NRSF-GNAO1 Pathway Contributes to the Regulation of Cardiac Ca2+ Homeostasis.

BACKGROUND: During the development of heart failure, a fetal cardiac gene program is reactivated and accelerates pathological cardiac remodeling. We previously reported that a transcriptional repressor, NRSF (neuron restrictive silencer factor), suppresses the fetal cardiac gene program, thereby maintaining cardiac integrity. The underlying molecular mechanisms remain to be determined, however. METHODS: We aim to elucidate molecular mechanisms by which NRSF maintains normal cardiac function. We generated cardiac-specific NRSF knockout mice and analyzed cardiac gene expression profiles in those mice and mice cardiac-specifically expressing a dominant-negative NRSF mutant. RESULTS: We found that cardiac expression of Gαo, an inhibitory G protein encoded in humans by GNAO1, is transcriptionally regulated by NRSF and is increased in the ventricles of several mouse models of heart failure. Genetic knockdown of Gnao1 ameliorated the cardiac dysfunction and prolonged survival rates in these mouse heart failure models. Conversely, cardiac-specific overexpression of GNAO1 in mice was sufficient to induce cardiac dysfunction. Mechanistically, we observed that increasing Gαo expression increased surface sarcolemmal L-type Ca2+ channel activity, activated CaMKII (calcium/calmodulin-dependent kinase-II) signaling, and impaired Ca2+ handling in ventricular myocytes, which led to cardiac dysfunction. CONCLUSIONS: These findings shed light on a novel function of Gαo in the regulation of cardiac Ca2+ homeostasis and systolic function and suggest Gαo may be an effective therapeutic target for the treatment of heart failure.

Cytokine receptor gp130 promotes postnatal proliferation of cardiomyocytes required for the normal functional development of the heart.

Mammalian ventricular cardiomyocytes are premature at birth and exhibit substantial phenotypic changes before weaning. Mouse ventricular myocytes undergo cell division several times after birth; however, the regulatory mechanisms and roles of cardiomyocyte division in postnatal heart development remain unclear. Here, we investigated the physiological role of glycoprotein 130 (gp130), the main subunit of multifunctional receptors for the IL-6 family of cytokines, in postnatal cardiomyocyte proliferation. Pharmacological inhibition of gp130 within the first month after birth induced significant systolic dysfunction of the left ventricle in mice. Consistently, mice with postnatal cardiomyocyte-specific gp130 depletion exhibited impaired left ventricular contractility compared with control mice. In these mice, cardiomyocytes exhibited a moderately decreased size and dramatically inhibited proliferation in the left ventricle but not in the right ventricle. Stereological analysis revealed that this change significantly decreased the number of cardiomyocytes in the left ventricle. Furthermore, IL-6 was mainly responsible for promoting ventricular cardiomyocyte proliferation by activating the JAK/STAT3 pathway. Taken together, the IL-6/gp130/JAK/STAT3 axis plays a crucial role in the physiological postnatal proliferation and hypertrophy of left ventricular cardiomyocytes to ensure normal cardiac functional development.NEW & NOTEWORTHY Although cardiomyocytes undergo proliferation in the early postnatal period, the regulatory mechanisms and physiological importance of this process have not been clarified. We found that the pharmacological and genetic depletion of gp130 in preweaning mice resulted in significant impairment of cardiomyocyte proliferation, thinning of the myocardium, and systolic dysfunction of the left but not right ventricle by perturbing JAK/STAT3 signaling. Thus, the IL-6/gp130/JAK/STAT3 axis is crucial for the postnatal functional development of the left ventricle.

Physical interaction of junctophilin and the CaV1.1 C terminus is crucial for skeletal muscle contraction.

Close physical association of CaV1.1 L-type calcium channels (LTCCs) at the sarcolemmal junctional membrane (JM) with ryanodine receptors (RyRs) of the sarcoplasmic reticulum (SR) is crucial for excitation-contraction coupling (ECC) in skeletal muscle. However, the molecular mechanism underlying the JM targeting of LTCCs is unexplored. Junctophilin 1 (JP1) and JP2 stabilize the JM by bridging the sarcolemmal and SR membranes. Here, we examined the roles of JPs in localization and function of LTCCs. Knockdown of JP1 or JP2 in cultured myotubes inhibited LTCC clustering at the JM and suppressed evoked Ca2+ transients without disrupting JM structure. Coimmunoprecipitation and GST pull-down assays demonstrated that JPs physically interacted with 12-aa residues in the proximal C terminus of the CaV1.1. A JP1 mutant lacking the C terminus including the transmembrane domain (JP1ΔCT) interacted with the sarcolemmal/T-tubule membrane but not the SR membrane. Expression of this mutant in adult mouse muscles in vivo exerted a dominant-negative effect on endogenous JPs, impairing LTCC-RyR coupling at triads without disrupting JM morphology, and substantially reducing Ca2+ transients without affecting SR Ca2+ content. Moreover, the contractile force of the JP1ΔCT-expressed muscle was dramatically reduced compared with the control. Taken together, JPs recruit LTCCs to the JM through physical interaction and ensure robust ECC at triads in skeletal muscle.

Prostanoid EP4 Receptor-Mediated Augmentation of I h Currents in Aß Dorsal Root Ganglion Neurons Underlies Neuropathic Pain.

An injury of the somatosensory system causes neuropathic pain, which is usually refractory to conventional analgesics, thus warranting the development of novel drugs against this kind of pain. The mechanism of neuropathic pain in rats that had undergone left L5 spinal nerve transection was analyzed. Ten days after surgery, these rats acquired neuropathic pain. The patch-clamp technique was used on the isolated bilateral L5 dorsal root ganglion neurons. The current-clamped neurons on the ipsilateral side exhibited significantly higher excitability than those on the contralateral side. However, only neurons with diameters of 40-50 µm on the ipsilateral side exhibited significantly larger voltage sags in response to hyperpolarizing current pulses than those on the contralateral side. Under the voltage clamp, only these neurons on the ipsilateral side showed a significantly larger density of an inward current at < -80 mV [hyperpolarization-activated nonselective cation (I h) current] with a rightward-shifted activation curve than that on the contralateral side. Ivabradine-an I h current inhibitor-inhibited I h currents in these neurons on both sides in a similar concentration-dependent manner, with an IC50 value of ∼3 µM. Moreover, the oral administration of ivabradine significantly alleviated the neuropathic pain on the ipsilateral side. An inhibitor of adenylyl cyclase or an antagonist of prostanoid EP4 receptors (CJ-023423) inhibited ipsilateral, but not contralateral I h, currents in these neurons. Furthermore, the intrathecal administration of CJ-023423 significantly attenuated neuropathic pain on the ipsilateral side. Thus, ivabradine and/or CJ-023423 may be a lead compound for the development of novel therapeutics against neuropathic pain.

Automaticity of pitch class-color synesthesia as revealed by a Stroop-like effect.

Pitch classes (e.g., do, re, and mi) in music evoke color sensations in pitch class-color synesthesia, which is a recently described form of synesthesia in musicians. The synesthetic color sensations were confirmed to be consistent over an extended time interval, fulfilling a widely-accepted criterion for the authenticity of synesthesia. However, it remains unclear whether the color sensations occurred automatically (i.e., without voluntary effort), which is another defining property of synesthesia. We utilized the Stroop paradigm to investigate this issue in 10 pitch class-color synesthetes. Participants were visually presented with pitch class names in font colors that were either congruent or incongruent with the participants' own color sensations. The speed for reporting the font color was slower when it was incongruent with the synesthetic sensation than when it was congruent. The finding verifies the authenticity of pitch class-color synesthesia by demonstrating that the color sensations occur automatically, even when unnecessary.

PDGF-induced migration of synthetic vascular smooth muscle cells through c-Src-activated L-type Ca2+ channels with full-length CaV1.2 C-terminus.

In atherosclerosis, vascular smooth muscle cells (VSMC) migrate from the media toward the intima of the arteries in response to cytokines, such as platelet-derived growth factor (PDGF). However, molecular mechanism underlying the PDGF-induced migration of VSMCs remains unclear. The migration of rat aorta-derived synthetic VSMCs, A7r5, in response to PDGF was potently inhibited by a CaV1.2 channel inhibitor, nifedipine, and a Src family tyrosine kinase (SFK)/Abl inhibitor, bosutinib, in a less-than-additive manner. PDGF significantly increased CaV1.2 channel currents without altering CaV1.2 protein expression levels in A7r5 cells. This reaction was inhibited by C-terminal Src kinase, a selective inhibitor of SFKs. In contractile VSMCs, the C-terminus of CaV1.2 is proteolytically cleaved into proximal and distal C-termini (PCT and DCT, respectively). Clipped DCT is noncovalently reassociated with PCT to autoinhibit the channel activity. Conversely, in synthetic A7r5 cells, full-length CaV1.2 (CaV1.2FL) is expressed much more abundantly than truncated CaV1.2. In a heterologous expression system, c-Src activated CaV1.2 channels composed of CaV1.2FL but not truncated CaV1.2 (CaV1.2Δ1763) or CaV1.2Δ1763 plus clipped DCT. Further, c-Src enhanced the coupling efficiency between the voltage-sensing domain and activation gate of CaV1.2FL channels by phosphorylating Tyr1709 and Tyr1758 in PCT. Compared with CaV1.2Δ1763, c-Src could more efficiently bind to and phosphorylate CaV1.2FL irrespective of the presence or absence of clipped DCT. Therefore, in atherosclerotic lesions, phenotypic switching of VSMCs may facilitate pro-migratory effects of PDGF on VSMCs by suppressing posttranslational CaV1.2 modifications.

Increase in phospholamban content in mouse skeletal muscle after denervation.

It is well-known that denervation of motor nerves induces atrophy and decreases contractile force of the skeletal muscle. However, it is not completely understood how denervation alters calcium handling in the skeletal muscle. We investigated the effect of denervation on the expression and function of proteins involved in calcium handling. Two weeks after denervation of the right sciatic nerve in mice, we observed a significant decrease in mass and cross-sectional area of the ipsilateral tibialis anterior (TA) and flexor digitorum brevis (FDB) muscles. Also, we observed a significant decrease in the specific tetanus contractile force in the ipsilateral TA muscle. Calcium imaging of the ipsilateral FDB showed that the peak twitch and tetanus calcium concentrations were significantly decreased due to a decrease in calcium content of the sarcoplasmic reticulum (SR). Denervation reduced the maximum rate of sarcoplasmic/endoplasmic calcium ATPase (SERCA) activity. Interestingly, the amount of phospholamban (PLN), but not its transcripts, was increased in the ipsilateral vs. contralateral side after denervation, suggesting that denervation impairs constitutive regulation of PLN. Immunohistochemical analysis revealed increased PLN in all major fiber types in TA with IIx fibers showing a threefold higher expression than the contralateral side. These results suggest that the abnormal increase in PLN in the ipsilateral fast-twitch fibers may be involved in decreased SERCA activity, SR calcium content, peak calcium transients, and contractile forces of denervated muscles.

Absolute pitch is not necessary for pitch class-color synesthesia.

Sounds evoke color sensations in sound-color synesthesia. Recently, we showed that pitch classes (do, re, mi, etc.) have rainbow hues and that colors are linked to the names of pitch classes rather than to their sounds in 15 subjects who had "pitch class-color synesthesia." However, all synesthetes in our previous study had high levels of absolute pitch (AP); therefore the effects of AP on the condition remained unclear. The present study investigated 18 additional pitch class-color synesthetes who had no or lower levels of AP, and confirmed the generality of the above findings. Furthermore, behavioral experiments indicated a two-step process underlying color sensations: pitches are first associated with their pitch class names, and then the pitch class names evoke color sensations. Two separable brain functions underlie pitch-to-color conversion in pitch class-color synesthesia: a musical function of pitch class identification, and the synesthetic association between pitch class and color.

Reliable diagnosis of IDH-mutant glioblastoma by 2-hydroxyglutarate detection: a study by 3-T magnetic resonance spectroscopy.

We have previously reported that reliable detection of 2-hydroxyglutarate (2HG) in isocitrate dehydrogenase (IDH)-mutant WHO grade 2 and 3 gliomas is possible utilizing 3.0-T single-voxel magnetic resonance spectroscopy (SVMRS). We set out to determine whether the same method could be applied to detect 2HG in IDH-mutant glioblastoma. Forty-four patients harboring glioblastoma underwent pre-operative MRS evaluation to detect 2HG and other metabolites. Presence of IDH-mutations was determined by IDH1 R132H immunohistochemical analysis and DNA sequencing of surgically obtained tissues. Six out of 44 (13.6%) glioblastomas were IDH-mutant. IDH-mutant glioblastoma exhibited significantly higher accumulation of 2HG (median 3.191 vs. 0.000 mM, p < 0.0001, Mann-Whitney test). A cutoff of 2HG = 0.897 mM achieved high sensitivity (100.0%) and specificity (92.59%) in determining IDH-mutation in glioblastoma. Glioblastoma with high 2HG accumulation did not have significantly longer overall survival than glioblastoma with low 2HG accumulation (p = 0.107, log-rank test). Non-invasive and reliable detection of 2HG in IDH-mutant glioblastoma was possible by 3.0-T SVMRS.

Angiotensin II activates CaV 1.2 Ca2+ channels through ß-arrestin2 and casein kinase 2 in mouse immature cardiomyocytes.

KEY POINTS: Angiotensin II (AngII) is crucial in cardiovascular regulation in perinatal mammalians. Here we show that AngII increases twitch Ca2+ transients of mouse immature but not mature cardiomyocytes by robustly activating CaV 1.2 L-type Ca2+ channels through a novel signalling pathway involving angiotensin type 1 (AT1 ) receptors, ß-arrestin2 and casein kinase 2. A ß-arrestin-biased AT1 receptor agonist, TRV027, was as effective as AngII in activating L-type Ca2+ channels. Our results help understand the molecular mechanism by which AngII regulates the perinatal circulation and also suggest that ß-arrestin-biased AT1 receptor agonists may be valuable therapeutics for paediatric heart failure. ABSTRACT: Angiotensin II (AngII), the main effector peptide of the renin-angiotensin system, plays important roles in cardiovascular regulation in the perinatal period. Despite the well-known stimulatory effect of AngII on vascular contraction, little is known about regulation of contraction of the immature heart by AngII. Here we found that AngII significantly increased the peak amplitude of twitch Ca2+ transients by robustly activating L-type CaV 1.2 Ca2+ (CaV 1.2) channels in mouse immature but not mature cardiomyocytes. This response to AngII was mediated by AT1 receptors and ß-arrestin2. A ß-arrestin-biased AT1 receptor agonist was as effective as AngII in activating CaV 1.2 channels. Src-family tyrosine kinases (SFKs) and casein kinase 2α'ß (CK2α'ß) were sequentially activated when AngII activated CaV 1.2 channels. A cyclin-dependent kinase inhibitor, p27Kip1 (p27), inhibited CK2α'ß, and AngII removed this inhibitory effect through phosphorylating tyrosine 88 of p27 via SFKs in cardiomyocytes. In a human embryonic kidney cell line, tsA201 cells, overexpression of CK2α'ß but not c-Src directly activated recombinant CaV 1.2 channels composed of C-terminally truncated α1C , the distal C-terminus of α1C , ß2C and α2 δ1 subunits, by phosphorylating threonine 1704 located at the interface between the proximal and the distal C-terminus of CaV 1.2α1C subunits. Co-immunoprecipitation revealed that CaV 1.2 channels, CK2α'ß and p27 formed a macromolecular complex. Therefore, stimulation of AT1 receptors by AngII activates CaV 1.2 channels through ß-arrestin2 and CK2α'ß, thereby probably exerting a positive inotropic effect in the immature heart. Our results also indicated that ß-arrestin-biased AT1 receptor agonists may be used as valuable therapeutics for paediatric heart failure in the future.

Abnormal distribution of GABAA receptors in brain of duchenne muscular dystrophy patients.

INTRODUCTION: In this study we sought to: (1) determine the distribution of GABAA receptors (GABAA -Rs) in the brain of Duchenne muscular dystrophy (DMD) patients; and (2) ascertain if the distribution pattern correlates with cognitive dysfunction. METHODS: Fourteen DMD patients [young adult (n = 7, 18-25 years old) and older adult (n = 7, 30-37 years old) groups] and 16 age-matched normal volunteers participated. GABAA -R distribution was assessed using 123 I-IMZ-SPECT. Neuropsychological assessments were performed using 3 different test batteries, the WAIS-III, WMS-R, and Wisconsin Card Sorting Test (WCST). RESULTS: All DMD patients showed significant decline in 123 I-IMZ uptake in the prefrontal cortex (P < 0.05). Although no differences were detected in the WAIS-III and WMS-R, the WCST scores of DMD patients (2.8 ± 1.9) were significantly lower (P < 0.01) than those of normal volunteers (5.4 ± 0.7). Both abnormalities were more pronounced in older adult patients. CONCLUSION: The findings demonstrate that DMD is accompanied by a reduction in the prefrontal cortex distribution of GABAA -Rs. Muscle Nerve 55: 591-595, 2017.

Ammonia exposure affects the mRNA and protein expression levels of certain Rhesus glycoproteins in the gills of climbing perch.

The freshwater climbing perch, Anabas testudineus, is an obligate air-breathing and euryhaline teleost capable of active ammonia excretion and tolerant of high concentrations of environmental ammonia. As Rhesus glycoproteins (RhGP/Rhgp) are known to transport ammonia, this study aimed to obtain the complete cDNA coding sequences of various rhgp isoforms from the gills of A. testudineus, and to determine their mRNA and protein expression levels during 6 days of exposure to 100 mmol l-1 NH4Cl. The subcellular localization of Rhgp isoforms in the branchial epithelium was also examined in order to elucidate the type of ionocyte involved in active ammonia excretion. Four rhgp (rhag, rhbg, rhcg1 and rhcg2) had been identified from the gills of A. testudineus They had conserved amino acid residues for NH4+ binding, NH4+ deprotonation, channel gating and lining of the vestibules. Despite inwardly directed NH3 and NH4+ gradients, there were significant increases in the mRNA expression levels of the four branchial rhgp in A. testudineus at certain time points during 6 days of ammonia exposure, with significant increases in the protein abundances of Rhag and Rhcg2 on day 6. Immunofluorescence microscopy revealed a type of ammonia-inducible Na+/K+-ATPase α1c-immunoreactive ionocyte with apical Rhag and basolateral Rhcg2 in the gills of fish exposed to ammonia for 6 days. Hence, active ammonia excretion may involve NH4+ entering the ionocyte through the basolateral Rhcg2 and being excreted through the apical Rhag, driven by a transapical membrane electrical potential generated by the apical cystic fibrosis transmembrane conductance regulator Cl- channel, as suggested previously.

Maturational decrease of glutamate in the human cerebral cortex from childhood to young adulthood: a 1H-MR spectroscopy study.

BackgroundThe aim of the present study was to investigate maturational changes in glutamate (Glu) in the human cerebral cortex from childhood to young adulthood using 3.0-Tesla proton magnetic resonance spectroscopy (1H-MRS), which is capable of quantifying Glu in vivo.MethodsNormal volunteers comprising 11 children (aged 4-13 years) and 11 young adults (aged 18-33 years) participated in the study. Single-voxel point-resolved spectroscopy (PRESS, repetition time/echo time=2,000/80 ms) was performed on the frontal and occipital cortices, and the Glu-to-creatine ratio (Glu/Cr) and N-acetylaspartate-to-creatine ratio (NAA/Cr) were determined.ResultsIn both the frontal and occipital cortices, Glu/Cr was significantly lower during young adulthood relative to that during childhood. NAA/Cr did not differ significantly between the two age groups.ConclusionThis study has provided objective evidence that cerebral cortical Glu/Cr decreases between childhood and young adulthood. The observed decrease in Glu/Cr may reflect the simultaneous occurrence of maturational changes, such as changes in cortical microstructure and the intercellular compartmentation of Glu metabolism.

Aquaporin-4 Functionality and Virchow-Robin Space Water Dynamics: Physiological Model for Neurovascular Coupling and Glymphatic Flow.

The unique properties of brain capillary endothelium, critical in maintaining the blood-brain barrier (BBB) and restricting water permeability across the BBB, have important consequences on fluid hydrodynamics inside the BBB hereto inadequately recognized. Recent studies indicate that the mechanisms underlying brain water dynamics are distinct from systemic tissue water dynamics. Hydrostatic pressure created by the systolic force of the heart, essential for interstitial circulation and lymphatic flow in systemic circulation, is effectively impeded from propagating into the interstitial fluid inside the BBB by the tightly sealed endothelium of brain capillaries. Instead, fluid dynamics inside the BBB is realized by aquaporin-4 (AQP-4), the water channel that connects astrocyte cytoplasm and extracellular (interstitial) fluid. Brain interstitial fluid dynamics, and therefore AQP-4, are now recognized as essential for two unique functions, namely, neurovascular coupling and glymphatic flow, the brain equivalent of systemic lymphatics.

The Posterior Limb of the Internal Capsule as the Subcortical Transitional Zone of the Anterior and Posterior Circulations: Insights from Human 7T MRI.

BACKGROUND: In patients with cerebral infarction, identifying the distribution of infarction and the relevant artery is essential for ascertaining the underlying vascular pathophysiological mechanisms and preventing subsequent stroke. However, visualization of the basal perforating arteries (BPAs) has had limited success, and simultaneous viewing of background anatomical structures has only rarely been attempted in living human brains. Our study aimed at identifying the BPAs with 7T MRI and evaluating their distribution in the subcortical structures, thereby showing the clinical significance of the technique. METHODS: Twenty healthy subjects and 1 patient with cerebral infarction involving the posterior limb of the internal capsule (ICpost) and thalamus underwent 3-dimensional fast spoiled gradient-echo sequence as time-of-flight magnetic resonance angiography (MRA) at 7T with a submillimeter resolution. The MRA was modified to detect inflow signals from BPAs, while preserving the background anatomical signals. BPA stems and branches in the subcortical structures and their origins were identified on images, using partial maximum intensity projection in 3 dimensions. RESULTS: A branch of the left posterior cerebral artery (PCA) in the patient ran through both the infarcted thalamus and ICpost and was clearly the relevant artery. In 40 intact hemispheres in healthy subjects, 571 stems and 1,421 branches of BPAs were detected in the subcortical structures. No significant differences in the numbers of stems and branches were observed between the intact hemispheres. The numbers deviated even less across subjects. The distribution analysis showed that the subcortical structures of the telencephalon, such as the caudate nucleus, anterior limb of the internal capsule, and lenticular nucleus, were predominantly supplied by BPAs from the anterior circulation. In contrast, the thalamus, belonging to the diencephalon, was mostly fed by BPAs from the posterior circulation. However, compared with other subcortical structures, the ICpost, which marks the anatomical boundary between the telencephalon and the diencephalon, was supplied by BPAs with significantly more diverse origins. These BPAs originated from the internal carotid artery (23.1%), middle cerebral artery (38.5%), PCA (17.3%), and the posterior communicating artery (21.1%). CONCLUSIONS: The modified MRI method allowed the detection of the relevant BPA within the infarcted area in the stroke survivor as well as the BPAs in the subcortical structures of living human brains. Based on in vivo BPA distribution analyses, the ICpost is the transitional zone of the anterior and posterior cerebral circulations.

Multiple therapeutic effects of progranulin on experimental acute ischaemic stroke.

In the central nervous system, progranulin, a glycoprotein growth factor, plays a crucial role in maintaining physiological functions, and progranulin gene mutations cause TAR DNA-binding protein-43-positive frontotemporal lobar degeneration. Although several studies have reported that progranulin plays a protective role against ischaemic brain injury, little is known about temporal changes in the expression level, cellular localization, and glycosylation status of progranulin after acute focal cerebral ischaemia. In addition, the precise mechanisms by which progranulin exerts protective effects on ischaemic brain injury remains unknown. Furthermore, the therapeutic potential of progranulin against acute focal cerebral ischaemia, including combination treatment with tissue plasminogen activator, remains to be elucidated. In the present study, we aimed to determine temporal changes in the expression and localization of progranulin after ischaemia as well as the therapeutic effects of progranulin on ischaemic brain injury using in vitro and in vivo models. First, we demonstrated a dynamic change in progranulin expression in ischaemic Sprague-Dawley rats, including increased levels of progranulin expression in microglia within the ischaemic core, and increased levels of progranulin expression in viable neurons as well as induction of progranulin expression in endothelial cells within the ischaemic penumbra. We also demonstrated that the fully glycosylated mature secretory isoform of progranulin (∼88 kDa) decreased, whereas the glycosylated immature isoform of progranulin (58-68 kDa) markedly increased at 24 h and 72 h after reperfusion. In vitro experiments using primary cells from C57BL/6 mice revealed that the glycosylated immature isoform was secreted only from the microglia. Second, we demonstrated that progranulin could protect against acute focal cerebral ischaemia by a variety of mechanisms including attenuation of blood-brain barrier disruption, neuroinflammation suppression, and neuroprotection. We found that progranulin could regulate vascular permeability via vascular endothelial growth factor, suppress neuroinflammation after ischaemia via anti-inflammatory interleukin 10 in the microglia, and render neuroprotection in part by inhibition of cytoplasmic redistribution of TAR DNA-binding protein-43 as demonstrated in progranulin knockout mice (C57BL/6 background). Finally, we demonstrated the therapeutic potential of progranulin against acute focal cerebral ischaemia using a rat autologous thrombo-embolic model with delayed tissue plasminogen activator treatment. Intravenously administered recombinant progranulin reduced cerebral infarct and oedema, suppressed haemorrhagic transformation, and improved motor outcomes (P = 0.007, 0.038, 0.007 and 0.004, respectively). In conclusion, progranulin may be a novel therapeutic target that provides vascular protection, anti-neuroinflammation, and neuroprotection related in part to vascular endothelial growth factor, interleukin 10, and TAR DNA-binding protein-43, respectively.

Diffuse brain abnormalities in myotonic dystrophy type 1 detected by 3.0 T proton magnetic resonance spectroscopy.

Patients with myotonic dystrophy type 1 (DM1) (n = 14) were compared with healthy controls (n = 13) using 3.0 T proton magnetic resonance spectroscopy ((1)H-MRS) to investigate brain pathophysiology. (1)H-MRS imaging revealed reduced N-acetylaspartate to creatine ratio (NAA/Cr) in multiple brain regions (average 24%), suggesting diffuse brain abnormalities among patients with DM1. Single-voxel (1)H-MRS among patients with DM1 showed (1) reduced NAA in both the frontal cortex (23%) and frontal white matter (31%) and unaltered myo-inositol, suggesting neuronal abnormalities without significant gliosis; and (2) elevated glutamine in the frontal cortex (36%) and reduced glutamate in the frontal white matter (20%) among patients with DM1, suggesting abnormalities in the glutamatergic system in the brain of patients with DM1. We consider that these results reflect brain abnormalities that cannot be detected by neuropathological assessment in patients with DM1.

Phlorizin prevents electrically-induced ventricular tachyarrhythmia during ischemia in langendorff-perfused guinea-pig hearts.

Phlorizin is a type of flavonoids and has a peroxynitrite scavenging effect. This study aimed to elucidate the effects of phlorizin on ischemia-induced ventricular tachyarrhythmia (VT). Optical signals from the epicardial surface of the ventricle or left ventricular end diastolic pressure (LVEDP) were recorded during acute global ischemia in 42 Langendorff-perfused guinea pig hearts. Experiments were performed in the control condition and in the presence of phlorizin or N-2-mercaptopropionylglycine (2-MPG), a peroxynitrite scavenger, respectively. Mean action potential duration at 20 min of ischemia did not differ among the three interventions. Impulse conduction time-dependently slowed during 20 min of ischemia in the control. Phlorizin but not 2-MPG improved the ischemic conduction slowing at 15 and 20 min of ischemia. Programmed stimulation induced VT at 20 min of ischemia in the control and in the presence of 2-MPG but not in the presence of phlorizin (p<0.05). LVEDP was increased during 30 min of ischemia in the control and in the presence of 2-MPG but not in the presence of phlorizin. These results indicate that phlorizin prevents VT through the improvement of impulse conduction slowing during ischemia. Phlorizin may be more useful for ischemia-induced VT than 2-MPG.

Virchow-Robin space and aquaporin-4: new insights on an old friend.

Recent studies have strongly indicated that the classic circulation model of cerebrospinal fluid (CSF) is no longer valid. The production of CSF is not only dependent on the choroid plexus but also on water flux in the peri-capillary (Virchow Robin) space. Historically, CSF flow through the Virchow Robin space is known as interstitial flow, the physiological significance of which is now fully understood. This article briefly reviews the modern concept of CSF physiology and the Virchow-Robin space, in particular its functionalities critical for central nervous system neural activities. Water influx into the Virchow Robin space and, hence, interstitial flow is regulated by aquaporin-4 (AQP-4) localized in the endfeet of astrocytes, connecting the intracellular cytosolic fluid space of astrocytes and the Virchow Robin space. Interstitial flow has a functionality equivalent to systemic lymphatics, on which clearance of ß-amyloid is strongly dependent. Autoregulation of brain blood flow serves to maintain a constant inner capillary fluid pressure, allowing fluid pressure of the Virchow Robin space to regulate regional cerebral blood flow (rCBF) based on AQP-4 gating. Excess heat produced by neural activities is effectively removed from the area of activation by increased rCBF by closing AQP-4 channels. This neural flow coupling (NFC) is likely mediated by heat generated proton channels.

Expression of a novel isoform of Na(+)/H(+) exchanger 3 in the kidney and intestine of banded houndshark, Triakis scyllium.

Na(+)/H(+) exchanger 3 (NHE3) provides one of the major Na(+) absorptive pathways of the intestine and kidney in mammals, and recent studies of aquatic vertebrates (teleosts and elasmobranchs) have demonstrated that NHE3 is expressed in the gill and plays important roles in ion and acid-base regulation. To understand the role of NHE3 in elasmobranch osmoregulatory organs, we analyzed renal and intestinal expressions and localizations of NHE3 in a marine elasmobranch, Japanese banded houndshark (Triakis scyllium). mRNA for Triakis NHE3 was most highly expressed in the gill, kidney, spiral intestine, and rectum. The kidney and intestine expressed a transcriptional isoform of NHE3 (NHE3k/i), which has a different amino terminus compared with that of NHE3 isolated from the gill (NHE3g), suggesting that NHE3k/i and NHE3g arise from a single gene by alternative promoter usage. Immunohistochemical analyses of the Triakis kidney demonstrated that NHE3k/i is expressed in the apical membrane of a part of the proximal and late distal tubules in the sinus zone. In the bundle zone of the kidney, NHE3k/i was expressed in the apical membrane of the early distal tubules known as the diluting segment. In the spiral intestine and rectum, NHE3k/i was localized toward the apical membrane of the epithelial cells. The transcriptional levels of NHE3k/i were increased in the kidney when Triakis was acclimated in 130% seawater, whereas those in the spiral intestine were increased in fish acclimated in diluted seawater. These results suggest that NHE3 is involved in renal Na(+) reabsorption, urine acidification, and intestinal Na(+) absorption in elasmobranchs.