The pharmacological profile of ovalbumin-induced paw oedema in rats

Rats are commonly used in anaphylaxis models, mainly in intestinal anaphylaxis. Hypersensitivity mechanisms are complex and they are not clearly defined. Ovalbumin (OVA) is commonly used for studies on the hypersensitivity mechanism. However, the potential pro-inflammatory mediators induced by this antigen in the model of paw oedema in immunized rats are still not completely understood. This work examines the pharmacological modulation of several mediators involved in rat hind paw immune oedema induced by OVA. Wistar rats were previously immunized (14-18 days) with OVA (30 microg, intraperitoneally) or sham-sensitized with aluminum hydroxide (control). The paw volumes were measured before the antigenic stimuli and 1, 2, 3 and 4 h after the intraplantar injection of OVA (10 microg/paw). Subcutaneous injection of dexamethasone, diphenhydramine, cyproheptadine, chlorpromazine or methysergide significantly inhibited (p < 0.05) the allergic paw oedema. The dual inhibitor of cyclooxygenase and lipoxygenase (NDGA), the cyclooxygenase inhibitor (indomethacin), the lipoxygenase inhibitor (MK-886), the PAF antagonist (WEB 2086), the mast cell stabilizer (ketotifen), and the anti-histamine (meclizine) did not inhibit the immune oedema. In addition, thalidomide and pentoxifylline (anti-tumour necrosis factor drugs) were ineffective against OVA-induced oedema. The fact that indomethacin, MK-886, NDGA and WEB 2086 are unable to inhibit this allergic oedema indicates that the dexamethasone action seems not to be via phospholipase A2, but possibly due to the synthesis and/or the inhibitory activity of cytokines. The paw oedema inhibition by diphenhydramine, but not by meclizine, may suggest a different mechanism, which is independent of the effect of histamine. These data indicate that allergic oedema is more sensitive to anti-serotonin drugs, mainly anti-5-HT2, suggesting that the principal mediator of this inflammatory response is serotonin.     

Effect of melatonin on 24h changes in plasma protein levels during the preclinical phase of Freund's adjuvant arthritis in rats

The 24h rhythms in plasma protein concentration were examined in rats on the third day after injection of Freund's complete adjuvant or adjuvant's vehicle, performed 3h after light on. In rats treated with adjuvant's vehicle, peak values of albumin and gamma globulin occurred during the nocturnal activity span (P < .02 and P < .0001, respectively), while those of alpha-1, alpha-2, and beta globulins were found late during the rest span (P < .002, P < .0001, and P < .0004, respectively). Freund's adjuvant administration abolished temporal changes in plasma albumin and beta globulin levels. It also decreased the amplitude of daily changes in alpha-1 and alpha-2 globulin (P < .05) and diminished mean values of alpha-2 globulin (P < .01). Pretreatment of rats with melatonin (30 microg daily) for 11 days, 11h after light on, counteracted mycobacterial adjuvant-induced suppression of the 24h rhythms in albumin and alpha-1, alpha-2, and beta globulins. The results further support the existence of preventive properties of a pharmacological dose of melatonin in situations in which a lost of circadian rhythmicity is expected.     

Influence of adjuvant arthritis on main urinary metabolites of prostaglandin F and E in rats

The influence of adjuvant arthritis in rats on main urinary metabolites (MUM) of prostaglandin (PG) F and E type was studied.1) In our model rats, urinary excretion of PGE-MUM increased on day 11 prior to the appearance of secondary lesions, but that of PGF-MUM did not change significantly during the observed period (21 days). The excretion of PGE-MUM was not proportional to the increase in both hind paws volume.2) Indomethacin, which diminished primary lesions but did not suppress secondary lesions, reduced the increase in urinary excretion of PGE-MUM.3) Prednisolone and azathiopurine, which suppressed both primary and secondary lesions, increased the excretion of PGE-MUM over adjuvant control values on days 4 and 8.The facts described above suggest that the increase of endogenous PGE during days 4 to 8 may be important in the suppression of secondary lesions in adjuvant arthritis in rats.     

Effect of benzopyrone derivatives on simultaneously induced croton oil ear oedema and carrageenin paw oedema in rats.

Carrageenin paw oedema and croton oil ear oedema induced simultaneously in rats are inhibited in a dose-dependent manner and to statistically significant degrees by lipoxygenase- and cyclooxygenase-blocker flavonoids (diosmin, fisetin, quercetin, myricetin, galangin, sophoricoside, hesperidin-methylchalcone, oligomeric procyanidin, anthocyanidins (delphinidin, pelargonidin], and the prostaglandin antagonist polyphloretin phosphate and di-4-phloretin phosphate. Outstanding anti-inflammatory effects are displayed by myricetin and delphinidin, which contain vicinal hydroxy groups in ring B. The results confirm the importance of hydroxy group substitution in ring B. The most effective of the examined substances proved to be the prostaglandin antagonist di-4-phloretin phosphate.     

Effects of acute prednisolone administration on plasma and liver copper in rats with adjuvant arthritis

Several studies in animals and humans have shown that copper metabolism could be affected by inflammation or by corticosteroids. The relative importance of these two factors, often imbedded in clinical practice, was assessed by investigating the effects of acute prednisolone administration (30 mg/kg, ip) on healthy and adjuvant arthritis rats. Plasma copper levels were significantly higher in arthritic rats compared to healthy animals, whereas there was a slight, but nonsignificant increase in liver copper. Acute prednisolone administration in healthy rats resulted in a significant increase in plasma copper (10–15%) as early as 4 h after corticosteroid administration, which was maintained for 12 h. In arthritic rats, the response was much higher (25–40%), but somewhat delayed and shorter. Liver copper was not clearly modified by prednisolone treatment in both groups. This time-controlled study showed that acute prednisolone administration increased plasma copper in both healthy and arthritic rats, but in different ways, indicating that inflammation and corticosteroids may act synergistically.     

T-kininogen--the major plasma kininogen in rat adjuvant arthritis

Total kininogen in plasma of Freund's adjuvant treated rats increased 20-fold 7 days following the injection. Analysis of the kininogens demonstrated that increases in T-kininogen was the major reason for the rise in kininogen. High molecular weight and low molecular weight kininogens showed little or no change. The increase in T-kininogen paralleled the inflammatory condition. Anti-inflammatory agents which reduced paw swelling also reduced plasma T-kininogen levels. Unidentified peaks on HPLC of kinin following plasma treatment by trypsin were shown to be oligopeptides containing T-kinin (Ile-serbradykinin). The relationship of T-kininogen to the inflammatory response is discussed.     

Effect of vitamin E on adjuvant arthritis in rats

Adjuvant arthritis was induced in rats fed a diet deficient in or supplemented with vitamin E, and its severity was scored according to the macroscopic findings of their legs, tails, and ears. The average score so obtained was higher in the vitamin E-deficient diet group than in the group of rats supplemented with vitamin E. Whereas the A/G ratio remained depressed in vitamin E-deficient rats, rats on a vitamin E-supplemented diet showed a fast recovery from A/G-ratio depression. The serum levels of beta-glucuronidase and acid phosphatase were elevated after administration of an adjuvant. The serum levels of these lysosomal enzymes showed a remarkable increase in rats fed a vitamin E-deficient diet, while the elevation in lysosomal enzyme levels in rats fed a vitamin E-supplemented diet was inhibited. The levels of thiobarbituric acid (TBA) reactants in the synovia were elevated at 2 weeks after exposure to the adjuvant and were decreased thereafter. In rats maintained on a diet supplemented with vitamin E, on the other hand, the increase in synovial level of TBA reactive substances was inhibited. These observations suggest that the aggravation of adjuvant arthritis may be associated with lipid peroxidation and that antioxidants, such as vitamin E, may be beneficial for arthritis.     

Changes in prostaglandin E2 (PGE2) levels in paw exudate, stomach and kidney of arthritic rats: effects of flosulide

To further examine the organ-specific toxic effects of selective and non-selective COX-2 inhibitors in adjuvant arthritis (CAA), we assessed the PGE2 concentration in various organs. AA was induced by intradermal injection of Mycobacterium butyricum. Fourteen days after inoculation, AA rats were selected and treated orally every day for two weeks with the selective COX-2 inhibitor, flosulide, or the COX-1-COX-2 inhibitor, indomethacin. The time-course of paw swelling was determined. At the end of treatments, PGE2 was extracted from paw, stomach (wall and mucosa) and kidney and its concentration was determined by ELISA. Paw edema increase was accompanied by a rise in PGE2 concentration. PGE2 also increased in stomach (mucosa and wall) and kidney. The anti-inflammatory treatment with flosulide (5 mg/kg x day), and indomethacin (1 mg/kg x day), reduced plantar edema by 98.0% and 74.4% respectively. Both drugs greatly decreased PGE2 levels in paw (73.7-53.2%), stomach wall (84.5-80.3%), stomach mucosa (109.9-110.9%) and kidney (92.9-97.5% respectively). However, PGE2 reductions in AA rats did not fall significantly below control values.     

The local edemogenic effects of leukotriene C4 and prostaglandin E2 in rats

Leukotriene C₄ (LTC₄) and prostaglandin E₂ (PGE₂) have been studied for their effects on vascular permeability in rats. LTC₄ and/or PGE₂ were dissolved in 0.3% ethanol and were administered subcutaneously (0.1 ml) in the plantar surface of one of the hind paws of different series of rats. The changes in vascular permeability were measured by the radioactive marker (HSA. I¹²⁵) method. LTC₄ administered in dose of 2 × 10⁻⁸M produced marked increase (77 and 133%) in the vascular permeability (local edemogenic effect). PGE₂ administered in a dose of 10⁻⁶M also produced significant increase (38 and 40%) in the vascular permeability. However, PGE₂ in the same dose either administered along with LTC₄ or administered at 30 minutes after the injection of LTC₄ (2 × 10⁻⁸M) did not have any potentiating effect on the edemogenic response of LTC₄.     

Enhanced intraarticular free radical reactions in adjuvant arthritis rats

One of the reasons of rheumatoid arthritis (RA) development is widely recognized the relation of free radical reactions in tissue injuries. The aim of this study was to evaluate the location where in vivo free radical reactions was enhanced in adjuvant arthritis (AA) model rats using in vivo electron spin resonance (ESR)/nitroxyl spin probe technique. The signal decay after intravenous injection of spin probe was enhanced in AA than that in control and suppressed by the pre-treatment of dexamethasone (DXT). Interestingly, the decay in joint cavity occurred prior to paw swelling of AA and suppressed by a simultaneous injection of free radical scavengers, indicating that the enhancement of free radical reactions in joint cavity of AA rats. This technique would be useful tool to determine the location of the enhanced free radical reactions and evaluate the activity of antioxidant medicine with non-invasive real-time measurement.     

Enhanced intraarticular free radical reactions in adjuvant arthritis rats

One of the reasons of rheumatoid arthritis (RA) development is widely recognized the relation of free radical reactions in tissue injuries. The aim of this study was to evaluate the location where in vivo free radical reactions was enhanced in adjuvant arthritis (AA) model rats using in vivo electron spin resonance (ESR)/nitroxyl spin probe technique. The signal decay after intravenous injection of spin probe was enhanced in AA than that in control and suppressed by the pre-treatment of dexamethasone (DXT). Interestingly, the decay in joint cavity occurred prior to paw swelling of AA and suppressed by a simultaneous injection of free radical scavengers, indicating that the enhancement of free radical reactions in joint cavity of AA rats. This technique would be useful tool to determine the location of the enhanced free radical reactions and evaluate the activity of antioxidant medicine with non-invasive real-time measurement.     

Brain and spinal cord neuropeptides in adjuvant induced arthritis in rats

The concentrations of brain and spinal cord beta-endorphin, met-enkephalin, dynorphin and substance P were measured in rats bearing the Freund adjuvant induced arthritis. Beta-endorphin brain concentrations decreased gradually in time with a nadir on day twenty-one, when arthritis was at its maximum, and were back to normal by day thirty-five, when arthritis was no more evident. Met-enkephalin concentrations increased in brain areas and in the lumbar spinal cord and returned to normal with the same time pattern, while dynorphin and substance P concentrations did not change. These data indicate that peripheral lesions can induce important changes in brain concentrations of some opioid peptides involved in the modulation of pain.     

Studies on the synergy between collagen and adjuvant arthritis in rats

Intravenous administration of subarthritogenic doses of anticollagen IgG and adjuvant-sensitized spleen cells to syngeneic naive rats induces an erosive arthritis in recipients. The onset of the clinical disease in recipients is rapid and the disease is severe when compared to those recipients receiving cells alone. Immunocytochemical analysis of the knee synovium indicates the accumulation in the adipose tissue of Ia+ (ED1+)macrophages, OX-19+ T lymphocytes, and neutrophils. A large proportion of the lining cells of the proliferative synovium are Ia+. The knee synovium is extremely edematous and contains fibrin. If recipient rats are decomplemented, clinical disease is delayed and the number of mononuclear and polymorphonuclear cells accumulating in the synovium is decreased. Similar results are observed if recipient rats are treated with anti-Ia+ antibody. However, anti-Ia+ treatment does not induce depletion of serum complement.     

Neurohypophyseal peptide levels in CSF and plasma during passive avoidance behavior in rats

Levels of vasopressin (AVP), oxytocin (OXT), and neurophysin (NP) in CSF and plasma of rats were determined during acquisition and retention of passive avoidance behavior. None of the levels of neurohypophyseal peptides in CSF were changed either during the adaptation period, or during acquisition or the retention of this behavior. Moreover, no differences were found in hormone levels in CSF of the various groups of rats subjected to different shock intensities during the acquisition trial. The marked differences in individual latencies of nonavoiding rats, and the differences in latencies due to a different shock intensity applied during the learning trial were not reflected by changes in CSF hormone levels. Neither AVP nor NP levels in plasma were affected by the different shock intensities applied, when measured at 20 min after the learning trial. In contrast, a decrease in plasma OXT levels was observed after application of a shock intensity of 0.25 mA during the learning trial. During retention of the passive avoidance response plasma levels of AVP, OXT and NP were not different from the levels found in the nonshocked groups. It is suggested that under the conditions used in this study the CSF is apparently not involved in the distribution of neurohypophyseal peptides to their possible sites of behavioral action in the brain.     

Blood leukotriene levels during the acute asthma attack in children

Leukotrienes (LT) have been proposed to be important mediators in the etiology of the acute asthma attack (AAA). We therefore studied blood LT levels in 18 children having AAA. Heparinized blood samples were obtained before and after treatment with epinephrine injections and/or metaproterenol inhalations in the emergency room. The samples were acidified and subjected to Sep-pak chromatography. Reverse phase high performance liquid chromatography (RP-HPLC), ultraviolet (UV) spectroscopy and bioassay on guinea pig ileum were used to identify the LT based on comparison to data produced by standard synthetic LT samples. Radioimmunoassay (RIA) was used to further confirm the presence of LT LT C, D and E were detected in the plasma of children having AAA. Only LT C levels were significantly elevated over control values. The mean blood LT C level of control patients was 1.6 ± 1.2 nanograms per milliliter (ng/ml, mean t SEM) while that of the asthma patients was 73.8 ± 18.2 ng/ml prior to treatment. After emergency room treatment the asthma patients had a mean blood LT C level of 22.5 ± 11.7 ng/ml. Lowered levels of LT C accompanied improved clinical condition of the patients. This finding indicates that the AAA in children is associated with elevated blood levels of LT C.