The effects of the phospholipase A2 inhibitor, manoalide, on cartilage degradation, stromelysin expression, and synovial fluid cell count induced by intraarticular injection of human recombinant interleukin-1 alpha in the rabbit.

OBJECTIVE: To evaluate the effects of the phospholipase A2 (PLA2) inhibitor manoalide on cartilage degradation, stromelysin expression, and inflammatory cell accumulation in rabbits treated intraarticularly with recombinant human interleukin-1 alpha (rHuIL-1 alpha). METHODS: Rabbits were given an intraarticular injection of rHuIL-1 alpha. At various time points over a 24-hour period, the rabbits were euthanized and the articular space was lavaged with sterile PBS. The proteoglycan content of the lavage fluid was measured using a dimethylmethylene blue assay. PLA2 activity and differential cell counts were also measured. The femur was removed and cartilage proteoglycan content determined. In some experiments, levels of synovial stromelysin messenger RNA (mRNA) were assessed. Manoalide or vehicle was administered 30 minutes before the rHuIL-1 alpha injection. RESULTS: The rHuIL-1 alpha-induced arthritic response is characterized by significant accumulation of inflammatory cells, loss of proteoglycan from the condylar cartilage, and induction of mRNA for stromelysin. PLA2 activity was also elevated in synovial fluids from rHuIL-1 alpha-injected joints. Pretreatment with manoalide (0.3 mg/joint) significantly inhibited PLA2 activity in the synovial fluid, prevented the loss of proteoglycan from the condylar cartilage, and reduced proteoglycan levels in lavage fluids. However, manoalide either had no effect on, or stimulated, cell accumulation. To assess the relationship between the induction of PLA2 and stromelysin, levels of stromelysin mRNA were measured in synovial tissue from manoalide- and vehicle-treated joints. Stromelysin message levels were significantly suppressed in a dose-dependent manner. CONCLUSION: These studies demonstrate that manoalide is a potent inhibitor of inflammation and cartilage catabolism, and suggest that PLA2 is involved in the pathophysiology of rHuIL-1 alpha-induced arthritis in rabbits.

Anti-inflammatory properties of Gö 6850: a selective inhibitor of protein kinase C.

Protein kinase C (PKC) regulates a variety of signal transduction events implicated in the pathogenesis of inflammation, including the biosynthesis of inflammatory cytokines and superoxide and the activation of phospholipase A2. Because of the significant role of PKC in these inflammatory processes, we evaluated a specific and potent inhibitor of C kinase for efficacy in several in vitro and in vivo murine models of inflammation. Unlike the relatively nonspecific kinase inhibitor staurosporine, the bisindolylmaleimide 3-[1-[-3-(dimethylaminopropyl]-1H-indol-3-yl]- 4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione monohydrochloride (Gö 6850) demonstrated increased selectivity for C kinase in purified enzyme assays (respective IC50 values (microM) for Gö 6850 and staurosporine: protein kinase C (0.032, 0.009); myosin light-chain kinase (0.6, 0.01); protein kinase G (4.6, 0.018); protein kinase A (33, 0.04); tyrosine kinase1 (94, 0.4); tyrosine kinase2 (> 100, > 1)). Topically applied Gö 6850 inhibited phorbol myristate acetate-induced edema, neutrophil influx and vascular permeability in murine epidermis in a dose- and time-dependent manner at levels comparable to indomethacin. In a murine model of delayed type hypersensitivity, Gö 6850 inhibited dinitrofluorobenzene-induced contact dermatitis with and ID50 value of 150 micrograms/ear. Cellular studies in mouse peritoneal macrophages demonstrated that Gö 6850 was a potent inhibitor of phorbol myristate acetate-induced prostaglandin E2 production. Superoxide production in phorbol myristate acetate-stimulated murine neutrophils was also inhibited by Gö 6850 (IC50 = 88 nM).(ABSTRACT TRUNCATED AT 250 WORDS)