Effects of Levofloxacin and Doxycycline on Interleukin-6 Production of Chlamydia trachomatis-Infected Human Synovial Fibroblasts

Abstract

Background: Alarge amount (80,000–100,000 pg/ml) of interleukin-6 (IL-6) was detected in cultures of human synoviocytes infected with Chlamydia trachomatis. In this study, we investigated the effect of antibiotics on the IL-6 production of C. trachomatis-infected human fibroblast-like synovial cells (HFLS). Methods: The minimum inhibitory concentrations of levofloxacin and doxycycline against C. trachomatis were determined in either HFLS or HeLa 229 cells. The number of live Chlamydia was also examined. IL-6 in the supernatants of infected cultures was quantified by capture ELISA. Results: The production of IL-6 was suppressed to as low as 1,800 pg/ml in the infected HFLS treated with levofloxacin or doxycycline immediately or early after infection. In HFLS treated with levofloxacin and doxycycline, the IL-6 levels decreased to 37,000 and 21,000 pg/ml, respectively, 48 h after infection, and levofloxacin was thus found to be less effective than doxycycline. In addition, the number of viable C. trachomatis in the infected cultures treated with levofloxacin 24 h after infection was higher than when treated with doxycycline. Conclusions: The early administration and proper selection of antibiotics is important for the suppression of inflammatory cytokine production. These findings indicate that antibiotic therapy will not only work in treating infections but might also be useful in treating reactive arthritis secondary to the infection.