Cytosolic phospholipase A(2)-Mediated ICAM-1 expression is calcium dependent

Background. Some human malignancies such as virus-related hepatocellular ca ncer arise in a setting of chronic inflammation. Upregulation of ICAM-1 is a seminal late event in malignant transformation following chronic inflamma tion. Cytosolic phospholipase A(2) (cPLA(2)) is a lipid-mediator activated by inflammatory stimuli, which has been shown to mediate ICAM-1 upregulatio n. As lipid mediators are known to work via calcium -dependent mechanisms i n nearly all mammalian cells, we hypothesize that inflammatory-mediated ICA M-1 upregulation is dependent on both cPLA(2) and intracellular calcium. Materials and methods. HUVEC were chosen as a representative cell line as t hey emulate hepatic sinusoids and are a well-established cell model. These were grown to confluence in T-25 flasks and stimulated with TNF-alpha or LP S for 6 h. Additional groups were preincubated with AACOCF3 (a specific cPL A(2) inhibitor) or BAPTA A.M. (a specific inhibitor of intracellular Ca2+) prior to being exposed to inflammatory stimuli. ICAM-1 expression was deter mined by mean fluorescent intensity (MFI) as measured by FITC-labeled moAb to ICAM-1 via FACS. The role of intracellular Ca2+ on cPLA(2) activity was determined by thin-layer chromatography. Groups were compared using ANOVA w ith Scheffe's post hoc analysis; *P < 0.05 vs control, daggerP < 0.05 vs LP S and TNF-alpha was considered significant; N greater than or equal to 4 al l experimental groups. Results. Both cPLA(2) and Ca2+ inhibition significantly inhibited inflammat ory upregulation of ICAM-1. Pretreatment with BAPTA A.M. attenuated HUVEC c PLA(2) activity in response to LPS. These findings suggest that appropriate molecular target suppression may prevent malignant degeneration in the pre sence of chronic inflammation. (C) 2001 Academic Press.