Human monocyte interactions with non-enzymatically glycated collagen.

We have previously shown that receptors for advanced glycation end products are expressed on activated human monocytes. We now report that activated human monocytes exhibit increased adhesion to non-enzymatically glycated collagen substrates (+32% +/- 1, p less than 0.001), and the increased adhesion can be competitively inhibited with non-enzymatically glycated albumin. Non-activated monocytes, which do not express receptors for advanced glycation end products, exhibit decreased adhesion (-16% +/- 1, p less than 0.001). Similar results were observed with substrates of fibronectin and endothelial cell matrix proteins. As the presence of glycation adducts on collagen interferes with the normal binding of monocytes/macrophages, one possible role for advanced glycation adduct receptors on activated monocytes is to counterbalance such decreased adherence. Overcompensation for long periods of time may lead to pathological changes. Additionally, such receptors may play a role in monocyte-mediated remodelling of glycated matrix proteins, as we have observed increased degradation of non-enzymatically glycated collagen substrates by activated human monocytes at 2 h (+52% +/- 11, p = 0.01), 3 h (+49% +/- 10, 10, p = 0.01), and 4 h (+36% +/- 6, p less than 0.01) after adding activated monocytes to 125I-labelled substrates.