Inhibitory Effect Of Indomethacin Research Articles

Doxorubicin-loaded redox-responsive micelles based on dextran and indomethacin for resistant breast cancer.

Multidrug resistance (MDR) against chemotherapeutic agents has become one of the major obstacles to successful cancer therapy and MDR-associated proteins (MRPs)-mediated drug efflux is the key factor for MDR. In this study, a redox-responsive polymer based on dextran (DEX) and indomethacin (IND), which could reduce MRPs-mediated efflux of chemotherapeutics, was synthesized, and the obtained polymer could spontaneously form stable micelles with well-defined core-shell structure and a uniform size distribution with an average diameter of 50 nm and effectively encapsulate doxorubicin (DOX); the micelles contain a disulfide bridge (cystamine, SS) between IND and DEX (DEX-SS-IND). In vitro drug release results indicated that DEX-SS-IND/DOX micelles could maintain good stability in a stimulated normal physiological environment and promptly depolymerized and released DOX in a reducing environment. After incubating DEX-SS-IND/DOX micelles with drug-resistant tumor (MCF-7/ADR) cells, the intracellular accumulation and retention of DOX were significantly increased under the synergistic effects of redox-responsive delivery and the inhibitory effect of IND on MRPs. In vitro cytotoxicity showed that DEX-SS-IND/DOX micelles exhibited higher cytotoxicity against MCF-7/ADR cells. Moreover, DEX-SS-IND/DOX micelles showed significantly enhanced inhibition of tumor in BALB/c nude mice bearing MCF-7/ADR tumors and reduced systemic toxicity. Overall, the cumulative evidence indicates that DEX-SS-IND/DOX micelles hold significant promise for overcoming MDR for cancer therapy.

Chemosensitizing indomethacin-conjugated dextran-based micelles for effective delivery of paclitaxel in resistant breast cancer therapy.

Multidrug resistance (MDR) against chemotherapeutic agents has become the major obstacle to successful cancer therapy and multidrug resistance-associated proteins (MRPs) mediated drug efflux is the key factor for MDR. Indomethacin (IND), one of the non-steroidal anti-inflammatory agents, has been demonstrated to increase cytotoxic effects of anti-tumor agents as MRP substrates. In this study, dextran-g-indomethacin (DEX-IND) polymeric micelles were designed to delivery paclitaxel (PTX) for the treatment of MDR tumors. The DEX-IND polymer could effectively encapsulate PTX with high loading content and DEX-IND/PTX micelles present a small size distribution. Compared with free PTX, the release of PTX from DEX-IND/PTX micelles could be prolonged to 48 h. Cellular uptake test showed that the internalization of DEX-IND/PTX micelles by drug-sensitive MCF-7/ADR cells was significantly higher than free PTX benefiting from the inhibitory effect of IND on MRPs. In vitro cytotoxicity test further demonstrated that DEX-IND/PTX micelles could enhance the cytotoxicity of PTX against MCF-7/ADR tumor cells. In vivo pharmacokinetic results showed that DEX-IND/PTX micelles had longer systemic circulation time and slower plasma elimination rate in comparison to PTX. The anti-tumor efficacy test showed that DEX-IND/PTX micelles exhibited greater tumor growth-inhibition effects on MDR tumor-bearing mice, with good correlation between in vitro and in vivo. Overall, the cumulative evidence indicates that DEX-IND/PTX micelles hold significant promise for the treatment of MDR tumors.

Central Administration of Indomethacin Mitigates the Injury-Induced Upregulation of Aromatase Expression and Estradiol Content in the Zebra Finch Brain.

Injury to the vertebrate brain causes neuroinflammation, characterized in part by increases in prostaglandins. In rodents and songbirds, brain injury also induces the transcription and translation of aromatase in reactive astrocytes around the site of damage. Interestingly, this induction is more rapid in female zebra finches relative to males. Induced aromatization is neuroprotective, as inhibition of aromatase and estrogen replacement, increases and decreases the extent of damage, respectively. Although the consequences of induced astrocytic aromatization are intensely studied, little is known about what factors induce aromatase. Inflammation is sufficient to induce astrocytic aromatase suggesting that the link between inflammation and aromatase expression may be causal. To test this hypothesis, adult male and female zebra finches received bilateral mechanical injuries through which either the cyclooxygenase (COX)-1/2 inhibitor indomethacin or vehicle was administered into contralateral hemispheres. Subjects were killed either 6 or 24 hours after injury. In both sexes, an enzyme immunoassay for prostaglandin E2 (PGE2) revealed that indomethacin decreased PGE2 relative to the contralateral hemisphere at both time points, suggesting that the dose and mode of administration used were successful in affecting neuroinflammation locally. Indomethacin reduced aromatase expression and 17β-estradiol (E2) content at 6 hours but not 24 hours following injury in females. However, in males, the inhibitory effect of indomethacin on aromatase and E2 was apparent at 24 but not 6 hours after treatment. These data suggest that COX activity, perhaps via consequent prostaglandin secretion, may induce aromatase expression and central E2, an effect that is detectable in temporally distinct patterns between sexes.

Abstract 13513: Roles of Endothelium-Dependent Hyperpolarization in Pulmonary Microcirculation in Mice

Background: The endothelium modulates vascular tone by synthesizing and releasing endothelium-derived relaxing factors, including prostacycline (PGI 2 ), nitric oxide (NO), and endothelium-dependent hyperpolarization (EDH). Although it is widely known that EDH plays an important role in systemic microcirculation, its role in pulmonary microcirculation remains largely unknown. Furthermore, although pulmonary hypertension (PH) is recognized as a progressive vasculopathy, the initiating mechanisms of the vasculopathy also remain to be elucidated. In this study, we thus aimed to elucidate the role of EDH in pulmonary microcirculation. Methods and Results: We performed experiments with isolated perfused mouse lungs. Isolated whole lungs were prepared from control mice and chronic hypoxic mice (10% O 2 for 1, 2 and 28 days). We evaluated the contribution of PGI 2 , NO, and EDH in isolated lungs by the inhibitory effect of indomethacin (Indo, 10 -5 mol/L), N ω -nitro-L-arginine (L-NNA, 10 -4 mol/L), and apamin (Apa, 10 -6 mol/L) plus charybdotoxin (CTx, 10 -7 mol/L), respectively. In control mice, endothelium-dependent relaxations to bradykinin (BK, 10 -5 mol/L) were resistant to Indo or L-NNA, but were highly sensitive to the combination of Apa and CTx, indicating the primary role of EDH in pulmonary microcirculation. Endothelium-dependent relaxations to BK were significantly reduced in the presence of L-NNA in mice exposed to hypoxia for one day, indicating a transition from EDH to NO in BK-mediated relaxations before developing PH. Importantly, endothelium-independent relaxations were subsequently reduced in the lungs from hypoxic mice for 2 and 28 days compared with normoxic lungs. Conclusions: These results indicate that EDH-mediated relaxations play primary roles in pulmonary microcirculation under physiological conditions and that hypoxia rapidly impairs EDH-mediated responses followed by vascular smooth muscle dysfunctions in pulmonary microcirculation. These findings may provide clues to elucidate the initiating mechanisms of hypoxia-induced PH.

PHARMACOLOGICAL INVESTIGATION OF THE CHLOROFORM EXTRACTS OF ALSTONIA SCHOLARIS (L.) R.BR

Chloroform extracts of Alstonia scholaris leaves (CLAS ) and stem barks ( CSAS ) have been evaluated for their analgesic, antimicrobial, antioxidant and cytotoxic activity. Acetic acid induced writhing method was used for evaluating analgesic activity . Both the extracts had reduced pain in dose dependent manner, at all the test ed doses (200 and 400 mg/kg body weight) . Maximum writhing inhibition (75.33 %) was observed at 400 mg/kg dose of CSAS while for CLAS, 400 mg/kg dose exhibited 70.13 % inhibition . The inhibitory effect of indomethacin (45.92 %) was lower than that of the highest dose of CLAS and CSAS. Antimicrobial activity of the extract s was evaluated against various Gram - positive, Gram - negative bacteria and fungi using disk diffusion technique. The average zone of inhibition exhibited by extract was found 10 - 1 4 mm and Kanamycin (30 μg/disc) was used as standard. Antioxidant potentiality of the extracts was investigated on DPPH scavenging activity and t he IC 50 value was found 47.72 µg/ml, 62.03 µg/ml and 45.77 µg/ml for CSAS, CLAS and standard ascorbic acid , respectively. Cytotoxic st udy was done by brine shrimp lethality bioassay and compared with LC 50 ( 8.90 μg/ml. ) values of standard vincristin sulphate as a positive control. The cytotoxicity exhibited CLAS and CSAS were promising with LC 50 value of 10.21 μg/ml and 9.12 μg/ml, respec tively. The se results suggest into the plant extracts could be used as a potential therapeutics in many pathological conditions.

Indomethacin Serves as a Potential Inhibitor of Protein Phosphatases

Background/Aims: We have shown that indomethacin has the potential to activate Ca2+/ calmodulin-dependent protein kinase II (CaMKII), regardless of cyclooxygenase (COX) inhibition. To understand the underlying mechanism, the present study investigated the effect of indomethacin on protein phosphatases such as protein phosphatase 1 (PP1), protein phosphatase 2A (PP2A), and protein tyrosine phosphatase 1B (PTP1B). Methods: Activity of CaMKII was assayed in cultured rat hippocampal neurons and under the cell-free conditions. Activities of protein phosphatases were monitored under the cell-free conditions. Indomethacin binding assay was carried out using a fluorescein-conjugated indomethacin. Results: Indomethacin enhanced CaMKII activity in cultured rat hippocampal neurons, that is abolished the CaMKII inhibitor KN-93. In the cell-free assay, no CaMKII activation was obtained with indomethacin, but indomethacin otherwise inhibited PP1 in a concentration (10 µM-1 mM)-dependent manner, the maximum reaching 70% of basal levels. This indicates that indomethacin indirectly activates CaMKII due to PP1 inhibition. Likewise, indomethacin still inhibited PP2A and PTP1B in a concentration (10 µM-1 mM)-dependent manner, reaching 80 and 10% of basal levels at 1 mM, respectively. In the indomethacin binding assay, indomethacin bound to all the investigated protein phosphatases. Conclusion: The results of the present study indicate that indomethacin inhibits PP1, PP2A, and PTP1B, possibly through its direct binding and that the inhibitory effect of indomethacin on PP1 could cause indirect CaMKII activation. This may represent the novel indomethacin action.

Impairment of acetylcholine-mediated endothelium-dependent relaxation in isolated parotid artery of the alloxan-induced diabetic rabbit

The aim of this study was to assess the effect of type 1 diabetes mellitus (induced by a single intravenous injection of 100 mg kg(-1) of alloxan) on acetylcholine (ACh)-induced relaxation in isolated rabbit parotid gland feeding artery. Isometric force measurements and quantification of inducible nitric oxide synthase (iNOS) mRNA by real-time RT-PCR were made in parotid artery rings from diabetic and control rabbits. Acetylcholine induced concentration- and endothelium-dependent vasorelaxation that was significantly decreased in parotid artery rings from diabetic rabbits. Schild analysis of the ACh vasorelaxant effect, in the presence of selective muscarinic receptor antagonists, revealed involvement of the M(3) receptor subtype in parotid artery rings from both control and diabetic rabbits, with no change in antagonist affinity constants. The inhibitory effects of indomethacin, a non-selective inhibitor of cyclooxygenase, and of high potassium, an inhibitor of hyperpolarization, on ACh vasorelaxation were increased. The effect of N(G) -nitro-l-arginine, a non-selective inhibitor of NOS, was decreased in diabetes. S-methylisothiourea, a selective inhibitor of iNOS, significantly reduced ACh vasorelaxation only in parotid artery rings from diabetic rabbits. Also, up-regulation of iNOS mRNA expression was detected in parotid artery rings from diabetic rabbits. These results suggest that in parotid artery rings from diabetic rabbits, impaired endothelium-dependent vasorelaxation to ACh appears to be caused by the loss of a nitric oxide-mediated component and increased iNOS expression, and is unlikely to be caused by a change at the M(3) receptor level.

Stimulation of PGE2 synthesis and water and electrolyte secretion by senna anthraquinones is inhibited by indomethacin.

The effect of dried senna pod extract, containing 10% sennoside B, on colonic electrolyte and fluid transport was examined in the anaesthetized rat in-situ. Oral administration of senna pod extract dose-dependently (17.5-30 mg kg-1, calculated as sennoside B) reversed net absorption of water, sodium and chloride to net secretion and increased potassium secretion. Senna pod extract stimulated the output of prostaglandin E2 into the colonic lumen. Inhibition of prostaglandin biosynthesis by pretreatment of the rats with indomethacin (10 mg kg-1) significantly inhibited the effects of senna pod extract (17.5-30 mg kg-1) both on net fluid transport and on prostaglandin E2 synthesis. The inhibitory effect of indomethacin on net fluid transport induced by senna pod extract (30 mg kg-1) was dose-dependent. It is concluded that anthraquinones exert their laxative action at least partially via stimulation of colonic fluid and electrolyte secretion, and that this secretion is mediated by stimulation of endogenous prostaglandin E2 formation.

Reversal by prostaglandin E2 of the inhibitory effect of indomethacin on contractions of guinea-pig ileum induced by angiotensin.

Reversal by prostaglandin E2 of the inhibitory effect of indomethacin on contractions of guinea-pig ileum induced by angiotensin.

ACh- and VIP-induced vasorelaxation in rabbit facial artery after carotid artery occlusion

Objectives The influence of carotid artery occlusion (10, 30 and 60 min) on regulatory mechanisms implicated in the vasorelaxant responses of isolated glandular branch of rabbit facial artery to acetylcholine (ACh) and vasoactive intestinal polypeptide (VIP) was examined. Design In organ bath studies with arterial rings precontracted with phenylephrine (1 μM), before and after carotid artery occlusion, changes in isometric tension were recorded. Results Endothelium-dependent vasorelaxation by ACh and endothelium-independent vasorelaxation by VIP were significantly reduced, started from 30 and 10 min of carotid occlusion, respectively. Inhibitory effect of indomethacin on ACh vasorelaxation was enhanced whilst effect of N G-nitro- l-arginine reduced, started from 30 min of carotid occlusion. Sodium nitroprusside-induced vasorelaxation was not changed after carotid occlusion. Inhibition of VIP vasorelaxation by l-N ω-nitroarginine-2,4- l-diaminobutyric-amide, was reduced, started from 30 min of carotid occlusion. Forskolin enhanced VIP-induced vasorelaxation in control rings but this effect was reduced started from 30 min of occlusion. In the presence of VIP, vasorelaxant effect of ACh was increased; the increase was reduced, started from 10 min of carotid occlusion. Conclusions The present investigation provides evidence for the decreased responsiveness to both, ACh-endothelium-dependent and VIP-endothelium-independent vasorelaxation in rabbit facial artery after carotid occlusion. In addition, the data suggest that ischaemia alters contribution of endothelial nitric oxide (eNO) and prostaglandin to ACh, and vascular smooth muscle's cAMP and neuronal NO to VIP vasorelaxant effects.

Role of cyclooxygenase in vasodilation of retinal blood vessels induced by bradykinin in Brown Norway rats

We investigated the role of cyclooxygenase (COX) in bradykinin (BK)-induced vasodilation of retinal blood vessels in Brown Norway rats using a novel in vivo fluorescent fundus imaging technique. Under artificial ventilation, the animals were treated with tetrodotoxin, and the decreased blood pressure and heart rate were adjusted to the normal ranges by infusing pressor agents. Diameters of retinal blood vessels contained in the fluorescent fundus images were measured. Intravenous infusion of BK (1–30 µg/kg/min) increased diameters of retinal blood vessels and decreased blood pressure in a dose-dependent manner. The retinal vasodilator responses to BK were significantly attenuated by treatment with either indomethacin, a non-selective COX inhibitor, or nimesulide, a selective COX-2 inhibitor, but not with SC-560, a selective COX-1 inhibitor. These COX inhibitors failed to affect the depressor responses to BK. Under conditions of nitric oxide (NO) synthase blockade with N G-nitro- l-arginine methyl ester, no inhibitory effects of indomethacin on BK-induced vasodilation of retinal blood vessels were observed. These results suggest that the vasodilator effects of BK on retinal blood vessels are partly mediated through a COX-2-dependent pathway in Brown Norway rats. The prostanoid-dependent component of BK-induced retinal vasodilator response seems to be mediated by a mechanism that involves NO.

Prostaglandin F2alpha Stimulates 11Beta-Hydroxysteroid Dehydrogenase 1 Enzyme Bioactivity and Protein Expression in Bovine Endometrial Stromal Cells1

11Beta-hydroxysteroid dehydrogenase (HSD11B) enzymes have important roles in regulating cortisol availability in target tissues. We previously demonstrated that HSD11B1 is expressed and active in bovine endometrium and that cortisol suppresses prostaglandin (PG) F2alpha and PGE2 production in cultured bovine endometrial stromal cells. The present study was conducted to examine whether locally synthesized PGF2alpha and/or PGE2 regulates the enzymatic bioactivity and/or the expression of HSD11B1 in bovine endometrium. The conversion rate of cortisone to cortisol in cultured endometrial stromal cells was significantly stimulated by PGF2alpha (1 and 10 microM). In a dose-dependent manner, PGF2alpha but not PGE2 increased the net conversion of cortisone to cortisol in stromal cells after 4 h of treatment. In addition, the bioactivity of HSD11B1 was significantly inhibited by indomethacin (10 microM). The inhibitory effect of indomethacin on HSD11B1 bioactivity was abolished by PGF2alpha (1 microM) but not by PGE2. Although PGF2alpha (1 microM) did not affect the expression of HSD11B1 mRNA in cultured stromal cells, it significantly stimulated the protein expression of HSD11B1. Cycloheximide, a general translational inhibitor, abolished the stimulatory effects of PGF2alpha on HSD11B1 protein expression in endometrial stromal cells, indicating that PGF2alpha increases HSD11B1 protein expression by stimulating a posttranscriptional process rather than a transcriptional mechanism. These results demonstrate that PGF2alpha but not PGE2 increases HSD11B1 bioactivity and protein expression by stimulating a posttranscriptional mechanism in stromal cells and suggest that cortisol has a physiologically relevant role in preventing excessive uterine PG production in nonpregnant bovine endometrium.

Growth inhibitory effects of indomethacin on human colon cancer cells are mediated, in-part, by effects on beta-catenin

Growth inhibitory effects of indomethacin on human colon cancer cells are mediated, in-part, by effects on beta-catenin

Effects of esomeprazole on glutathione levels and mitochondrial oxidative phosphorylation in the gastric mucosa of rats treated with indomethacin

Proton pump inhibitors exert their preventive and healing effects on gastropathy induced by nonsteroidal anti-inflammatory drug (NSAIDs) by a dual action: the antisecretory and the antioxidant effect. The latter was investigated by using esomeprazole against indomethacin-induced gastric mucosa lesions in rats and assessed by a histomorphometric analysis. Treatment by intragastric gavage were 1% methocel as vehicle; esomeprazole 10, 30, or 60 micromol/kg; indomethacin 100 micromol/kg; and esomeprazole 10, 30, or 60 micromol/kg plus indomethacin 100 micromol/kg. The evaluation of glutathione (GSH) levels and respiratory chain complex activities [nicotinamide adenine dinucleotide, reduced (NADH)-ubiquinone oxidoreductase, succinate dehydrogenase, cytochrome C reductase, cytochrome oxidase] was performed in the isolated gastric mucosa. Esomeprazole (10-60 micromol/kg) dose dependently reversed, up to complete recovery, the inhibitory effect of indomethacin on GSH levels (approximately 60% inhibition) and mitochondrial enzyme activities (inhibition ranging from 60% to 75%). Indomethacin-induced mucosal injuries were reduced by esomeprazole. Thus, in addition to inhibiting acid secretion, the gastroprotective effect of esomeprazole can be ascribed to a reduction in gastric oxidative injury.

Indomethacin induces small intestinal damage and inhibits amitrole-associated thyroid carcinogenesis in rats initiated with N-bis(2-hydroxypropyl)nitrosamine

Effects of intestinal damage on thyroid carcinogenesis due to amitrole (AT) were examined in F344 male rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). In experiment 1, rats were provided with diet containing 0.03% AT for 20 weeks after a single subcutaneous injection of DHPN (2800 mg/kg body weight), and concomitantly received 0.01% indomethacin (IM) in the diet to cause small intestinal damage or 1% dextran sodium sulfate (DSS) in the drinking water for induction of colitis following a schedule of intermittent 1-week administration and 1-week withdrawal for a total of 10 times. Groups without AT- and/or IM or DSS treatment were also included. Histopathological examination revealed significant reduction in the incidence and multiplicity of follicular cell adenomas and adenocarcinomas in the group concomitantly treated with IM, but no change in the DSS group, as compared with the AT alone group. In experiment 2, rats were similarly fed diet containing AT for 3 weeks with concomitant IM or DSS treatment after a DHPN initiation, and serum thyroid stimulating hormone levels were found to be significantly elevated only in the IM case. The increase in thyroid follicular cell proliferation due to AT was also clearly suppressed in the group concomitantly treated with IM. From these findings, IM-induced intestinal damage may inhibit thyroid carcinogeneisis in rats, although contributions of other factors, such as a direct inhibitory effect of IM to thyroid follicular cell proliferation cannot be ruled out.

Enhancement of Transformed Foci and Induction of Prostaglandins in Balb/c 3T3 Cells by Palytoxin: In Vitro Model Reproduces Carcinogenic Responses in Animal Models Regarding the Inhibitory Effect of Indomethacin and Reversal of Indomethacin's Effect by Exogenous Prostaglandins

Cell transforming activity of palytoxin, a non-TPA type tumor-promoter, was investigated with the two-stage transformation assay using Balb/c 3T3 cells. Palytoxin showed potent promoting activity; treatment at 1.9 pM or more increased the number of transformed foci after initiation by 3-methylcholanthrene (MCA). Determination of prostaglandin (PG) E2 and PGF(2alpha) concentrations in the culture medium revealed that palytoxin (1.9-3.7 pM for 24 h) stimulated the production of PG in Balb/c 3T3 cells (the concentration reached 3-4 microM), and treatment with PGE2 or PGF(2alpha) itself increased the number of transformed foci of Balb/c 3T3 cells after initiation by MCA. Neither palytoxin nor PGs showed initiating activity. Indomethacin suppressed the promoting activity of palytoxin, but not that of PGE2 and PGF(2alpha). Interestingly, concomitant treatment with PGE2 or PGF(2alpha) in addition to indomethacin markedly reversed the suppressive effect of indomethacin. These findings indicated that the in vitro transformation model could reproduce experiments that have been performed in animal models regarding the inhibitory effect of indomethacin on carcinogenic responses and reversal of indomethacin's effect by exogenous prostaglandin and, therefore, may provide insight into molecular modes of action of palytoxin. In the present study, palytoxin also induced prostaglandin synthesis, and therefore, the Balb/c 3T3 cell model should provide insight into the molecular mechanism by which palytoxin regulates prostaglandin biosynthesis.

Cellular mechanisms of acetaminophen: role of cyclo‐oxygenase

Acetaminophen is one of the most commonly used drugs for the safe and effective treatment of pain and fever. Acetaminophen works by lowering cyclo-oxygenase products preferentially in the central nervous system, where oxidant stress is strictly limited. However, the precise mechanism of action for acetaminophen on cyclo-oxygenase activity is debated. Two theories prevail. First, it is suggested that acetaminophen selectively inhibits a distinct form of cyclo-oxygenase, cyclo-oxygenase-3. Second, it is suggested that acetaminophen has no affinity for the active site of cyclo-oxygenase but instead blocks activity by reducing the active oxidized form of cyclo-oxygenase to an inactive form. Here, we have used an in vitro model of cyclo-oxygenase-2 activity (A549 cells stimulated with IL-1beta) to show that acetaminophen is an effective inhibitor of cyclo-oxygenase activity in intact cells. However, acetaminophen, unlike nonsteroidal anti-inflammatory drugs (NSAIDs), cannot inhibit activity in broken cell preparations. The inhibitory effects of acetaminophen were abolished by increasing intracellular oxidation conditions with the cell-permeable hydroperoxide t-butylOOH. Similarly the inhibitory effects of the cyclo-oxygenase-2 selective inhibitor rofecoxib or the mixed cyclo-oxygenase-1/cyclo-oxygenase-2 inhibitors ibuprofen and naproxen were significant reduced by t-butylOOH. By contrast, the inhibitory effects of indomethacin or diclofenac, which also inhibit both cyclo-oxygenase-1 and cyclo-oxygenase-2, were unaffected by t-butylOOH. These observations dispel the notion that cyclo-oxygenase-3 is involved in the actions of acetaminophen and provide evidence that supports the theory that acetaminophen interferes with the oxidation state of cyclo-oxygease. Moreover, they suggest for the first time that the inhibitory effects of some NSAIDs, including the newly introduced cyclo-oxygenase-2 selective inhibitor rofecoxib, owe part of their inhibitory actions to effects on oxidation state of cyclo-oxygenase. Our data with t-butylOOH and NSAIDs illustrates an, as yet, undeveloped therapeutic window for the "cyclo-oxygenase inhibitor". Specifically, combining active site selectively with actions on enzyme oxidation state would allow for a broader range of tissue selective drugs.

Cyclooxygenase-pathway participates in the regulation of regional cerebral blood flow in response to neuronal activation under normo- and hypercapnia

The present study was designed to investigate whether cyclooxygenase products are involved in the regulation of the regional cerebral blood flow, evoked by somatosensory activation (evoked rCBF) under normo- and hypercapnia. Indomethacin (IMC) was used as cyclooxygenase inhibitor. It was applied intravenously (i.v., 10 mg/kg/h) in two experimental protocols—before hypercapnia (i) and after hypercapnia (ii). Somatosensory activation was induced by electrical hind paw stimulation (5 Hz frequency, 5 s duration, 1.5 mA). The evoked rCBF-response was measured in α -chloralose anesthetized rats using laser-Doppler flowmetry. IMC abolished completely the effect of hypercapnia on the baseline level of CBF. The drug reduced significantly evoked rCBF-response also. The inhibitory effect of IMC on evoked rCBF-response is better expressed under normocapnia (∼70%) than that under hypercapnia (∼40%). After IMC application, the normalized evoked rCBF curves peaked earlier as compared to that before its application ( P<0.05), although the rise time of 0.5 s was nearly constant regardless of stimulus frequency. In conclusion, the results suggest a participation of IMC-sensitive and cyclooxygenase-dependent mechanisms in the regulation of evoked rCBF, induced by somatosensory stimulation.

Short-term regulation of basolateral organic anion uptake in proximal tubular OK cells: EGF acts via MAPK, PLA(2), and COX1.

The organic anion transport system of the kidney is of major importance for the excretion of a variety of endogenous compounds, drugs, and potentially toxic substances. The basolateral uptake into proximal tubular cells is mediated by a tertiary active transport system. Epidermal growth factor (EGF) leads to an increase in the basolateral uptake rate of the model substrate para-aminohippuric acid (PAH) in opossum kidney (OK) cells. This stimulation is mediated by successive activation of the mitogen-activated protein kinases,mitogen-activated/extracellular signal-regulated kinase kinase (MEK) and extracellular regulated kinase isoforms 1 and 2 (ERK1/2). This study investigates the regulatory network of EGF action on PAH uptake downstream ERK1/2 in more detail. EGF stimulation of the basolateral uptake rate of [(14)C]PAH was abolished by the phospholipase A(2) inhibitor AACOCF3.[(14)C]PAH uptake was enhanced by arachidonic acid. Furthermore, EGF led to an increase in arachidonic acid release and to the generation of prostaglandins. AACOCF3 did not influence EGF-induced ERK1/2 activation, indicating that ERK1/2 is upstream of PLA(2). In addition, EGF stimulated the influx of extracellular Ca(2+). However, Ca(2+)-influx was not required for the stimulatory action of EGF on [(14)C]PAH uptake. Inhibitors of COX and lipoxygenases reduced [(14)C]PAH uptake dose-dependently, whereas inhibition of cytochrome P450 did not. In the presence of indomethacin, EGF had no stimulatory effect on [(14)C]PAH uptake. The inhibitory effect of indomethacin was not due to competitive action on PAH uptake. Furthermore, prostaglandin E(2) (PGE(2)) increased basolateral [(14)C]PAH uptake rate dose-dependently, and this increase was also observed in the presence of indomethacin. Selective inhibition of COX2 by indomethacin amid or indomethacin n-heptyl ester did not inhibit [(14)C]PAH uptake, whereas selective inhibition of COX1 dose-dependently inhibited [(14)C]PAH uptake. This and previous data lead to the conclusion that EGF successively activates MEK, ERK1/2, and PLA(2), leading to an increased release of arachidonic acid. Subsequently, arachidonic acid is metabolized to prostaglandins via COX1, which then mediate EGF-induced stimulation of basolateral organic anion uptake rate.

Effects of indomethacin on energy metabolism in rat and human jejunal tissue in vitro

Non-steroidal anti-inflammatory drugs (NSAIDs) are known to cause enteropathy, but the mechanism by which this toxicity occurs is less well established. This paper sets out to test the hypothesis that these drugs affect oxidative phosphorylation in jejunal tissue, thereby interfering with energy metabolism and rendering the tissue vulnerable to damage. Jejunal tissue obtained from rats and humans was used for in vitro determinations of oxygen uptake, lactate production and energy charge levels in the presence of indomethacin, a commonly used NSAID. In the rat jejunal tissue, drug concentrations of 0.5 mM and 2.5 mM produced significant decreases in oxygen uptake (P<0.01) and energy charge levels in the tissue (P<0.05). There was a corresponding increase in lactate production by the tissue at these indomethacin concentrations (P<0.05). Rat jejunum examined by electron microscopy after incubation with various concentrations of indomethacin showed ultrastructural effects of the drug on mitochondrial morphology. In human tissue, an inhibitory effect of indomethacin on oxygen uptake was seen, but the effects on lactate production and energy charge were less conclusive. These findings suggest that indomethacin affects mitochondria and thereby impairs energy metabolism in jejunal tissue.