Hui Fu

Existence and distinction of acid-evoked currents in rat astrocytes.

Astrocytes are vital structures that support and/or protect neighboring neurons from pathology. Although it is generally accepted that glutamate receptors mediate most astrocyte effects, acid‐evoked currents have recently attracted attention for their role in this regard. Here, we identified the existence and characteristics of acid‐sensing ion channels (ASICs) and the transient receptor potential vanilloid type 1 (TRPV1) in astrocytes. There were two types of currents recorded under the application of acidic solution (pH 6.0) in cultured rat astrocytes. Transient currents were exhibited by 10% of the astrocytes, and sustained currents were exhibited by the other 90%, consistent with the features of ASIC and TRPV1 currents, respectively. Western blotting and immunofluorescence confirmed the expression of ASIC1, ASIC2a, ASIC3, and TRPV1 in cultured and in situ astrocytes. Unlike the ASICs expressed in neurons, which were mainly distributed in the cell membrane/cytoplasm, most of the ASICs in astrocytes were expressed in the nucleus. TRPV1 was more permeable to Na+ in cultured astrocytes, which differed from the typical neuronal TRPV1 that was mainly permeable to Ca2+. This study demonstrates that there are two kinds of acid‐evoked currents in rat astrocytes, which may provide a new understanding about the functions of ligand‐gated ion channels in astrocytes.

Reversal of aging-associated hippocampal synaptic plasticity deficits by reductants via regulation of thiol redox and NMDA receptor function

Deficits in learning and memory accompanied by age‐related neurodegenerative diseases are closely related to the impairment of synaptic plasticity. In this study, we investigated the role of thiol redox status in the modulation of the N‐methyl‐d‐aspartate receptor (NMDAR)‐dependent long‐term potentiation (LTP) in CA1 areas of hippocampal slices. Our results demonstrated that the impaired LTP induced by aging could be reversed by acute administration of reductants that can regulate thiol redox status directly, such as dithiothreitol or β‐mercaptoethanol, but not by classical anti‐oxidants such as vitamin C or trolox. This repair was mediated by the recruitment of aging‐related deficits in NMDAR function induced by these reductants and was mimicked by glutathione, which can restore the age‐associated alterations in endogenous thiol redox status. Moreover, antioxidant prevented but failed to reverse H2O2‐induced impairment of NMDAR‐mediated synaptic plasticity. These results indicate that the restoring of thiol redox status may be a more effective strategy than the scavenging of oxidants in the treatment of pre‐existing oxidative injury in learning and memory.

Hyperoside protects cortical neurons from oxygen-glucose deprivation-reperfusion induced injury via nitric oxide signal pathway.

Hyperoside is a flavonoid compound and widely used in clinic to relieve pain and improve cardiovascular functions. However, the effects of hyperoside on ischemic neurons and the molecular mechanisms remain unclear. Here, we used an in vitro ischemic model of oxygen-glucose deprivation followed by reperfusion (OGD-R) to investigate the protective effects of hyperoside on ischemic neuron injury and further explore the possible related mechanisms. Our results demonstrated that hyperoside protected cultured cortical neurons from OGD-R injury, it also relieved glutamate-induced neuronal injury and NMDA-induced [Ca(2+)](i) elevation. As for the mechanisms, hyperoside firstly attenuated the phosphorylation of CaMKII caused by OGD-R lesions. Meanwhile, hyperoside lessened iNOS expression induced by OGD-R via inhibition of NF-κB activation. Furthermore, ameliorating of ERK, JNK and Bcl-2 family-related apoptotic signaling pathways were also involved in the neuroprotection of hyperoside. Taken together, these studies revealed that hyperoside had protective effects on neuronal ischemia-reperfusion impairment, which was related to the regulation of nitric oxide signaling pathway.

The flavonoid baicalein promotes NMDA receptor-dependent long-term potentiation and enhances memory.

BACKGROUND AND PURPOSE There is growing interest in the physiological functions of flavonoids, especially in their effects on cognitive function and on neurodegenerative diseases. The aim of the current investigation was to evaluate the role of the flavonoid baicalein in long‐term potentiation (LTP) in the hippocampal CA1 region and cognitive behavioural performance.

Disruption of PICK1 attenuates the function of ASICs and PKC regulation of ASICs

Acid-sensing ion channels (ASICs) extensively exist in both central and peripheral neuronal systems and contribute to many physiological and pathological processes. The protein that interacts with C kinase 1 (PICK1) was cloned as one of the proteins interacting with protein kinase C (PKC) and colocalized with ASIC1 and ASIC2. Here, we used PICK1 knockout (PICK1-KO) C57/BL6 mice together with the whole cell patch clamp, calcium imaging, RT-PCR, Western blot, and immunocytochemistry techniques to explore the possible change in ASICs and the regulatory effects of PKC on ASICs. The results showed that PICK1 played a key role in regulation of ASIC functions. In PICK1-KO mouse cortical neurons, both the amplitude of ASIC currents and elevation of [Ca(2+)](i) mediated by acid were decreased, which were attributable to the decreased expression of ASIC1a and ASIC2a proteins in the plasma membrane. PKC, a partner protein of PICK1, regulated ASIC functions via PICK1. The agonist and antagonist of PKC only altered ASIC currents and acid-induced increase in [Ca(2+)](i) in wild-type, but not in KO mice. In conclusion, our data provided the direct evidence from PICK1-KO mice that a novel target protein, PICK1, would regulate ASIC function and membrane expression in the brain. In addition, PICK1 played the bridge role between PKC and ASICs.

AGE-RELATED SYNAPTIC CHANGES IN THE CA1 STRATUM RADIATUM AND SPATIAL LEARNING IMPAIRMENT IN RATS

1 Age‐related impairments in hippocampus‐dependent spatial learning and memory are not associated with a loss of neurons, but may be related to synaptic changes. In the present study, we analysed the behavioural performance of adult, middle‐aged and old Wistar rats using the Morris water maze, as well as the structure of synapses and the expression of autophosphorylated Ca2+/calmodulin‐dependent protein kinase II at threonine 286 (pThr286‐αCaMKII), a key post‐synaptic protein in the CA1 stratum radiatum, in the same rats. 2 Old Wistar rats showed significant cognitive deficits. Synaptic density, the area of post‐synaptic densities and the total number of synapses in the CA1 stratum radiatum of old rats were significantly decreased compared with adult rats. The decrease in autophosphorylated pThr286‐αCaMKII was age dependent. 3 These findings reveal that age‐related impairments in learning and memory are associated with synaptic atrophy. The decreased expression of pThr286‐CaMKII may result in reduced synaptic function with ageing.

Activation of Phosphatidylinositol-Linked Novel D1 Dopamine Receptors Inhibits High-Voltage-Activated Ca2+ Currents in Primary Cultured Striatal Neurons

Recent evidences indicate the existence of a putative novel phosphatidylinositol (PI)-linked D(1) dopamine receptor that mediates excellent anti-Parkinsonian but less severe dyskinesia action. To further understand the basic physiological function of this receptor in brain, the effects of a PI-linked D(1) dopamine receptor-selective agonist 6-chloro-7,8-dihydroxy-3-methyl-1-(3-methylphenyl)-2,3,4,5-tetrahydro-1H-3-benzazepine (SKF83959) on high-voltage activated (HVA) Ca(2+) currents in primary cultured striatal neurons were investigated by whole cell patch-clamp technique. The results indicated that stimulation by SKF83959 induced an inhibition of HVA Ca(2+) currents in a dose-dependent manner in substance-P (SP)-immunoreactive striatal neurons. Application of D(1) receptor, but not D(2), alpha(1) adrenergic, 5-HT receptor, or cholinoceptor antagonist prevented SKF83959-induced reduction, indicating that a D(1) receptor-mediated event assumed via PI-linked D(1) receptor. SKF83959-induced inhibitory modulation was mediated by activation of phospholipase C (PLC), mobilization of intracellular Ca(2+) stores and activation of calcineurin. Furthermore, the inhibitory effects were attenuated significantly by the L-type calcium channel antagonist nifedipine, suggesting that L-type calcium channels involved in the regulation induced by SKF83959. These findings may help to further understand the functional role of the PI-linked dopamine receptor in brain.

Acid-sensing ion channels in trigeminal ganglion neurons innervating the orofacial region contribute to orofacial inflammatory pain

Orofacial pain is a common clinical symptom that is accompanied by tooth pain, migraine and gingivitis. Accumulating evidence suggests that acid‐sensing ion channels (ASICs), especially ASIC3, can profoundly affect the physiological properties of nociception in peripheral sensory neurons. The aim of this study is to examine the contribution of ASICs in trigeminal ganglion (TG) neurons to orofacial inflammatory pain. A Western blot (WB), immunofluorescence assay of labelled trigeminal ganglion neurons, orofacial formalin test, cell preparation and electrophysiological experiments are performed. This study demonstrated that ASIC1, ASIC2a and ASIC3 are highly expressed in TG neurons innervating the orofacial region of rats. The amplitude of ASIC currents in these neurons increased 119.72% (for ASIC1‐like current) and 230.59% (for ASIC3‐like current) in the formalin‐induced orofacial inflammatory pain model. In addition, WB and immunofluorescence assay demonstrated a significantly augmented expression of ASICs in orofacial TG neurons during orofacial inflammation compared with the control group. The relative protein density of ASIC1, ASIC2a and ASIC3 also increased 58.82 ± 8.92%, 45.30 ± 11.42% and 55.32 ± 14.71%, respectively, compared with the control group. Furthermore, pharmacological blockade of ASICs and genetic deletion of ASIC1 attenuated the inflammation response. These findings indicate that peripheral inflammation can induce the upregulation of ASICs in TG neurons, causing orofacial inflammatory pain. Additionally, the specific inhibitor of ASICs may have a significant analgesic effect on orofacial inflammatory pain.

Aging-related alterations in the expression and distribution of GluR2 and PICK1 in the rat hippocampus

Deficit in synaptic plasticity in the hippocampus frequently occurs during normal aging. Although the protein level and calcium permeability of AMPARs alter with aging, the alteration of AMPARs and their regulatory proteins during aging are far from understanding. Dynamics of GluR2 subunit are dependent on the function of protein interacting with Cα kinase 1 (PICK1), PKCα and calcineurin (CaN). Here, we firstly show that the expression of PICK1 and CaN B decreased significantly in the hippocampus of old rats compared to that of young and adult rats. The decrease was accompanied by a reduction of GluR2 and PKCα and an increase in CaN A. Next, we found that in young and adult rats, the distribution of PICK1 and GluR2 diffused in the cytoplasm of hippocampal neurons, but closely around perinuclear in the hippocampal neurons of old rats. These results suggest that the expression of GluR2, PICK1, PKCα and CaN B significant decreased in the hippocampus and these alterations may lead to altered distribution of GluR2 and PICK1 during aging.