Cytosolic phospholipase A(2)-mediated ICAM-1 expression is calcium dependent.
BACKGROUND
Some human malignancies such as virus-related hepatocellular cancer arise in a setting of chronic inflammation. Upregulation of ICAM-1 is a seminal late event in malignant transformation following chronic inflammation. Cytosolic phospholipase A(2) (cPLA(2)) is a lipid-mediator activated by inflammatory stimuli, which has been shown to mediate ICAM-1 upregulation. As lipid mediators are known to work via calcium-dependent mechanisms in nearly all mammalian cells, we hypothesize that inflammatory-mediated ICAM-1 upregulation is dependent on both cPLA(2) and intracellular calcium.


METHODS
HUVEC were chosen as a representative cell line as they 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 LPS for 6 h. Additional groups were preincubated with AACOCF3 (a specific cPLA(2) inhibitor) or BAPTA A.M. (a specific inhibitor of intracellular Ca(2+)) prior to being exposed to inflammatory stimuli. ICAM-1 expression was determined by mean fluorescent intensity (MFI) as measured by FITC-labeled moAb to ICAM-1 via FACS. The role of intracellular Ca(2+) on cPLA(2) activity was determined by thin-layer chromatography. Groups were compared using ANOVA with Scheffe's post hoc analysis; *P < 0.05 vs control, daggerP < 0.05 vs LPS and TNF-alpha was considered significant; N > or = 4 all experimental groups.


RESULTS
Both cPLA(2) and Ca(2+) inhibition significantly inhibited inflammatory upregulation of ICAM-1. Pretreatment with BAPTA A.M. attenuated HUVEC cPLA(2) activity in response to LPS. These findings suggest that appropriate molecular target suppression may prevent malignant degeneration in the presence of chronic inflammation.
Barnett
C C
CC
Department of Surgery, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Avenue, Houston, TX 77030, USA. ccbarnet@mdanderson.org
Moore
E E
EE
Silliman
C C
CC
Abdalla
E K
EK
Partrick
D A
DA
Curley
S A
SA
D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014471:Umbilical Veins / Q000166:cytology; D015854:Up-Regulation / Q000502:physiology
D002614:Chelating Agents; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D004533:Egtazic Acid; D010741:Phospholipases A; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium