Tributyltin Inhibits Neural Induction of Human Induced Pluripotent Stem Cells

Tributyltin (TBT), one of the organotin compounds, is a well-known environmental pollutant. In our recent study, we reported that TBT induces mitochondrial dysfunction, in human-induced pluripotent stem cells (iPSCs) through the degradation of mitofusin1 (Mfn1), which is a mitochondrial fusion factor. However, the effect of TBT toxicity on the developmental process of iPSCs was not clear. The present study examined the effect of TBT on the differentiation of iPSCs into the ectodermal, mesodermal, and endodermal germ layers. We found that exposure to nanomolar concentration of TBT (50 nM) selectively inhibited the induction of iPSCs into the ectoderm, which is the first step in neurogenesis. We further assessed the effect of TBT on neural differentiation and found that it reduced the expression of several neural differentiation marker genes, which were also downregulated by Mfn1 knockdown in iPSCs. Taken together, these results indicate that TBT induces developmental neurotoxicity via Mfn1-mediated mitochondrial dysfunction in iPSCs

Induction of Adenosine A 1 Receptor Expression by Pertussis Toxin via an Adenosine 5Ј-Diphosphate Ribosylation- Independent Pathway

ABSTRACT Pertussis toxin ADP ribosylates G i and G o transducing proteins and functionally uncouples adenosine A 1 receptor (A 1 AR) from its effectors. We hypothesized that this loss in receptor coupling could lead to de novo A 1 AR synthesis by the cell in a futile attempt to re-establish normal receptor function. To test this hypothesis, we used hamster ductus deferens tumor (DDT 1 MF-2) cells, a cell culture model for studying A 1 AR, and showed that pertussis toxin (100 ng/ml) produced a time-dependent loss in A 1 AR-G i interaction and abolished A

Improvement of acquisition and analysis methods in multi-electrode array experiments with iPS cell-derived cardiomyocytes

AbstractIntroductionMulti-electrode array (MEA) systems and human induced pluripotent stem (iPS) cell-derived cardiomyocytes are frequently used to characterize the electrophysiological effects of drug candidates for the prediction of QT prolongation and proarrhythmic potential. However, the optimal experimental conditions for obtaining reliable experimental data, such as high-pass filter (HPF) frequency and cell plating density, remain to be determined.MethodsExtracellular field potentials (FPs) were recorded from iPS cell-derived cardiomyocyte sheets by using the MED64 and MEA2100 multi-electrode array systems. Effects of HPF frequency (0.1 or 1Hz) on FP duration (FPD) were assessed in the presence and absence of moxifloxacin, terfenadine, and aspirin. The influence of cell density on FP characteristics recorded through a 0.1-Hz HPF was examined. The relationship between FP and action potential (AP) was elucidated by simultaneous recording of FP and AP using a membrane potential dye.ResultsMany of the FP waveforms recorded through a 1-Hz HPF were markedly deformed and appeared differentiated compared with those recorded through a 0.1-Hz HPF. The concentration–response curves for FPD in the presence of terfenadine reached a steady state at concentrations of 0.1 and 0.3μM when a 0.1-Hz HPF was used. In contrast, FPD decreased at a concentration of 0.3μM with a characteristic bell-shaped concentration–response curve when a 1-Hz HPF was used. The amplitude of the first and second peaks in the FP waveform increased with increasing cell plating density. The second peak of the FP waveform roughly coincided with AP signal at 50% repolarization, and the negative deflection at the second peak of the FP waveform in the presence of E-4031 corresponded to early afterdepolarization and triggered activity.DiscussionFP can be used to assess the QT prolongation and proarrhythmic potential of drug candidates; however, experimental conditions such as HPF frequency are important for obtaining reliable data

Different prognostic outcomes in two cases of FDG-PET/CT-Positive and -negative cardiac angiosarcoma

Cardiac angiosarcoma is a rare malignant tumor with a poor prognosis, characterized by the high uptake of 18F-fluorodeoxyglucose (FDG). This case report presents two cases of cardiac angiosarcoma with a marked difference in FDG uptake and prognosis.Case Summary:Case 1: A 40-year-old male presented with syncope. Ultrasound echocardiography demonstrated a cardiac tumor with a high uptake of 18F-FDG (maximum standardized uptake value=9.2). The patient underwent heart catheterization and tumor biopsy. The pathological result was high-grade angiosarcoma, and the MIB-1(Ki-67) proliferation index was approximately 20%. Systemic chemotherapy was administered; however, the patient died 2 years and 5 months after disease onset.Case 2: A 65-year-old female had a right atrial tumor incidentally diagnosed during routine ultrasound echocardiography. The tumor exhibited a low uptake of 18F-FDG (maximum standardized uptake value=1.8). Open heart surgery was performed, and the tumor was completely resected. Histological analysis revealed low-grade angiosarcoma, and the MIB-1(Ki-67) proliferation index was less than 5%. The patient was followed-up and had not relapsed 2 years after surgery.Conclusion: 18F-FDG uptake may reflect pathological tumor grade and prognosis in cardiac angiosarcoma

Clustering and anchoring mechanisms of molecular constituents of postsynaptic scaffolds in dendritic spines

Abstract Recent technological progress has yielded great amounts of information about the molecular constituents of postsynaptic scaffolds in the dendritic spine. Actin filaments are major cytoskeletal elements in the dendritic spine, and they functionally interact with neurotransmitter receptors via regulatory actin-binding proteins. Drebrin A and a-actinin-2 are two major actin-binding proteins in dendritic spines. In adult brains, they are characteristically concentrated in spines, but not in dendritic shafts or cell bodies. Thus, they are part of a unique postsynaptic scaffold consisting of actin filaments, PSD protein family, and neurotransmitter receptors. Localization of NMDA receptors, actin filaments, and actin-binding proteins in spines changes in parallel with development, and in response to synaptic activity. This raises the possibility that clustering and anchoring of these characteristic molecular constituents at postsynaptic scaffolds play important roles in spine function. This article focuses on the clustering and anchoring mechanisms of NMDA receptors and actin filaments, and the involvement of actin-binding proteins, in dendritic spines, and the way in which characteristic postsynaptic scaffolds are built up

Neurons Induce Tiled Astrocytes with Branches That Avoid Each Other

Neurons induce astrocyte branches that approach synapses. Each astrocyte tiles by expanding branches in an exclusive territory, with limited entries for the neighboring astrocyte branches. However, how astrocytes form exclusive territories is not known. For example, the extensive branching of astrocytes may sterically interfere with the penetration of other astrocyte branches. Alternatively, astrocyte branches may actively avoid each other or remove overlapped branches to establish a territory. Here, we show time-lapse imaging of the multi-order branching process of GFP-labeled astrocytes. Astrocyte branches grow in the direction where other astrocyte branches do not exist. Neurons that had just started to grow dendrites were able to induce astrocyte branching and tiling. Upon neuronal loss by glutamate excitotoxicity, astrocytes’ terminal processes retracted and more branches went over other branches. Our results indicate that neurons induce astrocyte branches and make them avoid each other