Objective-Inflammation plays an important role in atherosclerosis. One of the most potent pro-inflammatory cytokines is tumor necrosis factor-␣ (TNF-␣), a cytokine identified to have a pathogenic role in chronic inflammatory diseases such as rheumatoid arthritis (RA). The aim of the study was to evaluate the importance of TNF-␣ in atherogenesis. Methods and Results-Mice deficient in both apolipoprotein E (apoE) and TNF-␣ were compared regarding their atherosclerotic burden. Mice were fed a Western-style diet (WD) or normal chow. Mice deficient in both apoE and TNF-␣ exhibited a 50% (Pϭ0.035) reduction of relative lesion size after 10 weeks of WD. Bone marrow transplantation of apoE o mice with apoE o tnf-␣ o bone marrow resulted in a 83% (Pϭ0.021) reduction after 25 weeks on WD. In apoE knockout mice treated with recombinant soluble TNF receptor I releasing pellets, there was a reduction in relative lesion size after 25 weeks of 75% (Pϭ0.018).Conclusions-These findings demonstrate that TNF-␣ is actively involved in the progression of atherosclerosis.Accordingly, TNF-␣ represents a possible target for prevention of atherosclerosis. This may be of particular importance in rheumatoid arthritis because these patients have an increased risk for cardiovascular disease.

Atherosclerotic lesions are asymmetric focal thickenings of the intima of arteries that consist of lipids, various cell types and extracellular matrix (ECM). These lesions lead to vascular occlusion representing the most common cause of death in the Western world. The main cause of vascular occlusion is rupture of atheromatous lesions followed by thrombus formation. Fibronectin (FN) is one of the earliest ECM proteins deposited at atherosclerosis-prone sites and was suggested to promote atherosclerotic lesion formation. Here, we report that atherosclerosis-prone apolipoprotein E-null mice lacking hepatocyte-derived plasma FN (pFN) fed with a pro-atherogenic diet display dramatically reduced FN depositions at atherosclerosis-prone areas, which results in significantly smaller and fewer atherosclerotic plaques. However, the atherosclerotic lesions from pFN-deficient mice lacked vascular smooth muscle cells and failed to develop a fibrous cap. Thus, our results demonstrate that while FN worsens the course of atherosclerosis by increasing the atherogenic plaque area, it promotes the formation of the protective fibrous cap, which in humans prevents plaques rupture and vascular occlusion.

PRELP (proline arginine-rich end leucine-rich repeat protein) is a heparin-binding leucine-rich repeat protein in connective tissue extracellular matrix. In search of natural ligands and biological functions of this molecule, we found that PRELP binds the basement membrane heparan sulfate proteoglycan perlecan. Also, recombinant perlecan domains I and V carrying heparan sulfate bound PRELP, whereas other domains without glycosaminoglycan substitution did not. Heparin, but not chondroitin sulfate, inhibited the interactions. Glycosaminoglycanfree recombinant perlecan domain V and mutated domain I did not bind PRELP. The dissociation constants of the PRELP-perlecan interactions were in the range of 3-18 nM as determined by surface plasmon resonance. As expected, truncated PRELP, without the heparin-binding domain, did not bind perlecan. Confocal immunohistochemistry showed that PRELP outlines basement membranes with a location adjacent to perlecan. We also found that PRELP binds collagen type I and type II through its leucine-rich repeat domain. Electron microscopy visualized a complex with PRELP binding simultaneously to the triple helical region of procollagen I and the heparan sulfate chains of perlecan. Based on the location of PRELP and its interaction with perlecan heparan sulfate chains and collagen, we propose a function of PRELP as a molecule anchoring basement membranes to the underlying connective tissue.

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