Thromboxane A2 and Prostacyclin Generation in the Microvasculature of Patients with Atherosclerosis – Effect of Low-Dose Aspirin

Generation of thromboxane A2 (TxA2) and prostacyclin (PGI2) at the site of platelet-vessel wall interaction, i.e. in blood emerging from a standardized injury of the microvasculature made to determine skin bleeding time was investigated in 7 patients with atherosclerosis (angiographically verified obstructions of the femoral arteries) and in 7 normal control subjects apparently free of atherosclerotic lesions. Similar amounts of TxA2 (measured as thromboxane B2, TxB2) were generated at the site of plug formation in the patients with peripheral vascular disease (PVD) and in the control subjects. Significantly lower levels of PGI2 (measured as 6-keto-prostaglandin F1α, 6-keto- PGF1α) were found in blood from an injury of the microvasculature in the patients compared with the controls. These data do not suggest a major role of the platelet prostaglandin metabolism in the development of atherosclerosis. However, decreased synthesis of PGI2 by endothelial cells might contribute to the development and/or progression of atherosclerotic lesions. In the patients with PVD, low-dose aspirin (50 mg/day for 7 days) resulted in a >90% inhibition of the TxB2 production at the site of plug formation. Following low-dose aspirin 6-keto-PcF1α levels were below 20 pg/ml (limit of sensitivity of our radioimmunoassay procedure) in the majority of the samples.

We therefore conclude that in patients with PVD a decreased synthesis of PGI2 by endothelial cells might contribute to the progression of atherosclerosis. Furthermore, low-dose aspirin treatment results in a similar inhibition of the platelet prostaglandin generation as recently observed in healthy subjects.

Association between health-related quality of life and clinical efficacy endpoints in rheumatoid arthritis patients after four weeks treatment with anti-inflammatory agents

BACKGROUND

Improvement of health-related quality of life (QoL) is increasingly recognized as a maj or treatment goal for patients with rheumatoid arthritis (RA). There are several measures of general health status and of physical functioning for assessing treatment effects on QoL in patients with RA, however, the relationship between QoL outcomes and conventional clinical efficacy endpoints is not completely understood.

OBJECTIVE

To describe the association between changes in QoL and changes in other efficacy measures, among patients with RA after four weeks of treatment with etoricoxib, naproxen or placebo, and to explore differences in the association of changes in efficacy and changes in QoL parameters across treatment groups.

METHODS

The study used data from 1684 patients with RA enrolled in two identical clinical trials (one US and one multinational). Patients were randomized to placebo, etoricoxib 90 mg once daily, or naproxen 500 mg twice daily in a 2 : 2: 1 allocation ratio. Primary efficacy endpoints were tender joint count, swollen joint count, patient global assessment of disease activity (100 mm VAS), and investigator global assessment of disease activity (0 - 4 Likert scale). QoL assessments were based on the Health Assessment Questionnaire (HAQ) and the Medical Outcomes Survey Short Form 36 (SF-36). Mean differences between baseline and week four were calculated for each parameter studied. Linear regression analysis was performed to assess the association between changes in clinical efficacy and changes in QoL parameters, adjusted for covariates.

RESULTS

The degree of association between changes in tender or swollen joint counts and changes in QoL variables was low, explaining less than 10% of the variability for most QoL variables, except bodily pain (SF-36). In contrast, changes in patient global assessment of disease activity explained 33% of the variability in the overall HAQ score, and in the physical component score (SF-36; adjusted regression models). Values for investigator global assessment of disease activity were below those for patient global assessment but above joint count measures. Results were similar between the etoricoxib, naproxen and placebo groups in the degree of association between changes in efficacy and QoL variables.

CONCLUSION

Currently used efficacy endpoints are less than ideal predictors of change in QoL. There is no evidence from this study that the association between changes in CE endpoints and QoL was different across treatments. Our results highlight the need to assess both conventional efficacy measures and QoL in clinical trials of RA treatments.

Access of HTB, main metabolite of triflusal, to cerebrospinal fluid in healthy volunteers

OBJECTIVE

Triflusal has been shown to exert neuroprotective effects by downregulating molecules considered responsible for the development of Alzheimer's disease (AD). The aim of this study was to develop a population pharmacokinetic model to characterize plasma and cerebrospinal fluid (CSF) pharmacokinetics of the main active metabolite of triflusal-HTB (2-hydroxy-4-trifluoro-methylbenzoic acid)-in healthy volunteers.

METHODS

Data from two studies were combined. Study A: subjects received single oral doses of triflusal 900 mg. Triflusal and HTB plasma concentrations were extensively measured. Study B: triflusal 600 mg once daily was administered orally for 14 days. HTB plasma and CSF concentrations were determined in healthy volunteers. Population pharmacokinetic modeling was performed using NONMEM.

RESULTS

A one-compartmental model with rapid first-order absorption for triflusal and first-order formation of HTB best described plasma concentrations. Triflusal elimination rate constant was 50 times faster than that estimated for the metabolite. CSF concentrations of HTB ranged between 0.011 microg/ml and 0.341 microg/ml. A CSF-plasma partition coefficient of 0.002 and a k(e0) value of 0.059 h(-1) were estimated by means of population modeling.

CONCLUSION

In the present study in healthy volunteers, HTB penetrated into the CSF in a range of concentrations experimentally proven to have protective effects in AD. These concentrations suggest that triflusal could be used in the treatment of central nervous system diseases in doses similar to those used in cardiovascular diseases. Access to the CSF compartment was characterized by a slow equilibrium rate constant and a low CSF-plasma partition coefficient.

Asthma severity and medical resource utilisation

Asthma represents a growing public health problem and the cost of asthma has been rising in many countries. The aim of this study was to estimate the direct and indirect cost of asthma among adult patients in Italy, and to assess the relationship between healthcare resource use and asthma severity according to the Global Initiative for Asthma (GINA) classification system. A multicentre cross-sectional study was conducted in 16 Italian hospital-based specialised asthma clinics. Data collection was based on self-administered questionnaires and took place during the period May 1-November 30, 1999, and 500 consecutive patients with asthma, aged 18-55 yrs, were enrolled during regularly scheduled visits. Direct costs (drugs, physician visits, emergency service use and hospitalisation), indirect costs (loss of paid workdays) and total costs were determined in euros (Euros) for 1999. Patients with more severe disease, as classified by the GINA guideline, exhibited more night-time and daytime symptoms and were more limited in performing normal daily activities. The mean total cost of asthma per patient per year was estimated to be Euros 1,260; drug costs accounted for 16%, physician costs 12%, emergency service and hospitalisation costs 20% and indirect costs 52% of the mean cost. Stratified by severity, the total annual cost per patient amounted to Euros 720, Euros 1,046, Euros 1,535 and Euros 3,328 for patients with intermittent, mild persistent, moderate persistent and severe persistent asthma, respectively. Asthma severity, as determined by the Global Initiative for Asthma classification, is significantly associated with symptoms, limitations in normal daily activities, asthma-related medical resource utilisation and both direct and indirect costs. Asthma control is not only a clinical but also an economic imperative.

Clonidine added to bupivacaine enhances and prolongs analgesia after brachial plexus block via a local mechanism in healthy volunteers

BACKGROUND AND OBJECTIVE

The addition of clonidine to local anaesthetics enhances pain relief after peripheral nerve block, but the site of action is unproven.

METHODS

Seven healthy volunteers underwent three brachial block procedures using bupivacaine 0.25% 1 mg kg(-1) + epinephrine 1:200,000 (=local analgesic) in a randomized, double-blind cross-over fashion: (a) control treatment: local analgesic with 0.9% sodium chloride solution for the block and an intramuscular injection of saline; (b) intramuscular treatment: local analgesic with 0.9% NaCl for block and an intramuscular injection of clonidine 2 microg kg(-1) and (c) block treatment: local analgesic with clonidine 2 microg kg(-1) for block and an intramuscular injection of saline.

RESULTS

The onset and duration of complete blockade (sensory/motor/temperature) was evaluated in the four nerve regions of the hand and forearm. Additionally, sedation score, blood pressure, heart rate and plasma clonidine concentrations were determined. The median duration of complete sensory blockade was 270 min (range 0-600) for block treatment compared to 0 min (range 0-480) for intramuscular treatment (P < 0.05) and 0 min (range 0-180) for control treatment (P < 0.05). Motor and temperature blockade exhibited similar results. Administration of clonidine was associated with sedation and a decrease in heart rate and blood pressure independent of the route of administration. Plasma clonidine concentrations were lower for block compared to the intramuscular treatment.

CONCLUSIONS

The admixture of clonidine to bupivacaine plus epinephrine prolongs and enhances brachial plexus blockade. Lower clonidine plasma concentrations for block treatment strongly suggest a local effect.

Initiation of antihypertensive therapy among new users of cyclooxygenase-2-selective and nonselective NSAIDs

BACKGROUND

The comparative effects of cyclooxygenase-2- (COX-2) selective inhibitors and nonselective, nonsteroidal anti-inflammatory drugs (NSAIDs) on blood pressure are debated. Clinicians have been concerned about the need for antihypertensive treatment following therapy with these agents.

OBJECTIVE

To compare initiation of antihypertensive treatment among new users of the COX-2-selective inhibitor rofecoxib and of nonselective NSAIDs in clinical practice.

METHODS

Retrospective cohort study using the MediPlus (UK) database that covers 1.8 million patients throughout the UK. Patients included were at least 50 years of age, had at least 1 prescription for either diclofenac, ibuprofen, naproxen or rofecoxib (drugs of interest, DOIs), and had no prescription for any NSAID, COX-2 inhibitor, or antihypertensive treatment during the 6 months prior to their first/index prescription date. A subset of patients, classified as chronic and persistent new users, had at least 3 prescriptions of the index prescription DOI and did not switch to another DOI during the 6-month follow-up period. Logistic regression analysis, adjusted for potential predictors, was used to assess initiation of new antihypertensive treatment.

RESULTS

18,737 suitable patients were identified (diclofenac 7,861, ibuprofen 8,423, naproxen 1,556 and rofecoxib 897). Those using rofecoxib were older and more likely to be female than those using NSAIDs. During the 6 months following the index prescription, 7.0% of all new users and 11.5% of chronic and persistent new users initiated antihypertensive treatment. After adjusting for potential predictors there were no statistically significant differences in the risk of initiating antihypertensive treatment between new or chronic and persistent new users of rofecoxib, diclofenac, ibuprofen and naproxen (p > 0.05).

CONCLUSION

The results of this study did not indicate any significant differences in the initiation of antihypertensive therapy among patients who were prescribed rofecoxib and NSAIDs, even after multiple prescriptions.

A randomized, double-blind, placebo controlled study on analgesic effects of botulinum toxin A

OBJECTIVE

Botulinum toxin type A (BTXA) is used to treat neurologic disorders associated with increased muscle tone. Its use is often associated with pain relief.

METHODS

A possible direct analgesic effect of BTXA on C and Adelta fibers was studied on 16 healthy volunteers receiving 30 U BTXA into one forearm and pure saline into the other. To exclude the secondary effect due to muscular tone reduction, BTXA was injected intradermally. Thermal sensory testing of heat pain (threshold and tolerance) and neuroselective current sensory testing of current pain threshold/tolerance were performed at baseline and 3, 14, and 28 days after treatment. Thereafter, on day 28, capsaicin was administered simultaneously into both forearms to evaluate a possible peripheral effect and central effect on pain processing and on the axon reflex flare.

RESULTS

The authors observed no significant difference in any of the perception outcome measures between BTXA and placebo pretreated areas. Flare areas as a result of the release of neuropeptides after capsaicin application showed no differences.

CONCLUSIONS

The results suggest that pain reduction after BTXA treatment is mediated through its effect on muscle tone rather than a direct analgesic effect.

Gastrointestinal transit and release of 5-aminosalicylic acid from 153Sm-labelled mesalazine pellets vs. tablets in male healthy volunteers

BACKGROUND

Mesalazine (5-aminosalicylic acid)-containing formulations, designed to optimize drug delivery to the ileo-caecal region, represent a cornerstone in the treatment of inflammatory bowel diseases.

AIM

: To test, by means of pharmaco-scintigraphy, whether novel mesalazine-containing pellets release 5-aminosalicylic acid in the same target region as mesalazine tablets (Salofalk).

METHODS

Fourteen healthy male volunteers received a single dose of either pellets or tablets containing 500 mg of mesalazine and 2 mg of 152Sm2O3 with a 1-week washout period. The gastrointestinal transit of 153Sm, incorporated into the formulations, was followed by gamma-scintigraphy. Mesalazine release was verified by assessing 5-aminosalicylic acid plasma pharmacokinetics.

RESULTS

The formulations reached the ileo-caecal target region almost at the same time (3.3 +/- 1 and 3.8 +/- 1 h for pellets and tablets, respectively). Plasma 5-aminosalicylic acid tmax values were comparable and corresponded to the time during which the formulations were located in the target region. Plasma AUC values were significantly lower for pellets, which might be explained by a more prolonged release of 5-aminosalicylic acid.

CONCLUSIONS

Novel mesalazine pellets and Salofalk tablets release active 5-aminosalicylic acid in the same target region and pass through the gastrointestinal tract under fasting conditions in healthy volunteers in a comparable time. From a comparison of in vitro dissolution and plasma concentration data, a slower and more prolonged release of 5-aminosalicylic acid from pellets is suggested.

Penetration of capecitabine and its metabolites into malignant and healthy tissues of patients with advanced breast cancer

Capecitabine is an oral prodrug of 5-fluorouracil (FU). Since FU concentrations achieved in malignant lesions are an important determinant of efficacy, we investigated the intratumoral transcapillary transfer of capecitabine and its metabolites in vivo. A total of 10 patients with skin metastases from breast cancer received a daily dose of 2500 mg m(-2) capecitabine administered orally in two divided doses for 2 weeks. Microdialysis probes were inserted into a cutaneous metastasis and subcutaneous connective tissue to evaluate the interstitial tissue pharmacokinetics of capecitabine and its metabolites 5'-deoxy-5-fluorocytidine (DFCR), 5'-deoxy-5-fluorouridine (DFUR), and FU by capillary electrophoresis. As intended with the prodrug design of capecitabine, FU was present in low concentrations in tumour interstitium (median c(max): 0.26 microg ml(-1)) when compared with capecitabine, DFCR, and DFUR (median c(max): 2.66, 4.22, and 2.13 microg ml(-1), respectively). Capecitabine and its metabolites easily penetrated malignant and healthy tissue and equilibrated within 45 min between plasma and tissue interstitium. Considering tissue exposure at the extracellular level, no significant differences between healthy and malignant tissues were observed. Our data show that absorption and metabolism determined the tissue pharmacokinetics of capecitabine. There was no evidence of drug tolerance, which may be attributed to impaired transcapillary transfer into tissue, even after repeated administration as shown for three patients.

Gastrointestinal transit and 5-ASA release from a new mesalazine extended-release formulation

BACKGROUND

Mesalazine (5-aminosalicylic acid, 5-ASA)-containing formulations represent a cornerstone in the treatment of inflammatory bowel diseases. Recently, a new formulation has been developed to provide selective and more homogeneous release of 5-ASA compared to traditional systems.

METHODS

In a first study, gastrointestinal transit was followed by gamma-scintigraphy after single-dose application of tablets containing 1200 mg mesalazine to 12 healthy male volunteers. 5-ASA release was verified by the assessment of plasma pharmacokinetics. In a second, 7-day, multiple-dose study, the steady state plasma pharmacokinetics, urinary excretion and safety profile were characterized after twice-daily tablet administration to 12 healthy volunteers.

RESULTS

Tablet erosion started after 6.9 +/- 1.1 h in the ascending or transverse colon. Radioactivity spread homogeneously throughout the colon, indicating the sustained release of active 5-ASA. Plasma kinetics indicated an earlier initial absorption of 5-ASA, i.e. during transit of the small intestine and ileum. Mean Cmax values (350.6 +/- 322.6 ng/mL) were observed during location in the ileo-caecal region. The mean relative absorption of 5-ASA was 19.9 +/- 18.2% in the small intestine and ileum and 80.1 +/- 18.2% in the colon.

CONCLUSIONS

The administration of the new mesalazine formulation was well tolerated, and 5-ASA was continuously released along the whole colon, a favourable prerequisite for the therapy of distally located inflammatory bowel disease.

Pharmacokinetic and mass balance study of unlabelled and (14)C-labelled emedastine difumarate in healthy volunteers

1. In a mass balance study, six healthy male volunteers received a single oral dose of 4 mg (14)C-labelled emedastine difumarate. The pharmacokinetics of the total radioactivity and unchanged drug were assessed over 48 h. Urinary and faecal excretion were measured over 120 h. Additionally, urinary metabolites were investigated. 2. In a single- and multiple-dose pharmacokinetic study, nine male and nine female healthy volunteers received 2 mg oral emedastine difumarate b.i.d. or 4 mg o.d. for 7 consecutive days. The plasma pharmacokinetics were assessed on day 1 and at steady-state. 3. The mass balance study demonstrated almost complete gastrointestinal absorption of the administered dose. A total of 94.2% of the radioactivity was eliminated via the kidneys. Unchanged emedastine in the urine accounted for <5% of dose. 5-Hydroxy, 6-hydroxy and N-oxide metabolites previously identified in the Japanese were present in Caucasian subjects. 4. AUC after single and multiple dosing were dose-proportional. On day 7, no statistical difference in AUC(0-24) could be detected between the two regimens, with AUC = 70.6 +/- 36.1 and 71.7 +/- 52.3 ng h ml(-1), respectively. There were no gender differences in the pharmacokinetics of emedastine. 5. The results corroborate the use of emedastine in a Caucasian population and support the extrapolation of safety and efficacy data from Asians to Caucasians.

Mucosal tolerance as therapy of type I allergy: intranasal application of recombinant Bet v 1, the major birch pollen allergen, leads to the suppression of allergic immune responses and airway inflammation in sensitized mice

BACKGROUND

Several studies have demonstrated that mucosal administration of soluble antigens can prevent the onset or reduce the severity of certain autoimmune diseases or allergies. Few studies exist showing the efficacy of mucosal tolerance for therapy of such diseases.

OBJECTIVE

The aim of the present study was to modulate an allergic immune response by intranasal antigen administration in an already sensitized organism.

METHODS

A murine model of allergic asthma to birch pollen (BP) and its major allergen Bet v 1 was utilized. Sensitized mice were intranasally treated with recombinant (r)Bet v 1 in different concentrations and at different intervals. On the day the mice were killed, blood and bronchoalveolar lavage fluids were taken and immediate type I skin tests were performed. T cell proliferation and cytokine production (interleukin (IL)-5, interferon (IFN)-gamma) were measured in spleen and lung cell cultures.

RESULTS

Mucosal treatment with rBet v 1 (3 x 50 microg in 4 day intervals) led to a reduction of type I skin reactions, suppressed immunoglobulin (Ig)G1/IgE antibody levels and markedly decreased IL-5 and IFN-gamma production in vitro in spleen and lung cell cultures. Moreover, lung inflammation (i.e. eosinophilia and IL-5 levels in bronchoalveolar lavage fluids) was significantly suppressed by the treatment.

CONCLUSION

Our results demonstrate that intranasal treatment with rBet v 1 reduced systemic allergic immune responses as well as airway inflammation in BP-sensitized mice. We therefore suggest that mucosal tolerance induction with recombinant allergens could be a promising concept for the therapy of allergic diseases.

Bcl-2 antisense oligonucleotides chemosensitize human gastric cancer in a SCID mouse xenotransplantation model

We used Bcl-2 antisense oligonucleotides (G3139) to chemosensitize human gastric cancer by downregulation of Bcl-2 expression in vivo. Oligonucleotides and cisplatin were administered systemically in a human gastric cancer SCID mouse model, and Bcl-2 expression, apoptosis, tumor size, and survival were assessed. Used alone, G3139 treatment led to downregulation of Bcl-2 and moderate tumor reduction compared to saline control. G3139 combined with cisplatin treatment markedly enhanced the antitumor effect of cisplatin (70% tumor size reduction vs. cisplatin alone), associated with increased apoptosis measured in tumor biopsy specimens. Combined treatment with G3139 and cisplatin prolonged survival of the tumor-bearing SCID mice by more than 50% without adding significant drug-related toxicity. Treatment with Bcl-2 antisense oligonucleotides is thus a promising novel approach to enhance antitumor activity of cisplatin or other drugs used in gastric cancer therapy and warrants further evaluation in clinical trials.

Retinal blood flow and systemic blood pressure in healthy young subjects

BACKGROUND

The aim of the present study was to investigate the association between systemic blood pressure and retinal blood flow in healthy young subjects.

METHODS

Three independent study cohorts were included. A cross-sectional study was performed in 420 young male subjects with systolic blood pressure < 160 mmHg and diastolic blood pressure <100 mmHg. Retinal white blood cell flux (n=210) and blood velocity in the central retinal artery (n=210) were measured. In addition, a longitudinal study was performed in 40 young male subjects in whom retinal and systemic haemodynamic parameters were measured thrice within 6 weeks. Retinal white blood cell flux was measured with the blue-field entoptic technique. Blood flow velocity in the central retinal artery was measured by means of colour Doppler imaging.

RESULTS

Retinal white blood cell flux (r=0.262; P<0.001) and mean flow velocity in the central retinal artery (r=0.174, P=0.010) were significantly associated with mean arterial pressure in the cross-sectional study. In the longitudinal study retinal white blood cell flux and mean flow velocity in the central retinal artery were also correlated with systemic blood pressure.

CONCLUSIONS

Our data indicate a slight but significant increase in retinal blood flow with blood pressure. Whether this is of clinical relevance in eye diseases with altered retinal perfusion, such as diabetic retinopathy, remains to be established.

Application of the minimal trauma tissue biopsy to transdermal clinical pharmacokinetic studies

Although the transdermal administration of drugs has gained considerable importance, reliable methods for the quantitative assessment of transdermal drug penetration are scarce. The aim of the present study was therefore to evaluate the scopes and limits of the minimal trauma tissue biopsy (MTTB) technique for the in vivo characterization of the transdermal penetration process and the assessment of dermal drug kinetics in humans following topical drug application. Nicotine TTS (21 mg/24 h) was administered transdermally to 13 healthy volunteers. Repeated minimally invasive dermal and subdermal tissue biopsies were obtained at defined time points from defined skin layers directly underlying the TTS. The position of the biopsy needle and depth of biopsate were determined by 2D ultrasound scanning. The biopsy procedure was well tolerated by all volunteers and up to six biopsies within a period of 10 h were easily accepted. Dermal pharmacokinetic profiles for nicotine were obtained in all experiments and corresponded well to the values measured in previous studies on transdermal nicotine penetration. Mean area under the nicotine concentration time curve (AUC) in subepidermal layers underneath the application site of the TTS was 70.0+/-55.1 microg/g per h. There was a correlation between the depth of biopsy sampling and dermal nicotine concentrations at steady state (r=0.7). The MTTB is a suitable, well tolerated technique for the detection of transdermally applied compounds in defined subepidermal tissue layers and could therefore become a valuable tool in the development and assessment of transdermal dosage forms.

Differential expression levels of Par-4 in melanoma

The pro-apoptotic prostate apoptosis response-4 gene product Par-4 sensitizes prostate cells to the induction of programmed cell death. In this study we examined Par-4 expression in human melanoma cell lines and melanoma metastases. The heterogeneous expression detected prompted us to investigate the biological relevance of Par-4 in a human melanoma xenotransplantation model. Overexpression of Par-4 by transfection decreased tumour development in xenotransplanted A375-C6 melanoma cells in SCID mice and correlated to an increase in tumour cell apoptosis. These data suggest that high expression of the pro-apoptotic protein Par-4 could qualify as a prognostic marker in human melanoma.

A double masked placebo controlled study on the effect of nifedipine on optic nerve blood flow and visual field function in patients with open angle glaucoma

AIMS

To investigate whether nifedipine affects ocular perfusion or visual fields in open angle glaucoma patients.

METHODS

In a parallel group study nifedipine or placebo was administered for 3 months (n = 30). Ocular fundus pulsation amplitude (FPA), cup blood flow (Flowcup) and visual field mean deviation (MD) were measured.

RESULTS

Five patients receiving nifedipine discontinued due to adverse events. Nifedipine did not affect FPA [difference: 0.3 microm (95% CI -0.3,0.9); P = 0.70], Flowcup: [difference: -9 rel.units (95% CI -133,114); P = 0.99], or MD [difference: 0.2dB (95% CI -2.2,2.7); P = 0.51] vs placebo.

CONCLUSIONS

Systemic nifedipine is not well tolerated in glaucoma patients and exerts no effect on visual fields or ocular perfusion.

Elevated procaspase levels in human melanoma

In this study procaspase expression levels were investigated by Western blotting in a panel of established melanoma cell lines, transformed melanocytic cell lines and normal primary melanocytes. Upstream caspases such as procaspase-8 that contain a death effector domain were found to be overexpressed in transformed melanocytes and melanoma cell lines compared with melanocytes. Heterogeneous levels of procaspase-8 were seen in melanoma cells, including one cell line that completely lacked procaspase-8 expression. Procaspase-10 is generally overexpressed in transformed melanocytes and melanoma cell lines. Expression of the downstream procaspases-3 and -7 was increased in melanoma cells compared with normal melanocytes. Procaspases containing caspase recruitment domains such as procaspase-2 were expressed at similar levels in nearly all the cell lines investigated. Reduced levels of procaspase-1 compared with normal melanocytes were detected in transformed melanocytes and melanoma cell lines. These data indicate that procaspase levels in general increase during the malignant transformation of melanocytic cells.

Effects of atropine and propranolol on retinal vessel diameters during isometric exercise

PURPOSE

There is controversy regarding the nervous control of retinal blood vessels in humans. Most in vitro studies indicate that the intraocular part of the central retinal artery lacks autonomic innervation. We investigated the response of retinal vessels to isometric exercise during blockade of beta-receptors (propranolol) or muscarinic receptors (atropine).

METHODS

Twelve healthy subjects performed squatting for 6 min during infusion of either propranolol atropine or placebo. Blood pressure and pulse rate were measured non-invasively. Retinal vessel diameters were measured continuously using the Zeiss Retinal Vessel Analyser.

RESULTS

Squatting induced a significant increase in blood pressure and pulse rate, which was paralleled by a decrease in retinal vein and artery diameters. Atropine did not change the retinal vessel response to isometric exercise. Propranolol significantly blunted the exercise-induced vasoconstriction in retinal arteries.

CONCLUSION

This result likely indicates propranolol-evoked vasoconstriction in the extraocular parts of the central retinal artery during isometric exercise.

Comparison of the effects of ketamine and memantine on prolactin and cortisol release in men. a randomized, double-blind, placebo-controlled trial

N-methyl D-aspartate (NMDA)-antagonists decrease neurotoxicity by inhibiting Ca2+ influx which is of interest for the treatment of acute cerebrovascular insults and chronic neurodegenerative disorders. Currently, there is no surrogate marker for quantification of NMDA-receptor-mediated drug effects, which hampers dose-finding clinical studies. As prolactin and cortisol liberation is in part influenced through NMDA-receptors we investigated whether the elevation of prolactin or cortisol plasma levels is a class effect of NMDA-antagonists and might be an appropriate marker for studying NMDA-antagonistic potency. Fifteen healthy male volunteers participated in this placebo-controlled, randomized, three-way crossover trial. Ketamine (0.5mg/kg), memantine (0.16 mg/kg; i.e., a well tolerated standard dose) or placebo were infused over 60 min. Ketamine increased serum prolactin and cortisol levels (p < 0.001), whereas memantine and placebo did not affect hormone levels. Further studies are needed to define whether higher doses of memantine or other NMDA antagonists can induce hormone release.

Effects of heparin and aspirin on circulating P-selectin, E-selectin and von Willebrand Factor levels in healthy men

As thrombin stimulates P-selectin expression on platelets and its release into plasma, we hypothesized that enhancing antithrombin activity by unfractionated heparin (UFH) could decrease plasma levels of circulating (c)P-selectin, (c)E-selectin, and von Willebrand Factor (vWF). Hence the effect of UFH and aspirin were examined on these activation markers in healthy volunteers. UFH decreased cP-selectin levels by -10% (CI: -16 - (-4%); P = 0.005) at 24 h, but did not change levels of vWF-Ag. In contrast, aspirin did not affect cP-selectin levels but decreased vWF-Ag levels by -12% (CI: -18 - (-7%); P = 0.005) at 24 h. Neither drug affected cE-selectin levels. Thus, UFH decreases cP-selectin levels, which may reflect decreased platelet activation in vivo. An increase in cP-selectin under UFH therapy should alert the clinician to look for platelet destruction.

Pharmacokinetics of emedastine difumarate, a new anti-histaminic agent in patients with renal impairment

OBJECTIVE

Emedastine difumarate is a new H1 receptor antagonist with well defined pharmacokinetic and pharmacodynamic profiles in healthy volunteers. However, to date it is not known whether impaired renal function in patients with chronic renal insufficiency affects its pharmacokinetics and probably also its tolerability. Therefore, we here set out to compare the pharmacokinetics of emedastine difumarate in patients suffering from different degrees of renal failure with a control group of healthy volunteers.

METHODS AND RESULTS

For this purpose we conducted an open, single-centre, comparative parallel group study in patients and healthy volunteers. Emedastine difumarate 2 mg was administered orally to the study population in single and seven repetitive doses twice daily (b.i.d.). Pharmacokinetics differed markedly between volunteers (n = 6) and patients (n = 17). The maximum serum concentration of emedastine (Cmax), area under the serum concentration-time curve, mean residence time and terminal disposition half-life were significantly higher in patients (P < 0.05), while time to reach Cmax and apparent volume of disposition were not statistically different after single and repeated (steady-state) oral administrations. Blood pressure and heart rate were also not affected by the study medication.

CONCLUSION

The present study shows that impaired renal function alters the pharmacokinetics of emedastine in plasma. Thus, dose adjustment of emedastine difumarate is advisable in patients with impaired renal function.

Impaired target site penetration of beta-lactams may account for therapeutic failure in patients with septic shock

OBJECTIVE

Current guidelines for adjusting antimicrobial therapy regimens commonly are based on drug concentrations measured in plasma. In septic patients, however, the interstitial space of soft tissues in addition to the central compartment represents the target site of infection. We thus hypothesized that one explanation for therapeutic failure during antibiotic treatment might be the inability to achieve effective antimicrobial concentrations in the interstitial space fluid of soft tissues. This is corroborated by the fact that piperacillin, a frequently administered beta-lactam antibiotic, often fails to be effective despite documented susceptibility of the causative pathogen in vitro.

DESIGN

Prospective comparative study of two groups.

SETTING

The intensive care unit and research ward of an university hospital.

SUBJECTS

Six patients with septic shock and a control group of six gender- and age-matched healthy volunteers.

INTERVENTIONS

To measure piperacillin penetration into the interstitial space fluid of skeletal muscle and subcutaneous adipose tissue, we employed microdialysis after a single intravenous administration of 4.0 g of piperacillin to patients and healthy volunteers. Piperacillin concentrations were assayed by using reversed-phase high-pressure liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

In septic shock patients, interstitial piperacillin concentrations in skeletal muscle and subcutaneous adipose tissue were five- to ten-fold lower than corresponding free plasma concentrations (p <.03). Mean piperacillin concentrations in subcutaneous adipose tissue never exceeded 11 microg/mL, which is below the minimal inhibitory concentration for a range of relevant pathogens in patients with septic shock.

CONCLUSION

The results of the present study demonstrate that in septic shock patients, piperacillin concentrations in the interstitial space may be subinhibitory, even though effective concentrations are attained in plasma. The lack of success of antimicrobial therapy in these patients thus might be attributable to inadequate target site penetration of antibiotics.

Ocular hemodynamics during isometric exercise

The autoregulatory capacity of the human retina is well documented, but the pressure-flow relationship of the human choroid is still a matter of controversy. Recent data, using laser Doppler flowmetry to measure choroidal blood flow, indicate that the choroid has some autoregulatory potential, whereas most data using other techniques for the assessment of choroidal hemodynamics indicate that the choroidal pressure-flow curve is linear. We used a new laser interferometric technique to characterize choroidal blood flow during isometric exercise. Twenty healthy subjects performed squatting for 6 min during normocapnia and during inhalation of 5% CO2 and 95% air. Ocular fundus pulsation amplitude, flow velocities in the ophthalmic artery, intraocular pressure, and systemic hemodynamics were measured in 2-min intervals. To gain information on choroidal blood flow fundus pulsation amplitude was corrected for changes in flow pulsatility using data from the ophthalmic artery and for changes in pulse rate. Ocular perfusion pressure was calculated from mean arterial pressure and intraocular pressure. The ocular pressure-flow relationship was calculated by sorting data according to ascending ocular perfusion pressure values. In a pilot study in 6 healthy subjects comparable ocular pressure flow relationships were obtained when choroidal blood flow was assessed with the method described above and with laser Doppler flowmetry. In the main study isometric exercise caused a significant increase in mean arterial pressure (56%, P < 0.001), pulse rate (84%, P < 0.001), and intraocular pressure (37%, P 0.004), but decreased fundus pulsation amplitude (-36%, P < 0.001). Significant deviations from baseline choroidal blood flow were observed only at ocular perfusion pressures >69% during normocapnia and 70% during hypercapnia. Our data indicate that during isometric exercise the choroid has a high capacity to keep blood flow constant despite changes in perfusion pressure and that this pressure-flow relationship is not altered by moderate changes in arterial carbon dioxide levels.

Effects of anticoagulation on thrombopoietin release during endotoxemia

Several lines of evidence suggest that coagulation may induce the release of thrombopoietin (TPO) into plasma and that TPO levels are higher in disseminated intravascular coagulation. Therefore we set out to illuminate the mechanism of TPO release in the setting of experimental endotoxemia, which induces activation of coagulation and platelets. Endotoxin (lipopolysachharide [LPS], 2 ng/kg) was infused into a total of 54 healthy men in two subsequent studies. Volunteers received infusions of unfractionated heparin, low-molecular-weight heparin, lepirudin, or placebo in a randomized, placebo-controlled fashion after bolus injection of LPS. TPO levels increased on average by 27% to 38% in all groups at 6 hours (P <.05 vs baseline), although all active drugs effectively blocked coagulation. Platelet counts dropped by about 15% at 1 hour after LPS infusion, recovered after 2 days, and exceeded baseline values by 8% to 18% after 7 days (P <.001 vs baseline for all groups). Yet lepirudin blunted the LPS-induced increase in circulating P-selectin by one half (P <.005 vs placebo), whereas both heparins did not diminish the increase in this platelet or endothelial activation marker as compared with placebo. Endotoxemia enhances TPO plasma levels independent of the degree of coagulation induction, which eventually results in increased platelet numbers. Of potential clinical interest is the observation that the direct thrombin inhibitor lepirudin, in contrast to heparins, mitigated LPS-induced platelet activation.

Systemic inflammation increases shear stress-induced platelet plug formation measured by the PFA-100

The PFA-100 measures platelet plug formation under shear stress and is strongly dependent on von Willebrand Factor (VWF) levels in plasma. We therefore hypothesized that elevated VWF levels, possibly as a result of acute inflammation, adversely influence PFA-100 results. Healthy volunteers received either 2 ng/kg endotoxin or placebo in a randomized controlled trial. Four hours after endotoxin (but not placebo) infusion VWF levels increased by 85%, collagen epinephrine-induced closure time (CT) decreased by 47% and collagen ADP-CT decreased by 38% (P < 0.0001) respectively. In conclusion, systemic inflammation has a major impact on the results obtained by PFA-100 and may confound interpretation of platelet function.

Evaluation of the Zeiss retinal vessel analyser

AIM

To investigate the reproducibility and sensitivity of the Zeiss retinal vessel analyser, a new method for the online determination of retinal vessel diameters in healthy subjects.

METHODS

Two model drugs were administered, a peripheral vasoconstrictor (the alpha receptor agonist phenylephrine) and a peripheral vasodilator (the nitric oxide donor sodium nitroprusside) in stepwise increasing doses. Nine healthy young subjects were studied in a placebo controlled double masked three way crossover design. Subjects received intravenous infusions of either placebo or stepwise increasing doses of phenylephrine (0.5, 1, or 2 microg/kg/min) or sodium nitroprusside (0.5, 1, or 2 microg/kg/min). Retinal vessel diameters were measured with the new Zeiss retinal vessel analyser. Retinal leucocyte velocity, flow, and density were measured with the blue field entoptic technique. The reproducibility of measurements was assessed with coefficients of variation and intraclass correlation coefficients.

RESULTS

Placebo and phenylephrine did not influence retinal haemodynamics, although the alpha receptor antagonist significantly increased blood pressure. Sodium nitroprusside induced a significant increase in retinal venous and arterial diameters (p<0.001 each), leucocyte density (p=0.001), and leucocyte flow (p=0.024) despite lowering blood pressure to a significant degree. For venous and arterial vessel size measurements short term coefficients of variation were 1.3% and 2.6% and intraclass correlation coefficients were 0.98 and 0.96, respectively. The sensitivity was between 3% and 5% for retinal veins and 5% and 7% for retinal arteries.

CONCLUSIONS

These data indicate that the Zeiss retinal vessel analyser is an accurate system for the assessment of retinal diameters in healthy subjects. In addition, nitric oxide appears to have a strong influence on retinal vascular tone.

A combined in vivo pharmacokinetic-in vitro pharmacodynamic approach to simulate target site pharmacodynamics of antibiotics in humans

We describe a new approach to quantify in vivo anti-infective activity by simulating effect site pharmacokinetics of antibiotics in vitro. This approach is based on (i) the in vivo measurement of interstitial drug pharmacokinetics (PK) at the target site and (ii) a subsequent pharmacodynamic (PD) simulation of the time versus drug concentration profile in an in vitro setting. To demonstrate the feasibility of this approach, individual time-concentration profiles of ciprofloxacin were measured in the interstitial space fluid of eight healthy volunteers by microdialysis following iv administration of 200 mg. Thereafter, different isolates of Pseudomonas aeruginosa were exposed in vitro to the interstitial ciprofloxacin concentration profile obtained from in vivo experiments. This led to a 1- to 3-log10 decrease in the number of viable organisms after 8 h. Significant correlations were observed between the maximal bactericidal effect and several PK surrogate parameters, notably the AUC/MIC ratio (P: = 0.0005), the C:max/MIC ratio (P: = 0.006) and the time > MIC (P: = 0.02). Furthermore, the data were analysed with an integrated PK-PD model allowing a much more detailed evaluation of the data than using MIC. The model employed an E:max relationship to link unbound ciprofloxacin concentration to bacterial kill rate. In conclusion, our experiments show that therapeutic success and failure in antimicrobial therapy may be explained by pharmacokinetic variability at the target site. Therefore, the in vivo PK-in vitro PD approach presented in our study may provide valuable guidance for drug and dose selection of antimicrobial agents.

Paroxetine decreases platelet serotonin storage and platelet function in human beings

BACKGROUND

Serotonin is a platelet agonist and potent vasoconstrictor that has recently received attention concerning its potential role in acute coronary artery thrombosis. Selective serotonin-reuptake inhibitors, such as paroxetine, are widely used antidepressant agents. We sought to characterize the potential inhibitory effect of paroxetine on platelet function.

METHODS

Healthy male volunteers received 20 mg/d paroxetine for 2 weeks in a randomized, double-blind, placebo-controlled, two-way cross-over trial.

RESULTS

Paroxetine decreased intraplatelet serotonin concentrations by -83% (P < .01). This inhibited platelet plug formation as reflected by a 31% prolongation of closure time measured with the platelet function analyzer-100 (P < .05). Furthermore, paroxetine lowered expression of the platelet activation marker CD63 in response to two different concentrations of thrombin receptor-activating peptide (P < .01). Plasma concentrations of prothrombin fragment, von Willebrand factor antigen, and circulating P-selectin remained unchanged in either period, indicating that paroxetine does not increase activation of coagulation, endothelium, or platelets in vivo, underlining a favorable safety profile.

CONCLUSIONS

Paroxetine substantially decreases intraplatelet serotonin content and thereby reduces platelet plug formation under shear stress, and responsiveness to thrombin receptor activating peptide-induced platelet activation. Further studies will reveal whether these pharmacodynamic effects can be exploited for treatment of thrombotic artery disease.

Granulocyte colony-stimulating factor (G-CSF) downregulates its receptor (CD114) on neutrophils and induces gelatinase B release in humans

Despite the increasing use of granulocyte colony-stimulating factor (G-CSF) for the mobilization of stem cells and neutrophils, its pharmacodynamic actions are not fully understood. Because of the roles of G-CSF and gelatinase B in leucokinetics, we set out to characterize the interaction of G-CSF with its receptor in humans and its effects on gelatinase B release. G-CSF was infused at bolus doses of 1 microg/kg and 5 microg/kg, and compared to placebo and dexamethasone (1 mg/kg b.i.d), which enhances the plasma levels of endogenous G-CSF. The study was randomized, double-blind, four-way crossover, in eight healthy male volunteers. G-CSF dose-independently induced profound neutropenia (> 95%) within minutes and downregulated its own receptor (CD114) on neutrophils by 75%. The G-CSF/CD114 interaction dose-independently induced degranulation of neutrophils as evidenced by a 300-400% increase in CD11b expression. Degranulation induced up to a 10-fold increase in plasma levels of gelatinase B, an enzyme known to precipitate neutropenia and subsequent neutrophilia in animals. In this study, it was shown that G-CSF downmodulates CD114 expression on the surface of neutrophils in humans and the consequent degranulation enhances gelatinase B release into plasma, which may contribute to mobilization of neutrophils or stem cells.

Age dependence of perimacular white blood cell flux during isometric exercise

PURPOSE

To investigate the age dependence of perimacular white blood cell flux (WBCF) during isometric exercise.

METHODS

Fourteen healthy young (age range: 21-29 years; 24 +/- 3 years, mean +/- SD, 12 male and 2 female) and 15 healthy middle-aged (age range: 45-57 years; 53 +/- 4 years, mean +/- SD; 5 male and 10 female) volunteers were studied. Subjects performed isometric handgrip for 10 minutes and squatting for 6 minutes. WBCF was assessed with the blue field entoptic technique, mean arterial pressure (MAP) was measured with an automated oscillometric device, intraocular pressure (IOP) was measured by Goldmann applanation tonometry and ocular perfusion pressure (OPP) was calculated as 2/3 MAP - IOP.

RESULTS

Baseline WBCF was significantly higher in young subjects than in middle-aged subjects (191 +/- 28 vs 142 +/- 23; p = 0.001). Isometric handgrip induced a significant increase in WBCF in the middle-aged subjects (23 +/- 24%; p = 0.005), but not in the young subjects. Squatting significantly increased WBCF in both groups (young: 42 +/- 23%; p = 0.004 and middle aged: 51 +/- 27%; p < 0.001). A significant deviation from baseline WBCF was observed when OPP increased by 42 +/- 4% (p = 0.003) and 35 +/- 4% (p < 0.001) for the young and middle-aged subjects, respectively. The OPP-WBCF relationship was not different between the two study groups.

CONCLUSION

Altered retinal autoregulation as observed in vascular ocular disease appears to be unrelated to the normal physiological aging process.

Effects of systemic NO synthase inhibition on choroidal and optic nerve head blood flow in healthy subjects

PURPOSE

There is evidence from animal studies that nitric oxide (NO) is a major determinant of ocular blood flow. In humans NO synthase inhibition reduces pulsatile choroidal blood flow, but no data on optic nerve head (ONH) vasculature are available yet. The goal of this study was to investigate the effects of NO synthase inhibition on human choroidal and ONH blood flow using laser Doppler flowmetry.

METHODS

The study design was a randomized, placebo-controlled, double-masked, balanced three-way crossover. On separate study days 12 healthy male subjects received infusions of N:(G)-nitro-L-arginine (L-NMMA; either 3 mg/kg over 5 minutes followed by 30 microg/kg per minute over 55 minutes or 6 mg/kg over 5 minutes followed by 60 microg/kg per minute over 55 minutes) or placebo. The effects of L-NMMA or placebo on choroidal and ONH blood flow were measured with laser Doppler flowmetry. In addition, laser interferometric measurement of fundus pulsation was performed in the macula to assess pulsatile choroidal blood flow.

RESULTS

L-NMMA reduced all outcome parameters in the choroid and the ONH. The higher dose of L-NMMA caused a significant decrease in blood flow in the choroid (-26% +/- 9%; P: < 0.001) and the ONH (-20% +/- 16%; P: < 0.001) as evidenced from laser Doppler flowmetry and a significant decrease in fundus pulsation amplitude (-26% +/- 5%; P: < 0.001).

CONCLUSIONS

These results indicate that NO is continuously released in human choroidal and ONH vessels.

Validation of urea as an endogenous reference compound for the in vivo calibration of microdialysis probes

Microdialysis is a widely used experimental technique, which offers the opportunity to measure drug and metabolite concentrations in the interstitial space fluid in animals and humans. However, microdialysis probes need to be calibrated in vivo to obtain a recovery factor, which describes the relative drug transfer across the membrane. Recently, novel time-saving calibration techniques, based on the use of reference compounds, have been developed. In particular, the use of endogenous urea levels has been advocated. In the present study we set out to validate the use of the urea reference technique for microdialysis probe calibration in healthy volunteers, employing glucose and paracetamol as model analytes. Urea calibration was compared with the results of two standard calibration techniques, i.e. the no net flux technique and the retrodialysis technique. For glucose, recovery values, calculated by the urea reference technique differed significantly from those values, which were assessed by the no net flux technique (p < 0.05), whereas for paracetamol recovery values did not differ significantly, albeit a high intramethod variability was observed (CV=66%). As a conclusion, we could not confirm the hypothesis that recovery values calculated by the urea reference technique provide equivalent results compared with standard calibration techniques.

Endotoxin down-modulates granulocyte colony-stimulating factor receptor (CD114) on human neutrophils

During infection, the development of nonresponsiveness to granulocyte colony-stimulating factor (G-CSF) may be influenced by the down-modulation of G-CSF receptor (G-CSFR) by cytokines. This down-modulation was studied during experimental human endotoxemia. Healthy volunteers received either 2 ng/kg endotoxin (lipopolysaccharide [LPS], n=20) or placebo (n=10) in a randomized, controlled trial. Endotoxin infusion increased the mean fluorescence intensity of the neutrophil activation marker CD11b >300% after 1 h (P<.001 vs. placebo). LPS infusion down-modulated G-CSFR expression in as early as 60 min (-17%; P=.001 vs. placebo). Down-modulation was almost maximal at 90 min and persisted for 6 h (-50% from baseline; P<.0001 vs. placebo). Plasma levels of G-CSF started to increase only after G-CSFR down-modulation had occurred and peaked 37-fold above baseline at 4 h (P<.0001 vs. placebo). In conclusion, LPS down-modulates G-CSFR expression in humans, which may render neutrophils less responsive to the effects of G-CSF and, thereby, compromise host defense mechanisms.

Surgery and intensive care procedures affect the target site distribution of piperacillin

OBJECTIVE

Therapeutic failure of antibiotic therapy has been ascribed to pharmacokinetic alterations in compromised patient populations. The present study, therefore, aimed at examining the influences of cardiac surgery and intensive care procedures on the postoperative target site distribution of piperacillin. For this purpose, the penetration of piperacillin to the interstitial space fluid, the relevant target site for most bacterial infections, was compared between patients after aortic valve replacement and healthy volunteers.

DESIGN

Comparative study in two study populations.

SETTING

The intensive care unit and research ward of a university hospital.

PATIENTS

The study population included six otherwise healthy patients scheduled to undergo aortic valve replacement and a control group of six healthy male volunteers.

INTERVENTIONS

After the administration of a single i.v. infusion of 4.0 g piperacillin, free piperacillin concentrations were measured in the interstitium of skeletal muscle and subcutaneous tissue by in vivo microdialysis and in venous serum. Piperacillin concentrations were assayed with reversed phase high-performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

Interstitial piperacillin concentrations in muscle and subcutaneous adipose tissue were significantly lower in patients compared with volunteers with the area under the curve for the interstitium/area under the curve for serum concentration ratios ranging from 0.25 to 0.27 and from 0.43 to 1.22 in patients and volunteers, respectively (p < .05 between groups). The terminal elimination half-life was markedly prolonged in patients, leading to a concomitant increase in t > minimal inhibitory concentration (MIC) values, the relevant surrogate for therapeutic success of therapy with beta-lactam antibiotics, for strains with MIC50 <4 microg/mL. For strains with MIC50 >20 microl/mL, however, inadequate target site concentrations were attained in the patient population.

CONCLUSIONS

During the postoperative and intensive care periods, target site concentrations of piperacillin are markedly altered and decreased. This may also be true for other antibiotic agents and may have clinical implications in that current dosing guidelines may result in inadequate target site concentrations for high-MIC strains. Conceivably, this could lead to therapeutic failure in some patients.

Hypercapnia-induced cerebral and ocular vasodilation is not altered by glibenclamide in humans

Carbon dioxide is an important regulator of vascular tone. Glibenclamide, an inhibitor of ATP-sensitive potassium channel (K(ATP)) activation, significantly blunts vasodilation in response to hypercapnic acidosis in animals. We investigated whether glibenclamide also alters the cerebral and ocular vasodilator response to hypercapnia in humans. Ten healthy male subjects were studied in a controlled, randomized, double-blind two-way crossover study under normoxic and hypercapnic conditions. Glibenclamide (5 mg po) or insulin (0.3 mU. kg(-1). min(-1) iv) were administered with glucose to achieve comparable plasma insulin levels. In control experiments, five healthy volunteers received glibenclamide (5 mg) or nicorandil (40 mg) or glibenclamide and nicorandil in a randomized, three-way crossover study. Mean blood flow velocity and resistive index in the middle cerebral artery (MCA) and in the ophthalmic artery (OA) were measured with Doppler sonography. Pulsatile choroidal blood flow was assessed with laser interferometric measurement of fundus pulsation. Forearm blood flow was measured with venous occlusion plethysmography. Hypercapnia increased ocular fundus pulsation amplitude by +18.2-22.3% (P < 0. 001) and mean flow velocity in the MCA by +27.4-33.3% (P < 0.001), but not in the OA (2.1-6.5%, P = 0.2). Forearm blood flow increased by 78.2% vs. baseline (P = 0.041) after nicorandil administration. Glibenclamide did not alter hypercapnia-induced changes in cerebral or ocular hemodynamics and did not affect systemic hemodynamics or forearm blood flow but significantly increased glucose utilization and blunted the nicorandil-induced vasodilation in the forearm. This suggests that hypercapnia-induced changes in the vascular beds under study are not mediated by activation of K(ATP) channels in humans.

Ocular haemodynamics and colour contrast sensitivity in patients with type 1 diabetes

BACKGROUND

There is evidence that altered ocular blood flow is involved in the development and progression of diabetic retinopathy. However, the nature of these perfusion abnormalities is still a matter of controversy. Ocular haemodynamics were characterised with two recently introduced methods.

METHODS

The cross sectional study was performed in 59 patients with type 1 diabetes with a diabetes duration between 12 and 17 years and an age less than 32 years and a group of 25 age matched healthy controls. Scanning laser Doppler flowmetry and laser interferometric measurement of fundus pulsation amplitude were used to assess retinal and pulsatile choroidal blood flow, respectively. In addition, colour contrast sensitivity along the tritan axis was determined.

RESULTS

Fundus pulsation amplitude, but not retinal blood flow, increased with the progression of diabetic retinopathy. Retinal blood flow was influenced by plasma glucose levels (r = 0.32), whereas fundus pulsation amplitude was associated with HbA(1c) (r = 0.30). In addition, a negative correlation between the colour contrast sensitivity along the tritan axis and retinal blood flow was observed.

CONCLUSIONS

The present study indicates that pulsatile choroidal blood flow increases with the progression of diabetic retinopathy. Increased retinal blood flow appears to be related to loss of colour sensitivity in patents with type 1 diabetes.

Effects of erythropoietin on platelet reactivity and thrombopoiesis in humans

A recent study in dogs suggested that erythropoietin (EPO) not only promotes the synthesis of increased numbers of reticulated platelets but that these newly produced platelets are hyperreactive compared with controls. Because of the increasing use of EPO in the perioperative setting, we characterized the effects of EPO on platelet reactivity in healthy human volunteers. In a randomized, controlled trial, we studied the effects of EPO on platelet reactivity, thrombopoiesis, and endothelial activation in circumstances similar to those of autologous blood donation. Thirty healthy male volunteers received placebo or EPO (100 or 500 U/kg of body weight given intravenously) three times a week for 2 weeks and underwent phlebotomy on days 8 and 15. Thrombin receptor-activating peptide induced expression of P-selectin, and CD63 increased 2- to 3-fold during EPO treatment. The enhanced platelet reactivity was also reflected by a 50% increase in soluble P-selectin in plasma. Plasma E-selectin levels increased in a dose-dependent fashion by more than 100% during EPO treatment, indicating substantial activation of endothelial cells. A 10% to 20% increase in platelet counts was observed in both EPO groups on day 5. In the placebo group, platelets increased only several days after the first phlebotomy. The increase in platelet counts was not reflected by changes in the amounts of reticulated platelets or circulating progenitor cells. In summary, we found that EPO markedly enhances endothelial activation and platelet reactivity, which may adversely affect patients at cardiovascular risk. However, the increased platelet reactivity could be exploited in patients with platelet dysfunction. (Blood. 2000;95:2983-2989)

Effects of hyperinsulinemia on plasma levels of circulating adhesion molecules

Plasma levels of circulating intercellular adhesion molecule-1 (cICAM-1), a potential cardiovascular risk factor, are increased in diabetics. Among other factors, hyperinsulinemia has been proposed to enhance its release into the circulation. Thus, we directly examined the effects of insulin infusion on plasma levels of circulating adhesion molecules, and two other endothelial markers, i.e. von Willebrand factor (vWF) and soluble thrombomodulin (sTM). The study design was balanced, randomized, placebo-controlled, double blind, and cross-over. Twelve healthy male subjects received, on separate study days, a euglycemic hyperinsulinemic clamp (3 mU/kg x min) or placebo over 6 h. Plasma levels of cICAM-1, vascular cell adhesion molecule-1, circulating E-selectin, and sTM were measured by enzyme immunoassay; vWF-Ag was measured using a STA clot analyzer. Plasma levels of these adhesion molecules and endothelial cell activation markers were not affected despite a 30-fold increase in insulin levels. Hyperinsulinemia has no adverse effect on circulating ICAM-1, vascular cell adhesion molecule-1, E-selectin, vWF, or sTM and therefore does not directly induce endothelial activation.

Micellar electrokinetic chromatography for the analysis of cefpirome in microdialysis and plasma samples obtained in vivo from human volunteers

Pharmacokinetics of drugs in the human interstitial space fluid can be monitored by means of microdialysis. However, the small-volume microdialysis samples containing low drug concentrations require a sensitive analytical method. In the present study, micellar electrokinetic chromatography (MEKC) is described for the quantification of cefpirome in human microdialysis and plasma samples. Sample preparation of human plasma samples by ultracentrifugation was suitable for comparison of plasma and microdialysate concentrations. Limits of quantification were 2 microg/mL and 0.3 microg/mL for plasma and microdialysate samples, respectively. The limit of detection (LOD) was estimated at 0.2 microg/mL for the plasma and microdialysate samples. In conclusion, MEKC is a reliable and reproducible technique for measuring cefpirome concentrations in microdialysates as well as centrifuged plasma samples.

Relationship between in vivo drug exposure of the tumor interstitium and inhibition of tumor cell growth in vitro: a study in breast cancer patients

A novel approach is described to simulate effect site pharmacodynamics of anticancer drugs. This approach is based on (i) the in vivo measurement of unbound, interstitial drug pharmacokinetics (PK) in solid tumor lesions in patients and (ii) a subsequent pharmacodynamic (PD) simulation of the time versus drug concentration profile in an in vitro setting. For this purpose, breast cancer cells (MCF-7) were exposed in vitro to the time versus interstitial tumor concentration profiles of 5-fluorouracil (5-FU) and methotrexate (MTX) from primary breast cancer lesions in patients. This led to a maximal reduction in the viable cell count of 69% on day 4, and of 71% on day 7 for 5-FU and MTX, respectively. This effect was dependent on the initial cell count and was characterized by a high interindividual variability. For 5-FU there was a significant correlation between the maximum antitumor effect and the intratumoral AUC (r = -0.82, p = 0.0005), whereas no correlation could be shown for MTX (r = 0.05, p = 0.88). We conclude, that the in-vivo-PK / in-vitro-PD model presented in this study may provide a rational approach for describing and predicting pharmacodynamics of cytotoxic drugs at the target site. Data derived from this approach support the concept that tumor penetration of 5-FU may be a response-limiting event, while the response to MTX may be determined by events beyond interstitial fluid kinetics.

Paracrine effects of angiotensin-converting-enzyme- and angiotensin-II-receptor- inhibition on transcapillary glucose transport in humans

The paracrine renin-angiotensin-system (RAS) is increasingly recognized to play an important role in the regulation of both, regional vascular tone and regional glucose metabolism. To date, however, a selective investigation of paracrine RAS effects in an in vivo clinical setting was beyond technical reach. We here set out to selectively study the metabolic effects of paracrine RAS inhibition at different levels in healthy volunteers (n = 8). For this purpose bradykinin, enalaprilate and losartan were administered locally to the interstitial space fluid in skeletal muscle by means of reverse microdialysis and transcapillary glucose transport was measured simultaneously. During reverse microdialysis with bradykinin and enalaprilate a significant decrease in arterial-interstitial-gradient for glucose (AIG(glu)) was observed (from 1.49 +/- 0.08 mM to 0.12 +/- 0.63 mM (p = 0.018) for bradykinin and from 1.5 +/- 0.07 mM to 0.24 +/- 0.67 mM (p = 0.043) for enalaprilate). In contrast, losartan had no effect on AIG(glu). The changes in transcapillary glucose transport during bradykinin and enalaprilate administration were accompanied by significant increases in interstitial lactate levels which was most pronounced for bradykinin (from 0.14 +/- 0.01 mM to 0.40 +/- 0.07 mM, p = 0.018). We conclude that paracrine angiotensin-converting-enzyme (ACE) inhibition but not angiotensin II (AT-II) receptor blockade decreases AIG(glu) and facilitates transcapillary glucose transport due to an increase in interstitial bradykinin concentration. These results support the concept that blood pressure control with ACE-inhibitors but not with AT-II-receptor-antagonists has beneficial long term metabolic consequences in hypertensive, hyperinsulinemic subjects.

Endothelin-1 contributes to hyperoxia-induced vasoconstriction in the human retina

PURPOSE

There is evidence that ocular blood flow strongly depends on arterial oxygen tension. Results from recent animal studies indicate that the vasoconstrictor response to hyperoxia may be mediated in part by an increased production of endothelin (ET)-1. In an effort to answer the question whether the retinal vasoconstrictive response to hyperoxia in humans is mediated through ET-1, changes in ocular hemodynamics induced by 100% O2 breathing were studied in the absence and presence of an ET(A) receptor antagonist (BQ-123).

METHODS

The study was a randomized, placebo-controlled, double-masked, balanced, three-way crossover design. On separate study days 15 healthy male subjects received infusions of BQ-123 (either 60 microg/min or 120 microg/min) or placebo. The effects of BQ-123 or placebo on hyperoxia-induced (100% O2 breathing) changes in retinal and pulsatile choroidal blood flow were assessed with the blue-field entoptic technique and with laser interferometric measurement of fundus pulsation, respectively.

RESULTS

During baseline conditions, hyperoxia caused a decrease in retinal blood flow between -29% and -34% (P<0.001) and a decrease in fundus pulsation amplitude between -7% and -8% (P<0.001). BQ-123 dose dependently blunted the response to hyperoxia in the retina (60 microg/min: -25%, 120 microg/min: -20%; P = 0.003), but not in the choroid.

CONCLUSIONS

These results indicate that ET-1 contributes to hyperoxia-induced retinal vasoconstriction in the human retina.

Dexamethasone lowers circulating E-selectin and ICAM-1 in healthy men

Plasma levels of circulating adhesion molecules (AMs) are increased in a number of inflammatory and cardiovascular disorders. Yet the mechanisms regulating the physiologic levels of soluble AMs are largely unknown. It has recently been postulated that glucocorticoids may exert their anti-inflammatory actions partially through the inhibition of cytokine-stimulated expression of E-selectin and intercellular adhesion molecule (ICAM-1). However, it remains controversial whether glucocorticoids affect the basal expression of AMs on resting cells. We have thus evaluated the effects of glucocorticoids by infusing therapeutic doses of dexamethasone (0.04 mg/kg and 1.0 mg/kg twice a day for 2 days) or placebo on plasma levels of circulating E-selectin (cE-selectin), soluble thrombomodulin (sTM), circulating ICAM-1 (cICAM-1), and circulating vascular cell adhesion molecule (cVCAM-1) in 9 healthy men. Plasma was obtained before infusion at 24 and 48 hours. Compared with baseline, levels of cE-selectin decreased by 16% and 22% with the lower and the higher doses, respectively, at 48 hours (P = .007), whereas sTM was unchanged. Both doses of dexamethasone reduced cICAM-1 by about 15% at 48 hours (P = .007), but there were no changes in cVCAM. Dexamethasone time-dependently decreases plasma levels of cE-selectin and cICAM-1 in healthy men. This demonstrates that a glucocorticoid-sensitive mechanism specifically down-regulates normal plasma levels of cE-selectin and cICAM-1 in healthy subjects, which could thus reflect minor baseline inflammation.

Lepirudin blunts endotoxin-induced coagulation activation

During sepsis, lipopolysaccharide (LPS) triggers the development of disseminated intravascular coagulation (DIC) via the tissue factor-dependent pathway of coagulation resulting in massive thrombin generation and fibrin polymerization. Recently, animal studies demonstrated that hirudin reduced fibrin deposition in liver and kidney and decreased mortality in LPS-induced DIC. Accordingly, the effects of recombinant hirudin (lepirudin) was compared with those caused by placebo on LPS-induced coagulation in humans. Twenty-four healthy male subjects participated in this randomized, double-blind, placebo-controlled, parallel group study. Volunteers received 2 ng/kg LPS intravenously, followed by a bolus-primed continuous infusion of placebo or lepirudin (Refludan, bolus: 0.1 mg/kg, infusion: 0.1 mg/kg/h for 5 hours) to achieve a 2-fold prolongation of the activated partial thromboplastin time (aPTT). LPS infusion enhanced thrombin activity as evidenced by a 20-fold increase of thrombin-antithrombin complexes (TAT), a 6-fold increase of polymerized soluble fibrin, termed thrombus precursor protein (TpP), and a 4-fold increase in D-dimer. In the lepirudin group, TAT increased only 5-fold, TpP increased by only 50%, and D-dimer only slightly exceeded baseline values (P <.01 versus placebo). Concomitantly, lepirudin also blunted thrombin generation evidenced by an attenuated rise in prothrombin fragment levels (F(1 + 2), P <. 01 versus placebo) and blunted the expression of tissue factor on circulating monocytes. This experimental model proved the anticoagulatory potency of lepirudin in LPS-induced coagulation activation. Results from this trial provide a rationale for a randomized clinical trial on the efficacy of lepirudin in DIC. (Blood. 2000;95:1729-1734)

Target site concentrations after continuous infusion and bolus injection of cefpirome to healthy volunteers

BACKGROUND

Recent data indicate a higher level of effectivity of beta-lactam antibiotics if serum concentrations are kept above the minimal inhibitory concentration (MIC) of the pathogen. This concept would favor continuous infusion over bolus dosing. However, it is usually not the serum concentration but the free interstitial concentration in the target tissue that determines antibiotic activity. We therefore set out to measure effective drug concentrations in the interstitial space of muscle and subcutaneous adipose tissue and to compare trough levels and times above the MIC after bolus versus continuous infusion of cefpirome.

METHODS

Twelve healthy volunteers received a single dose of 2 g cefpirome as an intravenous bolus or as a continuous infusion over 8 hours in a crossover design, and the resulting free interstitial tissue concentrations were measured with use of microdialysis.

RESULTS

After bolus injection, mean interstitial trough concentrations were 3.0 +/- 1.9 microg/mL and 2.1 +/-1.0 microg/mL for muscle and subcutaneous tissue, respectively; continuous infusion resulted in trough levels of 10.1 +/- 6.8 microg/mL and 10.1 +/- 4.6 microg/mL for muscle and subcutaneous tissue, respectively. This resulted in significantly longer times above the MIC with continuous infusion for Staphylococcus epidermidis and Enterobacter cloacae. Bacteria with an MIC < or =1 would be covered by either method, whereas higher doses seem to be necessary for Pseudomonas aeruginosa.

CONCLUSION

Although susceptible organisms will usually be covered sufficiently with standard dosing regimens, soft tissue infections with bacteria that have MIC values of 2 to 8 may profit from continuous application. Coverage of P aeruginosa, however, would be inadequate with conventional daily doses of 4 g cefpirome regardless of the method of application.