Dexamethasone-induced expression of the glucocorticoid response gene lipocalin 2 in chondrocytes.
Glucocorticoids (GC) are commonly used anti-inflammatory drugs, but long-term use can result in marked growth retardation in children due to their actions on growth plate chondrocytes. To gain an insight into the mechanisms involved in GC-induced growth retardation, we performed Affymetrix microarray analysis of the murine chondrogenic cell line ATDC5, incubated with 10(-6) M dexamethasone (Dex) for 24 h. Downregulated genes included secreted frizzled-related protein and IGF-I, and upregulated genes included serum/GC-regulated kinase, connective-tissue growth factor, and lipocalin 2. Lipocalin 2 expression increased 40-fold after 24-h Dex treatment. Expression increased further after 48-h (75-fold) and 96-h (84-fold) Dex treatment, and this response was Dex concentration dependent. Lipocalin 2 was immunolocalized to both proliferating and hypertrophic growth plate zones, and its expression was increased by Dex in primary chondrocytes at 6 h (3-fold, P < 0.05). The lipocalin 2 response was blocked by the GC-receptor antagonist RU-486 and was increased further by the protein synthesis blocker cycloheximide. Proliferation in lipocalin 2-overexpressing cells was less than in control cells (49%, P < 0.05), and overexpression caused an increase in collagen type X expression (4-fold, P < 0.05). The effects of lipocalin 2 overexpression on chondrocyte proliferation (64%, P < 0.05) and collagen type X expression (8-fold, P < 0.05) were further exacerbated with the addition of 10(-6) M Dex. This synergistic effect may be explained by a further increase in lipocalin 2 expression with Dex treatment of transfected cells (45%, P < 0.05). These results suggest that lipocalin 2 may mediate Dex effects on chondrocytes and provides a potential novel mechanism for GC-induced growth retardation.
Owen
H C
HC
Bone Biology Group, Roslin Institute, Edinburgh, UK. helen.owen@sheffield.ac.uk
Roberts
S J
SJ
Ahmed
S F
SF
Farquharson
C
C
D000209:Acute-Phase Proteins / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D003433:Crosses, Genetic; D003907:Dexamethasone / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D006132:Growth Plate / Q000187:drug effects / Q000502:physiology; D006651:Histocytochemistry; D000071068:Lipocalin-2; D054834:Lipocalins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D020411:Oligonucleotide Array Sequence Analysis; D015513:Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000209:Acute-Phase Proteins; D000893:Anti-Inflammatory Agents; D000071068:Lipocalin-2; D054834:Lipocalins; D015513:Oncogene Proteins; D012333:RNA, Messenger; C071332:Lcn2 protein, mouse; D003907:Dexamethasone