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.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

Lipoproteins

Intracellular Fluid: metabolism

Hydrolysis

Human

Growth Inhibitors: toxicity

Enzyme Activation: drug effects

Vascular: cytology

Calcium: metabolism

Apoptosis: drug effects

Endothelium

Caspases: metabolism

Carrier Proteins: metabolism

Calpain: physiology

Cell Line

DNA Fragmentation: physiology

Vascular: physiology

Vascular: enzymology

Endopeptidases: physiology

LDL: toxicity

Microfilament Proteins: metabolism

Oxidation-Reduction

Proto-Oncogene Proteins c-bcl-2: metabolism

Support

Non-U.S. Gov't

Ubiquitin: metabolism

Publikations- och innehållstyp

art (ämneskategori)

ref (ämneskategori)