In vitro senescence enhances IL-6 production in human gingival fibroblasts induced by lipopolysaccharide from Campylobacter rectus

Abstract

The production of interleukin-6 (IL-6) in human gingival fibroblasts (Gin cells) is increased by lipopolysaccharide (LPS) from Campylobacter rectus (C. rectus), which is associated with adult periodontitis; however, the age-related changes in the susceptibility of Gin cells to C. rectus LPS remain unclear. We examined the influence of in vitro senescence on C. rectus LPS-stimulated IL-6 production in Gin cells. LPS was prepared from C. rectus ATCC 33238 using hot phenol-water. The Gin cells were established from healthy gingival tissue removed from three patients, aged 10–12 years. The cells were cultured until confluence then stimulated with LPS (0.01, 0.1, 1.0 and 10.0 μg/ml). Levels of IL-6 released in the medium were measured after incubation for 3, 6, 9, 12 and 24 h. In both young (5–6 population doublings) and senescent (17–20 population doublings) cells. LPS stimulated IL-6 production in a dose- and time-dependent manner. In response to 0.01–10.0 μg/ml of LPS, IL-6 production in the senescent cells was higher than that in the young cells. Using cells from each of the three donors, we found that this phenomenon of higher LPS-stimulated IL-6 production in senescent cells was reproducible. The greater capacity of the senescent cells to synthesize IL-6 in response to LPS was a higher production of mRNA for IL-6. This increase of IL-6 production induced by C. rectus LPS in senescent Gin cells could help to explain the increased susceptibility to periodontal diseases shown by aged individuals.