Hypoxia/reoxygenation Regulates Expression of Tumor Suppressor PTEN in Rheumatoid Synovial Fibroblasts

Lee, Hak Yong; Yoo, Wan Hee

Abstract

OBJECTIVE
The lack of phosphatase and tensin homolgue deleted on chromosome ten (PTEN) expression was described in rheumatoid synovial tissues and synovial fibroblasts, but exact cause of that in RA is not well known. Hypoxic conditions are thought to exist in inflamed arthritic synovium and therefore, this study was designed to investigate the effects of hypoxia/ reoxygenation on the expression of PTEN in synovial fibroblasts of rheumatoid arthritis.
METHODS
Synovial fibroblasts were isolated from synovial tissues of patients suffering from RA and hypoxic culture was performed by incubating cells in 5% CO2 incubator held at 3% oxygen by the addition of nitrogen gas for 24 hours. Then synovial fibroblasts were cultured for 10 min under normoxic condition for reoxygenation. To know the expression of PTEN and phosphorylated Akt (p-Akt) in synovial fibroblasts, Western blotting analysis was performed. The expression of PIP3 kinase and PTEN was analyzed by immunocytochemical staining.
RESULTS
There were less PTEN expression in rheumatoid synovial fibroblasts than that of healthy controls. Hypoxic/reoxygenation stimuli induced down-regulation of PTEN expression in the rheumatoid synovial fibroblasts. In contrast, the expression of PIP3 and p-Akt was increased after stimulation with hypoxia/reoxygenation.
CONCLUSION
These studies suggest that hypoxia/reoxygenation could cause the reduced expression of PTEN in rheumatoid synovial fibroblasts and thus it might thereby contribute to the invasive behaviour of rheumatoid synovial fibroblasts by maintaining their aggressive phenotype in RA.