Nitric oxide (NO) toxicity is in part mediated by generation of peroxynitrite with concomitant production of superoxide under pathological brain conditions such as ischemia and Alzheimer’s disease. The pathophysiological relevance of endothelial nitric oxide synthase (eNOS) to brain embolism-induced neurovascular injury has not been documented. We found that microsphere embolism (ME)–induced aberrant eNOS expression in vascular endothelial cells likely mediates blood-brain barrier (BBB) disruption via peroxynitrite formation and in turn causes brain edema. We also demonstrated that a mild ME model was useful for investigating the sequential events of neurovascular injury followed by β-amyloid accumulation and tau hyperphosphorylation. Indeed, immunoblotting of purified brain microvessels revealed that β-amyloid accumulation significantly increased one week after ME induction and remained elevated for twelve weeks in those animals. Moreover, we also confirmed that peroxynitrite formation and eNOS uncoupling–mediated superoxide generation in microvessels are inhibited by a novel calmodulin inhibitor. Thus, peroxynitrite formation via elevated eNOS is associated with endothelial cell injury with concomitant β-amyloid accumulation in microvessels of aged rats. In this review, we focus on the detrimental effects of eNOS expression following brain embolism and introduce an attractive model representing progressive Alzheimer’s disease pathology in brain.
In the present study, we assessed the effects of gluco-obtusifolin, isolated from the seeds of Cassia obtusifolia L., and its aglycone, obtusifolin, on the learning and memory impairments induced by scopolamine using the passive avoidance and the Morris water maze tasks in mice. Gluco-obtusifolin (1, 2, and 4 mg/kg, p.o.) and obtusifolin (0.25, 0.5, 1, and 2 mg/kg, p.o.) significantly reversed scopolamine-induced cognitive impairments in the passive avoidance test (P<0.05). Moreover, gluco-obtusifolin (2 mg/kg, p.o.) and obtusifolin (0.5 mg/kg, p.o.) improved escape latencies, swimming times in the target quadrant, and crossing numbers in the zone where the platform previously existed in the Morris water maze test. In the acetylcholinesterase assay, gluco-obtusifolin and obtusifolin were found to inhibit acetylcholinesterase activity in vitro (IC50 = 37.2 and 18.5 μM, respectively) and ex vivo. These results suggest that gluco-obtusifolin and its aglycone may be useful for the treatment of cognitive impairment, and that its beneficial effects are mediated, in part, by the enhancement of cholinergic signaling.
The present study was conducted to investigate the effects of histamine on the lipid metabolic disorder in mice loaded with restraint stress. When Kun Ming (KM) mice were exposed to restraint stress for 20 h, the histamine level in both plasma and cerebral regions significantly increased (P<0.01). Moreover, when a lipid emulsion (10% Intralipid(R)) was injected intravenously into the mice, the elimination period of plasma triglyceride was prolonged in the restraint group. Plasma triglyceride was 523 ± 44 mg/dl at 35 min after the Intralipid(R) administration in the restraint stress group, while it was 436 ± 41 mg/dl in the restrained mice given histamine at a dose of 50 mg/kg. The improved plasma triglyceride metabolism was well explained by the observations of the significantly up-regulated hepatic triglyceride lipase (HTGL) activity and mRNA expression in response to histamine. These results suggested that the effects of stress-induced histamine on lipid metabolic disorder in mice loaded with restraint stress arose from its anti-stress action and promotion of lipase activity.
Nuclear transcription factor-κB (NF-κB) is constitutively activated in prostate and colon cancers and is related with the resistance of cancer cells against chemotherapeutics. Previously, we found that obovatol, an active compound isolated from Magnolia obovata, inhibited cancer cell growth through inhibition of NF-κB activity. We investigated here whether obovatol could sensitize cancer cells against docetaxel through inhibition of NF-κB activity in prostate cancer (LNCaP and PC-3) and colon cancer (SW620 and HCT116) cells. The combination treatment with each drug at one half the respective IC50 dose (5 μM obovatol + 5 nM docetaxel) was more effective and significant (60% – 70%) in the inhibition of cancer cell growth than single treatment by each drug (20% – 40%); inhibition was exerted through a significant increase of apoptosis induction (60% – 80%) by the combination treatment compared to the single treatment (10% – 30%). Correlating well with the synergistic inhibition (combination indices are less than 1 in all cell types), the combination significantly inhibited NF-κB activities as well as expression of NF-κB target apoptotic cell death proteins, but decreased anti-apoptotic cell death proteins. Similar combination effects of obovatol with other chemotherapeutic agents (paclitaxel, cisplatin, and doxorubicin) on the inhibition of cell growth and NF-κB activity were also found. These results indicate that obovatol augments cell growth inhibition by chemotherapeutics through inactivation of NF-κB and suggest that obovatol may have therapeutic advantages in the combination treatment with other chemotherapeutics. [Supplementary Figure: available only at http://dx.doi.org/10.1254/jphs.09048FP]
Silibinin is known for its hepatoprotective, anti-inflammatory, and anti-carcinogenic effects. We found that silibinin exhibited a protective effect against chemotherapeutic reagent mitomycin C–induced cell death in A375-S2 cells in a p53-dependent manner, which contradicted the findings of previous studies investigating the anti-neoplastic activity of silibinin and developing silibinin as a potential anti-neoplastic drug in clinical therapy. Mitomycin C administration triggered a time- and dose-dependent cell death in A375-S2 cells. Apoptotic morphology, DNA fragmentation, and caspase-3 activation demonstrated that the major cause of A375-S2 cell death by mitomycin C was apoptosis. This was associated with a marked increase of p53 level and changes in mitochondria associated proteins. However, preincubation with silibinin prior to mitomycin C treatment substantially suppressed cell apoptosis, attenuated the change of p53 and Bcl-2 expressions, blocked the translocation of Bax to mitochondrial outer membrane, and ameliorated the loss of mitochondrial membrane potential, but mitomycin C stimuli led to few changes in the protein levels of caspase 8, Fas ligand, and Fas-associated death domain protein, indicating that silibinin protected cells from mitomycin C–induced apoptosis mainly via suppressing the mitochondria-mediated intrinsic apoptosis pathway, but not in an extrinsic manner.
Partial liquid ventilation with various types of perfluorocarbon (PFC) has been shown to be beneficial in treating acute lung injury, a clinical outcome that may involve the anti-inflammatory activity of PFC. FC-77 is a type of PFC with relatively higher vapor pressure and evaporative loss than other PFCs during partial liquid ventilation. Overproduction of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been proposed to play a crucial role in the pathogenesis of inflammatory diseases. However, whether the iNOS/NO pathway is affected by FC-77 is unknown. Thus, the aim of this study was to investigate whether FC-77 inhibits iNOS expression and NO production in lipopolysaccharide (LPS)–treated RAW 264.7 macrophages. We found that treatment with FC-77 significantly attenuated LPS-induced iNOS expression/activity and production of NO and reactive oxygen species (ROS). FC-77 also attenuated LPS-induced pro-inflammatory cytokine formation, but enhanced interleukin-10 production. Furthermore, the LPS-induced degradation of cytosolic IκB-α and activation of nuclear transcription factor-κB (NF-κB) were also inhibited by FC-77. In conclusion, the present study is the first to demonstrate that FC-77 decreases LPS-induced NO production in macrophages, which may be associated with the suppression of pro-inflammatory cytokines, and ROS production, as well as NF-κB activation. These results also provide a novel explanation for its anti-inflammatory activity.
The pharmacological effects of rivoglitazone, a novel thiazolidinedione-derivative peroxisome proliferator–activated receptor (PPAR)-γ agonist, were characterized in vitro and in vivo. Rivoglitazone activated human PPARγ more potently compared with rosiglitazone and pioglitazone and had little effect on PPARα and PPARδ activity in luciferase reporter assays. In Zucker diabetic fatty (ZDF) rats, 14-day administration of rivoglitazone decreased the plasma glucose and triglyceride (TG) levels in a dose-dependent manner. The glucose-lowering effect of rivoglitazone was much more potent than those of pioglitazone (ED50: 0.19 vs. 34 mg/kg) and rosiglitazone (ED50: 0.20 vs. 28 mg/kg). In addition, rivoglitazone showed potent antidiabetic effects in diabetic db/db mice. In Zucker fatty rats, rivoglitazone at a dose of 0.1 mg/kg clearly ameliorated insulin resistance and lowered plasma TG levels by accelerating the clearance of plasma TG. Gene expression analysis in the liver and heart of ZDF rats treated with rivoglitazone for 14 days suggested that rivoglitazone may reduce hepatic glucose production and modulate the balance of the cardiac glucose/fatty acid metabolism in diabetic animals. In summary, we showed that rivoglitazone is a potent and selective PPARγ agonist and has a potent glucose-lowering effect via improvement of the insulin resistance in diabetic animal models.
Histamine H3 receptors inhibit the release of not only histamine itself, but also other neurotransmitters including dopamine. Previous papers have reported that histaminergic neurons inhibit psychostimulant-induced behavioral changes. To examine whether deficiency in histamine H3 receptors influences psychostimulant-induced behavioral sensitization and reward, we examined locomotor activity, conditioned place preference (CPP), and c-Fos expression in histamine H3 receptor–gene knockout mice (H3KO) and their wild-type (WT) counterparts before and after treatment with methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA). The increase in locomotion induced by treatment with METH or MDMA was lower in histamine H3KO mice than in WT mice, while the locomotor sensitization was developed by METH or MDMA in both strains. However, no significant difference in METH- and MDMA-induced preference scores of CPP between histamine H3KO mice and WT mice was observed. Following treatment with METH, the number of c-Fos–positive neurons in the the caudate-putamen of histamine H3KO mice was lower than that in the caudate-putamen of WT mice. In contrast, there was no significant difference in the number of the psychostimulant-induced c-Fos–positive cells in the nucleus accumbens between the two strains of mice. These findings suggest that deficiency in histamine H3 receptors may have inhibitory effects on psychostimulant-induced increase in locomotion, but insignificant effects on the reward.
Our previous studies showed that administration of a subtoxic dose of acetaminophen (APAP) to female rats increased generation of carbon monoxide from dichloromethane, a metabolic reaction catalyzed mainly by cytochrome P450 (CYP) 2E1. In this study we examined the changes in metabolism and toxicity of APAP upon repeated administration. An intraperitoneal dose of APAP (500 mg/kg) alone did not increase aspartate aminotransferase, alanine aminotransferase, or sorbitol dehydrogenase activity in serum, but was significantly hepatotoxic when the rats had been pretreated with an identical dose of APAP 18 h earlier. The concentrations and disappearance of APAP and its metabolites in plasma were monitored for 8 h after the treatment. APAP pretreatment reduced the elevation of APAP-sulfate, but increased APAP-cysteine concentrations in plasma. APAP or APAP-glucuronide concentrations were not altered. Administration of a single dose of APAP 18 h before sacrifice increased microsomal CYP activities measured with p-nitrophenol, p-nitroanisole, and aminopyrine as probes. Expression of CYP2E1, CYP3A, and CYP1A proteins in the liver was also elevated significantly. The results suggest that administration of APAP at a subtoxic dose may result in an induction of hepatic CYP enzymes, thereby altering metabolism and toxicological consequences of various chemical substances that are substrates for the same enzyme system.
In several types of cancer cells, prostaglandins produced via the over-expression of epidermal growth factor receptor (EGFR) and cyclooxygenases regulate cell growth. We investigated the signaling mechanisms for the release of arachidonic acid (AA, a precursor for prostaglandins) in human cervical carcinoma HeLa cells. Treatment with EGF and 4β-phorbol 12-myristate 13-acetate (PMA) with A23187 released AA accompanied by the phosphorylation of extracellular signal-regulated kinases (ERK1/2). Pharmacological experiments showed that the responses (ERK phosphorylation and AA release) induced by EGF and PMA were mediated by a mitogen-activated protein kinase/ERK kinase (MEK) – ERK – α-type cytosolic phospholipase A2 (cPLA2α) pathway and that EGFR couples with the pathway in a manner insensitive to sorafenib, an inhibitor of B- and C-Raf, enzymes upstream of MEK. Activation of protein kinase C by PMA couples with the pathway partly in a sorafenib-sensitive and probably C-Raf–mediated manner and partly in a family of Src tyrosine kinases (Src)–dependent and sorafenib-insensitive manner. Co-treatment with sorafenib and an inhibitor of Src family members additionally inhibited the PMA-induced release of AA. Cross-talk between EGFR and protein kinase C was not observed. In human lung carcinoma A549 cells, the release of AA by EGF was insensitive to sorafenib. Possible mechanisms for the sorafenib-insensitive activation of the MEK–ERK–cPLA2α pathway are discussed.
The present study investigated whether telmisartan, an angiotensin II type 1 receptor antagonist, has cardioprotective effects on monocrotaline-induced right ventricular (RV) remodeling in rats. Six-week-old male Wistar rats were divided into control group (CONT), monocrotaline (60 mg/kg, i.p.)–treated group (MCT), monocrotaline (60 mg/kg, i.p.) + telmisartan (3 mg/kg per day, p.o.)–treated group (MCT+TEL), and telmisartan (3 mg/kg per day, p.o.) alone–treated group (TEL). Hearts were excised after echocardiography examinations at day 25. Significant increase in RV weight and histologically remarkable fibrosis in RV sections were observed in MCT. Tricuspid annular plane systolic excursion, a parameter for RV systolic function, significantly decreased in MCT. These RV hypertrophy, fibrosis, and dysfunction were inhibited in MCT+TEL. In MCT, the acceleration time/ejection time ratio of pulmonary artery flow velocity, an index of pulmonary hypertension, significantly decreased. This decrease was not affected in MCT+TEL. In MCT, expressions and activities of matrix metalloproteinase (MMP)-2 and MMP-9, which play a critical role in cardiac remodeling, significantly increased in the RV. In MCT+TEL, these increases in expressions and activities were inhibited. MCT showed about 2-fold increase in transforming growth factor-β1 expression compared with CONT, and such an increase was not decreased in MCT+TEL. There were no significant changes of these parameters in TEL compared with CONT. These results suggest that telmisartan could attenuate the monocrotaline-induced RV remodeling through improvements of RV hypertrophy, fibrosis, dysfunction, and inhibition of MMPs.
Attenuating effects of peroxisome proliferators on the concentration of free arachidonic acid by inducing 1-acyl-2-lysophospholipid acyltransferases in the kidney were studied. The administration of the three structurally dissimilar peroxisome proliferators, 2-(4-chlorophenoxy)-2-methylpropionic acid (clofibric acid), di(2-ethylhexyl)phthalate, and 2,2'-(decamethylenedithio)diethanol, to rats or mice considerably increased the activities of microsomal 1-acylglycerophosphoethanolamine acyltransferase (LPEAT), 1-acylglycerophosphoinositol acyltransferase (LPIAT), 1-acylglycerophosphoserine acyltransferase (LPSAT), and 1-acylglycerophosphocholine acyltransferase (LPCAT), and the mRNA level of LPCAT3, but not the mRNA level of LPCAT1, LPCAT4, or LPEAT1, in the kidney and the liver. The proportions of arachidonic acid in phospholipids in renal microsomes are rather high for the low proportion of arachidonic acid in free fatty acids in renal microsomes of control rats. The treatment of rats with clofibric acid attenuated the concentration and the proportion of free arachidonic acid to about a half; nevertheless the treatment lowered slightly the proportions of arachidonic acid in phospholipids other than phosphatidylcholine. These results indicate that peroxisome proliferators upregulate the four 1-acyl-2-lysophospholipid acyltransferases of the kidney and, and the induced 1-acyl-2-lysophospholipid acyltransferases seem to play a physiologically crucial contribution in attenuating the pool of free arachidonic acid in the kidney.
This study examined the effect of ozagrel, a thromboxane A2 synthase inhibitor, on the accumulation of leucocytes and chemokine mRNA expression in lungs experimentally injured using oleic acid (OA). OA injection into guinea pigs rapidly increased thromboxane A2 generation and subsequently increased total protein concentration and the numbers of macrophages and neutrophils in bronchoalveolar lavage fluid and increased monocyte chemoattractant protein-1 and interleukin-8 mRNA expression in the whole lung. Administration of ozagrel prevented these changes associated with OA injection. Ozagrel is a promising drug candidate for preventing acute lung injury.
Isoliquiritigenin (ISL) suppresses cocaine-induced extracellular dopamine levels and has a neuroprotective effect in cocaine-treated rat brain. Here, we examine the effect of ISL on methamphetamine-induced striatal neurotoxicity. Repeated injections of methamphetamine cause the loss of striatal dopamine transporter (DAT) and tyrosine hydroxylase (TH). Intraperitoneal injection of ISL prior to methamphetamine injection significantly prevented methamphetamine-induced reduction of DAT and TH. ISL also suppressed methamphetamine-induced activation of glial cells. Moreover, ISL impeded the expression of nitric oxide synthase and the activation of NF-κB through blockage of its phosphorylation. Our results suggest that ISL protects against methamphetamine-induced neurotoxicity by inhibition of NF-κB activation.
We examined the effects of lomerizine on serotonin (5-hydroxytryptamine, 5-HT)–induced contraction of the basilar artery and compared them with those of nifedipine. Although both lomerizine and nifedipine completely blocked K+-induced vasoconstriction, 5-HT–induced vasoconstriction was more strongly inhibited by lomerizine than nifedipine. A 5-HT2A antagonist inhibited the 5-HT–induced vasoconstriction, but a 5-HT1B antagonist did not. Lomerizine, but not nifedipine, suppressed 5-HT–induced Ca2+ release in 5-HT2A–expressing HEK293 cells. Moreover, neither antagonist affected ATP-induced Ca2+ release. These results suggest that lomerizine may inhibit not only voltage-dependent Ca2+ channels but also 5-HT2A receptors and so inhibit 5-HT–induced contraction in the basilar artery.