Biomedical Engineering Reference
In-Depth Information
that are convected from plasma to arterial wall and modified in the intima.
Apolipoprotein-B100 binds to sulphated proteoglycans, fibronectin, and collagens,
that are all secreted by intimal vascular smooth myocytes.
Vascular smooth myocytes also possess ATP-binding cassette transporter ABCa1
that controls cholesterol efflux, transferring excess cholesterol to newly formed
HDL particles. The ABCa1 production that differs in arterial smooth myocytes and
macrophages depends on liver X receptor (nuclear receptor NR1h).
Lipid uptake comprises pinocytosis of small components in the fluid phase
and phagocytosis of nanometric molecular complexes, cell particles, or apoptotic
cells [
745
]. Cationic proteins are mainly internalized by absorption via interactions
with the negative charges of the glycocalyx; anionic proteins, such as LDLs, interact
mainly with LDLR receptors and modified LDLs with scavenger receptors.
Vascular smooth myocytes take up more modified LDLs than native LDLs due
to LDLR downregulation in response to LDLs. Scavenger receptors and lectin-like
oxidized low-density lipoprotein receptor-1 on vascular smooth myocytes VSMCs
are mainly involved in the endocytosis of acetylated or oxidized LDLs; low-density
lipoprotein receptor-related protein LRP1 in the internalization of aggregated LDLs.
In addition, minimally modified LDLs may activate Toll-like receptor TLR4 [
745
].
8.5.4
Vascular Smooth Myocyte Uptake
Sphingolipids, such as C2-, C8-, and C16-ceramides, and sphingosine, and neutral
sphingomyelinase (nSMase) participate in the regulation of the intracellular con-
centration of free magnesium ions from the extracellular Mg
2
+
pool in vascular
smooth myocytes. These sphingolipids rapidly increase in a sphingolipid and Ca
2
+
concentration-dependent manner the intracellular Mg
2
+
level [
757
]. Activity of
phospholipase-C, of certain PKC isozymes, Ca
2
+
-calmodulin, and Ca
2
+
AT P a s e
maybeinvolvedinMg
2
+
uptake.
8.5.5
Vascular Smooth Myocyte Activity
8.5.5.1
Vasomotor Tone
Vascular smooth myocyte carries out slow and sustained contractions, whereas
cardiomyocyte contractions are rapid and of short duration (
[100 ms]). Myogenic
activity has been demonstrated in arteries, arterioles, venules, veins, and lymphatics.
Unlike in cardiomyocytes, actin and myosin in smooth myocytes are not arranged
O
S100a10, calprotectin, CD14, a receptor of bacterial lipopolysaccharide and coreceptor of TLR4,
galectin-3, among others.
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