Prostacyclin production in rat aortic smooth muscle cells: role of protein kinase C, phospholipase D and cyclooxygenase-2 expression

Objective: The present study was designed to investigate the role of protein kinase C (PKC) and phospholipase D (PLD) in angiotensin II (AngII)- and phorbol ester (PMA)-induced cyclooxygenase-2 (COX-2) expression and prostacyclin (PGI2) production in rat aortic smooth muscle cells (VSMC). Methods: Prostacyclin production in cultured VSMC was determined by radioimmunoassay. PKC activity was examined by measuring the transfer of 32P from (γ-32P)ATP to histone III-S. COX-2 expression was determined by Western blotting. To measure PLD activity, thin layer chromatography was used. Results: AngII (50 nM) and PMA (100 nM) promoted the translocation of PKC activity from the cytosol to the membranes within 30 min, followed by a strong increase in PLD activity as well as COX-2 expression and PGI2 production. After 48 h exposure to PMA, PKC was downregulated resulting in a complete suppression of its activity. PKC-downregulation and the PKC inhibitor CGP41251 abolished PMA- and AngII-induced PLD activation, suppressed the stimulatory effect of PMA on COX-2 expression and PGI2 production and strongly inhibited that of AngII. Furthermore, AngII- and PMA-induced PGI2 production depended on protein synthesis and COX-2 but not COX-1 activity. Inhibition of PLD-mediated phosphatidic acid (PA) formation by 1% 1-butanol abolished AngII-induced COX-2 expression and PGI2 secretion, while dioctanoyl PA increased COX-2 expression and PGI2 production in a time- and concentration-dependent manner. Conclusion: Our results indicate that in VSMC, AngII promotes PGI2 production to a large extent through a rise in COX-2 expression which is mediated by PA generated from increased PKC-dependent PLD activit

Prostaglandin E2 activates Stat3 in neonatal rat ventricular cardiomyocytes: A role in cardiac hypertrophy

Objective: The purpose of this study was to investigate whether prostaglandin E2 (PGE2) induces Signal transducer and activator of transcription 3 (Stat3) activation in neonatal rat ventricular cardiomyocytes and if so to determine the possible role of this activation in PGE2-induced hypertrophic responses. Methods: Stat3 activation and its nuclear phosphorylation were determined by electrophoretic mobility shift assay (EMSA) and by Western blots, respectively. Protein synthesis was assessed by [3H]-leucine incorporation into total protein and cell surface was quantified by microscopic analysis. Results: We found that PGE2 induces a concentration- (1-100nM) and time-dependent increase in Stat3 activation, reaching maximal values after 90min of stimulation. Experiments with agonists and antagonists of the PGE2 receptor subtypes EP1-EP4 indicate that PGE2 activates Stat3 mainly through the EP4 receptor. We further observed that the extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor U0126 abolishes PGE2-induced Stat3 activation whereas the p38 MAP kinase blocker SB203580 has no effect. Nuclear Stat3 phosphorylation induced by PGE2 is also suppressed by the translation and transcription inhibitors, cycloheximide and actinomycin D, respectively. Transfecting ventricular cardiomyocytes with a small interfering RNA (siRNA) targeting rat Stat3, we obtained an approximately 70% reduction in Stat3 expression, 24 and 48h after electroporation. In these Stat3-silenced cells, the PGE2-induced increase in protein synthesis and cell surface is strongly inhibited. Conclusion: In ventricular cardiomyocytes, PGE2 induces the activation of Stat3 which plays an essential role in PGE2-induced increase in cell size and protein synthesis. The activation of Stat3 occurs mainly through EP4 and involves ERK1/2 as well as newly synthesized protein(s

BCI-Based Navigation in Virtual and Real Environments

A Brain-Computer Interface (BCI) is a system that enables people to control an external device with their brain activity, without the need of any muscular activity. Researchers in the BCI field aim to develop applications to improve the quality of life of severely disabled patients, for whom a BCI can be a useful channel for interaction with their environment. Some of these systems are intended to control a mobile device (e. g. a wheelchair). Virtual Reality is a powerful tool that can provide the subjects with an opportunity to train and to test different applications in a safe environment. This technical review will focus on systems aimed at navigation, both in virtual and real environments.This work was partially supported by the Innovation, Science and Enterprise Council of the Junta de Andalucía (Spain), project P07-TIC-03310, the Spanish Ministry of Science and Innovation, project TEC 2011-26395 and by the European fund ERDF

Focal Distribution of Hepatitis C Virus RNA in Infected Livers

Background: Hepatitis C virus (HCV) is a plus-strand RNA virus that replicates by amplification of genomic RNA from minus strands leading to accumulation of almost one thousand copies per cell under in vitro cell culture conditions. In contrast, HCV RNA copy numbers in livers of infected patients appear to be much lower, estimated at a few copies per cell. Methodology/Principal Findings: To gain insights into mechanisms that control HCV replication in vivo, we analyzed HCV RNA levels as well as expression of interferon beta (IFNb) and several interferon stimulated genes (ISGs) from whole liver sections and micro-dissected subpopulations of hepatocytes in biopsy samples from 21 HCV-infected patients. The results showed that intrahepatic HCV RNA levels range form less than one copy per hepatocyte to a maximum of about eight. A correlation existed between viral RNA levels and IFNb expression, but not between viral RNA and ISG levels. Also, IFNb expression did not correlate with ISGs levels. Replication of HCV RNA occurred in focal areas in the liver in the presence of a general induction of ISGs. Conclusion/Significance: The low average levels of HCV RNA in biopsy samples can be explained by focal distribution of infected hepatocytes. HCV replication directly induces IFNb, which then activates ISGs. The apparent lack of a correlation between levels of IFNb and ISG expression indicates that control of the innate immune response during HCV infection

PAT4 levels control amino-acid sensitivity of rapamycin-resistant mTORC1 from the Golgi and affect clinical outcome in colorectal cancer

Tumour cells can use strategies that make them resistant to nutrient deprivation to outcompete their neighbours. A key integrator of the cell’s responses to starvation and other stresses is amino-acid-dependent mechanistic target of rapamycin complex 1 (mTORC1). Activation of mTORC1 on late endosomes and lysosomes is facilitated by amino-acid transporters within the solute-linked carrier 36 (SLC36) and SLC38 families. Here, we analyse the functions of SLC36 family member, SLC36A4, otherwise known as proton-assisted amino-acid transporter 4 (PAT4), in colorectal cancer. We show that independent of other major pathological factors, high PAT4 expression is associated with reduced relapse-free survival after colorectal cancer surgery. Consistent with this, PAT4 promotes HCT116 human colorectal cancer cell proliferation in culture and tumour growth in xenograft models. Inducible knockdown in HCT116 cells reveals that PAT4 regulates a form of mTORC1 with two distinct properties: first, it preferentially targets eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), and second, it is resistant to rapamycin treatment. Furthermore, in HCT116 cells two non-essential amino acids, glutamine and serine, which are often rapidly metabolised by tumour cells, regulate rapamycin-resistant mTORC1 in a PAT4-dependent manner. Overexpressed PAT4 is also able to promote rapamycin resistance in human embryonic kidney-293 cells. PAT4 is predominantly associated with the Golgi apparatus in a range of cell types, and in situ proximity ligation analysis shows that PAT4 interacts with both mTORC1 and its regulator Rab1A on the Golgi. These findings, together with other studies, suggest that differentially localised intracellular amino-acid transporters contribute to the activation of alternate forms of mTORC1. Furthermore, our data predict that colorectal cancer cells with high PAT4 expression will be more resistant to depletion of serine and glutamine, allowing them to survive and outgrow neighbouring normal and tumorigenic cells, and potentially providing a new route for pharmacological intervention

Patterns of subregional cerebellar atrophy across epilepsy syndromes: An ENIGMA-Epilepsy study

\ua9 2024 The Authors. Epilepsia published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.Objective: The intricate neuroanatomical structure of the cerebellum is of longstanding interest in epilepsy, but has been poorly characterized within the current corticocentric models of this disease. We quantified cross-sectional regional cerebellar lobule volumes using structural magnetic resonance imaging in 1602 adults with epilepsy and 1022 healthy controls across 22 sites from the global ENIGMA-Epilepsy working group. Methods: A state-of-the-art deep learning-based approach was employed that parcellates the cerebellum into 28 neuroanatomical subregions. Linear mixed models compared total and regional cerebellar volume in (1) all epilepsies, (2) temporal lobe epilepsy with hippocampal sclerosis (TLE-HS), (3) nonlesional temporal lobe epilepsy, (4) genetic generalized epilepsy, and (5) extratemporal focal epilepsy (ETLE). Relationships were examined for cerebellar volume versus age at seizure onset, duration of epilepsy, phenytoin treatment, and cerebral cortical thickness. Results: Across all epilepsies, reduced total cerebellar volume was observed (d =.42). Maximum volume loss was observed in the corpus medullare (dmax =.49) and posterior lobe gray matter regions, including bilateral lobules VIIB (dmax =.47), crus I/II (dmax =.39), VIIIA (dmax =.45), and VIIIB (dmax =.40). Earlier age at seizure onset ((Formula presented.) =.05) and longer epilepsy duration ((Formula presented.) =.06) correlated with reduced volume in these regions. Findings were most pronounced in TLE-HS and ETLE, with distinct neuroanatomical profiles observed in the posterior lobe. Phenytoin treatment was associated with reduced posterior lobe volume. Cerebellum volume correlated with cerebral cortical thinning more strongly in the epilepsy cohort than in controls. Significance: We provide robust evidence of deep cerebellar and posterior lobe subregional gray matter volume loss in patients with chronic epilepsy. Volume loss was maximal for posterior subregions implicated in nonmotor functions, relative to motor regions of both the anterior and posterior lobe. Associations between cerebral and cerebellar changes, and variability of neuroanatomical profiles across epilepsy syndromes argue for more precise incorporation of cerebellar subregional damage into neurobiological models of epilepsy

Disruption of TLR3 Signaling Due to Cleavage of TRIF by the Hepatitis A Virus Protease-Polymerase Processing Intermediate, 3CD

Toll-like receptor 3 (TLR3) and cytosolic RIG-I-like helicases (RIG-I and MDA5) sense viral RNAs and activate innate immune signaling pathways that induce expression of interferon (IFN) through specific adaptor proteins, TIR domain-containing adaptor inducing interferon-β (TRIF), and mitochondrial antiviral signaling protein (MAVS), respectively. Previously, we demonstrated that hepatitis A virus (HAV), a unique hepatotropic human picornavirus, disrupts RIG-I/MDA5 signaling by targeting MAVS for cleavage by 3ABC, a precursor of the sole HAV protease, 3Cpro, that is derived by auto-processing of the P3 (3ABCD) segment of the viral polyprotein. Here, we show that HAV also disrupts TLR3 signaling, inhibiting poly(I:C)-stimulated dimerization of IFN regulatory factor 3 (IRF-3), IRF-3 translocation to the nucleus, and IFN-β promoter activation, by targeting TRIF for degradation by a distinct 3ABCD processing intermediate, the 3CD protease-polymerase precursor. TRIF is proteolytically cleaved by 3CD, but not by the mature 3Cpro protease or the 3ABC precursor that degrades MAVS. 3CD-mediated degradation of TRIF depends on both the cysteine protease activity of 3Cpro and downstream 3Dpol sequence, but not 3Dpol polymerase activity. Cleavage occurs at two non-canonical 3Cpro recognition sequences in TRIF, and involves a hierarchical process in which primary cleavage at Gln-554 is a prerequisite for scission at Gln-190. The results of mutational studies indicate that 3Dpol sequence modulates the substrate specificity of the upstream 3Cpro protease when fused to it in cis in 3CD, allowing 3CD to target cleavage sites not normally recognized by 3Cpro. HAV thus disrupts both RIG-I/MDA5 and TLR3 signaling pathways through cleavage of essential adaptor proteins by two distinct protease precursors derived from the common 3ABCD polyprotein processing intermediate

Viral Mediated Redirection of NEMO/IKKγ to Autophagosomes Curtails the Inflammatory Cascade

The early host response to viral infections involves transient activation of pattern recognition receptors leading to an induction of inflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα). Subsequent activation of cytokine receptors in an autocrine and paracrine manner results in an inflammatory cascade. The precise mechanisms by which viruses avert an inflammatory cascade are incompletely understood. Nuclear factor (NF)-κB is a central regulator of the inflammatory signaling cascade that is controlled by inhibitor of NF-κB (IκB) proteins and the IκB kinase (IKK) complex. In this study we show that murine cytomegalovirus inhibits the inflammatory cascade by blocking Toll-like receptor (TLR) and IL-1 receptor-dependent NF-κB activation. Inhibition occurs through an interaction of the viral M45 protein with the NF-κB essential modulator (NEMO), the regulatory subunit of the IKK complex. M45 induces proteasome-independent degradation of NEMO by targeting NEMO to autophagosomes for subsequent degradation in lysosomes. We propose that the selective and irreversible degradation of a central regulatory protein by autophagy represents a new viral strategy to dampen the inflammatory response

Regulation of Toll-like receptor signaling by NDP52-mediated selective autophagy is normally inactivated by A20

Toll-like receptor (TLR) signaling is linked to autophagy that facilitates elimination of intracellular pathogens. However, it is largely unknown whether autophagy controls TLR signaling. Here, we report that poly(I:C) stimulation induces selective autophagic degradation of the TLR adaptor molecule TRIF and the signaling molecule TRAF6, which is revealed by gene silencing of the ubiquitin-editing enzyme A20. This type of autophagy induced formation of autophagosomes and could be suppressed by an autophagy inhibitor and lysosomal inhibitors. However, this autophagy was not associated with canonical autophagic processes, including involvement of Beclin-1 and conversion of LC3-I to LC3-II. Through screening of TRIF-interacting ‘autophagy receptors’ in human cells, we identified that NDP52 mediated the selective autophagic degradation of TRIF and TRAF6 but not TRAF3. NDP52 was polyubiquitinated by TRAF6 and was involved in aggregation of TRAF6, which may result in the selective degradation. Intriguingly, only under the condition of A20 silencing, NDP52 could effectively suppress poly(I:C)-induced proinflammatory gene expression. Thus, this study clarifies a selective autophagic mechanism mediated by NDP52 that works downstream of TRIF–TRAF6. Furthermore, although A20 is known as a signaling fine-tuner to prevent excess TLR signaling, it paradoxically downregulates the fine-tuning effect of NDP52 on TLR signaling