Loss of Prolyl Hydroxylase-1 Protects Against Colitis Through Reduced Epithelial Cell Apoptosis and Increased Barrier Function

Background & Aims Hypoxia inducible factor (HIF) prolyl hydroxylase inhibitors are protective in mouse models of inflammatory bowel disease (IBD). Here, we investigated the therapeutic target(s) and mechanism(s) involved. Methods The effect of genetic deletion of individual HIF-prolyl hydroxylase (PHD) enzymes on the development of dextran sulphate sodium (DSS)induced colitis was examined in mice. Results PHD1-/-, but not PHD2+/- or PHD3-/-, mice were less susceptible to the development of colitis than wild-type controls as determined by weight loss, disease activity, colon histology, neutrophil infiltration, and cytokine expression. Reduced susceptibility of PHD1-/- mice to colitis was associated with increased density of colonic epithelial cells relative to wild-type controls, which was because of decreased levels of apoptosis that resulted in enhanced epithelial barrier function. Furthermore, with the use of cultured epithelial cells it was confirmed that hydroxylase inhibition reversed DSS-induced apoptosis and barrier dysfunction. Finally, PHD1 levels were increased with disease severity in intestinal tissue from patients with IBD and in colonic tissues from DSS-treated mice. Conclusions These results imply a role for PHD1 as a positive regulator of intestinal epithelial cell apoptosis in the inflamed colon. Genetic loss of PHD1 is protective against colitis through decreased epithelial cell apoptosis and consequent enhancement of intestinal epithelial barrier function. Thus, targeted PHD1 inhibition may represent a new therapeutic approach in IBD. © 2010 AGA Institute

Dexamethasone decreases the duration of rocuronium-induced neuromuscular block A randomised controlled study

BACKGROUND Several drugs influence the time course of neuromuscular block during general anaesthesia. OBJECTIVE To evaluate the effect of a single dose of dexamethasone 8 mg on the time course of a rocuronium-induced neuromuscular block. DESIGN A randomised controlled, unblinded, monocentre trial. SETTING Kreiskrankenhaus Dormagen, Dormagen, Germany. PATIENTS One hundred and eight adult patients scheduled for elective gynaecological laparoscopic surgery allocated to three groups. INTERVENTIONS Patients received dexamethasone 8 mg intravenously 2 to 3 h prior to surgery (Group A), during induction of anaesthesia (Group B) or after recovery of the neuromuscular block (Group C, control). MAIN OUTCOME MEASURES The time course of the neuromuscular block of rocuronium 0.3 mg kg(-1) was assessed using acceleromyography. The primary end point was the time from start of injection of rocuronium until recovery to a train-pof-pfour ratio of 0.9. RESULTS The clinical duration was decreased in Group A (15.8 +/- 4.5 min) compared with Group B (18.7 +/- 5.8 min; P = 0.031). The recovery index was reduced in Group A (6.8 +/- 1.8 min) compared with Group B (8.1 +/- 2.6 min; P = 0.018) and Group C (8.3 +/- 2.8 min; P = 0.01). The recovery to a train-pof-pfour ratio of 0.9 was shorter in Group A (30.4 +/- 6.9 min) than in Groups B (36.3 +/- 10.7 min; P 0.031) and C (36.8 +/- 11.3 min; P = 0.02). CONCLUSION A single dose of dexamethasone 8 mg attenuated rocuronium-pinduced block by 15 to 20% if administered 2 to 3 h prior to induction of anaesthesia. However, the administration of dexamethasone during induction of anaesthesia did not influence the time course of the neuromuscular block

HIF-1 alpha metabolically controls collagen synthesis and modification in chondrocytes

Endochondral ossification, an important process in vertebrate bone formation, is highly dependent on correct functioning of growth plate chondrocytes1. Proliferation of these cells determines longitudinal bone growth and the matrix deposited provides a scaffold for future bone formation. However, these two energy-dependent anabolic processes occur in an avascular environment1,2. In addition, the centre of the expanding growth plate becomes hypoxic, and local activation of the hypoxia-inducible transcription factor HIF-1α is necessary for chondrocyte survival by unidentified cell-intrinsic mechanisms3-6. It is unknown whether there is a requirement for restriction of HIF-1α signalling in the other regions of the growth plate and whether chondrocyte metabolism controls cell function. Here we show that prolonged HIF-1α signalling in chondrocytes leads to skeletal dysplasia by interfering with cellular bioenergetics and biosynthesis. Decreased glucose oxidation results in an energy deficit, which limits proliferation, activates the unfolded protein response and reduces collagen synthesis. However, enhanced glutamine flux increases α-ketoglutarate levels, which in turn increases proline and lysine hydroxylation on collagen. This metabolically regulated collagen modification renders the cartilaginous matrix more resistant to protease-mediated degradation and thereby increases bone mass. Thus, inappropriate HIF-1α signalling results in skeletal dysplasia caused by collagen overmodification, an effect that may also contribute to other diseases involving the extracellular matrix such as cancer and fibrosis.status: publishe

Loss or silencing of the PHD1 prolyl hydroxylase protects livers of mice against ischemia/reperfusion injury.

BACKGROUND and AIMS: Liver ischemia/reperfusion (I/R) injury is a frequent cause of organ dysfunction. Loss of the oxygen sensor prolyl hydroxylase domain enzyme 1 (PHD1) causes tolerance of skeletal muscle to hypoxia. We assessed whether loss or short-term silencing of PHD1 could likewise induce hypoxia tolerance in hepatocytes and protect them against hepatic I/R damage. METHODS: Hepatic ischemia was induced in mice by clamping of the portal vessels of the left lateral liver lobe; 90 minutes later livers were reperfused for 8 hours for I/R experiments. Hepatocyte damage following ischemia or I/R was investigated in PHD1-deficient (PHD1(-/-)) and wild-type mice or following short hairpin RNA-mediated short-term inhibition of PHD1 in vivo. RESULTS: PHD1(-/-) livers were largely protected against acute ischemia or I/R injury. Among mice subjected to hepatic I/R followed by surgical resection of all nonischemic liver lobes, more than half of wild-type mice succumbed, whereas all PHD1(-/-) mice survived. Also, short-term inhibition of PHD1 through RNA interference-mediated silencing provided protection against I/R. Knockdown of PHD1 also induced hypoxia tolerance of hepatocytes in vitro. Mechanistically, loss of PHD1 decreased production of oxidative stress, which likely relates to a decrease in oxygen consumption as a result of a reprogramming of hepatocellular metabolism. CONCLUSIONS: Loss of PHD1 provided tolerance of hepatocytes to acute hypoxia and protected them against I/R-damage. Short-term inhibition of PHD1 is a novel therapeutic approach to reducing or preventing I/R-induced liver injury

Loss or Silencing of the PHD1 Prolyl Hydroxylase Protects Livers of Mice Against Ischemia/Reperfusion Injury

BACKGROUND & AIMS: Liver ischemia/reperfusion (I/R) injury is a frequent cause of organ dysfunction. Loss of the oxygen sensor prolyl hydroxylase domain enzyme 1 (PHD1) causes tolerance of skeletal muscle to hypoxia. We assessed whether loss or short-term silencing of PHD1 could likewise induce hypoxia tolerance in hepatocytes and protect them against hepatic I/R damage. METHODS: Hepatic ischemia was induced in mice by clamping of the portal vessels of the left lateral liver lobe; 90 minutes later livers were reperfused for 8 hours for I/R experiments. Hepatocyte damage following ischemia or I/R was investigated in PHD1-deficient (PHD1(-/-)) and wild-type mice or following short hairpin RNA-mediated short-term inhibition of PHD1 in vivo. RESULTS: PHD1(-/-) livers were largely protected against acute ischemia or I/R injury. Among mice subjected to hepatic I/R followed by surgical resection of all nonischemic liver lobes, more than half of wild-type mice succumbed, whereas all PHD1(-/-) mice survived. Also, short-term inhibition of PHD1 through RNA interference-mediated silencing provided protection against I/R. Knockdown of PHD1 also induced hypoxia tolerance of hepatocytes in vitro. Mechanistically, loss of PHD1 decreased production of oxidative stress, which likely relates to a decrease in oxygen consumption as a result of a reprogramming of hepatocellular metabolism. CONCLUSIONS: Loss of PHD1 provided tolerance of hepatocytes to acute hypoxia and protected them against I/R-damage. Short-term inhibition of PHD1 is a novel therapeutic approach to reducing or preventing I/R-induced liver injury.status: publishe

Deficiency or inhibition of oxygen sensor Phd1 induces hypoxia tolerance by reprogramming basal metabolism.

HIF prolyl hydroxylases (PHD1-3) are oxygen sensors that regulate the stability of the hypoxia-inducible factors (HIFs) in an oxygen-dependent manner. Here, we show that loss of Phd1 lowers oxygen consumption in skeletal muscle by reprogramming glucose metabolism from oxidative to more anaerobic ATP production through activation of a Pparalpha pathway. This metabolic adaptation to oxygen conservation impairs oxidative muscle performance in healthy conditions, but it provides acute protection of myofibers against lethal ischemia. Hypoxia tolerance is not due to HIF-dependent angiogenesis, erythropoiesis or vasodilation, but rather to reduced generation of oxidative stress, which allows Phd1-deficient myofibers to preserve mitochondrial respiration. Hypoxia tolerance relies primarily on Hif-2alpha and was not observed in heterozygous Phd2-deficient or homozygous Phd3-deficient mice. Of medical importance, conditional knockdown of Phd1 also rapidly induces hypoxia tolerance. These findings delineate a new role of Phd1 in hypoxia tolerance and offer new treatment perspectives for disorders characterized by oxidative stress