Bisperoxovanadium complex promotes dopamine exocytosis in PC12 cells

Iron commensalism of mesenchymal glioblastoma promotes ferroptosis susceptibility upon dopamine treatment

The heterogeneity of glioblastoma multiforme (GBM) leads to poor patient prognosis. Here, we aim to investigate the mechanism through which GBM heterogeneity is coordinated to promote tumor progression. We find that proneural (PN)-GBM stem cells (GSCs) secreted dopamine (DA) and transferrin (TF), inducing the proliferation of mesenchymal (MES)-GSCs and enhancing their susceptibility toward ferroptosis. PN-GSC-derived TF stimulates MES-GSC proliferation in an iron-dependent manner. DA acts in an autocrine on PN-GSC growth in a DA receptor D1-dependent manner, while in a paracrine it induces TF receptor 1 expression in MES-GSCs to assist iron uptake and thus enhance ferroptotic vulnerability. Analysis of public datasets reveals worse prognosis of patients with heterogeneous GBM with high iron uptake than those with other GBM subtypes. Collectively, the findings here provide evidence of commensalism symbiosis that causes MES-GSCs to become iron-addicted, which in turn provides a rationale for targeting ferroptosis to treat resistant MES GBM.

Glioblastoma stem-cell derived mesenchymal cells become reliant on iron but vulnerable to ferroptosis and within patients of heterogeneous glioblastoma multiforme prognosis for those with high iron uptake is poorer than other subtypes.

Menthol, a bioactive constituent of Mentha, attenuates motion sickness in mice model: Involvement of dopaminergic system

Motion sickness (MS) occurs due to contradicting vestibular and visual inputs to the brain causing nausea and vomiting. Antidopaminergic drugs being effective in reducing MS create a path for effective therapy against MS by regulating dopamine levels. We aimed to evaluate the role of the striatum and brainstem dopamine and dopamine D2 receptor (DRD2) in MS and the efficacy of menthol (MNT) to modulate dopamine and DRD2 in vitro and in vivo for possible amelioration of MS. Evaluation of efficacy of MNT to inhibit dopamine release from PC12 cells and anti-MS efficacy in BALB/c mice model was performed. Dopamine, DRD2 expression in PC12 cells, mice striatum, and brainstem were detected using HPLC-ECD, RT-PCR, and Western blot analysis, respectively. DRD2 expression increased in calcium ionophore-treated PC12 cells compared with control cells. Pretreatment with 50 μg/ml menthol decreased dopamine and DRD2 expression. Similarly, dopamine and DRD2 levels in mice striatum and brainstem of MS group (rotation induced) increased significantly compared with control group NC (no rotation). Pretreatment with menthol at 50 mg/kg concentration (rotation induced) showed decreased dopamine and DRD2 expression, thus indicating ameliorative effect on MS. Hence, we suggest that increased striatum and brainstem dopamine and DRD2 levels might lead to MS symptoms, and menthol could be used as a potent herbal alternative medicine for MS. PRACTICAL APPLICATIONS: Antidopaminergic drugs being effective in reducing motion sickness (MS) creates a path for effective therapy against MS by regulating dopamine levels. Increased striatum and brainstem dopamine and Dopamine D2 receptor (DRD2) levels might lead to the MS symptoms induced by rotation stimulation in mice model. Menthol showed a prophylactic effect on rotation-induced MS by reducing striatal and brainstem dopamine levels, DRD2 mRNA, and protein expression. Menthol could be used as an herbal alternative to antidopaminergics to minimize the associated adverse effects.

Potassium bisperoxo (1,10-phenanthroline) oxovanadate suppresses proliferation of hippocampal neuronal cell lines by increasing DNA methyltransferases

Bisperoxo (1,10-phenanthroline) oxovanadate (BpV) can reportedly block the cell cycle. The present study examined whether BpV alters gene expression by affecting DNA methyltransferases (DNMTs), which would impact the cell cycle. Immortalized mouse hippocampal neuronal precursor cells (HT22) were treated with 0.3 or 3 μM BpV. Proliferation, morphology, and viability of HT22 cells were detected with an IncuCyte real-time video imaging system or inverted microscope and 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium, respectively. mRNA and protein expression of DNMTs and p21 in HT22 cells was detected by real-time polymerase chain reaction and immunoblotting, respectively. In addition, DNMT activity was measured with an enzyme-linked immunosorbent assay. Effects of BpV on the cell cycle were analyzed using flow cytometry. Results demonstrated that treatment with 0.3 μM BpV did not affect cell proliferation, morphology, or viability; however, treatment with 3 μM BpV decreased cell viability, increased expression of both DNMT3B mRNA and protein, and inhibited the proliferation of HT22 cells; and 3 μM BpV also blocked the cell cycle and increased expression of the regulatory factor p21 by increasing DNMT expression in mouse hippocampal neurons.

Vesicular roundness and compound release in PC-12 cells

The principal goals of this study were to establish a quantitative morphological analysis of spatial and regional properties of dense core vesicles, and to use this analysis to assess whether homotypic fusion is prominent in chronically treated PC-12 cells at elevated release levels. Simple computerized image processing of electron-micrographs provided the binary images of vesicular dense cores, whilst the artificial intelligence methods were needed to determine the vesicular membranes. As in the past, the presence of large, highly irregular vesicles, provided the morphological evidence of fused vesicles, but the irregularity of vesicular shape was assessed quantitatively-from its roundness. Free space of each vesicle was determined from the distance to its nearest-neighbor, or from the size of its Voronoi polygon. Within a Voronoi polygon, each point is closer to that vesicle than to any other vesicle. Large vesicles were not less round and did not have larger free space, as expected if they result from fusion of several smaller vesicles. In conclusion, we present a novel and rigorous morphological analysis of spatial and regional properties of dense core vesicles. The results demonstrate that the homotypic fusion is not prominent in PC-12 cells, before or following a chronic treatment that enhances release.

Rapid change of quantal size in PC-12 cells detected by neural networks

The basic building block of synaptic transmission-the number of molecules released per vesicle (quantal size (QS)) often changes with stimulation, but there is no agreement about what factors regulate it. To throw more light on this problem spontaneous quantal release was recorded amperometrically in PC-12 cells. Amperometric current spikes, representing single vesicle release, were detected by thresholding and were separated from spurious events on the basis of their amplitude and time course using a pattern recognition system based on the principal component neural network methods. The frequency of current spikes, their amplitude, quantal size, rise time and decay time were typically non-stationary, even in the absence of stimulation. Their running values changed much more than those of memoryless stationary random data with the same probability density distribution. Irrespective of how much the quantal size, rise and decay times varied, their amplitude dependence remained constant, or changed with a very different time course. In conclusion, the quantal size is highly labile in PC-12 cells. The lability does not appear to result from the changes of fusion pore dynamics or the mechanism of release of vesicular content, but because of the preferential release of large vesicles.

P2X(1)-mediated activation of extracellular signal-regulated kinase 2 contributes to platelet secretion and aggregation induced by collagen

Adenosine triphosphate (ATP) and its stable analog, alpha,beta-methylene ATP, activate the platelet P2X(1) ion channel, causing a rapid Ca(++) influx. Here, we show that, in washed apyrase-treated platelets, alpha,beta-methylene ATP elicits reversible extracellular signal-regulated kinase 2 (ERK2) phosphorylation through a Ca(++)- and protein kinase C-dependent pathway. In contrast, high-performance liquid chromatography-purified adenosine diphosphate (ADP) did not trigger ERK2 phosphorylation. alpha,beta-Methylene ATP also activated the ERK2 pathway in P2X(1)-transfected HEK293 cells but not in cells expressing mutated P2X(1)delL nonfunctional channels. Because ATP released from the dense granules during platelet activation contributes to platelet aggregation elicited by low doses of collagen, and because collagen causes ERK2 phosphorylation, we have investigated the role of P2X(1)-mediated ERK2 activation in these platelet responses. We found that the antagonism of P2X(1) with ADP or desensitization of this ion channel with alpha,beta-methylene ATP both resulted in impaired ERK2 phosphorylation, ATP secretion, and platelet aggregation induced by low concentrations of collagen (< or = 1 microg/mL) without affecting the minor early dense granule release. Selective MEK1/2 inhibition by U-0126 and Ca(++) chelation with EGTA (ethyleneglycoltetraacetic acid) behaved similarly, whereas the PKC inhibitor GF109203-X totally prevented collagen-induced secretion and ERK2 activation. In contrast, when elicited by high collagen concentrations (2 microg/mL), platelet aggregation and secretion no longer depended on P2X(1) or ERK2 activation, as shown by the lack of their inhibition by alpha,beta-methylene ATP or U-0126. We thus conclude that mild platelet stimulation with collagen rapidly releases ATP, which activates the P2X(1)-PKC-ERK2 pathway. This process enhances further degranulation of the collagen-primed granules allowing platelet aggregation to be completed.