Targeting G protein coupled receptor-related pathways as emerging molecular therapies

G protein coupled receptors (GPCRs) represent the most important targets in modern pharmacology because of the different functions they mediate, especially within brain and peripheral nervous system, and also because of their functional and stereochemical properties. In this paper, we illustrate, via a variety of examples, novel advances about the GPCR-related molecules that have been shown to play diverse roles in GPCR pathways and in pathophysiological phenomena. We have exemplified how those GPCRs’ pathways are, or might constitute, potential targets for different drugs either to stimulate, modify, regulate or inhibit the cellular mechanisms that are hypothesized to govern some pathologic, physiologic, biologic and cellular or molecular aspects both in vivo and in vitro. Therefore, influencing such pathways will, undoubtedly, lead to different therapeutical applications based on the related pharmacological implications. Furthermore, such new properties can be applied in different fields. In addition to offering fruitful directions for future researches, we hope the reviewed data, together with the elements found within the cited references, will inspire clinicians and researchers devoted to the studies on GPCR’s properties.

Influenza A virus (H1N1) increases airway epithelial cell secretion by up-regulation of potassium channel KCNN4

Influenza infects the epithelial cells lining the airways. Normally epithelial cells move solutes through ion channels to create the osmotic drive to hydrate the airways. Viral alteration of this process could explain, in part, the fluid imbalance in the lungs and the resulting pulmonary edema that occurs during severe influenza infections. Using western blot and RT-qPCR, we measured ion channel and cytokine expression in the Calu3 airway cell line after infection with influenza virus (H1N1) for 48 h. We simultaneously measured chloride and potassium channel function by means of a short-circuit current (I(sc)) produced in an Ussing chamber. At a multiplicity of infection (MOI) of 10, viral M1 protein and pro-inflammatory cytokine expression was observed 24h post-infection, despite a lack of measurable change in Isc. However, we observed a decreased secretory response in cAMP- and calcium-induced Isc 48 h post-infection. This correlated with a decrease in CFTR and KCNN4 protein levels. Interestingly, a viral dose of an MOI 0.6 revealed an increased secretory response that correlated with pro-inflammatory cytokine expression. This increased secretory response seemed to be primarily driven through KCNN4. We detected an increase in KCNN4 mRNA and protein, while CFTR function and expression remained unchanged. Furthermore, inhibition of the KCNN4-stimulated I(sc) with TRAM-34, a specific inhibitor, ameliorated the response, implicating KCNN4 as the main driving force behind the secretory phenotype.

Ethanolic extract of propolis inhibits atherosclerosis in ApoE-knockout mice

Background

The present study was undertaken to investigate the effects and underlying mechanism of ethanolic extract of propolis (EEP) on the development of atherosclerotic lesions in ApoE^−/− mice.

Methods

Eight-week-old male ApoE^−/− mice fed a high-fat diet were treated with EEP (160 mg/kg/d) or vehicle (the same dose) respectively for 14 weeks. The serum levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) were determined by enzymatic methods. Non-HDL-C was calculated as TC minus HDL-C. Serum interleukin-6 (IL-6), interleukin-17 (IL-17), endothelin (ET), inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor (VEGF) were determined with enzyme-linked immunosorbent assay methods. Nitric oxide (NO) content was measured with an enzymatic nitrate reductase assay. Analyses of atherosclerotic lesions in whole aorta and aortic root sections were performed with plaque staining using Oil Red O.

Results

Compared with the vehicle-treated group, serum contents of total cholesterol (TC), triglycerides (TG) and non-HDL-C reduced significantly by 31.88%, 21.01%, and 27.11% respectively in the EEP-treated group. Administration of EEP decreased the level of IL-6 and increased the level of IL-17 in ApoE^−/− mice with a high-fat diet. Compared with the vehicle-treated group,EEP significantly reduced the levels of ET and VEGF,and showed a trend to increase NO and inhibit iNOS. In the ApoE^−/− mice fed a high-fat diet, EEP significantly reduced atherosclerotic lesion development in the aortic root and whole aorta.

Conclusion

EEP can inhibit atherosclerotic lesion formation in ApoE^−/− mice fed a high-fat diet possibly through modulating cholesterol, regulating inflammatory reaction,inhibiting ET and VEGF, and protecting vascular endothelial cells.

History of bioelectrical study and the electrophysiology of the primo vascular system

Background. Primo vascular system is a new anatomical structure whose research results have reported the possibility of a new circulatory system similar to the blood vascular system and cells. Electrophysiology, which measures and analyzes bioelectrical signals tissues and cells, is an important research area for investigating the function of tissues and cells. The bioelectrical study of the primo vascular system has been reported by using modern techniques since the early 1960s by Bonghan Kim. This paper reviews the research result of the electrophysiological study of the primo vascular system for the discussion of the circulatory function. We hope it would help to study the electrophysiology of the primo vascular system for researchers. This paper will use the following exchangeable expressions: Kyungrak system = Bonghan system = Bonghan circulatory system = primo vascular system = primo system; Bonghan corpuscle = primo node; Bonghan duct = primo vessel. We think that objective descriptions of reviewed papers are more important than unified expressions when citing the papers. That said, this paper will unify the expressions of the primo vascular system.

UNC-13L, UNC-13S, and Tomosyn form a protein code for fast and slow neurotransmitter release in Caenorhabditis elegans

Synaptic transmission consists of fast and slow components of neurotransmitter release. Here we show that these components are mediated by distinct exocytic proteins. The Caenorhabditis elegans unc-13 gene is required for SV exocytosis, and encodes long and short isoforms (UNC-13L and S). Fast release was mediated by UNC-13L, whereas slow release required both UNC-13 proteins and was inhibited by Tomosyn. The spatial location of each protein correlated with its effect. Proteins adjacent to the dense projection mediated fast release, while those controlling slow release were more distal or diffuse. Two UNC-13L domains accelerated release. C2A, which binds RIM (a protein associated with calcium channels), anchored UNC-13 at active zones and shortened the latency of release. A calmodulin binding site accelerated release but had little effect on UNC-13’s spatial localization. These results suggest that UNC-13L, UNC-13S, and Tomosyn form a molecular code that dictates the timing of neurotransmitter release.

DOI:http://dx.doi.org/10.7554/eLife.00967.001

Neurons communicate with one another at junctions called synapses. When an electrical signal known as an action potential travels along a neuron and arrives at a synapse, the neuron releases a package of transmitter chemicals into the synapse. These chemicals then diffuse across the gap and bind to receptors on a second neuron, conveying the signal to the target neuron.

The strength of a synapse depends in part on the number of packages, or vesicles, of transmitter chemicals that are available for release. Most synapses contain multiple populations of vesicles: some that are released within a few milliseconds of the arrival of an action potential, and others that are released more slowly. The vesicles that are released rapidly are found close to sites at which calcium ions enter the neuron, whereas the others are located further from these sites. However, little is known about the molecular basis of the differences between fast and slow vesicle release.

Now Hu et al. have studied the proteins involved in these two processes in C. elegans, a nematode worm that is often used in neuroscience because it has a simple nervous system, consisting of just 302 neurons, and a well-characterized genome. Hu et al. showed that the release of synaptic vesicles at the neuromuscular junction between neurons and muscles in C. elegans also has slow and fast components. A long form of UNC-13, which is also found in mammals, promotes fast release of transmitter vesicles. Slow release is mediated by an independent pathway that involves both long and short UNC-13 proteins, as well as a protein called Tomosyn. As in mammals, long UNC-13 is localized to the sites at which calcium ions enter neurons, whereas short UNC-13 is more widely distributed throughout neurons.

The work of Hu et al. provides a molecular explanation for how the timing of transmitter release is determined. Because the UNC-13 and Tomosyn proteins are evolutionarily conserved, this mechanism is likely to be present in other animals too.

DOI:http://dx.doi.org/10.7554/eLife.00967.002

Modulation of synaptic depression of the calyx of Held synapse by GABA(B) receptors and spontaneous activity

The calyx of Held synapse of the medial nucleus of the trapezoid body is a giant axosomatic synapse in the auditory brainstem, which acts as a relay synapse showing little dependence of its synaptic strength on firing frequency. The main mechanism that is responsible for its resistance to synaptic depression is its large number of release sites with low release probability. Here, we investigated the contribution of presynaptic GABA(B) receptors and spontaneous activity to release probability both in vivo and in vitro in young-adult mice. Maximal activation of presynaptic GABA(B) receptors by baclofen reduced synaptic output by about 45% in whole-cell voltage clamp slice recordings, which was accompanied by a reduction in short-term depression. A similar reduction in transmission was observed when baclofen was applied in vivo by microiontophoresis during juxtacellular recordings using piggyback electrodes. No significant change in synaptic transmission was observed during application of the GABA(B) receptor antagonist CGP54626 both during in vivo and slice recordings, suggesting a low ambient GABA concentration. Interestingly, we observed that synapses with a high spontaneous frequency showed almost no synaptic depression during auditory stimulation, whereas synapses with a low spontaneous frequency did depress during noise bursts. Our data thus suggest that spontaneous firing can tonically reduce release probability in vivo. In addition, our data show that the ambient GABA concentration in the auditory brainstem is too low to activate the GABA(B) receptor at the calyx of Held significantly, but that activation of GABA(B) receptors can reduce sound-evoked synaptic depression.

Growth hormone is a cellular senescence target in pituitary and nonpituitary cells

Premature proliferative arrest in benign or early-stage tumors induced by oncoproteins, chromosomal instability, or DNA damage is associated with p53/p21 activation, culminating in either senescence or apoptosis, depending on cell context. Growth hormone (GH) elicits direct peripheral metabolic actions as well as growth effects mediated by insulin-like growth factor 1 (IGF1). Locally produced peripheral tissue GH, in contrast to circulating pituitary-derived endocrine GH, has been proposed to be both proapoptotic and prooncogenic. Pituitary adenomas expressing and secreting GH are invariably benign and exhibit DNA damage and a senescent phenotype. We therefore tested effects of nutlin-induced p53-mediated senescence in rat and human pituitary cells. We show that DNA damage senescence induced by nutlin triggers the p53/p21 senescent pathway, with subsequent marked induction of intracellular pituitary GH in vitro. In contrast, GH is not induced in cells devoid of p53. Furthermore we show that p53 binds specific GH promoter motifs and enhances GH transcription and secretion in senescent pituitary adenoma cells and also in nonpituitary (human breast and colon) cells. In vivo, treatment with nutlin results in up-regulation of both p53 and GH in the pituitary gland, as well as increased GH expression in nonpituitary tissues (lung and liver). Intracrine GH acts in pituitary cells as an apoptosis switch for p53-mediated senescence, likely protecting the pituitary adenoma from progression to malignancy. Unlike in the pituitary, in nonpituitary cells GH exerts antiapoptotic properties. Thus, the results show that GH is a direct p53 transcriptional target and fulfills criteria as a p53 target gene. Induced GH is a readily measurable cell marker for p53-mediated cellular senescence.

Cluster of differentiation 38 (CD38) mediates bile acid-induced acinar cell injury and pancreatitis through cyclic ADP-ribose and intracellular calcium release

Aberrant Ca(2+) signals within pancreatic acinar cells are an early and critical feature in acute pancreatitis, yet it is unclear how these signals are generated. An important mediator of the aberrant Ca(2+) signals due to bile acid exposure is the intracellular Ca(2+) channel ryanodine receptor. One putative activator of the ryanodine receptor is the nucleotide second messenger cyclic ADP-ribose (cADPR), which is generated by an ectoenzyme ADP-ribosyl cyclase, CD38. In this study, we examined the role of CD38 and cADPR in acinar cell Ca(2+) signals and acinar injury due to bile acids using pharmacologic inhibitors of CD38 and cADPR as well as mice deficient in Cd38 (Cd38(-/-)). Cytosolic Ca(2+) signals were imaged using live time-lapse confocal microscopy in freshly isolated mouse acinar cells during perifusion with the bile acid taurolithocholic acid 3-sulfate (TLCS; 500 μM). To focus on intracellular Ca(2+) release and to specifically exclude Ca(2+) influx, cells were perifused in Ca(2+)-free medium. Cell injury was assessed by lactate dehydrogenase leakage and propidium iodide uptake. Pretreatment with either nicotinamide (20 mM) or the cADPR antagonist 8-Br-cADPR (30 μM) abrogated TLCS-induced Ca(2+) signals and cell injury. TLCS-induced Ca(2+) release and cell injury were reduced by 30 and 95%, respectively, in Cd38-deficient acinar cells compared with wild-type cells (p < 0.05). Cd38-deficient mice were protected against a model of bile acid infusion pancreatitis. In summary, these data indicate that CD38-cADPR mediates bile acid-induced pancreatitis and acinar cell injury through aberrant intracellular Ca(2+) signaling.

Visual Working Memory in Human Cortex

Visual working memory (VWM) is the ability to maintain visual information in a readily available and easily updated state. Converging evidence has revealed that VWM capacity is limited by the number of maintained objects, which is about 3 - 4 for the average human. Recent work suggests that VWM capacity is also limited by the resolution required to maintain objects, which is tied to the objects' inherent complexity. Electroencephalogram (EEG) studies using the Contralateral Delay Activity (CDA) paradigm have revealed that cortical representations of VWM are at a minimum loosely organized like the primary visual system, such that the left side of space is represented in the right hemisphere, and vice versa. Recent functional magnetic resonance imaging (fMRI) work shows that the number of objects is maintained by representations in the inferior intraparietal sulcus (IPS) along dorsal parietal cortex, whereas the resolution of these maintained objects is subserved by the superior IPS and the lateral occipital complex (LOC). These areas overlap with recently-discovered, retinotopically-organized visual field maps (VFMs) spanning the IPS (IPS-0/1/2/3/4/5), and potentially maps in lateral occipital cortex, such as LO-1/2, and/or TO-1/2 (hMT+). Other fMRI studies have implicated early VFMs in posterior occipital cortex, suggesting that visual areas V1-hV4 are recruited to represent information in VWM. Insight into whether and how these VFMs subserve VWM may illuminate the nature of VWM. In addition, understanding the nature of these maps may allow a greater investigation into individual differences among subjects and even between hemispheres within subjects.

AQP1 expression alterations affect morphology and water transport in Schwann cells and hypoxia-induced up-regulation of AQP1 occurs in a HIF-1α-dependent manner

Aquaporin-1 (AQP1) is the principle water channel in the peripheral nervous system (PNS) and is specifically localized to Schwann cells in the PNS. However, the pathophysiological role of AQP1 in peripheral nerves is poorly understood. Here, we utilized RNA interference by lentiviral transduction to specifically down-regulate AQP1 expression and a lentiviral overexpression protocol to up-regulate AQP1 expression, in primary Schwann cell cultures. AQP1 gene silencing resulted in a cell shrinkage phenotype, while AQP1 gene overexpression caused a cell swelling phenotype, as validated by cell volume determinations. Secondly, we utilized an in vitro hypoxia model in Schwann cells to mimic in vivo facial nerve injury. We demonstrated that AQP1 expression was induced within 8h following hypoxia injury in vitro, and that AQP1 knockdown (KD) caused the cells to resist edema following hypoxia. Finally, we investigated the hypoxic regulation of the AQP1 gene, as well as the involvement of Hypoxia-inducible factor-1α (HIF-1α) in AQP1 modulation and we found that KD of HIF-1α decreased hypoxia-dependent induction of endogenous AQP1 expression at both the mRNA and protein levels. Taken together, these results indicate that (1) AQP1 is an important factor responsible for the fast water transport of cultured Schwann cells and is involved in cell plasticity; (2) AQP1 alterations may be a primary factor in hypoxia-induced peripheral nerve edema; (3) HIF-1α participates in the hypoxic induction of the AQP1 gene; (4) AQP1 inhibition might provide a new therapeutic alternative for the treatment of some forms of peripheral nerve edema.

Electrophysiological heterogeneity of fast-spiking interneurons: chandelier versus basket cells

In the prefrontal cortex, parvalbumin-positive inhibitory neurons play a prominent role in the neural circuitry that subserves working memory, and alterations in these neurons contribute to the pathophysiology of schizophrenia. Two morphologically distinct classes of parvalbumin neurons that target the perisomatic region of pyramidal neurons, chandelier cells (ChCs) and basket cells (BCs), are generally thought to have the same “fast-spiking” phenotype, which is characterized by a short action potential and high frequency firing without adaptation. However, findings from studies in different species suggest that certain electrophysiological membrane properties might differ between these two cell classes. In this study, we assessed the physiological heterogeneity of fast-spiking interneurons as a function of two factors: species (macaque monkey vs. rat) and morphology (chandelier vs. basket). We showed previously that electrophysiological membrane properties of BCs differ between these two species. Here, for the first time, we report differences in ChCs membrane properties between monkey and rat. We also found that a number of membrane properties differentiate ChCs from BCs. Some of these differences were species-independent (e.g., fast and medium afterhyperpolarization, firing frequency, and depolarizing sag), whereas the differences in the first spike latency between ChCs and BCs were species-specific. Our findings indicate that different combinations of electrophysiological membrane properties distinguish ChCs from BCs in rodents and primates. Such electrophysiological differences between ChCs and BCs likely contribute to their distinctive roles in cortical circuitry in each species.

Dynamics of cleft closure of the GluA2 ligand-binding domain in the presence of full and partial agonists revealed by hydrogen-deuterium exchange

The majority of excitatory neurotransmission in the CNS is mediated by tetrameric AMPA receptors. Channel activation begins with a series of interactions with an agonist that binds to the cleft between the two lobes of the ligand-binding domain of each subunit. Binding leads to a series of conformational transitions, including the closure of the two lobes of the binding domain around the ligand, culminating in ion channel opening. Although a great deal has been learned from crystal structures, determining the molecular details of channel activation, deactivation, and desensitization requires measures of dynamics and stabilities of hydrogen bonds that stabilize cleft closure. The use of hydrogen-deuterium exchange at low pH provides a measure of the variation of stability of specific hydrogen bonds among agonists of different efficacy. Here, we used NMR measurements of hydrogen-deuterium exchange to determine the stability of hydrogen bonds in the GluA2 (AMPA receptor) ligand-binding domain in the presence of several full and partial agonists. The results suggest that the stabilization of hydrogen bonds between the two lobes of the binding domain is weaker for partial than for full agonists, and efficacy is correlated with the stability of these hydrogen bonds. The closure of the lobes around the agonists leads to a destabilization of the hydrogen bonding in another portion of the lobe interface, and removing an electrostatic interaction in Lobe 2 can relieve the strain. These results provide new details of transitions in the binding domain that are associated with channel activation and desensitization.

Finding synchrony in the desynchronized EEG: the history and interpretation of gamma rhythms

Neocortical gamma (30–80 Hz) rhythms correlate with attention, movement and perception and are often disrupted in neurological and psychiatric disorders. Gamma primarily occurs during alert brain states characterized by the so-called “desynchronized” EEG. Is this because gamma rhythms are devoid of synchrony? In this review we take a historical approach to answering this question. Richard Caton and Adolf Beck were the first to report the rhythmic voltage fluctuations in the animal brain. They were limited by the poor amplification of their early galvanometers. Thus when they presented light or other stimuli, they observed a disappearance of the large resting oscillations. Several groups have since shown that visual stimuli lead to low amplitude gamma rhythms and that groups of neurons in the visual cortices fire together during individual gamma cycles. This synchronous firing can more strongly drive downstream neurons. We discuss how gamma-band synchrony can support ongoing communication between brain regions, and highlight an important fact: there is at least local neuronal synchrony during gamma rhythms. Thus, it is best to refer to the low amplitude, high frequency EEG as an “activated”, not “desynchronized”, EEG.

Cadmium and its neurotoxic effects

Cadmium (Cd) is a heavy metal that has received considerable concern environmentally and occupationally. Cd has a long biological half-life mainly due to its low rate of excretion from the body. Thus, prolonged exposure to Cd will cause toxic effect due to its accumulation over time in a variety of tissues, including kidneys, liver, central nervous system (CNS), and peripheral neuronal systems. Cd can be uptaken from the nasal mucosa or olfactory pathways into the peripheral and central neurons; for the latter, Cd can increase the blood brain barrier (BBB) permeability. However, mechanisms underlying Cd neurotoxicity remain not completely understood. Effect of Cd neurotransmitter, oxidative damage, interaction with other metals such as cobalt and zinc, estrogen-like, effect and epigenetic modification may all be the underlying mechanisms. Here, we review the in vitro and in vivo evidence of neurotoxic effects of Cd. The available finding indicates the neurotoxic effects of Cd that was associated with both biochemical changes of the cell and functional changes of central nervous system, suggesting that neurotoxic effects may play a role in the systemic toxic effects of the exposure to Cd, particularly the long-term exposure.

Chronic ethanol consumption disrupts the core molecular clock and diurnal rhythms of metabolic genes in the liver without affecting the suprachiasmatic nucleus

Chronic ethanol consumption disrupts several metabolic pathways including β-oxidation and lipid biosynthesis, facilitating the development of alcoholic fatty liver disease. Many of these same metabolic pathways are directly regulated by cell autonomous circadian clocks, and recent studies suggest that disruption of daily rhythms in metabolism contributes to multiple common cardiometabolic diseases (including non-alcoholic fatty liver disease). However, it is not known whether ethanol disrupts the core molecular clock in the liver, nor whether this, in turn, alters rhythms in lipid metabolism. Herein, we tested the hypothesis that chronic ethanol consumption disrupts the molecular circadian clock in the liver and potentially changes the diurnal expression patterns of lipid metabolism genes. Consistent with previous studies, male C57BL/6J mice fed an ethanol-containing diet exhibited higher levels of liver triglycerides compared to control mice, indicating hepatic steatosis. Further, the diurnal oscillations of core clock genes (Bmal1, Clock, Cry1, Cry2, Per1, and Per2) and clock-controlled genes (Dbp, Hlf, Nocturnin, Npas2, Rev-erbα, and Tef) were altered in livers from ethanol-fed mice. In contrast, ethanol had only minor effects on the expression of core clock genes in the suprachiasmatic nucleus (SCN). These results were confirmed in Per2^Luciferase knock-in mice, in which ethanol induced a phase advance in PER2::LUC bioluminescence oscillations in liver, but not SCN. Further, there was greater variability in the phase of PER2::LUC oscillations in livers from ethanol-fed mice. Ethanol consumption also affected the diurnal oscillations of metabolic genes, including Adh1, Cpt1a, Cyp2e1, Pck1, Pdk4, Ppargc1a, Ppargc1b and Srebp1c, in the livers of C57BL/6J mice. In summary, chronic ethanol consumption alters the function of the circadian clock in liver. Importantly, these results suggest that chronic ethanol consumption, at levels sufficient to cause steatosis, disrupts the core hepatic clock as well as the diurnal rhythms of key lipid metabolism genes.

Development of polymeric nanoprobes with improved lifetime dynamic range and stability for intracellular oxygen sensing

A class of core-shell nanoparticles possessing a layer of biocompatible shell and hydrophobic core with embedded oxygen-sensitive platinum-porphyrin (PtTFPP) dyes is developed via a radical-initiated microemulsion co-polymerization strategy. The influences of host matrices and the PtTFPP incorporation manner on the photophysical properties and the oxygen-sensing performance of the nanoparticles are investigated. Self-loading capability with cells and intracellular-oxygen-sensing ability of the as-prepared nanoparticle probes in the range 0%-20% oxygen concentration are confirmed. Polymeric nanoparticles with optimized formats are characterized by their relatively small diameter (<50 nm), core-shell structures with biocompatible shells, covalent-attachment-imparted leak-free construction, improved lifetime dynamic range (up to 44 μs), excellent storage stability and photostability, and facile cell uptake. The nanoparticles' small sensor diameter and core-shell structure with biocompatible shell make them suitable for intracellular detection applications. For intracellular detection applications, the leak-free feature of the as-prepared nanoparticle sensor effectively minimizes potential chemical interferences and cytotoxicity. As a salient feature, improved lifetime dynamic range of the sensor is expected to enable precise oxygen detection and control in specific practical applications in stem-cell biology and medical research. Such a feature-packed nanoparticle oxygen sensor may find applications in precise oxygen-level mapping of living cells and tissue.

Construction and Analysis of the Cell Surface's Protein Network for Human Sperm-Egg Interaction

Sperm-egg interaction is one of the most impressive processes in sexual reproduction, and understanding the molecular mechanism is crucial in solving problems in infertility and failed in vitro fertilization. The main purpose of this study is to map the sperm-egg interaction network between cell-surface proteins and perform an interaction analysis on this new network. We built the first protein interaction network of human sperm-egg binding and fusion proteins that consists of 84 protein nodes and 112 interactions. The gene ontology analysis identified a number of functional clusters that may be involved in the sperm-egg interaction. These include G-protein coupled receptor protein signaling pathway, cellular membrane fusion, and single fertilization. The PPI network showed a highly interconnected network and identified a set of candidate proteins: ADAM-ZP3, ZP3-CLGN, IZUMO1-CD9, and ADAM2-IZUMO1 that may have an important role in sperm-egg interaction. The result showed that the ADAM2 may mediate interaction between two essential factors CD9 and IZUMO1. The KEGG analysis showed 12 statistically significant pathways with 10 proteins associated with cancer, suggesting a common pathway between tumor fusion and sperm-egg fusion. We believe that the availability of this map will assist future researches in the fertilization mechanism and will also facilitate biological interpretation of sperm-egg interaction.

Recent progress in genetics of aging, senescence and longevity: focusing on cancer-related genes

It is widely believed that aging results from the accumulation of molecular damage, including damage of DNA and mitochondria and accumulation of molecular garbage both inside and outside of the cell. Recently, this paradigm is being replaced by the “hyperfunction theory”, which postulates that aging is caused by activation of signal transduction pathways such as TOR (Target of Rapamycin). These pathways consist of different enzymes, mostly kinases, but also phosphatases, deacetylases, GTPases, and some other molecules that cause overactivation of normal cellular functions. Overactivation of these sensory signal transduction pathways can cause cellular senescence, age-related diseases, including cancer, and shorten life span. Here we review some of the numerous very recent publications on the role of signal transduction molecules in aging and age-related diseases. As was emphasized by the author of the “hyperfunction model”, many (or actually all) of them also play roles in cancer. So these “participants” in pro-aging signaling pathways are actually very well acquainted to cancer researchers. A cancer-related journal such as Oncotarget is the perfect place for publication of such experimental studies, reviews and perspectives, as it can bridge the gap between cancer and aging researchers.

Childhood maltreatment is associated with larger left thalamic gray matter volume in adolescents with generalized anxiety disorder

BACKGROUND

Generalized anxiety disorder (GAD) is a common anxiety disorder that usually begins in adolescence. Childhood maltreatment is highly prevalent and increases the possibility for developing a variety of mental disorders including anxiety disorders. An earlier age at onset of GAD is significantly related to maltreatment in childhood. Exploring the underpinnings of the relationship between childhood maltreatment and adolescent onset GAD would be helpful in identifying the potential risk markers of this condition.

METHODS

Twenty-six adolescents with GAD and 25 healthy controls participated in this study. A childhood trauma questionnaire (CTQ) was introduced to assess childhood maltreatment. All subjects underwent high-resolution structural magnetic resonance scans. Voxel-based morphometry (VBM) was used to investigate gray matter alterations.

RESULTS

Significantly larger gray matter volumes of the right putamen were observed in GAD patients compared to healthy controls. In addition, a significant diagnosis-by-maltreatment interaction effect for the left thalamic gray matter volume was revealed, as shown by larger volumes of the left thalamic gray matter in GAD patients with childhood maltreatment compared with GAD patients without childhood maltreatment as well as with healthy controls with/without childhood maltreatment. A significant positive association between childhood maltreatment and left thalamic gray matter volume was only seen in GAD patients.

CONCLUSIONS

These findings revealed an increased volume in the subcortical regions in adolescent GAD, and the alterations in the left thalamus might be involved in the association between childhood maltreatment and the occurrence of GAD.

A kinase-independent function of CDK6 links the cell cycle to tumor angiogenesis

In contrast to its close homolog CDK4, the cell cycle kinase CDK6 is expressed at high levels in lymphoid malignancies. In a model for p185BCR-ABL+ B-acute lymphoid leukemia, we show that CDK6 is part of a transcription complex that induces the expression of the tumor suppressor p16INK4a and the pro-angiogenic factor VEGF-A. This function is independent of CDK6's kinase activity. High CDK6 expression thus suppresses proliferation by upregulating p16INK4a, providing an internal safeguard. However, in the absence of p16INK4a, CDK6 can exert its full tumor-promoting function by enhancing proliferation and stimulating angiogenesis. The finding that CDK6 connects cell-cycle progression to angiogenesis confirms CDK6's central role in hematopoietic malignancies and could underlie the selection pressure to upregulate CDK6 and silence p16INK4a.

Identification of molecular and physiological responses to chronic environmental challenge in an invasive species: the Pacific oyster, Crassostrea gigas

Understanding the environmental responses of an invasive species is critical in predicting how ecosystem composition may be transformed in the future, especially under climate change. In this study, Crassostrea gigas, a species well adapted to the highly variable intertidal environment, was exposed to the chronic environmental challenges of temperature (19 and 24°C) and pH (ambient seawater and a reduction of 0.4 pH units) in an extended 3-month laboratory-based study. Physiological parameters were measured (condition index, shell growth, respiration, excretion rates, O:N ratios, and ability to repair shell damage) alongside molecular analyses. Temperature was by far the most important stressor, as demonstrated by reduced condition indexes and shell growth at 24°C, with relatively little effect detected for pH. Transcriptional profiling using candidate genes and SOLiD sequencing of mantle tissue revealed that classical “stress” genes, previously reported to be upregulated under acute temperature challenges, were not significantly expressed in any of the treatments, emphasizing the different response between acute and longer term chronic stress. The transcriptional profiling also elaborated on the cellular responses underpinning the physiological results, including the identification of the PI3K/AKT/mTOR pathway as a potentially novel marker for chronic environmental challenge. This study represents a first attempt to understand the energetic consequences of cumulative thermal stress on the intertidal C. gigas which could significantly impact on coastal ecosystem biodiversity and function in the future.

Answering the ultimate question "what is the proximal cause of aging?"

Recent discoveries suggest that aging is neither driven by accumulation of molecular damage of any cause, nor by random damage of any kind. Some predictions of a new theory, quasi-programmed hyperfunction, have already been confirmed and a clinically-available drug slows aging and delays diseases in animals. The relationship between diseases and aging becomes easily apparent. Yet, the essence of aging turns out to be so startling that the theory cannot be instantly accepted and any possible arguments are raised for its disposal. I discuss that these arguments actually support a new theory. Are any questions remaining? And might accumulation of molecular damage still play a peculiar role in aging?

Recent discoveries in the cycling, growing and aging of the p53 field

The P53 gene and it product p53 protein is the most studied tumor suppressor, which was considered as oncogene for two decades until 1990. More than 60 thousand papers on the topic of p53 has been abstracted in Pubmed. What yet could be discovered about its role in cell death, growth arrest and apoptosis, as well as a mediator of the therapeutic effect of anticancer drugs. Still during recent few years even more amazing discoveries have been done. Here we review such topics as suppression of epigenetic silencing of a large number of non-coding RNAs, role of p53 in suppression of the senescence phenotype, inhibition of oncogenic metabolism, protection of normal cells from chemotherapy and even tumor suppression without apoptosis and cell cycle arrest.

Group sparse canonical correlation analysis for genomic data integration

BACKGROUND

The emergence of high-throughput genomic datasets from different sources and platforms (e.g., gene expression, single nucleotide polymorphisms (SNP), and copy number variation (CNV)) has greatly enhanced our understandings of the interplay of these genomic factors as well as their influences on the complex diseases. It is challenging to explore the relationship between these different types of genomic data sets. In this paper, we focus on a multivariate statistical method, canonical correlation analysis (CCA) method for this problem. Conventional CCA method does not work effectively if the number of data samples is significantly less than that of biomarkers, which is a typical case for genomic data (e.g., SNPs). Sparse CCA (sCCA) methods were introduced to overcome such difficulty, mostly using penalizations with l-1 norm (CCA-l1) or the combination of l-1and l-2 norm (CCA-elastic net). However, they overlook the structural or group effect within genomic data in the analysis, which often exist and are important (e.g., SNPs spanning a gene interact and work together as a group).

RESULTS

We propose a new group sparse CCA method (CCA-sparse group) along with an effective numerical algorithm to study the mutual relationship between two different types of genomic data (i.e., SNP and gene expression). We then extend the model to a more general formulation that can include the existing sCCA models. We apply the model to feature/variable selection from two data sets and compare our group sparse CCA method with existing sCCA methods on both simulation and two real datasets (human gliomas data and NCI60 data). We use a graphical representation of the samples with a pair of canonical variates to demonstrate the discriminating characteristic of the selected features. Pathway analysis is further performed for biological interpretation of those features.

CONCLUSIONS

The CCA-sparse group method incorporates group effects of features into the correlation analysis while performs individual feature selection simultaneously. It outperforms the two sCCA methods (CCA-l1 and CCA-group) by identifying the correlated features with more true positives while controlling total discordance at a lower level on the simulated data, even if the group effect does not exist or there are irrelevant features grouped with true correlated features. Compared with our proposed CCA-group sparse models, CCA-l1 tends to select less true correlated features while CCA-group inclines to select more redundant features.

Brain-derived neurotrophic factor interacts with astrocytes and neurons to control respiration

Respiratory rhythm is generated and modulated in the brainstem. Neuronal involvement in respiratory control and rhythmogenesis is now clearly established. However, glial cells have also been shown to modulate the activity of brainstem respiratory groups. Although the potential involvement of other glial cell type(s) cannot be excluded, astrocytes are clearly involved in this modulation. In parallel, brain-derived neurotrophic factor (BDNF) also modulates respiratory rhythm. The currently available data on the respective roles of astrocytes and BDNF in respiratory control and rhythmogenesis lead us to hypothesize that there is BDNF-mediated control of the communication between neurons and astrocytes in the maintenance of a proper neuronal network capable of generating a stable respiratory rhythm. According to this hypothesis, progression of Rett syndrome, an autism spectrum disease with disordered breathing, can be stabilized in mouse models by re-expressing the normal gene pattern in astrocytes or microglia, as well as by stimulating the BDNF signaling pathway. These results illustrate how the signaling mechanisms by which glia exerts its effects in brainstem respiratory groups is of great interest for pathologies associated with neurological respiratory disorders.

FGF21 regulates metabolism and circadian behavior by acting on the nervous system

Fibroblast growth factor 21 (FGF21) is a hepatokine that acts as a global starvation signal to modulate fuel partitioning and metabolism and repress growth; however, the site of action of these diverse effects remains unclear. FGF21 signals through a heteromeric cell-surface receptor composed of one of three FGF receptors (FGFR1c, FGFR2c or FGFR3c) in complex with β-Klotho, a single-pass transmembrane protein that is enriched in metabolic tissues. Here we show that in addition to its known effects on peripheral metabolism, FGF21 increases systemic glucocorticoid levels, suppresses physical activity and alters circadian behavior, which are all features of the adaptive starvation response. These effects are mediated through β-Klotho expression in the suprachiasmatic nucleus of the hypothalamus and the dorsal vagal complex of the hindbrain. Mice lacking the gene encoding β-Klotho (Klb) in these regions are refractory to these effects, as well as those on metabolism, insulin and growth. These findings demonstrate a crucial role for the nervous system in mediating the diverse physiologic and pharmacologic actions of FGF21.

An effective manual deboning method to prepare intact mouse nasal tissue with preserved anatomical organization

The mammalian nose is a multi-functional organ with intricate internal structures. The nasal cavity is lined with various epithelia such as olfactory, respiratory, and squamous epithelia which differ markedly in anatomical locations, morphology, and functions. In adult mice, the nose is covered with various skull bones, limiting experimental access to internal structures, especially those in the posterior such as the main olfactory epithelium (MOE). Here we describe an effective method for obtaining almost the entire and intact nasal tissues with preserved anatomical organization. Using surgical tools under a dissecting microscope, we sequentially remove the skull bones surrounding the nasal tissue. This procedure can be performed on both paraformaldehyde-fixed and freshly dissected, skinned mouse heads. The entire deboning procedure takes about 20-30 min, which is significantly shorter than the experimental time required for conventional chemical-based decalcification. In addition, we present an easy method to remove air bubbles trapped between turbinates, which is critical for obtaining intact thin horizontal or coronal or sagittal sections from the nasal tissue preparation. Nasal tissue prepared using our method can be used for whole mount observation of the entire epithelia, as well as morphological, immunocytochemical, RNA in situ hybridization, and physiological studies, especially in studies where region-specific examination and comparison are of interest.

The molecular biology of genetic-based epilepsies

Epilepsy is one of the most common neurological disorders characterized by abnormal electrical activity in the central nervous system. The clinical features of this disorder are recurrent seizures, difference in age onset, type, and frequency, leading to motor, sensory, cognitive, psychic, or autonomic disturbances. Since the discovery of the first monogenic gene mutation in 1995, it is proposed that genetic factor plays an important role in the mechanism of epilepsy. Genes discovered in idiopathic epilepsies encode for ion channel or neurotransmitter receptor proteins, whereas syndromes with epilepsy as a main feature are caused by genes that are involved in functions such as cortical development, mitochondrial function, and cell metabolism. The identification of these monogenic epilepsy-causing genes provides new insight into the pathogenesis of epilepsies. Although most of the identified gene mutations present a monogenic inheritance, most of idiopathic epilepsies are complex genetic diseases exhibiting a polygenic or oligogenic inheritance. This article reviews recent genetic and molecular progresses in exploring the pathogenesis of epilepsy, with special emphasis on monogenic epilepsy-causing genes, including voltage-gated channels (Na(+), K(+), Ca(2+), Cl(-), and HCN), ligand-gated channels (nicotinic acetylcholine and GABAA receptors), non-ion channel genes as well as the mitochondrial DNA genes. These progresses have improved our understanding of the complex neurological disorder.

Of mice and men: molecular genetics of congenital heart disease

Congenital heart disease (CHD) affects nearly 1 % of the population. It is a complex disease, which may be caused by multiple genetic and environmental factors. Studies in human genetics have led to the identification of more than 50 human genes, involved in isolated CHD or genetic syndromes, where CHD is part of the phenotype. Furthermore, mapping of genomic copy number variants and exome sequencing of CHD patients have led to the identification of a large number of candidate disease genes. Experiments in animal models, particularly in mice, have been used to verify human disease genes and to gain further insight into the molecular pathology behind CHD. The picture emerging from these studies suggest that genetic lesions associated with CHD affect a broad range of cellular signaling components, from ligands and receptors, across down-stream effector molecules to transcription factors and co-factors, including chromatin modifiers.

Combining fragment homology modeling with molecular dynamics aims at prediction of Ca²⁺ binding sites in CaBPs

The family of calcium-binding proteins (CaBPs) consists of dozens of members and contributes to all aspects of the cell's function, from homeostasis to learning and memory. However, the Ca²⁺-binding mechanism is still unclear for most of CaBPs. To identify the Ca²⁺-binding sites of CaBPs, this study presented a computational approach which combined the fragment homology modeling with molecular dynamics simulation. For validation, we performed a two-step strategy as follows: first, the approach is used to identify the Ca²⁺-binding sites of CaBPs, which have the EF-hand Ca²⁺-binding site and the detailed binding mechanism. To accomplish this, eighteen crystal structures of CaBPs with 49 Ca²⁺-binding sites are selected to be analyzed including calmodulin. The computational method identified 43 from 49 Ca²⁺-binding sites. Second, we performed the approach to large-conductance Ca²⁺-activated K⁺ (BK) channels which don't have clear Ca²⁺-binding mechanism. The simulated results are consistent with the experimental data. The computational approach may shed some light on the identification of Ca²⁺-binding sites in CaBPs.

Trichostatin A modulates thiazolidinedione-mediated suppression of tumor necrosis factor α-induced lipolysis in 3T3-L1 adipocytes

In obesity, high levels of tumor necrosis factor α (TNFα) stimulate lipolysis in adipocytes, leading to hyperlipidemia and insulin resistance. Thiazolidinediones (TZDs), the insulin-sensitizing drugs, antagonize TNFα-induced lipolysis in adipocytes, thereby increasing insulin sensitivity in diabetes patients. The cellular target of TZDs is peroxisome proliferator-activated receptor γ (PPARγ), a nuclear receptor that controls many adipocyte functions. As a transcription factor, PPARγ is closely modulated by coregulators, which include coactivators and corepressors. Previous studies have revealed that in macrophages, the insulin-sensitizing effect of PPARγ may involve suppression of proinflammatory gene expression by recruiting the corepressor complex that contains corepressors and histone deacetylases (HDACs). Therefore, we investigated whether the corepressor complex is involved in TZD-mediated suppression of TNFα-induced lipolysis in 3T3-L1 adipocytes. Trichostatin A (TSA), a pan HDAC inhibitor (HDACI) that inhibits class I and II HDACs, was used to examine the involvement of HDACs in the actions of TZDs. TSA alone increased basal lipolysis and attenuated TZD-mediated suppression of TNFα-induced lipolysis. Increased basal lipolysis may in part result from class I HDAC inhibition because selective class I HDACI treatment had similar results. However, attenuation of TZD-mediated TNFα antagonism may be specific to TSA and related hydroxamate-based HDACI rather than to HDAC inhibition. Consistently, corepressor depletion did not affect TZD-mediated suppression. Interestingly, TSA treatment greatly reduced PPARγ levels in differentiated adipocytes. Finally, extracellular signal-related kinase 1/2 (ERK1/2) mediated TNFα-induced lipolysis, and TZDs suppressed TNFα-induced ERK phosphorylation. We determined that TSA increased basal ERK phosphorylation, and attenuated TZD-mediated suppression of TNFα-induced ERK phosphorylation, consistent with TSA's effects on lipolysis. These studies suggest that TSA, through down-regulating PPARγ, attenuates TZD-mediated suppression of TNFα-induced ERK phosphorylation and lipolysis in adipocytes.

The biophysical and molecular basis of intracellular pH sensing by Na+/H+ exchanger-3

Epithelial Na(+)/H(+) exchanger-3 (NHE3) transport is fundamental for renal and intestinal sodium reabsorption. Cytoplasmic protons are thought to serve as allosteric modifiers of the exchanger and to trigger its transport through protein conformational change. This effect presupposes an intracellular pH (pHi) dependence of NHE3 activity, although the biophysical and molecular basis of NHE3 pHi sensitivity have not been defined. NHE3, when complexed with the calcineurin homologous protein-1 (CHP1), had a shift in pHi sensitivity (0.4 units) toward the acidic side in comparison with NHE3 alone, as measured by oscillating pH electrodes combined with whole-cell patch clamping. Indeed, CHP1 interaction with NHE3 inhibited NHE3 transport in a pHi -dependent manner. CHP1 binding to NHE3 also affected its acute regulation. Intracellular perfusion of peptide from the CHP1 binding region (or pHi modification to reduce the CHP1 amount bound to NHE3) was permissive and cooperative for dopamine inhibition of NHE3 but reversed that of adenosine. Thus, CHP1 interaction with NHE3 apparently establishes the exchanger set point for pHi, and modification in this set point is effective in the hormonal stimuli-mediated regulation of NHE3. CHP1 may serve as a regulatory cofactor for NHE3 conformational change, dependent on intracellular protonation.

Nutritional strategies to counteract muscle atrophy caused by disuse and to improve recovery

Periods of immobilisation are often associated with pathologies and/or ageing. These periods of muscle disuse induce muscle atrophy which could worsen the pathology or elderly frailty. If muscle mass loss has positive effects in the short term, a sustained/uncontrolled muscle mass loss is deleterious for health. Muscle mass recovery following immobilisation-induced atrophy could be critical, particularly when it is uncompleted as observed during ageing. Exercise, the best way to recover muscle mass, is not always applicable. So, other approaches such as nutritional strategies are needed to limit muscle wasting and to improve muscle mass recovery in such situations. The present review discusses mechanisms involved in muscle atrophy following disuse and during recovery and emphasises the effect of age in these mechanisms. In addition, the efficiency of nutritional strategies proposed to limit muscle mass loss during disuse and to improve protein gain during recovery (leucine supplementation, whey proteins, antioxidants and anti-inflammatory compounds, energy intake) is also discussed.

The efference cascade, consciousness, and its self: naturalizing the first person pivot of action control

The 20 billion neurons of the neocortex have a mere hundred thousand motor neurons by which to express cortical contents in overt behavior. Implemented through a staggered cortical "efference cascade" originating in the descending axons of layer five pyramidal cells throughout the neocortical expanse, this steep convergence accomplishes final integration for action of cortical information through a system of interconnected subcortical way stations. Coherent and effective action control requires the inclusion of a continually updated joint "global best estimate" of current sensory, motivational, and motor circumstances in this process. I have previously proposed that this running best estimate is extracted from cortical probabilistic preliminaries by a subcortical neural "reality model" implementing our conscious sensory phenomenology. As such it must exhibit first person perspectival organization, suggested to derive from formating requirements of the brain's subsystem for gaze control, with the superior colliculus at its base. Gaze movements provide the leading edge of behavior by capturing targets of engagement prior to contact. The rotation-based geometry of directional gaze movements places their implicit origin inside the head, a location recoverable by cortical probabilistic source reconstruction from the rampant primary sensory variance generated by the incessant play of collicularly triggered gaze movements. At the interface between cortex and colliculus lies the dorsal pulvinar. Its unique long-range inhibitory circuitry may precipitate the brain's global best estimate of its momentary circumstances through multiple constraint satisfaction across its afferents from numerous cortical areas and colliculus. As phenomenal content of our sensory awareness, such a global best estimate would exhibit perspectival organization centered on a purely implicit first person origin, inherently incapable of appearing as a phenomenal content of the sensory space it serves.

Epigenetic regulation of vascular smooth muscle cell function in atherosclerosis

Epigenetics involve heritable and acquired changes in gene transcription that occur independently of the DNA sequence. Epigenetic mechanisms constitute a hierarchic upper-level of transcriptional control through complex modifications of chromosomal components and nuclear structures. These modifications include, for example, DNA methylation or post-translational modifications of core histones; they are mediated by various chromatin-modifying enzymes; and ultimately they define the accessibility of a transcriptional complex to its target DNA. Integrating epigenetic mechanisms into the pathophysiologic concept of complex and multifactorial diseases such as atherosclerosis may significantly enhance our understanding of related mechanisms and provide promising therapeutic approaches. Although still in its infancy, intriguing scientific progress has begun to elucidate the role of epigenetic mechanisms in vascular biology, particularly in the control of smooth muscle cell phenotypes. In this review, we will summarize epigenetic pathways in smooth muscle cells, focusing on mechanisms involved in the regulation of vascular remodeling.

Evaluation of in vitro antioxidant capacity and reducing potential of polyherbal drug- Bhāraṅgyādi

Background:

Present work was designed to investigate antioxidant activity of polyherbal formulation in search for new, safe and inexpensive antioxidant. Clerodendrum serratum, Hedychium spicatum and Inula racemosa, were extensively used in ayurvedic medicine and were investigated together in the form of polyherbal compound (Bhāraṅgyādi) for their antioxidant potential.

Materials and Methods:

Hydroalcoholic extract was prepared from the above samples and was tested for total reducing power and in vitro antioxidant activity by ABTS⁺ assay, Superoxide anion scavenging activity assay and lipid per-oxidation assay.

Result:

Reducing power shows dose depended increase in concentration maximum absorption of 0.677 ± 0.017 at 1000 μg/ml compared with standard Quercetin 0.856±0.020. ABTS⁺ assay shows maximum inhibition of 64.2 ± 0.86 with EC₅₀ 675.31 ± 4.24. Superoxide free radical shows maximum scavenging activity of 62.45 ± 1.86 with EC₅₀ 774.70 ± 5.45. Anti-lipidperoxidation free radicals scavenge maximum absorption of 67.25± 1.89 with EC₅₀ is 700.08 ± 6.81. Ascorbic acid was used as standard with IC₅₀ value is 4.6 μg/ml. The result suggests polyherbal formulation to be a good potential for antioxidant activity. Oxidative stress results from imbalance between free radical-generation and radical scavenging systems. This will lead to tissue damage and oxidative stress.

Conclusion:

In conclusion, we strongly suggest that Polyherbal compounds are source of potential antioxidant for radical scavenging. The highly positive correlation of antiradical scavenging activity and total polyphenolic content in Polyherbal compounds indicates that polyphenols are important components which could be used for the free radical scavenging activity. Further study is needed for isolation and characterization of the active moiety responsible for biological activity and to treat in various stress condition.

Potentiometric-scanning ion conductance microscopy for measurement at tight junctions

Scanning Ion Conductance Microscopy (SICM) has been developed originally for high-resolution imaging of topographic features. Recently, we have described a hybrid voltage scanning mode of SICM, termed Potentiometric-SICM (P-SICM) for recording transmembrane ionic conductance at specific nanostructures of synthetic and biological interfaces. With this technique, paracellular conductance through tight junctions – a subcellular structure that has been difficult to interrogate previously – has been realized. P-SICM utilizes a dual-barrel pipet to differentiate paracellular from transcellular transport processes with nanoscale spatial resolution. The unique combination of voltage scanning and topographic imaging enables P-SICM to capture paracellular conductance within a nominal radius of several hundred nanometers. This review summarizes recent advances in paracellular conductance recording with an emphasis on the P-SICM based approach, which is applied to detect claudin-2 mediated permeability changes at the tight junction.

Bile duct epithelial tight junctions and barrier function

Bile ducts play a crucial role in the formation and secretion of bile as well as excretion of circulating xenobiotic substances. In addition to its secretory and excretory functions, bile duct epithelium plays an important role in the formation of a barrier to the diffusion of toxic substances from bile into the hepatic interstitial tissue. Disruption of barrier function and toxic injury to liver cells appear to be involved in the pathogenesis of a variety of liver diseases such as primary sclerosing cholangitis, primary biliary cirrhosis and cholangiocarcinoma. Although the investigations into understanding the structure and regulation of tight junctions in gut, renal and endothelial tissues have expanded rapidly, very little is known about the structure and regulation of tight junctions in the bile duct epithelium. In this article we summarize the current understanding of physiology and pathophysiology of bile duct epithelium, the structure and regulation of tight junctions in canaliculi and bile duct epithelia and different mechanisms involved in the regulation of disruption and protection of bile duct epithelial tight junctions. This article will make a case for the need of future investigations toward our understanding of molecular organization and regulation of canalicular and bile duct epithelial tight junctions.

Taste of sugar at the membrane: thermodynamics and kinetics of the interaction of a disaccharide with lipid bilayers

Sugar recognition at the membrane is critical in various physiological processes. Many aspects of sugar-membrane interaction are still unknown. We take an integrated approach by combining conventional molecular-dynamics simulations with enhanced sampling methods and analytical models to understand the thermodynamics and kinetics of a di-mannose molecule in a phospholipid bilayer system. We observe that di-mannose has a slight preference to localize at the water-phospholipid interface. Using umbrella sampling, we show the free energy bias for this preferred location to be just -0.42 kcal/mol, which explains the coexistence of attraction and exclusion mechanisms of sugar-membrane interaction. Accurate estimation of absolute entropy change of water molecules with a two-phase model indicates that the small energy bias is the result of a favorable entropy change of water molecules. Then, we incorporate results from molecular-dynamics simulation in two different ways to an analytical diffusion-reaction model to obtain association and dissociation constants for di-mannose interaction with membrane. Finally, we verify our approach by predicting concentration dependence of di-mannose recognition at the membrane that is consistent with experiment. In conclusion, we provide a combined approach for the thermodynamics and kinetics of a weak ligand-binding system, which has broad implications across many different fields.

Trichostatin A modulates thiazolidinedione-mediated suppression of tumor necrosis factor α-induced lipolysis in 3T3-L1 adipocytes

In obesity, high levels of tumor necrosis factor α (TNFα) stimulate lipolysis in adipocytes, leading to hyperlipidemia and insulin resistance. Thiazolidinediones (TZDs), the insulin-sensitizing drugs, antagonize TNFα-induced lipolysis in adipocytes, thereby increasing insulin sensitivity in diabetes patients. The cellular target of TZDs is peroxisome proliferator-activated receptor γ (PPARγ), a nuclear receptor that controls many adipocyte functions. As a transcription factor, PPARγ is closely modulated by coregulators, which include coactivators and corepressors. Previous studies have revealed that in macrophages, the insulin-sensitizing effect of PPARγ may involve suppression of proinflammatory gene expression by recruiting the corepressor complex that contains corepressors and histone deacetylases (HDACs). Therefore, we investigated whether the corepressor complex is involved in TZD-mediated suppression of TNFα-induced lipolysis in 3T3-L1 adipocytes. Trichostatin A (TSA), a pan HDAC inhibitor (HDACI) that inhibits class I and II HDACs, was used to examine the involvement of HDACs in the actions of TZDs. TSA alone increased basal lipolysis and attenuated TZD-mediated suppression of TNFα-induced lipolysis. Increased basal lipolysis may in part result from class I HDAC inhibition because selective class I HDACI treatment had similar results. However, attenuation of TZD-mediated TNFα antagonism may be specific to TSA and related hydroxamate-based HDACI rather than to HDAC inhibition. Consistently, corepressor depletion did not affect TZD-mediated suppression. Interestingly, TSA treatment greatly reduced PPARγ levels in differentiated adipocytes. Finally, extracellular signal-related kinase 1/2 (ERK1/2) mediated TNFα-induced lipolysis, and TZDs suppressed TNFα-induced ERK phosphorylation. We determined that TSA increased basal ERK phosphorylation, and attenuated TZD-mediated suppression of TNFα-induced ERK phosphorylation, consistent with TSA's effects on lipolysis. These studies suggest that TSA, through down-regulating PPARγ, attenuates TZD-mediated suppression of TNFα-induced ERK phosphorylation and lipolysis in adipocytes.

Vasoactive intestinal peptide regulates sinonasal mucociliary clearance and synergizes with histamine in stimulating sinonasal fluid secretion

Mucociliary clearance (MCC) is the primary physical airway defense against inhaled pathogens and particulates. MCC depends on both proper fluid/mucus homeostasis and epithelial ciliary beating. Vasoactive intestinal peptide (VIP) is a neurotransmitter expressed in the sinonasal epithelium that is up-regulated in allergy. However, the effects of VIP on human sinonasal physiology are unknown, as are VIP's interactions with histamine, a major regulator of allergic disease. We imaged ciliary beat frequency, mucociliary transport, apical Cl(-) permeability, and airway surface liquid (ASL) height in primary human sinonasal air-liquid-interface cultures to investigate the effects of VIP and histamine. VIP stimulated an increase in ciliary beat frequency (EC50 0.5 μM; maximal increase ∼40% compared with control) and cystic fibrosis transmembrane conductance regulator (CFTR)-dependent and Na(+)K(+)2Cl(-) cotransporter-dependent fluid secretion, all requiring cAMP/PKA signaling. Histamine activated Ca(2+) signaling that increased ASL height but not ciliary beating. Low concentrations of VIP and histamine had synergistic effects on CFTR-dependent fluid secretion, revealed by increased ASL heights. An up-regulation of VIP in histamine-driven allergic rhinitis would likely enhance mucosal fluid secretion and contribute to allergic rhinorrhea. Conversely, a loss of VIP-activated secretion in patients with CF may impair mucociliary transport, contributing to increased incidences of sinonasal infections and rhinosinusitis.

Two-photon excitation STED microscopy in two colors in acute brain slices

Many cellular structures and organelles are too small to be properly resolved by conventional light microscopy. This is particularly true for dendritic spines and glial processes, which are very small, dynamic, and embedded in dense tissue, making it difficult to image them under realistic experimental conditions. Two-photon microscopy is currently the method of choice for imaging in thick living tissue preparations, both in acute brain slices and in vivo. However, the spatial resolution of a two-photon microscope, which is limited to ~350 nm by the diffraction of light, is not sufficient for resolving many important details of neural morphology, such as the width of spine necks or thin glial processes. Recently developed superresolution approaches, such as stimulated emission depletion microscopy, have set new standards of optical resolution in imaging living tissue. However, the important goal of superresolution imaging with significant subdiffraction resolution has not yet been accomplished in acute brain slices. To overcome this limitation, we have developed a new microscope based on two-photon excitation and pulsed stimulated emission depletion microscopy, which provides unprecedented spatial resolution and excellent experimental access in acute brain slices using a long-working distance objective. The new microscope improves on the spatial resolution of a regular two-photon microscope by a factor of four to six, and it is compatible with time-lapse and simultaneous two-color superresolution imaging in living cells. We demonstrate the potential of this nanoscopy approach for brain slice physiology by imaging the morphology of dendritic spines and microglial cells well below the surface of acute brain slices.

Differential expression of functionality markers in mid-secretory endometrium of infertile women under treatment with ovulation-inducing agents

OBJECTIVES

To analyze the expression of protein markers related to cell proliferation and death, as well as oestrogen and progesterone receptors in the endometrium of infertile women with hypothalamic-pituitary dysfunction treated with clomiphene citrate (CC) or recombinant follicle-stimulating hormone (rFSH), and compare them with ovulatory women.

STUDY DESIGN

The study included 12 control ovulatory women and 29 anovulatory women, 19 of whom underwent ovulation induction with CC (n = 12) or rFSH (n = 5). Endometrial biopsies were obtained by Pipelle during the mid-secretory phase. Samples were stained with haematoxylin and eosin. Immunohistochemistry of proteins related to cell proliferation and cell death, as well as steroid receptors, was undertaken, and apoptosis was determined using TUNEL analysis.

RESULTS

Immunohistochemical analysis of Ki67 expression showed significantly higher expression in the glandular epithelium of ovulatory women compared with the other groups. Glandular oestrogen receptor α expression was significantly lower in rFSH-treated women compared with ovulatory women. The number of apoptotic cells, Bax expression and progesterone receptor expression were similar in all groups. In contrast, Bcl-2 expression was significantly lower in the glandular epithelium of rFSH-treated women.

CONCLUSIONS

In infertile women with hypothalamic-pituitary dysfunction, treatment with ovulation-inducing agents modifies the expression of proteins involved in cell proliferation and death, as well as the expression of steroid hormone receptors in the endometrium. These differences may help to explain, at the molecular level, the functionality of the endometrium during the implantation window, and may help to optimize pregnancy rates obtained with these treatments.

Soluble guanylate cyclase modulates alveolarization in the newborn lung

Nitric oxide (NO) regulates lung development through incompletely understood mechanisms. NO controls pulmonary vascular smooth muscle cell (SMC) differentiation largely through stimulating soluble guanylate cyclase (sGC) to produce cGMP and increase cGMP-mediated signaling. To examine the role of sGC in regulating pulmonary development, we tested whether decreased sGC activity reduces alveolarization in the normal and injured newborn lung. For these studies, mouse pups with gene-targeted sGC-α1 subunit truncation were used because we determined that they have decreased pulmonary sGC enzyme activity. sGC-α1 knockout (KO) mouse pups were observed to have decreased numbers of small airway structures and lung volume compared with wild-type (WT) mice although lung septation and body weights were not different. However, following mild lung injury caused by breathing 70% O2, the sGC-α1 KO mouse pups had pronounced inhibition of alveolarization, as evidenced by an increase in airway mean linear intercept, reduction in terminal airway units, and decrease in lung septation and alveolar openings, as well as reduced somatic growth. Because cGMP regulates SMC phenotype, we also tested whether decreased sGC activity reduces lung myofibroblast differentiation. Cellular markers revealed that vascular SMC differentiation decreased, whereas myofibroblast activation increased in the hyperoxic sGC-α1 KO pup lung. These results indicate that lung development, particularly during hyperoxic injury, is impaired in mouse pups with diminished sGC activity. These studies support the investigation of sGC-targeting agents as therapies directed at improving development in the newborn lung exposed to injury.

Ductal barriers in mammary epithelium

Tissue barriers play an integral role in the biology and pathobiology of mammary ductal epithelium. In normal breast physiology, tight and adherens junctions undergo dynamic changes in permeability in response to hormonal and other stimuli, while several of their proteins are directly involved in mammary tumorigenesis. This review describes first the structure of mammary ductal epithelial barriers and their role in normal mammary development, examining the cyclical changes in response to puberty, pregnancy, lactation and involution. It then examines the role of adherens and tight junctions and the participation of their constituent proteins in mammary tumorigenic functions such as migration, invasion and metastasis. Finally, it discusses the potential of these adhesion proteins as both prognostic biomarkers and potential therapeutic targets in breast cancer.

Cytoskeletal regulation dominates temperature-sensitive proteomic changes of hibernation in forebrain of 13-lined ground squirrels

13-lined ground squirrels, Ictidomys tridecemlineatus, are obligate hibernators that transition annually between summer homeothermy and winter heterothermy – wherein they exploit episodic torpor bouts. Despite cerebral ischemia during torpor and rapid reperfusion during arousal, hibernator brains resist damage and the animals emerge neurologically intact each spring. We hypothesized that protein changes in the brain underlie winter neuroprotection. To identify candidate proteins, we applied a sensitive 2D gel electrophoresis method to quantify protein differences among forebrain extracts prepared from ground squirrels in two summer, four winter and fall transition states. Proteins that differed among groups were identified using LC-MS/MS. Only 84 protein spots varied significantly among the defined states of hibernation. Protein changes in the forebrain proteome fell largely into two reciprocal patterns with a strong body temperature dependence. The importance of body temperature was tested in animals from the fall; these fall animals use torpor sporadically with body temperatures mirroring ambient temperatures between 4 and 21°C as they navigate the transition between summer homeothermy and winter heterothermy. Unlike cold-torpid fall ground squirrels, warm-torpid individuals strongly resembled the homeotherms, indicating that the changes observed in torpid hibernators are defined by body temperature, not torpor per se. Metabolic enzymes were largely unchanged despite varied metabolic activity across annual and torpor-arousal cycles. Instead, the majority of the observed changes were cytoskeletal proteins and their regulators. While cytoskeletal structural proteins tended to differ seasonally, i.e., between summer homeothermy and winter heterothermy, their regulatory proteins were more strongly affected by body temperature. Changes in the abundance of various isoforms of the microtubule assembly and disassembly regulatory proteins dihydropyrimidinase-related protein and stathmin suggested mechanisms for rapid cytoskeletal reorganization on return to euthermy during torpor-arousal cycles.

Impaired amino acid metabolism contributes to fasting-induced hypoglycemia in fatty acid oxidation defects

The importance of mitochondrial fatty acid β-oxidation (FAO) as a glucose-sparing process is illustrated by patients with inherited defects in FAO, who may present with life-threatening fasting-induced hypoketotic hypoglycemia. It is unknown why peripheral glucose demand outpaces hepatic gluconeogenesis in these patients. In this study, we have systematically addressed the fasting response in long-chain acyl-CoA dehydrogenase-deficient (LCAD KO) mice. We demonstrate that the fasting-induced hypoglycemia in LCAD KO mice was initiated by an increased glucose requirement in peripheral tissues, leading to rapid hepatic glycogen depletion. Gluconeogenesis did not compensate for the increased glucose demand, which was not due to insufficient hepatic glucogenic capacity but rather caused by a shortage in the supply of glucogenic precursors. This shortage in supply was explained by a suppressed glucose-alanine cycle, decreased branched-chain amino acid metabolism and ultimately impaired protein mobilization. We conclude that during fasting, FAO not only serves to spare glucose but is also indispensable for amino acid metabolism, which is essential for the maintenance of adequate glucose production.