Aflatoxin B-1 inhibits CD14-mediated nitric oxide production in murine peritoneal macrophages

Aflatoxin B-1 (AFB(1)), a potent hepatocarcinogen, has been known to impair non-specific and specific immunity. Macrophages play an important role in host defense against tumors and microorganisms and a number of compounds ar e implicated in macrophage cytotoxicity. Since activated by the reaction of LPS with CD14, macrophages produce nitric oxide (NO) that is a cytotoxic e ffector molecule in cell killing. In the present study, we investigated whe ther the alteration of CD14 level on macrophages by AFB(1) affects NO produ ction in murine peritoneal macrophages. When macrophages were stimulated wi th LPS after AFB(1)-pretreatment, or they were cotreated with LPS and AFB(1 ), the NO production decreased in a dose-dependent manner. In contrast, whe n macrophages were post-treated with AFB(1) after LPS-stimulation, NO produ ction was unchanged. DNA, RNA, and protein synthesis were reduced by AFB(1) -pretreatment of macrophages. The addition of anti-CD14 antibodies to the c ultures decreased NO production further. FACS analysis showed that the bind ing of anti-CD14 antibodies to the macrophages was suppressed by AFB(1)-pre treatment followed by LPS-stimulation. However, AFB(1) does not alter the b inding anti-CD14 antibodies to the macrophages without LPS-stimulation. In contrast, AFB(1) pretreatment increased an amount of CD14 released in cultu re medium. Taken together, these data indicate that the reduced NO producti on in murine peritoneal macrophages by AFB(1)-pretreatment is related to th e suppressed expression of CD14 on macrophage membrane and to the increased secretion of it to culture medium after LPS-stimulation. (C) 2000 Internat ional Society for Immunopharmacology. Published by Elsevier Science Ltd. Al l rights reserved.