Proteoglycans synthesized by arterial smooth muscle cells in the presence of transforming growth factor-beta1 exhibit increased binding to LDLs.
The "response-to-retention" hypothesis of atherogenesis states that atherogenic lipoproteins, such as low density lipoprotein (LDL), are retained in vessels by proteoglycans and undergo proatherosclerotic modifications. Transforming growth factor (TGF)-beta1 has been identified in atherosclerotic vessels and has been shown to stimulate the synthesis of chondroitin sulfate- and dermatan sulfate-containing proteoglycans by arterial smooth muscle cells (ASMCs), but whether it promotes lipid retention has not been addressed. We investigated whether TGF-beta1 modulates the biosynthesis of proteoglycans by ASMCs in a manner that promotes binding to LDL. Proteoglycans isolated from TGF-beta1-treated ASMCs exhibited enhanced binding to native LDL compared with the binding of proteoglycans isolated from control cultures (K(d) 18 microg/mL LDL versus 81 microg/mL LDL, respectively). The increase in proteoglycan-LDL binding caused by TGF-beta1 could be attributed primarily to the glycosaminoglycan portion of the proteoglycans, since the glycosaminoglycan chains liberated from the core proteins of these proteoglycans synthesized in the presence of TGF-beta1 exhibited increased LDL binding as well. Furthermore, glycosaminoglycan chains initiated on xyloside (an initiator of glycosaminoglycan synthesis) in the presence of TGF-beta1 were longer and displayed enhanced binding to LDL compared with the LDL binding of xyloside-initiated glycosaminoglycan chains from control cultures. These results indicate that TGF-beta1 promotes LDL-proteoglycan interaction primarily by its effects on the glycosaminoglycan synthetic machinery of the ASMCs. Therefore, this study supports a proatherogenic role for TGF-beta1.
Little
Peter J
PJ
Cell Biology of Diabetes Laboratory, Baker Medical Research Institute, Melbourne, Victoria, Australia.
Tannock
Lisa
L
Olin
Katherine L
KL
Chait
Alan
A
Wight
Thomas N
TN
D006025:Glycosaminoglycans / Q000096:biosynthesis; D006027:Glycosides / Q000494:pharmacology*; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D011509:Proteoglycans / Q000096:biosynthesis* / Q000737:chemistry; D016212:Transforming Growth Factor beta / Q000494:pharmacology* / Q000502:physiology; D053773:Transforming Growth Factor beta1
D006025:Glycosaminoglycans; D006027:Glycosides; D008077:Lipoproteins, LDL; D011509:Proteoglycans; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C010807:xylosides