Deactivated State Research Articles

Efficient Electronic Structure to Stabilize N2‐Bridged Dinuclear Complexes Intended for N2 Activation: Iminophosphorane Iron(I) and Cobalt(I)

We examined the stability of the N2‐ligated mononuclear and N2‐bridged dinuclear complexes for FeI and CoI with the tridentate iminophosphorane ligand, which are in potentially deactivated state for catalytic N2 fixation processes, using density functional theory (DFT) method. The calculated Gibbs free energies of the N2 binding and N2‐bridge formation reactions show that the N2‐bridged FeI‐dinuclear complex is more favorable than the N2 FeI‐mononuclear complex in contrast to the CoI‐mononuclear complexes, which is only the available complex, even if at –80 °C. The stability of the N2‐bridged dinuclear metal complexes has a close relation to the M–N2 bond strength ruled by occupation of the pairs of dπu orbitals, in which the ungerade couples of the dπ orbitals interact with the occupied π orbitals of N2 in antibonding manner. For the catalytic activity of FeI mononuclear complexes, the appropriate order of orbitals to occupy the dπu orbitals is necessary, which is produced by the T‐shaped coordination geometry the ancillary ligands construct.

Peritoneal macrophages have an impaired immune response in obesity which can be reversed by subsequent weight loss

IntroductionObesity is recognized as a risk factor for various microbial infections. The immune system, which is affected by obesity, plays an important role in the pathophysiology of these infections and...

How activation leads to gating

Ion Channels Voltage-gated sodium (Nav) channels are key players in electrical signaling. Central to their function is fast inactivation, and mutants that impede this cause conditions such as epilepsy and pain syndromes. The channels have four voltage-sensing domains (VSDs), with VSD4 playing an important role in fast inactivation. Clairfeuille et al. determined the structures of a chimera in which VSD4 of the cockroach channel NavPaS is replaced with VSD4 from human Nav1.7, both in the apo state and bound to a scorpion toxin that impedes fast activation (see the Perspective by Chowdhury and Chanda). The toxin traps VSD4 in a deactivated state. Comparison with the apo structure shows how interactions between VSD4 and the carboxyl-terminal region change as VSD4 activates and suggests how this would lead to fast inactivation. Science , this issue p. [eaav8573][1]; see also p. [1278][2] [1]: /lookup/doi/10.1126/science.aav8573 [2]: /lookup/doi/10.1126/science.aaw8645

Structural basis of α-scorpion toxin action on Nav channels.

Fast inactivation of voltage-gated sodium (Nav) channels is essential for electrical signaling, but its mechanism remains poorly understood. Here we determined the structures of a eukaryotic Nav channel alone and in complex with a lethal α-scorpion toxin, AaH2, by electron microscopy, both at 3.5-angstrom resolution. AaH2 wedges into voltage-sensing domain IV (VSD4) to impede fast activation by trapping a deactivated state in which gating charge interactions bridge to the acidic intracellular carboxyl-terminal domain. In the absence of AaH2, the S4 helix of VSD4 undergoes a ~13-angstrom translation to unlatch the intracellular fast-inactivation gating machinery. Highlighting the polypharmacology of α-scorpion toxins, AaH2 also targets an unanticipated receptor site on VSD1 and a pore glycan adjacent to VSD4. Overall, this work provides key insights into fast inactivation, electromechanical coupling, and pathogenic mutations in Nav channels.

Utilizing Neutral Affective States in Research: Theory, Assessment, and Recommendations

Even though researchers regularly use neutral affect induction procedures (AIPs) as a control condition in their work, there is little consensus on what is neutral affect. This article reviews five approaches that researchers have used to operationalize neutral AIPs: to produce a(n) (a) minimal affective state, (b) in-the-middle state, (c) deactivated state, (d) typical state, or (e) indifferent state. For each view, the article delineates the theoretical basis for the neutral AIP, how to assess it, and provides recommendations for when and how to use it. The goal of the article is to encourage researchers to state their theoretical assumptions about neutral affect, to validate those assumptions, and to make appropriate conclusions based on them.

Hyperoxia enhances slow-wave forebrain states in urethane-anesthetized and naturally sleeping rats.

Oxygen (O2) is a crucial element for physiological functioning in mammals. In particular, brain function is critically dependent on a minimum amount of circulating blood levels of O2 and both immediate and lasting neural dysfunction can result following anoxic or hypoxic episodes. Although the effects of deficiencies in O2 levels on the brain have been reasonably well studied, less is known about the influence of elevated levels of O2 (hyperoxia) in inspired gas under atmospheric pressure. This is of importance due to its typical use in surgical anesthesia, in the treatment of stroke and traumatic brain injury, and even in its recreational or alternative therapeutic use. Using local field potential (EEG) recordings in spontaneously breathing urethane-anesthetized and naturally sleeping rats, we characterized the influence of different levels of O2 in inspired gases on brain states. While rats were under urethane anesthesia, administration of 100% O2 elicited a significant and reversible increase in time spent in the deactivated (i.e., slow-wave) state, with concomitant decreases in both heartbeat and respiration rates. Increasing the concentration of carbon dioxide (to 5%) in inspired gas produced the opposite result on EEG states, mainly a decrease in the time spent in the deactivated state. Consistent with this, decreasing concentrations of O2 (to 15%) in inspired gases decreased time spent in the deactivated state. Further confirmation of the hyperoxic effect was found in naturally sleeping animals where it similarly increased time spent in slow-wave (nonrapid eye movement) states. Thus alterations of O2 in inspired air appear to directly affect forebrain EEG states, which has implications for brain function, as well as for the regulation of brain states and levels of forebrain arousal during sleep in both normal and pathological conditions. NEW & NOTEWORTHY We show that alterations of oxygen concentration in inspired air biases forebrain EEG state. Hyperoxia increases the prevalence of slow-wave states. Hypoxia and hypercapnia appear to do the opposite. This suggests that oxidative metabolism is an important stimulant for brain state.

Gas-solid catalytic dehydrogenation of propane and butanes to olefins

Catalytic dehydrogenation is an effective route to convert light alkanes to monoolefins with the same carbon number and H2. In this paper the research progress in the reaction mechanism, catalyst and reactor for propane/butane dehydrogenation in recent years has been introduced. Catalytic dehydrogenation of alkanes is a strong endothermic reaction and its conversion for single pass is limited by the thermodynamic equilibrium. Both the reaction and the product separation consume a large amount of energy. Improving the conversion of alkanes for single pass by optimizing the operating conditions, on the basis of guaranteeing the high selectivity to olefins and the long-term safety and stability of the unit operation, is the key to reduce energy consumption for the whole process. During the dehydrogenation of alkanes, two H atoms bonded with two adjacent C atoms adsorb on the same active site, and the active site draws the two H atoms closer to attract each other, leading to the scission of C–H bonds to form H2 and olefins. The olefins enter to the gas phase directly without adsorption. The widely used supported Pt and CrO x catalysts have been introduced systematically, including the preparation methods, existing state of active components, carriers, additives, deactivation and regeneration, as well as problems encountered in application. At the same time, the newly reported catalysts, such as supported metal catalysts (Ni, NiSn and Sn), metal oxide catalysts (Ga2O3/ZnO and ZnO/Nb2O5), other mixed metal oxides and/or composite metal oxides catalysts, as well as metal sulfide catalysts have also been discussed briefly. Furthermore, the performances of packed-bed, moving-bed and circulating fluidized-bed reactors have been analyzed comparatively. The circulating fluidized-bed reactor is optimal due to its continuous reaction and catalyst regeneration and the efficient heat supplying for the endothermic dehydrogenation by high-temperature regenerated catalyst. The ADHO process, based on environment-friendly metal oxide catalyst coupled with cocurrent circulating fluidized-bed reactor, offers a novel high-efficiency and low-consumption dehydrogenation technology for the chemical industry.

Structure of the Deactive State of Mammalian Respiratory Complex I

SummaryComplex I (NADH:ubiquinone oxidoreductase) is central to energy metabolism in mammalian mitochondria. It couples NADH oxidation by ubiquinone to proton transport across the energy-conserving inner membrane, catalyzing respiration and driving ATP synthesis. In the absence of substrates, active complex I gradually enters a pronounced resting or deactive state. The active-deactive transition occurs during ischemia and is crucial for controlling how respiration recovers upon reperfusion. Here, we set a highly active preparation of Bos taurus complex I into the biochemically defined deactive state, and used single-particle electron cryomicroscopy to determine its structure to 4.1 Å resolution. We show that the deactive state arises when critical structural elements that form the ubiquinone-binding site become disordered, and we propose reactivation is induced when substrate binding to the NADH-reduced enzyme templates their reordering. Our structure both rationalizes biochemical data on the deactive state and offers new insights into its physiological and cellular roles.

Implications of iterative communication for biological system performance

The performance of integrated biological systems can often be described by the behavior of component subunits: the proportion of subunits performing an activity, and the rate of recruitment to the activity, can be relevant to system performance. We develop a model for activation of subunits (receivers) to a task when activation requires repeated signals (iterative communication). The model predicts how system performance will be affected by the parameters of iterative communication. Receiver activation is influenced by the frequency of stimulation, by forgetting about past interactions, and by the number of stimuli needed to activate the receivers. These parameters, along with the probability of activated receivers returning to a de-activated state, modulate the system-wide time course of activation and the steady-state proportion of activated receivers. Parameters can interact to affect system-wide activation, and multiple parameter combinations can yield similar patterns of activation. Group performance is less variable at higher stimulation frequencies and in systems with greater numbers of receivers. Biological constraints on iterative communication, such as time and energy costs, may limit the parameter values that are feasible for a given system. Iterative communication parameters may be subject to natural selection at the system (group) level because they affect system performance.

Propene induced reversible deactivation effects in diesel oxidation catalysts

By applying different transient test protocols in a lab reactor, it is demonstrated that in the presence of C3H6 a Pt/Pd based oxidation catalyst experiences a persistent deactivation that can be attributed to the accumulation of propene partial oxidation products on the catalyst surface. The deactivation can be reversed by treating the catalyst at higher temperature in a hydrocarbon free atmosphere. The three most important scenarios giving rise to the activation/deactivation phenomenon are:(1) Consecutive heat-up/cool-down cycles: If several consecutive heat-up/cool-down cycles are performed with a catalyst pretreated in a propene free oxidative atmosphere, a lower ignition temperature is observed during the first heating ramp than during the following cycles. The effect can be explained by a reversible blocking of active sites by hydrocarbon (HC) intermediates, which are formed during the ignition branch, then entirely are removed after the HC ignition is completed and finally are formed again during the extinction branch, providing a deactivated state of the catalyst for the following ignition. The deactivation can be completely reversed either by a conditioning in an oxidizing HC free gas mixture at temperatures above 110°C or a conditioning in N2 above 140°C. The deactivation effect is more pronounced under conditions that lead to a low light-off temperature and completely disappears at conditions leading to higher light-off temperatures, i.e. high CO concentrations or high space velocities.(2) Light-off tests with varying temperature ramp rate: For faster ramp rates, CO/propene ignition is observed at lower inlet temperatures. This is the opposite behavior than would be expected based on thermal considerations and can be explained by a higher accumulation of HC intermediates during the slower ramp.(3) Transient observation of the deactivation effect: If an initially clean catalyst is operated at a constant temperature in the light-off range, a transient decrease in CO/HC conversion is observed that can be attributed to the gradual build-up of the blocking HC intermediates.A kinetic model is presented which considers not only the standard CO and hydrocarbon oxidation kinetics, but also the formation of site blocking intermediates by partial oxidation of propene and the removal of these blocking intermediates either by total oxidation with O2 or by thermal desorption. The model nearly quantitatively reproduces the experimental results of the different test protocols.

Multiple pathways for permanent deactivation of boron-oxygen defects in p-type silicon

In this work, it is shown that there are at least two separate pathways for the permanent deactivation of boron-oxygen defects – a purely thermal pathway involving the dissociation of defect precursors, and another mechanism based on passivation of the fully-formed defect during an illuminated annealing process (regeneration). Based on investigations on fired and non-fired p-type Czochralski silicon wafers, a thermal reduction in the net concentration of BO defects is confirmed and found to be caused by rapid cooling following a belt-furnace firing process. This thermal deactivation occurs independently of any subsequent permanent deactivation induced by illuminated annealing and is likely related to the dissociation of the defect and subsequent loss of defect precursors to other species. Further, by varying the surface dielectric present on the wafers during a rapid thermal process, it is demonstrated that in the absence of hydrogen in the wafer bulk, applying an illuminated annealing process does not result in any significant permanent deactivation of defects. In contrast, thermal deactivation occurs independently of the presence of hydrogen in the wafer bulk. This demonstrates that permanent deactivation via the thermal pathway and that via the illuminated annealing (regeneration) pathway occur independently of each other and have different underlying mechanisms. The implications of multiple pathways for permanent deactivation are discussed and the well-known three-state model is revisited in light of this information. A fourth state to represent the end point of thermal deactivation (State D) is proposed for more accurate modelling of BO defect kinetics.

A novel tarantula toxin stabilizes the deactivated voltage sensor of bacterial sodium channel.

Voltage-gated sodium channels (NaVs) are activated by transiting the voltage sensor from the deactivated to the activated state. The crystal structures of several bacterial NaVs have captured the voltage sensor module (VSM) in an activated state, but structure of the deactivated voltage sensor remains elusive. In this study, we sought to identify peptide toxins stabilizing the deactivated VSM of bacterial NaVs. We screened fractions from several venoms and characterized a cystine knot toxin called JZTx-27 from the venom of tarantula Chilobrachys jingzhao as a high-affinity antagonist of the prokaryotic NaVs NsVBa (nonselective voltage-gated Bacillus alcalophilus) and NaChBac (bacterial sodium channel from Bacillus halodurans) (IC50 = 112 nM and 30 nM, respectively). JZTx-27 was more efficacious at weaker depolarizing voltages and significantly slowed the activation but accelerated the deactivation of NsVBa, whereas the local anesthetic drug lidocaine was shown to antagonize NsVBa without affecting channel gating. Mutation analysis confirmed that JZTx-27 bound to S3-4 linker of NsVBa, with F98 being the critical residue in determining toxin affinity. All electrophysiological data and in silico analysis suggested that JZTx-27 trapped VSM of NsVBa in one of the deactivated states. In mammalian NaVs, JZTx-27 preferably inhibited the inactivation of NaV1.5 by targeting the fourth transmembrane domain. To our knowledge, this is the first report of peptide antagonist for prokaryotic NaVs. More important, we proposed that JZTx-27 stabilized the NsVBa VSM in the deactivated state and may be used as a probe to determine the structure of the deactivated VSM of NaVs.-Tang, C., Zhou, X., Nguyen, P. T., Zhang, Y., Hu, Z., Zhang, C., Yarov-Yarovoy, V., DeCaen, P. G., Liang, S., Liu, Z. A novel tarantula toxin stabilizes the deactivated voltage sensor of bacterial sodium channel.

Abstract 3776: Mechanistic evaluation of AG311 - an OXPHOS inhibitor - as a potential treatment for breast cancer

Abstract About fifty percent of breast cancer patients receiving a combination of surgery, radiation and systemic therapy will not remain cancer-free. Most solid tumors, including breast tumors, have hypoxic regions that can contribute to chemoresistance, radioresistance, and poor differentiation in tumors resulting in a poor clinical outcome in patients with advanced disease. It has been reported that mitochondrial respiration remains active in these hypoxic microenvironments. Complex I of the mitochondrial electron transport chain (ETC) has been shown to switch to a de-active catalytic state under hypoxic conditions. The purpose of this study was to investigate the potential anticancer action of a novel compound with antimitochondrial activity under hypoxic conditions. AG311 (5-[(4-Methylphenyl)thio]-9H-pyrimido[4,5-b]indole-2,4-diamine) is a small molecular weight compound shown to inhibit complex I activity in vitro and to drastically reduce mitochondrial oxygen consumption rate by 62.9% at 7.5 μM in breast cancer cells (p<0.001). In two triple negative breast cancer mouse models (MDA-MB-435 and 4T1), AG311 significantly reduced tumor volume by 85% and 81%, respectively (p<0.001 for both). In this current study, the effect of the microenvironment on AG311 mitochondrial inhibition was examined. First, it was shown that AG311 inhibited complex I activity not only in vitro, but also in breast cancer cells (54% inhibition, p<0.001) and tumor homogenate (50% inhibition, p = 0.01). AG311 induced greater cytotoxicity in cells (MDA-MB-435) cultured in glucose-depleted media (IC50 15.5 μM vs 20.0 μM, p<0.01), a condition favoring mitochondrial ATP production, as compared to normal glucose concentrations. Further, co-treatment of AG311 with dichloroacetate, a pyruvate dehydrogenase kinase inhibitor and stimulator of oxidative phosphorylation, showed a synergistic effect on cell kill (CI = 0.7 at 20 μM). Importantly, hypoxic conditions (1% O2) significantly sensitized cancer cells to AG311-induced cell death (from 43.3% to 30.1%, p = 0.019). Further, the effect of AG311 on the deactive form of complex I, which is promoted under hypoxic conditions was assessed by measuring NADH oxidation rate. The switch to the de-active state was thermally-induced in mitochondrial homogenates and once in this state, complex I activity was sensitized to AG311 inhibition (from 45.4% to 65.0% inhibition, p = 0.04). Thus, a mitochondrial inhibitor that preferentially inhibits the de-active state of complex I in hypoxic tumor regions could potentially provide a therapeutic benefit. Citation Format: Anja Bastian, Satoshi Matsuzaki, Kenneth M. Humphries, Lora C. Bailey-Downs, Aleem Gangjee, Michael A. Ihnat. Mechanistic evaluation of AG311 - an OXPHOS inhibitor - as a potential treatment for breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3776.

Interaction with slow waves during sleep improves discrimination of physiologic and pathologic high-frequency oscillations (80-500 Hz).

To characterize the interaction between physiologic and pathologic high-frequency oscillations (HFOs) and slow waves during sleep, and to evaluate the practical significance of these interactions by automatically classifying channels as recording from normal or epileptic brain regions. We automatically detected HFOs in intracerebral electroencephalography (EEG) recordings of 45 patients. We characterized the interaction between the HFOs and the amplitude and phase of automatically detected slow waves during sleep. We computed features associated with HFOs, and compared classic features such as rate, amplitude, duration, and frequency to novel features related to the interaction between HFOs and slow waves. To quantify the practical significance of the difference in these features we classified the channels as recording from normal/epileptic regions using logistic regression. We assessed the results in different brain regions to study differences in the HFO characteristics at the lobar level. We found a clear difference in the coupling between the phase of slow waves during sleep and the occurrence of HFOs. In channels recording physiologic activity, the HFOs tend to occur after the peak of the deactivated state of the slow wave, and in channels with epileptic activity, the HFOs occur more often before this peak. This holds for HFOs in the ripple (80-250 Hz) and fast ripple (250-500 Hz) bands, and different regions of the brain. When using this interaction to automatically classify channels as recording from normal/epileptic brain regions, the performance is better than when using other HFO characteristics. We confirmed differences in the HFO characteristics in mesiotemporal structures and in the occipital lobe. We found the association between slow waves and HFOs to be different in normal and epileptic brain regions, emphasizing their different origin. This is also of practical significance, since it improves the separation between channels recording from normal and epileptic brain regions.

Expression and Contributions of the Kir2.1 Inward-Rectifier K+ Channel to Proliferation, Migration and Chemotaxis of Microglia in Unstimulated and Anti-Inflammatory States

When microglia respond to CNS damage, they can range from pro-inflammatory (classical, M1) to anti-inflammatory, alternative (M2) and acquired deactivation states. It is important to determine how microglial functions are affected by these activation states, and to identify molecules that regulate their behavior. Microglial proliferation and migration are crucial during development and following damage in the adult, and both functions are Ca2+-dependent. In many cell types, the membrane potential and driving force for Ca2+ influx are regulated by inward rectifier K+ channels, including Kir2.1, which is prevalent in microglia. However, it is not known whether Kir2.1 expression and contributions are altered in anti-inflammatory states. We tested the hypothesis that Kir2.1 contributes to Ca2+ entry, proliferation and migration of rat microglia. Kir2.1 (KCNJ2) transcript expression, current amplitude, and proliferation were comparable in unstimulated microglia and following alternative activation (IL-4 stimulated) and acquired deactivation (IL-10 stimulated). To examine functional roles of Kir2.1 in microglia, we first determined that ML133 was more effective than the commonly used blocker, Ba2+; i.e., ML133 was potent (IC50=3.5 μM) and voltage independent. Both blockers slightly increased proliferation in unstimulated or IL-4 (but not IL-10)-stimulated microglia. Stimulation with IL-4 or IL-10 increased migration and ATP-induced chemotaxis, and blocking Kir2.1 greatly reduced both but ML133 was more effective. In all three activation states, blocking Kir2.1 with ML133 dramatically reduced Ca2+ influx through Ca2+-release-activated Ca2+ (CRAC) channels. Thus, Kir2.1 channel activity is necessary for microglial Ca2+ signaling and migration under resting and anti-inflammatory states but the channel weakly inhibits proliferation.

Colorimetric Stimuli-Responsive Hydrogel Polymers for the Detection of Nerve Agent Surrogates

The threat of chemical warfare agents (CWAs) necessitates the development of functional materials that not only quickly detect the presence of CWAs but also actively protect against their toxicity. We have synthesized responsive units that exhibit colorimetric responses upon exposure to CWAs and incorporated them into a versatile detection platform based on copolymers prepared by ring-opening metathesis polymerization (ROMP). The theoretical detection limits for CWA simulants in solution for these polymers are as low as 1 ppm. By incorporating hydrogel-promoting units as pendant chains, we are able to obtain polymers that instantly respond to CWA vapors and are easy to regenerate to the deactivated state by simple treatment with ammonium hydroxide vapor. We further demonstrate a collapse of the polymer gels in response to trifluoroacetic acid (TFA), a strong acid that produces a more fully ionized state as a result of its more caustic nature.

Monitoring Ni0 and coke evolution during the deactivation of a Ni/La2O3–αAl2O3 catalyst in ethanol steam reforming in a fluidized bed

This work studies the mechanism of coke deactivation of a Ni/La2O3–αAl2O3 catalyst in ethanol steam reforming conducted in a fluidized bed reactor under conditions of severe deactivation, at 500°C. Deactivation takes place in three consecutive stages with time on stream, corresponding to increasing values of ethanol concentration in the reaction system and decreasing values for CH4 and CO byproducts. The analysis of the nature of coke by means of several techniques in the different deactivation stages shows that high conversion values (low ethanol concentrations in the medium) give way to filamentous coke (with CO and CH4 as precursor), which has little effect on deactivation. For a highly deactivated catalyst, ethanol concentration is high, and a nonfilamentous deactivating coke is formed (mainly due to the evolution of filamentous coke). X-ray diffraction analysis of Ni particles in different deactivation states shows that a fraction of Ni crystallites are dragged by filamentous coke and the fraction of Ni crystallites that remain supported are blocked by nonfilamentous coke. A scheme has been established to explain the evolution of Ni and coke, the interaction between both dynamics, and its effect on catalyst deactivation.

Expression and contributions of the Kir2.1 inward-rectifier K(+) channel to proliferation, migration and chemotaxis of microglia in unstimulated and anti-inflammatory states.

When microglia respond to CNS damage, they can range from pro-inflammatory (classical, M1) to anti-inflammatory, alternative (M2) and acquired deactivation states. It is important to determine how microglial functions are affected by these activation states, and to identify molecules that regulate their behavior. Microglial proliferation and migration are crucial during development and following damage in the adult, and both functions are Ca2+-dependent. In many cell types, the membrane potential and driving force for Ca2+ influx are regulated by inward-rectifier K+ channels, including Kir2.1, which is prevalent in microglia. However, it is not known whether Kir2.1 expression and contributions are altered in anti-inflammatory states. We tested the hypothesis that Kir2.1 contributes to Ca2+ entry, proliferation and migration of rat microglia. Kir2.1 (KCNJ2) transcript expression, current amplitude, and proliferation were comparable in unstimulated microglia and following alternative activation (IL-4 stimulated) and acquired deactivation (IL-10 stimulated). To examine functional roles of Kir2.1 in microglia, we first determined that ML133 was more effective than the commonly used blocker, Ba2+; i.e., ML133 was potent (IC50 = 3.5 μM) and voltage independent. Both blockers slightly increased proliferation in unstimulated or IL-4 (but not IL-10)-stimulated microglia. Stimulation with IL-4 or IL-10 increased migration and ATP-induced chemotaxis, and blocking Kir2.1 greatly reduced both but ML133 was more effective. In all three activation states, blocking Kir2.1 with ML133 dramatically reduced Ca2+ influx through Ca2+-release-activated Ca2+ (CRAC) channels. Thus, Kir2.1 channel activity is necessary for microglial Ca2+ signaling and migration under resting and anti-inflammatory states but the channel weakly inhibits proliferation.

Abstract W P116: Cerebrovascular and Alzheimer’s Pathologies Combined in Mouse Models of Mixed Dementia Alter the Progression of Memory Impairment and Disease

Dementia is most often attributed to Alzheimer’s disease (~70%) or vascular dementia (~17%), yet 20-50% of dementia cases share aspects of both. Better understanding of dementias within this spectrum can improve diagnosis, inform interpretation of clinical data confounded by co-morbidity, and direct therapeutic approaches. We hypothesized that combined pathologies alter the time-course of memory impairment and the expression of primary disease pathology. We compared and combined aspects of cerebrovascular disease (chronic cerebral hypoperfusion) and Alzheimer’s disease (transgene-driven tau or amyloid pathology). We induced chronic cerebral hypoperfusion by wrapping each common carotid artery with a microcoil that remains in situ and reduces cerebral blood flow to approximately 80%; a procedure called bilateral carotid artery stenosis (BCAS). To create conditions of mixed dementia, we performed BCAS in two transgenic models of Alzheimer’s pathology; the rTg4510 which overexpresses mutant human tau, and APP/PS1 that develops ß-amyloid pathology. Transgenic mice and their wildtype littermates received BCAS or sham surgeries near the onset of pathology survived 1 or 6 months, or during advanced pathology and survived 1 month. This generated 12 experimental groups (n of 4-11 each). We evaluated spatial memory impairment, neuroimmune phenotype, white matter integrity, tau pathology and ß-amyloid pathology. The progression of memory impairment and disease pathology is altered in the mixed dementia models, and these changes are relative to the age of onset and duration of hypoperfusion. For example, hypoperfusion has a larger impact on spatial memory impairment in aged APP/PS1 mice. Additionally, BCAS reduced the expression of CD86, an immune marker associated with a de-activated immune state, only in rTg4510 mice. These findings highlight changes in the time-course of cognitive impairment and pathology that might be expected in the substantial clinical population with co-morbid vascular and Alzheimer’s dementias.

Age-associated dysregulation of microglial activation is coupled with enhanced blood-brain barrier permeability and pathology in APP/PS1 mice

Aging adversely affects inflammatory processes in the brain, which has important implications in the context of disease progression. It has been proposed that microglia become dysfunctional with age and may lose their neuroprotective properties leading to chronic neurodegeneration. Here, we sought to characterize inflammatory changes in a mouse model of Alzheimer's disease and to delineate differences between normal aging and those associated with disease pathology. A proinflammatory profile, characterized by the upregulation of markers of classical activation, was evident in APPswe/PS1dE9 mice, associated with increased interferon-γ (IFNγ) concentration and dysregulation of mechanisms designed to limit the proinflammatory response. The data indicate that microglia are not less active with age but alter their phenotype; indeed, changes observed in the deactivation state appear to relate to aging rather than disease pathology. We hypothesize that disruption of the blood-brain barrier, in tandem with an enhanced chemokine profile, permits the infiltration of immune cells serving to reinforce classical activation of microglia through their enhanced responsiveness to IFNγ.