Lipopolysaccharides attenuates growth of HS cells through the JNK pathway

Rheumatoid arthritis is characterized by inflammation of the synovial membrane, which can result in joint destruction within the first few years after onset. Lipopolysaccharides (LPS) are glycolipids found in abundance on the outer membranes of all Gram-negative bacteria and incite a vigorous inflammatory response. We studied the potential involvement of mitogen-activated protein kinase serine/threonine kinases in LPS-induced growth of HS synovial cells. Various concentrations of LPS were applied to cultured HS cells and growth rate, as well as changes in the phosphorylation states of extracellular regulated kinase 1/2, Jun N-terminal kinase (JNK), and p38 were determined. As results, growth of LPS-treated HS cells was inhibited primarily by phosphorylated JNK and this phosphorylation was mediated by the LPS receptor. Our results suggest that LPS inhibits growth of HS cells primarily through the JNK pathway.