Shymanskyi Ihor, Lisakovska Olha, Mazanova Anna, Labudzynskyi Dmytro, Veliky Mykola
Department of Biochemistry of Vitamins and Coenzymes, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv, Ukraine.
Front Endocrinol (Lausanne). 2018 Jun 7;9:303. doi: 10.3389/fendo.2018.00303. eCollection 2018.
The effectiveness of vitamin D (cholecalciferol) in counteracting the side effects of glucocorticoid (GC) therapy has been demonstrated previously. Abnormalities in systemic hormonal and local (cytokine) regulation of bone marrow (BM) cells may underlie GC-induced imbalance between osteosynthesis and bone resorption. The cytokine system receptor activator of nuclear factor kappa-B (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) is considered as an integrating link in the NF-κB-mediated interaction of various cells involved in maintaining osteoblastic-osteoclastic balance, which makes it a pharmacological target for regulation and correction of the bone remodeling process. We studied GC-induced impairments of the RANKL/RANK/OPG axis in BM cells depending on vitamin D bioavailability and whether these changes were mediated by glucocorticoid (GR) and/or vitamin D (VDR) receptors. Female Wistar rats administered with prednisolone (5 mg/kg b.w., 30 days) showed a decrease in the GR protein level and the number of GR-positive BM cells. GC caused a marked elevation of RANKL and RANK levels in BM, while OPG decreased. Flow cytometry data indicated GC-elicited increase in the number of circulating RANK-positive osteoclast precursors (OCPs) in BM, peripheral blood, and spleen. In full accordance with the data that the interaction of RANKL-RANK leads to transcriptional activation of NF-κB and subsequent differentiation of osteoclasts, we found an increase in the level of phosphorylated p65 subunit of NF-κB with a simultaneous decrease in the NF-κB inhibitor (IκB) level. These changes were accompanied by vitamin D insufficiency and downregulated expression of CYP27B1 and VDR, which are responsible for synthesis and hormonal signaling of 1,25(OH)D. Notably, we observed VDR and RANK co-localization in OCPs. Cholecalciferol co-administration (1,000 IU/kg b.w., 30 days) with prednisolone resulted in elevated GR synthesis in BM. Cholecalciferol prevented prednisolone-elicited disturbances of the RANKL/RANK/OPG, which correlated with improved bioavailability and vitamin D signaling through VDR. This caused the lowering of phosphoNF-κB p65 level and inhibiting NF-κB translocation to the nucleus that could reduce the circulating OCPs pool in BM, peripheral blood, and spleen. Our findings suggest that prednisolone-induced abnormalities in GR and RANKL/RANK/OPG signaling pathways are associated with the impairments of vitamin D auto/paracrine system in BM cells and can be ameliorated by cholecalciferol supplementation.
维生素D（胆钙化醇）在对抗糖皮质激素（GC）治疗副作用方面的有效性此前已得到证实。全身激素和骨髓（BM）细胞局部（细胞因子）调节异常可能是GC诱导的骨合成与骨吸收失衡的基础。核因子κB受体激活剂（RANK）/RANK配体（RANKL）/骨保护素（OPG）细胞因子系统被认为是参与维持成骨细胞 - 破骨细胞平衡的各种细胞在NF - κB介导的相互作用中的一个整合环节，这使其成为调节和纠正骨重塑过程的药理学靶点。我们研究了取决于维生素D生物利用度的GC诱导的BM细胞中RANKL/RANK/OPG轴的损伤，以及这些变化是否由糖皮质激素（GR）和/或维生素D（VDR）受体介导。给予泼尼松龙（5mg/kg体重，30天）的雌性Wistar大鼠显示GR蛋白水平和GR阳性BM细胞数量减少。GC导致BM中RANKL和RANK水平显著升高，而OPG降低。流式细胞术数据表明，GC引起BM、外周血和脾脏中循环RANK阳性破骨细胞前体（OCPs）数量增加。完全符合RANKL - RANK相互作用导致NF - κB转录激活及随后破骨细胞分化的数据，我们发现NF - κB磷酸化p65亚基水平升高，同时NF - κB抑制剂（IκB）水平降低。这些变化伴随着维生素D不足以及负责1,25(OH)D合成和激素信号传导的CYP27B1和VDR表达下调。值得注意的是，我们观察到OCPs中VDR和RANK共定位。胆钙化醇与泼尼松龙联合给药（1000IU/kg体重，30天）导致BM中GR合成增加。胆钙化醇预防了泼尼松龙引起的RANKL/RANK/OPG紊乱，这与通过VDR改善生物利用度和维生素D信号传导相关。这导致磷酸化NF - κB p65水平降低并抑制NF - κB向细胞核的转位，从而减少BM、外周血和脾脏中循环OCPs库。我们的研究结果表明，泼尼松龙诱导的GR和RANKL/RANK/OPG信号通路异常与BM细胞中维生素D自分泌/旁分泌系统的损伤有关，补充胆钙化醇可改善这种情况。
