Endoplasmic Reticulum Protein 72 Regulates Integrin Mac-1 Activity to Influence Neutrophil Recruitment.

BACKGROUND: Integrins mediate the adhesion, crawling, and migration of neutrophils during vascular inflammation. Thiol exchange is important in the regulation of integrin functions. ERp72 (endoplasmic reticulum-resident protein 72) is a member of the thiol isomerase family responsible for the catalysis of disulfide rearrangement. However, the role of ERp72 in the regulation of Mac-1 (integrin αMß2) on neutrophils remains elusive. METHODS: Intravital microscopy of the cremaster microcirculation was performed to determine in vivo neutrophil movement. Static adhesion, flow chamber, and flow cytometry were used to evaluate in vitro integrin functions. Confocal fluorescent microscopy and coimmunoprecipitation were utilized to characterize the interactions between ERp72 and Mac-1 on neutrophil surface. Cell-impermeable probes and mass spectrometry were used to label reactive thiols and identify target disulfide bonds during redox exchange. Biomembrane force probe was performed to quantitatively measure the binding affinity of Mac-1. A murine model of acute lung injury induced by lipopolysaccharide was utilized to evaluate neutrophil-associated vasculopathy. RESULTS: ERp72-deficient neutrophils exhibited increased rolling but decreased adhesion/crawling on inflamed venules in vivo and defective static adhesion in vitro. The defect was due to defective activation of integrin Mac-1 but not LFA-1 (lymphocyte function-associated antigen-1) using blocking or epitope-specific antibodies. ERp72 interacted with Mac-1 in lipid rafts on neutrophil surface leading to the reduction of the C654-C711 disulfide bond in the αM subunit that is critical for Mac-1 activation. Recombinant ERp72, via its catalytic motifs, increased the binding affinity of Mac-1 with ICAM-1 (intercellular adhesion molecule-1) and rescued the defective adhesion of ERp72-deficient neutrophils both in vitro and in vivo. Deletion of ERp72 in the bone marrow inhibited neutrophil infiltration, ameliorated tissue damage, and increased survival during murine acute lung injury. CONCLUSIONS: Extracellular ERp72 regulates integrin Mac-1 activity by catalyzing disulfide rearrangement on the αM subunit and may be a novel target for the treatment of neutrophil-associated vasculopathy.

Piericones A and B as Potent Antithrombotics: Nanomolar Noncompetitive Protein Disulfide Isomerase Inhibitors with an Unexpected Chemical Architecture.

Extracellular protein disulfide isomerase (PDI) is a promising target for thrombotic-related diseases. Four potent PDI inhibitors with unprecedented chemical architectures, piericones A-D (1-4), were isolated from Pieris japonica. Their structures were elucidated by spectroscopic data analysis, chemical methods, quantum 13C nuclear magnetic resonance DP4+ and electronic circular dichroism calculations, and single-crystal X-ray diffraction analysis. Piericones A (1) and B (2) were nanomolar noncompetitive PDI inhibitors possessing an unprecedented 3,6,10,15-tetraoxatetracyclo[7.6.0.04,9.01,12]pentadecane motif with nine contiguous stereogenic centers. Their biosynthetic pathways were proposed to include a key intermolecular aldol reaction and an intramolecular 1,2-migration reaction. Piericone A (1) significantly inhibited in vitro platelet aggregation and fibrin formation and in vivo thrombus formation via the inhibition of extracellular PDI without increasing the bleeding risk. The molecular docking and dynamics simulation of 1 and 2 provided a novel structure basis to develop PDI inhibitors as potent antithrombotics.

Anti-thrombotic effects mediated by dihydromyricetin involve both platelet inhibition and endothelial protection.

Classical antithrombotics and antiplatelets are associated with high frequencies of bleeding complications or treatment failure when used as single agents. The platelet-independent fibrin generation by activated endothelium highlights the importance of vascular protection in addition to platelet inhibition in thrombosis prevention. Dihydromyricetin (DHM), the most abundant flavonoid in Ampelopsis grossedentata, has unique vasoprotective effects. This study aims to characterize the antithrombotic potential of DHM. The effects of DHM on the activation of platelets and endothelial cells were evaluated in vitro. Calcium mobilization and activation of mitogen-activated protein kinases (MAPKs) were examined as the potential targets of DHM based on molecular docking analysis. The in vivo effects of DHM were determined in FeCl3-injured carotid arteries and laser-injured cremasteric arterioles. The results showed that DHM suppressed a range of platelet responses including aggregation, secretion, adhesion, spreading and integrin activation, and inhibited exocytosis, phosphatidylserine exposure and tissue factor expression in activated endothelial cells. Mechanistically, DHM attenuated thrombin-induced calcium mobilization and phosphorylation of ERK1/2 and p38 both in platelets and endothelial cells. Intravenous treatment with DHM delayed FeCl3-induced carotid arterial thrombosis. Furthermore, DHM treatment inhibited both platelet accumulation and fibrin generation in the presence or absence of eptifibatide in the laser injury-induced thrombosis model, without prolonging ex vivo plasma coagulation or tail bleeding time. DHM represents a novel antithrombotic agent whose effects involve both inhibition of platelet activation and reduction of fibrin generation as a result of endothelial protection.

Pharmacologic activation of cholinergic alpha7 nicotinic receptors mitigates depressive-like behavior in a mouse model of chronic stress.

BACKGROUND: It has been shown that chronic stress-induced depression is associated with exaggerated inflammatory response in the brain. Alpha7 nicotinic acetylcholine receptors (α7nAChRs) regulate the cholinergic anti-inflammatory pathway, but the role of cholinergic signaling and α7nAChR in chronic stress has not yet been examined. METHODS: In this study, we used a well-documented model of depression in which mice were exposed to 6 h of restraint stress for 21 consecutive days. Components of cholinergic signaling and TLR4 signaling were analyzed in the hippocampus. The main targets of neuroinflammation and neuronal damage were also evaluated after a series of tests for depression-like behavior. RESULTS: Chronic restraint stress (CRS) induced alterations in components of central cholinergic signaling in hippocampus, including increases in choline acetyltransferase protein expression and decreases in nuclear STAT3 signaling. CRS also increased TLR4 signaling activity, interleukin-1ß, and tumor necrosis factor-α expression, microglial activation, and neuronal morphologic changes. Cholinergic stimulation with the α7nAChR agonist DMXBA significantly alleviated CRS-induced depressive-like behavior, neuroinflammation, and neuronal damage, but these effects were abolished by the selective α7nAChR antagonist α-bungarotoxin. Furthermore, activation of α7nAChRs restored the central cholinergic signaling function, inhibited TLR4-mediated inflammatory signaling and microglial activity, and increased the number of regulatory T cells in the hippocampus. CONCLUSIONS: These findings provide evidence that α7nAChR activation mitigates CRS-induced neuroinflammation and cell death, suggesting that α7nAChRs could be a new therapeutic target for the prevention and treatment of depression.

Long-lasting spatial learning and memory impairments caused by chronic cerebral hypoperfusion associate with a dynamic change of HCN1/HCN2 expression in hippocampal CA1 region.

Chronic cerebral hypoperfusion (CCH) causes learning and memory impairments and increases the risk of Alzheimer disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the mechanisms underlying the disease process remained unclear particularly in a temporal manner. We performed permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO) to induce CCH. To determine whether hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are altered at different stages of cognitive impairment caused by CCH, adult male SD rats were randomly distributed into sham-operated 4, 8 and 12weeks group, 2VO 4, 8 and 12weeks group. Learning and memory performance were evaluated with Morris water maze (MWM) and long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Expression of NeuN, HCN1 and HCN2 in hippocampal CA1, DG and CA3 areas was quantified by immunohistochemistry and western blotting. Our data showed that CCH induced a remarkable spatial learning and memory deficits in rats of 2VO 4, 8, and 12weeks group although neuronal loss only occurred after 4weeks of 2VO surgery in CA1. In addition, a significant reduction of HCN1 surface expression in CA1 was observed in the group that suffered 4weeks ischemia but neither 8 nor 12weeks. However, HCN2 surface expression in CA1 increased throughout the ischemia time-scales (4, 8 and 12w). Our findings indicate spatial learning and memory deficits in the CCH model are associated with disturbed HCN1 and HCN2 surface expression in hippocampal CA1. The altered patterns of both HCN1 and HCN2 surface expression may be implicated in the early stage (4w) of spatial learning and memory impairments; and the stable and long-lasting impairments of spatial learning and memory may partially attribute to the up-regulated HCN2 surface expression.

Low dose ZD7288 attenuates the ischemia/reperfusion-induced impairment of long-term potentiation induction at hippocampal Schaffer collateral-CA1 synapses.

Focal cerebral ischemia can impair the induction of activity-dependent long-term potentiation (LTP) in the hippocampus. This impairment of hippocampal synaptic plasticity can be caused by excitotoxicity and subsequent perturbation of hippocampal LTP-relevant transmitter systems, which include NR2B and PSD-95. It has been suggested that hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels may play an important role in the control of membrane excitability and rhythmic neuronal activity. Our previous study has indicated that the selective HCN channel blocker ZD7288 can produce a dose-dependent inhibition of the induction of LTP at the Schaffer collateral-CA1 synapse of hippocampus by reducing the amount of glutamate released. It has also been demonstrated that ZD7288 can protect against neuronal injury caused by oxygen glucose deprivation. In the present study, we investigated the effect of ZD7288 on the induction of activity-dependent LTP and the expression of NR2B and PSD-95 after focal cerebral ischemia/reperfusion injury. The results showed that the induction of LTP was significantly impaired and the levels of NR2B and PSD-95 mRNA and protein were markedly decreased in the CA1 region of hippocampus following focal cerebral ischemia/reperfusion injury. Administration of low dose ZD7288 (0.25 µg) at 30 min and 3 h after the onset of ischemia attenuated the impairment of LTP induction and alleviated the NR2B and PSD-95 mRNA and protein down-regulation commonly induced by cerebral ischemia/reperfusion injury. These results suggest that low dose ZD7288 can ameliorate the ischemia/reperfusion-induced impairment of synaptic plasticity in the hippocampal CA1 region.

Protein disulfide isomerase cleaves allosteric disulfides in histidine-rich glycoprotein to regulate thrombosis.

The essence of difference between hemostasis and thrombosis is that the clotting reaction is a highly fine-tuned process. Vascular protein disulfide isomerase (PDI) represents a critical mechanism regulating the functions of hemostatic proteins. Herein we show that histidine-rich glycoprotein (HRG) is a substrate of PDI. Reduction of HRG by PDI enhances the procoagulant and anticoagulant activities of HRG by neutralization of endothelial heparan sulfate (HS) and inhibition of factor XII (FXIIa) activity, respectively. Murine HRG deficiency (Hrg-/-) leads to delayed onset but enhanced formation of thrombus compared to WT. However, in the combined FXII deficiency (F12-/-) and HRG deficiency (by siRNA or Hrg-/-), there is further thrombosis reduction compared to F12-/- alone, confirming HRG's procoagulant activity independent of FXIIa. Mutation of target disulfides of PDI leads to a gain-of-function mutant of HRG that promotes its activities during coagulation. Thus, PDI-HRG pathway fine-tunes thrombosis by promoting its rapid initiation via neutralization of HS and preventing excessive propagation via inhibition of FXIIa.

Clonidine suppresses the induction of long-term potentiation by inhibiting HCN channels at the Schaffer collateral-CA1 synapse in anesthetized adult rats.

Activation of alpha2-adrenoceptors inhibits long-term potentiation and long-term depression in many brain regions. However, effectiveness and mechanism of alpha2-adrenoceptors for synaptic plasticity at the Schaffer collateral-CA1 synapses in rat in vivo is unclear. In the present study, we investigated the effects of alpha2-adrenoceptors agonist clonidine on high-frequency stimulation (HFS)-induced long-term potentiation (LTP) and paired-pulse facilitation (PPF) at the Schaffer collateral-CA1 synapse of rat hippocampus in vivo. Clonidine (0.05, 0.1 mg/kg, ip) inhibited synaptic plasticity in a dose-dependent manner, accompanying with the decreasing of aortic pressure and heart rate (HR) in anesthetized rats. Clonidine (1.25, 2.5 µg/kg, icv, 10 min before HFS) also dose-dependently inhibited synaptic plasticity, which had no remarkable effect on HR and aortic pressure. But, 20 min after HFS, administration of clonidine (2.5 µg/kg) had no effect on LTP. The inhibitory effect of clonidine (2.5 µg/kg) on LTP was completely reversed by yohimbine (18 µg/kg, icv) and ZD7288 (5 µg/kg, icv). Moreover, the inhibition was accompanied by a significant increase of the normalized PPF ratio. Furthermore, clonidine at 1 and 10 µM significantly decreased glutamate (Glu) content in the culture supernatants of hippocampal neurons, and yohimbine at 1 and 10 µM had no effect on Glu release, while it could reverse the inhibition of clonidine (1 and 10 µM) on Glu release. In conclusion, clonidine can suppress the induction of LTP at the Schaffer collateral-CA1 synapse, and the possible mechanism is that activation of presynaptic alpha2-adrenoceptors reduces the Glu release by inhibiting HCN channels.

Asebogenin suppresses thrombus formation via inhibition of Syk phosphorylation.

BACKGROUND AND PURPOSE: Thrombosis is a major cause of morbidity and mortality worldwide. Platelet activation by exposed collagen through glycoprotein VI (GPVI) and formation of neutrophil extracellular traps (NETs) are critical pathogenic factors for arterial and venous thrombosis. Both events are regulated by spleen tyrosine kinase (Syk)-mediated signalling events. Asebogenin is a dihydrochalcone whose pharmacological effects remain largely unknown. This study aims to investigate the antithrombotic effects of asebogenin and the underlying molecular mechanisms. EXPERIMENTAL APPROACH: Platelet aggregation was assessed using an aggregometer. Platelet P-selectin exposure, integrin activation and calcium mobilization were determined by flow cytometry. NETs formation was assessed by SYTOX Green staining and immunohistochemistry. Quantitative phosphoproteomics, microscale thermophoresis, in vitro kinase assay and molecular docking combined with dynamics simulation were performed to characterize the targets of asebogenin. The in vivo effects of asebogenin on arterial thrombosis were investigated using FeCl3 -induced and laser-induced injury models, whereas those of venous thrombosis were induced by stenosis of the inferior vena cava. KEY RESULTS: Asebogenin inhibited a series of GPVI-induced platelet responses and suppressed NETs formation induced by proinflammatory stimuli. Mechanistically, asebogenin directly interfered with the phosphorylation of Syk at Tyr525/526, which is important for its activation. Further, asebogenin suppressed arterial thrombosis demonstrated by decreased platelet accumulation and fibrin generation and attenuated venous thrombosis determined by reduced neutrophil accumulation and NETs formation, without increasing bleeding risk. CONCLUSION AND IMPLICATIONS: Asebogenin exhibits potent antithrombotic effects by targeting Syk and is a potential lead compound for the development of efficient and safe antithrombotic agents.

Toll-like receptor 3 agonist Poly I:C protects against simulated cerebral ischemia in vitro and in vivo.

AIM: To examine the neuroprotective effects of the Toll-like receptor 3 (TLR3) agonist Poly I:C in acute ischemic models in vitro and in vivo. METHODS: Primary astrocyte cultures subjected to oxygen-glucose deprivation (OGD) were used as an in vitro simulated ischemic model. Poly I:C was administrated 2 h before OGD. Cell toxicity was measured using MTT assay and LDH leakage assay. The levels of TNFα, IL-6 and interferon-ß (IFNß) in the media were measured using ELISA. Toll/interleukin receptor domain-containing adaptor-inducing IFNß (TRIF) protein levels were detected using Western blot analysis. A mouse middle cerebral artery occlusion (MCAO) model was u sed for in vivo study. The animals were administered Poly I:C (0.3 mg/kg, im) 2 h before MCAO, and examined with neurological deficit scoring and TTC staining. The levels of TNFα and IL-6 in ischemic brain were measured using ELISA. RESULTS: Pretreatment with Poly I:C (10 and 20 µg/mL) markedly attenuated OGD-induced astrocyte injury, and significantly raised the cell viability and reduced the LDH leakage. Poly I:C significantly upregulated TRIF expression accompanied by increased downstream IFNß production. Moreover, Poly I:C significantly suppressed the pro-inflammatory cytokines TNFα and IL-6 production. In mice subjected to MCAO, administration of Poly I:C significantly attenuated the neurological deficits, reduced infarction volume, and suppressed the increased levels of TNFα and IL-6 in the ischemic striatum and cortex. CONCLUSION: Poly I:C pretreatment exerts neuroprotective and anti-inflammatory effects in the simulated cerebral ischemia models, and the neuroprotection is at least in part due to the activation of the TLR3-TRIF pathway.

Pathophysiological roles of cell surface and extracellular protein disulfide isomerase and their molecular mechanisms.

Protein disulfide isomerase (PDI) is the prototypic member of the thiol isomerase family that catalyses disulfide bond rearrangement. Initially identified in the endoplasmic reticulum as folding catalysts, PDI and other members in its family have also been widely reported to reside on the cell surface and in the extracellular matrix. Although how PDI is exported and retained on the cell surface remains a subject of debate, this unique pool of PDI is developing into an important mechanism underlying the redox regulation of protein sulfhydryls that are critical for the cellular activities under various disease conditions. This review aims to provide an overview of the pathophysiological roles of surface and extracellular PDI and their underlying molecular mechanisms. Understanding the involvement of extracellular PDI in these diseases will advance our knowledge in the molecular aetiology to facilitate the development of novel pharmacological strategies by specifically targeting PDI in extracellular compartments.

Guattegaumerine protects primary cultured cortical neurons against oxidative stress injury induced by hydrogen peroxide concomitant with serum deprivation.

Guattegaumerine is a natural product with characteristics of being lipophilic and reaching high concentration in the brain, but its function in the central nervous system has not yet been observed. This study was designed to evaluate the neuroprotective effects of guattegaumerine on rat primary cultured cortical neurons. Following a 24-h exposure of the cells to combined serum-starvation and hydrogen peroxide, a significant augment in neuron damage as determined by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) release were observed. Preincubation of guattegaumerine dramatically improved the cell viability and inhibited LDH release. Preincubation of guattegaumerine also dramatically inhibited malondialhehyde (MDA) production and elevated the decreased total antioxidative capacity in cells caused by the combined injury. Results of flow cytometry and immunohistochemistry showed that pre-addition of guattegaumerine interrupted the apoptosis of the neurons, reversed the up regulation of the pro-apoptotic gene (Bax) and the down regulation of the anti-apoptotic gene (Bcl-2). Furthermore, guattegaumerine suppressed the increase of intracellular calcium ([Ca(2+)](i)) stimulated by either H(2)O(2) or KCl in Ca(2+)-containing extracellular solutions, and high concentration of 2.5 microM guattegaumerine also suppressed the increase of [Ca(2+)](i) induced by H(2)O(2) in Ca(2+)-free solution. These observations suggested that guattegaumerine may possess potential protection against oxidative stress injury, which might be beneficial for neurons.

Probing the binding sites and mechanisms of action of two human ether-a-go-go-related gene channel activators, 1,3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea (NS1643) and 2-[2-(3,4-dichloro-phenyl)-2,3-dihydro-1H-isoindol-5-ylamino]-nicotinic acid (PD307243).

We studied the mechanisms and sites of activator actions of 2-[2-(3,4-dichloro-phenyl)-2,3-dihydro-1H-isoindol-5-ylamino]-nicotinic acid [PD307243 (PD)] and 1,3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea [NS1643 (NS)] on the human ether-a-go-go-related gene (hERG) channel expressed in oocytes and COS-7 cells. PD and NS affected hERG in a concentration-dependent manner, reaching a maximal increase in current amplitude by 100% and > or = 300% (1-s test pulse to 0 mV), with apparent K(d) values of 3 and 20 microM, respectively. Both drugs slowed hERG inactivation. NS additionally shifted the activation curve in the negative direction, accelerated activation, and slowed deactivation. Kinetic model simulations suggested that the activator effects of PD and NS could be largely accounted for by their effects on the hERG gating kinetics. Both drugs worked from outside the cell membrane but their binding sites seemed to be distinctly different. Perturbing the conformation of outer vestibule/external pore entrance (by cysteine substitution at high-impact positions or cysteine side chain modification at intermediate-impact positions) prevented the activator effect of NS but not that of PD. Furthermore, the peptide toxin BeKm-1, which bound to the outer mouth of the hERG channel, suppressed NS effect but potentiated PD effect. We propose that NS is a "gating-modifier": it binds to the outer vestibule/pore entrance of hERG and increases current amplitudes by promoting channel activation while retarding inactivation. The activator effect of PD was prevented by external quaternary ammonium cations or dofetilide, which approached the hERG selectivity filter from opposite sides of the membrane and depleted K(+) ions in the selectivity filter. We suggest that PD may work as a "pore-modifier" of the hERG channel.

Enhanced activity of GABA receptors inhibits glutamate release induced by focal cerebral ischemia in rat striatum.

Cerebral ischemia causes an excess release of glutamate, which can injure neurons. The striatum is one of the important regions vulnerable to hypoxia and ischemia. Using push-pull perfusion technique, we investigated the regulatory role of gamma-aminobutyric acid (GABA) and its receptors in modifying the amount of glutamate in rat striatum with ischemia. Perfusion with exogenous GABA (1 mM) inhibited cerebral ischemia-induced glutamate release by as much as 47%. We further characterized relative roles of subtype receptors of GABA on glutamate release by using pharmacological tools. While baclofen (500 microM), a GABA(B) receptor agonist, suppressed ischemia-induced glutamate release by 52%, GABA(B) receptor antagonist saclofen (500 microM) failed to produce a significant increase of glutamate release. The GABA(A) receptor agonist muscimol (500 microM) also reduced by 38% the release of glutamate induced by cerebral ischemia but the GABA(A) receptor antagonist bicuculline (500 microM) had very little effect. The present study demonstrates that the excessive release of glutamate or the overly activated glutamate receptor, triggered by cerebral ischemia, can be down-regulated by exogenous GABA or by increased activity of GABA receptors, especially the presynaptic GABA(B) receptors, which might be one of the important mechanisms to protect against striatum neuronal damage from over stimulation by excessive glutamate during ischemia.

ZD7288 inhibits the synaptic transmission in the pathway from perforant pathway fibers to CA3 region in rat hippocampus.

AIM: To study the effect of ZD7288 on synaptic transmission in the pathway from perforant pathway (PP) fibers to CA3 region in rat hippocampus. METHODS: The extracellular recording technique in vivo was used to record the CA3 region field potentials. High-performance liquid chromatography (HPLC) with fluorescence detection was applied to measure the content of amino acids in hippocampal tissues. The effect of ZD7288 and CsCl on the amplitudes of population spike (PS) in CA3 region evoked by stimulation (0.5 Hz) of the perforant pathway (PP) fibers, and the content of amino acids in hippocampal tissue were observed. RESULTS: Microinjection of ZD7288 (20, 100 and 200 nmol) and CsCl (1, 5 and 10 micromol) into CA3 region decreased the population spike (PS) amplitudes in a dose-dependent manner. The inhibitory effects appeared at 5 min after microinjection and lasted at least 90 min. In those rats treated with ZD7288 (100 nmol), the contents of glutamate, aspartate, glycine and GABA decreased significantly as compared to those of saline control (all P < 0.01, except P < 0.05 for that of glycine). A similar decrease in the contents of amino acids was observed when the rats were microinjected with CsCl (5 micromol). CONCLUSION; ZD7288 could obviously inhibit synaptic transmission in the pathway from PP fibers to CA3 region in rat hippocampus, and this action of ZD7288 may be associated with altered contents of amino acids.

[Effect of kang naoxueshuan tablet on protecting ischemic brain injury in rats].

OBJECTIVE: To observe the protective effect of Kang Naoxueshuan Tablet (KNT) on ischemic brain injury in rats, and explore its possible mechanism. METHODS: Rats were administrated with KNT twice per day for successive 14 days. Rat model of acute focal cerebral ischemia was established by middle cerebral artery occlusion (MCAO) with a nylon suture inserted through the right internal carotid artery to occlude the beginning of middle cerebral artery. After 24 hrs MCAO, the neurological deficit and the volume of cerebral infarct were observed, and the effect of KNT on the thrombosis of rats in vitro, platelet aggregation and blood viscosity were also determined. RESULTS: KNT could alleviate volume of cerebral infarct caused by focal cerebral ischemia in a dose-dependent manner and improve neurological symptoms. The volume of cerebral infarct was 11. 18 +/- 3. 35% , 14. 60 +/- 7.00% and 15. 37 +/- 7. 21% in the high, middle and low-dose groups, respectively, and they were decreased 59. 36% , 46. 93% and 44. 13% than that in the model group 27. 51 +/- 4. 71% (P <0. 01 ). The wet and dry weigh of thrombosis in vitro of the three different dose groups were significantly decreased, and they were significantly different than that of the model group (P <0. 05, P <0. 01). KNT could significantly inhibit platelet aggregation induced by ADP and decrease blood viscosity, but it had no effect on plasma viscosity and hematocrit. CONCLUSION: KNT has significant protective effect on ischemia, the mechanism is relateed to the improvement of blood viscosity and inhibiti on of platelet aggregation. But the exact mechanisms need to be probed into deeply.

ZD7288, a selective hyperpolarization-activated cyclic nucleotide-gated channel blocker, inhibits hippocampal synaptic plasticity.

The selective hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyrimidinium chloride (ZD7288) blocks the induction of long-term potentiation in the perforant path-CA3 region in rat hippocampus in vivo. To explore the mechanisms underlying the action of ZD7288, we recorded excitatory postsynaptic potentials in perforant path-CA3 synapses in male Sprague-Dawley rats. We measured glutamate content in the hippocampus and in cultured hippocampal neurons using high performance liquid chromatography, and determined intracellular Ca(2+) concentration [Ca(2+)]i) using Fura-2. ZD7288 inhibited the induction and maintenance of long-term potentiation, and these effects were mirrored by the nonspecific HCN channel blocker cesium. ZD7288 also decreased glutamate release in hippocampal tissue and in cultured hippocampal neurons. Furthermore, ZD7288 attenuated glutamate-induced rises in [Ca(2+)]i in a concentration-dependent manner and reversed 8-Br-cAMP-mediated facilitation of these glutamate-induced [Ca(2+)]i rises. Our results suggest that ZD7288 inhibits hippocampal synaptic plasticity both glutamate release and resultant [Ca(2+)]i increases in rat hippocampal neurons.

Fluoxetine ameliorates cognitive impairments induced by chronic cerebral hypoperfusion via down-regulation of HCN2 surface expression in the hippocampal CA1 area in rats.

Chronic cerebral hypoperfusion (CCH) causes cognitive impairments and increases the risk of Alzheimer's disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the underlying neurobiological mechanisms are still poorly understood. In this study, we investigated whether fluoxetine, a selective serotonin reuptake inhibitor (SSRI), could play a neuroprotective role against chronic cerebral hypoperfusion injury and to clarify underlying mechanisms of its efficacy. Rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO). Two weeks later, rats were treated with 30 mg/kg fluoxetine (intragastric injection, i.g.) for 6 weeks. Cognitive function was evaluated by Morris water maze (MWM) and novel objects recognition (NOR) test. Long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Western blotting was used to quantify the protein levels. Our results showed that fluoxetine treatment significantly improved the cognitive impairments caused by 2VO, accompanied with a reversion of 2VO-induced inhibitory of LTP. Furthermore, 2VO caused an up-regulation of hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) surface expressions in the hippocampal CA1 area and fluoxetine also effectively recovered the disorder of HCN2 surface expressions, which may be a possible mechanism that fluoxetine treatment ameliorates cognitive impairments in rats with CCH.

Activation of GABAB2 subunits alleviates chronic cerebral hypoperfusion-induced anxiety-like behaviours: A role for BDNF signalling and Kir3 channels.

Anxiety is an affective disorder that is commonly observed after irreversible brain damage induced by cerebral ischemia and can delay the physical and cognitive recovery, which affects the quality of life of both the patient and family members. However, anxiety after ischemia has received less attention, and mechanisms underlying anxiety-like behaviours induced by chronic cerebral ischemia are under-investigated. In the present study, the chronic cerebral hypoperfusion model was established by the permanent occlusion of the bilateral common carotid arteries (two-vessel occlusion, 2VO) in rats, and anxiety-related behaviours were evaluated. Results indicated that 2VO induced obvious anxiety-like behaviours; the surface expressions of GABAB2 subunits were down-regulated; Brain derived neurotrophic factor (BDNF), tyrosine kinase B (TrkB) and neural cell adhesion molecule (NCAM) were reduced; Meanwhile, the surface expressions of G protein-activated inwardly rectifying potassium (GIRK, Kir3) channels were up-regulated in hippocampal CA1 in 2VO rats. Baclofen, a GABAB receptor agonist, significantly ameliorated the anxiety-like behaviours. It also improved the down-regulation of GABAB2 surface expressions, restored the levels of BDNF, TrkB and NCAM, and reversed the increased surface expressions of Kir3 in hippocampal CA1 in 2VO rats. However, the effects of baclofen were absent in shRNA-GABAB2 infected 2VO rats. These results suggested that activation of GABAB2 subunits could improve BDNF signalling and reverse Kir3 channel surface expressions in hippocampal CA1, which may alleviate the anxiety-like behaviours in rats with chronic cerebral hypoperfusion.