Systematic pharmacological approach to the characterization of NSAIDs

Colorectal Cancer Chemoprevention: A Dream Coming True?

Colorectal cancer (CRC) is one of the deadliest forms of cancer worldwide. CRC development occurs mainly through the adenoma-carcinoma sequence, which can last decades, giving the opportunity for primary prevention and early detection. CRC prevention involves different approaches, ranging from fecal occult blood testing and colonoscopy screening to chemoprevention. In this review, we discuss the main findings gathered in the field of CRC chemoprevention, focusing on different target populations and on various precancerous lesions that can be used as efficacy evaluation endpoints for chemoprevention. The ideal chemopreventive agent should be well tolerated and easy to administer, with low side effects. Moreover, it should be readily available at a low cost. These properties are crucial because these compounds are meant to be used for a long time in populations with different CRC risk profiles. Several agents have been investigated so far, some of which are currently used in clinical practice. However, further investigation is needed to devise a comprehensive and effective chemoprevention strategy for CRC.

COX-2-Derived Prostaglandin E2 Produced by Pyramidal Neurons Contributes to Neurovascular Coupling in the Rodent Cerebral Cortex

Vasodilatory prostaglandins play a key role in neurovascular coupling (NVC), the tight link between neuronal activity and local cerebral blood flow, but their precise identity, cellular origin and the receptors involved remain unclear. Here we show in rats that NMDA-induced vasodilation and hemodynamic responses evoked by whisker stimulation involve cyclooxygenase-2 (COX-2) activity and activation of the prostaglandin E2 (PgE2) receptors EP2 and EP4. Using liquid chromatography-electrospray ionization-tandem mass spectrometry, we demonstrate that PgE2 is released by NMDA in cortical slices. The characterization of PgE2 producing cells by immunohistochemistry and single-cell reverse transcriptase-PCR revealed that pyramidal cells and not astrocytes are the main cell type equipped for PgE2 synthesis, one third expressing COX-2 systematically associated with a PgE2 synthase. Consistent with their central role in NVC, in vivo optogenetic stimulation of pyramidal cells evoked COX-2-dependent hyperemic responses in mice. These observations identify PgE2 as the main prostaglandin mediating sensory-evoked NVC, pyramidal cells as their principal source and vasodilatory EP2 and EP4 receptors as their targets.

SIGNIFICANCE STATEMENT

Brain function critically depends on a permanent spatiotemporal match between neuronal activity and blood supply, known as NVC. In the cerebral cortex, prostaglandins are major contributors to NVC. However, their biochemical identity remains elusive and their cellular origins are still under debate. Although astrocytes can induce vasodilations through the release of prostaglandins, the recruitment of this pathway during sensory stimulation is questioned. Using multidisciplinary approaches from single-cell reverse transcriptase-PCR, mass spectrometry, to ex vivo and in vivo pharmacology and optogenetics, we provide compelling evidence identifying PgE2 as the main prostaglandin in NVC, pyramidal neurons as their main cellular source and the vasodilatory EP2 and EP4 receptors as their main targets. These original findings will certainly change the current view of NVC.

COX-2-Derived Prostaglandin E2 Produced by Pyramidal Neurons Contributes to Neurovascular Coupling in the Rodent Cerebral Cortex

Vasodilatory prostaglandins play a key role in neurovascular coupling (NVC), the tight link between neuronal activity and local cerebral blood flow, but their precise identity, cellular origin and the receptors involved remain unclear. Here we show in rats that NMDA-induced vasodilation and hemodynamic responses evoked by whisker stimulation involve cyclooxygenase-2 (COX-2) activity and activation of the prostaglandin E2 (PgE2) receptors EP2 and EP4. Using liquid chromatography-electrospray ionization-tandem mass spectrometry, we demonstrate that PgE2 is released by NMDA in cortical slices. The characterization of PgE2 producing cells by immunohistochemistry and single-cell reverse transcriptase-PCR revealed that pyramidal cells and not astrocytes are the main cell type equipped for PgE2 synthesis, one third expressing COX-2 systematically associated with a PgE2 synthase. Consistent with their central role in NVC, in vivo optogenetic stimulation of pyramidal cells evoked COX-2-dependent hyperemic responses in mice. These observations identify PgE2 as the main prostaglandin mediating sensory-evoked NVC, pyramidal cells as their principal source and vasodilatory EP2 and EP4 receptors as their targets.

SIGNIFICANCE STATEMENT

Brain function critically depends on a permanent spatiotemporal match between neuronal activity and blood supply, known as NVC. In the cerebral cortex, prostaglandins are major contributors to NVC. However, their biochemical identity remains elusive and their cellular origins are still under debate. Although astrocytes can induce vasodilations through the release of prostaglandins, the recruitment of this pathway during sensory stimulation is questioned. Using multidisciplinary approaches from single-cell reverse transcriptase-PCR, mass spectrometry, to ex vivo and in vivo pharmacology and optogenetics, we provide compelling evidence identifying PgE2 as the main prostaglandin in NVC, pyramidal neurons as their main cellular source and the vasodilatory EP2 and EP4 receptors as their main targets. These original findings will certainly change the current view of NVC.

Herb-drug interactions between Scutellariae Radix and mefenamic acid: Simultaneous investigation of pharmacokinetics, anti-inflammatory effect and gastric damage in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Scutellariae Radix (SR), the dried root of Scutellariae baicalensis Georgi, has a lot in common with non-steroidal anti-inflammatory drugs (NSAIDs). Their similarities in therapeutic action (anti-inflammation) and metabolic pathways (phase II metabolisms) may lead to co-administration by patients with the potential of pharmacokinetic and/or pharmacodynamic interactions. The current study aims to investigate the potential interactions between SR and an NSAID, mefenamic acid (MEF), on the overall pharmacokinetic dispositions, anti-inflammatory effects and adverse effects in rats.

MATERIALS AND METHODS

The current study simultaneously monitored the pharmacokinetic and pharmacodynamic interactions in a single animal. Four groups of Sprague-Dawley rats (n=7 each) received oral doses of a standardized SR extract (300mg/kg, twice daily), MEF (40mg/kg, daily), combination of SR extract and MEF, and vehicle control, respectively, for 5 days. On Day 5, blood samples were collected after first dose over 24h for the determination of (1) plasma concentrations of SR bioactive components, MEF and its metabolites by LC-MS/MS, and (2) prostaglandin E2 (PGE2) production and cyclooxygenase-2 (COX-2) gene expression by ex vivo analyses using LPS-stimulated RAW264.7 macrophage cells, ELISA and real time-PCR. After the rats were sacrificed, stomachs were isolated to assess their gross mucosal damage. Statistical comparisons were conducted using ANOVA and t-test.

RESULTS

Minimal pharmacokinetic interaction between SR extract and MEF was observed. Co-administration of SR extract and MEF did not significantly alter the plasma concentration-time profile or the pharmacokinetic parameters such as Cmax, AUC0→24, Tmax or clearance. Pharmacodynamic interaction via the COX-2 pathway was observed. The PGE2 level in LPS-stimulated RAW264.7 cells treated with plasma collected from control group over the 24h sampling (AUC0→24[PGE2]) was 191981±8789pg/mlhr, which was significantly reduced to 174,780±6531 and 46,225±1915pg/mlhr by plasma collected from rats administered with SR extract and MEF, respectively. Co-administration of SR extract and MEF further potentiated the PGE2 inhibition, with an AUC0→24[PGE2] of 37013±2354pg/mlhr (p<0.05, compared to SR or MEF group). By analyzing the COX-2 gene expression, SR extract significantly prolonged the COX-2 inhibitory effect of MEF over the 24h (p<0.05). Furthermore, the MEF-induced stomach ulcer after the 5-day treatment, as evidenced by the increased gross ulcer index and sum of lesion length (p<0.05, compared to control), could be alleviated by co-administration with SR extract (p<0.05).

CONCLUSIONS

Co-administration of SR extract and MEF potentiated the anti-inflammatory effects, alleviated the MEF-induced stomach adverse effect while having minimal pharmacokinetic interactions. Our findings provide insight for combination therapy of SR extract and MEF against inflammatory diseases.

Anti-bovine viral diarrhoea virus and hepatitis C virus activity of the cyclooxygenase inhibitor SC-560

BACKGROUND

A number of compounds were examined for their inhibitory effect on bovine viral diarrhoea virus (BVDV) replication in cell cultures and found that some cyclooxygenase (COX) inhibitors had antiviral activity against the virus.

METHODS

Determination of compounds for their anti-BVDV activity was on the basis of the inhibition of virus-induced cytopathogenicity in Mardin-Darby bovine kidney (MDBK) cells. Anti-hepatitis C virus (HCV) activity was assessed by the inhibition of viral RNA synthesis in the subgenomic HCV RNA replicon cells.

RESULTS

Among the test compounds, 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole (SC-560) was the most active against BVDV, and its 50% effective and cytotoxic concentrations were 10.9 +/-2.8 and 93.9 +/-24.5 microM in virus and mock-infected MDBK cells, respectively. The compound also suppressed BVDV RNA synthesis in a dose-dependent fashion. Studies on the mechanism of action revealed that SC-560 did not interfere with viral entry to the host cells. Furthermore, it was assumed that the antiviral activity of SC-560 was not associated with its inhibitory effect on COX. The combination of SC-560 and interferon-alpha was additive to synergistic in inhibiting BVDV replication. More importantly, the compound proved to be a selective inhibitor of HCV replication.

CONCLUSIONS

SC-560 and its derivative might have potential as novel antiviral agents against HCV.

Differential inhibition of cyclooxygenase isoenzymes in the cat by the NSAID robenacoxib

Robenacoxib is a new nonsteroidal anti-inflammatory drug (NSAID) developed for use in companion animal medicine. The objectives of this study were: to quantify the inhibitory actions of robenacoxib on cyclooxygenase (COX) isoenzymes in feline whole blood assays; to establish blood concentration-time profiles of robenacoxib after intravenous and subcutaneous dosing in the cat and; to predict the time courses of inhibition of COX isoforms by robenacoxib. COX-1 and COX-2 activities in heparinized feline whole blood samples were induced with calcium ionophore and lipopolysaccharide, respectively. Inhibition of thromboxane B2 provided a marker of both COX-1 and COX-2 activities and a nonlinear parametric mixed effects modelling approach was used to establish the pharmacodynamic parameters describing this inhibition. Mean values (and prediction intervals) of IC50 were 28.9 (16.4-51.1) microM (COX-1) and 0.058 (0.010-0.340) microM (COX-2). These parameters were used to compute several selectivity indices. Selectivity IC ratios (COX-1:COX-2) were 502.3 (IC50/IC50), 451.6 (IC95/IC95) and 17.05 (IC20/IC80). Based on a clinically recommended dosage regimen of 2 mg/kg, it was predicted that the corresponding mean robenacoxib blood concentration over the first 12 h after drug administration corresponded to 5% inhibition of COX-1 and 90% inhibition of COX-2.

Novel selective inhibitors of hydroxyxanthone derivatives for human cyclooxygenase-2

AIM

To screen the selective inhibitors for human cyclooxygenase-2 ((h)COX-2) utilizing molecular simulation.

METHODS

Eight xanthone derivatives, compounds A-H, were employed by the structure-based research methodology. Resveratrol and NS-398 were selected as the control compounds for COX-1 and COX-2, respectively. The docking results were scored and the interaction energies of the complexes were calculated by CHARMm forcefield.

RESULTS

NS-398 could not dock into the active site of COX-1. However, resveratrol, the specific selective compound for COX-1, gained lower interaction energy while docked in COX-1. The lower interaction energies were investigated, while compound B and F were docked into the catalytic sites of COX-1 and COX-2, respectively. Compound A, 1,3,6,7-tetrahydroxyxanthone, revealed high inhibitory potency to both COX-1 and COX-2.

CONCLUSION

The conformations of the docking would influence the values of interaction energies. The hydrogen bond could also increase the stability of the whole complex, which might suggest that compound B had a suitable conformation in the tunnel-like active site of COX-1. Compound F, a potent agent for COX-2, revealed a strong hydrogen bond with Ser516 in human COX-2 to form a stable complex.

[In vitro effects of diclofenac and selective cyclooxygenase-2 inhibitors on prostaglandin release from inflamed bursa subacromialis tissue in patients with subacromial syndrome]

BACKGROUND

To compare the in vitro effects of selective COX-2 inhibitors (L-745,337, NS-398 and DFU) and of COX-unspecific diclofenac on release of PGE(2 )and 6-keto-PGF(1alpha) from inflamed bursa subacromialis tissue (IBST) obtained from a total of 35 patients with shoulder impingement syndrome (SIS).

PATIENTS AND METHODS

Bursal specimens were incubated in the presence of drugs (0.01-1000 microM) for 20 min and 16 h.

RESULTS

After 20 min 10 microM diclofenac significantly inhibited formation of PGE(2) and 6-keto-PGF(1alpha), whereas L-745,337 and NS-398 (10-1000 microM) induced significant inhibition only at concentrations > or =100 microM. In contrast to equimolar diclofenac, DFU (0.01-10 microM) induced no inhibition of bursal PGE(2) release but a dose-dependent, although statistically not significant inhibition after 16 h. The inhibitory potency of diclofenac (0.01-10 microM) was even more increased during long-term incubation showing greater inhibition than DFU at all concentrations studied.

CONCLUSION

The data suggest that in IBST in SIS in vitro the majority of PG is generated via the COX-1 pathway.

Effect of mefenamic acid on controlling irregular uterine bleeding in DMPA users

The objective of this double-blind, placebo-controlled study was to evaluate the effect of mefenamic acid and placebo on controlling irregular uterine bleeding in depot-medroxyprogesterone acetate (DMPA) users. A total of 48 DMPA users attending the Family Planning Clinic, Chulalongkorn Hospital were studied, all had abnormal bleeding. These participants were randomly divided into two groups. A total of 23 users received mefenamic acid, 500 mg, twice a day for 5 days, and placebos were given to the other 25 in the same manner. Total days of bleeding and spotting and percentage of women in whom bleeding was stopped were analyzed in the first and the fourth week. Percentage of subjects in whom bleeding was stopped during the first week after initial treatment was significantly higher in the mefenamic acid group than the placebo group (69.6%, 40.0%; p < 0.05). During the follow-up period (4 weeks after initial treatment), the mean of the bleeding-free interval during 28 days was found to be 16.1 days in the subjects treated with mefenamic acid and 12.39 days in the placebo group. However, the difference was not statistically significant. From the results of the study, we concluded that mefenamic acid was effective in very short-term control of bleeding during DMPA use, but not effective long-term.

Participation of cyclooxygenase-1 in prostaglandin E2 release from synovitis tissue in primary osteoarthritis in vitro

OBJECTIVES

To investigate the relative contribution of the cyclooxygenase (COX) isoenzymes COX-1 and COX-2 to prostaglandin E2 (PGE2) release from inflamed synovial tissue in N=10 patients with primary osteoarthritis (OA) in vitro and to determine possible effects of COX inhibitors on the gene expression of synovial COX-1 and COX-2.

DESIGN

The effects of a COX-unspecific nonsteroidal anti-inflammatory drug (NSAID; diclofenac), a selective COX-1 inhibitor (SC-560) and a selective COX-2 inhibitor (SC-58125) on PGE2 release from inflamed synovial tissue (0.1-10 microM, 3 and 6 h incubation time) were compared. Release of PGE2 into the incubation media was measured by means of the enzyme-linked immunosorbent assay. Expression of synovial COX-1/-2 was quantified by means of real-time reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

All agents inhibited synovial PGE2 release dose-dependently. Compared to short-term incubations, the inhibitory potency of diclofenac, SC-58125 and SC-560 was increased (0.1-10 microM) and decreased (0.1-1 microM), respectively, during 6 h: At 10 microM, SC-560 and SC-58125 had obviously lost their specificity for COX-1 and COX-2, respectively, indicated by a comparable inhibitory potency of the selective COX-1 inhibitor (86.6%) and the selective COX-2 inhibitor (96.6%) within identical tissue specimens. In contrast, at 1 microM, 83% and 62.8% inhibition was seen for diclofenac and SC-58125, respectively. SC-560 showed 30.6% inhibition (P<0.05). In contrast to synovial COX-1, RT-PCR revealed a significant induction of COX-2 through PGE2.

CONCLUSIONS

With respect to the concentrations studied, the data suggest that in inflamed synovial tissue in OA, up to 30% of PGE2 might be generated via the COX-1 pathway. In therapy of OA, the relative contribution of COX-1 in synovial inflammation should be considered, weighing the potency of COX-unspecific NSAID against the assumed superior gastrointestinal safety profile of selective COX-2 inhibitors.

The development of COX2 inhibitors

Aspirin, arguably the world's favourite drug, has been around since the late nineteenth century, but it wasn't until the late 1970s that its ability to inhibit prostaglandin production by the cyclooxygenase enzyme was identified as the basis of its therapeutic action. Early hints of a second form of the cyclooxygenase that was differentially sensitive to other aspirin-like drugs ultimately ushered in an exciting era of drug discovery, culminating in the introduction of an entirely new generation of anti-inflammatories. This article reviews the story of this discovery and looks at the future of cyclooxygenase pharmacology.

Volume-induced natriuresis in healthy women: renal metabolism of prostacyclin and thromboxane, and physiological role of prostanoids

In healthy women submitted to a short-term expansion in extracellular fluid volume we have evaluated the urinary excretory profile of the stable metabolites of prostaglandin(PG) I2 and thromboxane(TX) A2, 6-keto-PGF1 alpha(6KPGF) and TXB2 respectively, and assessed the physiological role played by the prostanoids in this experimental condition. Salt retention (SR group, n=9) was induced by repeated i.v. infusion of saline solution (0.9% NaCl). At the end of the treatment the body weight had increased by 0.7+/-0.2 kg (mean+/-SEM) (P<0.05). Renal functional exploration [clearance (cl.) method] was performed during hypotonic polyuria (induced by oral water load) and subsequent moderate antidiuresis (induced by low-dose infusion of an antidiuretic hormone analogue). Urinary 6KPGF and TXB2 concentrations were estimated by RIA method during polyuria (P cl. period), early and late antidiuresis (A1 and A2 cl. periods). Paired functional explorations were performed in absence (control study) and presence of indomethacin. Basal values of plasma sodium and potassium concentrations, plasma renin activity (PRA) and urinary aldosterone excretion were determined just before the control study. The results in salt retention were compared to those previously obtained in healthy women submitted to a moderate salt depletion (SD2 group, n=6), in absence and presence of the drug. Women in salt retention received 100 mg i.m. of the drug, whereas salt-depleted women received only a halved dose as in previous studies in salt depletion the full dose produced prolonged anuria. (I) Salt retention vs salt depletion. The basal values of PRA and urinary aldosterone excretion were significantly lower. During polyuria, urinary excretion of 6KPGF, 6KPGF/TXB2 ratio, urinary flow rate, creatinine cl. and absolute and fractional excretions of sodium and chloride were significantly higher. In salt retention during polyuria, significant positive correlations were found between 6KPGF excretion and functional excretory parameters. (II) Indomethacin in salt retention. The following effects were significant: (a) a reduction in prostanoid excretions in P and A1 cl. periods only; (b) during polyuria, an increase in arterial pressure, a reduction in urinary flow rate and creatinine cl. (saluresis showed not significant reduction). During polyuria significant positive correlations occurred between the absolute effects of indomethacin on 6KPGF excretion and those on functional excretory parameters. (III) Comparative effects of indomethacin in salt retention and salt depletion. Despite the double dosage of the drug, the significant reductions in urinary metabolite excretions were not significantly different during P cl. period and significantly lower in A1 cl. period compared to the corresponding significant reductions in salt depletion. During polyuria, the significant increase in arterial pressure was significantly different from the not significant effect in salt depletion; the not significant effect on saluresis was significantly different from the significant reduction in salt depletion. The results suggest the following conclusions: (1) The present model showed the functional pattern of the volume-natriuresis; (2) In salt retention, in contrast with salt depletion, indomethacin induced an increase in arterial pressure consistent with the inhibition of a PG-dependent vasodilator mechanism active at the systemic level; (3) In salt retention, in contrast with salt depletion, indomethacin failed to induce a significant reduction in saluresis. This failure can be attributed to the drug's blunted effectiveness in inhibiting the renal synthesis of saluretic PGs, and probably to the interference of the concurrent increase in arterial pressure in the renal treatment of sodium and chloride.

In vitro effects of nonsteroidal anti-inflammatory drugs on cyclooxygenase activity in dogs

OBJECTIVE

To establish an in vitro assay and determine the differential suppressive activity of non steroidal anti-inflammatory drugs (NSAID) on cyclooxygenase (COX)-1 and COX-2 isoenzymes in dogs.

PROCEDURE

COX activity was evaluated in the presence and absence of 4 NSAID (meloxicam, tolfenamic acid, carprofen, and ketoprofen), using a canine monocyte/macrophage cell line that constitutively expresses COX-1, but can be induced to express COX-2 when incubated with lipopolysaccharide. Inhibition of prostaglandin E2 TPGE2) synthesis by each NSAID was measured by enzyme immunoassay and attributed to specific COX-1 or COX-2 activity through assessment of COX messenger RNA expression by use of northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). The COX selectivity of each drug was evaluated from dose-response curves by calculating a ratio (COX-1:COX-2) of inhibitory concentration values on the basis of concentrations that reduced PGE2 by 50% in each COX model.

RESULTS

Meloxicam and tolfenamic acid preferentially inhibited COX-2, with meloxicam inhibiting COX-2 activity 12 times more effectively than COX-1 activity. Carprofen was only 1.75 times more selective for COX-2 than for COX-1, and ketoprofen was slightly more selective for COX-1.

CONCLUSIONS

COX-1 and COX-2 were differentially sensitive to inhibition in vitro by NSAID. Meloxicam and tolfenamic acid were selective for COX-2. Effects of carprofen and ketoprofen approached equipotency against both isoenzymes. Selective COX-2 inhibitors are a new class of drugs with anti-inflammatory effects similar to conventional NSAID but with fewer adverse effects. Development of these agents for veterinary use would be facilitated by the convenience of using a canine cell line as a model system to screen COX-1 and COX-2 inhibitor activities in vitro.