Cobalt chloride-induced signaling in endothelium leading to the augmented adherence of sickle red blood cells and transendothelial migration of monocyte-like HL-60 cells is blocked by PAF-Receptor antagonist
C. Sultana et al., Cobalt chloride-induced signaling in endothelium leading to the augmented adherence of sickle red blood cells and transendothelial migration of monocyte-like HL-60 cells is blocked by PAF-Receptor antagonist, J CELL PHYS, 179(1), 1999, pp. 67-78
In response to hypoxia, sickle red blood cells (SS RBC) and leukocytes exhi
bit increased adherence to the vascular endothelium, while diapedesis of le
ukocytes through the blood vessel increases. However, the cellular signalin
g pathway(s) caused by hypoxia is poorly understood. We utilized CoCl2 as a
mimetic molecule for hypoxia to study cellular signaling pathways. We foun
d that in human umbilical vein endothelial cells (HUVEC), CoCl2 at 2 mM con
centration induced the surface expression of a subset of CAMs (VCAM-1) and
activation of transcription factor NF-kB in the nuclear extracts of HUVEC.
Furthermore, CoCl2 also caused time-dependent tyrosine phosphorylation of m
itogen-activated protein (MAP) kinase isoform ERK2 without significantly af
fecting ERK1, indicating ERK2 is the preferred substrate for upstream kinas
e of the MAPK pathway. Inhibitors of MAP kinase (PD98059) or platelet-activ
ating factor(PAF)- receptor antagonist (CV3988) inhibited the CoCl2-induced
NF-kB activation and VCAM-1 expression. Augmented expression of VCAM-1 led
to increased SS RBC adhesion, inhibitable by a VCAM-1 antibody. Additional
ly, CoCl2 caused a two- to threefold increase in the rate of transendotheli
al migration of monocyte-like HL-60 cells and a twentyfold increase in phos
phorylation of platelet endothelial cell adhesion molecules (PECAM-1). The
transendothelial migration of monocytes was inhibited by an antibody to PEC
AM-1. Both phosphorylation of PECAM-1 and transendothelial migration of mon
ocytes in response to CoCl2 were inhibited by protein kinase inhibitor (GF1
09203X) and augmented by protein phosphatase inhibitor (Calyculin A). Our d
ata suggests that CoCl2-induced cellular signals directing increased expres
sion of VCAM-1 in HUVEC involve downstream activation of MAP kinase and NF-
kB, while the phosphorylation of PECAM-1 occurs as a result of activation o
f PKC. We conclude that PAF-receptor antagonist inhibits the CoCl2- or hypo
xia-induced increase in the adhesion of SS RBC, PECAM-1 phosphorylation, an
d the concomitant transendothelial migration of monocytes. J. Cell. Physiol
. 179:67-78, 1999. (C) 1999 Wiley-Liss, Inc.