| dc.description | Low density lipoprotein receptors (LDLR), capable of internalizing LDL, are expressed in polymorphonuclear
neutrophils (PMN). The expression was assessed using anti-LDLR antibody by flow cytometry.
The internalization of LDL was assessed by: (i) quantification of the uptake of labelled LDL with 1,10-
dioctadecyl-3,3,30,30 tetramethyl-indocarboxycyanine perchlorate (DiI) by flow cytometry; and (ii) the
binding of LDL-125I. In fresh purified cells, Lineweaver–Burk analysis of LDL binding (LDL-DiI)
revealed that the calculated Kd (internalized LDL) for PMN (15.0 10ÿ9
M) is lower than the Kd for
monocytes (1.1 10ÿ7
M) and the Kd for lymphocytes (3.2 10ÿ7
M). Scatchard analysis (LDL-125I)
revealed 25 000 binding sites and a Kd of 9.6 10ÿ9
M for PMN. The interaction of LDL with its
receptor caused a two-fold fast (peak at 1 min) and transient increase in the oxidative burst, measured by
the formation of 20,70 dicholoflurescein (DCF) by flow cytometry. This effect was not observed in
monocytes or lymphocytes, and it was blocked by anti-LDLR antibody. The stimulation of LDL was
optimal at 10 ¹g of protein/ml. LDL was able to suppress DCF formation induced by phorbol myristate
acetate (PMA) and PMA was unable to further stimulate LDL-treated cells, suggesting protein kinase-C
(PKC) involvement in LDL effects. Using a PKC assay, LDL was shown to induce a two-fold increase
in PKC translocation to the membrane. Thus, LDL increases PMN oxidative burst through a PKCdependent
pathway. | |
