Inhibitory effects of diclofenac and indomethacin on interleukin-1-induced changes in PGE2 release. A novel effect on free arachidonic acid levels in human synovial cells

In vivo joint synovial fluid disposition of a novel sustained-release formulation of diclofenac and hyaluronic acid in horses

Intra-articular administration of sustained-release anti-inflammatory drugs is indicated in horses suffering from joint inflammation, but no such drugs are labelled for veterinary use. To obtain initial data on synovial disposition and safety of a new sustained-release formulation of diclofenac (SYN321) in the joints of horses, an experimental interventional study of elimination and side effects of intra-articular administration of SYN321 was conducted. Nine clinically sound horses were included in the study, and SYN321 was administered by the intra-articular route. Dose ranges and sampling intervals were established in a pilot study with two horses, and then applied in a main study involving seven horses treated in the fetlock joint. Diclofenac was detected above lower limit of quantification (LOQ: 0.5 ng/ml) in synovial fluid throughout the study period (14 days), and below LOQ (0.1 ng/ml) in plasma after 4 days and in urine after 14 days. No obvious clinical side effects were detected. Clinical examination and objective lameness evaluation suggested that SYN321 has potential as a local joint NSAID treatment with sustained release in horses, but further studies on synovial fluid exposure, safety and clinical efficacy are warranted.

Suppression of inflammatory mediators and matrix metalloproteinase (MMP)-13 by Morus alba stem extract and oxyresveratrol in RAW 264.7 cells and C28/I2 human chondrocytes

This study aimed to investigate the effects of Morus alba stem extract (MSE) and oxyresveratrol on the suppression of pro-inflammatory mediators in LPS-stimulated RAW 264.7 macrophages and IL-1β-stimulated C28/I2 human chondrocyte cell line. The chondroprotective effect was also investigated using the chondrocyte cell line. First, MSE was prepared and analyzed for the amount of oxyresveratrol. The anti-inflammatory effects of MSE at various concentrations were evaluated through the inhibition of nitric oxide (NO), prostaglandin (PG)-E₂ and cyclooxygenase (COX)-2 production. Oxyresveratrol at the equivalent amount found in the extract was investigated in the same manner. The chondroprotective effect was investigated through the suppression of MMP-13 production. The results showed that oxyresveratrol content in MSE was 15%. In RAW 264.7 cells, MSE (5-50 μg/mL) could inhibit the NO (24-30%) and PGE₂ (11-82%) production. Oxyresveratrol at 0.75 and 7.5 μg/mL could suppress NO and also inhibited PGE₂ but at only at high concentration. In the chondrocyte cell line, MSE at 5-100 μg/mL significantly decreased the PGE₂ and COX-2 production by 44-93% and 17-65%, respectively. Again, oxyresveratrol at both concentrations could significantly inhibit PGE₂ production by 50-92% but it inhibited COX-2 only at high concentration. In addition, MSE and oxyresveratrol was shown to significantly inhibit MMP-13 production by 14-57% and 16-56%, depending on their concentrations. The MSE demonstrates the potential to be used as an alternative treatment for reducing inflammation and preventing cartilage degradation. Its component, oxyresveratrol, may exert these effects to some extent.

Diclofenac: an update on its mechanism of action and safety profile

BACKGROUND

Diclofenac is a proven, commonly prescribed nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-inflammatory, and antipyretic properties, and has been shown to be effective in treating a variety of acute and chronic pain and inflammatory conditions. As with all NSAIDs, diclofenac exerts its action via inhibition of prostaglandin synthesis by inhibiting cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) with relative equipotency. However, extensive research shows the pharmacologic activity of diclofenac goes beyond COX inhibition, and includes multimodal and, in some instances, novel mechanisms of action (MOA).

DATA SOURCES

Literature retrieval was performed through PubMed/MEDLINE (through May 2009) using combinations of the terms diclofenac, NSAID, mechanism of action, COX-1, COX-2, and pharmacology. Reference citations resulting from publications identified in the literature search were reviewed when appropriate.

METHODS

This article reviews the established, putative, and emerging MOAs of diclofenac; compares the drug's pharmacologic and pharmacodynamic properties with other NSAIDs to delineate its potentially unique qualities; hypothesizes why it has been chosen for further recent formulation enhancement; and evaluates the potential effect of its MOA characteristics on safety.

DISCUSSION

Research suggests diclofenac can inhibit the thromboxane-prostanoid receptor, affect arachidonic acid release and uptake, inhibit lipoxygenase enzymes, and activate the nitric oxide-cGMP antinociceptive pathway. Other novel MOAs may include the inhibition of substrate P, inhibition of peroxisome proliferator activated receptor gamma (PPARgamma), blockage of acid-sensing ion channels, alteration of interleukin-6 production, and inhibition of N-methyl-D-aspartate (NMDA) receptor hyperalgesia. The review was not designed to compare MOAs of diclofenac with other NSAIDs. Additionally, as the highlighted putative and emerging MOAs do not have clinical data to demonstrate that these models are correct, further research is necessary to ascertain if the proposed pathways will translate into clinical benefits. The diversity in diclofenac's MOA may suggest the potential for a relatively more favorable profile compared with other NSAIDs.

Risks and benefits of nonsteroidal anti-inflammatory drugs in children: a comparison with paracetamol

Nonsteroidal anti-inflammatory drugs (NSAIDs) possess antipyretic, analgesic and anti-inflammatory effects. They are frequently used in children and have numerous therapeutic indications, the most common ones being fever, postoperative pain and inflammatory disorders, such as juvenile idiopathic arthritis (JIA) and Kawasaki disease. Their major mechanism of action is through inhibition of prostaglandin biosynthesis by blockade of cyclo-oxygenase (COX). The disposition of most NSAIDs has been mainly studied in infants > or = 2 years of age. Compared with adults, the volume of distribution and clearance of NSAIDs such as diclofenac, ibuprofen (infants aged between 3 months and 2.5 years), ketorolac and nimesulide were increased in children. The elimination half-life was similar in children to that in adults. These pharmacokinetic differences might be clinically significant with the need for higher loading and/or maintenance doses in children. Ibuprofen, acetylsalicylic acid (ASA) and acetaminophen are the most frequently used agents for fever reduction in children. Over the past 20 years, because of the association between ASA use and Reye's syndrome, most of the interest has been directed toward ibuprofen and acetaminophen. In view of its comparable antipyretic efficacy, but superior tolerability profile, acetaminophen, when used appropriately with age-adapted formulations, should remain the first-line therapy in the treatment of childhood fever. At the moment, there is no scientific evidence to recommend simultaneous use of these two antipyretic drugs. Most NSAIDs provide mild to moderate analgesia, with the exception of ketorolac which has a strong analgesic activity. The analgesic efficacy of ketorolac, ketoprofen, diclofenac and ibuprofen in the treatment of postoperative pain has been mainly studied following a single dose, in children of > or = 1 year of age undergoing minor surgeries. In this setting, when used either alone or in adjunct to caudal or epidural anaesthesia, they were associated with an opioid-sparing effect and were well tolerated. With the exception of ketorolac use in children undergoing tonsillectomy, where controversy exists regarding the risk of postoperative haemorrhage, NSAIDs have not been associated with an increased risk of perioperative bleeding. NSAIDs are the first-line therapy in JIA. They appear to be equally effective and tolerated, with the exception of ASA which is associated with more adverse effects. ASA has been used for many years in the treatment of Kawasaki disease and is part of the standard modality of treatment in combination with intravenous gammaglobulins. More recently, lung inflammation associated with cystic fibrosis (CF) has become a new target for NSAIDs. Despite promising preliminary results with ibuprofen, numerous questions need to be answered before this new strategy becomes part of the conventional treatment of patients with CF. In summary, NSAIDs are effective in reducing fever, alleviating pain and reducing inflammation in children, with a good tolerance profile. Pharmacokinetic studies are needed to characterise the disposition of NSAIDs in very young infants in order to use them rationally. To date, no studies have been published on the disposition, tolerability and efficacy of specific COX-2 inhibitors in children. Further clinical experience with these agents in adults is warranted before undergoing trials with specific COX-2 inhibitors in children.

Corneal penetration of diclofenac from a fixed combination of diclofenac-gentamicin eyedrops

PURPOSE

To establish the corneal penetration of diclofenac in the presence of gentamicin in patients having cataract surgery.

SETTING

Kantonsspital Augenklinik, Aarau, and Hôpital Jules Gonin, Lausanne, Switzerland.

METHODS

Eligible patients having cataract surgery (39 women, 30 men) were treated with 4 drops of diclofenac 0.1%-gentamicin 0.3% (Voltamicin) instilled at 20 minute intervals. Paracentesis was performed 15, 30, or 60 minutes after the last instillation, and a sample of aqueous humor was collected for analysis of diclofenac by high-performance liquid chromatography. Blood samples of some patients were obtained before surgery for analysis.

RESULTS

Mean diclofenac levels (+/- SD) in the aqueous humor 15, 30, and 60 minutes after the last instillation were 72 +/- 84, 108 +/- 87, and 201 +/- 116 ng/mL (= 682 nMol/L), respectively. Diclofenac remained below the limit of detection (5 ng/mL) in all samples of blood serum. In general, local tolerance was good; no side effects were reported. Comparison of the data with published results of topically instilled diclofenac 0.1% suggests that the concentration of diclofenac in the aqueous humor achieved with 4 instillations of the combination product is similar to that achieved with 8 instillations of diclofenac 0.1% (Voltaren Ophtha) alone.

CONCLUSIONS

Drug levels of diclofenac in the aqueous humor well above IC-50 for cyclo-oxygenase were achieved with the regimen applied. No inhibitory effect by the gentamicin or vehicle was observed. Comparison of these data with published results of Voltaren Ophtha implies a 2-fold better penetration of diclofenac with the diclofenac-gentamicin combination.

Efficacy of diclofenac eyedrops in preventing postoperative inflammation and long-term cystoid macular edema. Italian Diclofenac Study Group

PURPOSE

To compare the efficacy and tolerance of diclofenac 0.1% eyedrops with a regimen that included a brief course of steroids in the treatment of postoperative inflammation after extracapsular cataract surgery and posterior chamber intraocular lens implantation. A second objective was to compare the efficacy of diclofenac 0.1% eyedrops in the same patients and control group in preventing cystoid macular edema (CME).

SETTING

Eight university/hospital centers and one company in Italy.

METHODS

The multicenter, controlled, randomized, prospective, double-blind study included 281 patients. All were evaluated at baseline, at surgery, and after 1, 5, 36, 67, and 140 days. Postoperative inflammation was measured by the clinical assessment of inflammation: conjunctival hyperemia, ciliary flush, Tyndall effect, and cells in the anterior chamber. Fluorescein angiography was performed to evaluate the presence/absence of CME before surgery and after 36 and 140 days.

RESULTS

During follow-up, no differences in intraoperative pressure were observed within or between groups or between operated and fellow eyes. No statistically significant between-group differences in postoperative inflammation were found. After 36 days, angiographic CME was found in 9 patients (6.43%) in the diclofenac group and 20 (15.15%) in the control group (P = .033) with a relative risk for developing CME of 0.40 (CI95 0.19 to 0.84). At the end of follow-up, it was found in 4 patients in the diclofenac group (3.31%) and 10 (9.26%) in the control group (P = .05) with a relative risk of 0.36 (CI95 0.12 to 0.90).

CONCLUSION

Diclofenac sodium was as effective as the control regimen in controlling postoperative inflammation after cataract surgery. It also had a protective effect on the development of angiographic CME after 36 and 140 days.

Effects of misoprostol and prostaglandin E2 on proteoglycan biosynthesis and loss in unloaded and loaded articular cartilage explants

The effects of misoprostol, a prostaglandin E1 analog, and prostaglandin E2 on proteoglycan biosynthesis and loss were studied in unloaded and mechanically loaded mature bovine articular cartilage explants. The prostaglandins were administered daily at dosages of 0, 10, 100 and 1000 eta g/ml for up to seven days, and proteoglycan biosynthesis determined by measurement of radiolabelled sulfate incorporation. The presence of misoprostol lead to a significant (p < 0.001) dose-dependent inhibition (30%-50%) in proteoglycan biosynthesis which was also dependent on exposure time (p < 0.05). A significant decrease in biosynthesis (34%) was also found for prostaglandin E2, but only at the highest dose (1000 eta g/ml). Proteoglycan catabolism rates were not affected by either substance as assessed by loss of newly synthesized proteoglycan. The application of a continuous cyclic mechanical compressive load (stress of 1.0 MPa at 1 hertz for 24 hours) resulted in a significant inhibition of proteoglycan biosynthesis (up to 50%) as compared to unloaded explants. However, there was no additive effect when mechanical load and misoprostol or prostaglandin E2 were combined. These results suggest that prostaglandins may have a role in the degenerative and repair process in various forms of arthritis where elevated intra-articular levels of prostaglandin E2 are present.

Effect of lipid-derived second messengers on electrophysiological taste responses in the gerbil

Integrated chorda tympani (CT) recordings were made to salty, sour, sweet, bitter, and glutamate tastants before and after a 4-min application of modulators of lipid-derived second messenger systems. The modulators included two membrane-permeable analogues of DAG, 1-oleoyl-2-acetyl glycerol (OAG) and dioctanoyl glycerol (DiC8); thapsigargin, which releases Ca++ from intracellular stores; ionomycin, a calcium ionophore; lanthanum chloride, an inorganic calcium channel blocker; nifedipine, a dihydropyridine calcium channel blocker; quinacrine diHCl, a phospholipase A2 antagonist; melittin, a phospholipase A2 agonist; and indomethacin, which decreases the release of prostaglandins by inhibiting the enzyme cyclo-oxygenase. The main findings were: OAG (125 microM) and DiC8 (100 microM) blocked the responses of several bitter compounds while enhancing the taste response to several sweeteners. Lanthanum chloride blocked all responses, which may be due to the fact that it blocks tight junctions. Quinacrine (1 mM) suppressed several bitter responses while enhancing the response to several sweeteners. The enhancement of sweet taste responses by DAG analogues suggests that there is cross-talk between the adenylate cyclase system and one (or more) pathways involving lipid-derived second messengers in taste cells.

Arachidonic acid lipoxygenation may mediate interleukin-1 stimulation of nerve growth factor secretion in astroglial cultures

Interleukin-1 beta (IL-1) stimulates by about fivefold NGF secretion from rat neonatal cortical astrocytes in primary culture. We investigated the possible intracellular second messenger mechanisms involved in the IL-1 induced NGF secretion. Basal NGF secretion did not require extracellular Ca2+, whereas Ca2+ was necessary for the maximal NGF secretion stimulated by IL-1 (10 units/ml). The protein kinase C activator TPA stimulated by sixfold NGF secretion, but in this case, TPA acted synergistically with IL-1 to increase NGF secretion. Treatment of cells with the phospholipase A2 inhibitor mepacrine (30 microM) inhibited basal (by 50%) and IL-1 stimulated (by 80%) NGF secretion. Indomethacin, a cyclooxygenase inhibitor, produced a slight increase in basal NGF secretion at low concentrations, while PGE2 (10 microM) inhibited basal and IL-1 stimulated NGF secretion. In contrast, treatment of cells with nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, blocked in a concentration-dependent manner (IC50 = 10 microM) IL-1 stimulation of NGF secretion. The leukotriene LTB4 increased basal NGF secretion and this effect was not additive with IL-1 when both agents were added at saturating concentrations, indicating a common mechanism of action for these two agents. Thus, one possible mechanism by which IL-1 stimulates NGF secretion from astrocytes is by activation of the phospholipase A2-lipoxygenase pathway.

Misoprostol: new frontiers; benefits beyond the gastrointestinal tract

Recent findings suggest that the protective role that misoprostol exerts in the gastrointestinal tract against nonsteroidal anti-inflammatory drug (NSAID) damage may be extended to a variety of other tissues and other noxious stimuli including those mediated by molecules such as interleukin 1 (IL-1), tumor necrosis factor (TNF), and endotoxin. The protective effects of misoprostol outside the gastrointestinal tract may involve prevention of triggering activities that would otherwise initiate a sequence of tissue damaging events. If this capacity of misoprostol to maintain homeostasis in a variety of settings is recognized, a cohesive pattern of action emerges. Numerous studies have shown that misoprostol is likely to act as a regulator within various cascades of immunological regulatory events. The in vitro and in vivo experimental data described in this paper suggest that the events which trigger episodes of pain and inflammation may be controllable by the administration of misoprostol. Mitigation of adverse effects of certain NSAIDs on renal function and cartilage metabolism has also been observed. Demonstration of this latter phenomenon in the clinical setting will greatly benefit the patient if it is shown to modify the arthritis disease process. The therapeutic applications of misoprostol beyond the gastrointestinal tract appear to be among the most interesting of therapeutic advances offered by any class of compound in the next decade. Because of the inflammatory and pain processes associated with arthritis disease progression, particular emphasis and confirmation through further clinical study should be placed on the potential effect of misoprostol on chondroprotection and synergy with NSAIDs.