Beyond the 5-HT3 receptors: A role for α7nACh receptors in neuroprotective aspects of tropisetron.

Accumulation of reactive oxygen species, such as hydrogen peroxide (H2O2), generated by inflammatory cells or other pathological conditions, leads to oxidative stress, which may contribute to the neuronal degeneration observed in a wide variety of neurodegenerative disorders such as Alzheimer's disease. Recent investigations have described effective properties of tropisetron, such as antiphlogistic action or protection against ß-amyloid induced-neuroinflammation in rats. Our data revealed that H2O2-induced cell death in rat pheochromocytoma cell line (PC12) can be inhibited by tropisetron, as defined by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide assay, caspase 3 and caspase 12 levels. We further showed that tropisetron exerts its protective effects by upregulation of heme oxygenase-1, glutathione, catalase activity, and nuclear factor-erythroid 2 p45-related factor 2 level. Moreover, tropisetron was recently found to be a partial agonist of α7 nicotinic acetylcholine receptor (α7nAChR). The activation of α7nAChR could inhibit inflammatory and apoptotic signaling pathways in the oxidative stress conditions. In this study, selective α7nAChR antagonists (methyllycaconitine) reversed the effects of tropisetron on caspase 3 level. Our findings indicated that tropisetron can protect PC12 cells against H2O2-induced neurotoxicity through α7nAChR in vitro.

Diagnostic accuracy of Cone Beam Computed Tomography, conventional and digital radiographs in detecting interproximal caries.

STATEMENT OF THE PROBLEM: Presently, various imaging methods are available for the disclosure of proximal caries. Some recent studies have attempted to determine the diagnostic accuracy of available modalities, but they have shown variable results. Aim: This study was carried out to recognize and examine the correctness of cone-beam computed tomography (CBCT), regular radiographs and the nondirect digital system in the disclosure of interproximal caries. Materials and Method: In this observational tryout study, forty-two extracted non-cavitated, unrestored person molar and premolar teeth were placed in the blocks with proximal surfaces in touch. Then they were appraised by CBCT, formal radiographs and the nondirect digital system for the disclosure of interproximal caries. Four oral and maxillofacial radiologists used a 4-point scale to assess the pictures for the existence or absence of proximal caries. Caries depth was specified by histological examination. The gathered data were assessed by SPSS software using Weighted Kappa and Friedman test. Results: Statistics demonstrated that the accuracy of the indirect digital system was somewhat better than conventional systems. The accuracy of the indirect digital system was better than cone beam system, and this difference was statistically significant. Conclusion: The digital system was better than CBCT in the disclosure of proximal caries. The formal radiography fell in between the two other systems without a statistically significant deviation in detecting caries. Thus, CBCT is not advised to detect proximal caries because of the higher radiation dose.

Pretreatment with clonidine caused desensitization to WIN 55,212-2 in guinea pig ileum.

Considering the existence of cross-tolerance between clonidine and morphine besides the same interaction between morphine and WIN 55,212-2 persuaded us to verify this fact between WIN 55,212-2 and clonidine in guinea pig ileum, which is a well-known model to examine the mode of action of cannabinoids and α2 -adenoceptor agonists The rectangular pulses were passed to the 0.5 g stretched ileum segments that were fixed in 20-ml organ bath. PowerLab system and Graphpad Prism were applied to record twitches and analyse the data. Electrically evoked contractions were dose-dependently inhibited by WIN 55,212-2 and clonidine (pD2 = 8.56 ± 0.41 and 7.65 ± 0.15, respectively). Tolerance to this effect could be induced by 4-h incubation with WIN 55,212-2 (3 × IC50 ) (pD2  = 6.36 ± 0.26, degree of tolerance: 159.32) (P < 0.01) but not with clonidine (2 × IC50 and 4 × IC50 ) for different time courses. Dose-response curve for inhibitory action of WIN 55,212-2 was shifted to the right after 4-h incubation with clonidine (3 × 10(-10) m) comparing to the untreated tissues (pD2  = 5.26 ± 0.69, degree of tolerance: 2000) (P < 0.001). This observation provides the evidence for the cannabinoid-noradrenergic systems interaction in the enteric nervous system as a simplified representative for central nervous system.

Tropisetron diminishes demyelination and disease severity in an animal model of multiple sclerosis.

Tropisetron, a selective 5-HT3 receptor (5-HT3R) antagonist, has been widely used to counteract chemotherapy-induced emesis. New investigations described the immunomodulatory properties of tropisetron which may not be 5HT3R mediated. In the present study, we assessed the potential effects of tropisetron on an animal model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). EAE was induced in C57BL/6 mice by myelin oligodendrocyte glycoprotein peptide (MOG35-55) immunization. Animals were treated with tropisetron (5 mg/kg/day); m-chlorophenylbiguanide (mCPBG), a selective 5-HT3R agonist (10 mg/kg/day); tropisetron (5 mg/kg/day) plus mCPBG (10 mg/kg/day), and granisetron (5 mg/kg/day) intraperitoneally on days 3-35 post-immunization. Treatment with tropisetron and granisetron markedly suppressed the clinical symptoms of EAE (p<0.001) and reduced leukocyte infiltration as well as demyelination in the spinal cord (p<0.05). In addition, in vivo tropisetron, granisetron or tropisetron plus mCPBG therapy greatly reduced in vitro MOG35-55-stimulated proliferation of mononuclear cells from spleens, and MOG35-55-induced IL-2, IL-6 and IL-17 production by splenocytes isolated from EAE-induced mice (p<0.05). Concurrent administration of tropisetron and mCPBG did not significantly alter the histological damage in the spinal cord. mCPBG had no effect on the mentioned parameters. Taken together, these findings indicate that tropisetron has considerable immunoregulatory functions in EAE and may be promising for the treatment of MS or other autoimmune and inflammatory diseases of the CNS. Furthermore, beneficial effects of tropisetron in this setting seem to be both receptor dependent and receptor independent in the early phase of the disease.

Noninvasive clinical assessment of port-wine stain birthmarks using current and future optical imaging technology: a review.

Port-wine stain (PWS) birthmarks are one class of benign congenital vascular malformation. Laser therapy is the most successful treatment modality of PWS. Unfortunately, this approach has limited efficacy, with only 10% of patients experiencing complete blanching of the PWS. To address this problem, several research groups have developed technologies and methods designed to study treatment outcome and improve treatment efficacy. This article reviews seven optical imaging techniques currently in use or under development to assess treatment efficacy, focusing on: reflectance spectrophotometers/tristimulus colorimeters; laser Doppler flowmetry and laser Doppler imaging; cross-polarized diffuse reflectance colour imaging system; reflectance confocal microscopy; optical coherence tomography; spatial frequency domain imaging; and laser speckle imaging.

Anti-inflammatory effects of 5-HT receptor antagonist, tropisetron on experimental colitis in rats.

BACKGROUND: There is a pressing need for research that will lead to the development of new therapeutic approaches for treating inflammatory bowel disease (IBD). The aim of this study was to investigate the effects of tropisetron, a 5-Hydroxytryptamine (5-HT)-3 receptor antagonist with anti-inflammatory properties in a model of experimental colitis in rat. MATERIALS AND METHODS: Acetic acid model of colitis in rats was used. Colitis was induced by intracolonal instillation of 4% (v/v) acetic acid. One hour after induction of colitis, intraperitoneal (IP) or intrarectal (IR) tropisetron (2 mg kg(-1), either route) or dexamethasone (1 mg kg(-1), either route) was administered. The severity of colitis was assessed 24 h later using macroscopic and microscopic changes of damaged colon, measurement of inflammatory cytokines interleukin-1beta, interleukin-6 and tumour necrosis factor-alpha levels and oxidative stress markers myeloperoxidase (MPO) and malondialdehyde (MDA) in colonic tissues. RESULTS: Tropisetron decreased colonic macroscopic and microscopic damage scores. This was associated with significant reduction in both neutrophil infiltration indicated by decreased colonic MPO activity and lipid peroxidation measured by MDA content, as well as a decreased colonic inflammatory cytokines. IR tropisetron decreased colonic damage that was associated with decreased neutrophil infiltration, lipid peroxidation and colonic inflammatory cytokines. Beneficial effects of tropisetron were lower than those of dexamethasone. No significant differences were observed between IP and IR administration with the exception of MDA level more diminished by IP tropisetron and dexamethasone. CONCLUSIONS: Tropisetron exert beneficial effects in experimental rat colitis and therefore might be useful in the treatment of IBD.

Hepatic over-expression of peroxisome proliferator activated receptor gamma2 in the ob/ob mouse model of non-insulin dependent diabetes mellitus.

Studies of the molecular basis of insulin resistance have focused on the peroxisome proliferator activated receptor gamma (PPARgamma, gamma1 and gamma2). The aim of this study was to determine whether the insulin resistance in liver of diabetic animals is associated with abnormal expression of these receptors. PPARgamma mRNA and protein expression levels were quantified in liver of 9-week-old male ob/ob mice as a model of diabetes and compared to age- and gender-matched wild type control animals of the same genetic background. Semi-quantitative reverse transcription-polymerase chain reaction, using 18S rRNA as an internal standard, indicated that PPARgamma2 mRNA was significantly upregulated in ob/ob liver vs. that in wild type mice. Western blotting revealed greater immunoreactivity of PPARgamma2 in liver from ob/ob mice relative to that in wild type mice. An index of insulin resistance (product of serum glucose and insulin concentration) was correlated with liver PPARgamma2 mRNA expression (r = 0.776; p < 0.001). The findings that liver PPARgamma2 expression is (1) significantly elevated in the ob/ob model of diabetes and (2) positively associated with an index of insulin resistance, suggests a possible compensatory response through which type II diabetic and obese organisms strive to maintain insulin sensitivity of the liver.

Gender difference in the basal intracellular Ca2+ concentration in rat valvular endothelial cells.

Intracellular Ca2+ concentration ([Ca2+]i) was measured by Fura 2/AM fluorescence imaging microscopy in freshly isolated valvular endothelial cells taken from female and male rats. The basal level of [Ca2+]i was significantly elevated in female valvular endothelial cells when compared to males (P < 0.05). Inhibition of the sarco-endoplasmic reticulum Ca(2+)-ATPase with cyclopiazonic acid (CPA, 10 microM) caused a greater increase in the [Ca2+]i in female than male endothelial cells. Removal of extracellular Ca2+ returned the [Ca2+]i to the basal level. The rate of [Ca2+]i decline was significantly slower in female endothelial cells compared to males. There were no differences in the unstimulated rate of Mn2+ quenching between two groups. These results demonstrate that estrogen affects NOS at least in part, by an alteration in Ca2+ homeostasis in endothelial cells.

Estrogen and selective estrogen receptor modulator LY117018 enhance release of nitric oxide in rat aorta.

We report on the modulatory effects of chronic subcutaneous or oral estrogen and LY117018, a selective estrogen receptor modulator, on the release of nitric oxide in rings of rat aorta studied under isometric conditions. Dilator responses to acetylcholine (ACh; 10[8] to 10[-5] M) were obtained in phenylephrine (PE; 2 microM)-contracted aorta, and constrictor dose-response curves to PE (10[-8] to 10[-5] M) were generated before and after pretreatment with N omega-nitro-L-arginine methyl ester (L-NAME; 200 microM), an inhibitor of nitric oxide synthase. Tissue segments were obtained from five groups of rats implanted with a subcutaneous pellet delivery system for 21 days: (1) male, (2) sham-operated placebo-treated female, (3) ovariectomized placebo-treated, (4) ovariectomized, 17beta-estradiol treated (0.5 mg/pellet) and (5) ovariectomized, progesterone (15 mg/pellet) and 17beta-estradiol (0.5 mg/pellet)-treated. Aortic rings from sham rats and ovariectomized rats receiving estrogen relaxed more to ACh (10[-6] to 10[-5] M) than did the rings from ovariectomized, progesterone plus estrogen-treated and male rats (P < .05). They were also characterized by a greater potentiation of the PE responses after L-NAME compared with male, progesterone plus estrogen-treated and ovariectomized rats (P < .05) and a similar sensitivity to PE. In addition, ACh-induced relaxation and L-NAME-induced potentiation of PE contractions in aortic rings from rats dosed orally with LY117018 were similar to responses of aortic rings from rats dosed orally with estrogen. These results demonstrate that chronically administered estrogen and LY117018 enhance the release of nitric oxide from endothelium in rat aortic rings.

Estrogen augments cyclopiazonic acid-mediated, endothelium-dependent vasodilation.

The modulatory effects of chronic estrogen treatment on the responses to cyclopiazonic acid, an endoplasmic reticulum Ca2(+)-ATPase inhibitor, were studied in rings of aorta and the isolated perfused kidney of the rat. Rings of aorta were obtained from the following groups of age-matched rats (i) male, (ii) female, and two groups of rats implanted with a subcutaneous pellet (iii) ovariectomized, placebo-treated, (iv) ovariectomized, 17beta-estradiol-treated (0.5 mg/pellet/21 days). In phenylephrine (2 microM) pre-contracted rings with intact endothelium, cyclopiazonic acid (10(-7) to 3 x 10(-5) M) produced endothelium-dependent relaxations in a concentration-dependent manner. The cyclopiazonic acid dilation as a percentage loss of phenylephrine tone was greater in aortic rings from female (72.9 +/- 2.4%) and estrogen-treated rats (65.5 +/- 4.8%) compared to those from male (51.5 +/- 3.4%) or ovariectomized rats (40.8 +/- 3.9%) (P < 0.05, one-way analysis of variance (ANOVA)). These relaxation responses of cyclopiazonic acid were converted to contractions by pre-treatment with an inhibitor of nitric oxide (NO) synthase, N(omega)-nitro-L-arginine methyl ester (L-NAME, 200 microM; 30 min). There were no differences in cyclopiazonic acid-induced contractions of aortas excised from either estrogen-treated or untreated-ovariectomized rats. In perfused kidneys, cyclopiazonic acid (10(-5) M) caused a larger decrease in perfusion pressure in kidneys from female rats (110 +/- 0.4 mmHg) than it did in kidneys from male rats (80 +/- 0.6 mmHg). These results demonstrate that cyclopiazonic acid causes a greater endothelium-dependent dilation in estrogen-treated ovariectomized and control female rats, possibly due to unmasking of estrogen-enhanced Ca2+ entry into the endothelial cells.

Possible role of protein kinase C in regulation of 5-hydroxytryptamine 2A receptors in rat brain.

This study was undertaken to evaluate the effect of acute in vivo treatment with 1-(2,5-dimethoxy-4-iodo-phenyl)2-aminopropane (DOI), a selective 5-hydroxytryptamine 2A/2C (5HT2A/2C) receptor agonist, on the kinetic parameters of [3H]ketanserin binding to 5HT2A receptors and on the protein kinase C (PKC) activity in subcellular fractions of rat brain tissue. A single injection of DOI (10 mg/kg i.p.) downregulated (by 50%) 5HT2A receptor density in a cortical synaptosomal preparation assayed 24 h later. This effect was dose dependent, since a single injection of 5 mg/kg of DOI reduced the Bmax of [3H]ketanserin binding by 23% (without a change in Kd) and a single 1 mg/kg dose of DOI was without effect. Repeated doses of DOI (10 mg/kg for 3 days) further downregulated (by 63%) 5HT2A sites in cortical synaptosomes. A similar degree (50%) of downregulation of 5HT2A receptors by DOI (10 mg/kg) was seen in p-chloroamphetamine (PCA) lesioned rats, suggesting that the site of action of DOI in downregulation of 5HT2A receptors in rat brain is postsynaptic. An increase (by 38%) of PKC activity in the particulate fraction of the cortical synaptosomal preparation following a single injection of DOI (10 mg/kg) paralleled the decrease in 5HT2A receptor density, suggesting that 5HT2A sites may be downregulated as a result of phosphorylation of the receptor by activation of PKC after receptor stimulation with agonist. This possibility is further supported by the observation that three consecutive daily injections of DOI resulted in a significant decrease (by 19%) in cytosolic PKC activity and an increase (by 24%) of PKC activity in the particulate fraction. A single injection of DOI also induced a translocation of PKC activity from the cytosolic to the membrane fraction in PCA-lesioned rats. The present investigation has shown that downregulation of 5HT2A receptors in rat cerebral cortex by in vivo DOI treatment is accompanied by translocation of PKC activity from the cytosolic to the membrane fraction.