Evidence against the participation of a pharmacokinetic interaction in the protective effect of single-dose curcumin against gastrointestinal damage induced by indomethacin in rats.

OBJECTIVE: To determine the role of a pharmacokinetic interaction in the protective effect of curcumin against the gastric damage induced by indomethacin administration as such or as its prodrug acemetacin. METHODS: Wistar rats orally received single dose of indomethacin (30 mg/kg) with and without curcumin (30 mg/kg); gastric injury was evaluated by determining the total damaged area. Additional groups of rats received an oral single dose of indomethacin (30 mg/kg) or its prodrug acemetacin (34.86 mg/kg) in the presence or absence of curcumin (30 mg/kg). Indomethacin and acemetacin concentrations in plasma from blood draws were determined by high-performance liquid chromatography.Plasma concentration-against-time curves were constructed, and bioavailability parameters, maximal concentration (Cmax) and area under the curve to the last sampling time (AUC0-t) were estimated. RESULTS: Concomitant administration of indomethacin and curcumin resulted in a significantly reduced gastric damage compared to indomethacin alone. However, co-administration of curcumin did not produce any significant alteration in the bioavailability parameters of indomethacin and acemetacin after administration of either the active compound or the prodrug. CONCLUSION: Curcumin exhibits a protective effect against indomethacin-induced gastric damage, but does not produce a reduction of the bioavailability of this nonsteroidal anti-inflammatory drug, indomethacin. Data thus suggest that a pharmacokinetic mechanism of action is not involved in curcumin gastroprotection.

Nitric oxide-releasing indomethacin enhances susceptibility to Trypanosoma cruzi infection acting in the cell invasion and oxidative stress associated with anemia.

Trypanosoma cruzi is the causative agent of Chagas disease. Approximately 8 million people are thought to be affected with this disease worldwide. T. cruzi infection causes an intense inflammatory response, which is critical for the control of parasite proliferation and disease development. Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) are an emergent class of pharmaceutical derivatives with promising utility as chemopreventive agents. In this study, we investigated the effect of NO-indomethacin on parasite burden, cell invasion, and oxidative stress in erythrocytes during the acute phase of infection. NO-indomethacin was dissolved in dimethyl formamide followed by i.p. administration of 50 ppm into mice 30 min after infection with 5×10(3) blood trypomastigote forms (Y strain). The drug was administered every day until the animals died. Control animals received 100 µL of drug vehicle via the same route. Within the NO-indomethacin-treatment group, parasitemia and mortality (100%) were higher and oxidative stress in erythrocytes, anemia, and entry of parasites into macrophages were significantly greater than that seen in controls. Increase in the entry and survival of intracellular T. cruzi was associated with inhibition of nitric oxide production by macrophages treated with NO-indomethacin (2.5 µM). The results of this study provide strong evidence that NO-NSAIDs potently inhibit nitric oxide production, suggesting that NO-NSAID-based therapies against infections would be difficult to design and would require caution.

Acemetacin antinociceptive mechanism is not related to NO or K+ channel pathways.

Indomethacin is a nonsteroidal anti-inflammatory drug (NSAID) used for the treatment of acute gout and inflammation. However, its use is limited due to side effects. Acemetacin is a prodrug of indomethacin that exhibits better gastric tolerability in preclinical and clinical trials. The aim of this study was to examine if the systemic administration of acemetacin involved the sequential participation of nitric oxide (NO) or K+ channel pathways to confer its antinociceptive effect, as compared to indomethacin. The antinociceptive effect of both drugs was studied with the formalin test. Equimolar doses of acemetacin or indomethacin were administered orally. The intraplantar administration of either L-NAME, glibenclamide, apamin or charybdotoxin plus indomethacin or acemetacin was studied using the formalin test and the anti-inflammatory and antihyperalgesic effects were measured. The antinociceptive effect of acemetacin or indomethacin was not significantly different when pretreatment with L-NAME, glibenclamide, apamin or charybdotoxin was done. The antihyperalgesic and antiinflammatory effects were also similar for both indomethacin and acemetacin. Our results suggest that the antinociceptive effect of indomethacin or acemetacin is not mediated by NO or K+ channel activation.

Lipid-core nanocapsules restrained the indomethacin ethyl ester hydrolysis in the gastrointestinal lumen and wall acting as mucoadhesive reservoirs.

The aim of this work was to investigate if the indomethacin ethyl ester (IndOEt) released from lipid-core nanocapsules (NC) is converted into indomethacin (IndOH) in the intestine lumen, intestine wall or after the particles reach the blood stream. NC-IndOEt had monomodal size distribution (242 nm; PDI 0.2) and zeta potential of -11 mV. The everted rat gut sac model showed IndOEt passage of 0.16 micromol m(-2) through the serosal fluid (30 min). From 15 to 120 min, the IndOEt concentrations in the tissue increased from 6.13 to 27.47 micromol m(-2). No IndOH was formed ex vivo. A fluorescent-NC formulation was used to determine the copolymer bioadhesion (0.012 micromol m(-2)). After NC-IndOEt oral administration to rats, IndOEt and IndOH were detected in the gastrointestinal tract (contents and tissues). In the tissues, the IndOEt concentrations decreased from 459 to 5 microg g(-1) after scrapping, demonstrating the NC mucoadhesion. In plasma (peripheric and portal vein), in spleen and liver, exclusively IndOH was detected. In conclusion, after oral dosing of NC-IndOEt, IndOEt is converted into IndOH in the intestinal lumen and wall before reaching the blood stream. The complexity of a living system was not predicted by the ex vivo gut sac model.

Pharmacokinetics of acemetacin and its active metabolite indomethacin in rats during acute hepatic damage and liver regeneration.

BACKGROUND AND AIM: The pharmacokinetics of acemetacin, a non-steroidal anti-inflammatory drug which is biotransformed to indomethacin by hepatic first-pass effect, was examined during the necrotic and regeneration phases resulting from acute hepatitis induced by carbon tetrachloride (CCl4). MATERIAL AND METHODS: Acute hepatitis was induced by oral CCl4 administration to male Wistar rats. On days 0, 1 and 3 after the insult, liver histological analysis was performed, biochemical markers of liver damage and regeneration were measured, and the pharmacokinetics of oral acemetacin and of its active metabolite, indomethacin, were determined. RESULTS: One day after CCl4 administration, liver necrosis was apparent and there was an increase in the circulating levels of indicators of liver damage and regeneration with regard to control conditions. Acemetacin bioavailability was increased, although not in a statistically significant manner. On the other hand, indomethacin bioavailability was significantly reduced. By day 3, histological analysis revealed liver recovery, although not complete, while biochemical indicators of hepatic damage had reverted either totally or partially. Markers of liver regeneration were still increased. Bioavailability acemetacin and indomethacin was comparable to control values. IN CONCLUSION: Indomethacin bioavailability after oral administration of its precursor, acemetacin, is significantly reduced by acute hepatitis produced by CCl4. Pharmacokinetic alterations, as liver damage, are reversible, but do not require complete liver regeneration to return to basal conditions.

Pharmacokinetic evaluation of indomethacin ethyl ester-loaded nanoencapsules.

Goals were to evaluate indomethacin ethyl ester-nanoencapsules (IndOEt-NC) pharmacokinetics in rats and the in vivo ester conversion to indomethacin (IndOH). After i.v. and oral administration exclusively IndOH was detected in plasma. The AUC(IndOEt-NC)/AUC(IndOH) ratio after i.v. dosing was 0.68, accounting for dose and molecular weight differences, probably due to increased IndOH clearance after IndOEt-NC administration (alpha=0.05). The results confirm that antiedematogenic activity reported for IndOEt-NC is due to IndOH. Encapsulation did not protect the ester which in vivo is rapidly released and converted to IndOH, acting as a pro-drug.

Lack of effects of acemetacin on signalling pathways for leukocyte adherence may explain its gastrointestinal safety.

BACKGROUND AND PURPOSE: Acemetacin is a non-steroidal anti-inflammatory drug which is rapidly bioconverted to indomethacin, but produces significantly less gastric damage than indomethacin. This study was performed to investigate several possible mechanisms that could account for the gastrointestinal tolerability of acemetacin. EXPERIMENTAL APPROACH: The gastric and intestinal damaging effects of acemetacin and indomethacin were examined in the rat. Effects of the drugs on blood levels of leukotriene B(4) and thromboxane B(2), on leukocyte-endothelial adherence in post-capillary mesenteric venules, and on gastric expression of tumour necrosis factor-alpha (TNF-alpha) were determined. The two drugs were also compared for gastric toxicity in rats pretreated with inhibitors of COX-2 and NOS. KEY RESULTS: Acemetacin induced significantly less gastric and intestinal damage than indomethacin, despite markedly suppressing COX activity. Indomethacin, but not acemetacin, significantly increased leukocyte adherence within mesenteric venules, and gastric expression of TNF-alpha. Pretreatment with L-nitro-arginine methyl ester or lumiracoxib increased the severity of indomethacin-induced gastric damage, but this was not the case with acemetacin. CONCLUSIONS AND IMPLICATIONS: The increased gastric and intestinal tolerability of acemetacin may be related to the lack of induction of leukocyte-endothelial adherence. This may be attributable to the reduced ability of acemetacin to elevate leukotriene-B(4) synthesis and TNF-alpha expression, compared to indomethacin, despite the fact that acemetacin is rapidly bioconverted to indomethacin after its absorption.

Selective cytotoxicity of indomethacin and indomethacin ethyl ester-loaded nanocapsules against glioma cell lines: an in vitro study.

Gliomas are the most common and devastating tumors of the central nervous system. Several studies have suggested that nonsteroidal anti-inflammatory drugs (NSAIDs) are promising anticancer agents. Biodegradable nanoparticulate systems have received considerable attention as potential drug delivery vehicles. The aim of this study was to evaluate the effects of indomethacin-loaded nanocapsules and indomethacin ethyl ester-loaded nanocapsules on glioma cell lines. In addition, the effect of these formulations on normal neural tissue was also evaluated. In order to investigate this, glioma cell lines (U138-MG and C6) and hippocampal organotypic cultures were used. The main finding of the present study is that indomethacin-loaded nanocapsules formulation was more potent than a solution of indomethacin in decreasing the viability and cell proliferation of glioma lines. Indomethacin and indomethacin ethyl ester associated together in the same nanocapsule formulation caused a synergic effect decreasing glioma cell proliferation. In addition, when the glioma cells were exposed to 25 microM of indomethacin-loaded nanocapsules or indomethacin ethyl ester-loaded nanocapsules, a necrotic cell death was observed. Interestingly, 5 microM of indomethacin-loaded nanocapsules was able to cause an antiproliferative effect without promoting necrosis in glioma cells. Another important finding was that the cytotoxic effect induced by 25 microM or 50 microM of indomethacin-loaded nanocapsules or indomethacin ethyl ester-loaded nanocapsules, in glioma cells was not observed in the organotypic cultures, indicating selective cytotoxicity of those formulations for tumoral cells. Further investigations using in vivo glioma model should be helpful to confirm the distinct effects of indomethacin-loaded nanocapsules and indomethacin ethyl ester-loaded nanocapsules, in normal versus tumoral cells.

Mechanisms underlying the anti-inflammatory activity and gastric safety of acemetacin.

BACKGROUND AND PURPOSE: Acemetacin is regarded as a pro-drug of indomethacin and induces significantly less gastric damage but the reasons for this greater gastric safety of acemetacin are unclear. The anti-inflammatory effects of acemetacin have been attributed, at least in part, to its hepatic biotransformation to indomethacin. The aim of this study was to determine the effects of acemetacin and indomethacin in an in vivo model of acute inflammation and to examine the importance of biotransformation of acemetacin (to indomethacin) to its anti-inflammatory actions. EXPERIMENTAL APPROACH: The zymosan airpouch model was used in rats. Indomethacin or acemetacin (2.7-83.8 micromol kg(-1)) were administered orally or directly into the pouch. Leukocyte infiltration, prostaglandin (PG) E(2) and leukotriene (LT) B(4) levels in exudates, and whole blood thromboxane (TX) B(2) synthesis were measured. KEY RESULTS: Acemetacin was rapidly converted to indomethacin after its administration. Both acemetacin and indomethacin elicited comparable, dose-dependent reductions of leukocyte infiltration and of PGE(2) and TXB(2) synthesis. However, indomethacin induced more gastric damage than acemetacin and elevated LTB(4) production in the airpouch. CONCLUSIONS AND IMPLICATIONS: The similar effects of acemetacin and indomethacin on leukocyte infiltration and PG synthesis are consistent with rapid biotransformation of acemetacin to indomethacin. Some of this biotransformation may occur extra-hepatically, for instance in inflammatory exudates. Acemetacin probably exerts actions independent of conversion to indomethacin, given the different effects of these two drugs on LTB(4) production. Such differences may contribute to the relative gastric safety of acemetacin compared to indomethacin.

Evaluation of the interaction between acemetacin and opioids on the hargreaves model of thermal hyperalgesia.

It has been shown that the association of opioids analgesic agents with non-steroidal anti-inflammatory drugs (NSAIDs) can increase their antinociceptive activity, allowing the use of lower doses and thus limiting side effects. Therefore, the goal of the present study was to examine the possible pharmacological interaction between acemetacin and two opioids in the Hargreaves model of thermal hyperalgesia in the mouse. Acemetacin, codeine, nalbuphine or fixed-dose ratios acemetacin-codeine and acemetacin-nalbuphine combinations were administrated systemically to mice and the antihyperalgesic effect was evaluated using the thermal hyperalgesia test. All treatments produced a dose-dependent antihyperalgesic effect. ED40 values were estimated for all the treatments and an isobologram was constructed. The derived theoretical ED40 for the acemetacin-codeine and acemetacin-nalbuphine combinations were 55.9+/-4.9 mg/kg and 40.3+/-3.8 mg/kg, respectively, being significantly higher than the actually observed experimental ED40, 14.5+/-1.7 mg/kg and 12.7+/-2.2 mg/kg, respectively. These results correspond to synergistic interactions between acemetacin and opioids on the Hargreaves model of thermal hyperalgesia. Highest doses of the individual drugs or the combinations did not affect motor coordination in the balancing test on a rota-rod. Data suggest that low doses of the acemetacin-opioids combination can interact synergistically at systemic level and therefore this drugs association may represent a therapeutic advantage for the clinical treatment of inflammatory pain.

Physico-chemical characterization and in vivo evaluation of indomethacin ethyl ester-loaded nanocapsules by PCS, TEM, SAXS, interfacial alkaline hydrolysis and antiedematogenic activity.

Nanocapsules are vesicular drug carriers constituted of an oil core, a polymeric wall, and surfactants. A general understanding about the influence of the polymeric wall of nanocapsules on the release profiles of drugs is not known. So, this work was devoted to characterize formulations prepared without polymer or containing it at different concentrations. The indomethacin ethyl ester was used as model and the strategy was based on its interfacial alkaline hydrolysis simulating a sink condition for the release. The antiedematogenic activity in rats for ester-loaded-nanocarriers was also evaluated. The nanocapsules (NC) and nanoemulsion (NE) presented particle sizes below 300 nm, polydispersity lower than 1.2 and pH around 5. SAXS analyses showed that the sorbitan monostearate is dissolved in the oil and the polymer presents regions of crystallinity independently on the PCL concentration. TEM analyses showed droplets (NE) and spherical particles (NC). The time for the total disappearance of the ester varied from 12 h to 24 h depending on the polymer concentration. The biexponential model showed that the indomethacin ester was essentially entrapped within the nanocarriers in an extension of 85 to 95%. The half-lives varied from 147 to 289 min for the sustained phases and from 3 to 6 min for the burst phases. The ester-loaded-NC showed significant antiedematogenic activity, while the ester-loaded-NE did not inhibit the carrageenin-induced paw edema. The nanocapsules promoted the absorption of the indomethacin ethyl ester and the presence of the polymer is important to achieve the pharmacological effect.

Diffusion and mathematical modeling of release profiles from nanocarriers.

The aim of this work was to establish models and to differentiate the kinetic release behavior of drug models from nanocapsules, nanoemulsion and nanospheres by physico-chemical characterization and release experiments. SAXS analysis showed that the polymer is organized in the nanocapsules, while in the nanospheres the sorbitan monostearate is organized and acts as an impurity of the poly(epsilon-caprolactone) suggesting that constituents in these nanocarriers are differently organized. Formulations presented particle sizes ranging from 178 to 297 nm, probe content from 0.981 to 0.997 mg/mL, pH values from 4.90 to 5.10 and zeta potential from -37.9 to -51.9 mV. The kinetic experiments showed that the nanostructures present similar behaviors when the probe is adsorbed on the nanocarriers (indomethacin-loaded formulations). However, when the probe is entrapped within the nanocarriers (indomethacin ethyl ester-loaded formulations), nanocapsules, nanospheres and nanoemulsion presented different kinetic behaviors. Mathematical modeling of the release profiles was conducted, showing that the presence of the polymer increases the half-lives of the burst phases (5.9, 4.4 and 2.7 min) while the presence of the oil increases the half-lives of the sustained phases (288.8, 87.7 and 147.5 min) for nanocapsules, nanospheres and nanoemulsion, respectively.

Alkaline hydrolysis as a tool to determine the association form of indomethacin in nanocapsules prepared with poly(eta-caprolactone).

To determine the association form of indomethacin in nanocapsules prepared with poly(eta-caprolactone) as polymer and a triglyceride as oil, two methods were studied. The indomethacin ethyl ester was prepared as control, which showed a higher affinity for the oil than the indomethacin. Two differently loaded nanocapsule formulations were prepared. For both formulations, a burst effect was detected using ethanol as release medium. Light scattering (PCS) and NMR analyses suggested the ethanol diffuses through the nanocapsule polymeric wall promoting the total release of indomethacin and its ester. The results showed the inability of this approach to determine the association form of indomethacin. On the other hand, the alkaline hydrolysis of indomethacin and its ester, followed by their disappearance (HPLC), were evaluated. The nanocapsule suspensions containing indomethacin or its ester were treated with 50 mM NaOH. The total disappearance of indomethacin associated with nanocapsules was determined after 2 min, whereas the ester associated with colloids was consumed during 24 h. The constant particle sizes (264 and 259 nm) during the hydrolysis reactions showed that neither the nanocapsules were dissolved nor the polymer sorbed water during the contact with NaOH aqueous solution. The ester rate hydrolysis was determined by its diffusion from the nanocapsules to the interface particle/water. Finally, the indomethacin association model considers the burst release of drug after the addition of NaOH by the formation of its carboxylate, followed by its hydrolysis in aqueous solution promoted by the excess of NaOH. The adsorption was the mechanism of indomethacin association with nanocapsules.

Assessment of the antiexudative and antiproliferative activities of non-steroidal anti-inflammatory drugs in inflammatory models developed in rats by subcutaneous implantation of bacterial cell walls from the dental plaque.

A purified bacterial cell walls suspension from human dental plaque were biochemically prepared to serve as flogogenous agent in producing experimental inflammatory models in rats. In the vascular permeability inhibition assay (edemogenic test), the subcutaneous implantation of the flogogenous agent elicited an acute inflammatory reaction highly susceptible to the effects of the non-steroidal anti-inflammatory drugs (NSAIDs). The intradermal injection of the flogogenous agent in the dorsum of rats developed experimental granulomas also susceptible to the anti-inflammatory effects of the NSAIDs. Otherwise, the antimitotic effect of drugs was carried out in the model of cellular proliferation of duodenal mucosa of rats by incorporation of tritiated thymidine (3H TdR) in the DNA. These models of acute and chronic inflammation, and the antimitotic model permitted us to evaluate the anti-inflammatory and antimitotic effects of sulindac, ibuprofen, naproxen and glucametacin. In the antiexudative activity, evaluated by the edemogenic test, naproxen was the more effective drug followed by sulindac, ibuprofen and glucametacin (in a decreasing order of potency) to inhibit the exudative response induced by the bacterial cell walls suspension, in all experimental periods. In the chronic anti-inflammatory activity, evaluated by the granuloma inhibition assay, all drugs were capable to demonstrate effectiveness against the development of the experimental granulomas induced by an intradermal injection of the flogogenous agent. In the model of cellular proliferation, all tested drugs demonstrated antimitotic activity in all experimental periods (4, 6 and 8 days), also. Sulindac induced the higher antimitotic effect, in all experimental periods, followed by ibuprofen, naproxen and glucametacin in a decreasing order of efficacy. There was a positive correlation between the antiexudative, anti-proliferative, and antimitotic effects.