Cholate-Containing High-Fat Diet Induces the Formation of Multinucleated Giant Cells in Atherosclerotic Plaques of Apolipoprotein E−/− Mice

Abstract

Objective-To determine the role of multinucleated giant cells (MGCs) in cardiovascular diseases. Methods and Results-MGCs are a hallmark of giant cell arteritis. They are also described in atherosclerotic plaques from aortic aneurysms and carotid and coronary arteries. Herein, we demonstrate that the cholate-containing Paigen diet yields many MGCs in atherosclerotic plaques of apolipoprotein EϪ/Ϫ mice. These mice revealed a 4-fold increase in MGC numbers when compared with mice on a Western or Paigen diet without cholate. Most of the MGCs stained intensively for cathepsin K and were located at fibrous caps and close to damaged elastic laminae, with associated medial smooth muscle cell depletion. During in vitro experiments, MGCs demonstrated a 6-fold increase in elastolytic activity when compared with macrophages and facilitated transmigration of smooth muscle cells through a collagen-elastin matrix. An elastin-derived hexapeptide (Val-Gly-Val-Ala-Pro-Gly [VGVAPG]) significantly increased the rate of macrophage fusion, providing a possible mechanism of in vivo MGC formation. Comparable to the mouse model, human specimens from carotid arteries and aortic aneurysms contained cathepsin K-positive MGCs. Key Words: multinucleated giant cells Ⅲ cathepsin K Ⅲ atherosclerosis Ⅲ cholate Ⅲ elastin T he presence of multinucleated giant cells (MGCs) in blood vessel walls is well described in patients with giant cell arteritis (GCA). The name of this disease reflects the presence of MGCs formed by the fusion of macrophages in inflammatory infiltrates of the arterial wall. 1,2 In atherosclerosis, MGCs have been described in plaques from aortic aneurysms and carotid and coronary arteries. 3 In 1 report, 4 CD11c-positive MGCs have been observed in advanced atherosclerotic plaques of apolipoprotein E (apoE)Ϫ/Ϫ mice receiving a "Western" high-fat diet (HFD). Conclusion-ApolipoproteinHerein, we report a mouse model that consistently generates MGCs in atherosclerotic lesions. We compared the effect of a cholate-containing Paigen diet with the widely used Western HFD and also with a Paigen diet without cholate and observed that the mice in the first group developed 4 times more cathepsin K (Ctsk)-expressing MGCs than their littermates on cholate-free HFDs. Researchers [5][6][7] have previously shown that cathepsin K is critical for the elastic lamina degradation in atherosclerotic lesions in apoEϪ/Ϫ mice. The identification of MGCs close to elastin fibers and especially in the proximity of elastin fiber breaks prompted us to investigate the effect of cathepsin K deficiency on the ability of MGCs to cleave elastin fibers and to facilitate smooth muscle cell (SMC) migration through an elastin-collagen layer. We also tested the effect of an elastin-derived hexapeptide (Val-Gly-Val-Ala-Pro-Gly [VGVAPG]) on the rate of interleukin (IL) 4 -induced fusion of thioglycolate-elicited peritoneal macrophages. Previously, it has been shown that this peptide has a diverse biological activity, including an induction of macrophage migration and agg...

Role of Cathepsin K, L and S in Blood Vessel Remodeling

“…1). Similarly to giant cells arteritis, they were mostly localized in the media-intima junction (Samokhin, 2010c). The lesions contained Langhans-type multinucleated giant cells recognizable by their circular arrangement of nuclei and foreign body-type giant cells with random arrangement of nuclei.…”

“…3). These giant cells were observed in atherosclerotic plaques within the brachiocephalic artery and the aortic root and were easily detectable by intensive cathepsin K immunostaining (Samokhin et al, 2010c). They were mostly localized in the fibrous cap region and close to the elastin laminae.…”

“…High level of cathepsin K expression is a marker of active osteoclasts; in these giant cells cathepsin K is a major enzyme responsible for bone resorption (Bromme et al, 1996). Similarly, cathepsin Kexpressing giant cells were found close to damaged elastin laminae in aorta, suggesting an important role for this enzyme in the development of cardiovascular diseases (Samokhin et al, 2010c;Chapman et al, 1997).…”

“…Thus, high cathepsin K concentration was found in rheumatoid arthritic joints, in epithelioid and multinucleated giant cells in lungs, and in thyroid glands (Buhling et al, 2004;Samokhin et al, 2010a;Tepel et al, 2000). Cathepsin K is not detectable in normal blood vessels, but is highly expressed in macrophages, smooth muscle cells, endothelial and multinucleated giant cells in atherosclerotic lesions and in giant cell aortitis (Sukhova et al, 1998;Platt et al, 2007;Chapman et al, 1997;Samokhin et al, 2010c). Cathepsin K is the most efficient elastinolytic enzyme (Bromme et al, 1996) and, in contrast to other cathepsins, has the ability to cleave triple-helical collagens both outside and inside the helical regions (Lecaille et al, 2008;Garnero et al, 1998).…”

“…These results were corroborated by in vitro experiments that revealed the differences in collageno-and elastolytic activities of smooth muscle cells and macrophages from mice expressing and lacking these cathepsins. The availability of specific cathepsin inhibitors allowed the conduction of in vitro and in vivo experiments that confirmed the involvement of cathepsins in aortic extracellular matrix destruction and atherosclerosis progression (Samokhin et al, 2010b) Immunostaining for cathepsin K revealed its high level of expression in multinucleated giant cells in human specimens from carotid arteries and abdominal aortic aneurysm as well as in mouse atherosclerotic plaques (Samokhin et al, 2010c;Chapman et al, 1997). High level of cathepsin K expression is a marker of active osteoclasts; in these giant cells cathepsin K is a major enzyme responsible for bone resorption (Bromme et al, 1996).…”