Toxin Homology Domain in Plant Type 2 Prolyl 4-Hydroxylases Acts as a Golgi Localization Domain.

Prolyl 4-hydroxylase (P4H) generates hydroxyproline residues in proteins. Two classes of P4H have been found in plants. Type 1 P4H has a signal anchor at the N-terminus, while type 2 P4H has both an N-terminal signal peptide and a C-terminal toxin homology domain (Tox1 domain) with six conserved cysteine residues. We analyzed the localization of tobacco type 2 P4H (NtP4H2.2) in tobacco BY-2 cells. Cell fractionation studies, immunostaining of cells, and GFP fusion study indicated that NtP4H2.2 localizes predominantly to the Golgi apparatus and is a peripheral membrane protein associated with the luminal side of organelles. Expression of the GFP-Tox1 domains of NtP4H2.2 and another tobacco type 2 P4H NtP4H2.1 in BY-2 cells and Arabidopsis epidermal cells indicated that these proteins were targeted to the Golgi. The Tox1 domains from Arabidopsis and rice type 2 P4Hs also directed GFP to the Golgi in tobacco BY-2 cells. The Tox1 domain of NtP4H2.2 increased the membrane association of GFP, and mutation of the cysteine residues in this domain abolished Golgi localization. Furthermore, the catalytic domain of NtP4H2.2 also directed GFP to the Golgi. Thus, the Tox1 domains of plant P4Hs are the Golgi localization domains, and tobacco P4H2.2 localizes to the Golgi by the action of both this domain and the catalytic domain.

Deleting the ribosomal prolyl hydroxylase OGFOD1 protects mice against diet-induced obesity and insulin resistance.

Type 2 diabetes predisposes patients to heart disease, which is the primary cause of death across the globe. Type 2 diabetes often accompanies obesity and is defined by insulin resistance and abnormal glucose handling. Insulin resistance impairs glucose uptake and results in hyperglycemia, which damages tissues such as kidneys, liver, and heart. 2-oxoglutarate (2-OG)- and iron-dependent oxygenases (2-OGDOs), a family of enzymes regulating various aspects of cellular physiology, have been studied for their role in obesity and diet-induced insulin resistance. However, nothing is known of the 2-OGDO family member 2-oxoglutarate and iron-dependent prolyl hydroxylase domain containing protein 1 (OGFOD1) in this setting. OGFOD1 deletion leads to protection in cardiac ischemia-reperfusion injury and cardiac hypertrophy, which are two cardiac events that can lead to heart failure. Considering the remarkable correlation between heart disease and diabetes, the cardioprotection observed in OGFOD1-knockout mice led us to challenge these knockouts with high-fat diet. Wildtype mice fed a high-fat diet developed diet-induced obesity, insulin resistance, and glucose intolerance, but OGFOD1 knockout mice fed this same diet were resistant to diet-induced obesity and insulin resistance. These results support OGFOD1 down-regulation as a strategy for preventing obesity and insulin handling defects.

Understanding Hypoxia-Driven Tumorigenesis: The Interplay of HIF1A, DNA Methylation, and Prolyl Hydroxylases in Head and Neck Squamous Cell Carcinoma.

Hypoxia-inducible factor 1-alpha (HIF1A) is a key transcription factor aiding tumor cells' adaptation to hypoxia, regulated by the prolyl hydroxylase family (EGLN1-3) by directing toward degradation pathways. DNA methylation potentially influences EGLN and HIF1A levels, impacting cellular responses to hypoxia. We examined 96 HNSCC patients and three cell lines, analyzing gene expression of EGLN1-3, HIF1A, CA9, VEGF, and GLUT1 at the mRNA level and EGLN1 protein levels. Methylation levels of EGLNs and HIF1A were assessed through high-resolution melting analysis. Bioinformatics tools were employed to characterize associations between EGLN1-3 and HIF1A expression and methylation. We found significantly higher mRNA levels of EGLN3, HIF1A, GLUT1, VEGF, and CA9 (p = 0.021; p < 0.0001; p < 0.0001; p = 0.004, and p < 0.0001, respectively) genes in tumor tissues compared to normal ones and downregulation of the EGLN1 mRNA level in tumor tissues (p = 0.0013). In HNSCC patients with hypermethylation of HIF1A in normal tissue, we noted a reduction in HIF1A mRNA levels compared to tumor tissue (p = 0.04). In conclusion, the differential expression of EGLN and HIF1A genes in HNSCC tumors compared to normal tissues influences patients' overall survival, highlighting their role in tumor development. Moreover, DNA methylation could be responsible for HIF1A suppression in the normal tissues of HNSCC patients.

P4HA2 hydroxylates SUFU to regulate the paracrine Hedgehog signaling and promote B-cell lymphoma progression.

Aberrations in the Hedgehog (Hh) signaling pathway are significantly prevailed in various cancers, including B-cell lymphoma. A critical facet of Hh signal transduction involves the dynamic regulation of the suppressor of fused homolog (SUFU)-glioma-associated oncogene homolog (GLI) complex within the kinesin family member 7 (KIF7)-supported ciliary tip compartment. However, the specific post-translational modifications of SUFU-GLI complex within this context have remained largely unexplored. Our study reveals a novel regulatory mechanism involving prolyl 4-hydroxylase 2 (P4HA2), which forms a complex with KIF7 and is essential for signal transduction of Hh pathway. We demonstrate that, upon Hh pathway activation, P4HA2 relocates alongside KIF7 to the ciliary tip. Here, it hydroxylates SUFU to inhibit its function, thus amplifying the Hh signaling. Moreover, the absence of P4HA2 significantly impedes B lymphoma progression. This effect can be attributed to the suppression of Hh signaling in stromal fibroblasts, resulting in decreased growth factors essential for malignant proliferation of B lymphoma cells. Our findings highlight the role of P4HA2-mediated hydroxylation in modulating Hh signaling and propose a novel stromal-targeted therapeutic strategy for B-cell lymphoma.

Arabidopsis pollen prolyl-hydroxylases P4H4/6 are relevant for correct hydroxylation and secretion of LRX11 in pollen tubes.

Major constituents of the plant cell walls are structural proteins that belong to the hydroxyproline-rich glycoprotein (HRGP) family. Leucine-rich repeat extensin (LRX) proteins contain a leucine-rich domain and a C-terminal domain with repetitive Ser-Pro3-5 motifs that are potentially to be O-glycosylated. It has been demonstrated that pollen-specific LRX8-LRX11 from Arabidopsis thaliana are necessary to maintain the integrity of the pollen tube cell wall during polarized growth. In HRGPs, including classical extensins (EXTs), and probably in LRXs, proline residues are converted to hydroxyproline by prolyl-4-hydroxylases (P4Hs), thus defining novel O-glycosylation sites. In this context, we aimed to determine whether hydroxylation and subsequent O-glycosylation of Arabidopsis pollen LRXs are necessary for their proper function and cell wall localization in pollen tubes. We hypothesized that pollen-expressed P4H4 and P4H6 catalyze the hydroxylation of the proline units present in Ser-Pro3-5 motifs of LRX8-LRX11. Here, we show that the p4h4-1 p4h6-1 double mutant exhibits a reduction in pollen germination rates and a slight reduction in pollen tube length. Pollen germination is also inhibited by P4H inhibitors, suggesting that prolyl hydroxylation is required for pollen tube development. Plants expressing pLRX11::LRX11-GFP in the p4h4-1 p4h6-1 background show partial re-localization of LRX11-green fluorescent protein (GFP) from the pollen tube tip apoplast to the cytoplasm. Finally, immunoprecipitation-tandem mass spectrometry analysis revealed a decrease in oxidized prolines (hydroxyprolines) in LRX11-GFP in the p4h4-1 p4h6-1 background compared with lrx11 plants expressing pLRX11::LRX11-GFP. Taken together, these results suggest that P4H4 and P4H6 are required for pollen germination and for proper hydroxylation of LRX11 necessary for its localization in the cell wall of pollen tubes.

Prolyl hydroxylase inhibition protects against murine MC903-induced skin inflammation by downregulating TSLP.

Previously, we reported an anti-inflammatory effect of mTORC1 in a mouse model of type 2 skin inflammation. TSLP, one of the epithelial cell-derived cytokines, was upregulated by Raptor deficiency or rapamycin treatment, which was inhibited by dimethyloxalylglycine (DMOG). However, it remains unclear how DMOG regulates TSLP expression and type 2 skin inflammation. In this study, we investigated the protective effect of DMOG on MC903 (calcipotriol)-induced type 2 skin inflammation. Morphological and immunological changes were assessed by H-E staining, flow cytometry and RT-qPCR. DMOG treatment attenuated MC903-induced skin inflammation in a T cell-independent manner. The anti-inflammatory effect of DMOG was accompanied by downregulation of TSLP and IL-33, and supplementation with recombinant TSLP and IL-33 abolished the effect of DMOG. MC903 increased ROS levels in skin tissue, which was prevented by DMOG. Furthermore, the ROS scavenger N-acetylcysteine (NAC) downregulated TSLP and ameliorated MC903-induced skin inflammation, as did DMOG. Finally, the effect of DMOG on ROS and TSLP was reduced by HIF knockdown. These results suggest that DMOG downregulates TSLP and ROS through the HIF pathway, which reduces MC903-induced skin inflammation.

Novel furan chalcone modulates PHD-2 induction to impart antineoplastic effect in mammary gland carcinoma.

Normoxic inactivation of prolyl hydroxylase-2 (PHD-2) in tumour microenvironment paves the way for cancer cells to thrive under the influence of HIF-1α and NF-κB. Henceforth, the present study is aimed to identify small molecule activators of PHD-2. A virtual screening was conducted on a library consisting of 265,242 chemical compounds, with the objective of identifying molecules that exhibit structural similarities to the furan chalcone scaffold. Further, PHD-2 activation potential of screened compound was determined using in vitro 2-oxoglutarate assay. The cytotoxic activity and apoptotic potential of screened compound was determined using various staining techniques, including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, 4',6-diamidino-2-phenylindole (DAPI), 1,1',3,3'-tetraethylbenzimi-dazolylcarbocyanine iodide (JC-1), and acridine orange/ethidium bromide (AO/EB), against MCF-7 cells. 7,12-Dimethylbenz[a]anthracene (DMBA) model of mammary gland cancer was used to study the in vivo antineoplastic efficacy of screened compound. [(E)-1-(4-fluorophenyl)-3-(furan-2-yl) prop-2-en-1-one] (BBAP-7) was screened and validated as a PHD-2 activator by an in vitro 2-oxo-glutarate assay. The IC50 of BBAP-7 on MCF-7 cells is 18.84 µM. AO/EB and DAPI staining showed nuclear fragmentation, blebbing and condensation in MCF-7 cells following BBAP-7 treatment. The red-to-green intensity ratio of JC-1 stained MCF-7 cells decreased after BBAP-7 treatment, indicating mitochondrial-mediated apoptosis. DMBA caused mammary gland dysplasia, duct hyperplasia and ductal carcinoma in situ. Carmine staining, histopathology, and scanning electron microscopy demonstrated that BBAP-7, alone or with tirapazamine, restored mammary gland surface morphology and structural integrity. Additionally, BBAP-7 therapy significantly reduced oxidative stress and glycolysis. The findings reveal that BBAP-7 activates PHD-2, making it a promising anticancer drug.

Association of Antenatal Evaluations with Postmortem and Genetic Findings in the Series of Fetal Osteogenesis Imperfecta.

INTRODUCTION: Counseling osteogenesis imperfecta (OI) pregnancies is challenging due to the wide range of onsets and clinical severities, from perinatal lethality to milder forms detected later in life. METHODS: Thirty-eight individuals from 36 families were diagnosed with OI through prenatal ultrasonography and/or postmortem clinical and radiographic findings. Genetic analysis was conducted on 26 genes associated with OI in these subjects that emerged over the past 20 years; while some genes were examined progressively, all 26 genes were examined in the group where no pathogenic variations were detected. RESULTS: Prenatal and postnatal observations both consistently showed short limbs in 97%, followed by bowing of the long bones in 89%. Among 32 evaluated cases, all exhibited cranial hypomineralization. Fractures were found in 29 (76%) cases, with multiple bones involved in 18 of them. Genetic associations were disclosed in 27 families with 22 (81%) autosomal dominant and five (19%) autosomal recessive forms, revealing 25 variants in six genes (COL1A1, COL1A2, CREB3L1, P3H1, FKBP10, and IFITM5), including nine novels. Postmortem radiological examination showed variability in intrafamily expression of CREBL3- and P3H1-related OI. CONCLUSION: Prenatal diagnosis for distinguishing OI and its subtypes relies on factors such as family history, timing, ultrasound, genetics, and postmortem evaluation.

Metabolic characteristics of transmembrane prolyl 4-hydroxylase (P4H-TM) deficient mice.

Transmembrane prolyl 4-hydroxylase (P4H-TM) is an enigmatic enzyme whose cellular function and primary substrate remain to be identified. Its loss-of-function mutations cause a severe neurological HIDEA syndrome with hypotonia, intellectual disability, dysautonomia and hypoventilation. Previously, P4H-TM deficiency in mice was associated with reduced atherogenesis and lower serum triglyceride levels. Here, we characterized the glucose and lipid metabolism of P4h-tm-/- mice in physiological and tissue analyses. P4h-tm-/- mice showed variations in 24-h oscillations of energy expenditure, VO2 and VCO2 and locomotor activity compared to wild-type (WT) mice. Their rearing activity was reduced, and they showed significant muscle weakness and compromised coordination. Sedated P4h-tm-/- mice had better glucose tolerance, lower fasting insulin levels, higher fasting lactate levels and lower fasting free fatty acid levels compared to WT. These alterations were not present in conscious P4h-tm-/- mice. Fasted P4h-tm-/- mice presented with faster hepatic glycogenolysis. The respiratory rate of conscious P4h-tm-/- mice was significantly lower compared to the WT, the decrease being further exacerbated by sedation and associated with acidosis and a reduced ventilatory response to both hypoxia and hypercapnia. P4H-TM deficiency in mice is associated with alterations in whole-body energy metabolism, day-night rhythm of activity, glucose homeostasis and neuromuscular and respiratory functions. Although the underlying mechanism(s) are not yet fully understood, the phenotype appears to have neurological origins, controlled by brain and central nervous system circuits. The phenotype of P4h-tm-/- mice recapitulates some of the symptoms of HIDEA patients, making this mouse model a valuable tool to study and develop tailored therapies.

Prolyl hydroxylase domain inhibitor is an effective pre-hospital pharmaceutical intervention for trauma and hemorrhagic shock.

Pre-hospital potentially preventable trauma related deaths are mainly due to hypoperfusion-induced tissue hypoxia leading to irreversible organ dysfunction at or near the point of injury or during transportation prior to receiving definitive therapy. The prolyl hydroxylase domain (PHD) is an oxygen sensor that regulates tissue adaptation to hypoxia by stabilizing hypoxia inducible factor (HIF). The benefit of PHD inhibitors (PHDi) in the treatment of anemia and lactatemia arises from HIF stabilization, which stimulates endogenous production of erythropoietin and activates lactate recycling through gluconeogenesis. The results of this study provide insight into the therapeutic roles of MK-8617, a pan-inhibitor of PHD-1, 2, and 3, in the mitigation of lactatemia in anesthetized rats with polytrauma and hemorrhagic shock. Additionally, in an anesthetized rat model of lethal decompensated hemorrhagic shock, acute administration of MK-8617 significantly improves one-hour survival and maintains survival at least until 4 h following limited resuscitation with whole blood (20% EBV) at one hour after hemorrhage. This study suggests that pharmaceutical interventions to inhibit prolyl hydroxylase activity can be used as a potential pre-hospital countermeasure for trauma and hemorrhage at or near the point of injury.

Deficiency in PHD2-mediated hydroxylation of HIF2α underlies Pacak-Zhuang syndrome.

Pacak-Zhuang syndrome is caused by mutations in the EPAS1 gene, which encodes for one of the three hypoxia-inducible factor alpha (HIFα) paralogs HIF2α and is associated with defined but varied phenotypic presentations including neuroendocrine tumors and polycythemia. However, the mechanisms underlying the complex genotype-phenotype correlations remain incompletely understood. Here, we devised a quantitative method for determining the dissociation constant (Kd) of the HIF2α peptides containing disease-associated mutations and the catalytic domain of prolyl-hydroxylase (PHD2) using microscale thermophoresis (MST) and showed that neuroendocrine-associated Class 1 HIF2α mutants have distinctly higher Kd than the exclusively polycythemia-associated Class 2 HIF2α mutants. Based on the co-crystal structure of PHD2/HIF2α peptide complex at 1.8 Å resolution, we showed that the Class 1 mutated residues are localized to the critical interface between HIF2α and PHD2, adjacent to the PHD2 active catalytic site, while Class 2 mutated residues are localized to the more flexible region of HIF2α that makes less contact with PHD2. Concordantly, Class 1 mutations were found to significantly increase HIF2α-mediated transcriptional activation in cellulo compared to Class 2 counterparts. These results reveal a structural mechanism in which the strength of the interaction between HIF2α and PHD2 is at the root of the general genotype-phenotype correlations observed in Pacak-Zhuang syndrome.

Zinc Supplementation Enhances the Hematopoietic Activity of Erythropoiesis-Stimulating Agents but Not Hypoxia-Inducible Factor-Prolyl Hydroxylase Inhibitors.

Since zinc is involved in many aspects of the hematopoietic process, zinc supplementation can reduce erythropoiesis-stimulating agents (ESAs) in patients undergoing hemodialysis. However, it remains unclear whether hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) have similar reduction effects. HIF-PHI stabilizes HIF, which promotes hematopoiesis, although HIF-1α levels are downregulated by zinc. This study aimed to investigate the effect of zinc supplementation on the hematopoietic effect of HIF-PHI in patients undergoing hemodialysis. Thirty patients undergoing maintenance hemodialysis who underwent periods of treatment with roxadustat or darbepoetin alfa during the past 3 years were retrospectively observed. Participants who underwent periods with and without zinc supplementation were selected, with nine treated with darbepoetin alfa and nine treated with roxadustat. Similarly to the ESA responsiveness index (ERI), the hematopoietic effect of zinc supplementation was determined by the HIF-PHI responsiveness index (HRI), which was calculated by dividing the HIF-PHI dose (mg/week) by the patient's dry weight (kg) and hemoglobin level (g/L). Zinc supplementation significantly increased ERI (p < 0.05), but no significant change was observed (p = 0.931) in HRI. Although zinc supplementation did not significantly affect HRI, adequate zinc supplementation is required to alleviate concerns such as vascular calcification and increased serum copper during the use of HIF-PHI.

Hypoxia-inducible Factor Prolyl Hydroxylase Inhibitors and Hypothyroidism: An Analysis of the Japanese Pharmacovigilance Database.

BACKGROUND/AIM: Hypothyroidism induced by roxadustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, was recently reported; however, information regarding roxadustat-associated hypothyroidism is still lacking. We explored the risk and time to onset of hypothyroidism associated with HIF-PH inhibitors using the Japanese Adverse Drug Event Report (JADER), a pharmacovigilance database. PATIENTS AND METHODS: The participants of this study were registered in the JADER database between April 2004 and March 2023. The association between HIF-PH inhibitors and hypothyroidism was evaluated using the reporting odds ratio (ROR) and information component (IC). We also calculated the period from the start of drug administration to the onset of hypothyroidism and determined the onset pattern using Weibull distribution. RESULTS: Roxadustat had positive signals for hypothyroidism among the HIF-PH inhibitors based on the ROR [31.03, 95% confidence interval (CI)=27.81-34.62] and IC (4.51, 95%CI=4.36-4.67) values, and a strong relationship was confirmed. In addition, the median time to roxadustat-associated hypothyroidism onset was 92 days, and over 50% of cases occurred within 100 days of starting treatment. Furthermore, the onset pattern was an early failure type. CONCLUSION: There is a possible association between roxadustat and hypothyroidism. Therefore, enhanced thyroid function testing within 100 days of treatment initiation may help detect roxadustat-associated hypothyroidism. However, further research is required to confirm these findings, considering study limitations using databases of spontaneous adverse event reports.

Hypoxia-induced P4HA1 overexpression promotes post-ischemic angiogenesis by enhancing endothelial glycolysis through downregulating FBP1.

BACKGROUND: Angiogenesis is essential for tissue repair in ischemic diseases, relying on glycolysis as its primary energy source. Prolyl 4-hydroxylase subunit alpha 1 (P4HA1), the catalytic subunit of collagen prolyl 4-hydroxylase, is a glycolysis-related gene in cancers. However, its role in glycolysis-induced angiogenesis remains unclear. METHODS: P4HA1 expression was modulated using adenoviruses. Endothelial angiogenesis was evaluated through 5-ethynyl-2'-deoxyuridine incorporation, transwell migration, and tube formation assays in vitro. In vivo experiments measured blood flow and capillary density in the hindlimb ischemia (HLI) model. Glycolytic stress assays, glucose uptake, lactate production, and quantitative reverse transcription-polymerase chain reaction (RT-PCR) were employed to assess glycolytic capacity. Transcriptome sequencing, validated by western blotting and RT-PCR, was utilized to determine underlying mechanisms. RESULTS: P4HA1 was upregulated in endothelial cells under hypoxia and in the HLI model. P4HA1 overexpression promoted angiogenesis in vitro and in vivo, while its knockdown had the opposite effect. P4HA1 overexpression reduced cellular α-ketoglutarate (α-KG) levels by consuming α-KG during collagen hydroxylation. Downregulation of α-KG reduced the protein level of a DNA dioxygenase, ten-eleven translocation 2 (TET2), and its recruitment to the fructose-1,6-biphosphatase (FBP1) promoter, resulting in decreased FBP1 expression. The decrease in FBP1 enhanced glycolytic metabolism, thereby promoting endothelial angiogenesis. CONCLUSIONS: Hypoxia-induced endothelial P4HA1 overexpression enhanced angiogenesis by promoting glycolytic metabolism reprogramming through the P4HA1/α-KG/TET2/FBP1 pathway. The study's findings underscore the significance of P4HA1 in post-ischemic angiogenesis, suggesting its therapeutic potential for post-ischemic tissue repair.

Discovery of Novel and Potent Prolyl Hydroxylase Domain-Containing Protein (PHD) Inhibitors for The Treatment of Anemia.

Stabilization of hypoxia-inducible factor (HIF) by inhibiting prolyl hydroxylase domain enzymes (PHDs) represents a breakthrough in treating anemia associated with chronic kidney disease. Here, we identified a novel scaffold for noncarboxylic PHD inhibitors by utilizing structure-based drug design (SBDD) and generative models. Iterative optimization of potency and solubility resulted in compound 15 which potently inhibits PHD thus stabilizing HIF-α in vitro. X-ray cocrystal structure confirmed the binding model was distinct from previously reported carboxylic acid PHD inhibitors by pushing away the R383 and Y303 residues resulting in a larger inner subpocket. Furthermore, compound 15 demonstrated a favorable in vitro/in vivo absorption, distribution, metabolism, and excretion (ADME) profile, low drug-drug interaction risk, and clean early safety profiling. Functionally, oral administration of compound 15 at 10 mg/kg every day (QD) mitigated anemia in a 5/6 nephrectomy rat disease model.

Efficacy of Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor on Clinical Parameters in Patients with Heart Failure.

Background and Objectives: Hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitors have been approved as an oral drug for treating anemia in chronic kidney disease (CKD). However, the clinical effect of HIF-PH inhibitors in patients with heart failure (HF) is unclear. Thus, this study investigated the effect of HIF-PH inhibitors in patients with HF and CKD. Materials and Methods: Thirteen patients with HF complicated by renal anemia who were started on vadadustat were enrolled. Clinical parameters were compared before and 1 month after vadadustat was started. Results: The mean left ventricular ejection fraction was 49.8 ± 13.9%, and the mean estimated glomerular filtration rate was 29.4 ± 10.6 mL/min/1.73 m2. The hemoglobin level was significantly increased (9.7 ± 1.3 mg/dL vs. 11.3 ± 1.3 mg/dL, p < 0.001), and the N-terminal prohormone of B-type natriuretic peptide was significantly decreased after the introduction of vadadustat [4357 (2651-15182) pg/mL vs. 2367 (1719-9347) pg/mL, p = 0.002]. Furthermore, the number of patients with New York Heart Association functional class ≥ 3 was also decreased after the introduction of vadadustat [8 (61.5%) vs. 1 (7.7%), p = 0.008]. No thromboembolic adverse events or new tumors were observed in any patient during the study period. Conclusions: The introduction of vadadustat in patients with HF complicated by renal anemia led to improvements in anemia and symptoms of HF.

Use of molidustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, in chronic kidney disease-associated anemia in cats.

BACKGROUND: Erythropoietic effects of molidustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, were previously demonstrated in healthy cats. OBJECTIVE: To evaluate the safety and erythropoietic effects of daily PO administration of molidustat in anemic cats with chronic kidney disease (CKD). ANIMALS: Twenty-one client-owned CKD cats (4-17 years old) with anemia. METHODS: Multicenter field study; randomized, masked, and placebo-controlled. Cats were treated PO once daily for 28 days with suspensions of control product (CP; n = 6) or 5 mg/kg of molidustat (n = 15). Hematocrit (HCT) was evaluated at weekly intervals. Individual cat treatment success was defined as a ≥4% point increase in HCT compared to baseline. RESULTS: Control group mean HCT remained low throughout the study (20.1%-23.4%). Mean HCT of molidustat-treated cats increased weekly, and a significant increase compared to baseline (23.6%) was first observed on Day 21 (27.3%; P < .001; 95% confidence interval [CI], 1.69-5.67). Compared to CP group, mean HCT was significantly higher on Day 21 (27.3% vs 20.1%; P < .001; 95% CI, 2.91-10.75) but not significantly higher on Day 28 (27.8% vs 23.4%; P = .06; 95% CI, -0.23 to 9.88). The number of individual treatment successes on Day 28 was higher among remaining molidustat-treated cats (7/14) compared to remaining control cats (1/5), but there was no significant difference between groups. CONCLUSIONS AND CLINICAL IMPORTANCE: Daily PO molidustat administration may stimulate a clinically relevant erythropoietic response in anemic cats with CKD. This HIF-PH inhibitor may be an alternative for managing anemia in cats compared to recombinant EPO treatment.

Collagen prolyl 4-hydroxylase isoenzymes I and II have sequence specificity towards different X-Pro-Gly triplets.

Collagen biosynthesis requires several co- and post-translational modifications of lysine and proline residues to form structurally and functionally competent collagen molecules. Formation of 4-hydroxyproline (4Hyp) in Y-position prolines of the repetitive -X-Y-Gly- sequences provides thermal stability for the triple-helical collagen molecules. 4Hyp formation is catalyzed by a collagen prolyl 4-hydroxylase (C-P4H) family consisting of three isoenzymes. Here we identify specific roles for the two main C-P4H isoenzymes in collagen hydroxylation by a detailed 4Hyp analysis of type I and IV collagens derived from cell and tissue samples. Loss of C-P4H-I results in underhydroxylation of collagen where the affected prolines are not uniformly distributed, but mainly present in sites where the adjacent X-position amino acid has a positively charged or a polar uncharged side chain. In contrast, loss of C-P4H-II results in underhydroxylation of triplets where the X-position is occupied by a negatively charged amino acid glutamate or aspartate. Hydroxylation of these triplets was found to be important as loss of C-P4H-II alone resulted in reduced collagen melting temperature and altered assembly of collagen fibrils and basement membrane. The observed C-P4H isoenzyme differences in substrate specificity were explained by selective binding of the substrate to the active site resulting in distinct differences in Km and Vmax values. Furthermore, our results clearly show that the substrate proline selection is not dependent on the collagen type, but the main determinant is the X-position amino acid of the -X-Pro-Gly- triplet. Although our data clearly shows the necessity of both C-P4H-I and II for normal prolyl 4-hydroxylation and function of collagens, the mRNA expression of the isoenzymes with various procollagens was, surprisingly, not tightly coordinated, suggesting additional levels of control. In conclusion, this study provides a molecular level explanation for the need of multiple C-P4H isoenzymes to generate collagen molecules capable to assemble into intact extracellular matrix structures.

Hypoxia-inducible factor-prolyl hydroxylase inhibitor Roxadustat (FG-4592) reduces renal fibrosis in Dahl salt-sensitive rats.

OBJECTIVE: Although hypoxia-inducible factor-prolyl hydroxylase (HIF-PH) inhibitors have been developed for the treatment of renal anemia, their effects on cardiac and renal dysfunction remain unknown. We previously reported on Dahl salt-sensitive rats, in a rat model of salt-sensitive hypertension, that exhibited anemia and impaired expression of duodenal iron transporters after the development of hypertensive cardiac and renal dysfunction. Therefore, we investigated the effects of Roxadustat (FG-4592), an HIF-PH inhibitor, on anemia, iron regulation, and cardiac and renal dysfunction in Dahl salt-sensitive rats. METHODS: Six-week-old male Dahl salt-sensitive rats were fed a normal or high-salt diet for 8 weeks. A further subset of Dahl salt-sensitive rats, that were fed a high-salt diet, was administered Roxadustat for 8 weeks. RESULTS: Dahl salt-sensitive rats fed a high-salt diet developed hypertension, cardiac and renal dysfunction, and anemia after 8 weeks of feeding. Roxadustat increased hemoglobin and serum erythropoietin levels in Dahl salt-sensitive rats fed a high-salt diet. With regard to the iron-regulating system, Roxadustat lowered hepatic hepcidin gene expression and increased the gene expression of duodenal iron transporters, such as cytochrome b and divalent metal transporter 1 , in Dahl salt-sensitive rats fed a high-salt diet. Roxadustat did not affect the development of hypertension and cardiac hypertrophy in Dahl salt-sensitive rats with a high-salt diet; however, Roxadustat treatment attenuated renal fibrosis in these rats. CONCLUSIONS: Roxadustat ameliorated anemia with affecting the gene expression of the iron-regulating system, and did not affect cardiac hypertrophy but attenuated renal fibrosis in Dahl salt-sensitive rats fed a high-salt diet.

Multimodal Imaging Reveals that Sustained Inhibition of HIF-Prolyl Hydroxylases Induces Opposing Effects on Right and Left Ventricular Function in Healthy Rats.

PURPOSE: Hypoxia-inducible factor (HIF) drives transcription of critical hypoxia response genes, increasing the production of red blood cells in low oxygen conditions. In the absence of hypoxia, HIF is degraded by prolyl hydroxylases (HIF-PHs). Pharmacological HIF-PH inhibition stabilizes HIF and is being studied as a treatment for anemia. However, like sustained hypoxia, HIF-PH inhibition may increase pulmonary arterial pressure leading to right ventricular hypertrophy. The aim of this study was to assess the cardiac effects of sustained pharmacological HIF-PH inhibition using multimodal imaging, blood analysis, and histology. METHODS: Rats were dosed daily with a pan HIF-PH inhibitor or vehicle for 4 weeks followed by a 2-week washout period and underwent longitudinal magnetic resonance imaging (MRI) and echocardiography to simultaneously assess RV and LV function. Blood samples from weeks four and six were analyzed to determine red blood cell composition. Histology was performed on the cardiac tissue from a subset of rats at weeks four and six to assess structural effects. RESULTS: Imaging revealed that RV ejection fraction was reduced in animals receiving HIF-PH inhibitor and resulted in RV hypertrophy. Interestingly, HIF-PH inhibition had the opposite effect on the left ventricle (LV), increasing contractility measured by LV ejection fraction. LV effects were reversed by week six, while RV effects (functional and structural) were sustained. CONCLUSION: These opposing cardiac effects of HIF-PH inhibition warrant further study to both understand the potential negative effects on RV structure and function and investigate the therapeutic potential of increased LV contractility for conditions like heart failure.