title: Human antimicrobial peptide LL-37 is present in atherosclerotic plaques and induces death of vascular smooth muscle cells: a laboratory study.
abstract: BACKGROUND
  Death of smooth muscle cells in the atherosclerotic plaques makes the plaques more prone to rupture, which can initiate an acute ischemic event. The development of atherosclerosis includes the migration of immune cells e.g. monocytes/macrophages and T lymphocytes into the lesions. Immune cells can release antimicrobial peptides. One of these, human cathelicidin antimicrobial peptide hCAP-18, is cleaved by proteinase 3 generating a 4.5 kDa C-terminal fragment named LL-37, which has been shown to be cytotoxic. The aim of the study was to explore a potential role of LL-37 in the pathophysiology of atherosclerosis.
  
  
  METHODS
  We investigated the presence of LL-37 in human atherosclerotic lesions obtained at autopsy using immunohistochemistry. The direct effects of LL-37 on cultured vascular smooth muscle cells and isolated neutrophil granulocytes were investigated with morphological, biochemical and flow cytometry analysis.
  
  
  RESULTS
  The neointima of atherosclerotic plaques was found to contain LL-37-like immunoreactivity, mainly in macrophages. In cultured smooth muscle cells, LL-37 at 30 mug/ml caused cell shrinkage, membrane blebbing, nuclear condensation, DNA fragmentation and an increase in caspase-3 activity as studied by microscopy, ELISA and enzyme activity assay, respectively. Flow cytometry demonstrated that LL-37 in a subset of the cells caused a small but rapidly developing increase in membrane permeability to propidium iodide, followed by a gradual development of FITC-annexin V binding. Another cell population stained heavily with both propidium iodide and FITC-annexin V. Neutrophil granulocytes were resistant to these effects of LL-37.
  
  
  CONCLUSIONS
  This study shows that LL-37 is present in atherosclerotic lesions and that it induces death of vascular smooth muscle cells. In a subset of cells, the changes indicate the development of apoptosis triggered by an initial mild perturbation of plasma membrane integrity. The findings suggest a role for LL-37 as a mediator of immune cell-induced death of vascular smooth muscle cells in atherosclerosis.
authors.affiliation: Department of Clinical Sciences, Division of Anaesthesiology and Intensive Care, Lund University, Lund, Sweden. cristina.ciornei@med.lu.se <cristina.ciornei@med.lu.se>
authors.forename: Cristina D
authors.initials: CD
authors.lastname: Ciornei
authors.forename: Hans
authors.initials: H
authors.lastname: Tapper
authors.forename: Anders
authors.initials: A
authors.lastname: Bjartell
authors.forename: Nils H
authors.initials: NH
authors.lastname: Sternby
authors.forename: Mikael
authors.initials: M
authors.lastname: Bodelsson
mesh_terms: D000818:Animals; D017304:Annexin A5; D023181:Antimicrobial Cationic Peptides / Q000032:analysis*; D001011:Aorta / Q000166:cytology*; D017209:Apoptosis / Q000276:immunology / Q000502:physiology*; D050197:Atherosclerosis / Q000503:physiopathology*; D053148:Caspase 3 / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000502:physiology; D002478:Cells, Cultured; D053938:DNA Fragmentation; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D006801:Humans; D007150:Immunohistochemistry; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008070:Lipopolysaccharides / Q000032:analysis*; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism; D009504:Neutrophils; D011419:Propidium; D051381:Rats; D054804:Cathelicidins
chemical_list: D017304:Annexin A5; D023181:Antimicrobial Cationic Peptides; C492760:FITC-annexin A5; D008070:Lipopolysaccharides; D011419:Propidium; D007770:L-Lactate Dehydrogenase; D053148:Caspase 3; D016650:Fluorescein-5-isothiocyanate; D054804:Cathelicidins