VDR dependent and independent effects of 1,25-dihydroxyvitamin D-3 on nitric oxide production by osteoblasts

作者：Willems Hubertine M E; van den Heuvel Ellen G H M; Carmeliet Geert; Schaafsma Anne; Klein Nulend Jenneke^*; Bakker Astrid D

来源：Steroids, 2012, 77(1-2): 126-131.

DOI：10.1016/j.steroids.2011.10.015

• Osteoblasts
• Mechanical loading
• 1,25-Dihydroxyvitamin D-3
• Vitamin D receptor
• VDR-/- mice
• Nitric oxide synthase

1,25-Dihydroxyvitamin D-3 (1,25(OH)(2)D-3) strongly mediates bone mass. Mechanical stimulation also affects bone mass, partly via enhancing nitric oxide (NO) production by osteoblasts. We aimed to determine whether 1,25(OH)(2)D-3 affects NO production by osteoblasts in the presence or absence of mechanical stimulation. We hypothesised that 1,25(OH)(2)D-3 stimulates NO production via nuclear actions of the vitamin D receptor (VDR), which requires hours of incubation with 1,25(OH)(2)D-3 to occur. %26lt;br%26gt;MC3T3-E1 osteoblasts and long-bone osteoblasts of adult wildtype and VDR-/- mice were pre -incubated for 24 h with or without 1,25(OH)(2)D-3 (10(-13)-10(-9) M), followed by 30 min pulsating fluid flow (PFF; 0.7 +/- 0.3 Pa, 5 Hz) or static culture with or without 1,25(OH)(2)D-3. NO production and NO synthase (NOS) expression were quantified. %26lt;br%26gt;10(-11) M 1,25(OH)(2)D-3 for 24h, but not 30 min, stimulated NO production by MC3T3-E1 osteoblasts (eightfold). 1,25(OH)(2)D-3 for 24 h increased inducible-NOS gene-expression (twofold), suggesting that 1,25(OH)(2)D-3 stimulated NO production via activation of NOS gene transcription. PFF rapidly increased NO production by MC3T3-E1 osteoblasts, wildtype osteoblasts, and VDR-/- osteoblasts. This PFF effect was abolished after incubation with 1,25(OH)(2)D-3 for 24 h, or during PFF only. %26lt;br%26gt;Our results suggest that 1,25(OH)(2)D-3 stimulates inducible-NOS expression and NO production by osteoblasts in the absence of mechanical stimulation, likely via genomic VDR action. In contrast, 1,25(OH)(2)D-3 may affect mechanical loading-induced NO production independent of genomic VDR action, since 1,25(OH)(2)D-3 diminished PFF-induced NO production in VDR-/- bone cells. In conclusion, 1,25(OH)(2)D-3 and mechanical loading interact at the level of mechanotransduction, whereby 1,25(OH)(2)D-3 seems to act independently of VDR genomic mechanism.

• 出版日期2012-1