Schisandra chinensis Baill is a Chinese traditional medicine with multiple pharmacological activities. In this study, chicanine, one of the major lignan compounds of Schiandra chinesis, was investigated for suppressive effects on lipopolysaccharide (LPS)-induced inflammatory responses in murine macrophages (RAW 264.7 cells). Chicanine was found to have anti-infammatory properties with the inhibition of nitric oxide (NO) and Prostaglandin E (2) (PGE2) production and nuclear factor-κB (NF-κB) signaling in LPS-stimulated RAW 264.7 cells with no cytotoxic effects. Treatment of RAW 264.7 cells with chicanine down-regulated LPS-induced expression of pro-inflammatory cytokines including TNFα, IL-1β, MCP-1, G-CSF, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). These inhibitory effects were found with the blockage of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinases 1 and 2 (ERK 1/2), and also IκB-α phosphorylation. These results indicated that anti-inflammatory actions of chicanine in macrophages involved inhibition of LPS-induced TLR4-IκBα/MAPK/ERK signaling pathways.
Chicanine; inflammatory cytokines; IκBα; MAPK; ERK
Exposure to high or repeated doses of methamphetamine can cause hyperthermia and neurotoxicity, which are thought to increase the risk of developing a variety of neurological conditions. Sigma receptor antagonism can prevent methamphetamine-induced hyperthermia and neurotoxicity, but the underlying cellular targets through which the neuroprotection is conveyed remain unknown. Differentiated NG108-15 cells were thus used as a model system to begin elucidating the neuroprotective mechanisms targeted by sigma receptor antagonists to mitigate the effects of methamphetamine. In differentiated NG108-15 cells, methamphetamine caused the generation of reactive oxygen/nitrogen species, an increase in PERK-mediated endoplasmic reticulum stress and the activation of caspase-3, -8 and -9, ultimately resulting in apoptosis at micromolar concentrations, and necrotic cell death at higher concentrations. The sigma receptor antagonist, 6-acetyl-3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one (SN79), attenuated methamphetamine-induced increases in reactive oxygen/nitrogen species, activation of caspase-3,-8 and-9 and accompanying cellular toxicity. In contrast, 1,3-di(2-tolyl)-guanidine (DTG), a sigma receptor agonist, shifted the dose response curve of methamphetamine-induced cell death towards the left. To probe the effect of temperature on neurotoxicity, NG108-15 cells maintained at an elevated temperature (40 °C) exhibited a significant and synergistic increase in cell death in response to methamphetamine, compared to cells maintained at a normal cell culture temperature (37 °C). SN79 attenuated the enhanced cell death observed in the methamphetamine-treated cells at 40 °C. Together, the data demonstrate that SN79 reduces methamphetamine-induced reactive oxygen/nitrogen species generation and caspase activation, thereby conveying neuroprotective effects against methamphetamine under regular and elevated temperature conditions.
Apoptosis; Caspase; Methamphetamine; Necrosis; Reactive oxygen species; Sigma receptors
Little is known of the interactions between diabetes and sex on vascular function. The objectives of this study were to investigate whether there were sex differences in rat aortic endothelial function one week after the induction of streptozotocin (STZ)-diabetes, and to examine the potential roles of superoxide and nitric oxide (NO) in this sex-specific effect. Endothelium-dependent vasodilatation to acetylcholine (ACh) was measured in rat aortic rings before and after treatment with MnTMPyP (25 μM), a superoxide dismutase. Contractile responses to phenylephrine (PE) were generated before and after treatment with L-NAME (200 μM), a nitric oxide synthase (NOS) inhibitor. The mRNA expression of NADPH oxidase (Nox) and endothelial nitric oxide synthase (eNOS) were also determined. We demonstrated that 1) STZ-diabetes impaired endothelium-dependent vasodilatation to ACh to a greater extent in female than male aortae, 2) inhibition of superoxide enhanced sensitivity to ACh only in diabetic females, and 3) Nox1 and Nox4 mRNA expression was significantly elevated only in aortic tissue of diabetic females. Furthermore, incubation of aortic rings with L-NAME potentiated PE responses in all groups, but aortae from control females showed a greater potentiation of the PE response after NOS inhibition compared with others. STZ-diabetes reduced the extent of PE potentiation after L-NAME and the aortic eNOS mRNA expression in females to the same levels as seen in males. These data suggest that a decrease in NO, resulting from either decreased eNOS or elevated superoxide, may partially contribute to the predisposition of the female aorta to injury early in diabetes.
Sex difference; diabetes; endothelial dysfunction; nitric oxide; superoxide
Controlling angiotensin AT1 receptor function has been shown to be protective for many pathophysiological disorders. Although estrogen metabolite, 2-methoxyestradiol (2ME2) can down-regulate angiotensin AT1 receptor expression independently of nuclear receptors, no specific cellular targets have been identified. This study was focused on identification and validation of a cellular target responsible for 2ME2-mediated angiotensin AT1 receptor down-regulation in a continuously passaged rat liver epithelial cell line. Cell membranes were isolated and used to determine 2ME2 specific binding. Cell membranes exposed to [3H]2ME2 showed specific saturable binding, which was found to be pertussis toxin (PTx) sensitive. Under similar conditions, G-protein coupled receptor 30 (GPR30) agonist (G1) and antagonist (G15) inhibited 2ME2 specific binding. In these cells GPR30 was found localized to endoplasmic reticulum (ER) membranes. In intact cells, G1 down-regulated angiotensin AT1 receptor expression and this effect was reversed by G15. Furthermore, 2ME2 mediated activation of epidermal growth factor receptor (EGFR) followed by ERK1/2 phosphorylation, an essential signaling step in angiotensin AT1 receptor down-regulation, was abrogated by G15, suggesting that this signal is GPR30 dependent. Additionally, EGF was found to independently down-regulate angiotensin AT1 receptor in an ERK1/2-dependent manner. In summary, our results demonstrate for the first time that 2ME2 down-regulation of angiotensin AT1 receptor is dependent on ER membrane-associated GRP30. Moreover, this effect is facilitated by GPR30 dependent transactivation of EGFR and ERK1/2 phosphorylation. This study provides further understanding of the physiological significance of 2ME2 and its role in modulating angiotensin AT1 receptor expression.
Angiotensin II; angiotensin AT1 receptor; 2-Methoxyestradiol (2ME2); G-Protein coupled receptor 30 (GPR30); MAP-Kinase; Epidermal growth factor receptor (EGFR)
Recent evidence of neuropathic pain among adults with sickle cell disease (SCD) reveals a need for adjuvant analgesic treatments for these patients. Ca2+/calmodulin protein kinase IIα (CaMKIIα) has a known role in neuropathic pain and trifluoperazine is a potent CaMKIIα inhibitor. The study aim was to determine trifluoperazine's acute effects, primarily on adverse effects and secondarily on pain intensity reduction, in adults with SCD. In a phase I, open-label study of 6 doses of trifluoperazine (0.5, 1, 2, 5, 7.5, 10 mg), we obtained 7-hourly and 24-hour repeated measures of adverse effects, pain intensity, and supplemental opioid analgesics in 18 adults with SCD (18 hemoglobin SS disease, 15 women, average age 35.8 ± 8.9 years, ranged 23-53) each of whom received a single dose. Data were analyzed with descriptive statistics. Subjects reported moderate to severe sedative effects at 7.5 and 10 mg doses, respectively. Eight subjects reported 50% reduction in chronic pain without severe sedation or supplemental opioid analgesics; one of these subjects had dystonia 24.5 hrs after the 10 mg dose. The analgesic effect lasted for at least 24 hrs in 3 subjects. Sedation resolved with caffeine and dystonia resolved with diphenhydramine. Adults with SCD experienced minimal adverse effects at doses under 10 mg. In this molecular mechanism-driven translational study, trifluoperazine shows promise as an analgesic drug that is worthy of further testing in a randomized controlled study of adults with SCD starting at a dose of 1 mg in repeated doses to determine long-term adverse and analgesic effects.
sickle cell disease; neuropathic pain; phase 1 study; safety; trifluoperazine
We previously found that estrogen exerts a novel protective effect on mitochondria in brain vasculature. Here we demonstrate in rat cerebral blood vessels that 17β-estradiol (estrogen), both in vivo and ex vivo, affects key transcriptional coactivators responsible for mitochondrial regulation. Treatment of ovariectomized rats with estrogen in vivo lowered mRNA levels of peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1α) but increased levels of the other PGC-1 isoforms: PGC-1β and PGC-1 related coactivator (PRC). In vessels ex vivo, estrogen decreased protein levels of PGC-1α via activation of phosphatidylinositol 3-kinase (PI3K). Estrogen treatment also increased phosphorylation of forkhead transcription factor, FoxO1, a known pathway for PGC-1α downregulation. In contrast to the decrease in PGC-1α, estrogen increased protein levels of nuclear respiratory factor 1, a known PGC target and mediator of mitochondrial biogenesis. The latter effect of estrogen was independent of PI3K, suggesting a separate mechanism consistent with increased expression of PGC-1β and PRC. We demonstrated increased mitochondrial biogenesis following estrogen treatment in vivo; cerebrovascular levels of mitochondrial transcription factor A and electron transport chain subunits as well as the mitochondrial/ nuclear DNA ratio were increased. We examined a downstream target of PGC-1β, glutamate-cysteine ligase (GCL), the rate-limiting enzyme for glutathione synthesis. In vivo estrogen increased protein levels of both GCL subunits and total glutathione levels. Together these data show estrogen differentially regulates PGC-1 isoforms in brain vasculature, underscoring the importance of these coactivators in adapting mitochondria in specific tissues. By upregulating PGC-1β and/or PRC, estrogen appears to enhance mitochondrial biogenesis, function and reactive oxygen species protection.
Cerebral blood vessels; Estrogen; Glutamate-cysteine ligase; Mitochondria; Peroxisome proliferator-activated; receptor-gamma coactivator-1 (PGC-1); Glutathione
The duration of action of a drug is commonly estimated using plasma concentration, which is not always practical to obtain or an accurate estimate of functional half life. For example, flumazenil is used clinically to reverse the effects of benzodiazepines like midazolam; however, its elimination can be altered by other drugs, including some benzodiazepines, thereby altering its half life. This study used Schild analyses to characterize antagonism of midazolam by flumazenil and determine the functional half life of flumazenil. Four monkeys discriminated 0.178 mg/kg midazolam while responding under a fixed-ratio 10 schedule of stimulus-shock termination; flumazenil was given at various times before determination of a midazolam dose-effect curve. There was a time-related decrease in the magnitude of shift of the midazolam dose-effect curve as the interval between flumazenil and midazolam increased. The potency of flumazenil, estimated by apparent pA2 values (95% CI), was 7.30 (7.12, 7.49), 7.17 (7.03, 7.31), 6.91 (6.72, 7.10) and 6.80 (6.67, 6.92) at 15, 30, 60 and 120 min after flumazenil administration, respectively. The functional half life of flumazenil, derived from potency estimates, was 57 ± 13 min. Thus, increasing the interval between flumazenil and midazolam causes orderly decreases in flumazenil potency; however, across a broad range of conditions, the qualitative nature of the interaction does not change, as indicated by slopes of Schild plots at all time points that are not different from unity. Differences in potency of flumazenil are therefore due to elimination of flumazenil and not due to pharmacodynamic changes over time.
midazolam; flumazenil; benzodiazepine; drug discrimination; rhesus monkey
The hemodynamic effects of the novel, selective adenosine A3 receptor agonist 2-chloro-N6-(3-iodobenzyl)adenosine-5′-N-methyl-carboxamide (2-Cl-IB-MECA) were investigated in conscious rats. Intravenous administration of 200 μg/kg 2-Cl-IB-MECA resulted in a short-lasting hypotension, which was accompanied by a 50–100-fold increase in plasma histamine concentrations. Administration of a second dose of 2-Cl-IB-MECA did not elicit any hemodynamic effects. Also no histamine release was observed after the second dose. The observation of rapid tachyphylaxis in combination with histamine release suggests that mast cell mediator release plays a key role in the hemodynamic effects of adenosine A3 receptor agonists.
Adenosine A3 receptor; Hemodynamics; Histamine release; Tachyphylaxis; 2-Chloro-N6-(3-iodobenzyl)adenosine-5-N-methylcarboxamide (2-Cl-IB-MECA); Rat, conscious
Nausea and vomiting (emesis) are important elements in defensive or protective responses that animals use to avoid ingestion or digestion of potentially harmful substances. However, these neurally-mediated responses are at times manifested as symptoms of disease and they are frequently observed as side-effects of a variety of medications, notably those used to treat cancer. Cannabis has long been known to limit or prevent nausea and vomiting from a variety of causes. This has led to extensive investigations that have revealed an important role for cannabinoids and their receptors in the regulation of nausea and emesis. With the discovery of the endocannabinoid system, novel ways to regulate both nausea and vomiting have been discovered that involve the production of endogenous cannabinoids acting centrally. Here we review recent progress in understanding the regulation of nausea and vomiting by cannabinoids and the endocannabinoid system, and we discuss the potential to utilize the endocannabinoid system in the treatment of these frequently debilitating conditions.
Cannabis; serotonin; emesis; brainstem; insular cortex; CB1 receptor; CB2 receptor
Nausea and vomiting are among the most frequently occurring symptoms observed by clinicians. While advances have been made in understanding both the physiological as well as the neurophysiological pathways involved in nausea and vomiting, the final common pathway(s) for emesis have yet to be defined. Regardless of the difficulties in elucidating the precise neurocircuitry involved in nausea and vomiting, it has been accepted for over a century that the locus for these neurocircuits encompasses several structures within the medullary reticular formation of the hindbrain and that the role of vagal neurocircuits in particular are of critical importance. The afferent vagus nerve is responsible for relaying a vast amount of sensory information from thoracic and abdominal organs to the central nervous system. Neurons within the nucleus of the tractus solitarius not only receive these peripheral sensory inputs but have direct or indirect connections with several other hindbrain, midbrain and forebrain structures responsible for the co-ordination of the multiple organ systems. The efferent vagus nerve relays the integrated and co-ordinated output response to several peripheral organs responsible for emesis. The important role of both sensory and motor vagus nerves, and the available nature of peripheral vagal afferent and efferent nerve terminals, provides extensive and readily accessible targets for the development of drugs to combat nausea and vomiting.
Vagus; Brainstem; NTS; DVC
Clinical research shows that postoperative nausea and vomiting (PONV) is caused primarily by the use of inhalational anesthesia and opioid analgesics. PONV is also increased by several risk predictors, including a young age, female sex, lack of smoking, and a history of motion sickness. Genetic studies are beginning to shed light on the variability in patient experiences of PONV by assessing polymorphisms of gene targets known to play roles in emesis (serotonin type 3, 5-HT3; opioid; muscarinic; and dopamine type 2, D2, receptors) and the metabolism of antiemetic drugs (e.g., ondansetron). Significant numbers of clinical trials have produced valuable information on pharmacological targets important for controlling PONV (e.g., 5-HT3 and D2), leading to the current multi-modal approach to inhibit multiple sites in this complex neural system. Despite these significant advances, there is still a lack of fundamental knowledge of the mechanisms that drive the hindbrain central pattern generator (emesis) and forebrain pathways (nausea) that produce PONV, particularly the responses to inhalational anesthesia. This gap in knowledge has limited the development of novel effective therapies of PONV. The current review presents the state of knowledge on the biological mechanisms responsible for PONV, summarizing both preclinical and clinical evidence. Finally, potential ways to advance the research of PONV and more recent developments on the study of postdischarge nausea and vomiting (PDNV) are discussed.
Nausea; Vomiting; Emesis; Anesthesia; Surgery; Opioid
The sympathetic neurotransmitter norepinephrine has been found to increase mucosal adherence of enterohemorrhagic Escherichia coli O157:H7 in explants of murine cecum and porcine distal colon. In the present study, we tested the hypothesis that norepinephrine augments the initial, loose adherence of this important pathogen to the intestinal mucosa. In mucosal sheets of porcine cecum or proximal, spiral and distal colon mounted in Ussing chambers, norepinephrine (10 µM, contraluminal addition) increased mucosal adherence of wild-type E. coli O157:H7 strain 85–170; in the cecal mucosa, this effect occurred within 15 – 90 min after bacterial inoculation. In addition, norepinephrine transiently increased short-circuit current in cecal and colonic mucosal sheets, a measure of active anion transport. Norepinephrine was effective in promoting cecal adherence of a non-O157 E. coli strain as well as E. coli O157:H7 eae or espA mutant strains that are incapable of intimate mucosal attachment. Nerve fibers immunoreactive for the norepinephrine synthetic enzyme dopamine β-hydroxylase appeared in close proximity to the cecal epithelium, and the norepinephrine reuptake blocker cocaine, like norepinephrine and the selective α2-adrenoceptor agonist UK-14,304, increased E. coli O157:H7 adherence. These results suggest that norepinephrine, acting upon the large bowel mucosa, modulates early, non-intimate adherence of E. coli O157:H7 and probably other mucosa-associated bacteria. Sympathetic nerves innervating the cecocolonic mucosa may link acute stress exposure or psychostimulant abuse with an increased microbial colonization of the intestinal surface. This in turn may alter host susceptibility to enteric infections.
Intimin; Type III secretion system; Mucosa-adherent bacteria; Norepinephrine; Cocaine; Enteric nervous system
Enteric neural activity modulates active transepithelial ion transport in the intestine. We investigated the neural circuits mediating neurogenic secretion in mucosal explants from porcine ileum. Transmural electrical stimulation increased short-circuit current, a measure of active ion transport, by 35 ± 2 µA/cm2. The neuronal Na+ channel blocker saxitoxin, the muscarinic cholinergic receptor antagonist atropine, the 5-hydroxytryptamine3 receptor antagonist tropisetron, and the cyclooxygenase inhibitor indomethacin inhibited this response. In addition, tropisetron inhibited the atropine-resistant portion of the response, and both atropine and indomethacin attenuated the saxitoxin-resistant component. Neurogenic secretion in porcine ileum appears to be mediated by tryptaminergic and prostanoid-sensitive cholinergic pathways.
Transmural electrical stimulation; Short-circuit current; 5-hydroxytryptamine 3 receptor; Muscarinic cholinergic receptor; Intestinal mucosa
The complement cascade is a highly sophisticated network of proteins that are well regulated and directed in response to invading pathogens or tissue injury. Complement C3a and C5a are key mediators produced by this cascade, and their dysregulation has been linked to a plethora of inflammatory and autoimmune diseases. Consequently, this has stimulated interest in the development of ligands for the receptors for these complement peptides, C3a receptor, and C5a1 (C5aR/CD88). In this study we used computational methods to design novel C5a1 receptor ligands. However, functional screening in human monocyte-derived macrophages using the xCELLigence label-free platform demonstrated altered specificity of our ligands. No agonist/antagonist activity was observed at C5a1, but we instead saw that the ligands were able to partially agonize the closely related complement receptor C3a receptor. This was verified in the presence of C3a receptor antagonist SB 290157 and in a stable cell line expressing either C5a1 or C3a receptor alone. C3a agonism has been suggested to be a potential treatment of acute neutrophil-driven traumatic pathologies, and may have great potential as a therapeutic avenue in this arena.
C3a receptor; C5a1 receptor; Peptide design; In silico sequence selection; Computational optimization; Label-free screening
Antipsychotic drugs provide limited efficacy for cognitive impairment in schizophrenia. Recent studies have found that the neurotensin NTS1 receptor agonist and putative atypical antipsychotic drug PD149163 reverses deficits in sensory-gating and novel object recognition, suggesting that this compound may have the potential to improve cognitive functioning in schizophrenia. The present study sought to extend these investigations by evaluating the effects of PD149163 on sustained attention using a visual signal detection operant task in rats. PD149163, the atypical antipsychotic drug clozapine, and the dopamine D2/3 receptor antagonist raclopride all significantly decreased percent “hit” accuracy, while none of these compounds altered “correct rejections” (compared to vehicle control). Clozapine and raclopride significantly increased response latency, while high doses of PD149163 and raclopride significantly increased trial omissions. Nicotine, which was tested as a positive control, significantly improved overall performance in this task and did not affect response latency or trial omissions. The present findings suggest that neurotensin NTS1 receptor agonists, like antipsychotic drugs, may inhibit sustained attention in this task despite having different pharmacological mechanisms of action.
neurotensin; NTS1 receptor; PD149163; antipsychotic; attention; visual signal detection
Cannabinoids both increase urine output and decrease urinary frequency in human subjects. However, these effects have not been systematically evaluated in intact mice, a species commonly used to evaluate the effects of novel cannabinoids. The present studies investigated whether cannabinoid agonists reliably produce diuresis in mice at doses comparable to those that produce other cannabinoid effects and, further, identified the receptors that may mediate these effects. Diuretic effects were measured in male mice over 6 h. In some studies, urine was collected and analyzed for electrolyte measurements. In other studies, agonist injections were preceded by pretreatment with cannabinoid CB1 or CB2 selective antagonists, including a peripherally constrained CB1 antagonist. Companion studies evaluated the antinociceptive effects of the cannabinoid agonists in a warm-water tail-withdrawal assay. Direct-acting cannabinoid CB1 agonists Δ9- tetrahydrocannabinol (THC), WIN 55,212, AM7418 and AM4054, had biphasic effects on diuresis, with peak diuretic effects occurring at lower doses than peak antinociceptive effects. Cannabinoid diuresis was similar to κ-opioid agonist–induced diuresis in terms of maximum effects with only moderate loss of Na+. Antagonism studies indicate that the diuretic effects of cannabinoids are CB1-receptor mediated, with both central and peripheral components. These findings suggest that mice may provide a model for understanding the mixed effects of marijuana on urine output, as described in clinical studies, and aid in the development of targeted cannabinoid based therapies for bladder dysfunction.
cannabinoid; diuresis; Δ9-tetrahydrocannabinol; THC; mice; bladder dysfunction
Oxidative stress plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and in the induction of corticosteroid (CS) insensitivity. Chronic ozone exposure leads to a model of COPD with lung inflammation and emphysema. Mitogen-activated protein kinase phosphatase-1 (MKP-1) may underlie CS insensitivity in COPD. We determined the role played by MKP-1 by studying the effect of corticosteroids in wild-type C57/BL6J and MKP-1−/− mice after chronic ozone exposure. Mice were exposed to ozone (3 ppm, 3 h) 12 times over 6 weeks. Dexamethasone (0.1 or 2 mg/kg; intraperitoneally) was administered before each exposure. Mice were studied 24 h after final exposure. In ozone-exposed C57/BL6J mice, bronchial hyperresponsiveness (BHR) was not inhibited by both doses of dexamethasone, but in MKP-1−/− mice, there was a small inhibition by high dose dexamethasone (2 mg/kg). There was an increase in mean linear intercept after chronic ozone exposure in both strains which was CS-insensitive. There was lesser inflammation after low dose of dexamethasone in MKP-1−/− mice compared to C57/Bl6J mice. Epithelial and collagen areas were modulated in ozone-exposed MKP-1−/− mice treated with dexamethasone compared to C57/Bl6J mice. MKP-1 regulated the expression of MMP-12, IL-13 and KC induced by ozone but did not alter dexamethasone׳s effects. Bronchial hyperresponsiveness, lung inflammation and emphySEMa after chronic exposure are CS-insensitive, and the contribution of MKP-1 to CS sensitivity in this model was negligible.
Ozone exposure; Emphysema; Lung inflammation; Bronchial hyperresponsiveness; Mitogen-activated protein kinase phosphatase 1 (MKP-1)
Glioblastoma, a highly malignant glioma, is resistant to both radiation and chemotherapy and is an intractable problem in clinical treatment. New therapeutic approaches are in urgent need. Calanquinone A, an herbal constituent, displayed anti-proliferative activity against glioblastoma cells, including A172, T98 and U87. Flow cytometric analysis showed an S phase arrest and a subsequent apoptosis to calanquinone A action. Further identification demonstrated a rapid increase of γH2A.X formation at S phase. The data together with comet tail formation and Chk1 activation indicated DNA damage response. N-acetyl cysteine (an antioxidant and a glutathione precursor) and exogenously applied glutathione, but not trolox (an antioxidant), completely abolished calanquinone A-induced effects. Immunofluorescence assay revealed that calanquinone A decreased the intracellular glutathione levels in both A172 and T98 cells. However, calanquinone A, by itself, did not conjugate glutathione. The data suggested that the decrease of cellular glutathione predominantly contributed to the anticancer mechanism. Furthermore, calanquinone A induced the activation of AMP-activated protein kinase (AMPK) and the inhibition of p70S6K activity. Rhodamine efflux assay showed that calanquinone A did not block efflux activity, indicating that calanquinone A was not a P-glycoprotein substrate. In summary, the data suggest that calanquinone A displays anti-glioblastoma activity through a decrease of cellular glutathione levels that subsequently induces DNA damage stress and AMPK activation, leading to cell cycle arrest at S-phase and apoptotic cell death. Furthermore, calanquinone A does not serve as a P-glycoprotein substrate, suggesting a potential for further development in anti-glioblastoma therapy.
Calanquinone A; Glutathione; DNA damage; AMPK; Glioblastoma
Patients are at high risk of developing serotonin-toxicity syndrome (toxidrome) when they take multiple serotonergic drugs, particularly co-administered with monoamine oxidase inhibitors or 5-hydroxytryptamine (5-HT) reuptake blockers. The toxidrome can vary from mild to severe. The primary goal of the present study was to understand the relationship between behavioral signs and degrees of toxidrome induced by 5-hydroxy-L-tryptophan (5-HTP) in clorgylinized rats. The severity was obtained by scoring behavioral signs including head shakes, penile erection, forepaw treading, hind limb abduction, Straub tail and tremor. It was found that 5-HTP produced a dose-dependent increase in degrees of the toxidrome. Furthermore, correlation between the toxidrome and changes in body-core temperature (claudqcTcor) was determined. There was hypothermia in the mild toxidrome (claudqcTcor < −1 °C), high hyperthermia in the severe toxidrome (claudqcTcor > +2 °C) and a small change in Tcor in the moderate toxidrome (−1 °C < claudqcTcor < +2 °C). Thus, claudqcTcor in response to drugs can be used to estimate the severity of the toxidrome. The second attempt was to identify the receptors mediating those changes. 5-HT1A receptors were involved in the hypothermic response while 5-HT2A and NMDA receptors mediated head shakes, hyperthermia, forepaw treading and Straub tail. Lastly, antidotal effect of cyproheptadine and (+)-MK-801 was examined. Both drugs blocked hyperthermia and death. However, the effects on mortality became poor when the antidotes were injected 60 min after high hyperthermia had been induced. These findings demonstrate the importance of the time frame using antidotes in the treatment of the 5-HT toxidrome.
Serotonin-toxicity syndrome; head shakes; hyperthermia; hypothermia; 5-HT1A receptor; 5-HT2A receptor
Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid that contracts most smooth muscles. Although S1P has been shown to contract bladder smooth muscle, the mechanism(s) by which S1P initiates contraction has not been extensively investigated. The goal of this study was to determine if S1P-induced force generation and myosin light chain (MLC) phosphorylation are dependent on calcium sensitization pathways mediated by protein kinase C (PKC) and Rho kinase (ROCK) and which S1P receptor is important in this response. Bladder smooth muscle strips from rabbit and rat were mounted for isometric force recording and contracted in response to carbachol or S1P in the presence and absence of an inhibitor of PKC (3 μM Bisindolylmaleimide-1) or ROCK (1 μM H-1172). 10 μM S1P produced approximately 40% of the force generated in response to 110 mM KCl in rabbit bladder smooth muscle. S1P, up to 100 μM, did not produce a response in rat bladder smooth muscle, any response evoked was due to solvent (NaOH). S1P-dependent force development was associated with a concomitant increase in Ser19, but not dual Thr18/Ser19 MLC phosphorylation. Inhibition of PKC decreased force development, whereas inhibition of ROCK abolished S1P-induced force. An inhibitor of the S1P2 receptor, JTE-013, relaxed a S1P-induced contraction; whereas, an agonist with low affinity to the S1P2 receptor, dihydro-S1P, did not elicit a contraction. Our results suggest that S1P contracts rabbit, but not rat, bladder smooth muscle via the S1P2 receptor and is dependent on MLC phosphorylation and myofilament calcium sensitization primarily in response to ROCK activation.
Rho kinase; Protein kinase C; Calcium sensitization; S1P2 Receptor; Myosin light chain phosphorylation
In vitro studies show that the abused inhalant toluene affects a number of ligand-gated ion channels. The two most consistently implicated of these are γ-aminobutyric acid type A (GABAA) receptors which are positively modulated by toluene and N-methyl-D-aspartate (NMDA) receptors which are negatively modulated by toluene. Behavioral studies also suggest an interaction of toluene with GABAA and/or NMDA receptors but it is unclear if these receptors underlie the abuse-related intoxicating effects of toluene. Seventeen B6SJLF1/J mice were trained using a two-choice operant drug discrimination procedure to discriminate 10 min of exposure to 2000 ppm toluene vapor from 10 min of exposure to air. The discrimination was acquired in a mean of 65 training sessions. The stimulus effects of 2000 ppm toluene vapor were exposure concentration-dependent but rapidly diminished following the cessation of vapor exposure. The stimulus effects of toluene generalized to the chlorinated hydrocarbon vapor perchloroethylene but not 1,1,2-trichloroethane nor the volatile anesthetic isoflurane. The competitive NMDA antagonist CGS-17955, the uncompetitive antagonist dizocilpine and the glycine-site antagonist L701,324 all failed to substitute for toluene. The classical nonselective benzodiazepines midazolam and chlordiazepoxide produced toluene-like stimulus effects but the alpha 1 subunit preferring positive GABAA modulator zaleplon failed to substitute for toluene. The barbiturates pentobarbital and methohexital and the GABAA-positive modulator neurosteroid allopregnanolone did not substitute for toluene. These data suggest that the stimulus effects of toluene may be at least partially mediated by benzodiazepine-like positive allosteric modulation of GABAA receptors containing alpha 2, 3 or 5 subunits.
drug discrimination; inhalants; toluene; GABA; NMDA
κ opioid receptor activation by traditional arylacetamide agonists and the novel neoclerodane diterpene κ opioid receptor agonist Salvinorin A (Sal A) results in attenuation of cocaine-seeking behavior in pre-clinical models of addiction. However, adverse effects such as sedation, depression and aversion limit their clinical utility. The Sal A analogue, 2-methoxymethyl salvinorin B (MOM Sal B) is a longer acting Sal A analogue with high affinity for κ opioid receptors. In this study, we tested MOM Sal B for its ability to modulate cocaine-seeking behavior in rats. MOM Sal B (0.3 mg/kg) successfully attenuated cocaine-seeking but also attenuated sucrose reinforcement. No change in activity was observed in either cocaine-induced hyperactivity or spontaneous open field activity tests but increased immobility and decreased swimming times in the forced swim test were observed. This study indicates that κ opioid receptor activation by more potent Sal A analogues modulates cocaine-seeking behavior non-selectively without causing sedation, suggesting an improved side effects profile. However, pro-depressive effects are seen, which may limit the therapeutic potential of this compound. Future studies with Sal A analogues having affinities at other opioid receptors are warranted as they have the potential to identify compounds having effective anti-addiction properties.
Cocaine; self-administration; salvinorin A; sucrose reinforcement; locomotion; forced swim test
A previous characterization of mecamylamine stereoisomers using nicotinic acetylcholine receptors expressed in Xenopus oocytes revealed only small differences between the activity of the R and S forms of mecamylamine. However, that work was limited in the breadth of receptor subtypes tested, especially in regard to the discrimination of high and low sensitivity receptors, which differ in the ratios of alpha and beta subunits. We report new data using subunit concatamers, which produce uniform populations of high-sensitivity or low-sensitivity receptors, as well as alpha2, alpha5, and alpha6-containing receptors, which were not studied previously. Consistent with previous studies, we found that beta4-containing receptors were most sensitive to mecamylamine and that the IC50 values for the inhibition of net charge were lower than for inhibition of peak currents. No large differences were seen between the activities of the mecamylamine isomers. Additionally, a previously reported potentiation of high-sensitivity α4β2 receptors by S-mecamylamine could not be reproduced in the oocyte system, even with mutants that had greatly reduced sensitivity to mecamylamine inhibition or when the selective agonist TC-2559 was used. In vivo studies suggested that the R-isomer might be somewhat more potent than the S isomer at blocking CNS effects of nicotine. Although the potency difference was no more than a factor of two, it is consistent with lower LD50 estimates previously reported for the R isomer. Our results significantly extend knowledge of the nicotinic acetylcholine receptor activity profile of mecamylamine and support the hypothesis that these effects are not strongly stereoisomer selective.
Tourette's syndrome; depression; nicotine addiction; TC-5214; TC-2559
Accumulating evidence is associating disorders of lipid and glucose metabolism, including the overlapping conditions of insulin resistance/metabolic syndrome, obesity and diabetes, with moderate cognitive impairment in normal aging and elevated risk of Alzheimer’s disease. It appears that a common feature of these conditions is deficient insulin signaling, likely affecting the brain as well as canonical peripheral target tissues. A number of studies have documented that insulin directly affects brain processes and that reduced insulin signaling results in impaired learning and memory. Several studies have also shown that deficient insulin signaling induces Ca2+ dysregulation in neurons. Because brain aging is associated with substantial Ca2+ dyshomeostasis, it has been proposed that deficient insulin signaling exacerbates or accelerates aging-related Ca2+ dyshomeostasis. However, there have been few studies examining insulin interactions with Ca2+ regulation in aging animals. We have been testing predictions of the Ca2+ dysregulation/diabetes/brain aging hypothesis and have found that insulin and insulin sensitizers (thiazolidinediones) target several hippocampal Ca2+-related processes affected by aging, including larger Ca2+ transients and Ca2+-dependent afterhyperpolarizations, and counteract the effects of aging on those processes. Thus, while additional testing is needed, the results to date are consistent with the view that effects of deficient insulin signaling on brain aging are mediated in part by neuronal Ca2+ dyshomeostasis.
afterhyperpolarization; thiazolidinediones; cognition; imaging; aging; learning
Serotonin (5-HT) 5-HT2C receptor agonists have shown promise as novel alcoholism pharmacotherapies, but developing selective agonists has been problematic. Female Sprague Dawley rats were given ethanol in a palatable gel vehicle during operant sessions. 5-HT2C receptor modulators (Ro60-0175, SB242,084, and (−)-trans-PAT) were administered before operant sessions. As a control for the effects of 5-HT2C receptor agonism on caloric intake, drugs were also tested using non-ethanol containing gelatin. Ro60-0175, a 5-HT2 family receptor agonist, decreased both ethanol and vehicle responding while (−)-trans-PAT, a 5-HT2C receptor agonist with 5-HT2A-2B receptor inverse agonist activity, selectively reduced only ethanol responding. The effect of 5-HT2C receptor agonists on self-administration after reinstatement of ethanol after a three week deprivation was also determined. (−)-trans-PAT eliminated increases in ethanol intake following ethanol deprivation whereas Ro60-0175 had no effect. These results emphasize the need for caloric controls and further support the idea that selective modulation of 5-HT2 family receptors is a potential pharmacotherapeutic approach in the treatment of alcoholism.
Ethanol; serotonin 2C receptor; alcoholism; operant self-administration; alcohol deprivation