Antagonistic Interaction between Histone Deacetylase Inhibitor: Cambinol and Cisplatin-An Isobolographic Analysis in Breast Cancer In Vitro Models

Breast cancer (BC) is the leading cause of death in women all over the world. Currently, combined chemotherapy with two or more agents is considered a promising anti-cancer tool to achieve better therapeutic response and to reduce therapy-related side effects. In our study, we demonstrated an antagonistic effect of cytostatic agent-cisplatin (CDDP) and histone deacetylase inhibitor: cambinol (CAM) for breast cancer cell lines with different phenotypes: estrogen receptor positive (MCF7, T47D) and triple negative (MDA-MB-231, MDA-MB-468). The type of pharmacological interaction was assessed by an isobolographic analysis. Our results showed that both agents used separately induced cell apoptosis; however, applying them in combination ameliorated antiproliferative effect for all BC cell lines indicating antagonistic interaction. Cell cycle analysis showed that CAM abolished cell cycle arrest in S phase, which was induced by CDDP. Additionally, CAM increased cell proliferation compared to CDDP used alone. Our data indicate that CAM and CDDP used in combination produce antagonistic interaction, which could inhibit anti-cancer treatment efficacy, showing importance of preclinical testing.

Antagonism or synergism? Responses of Hydrocharis dubia (Bl.) Backer to linear alkylbenzene sulfonate, naphthalene and their joint exposure

The presence of surfactants may affect the bioavailability of polycyclic aromatic hydrocarbons. A hydroponic experiment was conducted to investigate the response of Hydrocharis dubia (Bl.) Backer to different concentrations of linear alkylbenzene sulfonate (LAS), naphthalene (NAP) and their mixture (0.5, 5, 10, and 20 mg/L) for 14 days and 28 days. The results showed that LAS had a greater toxic effect on H. dubia growth than NAP at treatment concentrations of 0.5-20 mg/L. The combined effect of LAS and NAP was damaging to H. dubia at concentrations of LAS + NAP ≥5 + 5 mg/L. When LAS + NAP ≥10 + 10 mg/L, the underground parts of H. dubia suffered more significant damage than the aboveground parts. Under the treatments with LAS, NAP and their mixture, H. dubia experienced oxidative stress. Soluble proteins and antioxidant enzymes were the main substances protecting H. dubia from LAS stress, and superoxide dismutase (SOD) and peroxidase (POD) were the main protective enzymes. When exposed to NAP, H. dubia growth was stimulated and promoted at the same time. In the short-term treatment (14 d), catalase (CAT) activity was sensitive to NAP stimulation, and soluble proteins and SOD were the main protective substances produced. Soluble sugars, SOD and ascorbate peroxidase (APX) played important protective roles during the longer exposure time (28 d). The physiological response of H. dubia exposed to the combined toxicants was weaker than the response to exposure to individual toxicants. The responses of SOD and CAT activity were positive in the short term (14 d), and these were the main protective enzymes. As the exposure time increased (28 d), the plant antioxidant system responded negatively.

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.

Cannabinoid/agonist WIN 55,212-2 reduces cardiac ischaemia–reperfusion injury in Zucker diabetic fatty rats: role of CB2 receptors and iNOS/eNOS

BACKGROUND

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.

METHODS

Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.

RESULTS

WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.

CONCLUSIONS

This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Prothoracicotropic hormone induces tyrosine phosphorylation in prothoracic glands of the silkworm, Bombyx mori

In the present study, we investigated the tyrosine phosphorylation of Bombyx mori prothoracic glands using phosphotyrosine-specific antibodies and Western blot analysis. Results showed that prothoracicotropic hormone (PTTH) stimulates a rapid increase in tyrosine phosphorylation of at least 2 proteins in prothoracic glands, one of which was identified as extracellular signal-regulated kinase (ERK). The phosphorylation of another 120-kDa protein showed dose- and time-dependent stimulation by PTTH in vitro. In vitro activation of tyrosine phosphorylation was also verified by in vivo experiments: injection of PTTH into day-6 last-instar larvae greatly increased tyrosine phosphorylation. Treatment of prothoracic glands with the protein tyrosine phosphatase inhibitor, sodium orthovanadate, also resulted in tyrosine phosphorylation of several proteins and increased ecdysteroidogenesis. The PTTH-stimulated phosphorylation of the 120-kDa protein was markedly attenuated by genistein, a broad-spectrum tyrosine kinase inhibitor, but not by HNMPA-(AM)(3) , a specific inhibitor of insulin receptor tyrosine kinase. PP2, a more-selective inhibitor of the Src-family tyrosine kinases, partially inhibited PTTH-stimulated tyrosine phosphorylation, but not ecdysteroidogenesis. This result implies the possibility that in addition to ERK, the phosphorylation of the 120-kDa protein, which is not Src-family tyrosine kinase, is likely also involved in PTTH-stimulated ecdysteroidogenesis in B. mori.

WIN55212-2 ameliorates atherosclerosis associated with suppression of pro-inflammatory responses in ApoE-knockout mice

The role of inflammation in all stages of atherosclerosis has been actively investigated, with an emphasis on the discovery of novel and innovative drugs for treatment and prevention. The anti-inflammatory and immunomodulatory capacity of cannabinoids are well established, and these agents have a broad therapeutic potential in various inflammatory diseases, including cardiovascular diseases. The aim of this study was to investigate the effect of WIN55212-2, a synthetic cannabinoid, on atherosclerosis using the apolipoprotein E-knockout (ApoE(-/-)) mouse on a cholate-containing high-fat diet. Our results showed that WIN55212-2 reduced the size of atherosclerotic lesions in the aorta root, and did not affect serum lipid levels significantly. Furthermore, alleviation of atherosclerosis by WIN55212-2 was associated with a smaller content of macrophages in plaque lesion as well as decreasing pro-inflammatory gene expression and NF-κB activation in aortic tissues. Oxidized LDL (ox-LDL) dramatically induced NF-κB activation, and enhanced pro-inflammatory mRNA and protein expression in peritoneal macrophages isolated from ApoE(-/-) mice. It is noteworthy that all of the above-mentioned effects of ox-LDL were attenuated by WIN55212-2. Moreover, WIN55212-2 also attenuated the inflammatory response that LPS induced. AM630, a cannabinoid receptor 2 (CB₂) special antagonist completely abolished the protective effects of WIN55212-2 both in vivo and in vitro. Our data provide strong evidence that WIN55212-2 can potentially inhibit atherosclerosis in ApoE(-/-) mice. Importantly, all the beneficial effects of WIN55212-2 in our model were closely associated with the suppression of pro-inflammatory responses and were mediated by the CB₂ receptor.

[Evaluation of supplemental administration of Eviprostat in patients with benign prostatic hyperplasia with persistent symptoms following treatment with alpha1-adrenoceptor blocker]

We examined the effectiveness of supplemental administration of Eviprostat in patients with benign prostatic hyperplasia (BPH) whose lower urinary tract symptoms (LUTS) caused by BPH were not adequately relieved by an alpha1-adrenoceptor blocker. Twenty-nine patients with insufficient improvement in the International Prostate Symptom Score (IPSS) and quality of life (QOL) score after administration of 50 mg naftopidil for 4 weeks or more received 6 tablets of Eviprostat in addition to naftopidil for another 2 weeks or more. With supplemental administration of Eviprostat, significant improvement was observed in the symptoms of incomplete emptying, daytime frequency, intermittency, weak stream, total IPSS, sum of the IPSS subscores for voiding symptoms (intermittency, weak stream and straining), sum of the IPSS subscores for storage symptoms (daytime frequency, urgency and nocturia), and QOL score. Supplemental administration of Eviprostat is therefore effective for the improvement of LUTS and QOL in BPH patients resistant to an alpha1-adrenoceptor blocker.

Agonist-dependent cannabinoid receptor signalling in human trabecular meshwork cells

BACKGROUND AND PURPOSE

Trabecular meshwork (TM) is an ocular tissue involved in the regulation of aqueous humour outflow and intraocular pressure (IOP). CB1 receptors (CB1) are present in TM and cannabinoid administration decreases IOP. CB1 signalling was investigated in a cell line derived from human TM (hTM).

EXPERIMENTAL APPROACH

CB1 signalling was investigated using ratiometric Ca2+ imaging, western blotting and infrared In-Cell Western analysis.

KEY RESULTS

WIN55212-2, a synthetic aminoalkylindole cannabinoid receptor agonist (10-100 microM) increased intracellular Ca2+ in hTM cells. WIN55,212-2-mediated Ca2+ increases were blocked by AM251, a CB1 antagonist, but were unaffected by the CB2 antagonist, AM630. The WIN55,212-2-mediated increase in [Ca2+]i was pertussis toxin (PTX)-insensitive, therefore, independent of Gi/o coupling, but was attenuated by a dominant negative Galpha(q/11) subunit, implicating a Gq/11 signalling pathway. The increase in [Ca2+]i was dependent upon PLC activation and mobilization of intracellular Ca2+ stores. A PTX-sensitive increase in extracellular signal-regulated kinase (ERK1/2) phosphorylation was also observed in response to WIN55,212-2, indicative of a Gi/o signalling pathway. CB1-Gq/11 coupling to activate PLC-dependent increases in Ca2+ appeared to be specific to WIN55,212-2 and were not observed with other CB1 agonists, including CP55,940 and methanandamide. CP55940 produced PTX-sensitive increases in [Ca2+]i at concentrations>or=15 microM, and PTX-sensitive increases in ERK1/2 phosphorylation.

CONCLUSIONS AND IMPLICATIONS

This study demonstrates that endogenous CB1 couples to both Gq/11 and Gi/o in hTM cells in an agonist-dependent manner. Cannabinoid activation of multiple CB1 signalling pathways in TM tissue could lead to differential changes in aqueous humour outflow and IOP.

Cannabidiol displays unexpectedly high potency as an antagonist of CB1 and CB2 receptor agonists in vitro

BACKGROUND AND PURPOSE

A nonpsychoactive constituent of the cannabis plant, cannabidiol has been demonstrated to have low affinity for both cannabinoid CB1 and CB2 receptors. We have shown previously that cannabidiol can enhance electrically evoked contractions of the mouse vas deferens, suggestive of inverse agonism. We have also shown that cannabidiol can antagonize cannabinoid receptor agonists in this tissue with a greater potency than we would expect from its poor affinity for cannabinoid receptors. This study aimed to investigate whether these properties of cannabidiol extend to CB1 receptors expressed in mouse brain and to human CB2 receptors that have been transfected into CHO cells.

EXPERIMENTAL APPROACH

The [35S]GTPS binding assay was used to determine both the efficacy of cannabidiol and the ability of cannabidiol to antagonize cannabinoid receptor agonists (CP55940 and R-(+)-WIN55212) at the mouse CB1 and the human CB2 receptor.

KEY RESULTS

This paper reports firstly that cannabidiol displays inverse agonism at the human CB2 receptor. Secondly, we demonstrate that cannabidiol is a high potency antagonist of cannabinoid receptor agonists in mouse brain and in membranes from CHO cells transfected with human CB2 receptors.

CONCLUSIONS AND IMPLICATIONS

This study has provided the first evidence that cannabidiol can display CB2 receptor inverse agonism, an action that appears to be responsible for its antagonism of CP55940 at the human CB2 receptor. The ability of cannabidiol to behave as a CB2 receptor inverse agonist may contribute to its documented anti-inflammatory properties.

The catecholic antioxidant piceatannol is an effective nitrosation inhibitor via an unusual double bond nitration

Piceatannol (1) was found to be more effective than caffeic acid, an established antinitrosating agent, in inhibiting N-nitrosation of 2,3-diaminonaphthalene. Product analysis of the reaction mixture of 1 (20 microM) with nitrite ions (80 microM) at pH 3.0 and at 37 degrees C showed conversion to a single major nitration product, (E)-3,3',4,5'-tetrahydroxy-beta-nitrostilbene (2) (68% yield). This would result from an unexpected nitration at the double bond sector via the 4-phenoxyl radical, which was analyzed at the unrestricted DFT level.

Evidence that the plant cannabinoid Delta9-tetrahydrocannabivarin is a cannabinoid CB1 and CB2 receptor antagonist

Delta9-tetrahydrocannabivarin (THCV) displaced [(3)H]CP55940 from specific binding sites on mouse brain and CHO-hCB(2) cell membranes (K(i)=75.4 and 62.8 nM, respectively).THCV (1 microM) also antagonized CP55940-induced stimulation of [(35)S]GTPgammaS binding to these membranes (apparent K(B)=93.1 and 10.1 nM, respectively). In the mouse vas deferens, the ability of Delta9-tetrahydrocannabinol (THC) to inhibit electrically evoked contractions was antagonized by THCV, its apparent K(B)-value (96.7 nM) approximating the apparent K(B)-values for its antagonism of CP55940- and R-(+)-WIN55212-induced stimulation of [(35)S]GTPgammaS binding to mouse brain membranes. THCV also antagonized R-(+)-WIN55212, anandamide, methanandamide and CP55940 in the vas deferens, but with lower apparent K(B)-values (1.5, 1.2, 4.6 and 10.3 nM, respectively).THCV (100 nM) did not oppose clonidine, capsaicin or (-)-7-hydroxy-cannabidiol-dimethylheptyl-induced inhibition of electrically evoked contractions of the vas deferens. Contractile responses of the vas deferens to phenylephrine hydrochloride or beta,gamma-methylene-ATP were not reduced by 1microM THCV or R-(+)-WIN55212, suggesting that THCV interacts with R-(+)-WIN55212 at prejunctional sites. At 32 microM, THCV did reduce contractile responses to phenylephrine hydrochloride and beta,gamma-methylene-ATP, and above 3 microM it inhibited electrically evoked contractions of the vas deferens in an SR141716A-independent manner. In conclusion, THCV behaves as a competitive CB(1) and CB(2) receptor antagonist. In the vas deferens, it antagonized several cannabinoids more potently than THC and was also more potent against CP55940 and R-(+)-WIN55212 in this tissue than in brain membranes. The bases of these agonist- and tissue-dependent effects remain to be established.

Development and evaluation of a pharmacophore model for inhibitors of aldosterone synthase (CYP11B2)

Recently, we proposed inhibition of aldosterone synthase (CYP11B2) as a novel strategy for the treatment of congestive heart failure and myocardial fibrosis and synthesized a large number of inhibitors. In this work, a pharmacophore model for CYP11B2 inhibitors was developed by superimposition of active and non-active compounds. This model was confirmed by the synthesis of two pyridyl substituted acenaphthene derivatives (A,B). This new class of compounds as well as the pharmacophore could be helpful for the discovery of novel inhibitors.

CB1 cannabinoid receptor agonists increase intracranial self-stimulation thresholds in the rat

RATIONALE

Addictive drugs have a number of commonalities in animal behavioral models. They lower intracranial self-stimulation (ICSS) thresholds, support self-administration, and produce conditioned place preference (CPP). However, cannabinoids appear atypical as drugs of abuse, since there are controversial data in the literature concerning their reinforcing properties.

OBJECTIVES

The aim of the present study was to examine the effects of cannabinoids on brain reward using the rate-frequency curve shift paradigm of ICSS.

METHODS

Male Sprague-Dawley rats were implanted with electrodes into the medial forebrain bundle (MFB). Rate-frequency functions were determined by logarithmically decreasing the number of cathodal pulses in a stimulation train from a value that sustained maximal responding to one that did not sustain responding. After brain stimulation reward thresholds stabilized rats received intraperitoneal (IP) injections of the potent CB1 receptor agonists WIN 55,212-2 (graded doses 0.1, 0.3, 1 and 3 mg/kg), CP 55,940 (graded doses 10, 30, 56 and 100 microg/kg), or HU-210 (graded doses 10, 30, 100 microg/kg).

RESULTS

With the exception of the highest dose of all cannabinoid agonists tested, which significantly increased the threshold frequency required for MFB ICSS, all other doses of the tested drugs did not affect ICSS thresholds. The CB1 receptor antagonist SR141716A reversed the actions of WIN 55,212-2 and CP 55,940, but not HU-210. However, the selective CB1 cannabinoid receptor antagonist AM 251 counteracted the effect of HU-210. Both CB1 receptor antagonists, at the doses used in the present study, did not affect reward thresholds by themselves.

CONCLUSIONS

The present results indicate that cannabinoid agonists do not exhibit reinforcing properties in the ICSS paradigm, but rather have an inhibitory influence on reward mechanisms. The results suggest that the anhedonic effects of cannabinoids are probably mediated by cannabinoid CB1 receptors.

Prevention of naphthalene-induced pulmonary toxicity by glutathione prodrugs: Roles for glutathione depletion in adduct formation and cell injury

Naphthalene is metabolized in the lung and liver to reactive intermediates by cytochrome P450 enzymes. These reactive species deplete glutathione, covalently bind to proteins, and cause necrosis in Clara cells of the lung. The importance of glutathione loss in naphthalene toxicity was investigated by using the glutathione prodrugs (glutathione monoethylester or cysteine-glutathione mixed disulfide) to maintain glutathione pools during naphthalene exposure. Mice given a single intraperitoneal injection of naphthalene (1.5 mmol/kg) were treated with either prodrug (2.5 mmol/kg) 30 min later. Both compounds effectively maintained glutathione levels and decreased naphthalene-protein adducts in the lung and liver. However, cysteine-glutathione mixed disulfide was more effective at preventing Clara cell injury. To study the prodrugs in Clara cells without the influence of hepatic naphthalene metabolism and circulating glutathione, dose-response and time-course studies were conducted with intrapulmonary airway explant cultures. Only the ester of glutathione raised GSH in vitro; however, both compounds limited protein adducts and cell necrosis. In vitro protection was not associated with decreased naphthalene metabolism. We conclude that (1) glutathione prodrugs can prevent naphthalene toxicity in Clara cells, (2) the prodrugs effectively prevent glutathione loss in vivo, and (3) cysteine-glutathione mixed disulfide prevents naphthalene injury in vitro without raising glutathione levels.

Contribution of lipid second messengers to the regulation of phosphatidylcholine synthesis during cell cycle re-entry

During entry into the cell cycle a phosphatidylcholine (PC) metabolic cycle is activated. We have examined the hypothesis that PC synthesis during the G(0) to G(1) transition is controlled by one or more lipid products of PC turnover acting directly on the rate-limiting enzyme in the synthesis pathway, CTP: phosphocholine cytidylyltransferase (CCT). The acceleration of PC synthesis was two- to threefold during the first hour after addition of serum to quiescent IIC9 fibroblasts. The rate increased to approximately 15-fold above the basal rate during the second hour. The production of arachidonic acid, diacylglycerol (DAG), and phosphatidic acid (PA) preceded the second, rapid phase of PC synthesis. However, an increase in the cellular content of these lipid mediators was detected only for DAG. CCT activation and translocation to membranes accompanied the second phase of the PC synthesis acceleration. Bromoenol lactone (BEL), an inhibitor of calcium-independent phospholipase A(2) and PA phosphatase, blocked production of fatty acids and DAG, inhibited both phases of the PC synthesis response to serum, and reduced CCT activity and membrane affinity. The effect of BEL on PC synthesis was partially reversed by in situ generation of DAG via exogenous PC-specific phospholipase C to generate approximately 2-fold elevation in PC-derived DAG. Exogenous arachidonic acid also partially reversed the inhibition by BEL, but only at a concentration that generated a supra-physiological cellular content of free fatty acid. 1-Butanol, which blocks PA production, had no effect on DAG generation, or on PC synthesis. We conclude that fatty acids and DAG could contribute to the initial slow phase of the PC synthesis response. DAG is the most likely lipid regulator of CCT activity and the rapid phase of PC synthesis. However, processes other than direct activation of CCT by lipid mediators likely contribute to the highly accelerated phase during entry into the cell cycle.

Calphostin C as a rapid and strong inducer of apoptosis in human coronary artery smooth muscle cells

Vascular smooth muscle cells (VSMCs) play a major role in the development of atherosclerotic and restenotic lesions. The apoptotic process has been implicated in the development of this pathology. In this study, we characterized the induction of apoptosis by calphostin C (CC), a protein kinase C (PKC) inhibitor, in primary human coronary artery smooth muscle cells in the presence and absence of insulin-like growth factor-I (IGF-I). Additionally, we investigated the signal transduction pathways important for IGF-I mediated protection. Calphostin C induced apoptosis, as measured by terminal deoxy-UTP nick-end labeling (TUNEL), in a time- and dose-dependent manner, approaching 20% within 6 h of 50 nM calphostin C treatment. The amount of apoptosis increased to 44.58+/-8.08%, 47.54+/-1.66% and 78.1+/-11.9% after 8, 10 and 12 h of treatment, respectively (p<0.01 vs. control). IGF-I offered significant protection (p<0.05) at 8 and 10 h of treatment (60.6% and 52.5% protection, respectively). DNA ELISA confirmed the apoptotic effect of calphostin C and the protective effect of IGF-I. After 6 h of calphostin C treatment, DNA ELISA revealed 11.20+/-1.53 fold greater apoptosis as compared to baseline values. IGF-I treatment offered a level of protection of 46.6% as measured by DNA ELISA (p=0.06). Apoptosis was further qualitatively confirmed by time-lapse video microscopy and scanning electron microscopy. Interestingly, inhibitors of phosphatidylinositol-3-kinase (PI-3-K), p38 and extracellular regulated kinase (ERK) activation significantly (p<0.05 vs. calphostin C only treatment) increased apoptosis when used in conjunction with calphostin C. Inhibitors of phospatidylinositol-3-kinase and ERK activation reversed IGF-I protection. However, the p38 inhibitor SB203580 failed to reverse IGF-I protection. This study characterized an apoptotic system for human coronary artery smooth muscle cells offering a rapid and strong induction of programmed cell death (PCD) that remains responsive to the survival effects of IGF-I. Studies utilizing this system may prove useful in understanding the apoptotic response of VSMCs in the arterial wall.

The Role of Rho and Rho-Dependent Kinase in Serotonin-Induced Contraction Observed in Bovine Middle Cerebral Artery

The current study was designed to characterize the role of Rho and Rho-dependent kinase (Rho-kinase) in isometric contractile responses induced by serotonin (5-HT) and a solution containing 40 mM K(+) (high K(+)) in ring preparations of the middle cerebral artery of bovine. Application of W-7, a Ca(2+)-calmodulin inhibitor, reversibly and equally attenuated the amplitudes of contractions produced by both 5-HT and high K(+). Similar effects were observed with ML-7, an inhibitor of myosin light chain kinase. Surprisingly, the protein kinase C inhibitors, calphostin C and Ro-31-8220, had no effect on the 5-HT-induced contraction. Incubation of preparations with Clostridium difficile toxin A and B or with Clostridium botulinum C3 exoenzyme for 48 hours attenuated the 5-HT-induced response but not the high K(+)-induced response. Application of the Rho-kinase inhibitor, Y-27632, resulted in marked inhibition of the 5-HT-induced response but had negligible effect on the high K(+)-induced response. These results suggest that the activation of Rho and Rho-kinase may be involved in the generation of the contraction produced by 5-HT in the bovine middle cerebral artery, while protein kinase C plays, if any, an insignificant role on the contraction.

Development of a new medium useful for the recovery of dermatophytes from clinical specimens by minimizing the carryover effect of antifungal agents

Two surface-active compounds, egg lecithin and polysorbate 80, usually used as the deactivators of various preservatives were tested whether they also counteract either or all of the three major topical antifungal drugs, bifonazole (BFZ), lanoconazole (LCZ) and terbinafine (TBF). Both egg lecithin and polysorbate 80, when added to culture media up to final concentrations of 1.0 and 0.7%, respectively, antagonized the anti-dermatophytic activity of the three drugs in a concentration-dependent manner. A greater extent of antagonistic action was exerted when the two deactivators combined at their maximal levels tested were added; MIC's of BFZ were increased more than 30-fold and those of LCZ and TBF more than 200-fold compared with the values obtained in the absence of the deactivators. Using the agar medium supplemented with the combined deactivators, culture studies were carried out with skin tissues specimens taken from guinea pigs whose feet were infected with dermatophytes and subsequently treated with 1% topical preparations of the three antifungal drugs. The experimental data from this animal study demonstrated that the combined deactivators-supplemented medium yielded increased numbers of fungi compared with the basal medium. It looks, therefore, likely that the fungal recovery on the former medium more correctly reflects to actual fungal burden in the infected lesions than the latter. All these results suggest that the combined deactivators-supplemented medium is more useful for mycological evaluation of therapeutic efficacy of imidazole and allylamine drugs against dermatophytoses in both preclinical and clinical studies.

Effect of the cannabinoid receptor ligand, WIN 55,212-2, on superoxide anion and TNF-alpha production by human mononuclear cells

Cannabinoids are known to downregulate immune response but the role for cannabinoid receptors in cannabinoid-induced immunosuppression is still unclear. To address this question, the interference of CB1 and CB2 receptor antagonists with the inhibition of TNF-alpha production by synthetic cannabinoid WIN 55,212-2 was studied using human peripheral blood mononuclear cells (PBMC) in vitro. CB2 (SR 144528) but not CB1 (SR 141716A) receptor antagonist dose dependently interfered with WIN 55,212-2-induced inhibition of TNF-alpha synthesis. Also, WIN 55,212-2 decreased fMLP-induced reactive oxygen species generation in lipopolysaccharide (LPS)-primed PBMC. However, the high concentrations of cannabinoid receptor ligands needed to achieve significant effects suggest that the observed effects may be in part cannabinoid receptor independent.

The cannabinoid agonist WIN 55,212-2 reduces sensorimotor gating and recognition memory in rats

Cannabinoids can disrupt short-term memory in humans and animals and induce learning deficits and other cognitive impairments. In the present study we examined the role of a full cannabinoid agonist in short-term memory, sensorimotor gating, and the acquisition and expression of an operant learning paradigm in rats. We tested the effects of the synthetic cannabinoid WIN 55,212-2 (0.6 and 1.2 mg/kg) on short-term memory in social and object recognition tests, on prepulse inhibition (PPI) of startle, as well as on lever pressing for palatable food. Injections of 0.6 and 1.2 mg/kg WIN 55,212-2 impaired recognition memory and PPI in a dose-dependent manner, but had no effect on lever-pressing acquisition or expression, or on food preference. The PPI deficit was reversed by the administration of 0.1 mg/kg haloperidol. These data suggest that the synthetic cannabinoid WIN 55,212-2 does not lead to a general impairment of learning in an appetitive instrumental task, but significantly affects short-term memory and sensorimotor integration. The impairment in recognition and PPI might be due to deficits in attention-based short-term information processing.

Mechanism of prostaglandin E2-stimulated heat shock protein 27 induction in osteoblast-like MC3T3-E1 cells

We investigated the effect of prostaglandin E2 (PGE2) on the induction of heat shock protein 27 (HSP27) and HSP70, and the mechanism behind the induction in osteoblast-like MC3T3-E1 cells. PGE2 time-dependently increased the level of HSP27 without affecting the level of HSP70. PGE2 stimulated the accumulation of HSP27 dose-dependently in the range between 10 nM and 10 microM. PGE2 stimulated the increase in the level of the mRNA for HSP27. Staurosporine and calphostin C, inhibitors of protein kinase C (PKC), suppressed the PGE2-induced HSP27 accumulation. The effect of PGE2 on HSP27 accumulation was reduced in the PKC down-regulated cells. BAPTA/AM, a chelator of intracellular Ca2+, or TMB-8, an inhibitor of intracellular Ca2+ mobilization, reduced the accumulation of HSP27 induced by PGE2. Dibutyryl cAMP had little effect on the basal level of HSP27. PGE2 induced the phosphorylation of both p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase. PD98059 and U-0126, inhibitors of the upstream kinase of p44/p42 MAP kinase, reduced the accumulation of HSP27 induced by PGE2. SB203580, a specific inhibitor of p38 MAP kinase, suppressed the HSP27 accumulation induced by PGE2. U-73122, an inhibitor of phospholipase C, and calphostin C reduced the PGE2-induced phosphorylation of both p44/p42 MAP kinase and p38 MAP kinase. These results indicate that PGE2 stimulates the induction of HSP27 through PKC-dependent activations of both p44/p42 MAP kinase and p38 MAP kinase in osteoblasts.

The cannabinoid CB1 receptor antagonist SR 141716A reverses the antiemetic and motor depressant actions of WIN 55, 212-2

The dibenzopyran cannabinoids (delta-9 (Delta9)-tetrahydrocannabinol and nabilone) are clinically used to suppress nausea and vomiting produced by chemotherapeutic agents such as cisplatin. The purpose of this investigation was to investigate the antiemetic potential of the aminoalkylindole cannabinoid receptor agonist WIN 55, 212-2 [R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl) methyl] pyrolol [1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl) methanone mesylate] against cisplatin-induced vomiting. Different doses of WIN 55, 212-2 (0, 1, 2.5 and 5 mg/kg, i.p.) reduced both the frequency of cisplatin (20 mg/kg, i.p.)-induced emesis (ID(50)=0.5 mg/kg) as well as the percentage of shrews vomiting (ID50=1.2 mg/kg) in a dose-dependent manner. Significant reductions in emesis frequency occurred from 2.5 mg/kg dose of WIN 55, 212-2, whereas significant total protection from vomiting was afforded at its 5 mg/kg dose. The antiemetic actions of a 5-mg/kg dose of WIN 55, 212-2 against cisplatin (20 mg/kg, i.p.)-induced vomiting were reversed by nonemetic subcutaneous doses (0, 0.25, 0.5 and 1 mg/kg) of the cannabinoid CB1 receptor antagonist/inverse agonist SR 141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide] (ID50=0.27 and 0.47 mg/kg, respectively) but not by a 5-mg/kg dose of the cannabinoid CB2 receptor antagonist SR 144528 [N-[(1S)-endo-1,3,3-trimethylbicyclo [2.2.1] heptan-2-yl]5-(4-chloro-3-methylphenyl)-1-(4-methybenzyl) pyrazole-3-carboxamide]. The effects of the cited doses of WIN 55, 212-2 were also investigated on several motor parameters (spontaneous locomotor activity, duration of movement and rearing frequency). Significant reductions in motor parameters were only observed at its highest tested dose (ID50=1.97, 2.75 and 2.8 mg/kg; respectively). SR 141716A (0, 0.5, 1, 5 and 10 mg/kg) also reversed the motor suppressant effects of a 5-mg/kg dose of WIN 55, 212-2 (ID50=0.39, 0.1 and 0.3 mg/kg, respectively) and significant reversals were seen from its 0.5 and 1 mg/kg doses. These results suggest that WIN 55, 212-2 reduces both emesis and indeces of locomotion via the stimulation of cannabinoid CB1 receptors. However, cannabinoid CB1 receptors in different loci are most likely responsible for the antiemetic and motor suppressive effects of WIN 55, 212-2 since reduction in the frequency of vomiting occurred at lower doses relative to its sedative actions.

Protective effect of melatonin on naphthalene-induced oxidative stress and DNA damage in cultured macrophage J774A.1 cells

Naphthalene is a bicyclic aromatic compound that is widely used in various domestic and commercial applications. Previous studies in our laboratory have demonstrated enhanced production of reactive oxygen species, lipid peroxidation and DNA fragmentation in both in vitro and in vivo models following treatment with naphthalene. Melatonin (N-acetyl-5-methoxytryptamine), an indole hormone, is the chief secretory product of the pineal gland and is an efficient free radical scavenger and antioxidant, both in vitro and in vivo. In this study, we have investigated the ability of 1 mM melatonin to protect against naphthalene-induced oxidative stress and DNA damage in cultured macrophage J774A.1 cells. No significant changes were observed when these macrophage cells were treated with 100 microM naphthalene. Approximately 2.0-, 4.2- and 4.4-fold increases in cytochrome c reduction were observed at 200, 400 and 500 mM concentrations of naphthalene, demonstrating the increased production of superoxide anion. At 24 h, lipid peroxidation increased by approximately 1.4-, 2.1- and 2.2-fold following treatment of these cells with 200, 400 and 500 mM concentrations of naphthalene, respectively, while 1.6-, 2.8- and 2.8-fold increases in DNA fragmentation were observed at these same concentrations. Two hour pretreatment of these cultured cells with 1 mM melatonin provided approximately 26-44% decreases in lipid peroxidation, superoxide anion production and DNA fragmentation in cells treated with 400 and 500 microM naphthalene. Cellular viability decreased significantly when cells were incubated with concentrations of naphthalene greater than 100 microM, while preincubation with melatonin significantly increased the cellular viability. These results demonstrate that naphthalene may induce toxic manifestations by enhanced production of reactive oxygen free radicals, resulting in lipid peroxidation and DNA damage, while preincubation with melatonin significantly suppressed cytoxicity in J774A.1 macrophage cells.

Metabotropic and NMDA glutamate receptors participate in the cannabinoid-induced antinociception

The purpose of this study was to evaluate the possible contribution of metabotropic glutamate receptors (mGluRs) to cannabinoid-induced antinociception in the periaqueductal grey (PAG) matter of rats. Intra-PAG microinjection of WIN 55,212-2, a cannabinoid receptor agonist, increased the latency of the nociceptive reaction (NR) in a dose-dependent fashion in the plantar test. This effect was prevented by pretreatment with SR141716A, a selective antagonist of CB1 receptors. When injected alone, SR141716A produced, with the highest dosage used, a significant reduction in the latency of the NR. CPCCOEt, a selective mGlu1 receptor antagonist, was unable to prevent the analgesia produced by WIN 55,212-2. On the contrary, MPEP, a selective mGlu5 receptor antagonist, completely antagonized the effect of WIN 55,212-2. However, the analgesia induced by CHPG, a selective mGlu5 receptor agonist, was blocked by MPEP but not by SR141716A. When injected alone, CPCOOEt produced no effect, whereas MPEP produced, with the highest dosage used, a significant reduction in the latency of the NR. These data emphasize that mGlu5 receptors, but not mGluR1, may modulate nociception in the PAG. Similarly, a pretreatment with either 2-(S)-alpha-EGlu or (RS)-alpha-MSOP, selective antagonists for group II and III mGluRs, respectively, prevented the WIN 55,212-2-induced analgesia. When the higher dosage of (RS)-alpha-MSOP was used a decrease in the latency of the NR was observed. This was not the case for 2-(S)-alpha-EGlu. Pretreatment with DL-AP5, a selective antagonist of N-methyl-D-aspartate (NMDA) receptors, blocked the effect of WIN 55,212-2, and by increasing the dosage strongly reduced per se the latency of the NR. This study suggests that endogenous glutamate could tonically modulate nociception through mGlu and NMDA receptors in the PAG matter. In particular, the physiological stimulation of these receptors seems to be required for the cannabinoid-induced analgesia in this midbrain area.

Cannabinoids reveal the necessity of hippocampal neural encoding for short-term memory in rats

The memory-disruptive effects of Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and the synthetic cannabinoid WIN 55,212-2 (WIN-2) were assessed in rats exposed to varying doses of each drug (Delta(9)-THC, 0.5-2.0 mg/kg; WIN-2, 0.25-0.75 mg/kg) during performance of a delayed nonmatch to sample (DNMS) task. Cannabinoids affected performance in a dose x delay-dependent manner, with WIN-2 showing a potency more than four times that of Delta(9)-THC. These effects on DNMS performance were eliminated if the cannabinoid CB1 receptor antagonist SR141617A (Sanofi Research Inc.) was preadministered, but doses of the antagonist alone had no effect on performance. Simultaneous recording from ensembles of hippocampal neurons revealed that both WIN-2 and Delta(9)-THC produced dose-dependent reductions in the frequency (i.e., "strength") of ensemble firing during the sample phase of the task to the extent that performance was at risk for errors on >70% of trials as a function of delay. This decrease in ensemble firing in the Sample phase resulted from selective interference with the activity of differentiated hippocampal functional cell types, which conjunctively encoded different combinations of task events. A reduction in ensemble firing strength did not occur in the nonmatch phase of the task. The findings indicate that activation of CB1 receptors renders animals at risk for retention of item-specific information in much the same manner as hippocampal removal.

Effects of cannabinoid receptor agonist and antagonist ligands on production of inflammatory cytokines and anti-inflammatory interleukin-10 in endotoxemic mice

Previous studies have shown that mice primed with Corynebacterium parvum produce higher levels of inflammatory cytokines than unprimed mice upon challenge with lipopolysaccharide (LPS). Herein, we describe experiments in which two cannabinoid (CB) agonists, WIN 55212-2 [(R)-(+)-[2, 3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]1, 4-benzoxazin-6-yl](1-naphthyl)methanone) and HU-210 [(-)-11-hydroxy-delta(8) tetrahydrocannabinol-dimethylheptyl], were examined for their effects on LPS-induced cytokines in C. parvum-primed and unprimed mice. These agonists have been reported to bind selectively to the CB2 and CB1 receptor subtypes, respectively. WIN 55212-2 (3.1-50 mg/kg i.p.) and HU-210 (0.05-0.4 mg/kg i.p.) decreased serum tumor necrosis factor-alpha and interleukin-12 (IL-12) and increased IL-10 when administered to mice before LPS. The drugs also protected C. parvum mice (but not unprimed mice) against the lethal effects of LPS. The protection afforded to C. parvum mice could not be attributed to the higher levels of IL-10 present in these mice after agonist treatment. The WIN 55212-2- and HU-210-mediated changes in the responsiveness of mice to LPS were antagonized by SR141716A [N-(piperdin-1-yl)-5-(4-chloropheny)-1-(2, 4-dichloropheny)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride], a selective CB1 receptor antagonist, but not by SR144528 [N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2. 1]heptan-2-yl]5-(4-choro-3-methylphenyl)-1-(4-methylbenzyl)p yrazole-3 -carboxamide], a selective antagonist at the CB2 receptor. Therefore, both CB agonists modulated LPS responses through the CB1 receptor. Surprisingly, SR141716A itself modulated cytokine responses in a manner identical with that of WIN 55212-2 and HU-210 when administered alone to mice. The agonist-like effects of SR141716A, which were more striking in unprimed than in primed mice, suggested that the antagonist also could function as a partial agonist at the CB1 receptor. Our findings indicate a role for the CB1 receptor subtype in cytokine modulation by CB ligands.

Effects of 2-arachidonylglycerol, an endogenous cannabinoid, on neuronal activity in rat hippocampal slices

The monoacylglycerol 2-arachidonylglycerol is an endogenous ligand of cannabinoid receptors. We examined whether 2-arachidonylglycerol can influence excessive neuronal activity by investigating stimulation-induced population spikes and epileptiform activity in rat hippocampal slices. For this purpose, the effects of 2-arachidonylglycerol were compared with those of the synthetic cannabinoid agonist WIN 55,212-2. At concentrations of 10-50 microM, 2-arachidonylglycerol attenuated the amplitude of the orthodromic population spike and the slope of the field excitatory postsynaptic potential (field EPSP). However, the effect of the synthetic cannabinoid WIN 55,212-2 (R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolol[ 1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone; 0.1 microM and 1 microM) was significantly higher than that of the endogenous ligand. At a concentration of 1 microM, WIN 55,212-2 completely suppressed the field EPSP. However, none of the investigated compounds did affect the presynaptic fiber spike of the afferents. The CB1 receptor antagonist SR 141716 (N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorphenyl)-4-methyl-3- pyrazole-carboxamide) blocked the inhibition evoked by the cannabinoids. Both 2-arachidonylglycerol (30 microM) and WIN 55,212-2 (100 nM) shifted the input-output curve of the postsynaptic spike and the field EPSP to the right and increased the magnitude of paired-pulse facilitation, indicating a presynaptic mechanism of action. 2-Arachidonylglycerol and WIN 55,212-2 attenuated the frequency of spontaneously occurring epileptiform burst discharges in CA3 elicited by omission of Mg2+ and elevation of K+ to 8 mM. The antiepileptiform effect of these cannabinoids was blocked by SR 141716. In conclusion, 2-arachidonylglycerol seems to limit neuronal excitability via cannabinoid receptors of the CB1 type. By acting predominantly at a presynaptic site, it is capable of reducing excitatory neurotransmission, a mechanism which might be involved in the prevention of excessive excitability leading to epileptiform activity.

Effects of selective protein kinase C inhibitors on the proteolytic down-regulation of L-selectin from chemoattractant-activated neutrophils

The signaling factors that direct the rapid shedding of L-selectin from neutrophils upon chemoattractant stimulation are poorly understood. Protein kinase C (PKC) has been implicated, yet previous studies have relied on the use of phorbol esters and nonselective kinase inhibitors. We treated neutrophils with various selective kinase inhibitors to evaluate their effects on N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced L-selectin shedding. We found that three selective inhibitors of PKC, structurally related to staurosporine, largely blocked both fMLP- and phorbol 12-myristate 13-acetate (PMA)-induced L-selectin shedding; however, these inhibitors did not affect fMLP-induced up-regulation of Mac-1 (CD11b/CD18) expression, which has been shown not to involve PKC. Other selective serine, threonine, and tyrosine kinase inhibitors were found not to block fMLP-induced L-selectin shedding. These findings provide more definitive evidence for the role of PKC in chemoattractant-induced L-selectin proteolysis. It is interesting that certain highly selective PKC inhibitors, not structurally related to staurosporine, were found to directly induce L-selectin shedding from neutrophils.

Cytotoxicity of 1,2-epoxynaphthalene is correlated with protein binding and in situ glutathione depletion in cytochrome P4501A1 expressing Sf-21 cells

Naphthalene is metabolized by several cytochrome P-450 (CYP) monooxygenases to 1,2-epoxynaphthalene. However, the subsequent interactions of the epoxide with macromolecules in the cells, and the significance of these interactions to cellular injury, are not well characterized. Additionally, CYP1A1, which can metabolize naphthalene to 1,2-epoxynaphthalene, may be induced by a number of xenobiotics. Yet, the in situ interaction between naphthalene and CYP1A1 alone, without the influence of other xenobiotic metabolizing enzymes, has not been examined. Using a model eukaryotic expression system capable of over-expressing recombinant CYP1A1, we found that naphthalene was toxic to cells expressing CYP1A1 in a dose- (LC50: 0.3 mM) and time-dependent (LT50: 12 h) manner. Naphthalene treatment of CYP1A1-expressing cells resulted in a 47% decrease in cellular glutathione (GSH) levels. Pretreatment with ethyl ester GSH, a GSH analog, protected CYP1A1-expressing cells such that viability was 30% greater than for cells treated with naphthalene alone. Cytotoxicity was strongly correlated (r2: 0.96) with covalent binding of cellular proteins. Alkaline permethylation techniques showed that cysteinyl-SH groups of cellular proteins are a nucleophilic target of the epoxide metabolite. These results suggest that, in the absence of other pathways, naphthalene is modified by CYP1A1 to 1,2-epoxynaphthalene, which subsequently binds cellular sulfhydryl groups on proteins and GSH.

Calphostin C induces expression of amphiregulin mRNA via reactive oxygen species in IEC-6 cells

Calphostin C, a secondary metabolite of the fungus Cladosporium cladosporioides, is generally used as a specific inhibitor of protein kinase C. It is known that 12-O-tetradecanoyl-13-phorbol acetate (TPA), a protein kinase C activator, induces expression of mRNA for amphiregulin (AR), a member of EGF-related polypeptides, in mammalian epithelial cells. In this work, we determined the effect of calphostin C on AR mRNA expression in IEC-6 cells, a rat intestinal epithelial cell line, and unexpectedly found that this compound enhanced the TPA-induced expression of AR mRNA. Moreover, calphostin C alone induced expression of AR mRNA in a light-dependent manner, and this effect was abrogated by pretreatment with N-acetylcysteine. These results suggest that calphostin C can upregulate expression of AR mRNA via reactive oxygen species.

Analgesic, respiratory and heart rate effects of cannabinoid and opioid agonists in rhesus monkeys: antagonist effects of SR 141716A

This study characterized the antinociceptive, respiratory and heart rate effects of the cannabinoid receptor agonists Delta-9-tetrahydrocannabinol (Delta-9-THC) and WIN 55212 ((R)-(+)-2, 3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrol-[1,2,3-de]-1, 4-benzoxazin-6-yl)(1-naphtalenyl)methanone monomethanesulfonate), N-arachidonyl ethanolamide (anandamide) and the mu and kappa opioid receptor agonists heroin and U69593, alone and in conjunction with a cannabinoid receptor antagonist, SR 141716A [N-(piperidin-1-1-yl)-5-(4-chlorophenyl)-1(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride] and an opioid receptor antagonist, quadazocine, in rhesus monkeys (Macaca mulatta). Using 12 adult rhesus monkeys, latencies to remove the tail from a 50 degrees C water bath, respiration in 5% CO2 and heart rate were measured. When administered alone, SR 141716A (1.8, 5.6 mg/kg i.m.) did not alter nociception, respiration or heart rate. Delta-9-THC (0.1-10 mg/kg i.m.) and WIN 55212 (0.1-10 mg/kg i.m.) dose-dependently increased antinociception and dose-dependently decreased respiratory minute and tidal volumes and heart rate. These antinociceptive, respiratory and heart rate effects were reversed by SR 141716A but not by the opioid antagonist quadazocine (1 mg/kg i.m.). Anandamide (10 mg/kg i.m.) also produced antinociception. Heroin (0.01-10 mg/kg i.m.) and U69593 (0.01-3.2 mg/kg i.m.) also dose-dependently increased antinociception and decreased respiratory and heart rate measures; these effects were antagonized by quadazocine but not by SR 141716A. These results demonstrate selective and reversible antagonism of cannabinoid behavioral effects by SR 141716A in rhesus monkeys.

Continuous assay for acid phosphatase using 1-naphthyl phosphate as a substrate

The described continuous acid phosphatase assay is based on kinetics of the release of 1-naphthol in the course of the enzyme-catalyzed hydrolysis of 1-naphthyl phosphate, measured at 320 nm in aqueous solution and at 322 nm in sodium-bis(2-ethylhexyl)sulfosuccinate isooctane-water reverse micelles in a broad pH range (1.0-8.2). The method allows precise determination of the initial rate of the reaction and therefore may be used in the steady-state and pre-steady-state studies on the phosphatase-catalyzed reaction. The kinetic parameters (Km and kcat) for human prostatic acid phosphatase in aqueous solution and in reverse micelles, at pH 3.8, 4.5 and 5.7, by the proposed 1-naphthyl phosphate assay have been determined.

Effect of the cannabinoid receptor SPECT agent, AM 281, on hippocampal acetylcholine release from rat brain slices

The SPECT ligand AM 281, a less lipophilic analog of the cannabinoid receptor antagonist SR 141716A, robustly potentiated electrically-evoked release of acetylcholine from superfused hippocampal slices and prevented the inhibition of acetylcholine release by the cannabimimetic drug WIN 55212-2. These results, similar to earlier observations with SR 141716A, indicate that AM 281 is either a cannabinoid receptor antagonist or inverse agonist. Despite showing lower affinity than SR 141716A in hippocampal membrane binding experiments, AM 281 had slightly greater potency than SR 141716A in the hippocampal slice experiments, perhaps because of reduced drug absorption to slice membranes and to the apparatus.

Cannabinoid and heroin activation of mesolimbic dopamine transmission by a common mu1 opioid receptor mechanism

The effects of the active ingredient of Cannabis, Delta9-tetrahydrocannabinol (Delta9-THC), and of the highly addictive drug heroin on in vivo dopamine transmission in the nucleus accumbens were compared in Sprague-Dawley rats by brain microdialysis. Delta9-THC and heroin increased extracellular dopamine concentrations selectively in the shell of the nucleus accumbens; these effects were mimicked by the synthetic cannabinoid agonist WIN55212-2. SR141716A, an antagonist of central cannabinoid receptors, prevented the effects of Delta9-THC but not those of heroin. Naloxone, a generic opioid antagonist, administered systemically, or naloxonazine, an antagonist of micro1 opioid receptors, infused into the ventral tegmentum, prevented the action of cannabinoids and heroin on dopamine transmission. Thus, Delta9-THC and heroin exert similar effects on mesolimbic dopamine transmission through a common mu1 opioid receptor mechanism located in the ventral mesencephalic tegmentum.

Agonist-antagonist characterization of 6'-cyanohex-2'-yne-delta 8-tetrahydrocannabinol in two isolated tissue preparations

This investigation was directed at characterizing some of the pharmacological properties of 6'-cyanohex-2'-yne-delta 8-tetrahydrocannabinol (O-823), a compound with high affinity for cannabinoid binding sites (Ki = 0.77 nM). In mouse vasa deferentia, O-823 behaved as a potent partial cannabinoid CB1 receptor agonist (EC50 = 0.015 nM). In the guinea-pig myenteric plexus preparation, it antagonized WIN 55.212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholino)methyl]pyrrolo-[1,2,3-de ]-1, 4-benzoxazin-6-yl](1-naphthyl)methanone] and CP 55.940 [(-)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3-hydroxypropyl ) cyclohexan-1-ol] with Kd values of 0.65 and 0.27 nM, respectively. After in vivo delta 9-tetrahydrocannabinol pretreatment. the sensitivity of vasa deferentia to O-823-induced inhibition of electrically evoked contractions was reduced by 127-fold. 3.162 nM O-823 was inhibitory in unpretreated vasa deferentia but antagonized CP 55,940 in pretreated tissues (Kd = 0.26 nM). O-823 is probably an antagonist in the myenteric plexus preparation and delta 9-tetrahydro-cannabinol pretreated vasa deferentia but a partial agonist in unpretreated vasa deferentia because the first two of these preparations contain fewer receptors than the third.

Biochemical and pharmacological characterisation of SR141716A, the first potent and selective brain cannabinoid receptor antagonist

SR141716A is a selective, potent and orally active antagonist of the brain cannabinoid receptor with a long duration of action. This compound shows high affinity for the central cannabinoid receptor (Ki = 2 nM), displays low affinity for the peripheral cannabinoid receptor (Ki > 1000 nM). In vitro, SR141716A antagonizes the inhibitory effects of cannabinoid receptor agonists on both mouse vas deferens contractions and dopamine-stimulated adenylyl cyclase activities in rat brain membranes. After oral administration SR141716A totally inhibited the ex vivo [3H]-CP55,940 binding to cerebral membranes with a ED50 value of 3.5 mg/kg. Furthermore SR141716A antagonizes the classical pharmacological responses elicited by cannabinoid receptor agonists. In addition, SR141716A reverses the inhibitory effect of WIN55212-2 on isoniazid-induced elevation of cGMP in rat cerebellum. This compound will provide a powerful tool for studying the in vivo functions of the anandamide/cannabinoid system.

AM630, a competitive cannabinoid receptor antagonist

AM630 (iodopravadoline), a novel aminoalkylindole, has been found to attenuate the ability of a number of cannabinoids to inhibit electrically-evoked twitches of the mouse isolated vas deferens. It did not block the inhibitory effects of morphine or clonidine on the twitch response. AM630 behaved as a competitive antagonist of CP 55,940, WIN 55,212-2, anandamide and (R)-(+)-arachidonyl-1'-hydroxy-2'-propylamide (AM356), producing rightward shifts in the log concentration response curves of these cannabinoid receptor agonists that were concentration-dependent, essentially parallel and not accompanied by any decrease in the size of maximal response. AM630 also produced concentration-dependent, parallel rightward shifts in the log concentration-response curve of delta 9-THC. However, these shifts were accompanied by a decrease in the maximal response. AM630 was markedly more potent as an antagonist of delta 9-THC and CP 55,940 (Kd = 14.0 and 17.3 nM respectively) than as an antagonist of WIN 55,212-2, AM356 or anandamide (Kd = 36.5, 85.9 and 278.8 nM respectively). These differences in dissociation constant imply that the mouse vas deferens may contain more than one type of cannabinoid receptor. The data also indicate that the receptors for which AM630 has the highest affinity may not be CB1 cannabinoid receptors as the CB1 selective antagonist, SR141716A, is known to be equally potent in attenuating the inhibitory effects of CP 55,940 and anandamide on the twitch response of the mouse vas deferens.

Are 5-HT2 antagonists endowed with anxiolytic properties in rodents?

The precise role of serotonin (5-HT) in anxiety remains unclear. We report here on the effects of RP 62203, a new 5-HT2 antagonist, and ritanserin in different animal models of anxiety. In the elevated plus-maze in mice, RP 62203 increased dose-dependently the percentage of entries onto, and time spent on open arms, over the dose range 0.25-4 mg.kg-1 p.o. By contrast, ritanserin was ineffective up to the dose of 4 mg.kg-1 p.o. In addition, both compounds were tested against the anxiogenic compound FG 7142 (20 mg.kg-1, i.p.) in the plus-maze test in mice and via electrocorticographic recordings (ECoG) in rats. The anxiolytic effect of RP 62203 is antagonized by FG 7142 at a dose devoid of anxiogenic properties. A similar interaction between RP 62203 and FG 7142 is observed in ECoG studies. In contrast, ritanserin seemed to potentiate the anxiogenic and awakening activities of FG 7142. These results demonstrate that RP 62203, a selective 5-HT2 antagonist, possesses anxiolytic properties in rodents suggesting that 5-HT2 receptors are involved in the control of anxiety.

The behavioural, but not the hypothermic or corticosterone, response to 8-hydroxy-2-(DI-n-propylamino)-tetralin, is antagonized by NAN-190 in the rat

The 5-HT1A receptor antagonistic properties of 1-(2-methoxyphenyl)-4-[4-(2-phthalimmido)butyl] piperazine (NAN-190) were studied in rats: its effect on the 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)-induced behavioural syndrome (flat body posture and reciprocal forepaw treading), hypothermia and secretion of corticosterone, i.e. responses mediated by 5-HT1A receptors, were examined. The drug NAN-190 (1-8 mg/kg) antagonized dose-dependently behavioural effects of 8-OH-DPAT (in both non-reserpinized and reserpine-pretreated animals); however, when administered in doses of 0.5-4 mg/kg, it did not affect the hypothermic or the hormonal response to 8-OH-DPAT. However, NAN-190 (1-8 mg/kg) given alone, produced hypothermia and increased the concentration of corticosterone in serum. The latter effects of NAN-190 were not reduced by (-)pindolol or spiperone. Moreover, the NAN-190-induced secretion of corticosterone was not affected by ketanserin, prazosin or yohimbine. The above results indicate that NAN-190 acts as a 5-HT1A receptor antagonist, only in the model of the 8-OH-DPAT-induced behavioural syndrome. The lack of effect of NAN-190 on the hypothermic or corticosterone response to 8-OH-DPAT most probably results from its own action which mimics the effects of 8-OH-DPAT. The mechanisms responsible for the NAN-190-induced hypothermia and secretion of corticosterone are still unknown, though stimulation of 5-HT1A receptors (either effect), 5-HT2 receptors and alpha 1- and alpha 2-adrenoceptors (corticosterone response) seems to be excluded.

Antagonism by pindolol, but not betaxolol, of 8-OH-DPAT-induced facilitation of male rat sexual behavior

8-OH-DPAT (0.25 mg/kg s.c.) produced a facilitation of the male rat sexual behavior, characterized by a decrease in the number of intromissions preceding ejaculation and in the time to ejaculation. This facilitation of the sexual behavior was antagonized by administration of the 5-HT and beta-adrenoceptor antagonist pindolol (4 mg/kg i.p.), but not by the selective beta-adrenoceptor antagonist betaxolol (4 mg/kg i.p.). Neither pindolol (2-8 mg/kg), nor betaxolol (2-8 mg/kg), produced any statistically significant effects per se on the male rat sexual behavior, as observed here (mounts, intromissions, ejaculation latency or the post-ejaculatory interval). A higher dose (16 mg/kg) of betaxolol produced a statistically significant reduction in the number of intromissions preceding ejaculation and in the ejaculation latency. The antagonism by pindolol of 8-OH-DPAT-induced effects on male rat sexual behavior suggests an involvement of 5-HT1A receptors in the facilitation of this behavior produced by 8-OH-DPAT.

Blockade of 8-OH-DPAT-induced feeding by dopamine antagonists

Feeding elicited by the 5HT1A agonist 8-OH-DPAT was blocked by pretreatment with the DA antagonists SCH-23390 and sulpiride, in two experiments conducted in non-deprived rats and in three experiments conducted after 4 h food deprivation. In deprived animals, 8-OH-DPAT prolonged the initial period of feeding. However, in non-deprived animals, 8-OH-DPAT delayed the onset of eating, and suppressed post-prandial resting; both SCH-23390 and sulpiride restored the normal pattern of behaviour. All three drugs suppressed grooming. The results suggest that 8-OH-DPAT elicits feeding by a secondary disinhibition of activity postsynaptic to DA neurons. The consequences of this mechanism for the interpretation of 8-OH-DPAT-induced feeding are discussed.

Desenkephalin-gamma-endorphin and neuroleptics counteract the DP-7-ATN-induced hypomotility after intra-accumbens treatment

Injection of the selective presynaptic dopamine agonist N,N-dipropyl-7-hydroxy-2-aminotetralin (DP-7-ATN, 1 fg to 1 microgram) into the nucleus accumbens decreased motor activity. The reduction of motor activity was reversed by pretreatment with haloperidol (10 pg), (-)-sulpiride (10 pg) or desenkephalin-gamma-endorphin (DE gamma E) (100 pg). These results support the hypothesis that DE gamma E may interfere with presynaptically located D-2 dopamine receptor systems in the nucleus accumbens. Furthermore, the use of DP-7-ATN in the described test procedure might be a useful model for testing novel neuroleptic compounds in vivo.

(+)-8-OH-DPAT and 5-MeODMT induced analgesia is antagonised by noradrenaline depletion

In experiments with both rats and mice the 5-HT agonists 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and 5-methoxy-N,N-dimethyl-tryptamine (5-MeODMT) were shown to produce reliable analgesic effects after acute administration (1 mg/kg SC) in the tail-flick, hot-plate and shock-titration tests of nociception. Prior treatment with the noradrenaline neurotoxin, N-2-chloroethyl-N-ethyl-2-bromobenzylamine (DSP4), systemically administered to both rats and mice abolished the analgesic effects of both the 5-HT agonist compounds in all the tests of nociception used. Intrathecal 6-hydroxydopamine (6-OHDA) treatment also abolished the analgesic effects of 8-OH-DPAT and 5-MeODMT; in the tail-flick test the analgesia induced by 8-OH-DPAT was reversed to an hyperalgesia. Biochemical analyses confirmed notable noradrenaline depletions in the spinal cord. It is concluded that an important interaction between presynaptic noradrenergic terminals and serotonergic receptor sites, possibly 5-HT1A, mediates spinal nociception processes.

Partial prevention of compactin (ML-236B) inhibition of in vitro hematopoiesis by dolichol and dolichyl phosphate

We have reported that the exogenous addition of dolichyl phosphate (Dol-P) enhances the colony-forming capacities of early erythroid progenitors (BFU-E), late erythroid progenitors (CFU-E), and granulocyte-macrophage progenitors (CFU-GM) in adult mouse bone marrow, and that dolichol (Dol) enhances that of only CFU-E (Int. J. Cell Cloning 3:313, 1985). Compactin (2.5-10 microM), a specific inhibitor of mevalonate biosynthesis that causes a decrease of endogenous Dol biosynthesis, inhibited colony formation of CFU-GM. Exogenous addition of Dol-P partially prevented this inhibition, but Dol and the other mevalonate metabolites, such as cholesterol, coenzyme Q10, and isopentenyladenine, could not. In addition, we have found that the colony-forming capacity of CFU-E in fetal mouse liver was not enhanced by exogenous Dol or Dol-P. But the decrease of colony formation or DNA synthesis of fetal CFU-E in the presence of compactin was prevented by the exogenous addition of Dol or Dol-P.

Comparison of the arachidonic acid and NADPH-dependent microsomal metabolism of naphthalene and 2-methylnaphthalene and the effect of indomethacin on the bronchiolar necrosis

Naphthalene and 2-methylnaphthalene cause a highly organo- and species-selective lesion of the pulmonary bronchiolar epithelium in mice. Naphthalene- but not 2-methylnaphthalene-induced pulmonary bronchiolar injury is blocked by prior administration of the cytochrome P-450 monooxygenase inhibitor piperonyl butoxide, thus suggesting that metabolism by enzymes other than the P-450 monooxygenase inhibitor piperonyl butoxide, thus suggesting that metabolism by enzymes other than the P-450 monooxygenases may be important in 2-methylnaphthalene-induced lung injury. Since many of the polycyclic aromatic hydrocarbons are metabolized by the prostaglandin endoperoxide synthetase system and because detectable xenobiotic metabolizing activity has been associated with the prostaglandin synthetases in the Clara cell, the studies reported here were done to compare NADPH-versus arachidonate-dependent metabolism of naphthalene and 2-methylnaphthalene in vitro and to determine whether indomethacin, a potent inhibitor of prostaglandin biosynthesis, was capable of blocking the in vivo toxicity of these two aromatic hydrocarbons. The NADPH-dependent metabolism of naphthalene and 2-methylnaphthalene to covalently bound metabolites in lung or liver microsomal incubations occurred at easily measurable rates. Renal microsomal NADPH-dependent metabolism of either substrate was not detected. The formation of covalently bound naphthalene or 2-methylnaphthalene metabolites was dependent upon NADPH and was inhibited by the addition of reduced glutathione, piperonyl butoxide, and SKF 525A. Covalent binding of radioactivity from [14C]2-methylnaphthalene also was strongly inhibited by incubation in a nitrogen atmosphere or at 2 degree. The arachidonic acid-dependent formation of reactive metabolites from naphthalene or 2-methylnaphthalene was undetectable in microsomal incubations from lung, liver or kidney. Indomethacin, 1 hr before and 6 hr after the administration of 300 mg/kg naphthalene or 2-methylnaphthalene, failed to block the pulmonary bronchiolar injury induced by these aromatic hydrocarbons. These studies suggest that the major enzymes involved in the metabolic activation of naphthalene or 2-methylnaphthalene in vitro are the cytochrome P-450 monooxygenases and that cooxidative metabolism by the prostaglandin synthetases appears to play little role in the formation of reactive metabolites in vitro.

Para-chlorophenylalanine prevents feeding induced by the serotonin agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT)

The effects of para-chlorophenylalanine pre-treatment (PCPA, 150 mg/kg IP daily for 3 days) on feeding and stereotyped behaviour elicited by the serotonin agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) in rats were investigated. PCPA depleted brain serotonin and 5-hydroxyindoleacetic acid concentrations by 90% and increased feeding during a 2-h day-time test. 8-OH-DPAT (60-4000 micrograms/kg SC) increased food intake in control animals but decreased it in PCPA-treated animals during the 2-h test. PCPA treatment had no effect on 8-OH-DPAT-induced locomotion or serotonin-related stereotyped behaviour (i.e. forepaw treading, headweaving, wet dog shakes, etc). Since PCPA prevents the operation of pre-synaptic serotonergic mechanisms, the failure of 8-OH-DPAT to increase food intake in PCPA-treated rats suggests that 8-OH-DPAT-induced hyperphagia is autoreceptor mediated.

Failure to antagonize the 8-hydroxy-2-di-n-propylamino)tetralin-induced facilitation of male rat sexual behavior by the administration of 5-HT receptor antagonists

The administration of the putative 5-hydroxytryptamine (5-HT) agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and 5-hydroxytryptophan (5-HTP) produced a facilitation and an inhibition of male rat sexual behavior, respectively. The 5-HTP-induced inhibitory effects were at least partially antagonized by the administration of metergoline, methiothepine or pirenperone. However, none of these agents were able to counteract any facilitatory effects produced by 8-OH-DPAT. It is concluded that 8-OH-DPAT does not facilitate the expression of masculine sexual behavior in the rat by stimulation of 5-HT1 or 5-HT2 receptors.

Neuroleptic inhibition of 6,7-ADTN-induced hyperactivity after injection into the nucleus accumbens. Specificity and comparison with other models

The dopamine agonist 6,7-ADTN induced locomotor stimulation after injection into the nucleus accumbens of rats. This hyperactivity was stereospecifically antagonized by peripheral injection of typical and atypical neuroleptics, except sulpiride, regardless of structural class. The potency of 14 neuroleptics correlated significantly to that in other neuroleptic in vivo models in rats, i.e. cataleptogenic and amphetamine-antagonistic (stereotypy, circling) activity. Sulpiride was inactive after peripheral injection, whereas intraacumbens sulpiride antagonized 6,7-ADTN-induced hyperactivity with a higher potency than that found for locally injected cis-(Z)-flupentixol, haloperidol and clebopride. Blockade of alpha 1-adrenergic receptors by systemic prazosin or locally injected phentolamine also antagonized 6,7-ADTN, whereas antagonists of alpha 2-adrenergic, beta-adrenergic, muscarinic and serotoninergic receptors were without effect. Furthermore, the cis-(Z)-flupentixol and haloperidol-induced 6,7-ADTN blockade was only slightly or not reversed by additional antimuscarinic (scopolamine) or antiserotonergic (methysergide) treatment. It is concluded that antagonism of 6,7-ADTN-induced hyperactivity is a relevant model for detecting neuroleptic activity with minimal influence of anticholinergic and antiserotonergic activity, but that the dopamine receptor within the nucleus accumbens responsible for the locomotor stimulation is similar to that involved in other behavioural effects of neuroleptics. It is suggested that an apparent preferential limbic action of some neuroleptics (e.g. clozapine and chlorprothixene) is more likely to be explainable by their simultaneous blocking effect on dopaminergic, alpha-adrenergic and muscarinic receptors.