TY - JOUR
T1 - Phospholipase activation during monocyte adherence and spreading
AU - Lefkowith, J. B.
AU - Lennartz, M. R.
AU - Rogers, M.
AU - Morrison, A. R.
AU - Brown, E. J.
PY - 1992/9/1
Y1 - 1992/9/1
N2 - Phospholipase activation is an important element in cellular signal transduction. In our study we investigated the role and regulation of phospholipase activation during human monocyte adherence and spreading. In human monocytes, phospholipase inhibition (with bromophenacyl bromide (BPB) or manoalide) impaired cell adherence and spreading. In contrast, neither cyclooxygenase/lipoxygenase inhibition nor platelet activating factor receptor blockade affected these responses. The impaired adherence and spreading induced by phospholipase inhibition with BPB could be partially reversed by the addition of nM levels of arachidonate (20:4(n-6)). Dihomogammalinolenic acid (20:3(n-6)) could substitute for arachidonate, but other polyunsaturated fatty acids were ineffective in this regard. The phospholipase inhibitor, BPB was selective in its effects on cellular phospholipase activities. BPB inhibited adherence/spreading-related and PMA-stimulated phospholipase activities, but not Ca2+ ionophorestimulated phospholipase activity. To further probe for the role of Ca2+ in monocyte adherence and spreading, monocytes were loaded with MAPTAM (bis-(2-amino-5-methylphenoxy)-ethane-N,N,N′,N′, tetraacetic acid tetraacetoxymethyl ester), an EGTA analog. In contrast to phospholipase inhibition, intracellular Ca2+ chelation with MAPTAM did not affect monocyte adherence but did inhibit monocyte spreading. MAPTAM partially inhibited adherence/ spreading-stimulated phospholipase activity, but did not inhibit PMA-stimulated phospholipase activity. These data suggest that human monocyte adherence and spreading may sequentially activate Ca2+-independent and then Ca2+-dependent phospholipases to release arachidonate. The activation of phospholipase and the release of arachidonate appear to be integral parts of the adhesion process.
AB - Phospholipase activation is an important element in cellular signal transduction. In our study we investigated the role and regulation of phospholipase activation during human monocyte adherence and spreading. In human monocytes, phospholipase inhibition (with bromophenacyl bromide (BPB) or manoalide) impaired cell adherence and spreading. In contrast, neither cyclooxygenase/lipoxygenase inhibition nor platelet activating factor receptor blockade affected these responses. The impaired adherence and spreading induced by phospholipase inhibition with BPB could be partially reversed by the addition of nM levels of arachidonate (20:4(n-6)). Dihomogammalinolenic acid (20:3(n-6)) could substitute for arachidonate, but other polyunsaturated fatty acids were ineffective in this regard. The phospholipase inhibitor, BPB was selective in its effects on cellular phospholipase activities. BPB inhibited adherence/spreading-related and PMA-stimulated phospholipase activities, but not Ca2+ ionophorestimulated phospholipase activity. To further probe for the role of Ca2+ in monocyte adherence and spreading, monocytes were loaded with MAPTAM (bis-(2-amino-5-methylphenoxy)-ethane-N,N,N′,N′, tetraacetic acid tetraacetoxymethyl ester), an EGTA analog. In contrast to phospholipase inhibition, intracellular Ca2+ chelation with MAPTAM did not affect monocyte adherence but did inhibit monocyte spreading. MAPTAM partially inhibited adherence/ spreading-stimulated phospholipase activity, but did not inhibit PMA-stimulated phospholipase activity. These data suggest that human monocyte adherence and spreading may sequentially activate Ca2+-independent and then Ca2+-dependent phospholipases to release arachidonate. The activation of phospholipase and the release of arachidonate appear to be integral parts of the adhesion process.
UR - http://www.scopus.com/inward/record.url?scp=0026784595&partnerID=8YFLogxK
M3 - Article
C2 - 1506690
AN - SCOPUS:0026784595
SN - 0022-1767
VL - 149
SP - 1729
EP - 1735
JO - Journal of Immunology
JF - Journal of Immunology
IS - 5
ER -