Effects of New NSAID-CAI Hybrid Compounds in Inflammation and Lung Fibrosis

Pulmonary fibrosis is a severe lung disease with progressive worsening of dyspnea, characterized by chronic inflammation and remodeling of lung parenchyma. Carbonic anhydrases are a family of zinc-metallo-enzymes that catalyze the reversible interconversion of carbon-dioxide and water to bicarbonate and protons. Carbonic Anhydrase Inhibitor (CAI) exhibited anti-inflammatory effects in animals with permanent-middle-cerebral artery occlusion, arthritis and neuropathic pain. The pharmacological profile of a new class of hybrid compounds constituted by a CAI connected to a Nonsteroidal-Anti-Inflammatory Drug (NSAID) was studied in the modulation of inflammation and fibrosis. In-vitro tests were performed to assess their effects on cyclo-oxygenase enzyme (COX)-1 and COX-2, namely inhibition of platelet aggregation and thromboxane B2 production in the human-platelet-rich plasma, and reduction of Prostaglandin-E2 production in lipopolysaccharide-treated-RAW-264.7 macrophage cell line. The activity of compound 3, one of the most active, was studied in a model of bleomycin-induced lung fibrosis in C57BL/6 mice. The hybrid compounds showed a higher potency in inhibiting PGE₂ production, but not in modifying the platelet aggregation and the TXB₂ production in comparison to the reference molecules, indicating an increased activity in COX-2 inhibition. In the in-vivo murine model, the compound 3 was more effective in decreasing inflammation, lung stiffness and oxidative stress in comparison to the reference drugs given alone or in association. In conclusion, these CAI-NSAID hybrid compounds are promising new anti-inflammatory drugs for the treatment of lung chronic inflammatory diseases.

Pharmacokinetic/pharmacodynamic assessment of a novel, pharmaceutical lipid-aspirin complex: results of a randomized, crossover, bioequivalence study

Aspirin (acetylsalicylic acid, ASA) can lead to gastrointestinal mucosal injury through disruption of its protective phospholipid bilayer. A liquid formulation of a novel pharmaceutical lipid-aspirin complex (PL-ASA) was designed to prevent this disruption. We sought to determine the pharmacokinetic (PK)/pharmacodynamic (PD) characteristics of PL-ASA compared with immediate release aspirin (IR-ASA). In this active-control crossover study, 32 healthy volunteers were randomized to receive 1 of 2 dose levels (a single dose of 325 mg or 650 mg) of either PL-ASA or IR-ASA. After a 2-week washout period between treatment assignments, subjects received a single dose of the alternative treatment, at the same dose level. The primary objectives of the study were to assess, for PL-ASA and IR-ASA at 325 mg and 650 mg dose levels, PK and PD bioequivalence, and safety, over a 24-h period after administration of both drugs. PK parameters were similar for PL-ASA and IR-ASA, and met FDA-criteria for bioequivalence. Regarding PD, both drugs also showed C_min TxB2 values below 3.1 ng/mL (cut-off associated with decreased cardiovascular events) and > 99% inhibition of serum TxB2 ( ≥ 95% inhibition represents the cut-off for aspirin responders) along with similar results in several secondary PK/PD parameters. There were no serious adverse events or changes from baseline in vital signs or laboratory values in either of the 2 treatment groups. PL-ASA's novel liquid formulation has similar PK and PD performance compared with IR-ASA, supporting functional and clinical equivalence. These data coupled with the improved gastric safety of PL-ASA suggest that this novel formulation may exhibit an improved benefit-risk profile, warranting evaluation in future trials.Clinical trial registration: http://www.clinicaltrials.gov . Unique Identifier: NCT04008979.

Increased eicosanoid levels in the Sugen/chronic hypoxia model of severe pulmonary hypertension

Inflammation and altered immunity are recognized components of severe pulmonary arterial hypertension in human patients and in animal models of PAH. While eicosanoid metabolites of cyclooxygenase and lipoxygenase pathways have been identified in the lungs from pulmonary hypertensive animals their role in the pathogenesis of severe angioobliterative PAH has not been examined. Here we investigated whether a cyclooxygenase-2 (COX-2) inhibitor or diethylcarbamazine (DEC), that is known for its 5-lipoxygenase inhibiting and antioxidant actions, modify the development of PAH in the Sugen 5416/hypoxia (SuHx) rat model. The COX-2 inhibitor SC-58125 had little effect on the right ventricular pressure and did not prevent the development of pulmonary angioobliteration. In contrast, DEC blunted the muscularization of pulmonary arterioles and reduced the number of fully obliterated lung vessels. DEC treatment of SuHx rats, after the lung vascular disease had been established, reduced the degree of PAH, the number of obliterated arterioles and the degree of perivascular inflammation. We conclude that the non-specific anti-inflammatory drug DEC affects developing PAH and is partially effective once angioobliterative PAH has been established.

Dactyloditerpenol acetate, a new prenylbisabolane-type diterpene from Aplysia dactylomela with significant in vitro anti-neuroinflammatory activity

A new regular diterpene possessing an unusual 1,6-anti-3-methylcyclohex-2-en-1-ol ring system, dactyloditerpenol acetate (1), has been extracted from the tropical sea hare Aplysia dactylomela and its stereostructure elucidated by spectroscopic methods. The absolute configuration of 1 was determined as 1S, 6S, 7R, 10S, and 11R by application of Kishi's method for the assignment of absolute configuration of alcohols. The new diterpene potently inhibited in vitro thromboxane B2 (TXB2) (IC50 0.4μM) and superoxide anion (O2(-)) (IC50 1μM) generation from Escherichia coli lipopolysaccharide (LPS)-activated rat neonatal microglia, with concomitant low short-term toxicity.

Evaluation of the pharmacodynamics of acetylsalicylic acid 81 mg with or without esomeprazole 20 mg in healthy volunteers

BACKGROUND

The absence of a pharmacokinetic interaction between the proton pump inhibitor esomeprazole (40 mg) and acetylsalicylic acid (aspirin, ASA; 325 mg) has previously been established.

OBJECTIVE

This study set out to investigate the potential for pharmacodynamic interaction between low-dose ASA and esomeprazole in healthy volunteers, by measuring ASA antiplatelet activity.

STUDY DESIGN

This was a single-center, open-label, two-period, randomized crossover study.

PARTICIPANTS

Healthy male and female volunteers aged 18-75 years were included. All volunteers received ASA 81 mg once daily for 5 days prior to the study (pre-screen). Subjects were eligible for inclusion if they had aspirin reactivity units (ARU, as measured by the VerifyNow ASA assay) of <550 on Day 6.

INTERVENTION

After pre-screening and a washout period of at least 14 days, eligible volunteers received ASA 81 mg with or without esomeprazole 20 mg once daily for 5 days in randomized order, with a 14-day washout between treatments.

MAIN OUTCOME MEASURE

The main outcome measure was the antiplatelet activity of ASA, as assessed by ARU ratio relative to baseline in the VerifyNow ASA assay; suppression of serum thromboxane B(2) (TXB(2)) was a secondary endpoint. Statistical comparisons were made using linear mixed models.

RESULTS

A total of 29 volunteers (19 aged ≥50 years; 8 women; 21 men) were evaluable for pharmacodynamic analysis (per protocol). All volunteers on both treatments achieved ARU <550 at Day 6. The geometric mean ratio of Day 6 to Day 1 (baseline) platelet aggregation was 0.70 (95% confidence interval [CI] 0.68, 0.72) with ASA alone and 0.71 (95% CI 0.69, 0.74) with ASA + esomeprazole. The ratio of platelet aggregation (ASA + esomeprazole/ASA) was 1.02 (95% CI 0.99, 1.05). ASA administered alone or with esomeprazole reduced serum TXB(2) by more than 99.5%. The ratio of suppression of serum TXB(2) levels (ASA + esomeprazole/ASA) was 1.06 (95% CI 0.88, 1.29). The combination of ASA and esomeprazole was well tolerated.

CONCLUSION

No pharmacodynamic interaction between low-dose ASA and esomeprazole was found with regard to platelet function.

TRIAL REGISTRATION

Registered at ClinicalTrials. gov as NCT01199328.

Anti-inflammatory effects of benfotiamine are mediated through the regulation of the arachidonic acid pathway in macrophages

Benfotiamine, a lipid-soluble analogue of vitamin B1, is a potent antioxidant that is used as a food supplement for the treatment of diabetic complications. Our recent study (U.C. Yadav et al., Free Radic. Biol. Med. 48:1423-1434, 2010) indicates a novel role for benfotiamine in the prevention of bacterial endotoxin, lipopolysaccharide (LPS)-induced cytotoxicity and inflammatory response in murine macrophages. Nevertheless, it remains unclear how benfotiamine mediates anti-inflammatory effects. In this study, we investigated the anti-inflammatory role of benfotiamine in regulating arachidonic acid (AA) pathway-generated inflammatory lipid mediators in RAW264.7 macrophages. Benfotiamine prevented the LPS-induced activation of cPLA2 and release of AA metabolites such as leukotrienes, prostaglandin E2, thromboxane 2 (TXB2), and prostacyclin (PGI2) in macrophages. Further, LPS-induced expression of AA-metabolizing enzymes such as COX-2, LOX-5, TXB synthase, and PGI2 synthase was significantly blocked by benfotiamine. Furthermore, benfotiamine prevented the LPS-induced phosphorylation of ERK1/2 and expression of transcription factors NF-κB and Egr-1. Benfotiamine also prevented the LPS-induced oxidative stress and protein-HNE adduct formation. Most importantly, compared to specific COX-2 and LOX-5 inhibitors, benfotiamine significantly prevented LPS-induced macrophage death and monocyte adhesion to endothelial cells. Thus, our studies indicate that the dual regulation of the COX and LOX pathways in AA metabolism could be a novel mechanism by which benfotiamine exhibits its potential anti-inflammatory response.

Inhibition of platelet aggregation and immunomodulation of NK lymphocytes by administration of ascorbic acid

Platelets aggregation around migrating tumor cells offers protection against the cytotoxic activity of the natural killers cells (NKC). The ascorbic acid in 3 x 10(-3) M concentration completely inhibited platelet aggregation, decreased thromboxane B2 levels, and inhibited the expression of platelet membranic receptor GpIIb/IIIa in non stimulated platelets, and increased the NKC cytotoxicity in an average rate of 105, 61, and 285% in the NKC/targets cells ratios 12.5:1, 25:1 and 50:1 respectively. The results suggest the role of ascorbic acid in increasing the susceptibility of tumor cells to NKC; the ascorbic acid could be used as part of a multidrug therapy to treat diseases which up to now have been treated only through chemotherapy.

Dual inhibitory effect of Glycyrrhiza glabra (GutGard™) on COX and LOX products

Glycyrrhiza glabra and its phytoconstituents have been known to possess widespread pharmacological properties as an anti-inflammatory, anti-viral, antitumour and hepatoprotective drug. In this study, we examined the inhibitory potential of extract of G. glabra (GutGard™) root and its phytoconstituents (glabridin, glycyrrhizin, and isoliquiritigenin) on both cyclooxygenase (COX) and lipoxygenase (LOX) products in order to understand the mechanism of its anti-inflammatory action. Inhibitory effect of GutGard™ and its phytoconstituents on lipopolysaccharide (LPS) induced prostaglandin E(2) (PGE(2)), calcimycin (A23187) induced thromboxane (TXB(2)), and leukotriene (LTB(4)) release was studied using murine macrophages (J774A.1) and human neutrophil (HL-60) cells. Results revealed that, G. glabra and glabridin significantly inhibited PGE(2), TXB(2) (COX) and LTB(4) (LOX), while, isoliquiritigenin exerted inhibitory effect only against COX products but failed to suppress LOX product. However, glycyrrhizin at the tested concentrations failed to exhibit inhibitory effect on both COX and LOX products. Here, we report for the first time that G. glabra (almost devoid of glycyrrhizin) exhibits anti-inflammatory property likely through the inhibition of PGE(2), TXB(2) and LTB(4) in mammalian cell assay system, which could be influenced in part by glabridin and isoliquiritigenin.

Effect of maximum OTC doses of naproxen sodium or acetaminophen on low-dose aspirin inhibition of serum thromboxane B2

OBJECTIVES

This study evaluated the platelet inhibitory effects of low-dose enteric-coated aspirin (EC-ASA) when used concomitantly with maximum over-the-counter (OTC) doses of naproxen sodium (NAPSO) or acetaminophen to determine whether NAPSO and acetaminophen interfere with the anti-platelet effect of aspirin.

RESEARCH DESIGN AND METHODS

Phase I, randomized, open-label, multi-dose, three-period, parallel group, pharmacodynamic trial conducted in healthy male and female volunteers (n = 47 randomized subjects and n = 37 evaluable subjects), mean age 40.2 years. All subjects received 5 days of EC-ASA 81 mg once daily followed by 5 days of EC-ASA 81 mg once daily alone or co-administered with either NAPSO 220 mg three times daily or acetaminophen 1 g four times daily.

PRIMARY OUTCOME MEASURE

Inhibition of serum thromboxane B(2) (TXB(2)), as a marker of platelet cyclooxygenase-1 (COX-1) inhibition, measured on Day 11.

RESULTS

Mean inhibition of TXB(2) on Day 11 was >99% for subjects taking EC-ASA alone as well as for those who received EC-ASA co-administered with NAPSO or acetaminophen. For subjects taking EC-ASA monotherapy, mean serum TXB(2) inhibition was 99.7% (range 99.0-100%), for those taking EC-ASA with acetaminophen it was 99.6% (range 98.3-99.9%), and for those taking EC-ASA with NAPSO, mean serum TXB(2) inhibition was 99.7% (range 99.2-100%).

STUDY LIMITATION

Small sample size and open-label trial design.

CONCLUSIONS

The anti-platelet effect of EC-ASA 81 mg once daily was maintained following its co-administration with maximum OTC doses of NAPSO or acetaminophen.

New mechanism for an old drug: aspirin triggers anti-inflammatory lipid mediators with gender implications

Aspirin increases anti-inflammatory aspirin-triggered lipoxin A4 levels in healthy subjects in a gender-specific manner in a randomized clinical study. Thus, formation of aspirin-triggered lipoxin A4 may provide a novel mechanism underlying aspirin's clinical benefits, and shed light on gender-dependent therapeutics of aspirin.

Anticarcinogenic and antiplatelet effects of carvacrol

AIM

To investigate the effect of carvacrol on chemical carcinogenesis, cancer cell proliferation and platelet aggregation, and to find possible correlation between all these processes and the antioxidant properties of carvacrol.

MATERIALS AND METHODS

3,4-benzopyrene-induced carcinogenesis model using Wistar rats was used. Leiomyosarcoma cells from Wistar rats were used to study carvacrol antiproliferative activity in vitro. The carvacrol antiplatelet properties were investigated with platelet aggregation assay and flow cytometry technique. The production of thromboxane B2, final metabolite of platelet aggregation, was evaluated by radioimmunoassay.

RESULTS

Our study revealed significant anticarcinogenic properties of carvacrol. We observed 30% decrease of 3,4 benzopyrene carcinogenic activity in vivo. Antiproliferative activity of carvacrol (IC(50)) was 90 microM and 67 microM for 24 h and 48 h of incubation of cells, respectively. Carvacrol possessed also mild antiplatelet effect, inducing the decrease of thromboxane A2 production in platelets and as a result - restrictive expression of the GPIIb/IIIa platelet receptor.

CONCLUSION

Our data demonstrated that carvacrol possesses anticarcinogenic, antiproliferative and antiplatelet properties.

Inhibition of thromboxane biosynthesis by triflusal in type 2 diabetes mellitus

Triflusal is an antiplatelet drug related to aspirin, with different pharmacological properties and a lower haemorrhagic risk. We aimed at comparing their effects on platelet and endothelial activation in type 2 diabetes mellitus (T2DM). In a randomized, double-blind, parallel group study, we compared the effects of three daily regimens (300, 600, and 900 mg) of triflusal, and aspirin (100mg/day) on urinary 11-dehydro-thromboxane (TX)B(2), index of in vivo platelet activation, ex vivo platelet function using the analyzer PFA-100, plasma von Willebrand factor (vWF), P-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and serum nitrite and nitrate (NO(2)(-)+NO(3)(-)) in 60 T2DM patients. Triflusal induced a dose-dependent reduction in 11-dehydro-TXB(2) and a prolongation of closure time in the presence of collagen plus epinephrine (Coll/Epi-CT). The effects of the highest triflusal dose were not different from those of aspirin. The closure time in the presence of collagen plus ADP (Coll/ADP-CT), ICAM-1, VCAM-1, and NO(2)(-)+NO(3)(-) were not modified either by triflusal or aspirin. Plasma P-selectin and vWF were reduced by triflusal but not by aspirin. In T2DM triflusal causes a profound inhibition of platelet TXA(2) biosynthesis in vivo, acting on different targets involved in the platelet-endothelial cell interactions.

2-(2-Br-phenyl)-8-methoxy-benzoxazinone (HPW-RX2), a direct thrombin inhibitor with a suppressive effect on thromboxane formation in platelets

2-(2-Br-phenyl)-8-methoxy-benzoxazinone (HPW-RX2), a newly synthetic benzoxazinone derivative, has previously been shown to inhibit rabbit platelet aggregation caused by thrombin and arachidonic acid. In the present study, the mechanism for the antiplatelet effect of HPW-RX2 was further investigated. In human platelets, HPW-RX2 concentration-dependently inhibited platelet aggregation, ATP release, P-selectin expression, and intracellular calcium mobilization caused by thrombin. In contrast, HPW-RX2 had no significant effect on either SFLLRN- or GYPGKF-induced platelet aggregation, indicating that HPW-RX2 did not interfere with platelet thrombin receptors. Moreover, HPW-RX2 inhibited the amidolytic activity of thrombin and prolonged the fibrinogen clotting time. These results suggest that the inhibitory effect of HPW-RX2 on thrombin-induced platelet aggregation is via direct inhibition of thrombin proteolytic activity. Besides the inhibition on thrombin, HPW-RX2 also prevented platelet aggregation, ATP release, and increase in [Ca2+]i caused by arachidonic acid and low concentration collagen. In a parallel manner, both arachidonic acid-induced thromboxane B2 and prostaglandin D2 formations were decreased in platelets treated with HPW-RX2. This indicates that HPW-RX2 is able to inhibit the arachidonic acid cascade at the cyclooxygenase level. This is the first report of a benzoxazinone derivative possessing both thrombin and cyclooxygenase inhibitory properties. The dual effect of HPW-RX2 might provide extra therapeutic benefits for treatment of arterial thrombosis.

Double-blind, randomized, parallel, placebo-controlled study of ibuprofen effects on thromboxane B2 concentrations in aspirin-treated healthy adult volunteers

BACKGROUND

Patients taking aspirin for cardioprotection may occasionally take over-the-counter (OTC) ibuprofen for pain relief, which might interfere with the antiplatelet effects of aspirin.

OBJECTIVE

The present study was undertaken to determine whether ibuprofen, taken according to OTC label directions, would affect inhibition of thromboxane B2 (TXB2), a surrogate for platelet inhibition.

METHODS

This was a prospective, multiple-dose,single-center, double-blind, randomized, parallel, placebo-controlled study. Eligible subjects received chewable, immediate-release aspirin 81 mg QD for 8 days, and were then randomized to receive either ibuprofen 400 mg TID or placebo TID, in addition to aspirin, for 10 days.

RESULTS

Fifty-one subjects were randomized; 47(24 placebo, 23 ibuprofen) completed the study. No subjects withdrew prematurely. Subjects were predominantly white (49%) or black (38%), and 53% were male. The mean (SD) age was 38.4 (9.8) years and mean (SD) body weight was 173.2 (26.7) pounds. On days 1, 3, 7, and 10 of the study period, mean TXB2 inhibitions were 99.24%, 98.88%, 97.75%, and 98.17% for ibuprofen and 98.82%, 98.93%, 98.75%, and 98.83% for placebo. Although a statistically significant reduction of TXBZ inhibition was seen in the ibuprofen group at days 7 and 10 (P = 0.003 and P = 0.023, respectively), TXBZ inhibition was >90% on all days tested in all subjects. Aspirin, ibuprofen, and placebo were all well tolerated. There were 3 adverse events (1 mild and 2 moderate) during the aspirin run-in period and 8 (2 mild and 6 moderate) during the randomized study period.

CONCLUSIONS

No clinically meaningful loss of cardioprotection was found, as reflected by TXB2 inhibition in healthy volunteers who received OTC doses of ibuprofen. When using this regimen of OTC ibuprofen with immediate-release, low-dose aspirin, concerns about the loss of cardioprotective antiplatelet effects of aspirin are not supported by this study.

Characterization of inhibition of platelet function by paracetamol and its interaction with diclofenac in vitro

BACKGROUND

Paracetamol (acetaminophen) is an effective analgesic and a weak inhibitor of cyclo-oxygenase (COX). Clinically paracetamol is often used together with traditional NSAIDs, which are strong inhibitors of COX. We studied binding of paracetamol to COX and its action on platelet function together with diclofenac.

METHODS

Blood was collected from healthy donors and platelet function was assessed by photometric aggregometry, a platelet function analyser (PFA-100, Dade Behring, Deerfield, IL) and by measuring the release of thromboxane B(2) (TxB(2)), the stable metabolite of thromboxane A(2), after addition of paracetamol (10-80 microg ml(-1)). A concentration-inhibition relationship was established and the inhibition coefficient (K(i)) demonstrating 50% binding to COX was determined using a Schild-plot. Interaction of paracetamol (5-20 microg ml(-1)) and diclofenac (0.1-0.8 microg ml(-1)) was determined and an isobolographic analysis was performed.

RESULTS

Paracetamol added to platelet-rich plasma (PRP) caused a concentration-dependent inhibition of platelet function. Photometric aggregometry and TxB(2) release was significantly inhibited by paracetamol from 10 microg ml(-1) onwards. The PFA-100 closure time was significantly prolonged by paracetamol at a high concentration only. K(i) was 15.2 microg ml(-1) with a 95% confidence interval of 11.8-18.6 microg ml(-1). Inhibition of aggregation by diclofenac was augmented by paracetamol. Isobolographic analysis showed synergism.

CONCLUSIONS

The 95% confidence interval of K(i) equals the antipyretic plasma concentration of paracetamol, i.e. 10-20 microg ml(-1). High doses of paracetamol and a combination of diclofenac and paracetamol cause platelet inhibition and thus may increase risk of surgical bleeding.

Pharmacodynamic interaction of naproxen with low-dose aspirin in healthy subjects

OBJECTIVES

We investigated the occurrence of pharmacodynamic interaction between low-dose aspirin and naproxen.

BACKGROUND

The uncertainty of cardioprotection by naproxen has encouraged its combination with aspirin in patients with arthritis and cardiovascular disease.

METHODS

The incubation of washed platelets with naproxen for 5 min before the addition of aspirin reduced the irreversible inhibition of thromboxane (TX)B(2) production by aspirin. The pharmacodynamic interaction between the two drugs was then investigated in four healthy volunteers who received aspirin (100 mg daily) for 6 days and then the combination of aspirin and naproxen for further 6 days: aspirin 2 h before naproxen (500 mg, twice-daily dosing). After 14 days of washout, naproxen was given 2 h before aspirin for further 6 days.

RESULTS

The inhibition of serum TXB(2) production (index of platelet cyclooxygenase [COX]-1 activity) and platelet aggregation ex vivo and urinary 11-dehydro-TXB(2) levels (index of TXB(2) biosynthesis in vivo) by aspirin alone (99 +/- 0.2%, 95 +/- 0.6%, and 81 +/- 4%, respectively) was not significantly altered by the co-administration of naproxen, given either 2 h after aspirin or in reverse order. In a second study, the concurrent administration of a single dose of aspirin and naproxen did not affect platelet TXB(2) production and aggregation at 1 h after dosing, when aspirin alone causes maximal inhibitory effect. Moreover, the rapid recovery of platelet COX-1 activity and function supports the occurrence of a pharmacodynamic interaction between naproxen and aspirin.

CONCLUSIONS

Naproxen interfered with the inhibitory effect of aspirin on platelet COX-1 activity and function. This pharmacodynamic interaction might undermine the sustained inhibition of platelet COX-1 that is necessary for aspirin's cardioprotective effects.

Increased renal production of angiotensin II and thromboxane B2 in conscious diabetic rats

BACKGROUND

The mechanisms involved in development of cardiovascular complications associated with diabetes mellitus are not well elucidated. Among the vasoactive factors that may play a role in development of these complications are angiotensin II and thromboxane B2 (TXB2). We hypothesized that diabetes increases renal production of TXB2 through stimulation of angiotensin type-1 receptor.

METHODS

We used a microdialysis technique to monitor changes in renal interstitial fluid (RIF) TXB2 in conscious streptozotocin-induced diabetes rat model. The RIF levels of angiotensin II and TXB2 were monitored before and during 6 weeks after development of diabetes and during treatment with the angiotensin type-1 receptor blocker valsartan at 10 mg/kg. Measurement of the urinary albumin excretion (UAE) was used to monitor the development and progression of diabetic nephropathy.

RESULTS

The UAE was 81.62 +/- 1.31 ng/min, 184.75 +/- 9.41 ng/min (P < .01), and 229.84 +/- 4.49 ng/min (P < .0001) at baseline, week 3, and week 6, respectively, after induction of diabetes. Basal levels of RIF angiotensin II were 4.28 +/- 0.02 pg/mL and significantly increased to 6.24 +/- 0.31 pg/mL (P < .001) and 7.66 +/- 0.05 pg/mL (P < .001) at 3 and 6 weeks after development of diabetes. Similarly, basal RIF TXB2 was 197 +/- 27 pg/mL and increased to 488 +/- 80 pg/mL (P < .01) and 703 +/- 130 pg/mL (P < .01) at 3 and 6 weeks after development of diabetes. Valsartan caused further increase in RIF angiotensin II levels. In contrast, valsartan decreased RIF TXB2 levels at baseline to 85 +/- 11 pg/mL (P < .01), at 3 weeks to 141 +/- 17 pg/mL (P < .01), and at 6 weeks to 255 +/- 45 pg/mL (P < .01) after development of diabetes.

CONCLUSIONS

These results demonstrate that diabetes mellitus is accompanied by increased renal production of angiotensin II and TXB2. The increase in TXB2 is mediated through stimulation of angiotensin type-1 receptor.

Inhibition of cyclooxygenase activity, platelet aggregation and thromboxane B2 production by two environmental toxicants: m- and o-cresol

Cresol is a well-known environmental pollutant, toluene metabolite, uremic toxicant and accidental poisoning product. Formocresol, a preparation of formalin and cresol, is also used as a root canal medicament and for pulpotomy of primary teeth. However, little is known about its effect on cardiovascular system. In this study, m-cresol inhibited the AA-induced platelet aggregation by 43-97% at concentrations ranging from 0.25 to 1 mM. Collagen-induced platelet aggregation was also inhibited by 0.25-1 mM of m-cresol by 47-98%. Accordingly, o-cresol (0.1-0.5 mM) also inhibited the AA-induced platelet aggregation by 46-96% and the collagen-induced platelet aggregation by 35-88% at concentrations of 0.1-1 mM. AA- and collagen-induced platelet thromboxane B(2) (TXB(2)) production was inhibited by even 0.1 mM of m-cresol with 88 and 54% of inhibition, respectively. The o-cresol (0.1 mM) also inhibited the AA- and collagen-induced platelet TXB(2) production with 91 and 97% respectively. Although m- and o-cresol (<1 mM) showed little effect on thrombin-induced platelet aggregation, they effectively inhibited the thrombin-induced platelet TXB(2) production. The m-cresol (2 and 5 mM) inhibited the COX-1 activity by 55-99%, but showed little effect on COX-2 enzyme activity. Moreover, o-cresol (0.5 and 1 mM) inhibited the COX-1 activity by 40-95%. COX-2 enzyme activity was inhibited by 68% at a concentration of 5 mM o-cresol. These results indicate that acute cresol-poisoning, direct root canal medication with formocresol or long-term occupational exposure to cresol and toluene may potentially suppress blood clot formation and lead to tissue hemorrhage via inhibition of platelet aggregation, TXB(2) production and COX enzyme activity.

Aspirin triggers antiinflammatory 15-epi-lipoxin A4 and inhibits thromboxane in a randomized human trial

There is increasing evidence that aspirin initiates biosynthesis of novel antiinflammatory mediators by means of interactions between endothelial cells and leukocytes. These mediators are classified as aspirin-triggered 15-epi-lipoxins. Such compounds may account at least in part for aspirin's clinical benefits, which are distinct from the well appreciated action of aspirin as a platelet inhibitor. Here, we addressed whether aspirin-triggered 15-epilipoxinA4 (ATL) formation is aspirin-dependent in humans and its relationship to aspirin's antiplatelet activity. We conducted a randomized clinical trial among 128 healthy subjects allocated to placebo or to 81-, 325-, or 650-mg daily doses of aspirin for 8 weeks. Plasma thromboxane (TX)B2, an indicator of platelet reactivity, and ATL were assessed from blood collected at baseline and at 8 weeks. Plasma ATL levels significantly increased in the 81-mg aspirin group (0.25 +/- 0.63 ng/ml, P = 0.04), with borderline increases in the 325-mg group (0.16 +/- 0.71 ng/ml) and no apparent significant changes in the 650-mg group (0.01 +/- 0.75 ng/ml, P = 0.96). When ATL and TXB2 were compared, levels changed in a statistically significant and opposite direction (P < 0.01) for all three aspirin doses. These results demonstrated that low-dose aspirin (81 mg daily) initiates production of antiinflammatory ATL opposite to the inhibition of TX. Monitoring ATL may represent a simple clinical parameter to verify an individual's vascular leukocyte antiinflammatory response with low-dose aspirin treatment. These results also emphasize the importance of cell-cell interactions in the modulation of hemostatic, thrombotic, and inflammatory processes.

Inhibition of IL-6, TNF-alpha, and cyclooxygenase-2 protein expression by prostaglandin E2-induced IL-10 in bone marrow-derived dendritic cells

Several endogenously produced mediators, including cytokines such as IL-6, IL-10, and TNF-alpha and prostanoids such as prostaglandin E(2) (PGE(2)), regulate dendritic cell (DC) function and contribute to immune homeostasis. In this study, we report that exogenous PGE(2) enhances the production of IL-10 from bone marrow-derived DC (BM-DC). IL-6, but not TNF-alpha, release is enhanced by PGE(2) in the presence of anti-IL-10, suggesting that endogenous IL-10 masks PGE(2)-induced IL-6. Furthermore, both exogenous IL-10 and PGE(2) inhibit LPS-induced IL-6 and TNF-alpha, whereas selective inhibition of cyclooxygenase-2 (COX-2) or addition of anti-IL-10 causes the reverse effects. Exogenous IL-10, but not IL-6, dose-dependently suppresses COX-2 protein expression and PGE(2) production, and TNF-alpha does not reverse this effect. In contrast, anti-IL-10 up-regulates prostanoid production by LPS-stimulated BM-DC. Taken together, our results show that in response to PGE(2), BM-DC produce IL-10, which in turn down-regulates their own production of IL-6-, TNF-alpha-, and COX-2-derived prostanoids, and plays crucial roles in determining the BM-DC pro-inflammatory phenotype.

Lumiracoxib: pharmacokinetic and pharmacodynamic profile when coadministered with fluconazole in healthy subjects

This two-way crossover study evaluated the effect of fluconazole on the pharmacokinetics and selective COX-2 inhibition of lumiracoxib. Thirteen healthy subjects were randomized to fluconazole (day 1: 400 mg; days 2-4: 200 mg) or no drug. On day 4, all subjects received a single dose of lumiracoxib (400 mg). Lumiracoxib pharmacokinetics were assessed during the following 48 hours. Thromboxane B(2) (TxB(2)) inhibition was measured prior to lumiracoxib dosing and 2 hours afterwards. Fluconazole caused a small (18%) but not clinically relevant increase in lumiracoxib mean AUC(0- infinity ) but had no effect on lumiracoxib mean C(max). The geometric mean ratio (lumiracoxib plus fluconazole/lumiracoxib alone) for AUC(0- infinity ) was 1.19 (90% confidence interval [CI] = 1.12, 1.27) and for C(max) was 1.11 (90% CI = 0.98, 1.27). The decrease in TxB(2) from predose was not significantly different for lumiracoxib (11.8%) or lumiracoxib plus fluconazole (7.1%); no correlation between lumiracoxib concentration and TxB(2) decrease was seen. As fluconazole is a strong inhibitor of cytochrome P450 (CYP) 2C9, other CYP2C9 inhibitors are unlikely to affect lumiracoxib pharmacokinetics with clinical relevance, making dosage adjustment unnecessary.

The ingestion of Ginkgo biloba extract (EGb 761) inhibits arachidonic acid-mediated platelet aggregation and thromboxane B2 production in healthy volunteers

Twelve non-diabetic volunteers (age = 39 +/- 13 years, BMI = 23.5 +/- 3.5) undertook a randomized double-blind placebo-controlled crossover study in which they ingested either 120 mg of EGb 761 or a placebo daily for 3 months and then switched to the other test capsules for the next 3 months. Platelet aggregation in platelet-rich plasma (PRP) was performed at the end of each 3-month arm, with or without 1-min incubation with graded doses of EGb 761. In the placebo cycles, AA-stimulated TXB2 production was 2581 +/-1337 pg/10(6) platelets (range 897-5485) compared to 1668 +/- 992 pg/10(6) platelets (range 6-1668) in the EGb 761 cycles (p < 0.005). Incubation of PRP with EGb 761 (150 microg/ml) completely inhibited platelet aggregation accompanied by inhibition of TXB2 synthesis in all subjects both in the placebo (<200 pg TXB2/10(6) platelets) and EGb 761 cycles (< 120 TXB2/10(6) platelets) (p < 0.0001). These results support EGb 761-mediated inhibition of platelet TXB2 synthesis in vivo.

Effects of d-003, a new substance purified from sugar cane wax, on platelet aggregation and plasma levels of arachidonic acid metabolites in healthy volunteers

D-003 is a mixture of very high molecular weight aliphatic acids purified from sugar cane wax showing cholesterol-lowering and antiplatelet effects proven in experimental and clinical studies. Experimental evidence indicates that inhibition of platelet aggregation induced by D-003 is associated with a reduction of thromboxane B2 (TxB2) and an increase of prostacyclin (Pgl2) serum levels. This double-blinded, randomized, placebo-controlled study was undertaken to investigate whether D-003 (20 mg/day) modifies serum levels of TxB2 and Pgl2 and inhibits platelet aggregation in human healthy volunteers. Thirty-one subjects were randomized to placebo or D-003 at 20 mg/day for 14 days. Serum levels of TxB2 and Pgl2 and platelet aggregation to arachidonic acid (AA) (1.75 mM) and collagen (1 microg/ml) were assessed. D-003 (20 mg/day) significantly reduced (p < 0.001) TxB2by 36.4% and increased Pgl2 serum levels by 31% compared with baseline, and these changes were different from placebo. As expected, D-003 significantly inhibited (p < 0.001) platelet aggregation to AA (81.9-65.6%) and to collagen (75.3-62.3%). No subject withdrew from the study. No drug-related disturbances were observed. We conclude that D-003 at 20 mg/day for 14 days significantly inhibited platelet aggregation to AA and collagen and reduced TxB2 and increased Pgl2 serum levels. These results are consistent with those observed in experimental models, indicating that the antiplatelet effect of D-003 is associated with the observed changes on the levels of AA metabolites. Further studies, however, should explore the mechanism involved in this action in greater depth.

Dexamethasone suppresses peripheral prostanoid levels without analgesia in a clinical model of acute inflammation

PURPOSE

The therapeutic effects of glucocorticoids are generally attributed to suppression of multiple signaling pathways involved in the inflammatory response leading to decreased levels of inflammatory mediators at the site of injury. This study evaluated the in vivo relationship between levels of prostanoids at the site of tissue injury and analgesia after dexamethasone administration in a clinical model of tissue injury.

METHODS

Subjects were administered dexamethasone 4 mg or placebo 12 hours and 1 hour before the removal of 2 mandibular third molars. A microdialysis probe was implanted at each surgical site for measurement of immunoreactive prostaglandin E2 (PGE(2)) or immunoreactive thromboxane B(2) (TxB(2)), and pain was measured concurrently. Subjects received either ketorolac 30 mg intravenously or placebo at pain onset.

RESULTS

PGE(2) was detectable in the first postoperative sample, decreased over the next hour and then increased coincident with the onset of postoperative pain. Administration of dexamethasone suppressed PGE(2) levels in samples collected at pain onset in comparison to placebo and significantly suppressed TxB(2) at the surgical site but without any effect on pain report. Subsequent administration of ketorolac significantly reduced pain while decreasing both PGE(2) and TxB(2) levels at the surgical site.

CONCLUSION

The lack of an analgesic effect for dexamethasone while reducing both PGE(2) and TxB(2) at the site of injury in comparison to ketorolac analgesia accompanied by greater reductions in levels of these prostanoids suggests that glucocorticoids at this dose do not suppress PGE(2) release sufficiently to attenuate peripheral sensitization of nociceptors after tissue injury.

Differences in the effects of extended-release aspirin and plain-formulated aspirin on prostanoids and nitric oxide in healthy volunteers

This study was designed to evaluate the effects of extended-release aspirin on platelet aggregation and the production of prostanoids and nitric oxide. The participants in this double blind, randomized and crossover study were 20 healthy volunteers. Interventions were 150 mg of plain-formulated aspirin (PFASA) and 150 mg of extended-release aspirin (ERASA). Blood samples were collected before and 10, 20, 60, 120, 240, 480 and 1440 min after the first dose; 3, 7 and 14 days after daily administration and 24 h after the last dose. The main measures were platelet aggregometry, thromboxane B2, 6-keto-prostaglandin (PG) F1alpha and nitric oxide in each control. Platelet aggregation was inhibited by 50% with ERASA, and by 77% with PFASA. No differences were found in chronic treatment. Thromboxane B2 was inhibited more by the latter (51-67%), but 90% inhibition was observed in both groups after 3 days. The levels of 6-keto-PGF1alpha was reduced by 20% with ERASA and by 58% with PFASA. Nitric oxide production increased in both groups, but after 24 h, and 7-14 days, elevated concentrations of nitric oxide were found only in the ERASA. The antiplatelet effects of ERASA provide pharmacological advantages (greater prostacyclin synthesis and prolonged increase in nitric oxide production) over those provided by the plain formulation.

Chiral 3,3'-(1,2-ethanediyl)-bis[2-(3,4-dimethoxyphenyl)-4-thiazolidinones] with anti-inflammatory activity. Part 11: evaluation of COX-2 selectivity and modelling

Anti-inflammatory/analgesic 3,3'-(1,2-ethanediyl)-bis[2-(3,4-dimethoxyphenyl)-4-thiazolidinones] 1, obtained as racemic mixtures (a) and mesoforms (b), have two equivalent stereogenic centres (C-2 and C-2') and exist as RR, SS and RS isomers. The enantioseparation of 1a provided the single enantiomers that displayed different in vitro cyclooxygenase-1/cyclooxygenase-2 selectivity ratios. In particular the dextrorotatory compound is a highly selective COX-2 inhibitor and the levorotatory one is moderately selective. Instead, RS-meso isomer (1b) exhibited similar levels of inhibitory activity on both COX isozymes. The diastereo- and enantioselectivity has been explained by molecular modelling of RR, SS and RS compounds into COX-1 and COX-2 binding sites. Theoretical results indicated SS>RS>RR affinity order towards COX-2 isoenzyme, in agreement with in vitro and previous in vivo pharmacological results.

Differential effect of FR122047, a selective cyclo-oxygenase-1 inhibitor, in rat chronic models of arthritis

We investigated the effects of FR122047 (1-[(4,5-bis(4-methoxyphenyl)-2-thiazoyl)carbonyl]-4-methylpiperazine hydrochloride), a selective cyclo-oxygenase (COX)-1 inhibitor, in rat type II collagen-induced arthritis (CIA) and adjuvant-induced arthritis (AIA). Using an ex vivo rat whole blood assay, FR122047 (0.032 - 3.2 mg kg(-1)) inhibited COX-1-derived thromboxane (TX) B(2) production with ED(50) value of 0.059 mg kg(-1), indicating that it was orally active, but did not inhibit lipopolysaccharide-induced prostaglandin (PG) E(2) production derived by COX-2. Oral administration of FR122047 showed a dose-dependent anti-inflammatory effect in rat CIA with ED(50) value of 0.56 mg kg(-1). This drug also dose dependently suppressed the levels of PGE(2) and TXB(2) in CIA rat paws with ED(50) values of 0.24 and 0.13 mg kg(-1), respectively. FR122047 had no effect in rat AIA model. In contrast, indomethacin, a non-selective COX inhibitor, was anti-inflammatory and reduced the formation of PGs in AIA rat paws. Unlike indomethacin, chronic treatment of FR122047 did not damage the stomach mucosa in CIA rats. These results demonstrate that COX-1 contributes to the oedema and the formation of PGE(2) and TXB(2) in rat CIA model, but not in rat AIA model. We conclude that FR122047 has an orally active and anti-inflammatory effect mediated by inhibition of PGE(2) and TXB(2) produced by COX-1 at a site of inflammation induced by type II collagen and it may be a useful tool for studying the involvement of COX-1 in various in vivo models of inflammation.

Inhibition of platelet aggregation and expression of alpha granule membrane protein 140 and thromboxane B2 with pravastatin therapy for hypercholesterolemia

The drugs in the group of the "statins" lower blood lipids, especially cholesterol, thereby reducing a risk factor for, and diminishing the incidence of, clinically important cerebrocardiovascular events. Cardiovascular events and stroke are significant causes of morbidity and mortality in China and the United States. Statins reduce platelet-mediated thrombus formation and atherosclerotic progression through mechanisms not completely elucidated. While important, the lipid-lowering action of statins does not completely explain their multifaceted benefits. Nonlipid related mechanisms are essential to such effects. The authors explore these nonlipid related mechanisms of action of pravastatin that may translate into clinically relevant benefits. This study was conducted in Guangzhou, China. Twenty-one hypercholesterolemic patients were treated with pravastatin--10-20 mg/day for 12 weeks. Blood for tests was obtained at baseline and after 8 and 12 weeks of pravastatin therapy. After 8- and 12-weeks of therapy, significant decreases were observed in the following: (1) total blood cholesterol and low density lipoprotein-C (P < 0.01), (2) ADP-induced maximum platelet aggregation (P < 0.01), (3) TXB2 or thromboxane B2 in platelets (P < 0.01), and (4) expression of GMP-140 or granule membrane protein-140 (P < 0.01). The therapeutic effects of the drug did not vary significantly with length of therapy. Pravastatin induces inhibition of platelet aggregation and expression of TXB2 and GMP-140, the likely causes of thrombus formation, atherosclerotic progression, and subsequently cardiovascular events. These potential beneficial events occur within 8 weeks of pravastatin therapy.

Hydrogen peroxide induces a greater contraction in mesenteric arteries of spontaneously hypertensive rats through thromboxane A(2) production

1. Hydrogen peroxide (H(2)O(2)) caused a transient contraction in endothelium-intact (E+) and -denuded (E-) mesenteric arteries (MA) from 8 - 10-month-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) in a concentration-dependent manner (10(-5) M to 10(-3) M). 2. The contraction to H(2)O(2) in MA (E+ or E-) was greater in SHR than in WKY. Removal of endothelium potentiated the contraction to H(2)O(2) in WKY but not in SHR. Tachyphylaxis to H(2)O(2) was less prominent in SHR than in WKY. 3. The contraction of aorta to H(2)O(2) (5 x 10(-4) M), expressed as a percentage of 80 mM KCl-induced contraction, was approximately half of that found in the MA. A greater contraction was found in E+ but not E- SHR aortic rings. 4. The contraction of MA to H(2)O(2) (5 x 10(-4) M) was greatly inhibited by SQ 29548 and ICI 192605 (thromboxane A(2) (TXA(2))/prostaglandin H(2) receptor antagonists), quinacrine (a phospholipase A(2) (PLA(2)) inhibitor), indomethacin and diclofenac (cyclooxygenase (COX) inhibitors), and furegrelate (a TXA(2) synthase inhibitor). 5. Production of thromboxane B(2) induced by H(2)O(2) (5 x 10(-4) M) was greater in SHR MA than in WKY, and was inhibited by quinacrine, indomethacin and diclofenac, and furegrelate, but not by SQ 29584 and ICI 192605. 6. These results suggested (1) that SHR MA exhibits a higher contraction involving an increased smooth muscle reactivity and less tachyphylaxis to H(2)O(2) than WKY; (2) that a greater production of TXA(2) through activation of PLA(2)-COX-TXA(2) synthase pathway appeared to be responsible for the enhanced contraction in SHR MA. The enhanced vascular response to H(2)O(2) may be related to hypertension in SHR.

Incomplete thromboxane inhibition with 100 mg of intravenous acetylsalicylic acid in patients with acute ST elevation myocardial infarction: a placebo-controlled pilot trial

BACKGROUND

Acetylsalicylic acid (ASA) is now a standard treatment of acute myocardial infarction (AMI). ASA inhibits thromboxane A(2) (TXA(2)) production by blocking the constitutive cyclooxygenase (COX)-1 enzyme, but only to a small degree the inducible COX-2. COX-2 is induced by increased concentrations of cytokines, which is related to an enhanced inflammatory response. Previously, we have found a complete inhibition of TXA(2) synthesis in healthy volunteers after intravenous administration of 50 mg of ASA. We measured in a randomized, placebo-controlled pilot trial the effect of 100 mg of ASA injected intravenously on TXA(2) synthesis in AMI patients treated with streptokinase.

METHODS AND RESULTS

Nineteen patients with AMI treated with streptokinase were randomized to 100 mg of ASA or placebo injected intravenously. Se-TXB(2) and bleeding time were measured before and after drug administration. One hundred and eighty minutes after intravenous ASA administration, treatment with oral ASA was initiated. We found a significant decrease in serum concentrations of TXB(2) after 30, 60 and 180 min following ASA injection compared to placebo, but in none of the patients was complete inhibition of TXA(2) production achieved. No significant change in bleeding time could be demonstrated.

CONCLUSION

Intravenous ASA in a dosage of 100 mg did not completely prevent TXA(2) production in AMI patients treated with streptokinase. This may be due to synthesis of TXA(2) by the inducible COX-2 enzyme and/or to a transcellular metabolism in platelets of prostanoids generated by endothelial cells.

NCX4016 (NO-aspirin) inhibits thromboxane biosynthesis and tissue factor expression and activity in human monocytes

BACKGROUND

NCX4016 (2 acetoxy-benzoate 2-(2-nitroxymethyl)-phenyl ester, NicOx S.A., France) is an antithrombotic agent chemically related to acetylsalicylic acid (ASA). We hypothesised that NCX4016, being able to release nitric oxide (NO) and to inhibit cyclo-oxygenase, might inhibit the prothrombotic function in human monocytes.

MATERIAL AND METHODS

The effects of NCX4016 and ASA on the release of thromboxane (TX) B2 and tissue factor expression and activity were compared using adherent human monocytes. The tested drugs were added before stimulation with 10 Kg/ml LPS and incubation lasted 6 hours. TXB2 concentration was measured by RIA in the supernatant of cultured cells. Immunoreactive tissue factor (TF) concentration was determined by enzyme-linked immunoassay and TF activity was assayed by measuring the peptidyl activity of the tissue factor/ factor VII complex.

RESULTS

Both ASA and NCX4016 10-300 Kmol/L dose-dependently reduced TXB2 release. NCX4016 activity was comparable to that of equimolar ASA. Part of the activity of NCX4016 up to 100 Kmol/L was prevented by 10 Kml/L ODQ, inhibitor of cGMP generation. Immunoreactive TF was dose-dependently inhibited by 300 Kmol/L NCX4016, but not by ASA. Also tissue TF activity was reduced by 300 Kmol/L NCX4016, but not by ASA.

CONCLUSIONS

The present results indicate that NCX4016 not only has anti-platelet effects but also inhibits prothrombotic activities in human monocytes, partly via NO-dependent mechanisms. NCX4016 may prove effective in the clinical setting of athero-thrombosis.

Lignan and phenylpropanoid glycosides from Phillyrea latifolia and their in vitro anti-inflammatory activity

Three phenylpropanoid glycosides (salidroside, syringin and coniferin) and one lignan (phillyrin) isolated from the leaves of Phillyrea latifolia L. (Oleaceae) were tested for interactions with the cyclo-oxygenase and 5-lipoxygenase pathways of arachidonate metabolism in calcium-stimulated mouse peritoneal macrophages and human platelets, and for their effects on cell viability. These compounds are capable of exerting inhibitory actions on enzymes of the arachidonate cascade. Phillyrin, salidroside and syringin exert a preferential effect on the cyclo-oxygenase pathway, inhibiting release of the cyclo-oxygenase metabolites prostaglandin E2 (IC50 values 45.6 microM, 72.1 microM and 35.5 microM, respectively) and to a lesser extent reducing thromboxane B2 levels (IC50 values 168 microM, 154 microM and 29.3 microM, respectively). In contrast, coniferin can be classified as a "dual inhibitor", since it produces reduction in generation of both cyclo-oxygenase (IC50 values 75.2 microM for prostaglandin E2 and 619 microM for thromboxane B2) and 5-lipoxygenase metabolites, but the effects are greater against leukotriene C4 (IC50 value 63.6 microM). Structure-activity relationships of the three phenylpropanoid glycosides are discussed. Thus, like some other compounds found in medicinal herbs, our molecules possess an array of potentially beneficial anti-eicosanoid properties which may, alongside other constituents, contribute to the claimed therapeutic properties of the plant from which they are derived.

Rofecoxib, a COX-2 inhibitor, does not inhibit human gastric mucosal prostaglandin production

BACKGROUND & AIMS

Rofecoxib, an inhibitor of the inducible cyclooxygenase (COX)-2 enzyme, appears not to cause acute gastroduodenal injury or chronic ulceration. To attribute this to COX-2 selectivity with sparing of gastric mucosal prostaglandin synthesis requires direct proof.

METHODS

Twenty-four healthy, nonsmoking Helicobacter pylori-negative volunteers were randomized to 1 of 2 separate concurrent blinded crossover studies. Sixteen volunteers received rofecoxib, 50 mg once daily, for 5 days in one treatment period and placebo in the other. Eight volunteers similarly received naproxen, 500 mg twice daily, and placebo. On day 5 of each period, antral mucosal prostaglandin E2 (PGE2) synthesis was measured by radioimmunoassay after vortexing for 3 minutes. Whole blood COX-1 activity was measured as serum thromboxane (TXB)2- and COX-2 activity as lipopolysaccharide (LPS)-induced PGE2.

RESULTS

Naproxen decreased gastric mucosal PGE2 synthesis by 65% (90% confidence interval [CI], 53%-74%; P = 0.001 vs. placebo) in contrast to an 18% increase after rofecoxib (90% CI, -11% to 57%; P = 0.313 vs. placebo). Naproxen also significantly inhibited both serum TXB2 by 94% and LPS-induced PGE2 production by 77% (both P < or = 0.002 vs. placebo), but rofecoxib only inhibited COX-2-dependent LPS-induced PGE(2) (by 79%; P < 0.001 vs. placebo).

CONCLUSIONS

Rofecoxib (50 mg) lacked naproxen's ability to reduce the availability of gastroprotective prostaglandins.

A phase II study of the 5-lipoxygenase inhibitor, CV6504, in advanced pancreatic cancer: correlation of clinical data with pharmacokinetic and pharmacodynamic endpoints

PURPOSE

Primary objective was to determine response rate of patients with advanced pancreatic cancer to a novel lipoxygenase and thromboxane A2 synthetase inhibitor (CV6504); secondary objectives included estimation of pharmacokinetics of CV6504, target-enzyme inhibition, safety and tolerance, quality of life and survival.

PATIENTS AND METHODS

Thirty-one patients with advanced pancreatic cancer were planned to receive CV6504, 100 mg TDS, orally for three months, at which point CT scans were performed to assess therapeutic response rates. Steady state concentrations of CV6504 and thromboxane B2 (an indirect measure of thromboxane A2 synthetase (TA2S) inhibition) were made. Of the 31 patients entered into the study, 23 were considered fully evaluable for response.

RESULTS

The drug was well tolerated with few side effects; no partial or complete responses were seen, but 10 patients had stable disease at 3 months; quality of life was maintained during therapy; mean CV6504 steady state plasma concentrations of 14 +/- 6 ng/ml resulting in 75 +/- 18% inhibition of TA2S were achieved; median-survival time for all patients considered eligible for assessment of efficacy was 36.6 weeks after the initial dose of study medication. The actuarial one-year survival was approximately 25%.

CONCLUSION

CV6504 inhibits its target enzyme in vivo, maintains stable disease in 32% of evaluable patients and is well tolerated.

Flurbiprofen and enantiomers in ophthalmic solution tested as inhibitors of prostanoid synthesis in human blood

The purpose of this study was to assess the selectivity and potency of the nonsteroidal anti-inflammatory drug (NSAID), flurbiprofen, and its enantiomers in their inhibition of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). An assay was used with freshly drawn, heparinized human whole blood, incubated with 25 microM calcium ionophore A23187 during 60 min to produce thromboxane B2 (TXB2) by activity of COX-1 in platelets. Incubation with E. coli lipopolysaccharide (LPS) during 24 hr produced prostaglandin E2 (PGE2) by induction of COX-2 in monocytes, suppressing any possible contribution of COX-1 activity by the addition of acetylsalicylic acid. Concentration inhibition curves were determined with racemic, S(+), and R(-) flurbiprofen in final concentrations ranging from 10(-3) to 10(-10) M. The stereoselectivity of S(+) flurbiprofen vs. R(-) flurbiprofen, expressed as the reciprocal of the ratio of the concentrations giving 50% inhibition (IC50), is 340 for COX-1 and 56 for COX-2. The selectivity for COX-1 vs. COX-2, expressed as the reciprocal ratio of the IC50, was 32 for racemic, 16 for S(+), and 5.3 for R(-) flurbiprofen. Meloxicam in the same assay showed COX-2 selectivity with a ratio of 0.19.

Inhibition of prostaglandin E2 and leukotriene C4 in mouse peritoneal macrophages and thromboxane B2 production in human platelets by flavonoids from Stachys chrysantha and Stachys candida

Seven flavonoids of Stachys chrysantha and Stachys candida have been isolated. The structures of the compounds were elucidated by spectroscopic methods, particularly highfield NMR spectroscopy. The effects of the methanol extracts of these two endemic Greek Stachys sp. and their main flavonoids were examined on arachidonic acid (AA) metabolism in the cellular system (mouse peritoneal macrophages and human platelets). Their cytotoxicity on cells was also investigated. Most samples assayed did not exhibit any significant effect on prostaglandin E2 (PGE2)-release from calcium ionophore-stimulated mouse peritoneal macrophages. Only chrysoeriol-7-O-beta-(3''-E-p-coumaroyl)-glucopyranoside, at the highest non-cytotoxic dose (50 microM), inhibited the release of PGE2, but this effect is not statistically significant. The release of leukotriene C4 (LTC4) by mouse peritoneal macrophages stimulated with calcium ionophore was inhibited by a crude extract of S. chrysantha, with an IC50 value of 34.3 microg/ml. Xanthomicrol (IC50 = 29.2 microM) and chrysoeriol-7-O-beta-D-(3''-E-p-coumaroyl)-glucopyranoside (IC50 = 11.1 microM) also inhibited the release of LTC4, although it showed less potency than the reference compound nordihydroguaiaretic acid (NDGA) (IC50 = 2 microM). However, most samples assayed showed a significant effect on thromboxane B2 (TXB2)-release from calcium ionophore-stimulated human platelets, with inhibition percentages slightly lower than the reference drug ibuprofen (IC50 = 7 microM). The IC50 values are: crude extract of S. candida 23.3 microg/ml; crude extract of S. chrysantha 23.1 microg/ml; xanthomicrol 28.8 microM; calcycopterin 2.66 microM and chrysoeriol-7-O-beta-D-(3''-E-p-coumaroyl)-glucopyranoside 8.8 microM. Our results indicate that the selective inhibition of TX-synthase enzyme may be the primary target of action of most of these samples, and one of the mechanisms through which thus exert their antiinflammatory effects.

Cyclosporine-induced coronary artery constriction--dissociation between thromboxane release and coronary vasospasm

Cyclosporine influences vascular tone, including that of coronary arteries. But its effect on myocardial prostanoid release, which may contribute to a drug-induced coronary and/or myocardial dysfunction, remains unknown. We used the isolated perfused rat heart to study the effect of cyclosporine on both the mechanical function parameters and myocardial prostanoid release into the effluent by ELISA. Cyclosporine (5 microM) induced an increase of perfusion pressure from 40 +/- 3 to 73 +/- 4 mm Hg within 60 minutes (p < 0.001), reflecting an increase of coronary tone. Cyclosporine did not affect heart rate but contractility (+dp/dtmax) tended to decrease, although not significantly. The drug's effect on coronary tone was rapidly reversible upon withdrawal. Cyclosporine perfusion resulted in an increase of thromboxane B2 liberation from 236 +/- 150 to 1321 +/- 354 pg/ml effluent (p < 0.001), whereas the 6-keto-prostaglandin F1 alpha release was unaffected. The vehicle cremophor did not change any of these parameters. Neither inhibition of myocardial prostanoid formation with acetylsalicylic acid nor thromboxane receptor blockade prevented the cyclosporine-induced increase of perfusion pressure. However, perfusion with nitroglycerin or the voltage-sensitive calcium channel antagonist nifedipine in addition to cyclosporine were able to prevent the increase of perfusion pressure. This is the first time it has been demonstrated that cyclosporine induces an acute release of the prostanoid thromboxane within the myocardium. Despite the resulting imbalance in favor of the vasoconstrictive prostanoid, a dependency of the cyclosporine-induced increase of coronary tone on this imbalance was excluded. Conversely, nitric oxide donation or calcium channel blockade were able to prevent the negative effect of the drug on coronary tone, supporting the concept of endothelium-dependent and/or myogenic mechanism of cyclosporine toxicity on the coronary vascular bed.

[Isolation of resisting thrombus and arteriosclerosis compounds in leaves of Salix matsudana]

In this paper, three compounds were isolated and identified from the leaves of Salix matsudana. They are apigenin-7-0-beta-D-glucopyranside(I), luteolin-7-0-beta-D-glucopyranside(II), compound III. Compound I and II are isolated firstly from Salix spp., compound III is found firstly in the world. Furthermore, study on effect of arachidonic acid metabolisin in rat platelets by them with radio-chromatography found that they can significantly inhibit the production of 12-HETE(12-hydroxy-5,8, 10,14-eicosatetraenoic acid), which can induce allergy and arteriosclerosis. The production of apigenin-7-0-beta-D-glucopyranside being hydrolyzed was apigenin, it can inhibit TXB2(thromoxane B2) which can induce platelet aggregation.

Synthesis and evaluation of backbone/amide-modified analogs of leualacin

Leualacin (1), a cyclic depsi-pentapeptide, and its backbone/amide-modified analogs 2-4 were synthesized. Amide analogue 3 exhibited stronger vasodilatory effects. It also strongly inhibited collagen- and arachidonic acid (AA)-induced platelet aggregations with IC50s of 0.6 microM and 2.0 microM, respectively.

Antiinflammatory effect of tepoxalin: blood and synovial tissue studied in patients with knee arthrosis

Our aim was to determine the amounts of eicosanoids in blood and synovial tissue of patients with knee arthrosis and to examine the effects of 2 doses of tepoxalin (50 mg twice, 200 mg twice), administered p.o. for 3.5 days. Concentrations of leukotriene B4 (LTB4, LTC4, and thromboxane B2 (TXB2) were measured in blood before and after oral administration of tepoxalin and release of prostaglandin E2 (PGE2), 6-keto-PGF1alpha, and LTC4 was measured in incubation media of synovial tissue, taken at surgery from patients treated with tepoxalin. Radioimmunoassay (RIA) was used to determine the levels of the eicosanoids. LT and TXB2 release was reduced by tepoxalin in both doses used. Under these conditions, PGE2, 6-keto-PGF1alpha, and LTC4 release from synovial tissue was detectable only after stimulation with calcium ionophore A23187. Washed synovial tissue, in which tepoxalin concentrations should be reduced, released higher amounts of all eicosanoids measured than directly incubated synovial tissue did. Pain after tepoxalin administration was significantly reduced. Relevant drug concentrations were detected in plasma and synovial fluid. Tepoxalin was well tolerated and had no marked adverse effects. At 400 mg, tepoxalin is a dual inhibitor of cyclooxygenase (CO) and 5-lipoxygenase (5-LO) in blood and synovial tissue.

Further insights into the anti-aggregating activity of NMDA in human platelets

1. In the present study the effect of N-methyl-D-aspartate (NMDA) on thromboxane B2 synthesis and on [Ca2+]i was studied in human platelets. 2. NMDA (10(-7) M) completely inhibited the synthesis of thromboxane B2 from exogenous arachidonic acid (AA), while it did not interfere with the aggregating effect of the thromboxane A2 receptor agonist U-46619. 3. NMDA (0.1 microM - 10 microM) dose-dependently increased intracellular calcium in washed platelets preloaded with fura 2 AM, and this effect was not additive with that of AA. 4. NMDA shifted the dose-response curve of AA to the right. At the highest AA concentrations platelet aggregation was not inhibited. 5. The antiaggregating effect of NMDA was not antagonized by N(G)-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase (NOS) inhibitor. 6. Finally, NMDA (0.01 nM - 100 nM) associated with either aspirin or indomethacin significantly potentiated the antiaggregating activity of both cyclo-oxygenase inhibitors. 7. It was concluded that NMDA is a potent inhibitor of platelet aggregation and thromboxane B2 synthesis in human platelet rich plasma (PRP).

Ketoconazole in the prevention of acute respiratory distress syndrome

We conducted a critical review of the literature on ketoconazole in preventing acute respiratory distress syndrome (ARDS), a serious disorder associated with high mortality. Two double-blind, prospective, placebo-controlled, randomized trials compared ketoconazole with placebo for prophylaxis of ARDS. In one trial, compared with placebo, ketoconazole resulted in a reduced frequency of ARDS (6% vs 31%, p<0.01), lower plasma thromboxane B2 levels (33 vs 75 pg/ml, p<0.05), and shorter intensive care unit stay (7 vs 15.5 days, p<0.05). In the second trial the drug reduced the frequency of ARDS (15% vs 64%, p=0.002), lowered thromboxane B2 levels (83 vs 143 pg/ml), and reduced mortality (15% vs 39%, p=0.05) compared with placebo. Larger multicenter studies are warranted to validate the findings of these two trials.

Effect of garlic (Allium sativum) on blood lipids, blood sugar, fibrinogen and fibrinolytic activity in patients with coronary artery disease

Thirty patients with coronary artery disease (CAD) were administered garlic (study group) while another 30 patients received the placebo (control group). Various risk parameters were determined at 1.5 and 3 months of garlic administration. Garlic, administered in a daily dose of 2 x 2 capsules (each capsule containing ethyl acetate extract from 1 g peeled and crushed raw garlic), reduced significantly total serum cholesterol and triglycerides, and increased significantly HDL-cholesterol and fibrinolytic activity. There was no effect on the fibrinogen and glucose levels. In vitro effects of the garlic oil on platelet aggregation (PAg) and eicosanoid metabolism were examined; it inhibited PAg induced by several platelet agonists, and also platelet thromboxane formation. Two important paraffinic polysulphides - diallyl disulphide (DADS) and diallyl trisulphide (DATS) - derived from garlic and are usual constituents of garlic oil, showed antiplatelet activity, and also inhibited platelet thromboxane formation. In this respect DATS was more potent than DADS. The nature of inhibition of PAg by DATS was found to be reversible.

Long-term treatment with the dual antithromboxane agent picotamide decreases microalbuminuria in normotensive type 2 diabetic patients

Picotamide both inhibits thromboxane synthetase and acts as a thromboxane antagonist at the receptor level. We investigated the long-term effect of picotamide on urinary albumin excretion (UAE) at rest and induced by exercise in 30 type 2 diabetic patients who were normotensive and had microalbuminuria while at rest. The subjects of our study had a mean age of 52.5 +/- 1.6 years, BMI of 28.5 +/- 0.7 kg/m2, diabetes duration of 9.1 +/- 1.8 years, and HbA1c of 7.0 +/- 0.8%. The study was a randomized double-blind placebo-controlled trial. The patients were randomly allocated to receive for 1 year either picotamide, 300 mg, 3 tablets/day, or placebo, 3 tablets/day. The patients were asked to visit our outpatient clinic after 1, 3, 6, 9, and 12 months of treatment. At all times, blood pressure, microalbuminuria at rest, blood glucose, serum creatinine, serum picotamide, and creatinine clearance were measured; at baseline and after 6 and 12 months, all patients underwent submaximal physical exercise. After 6 months of picotamide, baseline and exercise-induced microalbuminuria were significantly decreased (up to one-third) as compared with the baseline and placebo level, with no further drops at month 12 of picotamide treatment. On placebo treatment, UAE at rest and after exercise was slightly increased compared with baseline values. The effects of picotamide occurred without significant side effects or changes in either blood pressure levels or glycometabolic control. Our study is the first long-term intervention trial in type 2 diabetes showing that an antithromboxane agent is able to decrease microalbuminuria, which in this disease is a dual marker of macro- and microangiopathy. Our findings suggest an important role for thromboxane in the pathophysiology of microalbuminuria in diabetes; moreover, we hypothesize that antithromboxane agents may have a place in the treatment/prevention of both macro- and microvascular complications in type 2 diabetic patients.

ACE inhibitor effects on platelet function in stages I-II hypertension

Angiotensin II enhances platelet aggregation through activation of the G protein-linked pathway present in platelets. Studies of several angiotensin-converting enzyme (ACE) inhibitors have demonstrated marked differences on platelets. Therefore this prospective, randomized, double-blind, crossover study compared the ex vivo effects of equivalent antihypertensive doses of captopril, enalapril, and fosinopril on platelet aggregation and thromboxane B2 (TxB2) formation in subjects with stage I-II essential hypertension. Nineteen male subjects with a baseline mean seated blood pressure of 141 +/- 3/100 +/- 1 mm Hg were enrolled. The decline in mean arterial pressure after 4 weeks of stable dosing was 10 +/- 1, 12 +/- 1, and 11 +/- 1 mm Hg for captopril, enalapril, and fosinopril, respectively (p = NS). There was no significant change in adenosine diphosphate (ADP)-, epinephrine-, or thrombin-stimulated platelet aggregation from baseline or between ACE inhibitors. Compared with baseline, fosinopril decreased TxB2 concentrations 27.5-67.6% with all stimuli after 1 and 5 min. Captopril also decreased TxB2 formation, but this effect was stimulus and time dependent. Enalapril consistently increased TxB2 concentrations, independent of stimuli or time. We conclude that different ACE inhibitors have distinct effects on platelet TxB2 formation without significant effects on platelet aggregation. Fosinopril may be a direct antagonist ofTxA2 synthase, suggesting benefit in syndromes of platelet activation or vascular occlusion.

Comparison of the cyclooxygenase-1 inhibitory properties of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors, using sensitive microsomal and platelet assays

Two forms of cyclooxygenase (COX) activity are involved in the synthesis of prostaglandins, prostacyclins, and thromboxanes in mammalian cells. There is now convincing evidence, obtained with a number of structurally distinct inhibitors, that selective COX-2 inhibitors possess anti-inflammatory effects with an improved gastrointestinal tolerability compared with conventional nonsteroidal anti-inflammatory drugs (NSAIDs) affecting both COX-1 and COX-2. As more selective COX-2 inhibitors are being developed, assays with a high degree of sensitivity to inhibition are needed to compare the relative effects of compounds on COX-1 activity. In the present report, we describe a sensitive assay for the inhibition of human COX-1 based on the production of prostaglandin E2 by microsomes from U937 cells incubated with a subsaturating concentration of arachidonic acid. More than 45 NSAIDs and selective COX-2 inhibitors were tested in this assay. IC50 values ranged from 1 nM for flunixin and flurbiprofen to about 200-500 microM for salicylate and acetaminophen. Potent and nonselective NSAIDs such as sulindac sulfide, diclofenac, and indomethacin showed IC50 values of < 20 nM. Among the compounds that have been reported to show selectivity for COX-2, the rank order of potency against COX-1 was DuP 697 > SC-58451 > celecoxib > nimesulide-meloxicam-piroxicam-NS-398-RS-57067 > SC-57666 > SC-58125 > flosulide > etodolac > L-745,337 > DFU-T-614, with IC50 values ranging from 7 nM to 17 microM. A good correlation was obtained between the IC50 values for the inhibition of microsomal COX-1 and both the inhibition of TXB2 production by Ca2+ ionophore challenged platelets and the inhibition of prostaglandin E2 production by CHO cells stably expressing human COX-1. However, the microsomal assay was more sensitive to inhibition than cell-based assays and allowed the detection of inhibitory effects on COX-1 for all NSAIDs and selective COX-2 inhibitors examined with discrimination of their potency under conditions of limited availability of arachidonic acid.

Increased spontaneous release of tumour necrosis factor-alpha by alveolar macrophages from wheezy infants

We determined if alveolar macrophages (AMs) from infants with severe recurrent wheezing episodes release increased amounts of tumour necrosis factor-alpha (TNF-alpha), as described in adults with asthma. We compared TNF-alpha release by unstimulated and lipopolysaccharide-stimulated AMs obtained by bronchoalveolar lavage in 13 wheezy and seven nonwheezy infants (aged 6-36 months) and analysed its regulation by dexamethasone. Metabolites in cell supernatants were quantified by enzyme-linked immunosorbent assay (ELISA) (TNF-alpha) or radioimmunoassay (thromboxane B2 and prostaglandin E2). Comparison of results was performed by the Mann-Whitney U-test and values were expressed as median (interquartile range) in ng x 10(6) cells(-1). Resting AMs from wheezy infants released larger amounts of TNF-alpha and thromboxane B2 as compared to controls: 2.67 (0.89-8.33) vs 0.48 (0.25-1.08) and 75.63 (38.07-158.91) vs 10.03 (7.36-76.08), respectively (p<0.05). When stimulated overnight with bacterial lipopolysaccharide, AMs from both groups released similar amounts of metabolites. Dexamethasone induced a consistent inhibition of the lipopolysaccharide-stimulated release of all the mediators. Our results show that alveolar macrophages from wheezy infants are activated to release increased amounts of tumour necrosis factor-alpha, as in asthma, and suggest that infants with recurrent wheezing may eventually benefit from treatment with glucocorticoids.

Complement activation and thromboxane secretion by liposome-encapsulated hemoglobin in rats in vivo: inhibition by soluble complement receptor type 1

Intravenous administration of liposome-encapsulated hemoglobin (LEH) in rats led to an early (within 15 min) decline of hemolytic complement (C) activity in the plasma along with a significant, parallel rise in thromboxane B2 (TXB2) levels. The TXB2 response was inhibited by co-administration of soluble C receptor type 1 (sCR1) with LEH, as well as by C depletion with cobra venom factor. These observations provide evidence for a causal relationship between LEH-induced C activation and TXB2 release, and suggest that sCR1 could be useful in attenuating the acute respiratory, hematological and hemodynamic side effects of LEH described earlier in the rat.