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.


CONCLUSIONS
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.
Schrier
D J
DJ
Parke Davis Pharmaceutical Research, Ann Arbor, Michigan, USA.
Flory
C M
CM
Finkel
M
M
Kuchera
S L
SL
Lesch
M E
ME
Jacobson
P B
PB
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001168:Arthritis / Q000139:chemically induced; D002356:Cartilage / Q000187:drug effects* / Q000378:metabolism; D002452:Cell Count / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007270:Injections, Intra-Articular; D007375:Interleukin-1; D008297:Male; D019278:Matrix Metalloproteinase 3; D008666:Metalloendopeptidases / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors* / Q000378:metabolism; D054467:Phospholipases A2; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins; D013582:Synovial Fluid / Q000166:cytology* / Q000201:enzymology; D013729:Terpenes / Q000494:pharmacology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D007375:Interleukin-1; D009363:Neoplasm Proteins; D010726:Phosphodiesterase Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013729:Terpenes; C045673:manoalide; D010741:Phospholipases A; D054467:Phospholipases A2; D008666:Metalloendopeptidases; D019278:Matrix Metalloproteinase 3