A cholecystokinin B receptor antagonist and cocaine interaction, phase I study

AIMS

RPR 102681, a cholecystokinin-B antagonist, increased dopamine (DA) release and reduced cocaine self-administration in animals. This pilot study sought to assess the safety and pharmacokinetics (PK) of co-administration of RPR 102681 and cocaine, and to confirm the DA release mechanism of RPR 102681.

METHODS

Sixteen cocaine-dependent participants were randomized to either placebo or RPR102681 at 3 ascending doses; cocaine was co-administered at steady state of RPR 102681. [¹¹ C]raclopride positron emission tomography scans were conducted at baseline and at each RPR102681 dose.

RESULTS

RPR 102681 was well tolerated, and safe to co-administer with cocaine. RPR 102681 did not alter the PK of either cocaine or its metabolite benzoylecgonine and showed no intrinsic abuse liability. There was a trend toward reduction of cocaine craving scores. In contrast to animal studies, RPR 102681 significantly increased the binding potential of [¹¹ C]raclopride in the ventral striatum (t test, P < .001) and caudate nucleus (t test, P < .0001) in a small subset of patients, suggesting that it may reduce intrasynaptic striatal DA.

CONCLUSION

Overall, this pilot study suggests that RPR 102681 would be unlikely candidate, as an agonist medication for the treatment for cocaine addiction but worth investigating further for possible role in reducing craving.

Placebo-controlled evaluation of a bioengineered, cocaine-metabolizing fusion protein, TV-1380 (AlbuBChE), in the treatment of cocaine dependence

BACKGROUND

TV-1380 (AlbuChE) is a novel recombinant fusion protein of mutated butyrylcholinesterase (BChE) that has increased catalytic efficiency for cocaine metabolism compared to wild-type BChE.

METHODS

Intra-muscular injections of TV-1380 (150mg or 300mg) or placebo were administered once weekly to participants (n=66-69 per group) in a randomized, double-blind study to evaluate the ability of TV-1380 to facilitate abstinence in treatment-seeking, cocaine-dependent individuals. The primary endpoint was the proportion of participants achieving abstinence from cocaine during the last three weeks of the 12 week treatment phase, based on daily self-report of "no use" confirmed by urine testing.

RESULTS

Although there were no significant differences between the TV-1380 treatment groups and placebo for the primary endpoint, 6% of participants in the 150mg and 300mg TV-1380 groups and no participants in the placebo group achieved abstinence. For the only declared secondary endpoint, there was a dose-dependent increase in the group mean percentage of urine samples testing negative for cocaine metabolites during weeks 5-12 (8.1% and 14.6% for the 150mg and 300mg TV-1380 groups, respectively, compared to 4.7% for the placebo group; p=0.0056 for 300mg vs. placebo). No meaningful differences in adverse events were seen between treatment groups.

CONCLUSIONS

While the apparent reduction in cocaine use may be of insufficient magnitude to justify further trials of TV-1380 in cocaine dependence, the results argue for development of improved enzymes with greater catalytic activity.

An Examination of the Employment Structure of Taiwanese Immigrants in Australia

Taiwanese emigration has reached a considerable level in the last ten years, with 20,0000 to 25,000 annually heading for mjaor destinations such as the United States, Canada, Australia, and New Zealand. Rapid economic growth, political instability, increased personal income, and relaxation of travel restrictions since 1989 are behind this increase. Particularly for Australia, the introduction of economic and business migration policies attracted skilled and entrepreneurial groups. This study examined the employment structure of the Taiwan-born in Sydney, Melbourne and Brisbane, the top destinations of Taiwanese immigrants in Australia. Unpublished census data for the years 1981, 1986, 1991 and 1996, supplemented by data from a survey of Taiwanese immigrants in the three cities, provided data for the study. Findings suggest that the employment rate of Taiwanese immigrants is among the lowest of all immigrant groups. Taiwanese men tend to be more economically successful than Taiwanese women in income levels, occupational status, and labor force participation. Most Taiwanese immigrants in Australia experience downward social mobility due to factors such as unaccredited overseas qualifications, the lack of English proficiency and local knowledge, and other institutional discriminatory factors.

Bupropion for the treatment of methamphetamine dependence in non-daily users: a randomized, double-blind, placebo-controlled trial

AIM

Bupropion was tested for efficacy to achieve methamphetamine (MA) abstinence in dependent, non-daily users.

METHODS

A randomized, double-blind, placebo-controlled trial, with 12-week treatment and 4-week follow-up, was conducted with 204 treatment-seeking participants having MA dependence per DSM-IV, who used MA on a less-than-daily basis. 104 were randomized to matched placebo and 100 to bupropion, sustained-release 150mg, twice daily. Participants were seen three times weekly to obtain urine for MA and bupropion assays, study assessments, and thrice weekly, 90-min, group psychotherapy. There was no biomarker for placebo adherence. The primary outcome was achievement of abstinence throughout the last two weeks of treatment; 'success' requiring at least two urine samples during each of Weeks 11 and 12, and all samples MA-negative (<300ng/mL).

RESULTS

Bupropion and placebo groups did not differ significantly in the percentage achieving abstinence for the last 2 weeks of treatment (chi-square, p=0.32). Subgroup analysis of participants with lower baseline MA use (≤18 of last 30 days before consent) also revealed no difference in success between groups (p=0.73). Medication adherence per protocol (detectable bupropion, >5ng/mL, in ≥50% of urine samples from Study Weeks 1-10 and ≥66% of urine samples from Weeks 11 to 12) was achieved by 47% of participants taking bupropion.

CONCLUSIONS

These data indicate that bupropion did not increase abstinence in dependent participants who were using MA less-than-daily. Medication non-adherence was a limitation in this trial. Psychosocial therapy remains the mainstay of treatment for MA dependence. Further research on subgroups who may respond to bupropion may be warranted.

The Concise Guide to PHARMACOLOGY 2013/14: overview

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties from the IUPHAR database. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. This compilation of the major pharmacological targets is divided into seven areas of focus: G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors & Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and GRAC and provides a permanent, citable, point-in-time record that will survive database updates.

Topiramate for the treatment of methamphetamine addiction: a multi-center placebo-controlled trial

AIMS

  Topiramate has shown efficacy at facilitating abstinence from alcohol and cocaine abuse. This double-blind, placebo-controlled out-patient trial tested topiramate for treating methamphetamine addiction.

DESIGN

  Participants (n = 140) were randomized to receive topiramate or placebo (13 weeks) in escalating doses from 25 mg/day [DOSAGE ERROR CORRECTED] to the target maintenance of 200 mg/day in weeks 6-12 (tapered in week 13). Medication was combined with weekly brief behavioral compliance enhancement treatment.

SETTING

  The trial was conducted at eight medical centers in the United States.

PARTICIPANTS

  One hundred and forty methamphetamine-dependent adults took part in the trial.

MEASUREMENTS

  The primary outcome was abstinence from methamphetamine during weeks 6-12. Secondary outcomes included use reduction versus baseline, as well as psychosocial variables.

FINDINGS

  In the intent-to-treat analysis, topiramate did not increase abstinence from methamphetamine during weeks 6-12. For secondary outcomes, topiramate reduced weekly median urine methamphetamine levels and observer-rated severity of dependence scores significantly. Subjects with negative urine before randomization (n = 26) had significantly greater abstinence on topiramate versus placebo during study weeks 6-12. Topiramate was safe and well tolerated.

CONCLUSIONS

  Topiramate does not appear to promote abstinence in methamphetamine users but can reduce the amount taken and reduce relapse rates in those who are already abstinent.

Modafinil for the treatment of methamphetamine dependence

AIM

Modafinil was tested for efficacy in decreasing use in methamphetamine-dependent participants, compared to placebo.

METHODS

This was a randomized, double-blind, placebo-controlled study, with 12 weeks of treatment and a 4-week follow-up. Eight outpatient substance abuse treatment clinics participated in the study. There were 210 treatment-seekers randomized, who all had a DSM-IV diagnosis of methamphetamine dependence; 68 participants to placebo, 72 to modafinil 200mg, and 70 to modafinil 400mg, taken once daily on awakening. Participants came to the clinic three times per week for assessments, urine drug screens, and group psychotherapy. The primary outcome measure was a methamphetamine non-use week, which required all the week's qualitative urine drug screens to be negative for methamphetamine.

RESULTS

Regression analysis showed no significant difference between either modafinil group (200 or 400mg) or placebo in change in weekly percentage having a methamphetamine non-use week over the 12-week treatment period (p=0.53). Similarly, a number of secondary outcomes did not show significant effects of modafinil. However, an ad-hoc analysis of medication compliance, by urinalysis for modafinil and its metabolite, did find a significant difference in maximum duration of abstinence (23 days vs. 10 days, p=0.003), between those having the top quartile of compliance (>85% of urines were positive for modafinil, N=36), and the lower three quartiles of modafinil 200 and 400mg groups (N=106).

CONCLUSIONS

Although these data suggest that modafinil, plus group behavioral therapy, was not effective for decreasing methamphetamine use, the study is probably inconclusive because of inadequate compliance with taking medication.

Effect of inhibition of heat-shock protein 90 on mutant c-Kit protein as modulated by mRNA expression and protein degradation through both proteasome and autophagy-mediated pathways

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Background: c-Kit is a known client protein of heat-shock protein 90 (Hsp90). Inhibition of Hsp90 can reduce the expression of c-Kit protein in human mastocytoma and gastrointestinal stromal tumor (GIST) cells, which is conceived through the proteasome degradation pathway.

Methods: COS-1 cells transfected with vectors containing CMV promoter-driven various c-Kit mutants (imatinib- sensitive or imatinib-resistant) and human GIST882 cells (with endogenous exon 13 mutant c-Kit) were used to investigate the efficacy NVP-AUY922, a new class of Hsp90 inhibitor, on suppressing the constitutive activation of mutated c-Kit. Detail mechanisms of protein regulation, as RNA transcription, RNA stability, and protein degradation were studied.

Results: NVP-AUY922 is more potent than 17-AAG to inhibit the proliferation of imatinib-sensitive GIST882 cells. Further study showed that NVP-AUY922 down-regulated both total and phosphorylated c-Kit proteins in dose- and time-dependent manners in both GIST882 cells and mutant c-Kit (including imatinib-resistant exon11/17 double mutants) expressed in COS-1 cells. Surprisingly, the NVP-AUY922-induced c-Kit degradation in both cell models could be reversed by proteasome-degradation inhibitor and autophagy inhibitor. The involvement of autophagy in NVP-AUY922-induced c-Kit protein degradation was further confirmed by co-localization of c-Kit and autophagosome by immuno-staining. In addition, NVP-AUY922 treatment resulted in a reduction of c-Kit mRNA level in GIST882 cells but not c-Kit expressing COS-1 cells, which could be explained by the use of CMV promoter in artificial COS-1 cell model.

Conclusions: Taken together, these findings provide the first evidence that down-regulation of mutant c-Kit protein by Hsp90 inhibitor involved both transcription and post-translation levels. Of the latter, autophagy- as well as proteasome-mediated degradation pathways were involved. These observations highlight the use of NVP-AUY922 either alone or in combination with autophagy modulators in imatinib-refractory, c-Kit-expressing GIST. Supported by 99D1-TC-CADOH03.

[Table: see text]

Modafinil for the treatment of cocaine dependence

AIM

Modafinil was tested for efficacy in facilitating abstinence in cocaine-dependent patients, compared to placebo.

METHODS

This was a double-blind placebo-controlled study, with 12 weeks of treatment and a 4-week follow-up. Six outpatient substance abuse treatment clinics participated in the study. There were 210 treatment-seekers randomized, having a diagnosis of cocaine dependence; 72 participants were randomized to placebo, 69 to modafinil 200mg, and 69 to modafinil 400mg, taken once daily on awakening. Participants came to the clinic three times per week for assessments and urine drug screens, and had one hour of individual psychotherapy weekly. The primary outcome measure was the weekly percentage of cocaine non-use days.

RESULTS

The GEE regression analysis showed that for the total sample, there was no significant difference between either modafinil group and placebo in the change in average weekly percent of cocaine non-use days over the 12-week treatment period (p>0.79). However, two secondary outcomes showed significant effects by modafinil 200mg: the maximum number of consecutive non-use days for cocaine (p=0.02), and a reduction in craving (p=0.04). Also, a post hoc analysis showed a significant effect of modafinil that increased the weekly percentage of non-use days in the subgroup of those cocaine patients who did not have a history of alcohol dependence (p<0.02).

CONCLUSIONS

These data suggest that modafinil, in combination with individual behavioral therapy, was effective for increasing cocaine non-use days in participants without co-morbid alcohol dependence, and in reducing cocaine craving.

Multi-center trial of baclofen for abstinence initiation in severe cocaine-dependent individuals

Cocaine dependence is a major public health problem for which there is no FDA-approved pharmacological treatment. Baclofen is a GABA(B) receptor agonist that in preclinical and early pilot clinical trials has shown promise for the treatment of cocaine dependence. The purpose of this multi-site, double-blind study, was to compare the safety and efficacy of baclofen (60 mg/day) vs placebo in an 8-week treatment of individuals with severe cocaine dependence. The primary outcome measure was subjects' self-reported cocaine use substantiated by urine benzoylecgonine (BE). Analysis of the data did not show a significant difference between the groups treated with baclofen and placebo. The current results do not support a role for 60 mg baclofen in treating cocaine dependence in the population studied. The contrast of this result to earlier, preclinical and human pilot data with baclofen may reflect the trial's focus on severe cocaine-dependent users, and/or the need for a higher baclofen dose. Baclofen's potential as a relapse prevention agent was not tested by the current design, but may be a useful target for future studies.

Bupropion for the treatment of methamphetamine dependence

Bupropion was tested for efficacy in increasing weeks of abstinence in methamphetamine-dependent patients, compared to placebo. This was a double-blind placebo-controlled study, with 12 weeks of treatment and a 30-day follow-up. Five outpatient substance abuse treatment clinics located west of the Mississippi participated in the study. One hundred and fifty-one treatment-seekers with DSM-IV diagnosis of methamphetamine dependence were consented and enrolled. Seventy-two participants were randomized to placebo and 79 to sustained-release bupropion 150 mg twice daily. Patients were asked to come to the clinic three times per week for assessments, urine drug screens, and 90-min group psychotherapy. The primary outcome was the change in proportion of participants having a methamphetamine-free week. Secondary outcomes included: urine for quantitative methamphetamine, self-report of methamphetamine use, subgroup analyses of balancing factors and comorbid conditions, addiction severity, craving, risk behaviors for HIV, and use of other substances. The generalized estimating equation regression analysis showed that, overall, the difference between bupropion and placebo groups in the probability of a non-use week over the 12-week treatment period was not statistically significant (p=0.09). Mixed model regression was used to allow adjustment for baseline factors in addition to those measured (site, gender, level of baseline use, and level of symptoms of depression). This subgroup analysis showed that bupropion had a significant effect compared to placebo, among male patients who had a lower level of methamphetamine use at baseline (p<0.0001). Comorbid depression and attention-deficit/hyperactivity disorder did not change the outcome. These data suggest that bupropion, in combination with behavioral group therapy, was effective for increasing the number of weeks of abstinence in participants with low-to-moderate methamphetamine dependence, mainly male patients, regardless of their comorbid condition.

Endogenous pro-resolving and anti-inflammatory lipid mediators: a new pharmacologic genus

Complete resolution of an acute inflammatory response and its return to homeostasis are essential for healthy tissues. Here, we overview ongoing efforts to characterize cellular and molecular mechanisms that govern the resolution of self-limited inflammation. Systematic temporal analyses of evolving inflammatory exudates using mediator lipidomics-informatics, proteomics, and cellular trafficking with murine resolving exudates demonstrate novel endogenous pathways of local-acting mediators that share both anti-inflammatory and pro-resolving properties. In murine systems, resolving-exudate leukocytes switch their phenotype to actively generate new families of mediators from major omega-3 fatty acids EPA and DHA termed resolvins and protectins. Recent advances on their biosynthesis and actions are reviewed with a focus on the E-series resolvins (RvE1, RvE2), D series resolvins (RvD1, RvD2) and the protectins including neuroprotectin D1/protectin D1 (NPD1/PD1) as well as their aspirin-triggered epimeric forms. Members of each new family demonstrate potent stereo-specific actions, joining the lipoxins as endogenous local signals that govern resolution and endogenous anti-inflammation mechanisms. In addition to their origins and roles in resolution biology in the immune system, recent findings indicate that these new mediator families also display potent protective actions in lung, kidney, and eye as well as enhance microbial clearance. Thus, these endogenous agonists of resolution pathways constitute a novel genus of chemical mediators that possess pro-resolving, anti-inflammatory, and antifibrotic as well as host-directed antimicrobial actions. These may be useful in the design of new therapeutics and treatments for diseases with the underlying trait of uncontrolled inflammation and redox organ stress.

The SRPHK1 outcome measure for cocaine-dependence trials combines self-report, urine benzoylecgonine levels, and the concordance between the two to determine a cocaine-use status for each study day

BACKGROUND

There is currently no FDA-approved medication for cocaine dependence and no standard primary outcome measure for reduction of cocaine use in cocaine-dependence trials. The ability to detect a significant medication effect will depend, in part, on the primary outcome measure utilized. The goal of the present paper is to compare self-report or either of two urine toxicology measures used alone to a relatively new measure -- the SRPHK1 -- which combines self-report, quantitative urine benzoylecgonine levels, and an estimate of the concordance between the two to determine the cocaine-use status of each study day.

METHOD

Datasets from two separate randomized, placebo-controlled cocaine-dependence trials were used to compare four cocaine-use outcome measures.

RESULTS

The two data sets yielded very similar findings and suggest that the combined measure is associated with significantly fewer missing data than urine toxicology and that estimated cocaine use varied significantly depending on which measure was used, with the lowest use estimate being yielded by self-report, the highest by the two urine toxicology measures evaluated, and an intermediate value obtained using the combined measure. The results also suggest that the concordance between self-report and urine toxicology is around 90% at the beginning of the clinical trial but decreases to around 75% by the end of the trial.

CONCLUSION

By combining the objectivity of urine toxicology with the reduced incidence of missing data characteristic of self-report, the SRPHK1 may provide advantages over self-report or urine toxicology measures used alone. In any case, the SRPHK1 provides an interesting complement to these other outcome measures and may warrant further evaluation.

Modafinil and cocaine interactions

This Phase I trial evaluated the interaction between modafinil steady-state and cocaine. Twelve non-treatment seeking, cocaine dependent volunteers received four sets of randomized blinded infusions of saline, 20 mg IV cocaine, and 40 mg IV cocaine. Modafinil was given open label at 0 mg, 400 mg, or 800 mg. Modafinil combined with IV cocaine did not result in any significant hemodynamic interactions. Modafinil significantly dampened scores on Visual Analog Scale measures as compared to baseline cocaine conditions. No significant alterations in labs occurred. Further outpatient trials of modafinil appear to be warranted.

Double-blind, placebo-controlled trial of selegiline transdermal system (STS) for the treatment of cocaine dependence

Cocaine dependence is a major public health problem for which there is no FDA-approved pharmacological treatment. Selegiline is an irreversible selective inhibitor of monoamine oxidase type B (MAO-B) which may affect cocaine addiction through several potential mechanisms. In this study, selegiline transdermal system (STS) was compared to placebo as a treatment for cocaine dependence. This multi-site, double-blind trial of 300 subjects with cocaine dependence assessed the efficacy of selegiline using subject self-reported cocaine use substantiated by urine benzoylecgonine (BE) as the primary outcome measure. Analysis of the data did not show a significant effect for selegiline over placebo. This study does not support a role for selegiline in treating cocaine dependence. The contrast of this result to earlier, promising preclinical and human pilot data could be due to factors associated with sample size, patient characteristics, dose, or poor predictive validity of preclinical models.

Bupropion reduces methamphetamine-induced subjective effects and cue-induced craving

Bupropion is an antidepressant with stimulant properties, which inhibits the reuptake of dopamine (DA) and norepinepherine, and is purported to enhance DA neurotransmission. Bupropion is considered an appealing candidate medication for the treatment of methamphetamine dependence. The current laboratory study was set forth to assess the impact of bupropion treatment on the subjective effects produced by methamphetamine in the laboratory. We also assessed the effects of bupropion treatment on craving elicited by exposure to videotaped methamphetamine cues. A total of 26 participants were enrolled and 20 completed the entire study (n=10 placebo and n=10 bupropion, parallel groups design). Bupropion treatment was associated with reduced ratings of 'any drug effect' (p<0.02), and 'high' (p<0.02) following methamphetamine administration. There was also a significant bupropion-by-cue exposure interaction on General Craving Scale total score (p<0.002), and on the Behavioral Intention subscale (p<0.001). Overall, the data reveal that bupropion reduced acute methamphetamine-induced subjective effects and reduced cue-induced craving. Importantly, these data provide a rationale for the evaluation of bupropion in the treatment of methamphetamine dependence.

Pharmacokinetics, bioavailability and opioid effects of liquid versus tablet buprenorphine

AIMS

Two tablet formulations of buprenorphine (a buprenorphine mono-product, Subutex, and a buprenorphine/naloxone combination product, Suboxone) are available for use in the treatment of opioid addiction; however, the bulk of the clinical studies supporting its approval by the US Food and Drug Administration (FDA) were conducted with a sublingual liquid preparation. To assist the clinician in interpreting the relevant literature in establishing dosing parameters for prescription of tablet buprenorphine, this study was designed to compare the steady state: (1) pharmacokinetics and bioavailability, and (2) physiological, subjective and objective opiate effects of two 8 mg buprenorphine tablets (16 mg) to those of 1 ml (8 mg/ml) buprenorphine solution based upon early reports suggesting that the bioavailability of the tablet was approximately 50% of that of the liquid.

DESIGN

Randomized, open-label, two-way crossover study.

SETTING

Inpatient hospitalization for 21 days.

PARTICIPANTS

Twenty-four male and females in general good health and meeting DSM-IV criteria for opiate dependence.

INTERVENTION

Subjects received one of the two buprenorphine formulations in the first 10-day period, and the other for the second 10-day period with no washout.

MEASUREMENTS

Pharmacokinetic analyses, opiate effects and adverse events.

FINDINGS

Drug steady state was reached by Day 7 of each 10-day period, area under the curve for 16 mg (two 8 mg) tablets was higher than the solution. The only non-kinetic statistically significant difference observed between the formulations was in changes in total opioid agonist score.

CONCLUSIONS

The serum concentration achieved by 16 mg of tablet buprenorphine is higher than that of the 8 mg solution, although differences between physiologic, subjective and objective opioid effects were not noted. The relative bioavailability of tablet versus solution is estimated to be 0.71; thus, with respect to dosing parameters for the tablet, clinicians should consider using less than 16 mg to achieve bioequivalence to the 8 mg solution.

RvE1 protects from local inflammation and osteoclast- mediated bone destruction in periodontitis

Periodontitis is a well-appreciated example of leukocyte-mediated bone loss and inflammation that has pathogenic features similar to those observed in other inflammatory diseases such as arthritis. Resolvins are a new family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammatory signals. Because it is now increasingly apparent that local inflammation plays a critical role in many diseases, including cardiovascular disease, atherosclerosis, and asthma, experiments were undertaken to evaluate the actions of the newly described EPA-derived Resolvin E1 (RvE1) in regulation of neutrophil tissue destruction and resolution of inflammation. The actions of an aspirin-triggered lipoxin (LX) analog and RvE1 in a human disease, localized aggressive periodontitis (LAP), were determined. Results indicate that neutrophils from LAP are refractory to anti-inflammatory molecules of the LX series, whereas LAP neutrophils respond to RvE1. In addition, RvE1 specifically binds to human neutrophils at a site that is functionally distinct from the LX receptor. Consistent with these potent actions, topical application of RvE1 in rabbit periodontitis conferred dramatic protection against inflammation induced tissue and bone loss associated with periodontitis.

A comprehensive assessment of the safety of intravenous methamphetamine administration during treatment with selegiline

Selegiline (L-deprenyl) is a selective irreversible monoamine oxidase B inhibitor shown to be effective in the treatment of Parkinson's and Alzheimer's diseases. Recent evidence suggests that selegiline may also be useful in treating specific aspects of cocaine and nicotine dependence, generating interest in this compound for the treatment of methamphetamine addiction. To investigate this, we performed a randomized, single-blind, placebo-controlled study to evaluate the safety of selegiline treatment (as compared to placebo), concurrent with intravenous methamphetamine (15 or 30 mg). Secondary study objectives included determinations of plasma levels of selegiline and its metabolites, evaluating whether selegiline administration altered the pharmacokinetics of methamphetamine or its metabolites, and evaluating whether selegiline treatment alters the subjective responses to methamphetamine. Twenty-four methamphetamine-dependent participants were randomized to treatment, and 9 of these (N = 5 selegiline, N = 4 placebo) completed the entire protocol. The principal finding from this study was that intravenous administration of moderate doses of methamphetamine was safely tolerated during treatment with selegiline. No participants had electrocardiogram changes, and there were no meaningful differences in any laboratory values either between groups at screening or as a result of the study procedures. In general, adverse events were mild or moderate, and no subjects were discontinued due to adverse events or serious adverse events. Selegiline treatment did not enhance any of the cardiovascular changes (heart rate, blood pressure) produced by methamphetamine administration. Selegiline treatment slightly increased methamphetamine associated "bad effects" but did not alter any other subjective effects. The elimination half-life of methamphetamine was approximately 12 h, and selegiline did not alter clearance of methamphetamine. The available data suggest that selegiline is likely to be safe if used as a pharmacotherapy for methamphetamine dependence.

Safety of intravenous methamphetamine administration during treatment with bupropion

RATIONALE

Methamphetamine dependence is a growing problem for which no medication treatments have proven effective.

OBJECTIVES

We evaluated bupropion, an antidepressant with beneficial effects for the treatment of nicotine dependence, in patients with methamphetamine dependence, to assess the safety and tolerability of methamphetamine administration during bupropion treatment.

METHODS

Twenty-six participants entered the study and 20 completed the protocol. Participants received intravenous methamphetamine (0, 15, and 30 mg) before and after randomization to twice-daily bupropion (150 mg SR) or matched placebo. Dependent measures included cardiovascular effects of methamphetamine, methamphetamine and amphetamine pharmacokinetics, and peak and trough plasma concentrations of bupropion and its metabolites.

RESULTS

Bupropion treatment was well tolerated, with bupropion- and placebo-treated groups reporting similar rates of adverse events. Methamphetamine administration was associated with expected stimulant cardiovascular effects, and these were not accentuated by bupropion treatment. Instead, there was a trend for bupropion to reduce methamphetamine-associated increases in blood pressure and a statistically significant reduction in methamphetamine-associated increases in heart rate. Pharmacokinetic analysis revealed that bupropion treatment reduced the plasma clearance of methamphetamine and also reduced the appearance of amphetamine in the plasma. Methamphetamine administration did not alter the peak and trough plasma concentrations of bupropion or its metabolites.

CONCLUSIONS

Methamphetamine administration was well tolerated during bupropion treatment. There was no evidence of additive cardiovascular effects when the drugs were coadministered. This study provides initial evidence for the safety of prescribing bupropion for the treatment of methamphetamine abuse and dependence. The impact of bupropion treatment in patients who abuse larger doses of methamphetamine remains undetermined.

Transdermal selegiline and intravenous cocaine: safety and interactions

RATIONALE

Because the dopamine system appears to be involved in both acute and chronic effects of cocaine, medication development efforts for cocaine addiction have focused largely on agents that interact with the dopamine system. Selegiline, a selective monoamine oxidase B inhibitor, indirectly modulates dopamine levels, and research suggests selegiline may modify subjective effects of cocaine.

OBJECTIVES

To evaluate further the safety and potential of transdermal selegiline as a treatment for cocaine dependence, interactions between transdermal selegiline and intravenous cocaine were studied in cocaine-dependent volunteers.

METHODS

Pharmacokinetics and subjective, physiological, and endocrinological effects of intravenous cocaine (0,20 and 40 mg) were evaluated both before and during transdermal selegiline treatment (20 mg/day, 10 days) in 12 cocaine-dependent subjects. A transdermal selegiline formulation was used to avoid the risks associated with oral administration of MAO inhibitors.

RESULTS

Selegiline attenuated some physiological (systolic blood pressure and heart rate) and subjective (good effects, liking, stimulated, high, desire for cocaine) effects of cocaine. Selegiline did not affect cocaine's pharmacokinetics or cocaine-induced prolactin decrease and growth hormone increase.

CONCLUSIONS

The combined administration of the transdermal selegiline patch and up to 40 mg cocaine was well tolerated. Selegiline may reduce physiological and subjective effects of cocaine. A randomized trial is needed to evaluate the efficacy of selegiline for cocaine abuse.

Cutting edge: nociceptin stimulates neutrophil chemotaxis and recruitment: inhibition by aspirin-triggered-15-epi-lipoxin A4

The nociceptin receptor (Noci-R) is a G protein-coupled receptor present in neural tissues and its activation by nociceptin is involved in the processing of pain signals. Here, we report that Noci-R is present and functional on peripheral blood polymorphonuclear leukocytes (PMN). Human PMN express mRNA for Noci-R, its nucleotide sequence determined, and specific binding with [(125)I]-labeled nociceptin gave an apparent K(d) approximately 1.5 nM for this PMN opioid receptor. Nociceptin evoked PMN chemotaxis with maximal activity at 100 pM, without intracellular Ca(2+) mobilization. When injected in murine air pouches, nociceptin elicited leukocyte infiltration in a concentration-dependent fashion. Nociceptin-stimulated PMN infiltration was inhibited by treating mice with a synthetic analog of the aspirin-triggered lipid mediator 15-epi-lipoxin A(4). The present results identify nociceptin as a potent chemoattractant and provide a novel link between the neural and immune systems that are blocked by aspirin-triggered lipid mediators and may be relevant in neurogenic inflammation.

Selectivity of recombinant human leukotriene D(4), leukotriene B(4), and lipoxin A(4) receptors with aspirin-triggered 15-epi-LXA(4) and regulation of vascular and inflammatory responses

Aspirin-triggered lipoxin A(4) (ATL, 15-epi-LXA(4)) and leukotriene D(4) (LTD(4)) possess opposing vascular actions mediated via receptors distinct from the LXA(4) receptor (ALX) that is involved in leukocyte trafficking. Here, we identified these receptors by nucleotide sequencing and demonstrate that LTD(4) receptor (CysLT(1)) is induced in human vascular endothelia by interleukin-1beta. Recombinant CysLT(1) receptor gave stereospecific binding with both [(3)H]-LTD(4) and a novel labeled mimetic of ATL ([(3)H]-ATLa) that was displaced with LTD(4) and ATLa ( approximately IC(50) 0.2 to 0.9 nmol/L), but not with a bioinactive ATL isomer. The clinically used CysLT(1) receptor antagonist, Singulair, showed a lower rank order for competition with [(3)H]-ATLa (IC(50) approximately 8.3 nmol/L). In contrast, LTD(4) was an ineffective competitive ligand for recombinant ALX receptor with [(3)H]-ATLa, and ATLa did not compete for [(3)H]-LTB(4) binding with recombinant LTB(4) receptor. Endogenous murine CysLT(1) receptors also gave specific [(3)H]-ATLa binding that was displaced with essentially equal affinity by LTD(4) or ATLa. Systemic ATLa proved to be a potent inhibitor (>50%) of CysLT(1)-mediated vascular leakage in murine skin (200 microg/kg) in addition to its ability to block polymorphonuclear leukocyte recruitment to dorsal air pouch (4 microg/kg). These results indicate that ATL and LTD(4) bind and compete with equal affinity at CysLT(1), providing a molecular basis for aspirin-triggered LXs serving as a local damper of both vascular CysLT(1) signals as well as ALX receptor-regulated polymorphonuclear leukocyte traffic.

Anti-microinflammatory lipid signals generated from dietary N-3 fatty acids via cyclooxygenase-2 and transcellular processing: a novel mechanism for NSAID and N-3 PUFA therapeutic actions

Aspirin therapy inhibits prostaglandin biosynthesis; yet via acetylation of cyclooxygenase 2 (COX-2) it leads to bioactive lipoxins epimeric at carbon 15 (15-epi-LX, also termed aspirin-triggered lipoxin or ATL). Here, we review our findings indicating that inflammatory exudates from mice treated with omega-3 PUFA and aspirin (ASA) generate a novel array of bioactive lipid signals. Also, human endothelial cells, both HUVEC and microvascular, with upregulated COX-2 and treated with ASA converted C20:5 omega-3 to 18R-hydroxyeicosapentaenoic acid (HEPE) and 15R-HEPE. Human PMN activated with serum treated zymosan (STZ) utilized each of these R-HEPEs to generate novel classes of trihydroxy-containing mediators including 5-series 15R-LX and 5,12,18R-triHEPE. The novel products were potent inhibitors of human PMN transendothelial migration and infiltration of PMN in dorsal air pouches in vivo. In addition to ASA, both acetaminophen and indomethacin also permitted 18R-HEPE and 15R-HEPE generation with recombinant human COX-2 as well as omega-5 and omega-9 oxygenations of other fatty acids that act on leukocytes, platelets and endothelial cells. These findings establish new transcellular routes for producing arrays of lipid mediators via COX-2-NSAIDs and cell-cell interactions that impact microinflammation. Moreover, they provide novel mechanism(s) that could underlie the many reported therapeutic benefits of omega-3 dietary supplementation of interest in inflammation, cancer, and vascular disorders.

Epitope location on tissue factor determines the anticoagulant potency of monoclonal anti-tissue factor antibodies

Tissue factor (TF), the cellular cofactor for the serine protease factor VIIa (F.VIIa), triggers blood coagulation and is involved in the pathogenesis of various thrombosis-related disorders. Therefore, agents which specifically target tissue factor, such as monoclonal antibodies, may provide promising new antithrombotic therapy. We mapped the epitopes of several anti-TF antibodies using a panel of soluble TF mutants. They bound to three distinct TF regions. The epitope of the 7G11 antibody included Phe50 and overlapped with a TF-F.VIIa light chain contact area. The common epitope of the antibodies 6B4 and HTF1 included residues Tyr94 and Phe76 both of which make critical contacts to the catalytic domain of F.VIIa. The antibodies D3 and 5G6 had a common epitope outside the TF-F.VIIa contact region. It included residues Lys 165, Lys 166, Asn199, Arg200 and Lys201 and thus overlapped with the substrate interaction region of tissue factor. The antibodies 5G6 and D3 were potent anticoagulants when infused to flowing human blood in an ex-vivo thrombosis model. Plasma fibrinopeptide A levels and fibrin deposition were completely inhibited. In contrast, 6B4 was a weak inhibitor in this ex-vivo thrombosis model, and HTF1 displayed no inhibition at all. These disparate activities were also reflected in TF-dependent F.X activation assays performed with human plasma. The potency differences could neither be explained by the determined binding affinities nor by the on-rates of antibodies. Therefore, the results suggest that antibody binding epitope and hence the particular mechanism of inhibition, is the main determinative factor of anticoagulant potency of anti-TF antibodies.

Novel functional sets of lipid-derived mediators with antiinflammatory actions generated from omega-3 fatty acids via cyclooxygenase 2-nonsteroidal antiinflammatory drugs and transcellular processing

Aspirin therapy inhibits prostaglandin biosynthesis without directly acting on lipoxygenases, yet via acetylation of cyclooxygenase 2 (COX-2) it leads to bioactive lipoxins (LXs) epimeric at carbon 15 (15-epi-LX, also termed aspirin-triggered LX [ATL]). Here, we report that inflammatory exudates from mice treated with omega-3 polyunsaturated fatty acid and aspirin (ASA) generate a novel array of bioactive lipid signals. Human endothelial cells with upregulated COX-2 treated with ASA converted C20:5 omega-3 to 18R-hydroxyeicosapentaenoic acid (HEPE) and 15R-HEPE. Each was used by polymorphonuclear leukocytes to generate separate classes of novel trihydroxy-containing mediators, including 5-series 15R-LX(5) and 5,12,18R-triHEPE. These new compounds proved to be potent inhibitors of human polymorphonuclear leukocyte transendothelial migration and infiltration in vivo (ATL analogue > 5,12,18R-triHEPE > 18R-HEPE). Acetaminophen and indomethacin also permitted 18R-HEPE and 15R-HEPE generation with recombinant COX-2 as well as omega-5 and omega-9 oxygenations of other fatty acids that act on hematologic cells. These findings establish new transcellular routes for producing arrays of bioactive lipid mediators via COX-2-nonsteroidal antiinflammatory drug-dependent oxygenations and cell-cell interactions that impact microinflammation. The generation of these and related compounds provides a novel mechanism(s) for the therapeutic benefits of omega-3 dietary supplementation, which may be important in inflammation, neoplasia, and vascular diseases.

Lipoxins, aspirin-triggered 15-epi-lipoxin stable analogs and their receptors in anti-inflammation: a window for therapeutic opportunity

LXs and 15-epimer LXs are generated during cell-cell interactions that occur during multicellular host response to inflammation, tissue injury or host defense. Results indicate that they are present in vivo during human illness and carry predominantly counter-regulatory biological actions opposing the action of well-characterized mediators of inflammation that appear to lead to resolution of the inflammatory response or promotion of repair and wound healing. The first selective receptor of LXA4 was identified by direct ligand binding and was cloned and characterized. Its signaling involves a novel polyisoprenyl-phosphate pathway that directly regulates PLD (Levy et al. 1999a). LX- and 15-epimer-LX-stable analogs that resist metabolic inactivation were designed, synthesized and shown to be potent LX mimetics and novel topically active anti-inflammatory agents in animal models. These new investigational tools enable structure-function studies of LX signal transduction, further elucidation of the role of LX and 15-epimer LX in host responses and exploitation of their potent bioactions in the design of novel pharmacologic agents.

Oxidoreductases in lipoxin A4 metabolic inactivation: a novel role for 15-onoprostaglandin 13-reductase/leukotriene B4 12-hydroxydehydrogenase in inflammation

The lipoxins (LX) are autacoids that act within a local inflammatory milieu to dampen neutrophil recruitment and promote resolution. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) and 15-oxoprostaglandin 13-reductase, also termed leukotriene B(4) 12-hydroxydehydrogenase (PGR/LTB(4)DH), are two enzymatic activities appreciated for their roles in the metabolism of prostaglandins and LTB(4). Here, we determined whether these oxidoreductases also catalyze the conversion of lipoxin A(4) (LXA(4)) and assessed the activities of these LXA(4) metabolites. 15-Oxo-LXA(4) was generated by incubating LXA(4) with 15-PGDH and NAD(+) for studies of its further conversion. PGR/LTB(4)DH catalyzed the NADH-dependent reduction of 15-oxo-LXA(4) to yield 13,14-dihydro-15-oxo-LXA(4). With NADH as a cofactor, 15-PGDH acted as a 15-carbonyl reductase and catalyzed the conversion of 13,14-dihydro-15-oxo-LXA(4) to 13, 14-dihydro-LXA(4). Human polymorphonuclear leukocytes (PMN) exposed to native LXA(4), 15-oxo-LXA(4), or 13,14-dihydro-LXA(4) did not produce superoxide anions. At concentrations where LXA(4) and a metabolically stable LXA(4) analog potently inhibited leukotriene B(4)-induced superoxide anion generation, the further metabolites were devoid of activity. Neither 15-oxo-LXA(4) nor 13, 14-dihydro-LXA(4) effectively competed with (3)H-labeled LXA(4) for specific binding to recombinant LXA(4) receptor (ALXR). In addition, introducing recombinant PGR/LTB(4)DH into a murine exudative model of inflammation increased PMN number by approximately 2-fold, suggesting that this enzyme participates in the regulation of PMN trafficking. These results establish the structures of LXA(4) further metabolites and indicate that conversion of LXA(4) to oxo- and dihydro- products represents a mode of LXA(4) inactivation in inflammation. Moreover, they suggest that these eicosanoid oxidoreductases have multifaceted roles controlling the levels of specific eicosanoids involved in the regulation of inflammation.

Aspirin-tolerant asthmatics generate more lipoxins than aspirin-intolerant asthmatics

Asthma is characterized by chronic airway inflammation resulting from overproduction of pro-inflammatory mediators, such as leukotrienes (LT). The authors questioned the biosynthetic capacity of asthmatic patients for lipoxins (LX) and 15-epimer lipoxins (15-epi-LX), endogenous regulators of inflammatory responses that inhibit pro-inflammatory events. Levels of LXA4, 15-epi-LXA4 and LTC4 were determined in 14 clinically characterized aspirin-intolerant asthmatics (AIA), 11 aspirin-tolerant asthmatics (ATA) and eight healthy volunteers using a stimulated whole blood protocol. Both LXA4 and 15-epi-LXA4 were generated in whole blood activated by the divalent cation ionophore, A23187. Higher levels of LXA4 were produced in ATA than either AIA or healthy volunteers. Exposure of AIA whole blood to interleukin-3 prior to A23187 did not elevate their reduced capacity to generate LXA4. Generation of a bronchoconstrictor, LTC4, was similar in both AIA and ATA. Consequently, the ratio of LXA4:LTC4 quantitatively favoured the bronchoconstrictor for AIA and differed from both ATA and healthy subjects. In addition, the capacity for 15-epi-LXA4 generation was also diminished in AIA, since whole blood stimulated in the presence of aspirin gave increased levels only in samples from ATA. The present results indicate that asthmatics possess the capacity to generate both lipoxins and 15-epimer-lipoxins, but aspirin-intolerant asthmatics display a lower biosynthetic capacity than aspirin-tolerant asthmatics for these potentially protective lipid mediators. This previously unappreciated, diminished capacity for lipoxin formation by aspirin-intolerant asthmatic patients may contribute to their more severe clinical phenotype, and represents a novel paradigm for the development of chronic inflammatory disorders.

Hepatocytes are a rich source of novel aspirin-triggered 15-epi-lipoxin A(4)

Novel aspirin (ASA)-triggered 15-epi-lipoxins (ATL) comprise new potent bioactive eicosanoids that may contribute to the therapeutic effect of this drug. ATL biosynthesis is initiated by ASA acetylation of cyclooxygenase (COX)-2 and was originally identified during the interaction of leukocytes with either endothelial or epithelial cells. Here, we examined ATL biosynthesis in rat hepatocytes either alone or in coincubation with nonparenchymal liver cells (NPC) and in liver homogenates from ASA-treated rats. Rat hepatocytes and CC-1 cells, a rat hepatocyte cell line, displayed COX-1 but not COX-2 mRNA expression and predominantly produced thromboxane A(2) (TXA(2)) and 15-hydroxyeicosatetraenoic acid (15-HETE). In these cells, ASA shifted the arachidonic acid metabolism from TXA(2) to 15-HETE in a concentration-dependent manner. In contrast, neither indomethacin, ibuprofen, valeryl salicylate, nor nimesulide was able to trigger 15-HETE biosynthesis. SKF-525A, a cytochrome P-450 inhibitor, significantly reduced the effect of ASA on 15-HETE biosynthesis. Furthermore, phenobarbital, a potent inducer of cytochrome P-450 activity, further increased ASA-induced 15-HETE production. ASA treatment of hepatocyte-NPC coincubations resulted in the generation of significant amounts of ATL. In addition, in vivo experiments demonstrated augmented hepatic levels of 15-epi-lipoxin A(4) in ASA-treated rats. Taken together and considering that ASA is hydrolyzed on its first pass through the portal circulation, these data indicate that, during ASA's consumption, liver tissue generates biologically relevant amounts of ATL by COX-2-independent mechanisms.

Leukotriene B4 receptor transgenic mice reveal novel protective roles for lipoxins and aspirin-triggered lipoxins in reperfusion

Polymorphonuclear neutrophil (PMN) activation is pivotal in acute inflammation and injury from reperfusion. To elucidate components controlling PMNs in vivo, we prepared novel transgenic mice with the human leukotriene (LT) B4 receptor (BLTR) for functional characterization. Overexpression of BLTR in leukocytes dramatically increased PMN trafficking to skin microabscesses and lungs after ischemia-reperfusion, whereas mice deficient in 5-lipoxygenase (5-LO) showed diminished PMN accumulation in reperfused lungs. Hence, both BLTR expression and LT biosynthesis are critical for PMN infiltration in reperfusion-initiated second-organ injury. Also, in BLTR transgenic mice, 5-LO expression and product formation were selectively increased in exudates, demonstrating that receptor overexpression amplifies proinflammatory circuits. Endogenous lipoxin (LX) A4 was produced in ischemic lungs and elevated by reperfusion. Because LXA4 and aspirin-triggered 15-epimeric LXA4 (ATL) selectively regulate leukocyte responses, they were tested in BLTR transgenic mice. Despite excessive PMN recruitment in BLTR transgenic mice, intravenous injection of ATL sharply diminished reperfusion-initiated PMN trafficking to remote organs, and topical application of LX was protective in acute dermal inflammation. These results demonstrate a direct role for BLTR with positive feedback, involving BLTR and 5-LO signaling in controlling PMNs. Moreover, LXA4 and ATL counter BLTR-amplified networks, revealing a novel protective role for LX and ATL in stress responses that has applications in perioperative medicine.

Lipoxin and aspirin-triggered 15-epi-lipoxin cellular interactions anti-inflammatory lipid mediators

Eicosanoids are known to play important roles in inflammation. Recent findings have given rise to several new concepts regulating the generation of eicosanoids, illustrated in Figure 1. Lipoxins (LX) are trihydroxytetraene-containing eicosanoids that are generated within vascular lumen by platelet-leukocyte interactions and at mucosal surfaces by leukocyte-epithelial cell interactions. During these cell-cell interactions, transcellular biosynthetic pathways are used as major routes, and thus, in humans, LX are formed in vivo during multicellular responses such as inflammation, atherosclerosis, and thrombosis. This branch of the eicosanoid cascade generates specific tetraene-containing products that appear to function as stop signals, since they inhibit key steps in leukocyte-mediated inflammation. Of special interest, it appears that aspirin also functions in part via production of novel epimers of lipoxins or 15-epi-lipoxins (Figure 1). Here, we review recent developments on the cellular interactions of these novel anti-inflammatory mediators.

Aspirin-triggered 15-epi-lipoxin A4 (ATL) generation by human leukocytes and murine peritonitis exudates: development of a specific 15-epi-LXA4 ELISA

Aspirin (ASA) triggers the formation of 15-epi-lipoxins (15-epi-LXs or ATL [ASA-triggered LX]), which are potent bioactive eicosanoids that may contribute to the therapeutic impact of ASA. To elucidate the role of these new compounds in vivo, it is essential to establish quick and sensitive detection methods. To this end, we prepared an enzyme-linked immunosorbent assay specific for 15-epi-LXA4 that proved to be highly sensitive (IC50 approximately 50 pg, minimum detection approximately 3.5 pg) and stereoselective. The amounts of 15-epi-LXA4 generated by human neutrophils from peripheral blood of healthy volunteers using this enzyme-linked immunosorbent assay were in agreement with those values obtained by liquid chromatography. Formation of 15-epi-LXA4 was cell ratio-dependent during THP-1 (a monocytic leukemia cell line)-neutrophil interactions with ASA-treated cells, and 15-epi-LXA4 was not detected with either cell type alone. Generation of 15-epi-LXA4 was also examined in murine peritonitis with ASA administration. Exudates from ASA-treated mice showed increased production of 15-epi-LXA4 that was diminished by indomethacin, a blocker of ASA-dependent acetylation of prostaglandin G/H synthase. A cytochrome P450 inhibitor administered in the presence of ASA did not prevent 15-epi-LXA4 formation, which suggests that P450 does not significantly contribute to formation of 15-epi-LXA4 in this murine model. These results indicate that the new enzyme-linked immunosorbent assay is both sensitive and selective for 15-epi-LXA4 and that 15-epi-LXA4 is produced by human leukocyte-leukocyte interactions. In addition, 15-epi-LXA4 is generated by inflammatory exudates when ASA is administered during murine peritonitis and when prostaglandin G/H synthase is upregulated and acetylated. This assay should provide rapid means to investigate 15-epi-LXA4 generation in both cellular and animal models.

The role of N-glycosylation of human thromboxane A2 receptor in ligand binding

Thromboxane A2 receptor (TXA2R) was expressed in insect Sf21 cells and demonstrated to interact with 8-iso-PGF2 alpha and 9 alpha, 11 beta-PGF2 alpha with a potency similar to that of TXA2 agonist U46619. TXA2R was shown to be a glycoprotein. The role of N-glycosylation of TXA2R in ligand binding was investigated in the insect cells over-expressed with recombinant TXA2R. Deletion of the carbohydrate moiety by adding tunicamycin during infection of Sf21 cells or mutation of both potential N-glycosylation sites (Asn-4 and Asn-16) abolished the ligand binding of TXA2R, suggesting that N-glycosylation is crucial for binding function. Mutation of either Asn-4 or Asn-16 to a leucine did not have much effect on maximal binding. However, the mutant receptors possess lower binding affinity toward TXA2R antagonist [3H]SQ29548. Furthermore, the binding specificity of the mutant receptors was shown to be altered. Our data suggest that both Asn-4 and Asn-16 are glycosylated and glycosylation on either site is sufficient for ligand recognition. However, glycosylation on both sites is required to maintain binding affinity and specificity.

Expression of rat steroid 5 alpha-reductase (isozyme-1) in Spodoptera frugiperda, SF21, insect cells: expression of rat steroid 5 alpha-reductase

The enzyme steroid 5 alpha-reductase (5 alpha R) catalyzes the reduction of testosterone (T) to 5 alpha-dihydrotestosterone (DHT). In this study, the baculovirus expression system was used to overexpress rat 5 alpha R type I isozyme (r5 alpha R 1). The full length of r5 alpha R1 cDNA was inserted into the Autographa californica nuclear polyhedrosis virus (Ac-MNPV) genome and expressed in Spodoptera frugiperda, Sf 21, insect cells. The expressed recombinant r5 alpha-R1 showed maximal enzymatic activity when the infected cells were harvested on day 3 of post-transfection. The K(m) values for NADPH and T were 17 microM and 2.7 microM, respectively. Inhibition of the recombinant r5 alpha R1 by N,N diethyl-4-aza-4-methyl-3-oxo-5 alpha-androstane-17 beta-carboxamide (4MA) was competitive with respect to the substrate (T), and a Ki of 3 nM was obtained. The enzyme was located primarily in the nuclear fraction, and the maximum velocity for the recombinant r5 alpha R1 in this fraction was 60 nmoles DHT/min/mg. Immunoblot analysis indicated a single immunoreactive band at 26 kDa, which corresponds to the molecular weight of r5 alpha R1. Photoaffinity labeling by [2'-32P]-2-azido-NAD P+ ([2'-32P]2N3-NAD P+) and [1,2(3)H] N-(benzylbenzoyl)-3-oxo-4-aza-4-methyl-5 alpha androstane-17 beta-carboxamide ([3H]-4MABP) also showed a labeled protein band at 26 kDa.

Site-directed mutagenesis of cysteinyl and serine residues of human thromboxane A2 receptor in insect cells

A thromboxane A2 receptor cDNA was isolated from a human placenta library by polymerase chain reaction (PCR) and was expressed in insect (Sf21) cells using baculovirus system. The recombinant receptor exhibited [3H]-SQ29548 and [125I]-BOP binding activities with Kd values of 1.01 +/- 0.09 nM and 1.63 +/- 0.23 nM, respectively. The receptor binding activity was inhibited by dithiothreitol in a time- and concentration-dependent manner, indicating the involvement of disulfide linkage in ligand binding. The role of the four conserved cysteinyl residues in ligand binding was further examined by site-directed mutagenesis. Each of the four cysteinyl residues was respectively mutated to a serine residue. C102S, C105S, and C183S mutants exhibited no ligand binding activity although successful expression was achieved as revealed by immunoblot analysis, whereas C257S mutant retained most of the binding activity. Homology analysis of all prostanoid receptors indicates that Cys-105 (first extracellular loop) and Cys-183 (second extracellular loop) are conserved and are presumed to form a disulfide bond for receptor stability as suggested by the inhibition of ligand binding by dithiothreitol reduction. Loss of binding activity by C102S mutant revealed that the sulfhydryl group of Cys-102 must play an essential role in ligand binding. Molecular modeling proposed that the Ser-201 is involved in interacting with TXA2 by forming hydrogen bonding. Point mutations of both Ser-201 and a conserved Ser-255 did not affect the ligand binding specificity and affinity for [3H]-SQ29548, but have significantly altered Kd values for [125I]-BOP. These results indicate that various cysteinyl and serine residues of thromboxane A2 receptor may play different roles in ligand binding.