AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 4 666-L673, Copyright © 1995 by American Physiological Society
Extracellular nucleotides stimulate leukocyte adherence to cultured pulmonary artery endothelial cells
D. D. Dawicki, J. McGowan-Jordan, S. Bullard, S. Pond and S. Rounds
Department of Medicine, Providence Veterans Affairs Medical Center, Rhode Island 02908, USA.
Adenosine, ATP, and various nucleotides were examined for their effects on
the adherence of leukocytes to bovine pulmonary artery endothelial cells.
Extracellular ATP enhanced adherence of HL-60 cells and human neutrophils
to endothelial cells in a dose-dependent fashion. Maximal adherence
occurred after 15 min coincubation of ATP and HL-60 cells or neutrophils
with endothelial cells. ATP stimulation was mediated by direct effects on
both HL-60 cells and endothelial cells. The potency profile of various
nucleotides was ATP = 2-MeSATP > beta,gamma-CH2ATP, indicative of a P2y
receptor. Interestingly, UTP was as potent as ATP in stimulating HL-60 cell
adherence, suggesting the presence of a pyrimidine nucleotide receptor.
Photoaffinity labeling of endothelial cells with 8-Az-[alpha-32P]ATP showed
the presence of two ATP binding proteins of 48 and 87 kDa. ATP and 2-MeSATP
inhibited binding by both proteins. Labeling of the 87-kDa protein was
inhibited by beta,gamma-CH2ATP, whereas UTP blocked binding by the 48-kDa
protein. Thus photoaffinity labeling experiments support the proposal that
endothelial cells possess two ATP receptors, one of which is a P2u
nucleotide receptor. These findings show that extracellular nucleotides
enhance leukocyte adherence to endothelial cells. Nucleotide release into
the extracellular space may be one mechanism of exacerbating vascular cell
injury relevant to conditions such as adult respiratory distress syndrome
and septic shock.
