Heat Shock Protein 47 Is Expressed in Fibrous Regions of Human Atheroma and Is Regulated by Growth Factors and Oxidized Low-Density Lipoprotein

Abstract

Background-Heat shock protein 47 (Hsp47) is a stress protein that may act as a chaperone for procollagen. Its involvement in atherosclerosis is unknown. Methods and Results-Hsp47 expression in human coronary arteries was assessed by immunostaining. Strong focal expression was evident in atherosclerotic, but not normal, arteries and was prevalent in the collagenous regions. Double immunostaining revealed that all cells expressing type I procollagen also expressed Hsp47. Moreover, parallel regulation of pro␣1(I)collagen and Hsp47 mRNA expression occurred with cultured human smooth muscle cells stimulated with transforming growth factor-␤1 or fibroblast growth factor-2. However, a proportion of Hsp47-expressing cells in plaque did not express type I procollagen, and this pattern could be reproduced in culture. Heat shock and oxidized LDL stimulated the expression of Hsp47 mRNA by smooth muscle cells, without a concomitant rise in pro␣1(I)collagen expression. Conclusions-These See p 1224The major collagen species in human atherosclerotic plaque is type I collagen. The synthesis of type I collagen involves the productive association, within the endoplasmic reticulum, of 2 pro␣1(I)collagen chains and one pro␣2(I)collagen chain. The sorting and processing of procollagen chains into a native triple helix is not spontaneous; instead, it likely depends on the participation of molecular chaperones. 2 Heat shock protein 47 (Hsp47) is a heat shockinducible glycoprotein that binds nascent type I procollagen chains as they translocate into the endoplasmic reticulum. 3 The duration of binding is longer if stable triple helix formation is inhibited, 4 and the inhibition of Hsp47 expression has been associated with the decreased production of type I collagen. 3 These findings suggest that Hsp47 may be a chaperone for type I procollagen.Factors that control the efficiency and fidelity of procollagen folding could be critical to the clinical course of atherosclerosis. Therefore, we determined whether Hsp47 was expressed in human atheromas, and we ascertained its spatial and regulatory interactions with type I procollagen. Methods ReagentsGene expression was assessed using a mouse monoclonal antibody to rat Hsp47, 5 a mouse monoclonal antibody to sheep pro␣1(I)collagen (SP1.D8, Developmental Studies Hybridoma Bank, University of Iowa), and partial cDNA clones for rat Hsp47 (pIP1) and human pro␣1(I)collagen (Hf677, ATCC). Human recombinant transforming growth factor (TGF)-␤1 and fibroblast growth factor (FGF)-2 were purchased from R&D Systems and Gibco/BRL, respectively. Copper-oxidized LDL was kindly provided by Dr M. Huff of the Robarts Research Institute. Human TissuesA total of 25 segments of the right coronary artery from 25 patients were obtained from postmortem tissue or native hearts harvested from cardiac transplant recipients at the London Health Sciences Center, London, Canada. The arteries were from patients aged 18 to 76 years. Specimens were fixed in 10% neutral-buffered formalin and embedded in paraffin. Sections of 4...

Expression of HSP47, a collagen-specific chaperone, in normal and diseased human liver

“…In human vascular smooth muscle cells, human embryonic lung fibroblasts, murine osteoblasts and rat cardiac fibroblasts, HSP47 expression is inducible by TGF-b1. [18][19][20]27 In contrast, we observed no effect of TGF-b1 on HSP47 expression in human HSC, consistent with the results of Kawada et al 11 in murine HSC. Likewise, factors known to stimulate HSP47 expression in other cell types were without effect on human HSC.…”

“…[18][19][20][21][22] These included superoxide-generating agents (xanthine-xanthine oxidase, menadione), TGF-b1, hypoxia, and culture on a variety of different matrices. As illustrated in Figure 5, HSP47 expression in activated human HSC was similar in the presence or absence of serum, or following treatment with angiotensin II, TGF-b1, xanthine-xanthine oxidase, menadione, or 1% O 2 for 24 h. Similarly, no effects on HSP47 abundance were observed in HSC treated with the lipid peroxidation-derived aldehyde 4-hydroxynonenal or grown on plates coated with fibronectin, laminin, or collagen types I or IV (data not shown).…”

Functional Linkage between the Endoplasmic Reticulum Protein Hsp47 and Procollagen Expression in Human Vascular Smooth Muscle Cells

“…Increased levels of Hsp47 have been observed in atherosclerotic plaque (18), keloid lesions (19), fibrotic lungs (20), and diseased kidneys (21,22). Furthermore, the fundamental importance of Hsp47 in collagen biosynthesis is unequivocal: Hsp47-null mice die before birth and the embryos display ruptured blood vessels and a marked reduction in the amount of mature type I collagen (23).…”

The Molecular Interactions of Heat Shock Protein 47 (Hsp47) and Their Implications for Collagen Biosynthesis

“…This early role must be significant. Increased Hsp47 expression has been linked to a number of diseases in which increased collagen deposition occurs, including arteriosclerosis (22,23), myocardial infarction (24), and hepatic (25), renal (26), and pulmonary fibrosis (27). Indeed Sunamoto et al (28) successfully reduced the progression of glomerulonephritis in a rat model by reducing Hsp47 expression.…”