Recombinant adenovirus can be administered in vivo to achieve transduction of a number of cell types including human synoviocytes. Immunogenicity of adenoviruses has limited their utility as vectors for gene delivery; however, specific mechanisms underlying the acute inflammatory response to adenovirus are not well understood. Activation of a number of signal transduction pathways occurs rapidly upon adenovirus binding to cell-surface receptors. We investigated stimulated expression of mitogen-activated protein kinases (MAPKs), cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)) in human primary synovial fibroblasts to adenovirus expressing the E. coli beta-galactosidase gene.
Cultured rheumatoid synoviocytes were exposed to transduction-competent Ad/RSVlacZ recombinant adenovirus or transduction-incompetent (psoralen/UV-irradiated) Ad/RSVlacZ. The effects on COX-2 expression, PGE(2) levels and MAPK signaling in synoviocytes were assessed using a combination of reverse-transcription polymerase chain reaction amplification and immunoblotting.
Adenovirus treatment of synoviocytes increased levels of COX-2 mRNA and protein as well as PGE(2). Psoralen-treated transcriptionally inactive adenovirus was equivalent to untreated adenovirus for early COX-2 induction suggesting that viral genes were not required. Adenovirus treatment stimulated phosphorylation of ERK-1/-2, p38 MAPK, and JNK. Inhibition of the ERK and p38 MAPK pathways inhibited COX-2 expression and PGE(2) production.
Taken together, these data demonstrate that a MAPK-dependent increase in COX-2 results in local prostaglandin production. These findings have clinical implications for use of adenovirus as vectors for in vivo gene delivery.