity laser could be a novel treatment for PAD patients.

Metabolic reprogramming due to hypoxia in pancreatic cancer: Implications for tumor formation, immunity, and more

Hypoxia is a common phenomenon in most malignant tumors, especially in pancreatic cancer (PC). Hypoxia is the result of unlimited tumor growth and plays an active role in promoting tumor survival, progression, and invasion. As the part of the hypoxia microenvironment in PC is gradually clarified, hypoxia is becoming a key determinant and an important therapeutic target of pancreatic cancer. To adapt to the severe hypoxia environment, cells have changed their metabolic phenotypes to maintain their survival and proliferation. Enhanced glycolysis is the most prominent feature of cancer cells' metabolic reprogramming in response to hypoxia. It provides the energy source for hypoxic cancer cells (although it provides less than oxidative phosphorylation) and produces metabolites that can be absorbed and utilized by normoxic cancer cells. In addition, the uptake of glutamine and fatty acids by hypoxic cancer cells is also increased, which is also conducive to tumor progression. Their metabolites are pooled in the hexosamine biosynthesis pathway (HBP). As a nutrition sensor, HBP, in turn, can coordinate glucose and glutamine metabolism. Its end product, UDP-GlcNAc, is the substrate of protein post-translational modification (PTM) involved in various signaling pathways supporting tumor progression. Adaptive metabolic changes of cancer cells promote their survival and affect tumor immune cells in the tumor microenvironment (TME), which contributes to tumor immunosuppressive microenvironment and induces tumor immunotherapy resistance. Here, we summarize the hypoxic microenvironment, its effect on metabolic reprogramming, and its contribution to immunotherapy resistance in pancreatic cancer.

Kinomic profile in patient-derived glioma cells during hypoxia reveals c-MET-PI3K dependency for adaptation

Hypoxic microenvironment is a hallmark of solid tumors, especially glioblastoma. The strong reliance of glioma-propagating cells (GPCs) on hypoxia-induced survival advantages is potentially exploitable for drug development. Methods: To identify key signaling pathways for hypoxia adaptation by patient-derived GPCs, we performed a kinase inhibitor profiling by screening 188 small molecule inhibitors against 130 different kinases in normoxia and hypoxia. Potential kinase candidates were prioritized for in vitro and in vivo investigations using a ranking algorithm that integrated information from the kinome connectivity network and estimated patients' survival based on expression status. Results: Hypoxic drug screen highlighted extensive modifications of kinomic landscape and a crucial functionality of c-MET-PI3K. c-MET inhibitors diminished phosphorylation of c-MET and PI3K in GPCs subjected to hypoxia, suggesting its role in the hypoxic adaptation of GPCs. Mechanistically, the inhibition of c-MET and PI3K impaired antioxidant defense, leading to oxidative catastrophe and apoptosis. Repurposed c-MET inhibitors PF04217903 and tivantinib exhibited hypoxic-dependent drug synergism with temozolomide, resulting in reduced tumor load and growth of GPC xenografts. Detailed analysis of bulk and single-cell glioblastoma transcriptomes associates the cellular subpopulation over-expressing c-MET with inflamed, hypoxic, metastatic, and stem-like phenotypes. Conclusions: Thus, our "bench to bedside (the use of patient-derived GPCs and xenografts for basic research) and back (validation with independent glioblastoma transcriptome databases)" analysis unravels the novel therapeutic indications of c-MET and PI3K/Akt inhibitors for the treatment of glioblastoma, and potentially other cancers, in the hypoxic tumor microenvironment.

Hypoxia-induced alternative splicing in human diseases: the pledge, the turn, and the prestige

Maintenance of oxygen homeostasis is an indispensable criterion for the existence of multicellular life-forms. Disruption of this homeostasis due to inadequate oxygenation of the respiring tissues leads to pathological hypoxia, which acts as a significant stressor in several pathophysiological conditions including cancer, cardiovascular defects, bacterial infections, and neurological disorders. Consequently, the hypoxic tissues develop necessary adaptations both at the tissue and cellular level. The cellular adaptations involve a dramatic alteration in gene expression, post-transcriptional and post-translational modification of gene products, bioenergetics, and metabolism. Among the key responses to oxygen-deprivation is the skewing of cellular alternative splicing program. Herein, we discuss the current concepts of oxygen tension-dependent alternative splicing relevant to various pathophysiological conditions. Following a brief description of cellular response to hypoxia and the pre-mRNA splicing mechanism, we outline the impressive number of hypoxia-elicited alternative splicing events associated with maladies like cancer, cardiovascular diseases, and neurological disorders. Furthermore, we discuss how manipulation of hypoxia-induced alternative splicing may pose promising strategies for novel translational diagnosis and therapeutic interventions.

Application of Advanced Mass Spectrometry-Based Proteomics to Study Hypoxia Driven Cancer Progression

Cancer is one of the largest contributors to the burden of chronic disease in the world and is the second leading cause of death globally. It is associated with episodes of low-oxygen stress (hypoxia or ischemia/reperfusion) that promotes cancer progression and therapeutic resistance. Efforts have been made in the past using traditional proteomic approaches to decipher oxygen deprivation stress-related mechanisms of the disease initiation and progression and to identify key proteins as a therapeutic target for the treatment and prevention. Despite the potential benefits of proteomic in translational research for the discovery of new drugs, the therapeutic outcome with this approach has not met expectations in clinical trials. This is mainly due to the disease complexity which possess a multifaceted molecular pathology. Therefore, novel strategies to identify and characterize clinically important sets of modulators and molecular events for multi-target drug discovery are needed. Here, we review important past and current studies on proteomics in cancer with an emphasis on recent pioneered labeling approaches in mass spectrometry (MS)-based systematic quantitative analysis to improve clinical success. We also discuss the results of the selected innovative publications that integrate advanced proteomic technologies (e.g. MALDI-MSI, pSILAC/SILAC/iTRAQ/TMT-LC-MS/MS, MRM-MS) for comprehensive analysis of proteome dynamics in different biosystems, including cell type, cell species, and subcellular proteome (i.e. secretome and chromatome). Finally, we discuss the future direction and challenges in the application of these technological advancements in mass spectrometry within the context of cancer and hypoxia.

Alternative regulation of HIF-1α stability through Phosphorylation on Ser451

The hypoxia-inducible factor (HIF-1α) functions as a master regulator of oxygen homeostasis. Oxygen-dependent hydroxylation of HIF-1α is tightly regulated by prolyl hydroxylase domain containing proteins (PHD1, PHD2, and PHD3). The prolyl hydroxylation facilitates the recruitment of the von Hippel-Lindau (VHL) protein, leading to ubiquitination and degradation of HIF-1α by the proteasomes. Besides prolyl hydroxylation, phosphorylation of HIF-1α is another central post-translational modification, which regulates its stability under hypoxic conditions as well as normoxic conditions. By use of LC/MS/MS-based analysis, we were able to identify a specific serine residue (Ser451) of HIF-1α phosphorylated under hypoxic conditions. Using plasmids expressing wild type (WT), non-phosphorylatable mutant HIF-1α (S451A), and phosphomimetic mutant HIF-1α (S451E), we demonstrated that the phosphorylation at Ser451 is important in maintaining the HIF-1α protein stability. Notably, phosphorylation at S451 interrupts the interaction of HIF-1α with PHD and pVHL. A phosphomimetic construct of HIF-1α at Ser451 (S451E) is significantly more stable than WT HIF-1α under normoxic conditions. Cells transfected with unphosphorylatable HIF-1α exhibited significantly lower HIF-1 transcriptional activity than WT cells and markedly reduced tumor cell migration. Further, tumors derived from the phosphomimetic mutant cells grew faster, whereas the tumors derived from non-phosphorylatable mutant cells grew slower than the control tumors, suggesting that the phosphorylation of HIF-1α at the Ser451 site is critical to promote tumor growth in vivo. Taken together, our data suggest an alternative mechanism responsible for the regulation of HIF-1α stability.

Tumor Microenvironment and Nitric Oxide: Concepts and Mechanisms

The cancer tissue exists not as a single entity, but as a combination of different cellular phenotypes which, taken together, dramatically contribute to the entirety of their ecosystem, collectively termed as the tumor microenvironment (TME). The TME is composed of both immune and nonimmune cell types, stromal components, and vasculature-all of which cooperate to promote cancer progression. Not all immune cells, however, are immune-suppressive; some of them can promote the immune microenvironment to fight the invading and uncontrollably dividing cell populations at the initial stages of tumor growth. Yet, many of these processes and cellular phenotypes fall short, and the immune ecosystem more often than not ends up stabilizing in favor of the "resistant" resident cells that begin clonal expansion and may progress to metastatic forms. Stromal components, making up the extracellular matrix and basement membrane, are also not the most innocuous: CAFs embedded throughout secrete proteases that allow the onset of one of the most invasive processes-angiogenesis-through destruction of the ECM and the basement membrane. Vasculature formation, because of angiogenesis, is the largest invader of the TME and the reason metastasis happens. Vasculature is so sporadic and omnipresent in the TME that most drug therapies are mainly focused on stopping this uncontrollable process. As the tumor continues to grow, different processes are constantly supplying it with the ingredients favorable for tumor progression and eventual metastasis. For example, angiogenesis promotes blood vessel formation that will allow the bona fide escape of tumor cells to take place. Another process like hypoxia will present itself in several forms throughout the tumor (mild or acute, cycling or permanent), starting mechanisms such as epithelial to mesenchymal transitions (EMT) of resident cells and inadvertently placing the cells in such a stressful condition that production of ROS and DNA damage is unavoidable. DNA damage can induce mutagenicity while allowing resistant cells to survive. This is where drugs and treatments can subsequently suffer in effectiveness. Finally, another molecule has just surfaced as being a very important player in the TME: nitric oxide. Often overlooked and equated with ROS and initially assigned in the category of pathogenic molecules, nitric oxide can definitely do some damage by causing metabolic reprogramming and promotion of immunosuppressive phenotypes at low concentrations. However, its actions seem to be extremely dose-dependent, and this issue has become a hot target of current treatment goals. Shockingly, nitric oxide, although omnipresent in the TME, can have a positive effect on targeting the TME broadly. Thus, while the TME is a myriad of cellular phenotypes and a combination of different tumor-promoting processes, each process is interconnected into one whole: the tumor microenvironment.