Induction of specific T cell immunity in patients with prostate cancer by vaccination with PSA146–154 peptide

T cell immunotherapy of prostate cancer (CaP) offers the potential for less toxic, more effective outcomes. A clinical trial was conducted in 28 patients with locally advanced or metastatic CaP to determine whether an HLA-A2 binding epitope of prostate-specific antigen, PSA146–154 (PSA-peptide), can induce specific T cell immunity. Patients were vaccinated either by intradermal injection of PSA-peptide and GM-CSF or by intravenous administration of autologous dendritic cells pulsed with PSA-peptide at weeks 1, 4 and 10. Delayed-type hypersensitivity (DTH) skin testing was performed at weeks 4, 14, 26 and 52. Fifty percent of the patients developed positive DTH responses to PSA-peptide. The size of the DTH induration progressively increased over time in the majority of responding patients. Skin biopsies from seven DTH-positive patients were available and T cells that developed in situ were also characterized. The phenotype of recovered T cells demonstrated variable proportions of CD4⁺CD8⁻, CD4⁻CD8⁺ and CD4⁺CD8⁺ T cell populations. Cytokine analysis of PSA-peptide stimulated T cells per bead array assay exhibited specific IFN-γ and TNF-α response in six of seven patients. Specific IL-4 response was observed in five patients, while IL-10 response was detected in one patient. Purified CD4⁻CD8⁺ T cells isolated from four patients demonstrated specific cytolytic activity per chromium release assay. In conclusion, immunization with PSA-peptide induced specific T cell immunity in one-half of the patients with locally advanced and hormone-sensitive, metastatic CaP. DTH-derived T cells exhibited PSA-peptide-specific cytolytic activity and predominantly expressed a type-1 cytokine profile.     

Hypothalamic AgRP-neurons control peripheral substrate utilization and nutrient partitioning

Obesity-related diseases such as diabetes and dyslipidemia result from metabolic alterations including the defective conversion, storage and utilization of nutrients, but the central mechanisms that regulate this process of nutrient partitioning remain elusive. As positive regulators of feeding behaviour, agouti-related protein (AgRP) producing neurons are indispensible for the hypothalamic integration of energy balance. Here, we demonstrate a role for AgRP-neurons in the control of nutrient partitioning. We report that ablation of AgRP-neurons leads to a change in autonomic output onto liver, muscle and pancreas affecting the relative balance between lipids and carbohydrates metabolism. As a consequence, mice lacking AgRP-neurons become obese and hyperinsulinemic on regular chow but display reduced body weight gain and paradoxical improvement in glucose tolerance on high-fat diet. These results provide a direct demonstration of a role for AgRP-neurons in the coordination of efferent organ activity and nutrient partitioning, providing a mechanistic link between obesity and obesity-related disorders.     

The Legionella pneumophila Effector VipA Is an Actin Nucleator That Alters Host Cell Organelle Trafficking

Legionella pneumophila, the causative agent of Legionnaires'' disease, invades and replicates within macrophages and protozoan cells inside a vacuole. The type IVB Icm/Dot secretion system is necessary for the translocation of effector proteins that modulate vesicle trafficking pathways in the host cell, thus avoiding phagosome-lysosome fusion. The Legionella VipA effector was previously identified by its ability to interfere with organelle trafficking in the Multivesicular Body (MVB) pathway when ectopically expressed in yeast. In this study, we show that VipA binds actin in vitro and directly polymerizes microfilaments without the requirement of additional proteins, displaying properties distinct from other bacterial actin nucleators. Microscopy studies revealed that fluorescently tagged VipA variants localize to puncta in eukaryotic cells. In yeast these puncta are associated with actin-rich regions and components of the Multivesicular Body pathway such as endosomes and the MVB-associated protein Bro1. During macrophage infection, native translocated VipA associated with actin patches and early endosomes. When ectopically expressed in mammalian cells, VipA-GFP displayed a similar distribution ruling out the requirement of additional effectors for binding to its eukaryotic targets. Interestingly, a mutant form of VipA, VipA-1, that does not interfere with organelle trafficking is also defective in actin binding as well as association with early endosomes and shows a homogeneous cytosolic localization. These results show that the ability of VipA to bind actin is related to its association with a specific subcellular location as well as its role in modulating organelle trafficking pathways. VipA constitutes a novel type of actin nucleator that may contribute to the intracellular lifestyle of Legionella by altering cytoskeleton dynamics to target host cell pathways.     

Maintaining phase of the crustacean tri-phasic pyloric rhythm

We construct and analyze a model network of the pyloric rhythm of the crustacean stomatogastric ganglion consisting of an oscillator neuron that inhibits two reciprocally inhibitory follower neurons. We derive analytic expressions that determine the phase of firing of the follower neurons with respect to the oscillator. An important aspect of the model is the inclusion of synapses that exhibit short-term synaptic depression. We show that these type of synapses allow there to be a complicated relationship between the intrinsic properties of the neurons and the synapses between them in determining phase relationships. Our analysis reveals the circumstances and ranges of cycle periods under which these properties work in concert with or independently from one another. In particular, we show that phase maintenance over a range of oscillator periods can be enhanced through the interplay of the two follower neurons if the synapses between these neurons are depressing. Since our model represents the core of the oscillatory pyloric network, the results of our analysis can be compared to experimental data and used to make predictions about the biological network.     

The effect of kinetin in relation to photocontrol of anthocyani biosynthesis in Brassica oleracea

Kinetin stimulates the synthesis of anthocyanin in dark-grown seedlings of red-cabbage. When applied for only 15 min its effect resembles that of 5 min R light and can be nullified by a subsequent exposure to 5 min FR. However, kinetin fails to stimulate PAL activity in the dark-grown seedlings. It is suggested that the effect of kinetin, like that of R light, may be to increase membrane permeability, allowing a pool of endogenous substrate to reach the site of anthocyanin biosynthesis.     

A Dietary Fat Excess Alters Metabolic and Neuroendocrine Responses Before the Onset of Metabolic Diseases

Early changes in neuroendocrine pathways are essential in the development of metabolic pathologies. Thus, it is important to have a better understanding of the signals involved in their initiation. Long-term consumption of high-fat diets induces insulin resistance, obesity, diabetes. Here, we have investigated early neural and endocrine events in the hypothalamus and hippocampus induced by a short-term high fat, low carbohydrate diet in adult male Wistar rats. The release of serotonin, which is closely associated with the actions of insulin and leptin, was measured, by electrochemical detection following reverse-phase liquid chromatography (HPLC), in the extracellular space of the medial hypothalamus and the dorsal hippocampus in samples obtained from non-anesthetized animals, by microdialysis. The high-fat diet had a specific effect on the hypothalamus. Serotonin release induced by food intake was reduced after 1 week, and effectively ceased after 6 weeks of the diet. After 1 week, there was an increased gene expression of the insulin receptor and the insulin receptor substrates IRS1 and IRS2, as measured by real-time PCR. After 6 weeks of diet, insulin gene expression increased. Leptinemia increased in all cases. This new data support the concept that high-fat diets, in addition to have peripheral effects, cause a rapid alteration in specific central mechanisms involved in energy and glucose homeostasis. The changes in the gene expression of insulin and signaling elements represent possible adaptations aimed at counterbalancing the reduced responsiveness of the serotonergic system to nutritional signals and maintaining homeostasis. Sophie M. Banas and Claude Rouch have contributed equally to this work.     

Explaining distortions in metacognition with an attractor network model of decision uncertainty

Metacognition is the ability to reflect on, and evaluate, our cognition and behaviour. Distortions in metacognition are common in mental health disorders, though the neural underpinnings of such dysfunction are unknown. One reason for this is that models of key components of metacognition, such as decision confidence, are generally specified at an algorithmic or process level. While such models can be used to relate brain function to psychopathology, they are difficult to map to a neurobiological mechanism. Here, we develop a biologically-plausible model of decision uncertainty in an attempt to bridge this gap. We first relate the model’s uncertainty in perceptual decisions to standard metrics of metacognition, namely mean confidence level (bias) and the accuracy of metacognitive judgments (sensitivity). We show that dissociable shifts in metacognition are associated with isolated disturbances at higher-order levels of a circuit associated with self-monitoring, akin to neuropsychological findings that highlight the detrimental effect of prefrontal brain lesions on metacognitive performance. Notably, we are able to account for empirical confidence judgements by fitting the parameters of our biophysical model to first-order performance data, specifically choice and response times. Lastly, in a reanalysis of existing data we show that self-reported mental health symptoms relate to disturbances in an uncertainty-monitoring component of the network. By bridging a gap between a biologically-plausible model of confidence formation and observed disturbances of metacognition in mental health disorders we provide a first step towards mapping theoretical constructs of metacognition onto dynamical models of decision uncertainty. In doing so, we provide a computational framework for modelling metacognitive performance in settings where access to explicit confidence reports is not possible.     

Diabetic β-Cells Can Achieve Self-Protection against Oxidative Stress through an Adaptive Up-Regulation of Their Antioxidant Defenses

Background

Oxidative stress (OS), through excessive and/or chronic reactive oxygen species (ROS), is a mediator of diabetes-related damages in various tissues including pancreatic β-cells. Here, we have evaluated islet OS status and β-cell response to ROS using the GK/Par rat as a model of type 2 diabetes.

Methodology/Principal Findings

Localization of OS markers was performed on whole pancreases. Using islets isolated from 7-day-old or 2.5-month-old male GK/Par and Wistar control rats, 1) gene expression was analyzed by qRT-PCR; 2) insulin secretion rate was measured; 3) ROS accumulation and mitochondrial polarization were assessed by fluorescence methods; 4) antioxidant contents were quantified by HPLC. After diabetes onset, OS markers targeted mostly peri-islet vascular and inflammatory areas, and not islet cells. GK/Par islets revealed in fact protected against OS, because they maintained basal ROS accumulation similar or even lower than Wistar islets. Remarkably, GK/Par insulin secretion also exhibited strong resistance to the toxic effect of exogenous H₂O₂ or endogenous ROS exposure. Such adaptation was associated to both high glutathione content and overexpression (mRNA and/or protein levels) of a large set of genes encoding antioxidant proteins as well as UCP2. Finally, we showed that such a phenotype was not innate but spontaneously acquired after diabetes onset, as the result of an adaptive response to the diabetic environment.

Conclusions

The GK/Par model illustrates the effectiveness of adaptive response to OS by β-cells to achieve self-tolerance. It remains to be determined to what extend such islet antioxidant defenses upregulation might contribute to GK/Par β-cell secretory dysfunction.     

Islet Endothelial Activation and Oxidative Stress Gene Expression Is Reduced by IL-1Ra Treatment in the Type 2 Diabetic GK Rat

Background

Inflammation followed by fibrosis is a component of islet dysfunction in both rodent and human type 2 diabetes. Because islet inflammation may originate from endothelial cells, we assessed the expression of selected genes involved in endothelial cell activation in islets from a spontaneous model of type 2 diabetes, the Goto-Kakizaki (GK) rat. We also examined islet endotheliuml/oxidative stress (OS)/inflammation-related gene expression, islet vascularization and fibrosis after treatment with the interleukin-1 (IL-1) receptor antagonist (IL-1Ra).

Methodology/Principal Findings

Gene expression was analyzed by quantitative RT-PCR on islets isolated from 10-week-old diabetic GK and control Wistar rats. Furthermore, GK rats were treated s.c twice daily with IL-1Ra (Kineret, Amgen, 100 mg/kg/day) or saline, from 4 weeks of age onwards (onset of diabetes). Four weeks later, islet gene analysis and pancreas immunochemistry were performed. Thirty-two genes were selected encoding molecules involved in endothelial cell activation, particularly fibrinolysis, vascular tone, OS, angiogenesis and also inflammation. All genes except those encoding angiotensinogen and epoxide hydrolase (that were decreased), and 12-lipoxygenase and vascular endothelial growth factor (that showed no change), were significantly up-regulated in GK islets. After IL-1Ra treatment of GK rats in vivo, most selected genes implied in endothelium/OS/immune cells/fibrosis were significantly down-regulated. IL-1Ra also improved islet vascularization, reduced fibrosis and ameliorated glycemia.

Conclusions/Significance

GK rat islets have increased mRNA expression of markers of early islet endothelial cell activation, possibly triggered by several metabolic factors, and also some defense mechanisms. The beneficial effect of IL-1Ra on most islet endothelial/OS/immune cells/fibrosis parameters analyzed highlights a major endothelial-related role for IL-1 in GK islet alterations. Thus, metabolically-altered islet endothelium might affect the β-cell microenvironment and contribute to progressive type 2 diabetic β-cell dysfunction in GK rats. Counteracting islet endothelial cell inflammation might be one way to ameliorate/prevent β-cell dysfunction in type 2 diabetes.