Prolyl Hydroxylase Inhibitor Dimethyloxalylglycine Research Articles

Abstract 2063: Endothelial Cell Scavenger Receptor Class B, Type I Expression Is Transcriptionally Controlled By HIF-1α

Background: Scavenger Receptor Class B, Type I (SR-BI), encoded by Scarb1, mediates LDL cholesterol transcytosis in endothelial cells (EC) to deliver circulating LDL into the subendothelial space to drive atherogenesis. Research Questions: It is unknown whether EC SR-BI expression is altered in atherosclerosis, and how EC SR-BI expression is regulated. Approach: Single cell RNAseq was performed on coronary arteries from 5 ischemic heart disease patients, in segments both with and without a grossly apparent atheroma. Transcription factor (TF) network analysis was done to reveal possible regulatory relationships between differentially-expressed genes (DEGs). The modulation of EC SR-BI was studied in primary human aortic EC (HAEC) and in vivo in mouse aortic EC. ChIP-seq, ChIP-qPCR and CRISPR-based mutagenesis were used to interrogate TF binding to the human Scarb1 gene. EC SR-BI expression was determined by immunoblotting and qPCR, and EC LDL transcytosis was studied in transwells using DiI-labeled LDL. Results: SR-BI expression was greater in EC in coronary segments with atheroma versus those without atheroma (p=0.003). TF networks for DEGs in atheroma versus non-atheroma EC, and for DEGs in EC with low versus high SR-BI revealed multiple TF with possible regulatory relationships with Scarb1. One TF in common was HIF-1α. In HAEC, an increase in HIF-1α with the HIF prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) caused upregulation of SR-BI mRNA and protein, and a parallel increase in LDL transcytosis that was entirely SR-BI-dependent. Expression of a constitutively-active HIF-1α variant also increased SR-BI and LDL transcytosis. ChIP-seq revealed a HIF-1α binding site in Scarb1 intron 1, and HIF-1α binding there increased 4-fold with DMOG. CRISPR deletion of the binding site fully prevented SR-BI upregulation by DMOG without affecting known HIF-1α target genes. In mice, 3d treatment with DMOG increased SR-BI in aortic EC. Conclusions: EC expression of SR-BI is upregulated with increasing atherosclerosis severity in human coronary artery. HIF-1α is upregulated in parallel, and HIF-1α causes the direct transcriptional upregulation of EC SR-BI leading to enhanced EC LDL transport. HIF-1α control of SR-BI in EC may be critical to atherogenesis.

Thiosulfinate-Enriched Allium sativum Extract Exhibits Differential Effects between Healthy and Sepsis Patients: The Implication of HIF-1α

Garlic (Allium sativum) has historically been associated with antioxidant, immunomodulatory, and microbiocidal properties, mainly due to its richness in thiosulfates and sulfur-containing phytoconstituents. Sepsis patients could benefit from these properties because it involves both inflammatory and refractory processes. We evaluated the effects of thiosulfinate-enriched Allium sativum extract (TASE) on the immune response to bacterial lipopolysaccharide (LPS) by monocytes from healthy volunteers (HVs) and patients with sepsis. We also explored the TASE effects in HIF-1α, described as the key transcription factor leading to endotoxin tolerance in sepsis monocytes through IRAK-M expression. Our results showed TASE reduced the LPS-triggered reactive oxygen species (ROS) production in monocytes from both patients with sepsis and HVs. Moreover, this extract significantly reduced tumor necrosis factor (TNF)-α, interleukin-1β, and interleukin-6 production in LPS-stimulated monocytes from HVs. However, TASE enhanced the inflammatory response in monocytes from patients with sepsis along with increased expression of human leukocyte antigen-DR. Curiously, these dual effects of TASE on immune response were also found when the HV cohort was divided into low- and high-LPS responders. Although TASE enhanced TNFα production in the LPS-low responders, it decreased the inflammatory response in the LPS-high responders. Furthermore, TASE decreased the HIF-1α pathway-associated genes IRAK-M, VEGFA and PD-L1 in sepsis cells, suggesting HIF-1α inhibition by TASE leads to higher cytokine production in these cells as a consequence of IRAK-M downregulation. The suppression of this pathway by TASE was confirmed in vitro with the prolyl hydroxylase inhibitor dimethyloxalylglycine. Our data revealed TASE's dual effect on monocyte response according to status/phenotype and suggested the HIF-1α suppression as the possible underlying mechanism.

Stabilization of HIF-1\u03b1 alleviates osteoarthritis via enhancing mitophagy

Mitochondrial dysfunction leads to osteoarthritis (OA) and disc degeneration. Hypoxia inducible factor-1α (HIF-1α) mediated mitophagy has a protective role in several diseases. However, the underlying mechanism of HIF-1α mediated mitophagy in OA remains largely unknown. This current study was performed to determine the effect of HIF-1α mediated mitophagy on OA. Therefore, X-ray and tissue staining including HE staining, safranin O-fast green (S-O) and Alcian Blue were used to assess imageology and histomorphology differences of mouse knee joint. Transcriptional analysis was used to find the possible targets in osteoarthritis. Western blot analysis, RT-qPCR and immunofluorescence staining were used to detect the changes in gene and protein levels in the vitro experiment. The expression of HIF-1α was increased in human and mouse OA cartilage. HIF-1α knockdown by siRNA further impair the hypoxia-induced mitochondrial dysfunction; In contrast, HIF-1α mediated protective role was reinforced by prolylhydroxylase (PHD) inhibitor dimethyloxalylglycine (DMOG). In addition, HIF-1α stabilization could alleviate apoptosis and senescence via mitophagy in chondrocytes under hypoxia condition, which could also ameliorate surgery-induced cartilage degradation in mice OA model. In conclusion, HIF-1α mediated mitophagy could alleviate OA, which may serve as a promising strategy for OA treatment.

Hypoxia sensing by hepatic stellate cells leads to VEGF-dependent angiogenesis and may contribute to accelerated liver regeneration

Portal vein ligation (PVL) induces liver growth prior to resection. Associating liver partition and portal vein ligation (PVL plus transection=ALPPS) or the addition of the prolyl-hydroxylase inhibitor dimethyloxalylglycine (DMOG) to PVL both accelerate growth via stabilization of HIF-α subunits. This study aims at clarifying the crosstalk of hepatocytes (HC), hepatic stellate cells (HSC) and liver sinusoidal endothelial cells (LSEC) in accelerated liver growth. In vivo, liver volume, HC proliferation, vascular density and HSC activation were assessed in PVL, ALPPS, PVL+DMOG and DMOG alone. Proliferation of HC, HSC and LSEC was determined under DMOG in vitro. Conditioned media experiments of DMOG-exposed cells were performed. ALPPS and PVL+DMOG accelerated liver growth and HC proliferation in comparison to PVL. DMOG alone did not induce HC proliferation, but led to increased vascular density, which was also observed in ALPPS and PVL+DMOG. Activated HSC were detected in ALPPS, PVL+DMOG and DMOG, again not in PVL. In vitro, DMOG had no proliferative effect on HC, but conditioned supernatant of DMOG-treated HSC induced VEGF-dependent proliferation of LSEC. Transcriptome analysis confirmed activation of proangiogenic factors in hypoxic HSC. Hypoxia signaling in HSC induces VEGF-dependent angiogenesis. HSC play a crucial role in the cellular crosstalk of rapid liver regeneration.

Stabilization of Hypoxia Inducible Factor-1α by Dimethyloxalylglycine Promotes Recovery from Acute Spinal Cord Injury by Inhibiting Neural Apoptosis and Enhancing Axon Regeneration.

Spinal cord injury (SCI) is a devastating neurological disorder that usually leads to a loss of motor and sensory function in patients. The expression of hypoxia inducible factor-1α (HIF-1α) is increased, and exerts a protective role after traumatic SCI. However, the endogenous activity of HIF-1α is insufficient for promoting functional recovery. The present study tested the potential effect of the sustained activation of HIF-1α by the prolylhydroxylase (PHD) inhibitor dimethyloxalylglycine (DMOG) on anti-apoptotic process and the regulation of axonal regeneration after SCI. Here, we found that treatment with DMOG significantly increased the expression of HIF-1α and that the stabilization of HIF-1α induced by DMOG not only decreased the expression of apoptotic proteins to promote neural survival, but also enhanced axonal regeneration by regulating microtubule stabilization in vivo and in vitro. In addition, we found that DMOG promoted neural survival and axonal regeneration by activating autophagy, which is induced by the HIF-1α/BNIP3 signaling pathway, and that the inhibition of HIF-1α or autophagy abrogated the protective effect of DMOG, as expected. Taken together, our results demonstrate that treatment with DMOG improves functional recovery after SCI and that DMOG may serve as a potential candidate for treating SCI.

Prolyl hydroxylase 3 stabilizes the p53 tumor suppressor by inhibiting the p53–MDM2 interaction in a hydroxylase-independent manner

Prolyl hydroxylase 3 (PHD3) has initially been reported to hydroxylase hypoxia-inducible factor α (HIFα) and mediate HIFα degradation. More recent studies have shown that, in addition to HIFα, PHD3 has also other substrates. Moreover, pHD3 is believed to act as a tumor suppressor, but the underlying mechanism remains to be elucidated. Here, we demonstrate that PHD3 stabilizes p53 in a hydroxylase-independent manner. We found that PHD3 overexpression increases and PHD3 knockdown decreases p53 levels. Mechanistically, PHD3 bound MDM2 proto-oncogene (MDM2) and prevented MDM2 from interacting with p53, thereby inhibiting MDM2-mediated p53 degradation. Interestingly, we found that PHD3 overexpression could enhance p53 in the presence of the prolyl hydroxylase inhibitor dimethyloxalylglycine, and the prolyl hydroxylase activity-deficient variant PHD3-H196A also inhibited the p53-MDM2 interaction and stabilized p53. Genetic ablation of PHD3 decreased p53 protein levels in mice intestinal epithelial cells, but a genetic knockin of PHD3-H196A did not affect p53 protein levels in vivo These results suggest that the prolyl hydroxylase activity of PHD3 is dispensable for its ability to stabilize p53. We found that both PHD3 and PHD3-H196A suppress the expression of the stem cell-associated gene NANOG and inhibited the properties of colon cancer stem cells through p53. Our results reveal an additional critical mechanism underlying the regulation of p53 expression and highlight that PHD3 plays a role in the suppression of colon cancer cell stemness in a hydroxylase-independent manner.

Perioperative Treatment with a Prolyl Hydroxylase Inhibitor Reduces Necrosis in a Rat Ischemic Skin Flap Model.

The hypoxia-inducible factor (HIF) pathway, regulated by prolyl hydroxylase, is central to tissue adaptation to ischemia. The authors tested whether the prolyl hydroxylase inhibitor dimethyloxalylglycine reduces skin flap necrosis. Dorsal skin flaps were raised on hairless rats, with dimethyloxalylglycine delivered intraperitoneally and/or topically for 7 days before and after surgery. After 14 treatment days, percentage of flap necrosis was compared grossly and tissue perfusion compared with an in vivo imaging system. Angiogenesis was compared using immunohistochemical CD31 staining and enzyme-linked immunosorbent assay for tissue vascular endothelial growth factor. Expression levels of HIF-1α and terminal deoxynucleotidyl transferase-mediated dUDP end-labeling were compared using immunohistochemical staining. Complete blood counts and gross necropsy specimens were obtained to assess systemic toxicity. Dimethyloxalylglycine administration significantly improved postoperative flap viability, with combined topical and intraperitoneal dimethyloxalylglycine administration leading to reduced necrosis on postsurgical day 7 at 6 mg/kg/day, 12 mg/kg/day, 24 mg/kg/day, and 48 mg/kg/day versus controls (all p < 0.05). Compared with controls (unperfused, 39.9 ± 3.8 percent), dimethyloxalylglycine treatment led to a dose-dependent decrease in unperfused tissue at 6 mg/kg/day (11.4 ± 1.7 percent), 12 mg/kg/day (9.4 ± 4.2 percent), 24 mg/kg/day (4.7 ± 2.6 percent), and 48 mg/kg/day (1.4 ± 0.9 percent) (all p < 0.001). Topical dimethyloxalylglycine application alone administered at 48 mg/kg/day was sufficient to improve flap viability (p = 0.005). Dimethyloxalylglycine-treated flaps exhibited higher CD31 staining (p = 0.004), tissue vascular endothelial growth factor (p = 0.007), HIF-1α staining (p < 0.001), and reduced terminal deoxynucleotidyl transferase-mediated dUDP end-labeling staining (p = 0.045). There were no differences in hematocrit or macroscopic organ changes on gross necropsy. Topical and systemic targeting of the HIF-1 pathway may be a promising therapeutic approach to improve flap resistance to ischemia.

Abstract 5062: Hypoxia-induced amoeboid cancer cell migration

Abstract Tumor hypoxia, by elevating hypoxia-inducible factors (HIFs), is an established inducer of epithelial-to-mesenchymal transition (EMT) and subsequent cancer cell invasion and metastasis. However, how hypoxia impacts on tumor cell invasion programs and translates into modes of dissemination of moving tumor cells remains unknown. Using breast cancer (BC) and head and neck cancer (HNC) cells which efficiently invade from multicellular spheroids into 3D fibrillar collagen, we addressed which signaling programs that control cell-cell adhesions, cell-matrix interactions and cytoskeletal dynamics and which modes of tumor cell migration are induced by hypoxia. While both cancer models primarily invaded collectively under normoxic conditions, severe hypoxia (0.2% oxygen) or pharmacological stabilization of HIF-1 using the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) induced EMT-like detachment and migration of single cells into collagen, exhibiting a 2- and 4-fold increase of single BC and HNC cells, respectively. Besides infrequent spindle-shaped movement, hypoxia or DMOG predominantly induced the transition from collective to amoeboid single-cell migration, with blebby amoeboid migration as the predominant migration mode (4- and 3-fold increase for BC and HNC, respectively) next to filopodial amoeboid migration. Hypoxia-induced amoeboid migration is characterized by variably fast and persistent migration, reaching up to several 100 μm/day, mediated by actin-rich filopodial or blebby protrusions at the leading edge. Criteria for amoeboid movement included (i) actin-containing blebs that interacted with collagen structures in a polarized fashion, (ii) weak dependence on matrix-metalloproteinase-mediated collagen remodeling, (iii) low dependence on focalized integrin-mediated matrix adhesions, and (iv) high dependence on RhoA-mediated actomyosin contraction for efficient bleb formation and migration speed. Interference with ROCK signaling using Y-27632 and myosin using blebbistatin significantly inhibited hypoxia-induced amoeboid dissemination and bleb formation. Thus, hypoxia induces plasticity of cancer invasion modes, with efficient blebby amoeboid dissemination as primary outcome. While blebby amoeboid motion is known as a rudimentary migration mode in embryonic stem cells, here we observe blebby amoeboid migration as a simple (low MMP- and integrin dependent) but efficient salvage migration mode of cancer cells under severe hypoxic stress. Citation Format: Veronika te Boekhorst, Liying Jiang, Steffi Lehmann, Alba Zuidema, Peter Friedl. Hypoxia-induced amoeboid cancer cell migration. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5062.

PHD/HIF-1 upregulates CA12 to protect against degenerative disc disease: a human sample, in vitro and ex vivo study

Intervertebral disc degeneration is a major cause of low back pain. The nucleus pulposus (NP) is an important intervertebral disc component. Recent studies have shown that carbonic anhydrase 12 (CA12) is a novel NP marker. However, the mechanism by which CA12 is regulated and its physiological function are unclear. In our study, CA12, hypoxia-inducible factor 1α (HIF-1α) and HIF-2α expression levels were examined in 81 human degenerated NP samples using real-time RT-PCR, immunohistochemistry and western blot. Rat NP cells were cultured in a hypoxic environment, and hypoxia-induced CA12 expression was examined. Rat NP cells were treated with HIF-1α siRNA or the prolyl hydroxylase (PHD) inhibitor dimethyloxalylglycine (DMOG) to evaluate the role of PHD/HIF-1 in regulating CA12 expression. Rat NP cells were treated with CA12 siRNA to determine the function of CA12. A rat ex vivo model was established to confirm that PHD, HIF-1, and CA12 have important roles in disc degeneration. We found that CA12 was significantly downregulated in degenerated human NP samples at the mRNA and protein levels. CA12 expression sharply increased by ~30-fold in response to hypoxia. The expression of HIF-1α, but not HIF-2α, also decreased in degenerated human NP samples and was positively correlated with CA12 expression. HIF-1α knockdown under hypoxia reduced the CA12 mRNA and protein expression levels. DMOG treatment increased HIF-1α and CA12 expression. CA12 knockdown significantly inhibited anabolic protein expression, whereas catabolic enzymes remained unchanged. The ex vivo experiments supported our in vitro studies of the role of PHD/HIF-1/CA12. In conclusion, CA12 is downregulated in degenerated NPs, and its expression may be regulated by the PHD/HIF-1 axis. Decreased CA12 expression may lead to decreased extracellular matrix synthesis, which contributes to degenerative disc disease progression.

Abstract 17750: Prolyl Hydroxylase Inhibition Induces Sdf-1 and Cxcr4 Expression to Increase Cxcr4+ Cell Homing and Myocardial Repair

Objective: Stabilization of the cardiac SDF-1/CXCR4 axis attenuates ischemic cardiomyopathy. However, HIF-1α dependent SDF-1 upregulation lasts only for 48-72 hours after myocardial infarction (MI) limiting the targeting of regenerative cells. Therefore, we hypothesized that activation of the HIF-1α target genes SDF-1 and CXCR4 by stabilization of HIF-1α through inhibition of prolyl hydroxylase stimulates myocardial repair. Methods: Genetically tagged SDF1-EGFP and CXCR4-EGFP mice were subjected to optimal doses (80mg/kg i.p.) of the prolyl hydroxylase Inhibitor dimethyloxalylglycine (DMOG). To examine the time frame of SDF-1 and CXCR4 expression in vitro (HEK cells) and in vivo (BM &amp; heart), DMOG was treated at different dosing regimens (50μM to 1000μM &amp; 80mg/kg i.p.) and time intervals (1 to 6 hrs). FACS and immunhistochemical analyses of CXCR4+ BM, peripheral blood, and heart cells as well as infarct size measurements and hemodynamic analyses were performed with and without DMOG treatment after MI. Results: SDF1-EGFP mice treated with DMOG showed robust induction of SDF-1 in heart vessels. In vitro , SDF-1 was transiently upregulated within 60 mins to 2 hrs after DMOG treatment, followed by significant decrease after 6hrs. CXCR4 was elevated at later time points (6h). In vivo , CXCR4 expression was significantly upregualted in BM (6h). FACS analyses of transgenic CXCR4-EGFP BM and hearts revealed that CXCR4+ was frequently expressed on CD11b+ monocytes, and at lower Levels on angiogenic CD31+ , CD34+, c-kit+, and Flk1+ cells, and stem cell populations like CD133+ and Lin-/c-kit+/Sca-1+. DMOG treatment after MI revealed a robust upregulation of CXCR4+ cell populations, predominantly of angiogenic CXCR4+/CD11b+ monocytes. Subanalysis of the latter showed that DMOG treatment leads to a shift of the CD206+/CD86 ratio in favor of M2 macrophages associated CD206+ subpopulation after MI associated by attenuated infarct remodeling. Myocardial function was significantly improved after DMOG treatment (EF: 33,5 vs. 16%). Conclusion: Our data suggest that inhibition of prolyl hydroxylase may be a promising target for HIF-1a mediated SDF-1 activation to increase CXCR4+ stem cell homing and myocardial repair.

Abstract 4141: Hypoxia-induced transition from collective to amoeboid single cell dissemination in epithelial cancer cells

Abstract Tumor hypoxia, by elevating hypoxia-inducible factors (HIFs), is an established inducer of epithelial-to-mesenchymal transition (EMT) and subsequent cancer cell invasion and metastasis. Using epithelial carcinoma spheroids in 3D fibrillar collagen, we characterized the invasion patterns as well as cellular and molecular mechanisms of hypoxia-induced cancer cell migration modes. While epithelial cancer cells show collective invasion under normoxic conditions, hypoxia or pharmacological stabilization of HIF-1 using the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) induced EMT-like detachment and migration of single cells. Besides mesenchymal movement, most epithelial cells converted to amoeboid migration with characteristic actin-rich filopodal or distinctive blebby protrusions towards the direction of migration. Whereas mesenchymal migrating cells moved with low velocities in a directionally persistent manner, amoeboid migrating cells generated a broad spectrum of low to high velocities, but with less persistent invasion paths. Sub-cellular molecular analysis showed typical amoeboid features particularly in hypoxic blebby single cell migration, including low to lacking collagen degradation along the migration path and insensitivity to broad-spectrum matrix metalloproteinase (MMP)-inhibitor GM6001, non-focalized cortical actin cytoskeleton within blebs that interacted with collagen structures and low-beta1 integrin expression with lack of integrin focalization. Thus, tumor hypoxia induces a diversity of single-cancer cell invasion modes, including blebby amoeboid migration, thereby enhancing predominantly MMP- and integrin-independent amoeboid dissemination in parallel to EMT induction. Citation Format: Steffi Lehmann, Veronika A M te Boekhorst, Julia Odenthal, Liying Jiang, Sjoerd van Helvert, Peter Friedl. Hypoxia-induced transition from collective to amoeboid single cell dissemination in epithelial cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4141. doi:10.1158/1538-7445.AM2015-4141

Dimethyloxalylglycine treatment of brain-dead donor rats improves both donor and graft left ventricular function after heart transplantation

Hypoxia inducible factor (HIF)-1 pathway signalling has a protective effect against ischemia/reperfusion injury. The prolyl-hydroxylase inhibitor dimethyloxalylglycine (DMOG) activates the HIF-1 pathway by stabilizing HIF-1α. In a rat model of brain death (BD)-associated donor heart dysfunction we tested the hypothesis that pre-treatment of brain-dead donors with DMOG would result in a better graft heart condition. BD was induced in anesthetized Lewis rats by inflating a subdurally placed balloon catheter. Controls underwent sham operations. Then, rats were injected with an intravenous dose of DMOG (30 mg/kg) or an equal volume of physiologic saline. After 5 hours of BD or sham operation, hearts were perfused with a cold (4°C) preservation solution (Custodiol; Dr. Franz Köhler Chemie GmbH; Germany), explanted, stored at 4°C in Custodiol, and heterotopically transplanted. Graft function was evaluated 1.5 hours after transplantation. Compared with control, BD was associated with decreased left ventricular systolic and diastolic function. DMOG treatment after BD improved contractility (end-systolic pressure volume relationship E'max: 3.7 ± 0.6 vs 3.1 ± 0.5 mm Hg/µ1; p < 0.05) and left ventricular stiffness (end-diastolic pressure volume relationship: 0.13 ± 0.03 vs 0.31 ± 0.06 mm Hg/µ1; p < 0.05) 5 hours later compared with the brain-dead group. After heart transplantation, DMOG treatment of brain-dead donors significantly improved the altered systolic function and decreased inflammatory infiltration, cardiomyocyte necrosis, and DNA strand breakage. In addition, compared with the brain-dead group, DMOG treatment moderated the pro-apoptotic changes in the gene and protein expression. In a rat model of potential brain-dead heart donors, pre-treatment with DMOG resulted in improved early recovery of graft function after transplantation. These results support the hypothesis that activation of the HIF-1 pathway has a protective role against BD-associated cardiac dysfunction.

SIRT3 Deficiency Impairs Hypoxic Signaling, Reprograms Basal Glycolytic Metabolism and Exacerbates Myocardial Ischemic Injury

Increased glycolytic metabolism is critical for maintaining homeostasis of cardiomyocytes and endothelial cells (EC) during myocardial ischemia. Sirtuin 3 (SIRT3) is involved in epigenetic regulation of variety of cellular functions. The present study investigated the role of SIRT3 in altering glycolytic metabolism and hypoxia/ischemia responses using SIRT3 knockout (SIRT3 KO) mice and SIRT3 deficient EC. In vitro, exposure of EC to hypoxia up to 24 hours resulted in a gradual increase in HIF‐2α expression in WT and SIRT3 KO‐EC. Interestingly, hypoxia‐induced HIF‐2α expression was less in SIRT3 KO‐EC compared to EC isolated from WT mice. Moreover, hypoxia‐induced VEGF expression was reduced in SIRT3 KO‐EC. Using Seahorse XFe24 analyzer, EC glycolysis and mitochondrial function were further examined. Basal glycolysis, glycolytic reserve and glycolytic capacity were dramatically reduced in Sirt3 KO‐EC compared to WT‐EC. Moreover, Sirt3KO EC exhibited higher oxygen consumption rate than WT‐EC. Intriguingly, treatment with prolyl‐hydroxylase inhibitor‐dimethyloxalylglycine (DMOG) or VEGF rescued the impaired basal glycolytic metabolism in Sirt3 KO‐EC. Treatment with DMOG resulted in a reduction of basal oxygen consumption in WT‐EC, but failed to reduce basal oxygen consumption in Sirt3 KO‐EC. In vivo, SIRT3 KO mice subjected to ischemia exhibited a larger infarct size and impaired cardiac function compared to WT mice. VEGF and glycolytic enzyme PFKFB3 levels were significantly decreased in the heart of SIRT3 KO relative to WT mice. These studies suggest that the loss of SIRT3 aggravates myocardial ischemic injury by altering hypoxic signaling, glycolytic metabolism and increasing oxygen consumption.

Treatment of Brain-Dead Donor Rats with Dimethyloxalylglycine Improves Both Donor and Graft Left-Ventricular Function after Heart Transplantation

Introduction: Cardiac transplantation is the most effective treatment of end-stage heart failure. Brain dead (BD) donors are currently the only reliable source for cardiac grafts. However, hemodynamic instability and cardiac dysfunction have been demonstrated in BD donors and this could therefore also affect posttransplant graft function. Hypothesis: Based upon the protective effect of Prolyl-Hydroxylase (PHD)-Hypoxia Inducible Factor (HIF)-1 pathway against ischemia/reperfusion injury (IRI), we tested the hypothesis that treatment of BD donor rats with the non-selective PHD inhibitor dimethyloxalylglycine (DMOG) results in a better graft heart condition in recipients after heterotopic transplantation. Methods: Lewis rats were injected with one shot DMOG (30 mg/kg i.v.) (n = 7) or equal volume of physiological saline (n = 7) and maintained BD for 5h by a subdurally placed and inflated balloon catheter. Controls were sham-operated (n = 11). Then, hearts were explanted, stored in cold preservation solution, heterotopically transplanted and after 1.5h reperfusion left-ventricular (LV) graft function was evaluated in vivo. Myocardial histological and molecular biological analyses were performed. Results: BD was associated with decreased LV function. DMOG treatment of BD animals resulted in better load-independent contractility and end-diastolic stiffness parameters (ESPVR E´max (mmHg/µl): BD+DMOG: 3.7 ± 0.6 vs BD: 3.1 ± 0.5; EDPVR (mmHg/µl): BD+DMOG: 0.13 ± 0.03 vs BD: 0.31 ± 0.06 p < 0.05). Following transplantation, DMOG treatment of BD donors significantly improved the altered LV systolic and diastolic function (at 80µL volume dP/dtmax (mmHg/s): BD+DMOG: 2284 ± 213 vs BD: 1854 ± 124 p < 0.05; dP/dtmin (mmHg/s): BD+DMOG: 1586 ± 183 vs BD: 1154 ± 74, p < 0.05; Tau-W (ms): BD+DMOG: 33 ± 4 vs BD: 43 ± 9 p < 0.05). Significantly lower myocardial inflammatory cell infiltration and necrosis were detected along with, significantly lower DNA-strand breakage in the DMOG treated BD group compared with BD group. Conclusions: Pre-treatment of BD heart donors with DMOG resulted in a significantly better LV graft function after transplantation. These results support the view that preconditioning of BD donors through the activation of HIF-1 pathway has a protective role against myocardial IRI after transplantation.

Abstract 12544: Dimethyloxalylglycine Treatment of Brain-Dead Donor Rats Improves Both Donor and Graft Left-Ventricular Function After Heart Transplantation

Introduction: Cardiac transplantation is the most effective treatment of end-stage heart failure. Brain dead (BD) donors are currently the only reliable source for cardiac grafts. However, hemodynamic instability and cardiac dysfunction have been demonstrated in BD donors and this could therefore also affect posttransplant graft function. Hypothesis: Based upon the protective effect of Prolyl-Hydroxylase (PHD)-Hypoxia Inducible Factor (HIF)-1 pathway against ischemia/reperfusion injury (IRI), we tested the hypothesis that treatment of BD donor rats with the PHD inhibitor dimethyloxalylglycine (DMOG) results in a better graft heart condition in recipients after heterotopic transplantation. Methods: Lewis rats were injected with one shot DMOG (30 mg/kg i.v.) (n=7) or equal volume of physiological saline (n=7) and maintained BD for 5h by a subdurally placed and inflated balloon catheter. Controls were sham-operated (n=11). Then, hearts were explanted, stored in cold preservation solution, heterotopically transplanted and after 1.5h reperfusion left-ventricular (LV) graft function was evaluated in vivo . Myocardial histological and molecular biological analyses were performed. Results: BD was associated with decreased LV function. DMOG treatment of BD animals resulted in better load-independent contractility and end-diastolic stiffness parameters (ESPVR E' max (mmHg/μl): BD+DMOG: 3.7±0.6 vs BD: 3.1±0.5; EDPVR (mmHg/μl): BD+DMOG: 0.13±0.03 vs BD: 0.31±0.06 p&lt;0.05). Following transplantation, DMOG treatment of BD donors significantly improved altered LV systolic and diastolic function (at 80μL volume dP/dt max (mmHg/s): BD+DMOG: 2284±213 vs BD: 1854±124 p&lt;0.05; dP/dt min (mmHg/s): BD+DMOG: 1586±183 vs BD: 1154±74, p&lt;0.05; Tau-W (ms): BD+DMOG: 33±4 vs BD: 43±9 p&lt;0.05). Significantly lower myocardial inflammatory cell infiltration, necrosis, and DNA-strand breakage were evident in DMOG treated BD group compared to BD group. Conclusions: Pre-treatment of BD heart donors with DMOG resulted in a significantly better LV graft function after transplantation. These results support the view that preconditioning of BD donors through the activation of HIF-1 pathway has a protective role against myocardial IRI after transplantation.

Abstract 18569: Inhibition of Prolyl Hydroxylase Stimulates Hif-mediated Sdf-1 Expression and CXCR4+ Cell Recruitment for Myocardial Repair

Objective: Data from our lab indicate that stabilization of the cardiac SDF-1/CXCR4 axis preserves myocardial function and attenuates ischemic cardiomyopathy. However, HIF-1α dependent SDF-1 upregulation lasts only for 48-72 hours after MI limiting the targeting of stem cells to ischemic myocardium. To overcome this caveat, we aimed to activate SDF-1 expression by stabilization of HIF-1α through inhibition of prolyl hydroxylase with the ratio to augment CXCR4+ stem cell recruitment and stimulate myocardial repair. Methods: To evaluate the effects on HIF-1α mediated SDF-1 expression, genetically taggedSDF1-EGFP mice were subjected to optimal doses (80mg/kg i.p.) of the prolyl hydroxylase Inhibitor dimethyloxalylglycine (DMOG). To track the fate of CXCR4+ cells, genetically tagged CXCR4-EGFP BAC reporter mice were utilized. FACS and immunhistochemical analyses of CXCR4+ bone marrowm(BM), peripheral blood, and heart cells as well as infarct sizes were analyzed under normoxaemic and ischemic conditions with and without DMOG treatment. Results: SDF1-EGFP mice treated with DMOG showed robust induction of SDF-1 in the heart. SDF-1 upregulation after DMOG treatment was further confirmed by SDF-1 ELISA of heart lysates. FACS of transgenic CXCR4-EGFP BM and hearts revealed that CXCR4+ was most frequently expressed on CD11b+ monocytes, and to a less amount on angiogenic CD31+ , CD34+, c-kit+, and Flk1+ cells, as well as stem cell populations like ACC133+ and Lin-/c-kit+/Sca-1+. After myocardial ischemia these cell populations were highly upregulated. A subpopulation of CXCR4-EGFP+ cells co-expressed CD31 in capillaries. Treatment with DMOG revealed a robust upregulation of CXCR4+ cell populations in the ischemic heart, predominantly of angiogenic CXCR4+/CD11b+ monocytes. Further analysis showed that DMOG Treatment after 7 days leads particularly to upregulation of CD206+ subpopulation in infarcted hearts in favor of repair mechanisms characterized by reduced infarct sizes. Summary and Conclusion: Our data suggest that inhibition of prolyl hydroxylase may be a promising target for HIF-1a mediated SDF-1 activation to increase stem cell homing and myocardial repair.

The prolyl hydroxylase inhibitor dimethyloxalylglycine enhances dentin sialophoshoprotein expression through VEGF-induced Runx2 stabilization.

Prolyl hydroxylase (PHD) inhibitors are suggested as therapeutic agents for tissue regeneration based on their ability to induce pro-angiogenic responses. In this study, we examined the effect of the PHD inhibitor dimethyloxalylglycine (DMOG) on odontoblast maturation and sought to determine the underlying mechanism using MDPC-23 odontoblast-like cells. DMOG significantly enhanced matrix mineralization, confirmed by alizarin red staining and by measurement of the calcium content. DMOG dose-dependently increased alkaline phosphatase activity and the expressions of dentin sialophosphoprotein (Dspp) and osteocalcin. To determine the underlying events leading to DMOG-induced Dspp expression, we analyzed the effect of DMOG on Runx2. Knockdown of Runx2 using siRNAs decreased Dspp expression and prevented DMOG-induced Dspp expression. DMOG enhanced the transcriptional activity and level of Runx2 protein but not Runx2 transcript, and this enhancement was linked to the inhibitory effects of DMOG on the degradation of Runx2 protein. The vascular endothelial growth factor (VEGF) siRNAs profoundly decreased the Runx2 protein levels and inhibited the DMOG-increased Runx2 protein. Recombinant VEGF protein treatment significantly and dose-dependently increased the transcriptional activity and level of the Runx2 protein but not Runx2 transcript. Dspp expression was also enhanced by VEGF. Last, we examined the involvement of the Erk mitogen-activated protein kinase and Pin1 pathway in VEGF-enhanced Runx2 because this pathway can regulate the stability and activity of the Runx2 protein. VEGF stimulated Erk activation, and the inhibitors of Erk and Pin1 hampered VEGF-enhanced Runx2 protein. Taken together, the results of this study provide evidence that DMOG can enhance Dspp expression through VEGF-induced stabilization of Runx2 protein, and thus, suggest that DMOG can be used as a therapeutic tool for enhancing odontoblast maturation in dental procedures.

Preconditioning of bone marrow mesenchymal stem cells by prolyl hydroxylase inhibition enhances cell survival and angiogenesis in vitro and after transplantation into the ischemic heart of rats

IntroductionPoor cell survival and limited functional benefits have restricted the efficacy of bone marrow mesenchymal stem cells (BMSCs) in the treatment of myocardial infarction. We showed recently that hypoxia preconditioning of BMSCs and neural progenitor cells before transplantation can enhance the survival and therapeutic properties of these cells in the ischemic brain and heart. The present investigation explores a novel strategy of preconditioning BMSCs using the Hypoxia-inducible factor 1α (HIF-α) prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) to enhance their survival and therapeutic efficacy after transplantation into infarcted myocardium.MethodsBMSCs from green fluorescent protein transgenic rats were cultured with or without 1 mM DMOG for 24 hours in complete culture medium before transplantation. Survival and angiogenic factors were evaluated in vitro by trypan blue staining, Western blotting, and tube formation test. In an ischemic heart model of rats, BMSCs with and without DMOG preconditioning were intramyocardially transplanted into the peri-infarct region 30 minutes after permanent myocardial ischemia. Cell death was measured 24 hours after engraftment. Heart function, angiogenesis and infarct size were measured 4 weeks later.ResultsIn DMOG preconditioned BMSCs (DMOG-BMSCs), the expression of survival and angiogenic factors including HIF-1α, vascular endothelial growth factor, glucose transporter 1 and phospho-Akt were significantly increased. In comparison with control cells, DMOG-BMSCs showed higher viability and enhanced angiogenesis in both in vitro and in vivo assays. Transplantation of DMOG-BMSCs reduced heart infarct size and promoted functional benefits of the cell therapy.ConclusionsWe suggest that DMOG preconditioning enhances the survival capability of BMSCs and paracrine effects with increased differentiation potential. Prolyl hydroxylase inhibition is an effective and feasible strategy to enhance therapeutic efficacy and efficiency of BMSC transplantation therapy after heart ischemia.

Oxygen tension controls the expression of the monocarboxylate transporter MCT4 in cultured mouse cortical astrocytes via a hypoxia‐inducible factor‐1α‐mediated transcriptional regulation

The monocarboxylate transporter MCT4 is a high capacity carrier important for lactate release from highly glycolytic cells. In the central nervous system, MCT4 is predominantly expressed by astrocytes. Surprisingly, MCT4 expression in cultured astrocytes is low, suggesting that a physiological characteristic, not met in culture conditions, is necessary. Here we demonstrate that reducing oxygen concentration from 21% to either 1 or 0% restored in a concentration-dependent manner the expression of MCT4 at the mRNA and protein levels in cultured astrocytes. This effect was specific for MCT4 since the expression of MCT1, the other astrocytic monocarboxylate transporter present in vitro, was not altered in such conditions. MCT4 expression was shown to be controlled by the transcription factor hypoxia-inducible factor-1α (HIF-1α) since under low oxygen levels, transfecting astrocyte cultures with a siRNA targeting HIF-1α largely prevented MCT4 induction. Moreover, the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) induced MCT4 expression in astrocytes cultured in presence of 21% oxygen. In parallel, glycolytic activity was enhanced by exposure to 1% oxygen as demonstrated by the increased lactate release, an effect dependent on MCT4 expression. Finally, MCT4 expression was found to be necessary for astrocyte survival when exposed for a prolonged period to 1% oxygen. These data suggest that a major determinant of astrocyte MCT4 expression in vivo is likely the oxygen tension. This could be relevant in areas of high neuronal activity and oxygen consumption, favouring astrocytic lactate supply to neurons. Moreover, it could also play an important role for neuronal recovery after an ischemic episode.

Systemic Preconditioning by a Prolyl Hydroxylase Inhibitor Promotes Prevention of Skin Flap Necrosis via HIF-1-Induced Bone Marrow-Derived Cells

BackgroundLocal skin flaps often present with flap necrosis caused by critical disruption of the blood supply. Although animal studies demonstrate enhanced angiogenesis in ischemic tissue, no strategy for clinical application of this phenomenon has yet been defined. Hypoxia-inducible factor 1 (HIF-1) plays a pivotal role in ischemic vascular responses, and its expression is induced by the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG). We assessed whether preoperative stabilization of HIF-1 by systemic introduction of DMOG improves skin flap survival.Methods and ResultsMice with ischemic skin flaps on the dorsum were treated intraperitoneally with DMOG 48 hr prior to surgery. The surviving area with neovascularization of the ischemic flaps was significantly greater in the DMOG-treated mice. Significantly fewer apoptotic cells were present in the ischemic flaps of DMOG-treated mice. Interestingly, marked increases in circulating endothelial progenitor cells (EPCs) and bone marrow proliferative progenitor cells were observed within 48 hr after DMOG treatment. Furthermore, heterozygous HIF-1α-deficient mice exhibited smaller surviving flap areas, fewer circulating EPCs, and larger numbers of apoptotic cells than did wild-type mice, while DMOG pretreatment of the mutant mice completely restored these parameters. Finally, reconstitution of wild-type mice with the heterozygous deficient bone marrow cells significantly decreased skin flap survival.ConclusionWe demonstrated that transient activation of the HIF signaling pathway by a single systemic DMOG treatment upregulates not only anti-apoptotic pathways but also enhances neovascularization with concomitant increase in the numbers of bone marrow-derived progenitor cells.