Tissue-type plasminogen activator (t-PA) administration has been approved for treating acute ischemic stroke, but delayed treatment is associated with increased risk of cerebral hemorrhage and brain injury. t-PA, a serine proteinase, converts plasminogen to plasmin. Plasmin participates not only in the degradation of fibrin, causing clot lysis, but also in the degradation of various extracellular matrix proteins, either directly or via the activation of matrix metalloproteinase (MMPs). We established an animal stroke model and observed a phenomenon of spontaneous rethrombosis and thrombolysis in the cerebral vessels after vessel damage. Endogenous t-PA protected brain damage by recanalization, but the protective effect deteriorated when the occluded vessels were not reopened. On studying intracranial hemorrhage (ICH) induced by t-PA treatment of ischemic stroke, we observed that MMP-3 is relatively important for the enhanced ICH induced by t-PA. MMP-3 was upregulated by t-PA in endothelial cells, but the upregulation was prevented by the inhibition of either low-density lipoprotein receptor–related protein (LRP) or nuclear factor kappa-B (NF-κB) activation. Thus, t-PA causes ICH via MMP-3 induction in endothelial cells, which is regulated through the LRP/NF-κB pathway, and could be targeted to improve the therapeutic efficacy of t-PA for acute ischemic stroke.
Halichlorine is a marine alkaloid isolated from the marine sponge Halichondria okadai KADOTA, and its pathophysiological effect on vascular cells remains unknown. Here, we examined the anti-atherosclerosis activity of halichlorine on endothelial cells by assessing the expression of adhesion molecules. In bovine aortic endothelial cells (BAECs), pretreatment with halichlorine (10 μM, 2 h) inhibited lipopolysaccharide (LPS) (3 μg/ml, 3 h)–induced mRNA expressions of vascular cell adhesion molecule (VCAM-1), intercellular adhesion molecule (ICAM-1), and E-selectin. Consistently, pretreatment with halichlorine (10 μM, 2 h) reduced LPS (3 μg/ml)–induced monocyte (U937) adhesion to endothelial monolayer. To investigate the mechanism underlying this phenomenon, we examined the effect of halichlorine on nuclear factor-κB (NF-κB) activity in endothelial cells. Treatment with LPS (3 μg/ml) for 1 h increased the ratio of cells showing NF-κB p65 translocation from cytosol to nucleus. Pretreatment with halichlorine (10 μM, 2 h) significantly inhibited the LPS-induced NF-κB p65 translocation. Finally, we examined the cytotoxicity of halichlorine on endothelial cells and found that halichlorine (10 μM, 24 – 48 h) did not influence BAECs proliferation and viability. Herein, we provided the first evidence that halichlorine inhibits LPS-induced NF-κB activation, which results in the suppression of VCAM-1, ICAM-1, and E-selectin gene expression and monocyte-adhesion to endothelial cells.
CV-159 is a unique dihydropyridine Ca2+ antagonist with an anti-calmodulin (CaM) action. A pathogenic feature of atherosclerosis is vascular inflammatory change. In the present study, we examined whether CV-159 exerts protective effects on smooth muscle inflammatory responses. After pretreatment of rat mesenteric arterial smooth muscle cells (SMCs) with CV-159 (0.1 – 10 μM, 30 min), TNF-α (10 ng/ml) was applied for 20 min or 24 h. CV-159 inhibited TNF (24 h)–induced vascular cell adhesion molecule (VCAM)-1 as determined by Western blotting. CV-159 inhibited TNF (20 min)–induced phosphorylation of Akt (Ser473) and NF-κB p65 (Ser536). An Akt inhibitor, LY294002, and an NF-κB inhibitor, pyrrolidine dithiocarbamate, inhibited TNF-induced VCAM-1. An antioxidant drug, N-acetyl-L-cysteine (NAC) inhibited TNF-induced VCAM-1. NAC also inhibited TNF-induced phosphorylation of Akt and NF-κB. Furthermore, CV-159 inhibited TNF-induced reactive oxygen species (ROS) production as determined fluorometrically using dichlorodihydrofluorescein diacetate. A CaM inhibitor, W-7, and a calcium/CaM-dependent protein kinase type II inhibitor, KN93, inhibited TNF-induced VCAM-1. W-7 and KN93 inhibited TNF-induced phosphorylation of Akt but not NF-κB. The present results indicate that in vascular SMCs, CV-159 inhibits TNF-induced VCAM-1 through inhibition of NF-κB and Akt phosphorylation. CV-159 prevents NF-κB phosphorylation by inhibiting ROS, while it prevents Akt phosphorylation by inhibiting both ROS and CaM.
A close interaction between adrenergic nerves and angiotensin systems has been documented. The present study was designed to investigate the mechanisms of angiotensin-receptor blocker (ARB) suppression of β-adrenergic receptor stimulation–induced cardiac hypertrophy. Chronic isoproterenol (ISO)–induced cardiac hypertrophy was inhibited in wild-type mice and AT1aR−/− mice treated with the ARB Candesartan (CV11974). Acute ISO–induced increase in phosphorylation levels of ERK MAPK was completely inhibited and increases in phosphorylation levels of p38 and JNK MAPKs were partially suppressed in both types of mice. Analysis of the activity of the small GTPase–regulating protein Raf indicated that the mechanisms by which ARB inhibits the Raf/MEK/ERK pathway under β-adrenergic receptor stimulation basically depended on changes in the binding activities of Ras (stimulatory to Raf cascade) and Rap-1 (inhibitory to Raf cascade). Binding activities of Ras and Rap-1 in the heart were markedly augmented by ISO, whereas ARB suppressed only Ras, but not Rap-1, binding activity. Raf immunoprecipitation results confirmed that ISO-induced increases in its association with total and phosphorylated forms of MEK were completely normalized by ARB. These results might provide a molecular basis for the beneficial effects of AT1-receptor antagonists on cardiac remodeling and functions in patients with sympatho-excitatory heart failure.
Astrocytes in the hypothalamic suprachiasmatic nucleus, site of the master circadian pacemaker, play an essential role in the regulation of systemic circadian rhythms. To evaluate involvement of noradrenergic systems in regulation of circadian variation of clock-genes in astrocytes, we investigated effects of noradrenaline (NA) on expression of several clock genes in C6 glioma cells by using real-time PCR analysis. Treatment with NA (10 μM) induced transient expression of Per1 mRNA, but not of Per2, Bmal1, Clock, Cry1, or Cry2 mRNA, through activation of β2 adrenoceptors. Action of NA was partially blocked by H-89 [protein kinase A (PKA) inhibitor] or KG-501 [inhibitor of cAMP response element binding protein (CREB)]. We found that pretreatment with genistein or PP2 (general or Src tyrosine kinase inhibitors, respectively) or LiCl [inhibitor of glycogen synthase kinase-3β (GSK-3β)] significantly inhibited NA-induced Per1 mRNA expression. In addition, treatment with H-89 and either genistein or LiCl completely blocked NA stimulatory effects. NA markedly induced tyrosine phosphorylation of Src and GSK-3β via activation of β2 adrenoceptors. Phosphorylation of GSK-3β by NA was completely eliminated by genistein or PP2. These results primarily suggest that two distinct NA-mediating pathways, PKA–CREB and Src–GSK-3β, play crucial roles in regulation of Per1 expression in astroglial cells.
Auranofin (2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranosato-S-[triethylphosphine] gold) is a gold(I)-containing antirheumatic drug that possesses anti-inflammatory properties. The pharmacological activity of this drug is associated with its ability to induce heme oxygenase-1 (HO-1). However, the mechanism underlying auranofin-mediated HO-1 induction remains unclear. We investigated the action of auranofin on activation of nuclear factor erythroid 2–related factor 2 (Nrf2), an activator of HO-1. Auranofin elevated cellular levels of Nrf2 by increasing protein stability but not transcriptional activation. Coimmunoprecipitation and Western blot analysis indicated that auranofin inhibited Nrf2 degradation by inducing the dissociation of the Nrf2 / Kelch-like ECH-associated protein 1 (Keap1) complex, which resulted in nuclear accumulation of Nrf2. In addition, auranofin treatment activated cellular Rac1 and induced inducible nitric oxide synthase (iNOS) expression. An inhibitor of Rac1 (NSC23766) blocked the iNOS induction as well as Nrf2 activation and HO-1 expression. NG-nitro-L-arginine methyl ester and aminoguanidine, inhibitors of iNOS, diminished the auranofin-induced Nrf2 activation and HO-1 expression. Phosphorylation of mitogen-activated protein kinases (MAPKs) was increased by auranofin treatment, and inhibitors of MAPKs partially diminished the Nrf2 activation. A chromatin immunoprecipitation assay showed that the Nrf2 activated by auranofin was involved in transactivation of the HO-1 gene. These findings indicate that auranofin leads to HO-1 upregulation by activating Keap1/Nrf2 signaling via Rac1/iNOS induction and MAPK activation.
We investigated pharmacological characteristics of the itch-associated response to chronic dermatitis induced by 4-ethoxymethylene-2-phenyl-2-oxazolin-5-one (oxazolone) repeated application in mice. Application of an oxazolone challenge to mice with oxazolone-induced chronic dermatitis evoked severe and transient scratching behavior for up to 1h. Thereafter, mild and continuous scratching behavior was observed for at least 8 h. Both severe and continuous scratching behaviors were suppressed by the opioid-receptor antagonist naltrexone, but not by the H1 histamine–receptor antagonist fexofenadine, 5-hydroxytryptamine-2 (5-HT2)–receptor antagonist methysergide, NK1-receptor antagonist LY303870, cyclooxygenase inhibitor indomethacin, or the platelet-activating factor–receptor antagonist YM264. The severe scratching behavior was suppressed by the 5-lipoxygenase inhibitor zileuton and leukotriene B4–receptor antagonist ONO-4057, but not by the cysteinyl leukotriene–receptor antagonist montelukast. The continuous scratching behavior was suppressed by pretreatment with the non-selective muscarinic acetylcholine–receptor antagonist atropine and M3 muscarinic acetylcholine–receptor antagonist darifenacin. These results suggest that leukotriene B4 receptor and M3 muscarinic acetylcholine receptor are involved in the itch-associated response induced by repeated application of oxazolone in mice.
We analyzed the functional properties of five single nucleotide polymorphisms (SNPs) in organic cation transporter OCT3 gene (SLC22A3) resulting in the amino acid changes with a transient expression system. Three SNPs (A116S, T400I, and A439V) exhibited reduced uptake of both [3H]histamine and [3H]MPP+, although their protein expressions were detected in the plasma membrane of transfected cells. This study suggests that the OCT3 variants will contribute to inter-individual variations leading to the differences in cationic drug disposition as well as certain disease processes such as hypertension, allergic diseases, and neuropsychiatric diseases by the clearance of endogenous organic cations such as biogenic amines.
We investigated the effects of treatment with trimethyltin (TMT) on the expression of glutathione-related enzymes in mouse hippocampus. TMT promoted the expression of glutathione S-transferase (GST) Ya/Yc mRNA, and GSTA2 protein, but not that of glutamate-cysteine ligase catalytic subunit mRNA, 1 day after injection. TMT produced a slight but significant elevation of GST activity during the period from day 1 to 7 post-treatment. No significant change was seen in the activity of glutathione peroxidase at anytime post-TMT treatment. Our data suggest the prolonged elevation of GST activity in the hippocampus following TMT treatment through enhanced expression of the GST Ya/Yc.
Dilazep dihydrochloride (dilazep) is used to treat ischemic dysfunction, although the mechanisms underlying the anti-inflammatory effects of the drug have not yet been elucidated. The present study evaluated the anti-inflammatory effect of dilazep. Dilazep suppressed the production of nitric oxide (NO) and the expression of TNF-α mRNA by lipopolysaccharide (LPS) in RAW 264 cells. However, 1400W, an inducible NO synthase inhibitor, suppressed the production of NO but did not suppress the expression of TNF-α mRNA following treatment with LPS. Caffeine, an adenosine antagonist, restored LPS-stimulated NO synthesis, which is suppressed by dilazep. Therefore, these observations may suggest that the suppression of NO synthesis after dilazep treatment in RAW 264 cells is caused by the inhibition of TNF-α expression via adenosine receptors.
The mechanism for sustained Ca2+ influx activated by G protein–coupled receptors was examined. In Chinese hamster ovary cells expressing recombinant human endothelin type B receptor (ETBR) and endogenous P2Y receptor (P2Y-R), endothelin-1 elicited a sustained Ca2+ influx depending on Gq/11 protein, phospholipase C (PLC), Na+/H+ exchanger (NHE), and p38 mitogen-activated protein kinase (p38MAPK), whereas P2Y-R–induced sustained Ca2+ influx was negligible. Functional studies showed that NHE activation by ETBR was mediated via p38MAPK but not Gq/11/PLC, while that by P2Y-R involves only Gq/11/PLC/p38MAPK. These results suggest that Gq/11/PLC-independent NHE activation via p38MAPK plays an important role in ETBR- mediated sustained Ca2+ influx.
We have reported previously that the concentration of intracellular Ca2+ evoked by serotonin (5-HT) was significantly augmented in differentiated NG108-15 (NG) cells treated with dibutyryl cAMP and the enhanced response occurred via 5-HT3 receptors. We investigated changes in the characteristics for specific binding of [3H]LY-278584 (a specific antagonist of the 5-HT3 receptor) on membranes from differentiated NG cells. The results indicated that the Kd and Bmax values for the specific binding to differentiated NG cells were significantly smaller and larger, respectively, than those for undifferentiated NG cells. The binding was significantly inhibited by 10 nM tropisetron, a specific 5-HT3–receptor antagonist, but not by any other types of 5-HT–receptor antagonists. These results suggested that the enhanced response by 5-HT in differentiated NG cells was due to both qualitative and quantitative changes in the 5-HT3 receptor.
Endoplasmic reticulum–associated degradation (ERAD) is a quality control mechanism in which unfolded proteins are retro-translocated to the cytosol for degradation. Our recent study showed that suppression of expression of ubiquitin ligase HRD1, which is involved in ERAD, caused amyloid precursor protein (APP) accumulation and amyloid-β (Aβ) production. Furthermore, HRD1 protein levels were significantly lower in the cerebral cortex of Alzheimer’s disease (AD) patients. To assess whether HRD1 is involved in AD pathology, we analyzed the relationship between HRD1 protein levels and Aβ production. We found that the HRD1 level was negatively correlated with the Aβ level, suggesting the possible involvement of HRD1 in Aβ generation.