Pantoprazole-induced thrombocytopenia

OBJECTIVE: To report 2 cases of thrombocytopenia associated with pantoprazole treatment and discuss existing reports on this drug-induced adverse event. CASE SUMMARIES: This paper describes the course of thrombocytopenia associated with pantoprazole 40 mg in 2 hospitalized patients. In both cases, thrombocytopenia appeared after the initiation of pantoprazole and rapidly improved after discontinuation of pantoprazole, although complete resolution of thrombocytopenia occurred in only one patient prior to discharge from the hospital. DISCUSSION: The mechanism of drug-induced thrombocytopenia is often poorly understood, and proton-pump inhibitors are generally not strongly suspected as a cause of thrombocytopenia. However, an objective causality assessment using the Naranjo probability scale revealed a probable relationship between thrombocytopenia and pantoprazole in both of the cases. It is unknown whether this is a class effect. CONCLUSIONS: Although drug-induced thrombocytopenia with pantoprazole appears to be rare, it represents a potentially severe adverse effect. This supports the judicious prescribing of pantoprazole and possibly other proton-pump inhibitors.     

Identification of a gene required for de novo DNA methylation of the zebrafish no tail gene.

The zebrafish no tail gene (ntl) is indispensable for tail and notochord development. We have shown previously that ntl is de novo methylated during early embryogenesis. To find the gene that de novo methylates ntl and understand the meaning of this methylation, we cloned seven genes that encode the conserved catalytic domain of methyltransferases. We found that injection of antisense morpholino oligonucleotides against one of them, termed dnmt7, into eggs significantly reduced the level of ntl methylation, although no apparent phenotype was induced by the injection. Inhibition of Dnmt7 activity did not change the level of genome-wide methylation nor did it affect de novo methylation of injected plasmid DNA, indicating that Dnmt7 specifically methylates ntl in the genome.     

IGSF4 is a novel TCR ζ-chain-interacting protein that enhances TCR-mediated signaling

Immunoglobulin superfamily member 4 (IGSF4) is a known ligand of CRTAM, a receptor expressed in activated NKT and CD8(+) T cells, but its function in T cell immunity has not been elucidated. In this study, we show that IGSF4 directly interacts with the T cell receptor (TCR) ζ-chain and enhances TCR signaling by enhancing ζ-chain phosphorylation. Ectopic overexpression of IGSF4 enhances TCR-mediated T cell activation. In contrast, IGSF4 knockdown shows a dramatic decrease in markers associated with T cell activation compared with those in control small interfering RNA. The transmembrane domain is essential for TCR ζ-chain association and clustering to the immunological synapse, and the ectodomain is associated with T cell interaction with antigen-presenting cells (APCs). IGSF4-deficient mice have impaired TCR-mediated thymocyte selection and maturation. Furthermore, these mice reveal attenuated effector T cell functions accompanied by defective TCR signaling. Collectively, the results indicate that IGSF4 plays a central role in T cell functioning by dual independent mechanisms, control of TCR signaling and control of T cell-APC interaction.     

Demethylation by 5-Azacytidine Results in the Expression of Hepatitis B Virus Surface Antigen in Transgenic Mice

In 14p3HB transgenic mice, which carry three tandem copies of hepatitis B virus (HBV) DNA, the HBV DNA was significantly methylated and no viral proteins were produced. To analyze the causal relationship between hypermethylation and gene inactivity, 5-azacytidine was injected into the mice to demethylate HBV DNA. When postnatal 14p3HB mice were treated with the drug, hepatitis virus surface antigen was produced in these mice by 3 weeks of age, and the integrated HBV DNA of the liver was less heavily methylated. Our results suggest that injection of 5-azacytidine can be used to efficiently activate a silent transgene such as HBV DNA in transgenic mice.     

The cell cycle regulator Cdh1 controls the pool sizes of hematopoietic stem cells and mature lineage progenitors by protecting from genotoxic stress

Various key cell cycle components, especially G0/G1 regulators, have effects not only on cell proliferation but also on cell differentiation. Cdh1, one of the co-activators that maintain anaphase-promoting complex/cyclosome activity, plays a crucial role in the mitotic phase, but has recently been identified as a G0/G1 regulator, suggesting that the role of Cdh1 in cell differentiation. Here, we generated Cdh1 conditional gene-trap mice to examine Cdh1 functions in adult tissues by overcoming the embryonic lethality of Cdh1 homozygous gene-trap mice. We focused on the hematopoietic system and found that Cdh1-deficient mice exhibited a general decrease in mature lineage progenitor cells and a significant increase in short-term hematopoietic stem cells. This phenomenon became conspicuous by irradiation shortly after Cdh1 downregulation, suggesting that Cdh1 regulates the pool sizes of the hematopoietic stem cells and mature lineage progenitor cells by protecting cells from genotoxic stress. We also found that the irradiation-induced G2/M checkpoint was defective in Cdh1-deficient BM cells, causing the loss of stem/progenitor cells. This is the first report revealing Cdh1 function in adult hematopoiesis and showing a role of Cdh1 in a G2/M checkpoint regulation in vivo.     

Lipid Peroxidation Induced by Adriamycin in Linolenic Acid-Loaded Cultured Hepatocytes

Abstract: Addition of more than 10 μM of adriamycin to cultured rat hepatocytes loaded with α-linolenic acid (linolenic acid-loaded hepatocytes) caused marked lipid peroxidation as measured by an accumulation of malondialdehyde during a 9 hr incubation. After addition of 50 μM of adriamycin to linolenic acid-loaded hepatocytes, malondialdehyde accumulation significantly increased at 3 hr, followed by cellular reduced glutathione decrease and lactate dehydrogenase leakage after 6 hr. Inhibition of adriamycin-induced lipid peroxidation by addition of N, N′-diphenyl-p-phenylenediamine or α-tocopherol, both lipid radical scavengers, or deferoxamine, which is a Fe ion chelator, prevented both glutathione decrease and lactate dehydrogenase leakage, indicating that lipid peroxidation caused cellular damage to linolenic acid-loaded hepatocytes exposed to adriamycin. The effect of SKF 525-A, which is a cytochrome P450 inhibitor, on adriamycin-induced lipid peroxidation and on 7-ethoxycoumarin O-deethylase activity was determined by 6 hr incubation of linolenic acid-loaded cells. Addition of SKF 525–A suppressed adriamycin-induced lipid peroxidation comparably with its 7-ethoxycoumarin 0-deethylase inhibitory activity. These results suggest that cytochrome P450 contributes to the one-electron bioreduction of adriamycin into its semiquinone radical in rat hepatocytes.     

MicroRNA‐204‐5p: A novel candidate urinary biomarker of Xp11.2 translocation renal cell carcinoma

Xp11.2 translocation renal cell carcinoma (Xp11 tRCC) is a rare sporadic pediatric kidney cancer caused by constitutively active TFE3 fusion proteins. Tumors in patients with Xp11 tRCC tend to recur and undergo frequent metastasis, in part due to lack of methods available to detect early‐stage disease. Here we generated transgenic (Tg) mice overexpressing the human PRCC‐TFE3 fusion gene in renal tubular epithelial cells, as an Xp11 tRCC mouse model. At 20 weeks of age, mice showed no histological abnormalities in kidney but by 40 weeks showed Xp11 tRCC development and related morphological and histological changes. MicroRNA (miR)‐204‐5p levels in urinary exosomes of 40‐week‐old Tg mice showing tRCC were significantly elevated compared with levels in control mice. MicroRNA‐204‐5p expression also significantly increased in primary renal cell carcinoma cell lines established both from Tg mouse tumors and from tumor tissue from 2 Xp11 tRCC patients. All of these lines secreted miR‐204‐5p‐containing exosomes. Notably, we also observed increased miR‐204‐5p levels in urinary exosomes in 20‐week‐old renal PRCC‐TFE3 Tg mice prior to tRCC development, and those levels were equivalent to those in 40‐week‐old Tg mice, suggesting that miR‐204‐5p increases follow expression of constitutively active TFE3 fusion proteins in renal tubular epithelial cells prior to overt tRCC development. Finally, we confirmed that miR‐204‐5p expression significantly increases in noncancerous human kidney cells after overexpression of a PRCC‐TFE3 fusion gene. These findings suggest that miR‐204‐5p in urinary exosomes could be a useful biomarker for early diagnosis of patients with Xp11 tRCC.