Serotonin activates catecholamine neurons in the solitary tract nucleus by increasing spontaneous glutamate inputs

Serotonin (5-HT) is a critical neurotransmitter in the control of autonomic functions. 5-HT(3) receptors participate in vagal afferent feedback to decrease food intake and regulate cardiovascular reflexes; however, the phenotype of the solitary tract nucleus (NTS) neurons involved is not known. A(2)/C(2) catecholamine (CA) neurons in the NTS are directly activated by visceral afferents and are important for the control of food intake and cardiovascular function, making them good candidates to respond to and mediate the effects of serotonin at the level of the NTS. This study examines serotonin's effects on NTS-CA neurons using patch-clamp techniques and transgenic mice expressing an enhanced green fluorescent protein driven by the tyrosine hydroxylase (TH) promoter (TH-EGFP) to identify catecholamine neurons. Serotonin increased the frequency of spontaneous glutamate excitatory postsynaptic currents (sEPSCs) in >90% of NTS-TH-EGFP neurons, an effect blocked by the 5-HT(3) receptor antagonist ondansetron and mimicked by the 5-HT(3) receptor agonists SR5227 and mCPBG. In contrast, 5-HT(3) receptor agonists increased sEPSCs on a minority (<30%) of non-TH neurons. 5-HT(3) receptor agonists increased the frequency, but not the amplitude, of mini-EPSCs, suggesting that their actions are presynaptic. 5-HT(3) receptor agonists increased the firing rate of TH-EGFP neurons, an effect dependent on the increased spontaneous glutamate inputs as it was blocked by the ionotropic glutamate antagonist NBQX, but independent of visceral afferent activation. These results demonstrate a cellular mechanism by which serotonin activates NTS-TH neurons and suggest a pathway by which it can increase catecholamine release in target regions to modulate food intake, motivation, stress, and cardiovascular function.

Aging differentially affects the re-entrainment response of central and peripheral circadian oscillators

Aging produces a decline in the amplitude and precision of 24 h behavioral, endocrine, and metabolic rhythms, which are regulated in mammals by a central circadian pacemaker within the suprachiasmatic nucleus (SCN) and local oscillators in peripheral tissues. Disruption of the circadian system, as experienced during transmeridian travel, can lead to adverse health consequences, particularly in the elderly. To test the hypothesis that age-related changes in the response to simulated jet lag will reflect altered circadian function, we examined re-entrainment of central and peripheral oscillators from young and old PER2::luciferase mice. As in previous studies, locomotor activity rhythms in older mice required more days to re-entrain following a shift than younger mice. At the tissue level, effects of age on baseline entrainment were evident, with older mice displaying earlier phases for the majority of peripheral oscillators studied and later phases for cells within most SCN subregions. Following a 6 h advance of the light:dark cycle, old mice displayed slower rates of re-entrainment for peripheral tissues but a larger, more rapid SCN response compared to younger mice. Thus, aging alters the circadian timing system in a manner that differentially affects the re-entrainment responses of central and peripheral circadian clocks. This pattern of results suggests that a major consequence of aging is a decrease in pacemaker amplitude, which would slow re-entrainment of peripheral oscillators and reduce SCN resistance to external perturbation.

Learning-related synaptic growth mediated by internalization of Aplysia cell adhesion molecule is controlled by membrane phosphatidylinositol 4,5-bisphosphate synthetic pathway

Long-term facilitation in Aplysia is accompanied by the growth of new synaptic connections between the sensory and motor neurons of the gill-withdrawal reflex. One of the initial steps leading to the growth of these synapses is the internalization, induced by 5-HT, of the transmembrane isoform of Aplysia cell-adhesion molecule (TM-apCAM) from the plasma membrane of sensory neurons (Bailey et al., 1992). However, the mechanisms that govern the internalization of TM-apCAM and how this internalization is coupled to the molecular events that initiate the structural changes are not fully understood. Here, we report that the synthesis of membrane phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)], which is known to be mediated by a signaling cascade through Aplysia Sec7 protein (ApSec7) and phosphatidylinositol-4-phosphate 5-kinase type I α (PIP5KIα) is required for both the internalization of TM-apCAM and the initiation of synaptic growth during 5-HT-induced long-term facilitation. Pharmacological blockade of PI(4,5)P(2) synthesis by the application of the inhibitor phenylarsine oxide blocked the internalization of apCAM. Furthermore, perturbation of the endogenous activation of ApSec7 and its downstream target PIP5KIα also blocked 5-HT-mediated internalization of TM-apCAM and synaptic growth. Finally, long-term facilitation was specifically impaired by blocking the ApSec7 signaling pathway at sensory-to-motor neuron synapses. These data indicate that the ApSec7/PIP5KIα signaling pathway is actively recruited during learning-related 5-HT signaling and acts as a key regulator of apCAM internalization associated with the formation of new synaptic connections during long-term facilitation.

How to make a living from anaerobic ammonium oxidation

Anaerobic ammonium-oxidizing (anammox) bacteria primarily grow by the oxidation of ammonium coupled to nitrite reduction, using CO2 as the sole carbon source. Although they were neglected for a long time, anammox bacteria are encountered in an enormous species (micro)diversity in virtually any anoxic environment that contains fixed nitrogen. It has even been estimated that about 50% of all nitrogen gas released into the atmosphere is made by these 'impossible' bacteria. Anammox catabolism most likely resides in a special cell organelle, the anammoxosome, which is surrounded by highly unusual ladder-like (ladderane) lipids. Ammonium oxidation and nitrite reduction proceed in a cyclic electron flow through two intermediates, hydrazine and nitric oxide, resulting in the generation of proton-motive force for ATP synthesis. Reduction reactions associated with CO2 fixation drain electrons from this cycle, and they are replenished by the oxidation of nitrite to nitrate. Besides ammonium or nitrite, anammox bacteria use a broad range of organic and inorganic compounds as electron donors. An analysis of the metabolic opportunities even suggests alternative chemolithotrophic lifestyles that are independent of these compounds. We note that current concepts are still largely hypothetical and put forward the most intriguing questions that need experimental answers.

Satiation and stress-induced hypophagia: examining the role of hindbrain neurons expressing prolactin-releasing Peptide or glucagon-like Peptide 1

Neural circuits distributed within the brainstem, hypothalamus, and limbic forebrain interact to control food intake and energy balance under normal day-to-day conditions, and in response to stressful conditions under which homeostasis is threatened. Experimental studies using rats and mice have generated a voluminous literature regarding the functional organization of circuits that inhibit food intake in response to satiety signals, and in response to stress. Although the central neural bases of satiation and stress-induced hypophagia often are studied and discussed as if they were distinct, we propose that both behavioral states are generated, at least in part, by recruitment of two separate but intermingled groups of caudal hindbrain neurons. One group comprises a subpopulation of noradrenergic (NA) neurons within the caudal nucleus of the solitary tract (cNST; A2 cell group) that is immunopositive for prolactin-releasing peptide (PrRP). The second group comprises non-adrenergic neurons within the cNST and nearby reticular formation that synthesize glucagon-like peptide 1 (GLP-1). Axonal projections from PrRP and GLP-1 neurons target distributed brainstem and forebrain regions that shape behavioral, autonomic, and endocrine responses to actual or anticipated homeostatic challenge, including the challenge of food intake. Evidence reviewed in this article supports the view that hindbrain PrRP and GLP-1 neurons contribute importantly to satiation and stress-induced hypophagia by modulating the activity of caudal brainstem circuits that control food intake. Hindbrain PrRP and GLP-1 neurons also engage hypothalamic and limbic forebrain networks that drive parallel behavioral and endocrine functions related to food intake and homeostatic challenge, and modulate conditioned and motivational aspects of food intake.

Analysis of morphological changes as a key method in studying psychiatric animal models

A major interest in the analysis of animal models of psychiatric diseases is their underlying cellular pathology and to gain information regarding whether pharmacological treatments, genetic differences or an altered environment exert an impact upon the brain morphology or on the morphology or activity of single neurones. In this review, several key methods will be introduced that allow the analysis of morphological changes that are frequently observed in psychiatric animal models. An overview of the techniques that enable dendritic arborisation, alterations in dendritic spines and changes in fibre densities to be analysed are described. Moreover, methods for the analysis of adult neurogenesis and neurodegeneration and for the analysis of neuronal activity in fixed brain tissue are described. An important step during the analysis of morphological changes is the estimation of the number of stained cells. Since conventional cell counting methods have several limitations, two different approaches that permit an estimate of the number of stained cells within three-dimensional tissue are also discussed.

Oligodendrogenesis from neural stem cells: perspectives for remyelinating strategies

Mobilization of remyelinating cells spontaneously occurs in the adult brain. These cellular resources are specially active after demyelinating episodes in early phases of multiple sclerosis (MS). Indeed, oligodendrocyte precursor cells (OPCs) actively proliferate, migrate to and repopulate the lesioned areas. Ultimately, efficient remyelination is accomplished when new oligodendrocytes reinvest nude neuronal axons, restoring the normal properties of impulse conduction. As the disease progresses this fundamental process fails. Multiple causes seem to contribute to such transient decline, including the failure of OPCs to differentiate and enwrap the vulnerable neuronal axons. Regenerative medicine for MS has been mainly centered on the recruitment of endogenous self-repair mechanisms, or on transplantation approaches. The latter commonly involves grafting of neural precursor cells (NPCs) or neural stem cells (NSCs), with myelinogenic potential, in the injured areas. Both strategies require further understanding of the biology of oligodendrocyte differentiation and remyelination. Indeed, the success of transplantation largely depends on the pre-commitment of transplanted NPCs or NSCs into oligodendroglial cell type, while the endogenous differentiation of OPCs needs to be boosted in chronic stages of the disease. Thus, much effort has been focused on finding molecular targets that drive oligodendrocytes commitment and development. The present review explores several aspects of remyelination that must be considered in the design of a cell-based therapy for MS, and explores more deeply the challenge of fostering oligodendrogenesis. In this regard, we discuss herein a tool developed in our research group useful to search novel oligodendrogenic factors and to study oligodendrocyte differentiation in a time- and cost-saving manner.

Mechanisms of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease affecting premature infants with long term effect on lung function into adulthood. Multiple factors are involved in the development of BPD. This review will summarize the different mechanisms leading to this disease and highlight recent bench and clinical research targeted at understanding the role of the mesenchyme (both its cellular and extracellular components) in the pathogenesis of BPD.

Eicosanoids and adipokines in breast cancer: from molecular mechanisms to clinical considerations

Chronic inflammation is one of the foremost risk factors for different types of malignancies, including breast cancer. Additional risk factors of this pathology in postmenopausal women are weight gain, obesity, estrogen secretion, and an imbalance in the production of adipokines, such as leptin and adiponectin. Various signaling products of transcription factor, nuclear factor-kappaB, in particular inflammatory eicosanoids, reactive oxygen species (ROS), and cytokines, are thought to be involved in chronic inflammation-induced cancer. Together, these key components have an influence on inflammatory reactions in malignant tissue damage when their levels are deregulated endogenously. Prostaglandins (PGs) are well recognized in inflammation and cancer, and they are solely biosynthesized through cyclooxygenases (COXs) from arachidonic acid. Concurrently, ROS give rise to bioactive isoprostanes from arachidonic acid precursors that are also involved in acute and chronic inflammation, but their specific characteristics in breast cancer are less demonstrated. Higher aromatase activity, a cytochrome P-450 enzyme, is intimately connected to tumor growth in the breast through estrogen synthesis, and is interrelated to COXs that catalyze the formation of both inflammatory and anti-inflammatory PGs such as PGE(2), PGF(2α), PGD(2), and PGJ(2) synchronously under the influence of specific mediators and downstream enzymes. Some of the latter compounds upsurge the intracellular cyclic adenosine monophosphate concentration and appear to be associated with estrogen synthesis. This review discusses the role of COX- and ROS-catalyzed eicosanoids and adipokines in breast cancer, and therefore ranges from their molecular mechanisms to clinical aspects to understand the impact of inflammation.

Troubleshooting and deconvoluting label-free cell phenotypic assays in drug discovery

INTRODUCTION

Central to drug discovery and development is to comprehend the target(s), potency, efficacy and safety of drug molecules using pharmacological assays. Owing to their ability to provide a holistic view of drug actions in native cells, label-free biosensor-enabled cell phenotypic assays have been emerging as new generation phenotypic assays for drug discovery. Despite the benefits associated with wide pathway coverage, high sensitivity, high information content, non-invasiveness and real-time kinetics, label-free cell phenotypic assays are often viewed to be a blackbox in the era of target-centric drug discovery.

METHODS

This article first reviews the biochemical and biological complexity of drug-target interactions, and then discusses the key characteristics of label-free cell phenotypic assays and presents a five-step strategy to troubleshooting and deconvoluting the label-free cell phenotypic profiles of drugs.

RESULTS

Drug-target interactions are intrinsically complicated. Label-free cell phenotypic signatures of drugs mirror the innate complexity of drug-target interactions, and can be effectively deconvoluted using the five-step strategy.

DISCUSSION

The past decades have witnessed dramatic expansion of pharmacological assays ranging from molecular to phenotypic assays, which is coincident with the realization of the innate complexity of drug-target interactions. The clinical features of a drug are defined by how it operates at the system level and by its distinct polypharmacology, ontarget, phenotypic and network pharmacology. Approaches to examine the biochemical, cellular and molecular mechanisms of action of drugs are essential to increase the efficiency of drug discovery and development. Label-free cell phenotypic assays and the troubleshooting and deconvoluting approach presented here may hold great promise in drug discovery and development.

Regulation of tumour intracellular pH: a mathematical model examining the interplay between H+ and lactate

Non-invasive measurements of pH have shown that both tumour and normal cells have intracellular pH (pHi) that lies on the alkaline side of neutrality (7.1-7.2). However, extracellular pH (pHe) is reported to be more acidic in some tumours compared to normal tissues. Many cellular processes and therapeutic agents are known to be tightly pH dependent which makes the study of intracellular pH regulation of paramount importance. We develop a mathematical model that examines the role of various membrane-based ion transporters in tumour pH regulation, in particular, with a focus on the interplay between lactate and H(+) ions and whether the lactate/H(+) symporter activity is sufficient to give rise to the observed reversed pH gradient that is seen is some tumours. Using linear stability analysis and numerical methods, we are able to gain a clear understanding of the relationship between lactate and H(+) ions. We extend this analysis using perturbation techniques to specifically examine a rapid change in H(+)-ion concentrations relative to variations in lactate. We then perform a parameter sensitivity analysis to explore solution robustness to parameter variations. An important result from our study is that a reversed pH gradient is possible in our system but for unrealistic parameter estimates-pointing to the possible involvement of other mechanisms in cellular pH gradient reversal, for example acidic vesicles, lysosomes, golgi and endosomes.

Molecular architecture of the chick vestibular hair bundle

Hair bundles of the inner ear have a specialized structure and protein composition that underlies their sensitivity to mechanical stimulation. Using mass spectrometry, we identified and quantified >1,100 proteins, present from a few to 400,000 copies per stereocilium, from purified chick bundles; 336 of these were significantly enriched in bundles. Bundle proteins that we detected have been shown to regulate cytoskeleton structure and dynamics, energy metabolism, phospholipid synthesis and cell signaling. Three-dimensional imaging using electron tomography allowed us to count the number of actin-actin cross-linkers and actin-membrane connectors; these values compared well to those obtained from mass spectrometry. Network analysis revealed several hub proteins, including RDX (radixin) and SLC9A3R2 (NHERF2), which interact with many bundle proteins and may perform functions essential for bundle structure and function. The quantitative mass spectrometry of bundle proteins reported here establishes a framework for future characterization of dynamic processes that shape bundle structure and function.

Brain insulin dysregulation: implication for neurological and neuropsychiatric disorders

Arduous efforts have been made in the last three decades to elucidate the role of insulin in the brain. A growing number of evidences show that insulin is involved in several physiological function of the brain such as food intake and weight control, reproduction, learning and memory, neuromodulation and neuroprotection. In addition, it is now clear that insulin and insulin disturbances particularly diabetes mellitus may contribute or in some cases play the main role in development and progression of neurodegenerative and neuropsychiatric disorders. Focusing on the molecular mechanisms, this review summarizes the recent findings on the involvement of insulin dysfunction in neurological disorders like Alzheimer's disease, Parkinson's disease and Huntington's disease and also mental disorders like depression and psychosis sharing features of neuroinflammation and neurodegeneration.

Cyclic strain dominates over microtopography in regulating cytoskeletal and focal adhesion remodeling of human mesenchymal stem cells

Human bone marrow-derived mesenchymal stem cell (hMSCs) function depends on chemical factors and also on the physical cues of the microenvironmental niche. Here, this physical microenvironment is recapitulated with controlled modes of mechanical strain applied to substrata containing three-dimensional features in order to analyze the effects on cell morphology, focal adhesion distribution, and gene expression. Ten percentage of strain at 1 Hz is delivered for 48 h to hMSCs cultured on flat surfaces, or on substrata with 15 μm-high microtopographic posts spaced 75 μm apart. Adding strain to microtopography produced stable semicircular focal adhesions, and actin spanning from post to post. Strain dominated over microtopography for expression of genes for the cytoskeleton (caldesmon-1 and calponin 3), cell adhesion (integrin-α2, vinculin, and paxillin), and extracellular matrix remodeling (MMP13) (p<0.05). Overall, attention to external mechanical stimuli is necessary for optimizing the stem cell niche for regenerative medicine.

MicroRNAs and Cardiovascular Disease

MicroRNAs (miRNAs) regulate gene expression by binding to their targets and promoting RNA degradation and/or inhibiting protein translation. In recent years, miRNAs have revolutionized our understanding of gene regulatory networks, providing new prospective tools to manage disease. Atherosclerosis and other cardiovascular diseases are a leading cause of disability and death in the US and in other western populations and pose an enormous burden on our healthcare system. Altered lipid homeostasis in liver or in the artery wall, and disruption of endothelial and smooth muscle cell function have been shown to contribute to the onset and progression of cardiovascular disease. This review focuses on recent advances in the field of vascular biology- and lipid metabolism-related miRNomics.

Cysteine oxidative posttranslational modifications: emerging regulation in the cardiovascular system

In the cardiovascular system, changes in oxidative balance can affect many aspects of cellular physiology through redox-signaling. Depending on the magnitude, fluctuations in the cell's production of reactive oxygen and nitrogen species can regulate normal metabolic processes, activate protective mechanisms, or be cytotoxic. Reactive oxygen and nitrogen species can have many effects including the posttranslational modification of proteins at critical cysteine thiols. A subset can act as redox-switches, which elicit functional effects in response to changes in oxidative state. Although the general concepts of redox-signaling have been established, the identity and function of many regulatory switches remains unclear. Characterizing the effects of individual modifications is the key to understand how the cell interprets oxidative signals under physiological and pathological conditions. Here, we review the various cysteine oxidative posttranslational modifications and their ability to function as redox-switches that regulate the cell's response to oxidative stimuli. In addition, we discuss how these modifications have the potential to influence other posttranslational modifications' signaling pathways though cross-talk. Finally, we review the increasing number of tools being developed to identify and quantify the various cysteine oxidative posttranslational modifications and how this will advance our understanding of redox-regulation.

Genetic inhibition of Na+-Ca2+ exchanger current disables fight or flight sinoatrial node activity without affecting resting heart rate

RATIONALE

The sodium-calcium exchanger 1 (NCX1) is predominantly expressed in the heart and is implicated in controlling automaticity in isolated sinoatrial node (SAN) pacemaker cells, but the potential role of NCX1 in determining heart rate in vivo is unknown.

OBJECTIVE

To determine the role of Ncx1 in heart rate.

METHODS AND RESULTS

We used global myocardial and SAN-targeted conditional Ncx1 knockout (Ncx1(-/-)) mice to measure the effect of the NCX current on pacemaking activity in vivo, ex vivo, and in isolated SAN cells. We induced conditional Ncx1(-/-) using a Cre/loxP system. Unexpectedly, in vivo and ex vivo hearts and isolated SAN cells showed that basal rates in Ncx1(-/-) (retaining ≈20% of control level NCX current) and control mice were similar, suggesting that physiological NCX1 expression is not required for determining resting heart rate. However, increases in heart rate and SAN cell automaticity in response to isoproterenol or the dihydropyridine Ca(2+) channel agonist BayK8644 were significantly blunted or eliminated in Ncx1(-/-) mice, indicating that NCX1 is important for fight or flight heart rate responses. In contrast, the pacemaker current and L-type Ca(2+) currents were equivalent in control and Ncx1(-/-) SAN cells under resting and isoproterenol-stimulated conditions. Ivabradine, a pacemaker current antagonist with clinical efficacy, reduced basal SAN cell automaticity similarly in control and Ncx1(-/-) mice. However, ivabradine decreased automaticity in SAN cells isolated from Ncx1(-/-) mice more effectively than in control SAN cells after isoproterenol, suggesting that the importance of NCX current in fight or flight rate increases is enhanced after pacemaker current inhibition.

CONCLUSIONS

Physiological Ncx1 expression is required for increasing sinus rates in vivo, ex vivo, and in isolated SAN cells, but not for maintaining resting heart rate.

Effect of nicotine on exocytotic pancreatic secretory response: role of calcium signaling

Background

Nicotine is a risk factor for pancreatitis resulting in loss of pancreatic enzyme secretion. The aim of this study was to evaluate the mechanisms of nicotine-induced secretory response measured in primary pancreatic acinar cells isolated from Male Sprague Dawley rats. The study examines the role of calcium signaling in the mechanism of the enhanced secretory response observed with nicotine exposure.

Methods

Isolated and purified pancreatic acinar cells were subjected to a nicotine exposure at a dose of 100 μM for 6 minutes and then stimulated with cholecystokinin (CCK) for 30 min. The cell’s secretory response was measured by the percent of amylase released from the cells in the incubation medium Calcium receptor antagonists, inositol trisphosphate (IP₃) receptor blockers, mitogen activated protein kinase inhibitors and specific nicotinic receptor antagonists were used to confirm the involvement of calcium in this process.

Results

Nicotine exposure induced enhanced secretory response in primary cells. These responses remained unaffected by mitogen activated protein kinases (MAPK’s) inhibitors. The effects, however, have been completely abolished by nicotinic receptor antagonist, calcium channel receptor antagonists and inositol trisphosphate (IP₃) receptor blockers.

Conclusions

The data suggest that calcium activated events regulating the exocytotic secretion are affected by nicotine as shown by enhanced functional response which is inhibited by specific antagonists… The results implicate the role of nicotine in the mobilization of both intra- and extracellular calcium in the regulation of stimulus-secretory response of enzyme secretion in this cell system. We conclude that nicotine plays an important role in promoting enhanced calcium levels inside the acinar cell.

Effects of eight-week supplementation of Ashwagandha on cardiorespiratory endurance in elite Indian cyclists

Background:

Cycling is an endurance sport relying mainly on aerobic capacity to provide fuel during long-duration cycling events. Athletes are constantly searching for new methods to improve this capacity through various nutritional and ergogenic aids.s

Purpose:

The aim of the study was to find out the effect of Ashwagandha on the cardiorespiratory endurance capacity, that is, aerobic capacity of elite Indian cyclists.

Materials and Methods:

Forty elite (elite here refers to the participation of the athlete in at least state-level events) Indian cyclists were chosen randomly and were equally divided into experimental and placebo groups. The experimental group received 500 mg capsules of aqueous roots of Ashwagandha twice daily for eight weeks, whereas the placebo group received starch capsules.

Outcome Measures:

The baseline treadmill test for the cyclists were performed to measure their aerobic capacity in terms of maximal aerobic capacity (VO₂ max), metabolic equivalent, respiratory exchange ratio (RER), and total time for the athlete to reach his exhaustion stage. After eight weeks of supplementation, the treadmill test was again performed and results were obtained.

Results:

There was significant improvement in the experimental group in all parameters, whereas the placebo group did not show any change with respect to their baseline parameters. There was significant improvement in the experimental group in all parameters, namely, VO₂ max (t = 5.356; P < 0.001), METS (t = 4.483; P < 0.001), and time for exhaustion on treadmill (t = 4.813; P < 0.001) in comparison to the placebo group which did not show any change with respect to their baseline parameters.

Conclusion:

Ashwagandha improved the cardiorespiratory endurance of the elite athletes.

Toll-like receptor signaling and regulation of intestinal immunity

The intestine is a complex organ that must maintain tolerance to innocuous food antigens and commensal microbiota while being also able to mount inflammatory responses against invading pathogenic microorganisms. The ability to restrain tolerogenic responses while permitting inflammatory responses requires communication between commensal bacteria, intestinal epithelial cells and immune cells. Disruption or improper signaling between any of these factors may lead to uncontrolled inflammation and the development of inflammatory diseases. Toll-like receptors (TLR) recognize conserved molecular motifs of microorganisms and, not surprisingly, are important for maintaining tolerance to commensal microbiota, as well as inducing inflammation against pathogens. Perturbations in individual TLR signaling can lead to a number of different outcomes and illustrate a system of regulation within the intestine in which each TLR plays a largely non-redundant role in mucosal immunity. This review will discuss recent findings on the roles of individual TLRs and intestinal homeostasis.

Effect of manipulation of incubation temperature on fatty acid profiles and antioxidant enzyme activities in meat-type chicken embryos

Eggs (n = 1,800) obtained from Ross broiler breeders at 32 and 48 wk of age were incubated at either a constant temperature of 37.6°C throughout (T1), or the temperature was reduced for 6 h to 36.6°C each day during embryonic age (EA) 10 to 18 (T2). Yolk sac, liver, and brain fatty acid profiles and oxidant and antioxidant status of liver and brain were measured at EA 14, 19, and day of hatch (DOH). Fatty acid profiles of yolk sac, liver, and brain were influenced by age of breeder with significant breeder hen age × incubation temperature interactions. At EA 14, higher levels of 20:4n-6 and 22:6n-3 had been transferred from the yolk sac to T2 embryos from younger than older breeders, whereas for T1 and T2 embryos, yolk sac 20:4n-6 and 22.6n-3 values were similar for older breeders. Accumulation of 20:4n-6 and 22:6n-3 fatty acids in the liver of T1 and T2 embryos from younger breeders was similar; however, T2 embryos from older breeders had higher liver levels of 20:4n-6 and 22:6n-3 than T1 embryos. At EA 19, liver nitric oxide levels were higher for T2 embryos from younger breeders than those from breeders incubated at T1. Brain catalase levels of T2 embryos from younger breeders were higher than those from older breeders at DOH. Thus, changes in fatty acid profiles and catalase and nitric oxide production of brain and liver tissues resulting from 1°C lower incubation temperature from EA 10 to 18 reflect adaptive changes.

Phase contrast imaging reveals low lung volumes and surface areas in the developing marsupial

Marsupials are born with immature lungs when compared to eutherian mammals and rely, to various extents, on cutaneous gas exchange in order to meet metabolic requirements. Indeed, the fat-tailed dunnart is born with lungs in the canalicular stage of development and relies almost entirely on the skin for gas exchange at birth; consequently undergoing the majority of lung development in air. Plane radiographs and computed tomography data sets were acquired using phase contrast imaging with a synchrotron radiation source for two marsupial species, the fat-tailed dunnart and the larger tammar wallaby, during the first weeks of postnatal life. Phase contrast imaging revealed that only two lung sacs contain air after the first hour of life in the fat-tailed dunnart. While the lung of the tammar wallaby was comparatively more developed, both species demonstrated massive increases in air sac number and architectural complexity during the postnatal period. In addition, both the tammar wallaby and fat-tailed dunnart had lower lung volumes and parenchymal surface areas than were expected from morphometrically determined allometric equations relating these variables to body mass during the neonatal period. However, lung volume is predicted to scale with mass as expected after the neonatal marsupial reaches a body mass of ∼1 g and no longer relies on the skin for gas exchange. Decreased lung volume in the marsupial neonate further supports the maxim that cutaneous gas exchange occurs in the marsupial neonate because the respiratory apparatus is not yet capable of meeting the gas exchange requirements of the newborn.

In situ molecular identification of the influenza A (H1N1) 2009 Neuraminidase in patients with severe and fatal infections during a pandemic in Mexico City

Background

In April 2009, public health surveillance detected an increased number of influenza-like illnesses in Mexico City’s hospitals. The etiological agent was subsequently determined to be a spread of a worldwide novel influenza A (H1N1) triple reassortant. The purpose of the present study was to demonstrate that molecular detection of pandemic influenza A (H1N1) 2009 strains is possible in archival material such as paraffin-embedded lung samples.

Methods

In order to detect A (H1N1) virus sequences in archived biological samples, eight paraffin-embedded lung samples from patients who died of pneumonia and respiratory failure were tested for influenza A (H1N1) Neuraminidase (NA) RNA using in situ RT-PCR.

Results

We detected NA transcripts in 100% of the previously diagnosed A (H1N1)-positive samples as a cytoplasmic signal. No expression was detected by in situ RT-PCR in two Influenza-like Illness A (H1N1)-negative patients using standard protocols nor in a non-related cervical cell line. In situ relative transcription levels correlated with those obtained when in vitro RT-PCR assays were performed. Partial sequences of the NA gene from A (H1N1)-positive patients were obtained by the in situ RT-PCR-sequencing method. Sequence analysis showed 98% similarity with influenza viruses reported previously in other places.

Conclusions

We have successfully amplified specific influenza A (H1N1) NA sequences using stored clinical material; results suggest that this strategy could be useful when clinical RNA samples are quantity limited, or when poor quality is obtained. Here, we provide a very sensitive method that specifically detects the neuraminidase viral RNA in lung samples from patients who died from pneumonia caused by Influenza A (H1N1) outbreak in Mexico City.

ATP-mediated transactivation of the epidermal growth factor receptor in airway epithelial cells involves DUOX1-dependent oxidation of Src and ADAM17

The respiratory epithelium is subject to continuous environmental stress and its responses to injury or infection are largely mediated by transactivation of the epidermal growth factor receptor (EGFR) and downstream signaling cascades. Based on previous studies indicating involvement of ATP-dependent activation of the NADPH oxidase homolog DUOX1 in epithelial wound responses, the present studies were performed to elucidate the mechanisms by which DUOX1-derived H₂O₂ participates in ATP-dependent redox signaling and EGFR transactivation. ATP-mediated EGFR transactivation in airway epithelial cells was found to involve purinergic P2Y₂ receptor stimulation, and both ligand-dependent mechanisms as well as ligand-independent EGFR activation by the non-receptor tyrosine kinase Src. Activation of Src was also essential for ATP-dependent activation of the sheddase ADAM17, which is responsible for liberation and activation of EGFR ligands. Activation of P2Y₂R results in recruitment of Src and DUOX1 into a signaling complex, and transient siRNA silencing or stable shRNA transfection established a critical role for DUOX1 in ATP-dependent activation of Src, ADAM17, EGFR, and downstream wound responses. Using thiol-specific biotin labeling strategies, we determined that ATP-dependent EGFR transactivation was associated with DUOX1-dependent oxidation of cysteine residues within Src as well as ADAM17. In aggregate, our findings demonstrate that DUOX1 plays a central role in overall epithelial defense responses to infection or injury, by mediating oxidative activation of Src and ADAM17 in response to ATP-dependent P2Y₂R activation as a proximal step in EGFR transactivation and downstream signaling.

L-type Ca(2+) channel contributes to alterations in mitochondrial calcium handling in the mdx ventricular myocyte

The L-type Ca(2+) channel is the main route for calcium entry into cardiac myocytes, and it is essential for contraction. Alterations in whole cell L-type Ca(2+) channel current and Ca(2+) homeostasis have been implicated in the development of cardiomyopathies. Cytoskeletal proteins can influence whole cell L-type Ca(2+) current and mitochondrial function. Duchenne muscular dystrophy is a fatal X-linked disease that leads to progressive muscle weakness due to the absence of cytoskeletal protein dystrophin. This includes dilated cardiomyopathy, but the mechanisms are not well understood. We sought to identify the effect of alterations in whole cell L-type Ca(2+) channel current on mitochondrial function in the murine model of Duchenne muscular dystrophy (mdx). Activation of the L-type Ca(2+) channel with the dihydropyridine agonist BayK(-) caused a significantly larger increase in cytosolic Ca(2+) in mdx vs. wild-type (wt) ventricular myocytes. Consistent with elevated cytosolic Ca(2+), resting mitochondrial Ca(2+), NADH, and mitochondrial superoxide were significantly greater in mdx vs. wt myocytes. Activation of the channel with BayK(-) caused a further increase in mitochondrial Ca(2+), NADH, and superoxide in mdx myocytes. The ratios of the increases were similar to the ratios recorded in wt myocytes. In mitochondria isolated from 8-wk-old mdx hearts, respiration and mitochondrial electron transport chain complex activity were similar to mitochondria isolated from wt hearts. We conclude that mitochondria function at a higher level of resting calcium in the intact mdx myocyte and activation of the L-type Ca(2+) channel contributes to alterations in calcium handling by the mitochondria. This perturbation may contribute to the development of cardiomyopathy.

The time course of serotonin 2C receptor expression after spinal transection of rats: an immunohistochemical study

In the spinal cord serotonin (5-HT) systems modulate the spinal network via various 5-HT receptors. Serotonin 2A receptor and serotonin 2C receptor (5-HT2A and 2C receptors) are likely the most important 5-HT receptors for enhancing the motoneuron excitability by facilitating the persistent inward current (PIC), and thus play an important role for the pathogenesis of spasticity after spinal cord injury. In conjunction with our 5-HT2A receptor study, using a same sacral spinal transection rat model we have in this study examined 5-HT2C receptor immunoreactivity (5-HT2CR-IR) changes at seven different time intervals after spinal injury. We found that 5-HT2CR-IR was widely distributed in different regions of the spinal gray matter and was predominantly located in the neuronal somata and their dendrites although it seemed also present in axonal fibers in the superficial dorsal horn. 5-HT2CR-IR in different regions of the spinal gray matter was seen to be increased at 14days after transection (with an average ∼1.3-fold higher than in sham-operated group) but did not reach a significant level until at 21days (∼1.4-fold). The increase sustained thereafter and a plateau level was reached at 45days (∼1.7-fold higher), a value similar as that at 60days. When 5-HT2CR-IR analysis was confined to the ventral horn motoneuron somata (including a proportion of proximal dendrites) a significant increase was not detected until 45days post-operation. 5-HT2CR upregulation in the spinal gray matter is confirmed with Western blot in the rats 60days post-operation. The time course of 5-HT2CR upregulation in the spinal gray matter and motoneurons was positively correlated with the development of tail spasticity (clinical scores). This indicates that 5-HT2CR is probably an important factor underlying this pathophysiological development by increasing the excitability of both motoneurons and interneurons.

Cortical gamma oscillations: the functional key is activation, not cognition

Cortical oscillatory synchrony in the gamma range has been attracting increasing attention in cognitive neuroscience ever since being proposed as a solution to the so-called binding problem. This growing literature is critically reviewed in both its basic neuroscience and cognitive aspects. A physiological "default assumption" regarding these oscillations is introduced, according to which they signal a state of physiological activation of cortical tissue, and the associated need to balance excitation with inhibition in particular. As such these oscillations would belong among a variety of generic neural control operations that enable neural tissue to perform its systems level functions, without implementing those functions themselves. Regional control of cerebral blood flow provides an analogy in this regard, and gamma oscillations are tightly correlated with this even more elementary control operation. As correlates of neural activation they will also covary with cognitive activity, and this typically suffices to account for the covariation between gamma activity and cognitive task variables. A number of specific cases of gamma synchrony are examined in this light, including the original impetus for attributing cognitive significance to gamma activity, namely the experiments interpreted as evidence for "binding by synchrony". This examination finds no compelling reasons to assign functional roles to oscillatory synchrony in the gamma range beyond its generic functions at the level of infrastructural neural control.

Exposure to bisphenol A induces dysfunction of insulin secretion and apoptosis through the damage of mitochondria in rat insulinoma (INS-1) cells

Bisphenol A (BPA) is widely used in plastic products, through which humans are exposed to it. Accumulating evidence suggests that BPA exposure is associated with β-cell dysfunction. Mitochondrial defects can cause impairment and failure of β cells, but there is little information about the effects of BPA on the mitochondrial function of β cells. In this study, we assessed the role of mitochondria-mediated mechanisms underlying BPA-induced β-cell dysfunction and resulting β-cell apoptosis. INS-1 cells were cultured with 0, 0.0020, 0.020, 0.20, or 2.0 μM BPA. Cell viability, glucose-stimulated insulin secretion (GSIS), and mitochondrial function were examined. The mitochondrial apoptotic pathway was also analyzed at molecular level. We found that BPA suppressed cell viability and disturbed GSIS in a dose-dependent manner. Positive Annexin- propidium iodide (PI) staining and altered expression of Bcl-2 family members and caspases in INS-1 cells indicated that the cells progressively became apoptotic after BPA exposure. Additionally, BPA-induced apoptosis was associated with mitochondrial defects in β cells, as evidenced by depletion of ATP, release of cytochrome c, loss of mitochondrial mass and membrane potential, and alterations in expression of genes involved in mitochondrial function and metabolism. Taken together, these findings provide strong evidence that BPA triggers INS-1 cells dysfunction and apoptosis may be meditated via the mitochondrial pathway.

Regulation of the cyclin-dependent kinase inhibitor 1A gene (CDKN1A) by the repressor BOZF1 through inhibition of p53 acetylation and transcription factor Sp1 binding

The human POZ domain and Krüppel-like zinc finger (POK) family proteins play important roles in the regulation of apoptosis, cell proliferation, differentiation, development, oncogenesis, and tumor suppression. A novel POK family transcription factor, BTB/POZ and zinc finger domains factor on chromosome 1 (BOZF-1; also called ZBTB8A), contains a POZ domain and two C2H2-type Krüppel-like zinc fingers and is localized at nuclear speckles. Compared with paired normal tissues, BOZF1 expression is increased in cancer tissues of the prostate, breast, and cervix. BOZF1 repressed the transcription of p21WAF/CDKN1A by acting on the proximal promoter concentrated with Sp1-binding GC boxes. BOZF1 competed with Sp1 in binding to GC boxes 1-5/6 of the CDKN1A proximal promoter. In addition, BOZF1 interacted with p53 and decreased the acetylation of p53 by p300, which reduced the DNA binding activity of p53 at the far distal p53-binding element. BOZF1 blocked the two major molecular events that are important in both constitutive and inducible transcription activation of CDKN1A. BOZF1 is unique in that it bound to all the proximal GC boxes to repress transcription, and it inhibited p53 acetylation without affecting p53 stability. BOZF1 might be a novel proto-oncoprotein that stimulates cell proliferation.

Separating in vivo mechanical stimuli for postpneumonectomy compensation: imaging and ultrastructural assessment

Following right pneumonectomy (PNX), the remaining lung expands and its perfusion more than doubles. Tissue and microvascular mechanical stresses are putative stimuli for compensatory lung growth and remodeling, but their relative contribution remains uncertain. To temporally separate expansion- and perfusion-related stimuli, we replaced the right lung of adult dogs with a customized inflated prosthesis. Four months later, the prosthesis was either acutely deflated (DEF) or kept inflated (INF). Thoracic high-resolution computed tomography (HRCT) was performed pre- and post-PNX before and after prosthesis deflation. Lungs were fixed for morphometric analysis ∼12 mo post-PNX. The INF prosthesis prevented mediastinal shift and lateral lung expansion while allowing the remaining lung to expand 27-38% via caudal elongation, associated with reversible capillary congestion in dependent regions at low inflation and 40-60% increases in the volumes of alveolar sepal cells, matrix, and fibers. Delayed prosthesis deflation led to further significant increases in lung volume, alveolar tissue volumes, and alveolar-capillary surface areas. At postmortem, alveolar tissue volumes were 33% higher in the DEF than the INF group. Lateral expansion explains ∼65% of the total post-PNX increase in left lung volume assessed in vivo or ex vivo, ∼36% of the increase in HRCT-derived (tissue + microvascular blood) volume, ∼45% of the increase in ex vivo septal extravascular tissue volume, and 60% of the increase in gas exchange surface areas. This partition agrees with independent physiological measurements obtained in these animals. We conclude that in vivo signals related to lung expansion and perfusion contribute separately and nearly equally to post-PNX growth and remodeling.

Reactive oxygen species as therapeutic targets in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by a progressive elevation of pulmonary arterial pressure due to alterations of both pulmonary vascular structure and function. This disease is rare but life-threatening, leading to the development of right heart failure. Current PH treatments, designed to target altered pulmonary vascular reactivity, include vasodilating prostanoids, phosphodiesterase-5 inhibitors and endothelin-1 receptor antagonists. Although managing to slow the progression of the disease, these molecules still do not cure PH. More effective treatments need to be developed, and novel therapeutic strategies, targeting in particular vascular remodelling, are currently under investigation. Reactive oxygen species (ROS) are important physiological messengers in vascular cells. In addition to atherosclerosis and other systemic vascular diseases, emerging evidence also support a role of ROS in PH pathogenesis. ROS production is increased in animal models of PH, associated with NADPH oxidases increased expression, in particular of several Nox enzymes thought to be the major source of ROS in the pulmonary vasculature. These increases have also been observed in vitro and in vivo in humans. Moreover, several studies have shown either the deleterious effect of agents promoting ROS generation on pulmonary vasculature or, conversely, the beneficial effect of antioxidant agents in animal models of PH. In these studies, ROS production has been directly linked to pulmonary vascular remodelling, endothelial dysfunction, altered vasoconstrictive responses, inflammation and modifications of the extracellular matrix, all important features of PH pathophysiology. Altogether, these findings indicate that ROS are interesting therapeutic targets in PH. Blockade of ROS-dependent signalling pathways, or disruption of sources of ROS in the pulmonary vasculature, targeting in particular Nox enzymes, represent promising new therapeutic strategies in this disease.

Design and validation of a homogeneous time-resolved fluorescence-based leptin receptor binding assay

The pleiotropic cytokine hormone leptin, by activating its receptor OB-R, plays a major role in many biological processes, including energy homeostasis, immune function, and cell survival and proliferation. Abnormal leptin action is associated with obesity, autoimmune diseases, and cancer. The pharmacological characterization of OB-R and the development of synthetic OB-R ligands are still in their infancy because currently available binding assays are not compatible with ligand saturation binding experiments and high-throughput screening (HTS) approaches. We have developed here a novel homogeneous time-resolved fluorescence-based binding assay that overcomes these limitations. In this assay, fluorescently labeled leptin or leptin antagonist binds to the SNAP-tagged OB-R covalently labeled with terbium cryptate (Tb). Successful binding is monitored by measuring the energy transfer between the Tb energy donor and the fluorescently labeled leptin energy acceptor. Ligand binding saturation experiments revealed high-affinity dissociation constants in the subnanomolar range with an excellent signal-to-noise ratio. The assay performed in a 384-well format shows high specificity and reproducibility, making it perfectly compatible with HTS applications to identify new OB-R agonists or antagonists. In addition, fluorescently labeled leptin and SNAP-tagged OB-R will be valuable tools for monitoring leptin and OB-R trafficking in cells and tissues.

CLOCK deubiquitylation by USP8 inhibits CLK/CYC transcription in Drosophila

A conserved transcriptional feedback loop underlies animal circadian rhythms. In Drosophila, the transcription factors CLOCK (CLK) and CYCLE (CYC) activate the transcription of direct target genes like period (per) and timeless (tim). They encode the proteins PER and TIM, respectively, which repress CLK/CYC activity. Previous work indicates that repression is due to a direct PER-CLK/CYC interaction as well as CLK/CYC phosphorylation. We describe here the role of ubiquitin-specific protease 8 (USP8) in circadian transcriptional repression as well as the importance of CLK ubiquitylation in CLK/CYC transcription activity. usp8 loss of function (RNAi) or expression of a dominant-negative form of the protein (USP8-DN) enhances CLK/CYC transcriptional activity and alters fly locomotor activity rhythms. Clock protein and mRNA molecular oscillations are virtually absent within circadian neurons of USP8-DN flies. Furthermore, CLK ubiquitylation cycles robustly in wild-type flies and peaks coincident with maximal CLK/CYC transcription. As USP8 interacts with CLK and expression of USP8-DN increases CLK ubiquitylation, the data indicate that USP8 deubiquitylates CLK, which down-regulates CLK/CYC transcriptional activity. Taken together with the facts that usp8 mRNA cycles and that its transcription is activated directly by CLK/CYC, USP8, like PER and TIM, contributes to the transcriptional feedback loop cycle that underlies circadian rhythms.

Cytoskeletal and scaffolding proteins as structural and functional determinants of TRP channels

Transient receptor potential (TRP) channels are six transmembrane-spanning proteins, with variable selectivity for cations, that play a relevant role in intracellular Ca(2+) homeostasis. There is a large body of evidence that shows association of TRP channels with the actin cytoskeleton or even the microtubules and demonstrating the functional importance of this interaction for TRP channel function. Conversely, cation currents through TRP channels have also been found to modulate cytoskeleton rearrangements. The interplay between TRP channels and the cytoskeleton has been demonstrated to be essential for full activation of a variety of cellular functions. Furthermore, TRP channels have been reported to take part of macromolecular complexes including different signal transduction proteins. Scaffolding proteins play a relevant role in the association of TRP proteins with other signaling molecules into specific microdomains. Especially relevant are the roles of the Homer family members for the regulation of TRPC channel gating in mammals and INAD in the modulation of Drosophila TRP channels. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.

Characterization of adult α- and β-globin elevated by hydrogen peroxide in cervical cancer cells that play a cytoprotective role against oxidative insults

Objectives

Hemoglobin (Hgb) is the main oxygen and carbon dioxide carrier in cells of erythroid lineage and is responsible for oxygen delivery to the respiring tissues of the body. However, Hgb is also expressed in nonerythroid cells. In the present study, the expression of Hgb in human uterine cervix carcinoma cells and its role in cervical cancer were investigated.

Methodology

The expression level of Hgb in cervical cancer tissues was assessed by quantitative reverse transcriptase-PCR (qRT-PCR). We applied multiple methods, such as RT-PCR, immunoblotting, and immunohistochemical analysis, to confirm Hgb expression in cervical cancer cells. The effects of ectopic expression of Hgb and Hgb mutants on oxidative stress and cell viability were investigated by cellular reactive oxygen species (ROS) analysis and lactate dehydrogenase (LDH) array, respectively. Both Annexin V staining assay by flow cytometry and caspase-3 activity assay were used, respectively, to evaluate cell apoptosis.

Results

qRT-PCR analysis showed that Hgb-α- (HBA1) and Hgb-β-globin (HBB) gene expression was significantly higher in cervical carcinoma than in normal cervical tissues, whereas the expression of hematopoietic transcription factors and erythrocyte specific marker genes was not increased. Immunostaining experiments confirmed the expression of Hgb in cancer cells of the uterine cervix. Hgb mRNA and protein were also detected in the human cervical carcinoma cell lines SiHa and CaSki, and Hgb expression was up-regulated by hydrogen peroxide-induced oxidative stress. Importantly, ectopic expression of wild type HBA1/HBB or HBA1, rather than mutants HBA1^H88R/HBB^H93R unable to bind hemo, suppressed oxidative stress and improved cell viability.

Conclusions

The present findings show for the first time that Hgb is expressed in cervical carcinoma cells and may act as an antioxidant, attenuating oxidative stress-induced damage in cervical cancer cells. These data provide a significant impact not only in globin biology but also in understanding of cervical cancer pathogenesis associated with oxidative stress.

Oleic acid stimulates complete oxidation of fatty acids through protein kinase A-dependent activation of SIRT1-PGC1α complex

Fatty acids are essential components of the dynamic lipid metabolism in cells. Fatty acids can also signal to intracellular pathways to trigger a broad range of cellular responses. Oleic acid is an abundant monounsaturated omega-9 fatty acid that impinges on different biological processes, but the mechanisms of action are not completely understood. Here, we report that oleic acid stimulates the cAMP/protein kinase A pathway and activates the SIRT1-PGC1α transcriptional complex to modulate rates of fatty acid oxidation. In skeletal muscle cells, oleic acid treatment increased intracellular levels of cyclic adenosine monophosphate (cAMP) that turned on protein kinase A activity. This resulted in SIRT1 phosphorylation at Ser-434 and elevation of its catalytic deacetylase activity. A direct SIRT1 substrate is the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α), which became deacetylated and hyperactive after oleic acid treatment. Importantly, oleic acid, but not other long chain fatty acids such as palmitate, increased the expression of genes linked to fatty acid oxidation pathway in a SIRT1-PGC1α-dependent mechanism. As a result, oleic acid potently accelerated rates of complete fatty acid oxidation in skeletal muscle cells. These results illustrate how a single long chain fatty acid specifically controls lipid oxidation through a signaling/transcriptional pathway. Pharmacological manipulation of this lipid signaling pathway might provide therapeutic possibilities to treat metabolic diseases associated with lipid dysregulation.

Differential effects of rapamycin and dexamethasone in mouse models of established allergic asthma

The mammalian target of rapamycin (mTOR) plays an important role in cell growth/differentiation, integrating environmental cues, and regulating immune responses. Our lab previously demonstrated that inhibition of mTOR with rapamycin prevented house dust mite (HDM)-induced allergic asthma in mice. Here, we utilized two treatment protocols to investigate whether rapamycin, compared to the steroid, dexamethasone, could inhibit allergic responses during the later stages of the disease process, namely allergen re-exposure and/or during progression of chronic allergic disease. In protocol 1, BALB/c mice were sensitized to HDM (three i.p. injections) and administered two intranasal HDM exposures. After 6 weeks of rest/recovery, mice were re-exposed to HDM while being treated with rapamycin or dexamethasone. In protocol 2, mice were exposed to HDM for 3 or 6 weeks and treated with rapamycin or dexamethasone during weeks 4-6. Characteristic features of allergic asthma, including IgE, goblet cells, airway hyperreactivity (AHR), inflammatory cells, cytokines/chemokines, and T cell responses were assessed. In protocol 1, both rapamycin and dexamethasone suppressed goblet cells and total CD4(+) T cells including activated, effector, and regulatory T cells in the lung tissue, with no effect on AHR or total inflammatory cell numbers in the bronchoalveolar lavage fluid. Rapamycin also suppressed IgE, although IL-4 and eotaxin 1 levels were augmented. In protocol 2, both drugs suppressed total CD4(+) T cells, including activated, effector, and regulatory T cells and IgE levels. IL-4, eotaxin, and inflammatory cell numbers were increased after rapamycin and no effect on AHR was observed. Dexamethasone suppressed inflammatory cell numbers, especially eosinophils, but had limited effects on AHR. We conclude that while mTOR signaling is critical during the early phases of allergic asthma, its role is much more limited once disease is established.

Protective effects of peroxisome proliferator-activated receptor agonists on human podocytes: proposed mechanisms of action

BACKGROUND AND PURPOSE

Peroxisome proliferator-activated receptor (PPAR) agonists exert anti-albuminuric effects. However, the nephroprotective effects of these drugs remain to be fully understood. We have investigated whether gemfibrozil, GW0742 and pioglitazone protect human podocytes against nutrient deprivation (ND)-induced cell death and the role of mitochondrial biogenesis as a cytoprotective process.

EXPERIMENTAL APPROACH

Immortalized human podocytes were pre-treated with the PPAR agonists and exposed to ND (5 h) under normoxia, hypoxia or in the presence of pyruvate. Cell death was measured at the end of the ND and of the recovery phase (24 h). Mitochondrial mass, cytochrome c oxidase (COX) subunits 1 and 4 were measured as markers of mitochondrial cell content, while membrane potential as an index of mitochondrial function. PGC-1α, NRF1 and Tfam expression was studied, as crucial regulators of mitochondrial biogenesis.

KEY RESULTS

Cell pre-treatment with gemfibrozil, GW0742, or pioglitazone significantly decreased the ND-induced cell loss, necrosis and apoptosis. These effects were attenuated by hypoxia and potentiated by pyruvate. Pre-treatment with these drugs significantly increased mitochondrial cell content, while it did not affect mitochondrial function. In all these experiments pioglitazone exerted significantly larger effects than gemfibrozil or GW0742.

CONCLUSIONS AND IMPLICATIONS

Gemfibrozil, GW0742 and pioglitazone may exert direct protective effects on human podocytes. Mitochondrial biogenesis is a cell response to the PPAR agonists related to their cytoprotective activity. These results provide a mechanistic support to the clinical evidence indicating PPAR agonists as disease-modifying agents for glomerular diseases.

Epithelium-dependent modulation of responsiveness of airways from caveolin-1 knockout mice is mediated through cyclooxygenase-2 and 5-lipoxygenase

BACKGROUND AND PURPOSE

Acute silencing of caveolin-1 (Cav-1) modulates receptor-mediated contraction of airway smooth muscle. Moreover, COX-2- and 5-lipoxygenase (5-LO)-derived prostaglandin and leukotriene biosynthesis can influence smooth muscle reactivity. COX-2 half-life can be prolonged through association with Cav-1. We suggested that lack of Cav-1 modulated levels of COX-2 which in turn modulated tracheal contraction, when arachidonic acid signalling was disturbed by inhibition of COX-2.

EXPERIMENTAL APPROACH

Using tracheal rings from Cav-1 knockout (KO) and wild-type mice (B6129SF2/J), we measured isometric contractions to methacholine and used PCR, immunoblotting and immunohistology to monitor expression of relevant proteins.

KEY RESULTS

Tracheal rings from Cav-1 KO and wild-type mice exhibited similar responses, but the COX-2 inhibitor, indomethacin, increased responses of tracheal rings from Cav-1 KO mice to methacholine. The phospholipase A₂ inhibitor, eicosatetraynoic acid, which inhibits formation of both COX-2 and 5-LO metabolites, had no effect on wild-type or Cav-1 KO tissues. Indomethacin-mediated hyperreactivity was ablated by the LTD₄ receptor antagonist (montelukast) and 5-LO inhibitor (zileuton). The potentiating effect of indomethacin on Cav-1 KO responses to methacholine was blocked by epithelial denudation. Immunoprecipitation showed that COX-2 binds Cav-1 in wild-type lungs. Immunoblotting and qPCR revealed elevated levels of COX-2 and 5-LO protein, but not COX-1, in Cav-1 KO tracheas, a feature that was prevented by removal of the epithelium.

CONCLUSION AND IMPLICATIONS

The indomethacin-induced hypercontractility observed in Cav-1 KO tracheas was linked to increased expression of COX-2 and 5-LO, which probably enhanced arachidonic acid shunting and generation of pro-contractile leukotrienes when COX-2 was inhibited.

Refeeding with a standard diet after a 48-h fast elicits an inflammatory response in the mouse liver

Unhealthy eating behaviors increase the risk of metabolic diseases, but the underlying mechanisms are not fully elucidated. Because inflammation contributes to the pathogenesis of metabolic diseases, it is important to understand the effects of unhealthy eating on the inflammatory state. The objective of our present study was to address the effects of a fasting-refeeding regime, a model of irregular eating, on the hepatic inflammatory responses in mouse. The animals were fasted for 48 h and then refed either a standard or low-carbohydrate/high-fat diet. Inflammatory gene expression in the liver was then sequentially measured for the first 17 h after initiation of refeeding. To assess the roles of dietary carbohydrates and toll-like receptor 2 (TLR2) in the refeeding-induced inflammatory changes, gene expression levels in mice refed only carbohydrates (α-corn starch and sucrose) at different doses and in TLR2-deficient mice refed a standard diet were also analyzed. Refeeding with a standard diet increased the liver expression of Tlr2, proinflammatory mediators (Cxcl10, Cxcl1, Cxcl2, Icam-1) and negative regulators of TLR-signaling (A20 and Atf3). These increases were attenuated in mice refed a low-carbohydrate/high-fat diet. Refeeding only α-corn starch and sucrose also increased the expression of these inflammatory pathway genes depending on the doses. TLR2 deficiency significantly attenuated the refeeding-induced increase in the liver expression of Cxcl10, Cxcl1, Icam-1 and A20. These findings suggest that an irregular eating behavior can elicit a liver inflammatory response, which is at least partly mediated by TLR2, and that dietary carbohydrates play critical roles in this process.

JTV519 (K201) reduces sarcoplasmic reticulum Ca²⁺ leak and improves diastolic function in vitro in murine and human non-failing myocardium

BACKGROUND AND PURPOSE

Ca²⁺ leak from the sarcoplasmic reticulum (SR) via ryanodine receptors (RyR2s) contributes to cardiomyocyte dysfunction. RyR2 Ca²⁺ leak has been related to RyR2 phosphorylation. In these conditions, JTV519 (K201), a 1,4-benzothiazepine derivative and multi-channel blocker, stabilizes RyR2s and decrease SR Ca²⁺ leak. We investigated whether JTV519 stabilizes RyR2s without increasing RyR2 phosphorylation in mice and in non-failing human myocardium and explored underlying mechanisms.

EXPERIMENTAL APPROACH

SR Ca²⁺ leak was induced by ouabain in murine cardiomyocytes. [Ca²⁺]-transients, SR Ca²⁺ load and RyR2-mediated Ca²⁺ leak (sparks/waves) were quantified, with or without JTV519 (1 µmol·L⁻¹). Contribution of Ca²⁺ -/calmodulin-dependent kinase II (CaMKII) was assessed by KN-93 and Western blot (RyR2-Ser(2814) phosphorylation). Effects of JTV519 on contractile force were investigated in non-failing human ventricular trabeculae.

KEY RESULTS

Ouabain increased systolic and diastolic cytosolic [Ca²⁺](i) , SR [Ca²⁺], and SR Ca²⁺ leak (Ca²⁺ spark (SparkF) and Ca²⁺ wave frequency), independently of CaMKII and RyR-Ser(2814) phosphorylation. JTV519 decreased SparkF but also SR Ca²⁺ load. At matched SR [Ca²⁺], Ca²⁺ leak was significantly reduced by JTV519, but it had no effect on fractional Ca²⁺ release or Ca²⁺ wave propagation velocity. In human muscle, JTV519 was negatively inotropic at baseline but significantly enhanced ouabain-induced force and reduced its deleterious effects on diastolic function.

CONCLUSIONS AND IMPLICATIONS

JTV519 was effective in reducing SR Ca²⁺ leak by specifically regulating RyR2 opening at diastolic [Ca²⁺](i) in the absence of increased RyR2 phosphorylation at Ser(2814) , extending the potential use of JTV519 to conditions of acute cellular Ca²⁺ overload.

Mucin-type O-glycosylation during development

Mucin-type O-glycosylation is an evolutionarily conserved protein modification present on membrane-bound and secreted proteins. Aberrations in O-glycosylation are responsible for certain human diseases and are associated with disease risk factors. Recent studies have demonstrated essential roles for mucin-type O-glycosylation in protein secretion, stability, processing, and function. Here, we summarize our current understanding of the diverse roles of mucin-type O-glycosylation during eukaryotic development. Appreciating how this conserved modification operates in developmental processes will provide insight into its roles in human disease and disease susceptibilities.

An integrative model of ion regulation in yeast

Yeast cells are able to tolerate and adapt to a variety of environmental stresses. An essential aspect of stress adaptation is the regulation of monovalent ion concentrations. Ion regulation determines many fundamental physiological parameters, such as cell volume, membrane potential, and intracellular pH. It is achieved through the concerted activities of multiple cellular components, including ion transporters and signaling molecules, on both short and long time scales. Although each component has been studied in detail previously, it remains unclear how the physiological parameters are maintained and regulated by the concerted action of all components under a diverse range of stress conditions. In this study, we have constructed an integrated mathematical model of ion regulation in Saccharomyces cerevisiae to understand this coordinated adaptation process. Using this model, we first predict that the interaction between phosphorylated Hog1p and Tok1p at the plasma membrane inhibits Tok1p activity and consequently reduces Na⁺ influx under NaCl stress. We further characterize the impacts of NaCl, sorbitol, KCl and alkaline pH stresses on the cellular physiology and the differences between the cellular responses to these stresses. We predict that the calcineurin pathway is essential for maintaining a non-toxic level of intracellular Na⁺ in the long-term adaptation to NaCl stress, but that its activation is not required for maintaining a low level of Na⁺ under other stresses investigated. We provide evidence that, in addition to extrusion of toxic ions, Ena1p plays an important role, in some cases alongside Nha1p, in re-establishing membrane potential after stress perturbation. To conclude, this model serves as a powerful tool for both understanding the complex system-level properties of the highly coordinated adaptation process and generating further hypotheses for experimental investigation.

Ion regulation is fundamental to cell physiology. The concentrations of monovalent ions, such as H⁺, K⁺ and Na⁺, determine many physiological parameters such as cell volume, plasma membrane potential and intracellular pH. In yeast cells, these parameters are maintained within a narrow range during the adaptation to external perturbations, including ionic, osmotic and alkaline pH stress. This is achieved by the remarkably coordinated activities of ion transporters, regulatory molecules and signaling pathways. The response characteristics of individual components in adaptation have been studied extensively. However, a coherent understanding of the coordinated adaptation process is lacking. In this study, we address this gap by constructing a mathematical model that integrates the characteristics of the ion transporters, regulatory molecules, signaling pathways and changes in cell volume. Using this model, we characterize the impact of ionic, osmotic and alkaline pH stresses on cellular physiology and analyze the role that individual components play in the cellular adaptation processes. Our results also reveal system level properties achieved by the concerted regulatory responses. Therefore, this integrated model serves as a suitable tool to understand the coordinated processes of ion regulation in response to environmental stresses, and to make predictions that are experimentally testable.

Stabilization of the skeletal muscle ryanodine receptor ion channel-FKBP12 complex by the 1,4-benzothiazepine derivative S107

Activation of the skeletal muscle ryanodine receptor (RyR1) complex results in the rapid release of Ca²⁺ from the sarcoplasmic reticulum and muscle contraction. Dissociation of the small FK506 binding protein 12 subunit (FKBP12) increases RyR1 activity and impairs muscle function. The 1,4-benzothiazepine derivative JTV519, and the more specific derivative S107 (2,3,4,5,-tetrahydro-7-methoxy-4-methyl-1,4-benzothiazepine), are thought to improve skeletal muscle function by stabilizing the RyR1-FKBP12 complex. Here, we report a high degree of nonspecific and specific low affinity [³H]S107 binding to SR vesicles. SR vesicles enriched in RyR1 bound ∼48 [³H]S107 per RyR1 tetramer with EC₅₀ ∼52 µM and Hillslope ∼2. The effects of S107 and FKBP12 on RyR1 were examined under conditions that altered the redox state of RyR1. S107 increased FKBP12 binding to RyR1 in SR vesicles in the presence of reduced glutathione and the NO-donor NOC12, with no effect in the presence of oxidized glutathione. Addition of 0.15 µM FKBP12 to SR vesicles prevented FKBP12 dissociation; however, in the presence of oxidized glutathione and NOC12, FKBP12 dissociation was observed in skeletal muscle homogenates that contained 0.43 µM myoplasmic FKBP12 and was attenuated by S107. In single channel measurements with FKBP12-depleted RyR1s, in the absence and presence of NOC12, S107 augmented the FKBP12-mediated decrease in channel activity. The data suggest that S107 can reverse the harmful effects of redox active species on SR Ca²⁺ release in skeletal muscle by binding to RyR1 low affinity sites.