losartan-potassium and pimonidazole

BackgroundWe determined whether maternal nutrient restriction (MNR) in guinea pigs leading to fetal growth restriction (FGR) impacts markers for tissue hypoxia, implicating a mechanistic role for chronic hypoxia.MethodsGuinea pigs were fed ad libitum (Control) or 70% of the control diet before pregnancy, switching to 90% at mid-pregnancy (MNR). Near term, hypoxyprobe-1 (HP-1), a marker of tissue hypoxia, was injected into pregnant sows. Fetuses were then necropsied and liver, kidney, and placental tissues were processed for erythropoietin (EPO), EPO-receptor (EPOR), and vascular endothelial growth factor (VEGF) protein levels, and for HP-1 immunoreactivity (IR).ResultsFGR-MNR fetuses were 36% smaller with asymmetrical growth restriction compared to controls. EPO and VEGF protein levels were increased in the female FGR-MNR fetuses, providing support for hypoxic stimulus and linkage to increased erythropoiesis, but not in the male FGR-MNR fetuses, possibly reflecting a weaker link between oxygenation and erythropoiesis. HP-1 IR was increased in the liver and kidneys of both male and female FGR-MNR fetuses as an index of local tissue hypoxia, but with no changes in the placenta.ConclusionChronic hypoxia is likely to be an important signaling mechanism for the decreased fetal growth seen with maternal undernutrition and appears to be post-placental in nature.

Topics: Animals; Cohort Studies; Erythropoietin; Female; Fetal Development; Fetal Growth Retardation; Guinea Pigs; Hypoxia; Immunohistochemistry; Male; Maternal Nutritional Physiological Phenomena; Maternal-Fetal Exchange; Nitroimidazoles; Placenta; Pregnancy; Signal Transduction; Vascular Endothelial Growth Factor A

Cerebral malaria (CM) is associated with high mortality and risk of sequelae, and development of adjunct therapies is hampered by limited knowledge of its pathogenesis. To assess the role of cerebral hypoxia, we used two experimental models of CM, Plasmodium berghei ANKA in CBA and C57BL/6 mice, and two models of malaria without neurologic signs, P. berghei K173 in CBA mice and P. berghei ANKA in BALB/c mice. Hypoxia was demonstrated in brain sections using intravenous pimonidazole and staining with hypoxia-inducible factor-1α-specific antibody. Cytopathic hypoxia was studied using poly (ADP-ribose) polymerase-1 (PARP-1) gene knockout mice. The effect of erythropoietin, an oxygen-sensitive cytokine that mediates protection against CM, on cerebral hypoxia was studied in C57BL/6 mice. Numerous hypoxic foci of neurons and glial cells were observed in mice with CM. Substantially fewer and smaller foci were observed in mice without CM, and hypoxia seemed to be confined to neuronal cell somas. PARP-1-deficient mice were not protected against CM, which argues against a role for cytopathic hypoxia. Erythropoietin therapy reversed the development of CM and substantially reduced the degree of neural hypoxia. These findings demonstrate cerebral hypoxia in malaria, strongly associated with cerebral dysfunction and a possible target for adjunctive therapy.

Topics: Animals; Brain; Disease Models, Animal; Erythropoietin; Female; Fluorescent Dyes; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Malaria, Cerebral; Mice; Nitroimidazoles; Parasitemia; Plasmodium berghei; Poly(ADP-ribose) Polymerases; Survival Analysis; Treatment Outcome

Hemoglobin is the major protein in red blood cells and transports oxygen from the lungs to oxygen-demanding tissues, like the brain. Mechanisms that facilitate the uptake of oxygen in the vertebrate brain are unknown. In invertebrates, neuronal hemoglobin serves as intracellular storage molecule for oxygen. Here, we show by immunohistochemistry that hemoglobin is specifically expressed in neurons of the cortex, hippocampus, and cerebellum of the rodent brain, but not in astrocytes and oligodendrocytes. The neuronal hemoglobin distribution is distinct from the neuroglobin expression pattern on both cellular and subcellular levels. Probing for low oxygen levels in the tissue, we provide evidence that hemoglobin alpha-positive cells in direct neighborhood with hemoglobin alpha-negative cells display a better oxygenation than their neighbors and can be sharply distinguished from those. Neuronal hemoglobin expression is upregulated by injection or transgenic overexpression of erythropoietin and is accompanied by enhanced brain oxygenation under physiologic and hypoxic conditions. Thus we provide a novel mechanism for the neuroprotective actions of erythropoietin under ischemic-hypoxic conditions. We propose that neuronal hemoglobin expression is connected to facilitated oxygen uptake in neurons, and hemoglobin might serve as oxygen capacitator molecule.

Topics: Animals; Antibodies, Monoclonal; Cell Hypoxia; Cells, Cultured; Cerebellum; Cerebral Cortex; Electrophoresis, Gel, Two-Dimensional; Erythropoietin; Female; Hemoglobins; Hippocampus; Mass Spectrometry; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neurons; Nitroimidazoles; Oxygen; Rats; Rats, Wistar; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Species Specificity

Relationship between haemoglobin levels and tumour oxygenation has been already reported. The purpose of this work was to compare in human malignant glioma-bearing mice the sensitivity of two well established techniques of tumour hypoxia assessment, especially their ability to detect expected weak variations of tumour oxygenation status associated to haemoglobin level modifications. The relationship between tumour hypoxia and glucose metabolism was also investigated. Experiments were performed on a human malignant glioma (GBM Nan1) xenografted into nude mice. Twenty-four hours after tumour implantation, animals were randomized into three groups: 'Anaemia' for mice subjected to repeated blood samplings, 'Control', and 'rHuEPO' for mice receiving recombinant human erythropoietin. Once the tumours reached a volume of 300+/-100 mm(3), tumour hypoxia was assessed both using the pO(2)-Histograph, Eppendorftrade mark and the pimonidazole binding assay. Glucose metabolism was evaluated by (18)F-FDG autoradiography and compared with the pimonidazole binding distribution pattern. Repeated blood samplings significantly reduced mean haemoglobin levels (10.9+/-2.0 g/dl), inducing chronic anaemia in mice, while daily administration of rHuEPO led to increase of haemoglobin levels (15.8+/-2.0 g/dl). Oxygenation status evaluated by a microelectrode was worsened in anaemic mice (mean pO(2) in tumour = 6.9+/-0.8 mmHg) and improved in rHuEPO-treated animals (mean pO(2)in tumour = 11.4+/-1.2 mmHg). No correlation was observed between the oxygen-sensitive probe and pimonidazole labelling results: both techniques give different but complementary information about tumour hypoxia. Areas of high pimonidazole binding and areas of high (18)F-FDG uptake superimposed well. Present results confirm that modification of haemoglobin levels leads to alteration of tumour oxygenation status. These variations were detectable using the oxygen-sensitive electrode but not the pimonidazole binding assay. The strong correlation between pimonidazole labelling and (18)F-FDG uptake suggests a positive relationship between hypoxia and increased glucose metabolism in this tumour model.

Topics: Anemia; Animals; Autoradiography; Electrodes; Erythropoietin; Fluorodeoxyglucose F18; Glioma; Hemoglobins; Humans; Hypoxia; Mice; Mice, Nude; Muscle, Skeletal; Neoplasm Transplantation; Nitroimidazoles; Recombinant Proteins; Transplantation, Heterologous

Erythropoietin, an oxygen-regulated glycoprotein hormone, is a hematopoietic cytokine that stimulates erythropoiesis by binding to its cellular receptor [erythropoietin receptor (EPOR)]. The recombinant form of human erythropoietin is used to prevent or treat anemia in cancer patients. However, in a recent randomized, placebo-controlled trial involving patients receiving curative radiotherapy for squamous cell carcinoma of the head and neck, erythropoietin treatment was associated with poorer locoregional progression-free survival. The purpose of our study was to determine whether EPOR and its ligand erythropoietin are expressed in primary head and neck cancer. We also investigated the hypothesis that erythropoietin expression in malignant cells may be associated with the presence of tumor hypoxia, an important factor involved in resistance to radiation treatment, tumor aggressiveness, and poor prognosis.. Twenty-one patients received an i.v. infusion of the hypoxia marker pimonidazole hydrochloride before multiple tumor biopsies. Contiguous sections from 74 biopsies were analyzed by immunohistochemistry for EPOR and erythropoietin expression and pimonidazole binding.. EPOR expression was present in tumor cells in 97% of the biopsies. Coexpression of erythropoietin was observed in 90% of biopsies. Erythropoietin and pimonidazole adduct staining did not always colocalize within tumors, but there was a significant positive correlation between levels of microregional erythropoietin expression and pimonidazole binding.. The coexpression of erythropoietin and EPOR in tumor cells suggests that erythropoietin may potentially function as an autocrine or paracrine factor in head and neck cancer. The expression of the hypoxia-inducible protein erythropoietin in tumor cells correlates with levels of tumor hypoxia.

Topics: Disease-Free Survival; Erythropoietin; Head and Neck Neoplasms; Humans; Hypoxia; Immunohistochemistry; Ligands; Nitroimidazoles; Prognosis; Radiation-Sensitizing Agents; Receptors, Erythropoietin; Recombinant Proteins; Time Factors