Aging is now recognized as one of major risk factors for cardiovascular disease (CVD). It is well documented that elderly populations show increased incidence of CVD symptomology but whether these changes are directly related to aging is not well understood since the possibility exists that other age-associated pathologies in different organ systems could impact on cardiovascular function. Hence, the development of an aging model with reduced systemic illness could invigorate efforts to understand the direct role of aging in CVD progression. The Fischer 344 / NNIaHSD × Brown Norway / BiNia rat (F344BN) has been proposed as a potential model for aging that exhibits reduced systemic pathology and increased longevity compared to other models. Here we examine the current literature regarding the F344BN, focusing on age-associated changes in aortic structure and function.
There is increasing evidence indicating the roles of aldosterone and mineralocorticoid receptor (MR) in the pathogenesis of renal injury. In rats, chronic treatment with aldosterone and salt results in severe proteinuria and renal tissue injury, characterized by glomerulosclerosis and tubulointerstitial fibrosis. Aldosterone-induced renal tissue injury is associated with increases in reactive oxygen species (ROS) levels and activation of mitogen-activated protein kinases (MAPKs) or Rho-kinase. Treatment with a selective MR antagonist, eplerenone, prevents aldosterone-induced increases in ROS levels and MAPK activity and ameliorates renal injury. In vitro studies have revealed that MR is highly expressed in glomerular mesangial cells (RMCs), podocytes, and renal interstitial fibroblasts. In these renal cells, aldosterone induces cellular injury through NADPH oxidase–dependent ROS production and activation of MAPKs or Rho-kinase. Such aldosterone-induced renal cellular injury is markedly attenuated by treatment with eplerenone. These data suggest that aldosterone induces renal injury via activation of MR through mechanisms that cannot be simply explained by changes in blood pressure. In this review, we summarized recent findings on the roles of aldosterone and MR in the pathogenesis of renal injury with particular emphasis on potential underlying mechanisms.
Nicotine, a primary component of tobacco, is one of the most abused drugs worldwide. Mesolimbic dopaminergic neurons mediate the rewarding effects of abused drugs, including nicotine. We show that the tissue plasminogen activator (tPA) – plasmin system regulates nicotine-induced reward and dopamine release in the nucleus accumbens (NAc) by activating proteinase-activated receptor 1 (PAR1). Nicotine-induced conditioned place preference and dopamine release in the NAc are diminished in tPA knockout (tPA−/−) mice. The defect of nicotine-induced dopamine release in tPA−/− mice is reversed by microinjection of either exogenous tPA or plasmin into the NAc. Acute nicotine treatment increases tPA protein levels and promoted the release of tPA into the extracellular space. The expression of PAR1 on dopaminergic neurons is evident and the activation of PAR1 by plasmin is demonstrated by assaying GTP-γS binding. Finally, nicotine-induced conditioned place preference and dopamine release are diminished in PAR1−/− mice. These findings suggest that targeting the tPA-plasmin–PAR1 system would provide new therapeutic approaches for the treatment of nicotine dependence.
Recently, the role of serine proteinases in the pathogenesis of inflammation and autoimmune diseases via interaction with the proteinase-activated receptor (PAR) has attracted attention. Activation of PAR has a pro-inflammatory effect through the overproduction of inflammatory cytokines such as interleukin (IL)-6 and IL-8. PAR2 activation in human esophageal epithelial cells by trypsin induces NFκB– and AP-1–dependent IL-8 production in association with activation of p38 MAPK and ERK1/2, suggesting that esophageal inflammation may be induced by PAR2 activation via reflux of trypsin. It has been also proposed that Helicobacter pylori (H. pylori) induces PAR expression in the gastric epithelial cells and H. pylori–derived serine proteinase promotes IL-8 production via PAR in the epithelial cells. In addition, an increase of PAR-dependent IL-8 production has been observed in H. pylori–infected human gastric mucosa, suggesting an important role for PAR2 in the modulation of gastric inflammation associated with H. pylori. Recent studies have strongly indicated that tryptase and PAR are implicated in the pathogenesis of inflammatory bowel disease and experimental colitis. We demonstrated that anti-tryptase therapy may become a new therapeutic strategy in human ulcerative colitis. Thus, the role of PAR in the gastrointestinal tract has been gradually clarified, but further investigations are needed because the receptor has a variety of functions.
During the menstrual cycle, dynamic morphological changes are observed in the ovarian follicle and the endometrium. These changes are associated with the onset of the inflammatory response in which many proteinases play various roles. Thrombin-induced activation of PAR1 (proteinase-activated receptor 1) stimulates the production of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) in human granulosa cells, suggesting a possible role for PAR1 in the ovulatory process. In the endometrium, PAR2 expression increases during the menstrual period. PAR2 activation induces IL-8 production and cell proliferation in human endometrial stromal cells. PAR1 also stimulates proinflammatory cytokine production in human endometrial stromal cells. Thus, the PARs may be important in directing the dynamic changes of the endometrium. PARs also appear to play a role in endometriosis, a common gynecological disease, since activation of PAR1 and PAR2 induces the secretion of inflammatory cytokines and the proliferation of stromal cells in endometriotic lesions. Taken together, PARs appear to play diverse roles in the human reproductive organs.
Cerebral vasospasm is one of the major complications of subarachnoid hemorrhage (SAH). The prevention and treatment of cerebral vasospasm thus plays a critical role in the management of SAH patients. However, the mechanism of cerebral vasospasm still remains elusive, while effective therapeutic strategies also remain to be established. The role of thrombin and its receptor proteinase-activated receptor 1 (PAR1) in cerebral vasospasm was investigated using a rabbit double hemorrhage SAH model. The expression of PAR1 was up-regulated and the contractile response to thrombin was markedly enhanced in the basilar artery of SAH models. The intrathecal administration of a PAR1 antagonist prevented the up-regulation of PAR1 and the enhancement of the contractile responses to thrombin in SAH. These observations thus suggest that PAR1 may play a pivotal role in post-hemorrhagic cerebral vasospasm in SAH. Following SAH, thrombin activates PAR1, thereby up-regulating the expression of PAR1, which culminates in the increased contractile response to thrombin in the basilar artery. PAR1 antagonists are thus anticipated to be a novel therapeutic strategy for cerebral vasospasm. However, further studies are needed before establishing the clinical usefulness of PAR1 antagonists.
Atherothrombotic disease is a leading public health problem. Although current antiplatelet agents, such as aspirin and adenosine diphosphate (ADP)-receptor antagonists, reduce the morbidity and mortality associated with atherothrombotic disease, the residual risk for ischemic events remains substantial. The high residual risk despite dual antiplatelet therapy can be attributed to the fact that platelets possess multiple pathways of activation that are not all inhibited by aspirin and ADP-receptor antagonists. Among these, binding of thrombin to the proteinase-activated receptor 1 (PAR1) is the most potent platelet activation pathway. In addition, the PAR1 pathway does not appear to be essential for initiating hemostasis. Inhibition of the PAR1 receptor thus offers a possible new therapeutic approach with a potentially improved benefit-to-risk profile for treatment of patients with atherothrombotic disease. Preclinical and clinical studies have confirmed that SCH 530348, a potent, orally active thrombin-receptor antagonist selective for PAR1, does not increase bleeding liability when added to dual antiplatelet therapy. Currently, two large ongoing phase 3 clinical trials are evaluating the efficacy and safety of SCH 530348 in combination with the standard of care in patients with acute coronary syndromes as well as for secondary prevention in patients with previous history of atherothrombotic disease.
The effect of isoliquiritigenin (ISL), a component of licorice, on the voltage-dependent, ultra-rapidly activating delayed-rectifier K+ current (IKur) was examined in H9c2 cells, a cell-line derived from rat cardiac myoblasts. IKur was recorded using the whole-cell patch clamp method with a pipette solution containing 140 mM K+. Depolarizing voltage pulses of 200-ms duration were given with 10-mV steps every 10 s from −40 mV holding potential. ISL inhibited IKur in a concentration-dependent manner. The median inhibitory concentration (IC50) of ISL was approximately 0.11 μM and the Hill coefficient was 0.71. Using CHO cells expressing Kv1.5 IKur channels, ISL also inhibited Kv1.5 IKur, but less potently than the IKur current in H9c2 cells. Furthermore, in H9c2 cells, the licorice extract itself inhibited IKur in a manner similar to ISL. We conclude that ISL, one component of licorice, is a potent inhibitor of K+ channels, which specifically in H9c2 cells could be Kv2.1, and that this inhibition may be involved in various pharmacological effects of licorice.
The involvement of protein kinase C (PKC) in myogenic constriction at physiological intraluminal pressure was investigated in rat posterior cerebral arteries. Changes in constriction and intracellular Ca2+ concentration ([Ca2+]i) were measured in fura 2-loaded arterial segments by pressurized arteriography. When intraluminal pressure was raised from 5 to 60 mmHg and maintained for 60 min, sustained constriction and [Ca2+]i elevation were elicited. The constriction and [Ca2+]i at 60 mmHg gradually declined in the presence of RO31-8220, a general PKC inhibitor, and rottlerin, a PKCδ inhibitor. In contrast, Gö6976, a conventional PKC inhibitor, significantly diminished the constriction with no inhibition on the [Ca2+]i. In the presence of nicardipine, the pressure stimulation to 60 mmHg still produced a small sustained [Ca2+]i elevation. The nicardipine-insensitive [Ca2+]i elevation gradually declined in the presence of rottlerin, and it was nearly abolished by ruthenium red. Immunohistochemical analysis showed positive staining for PKCα, γ, δ, and ε, but not PKCβ, in smooth muscle cells of rat posterior cerebral arteries. These results suggest distinct roles of PKC isoforms in myogenic constriction: conventional PKC mediates Ca2+ sensitization, whereas PKCδ mediates sustained [Ca2+]i elevation via the activation of cation channels, resulting in sustained constriction.
Recently, it was demonstrated that the priming stimulation effect (PSE) of intracranial self-stimulation (ICSS) with the runway method can be used as a model system to study the motivation that contributes to specific behaviors. It was postulated that these behaviors could be used to compare the effects of various drugs on the mechanism of motivation. In the present study, the influences of nicotine, methyllycaconitine (α7 nicotine-receptor antagonist), and dihydro-β-erythroidine (α4β2 nicotine-receptor antagonist) on motivation were examined using the runway method for ICSS. Electrodes were implanted into the medial forebrain bundle of Wistar rats. The rats ran to the goal lever to get the reward (50 – 200 μA, 0.2 ms, 60 Hz) and pretrial electric stimulation (priming stimulation) in the medial forebrain bundle was performed. The experiment measured the running time from the start box until the rat pressed the goal lever for the reward stimulation. Under these reward and priming stimulation conditions, nicotine (0.2 mg/kg) induced a significant increase in running speed. The nicotine receptor antagonist α4β2 rather than α7 showed a dose-dependent antagonistic action on the effect of nicotine on running speed. These results demonstrate that nicotine enhances the running speed towards the goal lever via α4β2 nicotinic receptors and suggest that α4β2 nicotinic receptors influence the brain mechanism of motivation.
QT prolongation, a risk factor for arrhythmias, can result from genetic variants in one (or more) of the genes governing cardiac repolarization as well as intake of drugs known to affect a cardiac K+ channel encoded by human ether-a-go-go–related gene (HERG). In this paper, we will report a case of drug-induced long QT syndrome associated with an H1-receptor antagonist, hydroxyzine, in which a mutation was identified in the HERG gene. After taking 75 mg of hydroxyzine for several days, a 34-year-old female began to experience repetitive syncope. The deleterious effect of hydroxyzine was suspected because QTc interval shortened from 630 to 464 ms after cessation of the drug. Later on, the patient was found to harbor an A614V-HERG mutation. By using the patch-clamp technique in the heterologous expression system, we examined the functional outcome of the A614V mutation and confirmed a dominant-negative effect on HERG expression. Hydroxyzine concentration-dependently inhibited both wild-type (WT) and WT/A614V-HERG K+ currents. Half-maximum block concentrations of WT and WT/A614V-HERG K+ currents were 0.62 and 0.52 μM, respectively. Thus, accidental combination of genetic mutation and intake of hydroxyzine appeared to have led to a severe phenotype, probably, syncope due to torsade de pointes.
The present study was undertaken to clarify how spinal muscarinic receptors are involved in the antinociceptive effects in thermal stimulation. Intrathecal (i.t.) injection of the muscarinic agonist McN-A-343 inhibited the tail-flick response to noxious thermal stimulation in a dose-dependent manner (31.5 – 63.0 nmol). This McN-A-343–induced antinociceptive effect was dose-dependently inhibited by intrathecal (i.t.) injection of a nonselective muscarinic receptor antagonist atropine, the selective muscarinic M1 antagonist pirenzepine, or the M4 antagonist himbacine. The inhibition of pirenzepine was greater than that of himbacine. In contrast, the selective muscarinic M2 antagonist methoctramine did not inhibit the antinociceptive effects of McN-A-343. In addition, the McN-A-343–induced antinociceptive effect was attenuated by i.t. injection of the GABAA antagonist bicuculline, but not by injection of the GABAB antagonist CGP35348. These results suggest that McN-A-343 produces its antinociceptive effect on the response to thermal stimulation via spinal muscarinic M1 receptors and, at least in part, through neuronal pathways involving spinal GABAA receptors in mice.
Antihistamines are effective for treatment of seasonal nasal allergy. Recently, prophylactic treatment with antihistamines in patients with pollinosis was reported to be more effective when started before the pollen season. The administration with antihistamines from 2 to 6 weeks before onset of the pollen season is recommended for management of allergic rhinitis in Japan. To determine the reason for the effectiveness of prophylactic treatment with antihistamines, the effects of repeated pre-treatment with antihistamines before provocation with toluene 2,4-diisocyanate (TDI) on their nasal allergy–like behavior and up-regulations of histamine H1 receptors (H1R) and interleukin (IL)-4 mRNAs in their nasal mucosa were examined. Provocation with TDI induced sneezing and up-regulations of H1R and IL-4 mRNAs in the nasal mucosa of TDI-sensitized rats. Repeated pre-treatments with antihistamines including epinastine, olopatadine, or d-chlorpheniramine for 1 to 5 weeks before provocation with TDI suppressed TDI-induced sneezing and the up-regulations of H1R and IL-4 mRNAs in the nasal mucosa more than their administrations once or for 3 days before TDI provocation. Our data indicate that repeated pre-treatment with antihistamines before provocation with TDI is more effective than their single treatment in reducing nasal allergy–like behavior by causing additional suppression of up-regulations of H1R and IL-4 mRNAs in the nasal mucosa.
Little is known about the influence of angiotensin converting enzyme (ACE) inhibitors on matrix metalloproteinase (MMP) in right ventricular remodeling. We investigated the effect of captopril, an ACE inhibitor, on MMP-2 and MMP-9 in monocrotaline-induced right ventricular hypertrophy. Six-week-old male Wistar rats were injected intraperitoneally with monocrotaline (60 mg/kg) or saline. The rats were administrated captopril (30 mg/kg per day) or a vehicle orally for 24 days from the day of monocrotaline injection. At day 25, echocardiography was performed and hearts were excised. Expressions and activities of MMP-2 and MMP-9 were measured by Western blotting and by gelatin zymography, respectively. In monocrotaline-injected rats, right ventricular weight/tail length ratio increased significantly. Histological analysis revealed cardiomyocyte hypertrophy and fibrosis in right ventricular sections. Echocardiography showed right ventricular dysfunction compared with saline-injected rats. The right ventricular hypertrophy, fibrosis, and dysfunction were inhibited by captopril. However, captopril did not attenuate an increase in pulmonary artery pressure. MMP-2 and MMP-9 expressions and activities in right ventricles increased significantly in monocrotaline-injected rats and captopril inhibited them. These findings indicate that captopril attenuates the development of monocrotaline-induced right ventricular hypertrophy in association with inhibition of MMP-2 and MMP-9 in rats.
Hepatic growth factor (HGF) has neurotrophic effects in the motor neurons and central nervous system. However, there has been no report about the neurotrophic action on perivascular nerves innervating the resistance artery. We investigated whether HGF can restore innervation or function of perivascular nerves, including neuropeptide Y (NPY)-containing sympathetic adrenergic nerves and calcitonin gene-related peptide (CGRP)-containing nerves, in rat mesenteric artery. To investigate HGF-mediated neurotrophic effects, Wistar rats under pentobarbital-Na anesthesia underwent in vivo perivascular denervation by topical application of phenol on the superior mesenteric artery, and then HGF or nerve growth factor (NGF) was administered for 7 days using an osmotic mini-pump after phenol-treatment. HGF significantly increased the density and number of CGRP-like immunoreactivity (LI)–containing nerve fibers compared with saline administration, while HGF did not affect the density of NPY-containing adrenergic nerve fibers. After 7-day treatment with HGF and phenol, the vascular response of vasodilation was recovered from nerve injury by phenol treatment, but vasoconstriction was not. HGF and NGF induced neurite outgrowth in rat cultured dorsal root ganglia (DRG). These results suggest that HGF has a specific neurotrophic action on reinnervation of vascular CGRP-LI–containing nerve fibers in the rat mesenteric artery and DRG.
System L (SL), a basolateral amino acid transporter, transports large neutral amino acids (LNAAs) in a Na+-independent manner. Previously, we identified two isoforms of transporters: L-type amino acid transporter 1 (LAT1) and 2 (LAT2) and revealed their distinct substrate selectivity and transport properties. In this study, to establish more stable human LAT1 (hLAT1) and LAT2 (hLAT2) in vitro assay systems, we established mouse cell lines stably expressing hLAT1 (S2-LAT1) and hLAT2 (S2-LAT2). Real-time quantitative RT-PCR analysis revealed that S2-LAT1 and S2-LAT2 cells express hLAT1 and hLAT2 mRNAs at 20 – 1000-fold higher levels than those of endogenous mouse Lat1 and Lat2. S2-LAT1 and S2-LAT2 mediated [14C]L-leucine transport properties were measured and corresponded to results observed via Xenopus oocytes. Using these cells, the data demonstrate that hLAT1 and hLAT2 exhibit different characters in the acceptance of α-methyl amino acids and amino acid–related compounds with bulky side chains such as thyroid hormones and melphalan. S2-LAT1 and S2-LAT2 cells are expected to facilitate hLAT1 and hLAT2 substrate recognition research and contribute to drug development by providing an efficient assay system to screen for chemical compounds that interact with hLAT1 and hLAT2.
K+ channels are key modulators of neuronal excitability, and mutations in certain types of these channels are known to cause epileptic seizures. Activation of K+ channels is reported to suppress epileptic discharge; however, the types of K+-channel openers that are most effective as anti-epileptic agents are not well understood. We established a quantitative fluorescence assay using the Na+ indicator sodium-binding benzofuran isophthalate (SBFI) for evaluation of various compounds on epileptiform activities induced by 4-aminopyridine (4-AP) in cultured rat hippocampal neurons. Among the K+-channel openers, the KV7.2/KV7.3-channel openers retigabine and flupirtine and KCa2-channel openers NS309, DCEBIO, and 1-EBIO showed potent anti-epileptic effects similar to conventional antiepileptic drugs (AEDs). In contrast, the KCa1.1-channel openers NS1619, isopimaric acid, and chlorzoxazone demonstrated moderate inhibition. The Kir6-channel openers minoxidil, cromakalim, and pinacidil did not show anti-epileptic effects. We concluded that KV7.2/KV7.3, KCa2, and, to some extent, KCa1.1-channel openers, but not Kir6-channel openers, suppress 4-AP–induced epileptiform activities in hippocampal neurons. These results suggest that the K+-channel openers for this category of K+ channels might have therapeutic potential as new classes of antiepileptic drugs.
Many studies have examined the efficacy of tacrolimus in rats and dogs, but few have reported its evaluation in cynomolgus monkeys. The aim of this study was to clarify the efficacy of tacrolimus in a cynomolgus monkey renal transplant model based on the efficacy of various doses. Monkeys that had undergone renal transplant were treated with a vehicle or 0.5, 1.0, or 2.0 mg/kg of tacrolimus by oral administration. Tacrolimus administration prolonged animal survival in a dose-dependent manner, and the median survival time (MST) was 11, 21, and >90 days for the 0.5, 1.0, and 2.0 mg/kg tacrolimus groups, respectively. The MST of the vehicle group was 6 days. Histopathological analyses of all transplanted kidneys were also performed. Typical pathological findings of acute rejection were observed in both the vehicle and tacrolimus (0.5 and 1.0 mg/kg)-treated groups. Only limited mononuclear cell infiltration and hemorrhage were present in the tacrolimus (2.0 mg/kg)-treated group. In conclusion, 2.0 mg/kg was considered to be a therapeutic dose in this model, and 0.5 or 1.0 mg/kg could be used for a study when efficacy of a new compound is evaluated in a combination therapy with tacrolimus.
Although peroxisome proliferator-activated receptor γ (PPARγ) is strongly expressed in the intestinal epithelium, the role of PPARγ in intestinal tumorigenesis has not yet been elucidated. To address this issue, we investigated the effect of PPARγ inhibition and its mechanism on intestinal tumorigenesis using a selective antagonist, T0070907. We treated ApcMin/+ mice and carcinogen-induced colon cancer model C57BL/6 mice with T0070907 and counted the number of spontaneous polyps and aberrant crypt foci and observed cell proliferation and β-catenin protein in the colon epithelium. To investigate its mechanism, the changes of β-catenin/TCF (T cell factor) transcriptional activity and location of β-catenin induced by T0070907 were investigated in the colon cancer cell lines. T0070907 promoted polyp formation in the small intestine of ApcMin/+ mice and aberrant crypt foci in the colon of C57BL/6 mice. PPARγ inhibition promoted cell proliferation and increased expressions of the c-myc and cyclin D1 genes and the β-catenin protein in the colon epithelium. In vitro, cell proliferation was promoted, but it was inhibited by the transfection of dominant-negative Tcf4. T0070907 increased β-catenin/TCF transcriptional activity and β-catenin protein in the cytsol and nucleus, but relatively decreased it on the cell membrane. PPARγ antagonist promotes tumorigenesis in the small intestine and colon through stimulation of epithelial cell proliferation. β-Catenin contributes to the promotion of tumorigenesis by PPARγ antagonist due to activation of TCF/LEF (lymphoid enhancer factor) transcriptional factor.
Scavenging activity of α-phenyl-N-tert-butyl nitrone (PBN) against singlet oxygen (1O2) and its effects on 1O2-induced neuronal cell death were examined. PBN at 1 – 4 mM dose-dependently suppressed 1O2 released from activated human neutrophils. PBN did not react with hydrogen peroxide or hypochlorite and did not affect myeloperoxidase activity, which are involved in the 1O2 formation in neutrophils. PBN also suppressed chemically generated 1O2 in a cell-free system. These findings collectively indicated that PBN certainly has scavenging activity against 1O2. Furthermore, PBN attenuated 1O2-induced neuronal cell death. The well-known neuroprotective effects of PBN might be attributed to its 1O2-scavenging activity.