Acute hypoxia up-regulates HIF-1α and VEGF mRNA levels in Amazon hypoxia-tolerant Oscar (Astronotus ocellatus)

Apelin is the endogenous ligand for the APJ receptor, and apelin and APJ are expressed in the gastrointestinal (GI) tract. Intestinal inflammation increases intestinal hypoxia-inducible factor (HIF) and apelin expression. Hypoxia and inflammation are closely linked cellular insults. The purpose of these studies was to investigate the influence of hypoxia on enteric apelin expression. Exposure of rat pups to acute hypoxia increased hepatic, stomach-duodenal, and colonic apelin mRNA levels 10-, 2-, and 2-fold, respectively ( P < 0.05 vs. controls). Hypoxia also increased colonic APJ mRNA levels, and apelin treatment during hypoxia exposure enhanced colonic APJ mRNA levels further. In vitro hypoxia also increased apelin and APJ mRNA levels. The hypoxia-induced elevation in apelin expression is most likely mediated by HIF, since HIF-activated apelin transcriptional activity is dependent on an intact, putative HIF binding site in the rat apelin promoter. Acute exposure of rat pups to hypoxia lowered gastric and colonic epithelial cell proliferation; hypoxia in combination with apelin treatment increased epithelial proliferation by 50%. In vitro apelin treatment of enteric cells exposed to hypoxia increased cell proliferation. Apelin treatment during normoxia was ineffective. Our studies imply that the elevation in apelin expression during hypoxia and inflammation in the GI tract functions in part to stimulate epithelial cell proliferation.

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Abstract 996: Growth Differentiation Factor-5 (GDF-5) Dictates Cardiac Remodelling in a Mouse Model of Myocardial Infarction

Circulation ◽

10.1161/circ.116.suppl_16.ii_198-a ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Syed Zaidi ◽

Ali M Riazi ◽

Qingling Huang ◽

Md A Momen ◽

Mansoor Husain

Keyword(s):

Myocardial Infarction ◽

Systolic Pressure ◽

Left Ventricular ◽

Cardiac Remodelling ◽

Postnatal Life ◽

Mrna Levels ◽

Vegf Mrna ◽

Foetal Development ◽

Differentiation Factor ◽

Growth Differentiation Factor 5

Background: Bone Morphogenetic Proteins (BMPs) regulate diverse cellular functions during foetal development and postnatal life. Growth Differentiation Factor 5 (GDF5 a.k.a. BMP-14) is a BMP, which is expressed in a variety of tissues including heart. We previously showed that cardiac GDF5 mRNA levels are elevated after experimental myocardial infarction (MI) caused by permanent left anterior descending coronary artery (LAD) ligation. However, the significance of this finding was not known. Methods & Results: GDF5 knock-out (KO; n = 18 for MI) and wild-type (WT; n = 18 for MI) littermate controls were subjected to chronic LAD ligation in order to investigate the consequences resulting from the loss of GDF5 signalling following MI. At 28 days post-LAD ligation or sham (n = 12 for KO; n = 10 for WT), invasive hemodynamic parameters of cardiac function were examined just prior to sacrifice. Histopathology was assessed by morphometric analyses of perfusion fixed hearts and subsequent immunostaining. At 28 days post-MI, GDF5-KO mice exhibited decreased left ventricular systolic pressure and peak positive- and negative- dP/dt , and increased heart rate as compared to WT littermates ( P < 0.005 for each parameters). GDF5-KO mice also exhibited a significant increase in the area, length and transmural expansion of the infarct, scar thinning and cardiac dilatation ( P < 0.05 for each parameter). In addition, GDF5-KO mice displayed significantly fewer myocardial vessels in the infarct and peri-infarct regions as compared to WT littermates ( P < 0.05) . To explore mechanisms underlying this phenotype, we assessed gene expression levels of relevant potential downstream targets of GDF5. At 7d post-MI, quantitative RT-PCR revealed a significant reduction (35%) in VEGF mRNA levels in hearts of KO (n = 6) as compared to WT mice (n = 5, P = 0.033). Summary & Conclusion: These data suggest that increased GDF5 expression observed in hearts after MI plays an important role in cardiac remodelling. Absence of GDF5 expression in KO mice confers detrimental effects on healing and repair of myocardial and vascular tissues after MI. Regulated levels of GDF5, a BMP family member, play an important role in the repair process following cardiac injury.

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Acute hypoxia stimulates renin secretion and renin gene expression in vivo but not in vitro

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.272.4.r1105 ◽

1997 ◽

Vol 272 (4) ◽

pp. R1105-R1111 ◽

Cited By ~ 4

Author(s):

T. Ritthaler ◽

K. Schricker ◽

F. Kees ◽

B. Kramer ◽

A. Kurtz

Keyword(s):

Gene Expression ◽

Acute Hypoxia ◽

Primary Cultures ◽

Renin Secretion ◽

Plasma Norepinephrine ◽

Mrna Levels ◽

Sprague Dawley ◽

Renin Gene ◽

Renin Mrna

This study aimed at examining the influence of acute hypoxia on renin secretion and renin gene expression in the kidney. To this end, male Sprague-Dawley rats were exposed to severe hypoxic stress (8% O2) or to carbon monoxide (0.1% CO) for 6 h, and plasma renin activity (PRA) and renal renin mRNA levels were determined. PRA values increased from 3 to 13 and 10 ng angiotensin I x h(-1) x ml(-1), and renin mRNA levels increased by 120 and 100% during hypoxia and CO, respectively. Lowering the PO2 from 150 to 20 or 7 mmHg in the gas atmosphere of primary cultures of renal juxtaglomerular cells had no influence on renin secretion and renin gene expression after 6 and 20 h. Our findings thus suggest that both arterial and venous hypoxia can be powerful stimulators of renin secretion and renin gene expression in vivo. Because renal denervation did not prevent stimulation of the renin system by hypoxia, the effect could be indirectly mediated via the baroreceptor-macula densa mechanism. Another potential mediator of the effect could be circulating catecholamines, since we found that plasma norepinephrine increased from 0.7 to 1.5 and 2.4 ng/ml and plasma epinephrine increased from 0.3 to 1.4 and 2.7 ng/ml during hypoxia and CO inhalation, respectively.

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Evaluation of pulmonary GLUT1 and VEGF mRNA levels in relation to lung weight in medicolegal autopsy cases

Legal Medicine ◽

10.1016/j.legalmed.2009.01.094 ◽

2009 ◽

Vol 11 ◽

pp. S290-S293 ◽

Cited By ~ 6

Author(s):

Dong Zhao ◽

Takaki Ishikawa ◽

Li Quan ◽

Tomomi Michiue ◽

Chiemi Yoshida ◽

...

Keyword(s):

Mrna Levels ◽

Vegf Mrna ◽

Lung Weight ◽

Medicolegal Autopsy

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Hypoxia Inducible Factor-1α Is over Expressed in CLL B Cells Because of an Impaired Proteasome Pathway Associated with Defective Interaction with von Hippel-Landau Protein.

Blood ◽

10.1182/blood.v106.11.2115.2115 ◽

2005 ◽

Vol 106 (11) ◽

pp. 2115-2115 ◽

Cited By ~ 1

Author(s):

Yean K. Lee ◽

Ann K. Strege ◽

Nancy D. Bone ◽

Linda E. Wellik ◽

D. A. Chan ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Target Genes ◽

Hypoxia Inducible Factor ◽

Nuclear Extract ◽

Degradation Pathway ◽

Mrna Levels ◽

Apoptosis Resistance ◽

Vegf Mrna ◽

Prolyl Hydroxylases

Abstract We have found that CLL B cells spontaneously secrete vascular endothelial growth factor (VEGF) and that a VEGF autocrine pathway can induce apoptosis resistance in these cells. Recently, we also found that hypoxia-inducible factor-1 alpha (HIF-1α) is highly expressed in CLL B cells. Since this protein is a potent transcription factor for the induction of VEGF, we were interested in further definition of HIF-1α regulation and its function in CLL B cells. CLL blood B cells overexpress HIF-1α protein but not mRNA for HIF-1α compared to normal blood and splenic B cells. Immunohistochemistry (IHC) showed that circulating blood CLL B cells and a subset of CLL marrow cells uniformly express HIF. Hypoxic conditions (i.e., 1% O2) did not increase the protein levels of HIF-1α nor mRNA for HIF-1α in CLL B cells, indicating that the high HIF-1α protein level is due to post-translation modification. Blockade of signaling pathways known to increase HIF-1α levels also did not alter the high levels of HIF-1α in CLL B cells. IHC and nuclear extraction assay demonstrated that HIF-1α was predominantly located in the CLL B cell nucleus. In addition, the nuclear extract when immunoprecipitated for HIF-1α was shown to be complexed with the co-activator p300, indicating that HIF-1α is transcriptionally active. Co-immunoprecipitation assay showed that HIF-1α from CLL B cells does not associate and form a complex with von Hippel-Landau protein tumor suppressor (pVHL), indicating that the proteasome dependent degradation pathway for HIF-1α protein in CLL B cells is dysfunctional. Using immunoblot or IHC methods, we were unable to detect pVHL protein in CLL B cells; however, we were able to use immunoprecipitation of CLL B cell lysates to demonstrate there is pVHL in CLL B cells. Prolyl hydroxylases (PHD 1, 2, and 3) are negative regulators for HIF-1α via hydroxylation of amino acid prolines in the oxygen degradation domain (ODD) which permits interaction with pVHL. RT-PCR results revealed that there is a subset of CLL patients who had ≥ 50% reduction of PHD 1 and 3 mRNA levels. However using a hydroxylation specific polyclonal antibody we found that HIF-1α from CLL B cells is indeed hydroxylated. Finally, silencing of HIF-1α by RNA interference in CLL B cells was associated with a selective decrease in VEGF mRNA levels but not VEGF-R1, Mcl-1 and prolyl hydroxylases (PHD 1–3) other downstream target genes of HIF-1α. These data show that the high endogenous HIF-1α levels in CLL B cells are due to a defect in HIF-1α degradation via the proteosomal pathway. We believe that this abnormality is linked to the autocrine VEGF pathway in CLL B cells and ultimately results in increases in their apoptotic resistance. Inhibition of HIF-1α levels may be of therapeutic benefit to CLL patients.

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Muscle microvascular adaptation and angiogenic gene induction in response to exercise training are attenuated in middle-aged rats

Comparative Exercise Physiology ◽

10.3920/cep150007 ◽

2015 ◽

Vol 11 (1) ◽

pp. 23-33

Author(s):

J. Suzuki

Keyword(s):

Exercise Training ◽

Acute Exercise ◽

Young Group ◽

Treadmill Running ◽

Mrna Levels ◽

Aged Rats ◽

Middle Aged ◽

Vegf Mrna ◽

Aged Group ◽

Exercise Induced

This study was designed to investigate exercise-induced changes in muscle capillarisation, the mRNA expression of angiogenic genes, and microRNA levels in young and middle-aged rats. Rats in the training groups were subjected to treadmill running 5 days a week for 3 weeks. The exercise protocol for the young (12-week old) group was 20-25 m/min, 40-60 min/day with a gradient of 15%, and for the middle-aged (12-month old) group was 18-20 m/min, 40-60 min/day with a gradient of 5%. The enzyme histochemical identification of capillary profiles was performed on cross-sections of gastrocnemius muscle. Total RNA was isolated, reverse transcription was performed, and mRNA and microRNA levels were determined by real-time PCR. The capillary-to-fibre ratio was significantly increased by exercise training in the young group (by 10%), but only slightly in the middle-aged (by 5%) group. Vascular endothecial growth factor (VEGF) mRNA levels were at significantly higher values after acute exercise (1.6-fold) and the 3-week training protocol (1.9-fold) in the young group, but not in the middle-aged group. VEGF protein expression levels were significantly increased after training in the young group only. Endothelial nitric oxide synthase, VEGF-R2 and thrombospondin-1 mRNA levels were significantly lower in the middle-aged group than in the young group. Anti-angiogenic miR-195 levels were significantly enhanced by exercise training in the middle-aged group only. These results indicated that the exercise-induced adaptation of muscle capillarity was attenuated in middle-aged rats, possibly by the lower induction of VEGF and up-regulation of anti-angiogenic miRNA expression.

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Inactivation of Tristetraprolin in Chronic Hypoxia Provokes the Expression of Cathepsin B

Molecular and Cellular Biology ◽

10.1128/mcb.01034-14 ◽

2014 ◽

Vol 35 (3) ◽

pp. 619-630 ◽

Cited By ~ 6

Author(s):

Dominik C. Fuhrmann ◽

Michaela Tausendschön ◽

Ilka Wittig ◽

Mirco Steger ◽

Martina G. Ding ◽

...

Keyword(s):

Chromatin Immunoprecipitation ◽

Cathepsin B ◽

Chronic Hypoxia ◽

Acute Hypoxia ◽

Hypoxia Inducible Factor ◽

Rna Stability ◽

Cellular Protein ◽

Mrna Levels ◽

Differential Gel Electrophoresis ◽

Dependent Mechanism

Macrophages play important roles in many diseases and are frequently found in hypoxic areas. A chronic hypoxic microenvironment alters global cellular protein expression, but molecular details remain poorly understood. Although hypoxia-inducible factor (HIF) is an established transcription factor allowing adaption to acute hypoxia, responses to chronic hypoxia are more complex. Based on a two-dimensional differential gel electrophoresis (2D-DIGE) approach, we aimed to identify proteins that are exclusively expressed under chronic but not acute hypoxia (1% O2). One of the identified proteins was cathepsin B (CTSB), and a knockdown of either HIF-1α or -2α in primary human macrophages pointed to an HIF-2α dependency. Although chromatin immunoprecipitation (ChIP) experiments confirmed HIF-2 binding to a CTSB enhancer in acute hypoxia, an increase of CTSB mRNA was evident only under chronic hypoxia. Along those lines, CTSB mRNA stability increased at 48 h but not at 8 h of hypoxia. However, RNA stability at 8 h of hypoxia was enhanced by a knockdown of tristetraprolin (TTP). Inactivation of TTP under prolonged hypoxia was facilitated by c-Jun N-terminal kinase (JNK), and inhibition of this kinase lowered CTSB mRNA levels and stability. We postulate a TTP-dependent mechanism to explain delayed expression of CTSB under chronic hypoxia.

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Differential regulation of VEGF by TGF-β and hypoxia in rat proximal tubular cells

AJP Renal Physiology ◽

10.1152/ajprenal.00040.2004 ◽

2004 ◽

Vol 287 (4) ◽

pp. F658-F664 ◽

Cited By ~ 46

Author(s):

Takahiko Nakagawa ◽

Hui Y. Lan ◽

Hong J. Zhu ◽

Duk-Hee Kang ◽

George F. Schreiner ◽

...

Keyword(s):

Renal Disease ◽

Transforming Growth Factor ◽

Acute Hypoxia ◽

Critical Role ◽

Capillary Endothelium ◽

Proximal Tubular Cells ◽

Vegf Expression ◽

Vegf Mrna ◽

Tubular Cells ◽

Proximal Tubular

VEGF expression by proximal tubular epithelial cells may play a critical role in maintaining peritubular capillary endothelium in renal disease. Two major processes involved in renal injury include hypoxia (from vasoconstriction or vascular injury) and transforming growth factor (TGF)-β-dependent fibrosis, both of which are known to stimulate VEGF. Because the TGF-β/Smad pathway is activated in hypoxia, we tested the hypothesis that the induction of VEGF in hypoxia could be partially dependent on TGF-β. Rat proximal tubular (NRK52E) cells treated with TGF-β under normoxic conditions secreted VEGF at 24 h, and this was significantly reduced by blocking Smad activation by overexpressing the inhibitory Smad7 or by blocking p38 and ERK1/2 MAP kinase activation or protein kinase C activation with specific inhibitors. With acute hypoxia, rat proximal tubular cells also express VEGF mRNA and protein as well as TGF-β. However, the induction of VEGF occurs before synthesis of TGF-β and is not blocked by either a TGF-β antagonist, by Smad7 overexpression, or by blockage of ERK1/2, whereas induction is blocked by PKC inhibition or partially blocked by a p38 inhibitor. Finally, the addition of TGF-β with hypoxia results in significantly more VEGF expression than either stimulation alone. Thus TGF-β and hypoxia act via additive/synergistic but distinct pathways to stimulate VEGF in proximal tubular cells, a finding that may be important in understanding how VEGF is stimulated in renal disease.

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Effect of acute exercise and exercise training on VEGF splice variants in human skeletal muscle

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00071.2004 ◽

2004 ◽

Vol 287 (2) ◽

pp. R397-R402 ◽

Cited By ~ 45

Author(s):

Lotte Jensen ◽

Henriette Pilegaard ◽

P. Darrell Neufer ◽

Ylva Hellsten

Keyword(s):

Skeletal Muscle ◽

Exercise Training ◽

Human Skeletal Muscle ◽

Acute Exercise ◽

Splice Variants ◽

Knee Extensor ◽

Vastus Lateralis Muscle ◽

Mrna Levels ◽

Vegf Mrna ◽

Exercise Induced

The present study investigated the effect of an acute exercise bout on the mRNA response of vascular endothelial growth factor (VEGF) splice variants in untrained and trained human skeletal muscle. Seven habitually active young men performed one-legged knee-extensor exercise training at an intensity corresponding to ∼70% of the maximal workload in an incremental test five times/week for 4 wk. Biopsies were obtained from the vastus lateralis muscle of the trained and untrained leg 40 h after the last training session. The subjects then performed 3 h of two-legged knee-extensor exercise, and biopsies were obtained from both legs after 0, 2, 6, and 24 h of recovery. Real-time PCR was used to examine the expression of VEGF mRNA containing exon 1 and 2 (all VEGF isoforms), exon 6 or exon 7, and VEGF165mRNA. Acute exercise induced an increase ( P < 0.05) in total VEGF mRNA levels as well as VEGF165and VEGF splice variants containing exon 7 at 0, 2, and 6 h of recovery. The increase in VEGF mRNA was higher in the untrained than in the trained leg ( P < 0.05). The results suggest that in human skeletal muscle, acute exercise increases total VEGF mRNA, an increase that appears to be explained mainly by an increase in VEGF165mRNA. Furthermore, 4 wk of training attenuated the exercise-induced response in skeletal muscle VEGF165mRNA.

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Rapid regulation of Na+ fluxes and ammonia excretion in response to acute environmental hypoxia in the Amazonian oscar, Astronotus ocellatus

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00640.2006 ◽

2007 ◽

Vol 292 (5) ◽

pp. R2048-R2058 ◽

Cited By ~ 32

Author(s):

Chris M. Wood ◽

Makiko Kajimura ◽

Katherine A. Sloman ◽

Graham R. Scott ◽

Patrick J. Walsh ◽

...

Keyword(s):

Atpase Activity ◽

Acute Hypoxia ◽

Ammonia Excretion ◽

Ammonia Production ◽

Uptake Capacity ◽

Rapid Reduction ◽

Plasma Ammonia ◽

Astronotus Ocellatus ◽

Delayed Recovery ◽

The Relationship

The Amazonian oscar is extremely resistant to hypoxia, and tolerance scales with size. Overall, ionoregulatory responses of small (∼15 g) and large oscars (∼200 g) to hypoxia were qualitatively similar, but the latter were more effective. Large oscars exhibited a rapid reduction in unidirectional Na+ uptake rate at the gills during acute hypoxia (Po2 ∼10 mmHg), which intensified with time (7 or 8 h); Na+ efflux rates were also reduced, so net balance was little affected. The inhibitions were virtually immediate (1st h) and preceded a later 60% reduction (at 3 h) in gill Na+-K+-ATPase activity, reflected in a 60% reduction in maximum Na+ uptake capacity without change in affinity (Km) for Na+. Upon acute restoration of normoxia, recovery of Na+ uptake was delayed for 1 h. These data suggest that dual mechanisms may be involved (e.g., immediate effects of O2 availability on transporters, channels, or permeability, slower effects of Na+-K+-ATPase regulation). Ammonia excretion appeared to be linked indirectly to Na+ uptake, exhibiting a Michaelis-Menten relationship with external [Na+], but the Km was less than for Na+ uptake. During hypoxia, ammonia excretion fell in a similar manner to Na+ fluxes, with a delayed recovery upon normoxia restoration, but the relationship with [Na+] was blocked. Reductions in ammonia excretion were greater than in urea excretion. Plasma ammonia rose moderately over 3 h hypoxia, suggesting that inhibition of excretion was greater than inhibition of ammonia production. Overall, the oscar maintains excellent homeostasis of ionoregulation and N-balance during severe hypoxia.

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