(1/905) Characterization of the analgesic and anti-inflammatory activities of ketorolac and its enantiomers in the rat.
The marked analgesic efficacy of ketorolac in humans, relative to other nonsteroidal anti-inflammatory drugs (NSAIDs), has lead to speculation as to whether additional non-NSAID mechanism(s) contribute to its analgesic actions. To evaluate this possibility, we characterized (R,S)-ketorolac's pharmacological properties in vivo and in vitro using the nonselective cyclooxygenase (COX) inhibitors [indomethacin (INDO) and diclofenac sodium (DS)] as well as the selective COX-2 inhibitor, celecoxib, as references. The potency of racemic (R,S)-ketorolac was similar in tests of acetic acid-induced writhing, carrageenan-induced paw hyperalgesia, and carrageenan-induced edema formation in rats; ID50 values = 0.24, 0. 29, and 0.08 mg/kg, respectively. (R,S)-ketorolac's actions were stereospecific, with (S)-ketorolac possessing the biological activity of the racemate in the above tests. The analgesic potencies for (R,S)-, (S)-, and (R)-ketorolac, INDO, and DS were highly correlated with their anti-inflammatory potencies, suggesting a common mechanism. (R,S)-ketorolac was significantly more potent than INDO or DS in vivo. Neither difference in relative potency of COX inhibition for (R,S)-ketorolac over INDO and DS nor activity of (S)-ketorolac at a number of other enzymes, channels, or receptors could account for the differences in observed potency. The distribution coefficient for (R,S)-ketorolac was approximately 30-fold less than for DS or INDO, indicating that (R,S)-ketorolac is much less lipophilic than these NSAIDs. Therefore, the physicochemical and pharmacokinetics properties of (R,S)-ketorolac may optimize the concentrations of (S)-ketorolac at its biological target(s), resulting in greater efficacy and potency in vivo. (+info)
(2/905) Cytokine-mediated inflammatory hyperalgesia limited by interleukin-4.
1. The effect of IL-4 on responses to intraplantar (i.pl.) carrageenin, bradykinin, TNFalpha, IL-1beta, IL-8 and PGE2 was investigated in a model of mechanical hyperalgesia in rats. Also, the cellular source of the IL-4 was investigated. 2. IL-4, 30 min before the stimulus, inhibited responses to carrageenin, bradykinin, and TNFalpha, but not responses to IL-1beta, IL-8 and PGE2. 3. IL-4, 2 h before the injection of IL-1beta, did not affect the response to IL-1beta, whereas IL-4, 12 or 12+2 h before the IL-1beta, inhibited the hyperalgesia (-30%, -74%, respectively). 4. In murine peritoneal macrophages, murine IL-4 for 2 h before stimulation with LPS, inhibited (-40%) the production of IL-1beta but not PGE2. Murine IL-4 (for 16 h before stimulation with LPS) inhibited LPS-stimulated PGE2 but not IL-1beta. 5. Anti-murine IL-4 antibodies potentiated responses to carrageenin, bradykinin and TNFalpha, but not IL-1beta and IL-8, as well as responses to bradykinin in athymic rats but not in rats depleted of mast cells with compound 40/80. 6. These data suggest that IL-4 released by mast cells limits inflammatory hyperalgesia. During the early phase of the inflammatory response the mode of action of the IL-4 appears to be inhibition of the production TNFalpha, IL-1beta and IL-8. In the later phase of the response, in addition to inhibiting the production of pro-inflammatory cytokines, IL-4 also may inhibit the release of PGs. (+info)
(3/905) The effects of inflammation and inflammatory mediators on nociceptive behaviour induced by ATP analogues in the rat.
1. We have studied the behavioural effects of intraplantar injections of adenosine 5'-triphosphate (ATP) and related compounds in freely moving rats and investigated whether these nociceptive effects are augmented in the presence of inflammatory mediators. 2. We find that in normal animals ATP and analogues produce dose-dependent nocifensive behaviour (seen as bursts of elevation of the treated hindpaw), and localized thermal hyperalgesia. The rank order of potency was: alpha,beta-methyleneadenosine 5'-triphosphate (alpha,beta-methylene ATP) > 2-methylthioadenosine triphosphate (2-methylthio ATP) > ATP. After neonatal treatment with capsaicin, to destroy small calibre primary sensory neurones, nocifensive behaviour was largely absent. 3. The effects of ATP analogues were assessed in three models of peripheral sensitization: 2 h after dilute intraplantar carrageenan (0.25% w v(-1)); 24 h after irradiation of the hindpaw with ultraviolet (U.V.) B; immediately following prostaglandin E2 (PGE2) treatment. In all models the effect of alpha,beta-methylene ATP was greatly augmented. After carrageenan, significant hindpaw-lifting behaviour activity was induced by injection of only 0.05 nmol of alpha,beta-methylene ATP, some 100 times less than necessary in normal skin. 4. Our data suggest that it is much more likely that endogenous levels of ATP will reach levels capable of exciting nociceptors in inflamed versus normal skin. Our data also suggest the involvement of P2X3 receptor subunits in ATP-induced nociception. (+info)
(4/905) Effect of sodium glycyrrhetinate on chemical peritonitis in rats.
AIM: To study the anti-inflammatory mechanisms of sodium glycyrrhetinate (SG). METHODS: Rat chemical peritonitis was used. The protein content and prostaglandin E2 (PGE2) content in exudate were measured by Folin-phenol assay and RIA, respectively. SOD activity in neutrophils (Neu) was determined by pyrogallol-NBT colorimetry. cAMP content in Neu was detected by competitive protein binding assay. RESULTS: In peritonitis caused by histamine, SG 10-20 mg.kg-1 i.m. reduced exudate volume and Neu counts, and 5-20 mg.kg-1 i.m. lowered the protein content in exudate. In peritonitis induced by carrageenan, SG 20 mg.kg-1 i.m. reduced exudate volume, Neu counts, protein content and PGE2 content in exudate, increased SOD activity in Neu, but did not affect beta-glucuronidase release from Neu. In peritonitis induced by arachidonic acid, SG 20 mg.kg-1 i.m. reduced Neu counts, protein content, and PGE2 content in exudate, and attenuated the reduction of cAMP level in Neu. CONCLUSION: SG exerts its anti-inflammatory action by lowering permeability of capillaries in inflammatory site, inhibiting Neu emigration and PGE2 biosynthesis, and scavenging oxygen free radicals. (+info)
(5/905) Beneficial effects of raxofelast (IRFI 016), a new hydrophilic vitamin E-like antioxidant, in carrageenan-induced pleurisy.
1. Peroxynitrite is a strong oxidant that results from reaction between NO and superoxide. It has been recently proposed that peroxynitrite plays a pathogenetic role in inflammatory processes. Here we have investigated the therapeutic efficacy of raxofelast, a new hydrophilic vitamin E-like antioxidant agent, in rats subjected to carrageenan-induced pleurisy. 2. In vivo treatment with raxofelast (5, 10, 20 mg kg(-1) intraperitoneally 5 min before carrageenan) prevented in a dose dependent manner carrageenan-induced pleural exudation and polymorphonuclear migration in rats subjected to carrageenan-induced pleurisy. Lung myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels, as well as histological organ injury were significantly reduced by raxofelast. 3. Immunohistochemical analysis for nitrotyrosine, a footprint of peroxynitrite, revealed a positive staining in lungs from carrageenan-treated rats. No positive nitrotyrosine staining was found in the lungs of the carrageenan-treated rats, which received raxofelast (20 mg kg 1) treatment. 4. Furthermore, in vivo raxofelast (5, 10, 20 mg kg(-1)) treatment significantly reduced peroxynitrite formation as measured by the oxidation of the fluorescent dihydrorhodamine 123, prevented the appearance of DNA damage, the decrease in mitochondrial respiration and partially restored the cellular level of NAD+ in ex vivo macrophages harvested from the pleural cavity of rats subjected to carrageenan-induced pleurisy. 5. In conclusion, our study demonstrates that raxofelast, a new hydrophilic vitamin E-like antioxidant agent, exerts multiple protective effects in carrageenan-induced acute inflammation. (+info)
(6/905) Bradykinin B1 and B2 receptors, tumour necrosis factor alpha and inflammatory hyperalgesia.
The effects of BK agonists and antagonists, and other hyperalgesic/antihyperalgesic drugs were measured (3 h after injection of hyperalgesic drugs) in a model of mechanical hyperalgesia (the end-point of which was indicated by a brief apnoea, the retraction of the head and forepaws, and muscular tremor). DALBK inhibited responses to carrageenin, bradykinin, DABK, and kallidin. Responses to kallidin and DABK were inhibited by indomethacin or atenolol and abolished by the combination of indomethacin + atenolol. DALBK or HOE 140, given 30 min before, but not 2 h after, carrageenin, BK, DABK and kallidin reduced hyperalgesic responses to these agents. A small dose of DABK+ a small dose of BK evoked a response similar to the response to a much larger dose of DABK or BK, given alone. Responses to BK were antagonized by HOE 140 whereas DALBK antagonized only responses to larger doses of BK. The combination of a small dose of DALBK with a small dose of HOE 140 abolished the response to BK. The hyperalgesic response to LPS (1 microg) was inhibited by DALBK or HOE 140 and abolished by DALBK + HOE 140. The hyperalgesic response to LPS (5 microg) was not antagonized by DALBK + HOE 140. These data suggest: (a) a predominant role for B2 receptors in mediating hyperalgesic responses to BK and to drugs that stimulate BK release, and (b) activation of the hyperalgesic cytokine cascade independently of both B1 and B2 receptors if the hyperalgesic stimulus is of sufficient magnitude. (+info)
(7/905) Limited anti-inflammatory efficacy of cyclo-oxygenase-2 inhibition in carrageenan-airpouch inflammation.
1. Cyclo-oxygenase-2 (COX-2) is expressed at sites of inflammation and is believed to be the major source of inflammation-associated prostaglandin synthesis. Selective inhibition of COX-2 has been suggested to produce anti-inflammatory effects with reduced toxicity in the gastrointestinal tract. We examined the extent to which suppression of COX-2 led to inhibition of various components of inflammation in the carrageenan-airpouch model in the rat. 2. Indomethacin (> or =0.3 mg kg(-1)), nimesulide (> or =3 mg kg(-1)) and the selective COX-2 inhibitor, SC-58125 (> or =0.3 mg kg(-1)), significantly suppressed the production of prostaglandin E2 at the site of inflammation. At higher doses, indomethacin (> or =1 mg kg(-1)) and nimesulide (30 mg kg(-1)), but not SC-58125 (up to 10 mg kg(-1)), significantly inhibited COX-1 activity (as measured by whole blood thromboxane synthesis). 3. All three test drugs significantly reduced the volume of exudate in the airpouch, but only at doses greater than those required for substantial (>90%) suppression of COX-2 activity. Similarly, reduction of leukocyte infiltration was only observed with the doses of indomethacin and nimesulide that caused significant suppression of COX-1 activity. 4. SC-58125 did not significantly affect leukocyte infiltration into the airpouch at any dose tested (up to 10 mg kg(-1)). A second selective COX-2 inhibitor, Dup-697, was also found to suppress exudate PGE2 levels without significant effects on leukocyte infiltration. 5. These results indicate that selective inhibition of COX-2 results in profound suppression of PGE2 synthesis in the carrageenan-airpouch, but does not affect leukocyte infiltration. Exudate volume was only reduced with the highly selective COX-2 inhibitor when a dose far above that necessary for suppression of COX-2 activity was used. Inhibition of leukocyte infiltration was observed with indomethacin and nimesulide, but only at doses that inhibited both COX-1 and COX-2. (+info)
(8/905) Spinal blockade of opioid receptors prevents the analgesia produced by TENS in arthritic rats.
Transcutaneous electrical nerve stimulation (TENS) is commonly used for relief of pain. The literature on the clinical application of TENS is extensive. However, surprisingly few reports have addressed the neurophysiological basis for the actions of TENS. The gate control theory of pain is typically used to explain the actions of high-frequency TENS, whereas, low-frequency TENS is typically explained by release of endogenous opioids. The current study investigated the role of mu, delta, and kappa opioid receptors in antihyperalgesia produced by low- and high-frequency TENS by using an animal model of inflammation. Antagonists to mu (naloxone), delta (naltrinodole), or kappa (nor-binaltorphimine) opioid receptors were delivered to the spinal cord by microdialysis. Joint inflammation was induced by injection of kaolin and carrageenan into the knee-joint cavity. Withdrawal latency to heat was assessed before inflammation, during inflammation, after drug (or artificial cerebral spinal fluid as a control) administration, and after drug (or artificial cerebral spinal fluid) administration + TENS. Either high- (100 Hz) or low- frequency (4 Hz) TENS produced approximately 100% inhibition of hyperalgesia. Low doses of naloxone, selective for mu opioid receptors, blocked the antihyperalgesia produced by low-frequency TENS. High doses of naloxone, which also block delta and kappa opioid receptors, prevented the antihyperalgesia produced by high-frequency TENS. Spinal blockade of delta opioid receptors dose-dependently prevented the antihyperalgesia produced by high-frequency TENS. In contrast, blockade of kappa opioid receptors had no effect on the antihyperalgesia produced by either low- or high-frequency TENS. Thus, low-frequency TENS produces antihyperalgesia through mu opioid receptors and high-frequency TENS produces antihyperalgesia through delta opioid receptors in the spinal cord. (+info)