The subtle side to hypoxia inducible factor (HIFalpha) regulation

β Cell and Autophagy: What Do We Know?

Pancreatic β cells are central to glycemic regulation through insulin production. Studies show autophagy as an essential process in β cell function and fate. Autophagy is a catabolic cellular process that regulates cell homeostasis by recycling surplus or damaged cell components. Impaired autophagy results in β cell loss of function and apoptosis and, as a result, diabetes initiation and progress. It has been shown that in response to endoplasmic reticulum stress, inflammation, and high metabolic demands, autophagy affects β cell function, insulin synthesis, and secretion. This review highlights recent evidence regarding how autophagy can affect β cells' fate in the pathogenesis of diabetes. Furthermore, we discuss the role of important intrinsic and extrinsic autophagy modulators, which can lead to β cell failure.

Mechanistic and therapeutic perspectives of baicalin and baicalein on pulmonary hypertension: A comprehensive review

Pulmonary hypertension (PH) is a chronic and fatal disease, for which new therapeutic drugs and approaches are needed urgently. Baicalein and baicalin, the active compounds of the traditional Chinese medicine, Scutellaria baicalensis Georgi, exhibit a wide range of pharmacological activities. Numerous studies involving in vitro and in vivo models of PH have revealed that the treatment with baicalin and baicalein may be effective. This review summarizes the potential mechanisms driving the beneficial effects of baicalin and baicalein treatment on PH, including anti-inflammatory response, inhibition of pulmonary smooth muscle cell proliferation and endothelial-to-mesenchymal transformation, stabilization of the extracellular matrix, and mitigation of oxidative stress. The pharmacokinetics of these compounds have also been reviewed. The therapeutic potential of baicalin and baicalein warrants their continued study as natural treatments for PH.

Hypoxia-inducible factors: master regulators of hypoxic tumor immune escape

Hypoxia, a common feature of the tumor microenvironment in various types of cancers, weakens cytotoxic T cell function and causes recruitment of regulatory T cells, thereby reducing tumoral immunogenicity. Studies have demonstrated that hypoxia and hypoxia-inducible factors (HIFs) 1 and 2 alpha (HIF1A and HIF2A) are involved in tumor immune escape. Under hypoxia, activation of HIF1A induces a series of signaling events, including through programmed death receptor-1/programmed death ligand-1. Moreover, hypoxia triggers shedding of complex class I chain-associated molecules through nitric oxide signaling impairment to disrupt immune surveillance by natural killer cells. The HIF-1-galactose-3-O-sulfotransferase 1-sulfatide axis enhances tumor immune escape via increased tumor cell-platelet binding. HIF2A upregulates stem cell factor expression to recruit tumor-infiltrating mast cells and increase levels of cytokines interleukin-10 and transforming growth factor-β, resulting in an immunosuppressive tumor microenvironment. Additionally, HIF1A upregulates expression of tumor-associated long noncoding RNAs and suppresses immune cell function, enabling tumor immune escape. Overall, elucidating the underlying mechanisms by which HIFs promote evasion of tumor immune surveillance will allow for targeting HIF in tumor treatment. This review discusses the current knowledge of how hypoxia and HIFs facilitate tumor immune escape, with evidence to date implicating HIF1A as a molecular target in such immune escape. This review provides further insight into the mechanism of tumor immune escape, and strategies for tumor immunotherapy are suggested.

Gain of HIF1 Activity and Loss of miRNA let-7d Promote Breast Cancer Metastasis to the Brain via the PDGF/PDGFR Axis

Early detection and adjuvant therapies have significantly improved survival of patients with breast cancer over the past three decades. In contrast, management of metastatic disease remains unresolved. Brain metastasis is a late complication frequently observed among patients with metastatic breast cancer, whose poor prognosis calls for novel and more effective therapies. Here, we report that active hypoxia inducible factor-1 (HIF1) signaling and loss of the miRNA let-7d concur to promote brain metastasis in a recently established model of spontaneous breast cancer metastasis from the primary site to the brain (4T1-BM₂), and additionally in murine and human experimental models of breast cancer brain metastasis (D2A1-BM₂ and MDA231-BrM₂). Active HIF1 and let-7d loss upregulated expression of platelet-derived growth factor (PDGF) B/A in murine and human brain metastatic cells, respectively, while either individual silencing of HIF1α and PDGF-A/B or let-7d overexpression suppressed brain metastasis formation in the tested models. Let-7d silencing upregulated HIF1α expression and HIF1 activity, indicating a regulatory hierarchy of the system. The clinical relevance of the identified targets was supported by human gene expression data analyses. Treatment of mice with nilotinib, a kinase inhibitor impinging on PDGF receptor (PDGFR) signaling, prevented formation of spontaneous brain metastases in the 4T1-BM₂ model and reduced growth of established brain metastases in mouse and human models. These results identify active HIF1 signaling and let-7d loss as coordinated events promoting breast cancer brain metastasis through increased expression of PDGF-A/B. Moreover, they identify PDGFR inhibition as a potentially actionable therapeutic strategy for patients with brain metastatis. SIGNIFICANCE: These findings show that loss of miRNA let-7d and active HIF1 signaling promotes breast cancer brain metastasis via PDGF and that pharmacologic inhibition of PDGFR suppresses brain metastasis, suggesting novel therapeutic opportunities. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/3/594/F1.large.jpg.See related article by Thies et al., p. 606.

Hypoxia-inducible factors and diabetes

Hypoxia can be defined as a relative deficiency in the amount of oxygen reaching the tissues. Hypoxia-inducible factors (HIFs) are critical regulators of the mammalian response to hypoxia. In normal circumstances, HIF-1α protein turnover is rapid, and hyperglycemia further destabilizes the protein. In addition to their role in diabetes pathogenesis, HIFs are implicated in development of the microvascular and macrovascular complications of diabetes. Improving glucose control in people with diabetes increases HIF-1α protein and has wide-ranging benefits, some of which are at least partially mediated by HIF-1α. Nevertheless, most strategies to improve diabetes or its complications via regulation of HIF-1α have not currently proven to be clinically useful. The intersection of HIF biology with diabetes is a complex area in which many further questions remain, especially regarding the well-conducted studies clearly describing discrepant effects of different methods of increasing HIF-1α, even within the same tissues. This Review presents a brief overview of HIFs; discusses the range of evidence implicating HIFs in β cell dysfunction, diabetes pathogenesis, and diabetes complications; and examines the differing outcomes of HIF-targeting approaches in these conditions.

Neddylation activity modulates the neurodegeneration associated with fragile X associated tremor/ataxia syndrome (FXTAS) through regulating Sima

Fragile X associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by expansion of CGG repeats in the 5' UTR of the fragile X mental retardation 1 (FMR1) gene. Using the well-established FXTAS Drosophila model, we performed a high-throughput chemical screen using 3200 small molecules. NSC363998 was identified to suppress the neurodegeneration caused by riboCGG (rCGG) repeats. Three predicted targets of a NSC363998 derivative are isopeptidases in the neddylation pathway and could modulate the neurotoxicity caused by the rCGG repeats. Decreasing levels of neddylation resulted in enhancing neurodegeneration phenotypes, while up-regulation could rescue the phenotypes. Furthermore, known neddylation substrates, Cul3 and Vhl, and their downstream target, Sima, were found to modulate rCGG₉₀-dependent neurotoxicity. Our results suggest that altered neddylation activity can modulate the rCGG repeat-mediated toxicity by regulating Sima protein levels, which could serve as a potential therapeutic target for FXTAS.

A biophotonic approach to measure pH in small volumes in vitro: Quantifiable differences in metabolic flux around the cumulus-oocyte-complex (COC)

Unfertilised eggs (oocytes) release chemical biomarkers into the medium surrounding them. This provides an opportunity to monitor cell health and development during assisted reproductive processes if detected in a non-invasive manner. Here we report the measurement of pH using an optical fibre probe, OFP1, in 5 μL drops of culture medium containing single mouse cumulus oocyte complexes (COCs). This allowed for the detection of statistically significant differences in pH between COCs in culture medium with no additives and those incubated with either a chemical (cobalt chloride) or hormonal treatment (follicle stimulating hormone); both of which serve to induce the release of lactic acid into the medium immediately surrounding the COC. Importantly, OFP1 was shown to be cell-safe with no inherent cell toxicity or light-induced phototoxicity indicated by negative DNA damage staining. Pre-measurement photobleaching of the probe reduced fluorescence signal variability, providing improved measurement precision (0.01-0.05 pH units) compared to previous studies. This optical technology presents a promising platform for the measurement of pH and the detection of other extracellular biomarkers to assess cell health during assisted reproduction.

The Phosphatase SHP-2 Activates HIF-1α in Wounds In Vivo by Inhibition of 26S Proteasome Activity

Vascular remodeling and angiogenesis are required to improve the perfusion of ischemic tissues. The hypoxic environment, induced by ischemia, is a potent stimulus for hypoxia inducible factor 1α (HIF-1α) upregulation and activation, which induce pro-angiogenic gene expression. We previously showed that the tyrosine phosphatase SHP-2 drives hypoxia mediated HIF-1α upregulation via inhibition of the proteasomal pathway, resulting in revascularization of wounds in vivo. However, it is still unknown if SHP-2 mediates HIF-1α upregulation by affecting 26S proteasome activity and how the proteasome is regulated upon hypoxia. Using a reporter construct containing the oxygen-dependent degradation (ODD) domain of HIF-1α and a fluorogenic proteasome substrate in combination with SHP-2 mutant constructs, we show that SHP-2 inhibits the 26S proteasome activity in endothelial cells under hypoxic conditions in vitro via Src kinase/p38 mitogen-activated protein kinase (MAPK) signalling. Moreover, the simultaneous expression of constitutively active SHP-2 (E76A) and inactive SHP-2 (CS) in separate hypoxic wounds in the mice dorsal skin fold chamber by localized magnetic nanoparticle-assisted lentiviral transduction showed specific regulation of proteasome activity in vivo. Thus, we identified a new additional mechanism of SHP-2 mediated HIF-1α upregulation and proteasome activity, being functionally important for revascularization of wounds in vivo. SHP-2 may therefore constitute a potential novel therapeutic target for the induction of angiogenesis in ischemic vascular disease.

Effects of islet neogenesis associated protein depend on vascular endothelial growth factor gene expression modulated by hypoxia-inducible factor 1-alpha

BACKGROUND

Pharmacology has provided efficient tools to improve insulin effect/secretion but the decrease in β-cell mass remains elusive. INGAP-PP could provide a therapeutic alternative to meet that challenge.

AIM

To further understand the mechanism that links INGAP-PP effects upon β-cell mass and function with islet angiogenesis.

METHODOLOGY

Normal male Wistar rats were divided into 2 groups and injected with a single dose of 100 mg/Kg suramin or saline. Both groups were divided into 2 subgroups that received daily doses of 2 mg/kg INGAP-PP or saline for ten days. Plasma glucose, triacylglycerol, TBARS, and insulin levels were measured. Pancreas immunomorphometric analyses were also performed. Pancreatic islets were isolated to measure glucose-stimulated insulin secretion (GSIS). Specific islet mRNA levels were studied by qRT-PCR. Statistical analysis was done using ANOVA.

RESULTS

No differences were recorded in body weight, food intake, or any other plasma parameter measured in all groups. Islets from INGAP-PP-treated rats significantly increased GSIS, β-cell mass, and mRNA levels of Bcl-2, Ngn-3, VEGF-A, VEGF-R2, CD31, Ang1 and Ang2, Laminin β-1, and Integrin β-1, and decreased mRNA levels of Caspase-8, Bad, and Bax. Islets from suramin-treated rats showed significant opposite effects, but INGAPP-PP administration rescued most of the suramin effects in animals treated with both compounds.

CONCLUSION

Our results reinforce the concept that INGAP-PP enhances insulin secretion and β-cell mass, acting through PI3K/Akt/mTOR pathways and simultaneously activating angiogenesis through HIF-1α-mediated VEGF-A secretion. Therefore, INGAP-PP might be a suitable antidiabetic agent able to overcome two major alterations present in T2D.

Stabilization of E2-EPF UCP protein is implicated in hepatitis B virus-associated hepatocellular carcinoma progression

Hepatitis B virus (HBV) X protein (HBx) is associated with hepatocarcinogenesis. E2-EPF ubiquitin carrier protein (UCP) catalyzes ubiquitination of itself and von Hippel-Lindau protein (pVHL) for degradation and associates with tumor growth and metastasis. However, it remains unknown whether HBx modulates the enzyme activity of UCP and thereby influences hepatocarcinogenesis. Here, we show that UCP is highly expressed in liver tissues of HBx-transgenic mice, but not non-transgenic mice. UCP was more frequently expressed in HBV-positive liver cancers than in HBV-negative liver cancers. HBx binds to UCP specifically and serotype independently, and forms a ternary complex with UCP and pVHL. HBx inhibits self-ubiquitination of UCP, but enhances UCP-mediated pVHL ubiquitination, resulting in stabilization of hypoxia-inducible factor-1α and -2α. HBx and UCP stabilize each other by mutually inhibiting their ubiquitination. HBx promotes cellular proliferation and metastasis via UCP. Our findings suggest that UCP plays a key role in HBV-related hepatocarcinogenesis.

β Cell Hypoxia-Inducible Factor-1α Is Required for the Prevention of Type 1 Diabetes

The development of autoimmune disease type 1 diabetes (T1D) is determined by both genetic background and environmental factors. Environmental triggers include RNA viruses, particularly coxsackievirus (CV), but how they induce T1D is not understood. Here, we demonstrate that deletion of the transcription factor hypoxia-inducible factor-1α (HIF-1α) from β cells increases the susceptibility of non-obese diabetic (NOD) mice to environmentally triggered T1D from coxsackieviruses and the β cell toxin streptozotocin. Similarly, knockdown of HIF-1α in human islets leads to a poorer response to coxsackievirus infection. Studies in coxsackievirus-infected islets demonstrate that lack of HIF-1α leads to impaired viral clearance, increased viral load, inflammation, pancreatitis, and loss of β cell mass. These findings show an important role for β cells and, specifically, lack of β cell HIF-1α in the development of T1D. These data suggest new strategies for the prevention of T1D.

Multiparametric High-Resolution MRI as a Tool for Mapping of Hypoxic Level in Tumors

Hypoxia is a condition, common to most malignant tumors, where oxygen tension in the tissue is below the physiological level. Among consequences of tumor hypoxia is also altered cancer cell metabolism that contributes to cancer therapy resistance. Therefore, precise assessment of tumor hypoxia is important for monitoring the tumor treatment progression. In this study, we propose a simple model for prediction of hypoxic level in tumors based on multiparametric magnetic resonance imaging. The study was performed on B16F1 murine melanoma tumors ex vivo that were first magnetic resonance scanned and then analyzed for hypoxic level using hypoxia-inducable factor 1-alpha antibody staining. Each tumor was analyzed in identical sections and in identical regions of interest for pairs of hypoxic level and magnetic resonance values (apparent diffusion coefficient and T₂). This was followed by correlation analysis between hypoxic level and respective magnetic resonance values. A moderate correlation was found between hypoxic level and apparent diffusion coefficient (ρ = 0.56, P < .00001) and lower between hypoxic level and T₂ (ρ = 0.38, P < .00001). The data were analyzed further to obtain simple predictive models based on the multiple linear regression analysis of the measured hypoxic level (dependent variable) and apparent diffusion coefficient and T₂ (independent variables). Among the hypoxic level models, the most efficient was the 3-parameter model given by relation (HL = k_ADCADC + k_T2T₂ + b), where k_ADC = 26%/µm²/ms, k_T2 = 0.8%/ms, and b = −32%. The model can be used for calculation of the predicted hypoxic level map based on magnetic resonance–measured apparent diffusion coefficient and T₂ maps. Similar prediction models, based on tumor apparent diffusion coefficient and T₂ maps, can be done also for other tumor types in vivo and can therefore help in assessment of tumor treatment as well as to better understand the role of hypoxia in cancer progression.

Progesterone attenuates airway remodeling and glucocorticoid resistance in a murine model of exposing to ozone

Airway remodeling is a vital component of chronic obstructive pulmonary disease (COPD). Despite the broad anti-inflammation effects of glucocorticoids, they exhibit relatively little therapeutic benefit in COPD, indicating the accelerating demands of new agents for COPD. We aim to explore the effect of progesterone on airway remodeling in a murine modeling of exposing to ozone and to further examine the potential effect of progesterone on glucocorticoid insensitivity. C57/BL6 mice were exposed to ozone for 12 times over 6 weeks, and were administered with progesterone alone or combined with budesonide (BUD) after each exposure until the 10th week. The peribronchial collagen deposition was measured. The protein levels of MMP8 and MMP9 in bronchoalveolar lavage fluid (BALF) and lungs were assessed. Western blot analysis was used to detect the levels of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), a-smooth muscle actin (α-SMA), glycogen synthase kinase-3β (GSK-3β). The expression of VEGF and histone deacetylase 2 (HDAC2) in the lung were determined by Immunohistochemical analyses. We observe that progesterone attenuates the peribronchial collagen deposition, as well as the expression of MMP8, MMP9, HIF-1α, VEGF, α-SMA, and GSK-3β in BALF or lung tissues. Progesterone or BUD monotherapy has no effect on HDAC2 production. Progesterone combines with BUD induce dramatically enhanced effects. Thus, these results demonstrate novel roles of progesterone for the pathogenesis and airway remodeling in COPD. Progesterone plus BUD administration exerts more significant inhibition on airway remodeling with dose-independent. Additionally, progesterone may, to some extent, improve the glucocorticoid insensitivity.

Mechanisms and Mitochondrial Redox Signaling in Photobiomodulation

Photobiomodulation (PBM) involves the use of red or near-infrared light at low power densities to produce a beneficial effect on cells or tissues. PBM therapy is used to reduce pain, inflammation, edema, and to regenerate damaged tissues such as wounds, bones, and tendons. The primary site of light absorption in mammalian cells has been identified as the mitochondria and, more specifically, cytochrome c oxidase (CCO). It is hypothesized that inhibitory nitric oxide can be dissociated from CCO, thus restoring electron transport and increasing mitochondrial membrane potential. Another mechanism involves activation of light or heat-gated ion channels. This review will cover the redox signaling that occurs in PBM and examine the difference between healthy and stressed cells, where PBM can have apparently opposite effects. PBM has a marked effect on stem cells, and this is proposed to operate via mitochondrial redox signaling. PBM can act as a preconditioning regimen and can interact with exercise on muscles.

Prognostic value of plasma levels of HIF-1a and PGC-1a in breast cancer

Cellular adaptive mechanisms are crucial for tumorigenesis and a common feature in solid tumor progression. Hypoxia-inducible factor-1α (HIF-1α) facilitates the biological response to hypoxia, advancing angiogenesis and metastatic potential of the tumor. The peroxisome proliferator–activated receptor γ coactivators 1α (PGC-1α) enhances mitochondrial biogenesis, favored by migratory/invasive cancer cells. We conducted a prospective, long-term follow up study to determine whether HIF-1α and PGC-1α can be implemented as predictive biomarker in breast cancer. HIF-1α and PGC-1α plasma concentrations were measured in patients and in healthy controls by enzyme linked immune sorbent assay. Breast cancer patients had significantly higher HIF-1α and PGC-1α levels, which correlated with clinicopathological features, overall with more aggressive cancer characteristics. Disease free and overall survival of breast cancer patients with high HIF-1α and PGC-1α were significantly poorer than in patients with low plasma levels. In multivariate analysis, high amount of PGC-1α showed independent prognostic value. Our data suggests that HIF-1α and PGC-1α may be promising, noninvasive, biomarkers with a high potential for future clinical implication to identify subgroups of patients with poorer prognosis and to indicate early, subclinical metastasis.