Endothelial cells upregulate eosinophil superoxide generation via VCAM-1 expression.
BACKGROUND
In vitro eosinophil (EOS) adhesion to recombinant human (rh)-vascular cell adhesion molecule (VCAM)-1 stimulates superoxide anion (O2-) generation and enhances formyl-methionyl-leucyl phenylalanine (FMLP)-activated O2- generation. Therefore, EOS adhesion via VLA-4 to VCAM-1 expressed on endothelium may be instrumental in the selective recruitment and function of EOS in airway inflammation.


OBJECTIVE
We hypothesized that EOS interaction with endothelial cells expressing VCAM-1 will undergo an enhancement in inflammatory function.


METHODS
To determine this possibility, human umbilical vein endothelial cells (HUVEC) were stimulated with either a combination of interleukin (IL)-4 and tumour necrosis factor (TNF)-alpha (100 pM) or medium alone for 24 h; the expression of adhesion proteins on HUVEC and their effect on EOS O2- generation was subsequently determined.


RESULTS
As determined by both enzyme-linked immunosorbent assay and flow cytometry, IL-4 and TNFalpha acted synergistically to induce VCAM-1 expression on HUVEC. Treating HUVEC with IL-4/TNFalpha also increased EOS adhesion and primed subsequent FMLP (0.1 microM) activated EOS O2- generation. Although EOS adhesion was partially inhibited by both antialpha4 and antibeta2 monoclonal antibodies (MoAbs), O2- generation was completely inhibited by either antialpha4 integrin MoAb (HP1/2) or anti-VCAM MoAb (BBIG-V1). Furthermore, enhanced O2- generation, but not adhesion, associated with IL-4 + TNFalpha-treatment of HUVEC was inhibited when EOS were treated with the platelet activating factor (PAF)-antagonist WEB 2086 (20 microM), thus suggesting an involvement of PAF in priming EOS. However, paraformaldehyde fixation of IL-4/TFN-alpha treated HUVEC did not significantly alter EOS function.


CONCLUSIONS
These results suggest EOS adhesion to endothelial cells via an VLA-4/VCAM-1 interaction may be important in the development of the function of this cell. Furthermore, our results suggest that modulation of EOS function involves two priming factors: EOS adhesion to HUVEC expressing VCAM-1 and PAF.
Nagata
M
M
Pulmonary Division, Second Department of Internal Medicine, Saitama Medical School, Saitama, Japan.
Sedgwick
J B
JB
Vrtis
R
R
Busse
W W
WW
D000328:Adult; D002448:Cell Adhesion; D004730:Endothelium, Vascular / Q000166:cytology*; D004804:Eosinophils / Q000378:metabolism*; D005260:Female; D019833:Genistein / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D039041:Integrin alpha4beta1; D016023:Integrins / Q000502:physiology; D015847:Interleukin-4 / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D016201:Receptors, Lymphocyte Homing / Q000502:physiology; D013481:Superoxides / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation; D019010:Vascular Cell Adhesion Molecule-1 / Q000502:physiology*
D039041:Integrin alpha4beta1; D016023:Integrins; D016201:Receptors, Lymphocyte Homing; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D013481:Superoxides; D015847:Interleukin-4; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019833:Genistein