BETA-CAROTENE IN-VITRO STIMULATES TUMOR-NECROSIS-FACTOR-ALPHA AND INTERLEUKIN-1 ALPHA-SECRETION BY HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS

Beta-carotene (BC) potentially affects cancer resistance by stimulatin g secretion of immunoregulatory cytokines and thereby modulating immun e defenses. Therefore, we investigated the effects of BC applied in vi tro on the secretion of interleukin-1 alpha (IL-1), tumor necrosis fac tor alpha (IL-1), tumor necrosis factor alpha (TNF) and interferon-gam ma (IFN) by human peripheral blood mononuclear cells (PBMC). PBMC from healthy individuals were activated with pokeweed mitogen (PWM; 0.1 ug /ml), or lipopolysaccharide (LPS; 10 ug/ml) for 24 hr, or phytohemaggl utinin (PHA; 5 ug/ml) for 74 hr. BC was encapsulated in liposomes and delivered to PBMC during mitogen activation at concentrations of 10(-6 ) to 10(-11) M. The concentration of cytokines in the supernatants of activated cells was measured by ELISA. BC had no impact on IFN release . The release of IL-1 was significantly (p < 0.05) stimulated by BC (1 0(-6) to 10(-8) M). No effect on IL-1 secretion was obtained when PBMC were incubated with BC-free liposomes. However, BC-free liposomes sup pressed significantly TNF secretion (from 1.5 to 0.2 ng/ml). When BC w as presented in liposomes at concentrations ranging from 10(-6) to 10( -8) M it stimulated significantly (p < 0.01) TNF secretion. We suggest that physiologically achievable concentration so BC stimulate monokin e secretion. Such changes might explain in part the observed immunomod ulatory effect of BC on lymphoid cells and reduced cancer risk associa ted with high intake of BC.