High-altitude pulmonary edema is aggravated by risk loci and associated transcription factors in HIF-prolyl hydroxylases.

High-altitude (HA, >2500 m) hypoxic exposure evokes several physiological processes that may be abetted by differential genetic distribution in sojourners, who are susceptible to various HA disorders, such as high-altitude pulmonary edema (HAPE). The genetic variants in hypoxia-sensing genes influence the transcriptional output; however the functional role has not been investigated in HAPE. This study explored the two hypoxia-sensing genes, prolyl hydroxylase domain protein 2 (EGLN1) and factor inhibiting HIF-1α (HIF1AN) in HA adaptation and maladaptation in three well-characterized groups: highland natives, HAPE-free controls and HAPE-patients. The two genes were sequenced and subsequently validated through genotyping of significant single nucleotide polymorphisms (SNPs), haplotyping and multifactor dimensionality reduction. Three EGLN1 SNPs rs1538664, rs479200 and rs480902 and their haplotypes emerged significant in HAPE. Blood gene expression and protein levels also differed significantly (P < 0.05) and correlated with clinical parameters and respective alleles. The RegulomeDB annotation exercises of the loci corroborated regulatory role. Allele-specific differential expression was evidenced by luciferase assay followed by electrophoretic mobility shift assay, liquid chromatography with tandem mass spectrometry and supershift assays, which confirmed allele-specific transcription factor (TF) binding of FUS RNA-binding protein (FUS) with rs1538664A, Rho GDP dissociation inhibitor 1 (ARHDGIA) with rs479200T and hypoxia upregulated protein 1 (HYOU1) with rs480902C. Docking simulation studies were in sync for the DNA-TF structural variations. There was strong networking among the TFs that revealed physiological consequences through relevant pathways. The two hydroxylases appear crucial in the regulation of hypoxia-inducible responses.

Strong Prolyl Hydroxylase Domain 1 Expression Predicts Poor Outcome in Radiotherapy-treated Patients with Classical Hodgkin's Lymphoma.

BACKGROUND: Hypoxia-inducible factors (HIFs) and prolyl hydroxylase domain (PHD) proteins control cellular oxygen homeostasis and a wide range of other processes. MATERIALS AND METHODS: We immunohistochemically assessed the expression of HIF1α, HIF2α, PHD1, PHD2 and PHD3 in 115 cases of classical Hodgkin's lymphoma, all treated in the first line with doxorubicin, bleomycin, vinblastine and darcabazine (ABVD) chemotherapy. RESULTS: In advanced-stage patients treated with involved-field radiotherapy (IFRT), nuclear HIF1α expression in reactive cellular infiltrate predicted prolonged relapse-free survival (RFS) (p=0.026). Strong cytoplasmic PHD1 expression in Reed-Sternberg cells was associated with poor RFS among patients treated with IFRT and advanced-stage patients treated with ABVD and IFRT (p=0.0028 and p=0.0058, respectively). In Cox regression analysis, PHD1 was a more significant predictor of relapse (risk ratio=18.383; 95% confidence interval(CI)=1.521-222.246; p=0.022) than the International Prognostic Score. CONCLUSION: HIF and PHD expression appear to be novel prognostic biomarkers in classical Hodgkin's lymphoma.

Structure-activity relationship for branched oxyquinoline HIF activators: Effect of modifications to phenylacetamide "tail".

HIF prolyl hydroxylase is a major regulator of HIF stability. Branched tail oxyquinolines have been identified as specific inhibitors of HIF prolyl hydroxylase and recently demonstrated clear benefits in various scenarios of neuronal failure. The structural optimization for branched tail oxyquinolines containing an acetamide bond has been performed in the present study using HIF1 ODD-luc reporter assay. The special attention has been paid to the length of a linker between acetamide group and phenyl ring, as well as substitutions in the phenyl ring in the other branch of the tail. The optimized version of branched tail oxyquinolines is 3-fold more potent than the original one identified before and shows a submicromolar EC50 in the reporter assay. The compounds have been studied in a "liver-on-a-chip" device to question their hepatotoxicity towards differentiated human HepaRG "hepatocytes": the absence of hepatotoxicity is observed up to 200 µM concentrations for all studied derivatives of branched tail oxyquinolines.

Prolyl hydroxylase domain proteins regulate bone mass through their expression in osteoblasts.

The roles of prolyl hydroxylase domain proteins (PHDs) in bone are incompletely understood. Here we deleted the expression of genes encoding PHD1, PHD2, and PHD3 in osteoblasts in mice by breeding the floxed Phd1-3 mice with Col1a1-Cre transgenic mice. Results showed that mice lacking PHD1-3 in osteoblasts (Phd1-3ob-/-) had increased bone mass. Bone parameters such as bone volume/tissue volume (BV/TV), trabecular number (Tb.N), and trabecular thickness (Tb.Th) were increased, while trabecular spacing (Tb.Sp) was decreased in Phd1-3ob-/- relative to wild-type (WT) femurs. In contrast, loss of PHD1-3 in osteoblasts did not alter cortical thickness (Cort.Th). The mineralization apposition rate (MAR) was increased in Phd1-3ob-/- bone compared to that of wild-type (WT) bone, demonstrating an enhancement of osteoblast function. Loss of PHD1-3 increased the number of osteoblast progenitors (CFU-OBs) in bone marrow cultures. Interestingly, deleting Phd1-3 genes in osteoblasts increased osteoclast formation in vitro and in bone.

Tuning the Transcriptional Response to Hypoxia by Inhibiting Hypoxia-inducible Factor (HIF) Prolyl and Asparaginyl Hydroxylases.

The hypoxia-inducible factor (HIF) system orchestrates cellular responses to hypoxia in animals. HIF is an α/ß-heterodimeric transcription factor that regulates the expression of hundreds of genes in a tissue context-dependent manner. The major hypoxia-sensing component of the HIF system involves oxygen-dependent catalysis by the HIF hydroxylases; in humans there are three HIF prolyl hydroxylases (PHD1-3) and an asparaginyl hydroxylase (factor-inhibiting HIF (FIH)). PHD catalysis regulates HIFα levels, and FIH catalysis regulates HIF activity. How differences in HIFα hydroxylation status relate to variations in the induction of specific HIF target gene transcription is unknown. We report studies using small molecule HIF hydroxylase inhibitors that investigate the extent to which HIF target gene expression is induced by PHD or FIH inhibition. The results reveal substantial differences in the role of prolyl and asparaginyl hydroxylation in regulating hypoxia-responsive genes in cells. PHD inhibitors with different structural scaffolds behave similarly. Under the tested conditions, a broad-spectrum 2-oxoglutarate dioxygenase inhibitor is a better mimic of the overall transcriptional response to hypoxia than the selective PHD inhibitors, consistent with an important role for FIH in the hypoxic transcriptional response. Indeed, combined application of selective PHD and FIH inhibitors resulted in the transcriptional induction of a subset of genes not fully responsive to PHD inhibition alone. Thus, for the therapeutic regulation of HIF target genes, it is important to consider both PHD and FIH activity, and in the case of some sets of target genes, simultaneous inhibition of the PHDs and FIH catalysis may be preferable.

Tetramethylpyrazine protects CoCl2-induced apoptosis in human umbilical vein endothelial cells by regulating the PHD2/HIF/1α-VEGF pathway.

Tetramethylpyrazine (TMP), one of the active ingredients isolated from a Chinese herbal prescription, possesses protective effects against apoptosis in endothelial cells. However, the underlying mechanism of its protective effects in endothelial cells remains to be elucidated. Using human umbilical vein endothelial cells (HUVECs), the present study assessed the protective effects of TMP on CoCl2-induced apoptosis. Following pre-incubation with CoCl2 (150 µM/ml) for 4 h, the HUVECs were treated with TMP at different concentrations (50, 100 and 200 µM/ml) for 8 h. TMP upregulated the expression of prolyl hydroxylase (PHD)2, reduced the protein and mRNA expression levels of vascular endothelial growth factor (VEGF), and reduced the expression of HIF-1α only at the protein level, not at the mRNA level in HUVECs, in a concentration-dependent manner. Furthermore, silencing of the PHD2 gene with small interfering (si)RNAs abolished the reduction in the expression of hypoxia-inducible factor (HIF)-1α and VEGF by TMP. In addition, TMP protected CoCl2-induced HUVEC injury via an apoptosis pathway, as characterized by the increased ratio of cell viability and the reduced percentage of apoptotic and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive HUVECs, activation of caspase-3, -8 and -9, B-cell lymphoma (Bcl)-2/Bcl-2-activated X protein expression, as well as the release of cytochrome c. The protective properties of TMP were partially attributed to the mRNA and protein expression levels of PHD, since silencing of the PHD2 gene with siRNAs abolished these effects. The present study demonstrated that the antiapoptotic effect of TMP in CoCl2-induced HUVECs was, at least in part, via the regulation of the PHD2/HIF-1α signaling pathway.

Ultrasound-targeted microbubble destruction (UTMD) assisted delivery of shRNA against PHD2 into H9C2 cells.

Gene therapy has great potential for human diseases. Development of efficient delivery systems is critical to its clinical translation. Recent studies have shown that microbubbles in combination with ultrasound (US) can be used to facilitate gene delivery. An aim of this study is to investigate whether the combination of US-targeted microbubble destruction (UTMD) and polyethylenimine (PEI) (UTMD/PEI) can mediate even greater gene transfection efficiency than UTMD alone and to optimize ultrasonic irradiation parameters. Another aim of this study is to investigate the biological effects of PHD2-shRNA after its transfection into H9C2 cells. pEGFP-N1 or eukaryotic shPHD2-EGFP plasmid was mixed with albumin-coated microbubbles and PEI to form complexes for transfection. After these were added into H9C2 cells, the cells were exposed to US with various sets of parameters. The cells were then harvested and analyzed for gene expression. UTMD/PEI was shown to be highly efficient in gene transfection. An US intensity of 1.5 W/cm2, a microbubble concentration of 300µl/ml, an exposure time of 45s, and a plasmid concentration of 15µg/ml were found to be optimal for transfection. UTMD/PEI-mediated PHD2-shRNA transfection in H9C2 cells significantly down regulated the expression of PHD2 and increased expression of HIF-1α and downstream angiogenesis factors VEGF, TGF-ß and bFGF. UTMD/PEI, combined with albumin-coated microbubbles, warrants further investigation for therapeutic gene delivery.

Expression of hypoxia-inducible factor prolyl hydroxylase 3 HIFPH3 in human non-small cell lung cancer (NSCLC) and its correlation with prognosis.

PURPOSE: To investigate the expression of hypoxia-inducible factor prolyl hydroxylase 3 (HIFPH3) in non-small cell lung cancer (NSCLC) and explore the correlation of HIFPH3 expression with lymph node metastasis and microvessel density (MVD). MATERIALS AND METHODS: A total of 73 cases of NSCLC specimens, 24 cases of para- cancerous tissues, and 20 normal pulmonary tissues were collected for HIFPH3 and CD31 immunohistochmical (IHC) study. Microvessel density (MVD) of the NSCLC tissues was also determined based on the expression of CD31. RESULTS: The expression of HIFPH3 in carcinoma tissue was statistically higher than para-cancerous and normal pulmonary tissues (χ2=48.806, p<0.05). Compared withthe negative lymph node metastasis group, the lymph node metastasis group showed significantly higher HIFPH3 expression (χ2=6.300, p<0.05). The strong HIFPH3+group displayed a significantly higher MVD than weak HIFPH3+ and HIFPH3- groups (p<0.05). No differences in positive HIFPH3 expression were noted regarding the tumor diameter, age, smoking status, gender of NSCLC patients, tumor size, histopathology, or differentiation. CONCLUSIONS: HIFPH3 expression in human NSCLC lesions is significantly higher than that in para-cancerous and normal lung tissues and is positively associated with lymph node metastasis and MVD.

Constitutive expression of HIF-α plays a major role in generation of clear-cell phenotype in human primary and metastatic renal carcinoma.

The extensive lipid accumulation occurring in clear-cell renal cell carcinoma (ccRCC) results in a clear-cell cytoplasm. Hypoxia-inducible factor α (HIF-α) is constitutively expressed in many ccRCC and transcriptionally regulates >100 genes. In a recent breakthrough study, HIF-1α induced ccRCC in transgenic mice. On the basis of these findings, we developed a hypothesis that accounted for HIF-α generation of the clear-cell phenotype. The aim of the present study was to use immunohistochemical staining methods in tissue microarray to determine the extent to which the clear-cell phenotype coincided with HIF-α expression in primary and metastatic ccRCC. In addition, we studied whether the prolyl-hydroxylases (PHD2,3) play a role in promoting the elevated expression of HIF-α in tumor cells. The clear-cell phenotype was observed in all primary and metastatic cases of ccRCC examined. A total of 168 renal cell carcinomas were evaluated by immunohistochemical methods; 141 of the 168 (84%) tumors expressed HIF-α (HIF-1α and/or HIF-2α). In contrast, HIF-α was expressed in only 1 of the 23 (4%) non-ccRCCs. These data supported the hypothesis that in the majority of the tumors HIF-α expression overlapped with the clear-cell phenotype and was indicative of an HIF-α-mediated lipid accumulation. In a smaller percentage of ccRCC cases (16%), HIF-α was not detected in the tumor cells and suggested that lipid accumulation by HIF-α-lipid-independent process. PHD3 was undetectable in both primary and metastatic ccRCC cases. We concluded that the undetectable PHD3 could contribute to the higher HIF-α expression in ccRCC.

Over-expression of prolyl hydroxylase-1 blocks NF-κB-mediated cyclin D1 expression and proliferation in lung carcinoma cells.

Prolyl hydroxylase-1 (PHD1), a member of the hypoxia inducible factor (HIF)-PHD family, plays an important role in regulating the stability of HIFs. The nuclear factor-κB (NF-κB) pathway consists of a family of transcription factors that play critical roles in inflammation, immunity, cell proliferation, differentiation, and survival. In this study, we demonstrate that PHD1 can inhibit NF-κB activity and its target genes in lung cancer cells based on both over-expression and RNA interference-mediated knockdown of PHD1 in human A549 lung cancer cells and HEK293 T cells. Of medical importance, PHD1 could induce cell cycle arrest in lung cancer cells, resulting in the suppression of cell proliferation. Xenograft tumor growth assays indicate that PHD1 plays a critical role in suppressing lung cancer growth. These findings reveal a new role of PHD1 in lung cancer and provide new treatment perspectives for cancer therapy by characterizing PHD1 as a potential target.