Introduction: Rheumatoid and psoriatic arthritis are both characterised by synovial destruction associated with a higher turnover of the extracellular matrix. In both conditions, inflammatory processes create hypoxic environments which destabilise members of the plasminogen activating system.
Aim: Comparing the effect of bioactive concentrations of urokinase (uPA) and serpine (PAI-1) on cellular survival of human fibroblast-like-synoviocytes (HFLS) in rich and hypoxic growth media.
Material and methods: Monocultures of HFLS were exposed to bioactive uPA and PAI-1 concentrations in both media conditions for 24, 48 and 72 h. Cellular survival was evaluated with a cell viability assay by spectrum absorbance of formazan reduced WST-8.
Results: PAI-1 at 0.1 and 1 μg/ml was found to stimulate cell viability under hypoxic stress at 48 and 72 h of incubation, with the effect increasing from 48 to 72 h. uPA increased cell viability in rich medium at 48 and 72 h of incubation between 5 and 40 ng/l, but was found to reduce viability at 80 ng/l at 24 and 48 h. PAI-1 increased cell viability in the hypoxic stress model, while high concentrations of uPA decreased cell viability in rich medium.
Conclusions: The alternative modes of function at extreme concentrations provide a novel description of PAI-1 and uPA activity based on their colocalization and mutual buffering capacity, helping to place these molecules more accurately in the context of arthritic synovial deterioration.
Keywords: plasminogen activation system; plasminogen activator inhibitors; psoriatic arthritis; rheumatoid arthritis; synoviocytes; urokinase plasminogen activator.
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