β-endorphin inhibits the production of interleukin-8 by human chorio-decidual cells in culture

Interleukin-8 (IL-8) is produced by human decidual cells in culture, and may play a role in the initiation of parturition. beta-endorphin is released in significant amounts into the maternal and fetal circulation during labour. The effect of beta-endorphin on IL-8 production by human chorio-decidual cells in culture was investigated. Mixed cells were obtained from the decidual surfaces of 35 term placentas. The cells were plated out at 10x10(6) cells per well in Roswell Park Memorial Institute 1640 culture medium. After 48 h the cells were washed and incubated with either plain culture medium (control), 1 mu mol/l progesterone, 1-100 nmol/l beta-endorphin or 1 nmol/l N-acetyl beta-endorphin. After 48 h, IL-8 concentrations were measured in the supernatants by enzyme-linked immunosorbent assay (ELISA). Experiments were repeated in the presence of naloxone (1 mu mol/l) and using calcium-deficient culture medium. Progesterone (P < 0.0002) and beta-endorphin (P < 0.0005) significantly inhibited the production of IL-8. The inhibitory effect of beta-endorphin was blocked by naloxone and by using calcium-deficient medium. N-acetyl beta-endorphin had no significant effect on IL-8 production. These findings suggest that beta-endorphin has an inhibitory effect on IL-8 production by decidual cells, and that the effect is mediated via opioid receptors and is calcium-dependent.