The mitochondrial calcium uniporter inhibitor Ru265 increases neuronal excitability and reduces neurotransmission via off-target effects.

BACKGROUND AND PURPOSE: Excitotoxicity due to mitochondrial calcium (Ca2+) overloading can trigger neuronal cell death in a variety of pathologies. Inhibiting the mitochondrial calcium uniporter (MCU) has been proposed as a therapeutic avenue to prevent calcium overloading. Ru265 (ClRu(NH3)4(µ-N)Ru(NH3)4Cl]Cl3) is a cell-permeable inhibitor of the mitochondrial calcium uniporter (MCU) with nanomolar affinity. Ru265 reduces sensorimotor deficits and neuronal death in models of ischemic stroke. However, the therapeutic use of Ru265 is limited by the induction of seizure-like behaviours. EXPERIMENTAL APPROACH: We examined the effect of Ru265 on synaptic and neuronal function in acute brain slices and hippocampal neuron cultures derived from mice, in control and where MCU expression was genetically abrogated. KEY RESULTS: Ru265 decreased evoked responses from calyx terminals and induced spontaneous action potential firing of both the terminal and postsynaptic principal cell. Recordings of presynaptic Ca2+ currents suggested that Ru265 blocks the P/Q type channel, confirmed by the inhibition of currents in cells exogenously expressing the P/Q type channel. Measurements of presynaptic K+ currents further revealed that Ru265 blocked a KCNQ current, leading to increased membrane excitability, underlying spontaneous spiking. Ca2+ imaging of hippocampal neurons showed that Ru265 increased synchronized, high-amplitude events, recapitulating seizure-like activity seen in vivo. Importantly, MCU ablation did not suppress Ru265-induced increases in neuronal activity and seizures. CONCLUSIONS AND IMPLICATIONS: Our findings provide a mechanistic explanation for the pro-convulsant effects of Ru265 and suggest counter screening assays based on the measurement of P/Q and KCNQ channel currents to identify safe MCU inhibitors.

Preserving and enhancing mitochondrial function after stroke to protect and repair the neurovascular unit: novel opportunities for nanoparticle-based drug delivery.

The neurovascular unit (NVU) is composed of vascular cells, glia, and neurons that form the basic component of the blood brain barrier. This intricate structure rapidly adjusts cerebral blood flow to match the metabolic needs of brain activity. However, the NVU is exquisitely sensitive to damage and displays limited repair after a stroke. To effectively treat stroke, it is therefore considered crucial to both protect and repair the NVU. Mitochondrial calcium (Ca2+) uptake supports NVU function by buffering Ca2+ and stimulating energy production. However, excessive mitochondrial Ca2+ uptake causes toxic mitochondrial Ca2+ overloading that triggers numerous cell death pathways which destroy the NVU. Mitochondrial damage is one of the earliest pathological events in stroke. Drugs that preserve mitochondrial integrity and function should therefore confer profound NVU protection by blocking the initiation of numerous injury events. We have shown that mitochondrial Ca2+ uptake and efflux in the brain are mediated by the mitochondrial Ca2+ uniporter complex (MCUcx) and sodium/Ca2+/lithium exchanger (NCLX), respectively. Moreover, our recent pharmacological studies have demonstrated that MCUcx inhibition and NCLX activation suppress ischemic and excitotoxic neuronal cell death by blocking mitochondrial Ca2+ overloading. These findings suggest that combining MCUcx inhibition with NCLX activation should markedly protect the NVU. In terms of promoting NVU repair, nuclear hormone receptor activation is a promising approach. Retinoid X receptor (RXR) and thyroid hormone receptor (TR) agonists activate complementary transcriptional programs that stimulate mitochondrial biogenesis, suppress inflammation, and enhance the production of new vascular cells, glia, and neurons. RXR and TR agonism should thus further improve the clinical benefits of MCUcx inhibition and NCLX activation by increasing NVU repair. However, drugs that either inhibit the MCUcx, or stimulate the NCLX, or activate the RXR or TR, suffer from adverse effects caused by undesired actions on healthy tissues. To overcome this problem, we describe the use of nanoparticle drug formulations that preferentially target metabolically compromised and damaged NVUs after an ischemic or hemorrhagic stroke. These nanoparticle-based approaches have the potential to improve clinical safety and efficacy by maximizing drug delivery to diseased NVUs and minimizing drug exposure in healthy brain and peripheral tissues.

Dinuclear nitrido-bridged osmium complexes inhibit the mitochondrial calcium uniporter and protect cortical neurons against lethal oxygen-glucose deprivation.

Dysregulation of mitochondrial calcium uptake mediated by the mitochondrial calcium uniporter (MCU) is implicated in several pathophysiological conditions. Dinuclear ruthenium complexes are effective inhibitors of the MCU and have been leveraged as both tools to study mitochondrial calcium dynamics and potential therapeutic agents. In this study, we report the synthesis and characterization of Os245 ([Os2(µ-N)(NH3)8Cl2]3+) which is the osmium-containing analogue of our previously reported ruthenium-based inhibitor Ru265. This complex and its aqua-capped analogue Os245' ([Os2(µ-N)(NH3)8(OH2)2]5+) are both effective inhibitors of the MCU in permeabilized and intact cells. In comparison to the ruthenium-based inhibitor Ru265 (k obs = 4.92 × 10-3 s-1), the axial ligand exchange kinetics of Os245 are two orders of magnitude slower (k obs = 1.63 × 10-5 s-1) at 37 °C. The MCU-inhibitory properties of Os245 and Os245' are different (Os245 IC50 for MCU inhibition = 103 nM; Os245' IC50 for MCU inhibition = 2.3 nM), indicating that the axial ligands play an important role in their interactions with this channel. We further show that inhibition of the MCU by these complexes protects primary cortical neurons against lethal oxygen-glucose deprivation. When administered in vivo to mice (10 mg kg-1), Os245 and Os245' induce seizure-like behaviors in a manner similar to the ruthenium-based inhibitors. However, the onset of these seizures is delayed, a possible consequence of the slower ligand substitution kinetics for these osmium complexes. These findings support previous studies that demonstrate inhibition of the MCU is a promising therapeutic strategy for the treatment of ischemic stroke, but also highlight the need for improved drug delivery strategies to mitigate the pro-convulsant effects of this class of complexes before they can be implemented as therapeutic agents. Furthermore, the slower ligand substitution kinetics of the osmium analogues may afford new strategies for the development and modification of this class of MCU inhibitors.

Fingolimod attenuates gait deficits in mice subjected to experimental autoimmune encephalomyelitis.

Fingolimod, used to treat relapsing-remitting multiple sclerosis (RRMS), reduces motor deficits in mice with established experimental autoimmune encephalomyelitis (EAE). To better characterize the therapeutic effects of fingolimod, kinematic gait analysis was employed to precisely measure movements of a hindleg while EAE mice walked on a treadmill. Relative to the vehicle group, oral dosing with fingolimod, beginning after disease onset (1 mg/kg/day), increased hip heights and knee joint movements, and reduced spinal cord demyelination. These findings suggest that fingolimod preserves gait in RRMS patients by protecting motor circuits in the spinal cord.

Mechanism of action and therapeutic route for a muscular dystrophy caused by a genetic defect in lipid metabolism.

CHKB encodes one of two mammalian choline kinase enzymes that catalyze the first step in the synthesis of the membrane phospholipid phosphatidylcholine. In humans and mice, inactivation of the CHKB gene (Chkb in mice) causes a recessive rostral-to-caudal muscular dystrophy. Using Chkb knockout mice, we reveal that at no stage of the disease is phosphatidylcholine level significantly altered. We observe that in affected muscle a temporal change in lipid metabolism occurs with an initial inability to utilize fatty acids for energy via mitochondrial ß-oxidation resulting in shunting of fatty acids into triacyglycerol as the disease progresses. There is a decrease in peroxisome proliferator-activated receptors and target gene expression specific to Chkb-/- affected muscle. Treatment of Chkb-/- myocytes with peroxisome proliferator-activated receptor agonists enables fatty acids to be used for ß-oxidation and prevents triacyglyerol accumulation, while simultaneously increasing expression of the compensatory choline kinase alpha (Chka) isoform, preventing muscle cell injury.

Altered circadian activity and sleep/wake rhythms in the stable tubule only polypeptide (STOP) null mouse model of schizophrenia.

Sleep and circadian rhythm disruptions commonly occur in individuals with schizophrenia. Stable tubule only polypeptide (STOP) knockout (KO) mice show behavioral impairments resembling symptoms of schizophrenia. We previously reported that STOP KO mice slept less and had more fragmented sleep and waking than wild-type littermates under a light/dark (LD) cycle. Here, we assessed the circadian phenotype of male STOP KO mice by examining wheel-running activity rhythms and EEG/EMG-defined sleep/wake states under both LD and constant darkness (DD) conditions. Wheel-running activity rhythms in KO and wild-type mice were similarly entrained in LD, and had similar free-running periods in DD. The phase delay shift in response to a light pulse given early in the active phase under DD was preserved in KO mice. KO mice had markedly lower activity levels, lower amplitude activity rhythms, less stable activity onsets, and more fragmented activity than wild-type mice in both lighting conditions. KO mice also spent more time awake and less time in rapid eye movement sleep (REMS) and non-REMS (NREMS) in both LD and DD conditions, with the decrease in NREMS concentrated in the active phase. KO mice also showed altered EEG features and higher amplitude rhythms in wake and NREMS (but not REMS) amounts in both lighting conditions, with a longer free-running period in DD, compared to wild-type mice. These results indicate that the STOP null mutation in mice altered the regulation of sleep/wake physiology and activity rhythm expression, but did not grossly disrupt circadian mechanisms.

Neuronal mitochondrial calcium uniporter deficiency exacerbates axonal injury and suppresses remyelination in mice subjected to experimental autoimmune encephalomyelitis.

High-capacity mitochondrial calcium (Ca2+) uptake by the mitochondrial Ca2+ uniporter (MCU) is strategically positioned to support the survival and remyelination of axons in multiple sclerosis (MS) by undocking mitochondria, buffering Ca2+ and elevating adenosine triphosphate (ATP) synthesis at metabolically stressed sites. Respiratory chain deficits in MS are proposed to metabolically compromise axon survival and remyelination by suppressing MCU activity. In support of this hypothesis, clinical scores, mitochondrial dysfunction, myelin loss, axon damage and inflammation were elevated while remyelination was blocked in neuronal MCU deficient (Thy1-MCU Def) mice relative to Thy1 controls subjected to experimental autoimmune encephalomyelitis (EAE). At the first sign of walking deficits, mitochondria in EAE/Thy1 axons showed signs of activation. By contrast, cytoskeletal damage, fragmented mitochondria and large autophagosomes were seen in EAE/Thy1-MCU Def axons. As EAE severity increased, EAE/Thy1 axons were filled with massively swollen mitochondria with damaged cristae while EAE/Thy1-MCU Def axons were riddled with late autophagosomes. ATP concentrations and mitochondrial gene expression were suppressed while calpain activity, autophagy-related gene mRNA levels and autophagosome marker (LC3) co-localization in Thy1-expressing neurons were elevated in the spinal cords of EAE/Thy1-MCU Def compared to EAE/Thy1 mice. These findings suggest that MCU inhibition contributes to axonal damage that drives MS progression.

Homeostatic state of microglia in a rat model of chronic sleep restriction.

Chronic sleep restriction (CSR) negatively impacts brain functions. Whether microglia, the brain's resident immune cells, play any role is unknown. We studied microglia responses to CSR using a rat model featuring slowly rotating wheels (3 h on/1 h off), which was previously shown to induce both homeostatic and adaptive responses in sleep and attention. Adult male rats were sleep restricted for 27 or 99 h. Control rats were housed in locked wheels. After 27 and/or 99 h of CSR, the number of cells immunoreactive for the microglia marker ionized calcium-binding adaptor molecule-1 (Iba1) and the density of Iba1 immunoreactivity were increased in 4/10 brain regions involved in sleep/wake regulation and cognition, including the prelimbic cortex, central amygdala, perifornical lateral hypothalamic area, and dorsal raphe nucleus. CSR neither induced mitosis in microglia (assessed with bromodeoxyuridine) nor impaired blood-brain barrier permeability (assessed with Evans Blue). Microglia appeared ramified in all treatment groups and, when examined quantitatively in the prelimbic cortex, their morphology was not affected by CSR. After 27 h, but not 99 h, of CSR, mRNA levels of the anti-inflammatory cytokine interleukin-10 were increased in the frontal cortex. Pro-inflammatory cytokine mRNA levels (tumor necrosis factor-α, interleukin-1ß, and interleukin-6) were unchanged. Furthermore, cortical microglia were not immunoreactive for several pro- and anti-inflammatory markers tested, but were immunoreactive for the purinergic P2Y12 receptor. These results suggest that microglia respond to CSR while remaining in a physiological state and may contribute to the previously reported homeostatic and adaptive responses to CSR.

The cell-permeable mitochondrial calcium uniporter inhibitor Ru265 preserves cortical neuron respiration after lethal oxygen glucose deprivation and reduces hypoxic/ischemic brain injury.

The mitochondrial calcium (Ca2+) uniporter (MCU) mediates high-capacity mitochondrial Ca2+ uptake implicated in ischemic/reperfusion cell death. We have recently shown that inducible MCU ablation in Thy1-expressing neurons renders mice resistant to sensorimotor deficits and forebrain neuron loss in a model of hypoxic/ischemic (HI) brain injury. These findings encouraged us to compare the neuroprotective effects of Ru360 and the recently identified cell permeable MCU inhibitor Ru265. Unlike Ru360, Ru265 (2-10 µM) reached intracellular concentrations in cultured cortical neurons that preserved cell viability, blocked the protease activity of Ca2+-dependent calpains and maintained mitochondrial respiration and glycolysis after a lethal period of oxygen-glucose deprivation (OGD). Intraperitoneal (i.p.) injection of adult male C57Bl/6 mice with Ru265 (3 mg/kg) also suppressed HI-induced sensorimotor deficits and brain injury. However, higher doses of Ru265 (10 and 30 mg/kg, i.p.) produced dose-dependent increases in the frequency and duration of seizure-like behaviours. Ru265 is proposed to promote convulsions by reducing Ca2+ buffering and energy production in highly energetic interneurons that suppress brain seizure activity. These findings support the therapeutic potential of MCU inhibition in the treatment of ischemic stroke but also indicate that such clinical translation will require drug delivery strategies which mitigate the pro-convulsant effects of Ru265.

Experimental autoimmune encephalomyelitis accelerates remyelination after lysophosphatidylcholine-induced demyelination in the corpus callosum.

Experimental autoimmune encephalomyelitis (EAE) and lysophosphatidylcholine (LPC)-induced demyelination were combined to study remyelination in a pro-inflammatory context. Two groups of female C57BL/6 mice were subjected either to EAE (EAE mice) or injected with just complete Freund's adjuvant (CFA) and pertussis toxin (PTX) followed by bilateral LPC and phosphate buffered saline injections in the corpus callosum on day 7 (CFA controls). Relative to CFA controls, EAE accelerated remyelination and increased innate immune cell activation, lymphocyte infiltration and cytokine gene expression in the LPC lesions. However, compared to CFA mice, remyelination was reduced (day 14) suggesting this aggressive immune response also compromised myelin repair in EAE mice.

Synergistic Benefits of Combined Aerobic and Cognitive Training on Fluid Intelligence and the Role of IGF-1 in Chronic Stroke.

BACKGROUND: Paired exercise and cognitive training have the potential to enhance cognition by "priming" the brain and upregulating neurotrophins. METHODS: Two-site randomized controlled trial. Fifty-two patients >6 months poststroke with concerns about cognitive impairment trained 50 to 70 minutes, 3× week for 10 weeks with 12-week follow-up. Participants were randomized to 1 of 2 physical interventions: Aerobic (>60% VO2peak using <10% body weight-supported treadmill) or Activity (range of movement and functional tasks). Exercise was paired with 1 of 2 cognitive interventions (computerized dual working memory training [COG] or control computer games [Games]). The primary outcome for the 4 groups (Aerobic + COG, Aerobic + Games, Activity + COG, and Activity + Games) was fluid intelligence measured using Raven's Progressive Matrices Test administered at baseline, posttraining, and 3-month follow-up. Serum neurotrophins collected at one site (N = 30) included brain-derived neurotrophic factor (BDNF) at rest (BDNFresting) and after a graded exercise test (BDNFresponse) and insulin-like growth factor-1 at the same timepoints (IGF-1rest, IGF-1response). RESULTS: At follow-up, fluid intelligence scores significantly improved compared to baseline in the Aerobic + COG and Activity + COG groups; however, only the Aerobic + COG group was significantly different (+47.8%) from control (Activity + Games -8.5%). Greater IGF-1response at baseline predicted 40% of the variance in cognitive improvement. There was no effect of the interventions on BDNFresting or BDNFresponse; nor was BDNF predictive of the outcome. CONCLUSIONS: Aerobic exercise combined with cognitive training improved fluid intelligence by almost 50% in patients >6 months poststroke. Participants with more robust improvements in cognition were able to upregulate higher levels of serum IGF-1 suggesting that this neurotrophin may be involved in behaviorally induced plasticity.

Pioglitazone is superior to quetiapine, clozapine and tamoxifen at alleviating experimental autoimmune encephalomyelitis in mice.

Recent evidence suggests that clozapine and quetiapine (atypical antipsychotics), tamoxifen (selective-estrogen receptor modulator) and pioglitazone (PPARγ agonist) may improve functional recovery in multiple sclerosis (MS). We have compared the effectiveness of oral administration of these drugs, beginning at peak disease, at reducing ascending paralysis, motor deficits and demyelination in mice subjected to experimental autoimmune encephalomyelitis (EAE). Mice were immunized with an immunogenic peptide corresponding to amino acids 35-55 of the myelin oligodendrocyte glycoprotein (MOG35-55) in complete Freund's adjuvant and injected with pertussis toxin to induce EAE. Unlike clozapine, quetiapine and tamoxifen, administration of pioglitazone beginning at peak disease decreased both clinical scores and lumbar white matter loss in EAE mice. Using kinematic gait analysis, we found that pioglitazone also maintained normal movement of the hip, knee and ankle joints for at least 44 days after MOG35-55 immunization. This long-lasting preservation of hindleg joint movements was accompanied by reduced white matter loss, microglial and macrophage activation and the expression of pro-inflammatory genes in the lumbar spinal cords of EAE mice. These results support clinical findings that suggest pioglitazone may reduce the progressive loss of motor function in MS by decreasing inflammation and myelin damage.

Tamoxifen-induced knockdown of the mitochondrial calcium uniporter in Thy1-expressing neurons protects mice from hypoxic/ischemic brain injury.

The mitochondrial calcium uniporter (MCU) mediates high-capacity mitochondrial calcium uptake that stimulates energy production. However, excessive MCU activity can cause ischemic heart injury. To examine if the MCU is also involved in hypoxic/ischemic (HI) brain injury, we have generated conditional MCU knockout mice by tamoxifen (TMX) administration to adult MCU-floxed (MCUfl/fl) mice expressing a construct encoding Thy1-cre/ERT2-eYFP. Relative to TMX/Thy1-cre/ERT2-eYFP controls, HI-induced sensorimotor deficits, forebrain neuron loss and mitochondrial damage were decreased for conditional MCU knockout mice. MCU knockdown by siRNA-induced silencing in cortical neuron cultures also reduced cell death and mitochondrial respiratory deficits following oxygen-glucose deprivation. Furthermore, MCU silencing did not produce metabolic abnormalities in cortical neurons observed previously for global MCU nulls that increased reliance on glycolysis for energy production. Based on these findings, we propose that brain-penetrant MCU inhibitors have strong potential to be well-tolerated and highly-efficacious neuroprotectants for the acute management of ischemic stroke.

Sagittal Plane Kinematic Gait Analysis in C57BL/6 Mice Subjected to MOG35-55 Induced Experimental Autoimmune Encephalomyelitis.

Kinematic gait analysis in the sagittal plane has frequently been used to characterize motor deficits in multiple sclerosis (MS). We describe the application of these techniques to identify gait deficits in a mouse model of MS, known as experimental autoimmune encephalomyelitis (EAE). Paralysis and motor deficits in mice subjected to EAE are typically assessed using a clinical scoring scale. However, this scale yields only ordinal data that provides little information about the precise nature of the motor deficits. EAE disease severity has also been assessed by rotarod performance, which provides a measure of general motor coordination. By contrast, kinematic gait analysis of the hind limb in the sagittal plane generates highly precise information about how movement is impaired. To perform this procedure, reflective markers are placed on a hind limb to detect joint movement while a mouse is walking on a treadmill. Motion analysis software is used to measure movement of the markers during walking. Kinematic gait parameters are then derived from the resultant data. We show how these gait parameters can be used to quantify impaired movements of the hip, knee, and ankle joints in EAE. These techniques may be used to better understand disease mechanisms and identify potential treatments for MS and other neurodegenerative disorders that impair mobility.

Global ablation of the mitochondrial calcium uniporter increases glycolysis in cortical neurons subjected to energetic stressors.

The effects of global mitochondrial calcium (Ca2+) uniporter (MCU) deficiency on hypoxic-ischemic (HI) brain injury, neuronal Ca2+ handling, bioenergetics and hypoxic preconditioning (HPC) were examined. Forebrain mitochondria isolated from global MCU nulls displayed markedly reduced Ca2+ uptake and Ca2+-induced opening of the membrane permeability transition pore. Despite evidence that these effects should be neuroprotective, global MCU nulls and wild-type (WT) mice suffered comparable HI brain damage. Energetic stress enhanced glycolysis and depressed Complex I activity in global MCU null, relative to WT, cortical neurons. HI reduced forebrain NADH levels more in global MCU nulls than WT mice suggesting that increased glycolytic consumption of NADH suppressed Complex I activity. Compared to WT neurons, pyruvate dehydrogenase (PDH) was hyper-phosphorylated in MCU nulls at several sites that lower the supply of substrates for the tricarboxylic acid cycle. Elevation of cytosolic Ca2+ with glutamate or ionomycin decreased PDH phosphorylation in MCU null neurons suggesting the use of alternative mitochondrial Ca2+ transport. Under basal conditions, global MCU nulls showed similar increases of Ca2+ handling genes in the hippocampus as WT mice subjected to HPC. We propose that long-term adaptations, common to HPC, in global MCU nulls compromise resistance to HI brain injury and disrupt HPC.

Kinematic gait parameters are highly sensitive measures of motor deficits and spinal cord injury in mice subjected to experimental autoimmune encephalomyelitis.

The preclinical selection of therapeutic candidates for progressive multiple sclerosis (MS) would be aided by the development of sensitive behavioural measures that accurately reflect the impact of autoimmune-mediated spinal cord damage on locomotion. Neurological deficits in mice subjected to experimental autoimmune encephalomyelitis (EAE) are typically scored using a clinical scale with 5-10 levels of increased disease severity. This ordinal scale represents a general impression of paralysis and impaired gait. By contrast, kinematic gait analyses generate ratio level data that have frequently been used to characterize walking deficits for MS patients and test the efficacy of treatments designed to improve them. Despite these advantages, kinematic gait analyses have not been systematically applied to the study of walking deficits for EAE mice. We have therefore used high speed video recordings (250 frames/s) of EAE mice walking on a treadmill to measure 8 kinematic parameters in the sagittal plane: average hip height (1), average toe height during swing (2), and average angle and range of motion for the hip (3-4), knee (5-6) and ankle (7-8). Kinematic measures of hip, knee and ankle movements were found to be early detectors of impaired locomotion for mice with mild EAE (median clinical score=1.0 at day post-immunization 26; DPI 26). These deficits occurred in the absence of reduced rotarod performance with impaired hip and knee movements observed 3days before disease onset as determined by clinical scores. Gait deficits for mild EAE mice were minor and often recovered fully by DPI 30. By contrast, severe EAE mice (median clinical score=2.5 at DPI 26) displayed much larger movement impairments for the knee and ankle that failed to completely recover by DPI 44. Moreover, impaired ankle movement was highly correlated with white matter loss in the spinal cords of EAE mice (r=0.96). Kinematic analyses therefore yield highly sensitive measures of motor deficits that predict spinal cord injury in EAE mice. These behavioural techniques should assist the selection of promising therapeutic candidates for clinical testing in progressive MS.

Mitochondrial Ca2+ uptake pathways.

Calcium (Ca2+) plays diverse roles in all living organisms ranging from bacteria to humans. It is a structural element for bones, an essential mediator of excitation-contraction coupling, and a universal second messenger in the regulation of ion channel, enzyme and gene expression activities. In mitochondria, Ca2+ is crucial for the control of energy production and cellular responses to metabolic stress. Ca2+ uptake by the mitochondria occurs by the uniporter mechanism. The Mitochondrial Ca2+ Uniporter (MCU) protein has recently been identified as a core component responsible for mitochondrial Ca2+ uptake. MCU knockout (MCU KO) studies have identified a number of important roles played by this high capacity uptake pathway. Interestingly, this work has also shown that MCU-mediated Ca2+ uptake is not essential for vital cell functions such as muscle contraction, energy metabolism and neurotransmission. Although mitochondrial Ca2+ uptake was markedly reduced, MCU KO mitochondria still contained low but detectable levels of Ca2+. In view of the fundamental importance of Ca2+ for basic cell signalling, this finding suggests the existence of other currently unrecognized pathways for Ca2+ entry. We review the experimental evidence for the existence of alternative Ca2+ influx mechanisms and propose how these mechanisms may play an integral role in mitochondrial Ca2+ signalling.

Disruptions of Sleep/Wake Patterns in the Stable Tubule Only Polypeptide (STOP) Null Mouse Model of Schizophrenia.

Disruption of sleep/wake cycles is common in patients with schizophrenia and correlates with cognitive and affective abnormalities. Mice deficient in stable tubule only polypeptide (STOP) show cognitive, behavioral, and neurobiological deficits that resemble those seen in patients with schizophrenia, but little is known about their sleep phenotype. We characterized baseline sleep/wake patterns and recovery sleep following sleep deprivation in STOP null mice. Polysomnography was conducted in adult male STOP null and wild-type (WT) mice under a 12:12 hours light:dark cycle before, during, and after 6 hours of sleep deprivation during the light phase. At baseline, STOP null mice spent more time awake and less time in non-rapid eye movement sleep (NREMS) over a 24-hour period, with more frequent transitions between wake and NREMS, compared to WT mice, especially during the dark phase. The distributions of wake, NREMS and REMS across the light and the dark phases differed by genotype, and so did features of the electroencephalogram (EEG). Following sleep deprivation, both genotypes showed homeostatic increases in sleep duration, with no significant genotype differences in the initial compensatory increase in sleep intensity (EEG delta power). These results indicate that STOP null mice sleep less overall, and their sleep and wake periods are more fragmented than those of WT mice. These features in STOP null mice are consistent with the sleep patterns observed in patients with schizophrenia.

Effect of deletion of cIAP2 on intestinal microcirculation in mouse endotoxemia and polybacterial sepsis.

Deletion of the cellular inhibitor of apoptosis protein 2 (cIAP2) is capable of rendering lipopolysaccharide (LPS)-activated macrophages highly susceptible to apoptotic triggers, thereby quickly eliminating the resident macrophage population soon after the initiation of a systemic inflammatory response. The aim of our study was to evaluate the impact of cIAP2 deletion on leukocyte recruitment and capillary perfusion in experimental endotoxemia and polybacterial sepsis using intravital microscopy of the intestinal microcirculation, which is crucial in the pathogenesis of septic multiple organ failure. We studied six groups of animals: wild-type (WT) control mice, cIAP2 knockout mice, endotoxemic WT mice (5 mg/kg LPS), endotoxemic cIAP2 knockouts (5 or 50 mg/kg LPS, respectively), and WT as well as knockout mice with polybacterial sepsis (colon ascendens stent peritonitis [CASP]). Intravital microscopy of the intestinal microcirculation was performed after 1 h of endotoxemia or 12 h of CASP-induced sepsis, respectively. Intestinal microvascular blood flow was measured using laser Doppler flowmetry. After 1 h of endotoxemia (5 mg/kg LPS), we observed a significant increase of leukocyte adhesion in intestinal submucosal venules of WT mice in comparison with control animals. The cIAP2 knockout mice showed a significant reduction in leukocyte recruitment within the intestinal submucosal microvasculature after 5 or 50 mg/kg LPS challenge, respectively. Lipopolysaccharide-induced decrease in intestinal microvascular blood flow was not affected by cIAP2 inhibition. In CASP-induced sepsis, cIAP2 deletion had no effect on intestinal leukocyte recruitment. Deletion of cIAP2 resulted in reduced microvascular leukocyte recruitment within the intestinal microcirculation in endotoxemia but not in polybacterial sepsis.

The flavonoid-enriched fraction AF4 suppresses neuroinflammation and promotes restorative gene expression in a mouse model of experimental autoimmune encephalomyelitis.

The anti-inflammatory and restorative effects of the flavonoid-enriched fraction AF4 were examined in a mouse model of experimental autoimmune encephalomyelitis (EAE). Relative to EAE mice that received vehicle (water, 10 ml/kg/day), oral administration of AF4 (25mg/kg/day) beginning 24h after the onset of clinical signs reduced disease severity from days 19-31 post-immunization. AF4-mediated recovery from EAE was preceded by reduced plasma concentrations of TNFα and IL-1ß on day 18 followed by decreased cytokine production and neuropathology in the cerebellum and spinal cord on day 31. Clinical improvement for EAE-AF4 mice from days 18 to 31 was accompanied by the elevated expression of genes that mediate remyelination. These findings suggest that AF4 decreased EAE severity by promoting the resolution of inflammation and improving functional recovery in the CNS.