Erythropoietin is involved in hemoprotein syntheses in developing human decidua.

Before establishment of feto-placental circulation, decidua can synthesize hemoproteins to maintain oxygen homeostasis in situ. Using the human decidua of induced abortions ranging from 5 to 8 weeks of gestation, we determined the expression levels of erythropoietin, erythropoietin receptor, cytoglobin, myoglobin, embryonic-, fetal- and adult hemoglobin mRNA by quantitative RT-PCR analysis and identified their proteins by Western blot and immunohistochemical analyses. Erythropoietin signaling was demonstrated in phosphatidylinositol-3-kinase/protein kinase B pathway by Western blot, and the transcriptional factors for erythroid and non-erythroid heme synthesis were examined by RT-PCR analysis. In decidua, erythropoietin and its receptor mRNAs, erythropoietin receptor protein and phosphatidylinositol-3-kinase, were expressed with a peak at 6 weeks of gestation. Moreover, the decidua during 5 to 8 weeks of gestation expressed embryonic, fetal and adult hemoglobins additionally cytoglobin and myoglobin at transcriptional and protein levels. The heme portion of these hemoproteins is considered to be synthesized by non-erythroid δ-aminolevulinate synthase. These hemoproteins were discernible especially in decidual cells concomitant with cytotrophoblast cells and macrophage in these developing decidua. Considering the different capacity for oxygen binding and dissociation among hemoglobins with the oxygen storage capacity for cytoglobin and myoglobin, these hemoproteins appear to play a role in oxygen demand in decidua in situ before development of feto-placental circulation under the control of erythropoietin signaling.

A combination of unnatural phosphatidyl acceptor and tandem electrospray ionization mass spectrometry for tracing phospholipase D activity.

Phospholipase D (PLD) is a biocatalyst in the synthesis of bioactive compounds and a key enzyme in a variety of biological signal transductions. A combination of unnatural phosphatidyl acceptor, N,N,N-triethyl-N-2-hydroxyethylammonium bromide 6, as a substrate for PLD, and tandem electrospray ionization mass spectrometry (ESI MS) was found to provide information as to whether a given phospholipid serves as a substrate for the PLD-catalyzed reaction. Thus 2-(13'-hydroperoxy-octadecadienoyl)-1-palmitoylglycerophosphocholine 1, and its degradation products 2-(13'-oxo-octadecadienoyl)-1-palmitoylglycerophosphocholine 9 and 2-(13'-hydroxy-octadecadienoyl)-1-palmitoylglycerophosphocholine 11, in a mixture were found to be a substrate of the PLD-catalyzed transphosphatidylation. The sensitivity of this method was exemplified by the observation that PLD activity in cabbage leaves was detected using a small amount of crude crushed leaves with little pretreatment. This simple method can be used in screening for PLD activity and searching for inhibitors of the enzyme from various natural sources.

Analyses of expression of cytoglobin by immunohistochemical studies in human tissues.

Cytoglobin (Cygb) is a recently discovered member of the vertebrate globin family, which includes probably most extensively studied proteins, hemoglobin (Hb), myoglobin (Mb) and neuroglobin (Ngb). It has been reported that Cygb is expressed ubiquitously at the mRNA or protein level. However, details of the distribution of Cygb in the various tissues have hitherto been unclear. In this experiment, we clarified the distribution of Cygb in various human tissues by immunohistochemical staining. First, we prepared a rabbit anti human Cygb polyclonal antibody. Using the antibody, we stained a tissue array slide containing 60 normal tissues from 40 human organs. We confirmed the staining patterns of the antibodies in these various tissues using autopsy samples from our university. In general, Cygb is positive in the epithelial cells, hepatocytes, pancreatic acinar cells, cardiomyocytes and skeletal muscle but rarely so in cells in the interstitial tissues. Cytoglobin is usually positive in the cytoplasm, but is also positive in the nucleus in some hepatocytes. In contrast, Cygb is negative in the smooth muscle. The distribution of Cygb could suggest its roles.

Death-resistant and nonresistant malignant human cell lines under anoxia in vitro.

BACKGROUND: Erythropoietin supports the survival of erythroblasts. We previously demonstrated that 24 malignant human cell lines expressed erythropoietin and its receptor and that erythropoietin secretion was enhanced under anoxia. In this study, we examined the viability of 22 of these cell lines excluding two leukemia cell lines under anoxia. METHODS: Twenty-two cancer cell lines of various origins were cultured under anoxia or normoxia for 4 days, and their viability was examined at 1-day intervals. The levels of lactate and ATP were measured. The expressions of hypoxia-inducible transcription factor 1alpha (HIF-1alpha) and Bcl-2 family proteins were examined by western blotting analysis. The cellular and mitochondrial features were examined by microscopy. RESULTS: Eleven of the 22 cancer cell lines examined showed 80% to 100% cell viability after 4 days under anoxia; 2 cell lines showed similar viability for 3 days, 3 cell lines showed similar viability for 2 days, and 6 cell lines showed similar viability for 1 day or less. These 11 death-resistant cell lines, which secrete various amounts of erythropoietin under anoxia, produced significantly more lactate during 2 days under anoxia than under normoxia, with ATP levels about 60% of those before anoxia. ATP returned to the normal level when normoxia was restored after 4 days of anoxia. However, the nonresistant cell lines responded to anoxia by yielding significantly more lactate without a reduction of the ATP level. The expression patterns of Bcl-2 family proteins revealed that apoptosis-inhibiting signals predominated over proapoptotic signals in the death-resistant cells under anoxia. CONCLUSION: The majority of the cancer cell lines examined survived under anoxia in vitro, through the Pasteur effect, in a dormant state without direct support of erythropoietin.