Discovery of Natural Ah Receptor Antagonists from Salvia miltiorrhiza Bunge and Synthesis of Analogs for Tumor Immunotherapy.

IDO/TDO/Kyn/AhR signaling plays a crucial role in regulating innate and adaptive immunity, and targeting Ah receptor (AhR) inhibition can potentially redirect immune cells toward an antitumoral phenotype. Therefore, AhR is an attractive drug target for novel small molecule cancer immunotherapies. In this study, natural products tanshinolic A-D (1-4), the first adducts composed of ortho-naphthoquinone-type tanshinone and phenolic acid featuring a unique 1,4-benzodioxan hemiacetal structure, were isolated and characterized from the roots of Salvia miltiorrhiza Bunge. Luciferase reporter gene assay revealed that these adducts exhibited significant AhR inhibitory activity. A linear strategy was developed to construct a cis-3,4-disubstituted 1,4-benzodioxan hemiacetal structure. Encouragingly, in both in vitro and in vivo experiments, (±)-13e demonstrated the ability to inhibit tumor cell proliferation, promote INF-γ secretion in CD8+ T cells, and inhibit PD-1/PD-L1 signal transduction, which could exert tumor inhibition properties by inhibiting AhR activity, positioning it as a promising candidate for tumor immunotherapy.

Fluparoxan: A Comprehensive Review of its Discovery, Adrenergic and CNS Activity and Treatment of Cognitive Dysfunction in Central Neurodegenerative Diseases.

BACKGROUND: The design, medicinal chemistry, pharmacokinetics and development of the highly selective α2-adrenoceptor antagonist fluparoxan are reviewed. METHOD: The drug's activity and selectivity in vitro, its efficacy in animals and its excellent oral pharmacokinetics and central α2-adrenoceptor antagonist activity in man, are evaluated as well as its ability to increase extracellular levels of noradrenaline, dopamine and acetylcholine in vivo. CONCLUSION: Furthermore, its potential for the treatment of central neurodegenerative diseases is highlighted, in particular its improvement of cognitive dysfunction in schizophrenia and in models of Alzheimer's disease.

Chronic treatment with the α2-adrenoceptor antagonist fluparoxan prevents age-related deficits in spatial working memory in APP×PS1 transgenic mice without altering ß-amyloid plaque load or astrocytosis.

Locus coeruleus degeneration and reduced central noradrenaline content is an early feature of Alzheimer's disease. In transgenic mouse models of Alzheimer's disease-like pathology, lesioning the locus coeruleus exacerbates ß-amyloid (Aß) pathology, neuroinflammation and memory deficits. Here we aimed to determine whether chronic treatment with the α(2)-adrenoceptor antagonist fluparoxan, that enhances noradrenaline release, can prevent the onset of Alzheimer's-like pathology and memory deficits in APP/PS1 transgenic mice (TASTPM). Fluparoxan (1mg/kg/day) was administered to TASTPM and wild type mice from 4 to 8 months of age. Memory was assessed at 4 and 8 months of age using the Morris water maze and contextual fear conditioning and at monthly intervals during the duration of treatment using the object recognition and spontaneous alternation task. Aß plaque load and astrocytosis were measured at 4 and 8 months of age by immunohistochemistry. Fluparoxan treatment prevented age-related spatial working memory deficits in the spontaneous alternation task but not spatial reference memory deficits in the Morris water maze. Aß plaque load and astrocytosis were unaltered by fluparoxan treatment in TASTPM mice. The findings suggest that fluparoxan treatment selectively prevent the decline of forms of memory where noradrenaline plays an integral role and that this beneficial effect is not due to altered Aß plaque pathology or astrocytosis.

Nasal trigeminal inputs release the A5 inhibition received by the respiratory rhythm generator of the mouse neonate.

Experiments were performed on neonatal mice to analyze why, in vitro, the respiratory rhythm generator (RRG) was silent and how it could be activated. We demonstrated that in vitro the RRG in intact brain stems is silenced by a powerful inhibition arising from the pontine A5 neurons through medullary alpha(2) adrenoceptors and that in vivo nasal trigeminal inputs facilitate the RRG as nasal continuous positive airway pressure increases the breathing frequency, whereas nasal occlusion and nasal afferent anesthesia depress it. Because nasal trigeminal afferents project to the A5 nuclei, we applied single trains of negative electric shocks to the trigeminal nerve in inactive ponto-medullary preparations. They induced rhythmic phrenic bursts during the stimulation and for 2-3 min afterward, whereas repetitive trains produced on-going rhythmic activity up to the end of the experiments. Electrolytic lesion or pharmacological inactivation of the ipsilateral A5 neurons altered both the phrenic burst frequency and occurrence after the stimulation. Extracellular unitary recordings and trans-neuronal tracing experiments with the rabies virus show that the medullary lateral reticular area contains respiratory-modulated neurons, not necessary for respiratory rhythmogenesis, but that may provide an excitatory pathway from the trigeminal inputs to the RRG as their electrolytic lesion suppresses any phrenic activity induced by the trigeminal nerve stimulation. The results lead to the hypothesis that the trigeminal afferents in the mouse neonate involve at least two pathways to activate the RRG, one that may act through the medullary lateral reticular area and one that releases the A5 inhibition received by the RRG.

Development of a segmented model for a continuous electrophoretic moving bed enantiomer separation.

With the recent demonstration of a continuous electrophoretic "moving bed" enantiomer separation at mg/h throughputs, interest has now turned to scaling up the process for use as a benchtop pharmaceutical production tool. To scale the method, a steady-state mathematical model was developed that predicts the process response to changes in input feed rate and counterflow or "moving bed" velocities. The vortex-stabilized apparatus used for the separation was modeled using four regions based on the different hydrodynamic flows in each section. Concentration profiles were then derived on the basis of the properties of the Piperoxan-sulfated beta-cyclodextrin system being studied. The effects of different regional flow rates on the concentration profiles were evaluated and used to predict the maximum processing rate and the hydrodynamic profiles required for a separation. Although the model was able to qualitatively predict the shapes of the concentration profiles and show where the theoretical limits of operation existed, it was not able to quantitatively match the data from actual enantiomer separations to better than 50% accuracy. This is believed to be due to the simplifying assumptions involved, namely, the neglect of electric field variations and the lack of a competitive binding isotherm in the analysis. Although the model cannot accurately predict concentrations from a separation, it provides a good theoretical framework for analyzing how the process responds to changes in counterflow rate, feed rate, and the properties of the molecules being separated.

Use of dyes to investigate migration of the chiral selector in CFFE and the impact on the chiral separations.

Continuous free flow electrophoresis was investigated as a tool for the preparative chiral separation of piperoxan enantiomers using sulfated beta-cyclodextrin (sbeta-CD) as the chiral additive. Bulk migration of sbeta-CD was confirmed using LC-MS analysis of the individual fractions collected and visualized with the addition of crystal violet to the separation buffer. In the absence of sbeta-CD, the crystal violet-containing buffer was reddish/purple and the crystal violet was deflected cathodically in the chamber. In the presence of sbeta-CD, the crystal violet-containing buffer was blue and was deflected anodically. However, formation of accumulation and depletion zones was apparent in both cases. The addition of sbeta-CD to the cathodic wash solution allowed for almost complete resolution of the piperoxan enantiomers with a processing rate of 0.45 mg/ h.

Continuous free flow electrophoresis for preparative chiral separations of piperoxan using sulfated beta-cyclodextrin.

Continuous free flow electrophoresis was investigated as a tool for the preparative chiral separation of piperoxan using a sulfated cyclodextrin chiral additive. In the absence of chiral additive, the sample stream was deflected cathodically. However, the presence of sulfated cyclodextrin in the run buffer caused anodic deflection and splitting of the sample stream into two streams, each enriched in one enantiomer. Although the sulfated cyclodextrin used was comprised of a mixture of homologues and isomers, this polydispersity did not seem to significantly impact band dispersion. Sample introduction rates ranged from approximately 0.9-7.2 mg h-1. Maximum resolution was 0.53, using an applied voltage of 220 V, buffer composition of 0.075% sulfated cyclodextrin, 7.6 mM citrate (pH 3), 4.5 degrees C.

Agonist and antagonist actions of yohimbine as compared to fluparoxan at alpha(2)-adrenergic receptors (AR)s, serotonin (5-HT)(1A), 5-HT(1B), 5-HT(1D) and dopamine D(2) and D(3) receptors. Significance for the modulation of frontocortical monoaminergic transmission and depressive states.

Herein, we evaluate the interaction of the alpha(2)-AR antagonist, yohimbine, as compared to fluparoxan, at multiple monoaminergic receptors and examine their roles in the modulation of adrenergic, dopaminergic and serotonergic transmission in freely-moving rats. Yohimbine displays marked affinity at human (h)alpha(2A)-, halpha(2B)- and halpha(2C)-ARs, significant affinity for h5-HT(1A), h5-HT(1B), h5-HT(1D), and hD(2) receptors and weak affinity for hD(3) receptors. In [(35)S]GTPgammaS binding protocols, yohimbine exerts antagonist actions at halpha(2A)-AR, h5-HT(1B), h5-HT(1D), and hD(2) sites, yet partial agonist actions at h5-HT(1A) sites. In vivo, agonist actions of yohimbine at 5-HT(1A) sites are revealed by WAY100,635-reversible induction of hypothermia in the rat. In guinea pigs, antagonist actions of yohimbine at 5-HT(1B) receptors are revealed by blockade of hypothermia evoked by the 5-HT(1B) agonist, GR46,611. In distinction to yohimbine, fluparoxan shows only modest partial agonist actions at h5-HT(1A) sites versus marked antagonist actions at halpha(2)-ARs. While fluparoxan selectively enhances hippocampal noradrenaline (NAD) turnover, yohimbine also enhances striatal dopamine (DA) turnover and suppresses striatal turnover of 5-HT. Further, yohimbine decreases firing of serotonergic neurones in raphe nuclei, an action reversed by WAY100,635. Fluparoxan increases extracellular levels of DA and NAD, but not 5-HT, in frontal cortex. In analogy, yohimbine enhances FCX levels of DA and NAD, yet suppresses those of 5-HT, the latter effect being antagonized by WAY100,635. The induction by fluoxetine of FCX levels of 5-HT, DA, and NAD is potentiated by fluparoxan. Yohimbine likewise facilitates the influence of fluoxetine upon DA and NAD levels, but not those of 5-HT. In conclusion, the alpha(2)-AR antagonist properties of yohimbine increase DA and NAD levels both alone and in association with fluoxetine. However, in contrast to the selective alpha(2)-AR antagonist, fluparoxan, the 5-HT(1A) agonist actions of yohimbine suppress 5-HT levels alone and underlie its inability to augment the influence of fluoxetine upon 5-HT levels.

Venlafaxine: discrepancy between in vivo 5-HT and NE reuptake blockade and affinity for reuptake sites.

Using an in vivo electrophysiological paradigm, venlafaxine and paroxetine displayed similar potency for suppressing the firing activity of dorsal raphe 5-HT neurons (ED50: 233 and 211 microg/kg i.v., respectively), while venlafaxine was three times less potent than desipramine (ED50: 727 and 241 microg/kg i.v., respectively) to suppress the firing activity of locus coeruleus NE neurons. The selective 5-HT1A receptor antagonist WAY 100635 (100 microg/kg, i.v.) reversed the suppressant effect of venlafaxine and paroxetine on the firing activity of 5-HT neurons and the alpha2-adrenoceptor antagonist piperoxane (1 mg/kg, i.v.) reversed those of venlafaxine and desipramine on the firing activity of NE neurons. The ED50 of venlafaxine on the firing activity of 5-HT neurons was not altered (ED50: 264 microg/kg) in noradrenergic-lesioned rats, while the suppressant effect of venlafaxine on the firing activity of NE neurons was greater in serotonergic-lesioned rats (ED50: 285 microg/kg). Taken together, these results suggest that, in vivo, venlafaxine blocks both reuptake processes, its potency to block the 5-HT reuptake process being greater than that for NE. Since the affinities of venlafaxine for the 5-HT and NE reuptake carriers are not in keeping with its potencies for suppressing the firing activity of 5-HT and NE neurons, the suppressant effect of venlafaxine on the firing activity of 5-HT and NE neurons observed in vivo may not be mediated solely by its action on the [3H]cyanoimipramine and [3H]nisoxetine binding sites. In an attempt to unravel the mechanism responsible for this peculiarity, in vitro superfusion experiments were carried out in rat brain slices to assess a putative monoamine releasing property for venlafaxine. (+/-)Fenfluramine and tyramine substantially increased the spontaneous outflow of [3H]5-HT and [3H]NE, respectively, while venlafaxine was devoid of such releasing properties.

Use of capillary electrophoresis as a method development tool for classical gel electrophoresis.

Capillary electrophoresis (CE) was used to optimize the buffer pH, ionic strength and sulfated cyclodextrin concentrations for enantiomeric separation of piperoxan. These enantioseparation conditions were then applied to a classical gel electrophoresis system. Binding constants of the sulfated beta-cyclodextrin-piperoxan couple were approximated using CE and the effects of organic solvents on the system were also investigated.

Cytochrome P4501A (CYP1A) induction in rat and man by the benzodioxino derivative, fluparoxan.

1. Fluparoxan is an alpha 2-adrenoceptor antagonist that has a relatively planar, tricyclic structure and was considered a potential substrate and inducer of cytochrome P4501A (CYP1A) enzymes. 2. Structure-activity analysis indicated some potential for CYP1A interaction, although its greater log P and molecular depth, compared with many CYP1A inducers, suggested fluparoxan would be a weak ligand for the aryl hydrocarbon (Ah) receptor and only a weak inducer. 3. In vitro, fluparoxan showed little affinity for the CYP1A enzymes. The compound was not metabolized by human CYP1A1 or 1A2 heterologously expressed in yeast and its rate of metabolism in rat and human microsomes was unaffected by the addition of the 1A inhibitor alpha-naphthoflavone. Furthermore, Ki's for fluparoxan against EROD activity were > 4000-fold higher than those of alpha-naphthoflavone. 4. In vivo, however, fluparoxan did show some capacity for CYP1A induction. In rat, hepatic EROD activity increased approximately 40-fold with seven once-daily oral doses of fluparoxan (50 mg/kg, solution), and immunoblotting studies confirmed induction of CYP1A2, though not of 1A1. In man, administration of 11 twice-daily oral doses of fluparoxan (8 mg tablet) produced some reduction in plasma levels of orally administered phenacetin and in the ratio of phenacetin AUC/urinary paracetamol, consistent with increased O-deethylation.

Acetylcholine release in the rat prefrontal cortex in vivo: modulation by alpha 2-adrenoceptor agonists and antagonists.

We have previously shown that the release of acetylcholine (ACh) in the medial prefrontal cortex of the conscious rat, as measured by microdialysis, is increased following intraperitoneal injection of the selective alpha 2-adrenoceptor antagonist (+)-efaroxan. To characterize further the receptor pharmacology of this response, the effects of other selective alpha 2-adrenoceptor ligands were examined. The alpha 2-adrenoceptor antagonists idazoxan (2.5 and 20 mg/kg), atipamezole (2.5 mg/kg), and fluparoxan (10 mg/kg) increased ACh outflow by up to 250-325% of basal levels over a 3-h period following intraperitoneal injection. The alpha 2-adrenoceptor agonists UK-14304 (2.5 mg/kg) and guanabenz (2.5 mg/kg) reduced ACh outflow by 80 and 60%, respectively. Clonidine (0.00063-0.16 mg/kg) had no significant depressant effect and at 2.5 mg/kg increased ACh outflow to 233% of basal levels. These results indicate a modulatory role for alpha 2-adrenoceptors on the release of ACh in the rat prefrontal cortex in vivo. Based on the facilitatory effects produced by the antagonists alone, this alpha 2-adrenoceptor modulation appears to be tonic and inhibitory. The ability of alpha 2-adrenoceptor antagonists to enhance ACh outflow suggests a therapeutic usefulness in disorders where cortical ACh release deficits have been implicated.

Characterization of the sympathetic nerve responses to amphetamine: role of central alpha 2-adrenergic receptors.

Although amphetamine has profound cardiovascular actions, the role of the sympathetic nervous system in these responses is largely unknown. The purpose of this study was to characterize the sympathetic nerve responses to amphetamine and to determine whether these neural responses involve an action of amphetamine in the rostral ventrolateral medulla (RVLM). In sinoaortically denervated (SAD) and sham-SAD rats, amphetamine dose-dependently increased mean arterial pressure (MAP) and heart rate (HR), while decreasing (-87 +/- 5%, max) renal sympathetic nerve discharge (SND) for 57 +/- 5 min. Comparison of the SND responses in SAD and sham-SAD rats revealed a small but significant contribution of the baroreceptor reflex to the sympathoinhibitory response. In separate studies, the bilateral microinjection of amphetamine into RVLM decreased HR, MAP, and SND. The magnitude and duration of the decrease in SND elicited by amphetamine were significantly attenuated by the prior intravenous (i.v.) administration of idazoxan (alpha 2-adrenergic antagonist). The prior bilateral microinjection of idazoxan or piperoxan into RVLM significantly attenuated the duration of the sympathoinhibitory responses elicited by i.v. amphetamine. Idazoxan and piperoxan also tended to decrease the magnitude of the SND response; however, this reduction was significant at only the highest doses. The MAP and HR responses were unaffected by idazoxan treatment. The microinjection of terazosin (alpha 1-adrenergic antagonist) or propranolol (beta-adrenergic antagonist) into RVLM did not alter the HR, MAP, or SND responses to i.v. amphetamine. We conclude that i.v. amphetamine decreases SND in anesthetized rats, in large part, by a mechanism involving the activation of alpha 2-adrenergic receptors in RVLM.

Blockade of alpha-2 adrenergic receptors in the rostral ventrolateral medulla attenuates the sympathoinhibitory response to cocaine.

The purpose of this study was to determine whether neurons in the rostral ventrolateral medulla play a role in the sympathoinhibitory response elicited by i.v. administration of cocaine and, if so, to identify the type(s) of receptors involved. Adrenergic antagonists were microinjected bilaterally into the rostral ventrolateral medulla in pentobarbital-anesthetized rats in an attempt to block the decrease in sympathetic nerve discharge (SND) elicited by cocaine (1 mg/kg i.v.). After the bilateral microinjection of saline, cocaine elicited a -56 +/- 5% (mean +/- S.E.) decrease in SND lasting 36 +/- 3 min. Cocaine also increased arterial pressure (21 +/- 3 mm Hg). Prior microinjection of the alpha-2 adrenergic antagonist idazoxan (0.3, 3 or 10 nmol) did not alter the magnitude of the sympathoinhibitory response to cocaine; however, the duration of the response was significantly reduced by all 3 doses (range 21 +/- 3 to 11 +/- 2 min). Similarly, microinjection of the alpha-2 adrenergic antagonist piperoxan (10 nmol) decreased the duration (from 45 +/- 8 to 23 +/- 4 min), but not the magnitude of the sympathoinhibitory response. Microinjection of either the alpha-1 adrenergic antagonist terazosin (0.24 nmol) or the beta adrenergic receptor antagonist propranolol (2 nmol) did not attenuate the decrease in SND elicited by cocaine. The cocaine-mediated pressor response was not affected by any of the antagonist treatments. These data show that the decrease in SND elicited by cocaine is mediated centrally and involves, at least in part, the activation of alpha-2 adrenergic receptors in the rostral ventrolateral medulla.

Synthesis of benzodioxinopyrroles as selective alpha 2-adrenoceptor antagonists.

A novel series of tetrahydrobenzodioxinopyrroles has been identified as potent and selective alpha 2-adrenoceptor antagonists. Convergent syntheses have been developed that allowed the preparation of analogues and their enantiomers. A compound of particular interest is the 5-fluoro substituted analogue (fluparoxan).

The role of pterins in depression and the effects of antidepressive therapy.

Urinary excretion of neopterins (N) and biopterins (B) was measured in 48 patients with depression before and after treatment with placebo, antidepressants, or electroconvulsive therapy (ECT), and in 26 healthy control subjects. Patients prior to and after treatment had a significantly greater neopterin/biopterin (N:B) ratio than control subjects. There was a significant correlation between N:B ratios and the severity of depression and plasma cortisol. As a raised N:B ratio implies failure to convert neopterin to biopterin, it is possible that reduced availability of tetrahydrobiopterin, the essential cofactor for the formation of noradrenaline, serotonin and dopamine, may exert rate-limiting control over the synthesis of monoamines implicated in the pathogenesis of depressive illness.

Influence of the alpha 2 noradrenergic antagonist piperoxane on longevity in the Fischer-344 rat: a preliminary report.

Piperoxane is an alpha 2-noradrenergic antagonist with demonstrated excitatory effects on neurons in the locus coeruleus, causing a corresponding increase in norepinephrine in many forebrain areas. 16 male Fischer-344 rats approximately 16 months of age were injected with 3 mg/kg of piperoxane or .09% saline. The piperoxane-treated rats lived an average of 127.1 days longer than the saline-treated rats. The results are discussed in terms of the effects of strategies designed to enhance brain levels of catecholamine and their effect on the aging process. A discussion of further research is also presented.

Antagonism of the effects of clonidine by the alpha 2-adrenoceptor antagonist, fluparoxan.

1. The effects of fluparoxan, an alpha 2-adrenoceptor antagonist, on the pharmacodynamic changes induced by clonidine were investigated in this placebo-controlled, double-blind, two-period, cross-over study in 16 healthy male volunteers (aged 19 to 44 years). 2. Subjects received either fluparoxan or placebo, twice-daily for 5 1/2 days (11 doses). One hour after the first and last dose of each treatment period, clonidine (200 micrograms) was infused intravenously over 5 min. 3. Indices of clonidine-mediated pharmacodynamic responses (growth hormone secretion, bradycardia, hypotension, xerostomia and sedation) were taken before and after clonidine infusion. Growth hormone secretion was assessed by quantifying serum growth hormone concentrations; sedation was assessed by both visual analogue scales (VAS) and by a visual psychomotor response meter, measuring critical flicker fusion (CFF). 4. The majority of subjects reported minor adverse events such as lethargy, headache and dry mouth following clonidine infusion. All adverse events were likely to be related to clonidine, as they occurred consistently between treatment groups. Fluparoxan has, however, in previous studies been reported to cause headache and light-headedness. 5. Prior to the clonidine infusion, fluparoxan caused small but statistically significant increases in systolic blood pressure (4 mm Hg) and salivary flow (approximately 30%) after both single and repeated doses. A small increase in heart rate (2 beats min-1) was seen after a single dose which was also statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)