Time-dependent expression of leukotriene B4 receptors in rat collagen-induced arthritis

Leukotriene B4 acts through its receptors, BLT1 and BLT2, however, their expression in rheumatoid arthritis is unknown. In this experiment, BLT1 and BLT2 mRNA expressions in the synovium of rats with collagen-induced arthritis (CIA) at days 1, 3, 7 and 14 after CIA onset were analyzed by RT-PCR. The expression of two immunological and inflammatory factors, S100A8 and S100A9, in the synovium of the arthritic rats was also determined at the indicated time. At d14, the differential expressions of BLT1 and BLT2 in the synovium, spleen, peripheral blood mononuclear cells (PBMC) and thymus of CIA rats were analyzed. The results showed that, in the synovium of the arthritic rats, the BLT1 mRNA expression increased after CIA onset, reached the highest value between d1 and d3, and declined afterwards while the BLT2 expression increased with time and reached its peak at d14. Both S100A8 and S100A9 expression reached the peak levels between d1 and d3, and decreased to lower levels between d7 and d14. For the analyzed tissues from CIA rats at d14, BLT1 mRNA was expressed in the thymus with the highest level, followed by the spleen, PBMC and synovium. BLT2 mRNA was expressed in the thymus the highest as well, but followed by the synovium, spleen and PBMC. Since BLT1 and BLT2 play distinct roles during CIA, this study may provide basis for new therapies targeting BLT1 and BLT2, respectively, for the treatment of arthritic inflammation at different stages.