A form of circulating interleukin-6 receptor component soluble gp130 as a potential interleukin-6 inhibitor in inflammatory bowel disease

Abstract

The presence and the role of soluble gp130, the soluble form of a component of the interleukin (IL)-6 receptor complex, were investigated in inflammatory bowel disease. The serum concentrations of soluble gp130 were increased in ulcerative colitis (active disease, median, 93.5 ng/ml; interquartile range, 26-125 ng/ml; inactive disease, 81 ng/ml, 24.8-137.3 ng/ml) and to a lesser extent in Crohn's disease (active disease, 66 ng/ml, 44.4-87.6 ng/ml; inactive disease, 63 ng/ml, 43.5-82.5 ng/ml) compared to normal controls (43 ng/ml, 27-59 ng/ml). Paired analysis of serum samples showed a decrease of IL-6 and soluble IL-6 receptor concentrations in both diseases and an increase of soluble gp130 concentrations, especially in ulcerative colitis, just after the resolution of disease exacerbation. Size fractionation of the serum revealed that a part of the IL-6 co-eluted with soluble gp130 and soluble IL-6 receptor. The IL-6-induced proliferation of murine B9 hybridoma was enhanced by recombinant soluble IL-6 receptor, whereas the proliferation was inhibited by recombinant soluble gp130. These results indicate that soluble gp130 may function as a natural inhibitor of the IL-6 actions in inflammatory bowel disease.

Fig. 1

Serum concentrations of soluble gp130 (sgp130) in patients with ulcerative colitis (UC) and Crohn's disease (CD), patients with other colitides and normal controls. The median is indicated by a horizontal line.

Fig. 2

Comparison of serum concentrations of interleukin (IL)-6, soluble IL-6 receptor (sIL-6R) and soluble gp130 (sgp130) in patients with inflammatory bowel disease before and after successful treatment. Paired serum samples were obtained from six patients with ulcerative colitis (a, UC) and seven with Crohn's disease (b, CD) during active phase and just after the resolution of disease exacerbation.

Fig. 3

Time-course of serum soluble gp130 (sgp130) concentrations in patients with inflammatory bowel disease. Four patients (a–d) were sampled serially over intervals where their disease status changed from active to inactive. (a) A 32-year-old man with ulcerative colitis who had total colonic involvement treated by sulphasalazine. (b) A 67-year-old man with ulcerative colitis who had left colonic involvement treated by 5-aminosalicylates and prednisolone. (c) A 27-year-old man with Crohn's disease who had colonic involvement treated by sulphasalazine. (d) A 44-year-old man with Crohn's disease who had colonic involvement treated by 5-aminosalicylates and prednisolone. SASP, sulphasalazine; 5ASA, 5-aminosalicylates; PSL, prednisolone; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate.

Fig. 4

Fast protein liquid chromatography profile of serum obtained from a patient with ulcerative colitis (a) and from a patient with Crohn's disease (b). Serum samples were fractionated by molecular sieving over a Superose 6 HR 10/30 column. Each fraction was assayed by enzyme-linked immunosorbent assays (ELISAs) for interleukin (IL)-6, soluble IL-6 receptor (sIL-6R) and soluble gp130 (sgp130), and results were plotted as immunoreactive concentrations versus fraction number. Elution positions of the molecular markers, thyroglobulin (669 kDa), IgG (150 kDa), BSA (67 kDa) and chymotrypsinogen A (25 kDa) indicated by arrows. The results are representative for five patients studied.

Fig. 5

Effect of soluble IL-6 receptor (sIL-6R) or soluble gp130 (sgp130) on interleukin (IL)-6-induced proliferation of murine hybridoma cell line B9. (a) The B9 cells were cultured with various concentrations of sIL-6R in the absence or presence of IL-6 for 4 days, and the cellular proliferation was determined by a colorimetric method using MTT dye as described in Materials and methods. (b) The B9 cells were cultured with various combinations of sIL-6R and sgp130 in the presence of IL-6 for 4 days, and the cellular proliferation was determined by a colorimetric method using MTT dye. Values represent the mean ± s.d. of triplicate cultures. The experiment was repeated three times and yielded comparable results.