Simultaneous analysis of antihyperglycemic small molecule drugs and peptide drugs by means of dual liquid chromatography high-resolution mass spectrometry

OBJECTIVES

The study aimed to evaluate dual liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS) for the simultaneous analysis of small and large molecule drugs by development and application of a validated bioanalytical method.

METHODS

The oral antihyperglycemic drugs (OAD) dapagliflozin, empagliflozin, glibenclamide, glimepiride, metformin, pioglitazone, repaglinide, saxagliptin, sitagliptin, and vildagliptin, as well as the antihyperglycemic peptides exenatide, human insulin, insulin aspart, insulin degludec, insulin detemir, insulin glargine, insulin glulisine, insulin lispro, and semaglutide were included in the analytical procedure. Analytes were extracted using a combination of protein precipitation and solid-phase extraction. Two identical reversed-phase columns were used for separation followed by Orbitrap high-resolution mass spectrometry. The whole procedure was validated according to international recommendations.

RESULTS

Different MS parameters had to be used for the two analyte groups, but dual LC separation allowed elution of all analytes within 12 min using the same column type. The analytical procedure was accurate and precise for most of the compounds except for exenatide, semaglutide, and insulin glargine, which were included qualitatively in the method. Analysis of proof-of-concept samples revealed OAD concentrations mostly within their therapeutic range, insulins could be detected in five cases but at concentrations below the lower limit of quantification except for one case.

CONCLUSIONS

Dual LC in combination with HRMS was shown to be a suitable platform to analyze small and large molecules in parallel and the current method allowed the determination of a total of 19 antihyperglycemic drugs in blood plasma within 12 min.

Further development of a liquid chromatography-high-resolution mass spectrometry/mass spectrometry-based strategy for analyzing eight biomarkers in human urine indicating toxic mushroom or Ricinus communis ingestions

Recently, we presented a strategy for analysis of eight biomarkers in human urine to verify toxic mushroom or Ricinus communis ingestions. However, screening for the full panel is not always necessary. Thus, we aimed to develop a strategy to reduce analysis time and by focusing on two sets of analytes. One set (A) for biomarkers of late-onset syndromes, such as phalloides syndrome or the syndrome after castor bean intake. Another set (B) for biomarkers of early-onset syndromes, such as pantherine-muscaria syndrome and muscarine syndrome. Both analyses should be based on hydrophilic-interaction liquid chromatography coupled with high-resolution mass spectrometry (MS)/MS (HILIC-HRMS/MS). For A, urine samples were prepared by liquid-liquid extraction using dichloromethane and subsequent solid-phase extraction of the aqueous supernatant. For B urine was precipitated using acetonitrile. Method A was validated for ricinine and α- and β-amanitin and method B for muscarine, muscimol, and ibotenic acid according to the specifications for qualitative analytical methods. In addition, robustness of recovery and normalized matrix factors to matrix variability measured by urinary creatinine was tested. Moreover, applicability was tested using 10 urine samples from patients after suspected mushroom intoxication. The analytes α- and β-amanitin, muscarine, muscimol, and ibotenic acid could be successfully identified. Finally, psilocin-O-glucuronide could be identified in two samples and unambiguously distinguished from bufotenine-O-glucuronide via their MS² patterns. In summary, the current workflow offers several advantages towards the previous method, particularly being more labor-, time-, and cost-efficient, more robust, and more sensitive.

Impact of a large dam on reproduction of a non-migratory teleost species, Acestrorhynchus lacustris (Characiformes: Acestrorhynchidae)

The release of water from the reservoir hypolimnion, lower concentration of oxygen and the anthropogenic regulation of the river flow, could affect the reproduction of fish, especially migratory species. However, little is known about the effects of these changes in water on non-migratory species. In this sense, the reproduction of Acestrohynchus lacustris was evaluated in two sections of São Francisco River, Minas Gerais, Brazil. Section 1, located immediately downstream from Três Marias Dam (18°09'31.65"S and 45°13'36.00"W) and section 2, located at the confluence of the São Francisco and the Abaeté Rivers (18°02'47.78"S and 45°10'57.95"W). For this, we obtained the physico-chemical parameters of water of each study section. Additionally, biometric data and biological indices of all specimens were measured. Fecundity and follicles diameters were measured in females. Temperature, dissolved oxygen and flow showed lower values in section 1. Fish captured in this section, had lower values of GSI in both sexes, and females presented decreased values of fecundity and follicles diameter. This species showed reproductive activity in the two sections analyzed, however, in section 1 where the temperature and dissolved oxygen presented significant lower values, the reproductive capacity of A. lacustris, was negatively affected.

Abuse of nutmeg seeds: Detectable by means of liquid chromatography-mass spectrometry techniques?

Numerous case reports of intoxications with nutmeg seeds (Myristica fragrans, Houtt.) can be found in literature often following their abuse, as psychotropic effects were described after ingestions of large doses. The successful detection of the main ingredients of the nutmeg seeds essential oil elemicin, myristicin, and safrole, as well as their metabolites in human urine by gas chromatography coupled to mass spectrometry (GC-MS) was already described. The aim of this study was to investigate the detectability of the main ingredients of nutmeg seeds and their metabolites in human blood and urine samples using liquid chromatography coupled to linear ion trap mass spectrometry (LC-LIT-MSⁿ ) and liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS/MS) after nutmeg seed abuse. Sample material of three individuals was retrospectively investigated after a systematic screening approach indicated an intoxication with nutmeg seeds as a likely cause of symptoms. Metabolic patterns in plasma and urine using GC-MS were comparable with those described in earlier publications. Investigations using hyphenated liquid chromatography techniques lead to the detection of myristicin and safrole, as well as further metabolites not described using GC-MS and revealed sulfation as an additional Phase II metabolic pathway. These results might help to detect or confirm future intoxications with nutmeg seeds by using LC-MS techniques.

Analysis of α- and β-amanitin in Human Plasma at Subnanogram per Milliliter Levels by Reversed Phase Ultra-High Performance Liquid Chromatography Coupled to Orbitrap Mass Spectrometry

Amatoxins are known to be one of the main causes of serious to fatal mushroom intoxication. Thorough treatment, analytical confirmation, or exclusion of amatoxin intake is crucial in the case of any suspected mushroom poisoning. Urine is often the preferred matrix due to its higher concentrations compared to other body fluids. If urine is not available, analysis of human blood plasma is a valuable alternative for assessing the severity of intoxications. The aim of this study was to develop and validate a liquid chromatography (LC)-high resolution tandem mass spectrometry (HRMS/MS) method for confirmation and quantitation of α- and β-amanitin in human plasma at subnanogram per milliliter levels. Plasma samples of humans after suspected intake of amatoxin-containing mushrooms should be analyzed and amounts of toxins compared with already published data as well as with matched urine samples. Sample preparation consisted of protein precipitation, aqueous liquid-liquid extraction, and solid-phase extraction. Full chromatographical separation of analytes was achieved using reversed-phase chromatography. Orbitrap-based MS allowed for sufficiently sensitive identification and quantification. Validation was successfully carried out, including analytical selectivity, carry-over, matrix effects, accuracy, precision, and dilution integrity. Limits of identification were 20 pg/mL and calibration ranged from 20 pg/mL to 2000 pg/mL. The method was applied to analyze nine human plasma samples that were submitted along with urine samples tested positive for amatoxins. α-Amanitin could be identified in each plasma sample at a range from 37–2890 pg/mL, and β-amanitin was found in seven plasma samples ranging from <20–7520 pg/mL. A LC-HRMS/MS method for the quantitation of amatoxins in human blood plasma at subnanogram per milliliter levels was developed, validated, and used for the analysis of plasma samples. The method provides a valuable alternative to urine analysis, allowing thorough patient treatment but also further study the toxicokinetics of amatoxins.

Evaluation of novel organosilane modifications of paper spray mass spectrometry substrates for analyzing polar compounds

Paper spray mass spectrometry (PSMS) is currently used in different analytical fields, but less effort has been made so far to use PSMS for highly polar compounds. Such analytes usually show poor performance in PSMS due to their high affinity for common paper substrates in addition to high matrix effects. In this study, strategies for hydrophobic modifications of commercially available paper substrates using ten different organosilanes were developed. The modified substrates were generated, characterized, and applied for PSMS analysis of polar toxins. By using the modified paper, PSMS performance of some of the toxins could be considerably increased, especially for orellanine, showing a more than 80-fold signal enhancement when substrates modified with chlorotrimethylsilane were used. For other toxins like ricinine, only small beneficial effects could be shown on PSMS performance when using modified substrates. Statistical equivalence tests showed sufficient ruggedness of the developed procedures also compared to conventional substrates. Thus, further systematic development of paper substrates modified with organosilane derivatives based on the presented study for application in PSMS should be encouraged.

Nano liquid chromatography-high-resolution mass spectrometry for the identification of metabolites of the two new psychoactive substances N-(ortho-methoxybenzyl)-3,4-dimethoxyamphetamine and N-(ortho-methoxybenzyl)-4-methylmethamphetamine

Among the emerging new psychoactive substances (NPS), compounds carrying an N-ortho-methoxybenzyl substituent, the so-called NBOMes, represented a highly potent group of new hallucinogens. Recently, 3,4-dimethoxyamphetamine (3,4-DMA)-NBOMe and 4-methylmethamphetamine (4-MMA)-NBOMe occurred, but no data on their pharmacokinetics were available. According to other NBOMes, they are expected to be extensively metabolized. For detection and identification of their phase I and II metabolites, nano liquid chromatography coupled to high resolution tandem mass spectrometry (nanoLC-HRMS/MS) was used. Rat urine was prepared by simple dilution and incubation mixtures with pooled human liver S9 fraction by precipitation. Furthermore, the results concerning detectability using the new nanoLC approach were compared to those obtained by conventional ultra-high performance LC (UHPLC). In addition, the detectability of the compounds by standard urine screening approaches (SUSAs) routinely used by the authors with UHPLC-HRMS/MS, LC-MSⁿ, and GC-MS was tested. Both NBOMes were extensively metabolized mainly by O-demethylation and conjugation with glucuronic acid (3,4-DMA-NBOMe) or oxidation of the tolyl group to the corresponding carboxylic acid (4-MMA-NBOMe). The developed nanoLC-HRMS/MS approach was successfully applied for identification of 38 3,4-DMA-NBOMe metabolites and 33 4-MMA-NBOMe metabolites confirming its detection power. Furthermore, the solvent saving nanoLC system showed comparable results to the UHPLC-HRMS/MS approach. In addition, an intake of an estimated low common user's dose of the compounds was detectable by all SUSAs only via their metabolites. Suggested targets for urine screening procedures were O-demethyl- and O,O-bis-demethyl-3,4-DMA-NBOMe and their glucuronides and carboxy-4-MMA-NBOMe and its glucuronide and N-demethyl-carboxy-4-MMA-NBOMe.

LC-HR-MS/MS standard urine screening approach: Pros and cons of automated on-line extraction by turbulent flow chromatography versus dilute-and-shoot and comparison with established urine precipitation

Comprehensive urine screening for drugs and metabolites by LC-HR-MS/MS using Orbitrap technology has been described with precipitation as simple workup. In order to fasten, automate, and/or simplify the workup, on-line extraction by turbulent flow chromatography and a dilute-and-shoot approach were developed and compared. After chromatographic separation within 10min, the Q-Exactive mass spectrometer was run in full scan mode with positive/negative switching and subsequent data dependent acquisition mode. The workup approaches were validated concerning selectivity, recovery, matrix effects, process efficiency, and limits of identification and detection for typical drug representatives and metabolites. The total workup time for on-line extraction was 6min, for the dilution approach 3min. For comparison, the established urine precipitation and evaporation lasted 10min. The validation results were acceptable. The limits for on-line extraction were comparable with those described for precipitation, but lower than for dilution. Thanks to the high sensitivity of the LC-HR-MS/MS system, all three workup approaches were sufficient for comprehensive urine screening and allowed fast, reliable, and reproducible detection of cardiovascular drugs, drugs of abuse, and other CNS acting drugs after common doses.

Towards a universal LC-MS screening procedure - can an LIT LC-MS(n) screening approach and reference library be used on a quadrupole-LIT hybrid instrument?

In contrast to libraries with highly reproducible gas chromatography electron ionization mass spectra, current liquid chromatography (LC-MS) libraries are limited to specific instrument types. Therefore, the aim of the study was to prove whether a recently developed linear ion trap (LIT) LC-MS(n) screening approach and reference library can be transferred to an LC-MS/MS system with a quadrupole-LIT hybrid mass analyzer using SmileMS, a sophisticated search algorithm. The LIT reference library was built with MS² and MS³ wideband spectra recorded on a ThermoFisher LXQ LIT with electrospray ionization in positive mode and full-scan data-dependent acquisition (DDA). Collision parameter optimizations, including different scan types and energies, were performed on an Applied Biosystems QTRAP 4000 system using electrospray ionization in positive mode and full-scan DDA. Modified library sets were generated to improve the detection of a compound by the used search algorithm. Additionally, 100 authentic human urine samples were screened by both systems for proof of applicability. In the applicability study, 533 compounds were detected by the LXQ and 477 by the QTRAP system using enhanced product ion scan and a modified database. The presented data showed that the LIT screening approach and reference library could be used successfully on a QTRAP instrument with some limitations. These should be overcome by further optimizations regarding DDA settings for better sensitivity and further library modifications to reduce spectra mismatches.

Metabolism studies of the Kratom alkaloids mitraciliatine and isopaynantheine, diastereomers of the main alkaloids mitragynine and paynantheine, in rat and human urine using liquid chromatography-linear ion trap-mass spectrometry

Mitragyna speciosa (Kratom in Thai), native in Southeast Asia, is increasingly misused as a herbal drug of abuse. During metabolism studies on the Kratom alkaloids mitragynine, its diastereomers speciogynine and speciociliatine as well as paynantheine in rats and humans, further isomeric compounds were detected in Kratom users' urine. The question arose whether these compounds were formed from the low abundant, isomeric alkaloids mitraciliatine (MC) and isopaynantheine (ISO-PAY). Therefore, the aim of the presented study was to identify using liquid chromatography-linear ion trap-mass spectrometry their phase I and II metabolites in rat urine after administration of pure MC or ISO-PAY, to confirm their formation in humans, and finally to confirm whether the above-mentioned isomeric compounds in human urine represent MC and ISO-PAY and/or their metabolites. The metabolic pathways of both alkaloids in rats were found to be comparable to those of their corresponding diastereomers. In the human urines tested, not all metabolites found in rats could be detected because of the much lower amounts of MC and ISO-PAY in Kratom. However, all the above-mentioned so far unknown isomeric compounds could be identified in the human urine samples as MC, ISO-PAY and/or their metabolites. The used LC separation was also suitable for the differentiation of all other Kratom alkaloids and their metabolites in human urine.

Phase I and II metabolites of speciogynine, a diastereomer of the main Kratom alkaloid mitragynine, identified in rat and human urine by liquid chromatography coupled to low- and high-resolution linear ion trap mass spectrometry

Mitragyna speciosa (Kratom in Thai), a Thai medical plant, is misused as herbal drug of abuse. Besides the most abundant alkaloids mitragynine (MG) and paynantheine (PAY), several other alkaloids were isolated from Kratom leaves, among them the third abundant alkaloid is speciogynine (SG), a diastereomer of MG. The aim of this present study was to identify the phase I and II metabolites of SG in rat urine after the administration of a rather high dose of the pure alkaloid and then to confirm these findings using human urine samples after Kratom use. The applied liquid chromatography coupled to low- and high-resolution mass spectrometry (LC-HRMS-MS) provided detailed information on the structure in the MS(n) mode particularly with high resolution. For the analysis of the human samples, the LC separation had to be improved markedly allowing the separation of SG and its metabolites from its diastereomer MG and its metabolites. In analogy to MG, besides SG, nine phase I and eight phase II metabolites could be identified in rat urine, but only three phase I and five phase II metabolites in human urine. These differences may be caused by the lower SG dose applied by the user of Kratom preparations. SG and its metabolites could be differentiated in the human samples from the diastereomeric MG and its metabolites comparing the different retention times determined after application of the single alkaloids to rats. In addition, some differences in MS(2) and/or MS(3) spectra of the corresponding diastereomers were observed.

Epac inhibits migration and proliferation of human prostate carcinoma cells

Background:

It was recently found that cAMP mediates protein kinase A-independent effects through Epac proteins. The aim of this study was to investigate the role of Epac in migration and proliferation of prostate carcinoma cells.

Methods:

The effect of Epac activation was determined by [³H]thymidine incorporation and scratch assays in PC-3 and DU 145 cells. Furthermore, cytoskeletal integrity was analysed by phalloidin staining. The participation of intracellular Epac effectors such as mitogen-activated protein (MAP) kinases, Rap1- and Rho-GTPases was determined by immunoblotting and pull-down assay.

Results:

The specific Epac activator 8-pCPT-2′-O-Me-cAMP (8-pCPT) interfered with cytoskeletal integrity, reduced DNA synthesis, and migration. Although 8-pCPT activated Rap1, it inhibited MAP kinase signalling and RhoA activation. These findings were translated into functional effects such as inhibition of mitogenesis, cytoskeletal integrity, and migration.

Conclusion:

In human prostate carcinoma cells, Epac inhibits proliferative and migratory responses likely because of inhibition of MAP kinase and RhoA signalling pathways. Therefore, Epac might represent an attractive therapeutic target in the treatment of prostate cancer.

Use of liquid chromatography coupled to low- and high-resolution linear ion trap mass spectrometry for studying the metabolism of paynantheine, an alkaloid of the herbal drug Kratom in rat and human urine

The Thai medicinal plant Mitragyna speciosa (Kratom in Thai) is misused as a herbal drug of abuse. During studies on the main Kratom alkaloid mitragynine (MG) in rats and humans, several dehydro analogs could be detected in urine of Kratom users, which were not found in rat urine after administration of pure MG. Questions arose as to whether these compounds are formed from MG only by humans or whether they are metabolites formed from the second abundant Kratom alkaloid paynantheine (PAY), the dehydro analog of MG. Therefore, the aim of the presented study was to identify the phase I and II metabolites of PAY in rat urine after administration of the pure alkaloid. This was first isolated from Kratom leaves. Liquid chromatography-linear ion trap mass spectrometry provided detailed structure information of the metabolites in the MS(n) mode particularly with high resolution. Besides PAY, the following phase I metabolites could be identified: 9-O-demethyl PAY, 16-carboxy PAY, 9-O-demethyl-16-carboxy PAY, 17-O-demethyl PAY, 17-O-demethyl-16,17-dihydro PAY, 9,17-O-bisdemethyl PAY, 9,17-O-bisdemethyl-16,17-dihydro PAY, 17-carboxy-16,17-dihydro PAY, and 9-O-demethyl-17-carboxy-16,17-dihydro PAY. These metabolites indicated that PAY was metabolized via the same pathways as MG. Several metabolites were excreted as glucuronides or sulfates. The metabolism studies in rats showed that PAY and its metabolites corresponded to the MG-related dehydro compounds detected in urine of the Kratom users. In conclusion, PAY and its metabolites may be further markers for a Kratom abuse in addition of MG and its metabolites.

cAMP is an important messenger for ADP-induced platelet aggregation

In rat platelets, basal cAMP levels were not changed upon stimulation with ADP and it was concluded that cAMP is not an important messenger for ADP-induced aggregation (Savi et al., Blood Coagul Fibrinolysis, 1996; 7: 249-52). In the present study, the effects of prostaglandin E(1) (PGE(1)) and ADP on human platelet aggregation, cAMP generation and VASP phosphorylation were studied. Phosphorylation of the protein kinase A (PKA) substrate VASP and inhibition of platelet aggregation by PGE(1) occurred without measurable changes in cellular cAMP levels. In addition, a marked inhibition of basal VASP phosphorylation by ADP was observed. It is concluded that cAMP determinations do not necessarily detect a possible activation or inhibition of the cAMPPKA pathway in platelets. Thus, cAMP might well be an important second messenger for ADP-induced platelet aggregation.

Synthesis of hyaluronan in oesophageal cancer cells is uncoupled from the prostaglandin-cAMP pathway

BACKGROUND AND PURPOSE

Cyclooxygenase-2 (COX2) and hyaluronic acid (HA) are common in tumours and both independently promote tumour progression. Furthermore, COX2-dependent synthesis of prostaglandins (PGs) stimulates HA synthase-1 (HAS1) and HAS2 mRNA expression, together with HA synthesis via the cAMP/protein kinase A pathway in vascular smooth muscle cells. Therefore, the aim of the present study was to elucidate whether COX2-mediated PGs induce transcription of HAS isoforms in cancer cells as well.

EXPERIMENTAL APPROACH

Human oesophageal squamous cell (OSC) carcinoma specimens were characterized with respect to HA, COX2 and CD44 expression by immunohistochemistry. OSC cell lines (OSC1, OSC2) and HeLa cell lines (D98, H21) were exposed to exogenous PG analoques (100 nmol.L(-1)), etoricoxib (10 micromol.L(-1)) and forskolin (10 micromol.L(-1)). Subsequently, cAMP levels, HA secretion and HAS isoform expression were determined by elisa and real-time RT-PCR (reverse transcriptase polymerase chain reaction) respectively.

KEY RESULTS

COX2, HA and CD44 were detected immunohistochemically in >90% of human oesophageal tumour samples. Under basal conditions, OSC1 and OSC2 cells express HAS2 and HAS3, COX2 and Galpha(s)-coupled EP(2) and EP(4) PG receptors. Neither stimulation with the PGI(2) analogue, iloprost, addition of exogenous PGE(2) nor forskolin induced HAS1 or HAS2 mRNA expression in OSC1 and OSC2 cells. Furthermore, in HeLa cells after induction of COX2 by tumour necrosis factor alpha and subsequent PGE(2) release, inhibition of COX2 by etoricoxib did not affect HAS expression or HA secretion.

CONCLUSIONS AND IMPLICATIONS

We conclude that in oesophageal and HeLa cancer cells, HAS1/2 expression was not responsive to the PG/cAMP pathway.

The significance of platelet-derived growth factors for proliferation of vascular smooth muscle cells

Platelets are important in acute thrombotic occlusion of injured vessels, e.g., subsequent to angioplasty. In contrast to these acute events of thrombus formation, much less is known about the significance of platelets for the control of smooth muscle cell (SMC) proliferation. A body of experimental and clinical evidence indicates an involvement of platelets in the pathology of atherosclerosis and restenosis. However, the precise role of platelet-derived growth factors for SMC proliferation in atherosclerotic and restenotic vessels is not clear and many questions remain unresolved. Platelet-dependent SMC mitogenesis is determined by a coordinate action of several classes of mitogenic factors which are either released from storage pools or generated upon platelet activation. Although platelet-derived growth factor (PDGF) is considered to be the most important platelet mitogen it is very likely that yet unknown factors and mechanisms are involved. Differential (stimulatory or inhibitory) effects on SMC growth and differentiation have been reported for different platelet-derived growth factors. Thus, for the overall response, complex interactions between multiple factors need to be considered. In addition, multicellular interactions, e.g., between platelets and endothelial cells may modulate the effects of platelet-derived factors on SMC mitogenesis. Taken together, the mechanisms of platelet-dependent SMC proliferation need to be reevaluated. The assessment of the precise role of platelet mitogens in the complex proliferative repair mechanisms of an injured vessel wall clearly requires further studies.

Screening for library-assisted identification and fully validated quantification of 22 beta-blockers in blood plasma by liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization

A liquid chromatographic-mass spectrometric assay with atmospheric pressure chemical ionization (LC-APCI-MS) is presented for screening for, library-assisted identification (both in scan mode) and quantification (selected-ion mode) of the beta-blockers acebutolol, diacetolol, alprenolol, atenolol, betaxolol, bisoprolol, bupranolol, carazolol, carteolol, carvedilol, celiprolol, esmolol, labetalol, metoprolol, nadolol, nebivolol, oxprenolol, penbutolol, propranolol, sotalol, talinolol and timolol in blood plasma after mixed-mode (HCX) solid-phase extraction (SPE) and separation by reverse-phase liquid chromatography with gradient elution. The validation data were within the required limits. The assay was successfully applied to authentic plasma samples allowing confirmation of diagnosis of overdose situations as well as monitoring of patients' compliance.

Screening, library-assisted identification and validated quantification of 23 benzodiazepines, flumazenil, zaleplone, zolpidem and zopiclone in plasma by liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization

A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (LC/APCI-MS) is presented for fast and reliable screening and identification and also for precise and sensitive quantification in plasma of the 23 benzodiazepines alprazolam, bromazepam, brotizolam, camazepam, chlordiazepoxide, clobazam, clonazepam, diazepam, flunitrazepam, flurazepam, desalkylflurazepam, lorazepam, lormetazepam, medazepam, metaclazepam, midazolam, nitrazepam, nordazepam, oxazepam, prazepam, temazepam and tetrazepam, triazolam, their antagonist flumazenil and the benzodiazepine BZ1 (omega 1) receptor agonists zaleplone, zolpidem and zopiclone. It allows confirmation of the diagnosis of an overdose situation and monitoring of psychiatric patients' compliance. The analytes were isolated from plasma using liquid-liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' LC/MS library, the analytes were quantified in the selected-ion monitoring mode. The quantification assay was fully validated. It was found to be selective proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes, except bromazepam. The corresponding reference levels the assay's accuracy and precision data for all studied substances are listed. The accuracy and precision data were within the required limits with the exception of those for bromazepam. The analytes were stable in frozen plasma for at least 1 month. The validated assay was successfully applied to several authentic plasma samples from patients treated or intoxicated with various benzodiazepines or with zaleplone, zolpidem or zopiclone. It has proven to be appropriate for the isolation, separation, screening, identification and quantification of the drugs mentioned above in plasma for clinical toxicology, e.g. in cases of poisoning, and forensic toxicology, e.g. in cases of driving under the influence of drugs.

Screening, library-assisted identification and validated quantification of fifteen neuroleptics and three of their metabolites in plasma by liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization

A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (APCI-LC/MS) is presented for the fast and reliable screening and identification and for the precise and sensitive quantification of 15 neuroleptic (antipsychotic) drugs and three of their relevant metabolites in plasma. It allows confirmation of the diagnosis of a neuroleptic overdose and monitoring of psychiatric patients' compliance. The neuroleptics amisulpride, bromperidol, clozapine, droperidol, flupenthixol, fluphenazine, haloperidol, melperone, olanzapine, perazine, pimozide, risperidone, sulpiride, zotepine and zuclopenthixol and the pharmacologically active metabolites norclozapine, clozapine N-oxide and 9-hydroxyrisperidone were extracted from plasma using solid-phase extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' new LC/MS library, the neuroleptics were quantified in the selected-ion mode. The quantification assay was fully validated. It was found to be selective and proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes. The corresponding reference levels are listed. The accuracy and precision data were within the required limits. The analytes were stable in frozen plasma for at least 1 month. The method was successfully applied to several authentic plasma samples from patients treated or intoxicated with various neuroleptics. The validated LC/MS assay has proved to be appropriate for the isolation, separation, screening, identification and quantification of various neuroleptics in plasma for clinical toxicology and therapeutic drug monitoring purposes.

Validated assay for quantification of oxcarbazepine and its active dihydro metabolite 10-hydroxycarbazepine in plasma by atmospheric pressure chemical ionization liquid chromatography/mass spectrometry

Oxcarbazepine (OX), a new antiepileptic, may lead to unwanted side-effects or even life-threatening intoxications after overdose. Therefore, a validated liquid chromatographic/mass spectrometric (LC/MS) assay was developed for the quantification of OX and its pharmacologically active dihydro metabolite (dihydrooxcarbazepine, DOX, often named 10-hydroxycarbazepine). OX and DOX were extracted from plasma by the authors' standard liquid/liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. The compounds were quantified in the selected-ion monitoring mode using atmospheric pressure chemical ionization electrospray LC/MS. The assay was fully validated. It was found to be selective. The calibration curves were linear from 0.1 to 50 mg l(-1) for OX and DOX. Limits of quantification were 0.1 mg l(-1) for OX and DOX. The absolute recoveries were between 60 and 86%. The accuracy and precision data were within the required limits. The analytes in frozen plasma samples were stable for at least 1 month. The method was successfully applied to several authentic plasma samples from patients treated or intoxicated with OX. The measured therapeutic plasma levels ranged from 1 to 2 mg l(-1) for OX and from 10 to 40 mg l(-1) for DOX. The validated LC/MS assay proved to be appropriate for quantification of OX and DOX in plasma for clinical toxicology and therapeutic drug monitoring purposes. The assay is part of a general analysis procedure for the isolation, separation and quantification of various drugs and for their full-scan screening and identification.

Screening, library-assisted identification and validated quantification of oral antidiabetics of the sulfonylurea-type in plasma by atmospheric pressure chemical ionization liquid chromatography-mass spectrometry

An atmospheric pressure chemical ionization liquid chromatographic-mass spectrometric (APCI-LC-MS) LC-MS assay is presented for fast and reliable screening and identification as well as precise and sensitive quantification of oral antidiabetics of the sulfonylurea-type (OADs) in plasma. It allowed the specific diagnosis of an overdose situation or a Munchausen syndrome caused by ingestion of OADs. After liquid-liquid extraction, the OADs glibenclamide, glibornuride, gliclazide, glimepiride, glipizide, gliquidone, glisoxepide, tolazamide and tolbutamide were separated using fast gradient elution. After screening and identification in the scan mode using our new LC-MS library, the OADs were quantified in the selected-ion mode. The quantification assay was validated according to the criteria established by the Journal of Chromatography B. All validation data were inside the required limits. The assay is part of a general LC-MS procedure for fast screening, identification and quantification of different toxicologically relevant compounds in plasma and has proven to be appropriate for OADs.

Negative ion chemical ionization gas chromatography-mass spectrometry and atmospheric pressure chemical ionization liquid chromatography-mass spectrometry of low-dosed and/or polar drugs in plasma

In clinical and forensic toxicology, doping control, and therapeutic drug monitoring, specific and sensitive detection and precise quantification of xenobiotics in biosamples are great challenges. Today, mass spectrometry techniques, coupled with gas chromatography or liquid chromatography, are the most powerful methods in analytic toxicology. The pros and cons of electron ionization (EI) and negative ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS) and of atmospheric pressure chemical ionization liquid chromatography-mass spectrometry (APCI-LC-MS) are described for determination of the low-dosed benzodiazepine flunitrazepam and its 7-amino and its nor-metabolite in plasma. In addition, application of NICI-GC-MS is described for sensitive chiral determination of amphetamine derivatives in plasma and application of APCI-LC-MS for screening, library-assisted identification, and validated quantification of oral antidiabetics and for validated quantification of the neuroleptic risperidone and its 9-hydroxy metabolite. These examples show that NICI-GC-MS and LC-MS are powerful tools for determination of low-dosed and/or rather polar drugs or poisons, thus becoming indispensable supplements to classic EI-GC-MS in clinical and forensic toxicology as well as in doping control.

Troglitazone and rosiglitazone inhibit the low density lipoprotein-induced vascular smooth muscle cell growth

Troglitazone (TRO) and rosiglitazone (RSG) belong to the thiazolidinedione class (insulin-sensitizing agents) and exert many of their metabolic effects as peroxisome proliferator-activated receptor gamma (PPARgamma) ligands. In the present study we examined the effects of TRO and RSG on LDL-induced VSMC growth. Pretreatment of VSMC with 1 microM TRO or 0.1 microM RSG completely blocked the LDL-induced cell proliferation as measured by [3H]thymidine incorporation into DNA and by determination of the cell number. We then examined with Western blotting whether these growth suppressing effects are mediated through the mitogen-activated protein kinase (MAPK) pathway, a common signaling pathway activated by growth factors. TRO and RSG had no effect on the LDL-induced stimulation of the MAP kinases ERK1/2, p38 and SAP/JNK. We conclude that thiazolidinediones are potent inhibitors of LDL-induced VSMC growth acting downstream of the cytoplasmic activation of MAPK.

Differential inhibition of adenosine diphosphate- versus thrombin receptor-activating peptide-stimulated platelet fibrinogen binding by abciximab due to different glycoprotein IIb/IIIa activation kinetics

The exposure of internal glycoprotein (GP) IIb/IIIa receptors has been proposed to explain the incomplete inhibition of aggregation of thrombin receptor-activating peptide (TRAP)-stimulated platelets by abciximab. However, a marked and rapid externalization of GPIIb/IIIa was also observed upon stimulation with 30 microM adenosine diphosphate (ADP). ADP-induced fibrinogen binding was completely inhibited by 10 microg/mL abciximab, 30 nM tirofiban, or 3 microg/mL eptifibatide, while fibrinogen binding induced by 100 microM TRAP was inhibited only by 50%. Interestingly, striking differences in fibrinogen binding kinetics in ADP- versus TRAP-stimulated platelets were observed. ADP-induced fibrinogen binding was much slower than that of abciximab. These differences in the fibrinogen binding rate were due to differential GPIIb/IIIa activation kinetics because the actual fibrinogen binding rate (measured by adding fibrinogen after platelet activation) was similar in ADP- and TRAP-stimulated platelets. Thus, the TRAP-induced GPIIb/IIIa activation rate would allow significant amounts of fibrinogen to occupy externalized GPIIb/IIIa receptors even in the presence of the inhibitor.

Recovery of platelet function after discontinuation of clopidogrel treatment in healthy volunteers

AIMS

To study the recovery of platelet function after discontinuation of clopidogrel treatment in healthy volunteers.

METHODS

Ten healthy volunteers were treated with clopidogrel (75 mg day(-1)) for 7 days. CD62P expression and PAC-1 binding were measured by flow cytometry.

RESULTS

Adenosine diphosphate (ADP, 30 microM)-induced platelet responses were almost completely inhibited by clopidogrel. After discontinuation of the drug, platelet function gradually increased and complete recovery was seen 7 days after the last clopidogrel dose. The mean difference (95% CI) for ADP-induced PAC-1 binding (fluorescence intensity) between baseline and 7 days after the last dose was 0.01 (0.61, -0.59). Single cell analysis provides direct evidence for an irreversible mode of action of clopidogrel.

CONCLUSIONS

This is the first report to directly demonstrate irreversibility of clopidogrel action in humans.

A prospective study of a caries prevention program in pregnant women and their children five and six years of age

A preventive dental program (PDP) instituted in pregnant women and comprising an educational and a preventive part was evaluated when their children were five and six years of age. Dental caries was examined in sixty-seven mother-child pairs belonging to the program and in sixty-nine control mother-child pairs. In the five-year-old children 87 percent of the PDP group were caries free compared with the 50 percent in the control group. Comparable figures for six-year-old children were 89 percent and 62 percent in the PDP and control group, respectively. The mean dft of the PDP children five and six years of age was 0.4 and 0.2, respectively, versus 1.3 and 1.4 for the control children. The differences in caries-free status and caries prevalence were statistically significant. In conclusion, the preventive dental program which started in pregnant women and continued in the mothers and their children were highly effective for a long-term reduction of dental caries.

Platelet CD40 ligand (CD40L)--subcellular localization, regulation of expression, and inhibition by clopidogrel

This study compares the subcellular localization and the regulation of expression of the platelet activation markers CD62P and CD63 with CD40 ligand (CD40L) on the surface of washed human platelets. CD40L was expressed upon stimulation with a wide range of platelet activators. However, quantitative flow cytometry demonstrated that, as compared with CD62P and CD63, CD40L expression was low. Upon stimulation with thrombin receptor-activating peptide (TRAP-6), all activation markers were expressed. In contrast, upon stimulation with low concentrations of collagen (1-3 microg/ml), CD40L, but not the granule proteins (CD62P, CD63), were expressed. Using immunofluorescence microscopy, a cytoplasmic staining was observed for CD40L, and cytoplasmic localization of CD40L was verified by Western blotting of subcellular platelet fractions. The staining of CD40L was different from that of filamentous actin and only little association of CD40L with platelet cytoskeleton was found. Surface expression of CD40L was dependent on internal Ca2+ stores and protein kinase C, while the mitogen-activated protein kinases (ERK, p38) or tyrosine kinases were not involved. ADP (30 microM)-induced CD40L expression was not inhibited by aspirin. In contrast, clopidogrel treatment completely abolished ADP-induced expression of CD40L. Finally, the expression level of CD40L was shown to be upregulated by phorbol myristate acetate (PMA) in the promegakaryocytic cell line MEG-01.

Effectiveness of a caries preventive program in pregnant women and new mothers on their offspring

OBJECTIVE

The medical centre at Almirante Nef Naval Hospital, Vina del Mar, Chile, operates a mother and child preventive dental program (PDP) which includes women from their fourth month of pregnancy and mothers with their offspring. The aim was to evaluate the effectiveness of this prenatal and postnatal prevention program after the first four years.

METHODS

The prevalence of early childhood caries of 180 1- to 3.5-year-old children enrolled in the PDP was compared with 180 non-participating children. The control group was randomly selected from the rolls of the healthy child system of of the Valparaiso-San Antonio Health Service and was comparable by age, socio-economic status and level of fluoride in the drinking water (1.0 p.p.m. F) with the PDP group. Clinical caries examinations were conducted by two calibrated examiners using the WHO visual criteria.

RESULTS

In the PDP group, 97% of the children were caries free compared with the 77% in the control group. The dft (mean +/- SD) of the PDP children was 0.11 +/- 0.78 versus 0.66 +/- 1.55 for the control children, a difference of 83.3%. The differences between the groups in caries-free status and caries prevalence were both statistically significant (P < 0.05).

CONCLUSIONS

The preventive dental program was effective in inhibiting caries in pre-school children, even in a population already receiving the benefits of community water fluoridation.

Troglitazone and rosiglitazone induce apoptosis of vascular smooth muscle cells through an extracellular signal-regulated kinase-independent pathway

Recent evidence suggests that apoptosis may be involved in the control of vascular smooth muscle cell (VSMC) number in atherosclerotic lesions. The peroxisome proliferator-activated receptor gamma (PPARgamma) ligands thiazolidinediones have been reported to induce apoptosis in macrophages and in a variety of tumor cell lines. To evaluate whether these agents also induce apoptosis in VSMC, cultured rat VSMC were treated with increasing doses of the thiazolidinedione analogues troglitazone (TRO) and rosiglitazone (RSG). Both ligands induced cell death in a concentration-dependent manner (EC50 12.1+/-3.3 microM and 1.43+/-0.39 microM, respectively), causing almost complete cell death at the highest concentrations (100 microM and 10 microM for TRO and RSG, respectively), along with an expected parallel decrease in [3H]thymidine uptake into cell DNA (EC50 6.7+/-2.4 microM and 0.75+/-0.19 microM, respectively). The cell count was determined by the coulter counter principle. Furthermore two apoptotic markers were measured, the caspase 3 activity and the cytoplasmic histone-associated DNA fragments, both of which were significantly increased when the aforementioned high concentrations were used. This indicates that apoptosis is involved in the TRO- and RSG-induced VSMC growth suppression. The same concentrations of TRO and RSG caused an unexpected stimulation of the extracellular signal-regulated response kinases 1 and 2 (ERK1/2) and stimulated the p38 mitogenic-activated protein (MAP) kinase as determined by Western blotting. In order to establish whether the proapoptotic effects of TRO and RSG are mediated through ERK1/2 activation, we used the selective MAP kinase kinase (MEK) inhibitor PD98059 (20 microM), which suppressed the TRO- and RSG-induced ERK1/2 activation but did not abolish their proapoptotic effects. We conclude that the thiazolidinedione analogues TRO and RSG induce cell death due to apoptosis in VSMC through an ERK1/2-independent pathway.

Validated electrospray liquid chromatographic-mass spectrometric assay for the determination of the mushroom toxins alpha- and beta-amanitin in urine after immunoaffinity extraction

Specific detection of amanitins in body fluids is necessary for an early diagnosis of an intoxication with amanita mushrooms. In this paper, a liquid chromatographic-mass spectrometric assay after immunoaffinity extraction (IAE-LC-MS) is described for the determination of alpha- and beta-amanitin in urine. The method has been validated according to the criteria established by the Journal of Chromatography B. The assay was found to be selective. The calibration curves for alpha- and beta-amanitin were linear from 5 to 75 ng/ml. Intra- and inter-day accuracy and precision were inside the required limits. Amatoxins in frozen urine samples or immunoaffinity extracts were stable for more than 6 months, and the IAE columns could be used more than fifty times without remarkable loss in performance. LOD for alpha- and beta-amanitin was 2.5 ng/ml and LOQ for both was 5.0 ng/ml. The absolute recoveries of alpha- and beta-amanitin were 63% and 58% for the low quality control and 61% and 57% for the high quality control. The absolute recovery for the internal standard gamma-amanitin methyl ether at 25 ng/ml was 60%. The analysis of 5 authentic urine samples from patients intoxicated by amanita mushrooms showed a good correlation between the results measured by radioimmunoassay and the IAE-LC-MS assay. A partial validation showed that the assay was also suitable for plasma analysis.

Habitual smoking causes an abnormality in platelet thromboxane A2 metabolism and results in an altered susceptibility to aspirin effects

The present study investigates the effects of aspirin (100 mg every second day for 14 days) on platelet function in nine healthy non-smokers and in nine healthy habitual smokers. There was a significantly (P < 0.05) stronger inhibition of collagen (0.6 microgram/ml)- and ADP (2 microM)-induced platelet aggregation by aspirin in smokers as compared to non-smokers. This difference occurred in the presence of an almost complete (> 95%) inhibition of thromboxane A2 (TXA2) synthesis in both groups. The platelet capacity to generate TXA2 in vitro was significantly reduced in smokers, urinary excretion of TXA2, however, was significantly increased. Thus, the better susceptibility of smokers to anti-aggregatory effects of aspirin is very likely to be related to a chronic smoking-induced alteration of platelet TXA2 system. Cessation of smoking should, therefore, be encouraged.

Studies on the metabolism and toxicological detection of the amphetamine-like anorectic fenproporex in human urine by gas chromatography-mass spectrometry and fluorescence polarization immunoassay

Studies on the metabolism and the toxicological analysis of fenproporex (R,S-3-[(1-phenyl-2-propyl)-amino]-propionitrile, FP) using GC-MS and fluorescence polarization immunoassay are described. The metabolites were identified in urine samples of volunteers by GC-MS after cleavage of conjugates, extraction and acetylation. Besides unchanged FP, fourteen metabolites, including amphetamine, could be identified. Two partially overlapping metabolic pathways could be postulated: ring degradation by one- and two-fold aromatic hydroxylation followed by methylation and side chain degradation by N-dealkylation to amphetamine (AM). A minor pathway leads via beta-hydroxylation of AM to norephedrine. For GC-MS detection, the systematic toxicological analysis procedure including acid hydrolysis, extraction at pH 8-9 and acetylation was suitable (detection limits 50 ng/ml for FP and 100 ng/ml for AM). Excretion studies showed, that only AM but neither FP nor its specific metabolites were detectable 30-60 h after ingestion of 20 mg of FP. Therefore, misinterpretation can occur. The Abbott TDx FPIA amphetamine/methamphetamine II gave positive results up to 58 h. All the positive immunoassay results could be confirmed by the described GC-MS procedure.

Platelet surface membranes are highly mitogenic for coronary artery smooth muscle cells--A novel mechanism for sustained proliferation after vessel injury?

The effects of isolated platelet surface membranes on DNA synthesis and proliferation of bovine coronary artery smooth muscle cells (SMC) were studied. Platelet membranes were very potent mitogens for SMC. The potency was about 10-fold higher than the maximum effects of platelet-derived growth factor-BB (PDGF). Platelet membrane-induced mitogenesis was inhibited by rapamycin, wortmannin or heating for 15 min at 70 degrees C but not by the PDGF receptor antagonist SCH 13.929 or by neutralizing PDGF antibodies. Only a partial (30%) inhibition was seen with PD 98059. In contrast, PDGF-induced SMC mitogenesis was heat-stable but sensitive to SCH 13. 929, PDGF antibodies, and PD 98059. These findings provide evidence for a novel mechanism for platelet-induced SMC proliferation that is independent of PDGF secretion. Platelet membranes, attached to or incorporated into the vessel wall, could maintain sustained SMC proliferation following injury.

Antimitogenic effects of vasodilatory prostaglandins in coronary artery smooth muscle cells

Vasodilatory prostaglandins (PGI2, PGE2, PGE1) are known inhibitors of proliferation of vascular smooth muscle cells (SMC) after stimulation with mitogenic factors. However, endogenous prostaglandins do not prevent SMC proliferation subsequent to vessel injury in vivo. Since vascular cells produce large amounts of antiproliferative prostaglandins, especially subsequent to COX-2 expression, insufficient vascular PGI2 formation is not likely to explain the failure of endogenous prostaglandins to prevent excessive SMC growth. In this paper we demonstrate a rapid development of tolerance to PGI2 in SMC, resulting in diminished antiproliferative activity. These findings may not only be relevant for the control of SMC growth by endogenously synthesized prostaglandins but also for clinical use of PGI2 mimetics.

Cyclooxygenase-2 expression in human esophageal carcinoma

On the basis of epidemiological observations that nonsteroidal antiinflammatory drugs reduce the risk of esophageal carcinoma, we studied the expression of cyclooxygenase-2 (COX-2) in esophageal squamous cell carcinomas (SCCs; n = 172) and in esophageal adenocarcinomas (ADCs; n = 27). Using immunohistochemistry, we observed COX-2 expression in 91% of the SCCs and in 78% of the ADCs. Western blot analysis showed enhanced expression of the COX-2 protein in some tumors as compared with normal esophageal squamous epithelium, whereas similar amounts of the COX-1 protein were found in normal and cancerous tissues. COX expression was also studied in two esophageal cancer cell lines (OSC-1 and OSC-2) to evaluate the functional relevance of COX-2-derived prostaglandins (PGs). OSC-2 cells expressed COX-2 but not COX-1, whereas OSC-1 cells expressed high levels of COX-1 but showed only a very weak COX-2 expression. Accordingly, PGE2 synthesis was 600 times higher in the OSC-2 cells as compared with the OSC-1 cells. Treatment of OSC-2 cells with the selective COX-2 inhibitors flosulide and NS-398 concentration dependently suppressed PGE2 synthesis and proliferation and also induced apoptosis. In contrast, no effect of the COX-2 inhibitors was seen in OSC-1 cells. Our data demonstrate that COX-2 is expressed in the majority of esophageal SCCs and ADCs and that COX-2-derived PGs play an important role in the regulation of proliferation and apoptosis of esophageal tumor cells. It is concluded that inhibition of COX-2 may be useful in the therapy of esophageal cancer.

Constitutive cyclooxygenase-2 expression in healthy human and rabbit gastric mucosa

Selective cyclooxygenase (COX)-2 inhibitors are expected to cause fewer gastric side effects because of sparing of COX-1-dependent prostaglandin (PG) synthesis in the gastric mucosa. However, the possible contribution of COX-2 to overall gastric PG biosynthesis is not known. This study demonstrates constitutive expression of COX-2 mRNA and protein in apparently healthy human and rabbit gastric mucosa. This basal expression of COX-2 protein in human gastric mucosa was increased by lipopolysaccharide and phorbol ester, indicating its up-regulation in response to appropriate stimuli. The functional significance of COX-2-dependent PG formation was studied in terms of PGE2 generation in the rabbit mucosa and its inhibition by the COX-2-selective inhibitor flosulide. There was concentration-dependent (IC50 = 107 +/- 55 nM) and ultimately complete inhibition of PGE2 generation by flosulide. In addition, gastric mucosa generated 15-hydroxyeicosatetraenoic acid upon treatment with acetylsalicylic acid. The data suggest an important role for COX-2-dependent PG production in apparently healthy gastric mucosa and raise the issue of whether selective COX-2 inhibitors might also interfere with physiological PG formation and actions in the stomach.

Antimitogenic effects of trapidil in coronary artery smooth muscle cells by direct activation of protein kinase A

The triazolopyrimidine trapidil has been found in controlled clinical trials to prevent restenosis after vascular injury. Although trapidil is widely regarded as a platelet-derived growth factor receptor (PDGF) antagonist, its precise mode of action is still unknown. This study was designed to investigate the inhibition of mitogenesis by trapidil in cultured bovine coronary artery smooth muscle cells (SMC) and to identify major signal transduction pathways involved. Trapidil inhibited PDGF-BB-induced mitogenesis in SMC in a concentration-dependent manner. Comparable inhibitory effects were obtained after stimulation of smooth muscle cells by phorbol ester, which suggests that the action of trapidil was not restricted to PDGF receptor-mediated mechanisms. Trapidil also inhibited PDGF- and phorbol ester-induced mitogen-activated protein kinase as well as Raf-1 kinase activity. As a possible target of trapidil, stimulation of cellular protein kinase A (PKA) activity was detected. Trapidil also induced the phosphorylation of vasodilator-stimulated phosphoprotein in SMC. Antimitogenic effects of trapidil were completely abolished by PKA inhibitors. Neither a direct stimulation of cAMP formation nor a phosphodiesterase inhibition was observed at antimitogenic concentrations of trapidil. However, trapidil directly activated purified PKA holoenzyme in a cAMP-independent manner. In conclusion, trapidil exerts its antimitogenic effects on SMC by direct activation of PKA. Thus, PKA-mediated inhibition of the Raf-1/MAP kinase pathway may be involved in the antimitogenic actions of the compound.

Thromboxane A2 potentiates thrombin-induced proliferation of coronary artery smooth muscle cells

The activation of thrombin is the key event in clot formation after vascular injury. Thrombin itself, but also other clot-derived factors, such as thromboxane A2 (TXA2), are mitogenic for vascular smooth muscle cells. We have studied the possible interactions between thrombin and TXA2 in stimulation of coronary artery smooth muscle cell (SMC) proliferation. Thrombin (1 U/ml) caused a significant proliferatory response in SMC. U 46619, a stable TXA2 mimetic, had only a minor stimulating effect by its own but markedly potentiated the thrombin-induced mitogenesis. A possible mechanism for these potentiating effects is provided by the demonstration of a marked (6 fold) but transient (maximum after 20 min) increase in the expression of TXA2 receptor (TP receptor) mRNA in SMC by thrombin. Since a significant clot-related TXA2 generation was detected for at least 2 hours, the up-regulation of TP receptors by thrombin may represent a mechanism that is relevant for the in vivo situation of SMC proliferation after vessel injury.

Tolerance development to antimitogenic actions of prostacyclin but not of prostaglandin E1 in coronary artery smooth muscle cells

This study compares the antimitogenic effects of iloprost and prostaglandin E1 on platelet-derived growth factor-BB stimulated DNA synthesis ([3H]thymidine incorporation) in bovine coronary artery smooth muscle cells. When added 20-24 h after stimulation with platelet-derived growth factor-BB (20 ng/ml), both iloprost and prostaglandin E1, concentration-dependently (IC50 3-5 nM) inhibited DNA synthesis. However, when added together with the growth factor (0-24 h), the inhibition of DNA synthesis by iloprost was markedly attenuated, indicating tolerance development. In contrast, no tolerance to antimitogenic effects of prostaglandin E1 or forskolin were observed. When added to iloprost-tolerant cells, both prostaglandin E1 and forskolin, still inhibited DNA synthesis. There was no evidence for transcriptional down-regulation of prostacyclin receptor gene by iloprost. The data demonstrate a tolerance development to antimitogenic actions of prostacyclin but not of prostaglandin E1 and suggest that the receptors, mediating the antiproliferative actions of these prostaglandins, may be different.