title: Nitric oxide boosts TLR-4 mediated lipocalin 2 expression in chondrocytes.
abstract: Lipocalin 2 (LCN2) has recently emerged as a novel adipokine involved in different processes including arthritis and chondrocyte inflammatory response. However, little is known about its activity on chondrocyte homeostasis and its regulation by nitric oxide (NO) Hence, we performed a set of experiments aimed to achieve a better understanding of this relationship. Cell vitality was tested in the ATDC5 cell line by the MTT colorimetric assay. Protein expression and gene expression was evaluated by Western blot and real time RT-PCR, respectively. NO production (determined as nitrite accumulation) was assayed by the Griess reaction. First, we demonstrated that LCN2 decreased murine chondrocytes vitality. Next, LCN2 co-stimulation with LPS enhanced NOS2 protein expression by murine chondrocytes. In addition, inhibition of LPS-induced nitric oxide production by aminoguanidine, a selective NOS2 inhibitor, significantly reduced LPS-mediated LCN2 expression. In contrast, treatment of murine chondrocytes with sodium nitroprussiate (SNP), a classic NO donor, scarcely induced LCN2 expression. Intriguingly, SNP addition to LPS-challenged chondrocytes, treated with aminoguanidine, provoked a strong induction of LCN2 expression. Finally, murine ATDC5 cells, co-cultured with LPS pre-challenged macrophages, had higher LCN2 expression in comparison with murine chondrocytes co-cultured with non pre-challenged macrophages. In this work we have described for the first time that NO is able to exert a control on LCN2 expression, suggesting the existence of a feedback loop regulating its expression.
authors.affiliation: SERGAS, Santiago University Clinical Hospital Research Laboratory 9 (NEIRID LAB: Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases), Institute of Medical Research (IDIS), Santiago de Compostela, 15706, Spain.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Gómez
authors.forename: Morena
authors.initials: M
authors.lastname: Scotece
authors.forename: Javier
authors.initials: J
authors.lastname: Conde
authors.forename: Veronica
authors.initials: V
authors.lastname: Lopez
authors.forename: Jesus
authors.initials: J
authors.lastname: Pino
authors.forename: Francisca
authors.initials: F
authors.lastname: Lago
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Gómez-Reino
authors.forename: Oreste
authors.initials: O
authors.lastname: Gualillo
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006146:Guanidines / Q000494:pharmacology; D000071068:Lipocalin-2; D054834:Lipocalins / Q000378:metabolism* / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D015513:Oncogene Proteins / Q000378:metabolism* / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D000209:Acute-Phase Proteins; D006146:Guanidines; D000071068:Lipocalin-2; D054834:Lipocalins; D008070:Lipopolysaccharides; D020030:Nitric Oxide Donors; D015513:Oncogene Proteins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C071332:Lcn2 protein, mouse; D009599:Nitroprusside; D009569:Nitric Oxide; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse; C004479:pimagedine