Regarding atherosclerosis, are the LDL molecules oxidized before or after they are phagocytized by the macrophage? Is it ROS’s in the irritated/weakened vessel wall which oxidize the LDL’s? Is the oxidizing of the LDL’s some sort of opsonization, to enhance the phagocytizing process by the macrophages, or is it just an unwanted process? Thank you for the good education!
Oxidation of LDL can take place in circulation, but the primary site of oxidation is probably the vessel intima. It is indeed ROS, produced by the macrophages/foam cells, that mediate the oxidation.
LDL can be taken up by macrophages both in it’s native form (nLDL) and once oxidized (oxLDL). In both cases, the uptake is receptor mediated. nLDL is taken up via the LDL receptor and expression of the LDL receptor is subsequently downregulated – this limits further nLDL uptake. oxLDL is taken up via scavenger receptors and expression of these scavenger recptors is subsequently increased, thus enabling even more uptake of oxLDL.