title: The antimicrobial peptide LL-37 alters human osteoblast Ca2+ handling and induces Ca2+-independent apoptosis.
abstract: The human antimicrobial peptide cathelicidin LL-37 has, besides its antimicrobial properties, also been shown to regulate apoptosis in a cell type-specific manner. Mechanisms involved in LL-37-regulated apoptotic signaling are not identified. Here, we show that LL-37 reduces the human osteoblast-like MG63 cell number and cell viability in the micromolar concentration range with an IC50 value of about 5 µM. Treatment with 4 µM LL-37 increased the number of annexin V-positive cells and stimulated activation of caspase 3 showing that LL-37 promotes apoptosis. Treatment with 4 µM LL-37 caused an acute and sustained rise in intracellular Ca(2+) concentration assessed by laser-scanning confocal microscopy of Fluo-4-AM-loaded MG63 cells. LL-37 increased Ca(2+) also in the presence of the respective L- and T-type voltage-sensitive Ca(2+) channel blockers nifedipine and NiCl2. LL-37 had no effect on Ca(2+) in cells incubated with Ca(2+)-free solution. LL-37 (4 and 8 µM) reduced the MG63 cell number both in the presence and absence of Ca(2+) in the medium. In conclusion, LL-37 reduces the osteoblast cell number by promoting apoptosis, and furthermore, LL-37 stimulates Ca(2+) inflow via a mechanism independent of voltage-sensitive Ca(2+) channels. Interestingly, LL-37-induced lowering of the cell number seems to be mediated via a mechanism independent of Ca(2+).
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Johanna
authors: J
authors: Säll
authors: Martin
authors: M
authors: Carlsson
authors: Olof
authors: O
authors: Gidlöf
authors: Anders
authors: A
authors: Holm
authors: Johan
authors: J
authors: Humlén
authors: Jenny
authors: J
authors: Ohman
authors: Daniel
authors: D
authors: Svensson
authors: Bengt-Olof
authors: BO
authors: Nilsson
authors: Daniel
authors: D
authors: Jönsson
mesh_terms: D017304:Annexin A5 / Q000276:immunology / Q000378:metabolism; D023181:Antimicrobial Cationic Peptides / Q000276:immunology / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D002118:Calcium / Q000276:immunology* / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000276:immunology / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006801:Humans; D010006:Osteoblasts / Q000276:immunology* / Q000378:metabolism; D054804:Cathelicidins
chemical_list: D017304:Annexin A5; D023181:Antimicrobial Cationic Peptides; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D002118:Calcium; D054804:Cathelicidins