The effect of anti-inflammatory compounds on the biochemical changes in the Arthus reaction

Future therapeutic trends in osteoarthritis

Since cartilage contains no nerve endings, symptoms of osteoarthritis (OA) are indirect. Therapy of OA, to date, has been directed at the symptoms of pain, signs of inflammation and loss of function. A major advance has been surgical joint replacement. This benefit however, is often limited by the joint area involved and to the survival of the endoprosthesis. Orthopedic new approaches to therapy of OA include removal of abnormal tissue to stimulate repair (e.g., burring, abrasion) and grafting (e.g., osteochondral grafts, perichondrium, periosteum) to the subchondral bone. Controlled activity (e.g., passive motion) has been studied alone and with the above. Can a medication retard or reverse the degradative process of OA? Several medications are being examined for potential "chondroprotective" characteristics. Some of these agents are not new: oversulfated glycosaminoglycans (Arteparon) derived from cartilage and glycosaminoglycan peptides (Rumalon) derived from cartilage and bone marrow extracts may be prototypes of this approach to therapy. Other agents demonstrating potential benefit in retarding cartilage degradation may include non-steroidal anti-inflammatory agents, tiaprofenic acid, sodium pentosan sulfate and low dose corticosteroids. This concept of "chondroprotection" provides us a new approach to a disease in need of a new approach.

Mechanism by which methylprednisolone inhibits acute immune complex-induced changes in vascular permeability

Intravital microscopy was used to quantitate protein leakage which resulted from the deposition of immune complexes in the vasculature of the rat cremaster muscle. Immune complex deposition was initiated by the addition of 80 micrograms/ml of ovalbumin to the bath surrounding the muscle, followed by the intravenous administration of antiovalbumin. Administration of 25 mg/kg of antiovalbumin produced significant leakage of protein from the third-order venules, while 7.5 and 2.5 mg/kg had no effect. Administration of methylprednisolone (MP), 30 mg/kg, 1 h prior to the deposition of immune complexes significantly inhibited protein leakage. In separate experiments, MP inhibited intradermal edema formation and protein exudation induced in rats by histamine, platelet activating factor, or C5a. However, MP had no effect on protein exudation or edema produced by xanthine oxidase or glucose oxidase. Intravenous administration of MP inhibited the ability of polymorphonuclear leukocytes (PMNs) to phagocytize bacteria, but failed to alter hydrogen peroxide production. These results suggest that MP prevents acute changes in vascular permeability following immune complex deposition by inhibiting the effects of soluble mediators of edema on vascular endothelium and by inhibiting PMN phagocytosis.

Reduction by dexamethasone of chemotactic activity in inflammatory exudates

Using an experimental model for allergic inflammation of the air pouch type in rats, the effects of dexamethasone and indomethacin on leukocyte infiltration and level of chemotactic activity in the inflammatory exudate were examined to clarify the mechanisms of anti-inflammatory effects of glucocorticoids. Both dexamethasone and indomethacin when locally administered inhibited leukocyte infiltration, while chemotactic activity of the exudate was reduced by dexamethasone only. Indomethacin failed to reduce the level of chemotactic activity. Suppression by dexamethasone of the level of chemotactic activity became evident prior to the decrease in the number of leukocytes in the inflammatory exudate. These results suggest that the anti-inflammatory steroids manifest their inhibitory effect on leukocyte infiltration by inhibiting the generation of chemotactic factors in the inflammatory site. Besides this, the possible production of some inhibitory factors by the steroids may be considered as an alternative mechanism.

A new model of osteoarthritis in rabbits. II. Evaluation of anti-osteoarthritic effects of selected antirheumatic drugs administered systemically

A battery of drugs with antirheumatic properties was tested for effects on the progress of osteoarthritis induced by a lateral meniscectomy procedure in knee joint cartilage of rabbits. Oral administration of the potent glucocorticoids, paramethasone acetate or triamcinolone, resulted in dramatic inhibition of cartilage degeneration. Significant protection against development of osteoarthritic lesions was also observed in rabbits treated with pirprofen or CGS 5391B but not with 9 other nonsteroidal antiinflammatory drugs. A marked reduction in joint pathology was also observed in rabbits treated with tribenoside (a glucofuranoside derivative) and with tamoxifen (an anti-estrogen). Slightly protective effects of borderline significance were observed with orgotein (a superoxide dismutase), gold sodium thiomalate, and D-penicillamine. Chloroquine and calcitonin were without effect. Therapeutic effectiveness of drugs in this model of osteoarthritis cannot be explained on the basis of their antiinflammatory properties.

Mediation of increased vascular permeability after complement activation. Histamine-independent action of rabbit C5a

Intradermal injection of zymosan into nonsensitized rabbits induces plasma exudation, which is dependent on two mediators: C5a generated in extravascular tissue fluid and a vasodilator prostaglandin generated from substrates localized in cell membranes. This relationship between the complement system and the prostaglandin synthesis system had not previously been explored, and complement activation has generally been associated with increased vascular permeability via histamine release. We report that C5a increases vascular permeability by a mechanism that is not dependent on histamine release; however plasma exudation is virtually undetectable in the absence of a vasodilator substance. Because the permeability-increasing activity is stable in plasma, analogy with other species suggests that the activity is a result of C5a devoid of its carboxyl terminal arginine (C5a des Arg). This relates the observed permeability-increasing activity with effects on leukocytes rather than effects as an anaphylatoxin.

The antinflammatory effects of glucocorticosteroids. A brief review of the literature

The effects of glucocorticosteroids on immune and inflammatory responses are reviewed. The steroids seem to change the number or function of cell receptors for regulating agents, so that in areas of inflammation: (a) blood vessels dilate less, (b) lymphocytes proliferate less, (c) all leukocytes infiltrate less, (d) macrophages become less activated (digesting and secreting less), and (e) fibroblasts produce less collagen and ground substance. In addition, the corticosteroids seem to alter the response of cells to various signals from their receptors by affecting the prostaglandin system, cyclic nucleotides, and perhaps other internal mediators.

The Arthus reaction in rats, a possible test for anti-inflammatory and antiheumatic drugs

The Arthus reaction is an immunologically induced inflammatory response characterized by immune complex deposition, complement fixation, polymorphonuclear leukocyte infiltration and tissue damage. Many of these same pathological tissue alterations are found in the lesions of rheumatoid arthritis (RA). The similarities between the reversed passive Arthus reaction (RPAR) and RA led us to investigate the usefulness of the RPAR in the search for new antirheumatic agents. The RPAR was elicited in the skin of rats using chicken ovalbumin and the IgG fraction of rabbit anti-ovalbumin. Paramethasone, hydrocortisone, indomethacin, pirprofen, sulfinpyrazone, thalidomide and theophylline all gave significant inhibition of the RPAR. Ibuprofen, naproxen, cyprohepatadine and cromolyn sodium were inactive, while phenylbutazone and ASA exhibited a dose-dependent effect. The data show that the Arthus reaction, which is the result of the complex interaction of many factors, can be affected either generally or selectively at different time intervals by various therapeutic agents. The RPAR in rats may prove useful in detecting new therapeutic agents for the treatment of RA.