In vitro production of interleukin-6 by human gingival, normal buccal mucosa, and oral submucous fibrosis fibroblasts treated with betel-nut alkaloids.

This study aimed to assess the possibility of a direct effect of betel-nut alkaloids arecoline and arecaidine on cell proliferation and interleukin-6 (IL-6) production by cultured fibroblasts from human normal gingiva, buccal mucosa and oral submucous fibrosis (OSF) buccal mucosa in vitro. Confluent monolayers of fibroblasts were incubated with or without alkaloids in the presence of 10% fetal calf serum for 48 h at 37 degree C in 5% CO2 and air. At the end of the culture period, supernatants were collected and assayed for IL-6 level. The cell proliferation was monitored by determining 5-bromo-2'-deoxy-uridine (BrdU) incorporated into cellular DNA. Except for the fact that arecoline inhibited cell growth at 100 micrograms/ml, arecoline and arecaidine had similar dose-dependent stimulant effects on the proliferation of these three groups fibroblasts. Concentrations of IL-6 in the control culture supernatants were greatest in healthy gingival fibroblasts, followed by normal buccal mucosa and OSF. Also, the presence of fetal calf serum could stimulate IL-6 release. Except for arecoline at the 100 microgram/mg, there were no significant differences in IL-6 levels between treated and control cultures of the same group when the data were expressed with mean +/- S.D.. However, two of six individuals' normal buccal mucosa fibroblasts significantly released less IL-6, and some cases of OSF and healthy gingiva exhibited slightly higher levels of IL-6 when cells were exposed to arecoline or arecaidine in cultures. Such findings suggests that arecoline and arecaidine can enhance cell proliferation and affect fibroblasts to synthesize IL-6. Furthermore, IL-6 may be a contributing molecular factor in the pathological features noted in OSF.