Objective: The pleiotropic cytokine interleukin (IL)-6 seems to play a pivotal role in sepsis, but contradictory findings in animal models impede a rationale for therapies directed against IL-6. IL-6 signals by two mechanisms via the ubiquitous transmembrane glycoprotein 130 (gp130): "classic" signaling using membrane-bound IL-6 receptor (IL-6R) and trans-signaling using soluble IL-6R (sIL-6R). Trans-signaling is selectively inhibited by soluble gp130 (sgp130). The aim of this study was to systematically compare complete blockade of IL-6 signaling (using a neutralizing anti-IL-6 antibody) and selective blockade of IL-6 trans-signaling (using a fusion protein of sgp130 and the crystallizable fragment of immunoglobulin G1, sgp130Fc) in a standardized cecal ligation and puncture (CLP) sepsis model.
Design: Animal study.
Setting: Animal laboratory.
Subjects: C57BL/6J mice.
Interventions: We performed a 96-hr dose-response study and a 24-hr study to investigate short-term mechanisms. In the 96-hr study, CLP was performed in 120 randomized mice (20 mice received vehicle, 10 mice per dose group). Mice were treated with equimolar doses of sgp130Fc (0.01/0.1/1/10 mg/kg) or anti-IL-6 (0.008/0.08/0.8/8 mg/kg) 24 hrs before CLP. Two additional groups received 0.5 mg/kg sgp130Fc 24 hrs before or 1 mg/kg sgp130Fc 24 hrs after CLP. Survival and activity scores were obtained daily until 96 hrs after CLP. In the 24-hr study, mice were randomized into four groups with 10 animals each (sham/vehicle, CLP/vehicle, CLP/anti-IL-6 [0.8 mg/kg], and CLP/sgp130Fc [1 mg/kg]) and killed after 24 hrs.
Measurements and main results: In contrast to anti-IL-6, pretreatment with sgp130Fc significantly and dose-dependently increased survival from 45% to 100%. In addition, 1 mg/kg sgp130Fc administered 24 hrs after CLP increased survival from 45% to 80%. Mechanistically, sgp130Fc efficacy was reflected by complete prevention of epithelial cell apoptosis in the jejunum after CLP, which was not achieved with anti-IL-6.
Conclusion: Selective inhibition of IL-6 trans-signaling by sgp130Fc has considerable potential for the treatment of sepsis and related disorders.