Oxidized low-density lipoprotein induces calpain-dependent cell death and ubiquitination of caspase 3 in HMEC-1 endothelial cells.

Oxidized low-density lipoprotein (oxLDL) is known to induce apoptosis in endothelial cells, and this is believed to contribute to the progression of atherosclerosis. In the present study we made the novel observation that oxLDL-induced death of HMEC-1 cells is accompanied by activation of calpain. The mu-calpain inhibitor PD 151746 decreased oxLDL-induced cytotoxicity, whereas the general caspase inhibitor BAF (t-butoxycarboryl-Asp-methoxyfluoromethylketone) had no effect. Also, oxLDL provoked calpain-dependent proteolysis of cytoskeletal a-fodrin in the HMEC-1 cells. Our observation of an autoproteolytic cleavage of the 80 kDa subunit of mu-calpain provided further evidence for an oxLDL-indunced stimulation of calpain activity. The Bcl-2 protein Bid was also cleaved during oxLDL-elicited cell death, and this was prevented by calpain inhibitors, but not by inhibitors of cathepsin B and caspases. Treating the HMEC-1 cells with oxLDL did not result in detectable activation of procaspase 3 or cleavage of PARP [poly(ADP-ribose) polymerase], but it did cause polyubiquitination of caspase 3, indicating inactivation and possible degradation of this protease. Despite the lack of caspase 3 activation, oxLDL treatment led to the formation of nucleosomal DNA fragments characteristic of apoptosis. These novel results show that oxLDL initiates a calpain-mediated death-signalling pathway in endothelial cells

HMG-CoA reductase inhibitors regulate inflammatory transcription factors in human endothelial and vascular smooth muscle cells

Objective-Pleiotropic atheroprotective effects of HMG-CoA reductase inhibitors may be mediated on the level of vascular gene transcription. The aim of this study was to characterize the effects of statins on the activation of transcription factors known to regulate inflammation and cell proliferation/differentiation. Methods and Results-Simvastatin, atorvastatin, and lovastatin (0.1 to 10 mumol/L) inhibited the binding of nuclear proteins to both the nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) DNA consensus oligonucleotides in human endothelial and vascular smooth muscle cells as assessed by electrophoretic mobility shift assay (EMSA). The inhibitory effects of statins on NF-kappaB or AP-1-dependent transcriptional activity were examined by transient transfection studies. HMG-CoA reductase inhibitors upregulated IkappaB-alpha protein levels in endothelial cells and decreased c-Jun mRNA expression in smooth muscle cells as analyzed by Western and Northern blotting, respectively. Furthermore, statins inhibited DNA binding of hypoxia-inducible factor-1alpha. Downstream effects of statins included inhibition of plasminogen activator inhibitor-1 and vascular endothelial growth factor-A mRNA levels in endothelial cells. Conclusions-HMG-CoA reductase inhibitors downregulate the activation of transcription factors NF-kappaB, AP-1, and hypoxia-inducible factor-1alpha. These, findings support the concept that statins have antiinflammatory and antiproliferative effects that are relevant in the treatment of atherosclerotic diseases

Elastin- and Collagen-Rich Human Carotid Plaques Have Increased Levels of the Cysteine Protease Inhibitor Cystatin C.

Background: Cystatin C is a major inhibitor of the elastin- and collagen-degrading cysteine proteases and may therefore have an important role in preserving atherosclerotic plaque stability. In this study we analyzed the associations between human carotid plaque cystatin C expression and the plaque content of collagen and elastin. Methods: Thirty-one plaques were removed by endarterectomy and homogenized. Cystatin C levels were analyzed by densitometry of Western blots and elastin and collagen levels were determined colorimetrically. Results: The plaque content of cystatin C correlated with total elastin (r = 0.58, p = 0.001) and collagen (r = 0.50, p = 0.004), as well as with cross-linked forms of elastin (r = 0.42, p = 0.022) and collagen (r = 0.52, p = 0.003). Immunohistochemical analysis demonstrated that cystatin C colocalized with elastin and collagen. No correlation was seen between cystatin C and the amount of degraded elastin or collagen in plaques. Conclusion: The positive correlation between cystatin C levels and collagen and elastin levels in plaques supports the notion that cystatin C plays an important role in maintaining atherosclerotic plaque stability. Copyright (c) 2008 S. Karger AG, Basel