Inflammation In Rabbits Research Articles

Topical Arachidonic Acid: A Model for Screening Anti-Inflammatory Agents

Products of arachidonic acid metabolism, prostaglandins and leukotrienes, play an important role in ocular inflammation. In this study, we investigated the efficacies of the cyclo-oxygenase inhibitors (aspirin, indomethacin, and piroxicam) and the lipoxygenase inhibitors (N-hydroxy-arachidonamide (AH) and phenidone) in reducing ocular inflammation induced by arachidonic acid. Administering arachidonic acid topically (0.50% for rabbits and 0.25% for humans) produced a simple model for evaluating the effects of inhibitors on prostaglandins. In rabbits, aspirin, piroxicam and indomethacin all blocked lid closure and chemosis significantly. In humans, aspirin and indomethacin significantly blocked arachidonic acid-induced conjunctival injection. Neither AH nor phenidone blocked any of the signs of ocular inflammation in rabbits or humans. Further testing of phenidone in the presence of the calcium ionophore, ionomycin, also proved negative. Species specificity in arachidonic acid metabolism may account for the different results in humans and rabbits. This model may be a useful tool for comparing the relative efficacies of topical cyclo-oxygenase inhibitors in treating ocular problems.

Relationships between pulmonary inflammation, plasma transudation, and oxygen metabolite secretion by alveolar macrophages.

We have previously shown that alveolar macrophages from normal rabbit lungs do not synthesize reactive oxygen intermediates unless first conditioned by culture in vitro in the presence of serum for 24 to 48 hr. This conditioning process is mediated by a serum constituent that partitions on gel exclusion columns with an apparent m.w. of 30,000 to 50,000 daltons. Alveolar macrophage conditioning in vitro requires protein synthesis, is associated with the generation of membrane NADPH oxidase activity, and is reversible. We have predicted therefore that during the course of pulmonary inflammation, as observed 3 wk after i.v. injection of M. butyricum in oil, alveolar macrophages might similarly become conditioned in vivo through exposure to plasma protein transudates reaching the alveolus. In support of this hypothesis we show that after experimental production of granulomatous pulmonary inflammation in rabbits, alveolar macrophages showed an augmented capacity to secrete superoxide anion when stimulated with phorbol ester, and this enhancement increases exponentially with increased plasma transudation. This augmented enhancement was reversible, and decreased after culture in vitro in the absence of serum. Mature alveolar macrophages were responsible for this enhanced superoxide anion production rather than freshly emigrated monocytes. Moreover, superoxide anion production in this model of pulmonary inflammation appears to be an "all-or-none" phenomenon, with superoxide anion production associated with a subpopulation of optimally conditioned alveolar macrophages, whereas the remaining unconditioned alveolar macrophages produce little or none. We feel that these two classes of alveolar macrophages may be derived from inflamed and noninflamed regions of the lung, respectively, thereby reflecting the discontinuous nature of the inflammatory lesions themselves. Thus we propose that measurements of reactive oxygen intermediate production by lavaged alveolar macrophages may provide a semi-quantitative measure of chronic pulmonary inflammation.

The induction of meningeal inflammation by components of the pneumococcal cell wall.

Pneumococcal cell wall induces meningeal inflammation in rabbits injected intracisternally with greater than 10(5) cell equivalents. Both of the major cell wall components, teichoic acid and peptidoglycan, contribute to this inflammatory activity although responses differ depending on the chemical nature, size, and complexity of these fractions. Challenge with teichoic acid (membrane or wall associated) results in greater inflammation at 5 hr than at 24 hr. Degraded teichoic acid is inactive. In contrast, the inflammation caused by whole cell wall or high-molecular-weight peptidoglycan-containing fractions increases in intensity from 5 to 24 hr. Peptidoglycan fractions lose activity at 24 hr when hydrolyzed to disaccharide-stem peptide moieties. Generation of free cell wall components in cerebrospinal fluid as, for example, during treatment with antibiotics that are bacteriolytic as well as bactericidal, could contribute to increased inflammation in the subarachnoid space.

Ocular anti-inflammatory action of a lipoxygenase inhibitor in the rabbit.

Among all lipoxygenase inhibitors studied, REV 5901 was found to be the most potent one to reduce lens protein-induced ocular inflammation in rabbits. It reduced ocular inflammation effectively by either injection into the ear vein (10 mg/kg) (65% inhibition) or topical administration (50 microliters of 5% ointment) (40% inhibition). Local administration was less effective than intravenous injection presumably because of slower drug delivery into the eyes.

Comparison of the effects of glucocorticoid and indomethacin treatment on the acute inflammatory reaction in rabbits

We have recently shown that indomethacin and ASA diminish the elevated blood flow, protein exudation, and leukocyte infiltration during acute inflammation induced by killed Escherichia coli, the reversed Arthus reaction, or zymosan-activated plasma (ZAP; C5ades-arg) in rabbit skin. All of these effects were likely due to the inhibition by these drugs of prostaglandin (PG) synthesis in the lesions. Because glucocorticoids are also reported to inhibit PG production and, in large doses, to suppress inflammation accompanying various clinical conditions, we investigated the effects of hydrocortisone (HC), and methylprednisolone (MP), administered in large doses (100 mg/m2/d of MP or 2.5 g/m2/d of HC) on the above three forms of acute inflammation in rabbits. The effect of indomethacin treatment was studied in parallel for comparison. Blood flow, protein exudation, and leukocyte infiltration were quantitated simultaneously with 86Rb Cl, 125I-labelled rabbit albumin and 51Cr labelled blood leukocytes. Systemic indomethacin therapy decreased the blood flow and permeability, while local indomethacin (2.5 μg) significantly inhibited leukocyte infiltration into the lesions. In contrast, HC and MP caused only a mild decrease in blood flow, without altering protein exudation or leukocyte influx. However, HC and MP did inhibit protein exudation induced by bradykinin or histamine injection. These results indicate that, at least in rabbits, HC and MP, in contrast to indomethacin, have very weak anti-inflammatory actions on three complement- and neutrophil-mediated inflammatory responses, i.e., E. coli, ZAP (C5ades-arg) and reversed Arthus reactions.

Chronic arthritis of rabbits induced by mycoplasmas. III. Induction with nonviable mycoplasma arthritidis antigens

Preexposure of rabbits to Mycoplasma arthritidis predisposed them to subsequent development of chronic inflammation in knee joints challenged with nonviable M arthritidis antigens. Rabbits sensitized by hyperimmunization developed a more severe arthritis than those sensitized by infection. Unsensitized rabbits responded minimally to intraarticular injection of nonviable organisms. These results suggested that an immune response to a persisting mycoplasmal antigen might be capable of sustaining chronic inflammation in rabbits with arthritis induced by viable M arthritidis.

The development of granulomatous pulmonary inflammation in rabbits by aerosol challenge: I. Release of plasminogen activator by alveolar macrophages

A rabbit model of hypersensitivity pneumonitis (HP) was employed to evaluate the release of plasminogen activator (PA) as a method for monitoring the degree of pulmonary inflammation. PA release from alveolar macrophages (AM) was shown to coincide with inflammation and was maximal at approximately 2 weeks of aerosol challenge. PA release could also be induced in normal AM by peripheral lymphocytes obtained from sensitized animals after incubation with antigen. Unseparated peripheral blood mononuclear cells from experimental animals also exhibited antigen-induced PA release. These results suggest that the measurement of PA release using several different cell populations can be used to evaluate pulmonary inflammation in HP.

Joint inflammation in rabbits induced by preformed immune complexes.

The rabbit knee joint was used to evaluate the inflammatory properties of immune complexes with different contents of antigen. Immune complexes made in vitro with antiserum from hyperimmunized rabbits and bovine serum albumin as antigen were injected into the joints. The reactivity of the individual animal was established by injection of normal rabbit serum into the contralateral joint. The number of leukocytes washed out from the joints at fixed intervals was used as a measure of the inflammatory properties of the immune complexes. With immune complexes formed at antigen excess the highest numbers of leukocytes, with a predominance of granulocytes, were found after 6 h of exposure. However, these complexes gave only weak complement activation in vitro, measured with a hemolysis assay. Complexes formed at optimal precipitation proportions gave high complement activation in vitro but only a small number of leukocytes in the joints at 6 h exposure. This finding may be explained by a rapid phagocytosis of the latter complexes while complexes formed at antigen excess are not readily phagocytized. This hypothesis is supported by the observation that higher leukocyte counts were found after shorter exposure times to complexes formed at optimal precipitation proportions than after exposure to complexes with antigen excess.

The reduction of experimentally induced inflammation by sulfhydryl compounds

The sulfhydryl compounds acetylcysteine and acetylpenicillamine were found to reduce the severity of induced dermal inflammation in rabbits when the compounds were administered in repeated doses. Treatment with acetylcysteine and salicylate given concomitantly resulted in an anti-inflammatory response which was equal to that obtained with thiosalicylate and was significantly greater than that obtained with either acetylcysteine or salicylate given individually.

Indomethacin in ocular inflammation in rabbits.

Acute ocular inflammation was produced in sensitized rabbits by the intracameral injection of bovine serum. When the rabbits were treated with hydrocortisone or the nonsteroid anti-inflammatory agent, indomethacin (Indocin), by the intramuscular or topical route the degree of inflammation was markedly reduced. Topical hydrocortisone and indomethacin did not alter wound healing in the rabbit cornea. Indomethacin did not alter the course of corneal infection due to the RE and PH strains of<i>Herpesvirus hominis</i>, whereas, hydrocortisone made the course of this infection worse. Indomethacin and hydrocortisone did not inhibit the antiviral effects of idoxuridine on herpetic keratitis of the rabbit cornea.

FURTHER PURIFICATION OF A PROTEASE INHIBITOR FROM RABBIT SKIN WITH HEALING INFLAMMATION.

A specific protease (peptide peptidohydrolase) inhibitor was isolated form the healing skin site of Arthus-type inflammation in rabbits and highly purified as a substance with a fibrous microscopic appearance. The purification procedures consisted of (1) preparation of an euglobulin fraction from the skin extracts with ammonium sulfate; (2) chromatography of the protein fraction with Sephadex G-50, DEAE-cellulose and CM-cellulose in the order stated; (3) concentration of effluent inhibitory fractions with polyvinyl pyrrolidone; and (4) precipiration of the inhibitory substance in the cold. The inhibitor behaved as a homogeneous substance paper-electrophoreticallly and ni ultracentrifugation. The isoelectric point of the substance was around pH 6.6 and its sedimentation coefficinet was 1.21 S. It inactivated papain (EC3.4.4.10) as well as the SH-dependent protease responsible for the cutaneous lesion of ARthus-type inflammation, but had no effect on trypsin (EC 3.4.4.4.4) or α-chymotrypsin (EC 3.4.4.5).

Experimental use of enzymes for hyphemas and conjunctival hematomas.

In recent years there has accumulated considerable clinical and experimental evidence which shows that specific proteolytic enzymes can act as potent anti-inflammatory agents. <h3>Review of the Literature</h3> Gordon et al. (1957)¹induced inflammation in rabbits by the subconjunctival instillation of mustard oil. The intravenous administration of streptokinase-streptodornase preparations prior to the elicitation of the inflammation was shown to be effective in decreasing the severity of the reaction produced. When purified streptodornase was used alone, the reaction of the treated animals did not differ from that of the controls. When streptokinase purified by chromatography was employed, a definite inhibition of inflammation was observed. All effective antiedema concentrations of streptokinase produced demonstrable fibrinolytic responses in the rabbit. Doses of heparin sufficient to render the blood incoagulable during the experimental period were found to be ineffective in reducing the degree of edema produced. Consequently, it must be assumed that fibrin deposition is

The rate of flow of the lymph in an inflammatory focus

Inflammation in rabbits was caused by xylol application to the skin of the abdomen (the hair being previously cut). The velocity of the lymph flow was determined by the rapidity of removal of the homologous I131 labeled serum, injected intradermally. The velocity of removal of labelled proteins is higher during the first 40 minutes following the application of xylol, and subsequently decreases. Thus, stagnation of the lymph develops in the focus of infection after a short period of accelerated velocity of the flow.

The disturbance of vascular permeability in burns. An electrophoretic investigation of the protein content of lymph flowing from the burned area

Electrophoretic investigations of the lymph draining from burned rabbits' paws were performed. It was established that the concentration of protein increases within the first hour after the burn and an additional β-globulin fraction (β2-globulin) appears. In 24 hours, the derangement of the protein content of the lymph is even more pronounced, i.e., the concentration of protein increases, the relative content of albumin diminishes, β2-globulin fraction is still present and the level of α2-globulin is also raised. In accordance with literature data on the effect of active β-globulins on the local capillary permeability the author suggests that these proteins play an important role in the appearance of general disturbances of capillary permeability in the areas free from inflammations. These disturbances were revealed by the author in experimentally induced inflammation in rabbits and dogs. They were described in his previous papers.

Effect of cortisone on horse serum uveitis in rabbits.

THERE have been numerous clinical reports of the beneficial effect of pituitary adrenocorticotropic hormone (ACTH) and cortisone on inflammatory ocular disease in humans. However, when the present study was begun, relatively little work had been reported on the results of cortisone or ACTH treatment of experimental uveitis. The intraocular injection of horse serum has been found to be a satisfactory method of producing a granulomatous type of uveitis in rabbits, 1 probably on the basis of an anaphylactic type of hypersensitivity. In view of the fact that ACTH and cortisone suppress many forms of systemic hypersensitivity, including cardiovascular lesions in rabbits induced with horse serum, 2 it might well be expected that these substances would be effective in horse serum uveitis. Since the present work was begun, Woods 3 has reported the dramatic effects of ACTH and cortisone on experimentally produced ocular inflammation in rabbits, including the injection of horse

Capillary permeability and inflammation in rabbits given heparin: Rigdon, R. H., and Wilson, H.: Arch. Surg. 43: 64, 1941

Capillary permeability and inflammation in rabbits given heparin: Rigdon, R. H., and Wilson, H.: Arch. Surg. 43: 64, 1941