Cell Death Signaling Pathway Induced by Cholix Toxin,a Cytotoxin and eEF2 ADP-Ribosyltransferase Produced by Vibrio cholerae

Pathogenic microorganisms produce various virulence factors, e.g., enzymes, cytotoxins, effectors, which trigger development of pathologies in infectious diseases. Cholera toxin (CT) produced by O1 and O139 serotypes of Vibrio cholerae (V. cholerae) is a major cytotoxin causing severe diarrhea. Cholix cytotoxin (Cholix) was identified as a novel eukaryotic elongation factor 2 (eEF2) adenosine-diphosphate (ADP)-ribosyltransferase produced mainly in non-O1/non-O139 V. cholerae. The function and role of Cholix in infectious disease caused by V. cholerae remain unknown. The crystal structure of Cholix is similar to Pseudomonas exotoxin A (PEA) which is composed of an N-terminal receptor-recognition domain and a C-terminal ADP-ribosyltransferase domain. The endocytosed Cholix catalyzes ADP-ribosylation of eEF2 in host cells and inhibits protein synthesis, resulting in cell death. In a mouse model, Cholix caused lethality with severe liver damage. In this review, we describe the mechanism underlying Cholix-induced cytotoxicity. Cholix-induced apoptosis was regulated by mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) signaling pathways, which dramatically enhanced tumor necrosis factor-α (TNF-α) production in human liver, as well as the amount of epithelial-like HepG2 cancer cells. In contrast, Cholix induced apoptosis in hepatocytes through a mitochondrial-dependent pathway, which was not stimulated by TNF-α. These findings suggest that sensitivity to Cholix depends on the target cell. A substantial amount of information on PEA is provided in order to compare/contrast this well-characterized mono-ADP-ribosyltransferase (mART) with Cholix.     

c-kit is required for cardiomyocyte terminal differentiation

c-kit, the transmembrane tyrosine kinase receptor for stem cell factor, is required for melanocyte and mast cell development, hematopoiesis, and differentiation of spermatogonial stem cells. We show here that in the heart, c-kit is expressed not only by cardiac stem cells but also by cardiomyocytes, commencing immediately after birth and terminating a few days later, coincident with the onset of cardiomyocyte terminal differentiation. To examine the function of c-kit in cardiomyocyte terminal differentiation, we used compound heterozygous mice carrying the W (null) and W(v) (dominant negative) mutations of c-kit. In vivo, adult W/W(v) cardiomyocytes are phenotypically indistinguishable from their wild-type counterparts. After acute pressure overload adult W/W(v) cardiomyocytes reenter the cell cycle and proliferate, leading to left ventricular growth; furthermore in transgenic mice with cardiomyocyte-restricted overexpression of the dominant negative W(v) mutant, pressure overload causes cardiomyocytes to reenter the cell cycle. In contrast, in wild-type mice left ventricular growth after pressure overload results mainly from cardiomyocyte hypertrophy. Importantly, W/W(v) mice with pressure overload-induced cardiomyocyte hyperplasia had improved left ventricular function and survival. In W/W(v) mice, c-kit dysfunction also resulted in an approximately 14-fold decrease (P<0.01) in the number of c-kit(+)/GATA4(+) cardiac progenitors. These findings identify novel functions for c-kit: promotion of cardiac stem cell differentiation and regulation of cardiomyocyte terminal differentiation.     

Long-period accelerometer monitoring shows the role of physical activity in overweight and obesity

CONTEXT: Physical activity (PA) plays an important role in obesity. A new accelerometer has been developed to assess total energy expenditure as well as PA. OBJECTIVE: To investigate the association of PA with overweight and obesity in Japanese men and women, a large cross-sectional study was performed using a single-axis accelerometer. DESIGN, SETTING AND PARTICIPANTS: Population-based cross-sectional study of Japanese 18-84 y of age. Height, body weight and PA were measured in 400 male and 388 female Japanese volunteers from 1999 to 2000. The outcome measurements were overweight and obesity, which are defined as a body mass index >/=25 kg/m(2). PA was measured for 1 to 4 weeks and was then categorized into three activity levels, which were defined as light, moderate and vigorous PA. RESULTS: Prevalence of overweight and obesity was 22.3%. Number of steps and time spent in moderate and vigorous PA per day were lower in overweight and obese individuals. No difference was found in time spent in light PA. Individuals who are in the 4th and 5th quintile of moderate and vigorous PA showed a significantly lower body mass index. When odd ratios (ORs) of overweight and obesity estimated by logistic regression were used as effect measures, overweight and obesity were negatively associated with vigorous PA (ORs=0.91). CONCLUSION: These results indicate that overweight and obese individuals have a lower step rate and are spending less time for moderate to vigorous PA. Participation in vigorous PA is an important predictor of overweight and obesity.     

Surveillance of pathogens in outpatients with gastroenteritis and characterization of sapovirus strains between 2002 and 2007 in Kumamoto Prefecture,Japan

Infectious acute gastroenteritis is an important public health problem worldwide. A total of 639 stool specimens were tested for the presence of diarrhea pathogens. The specimens were from outpatients with acute gastroenteritis who consulted the pediatric clinic in Kumamoto Prefecture, Japan, from June 2002 to December 2007. Of these, 421 (65.9%) were positive for diarrhea pathogens. Among them were norovirus (NoV) in 260 (61.8%), sapovirus (SaV) in 81 (19.2%), rotavirus in 49 (11.6%), adenovirus in 19 (4.5%), enterovirus in 13 (3.1%), astrovirus in 9 (2.1%), kobuvirus in 1 (0.2%), and bacterial pathogens in 11 (2.6%). Mixed infection (co‐infection of viruses) was found in 22 (5.2%) of the 421 pathogen‐positive stool samples. NoV was the most prevalent pathogen throughout the study period; however, the SaV detection rate was unexpectedly high and was found to be the secondary pathogen from 2005 to 2007. Genetic analysis of SaV with 81 strains demonstrated that SaV strains belonging to genogroup IV emerged in 2007, and dynamic genogroup changes occurred in a restricted geographic area. This study showed that SaV infection is not as rare as thought previously. J. Med. Virol. 81:1117–1127, 2009. © 2009 Wiley‐Liss, Inc.     

Helicobacter pylori induces mono-(adenosine 5'-diphosphate)-ribosylation in human gastric adenocarcinoma

Mono-(adenosine 5'-diphosphate) (ADP)-ribosylation, which transfers an ADP-ribose from nicotinamide adenine dinucleotide (NAD) to an acceptor protein, is an important post-translational modification of cellular proteins. Several bacterial toxins are known to possess the mono-ADP-ribosyltransferase activity to catalyze this reaction as a possible pathogenic factor. Therefore, the aim of this study was to examine whether H. pylori may also induce mono-ADP-ribosylation in a human gastric mucosal protein in association with gastric cancer development. Tumorous and adjacent non-tumorous mucosal tissue specimens were obtained from the surgically removed stomachs of 5 patients with gastric adenocarcinoma, and then were homogenized into cytosolic and membranous fractions. Each homogenate or an H. pylori extract was assayed for mono-ADP-ribosylation with [adenylate-(32)P]-NAD and 3-aminobenzamide, a potent inhibitor of poly-ADP-ribosylation. The radiolabeled proteins were separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis followed by radio-image analysis. In the extracts from H. pylori, a strain-dependent, endogenous radiolabeling of 70-kDa protein was detected. An assay of the membranous fractions from 5 gastric adenocarcinomas with the extract of OMH4, a clinical H. pylori isolate, revealed notable radiolabelings of 55- and 45-kDa proteins, which were not found without the OMH4 extract. In contrast, the radiolabelings were minimal in the membranous fractions from respective non-tumorous mucosae, and they were not detected in any of the examined cytosolic fractions. All three radiolabelings of 70-, 55-, and 45-kDa proteins were dependent on NAD, but not on ADP-ribose. Snake venom phosphodiesterase digestion of the 3 radiolabeled proteins released only AMP. We thus found that H. pylori had an enzymatic mono-ADP-ribosyltransferase activity which enabled it to modify the 55- and 45-kDa membranous proteins of human gastric adenocarcinoma, as well as the 70-kDa protein of H. pylori itself. The possible roles underlying our observations on carcinogenesis or development of human gastric carcinoma are yet to be elucidated.     

Management of severe hypertension due to lenvatinib in patients with advanced thymic carcinoma: A case report

Rationale:Thymic carcinoma (TC) is a malignant mediastinal tumor, and there are no established treatments for pre-treated patients with advanced TC. Recently, lenvatinib was approved for such patients in Japan, ahead of other countries. Higher dose lenvatinib may be more efficacious than conventional treatments, although many patients experience grade 3 hypertension. Therefore, lenvatinib dose reduction remains controversial in terms of efficacy and tolerability.Patient concerns:Case 1 involves a 72-year-old woman who underwent complete resection of TC and was taking cilnidipine and azilsartan for hypertension. Six years later, multiple lung metastases were observed, and lenvatinib was started. Case 2 involves a 60-year-old man with TC, and was taking amlodipine for hypertension. A chest computed tomography showed progression in primary and metastatic lesions, and the patient started lenvatinib.Diagnoses:In both patients, grade 3 hypertension was observed after the administration of lenvatinib.Interventions:In Case 1, lenvatinib dose was reduced 3 times because lenvatinib was not interrupted despite grade 3 hypertension. In contrast, in Case 2, lenvatinib was interrupted when grade 3 hypertension occurred and was resumed after a decrease in blood pressure to baseline.Outcomes:In Case 2, higher tumor regression may have been achieved because of the maintenance of a high dose of lenvatinib compared with that in Case 1.Lessons:Lenvatinib is a promising agent for advanced TC; however, hypertension should be addressed cautiously, especially at the outset of administration. Lenvatinib may have to be appropriately interrupted and resumed as soon as the blood pressure is controlled to maximize efficacy and minimize toxicity.     

Orally administered levofloxacin as prophylaxis against pacemaker infection

OBJECTIVES: Despite paying careful attention to surgical details and sterile procedures, infection often occurs after pacemaker implantation. The prophylactic use of intravenously or orally administered antibiotics should therefore be considered. The present study aimed to evaluate the efficacy of orally administered levofloxacin (LVFX) as prophylaxis against pacemaker infection. METHODS: Thirty-nine patients who underwent permanent pacemaker implantation or pacemaker generator replacement due to battery depletion were included in the present study. Patients were divided into two groups (groups 1 and 2) and administered different antibiotics accordingly. Group 1 included 19 patients (75.7+/-9.3 years of age; 10 men and nine women) who were intravenously administered 2 g of cefazolin daily for five days postoperatively. Group 2 included 20 patients (73.7+/-14.4 years of age; 10 men and 10 women) who were orally administered 200 mg of LVFX 2 h before surgery and then 400 mg daily for five days thereafter. RESULTS: In group 1, the mean white blood cell concentrations before, and one, four and seven days after surgery were 4979+/-1330/mm(3), 6453+/-1200/mm(3), 5463+/-1303/mm(3) and 5632+/-1154/mm(3), respectively, and in group 2, they were 5931+/-1316/mm(3), 7062+/-1774/mm(3), 5708+/-1402/mm(3) and 5345+/-1506/mm(3), respectively. In group 1, the mean blood C-reactive protein concentrations before, and one, four and seven days after surgery were 0.27+/-0.34 mg/dL, 0.48+/-0.48 mg/dL, 1.04+/-0.99 mg/dL and 0.52+/-0.48 mg/dL, respectively, and in group 2, they were 0.43+/-0.54 mg/dL, 0.52+/-0.27 mg/dL, 0.61+/-0.42 mg/dL and 0.56+/-0.63 mg/dL, respectively. The inflammatory parameters showed similar responses in both groups. CONCLUSIONS: Orally administered LVFX following permanent pacemaker implantation can prevent pacemaker infection as successfully as intravenously administered cefazolin.     

Inactivation and Elimination of Viruses during Preparation of Human Intravenous Immunoglobulin

We report here the results of our evaluation of virus inactivation during the manufacturing steps of two intravenous immunoglobulin (IGIV) preparations. Virus inactivation and/or removal by processing steps, such as ethanol fractionation and polyethylene glycol precipitation, and deliberate virucidal steps, such as solvent/detergent treatment and pasteurization, were tested on a variety of human pathogenic and experimental model viruses, including human immunodeficiency, Hepatitis C, Mumps, Vaccinia, Chikungunya, Vesicular Stomatitis, Sindbis, and ECHO viruses. All viruses were successfully inactivated and/or eliminated by the processing steps studied. In some cases, however, multiple steps were required. We conclude that the incorporation of steps deliberately designed to inactivate or remove viruses during the production of IGIV provides an extra measure of viral safety.     

Reperfusion-induced arrhythmias are suppressed by inhibition of the angiotensin II type 1 receptor

We examined antiarrhythmic effects of drugs, including renin-angiotensin system (RAS) inhibitors, on reperfusion arrhythmias in rats in vivo. Anesthetized rats were subjected to 5 min of coronary occlusion and 30 min of reperfusion. Arrhythmia scores, calculated as the product of the type of arrhythmia (1 for ventricular tachycardia, 2 for ventricular fibrillation) and its duration (in seconds), were adopted to evaluate the severity of arrhythmias. Reperfusion arrhythmias were suppressed by Na(+)/H(+) exchange inhibitor, Na(+)/Ca(2+) exchange inhibitor and L-type Ca channel antagonist by more than 90%. Angiotensin-converting enzyme inhibitor and angiotensin II (Ang II) type 1 receptor (AT(1)) antagonist also modestly (by 60-70%) but significantly decreased reperfusion arrhythmias. These effects were not reversed by co-administration of bradykinin B(2) receptor antagonist or AT(2) antagonist, respectively. Effects of superoxide dismutase (SOD) were also examined, but SOD proved ineffective. Effects of Na(+)/H(+) exchange inhibitor, Na(+)/Ca(2+) exchange inhibitor and L-type Ca channel antagonist suggest a causative relationship of Ca overload in reperfusion arrhythmias. These transport systems are known to be activated by Ang II. Thus, the antiarrhythmic action of RAS inhibitors might be attributable to the inhibition of the action of Ang II via AT(1).