Atherosclerosis, cell motility, calcium, and calcium-channel blockers.

Three key players in the humoral-cellular interactions that occur during the early development of atherosclerosis are presented as they activate platelets and vascular smooth muscle cells but eventually can be corrected by calcium-channel blockers. Platelet-activating factors via phospholipase C and phosphoinositides increase cytosolic calcium and phosphorylate contractile proteins, thereby inducing a change--aggregation and the secretory response of platelets. Low-density lipoprotein (LDL) has a similar hormone-like action and activates the signal transfer cascade that eventually leads to platelet aggregation as well as vascular smooth muscle cell proliferation. These effects can be greatly reduced by high-density lipoproteins. Platelet-derived growth factor stimulates the transcription of the LDL-receptor gene as well as the HMG-CoA reductase gene. The latter is inhibited by calcium-channel antagonists while the former is further enhanced. Thus, calcium-channel antagonists interfere with the stimulus-response coupling not only via slow calcium-channel influx inhibition but also by an additional membrane action and interference with gene activation.