Sensitization of small-diameter sensory neurons is controlled by TRPV1 and TRPA1 association.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Unique features of sensory neuron subtypes are manifest by their distinct physiological and pathophysiological functions. Using patch-clamp electrophysiology, Ca imaging, calcitonin gene-related peptide release assay from tissues, protein biochemistry approaches, and behavioral physiology on pain models, this study demonstrates the diversity of sensory neuron pathophysiology is due in part to subtype-dependent sensitization of TRPV1 and TRPA1. Differential sensitization is influenced by distinct expression of inflammatory mediators, such as prostaglandin E (PGE), bradykinin (BK), and nerve growth factor (NGF) as well as multiple kinases, including protein kinase A (PKA) and C (PKC). However, the co-expression and interaction of TRPA1 with TRPV1 proved to be the most critical for differential sensitization of sensory neurons. We identified N- and C-terminal domains on TRPV1 responsible for TRPA1-TRPV1 (A1-V1) complex formation. Ablation of A1-V1 complex with dominant-negative peptides against these domains substantially reduced the sensitization of TRPA1, as well as BK- and CFA-induced hypersensitivity. These data indicate that often occurring TRP channel complexes regulate diversity in neuronal sensitization and may provide a therapeutic target for many neuroinflammatory pain conditions.
10.1096/fj.201902026R
Modulatory and plastic effects of kinins on spinal cord networks.
Mandadi S,Leduc-Pessah H,Hong P,Ejdrygiewicz J,Sharples S A,Trang T,Whelan P J
The Journal of physiology
KEY POINTS:Inflammatory kinins are released following spinal cord injury or neurotrauma. The effects of these kinins on ongoing locomotor activity of central pattern generator networks are unknown. In the present study, kinins were shown to have short- and long-term effects on motor networks. The short-term effects included direct depolarization of interneurons and motoneurons in the ventral horn accompanied by modulation of transient receptor potential vanilloid 1-sensitive nociceptors in the dorsal horn. Over the long-term, we observed a bradykinin-mediated effect on promoting plasticity in the spinal cord. In a model of spinal cord injury, we observed an increase in microglia numbers in both the dorsal and ventral horn and, in a microglia cell culture model, we observed bradykinin-induced expression of glial-derived neurotrophic factor. ABSTRACT:The expression and function of inflammatory mediators in the developing spinal cord remain poorly characterized. We discovered novel, short and long-term roles for the inflammatory nonapeptide bradykinin (BK) and its receptor bradykinin receptor B2 (B2R) in the neuromodulation of developing sensorimotor networks following a spinal cord injury (SCI), suggesting that BK participates in an excitotoxic cascade. Functional expression of B2R was confirmed by a transient disruptive action of BK on fictive locomotion generated by a combination of NMDA, 5-HT and dopamine. The role of BK in the dorsal horn nociceptive afferents was tested using spinal cord attached to one-hind-limb (HL) preparations. In the HL preparations, BK at a subthreshold concentration induced transient disruption of fictive locomotion only in the presence of: (1) noxious heat applied to the hind paw and (2) the heat sensing ion channel transient receptor potential vanilloid 1 (TRPV1), known to be restricted to nociceptors in the superficial dorsal horn. BK directly depolarized motoneurons and ascending interneurons in the ventrolateral funiculus. We found a key mechanism for BK in promoting long-term plasticity within the spinal cord. Using a model of neonatal SCI and a microglial cell culture model, we examined the role of BK in inducing activation of microglia and expression of glial-derived neurotrophic factor (GDNF). In the neonatal SCI model, we observed an increase in microglia numbers and increased GDNF expression restricted to microglia. In the microglia cell culture model, we observed a BK-induced increased expression of GDNF via B2R, suggesting a novel mechanism for BK spinal-mediated plasticity.
10.1113/JP271152
+mRNA expression of LRRC55 protein (leucine-rich repeat-containing protein 55) in the adult mouse brain.
Zhang Ying-Ying,Han Xue,Liu Ye,Chen Jian,Hua Lei,Ma Qian,Huang Yang-Yu-Xin,Tang Qiong-Yao,Zhang Zhe
PloS one
LRRC55 (leucine-rich repeat-containing protein 55) protein is an auxiliary γ subunit of BK (Big conductance potassium channel) channels, which leftward shifts GVs of BK channels around 50 mV in the absence of cytosolic Ca2+. LRRC55 protein is also the only γ subunit of BK channels that is expressed in mammalian nervous system. However, the expression pattern of LRRC55 gene in adult mammalian brain remains elusive. In this study, we investigated the distribution of LRRC55 mRNA in the adult mouse brain by using in situ hybridization. We found that LRRC55 mRNA is richly expressed in the adult mouse medial habenula nucleus (MHb), cerebellum and pons. However, the potential role of LRRC55 in MHb and cerebellum could be different based on the function of BK channels in these brain regions.
10.1371/journal.pone.0191749
Serotonin Disinhibits a Sensory Neuron by Suppressing Ca-Dependent Negative Feedback.
Williams Paul D E,Zahratka Jeffrey A,Rodenbeck Matthew,Wanamaker Jason,Linzie Hilary,Bamber Bruce A
The Journal of neuroscience : the official journal of the Society for Neuroscience
Neuromodulators, such as serotonin (5-HT), alter neuronal excitability and synaptic strengths, and define different behavioral states. Neuromodulator-dependent changes in neuronal activity patterns are frequently measured using calcium reporters because calcium imaging can easily be performed on intact functioning nervous systems. With only 302 neurons, the nematode provides a relatively simple, yet powerful, system to understand neuromodulation at the level of individual neurons. hermaphrodites are repelled by 1-octanol, and the initiation of these aversive responses is potentiated by 5-HT. 5-HT acts on the ASH polymodal nociceptors that sense the 1-octanol stimulus. Surprisingly, 5-HT suppresses ASH Ca transients while simultaneously potentiating 1-octanol-dependent ASH depolarization. Here we further explore this seemingly inverse relationship. Our results show the following (1) 5-HT acts downstream of depolarization, through Gα-mediated signaling and calcineurin, to inhibit L-type voltage-gated Ca channels; (2) the 1-octanol-evoked Ca transients in ASHs inhibit depolarization; and (3) the Ca-activated K channel, SLO-1, acts downstream of 5-HT and is a critical regulator of ASH response dynamics. These findings define a Ca-dependent inhibitory feedback loop that can be modulated by 5-HT to increase neuronal excitability and regulate behavior, and highlight the possibility that neuromodulator-induced changes in the amplitudes of Ca transients do not necessarily predict corresponding changes in depolarization. Neuromodulators, such as 5-HT, modify behavior by regulating excitability and synaptic efficiency in neurons. Neuromodulation is often studied using Ca imaging, whereby neuromodulator-dependent changes in neuronal activity levels can be detected in intact, functioning circuits. Here we show that 5-HT reduces the amplitude of depolarization-dependent Ca transients in a nociceptive neuron, through Gα signaling and calcineurin but that Ca itself inhibits depolarization, likely through Ca-activated K channels. The net effect of 5-HT, therefore, is to increase neuronal excitability through disinhibition. These results establish a novel 5-HT signal transduction pathway, and demonstrate that neuromodulators can change Ca signals and depolarization amplitudes in opposite directions, simultaneously, within a single neuron.
10.1523/JNEUROSCI.1908-17.2018
Quantification of the functional expression of the Ca -activated K channel K 3.1 on microglia from adult human neocortical tissue.
Blomster Linda V,Strøbaek Dorte,Hougaard Charlotte,Klein Jessica,Pinborg Lars H,Mikkelsen Jens D,Christophersen Palle
Glia
The K 3.1 channel (KCNN4) is an important modulator of microglia responses in rodents, but no information exists on functional expression on microglia from human adults. We isolated and cultured microglia (max 1% astrocytes, no neurons or oligodendrocytes) from neocortex surgically removed from epilepsy patients and employed electrophysiological whole-cell measurements and selective pharmacological tools to elucidate functional expression of K 3.1. The channel expression was demonstrated as a significant increase in the voltage-independent current by NS309, a K 3.1/K 2 activator, followed by full inhibition upon co-application with NS6180, a highly selective K 3.1 inhibitor. A major fraction (79%) of unstimulated human microglia expressed K 3.1, and the difference in current between full activation and inhibition (ΔK 3.1) was estimated at 292 ± 48 pA at -40 mV (n = 75), which equals at least 585 channels per cell. Serial K 3.1 activation/inhibition significantly hyperpolarized/depolarized the membrane potential. The isolated human microglia were potently activated by lipopolysaccharide (LPS) shown as a prominent increase in TNF-α production. However, incubation with LPS neither changed the K 3.1 current nor the fraction of K 3.1 expressing cells. In contrast, the anti-inflammatory cytokine IL-4 slightly increased the K 3.1 current per cell, but as the membrane area also increased, there was no significant change in channel density. A large fraction of the microglia also expressed a voltage-dependent current sensitive to the K 1.1 modulators NS1619 and Paxilline and an inward-rectifying current with the characteristics of a K channel. The high functional expression of K 3.1 in microglia from epilepsy patients accentuates the need for further investigations of its role in neuropathological processes. GLIA 2016;64:2065-2078.
10.1002/glia.23040
A paternal methyl donor-rich diet altered cognitive and neural functions in offspring mice.
Ryan D P,Henzel K S,Pearson B L,Siwek M E,Papazoglou A,Guo L,Paesler K,Yu M,Müller R,Xie K,Schröder S,Becker L,Garrett L,Hölter S M,Neff F,Rácz I,Rathkolb B,Rozman J,Ehninger G,Klingenspor M,Klopstock T,Wolf E,Wurst W,Zimmer A,Fuchs H,Gailus-Durner V,Hrabě de Angelis M,Sidiropoulou K,Weiergräber M,Zhou Y,Ehninger D
Molecular psychiatry
Dietary intake of methyl donors, such as folic acid and methionine, shows considerable intra-individual variation in human populations. While it is recognized that maternal departures from the optimum of dietary methyl donor intake can increase the risk for mental health issues and neurological disorders in offspring, it has not been explored whether paternal dietary methyl donor intake influences behavioral and cognitive functions in the next generation. Here, we report that elevated paternal dietary methyl donor intake in a mouse model, transiently applied prior to mating, resulted in offspring animals (methyl donor-rich diet (MD) F1 mice) with deficits in hippocampus-dependent learning and memory, impaired hippocampal synaptic plasticity and reduced hippocampal theta oscillations. Gene expression analyses revealed altered expression of the methionine adenosyltransferase Mat2a and BK channel subunit Kcnmb2, which was associated with changes in Kcnmb2 promoter methylation in MD F1 mice. Hippocampal overexpression of Kcnmb2 in MD F1 mice ameliorated altered spatial learning and memory, supporting a role of this BK channel subunit in the MD F1 behavioral phenotype. Behavioral and gene expression changes did not extend into the F2 offspring generation. Together, our data indicate that paternal dietary factors influence cognitive and neural functions in the offspring generation.
10.1038/mp.2017.53
The absence of NIPA2 enhances neural excitability through BK (big potassium) channels.
Liu Na-Na,Xie Han,Xiang-Wei Wen-Shu,Gao Kai,Wang Tian-Shuang,Jiang Yu-Wu
CNS neuroscience & therapeutics
AIM:To reveal the pathogenesis and find the precision treatment for the childhood absence epilepsy (CAE) patients with NIPA2 mutations. METHODS:We performed whole-cell patch-clamp recordings to measure the electrophysiological properties of layer V neocortical somatosensory pyramidal neurons in wild-type (WT) and NIPA2-knockout mice. RESULTS:We identified that layer V neocortical somatosensory pyramidal neurons isolated from the NIPA2-knockout mice displayed higher frequency of spontaneous and evoked action potential, broader half-width of evoked action potential, and smaller currents of BK channels than those from the WT mice. NS11021, a specific BK channel opener, reduced neuronal excitability in the NIPA2-knockout mice. Paxilline, a selective BK channel blocker, treated WT neurons and could simulate the situation of NIPA2-knockout group, thereby suggesting that the absence of NIPA2 enhanced the excitability of neocortical somatosensory pyramidal neurons by decreasing the currents of BK channels. Zonisamide, an anti-epilepsy drug, reduced action potential firing in NIPA2-knockout mice through increasing BK channel currents. CONCLUSION:The results indicate that the absence of NIPA2 enhances neural excitability through BK channels. Zonisamide is probably a potential treatment for NIPA2 mutation-induced epilepsy, which may provide a basis for the development of new treatment strategies for epilepsy.
10.1111/cns.13119
CNTF-Treated Astrocyte Conditioned Medium Enhances Large-Conductance Calcium-Activated Potassium Channel Activity in Rat Cortical Neurons.
Sun Meiqun,Liu Hongli,Xu Huanbai,Wang Hongtao,Wang Xiaojing
Neurochemical research
Seizure activity is linked to astrocyte activation as well as dysfunctional cortical neuron excitability produced from changes in calcium-activated potassium (KCa) channel function. Ciliary neurotrophic factor-treated astrocyte conditioned medium (CNTF-ACM) can be used to investigate the peripheral effects of activated astrocytes upon cortical neurons. However, CNTF-ACM's effect upon KCa channel activity in cultured cortical neurons has not yet been investigated. Whole-cell patch clamp recordings were performed in rat cortical neurons to evaluate CNTF-ACM's effects upon charybdotoxin-sensitive large-conductance KCa (BK) channel currents and apamin-sensitive small-conductance KCa (SK) channel current. Biotinylation and RT-PCR were applied to assess CNTF-ACM's effects upon the protein and mRNA expression, respectively, of the SK channel subunits SK2 and SK3 and the BK channel subunits BKα1 and BKβ3. An anti-fibroblast growth factor-2 (FGF-2) monoclonal neutralizing antibody was used to assess the effects of the FGF-2 component of CNTF-ACM. CNTF-ACM significantly increased KCa channel current density, which was predominantly attributable to gains in BK channel activity (p < 0.05). CNTF-ACM produced a significant increase in BKα1 and BKβ3 expression (p < 0.05) but had no significant effect upon SK2 or SK3 expression (p > 0.05). Blocking FGF-2 produced significant reductions in KCa channel current density (p > 0.05) as well as BKα1 and BKβ3 expression in CNTF-ACM-treated neurons (p > 0.05). CNTF-ACM significantly enhances BK channel activity in rat cortical neurons and that FGF-2 is partially responsible for these effects. CNTF-induced astrocyte activation results in secretion of neuroactive factors which may affect neuronal excitability and resultant seizure activity in mammalian cortical neurons.
10.1007/s11064-016-1910-4
Downregulation of KCNMB4 expression and changes in BK channel subtype in hippocampal granule neurons following seizure activity.
PloS one
A major challenge is to understand maladaptive changes in ion channels that sets neurons on a course towards epilepsy development. Voltage- and calcium-activated K+ (BK) channels contribute to early spike timing in neurons, and studies indicate that the BK channel plays a pathological role in increasing excitability early after a seizure. Here, we have investigated changes in BK channels and their accessory β4 subunit (KCNMB4) in dentate gyrus (DG) granule neurons of the hippocampus, key neurons that regulate excitability of the hippocampus circuit. Two days after pilocarpine-induced seizures, we found that the predominant effect is a downregulation of the β4 accessory subunit mRNA. Consistent with reduced expression, single channel recording and pharmacology indicate a switch in the subtype of channels expressed; from iberiotoxin-resistant, type II BK channels (BK α/β4) that have higher channel open probability and slow gating, to iberiotoxin-sensitive type I channels (BK α alone) with low open probability and faster gating. The switch to a majority of type I channel expression following seizure activity is correlated with a loss of BK channel function on spike threshold while maintaining the channel's contribution to increased early spike frequency. Using heterozygous β4 knockout mice, we find reduced expression is sufficient to increase seizure sensitivity. We conclude that seizure-induced downregulation of KCNMB4 is an activity dependent mechanism that increases the excitability of DG neurons. These novel findings indicate that BK channel subtypes are not only defined by cell-specific expression, but can also be plastic depending on the recent history of neuronal excitability.
10.1371/journal.pone.0188064
Nerve injury increases brain-derived neurotrophic factor levels to suppress BK channel activity in primary sensory neurons.
Cao Xue-Hong,Chen Shao-Rui,Li Li,Pan Hui-Lin
Journal of neurochemistry
Abnormal hyperexcitability of primary sensory neurons contributes to neuropathic pain development after nerve injury. Nerve injury profoundly reduces the expression of big conductance Ca(2+) -activated K(+) (BK) channels in the dorsal root ganglion (DRG). However, little is known about how nerve injury affects BK channel activity in DRG neurons. In this study, we determined the changes in BK channel activity in DRG neurons in a rat model of neuropathic pain and the contribution of brain-derived neurotrophic factor (BDNF) to reduced BK channel activity. The BK channel activity was present predominantly in small and medium DRG neurons, and ligation of L5 and L6 spinal nerves profoundly decreased the BK current density in these neurons. Blocking BK channels significantly increased neuronal excitability in sham control, but not in nerve-injured, rats. The BDNF concentration in the DRG was significantly greater in nerve-injured rats than in control rats. BDNF treatment largely reduced BK currents in DRG neurons in control rats, which was blocked by either anti-BDNF antibody or K252a, a Trk receptor inhibitor. Furthermore, either anti-BDNF antibody or K252a reversed reduction in BK currents in injured DRG neurons. BDNF treatment reduced the mRNA levels of BKα1 subunit in DRG neurons, and anti-BDNF antibody attenuated the reduction in the BKα1 mRNA level in injured DRG neurons. These findings suggest that nerve injury primarily diminishes the BK channel activity in small and medium DRG neurons. Increased BDNF levels contribute to reduced BK channel activity in DRG neurons through epigenetic and transcriptional mechanisms in neuropathic pain.
10.1111/j.1471-4159.2012.07736.x
Blockade of ATP-sensitive potassium channels prevents the attenuation of the exercise pressor reflex by tempol in rats with ligated femoral arteries.
Yamauchi Katsuya,Stone Audrey J,Stocker Sean D,Kaufman Marc P
American journal of physiology. Heart and circulatory physiology
We reported previously that tempol attenuated the exercise pressor and muscle mechanoreceptor reflexes in rats whose femoral arteries were ligated, whereas tempol did not attenuate these reflexes in rats whose femoral arteries were freely perfused. Although the mechanism whereby tempol attenuated these reflexes in rats whose femoral artery was ligated was independent of its ability to scavenge reactive oxygen species, its nature remains unclear. An alternative explanation for the tempol-induced attenuation of these reflexes involves ATP-sensitive potassium channels (K(ATP)) and calcium-activated potassium channels (BK(Ca)), both of which are opened by tempol. We tested the likelihood of this explanation by measuring the effects of either glibenclamide (0.1 mg/kg), which blocks K(ATP) channels, or iberiotoxin (20 or 40 μg/kg), which blocks BK(Ca) channels, on the tempol-induced attenuation of the exercise pressor and muscle mechanoreceptor reflexes in decerebrated rats whose femoral arteries were ligated. We found that glibenclamide prevented the tempol-induced attenuation of both reflexes, whereas iberiotoxin did not. We also found that the amount of protein comprising the pore of the K(ATP) channel in the dorsal root ganglia innervating hindlimbs whose femoral artery was ligated was significantly greater than that in the dorsal root ganglia innervating hindlimbs whose femoral arteries were freely perfused. In contrast, the amounts of protein comprising the BK(Ca) channel in the dorsal root ganglia innervating the ligated and freely perfused hindlimbs were not different. We conclude that tempol attenuated both reflexes by opening K(ATP) channels, an effect that hyperpolarized muscle afferents stimulated by static contraction or tendon stretch.
10.1152/ajpheart.00310.2012
GDNF induces mechanical hyperalgesia in muscle by reducing I(BK) in isolectin B4-positive nociceptors.
Hendrich J,Alvarez P,Chen X,Levine J D
Neuroscience
We have assessed the mechanism underlying glial cell-derived neurotrophic factor (GDNF)-induced mechanical hyperalgesia in the gastrocnemius muscle, using patch clamp electrophysiology, in vivo electrophysiology and behavioral studies. Cultured isolectin B4-positive (IB4+) dorsal root ganglion neurons that innervated this muscle were held under current clamp; the majority developed an increase in action potential duration (a factor of increase of 2.29±0.24, compared to 1.13±0.17 in control, P<0.01) in response to GDNF (200 ng/ml) by 15 min after application. They also demonstrated a depolarization of resting membrane potential, but without significant changes in rheobase, action potential peak, or after-hyperpolarization. Large-conductance voltage- and calcium-activated potassium (BK) channels, which have recently been shown to play a role in the repolarization of IB4+ nociceptors, were inhibited under voltage clamp, as indicated by a significant reduction in the iberiotoxin-sensitive current. In vivo single-fiber recording from muscle afferents revealed that injection of iberiotoxin into their peripheral nociceptive field caused an increase in nociceptor firing in response to a 60s suprathreshold stimulus (an increase from 392.2±119.8 spikes to 596.1±170.8 spikes, P<0.05). This was observed in the absence of changes in the mechanical threshold. Finally, injection of iberiotoxin into the gastrocnemius muscle produced dose-dependent mechanical hyperalgesia. These data support the suggestion that GDNF induces nociceptor sensitization and mechanical hyperalgesia, at least in part, by inhibiting BK current in IB4+ nociceptors.
10.1016/j.neuroscience.2012.06.011
Inflammatory signals enhance piezo2-mediated mechanosensitive currents.
Dubin Adrienne E,Schmidt Manuela,Mathur Jayanti,Petrus Matthew J,Xiao Bailong,Coste Bertrand,Patapoutian Ardem
Cell reports
Heightened nociceptor function caused by inflammatory mediators such as bradykinin (BK) contributes to increased pain sensitivity (hyperalgesia) to noxious mechanical and thermal stimuli. Although it is known that sensitization of the heat transducer TRPV1 largely subserves thermal hyperalgesia, the cellular mechanisms underlying mechanical hyperalgesia have been elusive. The role of the mechanically activated (MA) channel piezo2 (known as FAM38B) present in mammalian sensory neurons is unknown. We test the hypothesis that piezo2 activity is enhanced by BK, an algogenic peptide that induces mechanical hyperalgesia within minutes. Piezo2 current amplitude is increased and inactivation is slowed by bradykinin receptor beta 2 (BDKRB2) activation in heterologous expression systems. Protein kinase A (PKA) and protein kinase C (PKC) agonists enhance piezo2 activity. BDKRB2-mediated effects are abolished by PKA and PKC inhibitors. Finally, piezo2-dependent MA currents in a class of native sensory neurons are enhanced 8-fold by BK via PKA and PKC. Thus, piezo2 sensitization may contribute to PKA- and PKC-mediated mechanical hyperalgesia.
10.1016/j.celrep.2012.07.014
Microglia: Housekeeper of the Central Nervous System.
Kabba John Alimamy,Xu Yazhou,Christian Handson,Ruan Wenchen,Chenai Kitchen,Xiang Yun,Zhang Luyong,Saavedra Juan M,Pang Tao
Cellular and molecular neurobiology
Microglia, of myeloid origin, play fundamental roles in the control of immune responses and the maintenance of central nervous system homeostasis. These cells, just like peripheral macrophages, may be activated into M1 pro-inflammatory or M2 anti-inflammatory phenotypes by appropriate stimuli. Microglia do not respond in isolation, but form part of complex networks of cells influencing each other. This review addresses the complex interaction of microglia with each cell type in the brain: neurons, astrocytes, cerebrovascular endothelial cells, and oligodendrocytes. We also highlight the participation of microglia in the maintenance of homeostasis in the brain, and their roles in the development and progression of age-related neurodegenerative disorders.
10.1007/s10571-017-0504-2
Modulation of cardiac vagal tone by bradykinin acting on nucleus ambiguus.
Brailoiu Eugen,McGuire Matthew,Shuler Shadaria A,Deliu Elena,Barr Jeffrey L,Abood Mary E,Brailoiu G Cristina
Neuroscience
Bradykinin (BK), a component of the kallikrein-kininogen-kinin system exerts multiple effects via B1 and B2 receptor activation. In the cardiovascular system, bradykinin has cardioprotective and vasodilator properties. We investigated the effect of BK on cardiac-projecting neurons of nucleus ambiguus, a key site for the parasympathetic cardiac regulation. BK produced a dose-dependent increase in cytosolic Ca concentration. Pretreatment with HOE140, a B2 receptor antagonist, but not with R715, a B1 receptor antagonist, abolished the response to BK. A selective B2 receptor agonist, but not a B1 receptor agonist, elicited an increase in cytosolic Ca similarly to BK. Inhibition of N-type voltage-gated Ca channels with ω-conotoxin GVIA had no effect on the Ca signal produced by BK, while pretreatment with ω-conotoxin MVIIC, a blocker of P/Q-type of Ca channels, significantly diminished the effect of BK. Pretreatment with xestospongin C and 2-aminoethoxydiphenyl borate, antagonists of inositol 1,4,5-trisphosphate receptors, abolished the response to BK. Inhibition of ryanodine receptors reduced the BK-induced Ca increase, while disruption of lysosomal Ca stores with bafilomycin A1 did not affect the response. BK produced a dose-dependent depolarization of nucleus ambiguus neurons, which was prevented by the B2 receptor antagonist. In vivo studies indicate that microinjection of BK into nucleus ambiguus elicited bradycardia in conscious rats via B2 receptors. In summary, in cardiac vagal neurons of nucleus ambiguus, BK activates B2 receptors promoting Ca influx and Ca release from endoplasmic reticulum, and membrane depolarization; these effects are translated in vivo by bradycardia.
10.1016/j.neuroscience.2017.09.034
The presynaptic ribbon maintains vesicle populations at the hair cell afferent fiber synapse.
Becker Lars,Schnee Michael E,Niwa Mamiko,Sun Willy,Maxeiner Stephan,Talaei Sara,Kachar Bechara,Rutherford Mark A,Ricci Anthony J
eLife
The ribbon is the structural hallmark of cochlear inner hair cell (IHC) afferent synapses, yet its role in information transfer to spiral ganglion neurons (SGNs) remains unclear. We investigated the ribbon's contribution to IHC synapse formation and function using KO mice lacking RIBEYE. Despite loss of the entire ribbon structure, synapses retained their spatiotemporal development and KO mice had a mild hearing deficit. IHCs of KO had fewer synaptic vesicles and reduced exocytosis in response to brief depolarization; a high stimulus level rescued exocytosis in KO. SGNs exhibited a lack of sustained excitatory postsynaptic currents (EPSCs). We observed larger postsynaptic glutamate receptor plaques, potentially compensating for the reduced EPSC rate in KO. Surprisingly, large-amplitude EPSCs were maintained in KO, while a small population of low-amplitude slower EPSCs was increased in number. The ribbon facilitates signal transduction at physiological stimulus levels by retaining a larger residency pool of synaptic vesicles.
10.7554/eLife.30241
Intracellular Ca mobilization pathway via bradykinin B receptor activation in rat trigeminal ganglion neurons.
The journal of physiological sciences : JPS
Bradykinin (BK) and its receptors, B and B, in trigeminal ganglion (TG) neurons are involved in the regulation of pain. Recent studies have revealed that B receptors are expressed in neonatal rat TG neurons; however, the intracellular signaling pathway following B receptor activation remains to be elucidated. To investigate the mechanism by which B receptor activation leads to intracellular Ca mobilization, we measured the intracellular free Ca concentration ([Ca]) in primary-cultured TG neurons. The application of Lys-[Des-Arg]BK (B receptor agonist) increased the [Ca] in these TG neurons even in the absence of extracellular Ca. Pretreatment with inhibitors of ryanodine receptors or sarco/endoplasmic reticulum Ca-ATPase suppressed the increase in Lys-[Des-Arg]BK-induced [Ca]. The Lys-[Des-Arg]BK-induced [Ca] increase was unaffected by phospholipase-C inhibitor. B receptor activation-induced [Ca] increase was suppressed by phosphodiesterase inhibitor and enhanced by adenylyl cyclase inhibitor. These results suggest that B receptor activation suppresses intracellular cAMP production via adenylyl cyclase inhibition and mobilizes intracellular Ca via ryanodine receptors that access intracellular Ca stores.
10.1007/s12576-018-0635-3
Injury-induced perivascular niche supports alternative differentiation of adult rodent CNS progenitor cells.
Ulanska-Poutanen Justyna,Mieczkowski Jakub,Zhao Chao,Konarzewska Katarzyna,Kaza Beata,Pohl Hartmut Bf,Bugajski Lukasz,Kaminska Bozena,Franklin Robin Jm,Zawadzka Malgorzata
eLife
Following CNS demyelination, oligodendrocyte progenitor cells (OPCs) are able to differentiate into either remyelinating oligodendrocytes (OLs) or remyelinating Schwann cells (SCs). However, the signals that determine which type of remyelinating cell is generated and the underlying mechanisms involved have not been identified. Here, we show that distinctive microenvironments created in discrete niches within demyelinated white matter determine fate decisions of adult OPCs. By comparative transcriptome profiling we demonstrate that an ectopic, injury-induced perivascular niche is enriched with secreted ligands of the BMP and Wnt signalling pathways, produced by activated OPCs and endothelium, whereas reactive astrocyte within non-vascular area express the dual BMP/Wnt antagonist Sostdc1. The balance of BMP/Wnt signalling network is instructive for OPCs to undertake fate decision shortly after their activation: disruption of the OPCs homeostasis during demyelination results in BMP4 upregulation, which, in the absence of Socstdc1, favours SCs differentiation.
10.7554/eLife.30325
Dental pulp-derived stem cells can counterbalance peripheral nerve injury-induced oxidative stress and supraspinal neuro-inflammation in rat brain.
Ullah Imran,Choe Yong-Ho,Khan Mehtab,Bharti Dinesh,Shivakumar Sharath Belame,Lee Hyeon-Jeong,Son Young-Bum,Shin Yurianna,Lee Sung-Lim,Park Bong-Wook,Ock Sun-A,Rho Gyu-Jin
Scientific reports
Previously, we reported the successful regeneration of injured peripheral nerves using human dental pulp stem cells (DPSCs) or differentiated neuronal cells from DPSCs (DF-DPSCs) in a rat model. Here, we attempted to evaluate oxidative stress and supraspinal neuro-inflammation in rat brain after sciatic nerve injury (SNI). We divided our experimental animals into three SNI groups based on time. The expression of a microglial (Iba1) marker and reactive oxygen species (ROS) was lower in DPSCs and higher in DF-DPSCs. In contrast, the expression of an astroglial (GFAP) marker was higher in DPSCs and lower in DF-DPSCs at 2 weeks. However, the expression of ROS, Iba1 and GFAP gradually decreased at 8 and 12 weeks in the SNI DPSCs and DF-DPSCs groups compared to the SNI control. Furthermore, anti-inflammatory cytokine (IL-4 and TGF-β) expression was lower at 2 weeks, while it gradually increased at 8 and 12 weeks after surgery in the SNI DPSCs and DF-DPSCs groups. Similarly, SNI DPSCs had a high expression of pAMPK, SIRT1 and NFkB at the onset of SNI. However, 12 weeks after surgery, pAMPK and SIRT1 expression levels were higher and NFkB was down-regulated in both DPSCs and DF-DPSCs compared to the control group. Finally, we concluded that DPSCs responded early and more efficiently than DF-DPSCs to counterbalance peripheral nerve injury (PNI)-induced oxidative stress and supraspinal neuro-inflammation in rat brain.
10.1038/s41598-018-34151-x
BK channels and a cGMP-dependent protein kinase (PKG) function through independent mechanisms to regulate the tolerance of synaptic transmission to acute oxidative stress at the Drosophila larval neuromuscular junction.
Bollinger Wesley L,Sial Nadia,Dawson-Scully Ken
Journal of neurogenetics
A cGMP-dependent protein kinase (PKG) has previously been shown to regulate synaptic transmission at the Drosophila neuromuscular junction (NMJ) during acute oxidative stress, potentially through modulation of downstream K channel kinetics; however, the specific K channels through which PKG functions remains unclear. In this study, we hypothesized that PKG may be acting on calcium-activated large-conductance Slo K channels, or BK channels. We found that genetic elimination and pharmacological inhibition of BK channel conductance increases synaptic transmission tolerance to acute HO-induced oxidative stress. Furthermore, we discovered that activation of PKG in BK channel loss-of-function (Slo) mutants significantly decreases time to stimulus-induced synaptic failure, providing the first evidence of PKG and BK channels functioning independently to control synaptic transmission tolerance to acute oxidative stress.
10.1080/01677063.2018.1500571
Functional Coupling of Cav2.3 and BK Potassium Channels Regulates Action Potential Repolarization and Short-Term Plasticity in the Mouse Hippocampus.
Gutzmann Jakob J,Lin Lin,Hoffman Dax A
Frontiers in cellular neuroscience
Voltage-gated ion channels are essential for signal generation and propagation in neurons and other excitable cells. The high-voltage activated calcium-channel Cav2.3 is expressed throughout the central and peripheral nervous system, and within CA1 hippocampal pyramidal neurons it is localized throughout the somato-dendritic region and dendritic spines. Cav2.3 has been shown to provide calcium for other calcium-dependent potassium channels including small-conductance calcium-activated potassium channels (SK), but big-conductance calcium-activated potassium channels (BK) have been thought to be activated by calcium from all known voltage-gated calcium channels, except Cav2.3. Here we show for the first time that CA1 pyramidal cells which lack Cav2.3 show altered action potential (AP) waveforms, which can be traced back to reduced SK- and BK-channel function. This change in AP waveform leads to strengthened synaptic transmission between CA1 and the subiculum, resulting in increased short-term plasticity. Our results demonstrate that Cav2.3 impacts cellular excitability through functional interaction with BK channels, impacting communication between hippocampal subregions.
10.3389/fncel.2019.00027
Expression of the LRRC52 γ subunit (γ2) may provide Ca-independent activation of BK currents in mouse inner hair cells.
Lang Isabelle,Jung Martin,Niemeyer Barbara A,Ruth Peter,Engel Jutta
FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Mammalian inner hair cells (IHCs) transduce sound into depolarization and transmitter release. Big conductance and voltage- and Ca-activated K (BK) channels are responsible for fast membrane repolarization and small time constants of mature IHCs. For unknown reasons, they activate at around -75 mV with a voltage of half-maximum activation () of -50 mV although being largely insensitive to Ca influx. Ca-independent activation of BK channels was observed by others in heterologous expression systems if γ subunits leucine-rich repeat-containing protein (LRRC)26 (γ1) and LRRC52 (γ2) were coexpressed with the pore-forming BKα subunit, which shifted by -140 and -100 mV, respectively. Using nested PCR, we consistently detected transcripts for LRRC52 but not for LRRC26 in IHCs of 3-wk-old mice. Confocal immunohistochemistry showed synchronous up-regulation of LRRC52 protein with BKα at the onset of hearing. Colocalization of LRRC52 protein and BKα at the IHC neck within ≤40 nm was specified using an proximity ligation assay. Mice deficient for the voltage-gated Ca1.3 Ca channel encoded by do not express BKα protein. LRRC52 protein was neither expressed in IHCs of BKα nor in IHCs of Ca1.3 knockout mice. Together, LRRC52 is a γ2 subunit of BK channel complexes and is a strong candidate for causing the Ca-independent activation of BK currents at negative membrane potentials in mouse IHCs.-Lang, I., Jung, M., Niemeyer, B. A., Ruth, P., Engel, J. Expression of the LRRC52 γ subunit (γ2) may provide Ca-independent activation of BK currents in mouse inner hair cells.
10.1096/fj.201900701RR
Ca-Activated K Channels Reduce Network Excitability, Improving Adaptability and Energetics for Transmitting and Perceiving Sensory Information.
The Journal of neuroscience : the official journal of the Society for Neuroscience
Ca-activated K channels (BK and SK) are ubiquitous in synaptic circuits, but their role in network adaptation and sensory perception remains largely unknown. Using electrophysiological and behavioral assays and biophysical modeling, we discover how visual information transfer in mutants lacking the BK channel ( ), SK channel ( ), or both ( ;; ) is shaped in the female fruit fly () R1-R6 photoreceptor-LMC circuits (R-LMC-R system) through synaptic feedforward-feedback interactions and reduced R1-R6 and K conductances. This homeostatic compensation is specific for each mutant, leading to distinctive adaptive dynamics. We show how these dynamics inescapably increase the energy cost of information and promote the mutants' distorted motion perception, determining the true price and limits of chronic homeostatic compensation in an genetic animal model. These results reveal why Ca-activated K channels reduce network excitability (energetics), improving neural adaptability for transmitting and perceiving sensory information. In this study, we directly link and experiments with detailed stochastically operating biophysical models to extract new mechanistic knowledge of how photoreceptor-interneuron-photoreceptor (R-LMC-R) circuitry homeostatically retains its information sampling and transmission capacity against chronic perturbations in its ion-channel composition, and what is the cost of this compensation and its impact on optomotor behavior. We anticipate that this novel approach will provide a useful template to other model organisms and computational neuroscience, in general, in dissecting fundamental mechanisms of homeostatic compensation and deepening our understanding of how biological neural networks work.
10.1523/JNEUROSCI.3213-18.2019
LRRC52 regulates BK channel function and localization in mouse cochlear inner hair cells.
Lingle Christopher J,Martinez-Espinosa Pedro L,Yang-Hood Aizhen,Boero Luis E,Payne Shelby,Persic Dora,V-Ghaffari Babak,Xiao Maolei,Zhou Yu,Xia Xiao-Ming,Pyott Sonja J,Rutherford Mark A
Proceedings of the National Academy of Sciences of the United States of America
The perception of sound relies on sensory hair cells in the cochlea that convert the mechanical energy of sound into release of glutamate onto postsynaptic auditory nerve fibers. The hair cell receptor potential regulates the strength of synaptic transmission and is shaped by a variety of voltage-dependent conductances. Among these conductances, the Ca- and voltage-activated large conductance Ca-activated K channel (BK) current is prominent, and in mammalian inner hair cells (IHCs) displays unusual properties. First, BK currents activate at unprecedentedly negative membrane potentials (-60 mV) even in the absence of intracellular Ca elevations. Second, BK channels are positioned in clusters away from the voltage-dependent Ca channels that mediate glutamate release from IHCs. Here, we test the contributions of two recently identified leucine-rich-repeat-containing (LRRC) regulatory γ subunits, LRRC26 and LRRC52, to BK channel function and localization in mouse IHCs. Whereas BK currents and channel localization were unaltered in IHCs from knockout (KO) mice, BK current activation was shifted more than +200 mV in IHCs from KO mice. Furthermore, the absence of LRRC52 disrupted BK channel localization in the IHCs. Given that heterologous coexpression of LRRC52 with BK α subunits shifts BK current gating about -90 mV, to account for the profound change in BK activation range caused by removal of LRRC52, we suggest that additional factors may help define the IHC BK gating range. LRRC52, through stabilization of a macromolecular complex, may help retain some other components essential both for activation of BK currents at negative membrane potentials and for appropriate BK channel positioning.
10.1073/pnas.1907065116
Hair cell maturation is differentially regulated along the tonotopic axis of the mammalian cochlea.
Jeng Jing-Yi,Ceriani Federico,Hendry Aenea,Johnson Stuart L,Yen Piece,Simmons Dwayne D,Kros Corné J,Marcotti Walter
The Journal of physiology
KEY POINTS:Outer hair cells (OHCs) enhance the sensitivity and the frequency tuning of the mammalian cochlea. Similar to the primary sensory receptor, the inner hair cells (IHCs), the mature functional characteristics of OHCs are acquired before hearing onset. We found that OHCs, like IHCs, fire spontaneous Ca -induced action potentials (APs) during immature stages of development, which are driven by Ca 1.3 Ca channels. We also showed that the development of low- and high-frequency hair cells is differentially regulated during pre-hearing stages, with the former cells being more strongly dependent on experience-independent Ca action potential activity. ABSTRACT:Sound amplification within the mammalian cochlea depends upon specialized hair cells, the outer hair cells (OHCs), which possess both sensory and motile capabilities. In various altricial rodents, OHCs become functionally competent from around postnatal day 7 (P7), before the primary sensory inner hair cells (IHCs), which become competent at about the onset of hearing (P12). The mechanisms responsible for the maturation of OHCs and their synaptic specialization remain poorly understood. We report that spontaneous Ca activity in the immature cochlea, which is generated by Ca 1.3 Ca channels, differentially regulates the maturation of hair cells along the cochlea. Under near-physiological recording conditions we found that, similar to IHCs, immature OHCs elicited spontaneous Ca action potentials (APs), but only during the first few postnatal days. Genetic ablation of these APs in vivo, using Ca 1.3 mice, prevented the normal developmental acquisition of mature-like basolateral membrane currents in low-frequency (apical) hair cells, such as I (carried by KCNQ4 channels), I and I (α9α10nAChRs) in OHCs and I and I (BK channels) in IHCs. Electromotility and prestin expression in OHCs were normal in Ca 1.3 mice. The maturation of high-frequency (basal) hair cells was also affected in Ca 1.3 mice, but to a much lesser extent than apical cells. However, a characteristic feature in Ca 1.3 mice was the reduced hair cell size irrespective of their cochlear location. We conclude that the development of low- and high-frequency hair cells is differentially regulated during development, with apical cells being more strongly dependent on experience-independent Ca APs.
10.1113/JP279012
A universal transportin protein drives stochastic choice of olfactory neurons via specific nuclear import of a -activating factor.
Alqadah Amel,Hsieh Yi-Wen,Xiong Rui,Lesch Bluma J,Chang Chieh,Chuang Chiou-Fen
Proceedings of the National Academy of Sciences of the United States of America
Stochastic neuronal cell fate choice involving notch-independent mechanisms is a poorly understood biological process. The AWC olfactory neuron pair asymmetrically differentiates into the default AWC and induced AWC subtypes in a stochastic manner. Stochastic choice of the AWC subtype is established using gap junctions and SLO BK potassium channels to repress a calcium-activated protein kinase pathway. However, it is unknown how the potassium channel-repressed calcium signaling is translated into the induction of the AWC subtype. Here, we identify a detailed working mechanism of how the homeodomain-like transcription factor NSY-7, previously described as a repressor in the maintenance of AWC asymmetry, couples SLO BK potassium channels to transactivation of expression for the induction of the AWC subtype through the identification of a unique (transportin 1) allele. loss-of-function mutants are not viable; however, we identify a viable allele from an unbiased forward genetic screen that reveals a specific role of in AWC olfactory neuron asymmetry. IMB-2 specifically drives nuclear import of NSY-7 within AWC neurons to transactivate the expression of the high mobility group (HMG)-box transcription factor SOX-2 for the specification of the AWC subtype. This study provides mechanistic insight into how NSY-7 couples SLO BK potassium channels to transactivation of expression for the induction of the AWC subtype. Our findings also provide structure-function insight into a conserved amino acid residue of transportins in brain development and suggest its dysfunction may lead to human neurological disorders.
10.1073/pnas.1908168116
An EP2 Agonist Facilitates NMDA-Induced Outward Currents and Inhibits Dendritic Beading through Activation of BK Channels in Mouse Cortical Neurons.
Hayashi Yoshinori,Morinaga Saori,Liu Xia,Zhang Jing,Wu Zhou,Yokoyama Takeshi,Nakanishi Hiroshi
Mediators of inflammation
Prostaglandin E2 (PGE2), a major metabolite of arachidonic acid produced by cyclooxygenase pathways, exerts its bioactive responses by activating four E-prostanoid receptor subtypes, EP1, EP2, EP3, and EP4. PGE2 enables modulating N-methyl-D-aspartate (NMDA) receptor-mediated responses. However, the effect of E-prostanoid receptor agonists on large-conductance Ca(2+)-activated K(+) (BK) channels, which are functionally coupled with NMDA receptors, remains unclear. Here, we showed that EP2 receptor-mediated signaling pathways increased NMDA-induced outward currents (I NMDA-OUT), which are associated with the BK channel activation. Patch-clamp recordings from the acutely dissociated mouse cortical neurons revealed that an EP2 receptor agonist activated I NMDA-OUT, whereas an EP3 receptor agonist reduced it. Agonists of EP1 or EP4 receptors showed no significant effects on I NMDA-OUT. A direct perfusion of 3,5'-cyclic adenosine monophosphate (cAMP) through the patch pipette facilitated I NMDA-OUT, which was abolished by the presence of protein kinase A (PKA) inhibitor. Furthermore, facilitation of I NMDA-OUT caused by an EP2 receptor agonist was significantly suppressed by PKA inhibitor. Finally, the activation of BK channels through EP2 receptors facilitated the recovery phase of NMDA-induced dendritic beading in the primary cultured cortical neurons. These results suggest that a direct activation of BK channels by EP2 receptor-mediated signaling pathways plays neuroprotective roles in cortical neurons.
10.1155/2016/5079597
Critical role of large-conductance calcium- and voltage-activated potassium channels in leptin-induced neuroprotection of N-methyl-d-aspartate-exposed cortical neurons.
Mancini Maria,Soldovieri Maria Virginia,Gessner Guido,Wissuwa Bianka,Barrese Vincenzo,Boscia Francesca,Secondo Agnese,Miceli Francesco,Franco Cristina,Ambrosino Paolo,Canzoniero Lorella Maria Teresa,Bauer Michael,Hoshi Toshinori,Heinemann Stefan H,Taglialatela Maurizio
Pharmacological research
In the present study, the neuroprotective effects of the adipokine leptin, and the molecular mechanism involved, have been studied in rat and mice cortical neurons exposed to N-methyl-d-aspartate (NMDA) in vitro. In rat cortical neurons, leptin elicited neuroprotective effects against NMDA-induced cell death, which were concentration-dependent (10-100 ng/ml) and largest when the adipokine was preincubated for 2h before the neurotoxic stimulus. In both rat and mouse cortical neurons, leptin-induced neuroprotection was fully antagonized by paxilline (Pax, 0.01-1 μM) and iberiotoxin (Ibtx, 1-100 nM), with EC50s of 38 ± 10 nM and 5 ± 2 nM for Pax and Ibtx, respectively, close to those reported for Pax- and Ibtx-induced Ca(2+)- and voltage-activated K(+) channels (Slo1 BK channels) blockade; the BK channel opener NS1619 (1-30 μM) induced a concentration-dependent protection against NMDA-induced excitotoxicity. Moreover, cortical neurons from mice lacking one or both alleles coding for Slo1 BK channel pore-forming subunits were insensitive to leptin-induced neuroprotection. Finally, leptin exposure dose-dependently (10-100 ng/ml) increased intracellular Ca(2+) levels in rat cortical neurons. In conclusion, our results suggest that Slo1 BK channel activation following increases in intracellular Ca(2+) levels is a critical step for leptin-induced neuroprotection in NMDA-exposed cortical neurons in vitro, thus highlighting leptin-based intervention via BK channel activation as a potential strategy to counteract neurodegenerative diseases.
10.1016/j.phrs.2014.06.010